Combining exergy-pinch and techno-economic analyses for identifying feasible decarbonization opportunities in carbon-intensive process industry: Case study of a propylene production technology

• New exergy-based framework methodology for cost-optimal industrial decarbonization. • Method identifies promising modifications for unabated and retrofitted processes. • Case study: Annual emissions of 189 ktCO 2 in highly diluted flue gas (<3 vol% CO 2 ). • Novel decarbonized propane dehydrogenation (PDH) plant configuration is identified. • Results: 67% lower CO 2 avoidance cost than CO 2 capture from unmodified PDH process. Decarbonizing carbon-intensive industries requires increased co-location and integration of decarbonization technologies at existing sites to meet net-zero CO 2 emissions targets. Pinch-based energy targeting methods are commonly applied to evaluate the energy performance of competing decarbonization options. However, these methods are restricted to process modifications in heat-transfer processes and are also inadequate for investigating process electrification as a decarbonization measure. This work presents an alternative exergy-based approach within a framework that aims to maximize exergy utilization and CO 2 emissions avoidance within industrial processes retrofitted with decarbonization technologies. The framework combines an iterative exergy-pinch analysis with techno-economic analysis to identify promising process modifications. The framework is demonstrated through a propane dehydrogenation (PDH) plant case study, which presents significant challenges for end-of-pipe CO 2 capture due to the highly diluted flue gases (2.5 vol% CO 2 ). The results illustrate how the identified process modifications lead to a substantial reduction in the CO 2 avoidance costs (55–71 €/tCO 2 ), approximately 54–67% lower than those for CO 2 capture from an unmodified PDH process (155–167 €/tCO 2 ). This reduction is achieved by integrating an industrial gas turbine into the PDH process, utilizing its exhaust gases as regeneration air to pre-concentrate the CO 2 in the flue gases up to 5.5 vol% before entering the CO 2 capture plant. The proposed configuration reduces the specific energy requirement for CO 2 capture by 11%, improves exergy efficiency by 15%, and achieves a substantially higher CO 2 avoidance (56%), due to the low-carbon electricity generated, compared to CO 2 capture from an unmodified PDH process.