Composite sea water desalination method and system based on cold energy of liquefied natural gas

Abstract

The invention provides a freezing-water adding-centrifugation composite sea water desalination method and system based on cold energy of liquefied natural gas. The method comprises the following steps: (1) exchanging heat between LNG (Liquefied Natural Gas) and a second refrigerant, and freezing sea water into sheet ice and concentrated sea water through the second refrigerant via a sheet ice maker; (2) conveying the obtained sheet ice into a filtering type centrifugal desalination device, and adding raw sea water; (3) centrifugating an obtained ice-water mixture; (4) melting separated ice. The invention further provides a sea water desalination system based on the cold energy of the LNG. According to the method and the system, the low-cost cold energy of the LNG is used as a cold source for the process; by the adding of the raw sea water, the melting of part of the ice is accelerated, and the brine viscosity on the ice surface is reduced, so that salt cells can be separated under the mechanically centrifugal action; by optimization of parameters of all stages of desalination operations, high desalinization rate and high water yield are realized; furthermore, the engineering cost is reduced, the time and the energy consumption are reduced, and balancing of factors such as an implementation factor is facilitated; the method and the system have extremely high industrial popularization value.

Description

technical field [0001] The invention relates to the interdisciplinary field of oil and gas storage and transportation, engineering thermophysics and water treatment technology, and specifically relates to a freezing-water-adding-centrifugal composite seawater desalination method and device based on the cold energy of liquefied natural gas. Background technique [0002] LNG is liquefied natural gas at normal pressure and low temperature (-162°C). It needs to be gasified before being transported into pipelines and used as fuel or chemical raw materials. When LNG is gasified, it will theoretically release 830kJ / kg of cold energy. Imported LNG receiving stations are generally built near seaports, and the cold energy released by LNG gasification is usually directly discharged into seawater. With the continuous expansion of the receiving station, a large amount of cold energy will affect the ecological environment of nearby sea areas. If this part of cold energy can be used for se...

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Problems solved by technology

At the same time, gravity desalination depends directly on the melting of ice, and the melting speed of the ice surface in direct contact with the outside world is fast while the melting speed of the interior is slow, which is not conducive to opening the salt cell structure from the inside, and it is also necessary to break the ice that has undergone gravity desalination to form a uniform Ice crystal particles, and in the subsequent centrifugal desalination step, high centrifugal speed can be used to achieve sufficient removal, resulting in complex and time-consuming process

[0005] In the freezing-microwave-centrifugal desalination process adopted in the prior art, the microwave treatment process needs to consume a certain amount of electric energy

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