Cambridge IGCSE Chemistry · Syllabus 0620 · Metals
Blast Furnace
What is Blast Furnace?
The tall furnace in which iron is extracted from its ore. Hematite, coke and limestone are fed in at the top and hot air is blasted in at the bottom; carbon monoxide formed from the coke reduces the iron(III) oxide to molten iron, while calcium oxide from the limestone removes sandy impurities as molten slag.
This definition is part of the Metals chapter in Cambridge IGCSE Chemistry.
Common mistakes with Blast Furnace
- 9. “Coke reduces the iron(III) oxide in the blast furnace.” Repair In the route you are required to give, the reducing agent is carbon monoxide: it is the substance that takes the oxygen away from the iron(III) oxide. The coke does two other jobs — it burns to release heat and carbon dioxide, and it then converts that carbon dioxide into the carbon monoxide that does the reducing. Extended Supplement 9.6.4 Extended candidates give the same repair as a symbol equation, \(\mathrm{Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2}\). Core candidates are not asked for it — the syllabus states that symbol equations are not required for the furnace. Where Lesson 9.6B. Core 9.6.2
- 21. “The coke reduces the iron(III) oxide in the blast furnace.” Core 9.6.2 Defect Names the wrong reducing agent for the required route. Reason The coke burns to carbon dioxide and then converts it to carbon monoxide; it is the carbon monoxide that reduces the ore. Repair “Carbon monoxide reduces the iron(III) oxide”, with coke named as the fuel and as the source of that carbon monoxide. Transfer Which stage makes the reducing agent? The stage in which carbon dioxide passes over hot coke and is converted to carbon monoxide. Extended Supplement 9.6.4 As symbol equations: \(\mathrm{Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2}\) for the reduction, and \(\mathrm{CO_2 + C \rightarrow 2CO}\) for the stage that makes the reducing agent.
Examiner tips on Blast Furnace
- Read the statement carefully. Core 9.6.2 lists five stages of the blast furnace and then says, in the syllabus itself, “Symbol equations are not required”. Everything in this lesson is therefore in words. Extended candidates write the same five stages as balanced symbol equations under Supplement 9.6.4, in the equation ladder that follows.