Coal mining in Illinois . at gas impregnates a coalbed just as water impregnates a porous substance and thatits escape results directly from a difference of pressure be-tween the interior and the exterior of the mass. The highestpressure of gas in the solid coal which was recorded by Dar-ton in this district was 33 pounds per square inch althoughthe pressure is probably higher in certain areas. However, VENTILATION 155 a difference in pressure of a few pounds only is sufficient toset up a steady flow of gas from the coal into the actual volume of gas found in the return air curren
Coal mining in Illinois . at gas impregnates a coalbed just as water impregnates a porous substance and thatits escape results directly from a difference of pressure be-tween the interior and the exterior of the mass. The highestpressure of gas in the solid coal which was recorded by Dar-ton in this district was 33 pounds per square inch althoughthe pressure is probably higher in certain areas. However, VENTILATION 155 a difference in pressure of a few pounds only is sufficient toset up a steady flow of gas from the coal into the actual volume of gas found in the return air current atany time will depend chiefly upon the number of active work-ing places in the mine unless the bed contains large storagebasins of gas, that is, it will depend upon the area of freshcoal face exposed daily. This statement is borne out by Dar-tons findings. In one mine 418 feet deep with a daily produc-tion of 2,300 tons he records 181 cubic feet of methame perminute in the return air current when the mine was operating. Fig. 47. Explosion-door in concrete-block,.stopping in District V and 78 cubic feet per minute after a suspension of 5 to 15days. In the flat-lying undisturbed Illinois beds, depth over200 feet does not seem to be a factor in the amount of gasin the The presence of large volumes of gas can not be predictedfor any area unless it is known by previous workings that thearea is one in which the coal is broken by structural movementso that it acts as a reservoir for a considerable surroundingarea of the bed. In the deeper mines of this district, however,there is a continuous emanation of gas from the fresh coal and 1J)arton, N. II., Occurrence of Explosive Gases in Coal Mines, !. S. Bureau ofMines, Bulletin 72. 156 COAL MINING INVESTIGATIONS such reservoirs may be broken into at any point. Althoughdifferent exposures of fresh coal do not give off uniformquantities of gas, some exuding none and some large quan-tities, the aggregate emanation is considerable. T
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectcoalmin, bookyear1915
