SHADYCHASE54
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Registered: 16-12-2010
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Simple concentration of ammonia 26
Hello all,
I have been interested for a while in the production of anhydrous ammonia from ammonia concentrate 30%. As I have now found a local source at $15.00
for 4 liters I can attempt the building of a small scale ammonia scrubber in the garage. Now my question is does anyone know of a way that I may
increase the concentration of the ammonia in the solution, simply. I was thinking somthing on the lines of the freeze point differentials between
ammonia and water, however I have no reference on the this toppic and yes I do realize to keep the ammonia in solution at greater concentrations I
will have to lower the solutions storage temp.
So to clarify what I am asking is if anyone might have reference(s) on the freeze points? or an alternate idea on how I may increase the
concentration simply? And whether anyone has any practical experience on this topic?
The reason I am interested in further increasing the concentration is, and now this is not proven but what I think is, I should be able to get away
with a shorter scrub column if the H2O concentration is limited. If I am not correct in this assumption feel free to educate. Thanks in advance for
your thoughts and direction on this issue.
SHADYCHASE54
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ScienceSquirrel
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The easiest way is to heat the solution to close to the boiling point and conduct the evolved gases into a cold trap containing iced water, that is
the normal way of concentrating ammonia solution.
If you want anhydrous ammonia the best way is to heat an ammonium salt with sodium hydoxide and then dry and condense the ammonia.
I am not totally sure what you are trying to achieve.
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bbartlog
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You can't (realistically) concentrate 30% aqueous ammonia by freezing it. Check out the phase diagram here (figure1): http://www.lpi.usra.edu/meetings/lpsc1994/pdf/1278.pdf . The temperatures required once you go past 20% aqueous ammonia are significantly below
what is required to just condense anhydrous ammonia gas. In principle it does look like you could freeze ammonia dihydrate (solid) out of a liquid
solution of ammonia monohydrate, at temperatures around 190K, which would get you up to ~50% ammonia... but really, this sounds like a project for
someone with cryogenic gear and an interest in ammonia hydrates, not part of a path to anhydrous ammonia.
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