BK1064-ch07_R2_260706 SHORTCUT EVALUATION OF ABSORPTION FOR SYNTHESIS OF GAS SEPARATION NETWORKS Margarita Martin, Megan Jobson, Nan Zhang, Peter J. Heggs Centre for Process Integration, School of Chemical Engineering and Analytical Science, The University of Manchester, PO Box 88, Manchester, M60 1QD, UK, E-mail: margarita.martin@postgrad.manchester.ac.uk A systematic and quantitative methodology for synthesis of gas separation networks is being developed to allow generation of effective and economic separation schemes. Synthesis includes selection of appropriate separation methods, e.g. absorption, low- temperature separation processes and membrane permeation. In the screening step of the methodology, a quick assessment of alternative separation techniques is needed. This work focuses on methods and performance indicators for such an assessment of physical absorption. To identify whether physical absorption is a promising technology, solubility differences of the components of a mixture in a non-volatile solvent may be assessed using heuristic rules. However, the selective solubility, which has been proposed pre- viously as a performance indicator, is shown to be inconclusive. Instead, this work proposes two complementary performance indicators: the separation factor and the distribution coefficient. This study derives relationships for these for two process con- figurations of equilibrium stages: countercurrent and crossflow. The relationships derived for the countercurrent configuration can be rearranged into a form analogous to the Kremser relationships. An analysis of the impact on the separation factor and distribution coefficient of key process design parameters (solvent-to-feed ratio and number of stages in the column) provides a criterion for process evaluation which is in agreement with existing heuristics for absorption column design: if an absorption column with an infinite number of stages allows complete removal of at least one component, the split is taken to be feasible. In such cases, the operating solvent-to-feed ratio lies between the equilibrium constants of the key components. This provides a quantitative basis for preliminary selection of the solvent-to-feed ratio. KEYWORDS: absorption, shortcut model, screening INTRODUCTION The separation of gas and vapour mixtures represents a large fraction of the vast number of industrial separation applications, such as the removal of acid gases from exhaust streams, the recovery of light gases from hydrocarbon gas streams and the production of enriched air. There are incentives to substitute energy-intensive conventional processes with alternative separation schemes including novel separation techniques. The synthesis of a gas separation system involves the selection of the most appropriate separation tech- nologies. There are typically several competing or complementary options. Whereas for SYMPOSIUM SERIES NO. 152 # 2006 IChemE 88