Extractive Metallurgy Notes

Extractive Metallurgy Overview

  • Definition: The field dealing with extracting metals from their ores and refining them.
  • Minerals: Inorganic compounds with multiple metals associated with non-metals (e.g., S, O, N).
  • Types of naturally occurring minerals:
    • Sulphides (e.g., CuFeS2, FeS2)
    • Oxides (e.g., Fe2O3, Fe3O4)
    • Halides (e.g., NaCl)

Sources of Metals

  • Earth's Crust Composition:
    • Aluminum: 8.1%
    • Iron: 5.1%
    • Calcium: 3.6%
    • Sodium: 2.8%
    • Potassium: 2.6%
    • Magnesium: 2.1%
    • Titanium: 2.1%
    • Manganese: 0.1%
  • Other Sources:
    • Ocean water (high concentrations of Na, Mg, Ca)
    • Recycled scrap metals

Types of Ores

  1. Oxide Ores:
    • Common examples: Fe2O3, Fe3O4
    • Metals produced: Manganese, Titanium, Uranium
  2. Sulphide Ores:
    • Common examples: Chalcopyrite, Sphalerite
    • Metals produced: Copper, Zinc, Nickel
  3. Halide Ores:
    • Common examples: Rock salts found in seawater

Commercial Production Factors

  • Factors affecting metal production:
    • Availability of ore deposits
    • Concentration of metal in the ore
    • Technology for extraction and refining
    • Metal's physical/chemical properties
    • Market demand for the metal

Unit Processes and Operations in Metal Extraction

  • Unit Operations:
    • Physical operations: Crushing, Grinding, Sizing
  • Unit Processes:
    • Chemical processes: Leaching, Smelting, Electrolysis, Roasting
  • Flow Sheets: Combinations of unit steps/processes to represent extraction operations.

Processing Steps and Equipment

  • Unit Processes Classification:
    • By phases involved: Gas-solid, Gas-liquid, Liquid-liquid, Solid-solid
    • By equipment involved: Fixed bed, Fluidized bed, Shaft furnace, Rotary kiln
    • By chemical reactions: Oxidation, Reduction
  • Processing Techniques:
    • Physical Separation: Involves crushing and grinding to concentrate metal content.
    • Pyrometallurgy: Smelting and refining under high temperature.
    • Hydrometallurgy: Metal precipitation in an aqueous solution.
    • Electrometallurgy: Metal extraction through electrolysis.

Recycling of Metals

  • Definitions:
    • Waste: Materials intended to be disposed of.
    • Reuse: Utilizing waste without further processing after cleaning.
    • Recycling: Processing waste into raw materials for production.
    • Recovery: Converting materials into products or energy using waste properties.
  • Benefits:
    • Saves raw materials and energy.
    • Reduces environmental contamination.
    • Aluminum recycling saves 85% energy compared to ore production.