Effect of process parameters on power requirements of vacuum swing adsorption technology for CO 2 capture from flue gas Jun Zhang, Paul A. Webley * , Penny Xiao Department of Chemical Engineering, P.O. Box 36, Monash University, Victoria 3800, Australia Received 10 September 2006; received in revised form 13 May 2007; accepted 4 June 2007 Available online 24 July 2007 Abstract This study focuses on the effects of process and operating parameters – feed gas temperature, evacuation pressure and feed concen- tration – on the performance of carbon dioxide vacuum swing adsorption (CO 2 VSA) processes for CO 2 capture from gas, especially as it affects power consumption. To obtain reliable data on the VSA process, experimental work was conducted on a purposely built three bed CO 2 VSA pilot plant using commercial 13X zeolite. Both 6 step and 9 step cycles were used to determine the influences of temperature, evacuation pressure and feed concentration on process performance (recovery, purity, power and corresponding capture cost). A simple economic model for CO 2 capture was developed and employed herein. Through experiments and analysis, it is found that the feed gas temperature, evacuation pressure and feed concentration have significant effects on power consumption and CO 2 capture cost. Our data demonstrate that the CO 2 VSA process has good recovery (>70%), purity (>90%) and low power cost (4–10 kW/TPDc) when operating with 40 °C feed gas provided relatively deep vacuum is used. Enhanced performance is obtained when higher feed gas concentration is fed to the plant, as expected. Our data indicates large potential for application of CO 2 VSA to CO 2 capture from flue gas. Crown Copyright Ó 2007 Published by Elsevier Ltd. All rights reserved. Keywords: CO 2 capture; Adsorption processes; Flue gas; Power requirements 1. Introduction and background More than 85% of the world’s commercial energy needs are met by burning fossil fuels, including coal, oil and gas. Power stations burning fossil fuels account for a large per- centage of CO 2 emission [1,2]. Capture of CO 2 from power stations (which account for three quarters of the total costs of carbon capture and storage (CCS) has become an important research issue of global proportions as more international attention is focused on global warming. Among the various capture approaches, absorption, mem- branes, cryogenic, adsorption and others, CO 2 capture by pressure/vacuum swing adsorption is a promising option for separating CO 2 from flue gas, considering its relatively low operating and capital costs. Although current commer- cial technologies such as liquid scrubbing are available for CO 2 capture from flue gas, the cost of capture is still too high. Cost (capital and operating) becomes the major bar- rier for the application of CO 2 capture in power plant sec- tors and other major CO 2 emission industry sectors [3–7]. In this introduction, we highlight some of the previous studies of CO 2 capture by adsorption with a view to plac- ing our current study in context. In the discussion below, we adopt the terminology ‘‘PSA’’ to denote pressure swing adsorption in which the feed gas is compressed substan- tially above atmospheric pressure and the CO 2 is recovered at atmospheric pressure and ‘‘VSA’’ to denote vacuum swing adsorption in which the feed is only ‘‘slightly’’ com- pressed (up to 1.5 atm at most) and the CO 2 is recovered under vacuum conditions. 1.1. 1992 IEA study In 1992, the International Energy Agency (IEA) con- tracted Monenco, Inc. to study the feasibility of using 0196-8904/$ - see front matter Crown Copyright Ó 2007 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.enconman.2007.06.007 * Corresponding author. Tel.: +61 3 9905 3628; fax: +61 3 9905 5686. E-mail address: paul.webley@eng.monash.edu.au (P.A. Webley). www.elsevier.com/locate/enconman Available online at www.sciencedirect.com Energy Conversion and Management 49 (2008) 346–356