Calculation of the amount of nitrogen added to the naphtha floating roof tank?
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Friends on the forum, I have a question and I would like you to help me. I have been thinking about connecting the gas phase of some naphtha tanks at my station. The purpose of this is to reduce the volatilization of some light components in the tank and save the nitrogen supply in the nitrogen sealing system. Now the air windows of all our naphtha floating roof tanks have been closed, and the tank tops adopt a nitrogen sealing automatic control system. I would like to know how many cubic meters of nitrogen is needed to add 6 kilograms of nitrogen into a tank space with a water column of 50 mm. If the liquid level in the tank drops by 1 meter? How to calculate? Sorry, because I am a high school student in the class of 1975, so I don't know many theoretical calculations. No one paid attention to my rational suggestions to the unit, so I had to ask my friends on the forum to help me. Thank you very much!
First calculate the volume V1 when the liquid level in the tank drops by 1 meter, then press P1* V1/T1=P2 * V2/T2, you can calculate the V2 that requires 6 kg of nitrogen.
Thank you very much for your reply. I have also asked someone about the amount of nitrogen used. When calculating costs, nitrogen is calculated based on the price of liquid nitrogen, which is about 800 yuan per cubic meter. Our naphtha tank uses 100 cubic meters per hour. Can it be said that the gas phase space it increases is 100 cubic meters? If you calculate with the above formula and the front and rear volume temperatures remain unchanged, then just convert the pressure into millimeters of water column, right?
Your understanding is correct. If 100% of the material is discharged, 100% of the air must be taken in. However, although the nitrogen pressure is 6bar, the nitrogen sealing pressure is definitely not 6bar, because the nitrogen enters the tank after passing through the self-regulating valve.
“"If the material is discharged 100, the air intake must be 100." There should be a problem with this statement. It can only be roughly estimated, and it can be calculated like this. The actual consumption should be less than the output.
Just use that formula to convert. Note that the formula is absolute pressure, and we usually use gauge pressure.
P1* V1/T1=P2 * V2/T2 The flow rate of the oil tank paid by my unit is 100 cubic meters per hour, the nitrogen flow meter is also about 100 cubic meters per hour, the nitrogen pressure is 0.5 kg, the nitrogen sealing pressure in the tank is 0.6KP, and the set temperature remains unchanged. According to the formula, the nitrogen flow rate is 16.9 cubic meters per hour, which is inconsistent with reality. Do I calculate the flow rate directly as the volume, or are liquid and gas constants different? Is this a problem? Could you please give me the correct calculation method? Thanks:)