Continuous Decomposition of Scheelite

China's tungsten reserves are the first in the world, but with wolframite resources becoming scarce, the mining focus has gradually shifted to scheelite. How to develop efficient scheelite smelting process has become an important subject of tungsten metallurgy.

The predecessor of Zhongnan University is Zhongnan College of Mining and Metallurgy. It has world-class academic standards in the fields of metal materials and mineral processing. In the field of non-ferrous metal smelting, it is the Beidou of Taishan Mountain in China. Over the years, the research scholars of this university have made great achievements in the field of tungsten ore treatment and smelting. Among them, Zhao Zhongwei, a well-known scholar, has published many papers expatiating on the relevant theories of leaching scheelite with phosphoric acid system and designing different schemes for different associated states of scheelite in China.

For example, a continuous decomposition method of scheelite can realize the continuous, stable and efficient decomposition of scheelite, reduce the concentration of sulphuric acid in the system, and ultimately realize the recycling of leaching agent. The experimental cases of this scheme are as follows:

1)The scheelite powder is added into the phosphoric acid solution in the pre-reaction tank 1, and the phosphoric acid solution in the pre-reaction tank 1 is converted into P₂O₅ with a concentration of 15%.

2)Phosphoric acid regeneration: adding sulfuric acid to the phosphoric acid regeneration tank continuously, so that the concentration of sulfate radical can be controlled at 40 g/L. After 3-5 hours of reaction, the sulfate radical can enter the aging desulfurization tank.

3)Aging sulfur control and pulp reflux: After the pulp in the aging desulfurization tank reacts for 3-5 hours, 1/2 volume of pulp in the final tank returns to the pre-reaction tank, the remaining pulp is filtered to obtain leaching solution and filtrate gypsum, and the leaching solution is extracted by D301 resin and returned to the pre-reaction tank; the temperature of the whole reaction system is controlled at 60 ℃, and the slurry flow rate is controlled between 95-105L/h; The medium WO3 concentration is 219.8g/L WO₃, the adsorption rate is 99.2%, and the decomposition rate of scheelite is 99.1%.

The continuous decomposition method makes scheelite mix with phosphoric acid solution through several reaction tanks, thus avoiding the direct contact between scheelite powder and high concentration sulfuric acid to form fine gypsum encapsulating tungsten ore; using self-generated calcium sulfate as seed to reduce the supersaturation of calcium sulfate through slurry circulation; and continuously replenishing sulfuric acid consumed in the reaction process to stabilize the upstream of the system. The concentration of sulphate radical is reduced to 30-50g/L and the pressure of subsequent treatment is reduced. Finally, the continuous leaching of scheelite and the recycling of leaching agent are realized.

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