Nickel extraction involves several processes depending on the type of ore being processed. The two main types of nickel ores are sulfide ores (e.g., pentlandite) and laterite ores (e.g., limonite and garnierite). Here’s an overview of the extraction methods:
1. Nickel from Sulfide Ores
Sulfide ores are typically processed via flotation, smelting, and refining.
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# Steps:
1. Crushing & Grinding: The ore is crushed and ground to liberate nickel-bearing minerals.
2. Froth Flotation: A process that separates nickel sulfide minerals (pentlandite) from waste rock using chemicals and air bubbles.
3. Smelting:
– The concentrate is roasted to remove sulfur.
– Smelted in a furnace (flash or electric) to produce a nickel-iron matte (~45% Ni).
4. Converting: The matte is further refined in a converter to remove iron and sulfur, producing high-grade matte (~75% Ni).
5. Refining:
– Electrorefining: Impure nickel anodes are dissolved, and pure nickel is deposited on cathodes.
– Carbonyl Process (Mond Process): Nickel reacts with CO to form volatile nickel carbonyl, which is then decomposed to yield pure nickel.
2. Nickel from Laterite Ores
Laterites are processed via either:
– Pyrometallurgical (smelting) – High-temperature processing.
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ometallurgical (leaching) – Chemical dissolution.
# (A) Pyrometallurgical Route (Ferronickel Production)
1. Drying & Calcination: Moisture removal and decomposition of minerals.
2. Reduction Smelting: Ore is melted in an electric arc furnace with coke/coal to produce ferronickel (~20–40% Ni).
3. Refining: Ferronickel is further refined for steelmaking or pure nickel production.
# (B) Hydrometallurgical Route (HPAL – High-Pressure Acid Leaching)
1. Leaching: Ore is treated with sulfuric acid under high pressure (~250°C) to dissolve nickel.
2. Neutralization & Precipitation: Impurities like iron are removed, and nickel is precipitated as mixed hydroxide precipitate (MHP).
3. Electrowinning or Reduction: MHP is further