(355j) Techno-Economic Analysis of Facilitated Transport Membranes for H2 Purification from Coal-Derived Syngas

A single-stage membrane process is designed for using facilitated transport membranes (FTMs) to decarbonize the coal-derived syngas from an integrated gasification combined cycle (IGCC) power plant. The necessary process model and costing method are developed to assess the technical feasibility and process economics. In order to account for the carrier saturation phenomenon associated with FTMs, a homogeneous reactive diffusion model is integrated into the process model. The techno-economic study reveals that the mitigated carrier saturation upon bulk CO₂ removal can lead to appreciable increases in the CO₂ permeance and CO₂/H₂ selectivity, which can be utilized to achieve 95% CO₂ purity and 95% H₂ recovery with a CO₂/H₂ selectivity of 50 at the complete carrier saturation. In comparison, non-reactive, solution-diffusion membranes are unsuitable for the single-stage membrane process. A CO₂/H₂ selectivity of 85 is required for 95% CO₂ purity, while a prohibitively high CO₂/H₂ selectivity of 300 is needed for >99% H₂ recovery. The optimal feed pressure is 30–40 bar in order to condition the syngas to a temperature (100–120°C) that is feasible for the FTM operation. In this case, the optimal CO₂ permeance at the complete carrier saturation is ca. 150 GPU. FTMs with different facilitated transport characteristics can also be arranged in a hybrid membrane configuration to render a H₂ recovery of 99% and a cost of electricity of $118.5/MWh, which is 12.5% lower than that of the benchmark Selexol process. In addition, a H₂S/CO₂ selectivity of 4 is required to reduce the H₂S content below 10 ppmv in the treated syngas, which can be directly fed to the combustion turbine without additional syngas sweetening.