Effects of particle size on CH_4 and CO_2adsorption and desorption characteristics of coals are investigated at 308 K and pressures up to 5.0 MPa.The gas adsorption and desorption isotherms of coals with particle sizes ranging from 250 μm to 840 μm are measured via the volumetric method,and the Langmuir model is used to analyse the experimental results.Coal particle size is found to have an obvious effect on the coal pore structure.With the decrease of coal particle size in the process of grinding,the pore accessibility of the coal,including the specific surface area and pore volume,increases.Hence,coal with smaller particle size has higher specific surface area and higher pore volume.The ability of adsorption was highly related to the pore structure of coal,and coal particle size has a significant influence on coal adsorption/desorption characteristics,including adsorption capacity and desorption hysteresis for CH_4 and CO_2,i.e.,coal with a smaller particle size achieves higher adsorption capacity,while the sample with a larger particle size has lower adsorption capacity.Further,coal with larger particle size is also found to have relatively large desorption hysteresis.In addition,dynamic adsorption performances of the samples are carried out at 298 K and at pressures of 0.1 MPa and 0.5 MPa,respectively,and the results indicate that with the increase of particle size,the difference between CO_2 and CH_4adsorption capacities of the samples decreases. Effects of particle size on CH 4 and CO 2 adsorption and desorption characteristics of coals are investigated at 308 K and pressures up to 5.0 MPa. The gas adsorption and desorption isotherms of coals with particle sizes ranging from 250 μm to 840 μm are measured via the volumetric method, and the Langmuir model is used to analyze the experimental results. Co particle size is found to have an obvious effect on the coal pore structure. Where the decrease of coal particle size in the process of grinding, the pore accessibility of the coal, including the specific surface area and pore volume, increases .ence, coal with smaller particle size has higher specific surface area and higher pore volume. the ability of adsorption was highly related to the pore structure of coal, and coal particle size has a significant influence on coal adsorption / desorption characteristics, including adsorption capacity and desorption hysteresis for CH_4 and CO_2, ie, coal with a smaller particle size achieves higher ads orption capacity, while the sample with a larger particle size has lower adsorption capacity. Fine, coal with larger particle size is also found to have relatively large desorption hysteresis. In addition, dynamic adsorption of the samples are carried out at 298 K and at pressures of 0.1 MPa and 0.5 MPa, respectively, and the results indicate that with the increase of particle size, the difference between CO_2 and CH_4adsorption capacities of the samples decreases.