Carbon dioxide recovery from a simulated dry exhaust gas by an internally heated and cooled temperature swing adsorption packed with a typical hydrophobic adsorbent

Abstract

• Internally heated / cooled temperature swing adsorption was tested for CO 2 capture. • Two typical hydrophobic adsorbents were employed for wet emission gas processing. • The separation performance of High Silica Zeolite was explored. • The unique separation behavior of Carbon Molecular Sieves was examined. This study focused on the carbon dioxide (CO 2 ) separation and recovery by an internally heated and cooled thermal swing adsorption process. As part of the preliminary investigation, the CO 2 capture and enrichment performance of carbon molecular sieve (CMS), a typical hydrophobic adsorbent, and high silica zeolite (HSZ), which indicates hydrophobic behavior among zeolites, were examined in a simulated dry exhaust gas. In addition, the hydroscopic adsorbent, CaA type zeolite, was employed for comparison. The effects of the regeneration temperature and the regeneration air flow rate on the separation performance were primarily investigated. In general, the CaA type of zeolite indicated a greater CO 2 concentration performance and recovery ratio due to its relatively larger adsorption capacity. Comparison between HSZ and CMS showed that the CO 2 separation and recovery performance of HSZ were greater than that of CMS. A CO 2 concentration four times higher than that of the feed gas was obtained at a regeneration temperature of 80 °C. Moreover, further enrichment of CO 2 at the desorption outlet was achieved by reducing the regeneration air flow rate to 1/40 of the feed gas of the adsorption process in exchange for lowering the CO 2 recovery ratio. In contrast, CMS could only produce three times greater the concentration of enriched CO 2 when compared to the feed gas. The enriched CO 2 concentration was almost independent of the regeneration air flow rate. This behavior was due to a lower CO 2 adsorption selectivity of CMS; this interpretation was supported by time profiles of desorption gas outlet volume and the CO 2 concentration.