The structure of cryogenic storage tank and the principle of decompression and supercharging

LNG cryogenic tank structure diagram and its decompression and pressure boosting principle

   The cryogenic storage tank has a double-layer structure. The inner tank stores low-temperature liquid and withstands the pressure and low temperature of the medium. The material of the inner tank is made of low-temperature resistant 30408 stainless steel; the outer shell is a protective layer of the inner liner, and a certain distance is maintained between the inner liner and the inner liner to form a heat insulation. Space, withstand the gravity load of the liner and medium and the vacuum negative pressure of the insulation layer. The outer casing is not exposed to low temperatures and is made of container steel. Most of the insulation layer is filled with pearl sand and a high vacuum is applied. The evaporation rate of cryogenic storage tanks is generally less than 0.2%.

The liquid from the cryogenic storage tank is powered by the self-pressure of the storage tank. After the liquid is sent out, the liquid level drops and the gas phase space increases, causing the pressure inside the tank to drop. Therefore, it is necessary to continuously replenish the gas in the tank and maintain the pressure in the tank to meet the process requirements. As shown in Figure 2, a pressurized gasifier and a booster valve are provided below the tank. The supercharged gasifier is an air-temperature gasifier that is installed at a lower level than the lowest level of the tank. The booster valve is opposite to the action of the pressure reducing valve, and is opened when the outlet pressure of the valve is lower than the set value, and is closed when the pressure rises above the set value.

   The pressurization process is as follows: when the pressure in the tank is lower than the set value of the booster valve, the booster valve is opened, and the liquid in the tank is slowly flowed into the pressurized gasifier by the liquid level difference, and the gas generated by the liquid gasification flows through the pressurization. The valve and gas phase tube are replenished into the tank. The constant replenishment of the gas causes the pressure in the tank to rise, and when the pressure rises above the booster valve setting, the boost valve closes. At this point, the pressure in the pressurized gasifier will prevent the liquid from continuing to flow in, and the pressurization process ends.