The role of water on postcombustion CO₂ capture by vacuum swing adsorption: Bed layering and purge to feed ratio

Abstract

The influence of water vapor on the adsorption of CO 2 in carbon capture by vacuum swing adsorption (VSA) was described. VSA experiments with single and multilayered columns using alumina and zeolite 13X were conducted to understand the migration of water. The penetration depth of water in the column could be controlled by maintaining the purge-to-feed ratio above a critical value. At high water content in the feed (>4%), employment of a water adsorbing prelayer was essential to prevent failure of the carbon capture process. A simple axial working capacity model predicts the penetration depth of water in the column for a given feed temperature and adsorption isotherm, and the layering ratio can be selected accordingly. Although water is detrimental to CO 2 capture with polar adsorbents, long-term recovery of CO 2 is still possible by appropriate layering and ensuring an adequate purge-to-feed ratio.Note: vacuum level decreases in the order of Run 5,7,8,9, and 10. (b) Dependence of CO 2 productivity, purity, and recovery on volumetric purge-to-feed ratio at CSS of single-layer 13X VSA processes with 3.5% water feed at 30 C. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] 678

Capture of low grade methane from nitrogen gas using dual-reflux pressure swing adsorption

“…The peak-to-peak temperature variations experienced in the middle (T-06, z/L = 0.5) and the bottom (T-11, z/L = 0.072) of the column are similar in magnitude but the average temperature at the bottom of the column is lower. This is mainly caused by the regenerative heat exchange effect [33] where more cold stream flowed down during desorption (steps II and III) than the hot stream that flowed up during adsorption (steps IV and I). We suggest no net energy gain or loss across a full cycle at CSS, but there is a spatial misalignment (or hysteresis) between the exothermic adsorption thermal wave and endothermic desorption thermal wave.…”

Application of polyethylenimine‐impregnated solid adsorbents for direct capture of low‐concentration CO2

“…In addition, the presence of water will detrimentally affect the selectivity for CO 2 . [23][24][25] In recent years, intensive research has focused on the technologies for adsorbing traces of CO 2 using a variety of solid amine adsorbents. The solid amine adsorbents based on primary, secondary, or tertiary amines operate near ambient conditions, are tolerant to water vapor and can be regenerated by mild temperature swings.…”

Water vapour adsorption by a coffee-based microporous carbon: effect on CO2capture

“…H 2 O is a polar molecule which is strongly adsorbed by many inorganic adsorbents like zeolites. For this reason, the adsorption processes that consider the use of this type of adsorbents generally include a dehumidifying unit that uses alumina to remove water from the feed gas prior to entering the capture unit or a multilayer alumina–zeolite adsorber column . The interaction of water molecules with the hydrophobic carbon surface is less favoured, especially at low relative pressures.…”

“…To date, the majority of the published literature on CO 2 capture by adsorption deals with dry gas mixtures. The influence of H 2 O on the CO 2 capture performance has only gained interest recently . In this work the effect of the coadsorption of water vapour over the adsorption of CO 2 on PPC has been evaluated under dynamic conditions using a fixed‐bed adsorption unit and synthetic flue gas mixtures in the presence and absence of water vapour.…”