Hybrid membrane/absorption-adsorption separation of hydrogen-blended natural gas at receiving terminal: Process modelling and multi-objective optimization

Abstract

Hydrogen energy is an important, abundant, green, low-carbon, and widely applicable source. Using natural gas pipelines for long-distance hydrogen transportation is expected to become a significant hydrogen transport method. Therefore, efficiently recovering hydrogen at the pipeline terminal is particularly critical, with the core challenge being the effective separation of H₂/CH₄. Traditional methods, such as single-stage membrane separation and fixed-bed pressure swing adsorption, struggle to purify low-concentration hydrogen with a high hydrogen recovery ratio efficiently. This study proposes a hybrid membrane/absorption-adsorption separation process. Mathematical models have been constructed for the membrane separation unit, the absorption-adsorption separation unit, and the hybrid membrane/absorption-adsorption separation process. The suitable ranges of operating parameters are determined using sensitivity analysis. Next, a multi-objective optimization model is used to optimize operating parameters, maximize the hydrogen recovery ratio, and minimize energy consumption. Results show that the H₂ concentration in product gas can be enriched from 20 to 99.97 mol%, the hydrogen recovery ratios ranges from 98 to 98.93 %, and the energy consumption per unit of feed gas ranges from 0.2233 to 0.2757 kW⋅h⁻¹/Nm³, while the energy consumption per unit of product gas ranges from 0.9417 to 1.1611 kW⋅h⁻¹/Nm³ under different scenarios at the natural gas receiving station.