Modelling of equilibrium working capacity of PSA, TSA and TVSA processes for CO2 adsorption under direct air capture conditions

• Published in: Journal of CO2 utilization Vol. 22; pp. 270 - 277
• Main Authors: Elfving, Jere, Bajamundi, Cyril, Kauppinen, Juho, Sainio, Tuomo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2017
• Subjects: CO2 capture; Direct air capture; Effect of humidity; Equilibrium modelling; Working capacity; Effect of humidity; Direct air capture; CO2 capture; Equilibrium modelling; Working capacity
• ISSN: 2212-9820; 2212-9839
• DOI: 10.1016/j.jcou.2017.10.010

[Display omitted] •Cold temperatures (0°C to −10°C) greatly increase CO2 adsorption capacity.•Humidity enhances CO2 adsorption capacity up to 65% in direct air capture.•Direct air capture using pressure swing adsorption is found not to be feasible.•Above 0.7mmolCO2/gsorbent can be achieved in temperature-swing adsorption.•Above 0.5mmolCO2/gsorbent can be achieved in temperature-vacuum-swing adsorption. In this study, direct air capture performance of polymeric adsorbent was studied by determining CO2-isotherms in very dilute conditions (CO2 partial pressure up to 5mbar). The effect of cold conditions (0°C and −10°C) and humidity on the CO2 capacity was also studied. The experimental isotherms were used in temperature-dependent equilibrium modelling to simulate equilibrium CO2 working capacities in pressure-swing adsorption (PSA), temperature-swing adsorption (TSA) and temperature-vacuum swing adsorption (TVSA). Experimental adsorption capacities of 0.80mmolCO2/gsorbent and 0.89mmolCO2/gsorbent were obtained from 400ppmv CO2 in dry cold conditions and at 25°C in humid conditions, respectively. The highest experimental capacity gained from 400ppmv CO2 was 1.06mmolCO2/gsorbent in humid cold conditions. In terms of the working capacity, PSA was found not to be a viable process option. Humidity promoted TSA working capacity up to by 0.36mmolCO2/gsorbent (78%). TSA could produce larger than 0.5mmolCO2/gsorbent working capacity levels even with very low regeneration temperatures (50–60°C) when adsorbing either in dry cold conditions or humid warm conditions. Such EWC levels with dry TVSA could only be achieved using 90°C regeneration temperature with adsorption in either cold conditions or from compressed air. Based on these results, TVSA should only be considered in PtX applications requiring high-purity CO2.