Method and device for preparing liquid CO2 (carbon diode) by cold energy of LNG (liquefied natural gas)

Abstract

The invention discloses a method and a device for preparing liquid CO2 (carbon diode) by cold energy of LNG (liquefied natural gas). The method comprises the following steps of pumping the LNG into a tube of a shell-and-tube heat exchanger, releasing the potential heat of the LNG in the tube of the shell-and-tube heat exchanger, cooling and liquefying the lower-temperature gaseous CO2, sending the gasifying byproduct of the LNG as a cold source into a multi-strand flow plate fin type heat exchanger, cooling the raw CO2, then sending into a CO2 compressor, cooling the outputted high-pressure and high-temperature CO2, raising the temperature of the LNG, and gasifying the LNG into the normal-temperature natural gas with the temperature of 10-20 DEG C; sending the cooled CO2 into a shell of the shell-and-tube heat exchanger, dividing the liquid CO2 flowing from an outlet of the shell of the shell-and-tube heat exchanger into two branches, sending one branch into a liquid CO2 storage tank, and sending the other branch into a dry ice machine to prepare carbon dioxide ice. The method has the advantages that the gradient utilization of the cold energy of the LNG is realized, and the utilization rate of the cold energy of the LNG is high; the preparation pressure of the liquid CO2 and the carbon dioxide ice is decreased to 0.6-1.0MPa by the cold energy of the LNG, the gaseous CO2 at the inlet of the compressor is cooled to the temperature of -40 to -30 DEG C, and finally the effect of saving the energy by more than 58% is realized in comparison with the effect of the common low pressure method.

Description

technical field [0001] The invention relates to the field of preparation of liquid carbon dioxide and dry ice, in particular to a process and a device for preparing liquid carbon dioxide and dry ice by utilizing cold energy of LNG. Background technique [0002] In recent years, my country's liquefied natural gas (LNG) market has developed rapidly, and in 2013 it reached an annual LNG import volume of about 18 million tons. Usually, at the LNG receiving station or satellite station, it is necessary to convert LNG into gaseous natural gas (NG for short) through heat exchange and temperature rise. Aiming at the cold energy released during the gasification process of LNG, many researchers have carried out relevant research, such as the use of LNG cold energy in air separation, cold storage and ice making. Therefore, the development of new LNG cold energy application fields has positive significance for enhancing the flexibility of LNG cold energy utilization projects and reduci...

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Problems solved by technology

[0005] None of the above prior art involves making full use of the cold energy of LNG gasification and liquid CO with low system energy consumption. 2 and dry ice preparation technology

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