Rapid co-extraction of coal and coalbed methane techniques: a case study in Zhangji coal mine, China

Coalbed methane (CBM) is one of elements of coal mine hazards, the high CBM content and low permeability coefficients of coal seams in Huainan coal filed result in high difficulty of coal exploitation and CBM drainage, and the potential risk of gas explosion and combustion. The CBM drainage works are time-consuming and they typically delay the coal mining operations. A set of novel techniques of rapid co-extraction of coal and CBM are proposed in this paper. In the practice of 1413A longwall panel of Zhangji coal mine, a set of overlying and underlying drainage galleries were replaced by two overlying drainage galleries which were excavated by TBM, thereby the stress of excavation works was reduced. The pre-drainage and roadway excavation are conducted simultaneously and the overlying drainage gallery can also be used for post-drainage purposes. The bolter miners and automatic or remote control of longwall mining have also been used in the practice. The 1413A longwall extracted 2.31 million tons of coal and 15.02 m(3) of CBM with the extraction rates of 93.5% and 63.8% respectively in 448 days. The speed and efficiency of co-extraction operations were improved significantly.