Experimental Studies of Some Regularities in the Underground Gasification of Inclined Coal Seams

摘要

Under natural conditions, the participation of underground water in the gasification process is considerably above the optimum level, and in coal seams 1 and 2 m thick is characterized by a specific water inflow of 1500 to 2500 kg/ton, and by a moisture content of 250 to 400 g/m exp 3 in the gas. The combustion heat of the gas in coal seams 1 and 2 m thick (especially in the first case) therefore is significantly below 1000 kcal/m exp 3 under such conditions. The decrease in the combustion heat of the gas with decreasing coal seam thickness is explained by the obvious increase in heat losses to the surrounding rock mass. An increase in the amount of underground water lowers the calorific value still further. The efficiency of gasification of coal seams 8.5, 2, and 1 m thick gradually decreases, being 65 to 70, 55 to 60, and 45 to 50%, respectively. Thus, as the thickness of the coal seam being gasified decreases, one must reduce the involvement of influent underground water in the gasification process. This can be accomplished by increasing the efficiency of the drying of the coal seam being gasified, or by intensifying the gasification process. During the underground gasification of coal seams of average thickness, a decrease was recorded in the combustion heat of the gas as the seams were gasified, from the start to the end of the gas generator's operation. For a long time, however, the quantitative value of this regularity was not recorded. After the decisive influence of the specific water inflow on the combustion heat of the gas was determined, a way of determining the dependence of the latter on the degree of gasification of the coal seam up-dip became clear. A small effect was found for the thinner seams. To avoid this loss in calorific value of the gas in these thinner seams, one must increase the rate of air delivery to the gas generator or use boreholes closer to the reaction surface. (ERA citation 05:021619)