2019年12月23日星期一

Sodium Tungstate Preparation From Scheelite Slime Recycle

Sodium tungstate is an important chemical raw material and an important intermediate product in tungsten metallurgy production.

Generally speaking, industrial production of sodium tungstate mainly uses scheelite concentrate or wolframite concentrate as raw material, and the production cost is higher.

In the tungsten concentrate production process, there are often some tungsten due to process or equipment reasons, lead to part of the tungsten ore grinding machine into powder or no successful flotation into the tailings, forming tungsten fine mud.

scheelite slime recycle image

The conventional recycle process of tungsten slime is tungsten slime - sodium tungstate - ammonium paratungstate. How can the sodium tungstate be recycled more efficiently by using tungsten slime? Compared with wolframite, fine scheelite slime is characterized by lower grade, more impurities, and more calcium containing molybdenum, which is more difficult to purify. In view of the above, we can use hot ball milling alkali decomposition ion exchange APT evaporation crystallization process. It has a strong adaptability to high calcium and low grade ore. It has three main stages:

1. The tungsten fine slime is decomposed by alkali method and hot ball milling, and most impurities are inhibited in the slag, so that the WO3 is transferred into the solution to produce sodium tungstate solution, and most of the impurities (P, As, Si, etc.) are left in the slag. 

2. The obtained sodium tungstate solution is evaporated and crystallized at once, and to recycle the alkali and remove impurities such as P, As, Si etc..

3. Sodium tungstate crystals were dissolved and filtered to obtain sodium tungstate solution. Unlike the sodium tungstate solution obtained from the scheelite concentrate, there is more molybdenum in sodium tungstate solution. The main work of this stage is to remove the molybdenum, can be selected by ion exchange or selective precipitation of tungsten and molybdenum separation. The sodium tungstate solution after molybdenum can be obtained by two times evaporation and crystallization, and can be converted into ammonium tungstate solution by ion exchange method, and then APT is prepared.

4. The above process can effectively deal with low grade and scheelite fine slime containing calcium and molybdenum. Some data show that the process of recycling scheelite fine slime from ore in Hunan, China, has a total recovery rate of 60-70%, and the effect is very good. Moreover, from the cost point of view, the majority of tungsten slime, according to WO3 measurement, the cost is only 60%-70% of the concentrate price. The recycle of tungsten slime is an effective way to reduce the cost of mining and prolong the mining life of the mine.

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