The process flow of preparing ammonium metatungstate hydrate by thermal decomposition method can be clearly summarized as follows:
- Preparation of raw materials
Main raw materials
Select high-quality ammonium paratungstate (APT) as raw material, and make sure its purity and particle size meet the production requirements.
Auxiliary materials
Prepare appropriate amount of additives, such as strong acidic cation exchange resin, according to the need, which is used to promote the conversion in the subsequent steps.
- Thermal decomposition process
Equipment preparation
Choose far-infrared rotary furnace or other high-temperature heating equipment to ensure that the equipment can accurately control the temperature and time.
Raw material input
Put the raw material of ammonium paratungstate into the heating equipment and spread it evenly so as to be heated evenly.
Temperature control
Set and control the heating temperature, usually between 200～280℃, the optimal temperature range may be adjusted according to the specific equipment and raw material characteristics.
Pyrolysis time
Control the pyrolysis time, usually around 1 hour, to ensure the full decomposition of ammonium paratungstate, but avoid overcooking to generate insoluble tungsten oxide.
Collection of pyrolysis products
Remove the pyrolysis products from the heating equipment, ready for the next step.
Dissolution and conversion
Dissolving pyrolysis products
Dissolve the pyrolysis product in deionized water preheated to 80～90℃, with the solid-liquid ratio controlled at about 1:7. During the dissolution process, the temperature will gradually rise to 90℃～98℃ to ensure that the pyrolysis products are fully dissolved.
Adjustment of pH value
During or after the dissolution process, add an appropriate amount of additives (e.g., strong acidic cation exchange resin) to adjust the pH value of the solution to the range of 3.5 to 4.5. This step is to promote the conversion of residual ammonium sec-tungstate.
Holding transformation
After adjusting the pH value, keep the solution at 90～98℃ for half an hour, so that the residual ammonium paratungstate is completely transformed into ammonium metatungstate.
Crystallization and drying
Evaporation crystallization
The transformed solution is subjected to evaporation and crystallization, and the concentration of ammonium metatungstate is gradually increased and crystals are precipitated by controlling the evaporation speed and temperature. The evaporation process should avoid too large crystals or incomplete crystallization.
Filtration and washing
The precipitated crystals are filtered and washed to remove impurities and residual solution. The washed crystals should meet certain purity requirements.
Drying
Dry the washed crystals at about 80℃ to remove residual water and solvent. The dried crystal is ammonium metatungstate hydrate product.
- Product collection and inspection
Product collection
Collect and package the dried ammonium metatungstate hydrate product, pay attention to moisture and humidity.
Quality Inspection
Conduct quality inspection on the product, including the determination of purity, particle size, moisture content and other indicators. Ensure that the product meets the requirements of relevant standards.
Through the above process, high-quality ammonium metatungstate hydrate products can be efficiently prepared. It should be noted that in the actual production process, the process should be adjusted and optimized according to the specific conditions to achieve the best production results.
More details of ammonium metatungstate product, please visit website: http://ammonium-metatungstate.com/
Please contact CHINATUNGSTEN for inquiry and order of ammonium metatungstate:
Email: sales@chinatungsten.com
Tel.: 86 592 5129595
