EQUILIBRIUM ADSORPTION MODELS FOR COALBED
METHANE AND CO2 SEQUESTRATION PROCESSES
K. A. M. Gasem*
R. L. Robinson, Jr.,
J. E. Fitzgerald
Z. Pan
M. Sudibandriyo
A. Arumugam
Oklahoma State University
423 Engineering North
School of Chemical Engineering
Stillwater, OK 74075
Voice: 405-744-9114
Fax: 405-744-6338
E-mail: gasem@okstate.edu
Adsorption equilibrium models are essential in optimizing coalbed methane (CBM) production and CO2 sequestration processes. Our recent studies indicate that models originate from three different frameworks: two-dimensional (2-D) equations of state (EOS), the simplified local density model (SLD-EOS), and the Ono-Kondo (OK) lattice model are effective in modeling near-critical and supercritical adsorption systems of the type encountered in CBM recovery and CO2 sequestration. Further, the use of matrix-calibrated models minimizes the experimental effort required to obtain accurate adsorption predictions for a specific CBM site. The model evaluations were conducted using our recent measurements for the adsorption of pure carbon dioxide, methane and nitrogen and their binary mixtures on activated carbon at 318 K and pressures to 12.5 MPa.
Our results indicate that a potential exists for developing a priori predictive models using fully-generalized parameters determined by accessible adsorbate and adsorbent characterizations. However, to fully exploit the potential of the models in CBM recovery and CO2 sequestration processes, we need to develop (a) a more rigorous approach to account for the effect of water on CBM adsorption systems, and (b) an accurate equation of state that exhibits accurate hard-sphere limiting behavior.