Comprehensive parametric investigation of methane reforming and hydrogen separation using a CFD model

Steam-methane reforming is the primary method for industrial hydrogen production. High energy consumption and elevated greenhouse gas (GHG) emissions call for a significant improvement in the reforming process for optimum methane conversion and hydrogen production. Enhanced fuel conversion also produces more CO₂ than CO, making the carbon capture process easier, consequently reducing harmful emissions. In this work, a membrane-integrated reformer reactor (MRR) has been investigated through an experimentally validated computational fluid dynamics (CFD) model using ANSYS-Fluent. The MRR model constitutes of Ni-based catalyst filled reforming zone, Pd-based hydrogen-selective membrane, and permeate zone for hydrogen recovery. The developed model has been examined for several parameters including steam-to-methane ratio, flow rate, sweeping conditions, flow direction, reformer pressure and membrane length. The results indicated a substantial increase in methane conversion with a higher steam-to-carbon (S/C) ratio for a given feed flow rate. The methane conversion increased from 34% to 63% when the S/C ratio is increased from 2 to 6 at a methane mass flow rate of 0.0018 kg/s. The results also indicate an increase in hydrogen recovery with the decrease in feed flow rate for a fixed steam-to-methane ratio. Hydrogen recovery decreased from 28% to 2% when the mass flow rate of methane is increased from 5 × 10^-5 kg/s to 1.8 × 10^-3 kg/s, at a fixed S/C of 4. The incorporation of sweeping steam demonstrated a significant improvement in hydrogen recovery increasing from 15% to 33% with a sweep flow rate equal to the feed flow rate and methane mass flow rate of 1.8 × 10^-4 kg/s. Further increase in sweep flow rate showed very small increase in hydrogen recovery, therefore in order to minimize the use of sweeping steam, a sweeping steam flow rate equal to the feed flow rate is suggested. Furthermore, flow direction, reformer pressure and membrane length were also found to play vital role in MRR performance.