Thermodynamic analysis and optimization of a dual-pressure Allam cycle integrated with the regasification of liquefied natural gas

Abstract A novel dual-pressure Allam cycle integrated with the cold energy recovery of liquefied natural gas is proposed and analyzed in this paper. The feature of this system is that the cold energy of liquefied natural gas is successively utilized in two condensers with different condensing pressures, thereby reducing the heat transfer temperature difference in the condensation process and improving the system performance. The proposed system is discussed in detail based on the results of thermodynamic analysis and optimization. According to the simulation results, the largest exergy destruction belongs to the combustion chamber. Moreover, the exergy destruction in the condenser is greatly reduced owing to the dual-pressure condensation process. The system exergy efficiency first increases and then decreases with the increment of combustor temperature and main turbine inlet pressure. However, the system performance would deteriorate as the main turbine outlet pressure and bottom turbine outlet pressure increase. According to the results of single-objective optimization, the electricity efficiency and specific work of the dual-pressure Allam cycle are 15.76% and 68.75% higher than the classical Allam cycle, respectively. In addition, the exergy efficiency of the dual-pressure Allam cycle is up to 51.88%, which is improved by 1.57% compared with the single-pressure Allam cycle.