Hello Rahul,

The composition of the gas mixture above the ethanol liquid is determined by the saturated vapor pressure of ethanol. From this and the ideal gas law follows:

x= M_ethanol/M_nitrogen*(p_ethanol/p_total) = 46/28*(p_ethanol/p_total) [kg ethanol/kg N2]

https://en.wikipedia.org/wiki/Ethanol_(data_page)

Hello Ron,

For finding the composition of the vapour gas your answer is right. But I wanted to know how to calculate the Working and Standing Losses in low-pressure(vacuum condition) tanks.

Seems to me the standing losses are determined by the leakage of the tank roof, and the temperature of the liquid. Therefor you have to estimate the solar heat gain of the tank. The working losses are determined by the volume of ethanol that is used and refilled again. I think the linked document should get you on the way.

https://www3.epa.gov/ttnchie1/ap42/ch07/final/c07s01.pdf

Hey Ron, 

Thanks a lot for your suggestion. I used the paper and have done a calculation for my project.

It would be really helpful if you could check whether my calculations are correct or not.

• I am not sure how to incorporate nitrogen blanketing(@60 mm of water column gauge pressure) in my calculation.
• I have assumed a bulk temperature and absorptance of the insulation coating instead of using equations from the paper(due to some reasons)
• Here is the link of my calculations: https://docs.google.com/spreadsheets/d/1kG_pHNxjAQnY0cxPxgwmKWcyaRWoDn6RdcDeRXWjWQY/edit?usp=sharing

Hello Rahul,

I am glad you were able to use the document I recommended. I personally am not familiar with these specific calculations, and I can't judge the formulas on their physics without further studying.

I suggest you take a closer look at the formulas for the pressure settings of the vents. You have 60mmH2O = 600Pa overpressure. The sum of the vapour pressures is 0.25 -0.30bar. So the influence of the overpressure is small. For the losses it makes no difference if the 'remaining' space is occupied with nitrogen or air. The reason to use N2 blanketing is primarily to protect the liquid (prevent oxidation).

Sorry I can't help you more than this.

Best regards,

Ron

Hello Ron,

Thanks for helping me out.

Best Regards,

Rahul