High-Performing Vacuum-Pressure Swing Adsorption Unit for Drying Hydrogen from Water Electrolysis

The growing demand for ultrapure hydrogen in fuel cell applications requires the development of efficient and cost-effective purification technologies. This study reports the development, optimization, and techno-economic assessment of a vacuum-pressure swing adsorption (VPSA) system for hydrogen drying in compliance with the ISO 14687-2 standard. Activated alumina was employed as the adsorbent, and experimental validation demonstrated a reduction in water content to dew points below -65.5 °C, with a concentration of 5 μmol of H₂O per mol of H₂. Adsorption isotherms for hydrogen and water were measured and modeled using the Langmuir and Toth-Aranovich-Donohue equations. Several regeneration strategies were evaluated, with the combined application of vacuum and purge gas identified as the most effective. A Box-Behnken response surface methodology was employed to optimize operating parameters, and the optimal conditions were experimentally validated. Under these conditions, the VPSA achieved a hydrogen recovery of 98.98%, a productivity of 3.92 kg_H2 ·kg_ads ^-1·cycle^-1, and a dew point of -66.76 °C. A techno-economic analysis of a hypothetical unit producing 300 kg·h^-1 of hydrogen, scaled from laboratory data, demonstrated the economic feasibility of the VPSA process. When hydrogen was fed in a compressed state at 7.34 bar, the additional specific energy consumption and cost associated with the purification step were estimated at 0.038 kWh·kg^-1 and 0.039 €·kg^-1 of H₂, respectively. These results highlight the VPSA system as a promising solution for high-purity hydrogen drying, combining robust operational performance with strong economic viability.