Heat flow characteristics of bituminous coal adsorption and desorption process

The process of coal adsorption and desorption of gas is accompanied by obvious thermal effects, and its variation pattern is of great value for the research of gas hazard prediction techniques such as coal and gas outburst prediction. Using self-designed multiparameter coal adsorption and desorption heat effect test system, we conducted pressure, temperature and heat flow test experiments for CO₂, N₂ and CH₄ gas adsorption and desorption of bituminous coal at 0. 5 MPa, 0. 8 MPa and 1. 1 MPa, and analyzed the characteristics of heat flow changes of bituminous coal during the adsorption and desorption process. The study showed that: (1) during the whole process of adsorption and desorption of bituminous coal specimens, the change of heat flow density on the coal wall is divided into five processes: ①in the evacuation stage, the heat flow increases rapidly and then decreases slowly to 0; ②in the inflation stage, the heat flow is positively correlated with the inflation rate; ③in the adsorption stage, the heat flow is first fast up and then fast down and finally decreases slowly; ④in the deflation stage, the heat flow is positively correlated with the pressure relief rate; ⑤in the desorption stage, it is divided into two stages: the stage of fast down and slow rise. (2) The maximum heat flux values of N₂, CH₄, and CO₂ three gases increase sequentially; for the same gas, the maximum heat flux values under the three gas pressures will increase with the increase of pressure. (3) The theoretical values of heat in the process of adsorption and desorption are always larger than the experimental values, but the overall trend is consistent. (4) The heat flux parameter has the characteristics of inflow and outflow direction vector, which is superior to the temperature index. The heat flux is consistent with the heat transfer change law, which can well characterize the change law of thermal effect of adsorption and desorption of bituminous coal, and provide reference for the research of new index of coal and gas outburst prediction.