Mathematical Model of Supercritical Co2 Adsorption on Activated Carbon Applied to Adsorption Scale-up

A general mathematical model for supercritical CO2 adsorption on activated carbon have been developed. Adsorption curves obtained with a laboratory plant (adsorber of 10 mL) have been adjusted with this model and the results have been extrapolated to adjust the breakthrough curves obtained with a pilot plant (adsorber of 1L). The proposed model is general and takes into account equilibrium (adsorption isotherm), diffusion in the solid (effective diffusion coefficient), mass transfer from the bulk of the fluid phase (supercritical solvent) to the surface of the solid, axial dispersion (effective dispersion coefficient) and a first order reversible adsorption/desorption reaction at the solid surface site. This model can be considered as general due to kinetics of the adsorption-desorption at a site as well as intraparticle diffusion, fluid-particle mass transfer, and axial dispersion are included and the contribution of these parameters (ka, kd, De, kf, Daz) have demonstrated to be essential for getting a good adjust. In order to get a suitable adjust, the experimental adsorption curves have been represented by this model by fitting the kinetic coefficients (ka, De and Daz) to the experimental curves, obtained from the laboratory installation. The parameters kf and kd are calculated, kf by wellknown correlation and kd by the determination of adsorption isotherm. With the optimised parameters it is possible to model the adsorption curve obtained with the pilot plant with reasonable accuracy. Therefore, the model is suitable to determine the kinetic parameters from a laboratory experiment and to scale-up the adsorption process.