"FUEL RESOURCES OF THE WORLD Before considering in detail some of the fuel problems of the immediate future, it may be well to pass in review the fuel position of the world in 1921, as it was disclosed by the most recent figures of production.
Coal and Lignite. - According to the estimate of the United States Geological Survey in 1920 the total world output of coal, including 143 million tons of brown coal and lignite, amounted to 1,300 million metric tons (see Coal). This is within 3% of the maximum output, which was reached in 1913 and 1918. Of this total output, the United States produced 45%, Great Britain and the British Empire 2 2%, Germany 19%, while other countries ranged from 21% downwards. One of the most significant features of this survey is the remarkably rapid development in the winning and use of brown coal and lignite on the continent of Europe and particularly in Germany. The output of brown coal and lignite in Germany in 1919 had reached 93.8 million tons, but this was overtopped in 1920 by an output of III6 million tons, out of a total output of 140.7 million tons on the continent of Europe that year. The output of ordinary coal in Germany for 1920 was 140.8 million tons.
The brown coal industry in Germany is of old standing, and its rapid development in recent years is based on sound knowledge and experience. Though in its natural state a less concentrated fuel than bituminous or anthracitic coal, brown coal has many points in its favour. The chief of these is the low cost at which it can be won as compared with ordinary coal. Where extensive deposits of great thickness occur, these can be worked opencast and excavated by machinery. The winning of brown coal is thus on an altogether different basis from ordinary coalmining with its deep and costly underground roads and workings which involve heavy costs for timbering, pumping and ventilation. The manual labour required is much smaller in amount for a given output, and is of a less highly specialized type, while the special dangers and uncertainties of coal-mining are practically absent. The capital charges, being mainly on surface roads and on excavating machinery, are relatively light as compared with the heavy initial and permanent charges involved in the sinking and equipment of shaft or mines. Brown coal, though it contains from 40 to 60% of water, is to-day by far the cheapest source of thermal units. Its further manufacture by drying, briquetting and carbonization can be carried out close to the point of excavation and under conditions favourable to production on a large scale, and therefore at a low cost. The glowing accounts of this development which appeared in the technical press during 1919-21 may have been somewhat exaggerated; but the solid fact remains that in 1920, with a production of III million tons of lignite in addition to ordinary coal, Germany had already faced the fuel problem of the future so far as she herself was concerned. According to the extent to which Germany could meet her own requirements for heat and power by the development of lignite, peat and water-power, the output of her coalmines would be set free for export.
It is not surprising that Germany's example has been followed, not only in Central Europe, but in Victoria (Australia) and in Canada. In Victoria extensive deposits of brown coal exist in Central Gippsland, which are estimated by Mr. H. Herman, the Director of Geological Survey, to contain 30 thousand million tons. The main deposits near Morwell are hundreds of feet in thickness, and lend themselves admirably to opencast working on an enormous scale. Considerable progress has already been made in the development of these deposits; and since the commencement of operations in 1916, 400,000 tons of brown coal had been mined and sold by 1921. When the excavating methods become more perfectly organized, it is expected that the coal will be produced at the mines at 2S. 3d. per ton. It contains from 40 to 50% of water, so that in heat value two tons is equal to about one ton of ordinary coal. A 50,000-kilowatt generating station was in 1921 being installed at Morwell for the transmission of current to Melbourne. It was intended to establish a plant at the mines for briquetting and carbonizing, so that fuels of higher availability might be produced from the raw coal. In 1920 a sample of this coal was received in England, and experiments on its carbonization were carried out at the Government Fuel Research Station. In the Dominion of Canada experiments were in progress in 1921 on the briquetting and carbonization of the brown coals of Manitoba and Saskatchewan. These experiments were being carried out under the auspices of the Dominion and of the Province of Saskatchewan.
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Of oil (see Petroleum), next to coal the chief natural source of fuel, the world's output for 1920 was about 97 million tons, of which the United States produced 64.8%, Mexico 23.3, Russia 3.5, the Dutch East Indies 2.5, India I2, Rumania 1 I, and Persia 1-o. The oil output amounted to 7% of the fuel output of the world, reckoned in tons. If reckoned in potential therms, the figure would be raised to io per cent. As the United States has extensive oil interests in Mexico, it may be taken that in 1920 she controlled 75 to 80% of the total output of the world. It is therefore significant that, in official quarters, grave anxiety has been expressed as to the probable exhaustion of these resources in view of the rapid development in the use of motor spirit for road transport and of fuel oil for transport by sea. The following extract from a statement by Mr.
J. O. Lewis, Chief Petroleum Technologist to the United States Bureau of Mines, expresses clearly the American view: " The United States Geological Survey during 1910-20 has made several estimates of the quantity of oil left in our oil fields. The most recent estimate, that of David White, indicates that about 40 of the oil had been brought to the surface, and that the 60% remaining underground would last barely 20 years at the present rate of consumption. As the period in which an oil field can be made to yield its oil is not wholly within the control of man, the domestic production will undoubtedly be spread over a much longer period than estimated; but, on the other hand, the peak of production will be passed long before 20 years, and thereafter production will be at a declining rate. Of course, such estimates are by no means infallible, as many obscure factors are involved. However, this statement represents the opinion of the agency best qualified to make such an estimate, and is indicative of a condition which, were there no other solution to the problem, would be highly unsatisfactory, and would be viewed by the automotive industry with the greatest concern. For, even were the estimate unduly pessimistic, and the actual reserve double, the condition would be unsatisfactory.
" The preceding statement refers only to the oil from oil wells in the United States. Fortunately there are enormous undeveloped resources in the rest of the world. The petroleum resources of this country have been developed and depleted in a ratio far beyond that of other countries, so that although we are producing to-day twothirds of the world's production, the opportunities elsewhere for increasing production are much greater than in the United States. Geologists and those well-informed on foreign resources believe that in all probability the world contains enormous reserves of oil that can be obtained upon demand. Although to obtain oil from these reserves may not be as satisfactory as to obtain it within the confines of the United States, the outlook tends to assure the future of the internal combustion engine.
" Fortunately oil may be obtained from other sources than oil fields. In various parts of the United States, particularly in Colorado, Wyoming and Utah, are enormous bodies of oil shales from which oil may be obtained by destructive distillation, as benzol is obtained from coal. The United States Geological Survey has estimated the quantity of oil locked up in the richer shales of the three States mentioned as perhaps ten times the amount of the oil reserve in the oil fields. In Scotland the retorting of oil from oil shales has been on a commercial basis for more than 50 years, and antedates the oil industry in the United States. Commercial and semi-commercial experiments are being made in order to determine whether the oil shales of the Western States can be mined and retorted profitably in competition with petroleum from oil fields. This problem has not yet been solved, but these shales constitute a latent reserve that protects the future needs of the country for motor fuel as far as these needs can be foreseen. However, oil cannot be obtained from the shales on a large scale without heavy investments and the development of the industry must be spread over many years. Also, when the time comes, the consumer will probably have to pay more for his gasoline." The oil shales not only of the United States, but of the whole world, await development as a source of oil fuel. The commercial possibilities of this development depend almost entirely on the relative cost of production and the selling price of natural oil and shale oil. In comparing the cost of production of natural oil from wells and of oil produced by distillation from shale, long experience has shown that in any field which is considered worthy of commercial development the cost of the oil at the wells should not exceed one penny per gallon, or 25s. per ton. In favourable cases it is only a fraction of this amount. In the shale field the shale has to be mined and transported to the retorts in which it is distilled, and the earthy residue, which amounts to from 15 to 17 cwt. for each ton distilled, has to be handled and disposed of. Labour and fuel have to be supplied for the retorting process and the retorts have to be kept in repair. With selected shales a yield of 30 to 40 gal. of crude oil per ton of shale may be obtained. The mining and retorting costs will amount to at least ios. per ton, without capital and general charges, or 3d. per gallon for the crude oil as compared with the above figure of one penny per gallon at the wells. It is clear that the initial cost of crude oil obtained from shale puts it quite out of court in competition with natural oil, except in situations so far from oil wells that the extra cost is compensated for by that of transport of natural oil. It is clear that, in times of plenty, the natural oil can, if necessary, be sold at a price of one penny per gallon, which will at least pay the cost of production; the shale oil works on the other hand would have to sell at a loss, or to shut down and disband the large staff of skilled workers required for the prosecution of the industry.
The history of the oil industry during the period 1870-1920 shows a succession of waves of over-production and low selling prices, as new oil fields have been developed. The effect of these periods of plenty and of low prices has on the whole been to develop consumption of oil as a fuel; but their effect on the shale industry of Scotland has been to make the profitable running of the industry so speculative that it has never been possible to develop it on a really large scale, though ample supplies of shale are known to exist there. With natural oil, cost of production per se has very little to do with the fixing of the selling price, but with shale oil cost of production is the vital consideration. The best hope for the development of the shale-oil resources of the world appears to depend on a continuance of the interest recently shown in the United States in this question as being of vital importance to the industrial welfare of that country. Great natural resources in oil shales have been proved to exist; it only remains to develop systems of mining and retorting on the best modern lines, by which shale oil can be placed on the market at a minimum cost.
Though in the opinion of experts in Great Britain this can never approach the actual cost of production of natural oils in existing fields, shale is thereby not necessarily excluded as one of the more important sources of oil fuel. First cost is only one among the conditions which will determine this development.
The production of oil by the carbonization of bituminous coal is also receiving much attention in the United States, as well as in Great Britain and Germany. This problem involves economic questions which do notarise in connexion with oil shales. Chief among these is the fact that, while in the distillation of shale about 70% of the shale distilled is a valueless earthy residue, 60 to 70% of the bituminous coal is retained after carbonization as a smokeless fuel of a higher value for domestic purposes than the original coal.
The scarcity of fuel in the United Kingdom during the World War led to considerable pressure upon the British Government for the establishment of a serious inquiry into the possible development of peat. The matter was considered by the Advisory Council of the Department of Scientific and Industrial Research, resulting in the institution of the Fuel Research Board, by whom an Irish Peat Inquiry Committee was appointed. The history of this inquiry has been dealt with in the published reports of the Fuel Research Board.' As the subject was recognized as one of world-wide importance, Prof. Pierce Purcell was appointed Peat Investigation Officer to the Fuel Research Board in 1919, and through him close touch was maintained with the principal peat developments in Europe and America. In the summer of 1920 Prof. Purcell visited Canada and the United States, and investigated the work of the Peat Committee of the Canadian Government at the Alfred Bog, near Ottawa. In the following summer he visited some of the more important peat stations in Germany, Denmark and Sweden.
In Germany the Wiesmoor peat station has been in operation since 1910. The peat is dredged, macerated and spread on the surface of the bog to dry. By stacking under cover, the moisture of the peat blocks can be reduced to 25% solely by air-drying. For steam-raising purposes two tons of air-dried peat are equal to about one ton of coal. At Wiesmoor eight water-tube boilers are fired with peat. The average fuel consumption is stated to be from 2.7 to 3 kilos of partially dried peat sods per kilowatt hour, and the cost of the peat is taken at five marks per ton. A scheme was stated to be on foot for the establishment of a line of peat generating stations from Konigsberg on the east to Wiesmoor. The promoters of this scheme appear to have ignored the fundamental difficulty which applies to the winning of peat in quantities sufficient to meet the day-by-day requirements of any large central station. When it is realized that the peat deposit in a good bog 20 ft. deep is only the equivalent of a 12 or r4-in. seam of coal, it will be evident that even an output of 1,000 tons a day of air-dried peat involves the laying out and development of an enormous surface. At the Zehlonbruck station, near Konigsberg, it was proposed to use 920,000 tons per annum, or about 2,500 tons per day. Prof. Purcell states that to win mechanically 900,000 tons of air-dried peat in one season at least 4,500 men, women and children would be required, and the area over which the spreading and drying operations would extend could not be less than 9,000 ac., or say 15 sq. miles. He suggests that, in dealing with any production over 60,000 to 80,000 tons per annum from any single district, the difficulty would increase as the square of the production; and he considers that it is only by the development of these smaller units that progress will be made. There was evidence in 1921 that a steady development on these lines was in progress in Germany.
In Canada and in Ireland the application to local conditions of mechanical cutting or dredging, maceration, air-drying and harvesting has been studied with encouraging results. In the summer of 1920 peat was cut, macerated, spread on the bog at Turraun in Ireland, air-dried and harvested there, and a hundred tons of this air-dried peat were sent to H.M. Fuel Research 1 Reports of the Fuel Research Board for the years 1918-9, and on the winning, preparation and use of peat in Ireland; reports and documents.
Station, where some interesting experiments were carried out on its use for boiler firing and for carbonization. The peat, when it reached the station, contained about 27% of moisture. After having been kept under cover for some months the moisture was reduced to about 17 per cent. This peat is in the form of hard blocks of various lengths, up to about 10 in. with a cross section of something like 2 by 2 inches. Its density is rather under 1, or about twice that of the ordinary hand-cut sods made on the same bog. The blocks can be cut and sawn like hard wood, and they stand transport with very little breaking up into " smalls." In this respect they contrast very favourably with the ordinary hand-cut sods, which break down seriously in transport by rail or road. Steam-raising trials have shown that this material is an excellent boiler fuel, and that it lends itself admirably to carbonization, either in vertical retorts at temperatures between 750° and 850°C. or in steel retorts at 550° to 60o C.
It is evident that maceration of the freshly cut or dredged peat is well worth the small expenditure of power which it entails. When spread on the surface of the bog it dries much more quickly than ordinary cut peat, while in drying a shrinkage occurs which almost doubles the density of the dried product and so produces a fuel which can be stored, transported and used under much more favourable conditions than the ordinary air-dried sods.
In view of the threatened shortage of petrol in England in 1918, Mr. Walter Long appointed a committee to consider the possibilities of alcohol as a motor fuel (see Alcohol). The report of this committee was considered by the Privy Council Committee for Scientific and Industrial Research, and it was recommended that the Fuel Research Board should be charged with the duty of investigating the technical and economic problems which are involved. As a first step to this end Sir Frederick Nathan was appointed Power Alcohol Investigation Officer. A preliminary survey was published in July 1920.' For the complete replacement of imported petrol by alcohol it was estimated that 250 million gallons of 95% alcohol would be required. To produce this from grain (barley), potatoes or mangolds, the following quantities would be necessary: - Investigations as to the possibilities of producing alcohol in the British Empire overseas indicate that, in the sugar-growing countries, molasses, from which alcohol might be obtained, is undoubtedly wasted, but that the wasted quantities are comparatively small, and in most cases would be insufficient, if so utilized, to meet even local requirements for alcohol. Alcohol might be made from suitable crops grown specially for the purpose in those British dominions and colonies where labour is available, and used to supplement or take the place of supplies from other sources. Some such course may be specially desirable where petrol is dear and difficult to obtain, for instance in the E. African protectorates and W. African colonies, which are very dependent on motor transport for their development.
The use of cellulosic materials was not yet possible in 1921, because although research work was in hand to find a process that could be employed on a commercial scale in those regions where such materials exist in sufficient abundance, it had not so far led to any definite results. Where, however, materials capable of easy hydrolysis exist, as for instance is the case with waste rice straw, the large-scale experiments in Burma, under the auspices of the Burma Oil Co., appear to indicate that the joint production of alcohol and paper should be a commercial possibility.
Until alcohol can be made from waste materials which can be collected and treated at small cost, it does not seem likely that British Empire-produced alcohol can be imported into the United Kingdom on any considerable scale; it is improbable that it will be produced cheaply enough, or in sufficient quantities, for export, even by those overseas portions of the Empire which may produce it in this way for local consumption.
f s. d.
Grain (barley). .
21 4 0
8 10 6
I 10 0
Uses Of Coal As Fuel Since coal is likely to remain the chief source of fuel for the world at large, the problems of its winning, preparation and use still occupy the foreground in all serious consideration of the subject. We know that in 1913 the output of coal of the mines of the United Kingdom was approximately 287 million tons, of which 98 million tons were exported. Out of the 189 million tons These figures were not encouraging, and generally it may be stated that the production of alcohol in any considerable quantities from vegetable materials grown in the United Kingdom is not economically possible, owing to (1) insufficient acreage; (2) the high cost of cultivation and harvesting; (3) the high cost of manufacture; and (4) the fact that the most suitable raw materials are also important food-stuffs. There was for these reasons no prospect in England of replacing any considerable quantity of petrol by home-produced alcohol. Moreover, it was unthinkable that land, for even a fraction of the quantity of the raw materials in the foregoing table, could be used for such a purpose when, for food itself, a week-end supply only was assured from the home production. It was, however, considered desirable to make a further study of the growth of mangolds and of Jerusalem artichokes for this purpose, and experiments were in progress during 1919-21. From these it appeared that it might be possible to grow artichokes for the supply of a limited quantity of alcohol for special purposes, such as aviation. An examination of the artichoke stems indicated that it might be possible to convert them by a simple treatment to paper pulp. Should this prove to be the case, both products would be cheapened.
" Fuel for Motor Transport ": an Interim Memorandum by the Fuel Research Board.
Iron and Steel
Other Metals. .
Brickwork, Potteries, Glass and Chemicals
Directly burnt as coal. .
One-third of the total used by gas undertakings .
One-half of the total used by electrical undertakings
consumed at home, 35 million tons represented the domestic use, and the remainder was taken for industries as follows: The uses of coal as fuel may be classed under three main heads: - (i) production of heat and light for domestic purposes; (2) production of heat for industrial purposes; (3) production of power for industrial purposes and for transport. Reclassifying the above figures under these three heads, we find that the consumption was as follows: (1.) Heat and Light for domestic purposes. Heat for industrial purposes. Iron, steel and other metals. .
Bricks, pottery, glass, cements Paper, textiles, food-stuffs, fertilizers, chemicals, as steam (3 .) Power for transport and industrial purposes. Railways and coasting steamers .
Coal used in the raw state. Domestic heating. .
Steam raising for heat .
Steam raising for power Transport, railways, steamers.. Brickworks, potteries, cement, glass, chemicals, soap, etc.. .. .
Coal carbonized and gasified. Gas undertakings. .
Iron, steel and other metals .
189 These figures show that 141 million tons, or three-fourths of the coal used in the United Kingdom, was burned in the raw state; that 35 million tons, or nearly one-fifth of the total consumption was used in the raw state for domestic heating; and that 97 million tons, or one-half of the total consumption was used in the raw state for steam raising. Before considering the technical and economic problems which are involved in the replacement of raw coal as a fuel by the products of its carbonization, gas, petrol, oils and coke, we shall review the position of these great outlets for raw coal, domestic heating and steam raising.
The domestic use of coal in the raw state affects the widest range of consumers in most civilized communities. In Great Britain the consumption per head of the population is in the neighbourhood of one ton per annum. In Ireland peat is still the chief domestic fuel, about six million tons of airdried peat being consumed per annum. In no other country but Great Britain does the consumption of raw coal for domestic purposes reach the high figure of one ton per head per annum. The ample supplies and the low price of bituminous coal for centuries prior to the World War have established the open room fire and the kitchen range on a popular foundation in Great Britain from which it is difficult to displace them. The British climate has had much to do with the popularity of the open room fire, the radiation from which can be so readily modified to meet the rapid changes of humidity and temperature which are liable to occur almost from day to day during the year. Only during exceptional winters, when really low temperatures have continued for weeks at a time, has the open fire broken down as a means of maintaining English homes at a habitable temperature. The work of Dr. Margaret Fishenden on open fires has definitely shown that, under reasonable conditions of firing, 20% of the total potential heat of the raw coal is radiated into the room, and that a further 20 to 30% is given up to the fabric of the building before the waste products of combustion leave the chimney. Smoke and soot are, however, an unduly heavy price to pay for the transient cheerfulness of the flaming coals in a well-stoked fire, especially when we remember that over long periods the ordinary fire is only smouldering and dreary-looking. The coalfired kitchen range, unlike the open room fire, has few if any sentimental associations and its replacement by gas-cookers and coke-fired water-heaters is only a matter of time.
In northern and central Europe, and in the United States and Canada, where really low winter temperatures prevail, close stoves and central heating systems are universally used, and the smoky combustion of bituminous coals has never gained a footing. In the United States and Canada anthracitic coals for domestic purposes are regarded as a necessity, and the Governments of these countries give every encouragement to schemes for the conversion of bituminous coals into smokeless fuel so as to avoid the transport from great distances of anthracitic coals. On the social side of civilization it is no exaggeration to say that the cheap and plentiful supplies of bituminous coal in Great Britain have not been an unmixed blessing. Even on the industrial side this is true, for it has led to the formation of habits of reckless extravagance in the use of fuel, which are so deeply rooted among workmen and manufacturers that it will take many years of high fuel prices to eradicate them. The gas undertakings of the United Kingdom have, however, done much to popularize the use of gas and coke for the replacement of raw coal for domestic use; and there is every prospect that a considerable proportion of the raw coal burned for domestic use will be displaced by the developments in the production of town gas on newer and more economical lines, and by the increased use of gas-works coke for domestic heating.
The fact that one-half of the coal used in Great Britain is consumed in raising steam for heating purposes and for power production, places the problems of fuel efficiency in this connexion in the forefront from an economic point of view. On the theoretical side these problems lend themselves to simple and direct treatment.
Steam-boiler efficiency depends first on the perfect combustion of the fuel, second on the utilization of the radiant heat of combustion, and third on the utilization of the sensible heat of the gaseous products of combustion before they are dismissed to the chimney. The heat for the conversion of water into steam has to pass through steel plates or tubes, and the rate at which this transference takes place is determined by the different temperature of the two sides of the plate or tube. The lower the temperature on the water side and the higher the temperature on the furnace side, the greater will be the amount of heat which is passed into the water, and the higher will be the evaporative efficiency of that portion of the boiler. Direct radiation from the burning fuel is by far the most effective means of maintaining the temperature on the furnace side of the plates and therefore of obtaining the highest evaporative efficiency per sq. ft. of metal surface. On the water side of the plate or tube the temperature can be kept down only by the maintenance of a very rapid circulation of the water over the metal surface. With adequate water circulation sufficient heat for the evaporation of 60 to 80 lb. of water per sq. ft. per hour can be safely passed through the metal. With inadequate circulation the metal may be raised to a destructive temperature, and the boiler may be ruined. In the ideal boiler the maximum proportion of the radiant heat of combustion ought to be absorbed by metal surfaces provided with ample water circulation on their inner side. The utilization of the sensible heat of the products of combustion involves the transfer of the heat of the gases to the metal by convection; the molecules of gas must actually come in contact with the metal surface. Rapid circulation is required in order to obtain this, and high velocity of the gases must be maintained. The work of Nicholson on this subject has received considerable attention during recent years and has to some extent been applied to boiler design. The importance of the direct absorption of the radiant heat of combustion is not as yet so generally recognized, but is likely to lead to important results in boiler design. The theoretical knowledge as to the utilization of the heat of combustion in boilers is still somewhat in advance of even the best engineering practice in steam-boiler construction. Unfortunately average practice still lags far behind the best knowledge on the subject.
Coal as ordinarily burned suffers from the disadvantage that it is not a homogeneous fuel like gas, oil or coke, but is in effect a mixture of these three forms of fuel. The only way in which coal can be made to approximate to a homogeneous fuel is by pulverizing it so that its particles are so fine that, when mixed with air, they at once ignite and burn like a jet of gas or a spray of oil. The degree of fineness required to produce this effect involves grinding till 80% of the coal will pass through a screen of 200 meshes to the square inch. For metallurgical and other high temperature purposes the advantages which result from pulverization may more than compensate for the cost of grinding and for the heavy initial cost of the grinding and distribution plant, but for steam raising it is still an open question whether the gain in the efficiency of combustion is sufficient to compensate for the greatly increased cost which is involved. In the best steam Million Tons 32 6 20 58 17 18 52 87 Million Tons 35 20 60 17 9 141 18 3 o 48 raising practice the disadvantage due to the non-homogeneity of raw coal as a fuel has been met by the design and working of the boilers, while by the use of automatic stoking and ash removal, the boiler house charges under these heads have been greatly reduced. In comparing the best practice on these lines with the most recent experiences in connexion with pulverized fuel in America it is still doubtful whether the latter can be justified on the score of expense.
The valuable papers of Mr. D. Brownlie 1 throw a much needed light upon the use of coal for steam raising. His analysis of the statistics which he has collected shows that the amount of coal used for steam generation in Great Britain for heat and power production is from 75 to too million tons per annum, or about one-half of the whole coal consumption. His conclusions as to the comparative efficiency of the numerous boiler plants he personally examined during seven or eight years, and the extension of these conclusions to cover the whole steam-raising practice of the United Kingdom, supply material on which some broad generalizations may be based. He divides the boiler installations of the United Kingdom into three classes - bad, average and highly efficient. Of the total number he classes: io % as bad, 85% as average and 5% as highly efficient. As regards the efficiencies of each class, with water-tube boilers the bad give 61%, the average give 69%, and the highly efficient give 82%, while with Lancashire boilers the bad give 49%, the average give 60% and the highly efficient give 79%.
If we take the minimum figure of 75 million tons as the amount of coal annually used for steam raising in Great Britain, it is clear that the scope for economy is enormous; for even a moderate increase of efficiency of io% over all would result in a saving of 72 million tons per annum. Mr. Brownlie's own experience of the savings to be effected by a reorganization of plants leads him to take a much higher saving as a possibility. In the case of the colliery steam boiler plants, the average efficiency of which he places at 51%, he estimates that the coal bill for all the British colliery plants is 182 million tons, and that the efficiency might easily be raised by io to 15%, while by the systematic use of colliery waste a further saving of salable coal would be realized. These facts and figures are well worth careful study of all who are seriously interested in fuel economy. They show the enormous possibilities existing for fuel economy, apart from any new revolutionary discoveries.
Before we leave the subject of steam raising, the use of gas, oil and coke for this purpose may be referred to.
A considerable amount of experience has been accumulated on the use of gas for steam raising. This experience covers a wide range of gases from blast-furnace gas of about too B.Th.U. per cub. ft. to coke-oven gas of over 500 B.Th.U. With the lowest grade gas the thermal efficiency in ordinary practice has generally been of a low order, but with proper care in boiler setting and firing there is no reason why a thermal efficiency of 80% should not be reached, even with low grade gas. The evaporative efficiency per sq. ft. of heating surface however is low, and in ordinary blast-furnace practice it is found that when coal-firing is replaced by gas, a larger number of boilers is required for the evaporation of the same amount of water.
With coke-oven gas there is no reason why the highest thermal efficiency - as well as a high evaporation efficiency per sq. ft. of heating surface - should not be obtained. From an economic point of view, however, the use of high-grade gas for steam raising can only be justified when it is a waste product for which there is no other outlet. As fuel for steam raising, the availability of the therms in coke-oven gas is only from to to 15% higher than that of the therms in the form of raw coal, or, with coal at 25s. per ton, about t 2d. per therm; but for distribution as town gas its value is from 2.5d. to 3d. per therm, while for use in internal combustion engines its value would be at least as high. For a possible gain in thermal efficiency of from to to 15%, it will obviously not pay to produce gas as a fuel for steam raising, except under very special conditions.
As fuel for land boilers, oil is definitely superior to coal in many respects. Chief among these are the ease with which it can be transported, stored and handled, its flexibility as a fuel, and the high efficiency with which it can be burned. These advantages would probably justify a price of 50 to too % higher than that of coal. As fuel for the ships of the navy, all the above advantages 1 Engineering, July 12 and 19 1918; July 25 and Aug. I 1919; Dec. to and 17 1920.
Percentage of total
Sail power only .
Oil etc. in internal combustion engines
Oil fuel for boilers .
over coal are emphasized, and in addition to these are the greatly enlarged range of action and the possibility of oil bunkering while at sea. As fuel for the ships of the mercantile marine its advantages are now so fully recognized that the only limits to its extended use are the uncertainty as to future supplies and as to its price. In 1914 there were on Lloyd's Register 364 steamers of 1,310,000 tons fitted for burning oil fuel, whereas in 1921 the total was 2,536 vessels of 12,797,000 tons. The following comparison shows the division of motor-power in the two years: - It will be seen that only 72% of the tonnage of the British merchant marine in 1921 required coal, while in 1914 the figure was 89%.
Much useful work has in recent years been done by the London Coke Committee on the use of coke and coke breeze for steam raising. This has led to the development of the " Sandwich " system of firing with a mixture of coke and bituminous slack. This system, which is in operation in London, Manchester and elsewhere, consists of feeding from a divided hopper on to the chain-grate stoker, coal slack and coke in superimposed layers, the coal being uppermost. With a natural draught of only 25 in. the coke layer may be from 5 to 6 in. in thickness. This layer prevents the percolation and consequent loss of coal dust through the grate. The coke layer being relatively porous permits the passage of air required for the combustion of the coal under favourable conditions, so that little or no smoke is produced. When coke alone is used on a chain grate it is difficult to maintain a sufficiently high temperature to ensure its ignition near the front of the grate. Under the Sandwich system the ignition temperature is maintained well to the front of the grate by the flame produced from the layer of slack. Each fuel therefore helps the more efficient combustion of the other. When coke is used by itself for steam raising, special provision has to be made to secure that its ignition takes place as near the front of the grate as possible. If this is secure, advantage can be taken of the high radiating efficiency of the bed of incandescent coke by the provision of ample water-cooled surfaces for the direct absorption of the radiant heat.
Direct combustion of coal is likely to maintain a leading place in steam raising for many years to come; and there is no direction in which the scope for increased economy and efficiency is so obvious and so extensive. By the closer association of steam electric-generating stations with gas-works and coke-ovens the use of the products of carbonization, gas, oils, tar and coke, may supplement the use of raw coal to some extent and may lead to higher efficiency and economy of fuel, but this form of association must be carefully thought out in each particular case. Certain general principles which affect this form of association can be laid down, but the purely local and individual condition must always determine the application of these general principles. Their merely superficial adoption will only lead to disappointment and loss. This aspect of fuel economy is referred to below in connexion with carbonization and gasification as a means of sorting out the elements of raw coal into fuels of higher availability and convenience, but it may be said at once that up to 192 I no case had been made out for the general replacement, by fuels of higher availability, of raw coal used for steam raising. There is every reason therefore for the concentration of skill and enterprise on the general application of the well-established principles which govern the most efficient use of raw coal for steam raising. In Great Britain alone it is certain that tens of millions of tons of coal per annum might be saved in this way.
Apart from steam raising the direct combustion of raw coal in industry does not bulk very large in the general fuel bill. In the metallurgical industries coke and gas are the more important fuels, though considerable quantities of raw coal are still used in steel-making. In pottery and brick-making raw coal is still the chief fuel, but movements have been set on foot which may lead to the more extensive use of gas. In the Portland cement industry raw coal is likely to remain the fuel, as it can be used in pulverized form in rotary cement kilns with high efficiency.
Power Production By Internal Combustion Engines While by far the larger proportion of the power requirements of the world is at present supplied by steam boilers and engines, the production of power by the direct combustion of fuel in internal combustion engines has taken an increasingly important place (see Internal Combustion Engines. In 1900 great hopes were entertained that gas-engine units of large size would be used for the generation of electricity at central stations. Great difficulties have however been experienced in maintaining gasengine cylinders of large size, and the tendency for some years previous to 1920 was to keep down the size of the individual cylinders and to multiply the number of cylinders running on one shaft. Under these conditions the size of the unit engine is necessarily limited to I,000-2,000 horse-power. Even with units of this size the cost of maintenance may be high, and considerable stand-by plant has to be kept in reserve. Sir Dugald Clerk has estimated that, in Great Britain, more than half a million B.H.P. per annum was derived in 1920 - I from gasengines combined with suction and other gas producers. The Diesel type of oil-engine also made great progress during 1910-20 on land as well as on sea.
The internal combustion engine made the most remarkable developments after 1910 in its application to motor vehicles and to aeroplanes. The fuel required for this purpose must conform to certain definite requirements, the most fundamental of which is that it must be an inflammable liquid which can be depended on to vaporize on mixture with air at a sufficiently low temperature to ensure that the mixture can be fired in the cylinders of the engine by an electric spark. Petrol or gasoline is the most widely used fuel for this purpose. It is a mixture of the more volatile hydrocarbons which are obtained in the fractional distillation of natural petroleum. It is also obtained from natural gas by compression or cooling, or by oil-stripping.
The enormously increased demands during recent years led to the adoption of cracking processes, by which during distillation the heavier and less volatile fractions of the crude oil are partially broken up into hydrocarbons of a volatility which brings them within the range covered by the motor-spirit requirements. It is estimated that the development of cracking methods in the United States has added 10% to the yield of petrol obtained from the crude oil; while other improvements in collection and refining have added a further 5 to 6%. In 1909 the yield was Io7%, while in 1918 it had risen to 26.1%. Thus fully onefourth of the crude oil refined in the United States is being put on the market as petrol. The petrol imported into Great Britain in 1920 was about 250 million gal., or 830,000 tons.
The only sources of motor fuel in Great Britain are shale oilworks, gas-works and coke-ovens. From the shale oil-works about four million gallons of petrol per annum might be obtained, and from gasand coke-works about 20 million gallons of benzol, though in 1921 the output was much less. Benzol is an excellent motor fuel for land purposes, alone or mixed with petrol.
Carbonization And Gasification In connexion with the fuel problems of coal in their wider aspects, the operations of carbonization and gasification can be most conveniently considered as processes for the sorting out of the constituents of coal into fuels of various degrees of availability and usefulness. Though the hydrocarbons and their derivatives which occur in, or are derived from, coal by destructive distillation must continue to have a deep interest and an economic significance from the chemical point of view, they are relatively insignificant when the use and disposal of hundreds of millions of tons as fuel are being considered. While this is the only safe attitude for the fuel expert to take, it should be clearly understood that this in no way excludes the due consideration of chemical and by-products questions when these arise as a necessary part of the fuel problem.
So long as the blast furnace remains the instrument for the conversion of iron ore into pig iron, the coke-oven must continue to supply the necessary fuel in the form of hard coke. The " sorting-out process " at the coke-ovens is necessarily coloured by the fact that its primary object is the production of the right kind of coke. So much is this the case that the beehive oven, in which coke is the only product obtained, has only been partially displaced by the recovery oven, in which the by-products, tar, benzol and ammonia, are saved. In the iron and steel industry to-day the most advanced opinion is in favour of the concentration of coke-ovens, blast furnaces, steel furnaces and rolling-mills on one site, so that the whole of the potential heat of the coal may be pooled and used in a closed cycle for the production of heat and power. Mr. Talbot has estimated that in this way the fuel required for the production of one ton of finished steel would be reduced from 45 to 35 cwt. As any general replacement of existing works, under the financial conditions prevalent in 1921, was likely to involve a prohibitive capital cost, a more general use of coke-oven gas for the purposes of town supply was not to be hoped for.
In gas-works the sorting-out process is influenced by the fact that the primary purpose is to supply potential light, heat and power in the form of gas. In the British gas industry the fuel problems of the future acquired a new interest after the publication of the report of the Fuel Research Board on the results of their inquiry into the subject of gas standards. The results of this inquiry led to the adoption by the Board of Trade of a new method of charging the consumer for the gas which passes through his meter. The volume of this gas was still measured and recorded, but the consumer no longer paid on thousands of cub. ft. but on the product of the multiplication of the number of cub. ft. passed by the standard calorific value of the gas per cub. foot. The unit of charge was made the " therm," the name adopted for ioo,000 British thermal units. Under this system it is now possible to give to the gas undertakings a wide latitude in the selection of the standard of calorific value which they adopt, and therefore a much wider choice of the methods by which gas is manufactured. In the report it was stated that the great gain for the gas undertakings under the new system would be that no undue legislative restrictions would limit them in their development of the most economical production of thermal units in the form of gas. It was pointed out that there was still great scope for this development; as, according to present practice, only from 21 to 24% of the total potential thermal units of the coal was being sold in the form of gas.
To increase this percentage two known methods are available, both depending on the production of water-gas by one or other of the reactions between steam and carbon at a high temperature. The first of these methods is the old-established one in which a portion of the coke produced in the retorts is transferred to a separate producer, in which it is raised to bright incandescence by an air-blast and then subjected to the action of a current of steam. The thermal efficiency of this operation ranges from 45 to 55% according to the method of blowing-up and steaming adopted. The second method has recently been developed in connexion with vertical retorts. In this case the water-gas reactions are carried out in the lower part of the column of red-hot coke in the retort itself, by passing through it a current of steam. The volume of gas produced is much increased, though its calorific value is reduced by the addition of water gas to the hydrocarbon gas resulting from the carbonization of coal.
During 1919-21 continuous experiments were carried out at H.M. Fuel Research Station on the use of steam in vertical retorts with various types of coal. It was proved that, by the use of a moderate percentage of steam, a much larger proportion of the thermal value of the coal can be converted into the fuels of higher availability and value, gas and tar. In the case of a S. Yorkshire coal of good quality the following results were obtained: At a working temperature of 126°C. and with 21% of steam, the gains per ton of coal were 22 therms in the form of gas, 34 lb. of tar, and 6 lb. of ammonium sulphate. While without steam only 23% of the potential heat of the coal was obtained in the form of gas, with steam 33% was obtained. The extra heat which had to be supplied to the retorts in order to produce these results was ten therms per ton of coal carbonized, or 3.3% of the thermal value of the coal. The gas obtained amounted to 22,580 cub. ft. per ton, with a calorific value of 460 B.Th.U. per cub. foot. Both thermally and economically these results are superior to those which would have resulted from the production of an equivalent amount of water-gas in separate producers. The independent production of water-gas will always be regarded by gas engineers as an invaluable means by which exceptional demands on the gas supply can be met at short notice.
For many years inventors have been endeavouring to develop a practical process for the production of a solid smokeless fuel for domestic purposes by the carbonization of selected coals at 550° to 600° C. The resulting coke is entirely free from smoke-producing hydrocarbons, though it still contains io to 12% of volatile combustible matter, which burns with a very slightly luminous, perfectly smokeless flame. When the coke is kindled it becomes enveloped by these flames, which quickly raise the surface to incandescence. Undoubtedly if this smokeless solid fuel could be produced at a cost permitting of its being sold at little more than the price of the coal which it would replace, it would lead to a complete revolution in domestic heating.
The problem really has two distinct sides - the technical and the economic. On the economic side the data for a final solution will only be obtained after the technical solution has been reached. In other words, until a fair-sized industrial plant has been worked continuously over a long period, making and disposing of all the products of carbonization under steady market conditions, no one can say whether or not the business will be a profitable one.
On the engineering side an efficient and not too costly apparatus must be designed and constructed in the working of which manual labour, fuel consumption and maintenance costs are all reduced to a minimum. In these respects - as well as in its output capacity on a given ground area - the apparatus must stand comparison with gas retorts and oil-shale retorts of the most modern types. Only when this ideal has been realized practically can the future of low-temperature carbonization as a business proposition be put to the test of continuous working on a large scale under the labour and market conditions of the day.
From the experience gained in 1919-21 at H.M. Fuel Research Station, with a considerable variety of coals, the yields and quality of the gas, oils and coke produced under definite conditions were ascertained; but this knowledge is only the first step in the inquiry. For, until the cost of producing these, and the markets in which they are to be disposed of, are known with equal certainty, no economic balance sheet of any real value can be arrived at. Low-temperature carbonization can only be established on a sound commercial basis with low operating costs and a very moderate margin of profit. Prior to 1914 the shale oil industry in Scotland was distilling three million tons of shale per annum. The entire cost of the carbonizing operation, for labour, maintenance and fuel, was is. 6d. per ton, and the margin of profit on which fair dividends were paid was 2S. 6d. per ton. Unless the costs and profit margins of low-temperature carbonization can be reduced to the modern equivalents of these figures, the prospects of its development on a large scale are not hopeful.
If low-temperature carbonization is proved to be a feasible operation commercially, it would find its first and most natural application in Great Britain to the 35 million tons of coal used for domestic purposes. Were this coal all carbonized, it would produce about two million tons of fuel oil for the navy, or considerably more than the peace requirements, though considerably less than the war requirements. The motor spirit produced would amount to about zoo million gallons.
CONCLUSIONS From this review it appears that coal is likely to remain for a long time the world's chief source of fuel. Its more efficient use may be secured: (I) by more careful sorting and preparation at the mine; (2) by the improvement of boiler and furnace firing on well-known lines; (3) by the sorting out of its combustible constituents into fuels of higher availability or convenience by preliminary carbonization carried out either at high or at low temperatures. The development of oil shales as a source of liquid fuels was still in 1921 only in its initial stages, but it had evidently a great future before it. The problems of the utilization of peat; which cover a wide range both technically and economically, are mainly of local importance, and are not likely to affect the fuel supplies of the world to any great extent. The production of alcohol on a really large scale as a motor fuel of high availability bristles with economic and technical difficulties, and it was still in 1921 too early to pronounce an opinion on the possibilities of the future. Most, if not all, of these problems on their technical side are probably capable of solution by the skill and application of the industrial pioneers of the world; but the most difficult of the fuel problems of the future, as viewed in 1921, were those into which industrial and economic factors - the relations between capital and labour, and the cost of production - so largely entered. (G. T. B.)
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