Unit 3: Outcome 2 Media analysis Portland aluminium smelter. Background A large aluminium smelter operates in Portland Victoria. It produces large amounts of aluminium and provides significant revenue and income for the residents of Portland. However, it uses large amounts of electricity, produces CO 2 emissions and is borderline in profitability. It has been under scrutiny this year because the contract guaranteeing cheaper electricity is to be renewed and it was severely damaged by a power failure late last year. Its future is under much discussion. Manufacture of aluminium. Northern Australia has large reserves of aluminium ore, bauxite (Al 2 O 3 ). This ore is mined in Queensland, refined to Al 2 O 3 and shipped to Victoria for the final stage of smelting. Alcoa Portland uses electrolysis to obtain aluminium. Alumina, Al 2 O 3 , is added to large vats, called pots. It is heated to melt the alumina and an electric current is passed through the solution. An outline of this cell is shown below. It is a continuous process. The anodes are made from carbon or graphite and the outside of the pot acts as the cathode. Power outage Early December 2016, a power outage hit the plant and the molten materials started to solidify where they are not supposed to – details below.
Transcript
Unit 3: Outcome 2 Media analysis
Portland aluminium smelter.
Background
A large aluminium smelter operates in Portland Victoria. It produces large amounts of aluminium and provides significant revenue and income for the residents of Portland. However, it uses large amounts of electricity, produces CO2 emissions and is borderline in profitability. It has been under scrutiny this year because the contract guaranteeing cheaper electricity is to be renewed and it was severely damaged by a power failure late last year. Its future is under much discussion.
Manufacture of aluminium. Northern Australia has large reserves of aluminium ore, bauxite (Al2O3). This ore is mined in Queensland, refined to Al2O3 and shipped to Victoria for the final stage of smelting.
Alcoa Portland uses electrolysis to obtain aluminium. Alumina, Al2O3, is added to large vats, called pots. It is heated to melt the alumina and an electric current is passed through the solution. An outline of this cell is shown below. It is a continuous process. The anodes are made from carbon or graphite and the outside of the pot acts as the cathode.
Power outage
Early December 2016, a power outage hit the plant and the molten materials started to solidify where they are not supposed to – details below.
Repercussions of power outage and energy review has left Alcoa in uncertain territory.
Questions
Manufacture
1. Electrolysis is conducted on alumina Al2O3.
a. Explain why the alumina is heated.
b. Cryolite is added to the alumina. Explain how this is a cost saving measure.
c. Explain the movement of ions that will occur when an electric current is passed through the molten mixture.
1 + 2 + 1 = 4 marks
2. If inert electrodes were used, the electrolysis of Al2O3 would produce aluminium and oxygen gas.
a. Write a balanced half equation for the formation of aluminium.
b. Write a balanced half equation for the formation of oxygen gas.
c. Write a balanced overall equation for this reaction.
d. Identify the oxidant and reductant in the above reaction.
e. Why do you think Alcoa does not allow the production of oxygen gas to occur?
1 + 1 + 1 + 1 + 1 = 5 marks
3. Graphite electrodes (assume carbon is the reactant) are used for anodes, producing CO2 instead of oxygen gas.
a. Write a balanced half equation for the formation of CO2 gas from carbon solid and oxygen ions.
b. Write a balanced overall equation for the reaction occurring in the Hall-Heroult cell.
c. The use of carbon solves one problem but creates another problem. What might this problem be?
1 + 1 + 1 = 3 marks
Gas emissions
4. Alcoa can produce 340000 tonnes of aluminium per year.
Calculate the volume of CO that will produced if 340000 tonnes of aluminium is produced. Assume the
temperature is 22 0C and the pressure 100 kPa.
5 marks
Power consumption
5. The current used in Portland is a massive 300000 amps. Calculate the time required to produce 1 tonne of
aluminium using this current.
4 marks
The issues
6. List 5 uses of aluminium.
3 marks
7. Provide three arguments for keeping this plant running.
3 marks
8. Provide three arguments for closing this plant down.
3 marks
9. For the aluminium industry, a power outage presents more of a problem than just a few hours loss of production.
a. Explain clearly the impact of power failure.
b. Why is the supply of electricity to Alcoa controversial?
3 + 2 = 5 marks
10. Explain the issues associated with using electricity produced from coal in the La Trobe Valley to power this
plant.
3 marks
11. There is a gas-fired power plant at Mortlake in the south west of the state.
a. What advantages does the expansion of this plant offer?
b. Does the expansion of this plant solve the issues associated with powering Alcoa. Explain your answer.
2 + 2 = 4 marks
Conclusion
Aluminium metal is produced by electrolysis of _________________.
_____________ temperature is required for this process.
During electrolysis, aluminium ions are _____________ to aluminium at the _____________.
It requires __ electrons to produce one atom of aluminium.
At the ___________, CO2 gas is produced.
Aluminium is a popular metal because it is ____________________ and _________________.
