Research on the main control factors of gas desorption in middle and low rank coals based on orthogonal testing

•Through the homemade experimental setup for gas desorption, obvious differences in desorption amount and desorption rate were obtained for low-and middle-rank coals.•The main controlling factors affecting the desorption of low-and middle-rank coal gas were obtained by designing orthogonal experiments using extreme difference analysis and variance analysis.•The influence of adsorption equilibrium pressure, temperature, particle size and water content on the desorption ability of middle-and low- rank coal gas was studied by sensitivity analysis.