Liquefied natural gas (LNG) cold energy-driving seawater desalination device and method with double functions of vaporization and freezing

Abstract

The invention discloses a liquefied natural gas (LNG) cold energy-driving seawater desalination device and method with double functions of vaporization and freezing. The operating principle of the device is based on the characteristic that the phase equilibrium pressure of water vapor decreases along with the decrease of the temperature, the cold energy of LNG is utilized to realize low temperature and vacuum, the water vapor on the surface of the raw material seawater is pumped to promote the vaporization of seawater and the endothermal effect of the vaporization process is utilized to ensure that the raw material seawater is frozen, i.e., fresh water is separated from seawater through the two phase transition processes of vaporization and freezing. The device mainly comprises a water pump, a filter, a degassing tower, an air-precooled heat exchanger, a vaporization-crystallization device, a crystallizer, a scrubbing separator, a melting device, a vacuum pump and the like. The deviceis mainly characterized in that LNG cold energy driving is adopted, gas-liquid-solid separation is performed at the triple point of seawater, and high-quality fresh water and sea icy freshwater are obtained; and the device has the advantages of cold energy cascaded utilization, higher energy efficiency, higher fresh water yield and the like. In addition, an LNG receiving station is usually built by the sea and has good geopolitical combinability with a seawater desalination project.

Description

technical field [0001] The invention relates to seawater desalination, in particular to a double-action seawater desalination device and method of vaporization and freezing driven by cold energy of liquefied natural gas. Background technique [0002] Natural gas is the third largest energy after coal and oil in the world, and it has become an important part of my country's current energy strategy because of its clean and efficient characteristics. In order to facilitate ocean transportation, gaseous natural gas is usually liquefied into liquefied natural gas (LNG), which reduces its volume by about 600 times. About 850kWh of energy is consumed to produce one ton of LNG, and a considerable part of the energy is stored in LNG in the form of cold energy. This part of the cold energy is released during the process of vaporizing the liquefied natural gas into normal temperature gas for use by users. The process of endothermic vaporization is generally carried out in the liquefie...

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Problems solved by technology

However, the freshwater products of this method still face problems such as poor desalination effect and even pollution by secondary refrigerants, and the post-treatment process is still cumbersome.

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