1. Extractive Metallurgy
Metallurgy for the Non-Metallurgists

2. Learning Objectives
Upon Completion of this lesson, you will be able to:
List several methods for concentration of ores and the methods and techniques for mineral processing
Define hydro-, pyro-, and electrometallurgy the techniques to provide the energy necessary for extraction of metals from metallic ores
Describe the processes of oxidation and reduction and understand that oxidation of metals is a naturally occurring process
Outline the steps in production of pig iron and steel

3. Mineral Processing
Earth’s crust contains oxygen containing minerals and sulfur containing minerals
An ore general is part of the crust that contains valuable minerals and metals
Mineral Processing extracts the valuable minerals from the rocks without changing them

4. Processing Techniques
Crushing—breaks down the ore rock to 4-6 inch pieces
Grinding—breaks up the crushed ore
Comminution—the process of crushing and grinding the ore
Classification—the separation of particles according to their settling rates in a fluid

5. The major types of crushers

6. Three basic types of crushing and grinding circuits: (a) conventional,
(b) autogenous, and (c) autogenous with separate fine grinding

7. Concentration
Gravity Devices—minerals are usually denser than the waste rock of the ore
Magnetic Devices—Iron minerals are magnetic
Electrostatic Devices—crushed ore is exposed to an ionizing electrode
Flotation—separates wettable from non-wettable particals

8. Spiral (mechanical) classifier. Courtesy of Mine and Smelter Corp.,
division of Kennedy Van Saun Corp.

9. Denver flotation cell mechanism. Courtesy of Joy Manufacturing Co.

10. Dewatering of Concentrate
First the concentrate is thickened
Thickened concentrate is sent to vacuum filter to reduce moisture
The ‘cake’ then goes to a smelter
Concentrated ore goes through a chemical process to extract the metal
Energy is used to extract the metal
Pyrometallurgy-heat
Hydrometallurgy-wet chemicals
Electrometallurgy-electrical energy

11. Cutaway view of thickener. Courtesy of Environmental Equipment
Div., FMC Corp.

12. Cutaway view of drum filter with scraper discharge. Courtesy of Filters
Vernay.

13. Extraction of copper from a low-grade ore

14. Extraction of aluminum from bauxite ore

15. Flow diagram for production of 900 kg (one ton, 2000 lb) of pig iron (when molten, “hot metal”) and further processing to steel

16. Oxidation and Reduction
Chemical processes involve reactions between mineral constituents and the environment that surrounds the mineral
Oxidation involves the reaction between the metallic elements and oxygen (ex. Rusting of steel)
Oxidation reactions release heat
Oxidation refers to a loss of electrons from the metal
Oxidation is an increase in valence because of the loss of electrons
Metal oxide is reduced to a metal when it regains its electrons

17. Oxidizing and reducing processes

18. Preparation for Pyrometallurgical Reduction
Drying—heating or vacuum system
Calcination—high temperature operation
Roasting—heating to just below the melting point of the ores
Sintering—variations of roasting

19. Pyrometallurgical Reduction
Pyrometallurgical equation: MX + R + heat = M + Rx
Reverberatory Furnaces—rectangular with an arched roof (figure 11)
Blast Furnaces—good for oxides that are not highly reactive
Iron Blast Furnace (figure 12)

20. Schematic views of copper matte smelting reverberatory furnace

21. Schematic illustration of an iron blast furnace, showing temperatures and chemical reactions

22. Iron and Steelmaking
Concentrated ore, coke, limestone and other solid materials are loaded in the top of the furnace
These materials are called the “burden”
Burden meets air as it moved down furnace
Carbon burns, producing heat and CO
Burden becomes molten as it reaches the hearth
Slag is removed and the metal hardens
Steel is Iron combined with less than 2% carbon
Pig iron is normally the product of the blast furnace—pig iron is iron with greater than 2% carbon
An Electric Arc furnace is also used to make steel (figure 14)

23. Basic oxygen furnace shop

24. Electric Arc Furnace
Schematic diagram of an electric arc furnace

25. Electroslag Remelting (ESR) Furnace
Schematic illustration of a basic electroslag remelting (ESR) furnace

26. Vacuum Arc Remelting (VAR) Furnace
Schematic diagram of a typical vacuum arc remelting (VAR) furnace

27. Lead Blast Furnace
Lead blast furnace, open-top type

28. Pierce-Smith Converter
Schematic of Pierce-Smith converter

29. Horizontal Zinc Retort

30. Vertical Zinc Retort
Vertical (New Jersey) continuous zinc retort

31. Pyrometallurgical Refining
Trying to remove impurities
Refining with Gaseous Reagents (oxygen is an example of a gaseous reagent)
Passing oxygen through molten pig iron removes some of the carbon
Chlorine is a gaseous reagent for refining

32. Hydrometallurgical Processes
Leaching—a separation process using liquids
Goal of Leaching:
Production of a pure compound
Production of a metal from impure metal or metal compounds
Direct production of a metal from an ore
Methods of Leaching
Situ Leaching
Heap Leaching
Agitation Leaching

33. Heap Leaching
Heap leaching cyanidation

34. Pahuca Tank Airflow
Schematic of airflow in a Pachuca tank

35. Purification Chemical and Physical Treatment Solvent Extraction
Precipitation
Results in physical change
Solvent Extraction
Use an aqueous and organic solution
Solvent removes metal ions from the aqueous solution
Ion Exchange
Exchanges ions between the aqueous solution and a solid

36. The Leaching/Electrowinning Process
Simplified block diagram showing the cyclical nature of the leaching/
electrowinning process

37. Hall-Heroult Aluminum Cell
Hall-Héroult aluminum production cell with self-baking anodes