Tin is a harmful impurity for tungsten, has a serious impact on the quality of tungsten products. To control the content of tin directly related the prosperity of tungsten products. Then, how to control the content of tin in tungsten metallurgy process? We are required to consider the quality of mineral and APT, using reasonable method to make sure the highest quality of APT at the lowest cost. We analyze from the following 6 aspects:

1. Source control, select fewer impurities like tin to reduce the subsequent tin removal process. However, due to the reducing of tungsten concentrate, the quality of ammonium (APT) can not be guaranteed;

2. Control of the reaction temperature, Sn leaching rate increased with the increase of temperature in the alkali decomposition. So control temperature in a proper range will make the Sn leaching remained at a low level, thus to ensure the quality of the APT;

3. Introduce additives，sodium phosphate is commonly used as an additive for tungsten concentrate;

4. Adjust the pH value. Tin will precipitate in alkaline environment. So control the pH value in an appropriate range will keep leaching rate of tin in a low level to achieve the goal of impurity removal;

5. Ion exchange adsorption. Trying to improve the exchange capacity of resin column, and increase the reaction time, then the removal rate of tin improved;

6. Reasonable solution of suction to cutting, to ensure the purity of ammonium tungstate solution.