Scheelite decomposing process

Abstract

The present invention relates to improved scheelite decomposing process and is especially one alkali pressure digestion scheelite decomposing process. The process includes three steps of the first pressure digestion, the second pressure digestion and phosphoric acid recovering. In the first pressure digestion, scheelite is first ground and then pressure digested together with high-phosphate Na2WO4 solution in a stirring pressure digestion reactor with solid-to-liquid weight ratio of 0.5-1.0, at temperature 120-160 deg.c and pressure 0.1-0.5 MPa for 0.5-1 hr, and the product is cooled to 50-80 deg.c, filtered to obtain low-phosphate Na2WO4 product and the first filtered slag. In the second pressure digestion, the first filtered slag is made to react with alkali and phosphoric acid in pressure reactor. In the phosphoric acid recovering, the second filtered slag is leached with concentrated sulfuric acid.

Description

technical field [0001] The invention relates to a method for decomposing scheelite, in particular to a method for decomposing scheelite by alkaline pressure cooking. Background technique [0002] Chinese Patent Publication No. 00126770.1 discloses a method for the decomposition of high-calcium tungsten minerals by alkaline pressure cooking. (Calcium>3% black tungsten concentrate, etc.), and then add the finely ground high-calcium tungsten mineral and high-concentration alkali 1.84 times the theoretical amount into an ordinary stirring pressure cooker, at a temperature of 130-200 ° C and a pressure of 0.15 Heat preservation and pressure cooking under the condition of -1.0MPa. After the pressure cooking material is discharged, it is filtered and washed at a certain temperature and NaOH concentration to obtain a washed sodium tungstate solution. The sodium tungstate solution contains WO 3 80-300g / L, containing free NaOH 90-280g / L, the invention has simple process flow, conv...

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Problems solved by technology

[0002] Chinese Patent Publication No. 00126770.1 discloses a method for the decomposition of high-calcium tungsten minerals by alkaline pressure cooking. (Calcium>3% black tungsten concentrate, etc.), and then add the finely ground high-calcium tungsten mineral and high-concentration alkali 1.84 times the theoretical amount into an ordinary stirring pressure cooker, at a temperature of 130-200 ° C and a pressure of 0.15 Heat preservation and pressure cooking under the condition of -1.0MPa. After the pressure cooking material is discharged, it is filtered and washed at a certain temperature and NaOH concentration to obtain a washed sodium tungstate solution. The sodium tungstate solution contains WO 3 80-300g / L, containing free NaOH 90-280g / L, the invention has simple process flow, convenient operation and high decomposition rate, but also has too high alkalinity, and a large amount of wolframite is needed to consume its residual alkali. The ratio of scheelite to wolframite reaches 1:3-4. The process is essentially a combined process of scheelite decomposition and black tungsten decomposition. Na 2 WO 4 The solution, because the alkali is too high, cannot be used as a final product, and further treatment with wolframite is required

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