Tungsten processing involves several steps to extract and refine tungsten from its ores, primarily wolframite (Fe,Mn)WO₄ and scheelite (CaWO₄). Here’s an overview based on *Encyclopædia Britannica* and other sources:
1. Mining & Ore Concentration
– Tungsten ores are mined through open-pit or underground methods.
– Gravity separation is commonly used to concentrate the ore due to tungsten’s high density.
– Froth flotation may be employed for finer particles or scheelite ores.
2. Chemical Processing
Tungsten is extracted from concentrates using two main methods:
# A. Alkali Leaching (for Scheelite)
– Scheelite reacts with sodium carbonate (Na₂CO₃) under high pressure/temperature:
\[ \text{CaWO}_4 + \text{Na}_2\text{CO}_3 \rightarrow \text{Na}_2\text{WO}_4 + \text{CaCO}_3 \]
– The sodium tungstate solution is purified and precipitated as calcium tungstate or converted to ammonium paratungstate (APT).
# B. Acid Leaching (for Wolframite)
– Wolframite is digested with hydrochloric acid (HCl) or sodium hydroxide (NaOH):
\[ \text{(Fe,Mn)WO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{WO}_4 + \text{(Fe,Mn)(OH)}_2 \] .jpg)
The resulting sodium tungstate is further processed into APT.
3. Production of Tungsten Powder
– Ammonium paratungstate (APT) is calcined to form tungsten trioxide (WO₃):
\[ (\text{NH}_4)_10\text{W}_{12}\text{O}_{41} \cdot 5\text{H}_2\text{O} \rightarrow 12\text{WO}_3 + 10\text{NH}_3 + 10\text{H}_2\text{O} \]
– WO₃ is reduced in hydrogen furnaces to produce tungsten powder:
\[ \text{WO}_3 + 3\text{H}_2 \rightarrow \text{W} + 3\text{H}_2\text{O} \]
4. Manufacturing Tungsten Products
– Cemented Carbides:
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