Effect of Stirring Speed on Ammonium Paratungstate Production
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- Category: Tungsten Information
- Published on Monday, 28 December 2015 16:21
Ammonium paratungstate (APT) is an important intermediate product of the production of tungsten metal powder. To ensure the quality of tungsten powder, the average particle size, particle size distribution and crystal morphology should also meet certain requirements while the APT chemical purity does. With the rapid development of modern science and technology, there’re more and more demands for different grain size and shape of tungsten powder production, and thus the requirements of raw material APT are also getting higher and higher.
For APT crystallization conditions, the scholars have carried out extensive exploration and discussion, but the overall reports are rare, and the results are not entirely consistent. In order to investigate the basic conditions of APT production, for the preparation of APT crystallization problems, this article attempts to make some analysis and discussion on theory and the process practice based on a number of experimental studies made recently and some views are put forward by reference.
The test results are shown in Figure 2. It’s complicated that stirring speed affects nucleation. On one hand, the stirring speed is accelerated, so that the newly formed crystals were minced and the form much crystal nucleus, particle size becomes fine, on the other hand, in a certain stirring speed range, increasing the stirring speed can increase the relative velocity between solid and liquid, thereby increasing the speed of nuclei grow.
To prepare coarse APT, the best speed is when the resulting APT does not precipitate, APT particle formed can make full contact with the solutes. It was also found the effect is not the same with different paddles stirring or different stirring intensity. Stirring has a great impact on the preparation of the different particle size of APT, APT prepared by gas stirring is more regular . For different production conditions, it’s generally required to determine the proper form and speed of stirring through practice.
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