Key technologies for collaborative mining of high gas and low permeabilitycoal seams in deep mining areas

In order to solve the typical engineering technical problems of the protective layer mining under complex conditions such as high gas content,low permeability and unstableoverlying strata in deep mining areas,based on the geological conditions of Pingdingshan mining area,the deep "complex mining method of protective layer→ coal gangue underground sorting → gas three-dimensional drainage →ptotected layer mixed mining → gas surface power generation" closed cycle "mining,separating,draining and filling" collaborative mining technology is developed.The requirements and practical significance of the "mining,selection,extraction,filling and utilization" collaborative mining technology were put forward,and the technical methods and basic principles of the protective layer under complex conditions were revealed,and the underground heavy medium shallow trench coal gangue separation system was established to realize the separation of coal flow gangue.On the basis of the original production system,a filling and caving mining method is developed and a mixed mining face with solid backfilling and traditional fully mechanized mining face was designed,which realized the coal mining and the waste rock backfilling under the separation gangue well.At the same time,the three-dimensional gas extraction and the ground low concentration gas power generation system were designed to realize the safe pressure relief extraction and clean utilization of the protected layer gas.Based on the above technical methods,the collaborative mining integration technology of "mining-dressing-gas draining-backfilling-using" was carried out in No.14 and No.15 coal seam group of No.12 Pingdingshancoal mine and the practical results show thatthe working face of the unconventional protective layer with a face length of 150 meters has a monthly advancement of 120 meters,the selection capacity of the underground sorting system has reached 4 million t/a,the filling and caving working face has a length of 220 meters,the production capacity has reached 3 million t/a,and all the gangues have been disposed underground.Since the application of the collaborative mining technology in 2015,a total of 5.88 million tons of coal resources have been liberated.At present,it has safely recovered 3.815 million tons of coal resources,90.879 million m3 of gas and 60.848 million kW·h of gas power has been generated.Significant economic benefits have been achieved,and safe,efficient and green co-mining of coal and gas has been realized.