High Calcium Tungsten Ore Decomposition Process Improvement

The alkaline decomposition method of high calcium tungsten ore is first grinding with high calcium tungsten minerals (tungsten concentrates, wolwolwoltungsten medium ore, wolframite, high calcium tungsten fine mud, calcium containing 3%), and then the grinding high calcium tungsten minerals and high concentration alkali are added together in the ordinary stirred autoclave, at the temperature of 130-200°C and pressure 0.15-1.0MPa. Under the conditions of heat preservation and pressure cooking, after the pressure cooking is unloaded, the filtration and washing are carried out at a certain temperature and NaOH concentration, and the sodium tungstate solution is purified. The sodium tungstate solution contains WO₃ 80-300g/L and the free NaOH is 90-280g/L.

Some scholars have improved the process. The technological characteristics of the improved process are: the process is made of three steps: first pressing, two times pressing, and phosphoric acid recovery. The first step is to grind the scheelite first, and then add the scheelite, the Na₂WO₄ solution containing Na₃PO₁ to the ordinary stirred autoclave, and control the solid and liquid weight ratio of 0.5-1.0 to the boiling. The temperature is 120-160°C, 0.1-0.5MPa, heat preservation time for 0.5-1 hours, cooling discharge to 50-80°C filter to get low phosphorus Na₂WO₄ products and one filter slag. The two step of boiling process is a theory of 1.2-1.5 times a theoretical amount of alkali and a theory calculated according to the Ca content in scheelite, according to the WO₃ content in the scheelite. The 0.8-1.2 times of phosphoric acid was added into the autoclave with the pressure of 0.5-0.8MPa, 160-180°C, the heat preservation time was 1 hours. The process of phosphoric acid recovery was completed by the leaching of the slag of two times and the leaching of concentrated sulfuric acid.

The 1000g 67%WO₃ containing scheelite was grinded to -0.045mm > 91% and added to NaWO₄ solution containing phosphorus 3g/L and added to the ordinary stirred autoclave. The phosphorus content in the Na₂WO₄ solution was reduced to 0.15g/L in the pressure of 0.5MPa at 160°C for 1h. After the first pressure, the wolfram ore containing WO₃58%, added to phosphoric acid (according to the Ca content in scheelite) and 1.3 times the theoretical amount of NaOH (according to the WO₄ content in the scheelite), the pressure is 0.8MPa, the temperature is 180°C, the heat preservation is 1 hours, the slag containing WO₃ is 0.7%, the decomposition rate is 99.5%.

The advantages of the improved process are that the decomposition rate is high and the operation is simple and easy to operate. After the first pressing, the Na₂WO₄ product with low phosphorus can be obtained, the phosphoric acid can be recovered, the cost is saved and the benefit is improved.

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