Efficient Simulation of Chromatographic Processes Using the Conservation Element/Solution Element Method

Chromatographic separation processes need efficient simulation methods, especially for nonlinear adsorption isotherms such as the Langmuir isotherms which imply the formation of concentration shocks. The focus of this paper is on the space–time conservation element/solution element (CE/SE) method. This is an explicit method for the solution of systems of partial differential equations. Numerical stability of this method is guaranteed when the Courant–Friedrichs–Lewy condition is satisfied. To investigate the accuracy and efficiency of this method, it is compared with the classical cell model, which corresponds to a first-order finite volume discretization using a method of lines approach (MOL). The evaluation is done for different models, including the ideal equilibrium model and a mass transfer model for different adsorption isotherms—including linear and nonlinear Langmuir isotherms—and for different chromatographic processes from single-column operation to more sophisticated simulated moving bed (SMB) processes for the separation of binary and ternary mixtures. The results clearly show that CE/SE outperforms MOL in terms of computational times for all considered cases, ranging from 11-fold for the case with linear isotherm to 350-fold for the most complicated case with ternary center-cut eight-zone SMB with Langmuir isotherms, and it could be successfully applied for the optimization and control studies of such processes

Modeling and Optimization of Rare Earth Element Chromatography

The Rare Earth Elements are a group of metals, that are of growing technical and economical importance. Current separation techniques can be detrimental to the environment, and a clean technology for separation has been devised, based on analytical chromatography of the REEs. The thesis presents column preparation and impregnation to give desired properties of the separation system, experimental and model based optimization for operating points and design of a chromatography step for separating REEs

INTEGRATED ADSORBENT AND PROCESS DESIGN FOR CARBON CAPTURE FROM POWER PLANT FLUE GAS

Ph.DDOCTOR OF PHILOSOPH

Efficient and accurate numerical simulation of nonlinear chromatographic processes

Models for chromatographic processes consist of nonlinear convection-dominated partial differential equations (PDEs) coupled with some algebraic equations. A high resolution semi-discrete flux-limiting finite volume scheme is proposed for solving the nonlinear equilibrium dispersive model of chromatography. The suggested scheme is capable to suppress numerical oscillations and, hence, preserves the positivity of numerical solutions. Moreover, the scheme has capability to accurately capture sharp discontinuities of chromatographic fronts on coarse grids. The performance of the current scheme is validated against other flux-limiting schemes available in the literature. The case studies include single-component elution, two-component elution, and displacement chromatography on non-movable (fixed) and movable (counter-current) beds. © 2010 Elsevier Ltd. All rights reserved. [accessed October 5th 2011