When producing violet tungsten oxide in the industrial furnace, different process parameters such as furnace temperature, furnace speed (the residence time of materials in the furnace), feed amount, ammonia flow, etc. will have an impact on the quality and output of violet tungsten. The above four impact of various process parameters on the production of violet tungsten mainly includes:
- The influence of furnace temperature, feed amount and furnace speed on the production of violet tungsten. Under the condition that other process conditions remain unchanged, too high furnace temperature or too small feed amount and too long residence time of materials in the furnace may cause high WO2 phase content in purple tungsten products; on the contrary, APT is not completely decomposed for W18O49. Therefore, the modulation of the three directly determines the phase composition of violet tungsten products. If the furnace temperature is too low or the amount of feed is too large, it will cause the product to agglomerate or even freeze the furnace, which will affect the product quality. Observation by scanning electron microscope shows that when the furnace temperature is low, the morphology of violet tungsten is needle-like crystal; when the furnace temperature is high, the morphology of violet tungsten is rod-like crystal. Needle and rod are the intrinsic crystal forms of violet tungsten. Through the reduction test, it is found that the tungsten powder prepared from the needle-shaped violet tungsten is finer, while the tungsten powder prepared from the rod-shaped violet tungsten is relatively coarse. Violet tungsten to meet the needs of finer-grained tungsten powder production.
- The influence of ammonia flow on the production of violet tungsten. Ammonia can be decomposed into N2 and H2 at high temperature. The production of H2 makes APT calcined in a mild reducing atmosphere, gradually decomposed, and reduced to W18O49. Therefore, in order to ensure the reducing atmosphere in the furnace, a certain amount of ammonia must be introduced.
This is mainly because the aggregates of APT crystallized by continuous evaporation are thicker and mostly equiaxed; while the aggregates of APT crystallized by intermittent evaporation are finer and more complex in shape. It shows that the performance of APT raw materials will affect the output and quality of purple tungsten produced by rotary kiln. Therefore, the stability of APT quality and performance should be guaranteed. On the other hand, in order to adapt to the changes in the APT performance of raw materials, the process conditions of the rotary kiln should also be adjusted accordingly.
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