Explosion Hazardous Methane Content at the Developed Space of the Working Faces
Coal mining at the Russian Federation gas mines is conducted at 16 coal basins and deposits. The grade composition of coals varies from long-flame to anthracites. The categories of coal mines estimated on methane are divided into nongaseous ones, which share is about 5 %, methane hazardous (25 %), super-categorical on methane and dangerous on sudden emissions of coal and gas (70 %). Explosions and methane-air mixtures ignitions for a long time occurred both in case of low absolute methane emissions into the mine workings, and at high levels (in cases of disturbance of the ventilation regime of the faces, with large volumes of sudden release of methane into the workings, during their gasification and ignition of methane-air mixtures). Gas hazard at the methane abundant mines remains quite high: despite the fact that the number of explosions in the last 30 years has decreased, their severity has increased. The emergence of gas hazards at the mines is facilitated by: complex mining and geological conditions of bedding of coal seams, great depth of mining, high methane content of coal, methane accumulations in the developed space, possible violations of norms and rules for mining, low efficiency or absence of degassing of coal seams and developed space, insufficient experience and qualification of individual engineering and technical personnel and miners. Insufficient level of implementation of new highly effective methods and means of reducing methane hazard at the mines was noted. Based on the results of the study of gas processes the proposals have been made for the normalization of methane situation at the coal mines.