In the process of smelting tungsten, ammonium paratungstate (APT) is a necessary intermediate material. Ammonium paratungstate is often used to calcine to get tungsten trioxide (WO3) in industry. Tungsten trioxide is a kind of important intermediate product in tungsten metallurgical process, also the main material for the production of tungsten powder and tungsten products. In the traditional production process of WO3, ammonium paratungstate powder is arranged in the furnace or rotary furnace for thermal decomposition. The shortcomings of this method lie in, longer production cycle of WO3, lower furnace heat efficiency, larger energy consumption, higher production cost, more difficult to guarantee the purity and the granularity of the product. Especially, the powder is easy to leak, poor working environment, product recycling affected.
 

With the properties of selective heating and internal rapid heating, microwave void material "cold center" effectively, and achieve the goal of automatic control and energy saving.
 

Microwave calcination method increases the thermal decomposition efficiency and reduces time to a great extent, and improves the high quality and qualified rate effectively. Microwave radiation heating technology has been widely used in national defense, food, medicine, agriculture, forestry and other industries, and continuously broaden the new applications in other areas, forming a cross discipline.

Ammonium paratungstate is a kind of white crystal of scatter, fluidity, began to lose ammonia in the air when heated to 60℃, dehydration with the temperature reaches 100℃, began to change to yellow WO3 with continue the temperature raising up to 450℃. Thermal decomposition chemical equation is as follows:

5 (NH4 = +16H2O = 2O12WO311H2O=12WO3+10NH3)

Table 1 shows decomposition mechanism of ammonium paratunstate: