Measurements of sorption capacities and kinetics of CO2 and coalbed methane (CH4) in coal are important for evaluating the feasibility and economics of CO2 storage in unminable coal seams and simultaneously enhancing coalbed methane recovery process (CO2-ECBM).Although using pulverized coal sample to perform the sorption measurements in the laboratory is more convenient and faster,the coal in situ conditions are compact coal monoliths.More knowledge is required on the influence of particle size on the sorption capacities and kinetics.In this study,the sorption measurements on two coals with four different grain size fractions (from<0.354 to 4 -10 mm) were assessed by manometric method.The results indicate that the variation of coal composition (ash,moisture and maceral composition) and cleat development with particle size influences the sorption capacity and kinetics.The sorption capacities of different particle sizes on ash-free basis are quite close except the particle size with highest ash content.The effective diffusion coefficients (Deff),derived from the fitted sorption kinetics data by unipore diffusion model,increased with particle size.This implies that the coal matrices rather than mineral matter-filled cleats are easy to be destroyed during grinding of coal,so the larger particles had better developed major cleats and smaller inter-cleat diffusion distances.For the same particle size,CO2 presented a higher sorption capacity and effective diffusion coefficient than CH4
Fengshuang Han Andreas Busch Niels van Wageningen Jianli Yang Zhenyu Liu Bernhard M. Krooss
State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences,0300 Shell International Exploration and Production B.V.,2288 GS Rijswijk-ZH,the Netherlands a State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences,03 State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology,Beij Institute of Geology and Geochemistry of Petroleum and Coal,RWTH Aachen University,D-52056 Aachen,Ge