Cyclic operation of a fixed-bed pressure and temperature swing process for CO₂ capture: Experimental and statistical analysis

An adsorption process that effectively separates CO₂ from high pressure CO₂/H₂ shift gas streams to meet the requirements of pre-combustion CO₂ capture has been evaluated. A commercial activated carbon, Norit R2030CO₂, was used as the adsorbent material and different batchwise regeneration conditions were investigated. Statistical analysis by means of response surface methodology (RSM) was employed to assess the combined effect of three independent variables, namely, desorption temperature (Tdes), desorption pressure (Pdes) and purge to feed ratio (P/F ratio) on the adsorbent performance. A bench-scale fixed-bed reactor enabled the simulation of the adsorption, heating and depressurization steps of a pressure and temperature swing adsorption-based process. Experimental data were then assessed by the statistical technique and a set of mathematical equations that describes the behaviour of the given set of data were generated. No interaction effects between the independent variables on the responses were found. P/F ratio was found to be the most influential variable on working adsorption capacity, CO₂ recovery, adsorbent productivity and H₂ and CO₂ purities. The maximum CO₂ purity was obtained at 60 °C, 5 bar and a P/F ratio of 0.05. On the other hand, desorption temperature had the largest impact on the maximum rate of desorption.