Experimental study on adsorption and desorption characteristics of anthracite by temperature shock

Anthracite has the characteristics of strong methane adsorption and low desorption rate. In order to improve the extraction efficiency of coalbed methane in anthracite, temperature shock was selected as the modification method. An orthogonal experimental scheme with 4 factors and 4 levels was set up, and the temperature difference between high temperature and low temperature was divided by the temperature conversion time (10 s) of the temperature shock test chamber to obtain the temperature rise and fall rate corresponding to each experimental scheme. The effects of temperature rise and fall rate, action time and cycle times on the adsorption-desorption characteristics of anthracite methane in temperature shock modification were further analyzed, and its mechanism was studied from the aspects of surface characteristics and pore structure.The results show that compared with the original anthracite, the maximum adsorption capacity of anthracite for methane decreases, the Langmuir pressure increases, the maximum desorption capacity and diffusion coefficient increase, and the order of influence effect is: temperature rise and fall rate > action time > cycle times. Compared with the original anthracite, the thermal shock modified sample has a decrease in the coal-water contact angle, an increase in the surface energy, the number of polar oxygen-containing functional groups (—OH) increased, and the number of methyls (—CH3) and methylene (—CH2) decreased; In terms of pore structure, the spores develop obviously, the number of micropores decreases, the average pore size and pore volume increase, and the specific surface area decreases.