Competition of CO2/H2O in Adsorption Based CO2 Capture

All flue gases contain water vapour along with carbon dioxide, nitrogen, etc. Vacuum Swing Adsorption (VSA), which has been successfully studied for post-combustion dry CO2 capture in our group, is strongly affected by the overwhelming competitive adsorption of water vapour on CO2 adsorbents. In this study, breakthrough experiments have been conducted to measure the single/binary adsorption isotherm data of CO2 and water vapour on zeolite 13X and a proprietary alumina-based adsorbent alumina CDX to study the competitive adsorption effect on each other. The CO2 adsorption data are well represented by the Dual site Langmuir isotherm equation. Based on the above understanding, a single column multilayered VSA unit was used with a guard-bed layer of superior desiccant and a main layer of 13X to simultaneously remove water (3-4% by volume) and capture CO2 (10-12%) at 30 degrees C within the same process. In this study, activated alumina CDX was selected as the appropriate pre-layer. Furthermore, we have investigated the effects of operating parameters on the multilayered CO2/H2O VSA performance. The water front was accurately located in the bed and the interaction of CO2 and water vapour indicates a clear indication of a water loaded zone and a CO2 loaded zone. The result demonstrates that water front has been successfully held in the pre-layer and CO2 product purity of 76.9 % and purity of 67 % were achieved for the double layered single column CO2/H-2 OVSA. (C) 2008 Elsevier Ltd. All rights reserved.