Study on Multifactor Regulation Mechanism and Priority of Gas Desorption in Soft Coal

Under the background of global energy low-carbon transformation, coalbed methane (CBM) reserves in soft coal-rich areas such as China's Shanxi Qinshui Basin account for over 30% of the national total, yet the extraction efficiency has long been below 35%. The core bottleneck lies in insufficient understanding of the mechanisms by which multiple factors (e.g., temperature, moisture content, particle size, and initial pressure) regulate gas desorption, coupled with the lack of quantitative comparison and priority ranking. Taking soft coal from a coal mine in Shanxi Province, China, as the research object, this study conducted 16 groups of single-factor experiments (temperature: 10-40 °C, moisture content: 2%-8%, particle size: 0.3-4.0 mm, initial pressure: 1-4 MPa). Combined with high-precision monitoring and a quantitative evaluation system of "curve separation degree-peak rate range-attenuation constant range", the regulation laws, mechanisms, and priority order were revealed. Results show that initial pressure is the absolute dominant factor: the cumulative desorption amount at 4 MPa is 5.5 times that at 1 MPa, with a 6-fold difference in peak desorption rate. It determines gas reserves and desorption driving force through Langmuir adsorption equilibrium and pressure difference. Moisture content is a key inhibitory factor: the desorption amount at 8% decreases by 68.55% compared to 2%, showing a sharp decline in the 2%-4% range and a slow decline in the 4%-8% range, attributed to pore blockage and adsorption competition. Temperature is an auxiliary promoting factor: the desorption amount at 40 °C increases by 40% compared to 10 °C, regulating desorption by breaking adsorption equilibrium via Le Chatelier's principle and accelerating molecular thermal motion, but is constrained by moisture content. Particle size has the weakest impact: the difference in final desorption amount between coal samples of 0.3-0.5 mm and 2.0-4.0 mm is less than 5%, only assisting in regulating the initial rate. Quantitative comparison establishes the priority order: initial pressure > moisture content > temperature > particle size. This study fills the gap in quantitative comparison of multifactor effects, provides support for precise gas control strategies of ″pre-extraction pressure control-drainage dehumidification-temperature control assistance-local coal fragmentation", and is of great significance for improving CBM development efficiency and preventing gas disasters.