Geology and emission of mine gas in Binchang mining area with low rank coal and high mine gas

In recent years,the number of high-gas mines in low-rank coal mining area has increased,but the law of gas occurrence and emission characteristics are not well understood. In this study,taking the Binchang mining area in Huan- glong coalfield of Shaanxi Province as an example,the gas parameters and gas enrichment rules of low coal rank mines were studied based on the exploration stage and the test in the coal mine production process. At the same time,the influ- ence of geological factors on the gas emission characteristics of low-rank coal mining area and its mechanism were dis- cussed. The research shows that the low-rank coal has a low degree of coalification,high porosity,high free gas content, good coal seam permeability,andmedium and high rank coals. There are three gas enrichment areas in Binchang mining area:Dafosi gas enrichment area, Xiaozhuang-Tingnan gas enrichment area and Hujiahe gas enrichment area. The geological structure is the main factor controlling the gas enrichment in low coal rank coal mines. The coal quality characteristics determine the gas occurrence state of low coal rank mining areas. The gas emission is controlled by the geological factors such as gas content,coal thickness,coal seam floor elevation and geological structure. The higher the in-situ gas content of the coal seam is,the larger the coal seam thickness is. The larger the coal seam floor elevation is,and the larger the gas emission from the mining-face is. The gas emission at the folded wing is obviously larger than that at the wide area in the shaft of syncline. The larger the inclination dip angle of the wing formation,the larger the gas emission from the mining area. The influence of the fold on the dip angle of the coal seam controls the low-rank coal gas emission characteristics. Because of the high free gas content near the fault,it is easy to cause a sudden increase in the amount of gas emission from the mining face. The fully mechanized top coal caving mining process has significantly increased the coal production,and also caused an increase in the number of high gas mines in the low coal rank mining area in recent years. the gas enrichment law and emission characteristics are obviously different from that of