Performance analysis of an eight-layered bed PSA process for H₂ recovery from IGCC with pre-combustion carbon capture

Integrated gasification combined cycle (IGCC) plants that are also capable of CO₂ capture have received significant attention as the next generation of coal-based power plants for the co-production of H₂ and electrical power. Accordingly, for a cost-effective and environmentally friendly poly-generation IGCC process, efficient techniques need to be developed to recover H₂ from the syngas of an IGCC plant with carbon capture. In this study, an eight-layered bed pressure swing adsorption (PSA) process using activated carbon and zeolite simultaneously was developed to produce high purity H₂ from the H₂-rich syngas of an IGCC plant. As a first step, the separation performance was compared between four-and eight-layered bed PSA processes. The eight-layered bed PSA process led to higher recovery of H₂ at the condition of a similar H₂ purity owing to a greater number of pressure equalization steps in the operational step configuration. It is noteworthy that the productivity could be greatly improved as the purge gas was replaced from the product gas to residual gas in a bed. When the adsorption bed was purged by using the residual gas after the first pressure equalization step, recovery improved by about 3 ∼ 6 % at the condition of 99.99+ mol% H₂ purity in comparison with the product-purge PSA configuration. On the other hand, the highest H₂ recovery that could be obtained for the requirement of 99.99 mol% H₂ purity, was ∼ 89.7 % from the eight-layered bed H₂ PSA process when the purge gas was provided from the residual gas of the adsorption bed after the last depressurization pressure equalization step. However, as the concentration of CO in the desired H₂ product was higher in the PSA configuration when using residual gas compared to the product gas, the operational configuration of PSA needed to be decided by the desired H₂ purity and impurity constraints for application. Furthermore, the tail gas from the PSA contained 45–66 mol% of H₂ and CO, depending on the applied PSA configurations, and could be used to drive a gas turbine without any loss of the syngas, even though the recompression energy loss required evaluation.