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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: kobirrr on April 22, 2020, 03:02:11 AM

Title: NH3 emissions- Charging ammonia solution into an empty vessel
Post by: kobirrr on April 22, 2020, 03:02:11 AM

Hello,
I would like to calculate the emission of NH3 vapors when transferring 25% ammonia solution into a 1000L vessel.
The partial pressure of NH3 vapors over aqueous solution of NH3 (NH4OH) is 8.69PSI and the partial pressure of H2O over 25% solution of NH3 is 0.37PSI.
The ratio between them (the mole fraction) is 0.959.
how can I calculate how much ammonia is emitted to the air.
thanks in advance,
Kobi
http://www.southernionics.com/pdf/Ammonia_Handbook.pdf

Title: Re: NH3 emissions- Charging ammonia solution into an empty vessel
Post by: Borek on April 22, 2020, 03:20:00 AM

Amount depends on the headspace.

Title: Re: NH3 emissions- Charging ammonia solution into an empty vessel
Post by: kobirrr on April 23, 2020, 12:52:33 AM

Hello,
What do you mean?
I thought that it would be possible to calculate it by using PV=nrt  n=PV/RT, when:

R=0.082,
T=299.6K (80F)
P would be the partial pressure of NH3 over NH4OH solution = 59915Pa
V would be transferred volume= 1000L= 1m3
in this case n is 24.04 moles  which is equal to 408.8g of NH3 per 1m3 of Ammonia solution.

i'm not sure that my assumptions are correct.
in this calculation I ignored that partial pressure of H2O over 25% solution of NH3.

I don't understand what i'm missing here.

Best regards,

Title: Re: NH3 emissions- Charging ammonia solution into an empty vessel
Post by: Borek on April 23, 2020, 07:14:28 AM

What you post is in many ways ambiguous.

Let's say you put 1000L of the solution in the 1000L tank. Tank is full, no headspace over the liquid, question about the amount of the gas is a moot.

Let's say you put 1000L of the solution in the very huge tank, thousands of cubic meters. Chances are everything dries out, amount of ammonia emitted is that of the ammonia present.

These are equilibirum conditions, where things can be calculated. And if your question is about how much ammonia is lost during a transfer, when for some time some of the liquid is in contact with air, some is in the tank, and at no point system is in the equilibrium, then the answer is: no way to calculate anything.

Title: Re: NH3 emissions- Charging ammonia solution into an empty vessel
Post by: kobirrr on April 26, 2020, 03:51:43 AM

Hello,
I see your point.
The 1000L vessel is a Rigid plastic IBC. It capacity is 1030L thus the headspace is 30L.
I'm trying to understand if what the EPA explains in clause 3.1.1 is relevant to my question:
https://www.epa.gov/sites/production/files/2015-08/documents/ii16_aug2007final.pdf
Best regards,
Kobi