CO2 capture from dry flue gas by means of VPSA, TSA and TVSA

Abstract

A systematic study of adsorption processes at lab-scale for CO2 capture from dry flue gas was presented to attain the specification of CCS (95% CO2 purity, 90% CO2 recovery) in this work. With zeolite 13X as adsorbent, two-stage vacuum swing adsorption (VPSA), temperature swing adsorption (TSA), and temperature/vacuum swing adsorption (TVSA) were designed, simulated, and systematically compared at lab-scale. Furthermore, key operating parameters including feed flowrate, purge to feed ratio, vacuum level, time of recycle step were investigated to obtain the optimized process performance. The results showed that CO2 products of all three processes could reach the specification of CCS. VPSA was capable to achieve a great advantage in productivity and energy consumption with the value of 3.8 molCO2/kgads/h and 0.79 MJ/kgCO2 respectively, and it seemed to be the most effective CO2 capture process compared with TSA and TVSA. TVSA performed best in CO2 purity and recovery with the value of 97.27% and 97.66% respectively, meanwhile the productivity was up to 1.63 mol/kgads/h with the energy consumption of 3.22 MJ/kgCO2. Moreover, it is worth noting that TVSA would be an energy saving adsorption process that can produce CO2 product with high CO2 purity and CO2 recovery if a suitable low-grade waste heat source was available. Nevertheless, TSA was suggested to be an inefficient way for CO2 capture due to its poor performance of productivity and energy consumption, as well as no advantage in terms of CO2 purity and recovery.