Membrane Separation Efficiency for Integrated Purification and Hydrogen Enrichment of Coal-Derived Synthesis Gas

This study investigates the effectiveness of membrane technologies for the integrated separation and purification of synthesis gas derived from coal gasification. Experiments were conducted using a three-stage hollow-fibre membrane system operating at temperatures between 45 and 55 °C and feed gas flow rates between 120 and 220 Nm³/h. The membrane process demonstrated high CO₂ removal efficiency, reducing the retentate CO₂ concentration from 6.1% to 0.9% and increasing the hydrogen content to 53.7%. The CO₂/H₂ separation factor ranged from 31 to 47, indicating strong selectivity. Energy consumption for single-pass processing was 58 kWh per 1000 Nm³ of synthesis gas, substantially lower than that of conventional absorption methods. The extended 48-hour operation confirmed the stability of membrane permeability and selectivity with minimal performance degradation. The final gas composition provided an optimal H₂/CO ratio suitable for Fischer–Tropsch synthesis. These results highlight the technological and economic potential of membrane separation as an efficient alternative for large-scale coal gasification applications. Beyond reporting performance, this work presents a three-stage hollow-fibre scheme with retentate recompression that maintains stable selectivity over 48 h and achieves energy use of 58–84 kWh per 1000 Nm³. In contrast to Scholes et al. (2015), who reported single-pass CO₂ removal efficiencies and CO₂/H₂ selectivities of 25–30 under different membrane materials and feed compositions, our cascade increases hydrogen in the retentate to 53.7% with CO₂ as low as 0.9%, while keeping CO₂/H₂ selectivity within 31–47 across practical flow rates. Compared with the operating windows surveyed by Brunetti et al. (2010), the 45–55 °C, ~18 bar regime used here couples higher CO₂ permeability with stable H₂ retention and documents sulfur reduction to <20 ppm, directly relevant for Fischer–Tropsch feed conditioning.