The flow chart of tungsten wet smelting is as follows:
Raw material preparation
Obtain tungsten concentrate as the starting raw material.
Concentrate decomposition (wet method)
For wolframite concentrate, use sodium hydroxide solution to leach at 110~130℃ or higher, the decomposition rate is 98~99%.
For scheelite concentrate, sodium carbonate solution is used for leaching at 200～230℃ in autoclave or hydrochloric acid is used for decomposition at 90℃ to obtain solid crude tungstic acid.
Purification of tungsten compounds
The sodium tungstate solution is purified to remove impurities such as silicon, phosphorus and arsenic.
Boil the solution and neutralize it with dilute hydrochloric acid to hydrolyze sodium silicate into a cohesive precipitate of silicate.
Add magnesium chloride and ammonium chloride solution, so that the phosphorus, arsenic generation of very small solubility of magnesium ammonium phosphate and magnesium ammonium arsenate precipitate removed.
Add sodium sulfide to sodium tungstate solution, so that molybdenum first in tungsten to form sodium thiomolybdate, and then neutralized with hydrochloric acid, so that molybdenum into insoluble molybdenum trisulfide precipitate removed.
In the purified sodium tungstate solution add calcium chloride solution, calcium tungstate (CaWO) precipitation, with hydrochloric acid decomposition of calcium tungstate precipitation to industrial tungstic acid.
The tungstic acid is calcined at 700～800℃ to get industrial pure tungsten trioxide.
Tungsten powder production
The most common method in modern industry is primary or secondary hydrogen reduction of tungsten trioxide or blue tungsten oxide.
This method can precisely control the particle shape, particle size and particle size composition of tungsten powder.
Production of Dense Tungsten
Tungsten powder is formed, sintered and melted to obtain dense tungsten.
The above flow chart is a simplified and generalized version, and the actual tungsten wet smelting process may contain more details and steps. In addition, the specific process parameters (e.g. temperature, concentration, time, etc.) may be adjusted according to the nature of raw materials, equipment conditions and product quality requirements.
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