Innovative utilization of waste heat in enhancing hydrogen liquefaction efficiency using heat recovery: comparative analysis of ABR, DAR, and ORC/Kalina cycles

Abstract

Various methods have been proposed and developed to reduce the energy required for hydrogen liquefaction and improve its thermodynamic and exergy efficiency. One effective strategy involves utilizing waste heat from power plants. This thesis investigates three novel scenarios for using 2000 kilowatts of excess heat in a hydrogen liquefaction cycle. The first scenario integrates an Ammonia-Water Absorption Refrigeration (ABR) Cycle to absorb waste heat and provide part of the required precooling. The second scenario directs waste heat to a Diffusion-Absorption Refrigeration (DAR) Cycle to aid hydrogen precooling. The third scenario employs a combination of Organic Rankine Cycle (ORC) and Kalina Cycle to convert waste heat into electrical power, supplementing the energy needed for liquefaction. Energy simulations revealed that the ORC/Kalina-based scenario achieved the lowest specific power consumption at 4.306 kWh/kg LH₂, slightly outperforming the DAR-based and ABR-based scenarios. All scenarios showed improved coefficients of performance, approximately 2% higher than the baseline and significantly better than reference values. Pinch analysis demonstrated high performance across all scenarios, with minimal temperature differences between hot and cold curves, indicating efficient energy utilization. Exergy analysis identified heat exchangers as the primary contributors to exergy destruction, accounting for nearly half of the total in each scenario. The ABR-based cycle exhibited the highest total exergy efficiency at 52.47%. The ORC/Kalina-based scenario showed the highest exergy efficiency for the H₂ pre-cooling process at 70.84% and the lowest overall exergy destruction. These findings underscore the potential of integrating waste heat recovery systems to enhance hydrogen liquefaction efficiency.

Date	23 Oct 2024
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Adrian Ilinca (Supervisor)