Cryogenic slurry to extinguish AML waste bank fires.
Kim-AG; Kociban-AM; Dalverny-LE
Reclaiming the future: proceedings of the 16th annual conference of the Association of Abandoned Mined Land Programs, September 18-21, 1994, Park City, Utah. Mesch MR; Malin L, eds. Springfield, IL: Association of Abandoned Mined Land Programs, 1994 Sep; :116-127
The U.S. Bureau of Mines has developed a cryogenic method to extinguish fires in abandoned waste banks; the method is potentially applicable to other types of remote smoldering combustion. A slurry of cryogenic materials, liquid N2 and granular C02, is injected into a waste bank at a temperature of approximately -180 degrees C. Changes in state from the solid or liquid to the gas phase produce a 500-fold increase in volume. The cold pressure wave created by this expansion moves isotropically away from the injection point, absorbing heat and producing an inert atmosphere. It forces heat, smoke and fumes from the combustion zone to the surface. The injected slurry causes a relatively quick cooling of the burning material, while the expansion of the evaporating fluid maintains the cold atmosphere for an extended period. The movement of the inert gas is controlled by pressure and buoyancy. The Bureau has developed and tested a prototype apparatus to produce and inject the slurry. In tests in an enclosed bed of 44 short tons of coal , the slurry was effective at lowering the temperature of the burning coal to below -100 degrees C. Low temperatures were maintained for 1 month. In a planned field test at a burning waste bank in Ohio, well servicing equipment, normally used to mix sand and fluids, will be adapted to produce the cryogenic slurry. Material requirements will be based on the waste bank volume and on the distribution of temperatures. Information required to plan the test has been obtained by geophysical site characterization techniques and by drilling an array of 2-in holes in the bank. The holes can subsequently be used as injection or monitoring points. Injection is planned for August 1994. Preliminary estimates indicate that the cost of injecting a cryogenic slurry should be comparable to the cost of more conventional control methods for AML fires.
cryogenic; mine fire; slurry; Mining; Mining industry; Coal mines; Coal mining; Underground mines; Underground mining; Fire fighting
Reclaiming the future: proceedings of the 16th annual conference of the Association of Abandoned Mined Land Programs, September 18-21, 1994, Park City, Utah