Research On Efficient Utilization Of LNG Cold Energy Integrated Combined Cycle Systems

To overcome the problem of energy supply security and environment protect in China,gas turbine industry has been accelerating developed,correspondingly the import quantum of LNG and LNG industries grows fast.During the vaporized process of LNG,it releases a great deal of cryogenic energy.Using the cryogenic energy of LNG cold energy efficiently helps save energy.For the application of LNG in refrigeration industry,a new model of ammonia-water absorption refrigeration system is proposed and analyzed.Cold energy which is released from the LNG vaporization will be used in the system as a low-temperature receiver,under the conditions,a small amounts of high-grade cold energy is absorbed by the system and amounts of low-grade cold energy is produced.After having a thermodynamic analysis of the system,the results show that: the proposed system presents a refrigeration performance.With the increasing amount of distilled ammonia from the top of distillation column,the coefficient of performance of the system will rise.Good performance can be gained when the evaporating temperature gets higher.The coefficient of performance of the system can reach above 1.8,as if the refrigeration temperature is 10?.Based on the above,this paper has proposed a novel combine cold and power system,in which low-temperature waste heat can be efficiently recovered and high-grade cold energy of liquefied natural gas(LNG)can be fully utilized as well.Under design condition,the coefficient of refrigeration performance of system is 1.6,with net electric efficiency and exergy efficiency of 38.8% and 36.1%.Parametric analyses are performed for the proposed combined cold,power system to evaluate the effects of key factors on the performance of the new system through simu lation calculations.Results show that: with the increase of distillation rate,ammonia concentration of generator and import pressure of ammonia turbine,the refrigeration effect of system will be enhanced.The thermal performance will be enhanced,when distillation rate of generator and LNG import pressure increase,the outlet pressure of ammonia turbine decreases.Based on the integration principle of energy system and the combined cycle,an LNG cold energy integrated combined cycle is proposed in this p aper.LNG low-temperature Rankine cycle is integrated to the combined cycle,meanwhile,LNG cold energy is applied to optimize the gas turbine on the top of the cycle and the condenser on the bottom of the cycle.The result shows that: compared to normal combined cycle,the new system has an increment of system efficiency 0.6%,power output 2.1%.