Targeted Stimulation Effects of CS2 Extraction on Methane Desorption in Coal.

Carbon disulfide (CS2) as a focus has been extensively studied in stimulating the coal macromolecular structure and pore structure. However, the desorption characteristics are not examined after CS2 extraction, limiting an insightful understanding of the targeted stimulation mechanism of CS2 extraction on desorption. The study further explores the effect of CS2 extraction on methane desorption through the isothermal adsorption experiment and the desorption stage theory. From the results, CS2 extraction induces the adsorption weakened effect and desorption enhanced effect, with a decrease in Langmuir constants a and b. By affecting key desorption pressure points, CS2 extraction alters the dynamic desorption process, with an expansion on slow desorption stage II and fast desorption stage III and a shortening of sensitive desorption stage IV. Additionally, the increase in desorption characteristic parameters in extracted coal, including the critical desorption pressure Pcd, gas saturation β, effective pressure drop Pe, and effective desorption quantity Ve, indicates that CS2 extraction lowers the required critical desorption condition and contributes to increasing the desorption capacity. Meanwhile, the targeted stimulation mechanism of CS2 extraction on the dynamics of physical desorption characteristic has been further revealed. We also validate the plateau extension effect and decrement weakening effect by CS2 extraction, promoting the conversion of adsorbed gas to free gas and prolonging the effective production process. The study provides a theoretical basis for CS2 extraction utilization in changing the desorption characteristic and increasing CBM production.