Tungsten Ore Decomposition Method – Hydrochloric Acid

Main mineral in tungsten scheelite is calcium tungstate. When calcium tungstate reacts with hydrochloric acid, it has large equilibrium constant. From the point view of chemical equilibrium, if amount of hydrochloric acid is deficient, reaction can be taken completely.

In the practical production, grain size of scheelite should be fine and use more hydrochloric acid as possible. It should be conducted under high temperature. This is due to decomposition rate.

Hydrochloric acid is the main method to process tungsten scheelite, chemical formula of reaction between calcium tungstate and hydrochloric acid:
CaWO₄+2HCI=H2WO₄+CaCl₂

Decomposition is a multiphase chemical reaction, reaction speed depends on the mechanism and speed control type. To promote tungsten scheelite decomposition rate, we need to add using amount of hydrochloric acid and promoting reaction temperature. However, it will intense the volatility of HCl and pollute environment. To deal with issue of HCl volatility, sealed measures should be taken during process. Apart from that, hydrochloric acid decomposition speed is controlled by solid membrane. Reaction speed constant ‘K‘ is small. It will be impeded by tungstic acid membrane. To promote tungsten scheelite decomposition rate, Coromant in Swiss destroys impeded function of tungstic acid membrane by ultrasonic and mechanical activation, decomposition rate is 55~60℃, decomposition rate reaches 99%.

Hydrochloric acid was once the main method of tungsten ore decomposition method. However, it has revealed many tricky problems. HCl is corrosive, results in the short service life of equipment. Hydrochloric acid waste water needs to be processed specially, or there will be water pollution and soil salinization. Moreover, HCl decomposition is fit for high grade scheelite. With shceelite grade getting lower, HCl can no longer keep up the pace with times.

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