Methane drainage and utilization technologies for high gassy and low permeability coal seams in tiefa mining area
Based on the high gassy and low permeability coal seams geo-conditions in Tiefa mining area in China, the features of mining-induced fractures and gas migration under U model exhaust ventiliation were studied by means of physical simulation and CFD (Computational Fluid Dynamics) numerical modeling. The results show that mining-induced fractures are mainly generated on the inside of the retreat drift, around 1/3 along the retreat direction, and th zone where gas mainly flows range from 30 to 80 m away from the tailgate and behind the coalface 100 m, in which the gas concentration is up to 60%. Secondly, the methane drainage boreholes layout principles and the echnical system were discussed combined with key technologies of surface boreholes in virgin coal seam, long cross-measure boreholes, long horizontal boreholes in-mines and burying pipe in upper corner of coalface and so on. Finally, the utilization technical problems of drained methane concentration non-uniform and heat unbalanced were solved by using gas compressors, heat unbalanced were solved by using gas compressors, heat balancing adjusters and spherical dehumidification gasholders. At the same time, the methane tranmission, storage, distribution system and the whole utilization system and the utilization modes for civil gas, commercial and industrial gas, low concentration gas power generation in Tiefa coalfield were introduced. The above-mentioned technologies have been applied in Tiefa coalfield and have got technical and economical benefits.