Industrial & Engineering Chemistry Research, Vol.48, No.9, 4445-4465, 2009
Separation of Concentrated Binary Gases by Hybrid Pressure-Swing Adsorption/Simulated-Moving Bed Processes
Stripping-type PSA (S-PSA) is a commonly used gas separation process for purification of the fight component. Rectifying-type PSA (R-PSA), not commonly used, is a gas separation process for purifing predominately the heavy component. Because S-PSA and R-PSA each tend to favor the production of a single product, these processes are typically not used for complete binary separation. On the other hand. the gas-phase simulated-moving bed (SMB) is capable of achieving complete binary separation however, its commercial application has been stymied by the need for carrier gas/desorbent recovery and unfavorable economics. In this work, S-PSA and R-PSA are combined with a two-zone SMB to develop S-PSA/SMB and R-PSA/SMB hybrid processes and these processes are integrated into combination-type C-PSA/SMB processes. Combining PSA and SMB eliminates the carrier gas/desorbent by taking advantage of-as expansion and by using both light and heavy purge streams. Separation of H-2 and CH4 mixtures with Zeolite 5A was Simulated to determine the feasibility of the hybrid processes. The primary products are H, and CH4 plus an impure offgas may be produced. Complete binary separation can be achieved by recycling the entire off-as stream. The best separation was achieved with an eight-bed combination of the S-PSA/SMB and R-PSA/SMB processes, the SRC-PSA/SMB. This process separated a 70% H-2/30% CH4 feed into 99.99% H-2, with 99.6% H-2 recovery and 99% CH4 With 99.9% CH4 recovery with productivity of 9.37 x 10(-5) mol feed/(kg.s) and an energy requirement of 260.9 kJ/mol feed.