404 THE COLLIERY GUARDIAN. September 1, 1916. ment of manual labour. With peat fuel costing 1*20 dots, per ton, the price at which it is said the German Government sells the fuel to this company under con- tract, the steam plant is able to generate power more cheaply than with coal costing 3’50 dols. per ton. The policy of the German Government has been one of conservation and encouragement in the utilisation of its natural resources in the most efficient manner, and this plant, it must be borne in mind, was an integral part of the scheme of the Prussian Government for convert- ing this large peat moor into fertile farm land. In this respect it has met with admirable success, but it is scarcely probable that private companies could have carried to completion such a vast and original scheme without Government assistance. Boiler Efficiency. Tests conducted at this plant showed that a thermal efficiency of 73-5 per cent, for the steam generator could be realised; this is equivalent to an evaporation of 3*01 kilogs. of water per kilog. of peat, or 3-01 lb. of water per lb. of peat. The average calorific value of the peat burned was 4,824 B.t.u. per lb., which, it might be remarked, is low compared with that determined for many of the Canadian peats so far examined. The moisture content of the peat fuel, of course, varies, but an effort is made to keep the average in the vicinity of 30 per cent. 6'0 35 40. iO. 2 4 S 8 IO Curves A show the effect of increase of fuel costs on cost of power. Curve B shows the nitrogen the fuel must contain in order to permit by-product recovery plant to compete with non- by-product recovery producer gas power plant. 12 !4 6 8 2 0 2 2 2 4 2 Fig. 2. The above result cannot be realised in every-day operation. Up to the time the plant was visited by the writer, it had been possible to attain a consumption of only 2’7 kilogs. (5’94 lb.) of peat per kw.-hour in rare and isolated cases. A consumption of 2-4 kilogs. (5’28 lb.) of peat has in fact been obtained. In wet weather the fuel consumption averages 3 kilogs. (6*6 lb.) per kw.-hour. If the cost of peat per ton is taken as 5 mk. (1-20 dels.) per ton, a fuel consumption of 2*4 to 2*8 kilogs. (5’28 to 6-16 lb.) per kw.-hour would cost 0-3c. to 0*35c. per kw., which at that place would be about the same price as when coal is burned. From the foregoing, it will be seen that peat fuel can be utilised in competition with coal for the production of power in steam plants, but only when the most rigid economies are introduced both in the manufacturing and handling of the peat fuel and in the conversion of its heat energy into useful work. The second method for the production of power from peat that will be considered is the conversion of the heat energy of a fuel into a combustible gas through the medium of a gas producer, and the employment of this gas in a gas engine. This method is by far the most efficient, and appears especially attractive, and the most desirable one to employ for this class of fuel. The production of power or fuel gas by means of gas producers may be divided into two main classes :— Production of gas without by-product recovery, and pro- duction of gas with by-product recovery. The producers included in the first class are known as non-by-product recovery producers, and those of the second class as by-product recovery producers. Non-By-product Recovery Producers. In non-by-product recovery producers the aim is to convert all the combustible components of a fuel into a combustible gas. No attempt is, therefore, made to recover such by-products as tar or ammonia. In fact, such by-products should not occur in the theoretical sense when the producer is properly designed for the most efficient gasification of the fuel, which, in the case considered, is, of course, of the bituminous variety. But though efforts have been made to convert all the combustible matter or peat, for instance, into gas, the results have not been entirely satisfactory, as certain quantities of hydrocarbons always escape gasification, and pass off as by-products. With this type of pro- ducer, excellent results have been obtained both with bituminous coal and peat fuel, and as the data avail- able concerning tests of both of these fuels are rather comprehensive, it is possible to compare their value for the production of power gas. The cost of a power plant for either of these fuels will be approximately the same, and the labour costs at the power plant cannot vary to any appreciable extent. It is therefore possible to estimate the pro- bable economies arising from the use of one or the other fuel by comparing the consumption and cost of fuel per brake horse-power year. The consumption of coal, bituminous or anthracite, in a well-designed producer gas power plant, may be put at 1-J-lb. for actual commercial operations — better results than this can be realised, and perhaps in a few cases have been obtained even in commercial practice. For peat fuel, it has been found, as a result of a large number of trials conducted under varying conditions, that 1 brake horse-power hour can be produced from 2 lb. of peat containing 25 per cent, moisture. For purposes of comparison, the consumption of peat per brake horse- power hour will be taken as 3 lb. From this it will be seen that the quantity of peat required to produce 1 brake horse-power hour is twice that of coal; hence, to com- pete on even terms with coal, other things being con- sidered equal, the peat fuel must not cost more than half as much as coal. The market price of coal is there- fore the deciding factor in determining the feasibility of generating power from peat. The utilisation of peat for power purposes in localities where coal can be purchased at a moderate price, or where low grades of coal, such as slack and screenings can be obtained, is entirely out of the question. But, on the other hand, there are numerous localities where coal for industrial purposes can be obtained only at a high price—in Canada this is especially pertinent. In such cases, peat might be the most economical fuel to employ, and its value as a fuel for the production of power naturally increases directly with the increase in the cost of coal, and the decrease, of course, in the cost of manufacturing at the bog. These comparisons hold only when the peat power plant is situated on or very near the bog where the fuel is manufactured, as the cost of the fuel rises rapidly with the distance it is hauled. In considering the feasibility of erecting any power plant for the production of power from peat, the importance of providing storage space for the large bulk of fuel it is necessary to always keep on hand, ready for instant use, must not be overlooked. This factor is important, especially in cold and damp climates, and the necessity of a large storage space may, under cer- tain conditions, militate against the economic employ- ment of this kind of fuel. Utilisation in By-product Recovery Producers. When a gas producer is designed to gasify a fuel in such a manner that the greatest quantity of by-products is obtained, the producer is termed a by-product-recovery producer. When such a type of producer is used, its efficiency as a power gas producer is sacrificed to1 a certain extent in favour of the by-product-recovery efficiency. Such a producer can, therefore, be employed only when the recovery of by-products proves a profitable venture outside of, and in addition to, the production of power or industrial gas. NITROGEN CONTENT OF ABSOLUTELY DR\ PEAT ±0 ol- io •2 4 6 8 1 0 1 2 1 4 1 6 1 8 2-0 2-2 2 • 6 8 10 1-2 1-4 16 1-8 2 0 2-2 2-4 2-6 yu 3 Fig. 3.—Nitrogen Content of absolutely Dry Peat. Curves A show cost of 1,000 cu. ft. gas when peat costs 0-50 to 3-00 dols. per ton. Curves B show cost of sulphate when peat costs 0-50 to 3-00 per ton. The by-products obtained when fuel is gasified in this type of producer are principally ammonia and tar, and of these two the ammonia is of the greater value. It is consequently apparent that the value of this process increases directly with the quantity of ammonia obtain- able with its use. Ammonia is a chemical compound composed of nitrogen (N) and hydrogen (H), and has the definite chemical formula NH3. The nitrogen is obtained from the fuel, and the hydrogen is obtained by the decomposition of steam when this is brought into contact with hot carbon. This reaction is a part of the process of gasification. Therefore the fuel that con- tains the largest amount of nitrogen is the most valuable for utilisation in this manner. However, the ammonia thus formed is not recovered as ammonia, but is caused to react with sulphuric acid in such a manner that all or very nearly all is converted into sulphate of ammonia according to the reaction :—■ 2NH3 + H2SO4 = (NH4)2S04. From the molecular formula (NH4)2SO4, the ratio of the pounds of ammonia sulphate to the pounds of nitrogen is found to be 4-7, that is, the quantity of ammonium sulphate formed is 4-7 times the quantity of nitrogen entering into combination. For example, if a ton of coal (2,0001b.) has a nitrogen content of 1 per cent., the quantity of nitrogen is 201b., and the ammonium sulphate that can be formed is 20 x 4*7 = 941b., a value that, of course, is theoretical, the quantity actually obtained in practice rarely exceeding 15 per cent, of this. Many of the peat bogs so far examined in the pro- vinces of Quebec and Ontario in the Dominion of Canada contain peat that has a nitrogen content averag- ing 2 to 2-5 per cent., and when the nitrogen content is as high as this, the by-product recovery process can be employed to advantage. The accompanying curves show the great effect of bhe nitrogen content on the cost of producing power gas and power. The plant and labour costs on which these curves were calculated are con- sidered by the writer to be conservative. But although this method of producing power or industrial gas is most attractive, and offers liberal profits when all goes well, the strictest economies, especially in the manufacture of peat fuel, must be introduced in all except such cases where the nitrogen content is over 2 per cent. The curves shown in fig. 2 illustrate the latter point. Plants of the above description are in successful opera- tion in Italy, and are utilising peat bogs from which the wanning of the fuel is difficult, and which produce a fuel of comparatively low nitrogen content—about 1 per cent. There is no good reason why the peat bogs of North America, especially those in the inhabited regions of Canada, cannot be utilised for this purpose, as many of them contain peat with a high average nitrogen content. In conclusion, it may be stated that peat fuel can be utilised for the production of power in either steam or producer-gas power plants as efficiently as can coal, and ■that the price at which coal can be bought and that at which peat fuel can be manufactured are the principal factors to be considered. EXPLOSIBILITY OF GASES FROM MINE FIRES.* By G. A. Burrell and G. G. Oberfell. The report opens with particulars of a mine fire, dis- covered in a certain drift coal mine early in the afternoon of a working day. The miners were immediately notified, and left the mine in safety. Two and a-half hours later a party of 12 men entered the mine to discover the location of the fire. While the men were in the mine the ventilating fan was reversed. About one-half hour after the entrance of the men into the mine an explosion happened, three of the men being severely burned. Seemingly, the explosion happened shortly after the fan had been reversed. It is believed that the fire started in a cut-through to an old room, probably being due to the accidental light- ing of brattice cloth by a miner’s lamp. The cover over the mine varies from 150 to 300 or 400 ft. There were many openings to the surface in the mine, making exclusion of outside air difficult during the quenching of the fire. Collection and Analysis of Gas Samples. No samples of mine gas were collected before the explosion occurred. The first gas sample, obtained about 24 hours after the explosion, wras taken in the return air 20 ft. inbye the fan. Just prior to the collection of the sample the fan had been started. The analysis of the sample gave the following results : Carbon dioxide, 3-00 per cent.; oxygen, 16-51; carbon monoxide, 0-33; methane, 0-84; and nitrogen, 79-32 per cent., and showed the presence of afterdamp and blackdamp that had accumulated as a result of the fire and explosion. Another sample was collected at the same place 24 hours later, or two days following the explosion. The atmosphere was then much better, as the following results of analysis show: Carbon dioxide, 0-55 per cent.; oxygen, 19*77; carbon monoxide, nil; methane, 0-47; nitrogen, 79*21 per cent. A third sample was collected on the same day, a few feet inbye the fifth right entry. Brattices had been put in place, and much work accomplished in seal- ing off and confining the fire to as small an area as possible. The analysis of this sample showed : Carbon dioxide, 1-10 per cent.; oxygen, 18*59*. carbon monoxide, 0-14; methane, 0-41; and nitrogen, 79*76 per cent. The foregoing results of analyses are interesting as showing something about the composition of the atmo- sphere in the mine shortly after the fire had been dis- covered. No samples were collected in or close to the fire, because no one could approach it. Hence the results given represent fire gases largely diluted with fresh air from other parts of the mine. Finally, the area wherein the fire was confined was entirely bratticed off, and the problem resolved itself into waiting until the fire should become quenched through lack of air. Gas Samples Collected Through Borehole. A borehole was sunk near the supposed origin of the fire, to procure gas samples from the fire ar< a and to take temperature readings. Pipes were placed in several of the stoppings on the main haulageway and at one of the drift entrances to the sealed area of the mine. From these various openings gas samples were collected at intervals during a period extending over several months. The results of analyses of the samples collected from the various openings follow :— * From Technical Paper 134, United States Bureau of Mines.