Research On Cold And Hrat Coupling Cascade Utilization Of Large LNG-powerd Ships

With the implementation of the 2020 emission regulations of International Maritime Organization,the scale of LNG-powered ships continues to grow rapidly.The traditional single waste heat utilization or cold energy utilization technology of the ship has low energy utilization efficiency,which can't make comprehensive and efficient use of cold energy and heat energy on the LNG ship,resulting in a large amount of energy waste.In this paper,the technology of cold and heat coupling cascade utilization for large LNG-powered ships is studied.Comprehensive analysis and calculation of key parameters of air conditioning,cold storage,seawater desalination,gas turbine,waste heat boiler and steam turbine of large LNG-powered ships.According to the temperature of different modules,combined with the actual needs of the ship,three kinds of cold and heat coupling cascade utilization schemes of large LNG-powered ships are designed.The process simulation software Aspen HYSYS was used to perform numerical simulation and analysis on the designed schemes,taking the maximum efficiency as the objective function,comprehensively considering the scheme output power,and optimizing the design scheme.Analyze the scheme and the exergy loss and exergy efficiency of each subsystem,and optimize the scheme based on energy analysis.Explore the influence of refrigerant type,evaporating pressure,condensing pressure and working fluid flow on Rankine cycle output work,exergy efficiency and recovery of cold energy and heat energy.Based on the orthogonal simulation test method,using Kalina cycle output power and exergy efficiency as evaluation indexes,the effects of ammonia molar concentration,pump outlet pressure,turbine outlet pressure and turbine inlet temperature on Kalina cycle were studied to determine the best operating parameters.Finally,the scheme is optimized and improved comprehensively to form the best scheme of cold and heat coupling cascade utilization schemes of large LNG-powered ships.The total output power of the scheme is 34210 kW,the net output power is 34060 kW,and the efficiency is 54.90%.This paper provides technical support for the comprehensive utilization of cold and heat energy for large LNG-powered ships.