KINETICS OF HYDROCARBON ADSORPTION ON ACTIVATED CARBON AND SILICA-GEL

Experimental breakthrough results of methane, ethane and propane in ac tivated carbon and silica gel obtained over a wide range of gas compos itions, bed pressures, interstitial velocities and column temperatures were analyzed using a dynamic, nonisothermal, nontrace column breakth rough model. A linear driving force (LDF) approximation is used for pa rticle uptake, and the Langmuir-Freundlich isotherm represents adsorpt ion equilibrium. The LDF mass-transfer-rate coefficient (and, hence, e ffective particle diffusivity) and column-wall heat-transfer coefficie nt were determined. The results show that hydrocarbon transport in the activated carbon particles used is essentially by Knudsen and surface flow while for the silica gel used the transport is primarily by Knud sen flow For activated carbon, the experimentally derived LDF coeffici ents for all three sorbates are well correlated using an average effec tive diffusivity value. With regard to heat transfer, the column-wall Nusselt number is approximately constant for the range of Reynolds num bers considered. Simulations of multicomponent breakthrough in the act ivated-carbon bed based on independently measured single-component kin etic parameters and the extended Langmuir-Freundlich isotherm agree ve ry well with experimental results. The computational efficiency gained by adopting the simpler extended Langmuir isotherm model is also inve stigated.