Technical and Economic Feasibility of Flare Gas-to-Energy Conversion at a Gas Refinery

Abstract

Worldwide gas flaring has long been a major environmental waste and a significant source of greenhouse gases and local air pollution. Driven by increasingly stringent environmental regulations and growing ecological consciousness, modern refineries are now designed and operated with a strong focus on minimizing flaring as a vital means of balancing environmental sustainability with economic viability. While the Flare Gas Recovery (FGR) system is an efficient solution for recovering lowpressure off-gases, it introduces a unique engineering paradox: the compression systems required for these streams demand substantial electrical power, creating an indirect carbon footprint from power generation that must be carefully managed. To resolve this trade-off for the Skikda gas refinery, a steady-state simulation model was established using Aspen HYSYS. This model demonstrated that continuous gas recovery is structurally and safely feasible across one-, two-, and three-stage compression configurations. A critical time-based evaluation further confirmed the technical feasibility of both NGL recovery and direct power generation options. The comprehensive assessment definitively showed that while both are viable, directing the captured gas to a turbine network for direct electricity production is the superior financial and environmental strategy. This route demonstrably outperforms NGL recovery, yielding a significantly higher power output (217.56 MW), generating a considerably larger annual net profit—roughly 11.3 times greater—and achieving the shortest payback period of just 2.33 years. Moreover, this approach provides substantial environmental benefits by avoiding approximately 1.1 million tonnes of CO2 emissions annually. The performance measures for this optimization identify a design sweet spot with two gas turbines in series utilizing a conveyance pipeline of 0.0889m internal diameter, which achieves the maximum annual net profit at a perfectly balanced capital investment. Although this option entails higher complexity and upfront capital costs (USD 102.18 million for key equipment), its unmatched annual net profit of $14.06 million and exceptional scalability make it the best option for efficient flare gas recovery. This alignment with global climate policy goals and the ability to transform a legacy waste stream into high-yield, sustainable utility power ultimately offers a replicable, data-driven blueprint for the development of modern, sustainable refining infrastructure.