5 replies to this topic

[Raj Mehta]

I have an Ethanol tank of gross capacity 450 m3 (total volume = 469 m3). 

 

Storage press = 1 atm 

Storage temp = 30 deg C

Tank height = 8.75m

Tank dia = 8.125m 

 

No insulation to the tank. 

 

I want to size a vent condenser for the same.

 

I referred API 2000 and considered normal thermal venting scenario. I calculated the surface area of the tank followed by Q using Q = 63,400*A^0.338 (ref. pg - 8 section 4.3.3.2.1 table 1-B for metric units) 

Latent heat of vaporization of ethanol = 846 KJ/Kg. 

T = boiling point = 78 deg C (351 K)

M = Molecular weight = 46. 

 

Using all the above values i used equation 1-B to calculate the venting capacity. I see that it is gigantic value.

 

Can someone verify the calculations or share some excel sheet for the same. ? Also tell me, the thermal venting tables (2-B ) are for what ambient temperature ? because as the temperature between storage and ambient increases, venting capacity would also increase, so I believe the tables are at specific temperatures? 

 

Thank you.

Edited by Raj Mehta, 28 June 2013 - 12:56 AM.

[CMA010]

Because you're using external fire heat input for normal venting.

 

Background of the thermal venting tables are in the API standard. annex A and annex E.

[MI_Sidd]

You don't require latent heat for normal venting..what you are doing is for emergency fire case used to design ERV.

 

If you need a spreadsheet, Ankur has already uploaded one here:

 

http://webwormcpt.bl...estimation.html

 

Regards

Edited by MI_Sidd, 25 June 2013 - 06:12 AM.

[Raj Mehta]

1. the equation used for outbreathing in the link that you shared takes into consideration only the tank as it appear from the equation. How does it take into consideration different fluids stored ? 

 

2. After caluclation I get the value in Nm3/h (1 atm and 273 K) of air -- should I now calculate it for ethanol (mol. wt = 46, storage P = 1atm, and storage temp = 303 K) which will change the units as m3/hr of ethanol vapors ? Am i right here ?? 

[ankur2061]

Raj,

 

The API STD 2000 equations are in terms of air venting (both for normal and emergency venting) and if you recall that this was discussed earlier on the forum and this is what you need to specify if you want to provide a PVRV or emergency blow-off hatch for normal & emergency venting respectively from the tank.

 

For the design of a vent condenser you need to know the vent losses from your tank. These calculations are totally different from the venting calculations as per API STD 2000. Refer the link below for the attachment where the vent or evaporation losses can be calculated based on the equations given in the attachment.

 

http://www.cheresour...ion/#entry70482

 

Additionally you can use the downloadable software "Tanks" from the link below to estimate emissions to the atmosphere from your tank at the following link:

 

http://www.epa.gov/t...software/tanks/

 

Regards,

Ankur.

[Raj Mehta]

Thank you very much sir for guiding once again...