Advanced exergy and exergoeconomic assessment of a flare-gas-fired GT–HRSG–ST–ORC–LiBr polygeneration system under a locked thermodynamic boundary

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Chinese explanation / 中文解读

中文解读待补充：本站会优先为光伏效率、钙钛矿太阳能电池、储能技术、太阳能热利用、BIPV、并网技术等高价值论文补充中文说明。

Original abstract

Routine flaring of associated gas remains a major source of energy wastage, thermodynamic inefficiency, and environmental impact in hydrocarbon-producing regions. Although integrated combined-cycle and multigeneration systems have been widely investigated for waste-heat recovery and efficiency improvement, comparatively limited attention has been directed toward the combined application of conventional exergy analysis, advanced exergy decomposition, and SPECO-based exergoeconomic assessment within flare-gas-fired cascaded thermal-recovery architectures. In addition, differences in methodological treatment remain regarding thermodynamic boundary definition, refrigeration integration, and exergy-loss accounting in highly integrated polygeneration systems. This study presents a thermodynamic, advanced exergy, and exergoeconomic assessment of a flare-gas-fired gas turbine–heat recovery steam generator–steam turbine–organic Rankine cycle–LiBr–H₂O absorption refrigeration (GT–HRSG–ST–ORC–LiBr) polygeneration system operating under steady-state conditions representative of Nigerian ambient conditions. Aspen Plus was employed to develop the simulation framework, while conventional exergy analysis, avoidable/unavoidable exergy decomposition, endogenous/exogenous exergy analysis, and SPECO-based exergoeconomic evaluation were integrated within a locked thermodynamic boundary and single-product economic convention. The integrated system achieved a net electrical output of approximately 165 MW, with an electrical efficiency of 55.1% and an exergy efficiency of 53.0%. Total fuel exergy input, exergy destruction, and external exergy loss were approximately 311.43 MW, 142.10 MW, and 4.20 MW, respectively. The combustion chamber exhibited the largest exergy destruction and exergoeconomic penalty because of irreversible combustion processes and high-temperature entropy generation. Advanced exergy analysis further revealed that approximately 86.22 MW of the total exergy destruction was avoidable under realistic engineering conditions. The combustor, gas-turbine subsystem, HRSG, and steam-cycle expansion stages were identified as the primary contributors to avoidable thermodynamic degradation, whereas the ORC and LiBr subsystems mainly enhanced low-grade thermal utilisation and reduced residual thermal rejection. Parametric analysis showed that part-load ratio, steam-turbine back pressure, and HRSG pinch-point temperature difference exert strong influence on overall system performance and thermal-recovery effectiveness. The results indicate that the dominant optimisation opportunities remain concentrated within the high-temperature sections of the integrated architecture. The study presents a thermodynamically consistent framework for integrated exergy and exergoeconomic interpretation of flare-gas-fired polygeneration systems while maintaining consistency between exergy accounting, subsystem interaction assessment, and economic cost propagation. Overall, the results demonstrate the potential of integrated GT–HRSG–ST–ORC–LiBr architectures for improved flare-gas utilisation and enhanced thermal-energy recovery.

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