Characteristics of pulverized coal during coalbed methane drainage in Linfen block

Based on continuous monitoring of pulverized coal concentration of CBM wells, the characteristics of pulverized coal during coalbed methane drainage in Linfen block was studied, the factors that influence the characteristics of the pulverized coal were analyzed, and output mechanism of pulverized coal was discussed from the aspect of concentration, particle size, composition and surface characteristics by using pulverized coal concentration monitor, laser particle size analyzer, X-ray diffraction, reflection polarizing microscope, electronic scanning electron microscopy (SEM), X-ray energy dispersive spectrometer. The results show that the trend of average pulverized coal concentration of Linfen block during coalbed methane drainage is drainage depressurizing stage < hold pressure drainage stage < gas hydrate stage, and the trend of different layers is the pulverized coal concentration of single-mined coal seam 5 < that of combined mined coal seam 5, that of coal seam 8 < that of combined mined coal seams 8+9 and 4+5. The particle size distribution of the pulverized coal is wide, ranging from 0.5μm to 1 000 μm and most of the particles are concentrated below 100 μm. The mineral content of pulverized coal was mainly inorganic mineral and the lens group. The inorganic minerals are mainly hard gypsum, pyrite and illite. The pulverized coal particles were divided into smooth surfaces and rough surfaces. The smooth surfaces of coal particles was composed mainly of element C, and the rough surface of coal particles was mainly composed of elements Fe, S and O. The output of pulverized coal is related to the mineral content of coal, vitrinite content, the development degree of tectonic coal and drainage stage.