Development And Optimization Of Power Generation And Air-conditioning Utilizes LNG Cryogenic Energy

Liquefied natural gas (LNG) is a kind of liquid mixture after desulfurizated, it should begasified and release a large amount of cold energy which value is about830kJ/kg beforesupplied to the downstream users. These cold energy is carried away by the seawater or airwhich is not only causing great waste of energy, but also polluting the environment. Somaking full use of the cold energy of LNG can have some very important theoretical andpractical significance. However recovery and use these cold energy of LNG is facing sometroubles, such as tight supply of resources, the spot price and the long-term contract price,slow development of LNG cold energy utilization projects, the way of utilization is single andefficiencies is low, the cold energy users and cold energy suppliers is not synchronized and soon. So these troubles make large-scale development of LNG cold energy hampered.High-grade cold energy of LNG is proposed to recycle for power generation andlow-grade cold energy of LNG is proposed to recycle for ice storage air-conditioning base onthe advantages of power generation using cold energy and ice storage air-conditioningsupplying cold energy to living area according to the analysis of exergy and thevariable-temperature trend of working fluid. Using process simulation techniques, pinchanalysis, exergy analysis, comparing the exergy efficiency change of working fluids in thekey equipments under different flow, selecting the optimal system parameters. The massconcentration of32%aqueous solution of ethylene glycol is used as ice storageair-conditioning refrigerant. Propane mass concentration of50%propane-butane mixture asthe working fluid is used in the power generation process. When the flow of LNG is1000kg/hr, the optimal flow of the working fluid is1270kg/hr, evaporating temperature is10℃，evaporating pressure is0.35MPa, the condensing temperature is-22℃, condensingpressure is0.11MPa.From these results, based on a power plant, using this process to case simulation andanalysis, link with the value-benefit analysis calculated the economic benefits of LNG coldenergy recovery. For a LNG gasification station with the scale of35000Nm3/hr, recoveryhigh-grade cold energy for power generation can achieve annual net benefit of0.603millionyuan, recovery low-grade cold energy for ice storage air-conditioning can save about10.78million yuan every year, the totle value of benefit is approximately11.38million yuan.