A question regarding the nitrogen sealing of storage tanks
Thread Content
We have a storage tank for ester products, which is sealed with nitrogen. During loading, the material is poured in from the bottom. There is a vapor equilibrium port on the tank of the transport vehicle, connected to the storage tank. When loading, as the material is pumped from the storage tank into the transport vehicle’s tank, the air inside that tank, along with the material gases, flows back to the final product tank through the equilibrium pipeline. In this case, won’t nitrogen from the sealing system end up inside the transport vehicle? Would the sealing function then be lost? Thank you
During loading, the volume of the liquid phase in the tank increases while the gas phase space decreases. Therefore, the vapor phase should pass through the equilibrium line to the product storage tank.
No gas will enter, but the nitrogen seal is also designed for storage tanks, not tank trucks
When loading, the vapor from the tank truck enters the storage tank, which means the vapor pressure in the storage tank remains balanced. As a result, the nitrogen used for nitrogen sealing does not enter the storage tank, right?
My understanding is that the vapor line of the tank truck should be connected to the emission system, where the gas is washed or burned before being released. If it can be ensured that the gas in the tank car contains no oxygen, it should be possible to connect it to the storage tank.
Some nitrogen will dissolve in the liquid phase; as long as the liquid level in the storage tank is properly controlled and the tank is not emptied, a large amount of nitrogen will not enter the tank truck. According to the process you described, when filling the tank truck, a small amount of nitrogen dissolved in the liquid phase enters the tank truck along with the liquid phase ； At the same time, the vapor phase from the tank truck will flow back to the storage tank.
It’s fine if nitrogen gets in, but it becomes dangerous when air from the truck gets in
Nitrogen sealing is primarily used to maintain a positive pressure in the storage tank and prevent air from entering it. If gas phase returns from the tank truck during loading, the amount of nitrogen introduced will decrease accordingly, thus maintaining equilibrium.
Some air will enter the tank from the tank truck, right? For materials that are sensitive to air, it’s best for the gas from the tank truck to enter the negative-pressure exhaust pipeline.
The vapor from the tank truck does not reach the finished product storage tank; it should be the vapor from the finished product storage tank (nitrogen) that goes to the tank truck