Optimization of the hydrogen production process coupled with membrane separation and steam reforming from coke oven gas using the response surface methodology

As a by-product of the coking industry, coke oven gas (COG) is often burned as fuel gas. However, COG contains a large amount of hydrogen. If hydrogen is recovered, the economic and environmental benefits of the coking industry can be improved. In this work, a novel automotive fuel cell hydrogen production process coupled with membrane separation (PRISM® Membrane Separator, polyimide hollow fiber membrane), pressure swing adsorption (PSA) and methane steam reforming (SMR) is proposed. The process uses membrane separation and PSA to produce high-purity hydrogen for fuel cells. The methane-rich membrane residue gas is used as the feed gas of the reforming reactor. The hydrogen-containing gas at the outlet of the reactor enters the membrane separator to further improve the hydrogen yield. In addition, based on the principle of temperature gradient utilization, the high-temperature gas at the outlet of the reactor is used as the heat source for the system. Through a synergy of separation and reaction, the process supports the low-cost and efficient production of fuel cell hydrogen from COG. The proposed process was established using UniSim Design. The key variables were determined by sensitivity analysis, and the response surface methodology based on Box–Behnken design (BBD) method was further used to optimize the key variables. The optimal operating variables are as follows: the area of the third hydrogen membrane (HM3) is 3000 m2, the reaction temperature is 917 K and the molar ratio of steam to methane (S/C) is 1.12. The cost of the hydrogen production process is 1.56 $/kg, which means it has good prospects for use in industrial applications.