Extraction of Tungsten from Wolframite [(Fe,Mn)WO₄] Ore
The whole extraction falls into two major phases: mineral beneficiation (physical concentration) and hydrometallurgical/ pyrometallurgical refining to metallic tungsten, with standard industrial flow below：
Phase 1: Ore Beneficiation (Upgrade raw ore into wolframite concentrate)
Raw wolframite ore only contains ~0.5%–1.5% WO₃; physical separation upgrades it to 60%–70% WO₃ concentrate before chemical leaching中国地质调查局西安矿产资源调查中心.
Crushing & controlled grinding Raw rock is crushed by jaw/cone crushers, then rod-milled (instead of ball mill to avoid over-grinding fine tungsten slime) to liberate wolframite grains from gangue (quartz, sulfide waste rock).
Core gravity separation (dominant for wolframite) Rely on wolframite's high specific gravity (7.1–7.5 g/cm³ vs 2.6–3.0 for gangue):
Coarse particles: jig concentrator for rough separation;
Fine particles: shaking tables, spiral chutes for cleaning and rough concentrate collection.
Auxiliary magnetic separation & flotation Strong magnetic separator removes iron-bearing gangue/pyrite; froth flotation strips associated sulfide impurities (arsenopyrite, chalcopyrite) locked in middling ores; ultra-fine tungsten slime is recycled by centrifugal separators.
Phase 2: Chemical Refining (from concentrate to pure tungsten metal)
Two mainstream industrial decomposition routes: alkaline pressure leaching (hydrometallurgy, most widely used) and soda ash sintering (pyrometallurgy).
Route A: Caustic soda (NaOH) pressure leaching (preferred for wolframite)
Alkali digestion & water leaching Wolframite concentrate reacts with concentrated NaOH solution in autoclave at 110–130 ℃: After reaction, hot water leaching dissolves soluble ; filter out Fe/Mn hydroxide slag to get crude sodium tungstate liquor.
Solution purification
Adjust pH=8~9 to precipitate silicon impurity; add MgCl₂/NH₄Cl to remove phosphorus & arsenic; add Na₂S to precipitate molybdenum sulfide residue;
Further refined via ion-exchange resin to strip residual impurities, obtaining high-purity solution.
APT crystallization (key intermediate) Add concentrated ammonia water to purified tungstate solution, convert sodium tungstate into ammonium tungstate; evaporative crystallization produces Ammonium Paratungstate (APT, )-core industrial tungsten precursor.
Calcination to tungsten trioxide APT is calcined at 500–800 ℃ to decompose into yellow tungsten trioxide ():
Hydrogen reduction to metallic tungsten powder Two-step tubular furnace reduction under pure hydrogen atmosphere:
First stage: 550–700 ℃, ;
Second stage: 800–950 ℃, (high-purity tungsten powder >99.95%).
Sintering for bulk tungsten ingot Tungsten powder is compacted by cold isostatic pressing, then vacuum sintered at 2300–2800 ℃ to produce dense solid tungsten metal blank for rolling/wire drawing.
Route B: Sodium carbonate sintering (pyrometallurgical alternative)
Mix wolframite concentrate with , sinter in rotary kiln at 800–900 ℃ to form solid , then hot water leach to dissolve tungstate; follow identical purification → APT → calcination → reduction flow as above.
Optional minor route: Acid decomposition
Concentrate digested by hot concentrated HCl to precipitate crude tungstic acid (); purified tungstic acid calcined to , then hydrogen reduced to W (mainly for lab/small-scale production).
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