(122f) A Dual-Adsorbent, Two-Bed VSA Process for CO2 Capture from Wet Flue Gas

Various options for the capture and concentration of CO₂ from a wet flue gas at 25^oC containing 15% CO₂ in 82% N₂ and 3% moisture have been analysed through detailed simulation and optimization based on equilibrium data of CO2 and N2 that were measured in our laboratories. Dynamic column breakthrough experiments were performed to validate the binary equilibrium between CO2 and N2. The data for water adsorption was obtained from the literature [1, 2].

First, the best cycle for dry flue gas, consisting of 4 steps including light product pressurization in a column packed with zeolite 13X established in an earlier communication [3] and demonstrated at a pilot scale [4], was applied to wet flue gas. The minimum energy consumption in this process, in order to achieve 95% purity (dry basis) and 90% recovery was 195.1 kWh/tonne CO₂ captured with a productivity of 1.32 tonne CO₂/m³ adsorbent/day. This energy consumption was considerably higher and productivity considerably lower than those reported for dry flue gas. Next, in order to improve the energy performance, a new dual adsorbent, 4-step VSA process with silica gel and zeolite 13X. The process was then simulated and optimized. With the proposed new cycle, it is shown that 95% purity and 90% recovery target is achievable at a lower energy penalty (177 kWh/tonne CO₂ captured) while also improving the productivity (1.82 tonne CO₂/m³ adsorbent/day). 

References

1.  Wang, Y.; LeVan, M. D., Adsorption equilibrium of carbon dioxide and water vapor on zeolites 5A and 13X and silica gel: Pure components. J Chem EngData 2009, 54, (10), 2839-2844.
2. Wang, Y.; LeVan, M. D., Adsorption equilibrium of binary mixtures of carbon dioxide and water vapor on zeolites 5A and 13X. J Chem EngData 2010, 55, 3189-3195.
3. Haghpanah, R.; Nilam, R.; Rajendran, A.; Farooq, S.; Karimi, I. A., Cycle synthesis and optimization of a VSA process for post combustion CO₂ capture. AIChE J 2013, 59, 4735-4757.
4. Krishnamurthy, S.; Ramarao, V.; Guntuka,S.; Haghpanah,R.; Sharratt, P.; Rajendran, A.; Karimi, I.A.; Ullah, M.A.; Farooq, S., Post combustion CO₂ capture by vacuum swing adsorption: A pilot plant study. AIChE J 2013, 60, 1830-1842.