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L̶e̶t̶'̶s̶ ̶m̶a̶k̶e̶ ̶i̶t̶ ̶s̶i̶m̶p̶l̶e̶.̶ ̶I̶ ̶h̶a̶v̶e̶ ̶a̶ ̶p̶o̶o̶l̶ ̶o̶f̶ ̶a̶m̶m̶o̶n̶i̶a̶ ̶w̶a̶t̶e̶r̶,̶ ̶a̶n̶d̶ ̶w̶h̶e̶n̶ ̶I̶ ̶h̶e̶a̶t̶ ̶t̶h̶e̶ ̶a̶m̶m̶o̶n̶i̶a̶ ̶w̶a̶t̶e̶r̶,̶ ̶a̶m̶m̶o̶n̶i̶a̶ ̶w̶i̶l̶l̶ ̶d̶e̶s̶o̶r̶b̶ ̶a̶n̶d̶ ̶v̶a̶p̶o̶r̶i̶z̶e̶.̶ ̶I̶n̶ ̶t̶h̶i̶s̶ ̶c̶a̶s̶e̶,̶ ̶(̶1̶)̶ ̶w̶i̶l̶l̶ ̶t̶h̶e̶ ̶w̶a̶t̶e̶r̶ ̶b̶e̶ ̶v̶a̶p̶o̶r̶i̶z̶e̶d̶ ̶a̶s̶ ̶w̶e̶l̶l̶?̶ ̶(̶2̶)̶H̶o̶w̶ ̶d̶o̶ ̶I̶ ̶d̶e̶t̶e̶r̶m̶i̶n̶e̶ ̶h̶o̶w̶ ̶m̶u̶c̶h̶ ̶o̶f̶ ̶t̶h̶e̶ ̶w̶a̶t̶e̶r̶ ̶w̶i̶l̶l̶ ̶b̶e̶ ̶v̶a̶p̶o̶r̶i̶z̶e̶d̶?̶ ̶ ̶T̶h̶a̶n̶k̶s̶ ̶i̶n̶ ̶a̶d̶v̶a̶n̶c̶e̶.̶

Thanks for the replies. Since now I have known that no matter how I boil the ammonia water to desorb ammonia, water will always present. And since there is people that wanted me to elaborate my question, here it goes.

I am doing a Fluent simulation of boiling 20% ammonia water under 4 atm using multiphase model. The issue is I need to define the mass transfer from liquid phase to vapor phase, and the mass transfer model I plan to use is evaporating-condensation. However, to use this evaporation-condensation model, I will need the saturation temperature. As far as I know, the saturation temperature is used to define the further dissolving of ammonia. However, since a small fraction of water will be vaporized as well, how do I determine the temperature for the water to start vaporizing (can I use the boiling point of water under 4 atm)?

Thanks in advance.

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    $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Aug 30 at 18:20
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If you heat the commercial concentrated ammonia solution ($25$% $\ce{NH3}$) at usual pressure, it will boil at $32$°C and the vapor contains $3$% $\ce{H2O}$ (and of course $97$% $\ce{NH3}$). So the liquid looses much ammonia and nearly no water. Its total volume decreases a bit but the concentration of ammonia decreases more, so that it is necessary to heat to a higher temperature to continue distillation.

When the concentration of ammonia is down to $23$%, the liquid has to be heated at $35$°C, and the vapor contains $4$% water.

When $\ce{[NH3]}$ = $21$%, the liquid boils at $40$°C, and the vapor contains $5$% water.

When $\ce{[NH3]}$ = $18$%, the liquid boils at $50$°C, and the vapor contains $9$% water.

When $\ce{[NH3]}$ = $15$%, the liquid boils at $55$°C, and the vapor contains $12.5$% water.

When $\ce{[NH3]}$ = $10$%, the liquid boils at $70$°C, and the vapor contains $30$% water

If you want other numerical values, look for "Diagram ammonia - water" over Google. And you will find all the data you want, even at higher pressures.

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