Extraction of Ammonium Tungstate by Reverse Osmosis

The tungsten concentrate is decomposed by alkali and the sodium tungstate solution is obtained. Ammonium tungstate solution is produced by ion exchange. The ammonium tungstate solution is evaporated and condensed to get APT.

The main components of ammonium tungstate solution are NH₄⁺, WO₄^2-, OH^-, H²O. The concentration of ammonium tungstate solution obtained by ion exchange is unstable, and the concentration of WO₃ varies from 160 to 280g/l, while the concentration of WO₃ must be above 360g/l when APT is produced. At present, Chinese enterprises get APT by evaporation of H₂O in ammonium tungstate solution. A large amount of coal production steam must be consumed to evaporate and concentrate ammonium tungstate solution. The consumption of coal is more than 1.2 tons of /TAPT, and the energy consumption is large.

In order to improve this traditional form, researchers have proposed that the concentration of low concentration ammonium tungstate solution in the reverse osmosis device to WO₃ concentration of 320 ~ 360g/l, and then evaporate crystallization. The specific methods are as follows:

1.The ammonium tungstate solution (10m³ WO₃ 184.6g/l) is placed in a plastic container after the alkali decomposition and ion exchange of the tungsten concentrate.

2, the upper step tungsten ammonium tungstate solution is pumped into the reverse osmosis with a 0 ~ 30m³/h pressure of 0 ~ 50kgf, and the flow rate of the valve is 18m³/h after adjusting the pump.

3.After all the ammonium tungstate solution is pumped, 3m³ pure water will be added to clean the reverse osmosis plant.

4.Collect the concentrated ammonium tungstate solution for 5.24m³ and analyze the WO₃ concentration of 352.4g/l. The collected H2O meter 7.52m³, the remaining 0.24m3H₂O in the pipeline and reverse osmosis device.

5.Add the concentrated ammonium tungstate solution 5.24m³ into the evaporator and steam the 170min to the crystallization end-point to get APT1662Kg.

If the ammonium tungstate solution before concentration of 5.24m³ is added directly into the evaporative crystallizer and heated by steam to heat 170min to the end point of crystallization, only APT623Kg is obtained, and the coal consumption is 623X1.2/1662 = 0.45T, and the effect of energy saving of reverse osmosis concentration is remarkable.

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