The Decomposition of Tungsten Concentrate by Closed Hydrochloric Acid Method

In the process of hydrometallurgy of tungsten, due to the depletion of wolframite resources, hydrometallurgy of tungsten will also turn to scheelite and artificial scheelite as the main raw materials. The production of tungstic acid from Scheelite (powder) and artificial scheelite pulp is one of the key processes. It is also an important process for further processing of deep processed products with tungsten as the main component.

The traditional method of making tungstic acid from Scheelite is in an open reactor (kettle), which is directly added to the excess hydrochloric acid, and decomposes the mineral powder or pulp under the condition of high temperature (boiling point temperature) and pumping air to produce tungstic acid, that is, acid decomposition method. The method has many disadvantages, such as large consumption of raw and auxiliary materials, high energy consumption, high environmental pollution and low productivity.

In view of the disadvantages of acid technology, a method of separating Scheelite from Scheelite with closed hydrochloric acid is designed to reduce the amount of hydrochloric acid and energy consumption, reduce environmental pollution and improve the effect, speed and productivity of decomposition treatment. The improved process flow is as follows:

An anticorrosive pressure reactor with a volume of 3 m3 lined EPDM and stirrer and steam injection pipe was used as the decomposition reactor.

A.Preparation: first, the WO₃65% containing wolframite powder 550Kg is placed in the mill to grind the fine powder with a grain size of 55 um to 45 um, and the industrial hydrochloric acid with a concentration of 31%, 800L (liter), is used for use.

B.Decomposition treatment: the hydrochloric acid is added to the reaction kettle. After heating to 55 centigrade, the agitator is started and the concentrate powder 550Kg is added, and the reaction is decomposed for 70 minutes at the pressure of 120 and 0.2Mpa.

C.Washing and filtering: the solution after the above decomposition of the liquid pressure into a square vacuum filter, using 90 degrees of hot water filtration for 85 minutes, its solid filter is H₂WO₄ products. Finally, the decomposition rate of tungsten concentrate powder is 99.75%, and the product has uniform particle size, good water permeability and excellent quality.

The improvement of the process is to add hydrochloric acid to scheelite ore or artificial scheelite in a closed reactor, heat and press decomposition reaction under the conditions of agitation, thus greatly improving the efficiency of the decomposition of scheelite, reducing the consumption of hydrochloric acid, and avoiding the pollution of the gas to the environment and the dissipation of heat. Experiments show that the dosage of hydrochloric acid can be saved by 30 to 35% compared with the traditional technology, and energy saving is about 30%, and the productivity can be increased by 25 to 30%. Therefore, the improved closed hydrochloric acid method has the characteristics of low consumption of hydrochloric acid, low energy consumption, little environmental pollution and effective increase of productivity.

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