Tungsten Trioxide Preparation by Microwave Calcination of Ammonium Paratungstate

Tungsten trioxide is an important intermediate product in the process of tungsten extraction and gold treatment. It is the main raw material for the production of tungsten powder and tungsten related products. It is usually obtained by calcining ammonium paratungstate. The traditional production process of tungsten trioxide is to place the powdered ammonium paratungstate in a fixed furnace or a rotary furnace for calcination. 

The disadvantages of this production method are long production time, high production cost, low furnace thermal efficiency, large energy consumption, and difficult to guarantee the purity and particle size of the product, especially the powder is easy to leak, the workshop working environment is poor, which affects the recovery of the product. Therefore, it is imperative to explore a new technology of drying and calcining ammonium paratungstate to produce tungsten trioxide.

Microwave has the characteristics of rapid internal heating, selective heating, overcoming the "cold center" in materials, easy to realize automatic control, energy saving, etc., which can effectively improve the quality rate and qualified rate of products. Wave radiation heating technology has been widely used in national defense, food, medicine, agriculture and forestry and other industries. New applications in other fields are constantly expanding, forming new interdisciplinary subjects. The purpose of this experiment is to reform the traditional method, shorten the production time, reduce the energy consumption and seek a new calcination process.

1.The Yellow tungsten oxide powder can be obtained by calcining ammonium paratungstate by microwave.

2.The decomposition rate of ammonium paratungstate can reach 96.67% after 4 min microwave calcination with 650W power.

3.The main factor affecting the calcination process of ammonium paratungstate is the weight of the material, the second is the calcination time, and the smallest factor is the microwave power.

4. In the range of this experiment, the best conditions are: microwave power 650W, calcination time 4min, material weight 10g.

5.The microwave calcination of ammonium paratungstate only takes 4 minutes, while the traditional method takes about 2 hours. Microwave calcination time is only 1 / 30 of the traditional method, which fully embodies the advantages of microwave heating technology.

6.The production of WO₃ by microwave calcination of ammonium paratungstate has the advantages of short calcination time, good product quality and industrial development value.

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