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Author: Subject: Liquefaction of Ammonia (Anhydrous)

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shocked.gif posted on 2-4-2009 at 00:48
Liquefaction of Ammonia (Anhydrous)

I am starting a topic:o

There is a good reason for this, on another site several people are discussing ways to generate & liquify anhydrous ammonia @ home/office.

Thus I'd love some input, if you are at all concerned about the ultimate use thereof, avoid responding to the topic is about all I can suggest (unless of course your name is Polverone/Nicodem/something similar, then feel free to delete the post/topic:D)

Now my thoughts to date would be to use the driest source of ammonia gas I know, that produced by heating carefully dried, anhydrous monoammonium/diammonium phosphate (fertiliser - washed to remove the organics, then recrystalised to remove the insolubles). I would suggest this on the principle of dry in = dry out.

My next thought would be to use other pressurised gases to liquify it - in one of two ways, both starting with putting the ammonia gas into a container that can withstand the pressure necessary to liquify ammonia at a given temperature. I would personally prefer that this be done by flushing said container, applying vacuum, then flushing again, finishing with vacuum. Then fill it to whatever pressure you are capable of getting from the gas generator.

Idea 1

To directly add that pressure in the form of an inert gas, probably oxygen/argon (argon for preference). Just by increasing the volume of gas within the container, surely we would achieve our goal simply & cheaply. If we use an inert gas, then surely it would stay above the liquid? So we could, theoretically at least, simply tap off the liquid (taking into account it will be under considerable pressure, like an aerosol)?

Idea 2

Use the basics of refrigeration design to cool the stream of anhydrous ammonia gas by passing it through a gas condenser cooled by the expansion of another pressurised gas (even CO2).

Please feel free to use ridicule, etc;), but above all, I'd love some input on why it won't work. Ideas on what effect the input gas would have on the effect of the pressure required would also be welcomed.
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PHILOU Zrealone
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[*] posted on 2-4-2009 at 02:33

Aceton + CO2 will get you safely to -80°C, low enought to allow condensation of NH3(g) into liquid NH3 (T.eb.:-33°C) at atmospheric pressure....The gas genarted must pass into drying tube and then into a condensing flask into the cooling mix....

2NH4Cl + CaO --> 2NH3(g) + CaCl2(s) + H2O(l)
Most of the H2O will be caught by the CaCl2 produced, but it is good to put an extra CaCl2(s) drying tube before condensing NH3 into the cold trap.

[Edited on 2-4-2009 by PHILOU Zrealone]

PH Z (PHILOU Zrealone)

"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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[*] posted on 2-4-2009 at 06:11

Ammonia is a refrigerant. Put it inside the cooling loop inside a suitable refrigerator. Feed gas into the low pressure return and extract liquid before the metering device.
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Mr. Wizard
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[*] posted on 2-4-2009 at 08:43

A couple of things to remember. Anhydrous ammonia can safely be handled in non galvanized (no Zinc or Brass or Copper) steel pipe. The pressure to liquify it is about the same as propane. Anhydrous ammonia has a TREMENDOUS heat capacity. A glass of it will keep itself refrigerated for 24 hours, without insulation. His means you will have to remove the same amount of heat to liquify it. This could be a lot of dry ice using the brute force cooling method. I would recommend using pressure and cold water.

Ammonia has a great affinity to Calcium Chloride and will absorb into it just as it will in water. This precludes using it to remove water. This is actually used in a solar refrigerator:

I would try making a saturated solution of ammonia in water using the ammonia salt/ alkali method or distilling ammonia from diluted solutions. Take this cooled concentrated solution and put it into a steel container that will handle the pressure and heat the solution, forcing the ammonia out of the solution into a cooled container where it can liquify, as in the Icy Ball method:
And this really hands on method:

Lastly, be careful. This stuff will make short work of your eyes. If you get a leak, you will NOT be staying around to stop it, trust me. Even holding your breath doesn't work, as it attacks everything with any moisture in it, eyes, lips, and hidden parts under clothes.

The good news is it quickly dissolves in water from a hose, and the flammable range is so narrow it actually is hard to get it to explode with air. Hard but not impossible.
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