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 P_cd, gas saturation β, effective pressure drop P_e, and effective desorption quantity V_e, 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.