Heat integration and heat recovery steam cycle optimization for a low-carbon lignite/biomass-to-jet fuel demonstration project

This paper reports the heat integration study for a demonstration plant to co-process lignite and woody biomass into jet fuel with CO2 capture and storage. Since all the main process reactions are exothermic and convert approximately 65% of the feedstock chemical energy into heat, designing an efficient heat recovery steam cycle and heat exchanger network is essential for the overall thermo-economic performance. Different integration options for the plant's heat recovery steam cycle are analyzed and compared, considering costs and the key technical limitations. The design of the heat recovery steam cycle and heat exchanger network is optimized with an energy targeting methodology, a sequential synthesis method and a recently proposed simultaneous methodology. Given the high specific costs of the units caused by the novelty and small size and of the demonstration plant, the techno-economic optimization returns solutions with considerably lower efficiency (up to −5% percentage points) and power output (up to −18%) compared to the energy targeting methodology. The difference in optimal HRSC designs and performance are minor (less than −2% power output) for full-scale plants based on mature technologies.