Title: Energetics for gas separation in microporous membranes

Authors: P. Smith Schneider, M.C. Duke, S. Liu, M. Abdel-jawad, J.C. Diniz Da Costa

Addresses: Department of Mechanical Engineering, Federal University of Rio Grande do Sul, 90050-170, Rua Sarmento Leite 425, 90050-170, Porto Alegre, RS, Brazil. ' Films and Inorganic Membrane Laboratory (FIMLab), ARC Centre for Functional Nanomaterials, School of Engineering, The University of Queensland, Brisbane Qld 4072, Australia. ' Films and Inorganic Membrane Laboratory (FIMLab), ARC Centre for Functional Nanomaterials, School of Engineering, The University of Queensland, Brisbane Qld 4072, Australia. ' Films and Inorganic Membrane Laboratory (FIMLab), ARC Centre for Functional Nanomaterials, School of Engineering, The University of Queensland, Brisbane Qld 4072, Australia. ' Films and Inorganic Membrane Laboratory (FIMLab), ARC Centre for Functional Nanomaterials, School of Engineering, The University of Queensland, Brisbane Qld 4072, Australia

Abstract: Gas separation by inorganic membranes has proven to be effective at laboratory scales, but is now facing challenges in developing for industrial scales. A particular type of inorganic membrane is the class of porous molecular sieves formed by sol-gel method deposited on ceramic substrates. These molecular sieve silica (MSS) membranes are ideally suited to high temperature He, H₂, CO₂ and CH₄ separation, but one of the major understandings lacking is energy modelling enabling industrial level simulations for technology potential forecasting. In this paper we report experimental results of high quality membranes and use as a basis for predicting the exergetic efficiency of mixture separation. A specifically exergetic analysis was derived and successfully implemented. The more selective two-step membrane offered better exergetic efficiency for widely different gas molecule pair sizes like He/CH₄, but lower improvement to less different pair sizes like H₂/CH₄. For instance, at 10 bar pressure difference, He/CH₄ exergetic efficiency was around 54% while being around 35% for H₂/CH₄. Likewise, the higher CO₂/CH₄ selectivity of the single-step membrane leads to better exergetic efficiency prediction. This technique has therefore provided a working method to evaluate membrane unit performance for optimal industrial outcomes. Permselectivities were shown to correlate to exergetic efficiencies leading to a practical analysis of membrane performance.

Keywords: single-step silica membranes; two-step silica membranes; permeation; permselectivity; energetics; exergetics; gas separation; microporous membranes; nanotechnology; porous molecular sieves; sol-gel method; ceramic substrates; energy modelling; exergy efficiency; performance evaluation; membrane performance.

DOI: 10.1504/IJNT.2007.014745

International Journal of Nanotechnology, 2007 Vol.4 No.5, pp.468 - 481

Published online: 06 Aug 2007 *

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