Method for generating by graded use of cold energy of liquefied natural gas

Abstract

The invention discloses a method for generating by graded use of cold energy of liquefied natural gas, which comprises two parts of natural gas medium Rankine cycle and cold medium Rankine cycle, and is characterized in that vaporized natural gas and another refrigerant are taken as a generating working medium, the pressure of the natural gas medium and the refrigerant medium can be controlled to realize the multiple grades heat exchange with LNG, on one hand, a problem of large available energy loss during a process that the refrigerant recovers the LNG cold energy while Rankine cycle generating can be solved (compared with a conventional method, the method provided by the invention can increase the Rankine cycle efficiency by 60-80% through the usage of LNG cold energy generating), on the other hand, the pressurized cold energy carried by the liquefied refrigerant in the Rankine cycle through system integration can be reused, the utilization efficiency of the cold energy can be enhanced; simultaneously, the heat medium water is taken as a medium, a combustion gas-steam combined power plant near a receiving station is used for generating and the heat medium water is discharged to flue gas waste heat of atmosphere as a low-temperature heat source of cold energy generating, the generating efficiency of Rankine cycle can be enhanced, the waste heat utilization can not generate unfavorable influence on the generating efficiency of the combustion gas power plant, and the thermal pollution of flue gas waste heat on environment can be reduced.

Description

technical field [0001] The invention belongs to the field of liquefied natural gas (LNG) cold energy power generation, and in particular relates to a method for cascade utilization of liquefied natural gas cold energy to generate electricity. Background technique [0002] In order to optimize my country's energy structure, improve energy utilization efficiency, and reduce carbon dioxide emissions, my country has actively developed the natural gas industry in recent years. On the one hand, it vigorously develops domestic natural gas resources, and on the other hand, it imports a large amount of natural gas from abroad to make up for the shortage of domestic resources. At present, my country has planned and constructed a number of liquefied natural gas (LNG) station line projects in coastal areas such as Guangdong, Fujian, Zhejiang, Shanghai, Jiangsu, Shandong, Hebei, and Liaoning. According to data released by the General Administration of Customs, my country imported a total...

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Problems solved by technology

[0022] The purpose of the present invention is to provide a method for cascade utilization of liquefied natural gas (LNG) cold energy to generate electricity. The method uses vaporized natural gas and another refrigerant as working media for power generation, and realizes the integration with LNG by controlling the pressure of the natural gas medium and the refrigerant medium. On the one hand, it solves the problem of excessive effective energy loss in the process of refrigerant recovery of LNG cold energy during Rankine cycle power generation, and on the other hand, through system integration, the refrigerant carried by the pressurized liquefied refrigerant in the Rankine cycle It can be reused to improve the utilization efficiency of cold energy; at the same time, the present invention uses the heat medium water as the medium to utilize the waste heat of flue gas discharged to the atmosphere after the gas-steam combined power plant near the receiving station generates electricity as a low-temperature heat source for cold energy power generation, which can not only Improve the power generation efficiency of the Rankine cycle, and the utilization of waste heat will not adversely affect the power generation efficiency of gas-fired power plants, and can reduce the heat pollution caused by waste heat of flue gas to the environment

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