Questions
6–10 questions in major PSU papers
Difficulty
Medium
Importance
Core — never skip
Overview
Extractive metallurgy is a critical domain in materials engineering that focuses on the recovery of valuable metals from their ores through physical, chemical, and electrolytic processes. For PSU exams, mastering the specific reactors, chemical reactions, and separation techniques used in ferrous and non-ferrous production is essential for securing high marks.
Iron & Steel Making
Iron production primarily occurs in a Blast Furnace using the reduction of iron oxides by carbon monoxide. Steel production follows in secondary vessels like the Basic Oxygen Furnace (BOF) or Electric Arc Furnace (EAF) to control carbon content and remove impurities.
- Blast Furnace: Coke acts as fuel and reducing agent
- Slag formation: CaO + SiO2 -> CaSiO3
- BOF: Uses oxygen lancing to lower carbon content
- EAF: Primarily used for recycling steel scrap
- Direct reduction: Hydrogen/CO used in DRI processes
Non-Ferrous Extraction
Extraction of metals like Al, Cu, and Zn involves distinct thermodynamic pathways based on their reactivity series. Aluminium is recovered via electrolysis, while Copper and Zinc often undergo roasting followed by smelting or leaching.
- Hall-Heroult process for Al: Electrolysis of Al2O3 in cryolite
- Copper extraction: Roasting of chalcopyrite (CuFeS2)
- Zinc extraction: Roasting followed by carbon reduction
- Ellingham diagram: Used to predict metal oxide stability
- Self-reduction: Used in extraction of copper from Cu2S
Mineral Processing
Before smelting, ores undergo concentration to increase metal content. Froth flotation leverages surface wettability differences, while gravity separation utilizes density variations between ore and gangue.
- Froth flotation: Uses collectors (pine oil) and frothers
- Gravity separation: Wilfley table or jigging
- Magnetic separation: Used for ferromagnetic ores like magnetite
- Leaching: Chemical extraction using reagents like NaCN
Formula Sheet
Fe2O3 + 3CO -> 2Fe + 3CO2
2Al2O3 + 3C -> 4Al + 3CO2
Cu2S + O2 -> 2Cu + SO2
Exam Tip
Focus on the specific reducing agents and furnace types used for each metal, as PSU exams frequently test these via matching-type questions.
Common Mistakes
- Confusing the roles of collectors and frothers in flotation processes.
- Ignoring the temperature dependencies shown in Ellingham diagrams.
- Mixing up the electrolyte composition used in the Hall-Heroult process.
More Revision Notes
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