Results of analyses of gas from representative lignite samples. a The samples were partly air dried, containing 8 to 27 per cent moisture. 1888°-Bull. 89-15-3 Average results of gas tests of 10 North Dakota lignite samples. Analysis of coal: Moisture in lignite as received (partly dried)........ Volatile matter (partly dried).. Fixed carbon (partly dried).. Ash (partly dried). Heating value of lignite (partly dried), B. t. u. per pound, 10,160. Yield of unpurified gas from partly dried lignite, cubic feet per ton, 12,487. Analysis of unpurified gas: Illuminants... Carbon monoxide. Hydrogen... Methane... Ethane.. Nitrogen... Carbon dioxide.. Oxygen..... Residue yield from partly dried coal..... Analysis of dry residue: Volatile matter.... Fixed carbon.. Ash........ Heating value, B. t. u. per pound, 11,710. Per cent. 6.98 39.50 44.64 8.88 1.49 22.52 44. 44 12. 84 .36 7.88 9.15 1.32 55. 34 7.99 73.97 18.04 Average results of gas tests of four Montana lignites. Analysis of lignite: Moisture in lignite as received.. Volatile matter in dry coal.. Fixed carbon in dry coal. Ash in dry coal...................... British thermal units per pound (coal as received), 8,675. Yield of unpurified gas from lignite as received, cubic feet per ton, 10,243. Analysis of unpurified gas: Per cent. 9.55 38.20 44.90 16.90 Heating value of lignite as received, B. t. u. per pound, 10,348. Yield of unpurified gas from lignite as received, cubic feet per ton, 8,746. Heating value of lignite as received, British thermal units per pound, Yield of unpurified gas from lignite as received, cubic feet per ton, 10,557. Per cent. Heating value, British thermal units per cubic foot, 335. Yield of residue from lignite as received....... 52.11 Heating value, British thermal units per pound, 12,836. COMMENTS ON TABULATED DATA. The results presented are typical of those from several hundred tests conducted. During the work several hundred tons of lignite was carbonized, and probably 1,000,000 to 2,000,000 cubic feet of lignite gas was produced. It has been necessary, from start to finish, to develop the whole process for the treatment of lignite. During the work many peculiarities of lignite, lignite gas, residue, and by-products, as well as peculiarities and difficulties in the adaptation of the process of treatment have been encountered and in a great measure overcome. The method evolved seems to be thoroughly practical and to possess many commercially attractive features. TEMPERATURE OF CARBONIZATION. IMPORTANCE OF DISTILLATION TEMPERATURE USED FOR ANY COAL. In the production of gas from coal, whatever the variety of coal used and whatever the type of retort or oven in which the gas is generated, the temperature required and the time necessary to remove the gas are important practical considerations. Not only is there a great difference in the products derived at different temperatures, but there is also a great difference in the necessary cost of operation. Because the length of life of the retorts or ovens is rapidly reduced as the temperature to which they are subjected is increased, and because the operating expenses are greatly increased by the necessity of high-temperature distillation, it is a matter of double consequence to procure materials and to use methods that will permit a high degree of carbonization at as low a temperature and in as short a period as is consistent with the recovery of gas and by-products of satisfactory quality. In the production of gas from ordinary bituminous coals there has been considerable discussion among practical and technical authorities as to the relative merits of high and low temperature distillation. It may be said that products of somewhat the same characteristics as those obtained in the treatment of bituminous coal are met with to a certain degree in the treatment of lignite, but the conditions necessary for obtaining the best results in the carbonization of lignites are widely different from those demanded for bituminous coal. Much of the lignite as mined contains 30 to 35 per cent moisture. The question that immediately rises is as to the effect of this moisture on the gases, residue, and by-products and also on the time and temperature required for carbonization. INFLUENCE OF MOISTURE CONTENT OF LIGNITE ON TEMPERATURE OF DISTILLATION. In the experiments it was quickly found that in the use of the ordinary gas retort of standard size the large proportion of water in the lignite immediately reduced the retort temperature, thereby delaying the time at which the distillation of gas began, and at the same time additional fuel and labor were required to bring the retort temperature back to the heat required for carbonization; thus there was an immediate loss of time, fuel, and labor in the use of lignite with its normal moisture content, and unless the yield of gas and byproducts in quantity or quality would repay for the losses it was evident that it would be advisable to at least partly dry the lignite before introducing it into the retort. Accordingly many experiments were performed to ascertain the yield and quality of gas and the residue and by-products recovered from the distillation of lignite with the moisture content as high as when mined. The results of the investigations indicate clearly that, as explained later, the proper retort temperature for lignite carbonization seems to be about 1,200° F., and at that temperature the retorting of wet lignite increases the quantity of gas but greatly reduces its quality, producing a relatively large volume of the oxides of carbon usually accompanied by a reduction of residue. USE OF ROTARY DRIER. The losses in the quality of the gas and in the residue are far from being compensated for by the increased yield of gas, to say nothing of the loss of fuel and labor required in maintaining the proper temperature of the retort. For this reason there is no question but that the lignite as mined should either be air dried or passed through some type of drier capable of rapid and cheap removal of the moisture. For this purpose the experiments indicated that a rotary drier of the standard type used for drying coal and a variety of other materials |