Simulation of the Allam cycle with carbon dioxide working fluid and comparison with Brayton cycle


The Allam Cycle takes a novel approach to reducing emissions by employing oxy-combustion that utilizes carbon dioxide (CO2) working fluid, highly recuperated cycle. In this research, the main parts of the Allam cycle, including the combustion chamber, air separation unit, heat exchanger and cooling tower, have been simulated in Thermoflow software. This cycle is based on combustion using pure oxygen instead of ambient air and the working fluid of this cycle is carbon dioxide. According to the results of the validation part of the initial simulation, the efficiency of the supercritical carbon dioxide cycle with three cooling stages in the compression part (in non-optimal and initial state) is 54%, which is approximately 4% of the cycle efficiency. By reducing the inlet fluid pressure to the pump from 75.38 to 73.43 bar, the cycle efficiency increases from 53.9 to 54. According to the second part of the results, which shows the effect of combustion chamber temperature (in the range of 800–1300 °C) on cycle performance, by increasing the combustion chamber temperature from 800 to 1200 °C, the cycle efficiency increases from 44.61 to 61.38. Also, the highest efficiency of the Brayton cycle is obtained in the pressure ratio of 20, which is approximately equal to 38% for the cycle with real specifications, while the highest efficiency is obtained in the Allam cycle with a pressure ratio of 10, which is about 55%. Therefore, in addition to being able to absorb 100% of carbon dioxide, the Allam cycle has a much higher efficiency than the Brayton cycle.

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adapted from Allam et al., [19]

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Correspondence to Alireza Saraei.

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Dokhaee, E., Saraei, A., Jafari Mehrabadi, S. et al. Simulation of the Allam cycle with carbon dioxide working fluid and comparison with Brayton cycle. Int J Energy Environ Eng 12, 543–550 (2021).

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  • Gas turbine
  • The Allam cycle
  • Brayton cycle
  • Carbon dioxide
  • Pressure ratio