Adsorption Of CH₄, N₂, CO₂ Single And Multicomponent Gas On Coal

Comprehensive studies on adsorption of CH4, N2, CO2 single gas and their multicomponent gas on coal are conducted by applying physical chemistry, interface chemistry, coal petrology and coal chemical engineering knowledge. Firstly, adsorption characteristics of methane on different rank coals are investigated and the diversities among CH4, N2 and CO2 are compared. Several classical adsorption models are evaluated and the optimal one is selected out for describing adsorption process of gas on coal. Secondly, according to the adsorption feature of gas on solid under high pressure, the relation between apparent capacity and absolute capacity is explained from different points. The defect of the conversion method used currently for apparent capacity and absolute capacity is pointed out. Furthermore, the two new methods of determining absolute capacity are proposed for improving the test precision. In order to that non-technical person can convert apparent capacity and absolute capacity conveniently, two quick and easy methods are presented. Thirdly, according to the thermodynamic parameters calculated from adsorption test data, further studies of adsorption mechanism of methane on coal are made. It's put forward that, adsorptivity should be evaluated from the three aspects, including specific surface area, adsorption capacity on per surface area and interaction between methane molecule and coal surface. From the adsorption characteristic curve based on potential theory, a formula for adsorption capacity, pressure and temperature is obtained and will be useful in the CBM resource evaluation in deep or virgin areas and other aspects. Fourthly, a new high pressure gas mixing apparatus is established, and experimental procedures for gas mixing and multicomponent gas adsorption test are suggested. Tests of multicomponent gas adsorption of CH4+N2 and CH4+CO2 on different coals are performed, and the predicting model for multicomponent gas adsorption is optimized, which can guide the Enhanced CBM Recovery process by injection of CO2 or N2 gas. In summary, the results of this paper will improve coal adsorption theory and testing method, and provide the theoretical basis for researching CBM storing mechanism and technical support for CBM resource evaluation and economical recovery.