High-desalting-rate seawater desalination method and device based on liquefied natural gas cold energy

Abstract

The invention discloses a high-desalting-rate seawater desalination method based on liquefied natural gas cold energy, which comprises the following steps: sufficiently carrying out indirect heat exchange on liquefied natural gas and a gas-state secondary coolant, and sufficiently carrying out indirect heat exchange on the obtained liquid-state secondary coolant and seawater to obtain ice and concentrated seawater; (2) taking the ice obtained in the step (1), standing under atmospheric pressure until the melting rate of ice is 10-50%, recovering the liquid, and taking the residual ice for later use; (3) crushing the residual ice obtained in the step (2) to obtain ice crystal granules, centrifuging, recovering the liquid, and taking the ice crystal granules for later use; and (4) completely melting the ice crystal granules obtained in the step (3). The invention also discloses a seawater desalination plant based on liquefied natural gas cold energy. The method utilizes the cold energy released in the liquefied natural gas gasification process, comprehensively utilizes the freeze desalting, gravity desalting and centrifuging desalting techniques, has the advantages of simple steps, energy saving and environment friendliness, and enhances the seawater desalting rate on the basis of freeze desalting.

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 method and device for desalination of seawater with high desalination rate based on the cold energy of liquefied natural gas. Background technique [0002] LNG (Liquefied Natural Gas) is liquefied natural gas at normal pressure and low temperature (-162°C). Theoretically, 830kJ / kg cold energy will be released. 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 the cold energy can be used for seawater desalination, it will have the following advantages: reduce the impact of LNG gasification process on th...

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Problems solved by technology

[0006] Patent document CN102583848A "Seawater Desalination System and Method Based on Liquid Natural Gas Cold Energy" and Patent Document CN101628740A "Direct Contact Freezing Seawater Desalination Method Utilizing Liquefied Natural Gas Cooling Energy" both use an ice-making device in which the secondary refrigerant directly contacts seawater , although the heat exchange efficiency is high, there are problems that the secondary refrigerant needs to be separated from the ice crystals, the ice crystals are washed, and the desalination rate of the simple freezing method is low

[0007] Patent document CN101624224A "Using the cooling capacity of liquefied natural gas with phase-change indirect freezing seawater desalination method" and patent document CN101628741A "Using the cooling capacity of liquefied natural gas without phase-change indirect freezing seawater desalination method", although the secondary refrigerant and seawater indirect exchange The method of thermal ice production does not need to separate the secondary refrigerant and ice, but it is still a pure freezing seawater desalination technology, which cannot solve the problem of low desalination rate

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