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5
Cassier's Magazine
Engineering Illustrated
Volume IX November, 1895 — April, 1896
The Cassier Magazine Company
World Building, New York 33 Bedford Street, London
68462
Copyright, 1896, by The Cassier Magazine Company.
Press of Louis Cassier
SS^p
Co.
& Company, New York.
APR 2 1896
NDEX TO VOLUME IX
PAGE
Adams, E. T. : Shaft Governor, The 477
Illustrated.
American vs. European Shop Practise Robert Grimshaw 532
Antiquated Machine Tools in English Workshops 581
Atkinson, Llewelyn B. : Electric Power in Collieries 107
Baylor, A. K. : Power Consumption on Electric Railways 137
Becks, Geo. A. : Mill Equipment 27
Illustrated.
Bell, Dr. Louis : Electric Power from the Coal Regions 57
Induction Motor, The 241
Illustrated.
Benjamin, Park : On a Letter to Benjamin Franklin 273
Illustrated.
Billings, F. C. : Origin and Evolution of the Drop-Hammer, The 393
Illustrated.
Biographical Sketches :
Armstrong, Lord, C. B 488
Franklin, Benjamin 273
Head, Jeremiah 74
Mudd, Thomas 575
Scott, Irving Murray P. M. Randall 172
Thornycroft, John I., F. R. S C.J. Cornish 398
Blast Furnaces Struck by Lightning 503
Boilers :
Accessibility in 76
Blow-off Pipes 77
Bulged Plates from Using Oil 412
Burning Pulverised Coal Under 501
Pressure Required to Burst Tubes 412
Some American Vertical Boilers 157
Too Many Tubes in Boilers 498
Brookman, F. W. : Power from Town Refuse 569
Illustrated.
Carborundum : What it is and How it is Made Francis A. J. Fitzgerald. . . 387
Illustrated
Carpenter, Prof. R. C. : Steam Plant for a Small Electric Light and Power Station, A. 339
Illustrated.
Castings, Light Iron 175
Catalogues, Machinery, for Foreign Circulation 581
Cheap Gas Power B. H. Thwaite, C. E 37
Illustrated.
Chinese Railroad, The First 582
Coal Regions, Electric Power from the Dr. Louis Bell 57
Coal Handling Machinery, Modern A. J. Webster 62
Illustrated.
Coalless Cities Prof. Francis B. Crocker. . 231
Illustrated.
Coal Under Boilers, Burning Pulverized 501
iv INDEX.
PAGE
Compressed Air, Experiments with Men and Animals in 415
Colwell, A. W. : Sugar-Making Machinery in Cuba 507
Illustrated.
Contraband Goods in an Electric Storage Battery Box, Carrying 500
Co-operative Factory Management 503
Cornish, C. J. : Biography of John I. Thornycroft, F. R. S 398
Illustrated.
Cranes and Derricks in Harbour of Genoa, Floating Chev. L. Luiggi 538
Illustrated.
Crocker, Prof. Francis B. : Coalless Cities 231
Illustrated.
Crompton, R. E. B. : Electrically Operated Factories 291
Illustrated.
Culm and Other Low Grade Fuels for Steam Raising,
Burning Anthracite John R. Wagner 3
Illustrated.
Danger of Wood-Working Shop Dust, The 502
Duncan, Dr. Louis : Direct Production of Electrical Energy, The 285
Dunlap, Orrin E. : New Power Developments at Niagara Falls 484
Illustrated.
Electricity :
Electric Heating for Buildings on a Large Scale 176
Electric Ferry Boats in Norway 80
Electric Boat Elevator, An 176
Electric Mountain Railroad on the Isle of Man, An 175
Illustrated.
Electric Power from the Coal Regions Dr. Louis Bell 57
Electric Power in Collieries Llewelyn B. Atkinson, A. M. I. C. E 107
Electric Power in Canada J. S. Robertson 301
Illustrated.
Electric Pumping Machinery Chas. A. Hague 257
Illustrated.
Electric Railways, Power Consumption on A. K. Baylor 137
Electric vs. Steam Heating A. F. Nagle 42
Electric vs. Steam Efficiency 80
Electric Power Stations, The Development of 419
Illustrated
Electrical Energy, the Direct Production of Dr. Louis Duncan 285
Electrically Operated Factories R . E. B. Crompton 29 1
Illustrated. Electricity for Propelling Railroad Trains at Very
High Speeds Hiram S. Maxim 250
Electricity in 1895 : Retrospect and Prospect. . .Thomas Commerford Martin 312
Electro-Chemistry in Germany 410
Electro-Magnets for Lifting Weights 503
Gas Engines for Electric Light and Power Nelson W. Perry 207
Illustrated.
Long Distance Transmission of Power by Electricity
in the United States John McGhie 359
Illustrated.
Power Consumption on Electric Railways A. K. Baylor 137
Protection of Electrical Apparatus Against Lightning. .Alexander J. Wurts 435
Illustrated.
Steam Plant for a Small Electric Light and Power
Station Co Prof. R. C. Carpenter 339
Illustrated.
Electric Metal Heating and Working Joseph Sachs 522
Illustrated.
Emery, Chas. E., Ph. D. : When it is Advantageous to Use Water Power and Electric Transmission 219
Illustrated.
Saving Fuel in a Large Oil Refinery 356
INDEX. v
Page
Engineer, The Expert H. de B. Parsons 494
Engine Foundation Block, A Concrete J. Hetherington 577
Illustrated.
Engine, The Evolution of the Portable W. D. Wansbrough 83
Illustrated.
Engines :
Gas Engines for Electric Light and Power Nelson W. Perry, E. M 207
Illustrated.
Selling Engines in Foreign Countries 580
Steam Engine Piston Construction, Some Recent
Departures in Prof. John E. Sweet 450
Illustrated.
Equipment of a Mill Geo. A. Becks 27
Illustrated.
Factory Management, Co-operative 503
Factories, Electrically Operated R. E. B. Crompton 291
Illustrated.
Ferry Boats in Norway, Electric 80
Field, C. J. : Development of Electric Power Stations, The 4J9
First Pair of Horizontal Turbines Ever Built, The 77
Fitzgerald, Francis A. J. : Carborundum ; What it is and How it is Made 387
Illustrated.
Fletcher William : Thomas Newcomen and His Work 141
Illustrated.
Folsom, Clarence P. : Power Plant for a Modern Paper Pulp Mill 560
Illustrated.
Fog Signalling by Oil Engines and Compressed Air 414
Foundation Block, A Concrete Engine J. Hetherington 577
Illustrated.
Foundry Equipment, False Economy in H. Hansen 17°
Franklin, On a Letter to Benjamin Park Benjamin 273
Illustrated.
Fuel in a Large Oil Refinery, Saving Dr. Chas. E. Emery 356
Fuels, Gaseous H. L. Gantt 46
Illustrated.
Furnaces Struck by Lightning, Blast 5°3
Gantt, H. L. : Gaseous Fuels 46
Illustrated.
Gas Power, Cheap B. H. Thwaite 37
Illustrated.
Gas Engines for Electric Light and Power Nelson W. Perry, E. M 207
Illustrated. Gaseous Fuels H. L. Gantt, A.B., M.E.... 46
Illustrated.
Governor, The Shaft E. T. Adams 477
Illustrated.
Governors for Fire Pumps 4*3
Gray, J. Arthur : Modern Shipbuilding Tools 323, 455
Illustrated.
Grimshaw, Robert : American vs. European Shop Practise 532
Guard for Water Gauge Glasses 5°°
Hague, Chas. A. : Electric Pumping Machinery 257
Illustrated.
Hammer, The Origin and Evolution of the Drop F. C. Billings 393
Illustrated
Hansen, H.: False Economy in Foundry Equipment 170
Heating for Buildings on a Large Scale, Electric 176
Heating, Electric vs. Steam A. F. Nagle 42
Hetherington, J.: A Concrete Engine Foundation Block 577
Illustrated. Horseless Carriage, The Evolution of the B. F. Spalding 543
Illustrated.
vi INDEX.
Horseless Carriages x73
Illustrated.
Horses, Hauling Power of, on Different Roads 584
Houston, Edwin J., Ph.D., and Kennelly, A. E., Sc.D.: Municipal Lighting from Underground Mains 179
Illustrated.
Induction Motor, The Dr. Louis Bell 241
Illustrated.
Labour-Saving Device, A Valuable 5°°
Letter to Benjamin Franklin, On a Park Benjamin 273
Illustrated.
Lightning, Protection of Electrical Apparatus Against Alexander Jay Wurts 435
Illustrated.
Locomotive Whistle, The Invention of the 4°9
Long Distance Transmission of Power by Electricity in
the United States John McGhie 359
Illustrated. Luiggi, L. : Floating Cranes and Derricks in Harbour of Genoa 538
Illustrated.
Machinery for Export 580
Machinery Catalogues for Foreign Circulation 581
Machine Tools, Some Historical 4T5
Machine Tools at Full Capacity, Running 79
Machine Tools in English Workshops, Antiquated 581
Magnets for Lifting Weights, Electro 503
Martin, Thomas Commerford : Electricity in 1895 : Retrospect and Prospect 312
Maxim, Hiram S. : Electricity for Propelling Railroad Trains at Very High Speeds. ... 250 McGhie, John : Long Distance Transmission of Power by Electricity in the United States 359
Illustrated.
Mechanical Traction on Street Railroads, Economy of 583
Metal Heating and Working, Electric Joseph Sachs 522
Illustrated.
Mill Equipment Geo. A. Becks 27
Illustrated.
Modern Shipbuilding Tools J. Arthur Gray 323-455
Illustrated.
Motor, The Induction , Dr. Louis Bell 241
Illustrated.
Mudd, Thomas : An International Standard of Screw Threads 563
Illustrated.
Municipal Lighting from Undergound Mains Edwin J. Houston, Ph.D.,
illustrated. and A. E. Kennelly, Sc.D. . 179
Nagle, A. F. : Electricity vs. Steam Heating 42
Newcomen and His Work, Thomas William Fletcher 141
Illustrated.
Niagara Falls, New Power Developments at Orrin E. Dunlap 484
Illustrated.
Night Watchmen for Factories 502
Oil in Boilers, Bulged Plates from Using 412
Paper Machines Worked by Electricity 584
Parsons, H. de B. : Expert Engineer, The 494
Perry, Nelson W., E. M. : Gas Engines for Electric Light and Power 207
Illustrated.
Pipe Head, a Simple Exhaust 411
Illustrated.
Pipes, Boiler Blow-Off 77
Portraits :
Armstrong, Lord, C. B Frontispiece
Benjamin, Park 272
INDEX. vii
Bell, Louis 240
Crompton, R. E. B 290
Crocker, Francis B 230
Duncan, Louis 284
Emery, Chas. E . 218
Franklin, Benjamin Frontispiece 178
Hague, Chas. A 256
Head, Jeremiah Frontispiece 2
Houston, Edwin J 181
Kennelly, A. E 182
Martin, T. C 313
Maxim, Hiram S 251
Mudd, Thomas Frontispiece 506
Perry, Nelson W 209
Robertson, J. S 300
Scott, Irving M Frontispiece
Thornycroft, John I., F. R. S Frontispiece 398
Power :
Cheap Gas B. H . Thwaite 37
Illustrated.
The Development of Electric Power Stations C. J. Field 419
Illustrated.
Electric Power from the Coal Regions Dr. Louis Bell 57
Electric Power in Collieries Llewelyn B. Atkinson, A. M. I. C. E. . 107
Electric Power in Canada J. S. Robertson 301
Illustrated.
Gas Engines for Electric Light and Power Nelson W. Perry, E. M. . . 207
Illustrated.
Long Distance Transmission of Power by Electricity in
the United States John McGhie 359
Illustrated.
New Developments at Niagara Falls Orrin E. Dunlap 484
Illustrated.
Plant for a Modern Pulp Mill Clarence P. Folsom 560
Illustrated.
Power Expended in Playing on a Piano 175
Power from Town Refuse F. W. Brookman 569
Illustrated.
Power Consumption on Electric Railways A. K. Baylor 137
Water Power Samuel Webber 375
Illustrated.
When it is Advantageous to Use Water Power and
Electric Transmission Chas. E. Emery 219
Illustrated.
Pressure Required to Burst Boiler Tubes, The 412
Pumping Machinery, Electric Chas. A. Hague 257
Illustrated.
Pumps, Governors for Fire 413
Rack Railroad Data 582
Railroad on the Isle of Man, an Electric Mountain 175
Illustrated.
Railroad, The First Chinese 582
Railroad Trains at Very High Speeds, Electricity for
Propelling Hiram S. Maxim 250
Railways, Power Consumption on Electric A. K. Baylor 137
Richards, Francis H. : The Automatic Weighing Machine 541
Robertson, J. S. : Electric Power in Canada 301
Illustrated.
Sand Track, The 414
viii INDEX.
PAG
Screw Threads, International Standard of Thomas Mudd 563
Illustrated.
Shipbuilding, Quick 409
Shipbuilding Tools, Modern J. Arthur Gray 323, 455
Illustrated. Ship Windlass, The Development of the Edwin H. Whitney, M. E. . 1 13
Illustrated.
Shop Practice, American vs. European Robert Grimshaw 532
Shops, Extending Old 77
Spalding, B. F. : The Evolution of the Horseless Carriage 543
Illustrated.
Spies, Albert : Some American Vertical Boilers 157
Illustrated.
Steady Platform at Sea, A Beauchamp Tower 151
Illustrated.
Steam Plant for a Small Electric Light and Power Station, A . Prof. R. C. Carpenter 339
Illustrated.
Steam Pipe Accidents 78
Steam Engine Piston Construction, Some Recent Depart- ures in Prof. John E. Sweet 450
Illustrated.
Steam Heating, Electric vs A. F. Nagle 42
Street Railroads, Economy of Mechanical Traction on 583
Step Bearing, A Noteworthy 584
Storage Battery Box, Carrying Contraband Goods in an Electric 500
Sugar-Making Machinery in Cuba A. W. Colwell 507
Illustrated.
Sweet, Prof. John E. : Some Recent Departures in Steam Engine Piston Construction 450
Illustrated.
Testing Machine for Bicycle Wheels 583
Illustrated.
Theatre Cars on Electric Street Railroads 504
Thornycroft, John I., F. R. S C. J. Cornish 398
Illustrated.
Thurston, Prof. R. H. : Evolution of the Fittest Education, The 472
Thwaite, B. H. : Cheap Gas Power 37
Illustrated.
Tower, Beauchamp : Steady Platform at Sea, A 151
Illustrated.
Tubes in Boilers, Too Many .-. 498
Turbines Ever Built, First Pair of Horizontal 77
Tyranny of Trades Unions, The 411
Unnecessary Refinement in Machine Work 79
Vibration of Buildings Due to Machinery 499
Wagner, John R. : Burning Anthracite Culm and other Low Grade Fuels for Steam
Raising 3
Illustrated.
Wansbrough, W. D. : Evolution of the Portable Engine, The 83
Illustrated.
War Ships, The Cost of English 501
Water Gauge Glasses, A Guard for 500
Water Power Samuel Webber 375
Illustrated.
Webster, A. J. : Modern Coal Handling Machinery 62
Illustrated.
Weighing Machine, The Automatic Francis H. Richards 541
Whitney, Edwin H., M.E.: Development of the Ship Windlass, The 113
Illustrated.
Wurts, Alexander J.: Protection of Electrical Apparatus Against Lightning 435
Illustrated.
(/lA^es*****^^**
PAST PRESIDENT OF THE BRITISH INSTITUTION OF MECHANICAL ENGINEERS.
i NOV 1 1895 j
^Hr
Cassier's Magazine
Vol. IX.
NOVEMBER, 1895.
No. 1,
BURNING ANTHRACITE CULM AND OTHER LOW-GRADE FUELS FOR STEAM RAISING.
By John R. Wagner.
IT is only a short time ago that all eyes were turned to the develop- ment of cheap power by the utilisation of the gigantic water falls at Niagara, and yet, even now, attention is being turned into a new direction — towards the vast storehouses of energy in the American anthracite coal fields in the shape of the immense accumula- tions of waste coal known as " culm."
The term culm is very elastic, and has often been applied to any mixture
of anthracite below that known in the market as pea coal, or anything mixed of sizes from $/% inch down to dust. Before discussing the various appli- ances and systems of utilising culm, I will define this product, as we often hear of the successful burning of culm, which, upon investigation, is found to be a very much different fuel from what was expected.
It has long been understood that anthracite coal will give the best results
A TYPICAL CULM BANK.
Copyright, 1895, by The Cassier Magazine Company. All rights reserved.
CASSIER'S MAGAZINE.
BURNING ANTHRACITE CULM.
in burning when it is of a uniform size. Twenty-five years ago the market was already supplied with seven sizes — lump, steamer, broken, egg, stove, chestnut, and sometimes pea coal. The operators or coal miners at that time attempted to do away with this large number of sizes, together with the buildings known as "breakers," and to have but two or three sizes, and to impress on the minds of the consumers that they were paying for the loss oc- casioned by breaking the coal into so many sizes. The trade, however, in- sisted on getting what it wanted, and not then knowing how to burn, for steam purposes or otherwise, anything smaller than pea, and sometimes chest- nut, all below this size was hauled out and stocked in large piles, constituting the present culm banks. Many of these banks contain pea coal mixed with all the smaller sizes, varying from that down to dust.
In the earlier days of anthracite mining, when much pea coal was yet thrown on these banks, only the purer coal was taken from the mines, carry- ing with it very little slate ; conse- quently these culm banks prove to be low enough in impurities to become a good steam fuel, and which could be furnished in the boiler house of manu- facturers in many localities in the an- thracite region at a cost not exceeding 50 cents (2 sh.) per ton. There are, of course, many banks where this culm was at the same time mixed with slate and other refuse, which it would not pay to separate. More recently, culm banks would be those containing nothing larger than buckwheat coal, and others, again, containing nothing larger than No. 2 buckwheat, also called rice. Again, some of the coal companies would now call culm that which they could not sell as buckwheat, but which had part of the dust washed out.
To give an idea of the actual size of the small prepared anthracites, I might mention that the following are the most generally used diameters of the per- forations in the screens through and over which these sizes are made to pass:
Pea coal passes through J& inch and over 9-16, occasionally y% inch ; buck- wheat, through 9-16 or $/% inch and over j4, inch ; No. 2 buckwheat (rice, bird's eye), through ^ inch and over 3-16 inch, occasionally }( inch ; No. 3 buckwheat (barley), through 3-16 and over 3-32 or 1-16 inch ; bird's eye, through 5-16 inch and over }i.
That which passes through 3-32 or 1 -16 inch is properly regarded as dust. When investigating the subject of burn- ing culm by means of the appliances offered to the trade for the purpose, such data as a clear idea of the exact size or what percentage of each of the above sizes it contains, the proxi- mate analysis of the coal, the pressure of blast under the grate and the draught over the grate and in the stack, the weight of coal consumed per square foot of grate per hour, and the compo- sition of the ash as dumped into the ash-pit, are necessary to enable us to compare a certain system with others with which we are familiar.
Preparatory to a description of the various appliances for burning the smaller sizes of coal, I will give the principal requirements. These are pretty clearly understood, but the ful- fillment of them is not. The question of burning low grades of fuel, such as anthracite culm, barley, rice, bird's eye and buckwheat, breeze or coke dust, bituminous slack, etc., is one mainly of undergrate air blast and involves the following features :
1 st. Undergrate blast, produced by fan or steam jet.
2d. Large grate area.
3d. Grate so constructed as to con- stitute a plane surface ; that is, without narrow grooves or depressions where an appreciable amount of coal could lodge.
4th. Type of grate that will admit of rapid and easy removal of ash or clinker.
5th . Air spaces from 1 - 1 6 to 3- 1 6 inch wide, and not more, except for buck- wheat or bituminous slack when they may be }( inch wide.
6th. Admitting of the cleaning of fires without having the fire doors open
CASS 7 ER'S MAGAZINE.
mm
m
*8P 4
m
\
BURNING ANTHRACITE CULM.
for any length of time ; also the drop- ping of ash into a closed ash-pit.
7th. Thin fires and frequent and careful firing. Thickness of bed should diminish with rate of combustion.
8th. Reduction of draught over fire as the value of the fuel or the rate of combustion diminishes, effected by means of a damper in the flue or stack.
The systems that will here be de- scribed will include only those with undergrate blast, as there are no others i n successful operation where small coal is used. One of the earliest of these, introduced to burn coke dust or breese, house refuse and other low grade fuels is Perret's furnace. The essential feature of this fur- nace is a forced blast, pro- duced by a steam jet blower, and narrow deep bars, dipping into water to prevent their warping and the adhering of clinkers. The air spaces between the bars are from 1-16 to 3-16 of an inch wide. It has been successfully used in the service of internally fired boilers to burn all low grade fuels. The manu- facturers of this furnace, Messrs. Bryan Donkin & Co., of London, do not limit themselves to the use of steam jets for blowing purposes and in their cata- logue make the following statement :
1 ' The first cost of putting in a steam jet to produce the blast, instead of a fan and engine, is rather less ; but although our furnace thus fitted works far more economically than any other furnace fitted with steam jets (and there are many such) the economy is not so great as when a fan is used ; besides this, all steam jets are noisy." This system has been in use in England since 1885.
A furnace similar with respect to air supply, is that known as Meldrum's forced draught and waste fuel furnace. This furnace, patented 1889, *s a later
rival of the Perret furnace, and^its dis- tinctive feature is that of the construc- tion of the steam blower, the curves in the main blower tube being constructed according to the principles of hydraulics to counteract the effect of the " con- tracted vein. ' ' The blower consists of a long cast-iron tube, parallel for a por- tion of its length, and widening out into a trumpet shape at its inner end. A very small nozzle is fixed to the outer end and through it a jet of steam Lis in-
THE MELDRUM FURNACE, MADE BY MESSRS. MELDRUM BROS. MANCHESTER, ENGLAND.
jected. It is claimed by the patentee that the steam used by this blower does not exceed two per cent., under favour- able conditions of combustion, or 3 or 4 per cent, in extreme cases, of the total evaporation. The percentage of the generated steam used would evidently increase as the size of the coal dimin- ished, and would, no doubt, in some cases much exceed these limits.
The Perret and Meldrum furnaces have met with success in. many cases, such as internally fired boilers where a restricted grate area prevailed. A lower
CASSIER'S MAGAZINE.
THE BOTTOM OF A MINE SHAFT.
grade of fuel could be used, owing to the feature of forced blast. In other cases, when firing good fuel, with only a slight chimney draught, an increased rate of combustion was obtained with the use of either of these furnaces, but also in ordinary furnaces supplied with fan blast. Great claims have been made for them with regard to the suc- cessful burning of low grades of fuel, but with the reported quantities of coal consumed per hour per square foot of grate surface, and a pressure of blast
equal from l/2 to % of an inch water column, it is evident that the fuel was not as small and as difficult to handle as American anthracite culm or No. 3 buckwheat.
In 1876 Mr. John E. Wootten com- municated a paper to the American Philosophical Society, describing a "combination of apparatus by which ordinary anthracite coal waste from the dirt banks at the mines can be success- fully and profitably burned in the fur- naces of stationary and locomotive
BURNING ANTHRACITE CULM.
boilers." The apparatus consisted of what is commonly known as the Woot- ten wide fire-box with a flat grate con- sisting of plates with perforations, from Y% to Y± of an inch in diameter, and from 2 to 3 inches from centre to centre. As a substitute for the ordinary exhaust nozzle and draught Mr. Wootten used an undergrate steam blower similar to that of the commonly used McClave system (described further on) delivering steam and air into a closed ash-pit. This was aided by very small jets of steam in the stack, giving a constant induced draught. Frequent stirring was claimed to be necessary ; yet this grate was said not to allow more than 2 per cent, of the coal charged to fall through the air spaces.
This fire box is still extensively used on many of the American anthracite railroads, especially on the Philadelphia and Reading, which company has about 45 per cent, of their locomotives equipped with it. It is now used with
modified grate bars and induced draught produced by a large exhaust nozzle, instead of blowing with steam jets into a closed ash-pit. The sharp exhaust of simple locomotives, when running at a high speed, has a tendency to tear up the fire of small-sized anthracite, and also to draw a considerable amount oi the smaller pieces out through the stack, which, in addition to being unpleas- ant to the passengers, is a loss of fuel.
Recent experiments on the Philadel- phia and Reading railroad show that by using compound locomotives, the ex- haust nozzles of which are larger, and the exhaust consequently less sharp, and where the amount of steam required to run is less than on simple locomotives, pea and buckwheat can be used even on the fastest trains. For locomotive pur- poses nothing smaller than buckwheat can be used, even this requiring very close attention and careful firing. Re- cent statements by the above-mentioned
BREAKER' BOYS.
IO
CASSZEX'S MAGAZINE.
railroad show a saving of 70 per cent, in the cost of fuel.
The McClave rocking grate and Argand steam blower were among the first appliances introduced to burn the smaller sizes of anthracite and culm. The system is one of undergrate forced draught, produced by a steam blower, and of rocking bars of excellent de-
of each bar, and locating the journaFa suitable distance from the back and top edges. From Fig. 1 it will be seen that the difference between the radius to the back edge and the shortest radius, is not sufficient to so break up the bed as to allow the fine coal to mix with the ash and thereby cause a waste, but only to rasp off some of the loose ash or
SLAT1. PIC KICKS IN A COAL I'.RKAKEK.
sign, especially as now put on the mar- ket. The main feature of the grate is a rocking motion to the bars, having two functions. The first of these is the cutting off of ash and clinker, which is accomplished by the back edges of the bars, as in Fig. 1, on the opposite page, without increasing the opening between the successive bars.
This result is obtained by giving a certain curve to the back or web part
small clinkers and to loosen up the bed which is especially adapted to a soft coal fire, when of caking quality. To use this cutting-off movement, the act- uating lever is pushed inward, which throws the upper portion of the bars forward.
The second function of the rocking motion is the rapid dumping of the ash into the ash-pit. Fig. 2 shows one 01 a number of sections, the half or the
BURNING ANTHRACITE CULM.
FIG. I. THE MCCLAVE GRATE, MADE BY MESSRS. MC CLAVE, BROOKS & CO., SCRANTON, PA., U. S. A.
whole of which can be moved at wi by engaging a stop to the levers on the outside, giving either a cutting- off movement or a dumping movement. In the same view the back half of the section is shown in its normal position, while the front portion is in the extreme position, when the dumping movement is used, and the successive bars are arranged with fingers elevated to form pockets to contain the ash and clinkers which will be dropped into the ash-pit when an inward movement is given to the lever. This brings the upper por-
tion forward and into its normal posi- tion, indicated by a stop. The great difference in the shortest and longest radius (shown in the cut) will enable the clinker to be rapidly broken up, as they have considerable rise^ and leverage.
The advantage of dividing the grate into three, four or five sections, each consisting of two portions, lies in the fact that, when cleaning fire, the live coal can be pushed back onto the rear part of the grate, and, if it is not desired to "burn down," the ash and clinker
FIG. 2. ANOTHER VIEW OF THE MCCLAVE GRATE.
12
CASSIER'S MAGAZINE.
can be instantly dumped off the front portion of each section. The bars of the front portion of the grate having been brought into their normal posi-
AN ARGAND STEAM BLOWER.
tion, the live coal can readily be pulled forward, and the back ash "burned down," if desired, or instantly dumped into the pit. The live coal or fire can then be distributed over the whole grate and coaled over ; or one section can be cleaned and coaled at a time,
closed, thereby preventing any cooling down of the furnace by cold air.
The construction and design of the bars is not only such as to admit of a mechanism by which the two definite motions, above described, can be ob- tained, but to give the best results with regard to durability. An extended series of experiments at the experi- mental laboratory of the late E. B. Coxe, with bars of different designs to burn barley or No. 3 buck- wheat coal, without allowing the dust to sift through into the ash-pit, led the writer to ap- preciate the following points of excellence in the McClave bar :
1 st. All the metal surface on which the coal lies is in one plane, except the slight wave in it due to the curvature of the bars, with no recesses in which coal can lodge and burn or warp the adjacent projecting metal. The short lengths of metal with sufficient depth to transmit the heat to the pendent or supporting rib, which, in turn, is of sufficient depth to be relieved of its heat by the blast, whereby warping and burning out is pre- vented.
2d-
SECTION OF AN ARGAM) BLOWER,
AX ARGAND BLOWER Al'l'l II I. TO A BOILER FURNACE.
which might be preferred where only a few boilers are fired and where a drop in steam pressure would be objection- able. The foregoing movements can be made with the fire and ash-pit doors
3d. The curve to the pendant or supporting rib and the position of the journal with reference to the back and top surface, so as to allow a wide range of motion, as in Fig. 1, without leaving
BURNING ANTHRACITE CULM.
*3
AT THE HOISTING CHUTE IN A COAL BREAKER.
an opening through which coal could pass.
4th. The air spaces can be made small without becoming clogged.
At the time of these experiments the weakest point in the bar was observed to be in the fingers, which would occa- sionally have a portion knocked off by the careless dropping of the hoe used in spreading the live coal when clean- ing. This weakness has been eliminated by casting a tie between each pair of fingers, which also afforded a more equal distribution of the air. The top journal bearing bar has also been im- proved to better allow for expansion.
The steam blower, in its improved form, is shown on the opposite page. Instead of the perforated ring, formerly made of cast iron and of circular cross section, it is now made of phosphor bronze and is of the cross section, shown, which allows the air to have better access to the steam jets. With
this metal the size of the small open- ings will be better maintained, and by making the supply pipe from the steam main of brass, the tendency to clogging by particles of rust is obviated. This system of bars and blower has been on the market for a period of ten years, and has a wide distribution out- side of the coal regions, giving very satisfactory results.
For hand-fired grates there certainly seems very little chance for any marked improvement over the McClave grate as now constructed. It must, however, be borne in mind that the McClave or any other grate will not burn the fine coal, but that it is effected by the air that passes through the bed of fuel, and that the best a grate can do is to hold the fine coal, present the best form of air spaces, to have the distri- bution of metal such as to best resist warping and burning, and to admit ot rapid, easy and economical cleaning of
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CASSJER'S MAGAZINE,
V \ BREAKER,
fires. Having then a grate fulfilling all these necessary conditions, the fuel-bed must be so managed as to allow the necessary air to pass through or the expected results will not be obtained. This involves the carrying of thin and uniform fires, with frequent coaling.
One of the difficulties experienced in the attempt to burn barley and rice coal with") a strong undergrate forced blast was due to the formation of blow holes or miniature volcanoes. When these were once formed, the air would continue to blow through, producing a
very intense local heat by the excessive blast and resulting in the formation of clinkers at these points. After a num- ber of these blowers are formed, the air no longer passes up through other por- tions of the bed, although, ultimately, the production of ash in the entire bed will result, radiating from these blow- ers outwardly. The Leisenring shak- ing grate, recently put on the market by the LeisenringManufacturingCompany, of Scranton, Pa., is a compromise between the McClave dumping grate and a stationary grate with undergrate
BURNING ANTHRACITE CULM.
15
steam blowers. It has a tendency to overcome the difficulty due to this blowing.
The grate consists of a series of fixed bars with central webs from which fingers project on both sides, two adja- cent sections of which leave a space and form a shallow trough tapering to the centre to receive a sliding bar of similar construction. The fingers of this are wide enough to completely cover the spaces between the lower fingers. By the shifting of the upper section on the lower one it can be made to offer an air space of from 40 per cent, to nothing. The sections are seven inches wide and the alternate bars move in opposite di- rections, each having a movement of two inches.
By an occasional movement of the bars, the blow-holes above mentioned will become closed and others will be
formed, so that the bed may be con- sumed uniformly in all portions before cleaning time. Where the coal is not of a clinkering character a part of the ash may, by this movement, be sifted through the lower bars. In strongly clinkering coals, the cleaning of fires would, however, be effected in the same manner as in stationary grates. The blast under the grate is produced by jet blowers, somewhat similar in princi- ple to the McClave.
The advantage of using steam jets to produce the air blast is that they lessen the tendency to the formation of hard clinker, and increase the life of the grate bars, and that the first cost and subsequent repairs of the undergrate forced draught system is less than that of the fan. Another effect of the in- troduction of steam into a furnace is to give to the process of combustion the
W^M
THE WILKINSON AUTOMATIC STOKER, MADE BY THE WILKINSON MFG. CO., BRIDGEPORT, PA , TJ. S. A.
i6
CASSIER'S MAGAZINE.
BURNING ANTHRACITE CULM.
17
nature of that in making producer gas, and thus giving more volume and a longer flame than is ordinarily produced with anthracite coal. Such a flame is in some boiler settings an advantage, but always requires sufficient space and time for the gases to mix with the air and to burn before they leave the final water heating surface. Where there is a weak chimney draught and hard forcing of the fires with the steam blower, there is danger that some of the gases escape combustion, and re- ignite above the stacks, which is often seen, especially where short stacks and high temperatures of escaping gases prevail.
The same thing might occur, though not visible, when the boilers all dis- charge into one large but low stack, in which they might burn in the stack with the air coming from a boiler fur- nace where there was an excess of air, although the burning of the gases would give no available heat, as it would be beyond any heating surface.
The question as to the economic evaporation per pound of fuel and the relative economy between forced draught produced by the steam blower or by a fan blower need not here be discussed, as the saving effected in burning small coal by any system is not due to a more complete combus- tion by one system than in another, but is entirely due to the difference in the price of fuel and the ability to burn, in sufficient quantity, what would be in many cases a waste product. The question as to what advantage, if any, in economy, the fan blower has over the steam blower will, no doubt, be settled by experiments within the next year or two. Indications now point to a greater consumption of steam by the steam blower than by the fan blower, one reason being that in the case of a fan there is no power consumed except the friction of the fan, when there is no air propelled or passing through the fuel, whereas in the case of the steam blower the same amount of steam issues from the blower, whether there is any movement of air through the fuel or not. From this it would appear that
the smaller the fuel the more efficient would the fan become as compared with the steam blower.
The firing of culm or the smaller anthracites with admixture of bitu- minous coal is worthy of consideration. Very good results are obtained both as far as capacity and economy is con- cerned, by sprinkling several hundred pounds of culm, more or less spread out on the floor, with about eight per cent, of crushed bituminous coal. This way of mixing will enable the firemen, while coaling the fire, to do better than if the two coals were intimately mixed, as he will instinctively take a shovelful from such a portion of the pile, either rich or lean in soft coal, as will suit the particular spot on which it is to be thrown. The bituminous coal will im- mediately become more or less incor- porated or agglomerated with the anthracite, preventing the dust in the latter either to blow out through the flues or drop through the grate. It also serves to keep the bed more open, and thus increases the rate of combus- tion. In this manner culm and rice coal are fired, giving results as to capacity of boiler unable to be ap- proached by the same anthracite alone.
At centres where yard screenings or screenings from the docks can be ob- tained, its use will show an appreciable economy when mixed with from 8 to 10 per cent, of bituminous, even when its cost is fifty cents (2 sh.) a ton more than the screenings. This method also has the advantage of producing no more smoke than would be allowable by the ordinary smoke ordinance. Forced draught is also required with this method of firing, but as the mix- ture is more free-burning, it need not be as strong as with the anthracite alone of the same size.
The Wilkinson automatic stoker is one of the class which may be called " inclined reciprocating stokers." On page 15 is shown a sectional elevation of it as applied to a horizontal return tubu- lar boiler. This stoker consisted, until recently, of a series of hollow, inclined reciprocating grate bars, a worm gear and toggle-joint mechanism for oper-
CASSIER'S MAGAZINE.
A CULM BANK AND CONVEYOR.
ating them, a series oi steam jets, one blowing into each bar, a feed hopper in which revolves a feed roller, a hollow casting on which the lower ends of the bars reciprocate, and of the stationary table which is supported by this hollow casting.
The grate bars are a series of hollow castings, approximately of rectangular cross section, 4*/ inches wide by 6 inches deep, placed side by side and inclined towards the bottom of the fur- nace at an angle, suited to the repose of the fuel (28 to 30 degrees). The upper end, which is open to admit the blast pipe, projects through and is sup- ported by the stoker front. The lower end slides on and is supported by a hollow casting termed the bearer bar, as shown in the cut. Throughout the inclined length and in the face or upper side of the bar, is cast a succes- sion of steps. Through the rise of each step a vent or tuyere is provided, through which the air and steam issues, passing up through the bed of fuel. To move the mass of fuel forward and to keep it open, the alternate bars
move in opposite directions, being con- nected in two series. The motion is constant and uniform, the one series being always ready to advance and carry the fuel forward at the instant the other is receding. The extent of the movement varies from nothing to 1 and 1 y± inches, being the greater, the smaller the coal.
The revolving feed roll, shown in the hopper, feeds the fuel at a uniform rate from the hopper to the upper end of the grate bar, the continuous back-and- forth motion of the grate bars, there- after insuring a uniform thickness of the fuel bed. This motion prevents the ash from melting to the bars, or the formation of large clinkers, and causes a slow but gradual advance of the partially consumed fuel to the bottom of the grate, by which time it is con- sumed, and the ash is deposited on the stationary table, shown bolted to the hollow bearer bar. The ash on this stationary table nearly fills the space between the hollow bearer bar and the over-hanging bridge- wall, thereby pro- ducing a partial seal between ash-pit
BURNING ANTHRACITE CULM.
19
and furnace and preventing any inrush of air through ash-pit and the conse- quent cooling of the combustion cham- ber. The same movement of the bars also forces the ash off the table into the pit, to be removed in the usual manner or by a conveyor of some kind.
The mechanism for effecting the entire operation consists of a pulley, a worm and a worm wheel on one end of the feed roll shaft, on the other end of which it has a crank disk of variable throw which, by means of a link, oscillates the shaft carrying a series of rocker arms. It can, therefore, readily be seen that the power required to drive the moving parts is nominal. The blast is saturated steam, through a
any great care in bringing the over- hanging bridge-wall to form a seal with the ash on the fixed extension grate to avoid leakage of air into the combustion chamber at that point.
The air for cumbustion passes through perforations in the outer wall of the wind saddle and up through large open- ings in its top, corresponding to similar ones in the bars, through which it is drawn and propelled forward by the action of the steam jet, as shown in the cut. By closing the upper ends of the bars with a plate through which the steam jets pass, and by delivering the air in this manner and having a closed ash-pit, both the noise and an excess of air into the furnace is avoided. The
THE COXE AUTOMATIC STOKER, MADE BY MESSRS. COXE BROS. & CO., DRIFTON, PA., U. S. A.
i -1 6 inch nozzle, into each bar, or one nozzle for every 4^ inches in width of grate. In this form it has given very satisfactory results with buckwheat coal. This stoker is simple in construction and seems durable and not likely to get out of order. Of course, it is rather soon to judge on this point. Since its introduction in 1892, it has undergone many important changes and improvements, the most recent of which are the use of a closed ash-pit, the manner of introducing the air, and the provision made to introduce a slice- bar to free the bars from clinkers. The ash-pit is entirely closed and with- out any entrance of air, except that which forces back through the bars or leaks in through the ash-pit front ; consequently, there is no necessity for
cut shows the opening at the base of the fuel hopper whereby a slice-bar may be used to clean every portion of the grate. This is especially important with some coals. The projecting shelf below this opening holds any coal that may escape through it. In dotted lines, immediately above the feed roller, is shown a spout-like projection, one adjacent to each side wall, for the purpose of inserting a slice-bar to re- move any clinker that may adhere to the sides, which is however not often the case. These openings are provided with caps or lids, and offer a ready means for examining the condition ot the fire.
From the sectional elevation given, the process of burning will become clear, and it will be seen that the upper
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CASSIER'S MAGAZINE.
two-thirds of the grate partake of the nature of a gas producer, while the lower one-third is a zone of intense and complete combustion. The reason for this action is : ist. The upper por- tion of the bed is so thick and im- perfectly ignited as to prevent the air from readily passing through it in sufficient quantity and of suitable temperature to burn the volatile gases there given off. 2d. Steam is forced through the incandescent bed and part of it is decomposed by the latter. With an insufficient air supply accom- panied by steam, a certain amount of hydrogen and carbonic oxide is formed. At this stage some of the hydrocarbons also escape combustion. On the other hand, the lower third of the bed is composed of loose ash with only a thin layer of incandescent coal on the sur- face, through which an excess of air readily passes.
Any excess of air that may find its way into the furnace at the upper end through the hopper, or at the lower end and under the bridge- wall, will become thoroughly mixed with the gases from the upper portion of the grate and thus bring about their com- plete combustion before passing over the bridge- wall. It will thus be seen that the good results which have been obtained are due to the fact that the producer action of the upper part of the grate serves to counteract any de- fective working at the lower end, such as may be produced by a leakage of air under the bridge-wall or through the burned-out spots in the ash. This view of the producer action will be somewhat modified by a very recent design, in which the ash-pit is closed.
The Coxe automatic stoker is one of the type known as "travelling chain grate stokers." The travelling fire grate was first patented in England in 1834 by Mr. J. J. Bodmer, and differed from that of John Juckes, patented in 1841, in the manner of moving forward and returning the fire bars, the latter being a travelling chain grate, while in the former's modification of his original grate they were carried along on screws. They were mainly introduced
for the prevention of smoke, and tests, made in 1843, showed complete com- bustion without smoke and a gain of 1 1 per cent, in economy.
Slack and other inferior coals were successfully burned. The boilers then, being of small capacity, would make the relative cost of these stokers so high as to exclude their introduction. But as boilers are now constructed, in units of large horse-power, the relative cost is diminished, which, together with the question of smoke prevention, has again brought about the introduction of this type of stoker. A number of these chain grate stokers, introduced by Mr. N. W. Pratt, of the Babcock & Wil- cox Boiler Co., of New York, are in successful operation with bituminous coal, effecting economy and the com- plete prevention of smoke.
The Coxe stoker, while patented about the same time as that of the Babcock & Wilcox Co., was not in- tended for the burning of bituminous coal, but for the smaller sizes of anthracite and culm. The experiments made by the late Eckley B. Coxe to determine the correct principles for burning small anthracite coal economi- cally, proved, among other things, the necessity of having a travelling fire grate on which the coal could be fed, ignited, burned out, and the resulting ash dumped without in anyway disturb- ing the mass of fuel or mixing fresh coal with it ; hence, the application of an old principle to a new purpose.
The construction of the fire grate floor, owing to the absence of caking in anthracite, must be very different from that which may be used for burn- ing bituminous coal. As small anthra- cite ignites with difficulty, or very much slower than bituminous coal, special provision had to be made for increasing the rate of ignition. Provision had also to be made to submit the bed of fuel, in its different stages of reduction, to different air pressures, as the small particles form a compact bed and do not swell up as in the case of soft coal, thus preventing a free passage of the air ; and, further, because with this fine coal the pressure required for it to
BURNING ANTHRACITE CULM.
21
pass through the bed, increases very rapidly with the increase in thickness, so that, unless provided against, all the air would pass up through the bed where it was burned out.
The engraving used for the general description of the travelling grate, is not an exact representation of it as built, but is intended more especially to ex- plain the principle of its action and to show how the conditions above referred to are fulfilled. The coal which is brought to the feed hopper by a drag, spout, or any other convenient method, feeds down by gravity over a fire brick, called the "ignition brick," onto the travelling grate. It is then carried slowly at the rate of from 3}^ to 8 feet per hour towards the other end.
In the beginning of the operation, the coal on the right-hand side of the furnace is ignited, the other part being covered with ashes or partially con- sumed coal. When the coal next to the ignition brick is ignited, the latter remains highly heated, and the coal, passing down under the regulating gate, and over this fire brick, becomes gradually heated, so that by the time it reaches the foot of the ignition brick it is incandescent. In some cases the coal becomes hot enough to ignite soon after it passes the regulating gate.
Under the grate there are a number of chambers, made of sheet iron. The air blast from the fan enters the large air chamber. These air chambers are open on top, but the partitions are covered by plates of such width that, no matter what may be the position of the grate bars, there is always one resting upon this plate, so that the air cannot pass from one chamber to another ex- cept by leakage along the bars. The result of this arrangement is that if blowing into the large air-chamber with a pressure, say, of one-inch water- gauge, the pressure in the next air chamber to the left would be about S/s inch, in the next to that Y% inch, and in the next to that }i inch. The press- ure in the air chamber to the right would be, say, S/q inch, so that the coal when it arrives on the grate is subjected to a pressure of blast sufficient to ignite it,
but not too strong to impede ignition. In order to regulate exactly the press- ure of the air in each of the compart- ments, the partitions are provided with registers, by the opening and closing of which the pressure in the air chambers can be varied to suit the conditions.
As the thoroughly ignited coal passes slowly over the large compartment, where the air pressure is a maximum, it burns briskly, continuing to do so during its slow passage over the suc- cessive compartments, in which the air pressure is less and better suited to the combustion of the thinner layer of partly consumed coal. The bed continues to diminish in carbon, and to be subjected to less blast, until finally the gentle current of air passing through the con- sumed bed is only heated and mingles with the carbonic oxide produced in the zone A and part of B, and converts it into carbonic acid gas. The object is to subject the coal, as soon as it arrives on the grate, to a pressure of blast which is the proper one to ignite it ; then to burn it with a blast as strong as will produce the desired rate of com- bustion, and as the carbon is eliminated and the bed becomes thinner, to diminish the blast to correspond with these conditions. The mass of coal re- mains all the time in practically the same position and condition in which it was placed on the grate, except so far as altered by the combustion.
This automatic stoking furnace has been in continuous operation, the first three, for a period of three years, night and day, and two more since May, 1893, having in all built forty- one which are either running or in process of erection. About a month prior to the death of the inventor, he made another design which would be adapted equally as well for bituminous slack as for anthracite, involving, however, no changes in the principle, but only in the side frames and omitting the water pan under the grate and the water jackets in the side walls which were used in the earlier furnaces constructed, but which have been found unnecessary. Many other substantial improvements have been made in this new design,
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CASSIER'S MAGAZINE.
BURNlJSiG ANTHRACITE CULM.
23
such as the driving mechanism, air pan and grate-bars, which are fully described in a paper read by him last April before the New England Cotton Manufactur- ers Association and entitled ' ' Some Thoughts Upon the Economical Pro- duction of Steam, with Special Refer- ence'to the Use of Cheap Fuel."
the machinery, the coal and ashes being automatically handled. In the old boiler plant five men were required, even when firing pea coal. Owing to the first cost, stokers will not make such a good showing in small plants, nor where boilers of small horse-power are used, and further, where they are
A BOILER PLANT EQUIPPED WITH COXE AUTOMATIC STOKERS.
On page 23 is a reproduction of a pho- tograph of a series ten of these stokers under Stirling water tube boilers, in operation at the Philadelphia & Read- ing Coal & Iron Co.'s plant at Mahanoy Planes, in Pennsylvania. The advan- tage in mechanical stoking lies not only in the ability to burn the cheaper grades of fuel, but also in the saving of labour. In the above plant, for ex- ample, only two men are employed, — a water tender and a man to look after
run only from ten to twelve out of the twenty-four hours.
In the description of the last three grates, the writer has endeavoured to bring out clearly the requirements for the burning of small anthracite coal by a somewhat detailed description of the merits of the various actions of the grate bars and in the handling of the fuel bed. From what has been said in this description, the reader will be able to decide on the development
24
CASSIEX'S MAGAZINE.
A CONVEYOR TAKING OT.M l'RO.M ONE OF THE BANKS TOR RE-WORKING.
of grates and furnaces for the utilisation of the low grade fuels and the diffi- culties to be met with and overcome. The reader, however, still lacks the information to proceed to avail him- self of the abundant supply of cheap fuel. This information he must get from some points which follow.
Some definite figures as to cost of fuel at the mines, delivered in boiler- houses, both in and out of the coal regions, and the relative steaming value of the various grades of available cheap fuel would be very desirable, but these cannot now be given as there are so many factors influencing their value. The Scranton, Pa., Engineers' Club undertook a series of boiler tests with a view to furnish manufacturers looking for cheap power with the cost per boiler horse-power in their city. These tests are being made with different grades of fuel, and include the cost of fuel, cost of firing, getting rid of ashes and cost of water. While they have made a number of tests, they are still engaged
in making others, which, when com- pleted, will enable them to give to manufacturers and the public fairly conclusive figures as to the cost per boiler horse-power in the American anthracite regions.
Attention will be called to some important facts which must necessarily be given without regard to order or classification. Buckwheat coal, sold at the mines for from 55 to 65 cents (2 sh. 2\ d. to 2 sh. *j\ d.) a ton, can be fired by almost anyone, and by means of un- dergrate forced blast the rated capacity of tlie boiler can be obtained, and in good types of boilers the rated capacity can be much exceeded. Rice coal, some- times known as No. 2 buckwheat or bird's eye, sold at the mines at twenty- five cents (1 sh.) a ton, is also a good steam fuel, but requires for its adoption, in order to get the rated capacity, a reconstruction of the furnace, giving larger grate surface and undergrate forced draught, and often necessitates an addition of new boilers to produce
BURNING ANTHRACITE CULM.
25
the required amount of steam. There is no simple and cheap device which can be applied to an existing boiler plant by which rice coal, or smaller, can be made to replace buckwheat coal. Nor has any one yet found a method by which a pound of culm or a pound of barley coal can, by the injection of steam or the introduc- tion of firebrick arches, etc., be made to produce more or as much steam as a pound of buckwheat coal. The econ- omy must be sought alone in the lower cost per ton of fuel. There is a possi- bility of making considerable saving in the fuel bill and in the firing by the introduction of either of the foregoing automatic stokers, but the expense of their introduction is very often beyond that to which the owners of the boiler plant are willing to go.
The adoption of a cheaper grade of fuel always calls for an extra outlay of capital in the boiler plant. The Mc- Clave grate is the cheapest of the efficient grates for the burning of the smaller anthracites, but even this re- quires a larger grate area and skillful firing. The Wilkinson and the Coxe
stokers have the advantage over the McClave grate, that they reduce the number of firemen required to one third, and, in some cases, to twenty- five per cent, of that required in hand firing in these cheaper fuels. But neither of these will show much of a saving unless the total consumption of coal is, say, four tons an hour, and a complete installation of coal and ash conveying machinery is at the same time introduced.
Of course, there are boiler-houses where the tracks are so situated that no machinery is required for delivering the coal, and a convenient location exists for the removal of the ashes by loading them direct into carts. As the firing of smaller fuel requires frequent opening of the doors, it can readily '^be seen that the automatic stokers will retain the same economy at high rates of combustion as at low rates. When forcing a boiler much above the rated capacity with hand firing, the fire-doors in many cases remain open fifty-five per cent, of the time, which lowers the efficiency materially. Not only should the furnace or grate be adapted to the
CONVEYING CULM FOR FILLING MINE CHAMBERS.
26
CASSIER'S MAGAZINE.
burning of low grade fuels, but the boiler setting should also be modified to conform with the requirements.
While the firing of the rice coal may be adopted without any consider- able increase in the boiler plant, the firing of the next size below, barley (No. 3 buckwheat and culm) and such culm as is a mixture of rice, barley and dust, do require a very considerable outlay in furnace as well as boiler capacity, as not more than from one- half to one-third as much of this grade can be burned in the same time and on the same grate surface as in the case of buckwheat. The reason for this, as before mentioned, is the great difficulty which the air experiences in passing through the bed. An inch difference in its thickness requires a considerable increase in the pressure of the air. Chimneys or strong induced draught do very little good with this tine coal, as the leakage over the fire through the boiler front and brickwork will be very large compared to the amount of air drawn up through the fuel.
Culm from old culm banks which contain pea coal and even a little chest- nut mixed with dust, while increasing the rate of combustion by an easier passage of the air through it, will not give as good results as an intermediate size containing less of the larger pieces and of the actual dust (through 1-16 inch mesh). The reason for this is that the larger pieces will not be entirely consumed by the time that the smaller particles are. In the case of the more free-burning coals, it is pos- sible with efficient undergrate blast to get nearly the rated capacity out of the boilers with what might be called a dirty rice coal and containing as much as forty per cent, of ash. It would, however, be poor economy to pay any tr.i importation on such fuel as this, even ;is a gift, or any fuel containing more than twenty-rive per cent, of ash. Where it is desired to utilise culm
banks with larger pieces of coal and bone, it is necessary to crush it to the size of buckwheat and to remove the actual dust, i. e., all through 1-16 inch mesh.
Where manufacturers see fit to gene- rate steam in the anthracite regions, because of the cheap fuel, for power to be used there or transmitted to the manufacturing centres, the boiler plant should not only be located adjacent to a culm bank, but near and along the tracks of some breaker which is likely to have a coal supply for some time to come, as then the smaller sizes of fresh mined coal can be obtained at the same price as that of the culm banks. This would be the case when there was no demand for these sizes.
From what has been said regarding the burning of culm which contains a considerable amount of dust, it is evi- dent that it will not pay to burn culm or barley coal in preference to rice while the existing difference in price is so slight and where it had to be trans- ported to tide or to such a point where the relative cost would differ by only a small percentage, which would be the case when the transportation would raise the cost to two or three dollars per ton (8 to 12 sh.).
The difference in price which now exists between rice and barley coal is not commensurate with the relative value of the two fuels. When we pass from rice to barley coal or culm con- taining a large amount of dust, which impedes the passage of the air through the fuel bed, the value diminishes rapidly with the degree of fineness, although the two coals may have the same percentage of fixed carbon and ash. The difference in value between buckwheat and rice coal is much less and not as great as the difference in price, rice coal being, therefore, the more economical fuel, providing the slight change due to the required difference in great area and boiler capacity could be made.
MILL EQUIPMENT.
By Geo. A. Becks, Assoc. M. Inst. C. E.
T
com- mill-
O be a petent
wrightaman should be familiar with the ordinary methods adopted in designing, con- structing, erecting and repairing all classes of machin- ery, having all the principles involved therein, thoroughly in his mind. He should also be able to calculate with tolerable accuracy the strains to which machinery, shafting and gearing are subjected, quick to observe defects, and have considerable inventive genius to overcome difficulties encountered in the execution of his work. He should furthermore be able to look considerably ahead, so as to make arrangements for the completion of his work without any delays, and should never do work which will have to be undone to admit of something which he has overlooked being carried out. As an instance of what is meant, he might joint up the steam chest cover of a new steam engine, and for- get to set the valves.
The author proposes in the following article to point out some of the duties which a millwright will be called upon to perform, and also to describe some- what in detail the method of executing them. Whenever it is practicable, a mill is designed specially with a view to the class of machinery it is to accom- modate, and the work it has to turn out, "but it frequently happens that an exist- ing building has to be used for an
entirely different class of plant from that for which it was built. A very good method, and that adopted by the author, of setting out on a drawing the machinery of a mill, is to make little tracings, showing each machine in plan to the scale it is proposed to draw the general plan. These little plans can then be adjusted and re-adjusted until the arrangement is as nearly perfect as possible, when the leading points are pricked through to the general draw- ing and the details completed.
Setting Out.
Assuming that a millwright has been ordered to carry out all the mechanical work in connection with a new mill, he will, on his arrival, probably find chaos, no floors complete and everything wrong side up, so to speak. The first thing he should determine is a datum line from which to work, and the author considers that, for the purposes of a millwright, the floor level of the mill on which the machines are to stand is the simplest to work from. This line should be marked out on boards, firmly secured to the walls at intervals, and lines should be drawn across them, representing the thickness of the floor boards, and the depth of the joists.
If the main shaft is to be carried below the floor, — which is by far the best place for it, if the machines will drive from the underside, — a centre line must be laid down by driving stakes in the ground, or by nailing boards to the walls, marking the exact points with a notch, so that a line can be stretched the entire length, parallel with, or at right angles to, any existing wall or shafting. From this centre line the width of the excavations is staked out and the ground removed.
27
28
CASSIER'S MAGAZINE.
While the men are excavating this pit, the belt races to the machines should be marked out, so that they can be cut before the brickwork is commenced. It sometimes happens
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that, owing to bad ground, the excava- tions have to be carried to a greater depth than originally intended. This, however, makes no difference to the centre line of the shaft ; the only thing affected is the height in the pit of the piers which carry it.
When the excavating is finished, a layer of concrete (4:1) about 6 inches thick, should be laid over the entire width of the cutting, and when this is sufficiently set, the bricklayers can commence building the retaining walls and the piers for the shaft. If the depth below ground line, not floor line, exceeds 4 feet, it is better to make the lower portions of the retaining walls thicker, 9 inches doing very well to a depth of 4 feet, and 14 inches afterwards, unless very deep, when the thickness must be increased again.
All the brickwork below ground for the shafting should be set in cement, as this makes a much better job than mortar, although for light countershafts below the floor, mortar may be used in the piers. While the bricklayers are busy with the main shaft pit, the exca- vators can be cutting for the founda- tions of the various machines which are to stand on the ground floor of the mill. The positions of these are set out in the same manner as the shaft
pit, but the centre lines are squared oft the centre line of the main shaft.
Foundations.
The best foundations for machinery consist of brick in cement upon a bed of concrete resting on solid ground, I the top of the brickwork being covered with a stone slab varying in thickness from 6 to 12 inches or more, according to the nature and size of the ma- chine. Bolt holes, for hold- ing-down bolts, which are left through the masonry are usually 3 inches square through the brickwork, and 2 inches in diameter through the stone. Stone slabs should be imbedded brickwork at the lower end of holes, to give a good bearing the washer plates, which,
in the the bolt surface to
together with cotters, form the heads of the holding-down bolts. (See Figs. 1 and 2.)
Concrete foundations are frequently
MILL EQUIPMENT.
29
used on account of their cheapness, and when properly made are really very good, care being taken to ensure that the Portland cement used is sound. Concrete foundations composed of 1 part of Portland cement to 4 parts of gravel will be found to be quite satis- factory. One of the drawbacks to con- crete foundations, however, is the diffi- culty of leaving bolt holes in accurate positions. Iron or wood piping is built in, and the usual hand-hole is left for the bolt head down below, but great care will have to be taken to protect these pipes from displacement. When lewis bolts are used it is a very simple thing to put in a concrete foundation, and build in short pieces of wood which can easily be drawn when the concrete is set ; but if a foundation is complicated, it is almost, if not quite, as cheap to build it of brick, as so much moulding of the concrete would materially increase the cost.
It is a great mistake to build bolts into concrete, for, when the cement has set, there is no moving them, and if they do not come right, it is a very troublesome job. It is also no easy matter to keep bolts true to }i inch while a lot of labourers are shovelling in concrete. Bolt holes should always be left, although occasionally it may be necessary to put in a solid block of con- crete and punch the holes afterwards, but this is a bad plan, as it both wastes time and tends to disintegrate the mass. Furthermore, it should be attempted only in the case of lewis bolts.
Wherever it is practicable, a clear passage should be left round founda- tions to enable a man to get up to the holding- down bolts. It also allows of the flooring being completed right up to the foundations before the machin- ery arrives, which, it may be men- tioned, is no small consideration. (See Fig. 1.) Foundations should remain undisturbed until perfectly set.
Erection of Machinery.
The first and chief machine is the engine, which should be erected with the greatest possible care in every de- tail. When the engine foundation
is set, the bed-plate ot the engine is placed on it, and the holding-down bolts are passed through it, washers and nuts being put on, and the washer plates and cotters attached to the lower ends of them. The bed-plate is then levelled, iron strips or wedges being- inserted between the casting and top of the stone where necessary. The hold- ing-down bolts are then tightened slightly, and the whole of the underside of the bed-plate should be flooded with Portland cement grout, which should be allowed to set perfectly hard before any further work is done to the engine. In the meantime, the main driving shaft, in the pit below the floor, has been got ready and the wall- plates on the shaft piers have been levelled, grouted up and firmly bolted down with through bolts. The plummer blocks
?3S$$£\i ffff 3>|^u^^u#
FIG. 3
are then placed on the wall plates and when both they and the shaft have been thoroughly cleaned, the latter is lifted into position and left until the crank shaft and fly-wheel of the engine are erected. Then the shaft is squared off them and the plummer blocks are bolted down firmly.
As regards pulleys on shafting, the author almost always prefers split ones, as they are so much more convenient, and are quite as cheap as solid cast ones. Wrought-iron split pulleys are also lighter and consequently there is not so much deadweight in the bearings.
In leaving belt races, it is desirable to have plenty of room both underneath the belt, to allow for the sagging, and at its sides, to allow of its being taken off and put on the pulley without jam- ming. Traps should be left in the floor to enable a man to get down to all the
3o
CASSIER'S MAGAZINE.
main bearings, and the shaft piers should not extend the whole width of the shaft pit, but there should be suf- ficient space, about 12 to 15 inches at one side, to permit of a man passing without having to climb over, and also to enable the place to be more easily brushed out and kept clean. These openings should be on the side of the pit remote from the engine on account of the pull of the main driving belt (Fig. 3). One of the first things to do when erecting an engine or machine of con- siderable size, is to rig up a strong beam over it for purposes of lifting. This will be found extremely useful and will save much time. A good baulk of timber, about 12 inches square, will be found sufficient for almost anything, and should extend the whole length of the machine.
Location of Machines.
The location of machines requires much thought, the chief points being: —
1st. To get the machines absorbing most power near the engine.
2d. To ensure that each man working the machines shall have ample light.
3d. To so arrange the machines that the operators shall not be closer to each other than necessary, for if they are within talking distance, the output of work will not be as high as it would otherwise.
4th. To arrange machines so that the material passes from one to another without having to be carried unneces- sary distances.
Of course it is almost impossible to have all these desirable conditions, but, with a little care and thought, many of them can be attained. Another im- portant thing to locate, is the foreman's office, which should be well in sight of all the workmen and should have glass windows so arranged that he can see all over the shop.
Belting and Transmission of Power.
By far the most common system of transmitting power is by the leather or cotton belt, although, where long centres can be arranged between the pulleys,
the author is rather favourably inclined towards rope driving, as a good rope drive runs so very smoothly, and, with care, will last almost as long as leather. The life of ropes is about 7 years, and the best speed for them to travel is be- tween 4000 and 5000 feet per minute. Care should be taken that the pulleys are as large as possible in diameter, no pulley being less than 30 times the di- ameter of the rope, as the continual bending round a small pulley causes much internal friction, which is very detrimental. The size of rope usually adopted is 4^ inches in circumference, which will allow a safe working strain of from 250 to 300 pounds. The cost of ropes, again, is in their favour, as it is only about yi the amount that would be paid for leather.
The best lubricant for ropes is soft soap. The friction of a rope working in a taper groove on a cast-iron pulley is three times greater than that of a rope working on a cast iron pulley with- out a groove. The co-efficient of fric- tion for a rope on a cast-iron pulley without a groove is 0.28, while that of a rope working in a taper groove on a cast-iron pulley is about 0.8 when the groove is not greased. If the groove be greased, the co-efficient of friction is reduced about one- half.
Rope gearing absorbs more power than toothed wheel gearing. The per- centage of the total power developed by the engine expended in overcoming the friction of the engine, shafting and machinery in factories, averages about 25 per cent, when driven by toothed gearing, and 32 per cent, when driven by rope gearing. Of course, there are cases where ropes could not be used at all, as, for instance, where pulleys are close together, or where a fast and loose pulley have to be used.
Leather does not require such a large margin for sagging, which will be very considerable in the case of ropes, if the pulley centres are far apart and the lower rope is the slack one. Leather belting requires a good deal of care to work economically. When a belt be- gins to slip, it is usual to apply powdered rosin, but this is somewhat damaging
MILL EQUIPMENT.
3i
to the leather. A little printer's ink or currier's grease, is much better for it, the result obtained being the same and the belt remaining in better con- dition. Oil, too, is commonly used with rosin, which has the effect of caus- ing the belt to rot and stretch. Belts should be cleaned and re-dressed about every four months, by sponging the dirt from them with warm water and soap, then drying with a cloth, and, while still damp, rubbing in currier's grease. When a belt has been allowed to become saturated with oil and breaks, as it will do when in that condition, it has the appearance of being burnt.
The ultimate strength of leather may be taken at about 3360 pounds per square inch of section, but as the strength of a belt is that of the joint, it is reduced to about 1320 pounds per square inch of section, and, allowing a factor of safety of T/i , we get a working strength of about 440 pounds.
It would perhaps be well to mention, in connection with belting, one or two little things which probably are not well enough known. If a belt is re- quired to do more work than was orig- inally intended, say by an addition to the machinery in the mill, a very good plan is to place another belt over it, not connecting them in any way, and it will be found to do its own share of work. An experiment was made with four 6-inch single belts, running, one on top of the other, over 4-foot pulleys, and collectively they transmitted 80 H. P., the belts travelling at the rate of 1800 ft. per minute. Each of these belts did its own share of work, and while run- ning over its own circumference, each gained a little over 30 ft. per minute upon the one below, so that the outside belt travelled over 90 ft. per minute faster than the inside one.
One of the most important things to ensure good running of belts, is to have absolute accuracy in the positions of the pulleys and shafts, which should be perfectly parallel with each other, for if the shafts be not parallel, then the pul- ley faces will not be so either, and the strap, with its natural tendency to find the highest point, will either rise until
it slips off, or, if forks be used, there will be a continual rubbing against them, with much damage to the belt.
All belt pulleys should be rounded slightly towards the centre of the rim, except pulleys which drive on to fast and loose pulleys. The amount of con- vexity should be about yi inch in 12 inches width, and lor pulleys running at very high speeds and of small diameter the rounding should be double this. It is distinctly a bad practice to make pulleys with enormous convexity, as may be seen on some high speed ma- chinery.
It has been asserted that belts run- ning with the flesh side outwards will drive 30 per cent, more than in the or- dinary way, but the author does not approve of the practice, as the inside of the belt would be considerably crushed,
ofer^
since the natural tendency of the leather to bend is in the other direction. An inexperienced millwright is very apt to pay too little attention to belting. He ought to know thoroughly how to put on, take up, and joint belts, but unless he understands his work he will almost invariably punch the holes for laces in parallel rows across the belt, where- as they should be punched in a dia- mond, or pointed form, as shown in Fig. 4, so that the belt section is not reduced unnecessarily at this, the weak- est, point.
In punching a belt for lacing, it is de-
32
CASSIER'S MAGAZINE.
sirable to use an oval punch, the larger diameter of the punch being parallel with the belt, so as to cut out as little of the effective section as possible. All the lace holes should be properly marked out before commencing to punch them,
FIG. 5.
and in putting on a belt with a lapped joint, the joint should run with the pul- leys and not against them.
Wheel Gearing.
There are several kinds of gearing, the most common being cog wheels parallel with, or at right angles to, each other. This kind of gearing is used when the wheel centres, being short, will not allow of a belt, where no slip between driver and driven is allowable, or where very great power is to be transmitted, as in the case of heavy rolls. The noise of gearing is rather objectionable, but this can be greatly reduced by forming the larger of the wheels with wooden teeth, made of horn beam, crabtree, beech, maple, iron wood, oak or other tough wood, driven into the mortises in the wheel rim and keyed on the other side (Fig. 5). No clearance need be left between the wooden teeth and the iron ones of the other wheel, the wood cogs being trim- med to fit accurately between them. When running at a high speed, mortise teeth are said to be as safe as iron teeth, but at low speed they are weaker.
Gear wheels should be well lubricated with wheel grease, which can be made with soft soap and plumbago, to reduce the friction of the teeth against each other and to reduce, also, the noise. The maximum working speed of toothed wheels, at the pitch line, in feet per
minute, consistent with freedom from excessive wear and tear is,
For cast-iron wheels with straight teeth r , £00
cast steel " " 2,100
mortise wheels with wooden teeth 2,000
cast-iron wheels with double helical teeth.. 2, 00 cast steel " " " " " .. 2,400 worm wheels of iron or steel 270
It might here be observed, in passing, that the head of key securing a bevel wheel to a shaft should be on the back of the wheel, so that the thrust of the fellow wheel forces it more securely on to the key (Fig. 6). The author cannot urge too strongly the necessity of keep- ing shafts parallel, or at the correct angle for toothed gearing, or else the teeth will get all the pressure on one corner, will work badly, and finally will break off, when repairs will become necessary with attendant delays. Teeth repairs are usually effected as shown in Fig. 7 on the opposite page.
The load which a tooth of a wheel will bear may be arrived at by considering the tooth as a cantilever, its length being that from root to point ; its depth, the thickness at the root, and its width, that of the wheel. A cantilever of good cast iron, 1 inch square and 1 inch long,
t
will sustain a dead load of 6000 pounds before rupture, but it is safer to estimate the strength of the tooth on the suppo- sition that the load is concentrated at one corner. Properly formed teeth, however, as now produced, if accurately geared, may be assumed to work throughout their entire width, and, further, it may be assumed that two teeth are in contact at the same time,
MILL EQUIPMENT.
33
thus reducingrthe strain by one-half on each tooth.
The ordinary method of increasing the strength of teeth of wheels is to carry a flange up to the pitch line of the teeth on both sides of the wheel. This is called shrouding, and increases the strength of the wheel from 40 per cent, to 50 per cent. This is shown in Fig. 8.
Bearings.
In passing on to bearings, it is of the utmost importance that the surface should be ample for the load it has to bear, and that there be not too great a distance between bearing centres. As regards bearing surface, the common rule is to make the length equal to two diameters, up to 3^ inches in diameter. When the diameter is greater than 3^ inches, this proportion is not main-
|
m |
FIG. 7.
tained, but is reduced. Of course, these sizes refer only to bearings of or- dinary line shafting and not to special bearings, such as those of engines or high speed journals. When designing main bearings, the author allows a press- ure of from 400 to 600 pounds per square inch, measured by multiplying the diameter by the length, which, he has found, gives good results. It is somewhat lower than some engineers allow; but in actual work no trouble will be had, and bearings will be found to work without heating and with gen- eral economy.
When laying out the shafting arrange- ments of a mill, for shafting up to 3^ inches in diameter, the author uses the following rule for centre distances be- tween bearings : — Multiply the diameter of the shaft in inches by 3, and call the result, feet. It is a simple rule, and unless the work to be taken off is un- usually heavy, it is a good one to work
1
to ; but when the diameter of the shaft is 4 inches or more, the distance be- tween the bearings is not so great. Where the main driving belts are taken off, it is usual to place a bearing close in on each side of the pulley, taking care to leave sufficient room between them for putting on the belt.
The lubrication of bear- ings is a subject which ought not to be omitted in a paper of this kind, but as there is matter enough in this for a long paper, the author can only briefly mention a few points, gleaned from practical expe- rience. In starting a new mill, it is usual to hear of hot bearings at different points, notwithstanding the care taken during erection, and in such cases a little castor oil and white lead, mixed into a thick cream, will be found to be a very efficient lubricant, the castor oil having sufficient viscosity at a somewhat high temperature to remain in the bear- ing, and the white lead forming a good body between the two rubbing surfaces.
It is important to use oil having a high flashing point in mills where in- flammable material is being worked, as the heat generated by a bad bearing is occasionally sufficient to set fire to the oil. The best lubricant for general work is that which has a high specific gravity and good viscosity at high tem- peratures, but this, again, greatly de- pends upon the class of machinery which is at work. For instance, light- running machinery is well cared for by sperm oil ; heavy machinery, by rape oil ; while olive oil does for almost any kind of machinery, excepting steam cylinders and slides, in which places it has not sufficient body owing to the heat, whereas neatsfoot oil and tallow or heavy mineral oil answer very well. There are now on the market some lubricating greases, of which the chiet function is to melt freely by the heat generated by friction, and so supply more lubricant ; but, although they may be good in certain places, the author does not like them for general use, as they depend for their action
34
CASSIER'S MAGAZINE.
upon the very thing that they are in- tended to reduce, namely, frictional heat.
When erecting a line of shafting either underground or overhead, the first thing to do is to fix either a plum- mer block, wall plate or bracket, as the case may be, and level up to the next one from it, and so travel the entire length ; but to ensure the bearings being in line the author, prefers a thin steel wire, stretched the entire length as tightly as possible. To this line the bearings can be set with great nicety, so that, when the shaft is lifted into position, there will be no adjusting necessary. A piece of hard wood should also be inserted between the foot of the plummer blocks and the
a
FIG. 9.
wall brackets or plates, in order that a more even bearing may be obtained and to enable the bolts to take a firmer hold.
If the accuracy of a line of shafting be at any time doubted, the coupling bolts should be drawn, when, if the shaft be not truly in line, a wedge- shaped opening will appear between the faces, as shown in Fig. 9.
Lifting Heavy Weights.
The subject of lifting is of such a varied character that the author cannot do more than explain broadly the prin- ciples of lifting and moving heavy weights from a practical point of view. The best appliance, undoubtedly, is an overhead crane, but as this is a luxury seldom, if ever, to be found in a new mill, all lifting has to be done by tem- porary tackle.
Assuming that a truck has just ar- rived with a heavy machine, the ques- tion arises, how to get it out? If several machines were coming, the best
arrangement would be to rig up a lifting tackle, under which the trucks can be run. This tackle may be of any description, the most common being shear legs. If a single lift is all that is required, then a derrick may be up- ended and guyed, care being taken to incline it as little as possible. A com- mon method of strengthening a derrick is to lash 3 or 4 poles together, which will be found to answer the purpose almost as well as one large one. Another way of getting a heavy weight from a truck, is to erect a few planks at the same height as the truck bottom, and roll the weight on to them. Then the truck can be moved off, and the weight lowered gradually, one end at a time, by jacks or pinch bars.
The author well remembers an inci- dent which occurred while erecting machinery in Liverpool. A case, con- taining a machine weighing some tons, was being brought along in a low truck over soft ground, when suddenly the wheels of the truck sunk to their hubs and the bottom rested on the earth. The case could not be moved by hand, no lifting tackle was available, and, owing to its being confined on three sides by the truck, only one roller could be got under it at the front end. Two jacks were obtained and got to work in the back of the truck, and a strong horse was harnessed to the case. All the available force was thus brought to bear on the case, which rolled out of the truck on to timbers placed to receive it. The rest of the journey, fortunately not very far, was performed on rollers.
When it is required to lift a weight and place it in another spot, no travel- ling crane being at hand, a block and tackle should be erected over the weight, and another over the new spot; the first tackle then lifts while the sec- ond pulls over ; the first then pays out, and second lowers into new position (Fig. 10).
Great care should be taken of lifting- slings, so that they be not damaged, a sack being placed over any sharp edge against which the sling binds. The author prefers rope slings to chain ones for general work, as they are more
MILL EQUIPMENT.
35
likely to give warning in case of break- age than chain. A sudden sag in a chain carrying a weight frequently snaps it, while a rope would give. As a rule, new white ropes are stronger
V/////////////////,///////////////
^///S/Ss s/s/ss
NEW POSITION
OLD POSITION
Chimneys and Boilers.
When designing a mill, care should be taken to have boilers and engines in a convenient and accessible place, so that coal and stores may be brought in without much trouble. It should, likewise, not be forgotten to leave space enough for drawing the boilers when new ones are required. It is usual to rest boilers on fire brick set in fire clay, but the author prefers cast- iron standards, when they can be used, to take the weight of the boiler.
The outside diameter at the base of a brick chimney should not be less than one- tenth the height, and the thickness of material in the sides of the chimney should be 9 inches for the top 20 feet,
and more pliable than tarred ones. The and 14, 18, 24, 27 and 31^ inches, re- tarred rope, however, retains its orig- spectively, for the lower 20-foot lengths.
inal strength for a longer period, espe- The batter should be 2 S/q to 3 inches
cially when exposed to wet. The
ultimate strength of ropes is usually
considered to be about 6400 pounds
per square inch of sectional area.
There is a great loss of strength from
exposure, wear and tear, during a few
months of working, the loss varying
from 20 per cent, to 50 per cent.;
therefore, a large margin should always
be left for safety, about 1-5 the ulti- mate strength being the usual load. A
still further allowance should be made
in the case of a sling passing over a
crane hook, which causes a sharp bend,
the strength of a double sling in this
case being only about 1^ times that
of the single ; but if the rope passes
over pulleys, its full strength would
be retained.
Staging.
It frequently happens that a mill- mm*>^>'^^mv^<M
wright has to direct his men to put up a staging to enable him to erect plant at a considerable height above ground, but as the form which this will assume will be entirely governed by local cir- cumstances, it is impossible to give any detailed explanation concerning it. The best men to do this work, however, are sailors, if they can be obtained, and if the work be of sufficient importance, to have men for this job. Fig 1 1 shows the most common methods in use.
-^^^hw
in 10 feet. The top cap is preferably of cast iron, although stone is fre- quently used, and the firebrick lining, one or one and a half bricks thick, should be carried up at least 20 feet, with an air space 4^ inches wide be- tween it and the outer brickwork. The bottom of the chimney should be closed
36
CASSJER'S MAGAZINE.
by an invert, not less than 14 inches in thickness, depending on height and weight.
Long horizontal flues should be avoided as much as possible, as they tend to lessen the draught, and their area should be greater than that of the chimney. The use of internal scaffold- ing when erecting brick chimneys will be found very convenient, if the size of chimney will permit of it, as it is much cheaper than external, and is much safer for the men. A small winch can be used for hoisting materials up the cen- tre, and the permanent iron ladder, which should always be on the inside of every chimney, can be used during its erection.
An iron chimney can be very easily erected by means of a tall and strong derrick, which will lift it about the centre of its length. Ropes and tackle can be secured to the lower end of the
chimney to pull it into position ; but be sure everything is sound and strong before attempting to do a job of this kind, and also see that the chimney cannot slip through its sling. Lastly, do not forget to put on the chimney guy ropes before you commence lifting. There are many things left unsaid and many things which can be learned only by experience. Almost every item, briefly touched upon in the foregoing paper, could be enlarged to occupy several pages. There is always a sense of satisfaction in having executed work with only the very crudest of tackle, such as is to be found in new countries. Residence for some years abroad has taught the author how to dispense with many of the appliances which are con- sidered absolutely necessary at home, and he has more than once been con- vinced of the truth of the old saying, 11 Where there's a will there's a way."
CHEAP GAS POWER.
B. H. Thwaite^C. E.
T
HE law of the survival of the fittest, under the influence of the fierce struggles associated with modern industrial warfare, is forcing the governing heads of the great manufacturing concerns to search for the cheapest and best means of generating the motive power essen- tial to the running of machinery. The corn millers of the last and the preceding centuries located their mills alongside a stream or on the summit of a hill, so that the water-fall in one instance and the winds in the other, supplied the power required and under the most favourable economic conditions in pro- portion to the limited output of these picturesque factories.
The metamorphosis in our industrial methods, involving an increase of out- put measured in thousand folds, called for the displacement of the water- wheel and wind-mill by apparatus that enabled the conversion of the heat stored up in fuel, into dynamic energy or motive power, and the choice of the location of a great manufactory was more or less influenced by proximity to a navigable waterway or railway by which the fuel could be easily and economically obtained.
Immense manufactories, surrounded by well populated townships, whose inhabitants depend upon the staple industries carried on, have resulted from the application of fuel as a means of obtaining unlimited power produc- tion, and yet industrial concerns will, in the near future, have to be carried on more or less in the face of competi-
tion with modern types of water- propelled or turbine machinery, from which dynamic energy may be elec- trically transmitted under ideal arrange- ments for acquiring the highest efficiency. The initiation of this new water and electric power in Switzer- land, France, Germany and at Niagara, in the United States, represents another phase in industrial history, the immense influence of which it is impossible to forecast.
In one direction, its influence will be welcomed by thermo-dynamists. This harnessing of the power of gravity of falling water by that masterpiece of practical mathematics, the turbine, will compel the users of fuel-driven ma- chinery to adopt thermo- dynamic means of power production that will leave the least margin in favour of waterfall power. That the margin is intrinsically of serious proportions will be evident to the most casual observer who examines the following side- by-side comparison of the labour and essentials required for the production of power, by the two sytems.
Water Fall Power.
Fuel Power.
Water Fall, Water Con- Coal Mine or Pit.
duits. Coal Cutting and Hoist-
Turbine Tunnel or Shaft. ing Machinery.
Turbine. Railway and Cartage.
Electrical Conversion and Coal Depots.
Energy Transmission SteamBoiler and Chimney. Plant. Steam Engine and Con-
denser. Gearing and Shafting Power Transmission Arrangements.
There is quite as great a disparity in the labour requirements of the two systems, and the charges of main- tenance, plus the charges for boiler insurance, associated with steam plant, have no equivalent counterpart in the turbine practice. That the competition of this scientific utilisation of the force of falling water will accelerate the prog-
37
38
CASSIER'S MAGAZINE.
AN ECONOMIC POWER GAS ENGINE AND ELECTRIC PLANT, DRIVEN BY CHEAP GAS.
ress of the displacement ot the steam power system for land use, is certain. A system of power production that involves so many sources of waste, as does a steam power plant, cannot long survive in the race for supremacy with the turbine as a rival. The steam power invention, although a glorious victory for science and a great honour to Watt and his illustrious contem- poraries, Papin and others, cannot be considered, except in its application for marine purposes, to be worthy of our existing knowledge of practical thermodynamics.
""Thanks to the genius of Otto, of Lenoir, and of their co-workers, we have another instrument by which the power potential of our fuel can be recovered for thermo-dynamic use and with incomparably greater efficiency than is obtained from steam engines of even the highest excellence of design and workmanship. The theoretic effi- ciency of the latter is only about equal
to the practical efficiency of the gas engine.
Let us broadly compare the different phases of the two systems of converting the heat potential of fuel into motive power or dynamic energy. The gas engine in this comparison is assumed to be driven with generator gas, for which one-fourth of the heat value is taken as being absorbed in the work of fuel gasi- fication. Let x represent the combus- tible value of the fuel.
Steam Plant Type.
x Burnt in steam boiler.
fax I.ost in radiation and chimney gases.
Y^x Carried forward to steam engine and of this y,x, one-tenth may be taken to represent the proportion of the heat value converted into dynamic energy or motive power. There- fore, the efficiency of the steam engine equals
Equivalent to 6.6 per cent, efficiency.
Gas Power Type.
Y^x Absorbed gasification.
Y±x Is carried and sup- plied to engine, of which by direct con- version 1-5 may be taken to represent the degree of thermo-dynamic con- version. Therefore, the efficiency of the gas engine may be taken to
equal <&L\
Equivalent to 15 per cent, efficiency.
CHEAP GAS POWER.
39
The heat loss (represented by %x) involved in thermo-chemical work of gasification will be very much reduced in large installations. In these, part of the heat carried from the gas generator in a sensible form, will be recovered for gasification work, and part of the heat of the cylinder jacket water will also be utilised for the same purpose, so that the superior efficiency of the gas engine will be further augmented.
In the gas engine three-fourths of the combustible value of the fuel is secured
|
% |
LENOIR J OTTO LANGEN |
OTTO CHARON |
OTTO BRITISH |
% |
|
|
100 90 |
100 90 |
||||
|
80 |
80 |
||||
|
TO |
70 |
||||
|
GO |
60 |
||||
|
:„;. |
50 |
||||
|
10 |
' |
10 |
|||
|
30 |
. |
||||
|
20 |
MAXIM |
UM THEORETIC E |
FlClENCY STEAM |
ENGINE engi_ne" |
20 |
|
"TO" |
ACTUAL |
EFFICIENCY HIGH |
CLASS-STEAM E |
IGINE |
~ rr |
|
ACTUAL |
EFFICIENCY |
||||
|
I860 |
1864 |
1890 |
1892 |
DIAGRAM OF GAS ENGINE EFFICIENCIES.
in the cylinder for direct conversion into power under the most perfect con- ditions of combustion.
In the steam plant, this fuel is burnt, under the worst possible conditions, in the furnaces of a steam boiler, and from the author's own experience, he avers that this fuel, burnt in steam boilers of the best design, never gives out more than 9-13 of its actual evaporative value. Certain data giving evaporative results have been published by well known engineering professors, giving much higher evaporative values than this 9-13 factor, but the author refuses to accept these higher results as close reflections of the actual work of
evaporation, accomplished in day-by- day, useful work.
A test of a steam power plant should be of at least 8 hours' duration ; one .of a shorter period is worse than useless, as it is likely to give results that are misleading. The author ventures to throw out a suggestion to the effect that every government having any pre- tensions to industrial greatness should institute a committee of experts to carry out official tests of new improvements and inventions relating to engineering, and an international congress of experts should arrange a standard by which all the tests should be regulated. The ordinary power user would soon learn to insist upon tests by this officially appointed committee, whose members should be precluded from testing or reporting unofficially. This is a digres- sion, prompted by a knowledge of the misleading character of many of the reports of evaporation tests.
The factor 9-13, noted above, is sometimes seriously reduced by steam pipe condensation. Few, perhaps, realise the extent of the loss in long lengths of steam pipes, especially if exposed to open air influences. This fact gives electrical transmission methods an unapproachable advantage. In the burning of hydro-carbonaceous fuel in furnaces of steam boilers, the greater part of the hydro- carbons, owing to the high volatility and the irrational combustion arrangements, escape un- burnt, and as certain coals contain a considerable proportion of these hydro- carbons, the loss is occasionally very material.
In a power gas plant, on the other hand, most of the combustible con- stituents of the hydro- carbon series are utilised, either in the form of heat assets, convertible into power, or in the form of pitch or tar, both of which are saleable residuals. For large power installations, and it may at once be said that these will be necessary to place fuel power users on the same plane of advantage with those employ- ing water power, the power gas plant offers still further economical advan- tages, permitting the recovery of the
4o
CASSIER'S MAGAZINE.
A POWER GAS GENERATING PLANT.
nitrogenous constituents as well as the pitch and tar already mentioned.
It may be argued that these advan- tages could be obtained by converting the fuel into combustible gas and burn- ing this gas in steam boilers. This will be conceded, but the author's own experience has satisfied him that the combustion of gas is not by any means effected under the best conditions in a
boiler furnace, and that no man in his senses, having gone so far as to put down a gas plant, would do other than burn this gas directly inside the cylinder of a thermo-dynamic motor or gas engine itself.
In a large power gas installation, the putting down of a sulphate of ammonia (nitrogenous recovery) and pitch and tar plant, using an average hydro
CHEAP GAS POWER.
4i
carbonaceous fuel, would enable the following results to be obtained. An experience of such a recovery in Eng- land has shown an average production of about 17 or 18 pounds of sulphate of ammonia per ton of fuel burnt, the marketable value of which in England varies between £\o and £>\ox/i per ton. Ammonia sulphate is a most valuable fertiliser, and the return of this nitro- genous agent to the earth fulfills, in a natural order, the cycle of the con- servation of energy.
Besides the fertiliser, an amount of pitch, equal to 0.062 tons, is obtained from each ton of coal charged into the gas generator. This pitch is worth from 20/- to 25/- per ton. In addi- tion, from 5^ to 6 gallons of oil are recovered per ton of coal used, and this realises from i^d. to i%&. a gallon. The net profit, after deducting all charges, will vary between 2/6 to 3/- a ton, depending upon the market value of the three residuals.
For large power installations, the cost in coal consumption with a gas power plant should not exceed i}{ lb. per kilowatt- hour, and if we take the cost of coal fuel to be 12 /-a ton, the monetary cost of the fuel per kilowatt- hour, after deducting the profit value of the residuals, will be 0.0602 pence.
Compared with the monetary value of fuel equal to 0.144 pence per kilo- watt-hour, representing the best work of a triple-expansion steam engine, the steam power plant is conspicuously more costly. It may be, therefore, well claimed that the cheapest coal fuel power plant is one that includes a gas plant, a nitrogenous recovery installa- tion and a suitable Otto- cycle gas engine. If the power plant were in- stalled on the coal field, it is quite pos- sible that the value of the recovered agents would be equal to half the cost of the fuel.
The entire absence, in gas power in- stallations, of high-pressure retaining vessels, removes the possibility of ex- plosive dangers, and the associated in- surance costs are therefore unnecessary. The absence of any considerable de- mand for water, and the comparative
independence of its quality of purity and hardness, are advantages that will be appreciated by power users. Then the absence of that curse of steam plant engineering system, the smoky chim- ney, is something for which to be thankful.
The economic quality possessed in such a high degree by the gas-power system is amplified by the advantages of convenience, and the absence of the explosive associates of steam boilers will remove one of the sources of worry that accompanies the daily cares of steam-power users. Therefore, in com- parison with water power which we will place in the first position, and where solid coal is the only fuel available, the gas-power system takes precedence of the steam plant, and this decision is amply confirmed when the respective merits are measured by the equation of efficiency which we owe to that illus- trious engineer, Sadi Carnot.
If, in the natural gas districts, the gas were available at a price that would com- pare with generator gas on a heat valu- ation basis — then a natural gas-power plant would, obviously, be superior to a generator gas plant, although for such an installation it would be advisable to have an auxiliary generator plant as a stand-by.
There is very little probability that oil engines will ever be able to seriously compete with large gas-power plants. The limited proprietorship and insig- nificance of the weight output of the oil fields are facts too potent to prevent large competition against coal generator plants.
For municipal purposes, use may be made of the organic and other com- bustible refuse of towns for generating power, but to a very contracted extent. The heating value of this refuse fuel has been very much over-valued. When it is known that the vegetable organic matter that enters so largely into the constitution of town refuse, contains from 50 to 80 per cent, of moisture, it requires no lengthy explanation to show that before any heat energy is available for useful external evapora- tion work, a considerable proportion of,
42
CASSIER'S MAGAZINE.
if not all, the heat available in the burn- ing of the solid portion of the organic matter is absorbed in the internal work of evaporating this moisture. It is diffi- cult to estimate the calorific or heating value of this refuse fuel, as every town will have its own characteristic kind of refuse. The author, some years ago, prepared a guiding equation which makes out that with good average re- fuse, an evaporative value not exceed- ing one-fifth of that of ordinary common coal might be taken.
The low heating value necessarily in- volves a large expenditure in steam generation plant, to obtain equivalent power output. But even allowing for this fact, involving high prime cost of
steam boiler plant, it is conceivable under certain circumstances that for limited municipal purposes, this refuse fuel may be economically employed ; but it can never, except to a very in- significant extent, come into commer- cial competition with the use of coal.
A central, coal field gas-power instal- lation on the lines outlined in the fore- going pages will permit dynamic energy to be produced for transmission by high-pressure, alternating electric cur- rents, to distances up to ioo miles, at a cost, if we assume the employment of approved electrical methods of driving manufactories, that would bring this en- ergy well within the limit prescribed by the expression, cheap power.
ELECTRIC VS. STEAM HEATING.
By A. F. Nagle.
WHILE electrical appliances of every kind are vigorously pushed upon the market, none are looked upon by the public with more favour than those designed for electric heating. They are sim- ple and neat in construction ; perfectly free from dust, smoke or ashes ; and are easily managed, requiring no skill or special training or fitness for the work; in fact, a child can manage them. Altogether the electric system is an ideal one of heating, except for one thing, — its cost. There may be circum- stances where cost cuts no figure, or where some of the advantages above enumerated outweigh it, but in either case, it may be well to know what the cost of electrical heating really is as compared with steam heating, and this inquiry is instituted for that purpose.
Steam is generated at greatly varying cost. Steam plants themselves vary in first cost, and the subsequent cost of evaporating water is considerably affec- ted thereby. But more than the plants themselves vary the costs of fuels. Coal
as low as $i a ton, and as high as $5 (from 4 to 20 sh. ) is used for making steam, and it is a singular fact that the price of coal is rarely based upon its evaporating, or steam-making, qualities. The cheapest coal will evaporate, in good furnaces, more than one-half as much water as the very best coal cost- ing five and six times as much ; and a good, yet cheap, coal will evaporate 75 per cent, as much water as a somewhat better coal costing two or three times as much. This is owing to the difficulty of burning the very cheap coal free from excessive smoke. There is no doubt that as soon as it becomes known how to burn cheap coal, dust and screenings quite successfully — and it can be done— the price will approximate to its evapo- rative power.
From this statement of the cost and qualities of different coals, it is evident that in making an estimate of the com- parative costs of steam and electric heating, some fixed basis must be taken. The price of coal can be left out of this calculation entirely, but a
ELECTRIC vs. STEAM HEATING.
43
definite evaporative quality can be assumed, and subsequent corrections can be made when applied to any par- ticular case. We will therefore assume that steam is being generated at the rate of 10 lbs. of water per pound of coal. It is understood by professional engineers that this means from and at 212 degrees, — that is, 9657 British thermal units are being obtained from each pound of coal burned. These 9657 heat units represent the latent heat of steam, or the amount of heat necessary to change water into steam, — a liquid into a vapour.
A steam-heating system can be con- structed where nearly every unit of heat as above assumed can be utilised. Its efficiency in that case would be 100 per cent. This is found in direct return heating systems. In a large building, where the main supply pipes are very long, but well covered with a good non-conducting material, the waste heat should not exceed 10 per cent., and there an efficiency of 90 per cent, can be realised. Sometimes it is not pos- sible to save the condensed steam. In that case the entire waste might amount to 25 per cent., or an efficiency of only 75 per cent, might be obtained ; but this would be decidedly the worst case of steam heating.
Now let us look at the process fol- lowed in electric heating. Practically, we begin with the same steam that is used in steam heating, except that it is of a higher pressure. This steam passes through a steam engine, and a small part of its heat is converted (transmuted, is perhaps a better word) into mechanical motion, and the larger part is wasted either into the atmos- phere or into a condenser. This larger waste is unavoidable, because it is the heat necessary to maintain itself as a vapour in passing from a liquid to a gaseous state. The amount of this waste may be reduced by skillful designs, but it can never be entirely avoided. Just what this waste amounts to under certain conditions will be in- vestigated later.
The mechanical motion of the engine gives motion to an electric generator,
thus producing electricity, and the latter is carried by conductors to the place where heat is to be used, being there converted into heat by means of electric heaters. These perform precisely the same function as steam radiators. It makes no difference how the heat is ob- tained, whether from steam, hot water, hot air, electricity, or fire, — to produce equally good results, the same quantity of heat, or number of British thermal units, must be supplied in each case.
The electric heater is nothing more than a resistance box, — a device which wastes electric power by converting it into heat, just as one might waste his own muscular power by rubbing his hands together and thereby convert muscular power into heat. The resist- ance, or friction, which the electric cur- rent meets in passing through this re- sistance box, converts its power into heat. This process is a very perfect one, in fact, absolutely perfect, because all of the power is converted into heat, hence its efficiency is 100 per cent. To bring the electricity from a central station to the house, or railroad train, to be heated will entail a loss, depending upon the length and size of wire used, but 5 per cent, loss is a fair one to be taken, so that, the efficiency of the line being 95 per cent., the combined efficiency of line and heater remains 95 per cent.
The electric generator is a machine which converts the mechanical power of the engine into electricity. In skillfully designed generators this transformation is effected very efficiently. As high as 97 per cent, is at times obtained, but 92 per cent, is a very common result under good conditions, while it runs down to 80 per cent, and less, under less favourable conditions. Perhaps 90 per cent, efficiency would be a fair average under good conditions, making the combined efficiency of heater, line and generator equal to 85.5 per cent.
The steam which gives motion to an engine, and indirectly to a generator, has also to overcome the mechanical friction of the engine. This friction is about 10 per cent., so that only 90 per cent, is available for driving the electric
44
CASSIER'S MAGAZINE.
generator. When we say then that the engine has a mechanical efficiency of 90 per cent. , the entire efficiency of the mechanism, from the engine to the heater, is only 77 per cent.
We will now investigate the efficiency of the steam supplied to the engine as a motive power. Correctly speaking, electricity is not a motive power; it is not a prime, or first, mover. It only conveys power given to it from some other source. Electricity, once gene- rated, does its future work very eco- nomically— far more economically than steam ; but the difficulty is to generate it economically. Thus far, no way has been found to generate it more economically than is now done by mechanical power.
In the case of steam engines used for electric station work we need consider only those of a fairly economical type. It is customary to speak of steam engine economy by the number of pounds of feed water (steam) they consume per indicated horse-power (I. H. P.) per hour. The very best steam engines consume about 12 lbs. of water per I. H. P. per hour, and from this they range up to 20 lbs. and 24 lbs. There another type steps in which consumes from 25 lbs. to 35 lbs. and 40 lbs. But for the purposes of this inquiry we will take a good, modern, compound condensing engine, consuming say 18 lbs. of feed water per I. H. P. per hour. What is the efficiency of such an engine ?
By efficiency in this connection is meant the ratio of the heat contained in the steam, which goes to make the power of the steam engine, to the total heat it contained before it went to the engine. We must put figures to these expressions. A pound of water, of say 100 degrees temperature, turned into steam of 125 lbs. pressure, contains 1,090 units of heat (B. T. U.). We have assumed that 18 lbs. of water would be consumed in producing one horse-power in the engine. Then 19,620 B. T. U. would be required to develop one mechanical horse-power for an hour. It is commonly known that a horse-power is the expression for
the mechanical work of 33,000 foot- pounds per minute, or 1,980,000 foot- pounds per hour.
Science has taught us that mechani- cal work and heat are convertible, one into the other, in the proportion of 772 foot-pounds of work to 1 unit of heat (B. T. U.). This figure is found by a simple experiment. If a paddle wheel be submerged in a vessel of water well protected against being heated or cooled by outside influences, and ro- tated, the agitation, or friction, of the water will warm it. Just as rubbing two solid bodies together will cause them to heat, so will fluids be heated by agitation, or friction, of their parti- cles. If a crank, turning this paddle wheel, have applied to it 1 lb. pressure, and describe say one foot in one revo- lution, then when it has made 772 revolutions it will be found that it has heated the water one degree on the Fahrenheit thermometer, providing there were just one pound of water in the vessel. If there were 10 lbs. then the rise in temperature would be one- tenth of a degree, and so on. This experiment has been made many times with great care, and it is finally settled among scientific men that 772 foot- pounds of work are the exact equiva- lent of one unit of heat. A mechanical horse- power per hour, — 1,980,000 foot- pounds,— is therefore equivalent to 2565 B. T. U. We have seen that the 18 lbs. of steam, furnished to the engine, contained 19,620 B. T. U. for each horse-power developed ; hence the efficiency of this engine is expressed by the ratio of 2565 to 19,620, which is 13 per cent.
Finally, to obtain the efficiency of the entire electric heating system, we must multiply the electrical and mechanical efficiencies already obtained, namely, 77 per cent., by the steam efficiency just found (13 per cent.) and we have an ultimate efficiency of only 10 per cent. The foregoing calculations have been based upon steam consumption. Let us carry it a little further and see what the efficiency would be if based upon coal consumption.
In the case of steam heating, we
ELECTRIC vs. STEAM HEATING.
45
assumed an evaporation of 10 lbs. of water, from and at 212 degrees, per pound of coal. Each pound of this steam contains and gives up 966 units of heat. In the case of the steam furnished to the engine at 125 lbs. pressure, we found that each pound of steam contained 1090 units of heat, so that for each pound of steam used in the engine 13 per cent, more heat had to be supplied by the coal than in case the steam were used directly for steam heating. That is, instead of getting an efficiency of 10 per cent., if based upon equal weights of steam used, regardless of the amount of heat contained in the steam, and if correction be made, as properly it should be, for the difference in the amounts of heat contained in the steam used in the two cases, an efficiency of only 8.85 per cent, would finally be realised, or, fully above eleven times as much coal would be necessary to heat by electricity than by a simple system of direct steam heating.
We have now a constant, expressing the economic ratio between electric and steam heating. We have given the data upon which this constant is founded. Should other data be as- sumed, or known to exist in any prac- tical case, a new value could readily be found by simple substitution of other data. If, for example, the engine re- quired 24 lbs. of steam per I. H. P. per hour instead of 18 lbs., then the efficiency would be only 6.63 per cent., or, 15 times as much coal would be re- quired for electric heating as for steam heating.
If, on the other hand, steam heating were obtained with an evaporation of only 7 lbs. of water, instead of 10 lbs. and the engine still required only 18 lbs. of feed water per I. H. P. per hour then the ratio of electric to steam economy would be increased from 8.5 per cent, to 12.64 Per cent 5 or> eight times as much coal would still be required for electric heating as for steam heating. We may take this last case as representing, fairly, the relative economy of steam in a large plant, and a small house heating system, but with this difference that the cost of coal used in house heating would be about $5 (20 sh.) per ton, while the coal for the elec- tric plant would cost only about $1.25 (5 sh.) per ton, making the relative cost in money for fuel consumption only 2 to 1, instead of 8 to 1, as previously found in weight of coal used. That is to say, taking a first-class, modern, elec- tric generating plant, using cheap coal, and an ordinary house steam-heating system using hard, or anthracite coal, and leaving out of consideration the value of the investments, cost of operat- ing and other necessary expenses, but considering only the cost of coal in the two cases, electric heating will still cost twice as much as steam heating. Summing up briefly, we have the fol- lowing : —
RELATIVE COST OF ELECTRIC AND STEAM HEATING.
Electric. Steam.
For equal weights of feed water. _ .
For equal weights of coal
For equal cost of coal under extreme and most favourable conditions...
to
GASEOUS FUELS.
By H. L. Gantt, A. £., M. E.
HE fact that carbon forms with oxygen two 'gaseous compounds, — one by its incomplete, and one by its complete combustion, — is the foun- dation on which is based the manufacture of all producer gas. The first of these gases is known as carbonic oxide (CO), and in its formation thirty per cent, of the heating power of the carbon is de- veloped, leaving seventy per cent, to be developed on its further combustion to carbonic acid (C 02).
The carbonic oxide is, of course, very hot, and if burned at once to carbonic acid and the heat utilised, there would be no waste ; but if the gas should be conveyed any distance the sensible heat, amounting to thirty per cent, of the whole, would be lost by radiation. If it is desirable to utilise the gas at a dis- tance from the point at which it is gen- erated, it should have, on leaving the producer, as low a temperature as pos- sible, the loss from radiation being thus lessened.
The fact that incandescent carbon decomposes water, taking to itself the oxygen to form carbonic oxide, and setting free the hydrogen, and in this operation absorbs a large quantity of heat, now comes to our aid. If the carbon be burned with a mixture of oxygen and steam, we have formed a gas much lower in temperature, but containing, besides the carbonic oxide, a certain amount of hydrogen, the loss of sensible heat being made good by its higher calorific value. This would be what is known as water-gas, but what obtains in practice, while based on the same properties of carbon, oxygen
46
and hydrogen, is much more compli- cated.
First, in place of carbon we have coal, which contains, besides carbon, volatile hydrocarbons and ash. Then we do not use oxygen, but air, — a mixture of oxygen and nitrogen ; and lastly, we cannot convert all the carbon into carbonic oxide without converting a portion of it into carbonic acid. The result of this is that producer gas con- sists of carbonic oxide, carbonic acid, hydrogen, hydrocarbons and nitrogen, the combustible portion of the mixture being usually considerably less than 50 per cent. The fact that it is so poor in combustible, and consequently low in calorific power, is a great drawback to its extended use ; but for a number of purposes it has become the standard fuel, and its use is rapidly growing.
Before going more into the details of what goes on in the gas producer, it will be well for us to understand more thoroughly the substances with which we have to deal. Air, by weight, con- tains 23 parts of oxygen (O) and 77 parts of nitrogen (N). Air, by volume, contains 21 parts of oxygen (O) and 79 parts of nitrogen (N). One pound of carbon, burned to carbonic oxide, consumes 1.33 pounds of oxygen, which carries with it 4.46 pounds of nitrogen, making, in all, 6.79 pounds of gas, of which 2.33 pounds are car- bonic oxide. One pound of carbon, burned to carbonic acid (C 02), con- sumes 2.667 pounds of oxygen, which carries with it 8.927 pounds of nitro- gen, making the products of combus- tion, in all, amount to 12.594 pounds.
In the following table will be found the calorific power of the various sub- stances to be dealt with, expressed in British thermal units (B. T. U. )• For
GASEOUS FUELS.
47
the information of those who may not remember exactly what a British thermal unit is, I may state that it is the amount of heat required to raise one pound of water through i° Fahren- heit.
Heat Units Developed B. T. U. B. T. U. for
in Burning. for 1 pound of 1 cu. ft. of
combustible, combustible.
CtoCO 4,400
C to C 02 14,500
COtoC02 -- 4,825 319.
H to H2 O 62,000 327.
CH4 to C 02 and H2 O .... 23,500 1007.
C2 H2 to C Oa and H2 O ... 21,400 1593.
The heat energies are calculated upon the assumption that 620 F. is the initial temperature, and that the prod- ucts of combustion are reduced to that temperature.
To further facilitate our calculation, the following table gives the number of cubic feet in one pound of the following gases at 620 F. and at atmospheric pressure :
Volume in Cubic Feet at One Pound at 62° F. and Atmospheric Pressure.
Air .... 13.14 Cubic feet.
Nitrogen N 13.50
Oxygen O 11.88
Hydrogen H 189.79
Carbonic oxide CO 13.55
Carbonic acid .... C 02 8.60
Marsh-gas C H4 23.32
Producer gas is made from all kinds of coal, and varies in composition accordingly. Hence to study what actually goes on in the producer, we have to assume a definite composi- tion for the coal which we are using, and measure the actual amount of carbonic acid in the gas generated. The carbonic acid in producer gas varies from 2 per cent, to 8 per cent. ; the former representing very good practice, and the latter a practice that should not be tolerated. Four per cent, is the amount usually found when the producers are working rapidly and are carefully tended, and should not be much exceeded.
A low percentage of carbonic acid is usually associated with slow, cold work- ing of the producer, and a high per- centage with the reverse condition. A high percentage may also be pro- duced by uneven firing, the gas coming up around the sides, and through "holes" in the fire, being richest in
carbonic acid. The surest way to get a low percentage of carbonic acid is to run the producer slowly ; but this is not usually possible, and the best re- sults are obtained by keeping the body of the fire well "poked" down, so that no large holes exist, and the top spread over evenly with fresh coal.
In the following tables we have assumed the composition of the coal and calculated the theoretical composi- tion of the gas under different condi- tions, our object being to show what good producer practice is and to give some small impression of what is lost when the gas maker is ignorant or careless.
First we will consider anthracite coal containing 10 per cent, of ash and 5 per cent, of volatile hydrocarbons, which are practically all marsh gas (C H4), and suppose it to be gasified by air alone. Under such conditions good gas would have about 4 per cent, of carbonic acid in it, and we remain on the safe side by assuming the gas to contain only 3.7 per cent. On this basis, column 1, in Table I, represents the pounds of gas formed ; column 2, the number of cubic feet ; column 3, the heating capacity ; column 4, the heating capacity per pound ; column 5, the heating capacity per cubic foot. The last column contains the analysis by volume. All these calculations are based on the assumption that the gas is cooled after being made ; in other words, no account whatever is taken of the sensible heat. The sum of column 3 gives the total heating capacity of the gas in terms of British thermal units. The ratio of this number to the number of heat units originally in the coal gives what we call the efficiency of conver- sion, or the proportion of the total heating capacity of the coal that we have in the cold gas. In this case we find it to be 64.77 Per cent., but we must remember that the gas as it comes from the producer contains a large amount of sensible heat, which, under many conditions, may be utilised, but which we are disregarding.
In Tables II, III and IV we have the theoretical composition of producer
48
CASSIER'S MAGAZINE.
TABLE I.— ANTHRACITE GAS, WITHOUT STEAM.
12 3 4
100 Lbs. Coal. v> a r rt Total. B. T. U.
Pounds. Cu. Ft. B T u per Lb
75 lbs. C to CO 175.0 2,371.3 756,875 4,325
10 1bs.CtoCO2 36.7 315.3
5 lbs. marsh-gas C H4 .. 5.0 116.6 117,500 23,500
126.7 lbs. O required, associated with N 424.4 5,729.9
Average.
Total 641.1 8,533.1 874,375 1,363.9
Total energy in 100 lbs. coal . 1,350,000
Efficiency of conversion .. 64.77 per cent.
B. T. U. Per Cu. Ft
319
1007"
Anal.
PerCt.
by Vol.
27.79
3.70
1.37
67.14
Average. 102.5 100.00
TABLE II.— ANTHRACITE GAS, STEAM BLOWN PRODUCER. (Good.)
12 3 4 5
100 Lbs. Coal. Pounds. Cu. Ft
80 lbs. CtoCO
51bs. C to C 02
5 lbs. volatile hydrocarbon
-ion ik r> ■ a j 30 lbs. from H2 O = H..
120 lbs. O required j 90 lbs> from ^ = N ^
Total
Total energy in 100 lbs. coal Efficiency of conversion
Total. B. T.U.
B. T. U. B. T. U. Per Lb. PerCu.Fr
186.66
18.33
5.00
3.75
301.05
514.79
2,529.24 157.64 116.60 712.50
4,064.17
,680.15
,304
117,500 232,500
4,325
23,500 62,000
1,157,304 1,349,500 86 per cent
Average, 2,248
319
858 327
6
Anal. Per Ct.
by Vol. 33.4
20
1 6
9.4 53.6
Average.
152.7 100.00
TABLE 1II.-ANTHRACITE GAS, STEAM BLOWN PRODUCER. (Normal.)
12 3 4 5 6
100 Lbs. Coal. Pounds. Cu. Ft. £%% ^Lb/ P«Cu. Vi. P«|^
751bs. CtoCO --.. 175.0 2,371.3 756,875 4,325 319 30.24
10 lbs. CtoC02 - 86.7 315.3 .... .... 4.02
5 lbs. marsh-gas C H4 5.0 116.6 117,500 83,500 1007 1.49
19R71Kc nr„n„;rprl I 32 lbs. from H20 = H. 4.0 758.8 248,000 62,000 327 9.68
l^b.71bs.U required. ((J471bsfrom air= N m g 427Q5 » _ ___ ^^
Average. Average.
Total ..- 537.9 7,841.5 1,122,375 2U86 143.1 100.00
Total energy in 100 lbs. coal 1,850,000
Efficiency of conversion 83.14 per cent.
TABLE IV.— ANTHRACITE GAS, STEAM BLOWN PRODUCER. (Poor.)
12 3 4 5
100 Lbs. Coal. Pounds. Cu. Ft. }^% $Jj£' **'&&
70 lbs. CtoCO 163.3 2,212.7 706,272 L826 819
151bs.CtoC02 55.0 478.
5 lbs. marsh-gas, C H4 5.0 116.6 117,500 23,500 1007
133.3 lbs. O required \ f™*' ffrom *!> °= H *-1G 4 ffi S57'920 62'°°° 3*7 M I 100 lbs. from air = N._ 33o. 4,522.5
Average. Average.
Total 562.46 8,114.0 1,081,692 1923 133.3
Total energy in 100 lbs. coal 1,350,000
Efficiency of conversion 80 per cent.
Anal.
PerCt.
by Vol.
27.3
5.8
1 4
9.8
55.7
100.0
TABLE V.— BITUMINOUS GAS, WITHOUT STEAM. 12 3 4
100 Lbs. Coal. Pounds. Cu. Ft. B^'T'v Per I b'
471bs. CtoCO 109.7 1,486.4 474,460 4,325
8 lbs. CtoC02 29.3 252.0
32 lbs. volatile hydrocarbons 32.0 746.0 640.000 20,000
Required 84 lbs. O, associated with N 291.2 3,796.2
Average
Total. 452.2 6,280.6 1,114,460 2,464.6
Total energy in 100 lbs. coal 1,437.500
Efficiency of conversion 77.53 per cent.
B. T. U.
Per Cu. Ft.
319
*858
Average 177.4
Anal. Per Ct. by Vol. 23.67
4.01 11.88 60.44
100.00
GASEOUS FUELS.
49
TABLE VI.— BITUMINOUS GAS, PRODUCER STEAM BLOWN (Good).
12 3 4 5
100 Lbs. Coal. Pounds. Cu. Ft. ^^ B.T\U. pB. T. TL
50 lbs. C to CO 116.66 1,580.7 504,554 4,325 319
5 1bs. CtoCOg.- - 18.33 157.6
32 lbs. volatile hydrocarbons 32.00 746.2 640.000 20,000 858
p • ^ fin ik nj201bs. from H2 0=H . 2.50 475.0 155,000 62,000 337
Required 80 lbs. O "j 60 lbs. from Air=N.... 201.00 2.709.4
Average Average
Total 370.49 5,668.9 1,299,554 3,507 229.2
Total energy in 100 lbs. of coal 1,437,500
Efficiency of conversion 90.0 per cent.
Anal.
Per Ct.
by Vol.
27.8
2.7
13.2
8.3
48.0
99.8
TABLE VII.— BITUMINOUS GAS, PRODUCER STEAM BLOWN (Normal). 1 2 3 4 5
100 Lbs. Coal. Pounds. Cu. Ft. ^% ^ *£•£ pB. ■ T-U^
45 lbs. C to CO 105.0 1,422.7 454,125 4,325 319
101bs.CtoCO2 367 315.3
32 lbs. volatile hydrocarbons 32.0 746.2 640,000 20,000 858
b • ahr7iu nJ21-71bs-fr0mH2O = H 2-7 512-2 167,400 62,000 327
Required 86.7 lbs. Oj651bs< fromA?r=N_ m Q 2gm6 __>____
Average Average
Total 391.0 5,934.0 1,261,525 3,201.8 212.6
Total energy in 100 lbs. coal 1,437,500
Efficiency of conversion 87.8 per cent.
Anal.
Per Ct.
by Vol.
24.0
5.3
12.6
8.6
49.5
100.0
TABLE VIIL— BITUMINOUS GAS, PRODUCER STEAM BLOWN (Poor). 12 3 4 5
100 Lbs. Coal. Pounds. Cu. Ft. BT°ta{j ^1^ Per' Cu.^t.
40 lbs. C to CO. -... 93. 1,260.2 402,225 4,325 319
15 lbs. CtoCOj . 55. 473.0
32 lbs. volatile hydrocarbon 32. 746.2 640,000 20,000 858
oo ik r> • , j 23.2 lbs. from H2 0 = H 2.9 550.1 179,800 62,000 327
93 lbs. O required { 69.8 lbs. from Air=N .. 233.8 3,156.1 ....
Average Average
Total 416.7 6,185.6 1,222,025 293.3 197.5
Total energy in 100 lbs. of coal. 1,437,500
Efficiency of conversion -. 85.0 per cent.
6
Anal.
Per Ct.
by Vol. 20 4
7.7 12.0
8.9 51.0
100.0
Per Cent.
Carbonic acid, CO
Volatile hydrocarbon
Hydrogen, H
Carbonic acid, C 02
Nitrogen, N
Combustible
Of original energy in gas.
B. T. U. per lb. gas
B. T. U. per cu. ft. gas..
|
TABL |
,E IX. |
||||||
|
Without Steam. |
Steam Blown Produc |
:er. |
|||||
|
Bituminc Gas. |
Anthracite Gas. |
Bituminous |
Gas. |
||||
|
Anthracite Gas. |
,us Good. |
Normal. |
Poor. |
Good. |
Normal |
Poor. |
|
|
27.79 |
23.67 |
33.4 |
30.24 |
27.3 |
27.8 |
24.0 |
20.4 |
|
1.37 |
11.88 |
1.6 |
1.49 |
1.4 |
13.2 |
12.6 |
12.0 |
|
94 |
9.68 |
9.8 |
8.3 |
8.6 |
8.9 |
||
|
3.70 |
4.01 |
20 |
4.02 |
5.8 |
2.7 |
5.3 |
7.7 |
|
67.14 |
60.44 |
53.6 |
54.57 |
55.7 |
48.0 |
49.5 |
51.0 |
|
29.16 |
35.55 |
44.4 |
41.41 |
38.5 |
49.3 |
45.2 |
41.3 |
|
64.77 |
77.53 |
86.0 |
83.14 |
80.0 |
90.00 |
87.8 |
85.0 |
|
1364.00 |
2464.00 |
2248.00 |
2086.00 |
1923.00 |
3507.00 |
3202.00 |
2933.00 |
|
102.5 |
177.4 |
152.7 |
143.00 |
133.30 |
229.00 |
212.6 |
197.5 |
gas from the same coal, on the supposi- tion that one-fourth of the oxygen needed is derived from the steam, which both theory and practice indicate as about the proper amount.
These tables give the composition of the gas with increasing amounts of carbonic acid ; and it will be noted that with increase of carbonic acid, not only does the efficiency of conversion de-
4-1
crease, but also do the number of heat units per pound and per cubic foot of gas. As a matter of fact, the amount of carbonic acid in gas is a very good index of its quality.
In Table V we have a composition of bituminous coal gas made without steam, such as is made in the Siemens producer, the coal being assumed to contain 55 per cent, carbon and 32 per
5o
CASSIER'S MAGAZINE.
cent, volatile hydrocarbon ; and we find the efficiency of conversion to be 77-53 Per cent. It must be remem- bered, however, that this gas is very hot when it comes from the producer, and, if used without cooling, would have a much higher efficiency. The increase of efficiency over anthracite gas of like manufacture is due to the high percentage of volatile hydro- carbons, which, while they may not be all marsh-gas, will have a heating capacity of at least 20,000 B. T. U. per pound. On the other hand, however, if the gas is cooled, a large proportion of the volatile hydrocarbons will be de- posited as tar. In fact, if we analyse the cool, fixed gas, we shall not find it very different from similar anthracite gas ; but if we use it hot from the pro- ducer before the hydrocarbons have been deposited, it is much richer.
Tables VI, VII and VIII give the compositions of steam-blown bituminous gas with increasing proportions of carbonic acid. It will be noted here also, that as the carbonic acid per- centage increases, the efficiency of con- version and the richness of the gas decrease. For the sake of accurate comparison, the volumetric analysis and the results of the foregoing calculations for different gases are arranged together in Table IX.
It must be remembered, however, that the first two gases came from the producer hot, and should, if possible, be used at once, in which case they will be more efficient than the figures indi- cate ; but if allowed to cool, the anthracite gas will lose nothing but its sensible heat, while the bituminous gas will lose some of its hydrocarbons by condensation. As many of the volatile hydrocarbons in bituminous coal are readily condensable, no gas from such coal, if allowed to cool at all, is as rich as the figures in the table indicate.
The facts that bituminous coal can be converted into gas with less loss than anthracite, and that the resulting gas is richer, are strong points in favour of its use in the producer. In many places, however, especially where the presence of tar and soot cannot be
tolerated, anthracite gas does very well, but the 50 per cent, more heat units per cubic foot in the bituminous gas count enormously in the production of high temperatures. Indeed, for the production of temperatures comparable with those of the Siemens steel melting furnace a rich gas is essential for eco- nomical working, and a steel melter can tell at once by the action of the furnace whether the producers are being prop- erly tended or not.
Table IX may be very advan- tageously studied by the users of pro- ducer gas, and the calculations carried out for larger percentages of carbonic acid. With increasing percentages of carbonic acid in the gas, we find not only a decrease in the efficiency of the gas making, but an increase in the amount of nitrogen, and a marked de- crease in the amount of combustible material in the gas. It is hard to over- estimate the effect of this impoverish- ment, especially in the production of high temperatures. The loss in con- version is only a small part ; the great loss comes in the increased amount of gas needed to do the same work, and if the required temperatures are very high the poor gas soon becomes entirely inadequate, no matter in what quantity it may be used.
A brief reference to some of the vari- ous kinds of producers now in use, may not be uninteresting here. The one first demanding our attention is the Siemens producer, which is the oldest form, having made its advent with the open hearth furnace. In it no steam is used, and natural draught, induced by the syphon- like action of large cooling tubes, is the means by which gas is conveyed to the furnace. The gas from the Siemens producer is essentially a hot gas ; hence, the waste from loss of heat in the cooling tubes- must make its efficiency low, although not as low as is indicated in our table, which supposes the gas to be cooled to 620 F.
This producer seems to us to-day very wasteful and crude, but we must remember that it made a success of the Siemens furnace, and while we are at
GASEOUS FUELS.
5i
GAS PRODUCER BUILT BY MESSRS. SWINDELL & BROS., PITTSBURGH, PA.. U. S. A.
liberty to show the advance in the art by comparing more recent producers, our criticism should always be made with a proper appreciation of what it has done for metallurgy. If we close up the ash-pit of the Siemens producer and put on a steam blast, we improve it very much, and get the producer which, in various shapes and under as many names, is in most common use.
All these later producers have what may be called a cinder grate ; in other words, the bars are always kept covered with a deep bed of cinders, which are always small and soft, due to the fact that producers blown with steam are never hot enough to fuse the cinders into large, hard masses.
Among this class of producers may be mentioned the Swindell, which is a modified Siemens with a closed ash- pit, and shaking-grate bars, illustrated on this page. These producers are giving good results, and are being introduced in large numbers. As an example of a continuous producer with a water seal, may be mentioned the
Smythe, shown on page 53. This producer, having a large grate area, would seem well adapted for burning waste coal, and, indeed, this is what its makers specially claim for it.
Attention, too, may be called to the Taylor producer, which differs from all the others in that it has no grate, properly speaking, but a circular re- volving plate on which rests the entire burden. A bed of cinders of consider- able depth rests on this plate, through the centre of which is a pipe for the admission of air and steam. This means of admitting the air avoids, to the greatest possible extent, one serious trouble in producer practice, namely, " blowing through " along the walls.
A glance at the cut on page 54 will show the apparatus and method of cleaning the fire. When the plate is revolved by means of the crank, the cinders are ground up and fall over the edge, the frequency of grinding and the number of revolutions depending on the rate at which the producer is being forced. The fact that here the
52
CASSIER'S MAGAZINE.
grate is practically a large bed of cinders, would indicate the possibility of using in this producer the smaller grades of coal. In fact, a large number of these producers are being run with satisfactory results on anthracite, buckwheat and bituminous slack. For many purposes it has been found advisable to dispense
GAS PRODUCER BUILT BY THE PHILADELPHIA
ENGINEERING WORKS, PHILADELPHIA,
PA., U. S. A.
with a brick lining in this producer, and to use, instead, a water-jacket.
The fact that we can get good producer gas from waste coal by means of any one of the two or three pro- ducers, suggests the possibility of this method of utilising such coal for the firing of boilers. Quite a little work was done in this line a few years ago by some engineers, and the results were very satisfactory ; but the advent of the successful mechanical stoker seemed so completely to fill the gap, that, for the most part, experiments in this line were discontinued.
There is, however, one boiler plant fired in this manner now running in the United States with such excellent re- sults that it may be interesting to present it in detail. We are able to do this, as the plant was an experiment,
and subjected to a scientific investiga- tion. The plant in question, the results of which have been kindly put at my disposal, is at the works of R. D. Wood & Co., at Camden, N. J., Taylor producers being used. The boilers were erected for direct firing, and in taking the gas from the producer, the conduits and other details were not arranged as they would have been in a plant specially designed for the purpose. In fact, the gas conduits run through sandy ground with clay immediately underneath, and, being of a temporary character, there was more or less leak- age of water into them, so much so that while the test in question was going on, a stream of boiling water was drawn from the conduit to keep it clear. The result of this was that not only the temperature of the gas fell from over 6oo° F. at the producer to 3000 F. at the boiler, but the gas carried with it a large quantity of vapour which further reduced its efficiency.
In this experimental plant two No. 7 producers are used, — one of the ordi- nary brick-lined type, and the other, water-jacketed, the jacket serving as a feed-water heater. The feed -water enters the boilers at a temperature of 2980 F. The coal used was anthracite buckwheat, containing about 25 per cent, of ash and refuse, and the result- ing gas contained about 4 per cent, ot carbonic acid. The temperature of the air entering the boilers through ducts in the setting was 2000, and that of the chimney gases 41 50 F. The steam used to blow the producers was 62^ per cent, of the water evaporated ; the chimney gases contained 1 per cent, ot C O, 13.7 per cent, of C Os, and 4.7 per cent, of O.
The test made under the above con- ditions gave the following results :
Water evaporated per pound of fuel 7 lbs.
combustible 8.7 "
Water evaporated per pound of combustible from
andat2l5>°F 10.5 "
Horse-power of boiler with gas firing 91
" ' direct firing 65
The most interesting fact to be noted in these results is an increase of nearly 50 per cent, in the capacity of the boiler. This is, undoubtedly, due to a number
GASEOUS FUELS.
53
of conditions which accompany gas firing, among which may be cited the following : — The tubes do not become clogged with dust ; the door is never open to admit cold air ; and the fire is never cooled down with fresh coal. The generation of steam is absolutely uniform, and the evaporative efficiency is good considering the conditions under which the test was made. The net result of the test is that in a prop- erly designed plant we may expect very good evaporative results from producer gas made from buckwheat coal.
It would be of considerable interest to carry out the experiments more fully, using bituminous slack, and also a mixture of bituminous slack and anthracite buckwheat. The object of applying producer gases made from waste coal to steam raising is, of course, to utilise such coal for the production of power. After the coal is changed into gas it may be burned either under a boiler or in a gas engine.
Having seen what has been accom- plished in boiler firing, it is interesting to note what has been done by the use of such gas in a gas engine direct.
The writer has available the record of two tests, one of a ioo horse-power Otto gas engine, running on producer gas at the works of the Otto Gas
PRODUCER BUILT BY THE S. R. SMYTHE CO., PITTSBURGH, PA., U. S. A.
54
CASSIER'S MAGAZINE.
THE TAYLOR REVOLVING BOTTOM GAS PRODUCER, BUILT BY MESSRS. R. D. WOOD & CO. PHILADELPHIA, PA., U. S. A.
GASEOUS FUELS.
55
Engine Company, of Philadelphia ; and the other, of two ioo horse-power Otto gas engines at the plant of the Danbury & Bethel Gas and Electric Light Com- pany, at Danbury, Conn., U. S. A. A detailed account of the first test, made by Prof. H. W. Spangler, of the Uni- versity of Pennsylvania, is given in the journal of the Franklin Institute for May, 1893. The second account was presented by Mr. A. W. Burchard, M. E., before the American Society of Mechanical Engineers in May, 1895.
We shall describe somewhat in de- tail the method employed at the Otto Gas Engine Works, following Prof. Spangler' s paper. The engine used for the tests, and which furnishes the power for the shops, does not differ materially from the ordinary Otto gas engine. The gas used is made from anthracite buckwheat coal by a Taylor producer, and passes through two scrub- bers to a holder. The first scrubber is divided horizontally in the centre by a water-seal, and the gas entering the bottom of the upper section, rises to the top and is conveyed to the bottom of the second scrubber, from the top of which it passes to the gas-holder. The producer is blown by a Root blower, the blast from which enters the bottom of the lower section of the first scrubber, and, rising through the heated water, issues from the top of this section quite hot and thoroughly charged with moisture. It is then led directly to the producer.
The water for the scrubbers comes from a tank above, and, in the first scrubber, is highly heated by the gas as it comes from the producer ; but it gives up the larger portion of its heat to the air of the blast, and leaves the scrubber at the bottom, much reduced in temperature. It is found that the air passing through the heated water of the scrubber takes up enough water to obviate the necessity of a steam boiler in connection with the producer.
The fuel used was anthracite buck- wheat, and the average composition of the gas, from seven determinations, extending over three days, was as follows :
Per Ct. Per Ct.
by Vol. by Wt.
Carbonic oxide CO 25.38 26.08
Hydrogen H 4.51 0.33
Marsh-gas C H4 1.79 1.05
Oxygen O 0.26 0.23
Carbonic acid CO, 4.02 6.50
Nitrogen N 64.04 65.81
The composition of the exhaust gases was as follows :
PerCt. PerCt.
bv Vol. by Wt.
Carbonic acid C Oa 15.60 22.44
Oxygen O 2.24 2 34
Carbonic oxide CO 0.23 0.22
Nitrogen N 81.93 75.00
Without going into any long and intricate calculations the results may be stated as follows :
Coal used per indicated horse-power per hour, .0.9511 lbs. Coal used per brake " ..1.315
Combustible per indicated " " ..0.8302 "
Combustible per brake " ..1.148 "
The difference between the indicated horse-power and that measured by the brake seems very large, — in fact, the actual horse-power is only 72 per cent, of the indicated. This may be ac- counted for, to a large extent, by the fact that the engine was entirely new.
In the test of the Danbury engines, the brake horse-power was found to be 87 per cent, of the indicated ; hence, it is reasonable to suppose that when the engine considered above got into equally good working shape, its mechanical efficiency would also be 87 per cent. , both being the same kind of engine. Calculating its effective horse- power on this basis, we find that it should require only 1.09 lbs. of coal, or 0.95 lbs. of combustible per brake horse-power per hour. But little work has been done in this line, and the fact that such favourable results have already been obtained argues very well indeed for the future.
So far, we have dealt with the sub- ject purely from an engineering stand- point, but, however favourable the results may appear when looked at in this way, we must always remember that there is another and more import- ant side to the question. What we are seeking in this work is to get power at as small a cost as possible, and we must remember that cost of plant always enters into the question as a large factor.
For small powers, undoubtedly the
56
CASSIER'S MAGAZINE.
cost of producer, scrubbers, gas-holder, blower and gas engine seem very large when compared with that of a steam boiler and engine ; and it is a question of calculation as to how much more we can afford to pay for the gas plant than for the steam boiler. For larger powers, however, the cost of the gas plant compares more favourably with that of the boiler, as the most expensive part, the holder, need not be any larger for a thousand horse-power than for a hundred. We may safely say that there is a point somewhere between one hundred and one thousand horse- power at which the cost of the gas plant does not exceed that of the boiler plant ; and also, that beyond this point, a gas engine, working under the conditions described, is more economi- cal than a steam engine. The location of this point is determined solely by commercial considerations ; and the question as to whether a small gas power can be used economically is quite susceptible of calculation when we know the cost, both of the steam and of the gas plant, and the saving in coal of the latter over the former.
To day all steam engines are sold on a guaranteed steam consumption, and the boilers on an evaporation per pound of coal or combustible, so that it is easy to estimate the cost of the power gener- ated by steam. Can we as easily calculate the cost of power generated by the gas plant? We can at least safely say that what has already been done can be done again, and the writer believes that it will be done better in the near future.
It is too soon to make any kind of a prediction, but the indications are that the gas engine has before it a much wider field than has been hitherto sup- posed, and we need not be greatly surprised if in a short time we hnd engineers considering, not the question of the kind of steam engine they need, but whether they want a steam engine at all. When as much attention and study is given to gas engines as is devoted to steam engines, and when people are willing to place in them the confidence that they deserve, we must not be surprised to see the gas producer as a formidable competitor of the steam boiler.
ELECTRIC POWER FROM THE COAL REGIONS.
By Dr. Louis Bell.
HE rise of electric power transmis- sion has opened to us the gateway to many economic and social ad- vances as yet only partially under- stood and half appreciated. The work of evolving methods and put- ting them into practice has gone on with immense rapidity in the last two or three years, yet with so little blare of trum- pets that very few, outside of those most immediately interested, realise how effective are the methods and how certain the results.
The public knows that Niagara has, after several years of hard work, been "harnessed," to use the pet reportorial word, and, as a beginning, that colossal plant has gone into service making aluminum. The public knows, too, that the reporter, with facile pen and deft imagination, has published weird accounts of how Niagara is to run all the railroads in the country, supply light and power to every city and irradiate the country generally. In fact, sun, moon and stars might well be forgot on and after the full starting of the Niagara plant if b'r'er reporter has the facts correctly.
But the public does not know how much of the credit for the splendid work at Niagara lies not with the electrician but with the determined, hard-working, persistent men who, with the courage of their convictions,
pushed ahead, year after year, carry- ing the financial burdens of the gigantic enterprise in face of seven legions of croakers. Long before a wheel turned at Niagara the electric railroads had proved, beyond dispute, that electric power could be distributed over wide areas with entire success and without inordinate expense, and when, a few months since, Niagara went steadily to work there were already running half a hundred plants for the electrical trans- mission of power, that had tested and proved every principle of the art by the final touchstone of experience, so that it was absolutely certain that nothing save bungling could make Niagara a failure.
There is many a question asked to- day that shows only too clearly how little impression all this unheralded work makes on the public mind, and how feeble is the realisation of what has already been accomplished and its bearing on what is about to be done. It is the purpose of this brief article to answer some of the pertinent and searching questions that intelligent men are still asking, not after the manner of the scribes, who paint in glowing colors the marvels which they think ought to be accomplished by the ' ' mysterious force ' ' of which they love to speak, nor yet after the manner ol those who prove it all by well mar- shalled equations recruited from half a dozen alphabets. On the contrary, these questions are to be answered by a direct reference to the facts which experience has already shown regard- ing them. We will not venture to go beyond experience save on roads con- structed of it.
The first and most natural question is : Can electrical power be distributed
57
58
CASSIER'S MAGAZINE.
cheaply over large areas ? In the first place, we may note that nearly every large city is provided with a network of electric railways that stretch far out into the suburbs. The horse has practically been driven out of the busi- ness. These railways adopted the electric system not for humane or aesthetic reasons, but because it was cheap and effective. The rapid transit system of Boston, Mass., U. S. A., for example, has been steadily growing for half a dozen years. It serves to- day a population of nearly a million people over a radius often miles or so, and it has thus grown because it was cheap and did its work well. Passing from this special class of work, we find the Edison central stations for the supply of electric light in New York city now operating over its entire light- ing area, electric motors to the aggre- gate capacity of something like eight thousand horse-power, — an amount that has been steadily increasing for years. These motors are employed in almost every imaginable kind of service and place.
These stations are by no means eleemosynary institutions, nor are the hundreds of people who use motors, engaged in unprofitable recreation. The stations furnish electric power be- cause it is profitable, and the users employ it because it is cheap and by far the best power to be had. In every large city it will be found, on investi- gation, that electric power is being used with growing frequency, in large amounts and over areas of many square miles. Those who sell electric power, find that it pays to do so, and those who buy it find it to their interest.
But, granting this, is electric power reliable ? Well, people are not in the habit of using unreliable power when there is better to be had, and the growth of electric motor service shows that experience has answered the ques- tion in the affirmative. You frequently hear of people taking out steam engines and putting in electric motors, but you seldom find them throwing those motors out because they are unreliable, or for any other reason. In similar fashion
the street railway men, while they are using motors in every sort of fashion, find them, on the whole, reliable. Now and then a motor may be indisposed and laid up for a few days in the repair shop, but, in general, motors do not go lame, or cast a shoe, or have the blindstaggers, or the epizootic or any- thing of the sort. They are not per- fect,— few machines of human con- trivance are, — but they are perfect enough to have assumed the responsi- bility of the rapid transit work in nearly every American city, and to have acquitted themselves well. If this is not enough evidence that the electric motor is trustworthy, we may cite some of the newspapers that run their presses by electric power and generally manage to come out on time ; and a couple of big cotton mills, one at Columbia, S. C, U. S. A., and the other at Pelzer, in the same State, that have no power but electric to drive their looms and spindles.
Cotton mills are peculiarly fussy about the continuity of their power, for stopping even a few minutes means serious loss. And when one has been running a year and a half, as at Columbia, driven by electric power alone, and its managers are outspoken in their satisfaction, we may conclude that the service has been trustworthy. The fact is that in spite of no small popular distrust at the start, electric power has proved reliable and has gradually made its good character known.
But granted that the distribution oi electrical energy from central stations has proved its advantages, how about transmitting it long distances, so as to supply large districts, not from some central point, but from a distant source of power? Of the mere fact of trans- mission and distribution for motor service we have plenty of evidence. For a couple of years there has been a power plant supplying electrical energy to the city of Genoa, in Italy, from a point eighteen miles distant. It has done steady and excellent service, supplying several scores of motors employed in all sorts of industries, and
ELECTRIC POWER FROM THE COAL REGIONS.
59
this although the methods are, from our present standpoint, somewhat crude. For an equal length of time power has been regularly supplied for the driving of the electric light ma- chinery at Hartford, Conn., U. S. A., from a water-power eleven miles away ; for working the machine shops of the Oerlikon Company, at Zurich, Switzer- land ; for running the ore mills in Telluride, Col., U. S. A.; and for operating an artificial ice factory and doing miscellaneous lighting and power at Redlands, Cal., U. S. A., at dis- tances only slightly less than the above. In all these cases the power has proved to be steady and economical.
For periods of time ranging from two years down to a few months, not less than fifty power transmission plants have been working regularly in different parts of the world, ranging in magnitude from Niagara down to fifty horse-power, and in distance from the Folsom-Sacramento transmission, in the United States, having an extreme length of about 25 miles, down to a mile or two. All these plants have been singularly free from trouble, and have done their work well.
Admitting that distances up to twenty or twenty-five miles can be successfully overcome, is there a reasonable proba- bility that the transmission of power can be extended over distances much greater ? Yes, if necessary. We have no plants over twenty- five miles, but the methods and apparatus for longer transmission have already been thor- oughly tested, and up to at least fifty miles we are sure of our ground, — per- haps up to a hundred miles. The transmitting and receiving machinery would be quite identical whether the line between them were twenty or fifty miles long, so that, as regards appa- ratus, the ground is well trodden.
For very long transmissions, high electrical pressure is necessary to keep down the cost of the line, since the amount of copper required to meet given conditions decreases with the square of the voltage. And we have already experience with the voltage just as with the apparatus,— at least
with voltages ample for a fifty- mile transmission. For example, without counting the famous LaufTen-Frankfort experimental plant, with a line 108 miles long, and operated part of the time at a pressure of nearly 30,000 volts, there are now in commercial service four plants, running steadily and successfully at pressures of 10,000 volts and more. Chief among them is the Oerlikon installation in Switzer- land, working at over 14,000 volts ; then come Folsom-Sacramento, in the United States, and Guadalajara, in Mexico, at 11,000 each ; and finally the San Antonio canon plant, in the United States, at 10,000. The first and last mentioned have been in operation nearly three years without having encountered any appreciable difficulty from the very high pressure. The other two have been operated some months without a trace of trouble. From these experiences there is the best of reason to believe that voltages up to fourteen or fifteen thousand are entirely justified by present practice.
Concerning distances of 100 miles or more, and pressures exceeding 15,000 volts, we have only the results at Lauffen by way of data. While these make no pretense of representing com- mercial practice, they still are good evidence that, as an engineering feat, a transmission of a hundred miles at 25,000 or 30,000 volts is quite practi- cable. While the feasibility of cover- ing far greater distances at much greater voltage is more or less a matter of speculation, those who know most about the difficulties to be met fear them the least.
But, after all, does this sort of thing pay ? This is the real crucial question, and the future of power transmission depends upon the answer. With most of the transmissions mentioned, in fact nearly or quite all of those which have been running long enough to draw any conclusions, experience has said ' ' Yes " in unmistakable tones. So far as has yet appeared, any lack of commercial success has been due to other causes than the cost of electrical transmission.
Up to the present time substantially
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all the transmissions of any magnitude have been from water powers, and it is singular to note how their success has stimulated their production. Water powers have been discovered in un- heard-of nooks, and even where they were hardly suspected. But there is an end to such discoveries, and sooner or later, beginning in the very near future, something must be done with the next largest amount of unused energy remaining. This is to be found in the huge store of fuel that is our legacy from the carboniferous age. How great it is we can only guess, for we have perhaps hardly begun to take account of it. Yet this is no reason why we should play the spendthrift with that which we now have. Huge piles of waste coal are landmarks in every mining region, and below ground are enormous masses, untouched as yet because of poor quality.
The transportation of coal is really a special case of the transmission of energy, and we may with perfect fair- ness compare it with electrical trans- mission. If it be cheaper and easier to ship coal from the mine to the point of consumption than it is to burn the coal at the mine and transmit the resulting energy, then the latter course must show cause for its existence. Coals, we know, have varying values as fuel, while the cost of mining and transporta- tion is fairly uniform. Hence, any examination of the question just raised must take this difference into account.
The first thing to be done in study- ing the problem of the transmission of power from cheap coal at the mines is to get at some common basis of com- parison between carrying the energy in bulk and sending it over a wire. Fortunately, experience has already shown that in ordinary distribution of power through a city, there is a gain in generating it in large quantities and distributing it electrically in the ordi- nary small industrial units. Hence, we can confine ourselves to compari- sons on a large scale.
Knowing that a large central station can distribute power economically, can it the more cheaply generate it by coal
burned on the spot, or by power trans- mitted from a region of cheaper coal ? What is true in this case will be also true of large units of power devoted to other purposes. We can get our com- mon unit in the following way : —
A good engine, of compound con- densing pattern, is capable of producing \x/i horse-power-hours, i. e., i kilo- watt-hour by the consumption of about 2 pounds of good coal. Whether the coal or the current be transmitted, the engine will be used, so that, for a rough approximation to the economics of the matter, we need only compare the cost of the electric transmission per iooo kilowatt-hours with the expense of freighting and handling one ton of coal. The cost of the transmission means here simply the interest, care and depreciation on the electrical part ot the total plant. This we can very readily approximate.
The cost of line and apparatus for a fifty-mile 15,000 volt transmission in large amount may be reckoned at something like $100, or about ^20, per kilowatt transmitted. Taking interest, labour and maintenance at twenty per cent, and assuming 3000 working hours per year the charge for transmission becomes over 0.6 cent or about 0.3d. per kilowatt-hour. This evidently cor- responds to a prohibitive and absurd freight rate for the distance. Even if by increasing the magnitude of the transmission and raising the voltage we were able to reduce this by one- half, we should still have a cost of transmis- sion far greater than the cost of trans- porting the necessary coal. In the present condition of affairs it is then quite evident that with good coal, transportation can more than hold its own against electric transmission. Even with coal only half as good as that which we have assumed, the same con- dition holds good.
On the other hand, the transportation under certain circumstances may be so expensive as to throw the balance quite the other way. In some mining regions, where fuel has to be carried for miles over the mountains on mule back, such a transmission as we have
ELECTRIC POWER FROM THE COAL REGIONS.
61
been considering might very well pay handsomely. Nevertheless, we are entirely safe in saying that where there are fairly good facilities for transporta- tion, and good coal is under considera- tion, electric transmission is at a very manifest disadvantage.
But there is another side to the ques- tion. In all mining there is produced a varying, but considerable, proportion of coal which is unfit for transportation and sale, and now simply encumbers the earth. It is worse than useless, because it has to be disposed of in some way. It is this coal to which we must look for energy which can profitably be transmitted. The competition is not here between freightage and electrical transmission, but between power pro- duced from coal costing, perhaps, three or four dollars (12 to 16 sh.) per ton, and coal costing a few cents per ton. The latter may be poor, indeed, but, still, it is cheap fuel. If it can be util- ised to generate power twenty-four hours a day, the charge for transmis- sion, plus the cost of fuel, may sink so low as to fall below the fuel cost at some outside point under consider- ation.
For instance, the charge of 0.6 cent or 0.3d. per kilowatt-hour previously computed, may readily sink to 0.4 cent oro.2d. at a more moderate distance, and to less than half that for twenty- four-hour service, even including culm for fuel. At this cost it would come into active competition with power pro- duced on the spot, even with fairly cheap coal and very good engines. A plant deliberately installed to burn culm, on a very large scale, and running 24 hours a day with a fair load, can probably be made to put electrical energy on the line at or very near 0.3 cent or about o. I5d. per kilowatt-hour. Taking into account the cost of a moderately long transmission, as noted above, it seems probable that, including the losses of efficiency in transmission, one mechan- ical horse-power-hour could be delivered anywhere within, say a radius of twenty miles, at an actual cost of one-half to two-thirds of a cent, or say about o. 25d. And the horse-power-hour could cer-
tainly be sold for decidedly less than it now costs the average large consumer of power. The economy of such a plant is based both on cheap fuel and a large and relatively continuous service. The former item is acquired in virtue of the electrical transmission for which it more than pays.
Another and equally interesting field for transmission on a large scale lies in the existence of much coal of poor in- trinsic quality which stands shipment poorly, being too soft and friable. Such coal can, and does, often exist in re- gions where good coal is very dear. In this case the ability to substitute cheap for costly fuel is quite sufficient to over- come the cost of even a long electric transmission. It may pay to carry the power even fifty miles or so, and one such case, carefully investigated by the author in some detail, showed that it actually would pay even with so long a distance to be overcome.
While coal is plentiful and water powers still remain unutilised, of course the temptation to work in the direction of colossal transmissions from cheap coal is partially removed. Yet it should not be forgotten that coal ought never to be cheap enough to throw away, and water powers are often of deceptive value. It often happens that the ex- pense of developing them makes the investor sad, and wherever cheap coal is available it deserves to be thoroughly investigated with reference to the possi- bility of electrical transmission.
The present state of the case is that on a large scale the transmission of power from the culm pile, or the now unworked coal mine, over even con- siderable distances stands a good chance of commercial success. The larger the plant and the steadier the service, the greater the distance over which power can be sent to compete with that gen- erated on the spot. In a desultory way and on a small scale the chances of suc- cess are not particularly good, unless under very unusual circumstances.
Aside from all the commercial aspects of the case there is something to be said for the aesthetics of it. Large cities and small ones, too, suffer from the
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abominable soot and smoke that pour out from scores or hundreds of ill-man- aged steam plants. On a muggy day the very fumes of the pit settle down over the habitations of men and burden the air. The time ought to come when London fog and the passable imitations of it to be found elsewhere shall have become matters of ancient history, with plague and famine. The place to burn fuel is where it will least interfere with human avocations and pleasures, — not
about the dwelling places and under the noses of all mankind.
Some day we may reach a state of civilisation that will realise all this to the extent of reformation. This briel paper will have served its purpose if it has pointed out that even now the means are at hand, and the end may be served even by selfish interest. As the art grows so will the commercial oppor- tunity and the hope of a more rational conduct of industry.
MODERN COAL HANDLING MACHINERY.
By A. J. Webster.
iERE are few factors more necessary to the successful management of m an ufa cturing enterprises than cheap fuel. This appeared to be fully recognized when natural gas was discovered in quantity in the United States, and the massing of manufacturing plants within the gas belts immediately followed. With the partial failure of the gas, however, the problem of utilising the cheaper fuels became a living question to the progressive manufacturer and engineer. Power plants of every description in- creased rapidly in size, and the heavy daily consumption of fuel brought for- ward prominently also the problem of its cheap storage and handling. The time was,' when the steam users thought it compulsory to use nothing but the best lump fuel, but under the changed conditions of to-day, the culm piles of both anthracite and bituminous regions furnish not a little of the fuel for large steam users.
The first step toward the practical utilisation of the cheaper fuels was the introduction of the mechanical stoker. This device made it possible to use them with marked economy and better general results. Coincident with its in- troduction came the elimination of the slow and expensive barrow and shovel as factors in stoking, and the substitu- tion of fuel handling machinery, — not the modern outfit of to-day, but a crude imitation of appliances used for handling cereals and other light substances, in- adequate in all or many respects.
Gradually, did the magnitude of the field opened up to manufacturers in this particular line of machinery impress itself upon them, and the brains of inventors and the skill of engineers were called into requisition to evolve systems for hand- ling fuel, strong and efficient in construc- tion, and inexpensive in first cost and maintenance, compared with the benefi- cial results secured. With improved devices, better materials and skilled en- gineering, results are now obtained that a few years ago would have been deemed impossible. Distance counts for little as a factor in the installation ol these plants ; railway tracks and road- ways are tunnelled or spanned by steel trusses and in many instances fuel is de- livered to power buildings located fully
MODERN COAL HANDLING MACHINERY.
63
A CONVEYOR OUTFIT, BUILT BY THE JEFFREY MFG. CO., COLUMBUS, OHIO, U. S. A.
a thousand feet from the storage grounds.
Modern fueling plants are no longer a luxury. With the imperative demand for the closest economy and the arbitrary re- quirement of a reserve quantity of fuel of greater or less magnitude to draw upon in case of strikes, storms or other causes that lead to short fuel supplies, the best machinery for handling coal has become a necessity, and to the engineer no less than to the power user the study of its design and construction is full of interest and profit.
It is a common idea that because coal is heavy and dusty, coal machinery is rough and coarse ; but this is a wholly mistaken belief. No Waltham watch or compound locomotive is more carefully designed, the details more thoroughly studied, or the materials
more carefully selected and put into shape, than are the working parts of the coal handling appliances turned out by the high-class makers of to-day. It may seem, at first sight, to be a useless re- finement to work to templets, to turn shafts to vary less than a minute fraction of an inch, to make taper fits, and to indulge in various other refinements of modern mechanism on machinery that is to be roughly handled, covered with grease and dust, and exposed often to all the inclemencies of the weather ; and yet, all this has been found to be right in the line of positive economy. Dur- ability and freedom from delays have generally demonstrated the wisdom of this painstaking care and expense.
One very good example of coal hand- ling equipment is given in the illustra- tion on this page, representing a boiler
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ffi
-
A DOCK HOISTING AND CONVEYING fLANT, 15UILT BY THE C. W. HUNT CO., NEW YORK
room interior of an electric light and power plant, fitted up with machinery from the works of the Jeffrey Manufact- uring Company, of Columbus, O., U. S. A. The special conditions existing in this case were a power house on one side of a street, and a railroad switch on the other. Fuel, of necessity, had to be stored where the switch was located. Hoppers were built paralleling this switch, and into these the fuel was de- livered from the cars. Thence it was fed to a modern drop flight conveyor which crossed the street in a tunnel,
and this delivered the fuel to a continu- ous bucket elevator, — a type of eleva- tor which is practically a series of con- tinuous buckets or pans bolted to a wrought steel chain in their centres.
This elevator, in turn, delivered the fuel to a conveyor similar in construc- tion to the one below, placed immedi- ately over the boiler house hoppers which are constructed of steel plate and usually have a capacity of a day's con- sumption for the boilers which they feed. Gates in this conveyor trough, controlled by mechanism which is oper-
MODERN COAL HANDLING MACHIAERY.
65
ated from the floor below, deliver the fuel to the boiler house hoppers. From the hoppers, spouts run to the mechan- ical stokers on the boilers, with valves inserted to control the flow of fuel. No supplementary labour is needed in the boiler room whatever. The handling capacity is thirty tons an hour and the whole operation is practically automatic from start to finish.
The problem of how to best handle coal, of course, varies with each new set of conditions. What may answer very well in one case, may be alto- gether unsatisfactory in another, mak- ing it necessary to carefully study the requirements in every instance. For hoisting coal from boats at a wharf the C. W. Hunt Company, of New York,
have built a number of excellent plants, one of which is shown on this page. Although the coal, in this case, is received in vessels, it was necessary, in the event of failure of this source of supply, to provide means to receive it from wagons. Accordingly, the con- veyor proper was carried under the street to receive coal from local dealers should this become necessary. The unloading from the boats alongside is accomplished by means of a steam shovel, operated by a double-cylinder rapid hoisting engine, contained in the tower, and taking steam from the main boilers. The parabolic steel booms which are shown on page ^64, project- ing over the hatch of the vessel, are pivoted on a vertical axis, so that they can be swung horizontally over the wharf, leaving the dock unobstructed when not unloading coal.
After having been discharged into the hopper in the elevator tower, the coal is drawn off into the conveyor buckets by means of a filler of the kind shown on page 66, and is carried to pocket at the top of the building, 100 feet above the wharf, directly over the boilers, and so ar- ranged that the coal can be conveniently weighed
-^~S§?--S^
SECTIONAL VIEW OF A HUNT COAL HOISTING AND CONVEYING PLANT.
5-i
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CASSJER'S MAGAZINE
and spouted to either of the boiler room floors at a distance from the furnaces that is most convenient for hand firing. The necessity for a special method of filling the buckets will be apparent
perfectly that it would not occur to an observer that there was any liability of the buckets swinging or of being un- evenly loaded. The filler also guides the proper amount of material into each
HUNT S FILLER FOR CONVEYOR BUCKETS.
THE DRIVING MECHANISM OI
IUNT CONVEYOR.
when it is considered that the buckets swing freely on pivots, and might oscil- late to a harmful extent or might be loaded on one side and remain at an angle throughout the trip. The loading is accomplished by the filler shown, so
bucket as it passes, and prevents dust from reaching the joints of the chain or the bearings of the wheels, both of which can be kept thoroughly lubri- cated. A very interesting feature of the Hunt conveyor is found in the driv-
MODERN COAL HANDLING MACHINERY.
67
n — v
ing method adopted, the conveyor chain being- driven by pawls instead of by sprocket wheels, so that wear is re- duced to a minimum.
One of the prominent locomotive coaling stations equipped by the Hunt Company is shown in section on this page. The plan there adopted is to dump the coal from the cars into large hop- pers below the tracks, and to elevate it, by a conveyor, to storage bins from which it is drawn into the locomotive tender, as required, through chutes. The arrangement of the chutes and hoppers is such that four locomotives can simultaneously take coal, sand and water, and dump ashes, and at the same time the conveyor is carrying both the coal and the ashes to the bins. The
ashes are dumped from the fire- boxes into hoppers under the tracks where they are wet down, and after- wards carried to the storage bin at one end of the building from which they are drawn daily for removal. The sand is carried by the coal con- veyor to a bin situated between the coal and ashes and thence is delivered to the locomotives.
A form of tray conveyor and also a push plate conveyor, built by the New Conveyor Company, of London, Eng- land, are shown on the next page. The illustrations there explain them- selves. A great many conveyors of this type have been installed by the makers for retort houses in gas works and coal stores, and in some instances the push plate conveyors have been arranged with steel ropes instead of chains.
An example of a bridge tramway conveyor plant, turned out by the Brown Hoisting and Conveying Ma- chine Company, of Cleveland, O., U. S. A., for the coal stocking yard of Messrs. Coxe Bros. & Co.. at Roam, Pa., is shown on page 70. The bridge tramway system is especially adapted to the handling of soft or bituminous coal, either in taking it from a vessel to cars or the stock-pile, or vice versa, as the coal
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A PUSH PLATE CONVEYOR, MADE BY THE NEW CONVEYOR CO., LONDON.
can be lowered into a vessel or on board cars and dumped close to the bottom of these without breakage. Bridge tram- ways are generally built in plants of three or four bridges, two of the bridges being supported at their back ends upon one double back pier, and the other bridge or bridges being supported singly on a single back pier. An engine and boiler house is erected on the double back pier, and contains the
boiler and three or four hoisting engines for the three or four bridges, as the case may be. The double back pier also supports, near its top, a covered plat- form, from which the operators can overlook the dock and control and ope- rate the engines and hoisting machinery. Each bridge is supported in front by an independent pier, which permits the front to be skewed or moved sideways to suit the hatchways ol a vessel without
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A TRAY CONVEYOR, MADE BY THE NEW CONVEYOR CO.
MODERN COAL HANDLING MACHINERY.
69
moving the rear end, the bridges being hung to the piers with hinged connec- tions for this purpose. The front piers are mounted on wheels, and move on a track of a single line of rails ; the back piers are on wheels moving on a track of two rails. These machines hoist the buckets of coal from the vessel, convey it to any desired point on the tramway and automatically dump the material on the dock, or lower the bucket to the
to the railroad, the difference in eleva- tion between the terminal points being 820 feet, and the total length of the line amounting to 2800 feet. The line is located on the side of a steep moun- tain, and pitches from the landing station at an angle of about 30 degrees. On pages 72, 73 and 74 finally are given illustrations of several conveying plants installed by the Link-Belt Engi- neering Company, of Philadelphia, Pa.
A CONVEYOR AND ELEVATOR, BUILT BY THE EXETER MACHINE WORKS, PITTSTON, PA., TJ. S. A.
dock or cars below, as may be required. They will equally well reverse the pro- cess, i. <?., take the bucket from the dock or car, convey it to the vessel and lower and dump the contents into the hold, or take it from any point under the bridge and deliver it at any other point under the bridge.
An example of cable-way conveying plant is given on page 71, which repre- sents a Bleichert installation erected by the Trenton Iron Company, of Trenton, N. J., for the Royal Coal and Coke Company, of Prince, W. Va. The plant serves for carrying coal from the company's mine across the New river
The first ot these shows some conveyors employed in working out culm banks in the anthracite regions of Pennsyl- vania. The culm, containing large quantities of small coal, is carried by the 475-foot conveyor shown, and an inclined conveyor, in turn, carries it to the washery shown at the right of the illustration. The first conveyor is fed at a point about midway of its length by another horizontal conveyor or reloader, which is swung against the base of the culm bank and follows it up as the working proceeds.
The second illustration, on page 73, shows a coal conveyor designed to
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CASSIER'S MAGAZINE.
A BRIDGE TRAMWAY CONVEYOR, BUILT BY THE BROWN HOISTING AND CONVEYING MACHINE CO.,
CLEVELAND, OHIO, U. S. A.
A MOVABLE COAL HOISTING AND CONVEYING APPARATUS, BUILT BY THE SAME C<
MODERN COAL HANDLING MACHINERY.
7i
meet conditions which frequently occur, the coal being received from cars on a siding and delivered into the lantern of the building for further distribution. The third illustration, on page 74,
of 40 feet. Then it is carried along horizontally for about 60 feet, and is finally delivered to a conveyor which, through gates, discharges it into the various bins of the storage house.
A CABLE-WAY CONVEYING PLANT, BUILT BY THE TRENTON IRON CO., TRENTON, N. J., TJ. S. A.
finally represents a plant installed for one of the big railroad companies. The coal, as received in a track hopper from the cars, is fed through a regu- lating gate to the combined elevator and conveyor, and is raised to a height
Delivery to wagons for distribution is effected by gravity through chutes from the hoppered bins of the store house. \ For stocking and reloading