Optimizing hydrogen purification from steel mill off-gas by pressure swing adsorption mediated by activated charcoal containing iron

Coke oven gas (COG) is a medium-calorific fuel gas generated in steel production, characterized by its high hydrogen (H₂) content. However, its purity falls short of the 99.97 % threshold required for H₂ fuel applications. This study introduces iron-impregnated magnetic activated charcoal (FeMAC) as a novel adsorbent in a four-step pressure swing adsorption (PSA) system to enhance H₂ purification. The incorporation of ferromagnetic iron onto commercial activated charcoal significantly improved the separation efficiency of H₂, CH₄, and CO₂, demonstrating enhanced adsorption and desorption loading rates. Compared to conventional activated charcoal, FeMAC exhibited superior H₂ purity and recovery, underscoring its potential for systematic optimization toward fuel-grade H₂ production. To investigate the effects of key process parameters, feed H₂ content, adsorption time, and pressure, on H₂ purity and recovery, an Aspen Adsorption dynamic model was developed and validated against breakthrough and PSA experimental data. Optimization using response surface methodology (RSM) and desirability function yielded an optimal PSA operating condition, achieving 99.988 % H₂ purity and 67.020 % recovery at a feed H₂ content of 56.826 %, an adsorption time of 60.423 s, and an adsorption pressure of 2.305 bar. These findings highlight FeMAC's efficiency in purifying H₂ from CH₄ and CO₂, demonstrating its potential for achieving stringent H₂ fuel quality standards. The study advances PSA-based H₂ purification technologies, offering a promising pathway for high-purity hydrogen recovery from steel industry off-gases.