Design and simulation of a process-integrated Pressure Vacuum Swing Adsorption system for high-purity hydrogen recovery from methane cracking

Catalytic Methane Decomposition (CMD) is one of the environmentally friendly methods for hydrogen production without emitting CO 2 . Despite this advantage, methane conversions below 35 mol% have been reported during methane cracking over carbon-based catalysts. This study proposes an integrated and energy-efficient approach to promote CMD as a viable and environmentally friendly option for hydrogen production. This research concentrated on developing a CMD unit integrated with an efficient Pressure Vacuum Swing Adsorption (PVSA) system to produce high-purity hydrogen even at higher gas hourly space velocity levels. The results of designing a 3-bed, 4-step PVSA unit using activated carbon as the adsorbent indicate that the hydrogen purity of outlet gas from the CMD unit could be increased from 45 mol% to 95 mol% through employing a PVSA unit working under feed pressure above 4 atm. The model used for this purpose was validated against experimental data, showing good agreement with an average absolute relative error below 6 %. To evaluate economic performance, this work introduces the Energy-to-Productivity Ratio (EPR), defined as the ratio of total power consumption to hydrogen productivity. Based on this parameter, working under a minimum feed pressure of 8 atm, a space velocity around 3, and a vacuum pressure of 0.15 atm guarantee high-purity hydrogen (>95 mol%) while maintaining a moderate level of EPR. Finally, recycling the off-gas stream back into the methane cracker further improved system performance through a >70 % reduction in fresh methane demand and an 11.9 % decrease in total power consumption, with hydrogen output and purity maintained. • A 3-bed, 4-step PVSA system was designed to separate hydrogen from methane. • A feed pressure above 4 atm is needed to improve hydrogen purity from 45 to 95 mol%. • Optimum energy-performance operating conditions are Pf = 8 atm, SV = 3, and Pv = 0.15 atm. • Recycling the off-gas stream leads to a >70 % reduction in fresh methane demand. • Recycling the off-gas stream reduces power consumption by 11.9 %.