Optimized process configuration for CO2 recovery from crude synthesis gas via a rectisol wash process

Rectisol wash is an economical and effective purification process which has been widely applied in the removal of acid gases (e.g. carbon dioxide (CO2)). In the present work, improvements on a typical one-stage Rectisol wash process were developed in order to increase the CO2 recovery rate and purity of the CO2 gas stream from the crude synthesis gas. The desorption of the CO2 from the solvent was accomplished by means of expansion with internal heat. Sensitivity analyses were performed to study the influence of operating parameters on the CO2 gas and sour gas streams, and the energy consumption of the improved process. Comparisons between the improved and the original processes showed that the CO2 recovery rate was greatly increased from 35% with the original process to 92% with the same CO2 purity, and the total equivalent work per unit CO2 significantly dropped from 1014 kJ/kg CO2 to 388 kJ/kg CO2. The results also showed that the changes in CO2 and H2S concentrations in the purified synthesis gas of the improved process were small and not significant, while the H2S concentration in the sour gas stream was improved.