In order to ensure the quality of the chemical concentrate, the impurity content in the raw material should be lower than a certain value, such as arsenic not more than 0.3-0.5%, sulfur not more than 1.3-1.5%, when the content of impurities is high, it should be reduced to a certain amount when the material is prepared. Value; in order to improve the decomposition efficiency of minerals, the requirements for the fineness of materials depend on the decomposition method of the subsequent operations and the characteristics of the raw materials. For example, the soda sintering method needs to be ground to below 100-150 mesh; the direct leaching needs to be ground to below 200-300 mesh.

1.2 Sintering - Leaching of materials

Industrial production uses soda sintering-water immersion method, soda solution pressing method, caustic soda solution leaching method and acid decomposition method. Its purpose is to decompose tungsten minerals to form water-soluble tungstates. The choice of decomposition method depends mainly on the characteristics of the tungsten mineral raw materials and the specific conditions and conditions of the manufacturer. Method can be divided into

1. Soda sintering - water immersion method. It is suitable for processing with a small amount of low-grade wolframite quartz material, such as tungsten fine mud, sand iron-tungsten, tungsten, tin ore may be treated with a small amount of low-grade scheelite quartz material, water-insoluble when sintering The black tungsten ore and scheelite react with soda to form water-soluble sodium tungstate, and the water-soaked agglomerate converts the tungsten into the solution, and the solid-liquid separation removes the insoluble impurities. The sintering temperature of the black tungsten ore raw material is 700-850 degrees, and the white tungsten raw material is about 860 degrees.

2. The caustic soda solution leaching method is carried out by using a 35-40% caustic soda solution to a temperature of 110-120 degrees, and leaching the fine mineral raw material under pressure to transfer the tungsten into the leachate in the form of soluble sodium tungstate. There are two treatment methods for leaching: one is to directly dilute to a density of 1.3 g / cm 3 and then sent to purification; the second is to dilute it to a density of 1.45 g / cm 3 to precipitate sodium tungstate crystals, the crystallization liquid returns In the leaching operation, the aqueous solution of the crystal is sent for purification. Compared with the soda sintering-water immersion method, this method has simple process, low investment, and can process tungsten mineral materials such as tungsten fine mud and tungsten-tin ore with higher silicon content.

The reaction of leaching scheelite by caustic soda solution under normal pressure is a reversible reaction. Generally, a mixed solution of caustic soda and sodium silicate should be used as a leaching agent to obtain a satisfactory leaching result. However, when the scheelite raw material contains a considerable amount of silicon oxide, a single caustic soda can be used.

3, acid decomposition acid decomposition method can be used to treat scheelite and wolframite two raw materials, with 32-38% concentrated hydrochloric acid or nitric acid as a leaching agent, at a temperature of about 100 degrees, the tungsten mineral is directly decomposed to form tungsten Acid precipitation. In order to increase the leaching rate of tungsten, the material must be ground to -300 mesh. When the acid is decomposed, a considerable part of the impurities enter the solution and are separated from the tungstic acid by solid-liquid separation. The residue is separated and that the tungstic acid, alkali fusion of the tungsten used was an alkali metal tungstate solution into shape to obtain a more pure solution of ammonium tungstate or sodium tungstate. The acid decomposition tungsten has a high leaching rate, but the reagent consumption is large.

4, soda solution pressing method This method can be used to treat white tungsten and black tungsten mineral raw materials. The leaching process is carried out in a press cooker, and the raw material is ground to -300 mesh, and the tungsten leaching rate is related to the amount of soda, the leaching pressure, and the leaching temperature.

The advantage of this method is that a good applicability, not suitable for processing low-grade scheelite (5-15%), further adapted to process sulfide concentrates containing tungsten, such as tungsten ore bismuth, bismuth, molybdenum and tungsten ore. When the high sulfur tungsten is leached, the cassiterite, stibnite and stibnite remain in the residue, and all the copper , some silicon oxide, fluorine, phosphorus , arsenic and other impurities in the oxide are transferred into the immersion liquid together with the tungsten. The immersion liquid is sent to the purification treatment.

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