Zero Pollution Preparation of Ammonium Para Tungstate

Ammonium para tungstate is prepared mainly by caustic soda or soda decomposition, and pure ammonium tungstate solution is obtained. Then APT products are obtained by evaporation crystallization. No matter which method is adopted, the result is large water consumption and large amount of waste water is needed.

zero pollution preparation of ammonium para tungstate image

If the open circuit of the polluted discharge is turned into a closed circuit without pollution, it is not without the technical possibility, but the investment may even be greater than the profit. Therefore, the enterprise has to choose the discharge, which results in serious environmental pollution.

A large mining enterprise adopts a tungsten mineral raw material metallurgical process that can achieve zero pollution discharge. The preparation of ammonium para tungstate from tungsten mineral material is short, the solution can be recycled, the waste water is almost eradicated and the cost is low, and the general content of this method is as follows:

According to the ratio of (CaO+FeO+MnO) /WO3 molecule to 3.4, a wolframite (the content of WO3 content is 62.40%, the content of Fe is 14.08%, the content of Mn is 2.25%), the raw material is obtained with the grinding and mixing of the clinker leaching residue and calcium fluoride, and the addition of calcium fluoride is 7% (mass percentage) of the raw material of dry tungsten. The size of the material is less than 40μm, then, in a tube calciner, the clinker is roasted at 800°C under neutral atmosphere to get the clinker. After the clinker is cooled to room temperature, the grinder is grinded by a rod mill and the clinker size is less than 45μm; the leaching equipment is selected by a ball mill, with a saturated solution of ammonium carbonate and added to ammonium bicarbonate in accordance with the theoretical amount of 1 times. The material is placed in the leaching equipment and reacts to 4h at 80°C. After the reaction was finished, the leached pulp was vacuum filtered and washed with pure water for three times. The leaching rate of tungsten is 97.13%. Then, the crude ammonium tungstate solution is purified and removed. After purification, the solution is precipitated by evaporation crystallization of APT. At the same time, ammonia and carbon dioxide gas are obtained. The crystallization of the slurry is liquid-solid. The crystallization mother liquid and solid phase are obtained. After the solid phase is washed by water, the APT product is obtained, and the APT product reaches the national standard requirement for the 0 grade product. Ammonia and carbon dioxide are returned together to the leaching plant and the clinker is recycled after the loss of ammonium carbonate. 

This innovative process eliminates the transformation step of sodium tungstate solution that produces a large amount of waste water, directly obtains ammonium tungstate solution, fundamentally eliminating the discharge of waste water in the APT production process, and the recycling of auxiliary materials.

 

 

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