Technology status and fluidized mining conception for steeply inclined coal seams

The steeply inclined coal seams are difficult to mine and it is urgent to develop new,safe, efficient and green mining methods. The current status of three technologies commonly used for steeply inclined coal seam mining, horizontal sublevel top-coal caving, strike longwall fully mechanized mining and strike longwall fully mechanized top-coal caving technology, were summarized and analyzed. For horizontal sublevel top-coal caving technology, in-depth research on mining and drawing technology, reasonable sublevel height,top-coal cavibility, top-coal drawing at face end, and intelligent mining are need to be carried out for further improving the top-coal recovery and mining efficiency. For the fully mechanized longwall mining technology, it is necessary to continue to study the working face layout, anti-sliding and anti-skid of equipment, and mining technology. For the longwall fully mechanized top-coal caving technology, it is necessary to use the top-coal drawing law scientifically and formulate reasonable mining and drawing technology to improve the stability of the shield supports and top-coal recovery. According to the occurrence characteristics of steeply inclined coal seams, two fluidized mining technology concepts, modern underground gasification mining and new hydraulic coal mining, were proposed. With the idea of creating effective airflow, ideal reaction intensity and highest energy utilization efficiency, two types of gasifiers for steep coal seams are proposed: linear mining gasifier with single gasification face and U-type underground gasifier with double gasification faces. It is concluded that the gasification of steeply inclined coal seams still requires in-depth research on key technologies such as gasification process control and enhancement, gasification reaction space management, gasification face detection technology, groundwater pollution prevention and control. For steeply inclined thick coal seams that cannot be mined with horizontal sublevel top-coal caving technology, hydraulic mining can be tried and a roadway layout concept for hydraulic mechanized mining under this condition was proposed; for steeply inclined coal seams with a small thickness, fluidized mining technology like underground coal gasification can be explored to realize unmanned remote underground hydraulic mining without driving roadways, which is an important research direction for fluidized mining of difficult-to-mine steeply inclined coal seams in the future.