April 12, 1918. THE COLLIERY GUARDIAN. 747 THE POWER BY-PRODUCT PROBLEM.* By T. Roland Wollaston, M.I.Mech.E. Before considering the by-product aspect of the subject, some thoughts upon gas firing as compared with direct firing of coal to boilers may be interesting. The average boiler-house efficiency in electrical stations in the country is probably below 70 per cent. Some engineers reach 75 per cent, with fair consistency, but a series of snap CO2 tests taken at any station from any well-known type of boiler furnace will show that the results very greatly, a sure indication of erratic, and therefore more or less imperfect, combustion. Engineers are generally satisfied with an average of 12 per cent. C(J2. The ideal would be about 19 per cent. In short tests of boilers one frequently sees as much as 82 per cent, or 83 per cent, efficiency recorded. The cause of the failure to maintain this efficiency is that an attempt is made .to effect intricate chemical exchanges in a fuel bed 3 or 4 inches deep, when as many feet are needed to secure reasonable consistency. It is by skilled stoking alone only that these high results are obtained during a test. In other words, it is submitted there is only one way of burning coal to ash efficiently, and that is on the lines of a gas producer. Gas firing has not yet had fair play, in that it has almost always been carried out in boilers specifically designed round coal grates and intended for direct firing. Even in such cases the ease and consistency of management must appeal to every engineer. The writer has conducted tests on Lancashire boilers extending over many days, with producer gas of none too regular quality, and with crude burners. Half- hourly snap gas tests from the side flues have shown consistently :—17 per cent. C02 minimum ; 2 per cent. O maximum; 1 per cent. CO maximum. Only one man was attending to nine boilers. Dr. Bone has shown that 90 per cent, or more gas efficiency can be con- sistently obtained; and efficiencies equal to or approaching this will be readily shown so soon as practical makers seriously tackle the problem of boiler design solely and wholly for gas firing. The essence of the matter is that, in firing with gas, one can maintain substantially perfect chemical combustion. If, then, we take ordinary gas producer efficiency as 70 per cent., we get 0 7 X 0 9 = 63 per cent, over all efficiency for gas firing as against, say, 70 per cent, of the average direct-fired boiler, or, in other words, the combustion of, say, 12 per cent, more coal for the same steam output. The gas producer coal may be physically of poorer and often much cheaper quality. Without attempting to draw a money value com- parison, the following balance of merits may be interesting:— Advantages Credited to Normal Direct Coal Firing.— 12 per cent, lower coal consumption; no capital charges for gas producers, site for same, or mains; no labour on gas plant. Advantages Credited to Non-Recovery Gas Firing.— Reduction in boiler-house space; cleanliness in boiler- house ; elimination of chain grate or like upkeep charges ; reduction in total cost of labour by, say, 50 per cent.; reduction in flue upkeep and cleaning; reduction in coal and ash conveying conveying charges by, say, 40 per cent, due to concentration; more flexible response to peak demands ; possibly cheaper fuel. The gas producer efficiency assumed above is reasonable. Recently published patent specifications and data indicate that more than one inventor is endeavouring, by embodying gas producers as integral parts of steam boilers, to catch the radiant heat of the combustion zones and attain higher efficiency thereby. So far as the writer’s experience goes, the power plant engineers’ grasp of the fuel by-product question is somewhat confused. Those electrical engineers who have contributed papers on the subject and joined in discussions, generally associate it with coke ovens and blast furnaces, rising out of the north east coast enter- prise. Few seem to realise that, when collieries and ironworks substitute electrical transmission for the present uneconomical steam winding, haulage, pumping, compression, etc., there will pro! ably be no surplus gas from these sources for public supply. For purely power supply purposes it seems obvious that by-products, important as they are, must always be secondary to the highest possible yield of B.T.U. convertible into electrical energy from the fuel. . An attempt is made to co-ordinate ideas from this view-point in the brief summary which follows, covering the chief systems of gasifying coal, which is assumed to be of 12,000 B.T.U. value per lb. for comparison. It is believed that the method is original, and, although elementary and superficial, it may assist those who have not studied gasification systems. To be complete, this summary should have included raw fuel, capital, labour, and maintenance costs, site charges and the like, but these, involving intricate reasoning in normal times, are, in present conditions, utterly impracticable for general survey, though they would not be in an analysis of a specific case with all the facts known. In consider- ing these it must be remembered that the chemical and physical nature of the coal available would be important factors as affecting yields of each specific by-product; as examples, low temperature distillation plants would show their best results with high volatile cannel coals, while non-caking high-nitrogen fuels would do best in producers. Then again, the most important, while good clean coal of consistent size and low ash is advantageous for direct firing and distillation, the commonest varieties, indeed, much that has hitherto been relegated to the waste heap, and containing ash up to 35 or 40 per cent, are good producer fuels, providing that they have high nitrogen content leading to a good yield of ammonia. On all these points the engineer must seek the chemist’s and mining engineer’s assist- ance and advice. The gas yield from each system is, for our purposes, translated mto electrical units on the bases (a) That one can obtain an electrical unit from 20,000 B.T.U.; * From a paper read before the Society of Engineers on (5) That the fuel cost chargeable against the electrical unit is one-sixth of a penny. Estimates of Gross Receipts from 1 ton of Coal Consumed. (a) Town’s Gas. (Mr. Woodward.) £ s. d. 12,000 cu. ft. of 500 B.T.U. gas = 300units at id. 0 4 2 10 cwt. of coke .................... „ 15s. 0 7 6 25 lb. of sulphate of ammonia........ „ l|d. 0 3 2 11 gals of good tar ................ „ P3d. 0 12 0 16 0 (6) Coke Ovens. (Mr. Lloyd.) 6,000 cu. ft. of 475 B.T.U. gas = 143 units at ^d. 0 2 0 16 cwt. of blast-furnace coke .......... ,, 20s. 0 16 0 30 lb. of sulphate of ammonia........... „ Hd. 0 3 9 3 gals, of crude benzol ................ „ 9d. 0 2 3 4 gals, of good tar ................... „ P3d. 0 0 5 14 5 c) A Low Temperature Distillation System plus Producers. (Mr. Paton.) 80,000 cu. ft. of 120 B.T.U. gas = 480 units at id. 0 6 8 12 gals, crude oil........................ ,, 4d. 0 4 0 2 gals, benzol........................... „ Is. 0 2 0 70 lb. of sulphate of ammonia ........... „ lid. 0 8 9 1 1 5 (d) Mond Producer System. (Power Gas Corporation Ltd.) 127,000 cu. ft. of 120 B.T U. gas = 871 units at id. 0 12 1 74 lb. sulphate of ammonia................. „ l|d. 0 9 3 7 gals, of poor tar ..................... „ id. 0 0 7 1 1 11 (e) Proposed Improved Mond Plant. (The Author). 156,800 cu.ft. of 120 B.T.U. gas = 1,078 units at id. 0 14 11 90 lb. of sulphate of ammonia ........... ,, l|d. 0 11 3 1 gal. crude benzol ....................... 9d. 0 0 9 4 gals, crude oil........................ ,, 3d. 0 10 1 7 11 (f) Direct Firing to Boilers. 1,344 units at id. 0 18 8 The low temperature distillation figures (c) are averaged from data of schemes under preparation for a combination of Tozer retorts with coke gas producers, and are provided by Mr. J. Drummond Paton, of Man- chester. The Tozer retort is of cast iron, in the form of a narrow annulus, for the fuel, heated as regards both outer and inner walls, so that the fuel is equally coked throughout its mass, and working under considerable vacuum. The gases, containing the volatile products and some ammonia, are condensed for their products as listed, and the coked or semi-coked fuel is dropped directly into the gas producer, where, in yielding producer gas and the balance of ammonia, it is burnt to ash. In the Mond process, operating at an electrical station, some 18 per cent, of the total fuel would be required to generate blast steam ; and the Moore recovery producer is an effort to eliminate this economic shortcoming by surrounding the upper part of the producer with a water jacket so as to generate, by the waste heat of out- going gas, a substantial portion of the blast steam necessary for ammonia recovery equal to Mond. By making the producer oval instead of circular, and thus reducing the thickness of the mass of fuel therein, the hot-zone temperature is also reduced by direct radiation. The author has made an attempt to carry this vital improvement a step further. A circular producer is proposed surrounded by an annular jacket or boiler. Centrally within the producer is a hollow core through which the air blast is introduced from below. This core, traversing the hottest fuel zones, becomes very hot, and steam from the jacket-boiler, together with atomised hot water, is forcibly introduced at the top, where it flashes into steam and mingles with the already super- heated air blast on its way to the grate. Heat is thus abstracted radially both inwards and outwards from the narrow annular fuel bed, and it is believed the effect of the Mond plant (so far as good ammonia yield is concerned) will be secured without any steam being borrowed from outside sources. This design aims at still further practical objects, for example, the utilisa- tion of almost any fuel, with separate recovery of a portion of the volatile products, and a rich producer gas, but it might savour of personal advertisement to intrude these details upon you, and, as results have still to be demonstrated on a working scale, it is clearly undesirable to do so. Considered purely from the view point of cheap elec- tricity generation, those gas systems which show the highest yield in thermal energy are the most promising, namely, of types (d) and (e). The Mond system showed wonderful results at many places 10 or 15 years ago, when common slack could be purchased at 5s. or 6s. per ton. It is highly probable that some users then obtained power for less than nothing, the sales of sulphate of ammonia exceeding in value the aggregate cost of fuel, labour, maintenance, and capital charges. Perhaps the most important economic phase of the whole problem is the compulsion of coal owners to bring to the surface the enormous residues hitherto left underground and wasted, since coal hitherto regarded as undesirable for boiler firing may be absolutely the best for one or other of the by-product processes; and it is largely on this point that future success or failure depends. Conclusions. Under certain condions, mainly those of utilisation of cheap inferior coal, demand for nitrogen products, and high load factor, the installation of producer recovery gas plant as an integral portion of large electricity generating stations offers promise of large rebates on current cost and important conveniences in handling and maintenance. This particularly applies when large quantities of electricity are needed in nitrogen fixation, electrolytic, or metallurgical understakings. In connection with low temperature distillation systems for fuels rich in volatile products, and in coke oven plants, blast furnace installations and the like producing surplus gas, electrical generating stations capable of using this surplus gas to the utmost, and acting as feeder stations to a larger system, should be put down; but, as in plants of these types the gas is really a minor by-product, these are suitable for consideration only as incidental to a large electricity scheme. In view of the increasing use of electricity and the incandescent system of gas lighting for domestic light- ing, the extended use of gas for domestic cooking and heating, and the slow progress of electricity in these last services, the steady conversion of “ town’s ” gas systems for higher yields of by-products and for distribution of larger volumes of low-grade heating gas is desirable. Having in view the aforementioned possibilities of gas recovery systems in relation to the generation of cheap electricity and the proper use of coal, existing electrical stations provide excellent opportunities for trial and demonstration. The assumed- demand for semi-coke or like smokeless fuel for domestic purposes is problematical. In any system involving distribution of coke or semi- coke for electrical generation the loss of sensible heat entailed between discharge from retorts and shipment is sufficiently importamt to be regarded. Against this, the distribution of “ low grade heat,” provides an attractive idea for consideration as an argument in favour of smaller local stations. THE AMERICAN COAL TRADE. The demand for coal continues to exceed the supply in virtually all grades (says the Coal Age, March 16). A slight improvement is evident in the production of bituminous coal—an improvement which can be traced directly to a better supply of cars at the mines. A large number of locomotives that were being built for the Russian Government were purchased for use on the various roads in the Pennsylvania coal-mining region, and many of them are now in service. It can safely be asserted that with this increase in motive power and a better supply of cars, the bituminous mines will soon be producing enough soft coal to meet the country’s needs. As regards anthracite coal, the situation is not so favourable. The production of hard coal has about reached its zenith, and it is doubtful if the 77,000,000 tons mined in 1917 will be approximated this year, much less bettered. Indications point to a heavy contract demand. The trade is fixing no prices in contracts. Agreements are being made which simply state that a certain number of tons of a certain kind of coal will be furnished, subject to existing and future Government regulations, and to whatever other contingencies may arise to affect either the price or the supply. The trade is gratified at the decision made by the Government to expend vast sums in the purchase of increased motive power for all the coal roads. Boston reports state that there is less anxiety regarding current needs. The railroads are still worrying along on an extremely close basis. All the industrials, too, are working on small coal reserves, but all will admit less apprehension over the near future. Under present conditions distribution is bound to be uneven. Loading despatch at Hampton Roads has slackened enough so that two or three days is the best that cargo ships can rely upon. The plan of making a flat reduction of 30c. a ton on domestic sizes of anthracite to remain effective, from April 1 to September 1, seems to meet with the approval of most interests. Much time and thought are being given by the various shippers as to the distribu- tion during the coming coal year. All figures are based on purchases of the past two years. The Philadelphia authorities continue to wage the campaign against dirty coal, and this week condemned several shipments that had been dumped in the yards of retailers. Operators are interested to see how the inspection system of the Fuel Administration will work out. Undoubtedly the district representatives of the Fuel Administration can find many men willing, or even anxious, to act as inspectors, but it is pointed out that the test of the inspector’s ability is not clearly defined. All the operators express themselves as favourable to the elimination of slate and other refuse matter as a material to be carried by the railroads under the guise of “ coal,” as its elimination would increase the real capacity of the railroads; but none of the operators is willing individually to plead guilty to the charge of shipping 9 per cent, waste matter with his coal. The fact that inspection is at least a possibility may have a good moral influence at the mines. Connellsville coke market on the whole continues quiet, with only occasional sales of small lots. So far as known, all transactions are at the set prices: — Furnace, 6 dols. ; foundry, 72 hr. selected, 7 dols.; crushed, over 1 in., 7*30 dols., per net ton at ovens. Peat Supplies for Power.—The Dublin Local Section of the Institution of Electrical Engineers recently considered the report of the Coal Conservation Sub-Committee on Electric Power Supply, in so far as it affects Ireland. Mr. G. Marshall Harris, manager of the Dublin United (Electric) Tramways, expressed doubt as to ability to raise Irish coal to compete with supplies from England, but he thought their peat would be nearly as good and cheap as coal for power production. Mr. J. P. Tierney said that one of the difficulties was the cost of acquiring rights to -work the peat deposits, and he suggested the Belgian method, by which the State fixed prices and advanced capital to public companies. Mr. L. J. Kettle said that before anything was done there should be a national survey of the power resources of the country. Squatters Acquiring Canadian Coal Rights.—A formal petition has recently been lodged with the Dominion Government on behalf of Canadian Collieries (Dunsmuir) Limited, to “ disallow ” the Vancouver Island Settlers’ Act (1917). The question concerns the validity of a land title granted by the Dominion Government. This title now belongs to the Canadian Collieries (Dunsmuir), but the Act enables squatters to acquire on their own account a title to the under-surface rights in coal or other minerals, in addition to the surface rights reserved to them. Appli- cations under the Act have now been filed by such squatters, covering 33,000 acres, and the effect obviously is to block the colliery’s development and thus deprive it of a large part of the security on which, as lately as 1910, some £3,000,000 of British money was invested in this undertaking.