3. The choice of removing molybdenum

Because of the similarity of chemical properties between tungsten and molybdenum, we can hardly separate them by chemical method. It once considered as a difficult problem to break through which plagued technical personnel and production manufacturers. Relevant technical personnel studied on tungsten and molybdenum separation after decades, and get a large number of theoretical research and practice, and achieved good results. The main precipitation methods are extraction, ion exchange and other methods. Extraction and ion exchange method can completely remove the molybdenum, but need to deal with ammonium molybdate solution, also making certain requirements on equipment and operation technology. In contrast, the biggest advantages of precipitation method are easy to operate, no special requirements on the equipment, high rate of removing molybdenum, removing As and other impurities at the same time, so tungsten recovery is very high.

 

4. Choice of the process for the crystallization of ammonium paratungstate solution

Crystallization ammonium paratungstate from ammonium tungstate solution is one of the most important processes in the tungsten metallurgy process, and also the necessary procedure in the production of pure tungsten compounds. At present, the common methods are evaporation, neutralization and freezing crystallization. Freezing crystallization will carry out higher APT purity and yield, but need a special refrigeration equipment. In the process of neutralization crystallization, we need to add hydrochloric acid which is a new impurity, reducing the purity of APT. Evaporation crystallization method consumes a certain amount of energy, but not too much, and high production efficiency. For a small demand of APT, the most common jacket heating and stirring enamel reactor will be enough, a large amount of money can be used to buy continuous evaporator APT.

 

5. Choice of ammonium paratungstate mother liquor recovery   

The process of crystallization on both evaporation and neutralization  will bring out mother liquor, consistent of WO3 about 30~80g/L. Transformation, extraction and ion exchange method are taken for mother liquor recovery in the industrial. Extraction and ion exchange method are more complex, also require specialized equipments and highly investment. However, transformation method is widely used in production because the advantage of easy to operated, low cost. 

 

For ammonium paratungstate production process analysis, plesase see in
http://news.chinatungsten.com/en/tungsten-information/81827-ti-10585