3. Extractive metallurgy

3.1 General

The aim of extractive metallurgy is to convert the tungsten value of an ore into a pure intermediate compound (tungstic acid or ammonium paratungstate APT), which is then reduced to metallic tungsten in high-purity powder form. The concentrate is usually pre-treated to remove impurities that would be difficult and expensive to remove later.

The next stage is ore decomposition, during which the tungsten is isolated from the other ore constituents and converted into an easily purifiable form. Some purification is achieved during ore decomposition.

Finally, the remaining impurities are removed, and the desired intermediate compound is obtained. The reduction of the intermediate compound to tungsten metal has virtually no purifying...