Techno-economic Analysis and Optimization of Water-Gas Shift Membrane Reactors for Low-Carbon Hydrogen Production

Hydrogen (H2) is an important energy carrier for transitioning into a decarbonized economy. H2-producing membrane reactors (MRs), such as those used for fuel reforming or water-gas shift reactions, can enable low-cost low-carbon H2 production from a variety of feedstocks, e.g., biomass, coal, or natural gas. This is a consequence of the enhanced feed utilization (i.e., kg of H2 produced per kg of eed) for the MR compared to conventional multi-step H2 generation/purification schemes. Furthermore, H2 MRs simultaneously separate H2 and concentrate CO2, thereby increasing the overall process efficiency and facilitating pre-combustion carbon capture. This work describes an equation-oriented, technoeconomic optimization model for a water-gas shift membrane reactor (WGS-MR) integrated within a 155,000 kg·H2 day−1 capacity biomass gasification process with carbon capture to produce low-carbon H2. We estimate using a WGS-MR decreased the levelized cost of H2 (LCOH) by ∼10% from $3.33 kg·H2−1 to $3.01 kg·H2−1 (2016 USD) compared to the baseline process with conventional WGS reactors and pressure swing adsorption. Sensitivity analysis elucidates the influence of operating conditions (e.g., temperature, pressure, space velocity) on performance (i.e., CO conversion, H2 recovery). Finally, we show that the LCOH could be further decreased to $2.57 kg·H2−1 (∼23% lower than the baseline) through feedstock blending (50 wt% biomass/50 wt% coal) or $2.17 kg·H2−1 (∼35% lower than the baseline) through onsite utilization of captured CO2 by avoiding transport and storage costs. This study provides a blueprint for applying MRs in low-carbon H2 production and motivates further studies on their optimal integration.