Radically New Adsorption Cycles for Carbon Dioxide Sequestration

Abstract

In Parts I and II of this project, a rigorous pressure swing adsorption (PSA) process simulator was used to study new, high temperature, PSA cycles, based on the use of a Kpromoted HTlc adsorbent and 4-and 5-step (bed) vacuum swing PSA cycles, which were designed to process a typical stack gas effluent at 575 K containing (in vol%) 15 % CO 2 , 75% N 2 and 10% H 2 O into a light product stream depleted of CO 2 and a heavy product stream enriched in CO 2 . Literally, thousands (2,850) of simulations were carried out to the periodic state to study the effects of the light product purge to feed ratio (γ), cycle step time (t s ) or cycle time (t c ), high to low pressure ratio (π T ), and heavy product recycle ratio (R R ) on the process performance, while changing the cycle configuration from 4-to 5-step (bed) designs utilizing combinations of light and heavy reflux steps, two different depressurization modes, and two sets of CO 2 -HTlc mass transfer coefficients. The process performance was judged in terms of the CO 2 purity and recovery, and the feed throughput.The best process performance was obtained from a 5-step (bed) stripping PSA cycle with a light reflux step and a heavy reflux step (with the heavy reflux gas obtained from the low pressure purge step), with a CO 2 purity of 78.9%, a CO 2 recovery of 57.4%, and a throughput of 11.5 L STP/hr/kg. This performance improved substantially when the CO 2 -HTlc adsorption and desorption mass transfer coefficients (uncertain quantities at this time) were increased by factors of five, with a CO 2 purity of 90.3%, a CO 2 recovery of 73.6%, and a throughput of 34.6 L STP/hr/kg. Overall, this preliminary study disclosed the importance of cycle configuration through the heavy and dual reflux concepts, and the importance of knowing well defined mass transfer coefficients to the performance of a high temperature PSA process for CO 2 capture and concentration from flue and stack gases using an HTlc adsorbent. This study is continuing.

Carbon Dioxide Separation Technologies: Applicable to Net Zero

“…However, TSA is observed to be 95% effective in recovering CO 2 from adsorbed surfaces, although it has a longer regeneration time than PSA. The requirement of high temperature during TSA and high energy during PSA methods are the most significant drawbacks of these two methods [6,7,45,46]. Yong et al [47] reviewed the various adsorbents at high temperatures.…”