Principle Of Increasing And Reducing Pressure Of LNG Storage Tank

Principle of increasing and reducing pressure of LNG storage tank
Pressurization of LNG storage tank:
With the use of LNG, the liquid level in the tank continues to decline, and the increase of gas phase space makes the pressure in the LNG storage tank continuously decrease, and the outflow rate of LNG gradually slows down until it stops. Therefore, it is necessary to constantly supplement gas to the tank during normal operation to maintain the pressure in the tank within a certain range. This process is called supercharging. Its principle is as follows: the pressurization of the storage tank is completed by the automatic pressurization system composed of self-reliant pressurization regulator and small air temperature gasifier.
Principle of increasing and reducing pressure of LNG storage tank
When the pressure in the LNG tank is lower than the set value of the automatic supercharger, the voltage regulator opens, and the liquid in the tank slowly flows into the supercharger by the liquid level difference, and the gas generated by liquid gasification flows through the voltage regulator and the gas phase pipe to the storage tank. The continuous replenishment of gas makes the pressure in the tank rise, when the pressure rises to the regulator set value above, the regulator shuts down. At this point, the pressure in the pressurized gasifier will prevent the continued flow of liquid, and the pressurization process is over.
Decompression of LNG storage tanks: (overpressure protection)
In the process of storage, LNG will slowly evaporate due to environmental heat leakage in the LNG tank, resulting in a gradual increase in tank pressure, and ultimately endangering the safety of the tank. Therefore, the upper pressure limit must be controlled by releasing the gas in the tank. The method is to set a voltage regulator on the gas phase pipeline of the tank. When the pressure in the tank rises to the set value, the pressure reducing valve will slowly open, and the gas in the LNG tank will be released. When the pressure drops back below the set value, the automatic voltage regulator will automatically close. It should be pointed out that the voltage regulator mentioned here is not our commonly used gas regulator. General voltage regulator by the outlet end of the pressure control valve action, and the pressure regulator by the inlet end of the pressure control valve action, like our commonly used release valve, in addition to it to withstand low temperature. The released gas is generally not put into the atmosphere, and later processes will recover it. This gas is called BOG