The numerical simulation pf coalbed seam processes (obtaining gas from and storing gas within) requires thermodynamic data on equilibrium sorption capacity and selective sorption, and information on the kinetics of the sorption and desorption processes (sorption rates, characteristic times). To make this information available for the in-situ conditions of gas storage in coal bed seams, the kinetics of CO 2 and CH 4 sorption on dry and moist coal samples from the Silesian basin in Poland were studied. The experimental measurements were made at 32° and 45°C with six different particle sizes (< 63 μm to ∼ 3 mm). The sorption equilibrium occurred with high time resolution at from 3 to 6 different pressure stages (5-150 bar). The primary study goal was to obtain simple semi-empirical expressions to describe the sorption kinetics of both gases on coal from the study area. The experimental results and the kinetics derived from them will be used in the general model of underground storage of CO 2 in connection with CO 2 stimulated coal bed seam production (Enhanced Coalbed Methane). The discussion covers introduction; sample material; methodology (sample preparation, experimental setup for the sorption kinetic experiments); results (dependence of the sorption rate on the particle size, temperature dependence of the sorption rate, sorption rates on dry and moist coal); interpretation of the data (single pore model, two combined kinetic functions first order (bi-disperse model); results; considerations of the influence of particle size and moisture content, CH 4-CO 2 comparison, up-scaling from laboratory to reservoir scale; and conclusions. The study revealed that there are qualitative differences in the characteristic times for equilibrium sorption of CH 4 and CO 2 on natural coals. A convergence of the transport parameter with use of the mono-disperse pore model and the determination of an effective diffusion coefficient in spherical particles according to Crank (1975) is possible. A simple semi-empirical expression to fit the data with use of the two combined functions of the first order is sufficient to describe the data quantitatively.
|Translated title of the contribution||Carbon dioxide storage in coalbed seams: Sorption kinetic studies within the framework of the EU-RECOPOL project|
|Number of pages||12|
|Publication status||Published - 2004|
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