Integrated environmental and techno-economic assessment for membrane-based gas-to-liquid process to green flare gas valorisation

Abstract

This study provides a detailed techno-economic and environmental analysis of the Gas-to-Liquid (GTL) conversion process, comparing an innovative membrane-based design with the traditional GTL process. Both designs were validated through comprehensive simulations, with mass and energy balances aligned with literature data. Due to economic and environmental factors, the membrane-based design was iteratively refined to develop an efficient GTL configuration. Using an integrated environmental-economic algorithm, lifecycle assessment and economic analysis were conducted simultaneously. Results indicate that the total capital investment for the membrane-based design, approximately $1941 million, is 26 % lower than the conventional design, which costs $2616 million. Production costs in the membrane-based design decreased by about 10 %, reaching $1298 per ton compared to $1503 per ton for the conventional design. Additionally, the payback period and internal rate of return improved by 47 % and 86 %, respectively. Environmentally, the membrane-based design reduced the total carbon footprint by 14 % (from 41.20 to 20.83 tons of CO₂ per hour) and water footprint by 13 %. Other environmental impacts include reductions in acidification potential (19.4 %), eutrophication potential (19.6 %), ozone depletion potential (51.3 %), photochemical ozone creation potential (17.4 %), and human toxicity potential (22.3 %). Sensitivity analysis identified a flare gas flow rate of 138 kg per unit performance as the optimal balance between carbon footprint and payback period. This study demonstrates the superiority of the membrane-based design in maximizing the value of flare gas, offering an innovative solution for GTL processes.