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Thermo⁃Economic Analysis of Dual⁃Flash Combined Cycle System Using LNG Cold Energy
Zhongrui ZHANG, Yuanyuan JIANG, Yingju CAO, Xuyang CHEN, Changshun WANG, Wenquan JIANG
Abstract622)   HTML3)    PDF (1851KB)(26)      

A new type of combined cooling, heating and power (CCHP) system is proposed, consisting of a dual recompression Brayton cycle, a CO2 reheat Rankine cycle and a two?stage flash cycle, to achieve synergistic waste heat recovery from a natural gas?fueled solid oxide fuel cell, utilization of liquefied natural gas (LNG) cold energy, and capture of CO? from flue gas. The cycle system was simulated using thermodynamic simulation software to analyze the effects of the mass fraction of mixed workmass Xe, the inlet pressure p23 of the CO2 reheat Rankine cycle expander, the pump outlet pressure p26 of the flash cycle, and the shunt ratio x on the system's thermal efficiency, saprophytic efficiency, net work output, and cold water recovery rate. The results demonstrate that increasing p23 is favorable to improve the net output work, thermal efficiency and hydronic efficiency of the system; decreasing p26 is favorable to improve the net output work and thermal efficiency of the system, and increasing the Xe mass fraction and shunt ratio can improve the net circulating work, thermal efficiency and hydronic efficiency of the system. When the mass fraction of Xe is 0.3, p23 is 16 MPa and p26 is 13.5 MPa, the thermal efficiency, the net efficiency and the net output work of the system are 67.17%, 58.13% and 2 587.96 kW, respectively.

2025, 45 (5): 73-80. DOI: 10.12422/j.issn.1672-6952.2025.05.009
Performance Analysis of the Kalina⁃Three⁃Stage Organic Rankine Combined Cycle Based on LNG Cold Energy
Xuyang CHEN, Fan YANG, Wenquan JIANG, Haotian ZHENG, Dawei TIAN
Abstract1763)   HTML11)    PDF (2059KB)(967)      

A power cycle (KC-TORC) combining a Kalina cycle and a three?stage organic Rankine is proposed to address the problems of large flue gas discharge with high temperature and low flue gas outlet temperature that is easy to cause corrosion of industrial pipelines in the industrial production process. A circulation system was constructed by using the method of thermodynamic simulation, taking industrial flue gas as the heat source and liquefied natural gas (LNG) as the cold source,and the effects of kalina cycle evaporation temperature, LNG post?pump pressure and three?stage organic Rankine cycle (ORC) turbine inlet temperature on the thermodynamic performance were analyzed by varying the flue gas outlet temperature. The results show that the maximum exergy efficiency is 62.89% at a flue gas outlet temperature of 30 ℃ and a Kalina cycle evaporation temperature of 112 ℃. The maximum thermal efficiency is 32.09% at a flue gas outlet temperature of 120 ℃ and three?stage ORC turbine inlet temperature of 160 ℃, and the net output power can be up to 2.04 MW. The annual NAV could be up to 5.773×106 dollars. The KC?TORC power cycle shows good advantages in thermodynamic and economic aspects, which is important for environmental protection.

2024, 44 (5): 90-96. DOI: 10.12422/j.issn.1672-6952.2024.05.013