Simulation and Optimization of a Pressure Swing Adsorption System: Recovering Hydrogen from Methane

Recent developments in the fuel cell industry have yielded an increase in expected demand for a pure hydrogen source; one attractive method for meeting this demand involves separating hydrogen from a hydrogen-methane mixture using pressure swing adsorption (PSA). In designing PSA systems, the selection of the adsorbent and operational flowsheet are the most important and limiting decisions; beyond this, implementing systematic methods to find optimal operating conditions and bed parameters is essential. These decision variables include flowrates, bed pressures, step times and bed dimensions. This research examines this PSA system via dynamic simulation and optimization; the primary purpose of the optimization is to maximize the recovery of the key components while meeting both the hydrogen purity and cyclic steady state requirements. In this study, the process model is formulated for this separation using gPROMS. The model discretizes the spatial domain, and binary variables are used to adjust the boundary conditions for the bed as the system runs through the four-step PSA cycle. Two alternative PSA cycles are simulated, optimized and compared to assess the best performance for this PSA separation.