Removal of toluene vapour with dispersed activated carbon

This work considers the mechanisms of mass transfer in a process of dispersed sorbent injection. During experiments, an air supply was dosed with toluene vapor, at partial pressures between 4 and 15 Pa. Powdered activated carbon (PAC) was added to remove the toluene from the air, and the resulting mixture was passed through a 3-m-long, tubular, aluminum test section. Toluene concentrations were measured at seven axial locations within the test section. Comparing the measurements with mathematical models indicated the importance of adsorption kinetics. At reduced toluene inlet concentrations the PAC removed a slightly bigger fraction of toluene from the air stream. This fraction increased with PAC concentration. The effect on removal of varying the air temperature between 25 and 85°C was small. Alternative models incorporating either pore diffusion or surface diffusion were fitted to the results. The quality of the fits was fair only, but sufficient to show that the pore diffusivity that gave the best fit was far larger than would be expected from the Knudsen diffusivity in the pores. That is, surface diffusion was an important part of the intraparticle mass transfer.