Experimental Study On The Modification Of Coal During The Extraction By Supercritical Carbon Dioxide

Since most of the coal seam in our country is of low-permeability, the exploiting of coal methane is very difficult and the accident caused by coal methane is severe.The article is mainly focused on the problems of low-permeability of coal seam and the advantages of supercritical CO2, and it is aimed at find ways to improve the permeability of low permeability coal seam and to improve the efficiency of the extraction of coal methane. In this respect, the experiment of adsorption of CO2 and CH4, and the experiment of the extraction of coal by supercritical CO2 have been done in the laboratory. The testing of permeability before and after the supercritical experiment of coal and the Micro-CT experiment of coal before and after the extraction by supercritical CO2 have also been done. Some further analysis of the results has been done based on the Physical and Chemical Character, the Mechanical properties and the Seepage of coal. It discussed the law and the Mechanism of the Development of the fracture and porosity in coal. The process can essentially been described as the transfer of the quality. The results show that the adsorptive ability of CO2 is higher than that of CH4. And many obvious changes have appeared after the experiment, no matter it is focused on microcosmic or on microcosmic. The number of fracture and porosity increased greatly, that's to say that the rate of the pore of coal increased. The penetrative ability of coal has been improved significantly after extractive experiments by supercritical CO2. The permeability of coal increased nearly 10 times on average.In conclusion, supercritical CO2 in the transformation process of low-permeability coal seam permeability obvious effect on the safety of coal mine safety and coal bed methane, efficient exploitation of important guiding significance. ?...