Techno-Economic Assessment of Facilitated Transport Membranes for H2 Purification and CO2 Capture from Steam Methane Reforming Syngas

A single-stage membrane process is designed for using facilitated transport membranes (FTMs) to decarbonize the syngas produced from the steam methane reforming (SMR) process. 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 75 is required for 95% CO₂ purity, while a prohibitively high CO₂/H₂ selectivity of 250 is needed for >95% H₂ recovery. The optimal feed pressure is 10 – 15 bar in order to condition the syngas to a temperature (100 – 120°C) that is optimal for the FTM operation. In this case, the optimal CO₂ permeance at the complete carrier saturation is ca. 350 GPU (1 GPU = 10^–6 cm³(STP) cm^–2 s^–1 cmHg^–1). FTMs with different facilitated transport characteristics can also be arranged in a hybrid membrane configuration to render a H₂ recovery of 99% with a H₂ purification cost of $1.4/kg of H₂ and a carbon capture cost of about $44/tonne of CO₂.