Iron extracted from oxide using coke.Temp 2000K. Carbon dioxide is formed which then reacts with more carbon to form carbon monoxide.
Carbon monoxide is the reducing agent. It reacts with iron oxide to produce molten iron.
Continuous process. Carbon dioxide produced.
Ore = bauxite - aluminium oxide. Dissolved in molten cryolite to form solution which melts at 1240K (lower than pure aluminium oxide 2345K). Solution is electrolysed with current up to 300 000A.
At the cathode:
At the anode:
Continuous process. Oxygen burns the carbon electrodes to carbon dioxide - must be replaced regularly. Main cost - electricity.
Ore = rutile - titanium oxide. Converted to titanium chloride by reacting with coke and chlorine. Temp 1173K
Titanium chloride reduced with molten sodium. Inert argon atmosphere. Temp 1300K
Titanium oxide not reduced with carbon - titanium carbide makes the metal brittle. Reduced by more reactive and expensive metal - sodium or magnesium.
Batch process - less efficient. Reaction vessels must be heated back up. Carbon monoxide produced.
Tungsten extracted from its oxide by reduction with hydrogen. High temp.
Tungsten ore not reduced with carbon - carbide forms.
Hydrogen is a flammable gas - main risk.
Original copper ore converted to copper oxide. This is then reduced with carbon.
Eg. malachite, which containts copper carbonate. Heat it.
The oxide is then heated with coke.
Or, spray copper mining waste with dilute acid in the presence of a bacterium. The bacteria will work on low grade ores. The copper is extracted from the solution by reduction with scrap iron.
Iron must be extracted from its own ore - requires energy. Carbon dioxide produced.
- Metals can be melted down and reformed - straightforward
- Reduces scrap metal
- Scrap is already extracted from ore
- Scrap iron easily separated - magnetic
- Less carbon dioxide produced
- Recycled aluminium uses only 5% of energy used to extract from ore
- Financial and energy costs to sort and transport material