2.3.6Chemical Bonding, Application Of Chemical Reactions and Organic Chemistry
Extraction of Iron
5 min read 7 parts Lesson 30 of 54 1 quiz
Section 1 of 7The blast furnace
Continuous process
- Continuous process Iron is extracted from its ore, haematite (Fe2O3), in a very large blast furnace.
- Raw materials are fed in at the top and products are removed all the time,
- since reheating a furnace would take too much time and money;
- a modern furnace makes about 10,000 tonnes a day.
- since reheating a furnace would take too much time and money;
Inputs
- Inputs Haematite, coke and limestone enter at the top and hot air is blown in at the bottom.
Section 2 of 7Raw materials
| Raw material | Formula | Purpose |
|---|---|---|
| Haematite (iron ore) | Fe2O3 | Source of iron |
| Coke | C | Provides carbon, which is burned for heat and makes the reducing agent |
| Limestone | CaCO3 | Removes acidic impurities |
| Hot air | Contains O2 | Supplies oxygen to burn the coke |
Section 3 of 7Reactions in the furnace
1Coke burns
- Coke burns Carbon burns in the hot air in an exothermic reaction that heats the furnace: C(s) + O2(g) → CO2(g).
2Carbon monoxide forms
- Carbon monoxide forms At high temperature more coke reduces the carbon dioxide: CO2(g) + C(s) → 2CO(g).
3Iron oxide is reduced
- Iron oxide is reduced Carbon monoxide removes oxygen from the ore: Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g).
4Iron collects
- Iron collects The molten iron is dense, runs to the bottom of the furnace and is tapped off.
Section 4 of 7Removing impurities
1
Limestone decomposes in the heat: CaCO3(s) → CaO(s) + CO2(g).
2
Calcium oxide is a base, so it reacts with the acidic impurity silicon dioxide in the ore in a neutralisation: CaO(s) + SiO2(s) → CaSiO3(l).
3
Calcium silicate is molten slag, which floats on top of the molten iron because it is less dense.
4
Slag is tapped off separately from the iron.
Section 5 of 7Worked example: balancing and redox
Balance the equation
- Balance the equation Fe2O3 + CO → Fe + CO2 has three oxygen atoms in Fe2O3, so three CO are needed to take them: Fe2O3 + 3CO → Fe + 3CO2.
- Now balance iron by writing 2Fe: Fe2O3 + 3CO → 2Fe + 3CO2.
What is oxidised?
- What is oxidised? Carbon monoxide is oxidised because it gains oxygen to become carbon dioxide.
- Iron(III) oxide is reduced because it loses oxygen.
Section 6 of 7Key terms
| Term | Meaning |
|---|---|
| Blast furnace | A tall furnace in which iron ore is reduced to iron using carbon-based materials. |
| Coke | An impure form of carbon made from coal. |
| Slag | Molten calcium silicate formed from impurities, which floats on the iron. |
| Reduction | Loss of oxygen. |
| Oxidation | Gain of oxygen. |
| Thermal decomposition | Breaking down a compound using heat. |
Section 7 of 7Exam technique
1
Saying limestone reduces the iron oxide — it removes impurities; carbon monoxide does the reduction.
2
Writing that carbon reduces the ore directly in all stages; the main reducing agent is carbon monoxide.
3
Forgetting that the process is continuous.
4
Stating that the slag sinks below the iron; it floats on top.
5
Not balancing Fe2O3 + 3CO → 2Fe + 3CO2 correctly.