Energy transfer and conversion in the Allam cycle with a multi-stream heat exchanger

Abstract

The Allam cycle is renowned for its high efficiency and low emissions in power generation, utilizing supercritical carbon dioxide as the working fluid. The regenerator, one of the key heat exchangers, plays a crucial role in the system. However, modeling the regenerator is challenging due to the presence of multiple pinch points. This study proposes a regenerator model that employs three multi-stream heat exchanger modules in Aspen Plus. A thermodynamic and economic analysis of the system was conducted and compared with a conventional system utilizing the two multi-stream heat exchanger modules. Simulation results show that the combustion chamber has the highest exergy loss in the system, accounting for 46.9 % of the total exergy loss. The turbine is identified as the most capital-intensive component, representing 44.9 % of the total equipment investment. Furthermore, a sensitivity analysis was conducted on key parameters. The results indicate that under certain operating conditions, the heat provided by the air separation unit is insufficient to reduce the temperature difference at the hot outlet of the regenerator. Compared to the conventional Allam cycle system using the 2R model, the 2R model predicts deviations of up to 28.9 %. This proposed model provides a new approach for the efficient allocation of energy utilization in the multi-stream heat exchange process within the Allam cycle system.