Preparation of High Purity Ammonium Paratungstate

The production of APT in China is mainly ion exchange and extraction. The quality of APT products produced by the two processes is generally the national standard zero grade products. The rest are the first grade or unqualified products of the national standard, and the disqualified products can only be sold at a low price, which not only directly affects the production efficiency of the enterprises, but also affects the quality of the subsequent tungsten deep processing products.

How to deal with APT substandard products, at present our country enterprises have technical means to some of the impurities exceeded the product as raw material, through the preparation of APT calcined tungsten oxide; How to deal with APT substandard products, at present our country enterprises have technical means to some of the impurities exceeded the product as raw material, through the preparation of APT calcined tungsten oxide;

The ammonium paratungstate or unqualified ammonium paratungstate as raw material, through the APT calcined tungsten oxide; tungsten trioxide dissolved ammonia to generate ammonium tungstate solution; ammonium tungstate solution evaporation and crystallization; APT drying and screening to obtain high purity ammonium paratungstate, it is characterized by:

APT calcined WO₃ process, by controlling the feed rate control of 50-250kg/h, calcination temperature control atmosphere at 500-700 DEG C in the furnace, to ensure the transformation of APT in the production of tungsten trioxide calcining rate reached more than 98.5%. The feed volume is optimized by 100-200kg/h, and the calcining temperature is optimized at 550-690.

In the process of tungsten trioxide dissolved ammonia, dissolved when solution temperature at 50-110 DEG C, the ratio of liquid to solid control in 2: 1-6: 1ml/g, reaction time 0.5-3h, concentration of ammonia 50-160g/l. The optimum temperature is 60-100 DEG C, the optimum ratio of liquid to solid is 2: 1-5: 1ml/g, the reaction time is 1-2h, and the concentration of ammonia is optimized by 60-150g/l.

After the solution of ammonium tungstate is dissolved, the solution is metered into the evaporating crystallization pot to evaporate and crystallize, the evaporating crystallization vapor is controlled at 1-4kgf / cm², and the final proportion of evaporating crystallization is controlled at 1.01-1.10g / cm³ to obtain aqueous ammonium paratungstate.

Ammonium parotungstate is dried by steam to remove excess water to obtain high purity ammonium paratungstate product. This method of ammonia dissolution by calcining APT, effectively solve the problem of APT ammonia process of dissolution effect is not good; APT calcination process more effectively remove the hard part impurities, for the production of high pure APT products to create the conditions, then, low quality APT no longer need to use after alkali dissolution back to the practice process, improve the recovery rate of the production process, reduce production cost, and can be used to produce high purity APT products.

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