Membrane-assisted natural gas liquids recovery: Process systems engineering aspects, challenges, and prospects

Membrane-based natural gas liquid (NGL) recovery processes are still far from their large-scale applications owing to communication gaps among academic researchers and industry practitioners. A comprehensive process systems engineering (PSE) assessment of membrane-based NGL recovery processes is required to determine their commercial suitability. This PSE-based review presents the technical and economic aspects of standalone and integrated membrane processes. Literature review shows that polymeric membranes (e.g., cellulose acetate) are primarily evaluated in NGL recovery processes despite their low separation efficiencies. So far, multiple multistage membrane models with standalone and integrated designs have been suggested by analyzing different configurations to improve separation efficiency. In standalone processes, cellulose acetate membrane modules with high selectivity ratio can improve methane recovery by up to 100%. Absorption or cryogenic integrated processes exhibit high methane recovery (up to 99%) but demonstrate high energy consumption. The integrated absorption-membrane process is more capital cost intensive (i.e., 0.41 m$) than the cryogenic-membrane process (0.39 m$). Furthermore, in this review, the key challenges encountered by membrane processes and related issues are identified to improve their commercial viability by capitalizing on their maximum potential benefits. The major challenges associated with membrane processes constitute the lack of rigorous multistage membrane models and inflexibility in product purity and recovery. The policy implications and future directions suggest that owing to the growing demand for NGLs, membranes that can sustain varying natural gas compositions and conditions may be required. This PSE assessment will help process engineers and policymakers to improve natural gas supply chain economics.