Can a nitrogen seal reduce the evaporation of liquid in the storage tank?
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Can a nitrogen seal reduce the evaporation of liquid in the storage tank? Dalton’s law of partial pressures: In a gas mixture contained in any container, if no chemical reactions occur between the various components, then each gas is distributed evenly throughout the entire container. The pressure exerted by each gas is equal to the pressure it would exert if it occupied the entire container on its own. The volatility of the substance inside the tank depends solely on its temperature. In other words, whether or not nitrogen blanketing is applied to the tank, the partial pressure of the material’s vapor in the tank’s vapor phase remains unchanged. The addition of nitrogen actually increases the total pressure in the tank’s vapor phase; that is, the pressure in the tank’s vapor phase is equal to the sum of the partial pressure of the material’s vapor and the partial pressure of nitrogen. Therefore, nitrogen sealing does not reduce the evaporation of the liquid in the storage tank; on the contrary, it leads to greater material loss. Is this understanding correct? Everyone is welcome to share their opinions
If there is continuous intake and exhaust in the nitrogen purge system, your statement is correct. However, it’s possible to control the pressure within the nitrogen purge system so that there is no exhaust at all
Without any pressure setting, the main function of nitrogen blanketing is to isolate the material from oxygen, thereby preventing the formation of explosive gas mixtures inside the storage tank； Nitrogen sealing is carried out without pressure; it simply replaces the air inside the tank with nitrogen. This does not reduce the volatilization of the material, nor does it increase it.
The main purpose is still to isolate air. However, maintaining a certain nitrogen seal pressure should still help to suppress the evaporation of chemicals.
You were correct regarding Dalton’s law of partial pressures earlier, but an increase in the nitrogen sealing pressure only leads to an increase in the partial pressure of nitrogen; it does not change the partial pressures of the other substances. Therefore, purely according to Dalton’s law, the addition of nitrogen does not change the volatility of the material. That’s how I understand it
For nitrogen sealing, there is first the nitrogen sealing pressure. Only when they have the same vapor pressure at the tank top can storage tanks with nitrogen blanketing and those without it be compared. It is precisely because of the pressure division that, when the same total amount of gas is released due to material handling, a tank with a nitrogen seal loses both the material vapor and nitrogen, whereas a tank without such a seal loses only the material vapor.