MODELING OF FLUID-SOLID MASS-TRANSFER IN PACKED-BEDS - CASES OF NONUNIFORM PARTICLES AND CONCENTRATION-DEPENDENT INTERNAL DIFFUSIVITY

An advanced model for the description of fluid-solid mass transfer in packed beds is proposed, in which the effects of particle size distrib ution, grain swelling or shrinking and concentration dependence of dif fusivity in the particle are taken into account. These effects are dis cussed regarding two situations encountered in chemical technology pra ctice: extraction of low molecular compounds from polycaproamide and i on exchange recovery of aurocyanide ions from waste water of gold plat ing. Experimental data for these two processes are compared with model predictions. A very good coincidence is obtained in the case of extra ction and qualitative agreement-in the case of ion exchange. (C) 1997 Published by Elsevier Science S.A.