DYNAMICS OF SIMULATED MOVING-BED ADSORPTION SEPARATION PROCESSES

Two mathematical models, namely the continuous moving-bed model (stead y-state model) and the intermittent moving-bed model (transient model) , have been used to describe simulated moving-bed adsorption separatio n processes. Four-column and 12-column simulated moving-bed systems fo r the separation of optical isomers with nonlinear adsorption isotherm s were studied with the two models, respectively. The model equations were solved by using the numerical method of orthogonal collocation in finite elements. For the 4-column simulated moving bed, the differenc es between the simulation results from the two mathematical models are very obvious. Process dynamics, i.e., evolution of the species concen trations in the extract and raffinate and the axial profiles at differ ent times, of the above systems in one switching period at the cyclic steady state are presented and discussed. They were numerically simula ted with the intermittent moving bed model. The computations in a Gray J916 computer were very time consuming for the 12-column system.