HYDROGEN PURIFICATION THROUGH PRESSURE SWING PROCESSES – A CONFIGURATION OPTIMISATION STUDY

Abstract

This study investigated the novel pressure swing adsorption (PSA) configurations to improve the system H2 recovery and purify of carbon dioxide in the tail gas in order to achieve low-carbon hydrogen production. Two systems were developed to increase H2 recovery and purify CO2 for sequestration. These purification systems used syngas that was produced by using a biomass gasification process. Both systems contained two adsorption cyclic units. System 1 produced H2 with 98% combined purity from both units, while H2 with 99.9% purity was generated by the first unit and the second unit applied to increase CO2 to reach 95%. The tail gas from the first adsorption cycle was used as an inlet for the second unit. This feed inlet was binary gas contains only H2 and CO2. Moreover, Aspen Adsorption software was employed to conduct a dynamic simulation for these systems. A comparison between different adsorption processes was implemented to select the suitable process for recovery increment and CO2 purification. Four-bed PSA unit was the best system to be utilised to increase the system performance. Since using the four-column PSA led to a growth in the overall recovery of H2 by around 4%. By applying second the recovery of H2 expanded to 84% when the first unit recovered about 80% of H2. However, two-bed VSA showed a high performance when it was employed as CO2 capture unit. This unit consumed 0.11 MJ kg-1 CO2 of energy to recover about 48% of CO2. A sensitivity study was performed to investigate the adsorption pressure and vacuum level. Increasing the adsorption pressure caused a rise in H2 purity by 3% in PSA. Also, CO2 recovery was grown by 30% when the vacuum pressure dropped in VSA. Extensive study by increasing the bed number and applying different adsorption processes can improve the H2 and CO2 recovery in the tail.