Targeted Stimulation Effects of CS ₂ 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.