Performance evaluation of the conservation element and solution element method in SMB process simulation

Abstract

The computational performance of the space-time conservation element and solution element method (CESE) is evaluated in solving simulated moving bed (SMB) chromatographic models, compared with a 2nd-order upwind discretization method (UDS2) and 4th-order orthogonal collocation finite element method (OCFE4) of ASPEN chromatography (ASPEN Tech, USA). A novel finite volume discretization is proposed for the CE/SE method to treat the exit boundary condition in the adsorption column close to plug-flow operation. A single column model and a linear/equilibrium SMB model which have the analytic solutions are used for the computational performance assessment of the numerical methods. For the two examples, CESE shows the superiority over UDS2 and OCFE4 in terms of computational efficiency and accuracy. Other five practical SMB examples which have no analytic solution are used to examine computational features of the three numerical methods. Using UDS2, it shows a fast calculation but the sufficient number of mesh points is required to enhance accuracy. The accuracy of CESE is comparable with OCFE4. Since CESE enforces both local and global flux conservation in space and time and is combined with the finite volume discretization of the exit boundary condition, its numerical solution of SMB adsorption models is accurate and computationally efficient. © 2008 Elsevier B.V. All rights reserved.