How is ammonia separated from unreacted hydrogen and nitrogen?

When the gases leave the reactor they are hot and at a very high pressure. Ammonia is easily liquefied under pressure as long as it isn't too hot, and so the temperature of the mixture is lowered enough for the ammonia to turn to a liquid. The nitrogen and hydrogen remain as gases even under these high pressures, and can be recycled.

Another way is to add the water to the mixture (or pass the mixture from cold water) Ammonia is highly soluble in water but other two gases are not.