Indirect Condensation Absorption Disposing Ammonia in Ammonium Paratungstate Crystallization

Ammonium paratungstate (APT) crystallization is the process of the polymerization of ammonia and acid. Ammonia (NH₃) volatiles out from the solution the volatilized ammonia in the heating process. It will cause atmospheric pollution if ammonia discharged directly into the air. Ammonia combines with hemoglobin easily and destroys the function of oxygen transportation, even lead to death.

Ammonia, commonly known as NH₃, is a colorless and tasteless gas, with a strong pungent odor, easily soluble in water, 1 volume of water can be dissolved 700 times the volume of ammonia under normal temperature and pressure. The environment department of China stipulates that waste water of tungsten smelting is the first class of elements to discharge the waste gas, zero discharge requirements is demanded. So, it is necessary for enterprises to take a new and efficient way of recycling tail gas in APT crystallization, in order to achieve the goal of zero emissions of ammonia gas.


Indirect condensation method is an effective method for recovery of ammonia from APT tail gas. Two ways to recover ammonia produced from ammonium paratungstate crystallization.
1.    Condensed into ammonia and returned to the reaction process;
2.    Converted into NH₄Cl and return to desorption of ion exchange process.
Compared the two ways, the front is of higher economic value. NH₃ and water are polar molecules, ammonia and water molecules combining and becoming a hydrogen bond when NH₃ soluble in water. With temperature increasing, the solubility of ammonia in water becoming lower, so the low-temperature condensation is an effective way to improve the recovery rate of ammonia.

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