Below are the affecting factors of spherical crystal ammonium paratungstate preparation:

1.Under low speed of stirring, granulation rate of ammonium paratungstate is lower. When the stirring speed reaches to 80-90r/min, the granulation rate is ideal. With the increase of stirring speed, the granulation rate falls down.

2.With the increase of crystallization temperature, the granulation rate of ammonium paratungstate falls down. Consider of production cycle, crystallization should be under 85 degree Celsius.

3.With the postponed of time for adding liquid material, the granulation rate of ammonium paratungstate goes up. Consider of fisher particle size, loose density, flow ability and uniformity of particle, liquid material should be added under the solution density 16Be.

4.With the increase of liquid material amount, the granulation rate of ammonium paratungstate gose up. It reaches the maximum level when the adding amount is one time more than the original value. As the adding amount increasing, granulation rate falls down.

5.With the raising of adding speed, the granulation rate also goes up. Consider of fisher particle size, loose density, flow ability and uniformity of particle, liquid material should be added every three hours.


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The spectrophotometric determination of impurities in the ammonium paratungstate is mainly determined by the reaction temperature, reaction time, NaOH concentration and stirring speed on the active ingredients wolframite tungsten leaching. Also investigate the properties of the resin in the ion exchange process, the exchange of the solution before concentration and flow rate, desorbent concentration, flow rate and temperature and other factors on the impurity removal rate during crystallization temperature.

Ammonium paratungstate is an important raw material which is used as a source for high-purity tungsten oxides, tungsten metal powders, carbides, or as a laboratory reagent. Also tungsten powder including tungsten trioxide, tungsten blue oxide. Those powders are then used to make numerous products including wire, cutting tools, billets, welding electrodes, mining tools and many others. There are alloy series too, such as tungsten carbide alloy blade, alloy drill, alloy molds, etc.; and other wear, pressure, temperature and other machinery and equipment components. Also used in the manufacture ammonium metatungstate and other tungsten compounds as additives for the petrochemical industry. 



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Compared to traditional tungsten powder, preparation of fine tungsten powder can reduce sintering temperature. If the distribution of grain is close, structure of material after sintering will remain the nano-size.

A lot of researches have been done for super fine tungsten powder, like gas evaporation method, high energy ball milling; other method like control the hydrogen amount, temperature, adding dopant, etc. This method is easy to operate, low cost; the finished product is of high quality. Also yellow tungsten oxide, blue tungsten oxide, violet tungsten oxide is being used as raw materials to produce fine tungsten powder. Electrolyzation of tungsten oxide is also applied in the producing. But it is of high cost and low efficiency.

Ammonium paratungstate prepared by hydrogen reduction used to prepare tungsten powder is feasible. The ammonium paratungstate grain size is between 25-60um, which is not suitable for producing super fine tungsten powder. So the preparation of micron-sized ammonium paratungstate is the key problem.



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Tungsten hexafluoride (WF6) is the A-level inorganic virulent, highly corrosive, strong irritant, if exposure to this product by careless may cause eye, skin and respiratory mucosa very serious burning. The US Occupational Safety and Health Administration regulations allow WF6 exposure limit of 0.2ppm. Workplace air fluoride hygiene standards (GB 16228-1996) provide the workshop air maximum allowable fluoride of 1.0mg / m3 (in fluorine). Health standard for tungsten in the workshop air (GB 16229-1996) provide workplace air tungsten maximum allowable of 6mg / m3. The following table is the relevant provisions of China's environmental standards.

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