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Pressure control method for LNG storage tank
Date: Nov 21, 2019
Leakage of the system during storage can result in partial vaporization of the liquid, causing the pressure of the LNG storage tank to rise. In order to achieve no LNG gas release during the set storage time, many LNG filling stations adopt a zero-distribution design process.
Raw material conditions of LNG filling station: -146 ° C, 0.3 MPa; lng storage tank LNG state: 50 psig. When the unloading procedure is run, the gas of the LNG tank is first reversed to the liquid phase of the tank truck through the process pipeline, and the fresh LNG can be cooled to a liquid with the gas of this part.
When the pressure of the LNG storage tank is balanced with the pressure of the tank truck, the LNG pump is started to take the LNG out of the tank truck, spray it into the tank from the top of the tank, and cool the gas in the tank to a liquid by using fresh LNG cooling. Due to the liquefaction of the capping gas, the pressure of the capping is lowered and lower than the tank truck pressure. When the pressure difference is greater than 15 psig, the inlet valve at the bottom of the LNG storage tank is opened, and the LNG flows into the LNG tank from the pipe body and the bottom at the same time, thereby achieving a fast and stable unloading process.
During the process of filling the tank for the LNG vehicle, the LNG pump draws the LNG from the bottom of the tank and is pressurized to 220 psig (10 psi below the set pressure of the vehicle tank safety valve) driven by the frequency converter. ), from the top of the irrigation sprinkler into the vehicle storage tank, using the cold amount of fresh LNG to condense the departmental gas in the vehicle storage tank into a liquid, thereby reducing the pressure of the vehicle storage tank.
In the normal driving process, in order to effectively control the pressure of the vehicle storage tank, an economic valve is set in the gas supply pipeline system. When the storage tank pressure is higher than the set pressure of the economic valve, the economic valve is opened, and the inside of the storage tank The gas phase is supplied to the engine due to the liquid phase flowing out of the storage tank. When the tank pressure is below the economic valve setting, the economy valve closes.
Raw material conditions of LNG filling station: -146 ° C, 0.3 MPa; lng storage tank LNG state: 50 psig. When the unloading procedure is run, the gas of the LNG tank is first reversed to the liquid phase of the tank truck through the process pipeline, and the fresh LNG can be cooled to a liquid with the gas of this part.
When the pressure of the LNG storage tank is balanced with the pressure of the tank truck, the LNG pump is started to take the LNG out of the tank truck, spray it into the tank from the top of the tank, and cool the gas in the tank to a liquid by using fresh LNG cooling. Due to the liquefaction of the capping gas, the pressure of the capping is lowered and lower than the tank truck pressure. When the pressure difference is greater than 15 psig, the inlet valve at the bottom of the LNG storage tank is opened, and the LNG flows into the LNG tank from the pipe body and the bottom at the same time, thereby achieving a fast and stable unloading process.
In the normal driving process, in order to effectively control the pressure of the vehicle storage tank, an economic valve is set in the gas supply pipeline system. When the storage tank pressure is higher than the set pressure of the economic valve, the economic valve is opened, and the inside of the storage tank The gas phase is supplied to the engine due to the liquid phase flowing out of the storage tank. When the tank pressure is below the economic valve setting, the economy valve closes.
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