EQUILIBRIUM ADSORPTION OF CARBON DIOXIDE, METHANE, AND NITROGEN GASES

							              EQUILIBRIUM ADSORPTION OF CARBON DIOXIDE, METHANE,
                AND NITROGEN GASES ON ARGONNE PREMIUM COALS
            AND AN ACTIVATED CARBON AT VARIOUS MOISTURE CONTENTS

                                      Khaled A. M. Gasem*
                                      James E. Fitzgerald
                                     Robert L. Robinson, Jr.
                                    Oklahoma State University
                                              EN423
                                       Stillwater, OK 74078
                                      Voice: 405-744-5280
                                        Fax: 405-744-6338
                                       gasem@okstate.edu


As part of our efforts to model enhanced coalbed methane recovery and CO2 sequestration in
coalbeds, we have investigated the equilibrium, pure-gas adsorption behavior of five wet Argonne
premium coals: namely, Illinois #6, Wyodak sub-bituminous, Pocahontas, Beulah Zap, and Upper
Freeport coal; in addition, adsorption was measured on wet F-400 Calgon activated carbon.
Using a volumetric technique, isotherms of CO2, methane, and nitrogen were measured at a
temperature of 131°F and pressures to 2000 psia at select moisture contents of the adsorbents.
Through the simplified local density (SLD) model for adsorption, comparisons are made between
the new adsorption measurements on wet adsorbents and the previous adsorption
measurements on dry adsorbents.

We have previously used the SLD model to describe isotherm component adsorptions (binary
and ternary gas) at temperatures from 113°F to 131°F and for pressures to 2000 psia; the
adsorbents were either dry or water-saturated. Here, the SLD model is used to describe how the
water content of the adsorbent affects the gas adsorption. The SLD model incorporates a hard-
sphere equation of state and a fluid-solid potential function to calculate the local fugacity of the
fluid confined in a slit pore.