Superstructure based techno-economic optimization of the organic rankine cycle using LNG cryogenic energy. (15th October 2017)

• Record Type: Journal Article
• Authors: Lee, Ung; Jeon, Jeongwoo; Han, Chonghun; Lim, Youngsub
• Is Part Of: Energy. Volume 137(2017)
• Page Start: 83
• Page End: 94
• Publication Date: 2017-10-15
• Subjects: LNG -- ORC -- Multi component working fluid -- Superstructure -- Genetic algorithm -- Multi stage rankine cycle -- Direct contact heater -- Optimization; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2017.07.019
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: A process design of the organic Rankine cycle utilizing LNG cryogenic exergy is proposed using superstructure optimization. The superstructure imbeds about 1024 possible process alternatives, and the most profitable process configuration and the operating condition are decided simultaneously using a stochastic optimization solver and Aspen Plus-MATLAB interface. The optimum process configuration includes a multi stream cryogenic heat exchanger, a five-stage turbine with reheaters, three stage vapor re-condensation processes and direct contact heaters. In addition, the exergy transfer from the LNG to the working fluid is maximized by using a multi component mixture as working fluid. The 1st law efficiency of the proposed process reaches about 26.2% with 85 °C of waste heat source and it is about 42% higher than that of the conventional ORC. The annual profit of the optimum process is about 39 M$ and it can be interpreted as 24$ of profit per kg LNG evaporation. Sensitivity analysis is also presented to show the reliability of the stochastic solution found in this study. Graphical abstract: Highlights: Optimum process design of the ORC utilizing LNG cold exergy is proposed. A superstructure imbedding most process alternatives is constructed. Optimum process is obtained in systematic way using stochastic optimization. Optimum process generates 40% more power than simple ORC.