MrChemCoach

Extraction of Iron · Blast Furnace

IGCSE 0620 & 0971 · CBSE Class 10 · 3D virtual lab
All labs
1 ChargeOre, coke, limestone
2 Hot blastAir in at the tuyeres
3 Let it runIron collects
4 TapSlag, then iron
Close-up ·
Blast off · idleCharge ore, coke and limestone
Building the furnace…
What the meters say Blast off
Tuyere zone1450°C
Top gas90°C
CO in top gas0.0%
Iron in hearth0t
Slag in hearth0t
Iron tapped0t

Drag to turn the furnace. Scroll or pinch to zoom; right-drag or two fingers to pan. With the cut-away on, tap inside the furnace to inspect that zone.

The furnaceRun it yourself

1 · Charge the top

HematiteFe2O3 · the ore 3.0 layers
CokeC · fuel and reducing agent 4.0 layers
LimestoneCaCO3 · removes the sand 2.0 layers

Each layer drops from the skip into the top of the shaft. The burden sinks as the coke burns away at the bottom.

2 · Hot blast temperature

1100 °C

Hotter air burns the coke hotter and faster, so the furnace makes iron faster.

3 · Tap the hearth

Slag leaves from the higher outlet because it floats on the iron. Iron leaves from the tap hole at the very bottom.

4 · Inspect a zone

Turn on the cut-away and tap anywhere inside the furnace to see the temperature there and the reactions happening.

5 · Close-ups of the reactions

6 · Show

7 · What to look for

8 · Go further

Where this sits in your course
IGCSE 0620 & 0971 Metals: extraction of metals. Core: the raw materials and what each does. Extended: the full set of equations, including slag formation. Fe2O3 + 3CO → 2Fe + 3CO2
CBSE Class 10 Metals and Non-metals: metals in the middle of the reactivity series are extracted by reduction with carbon. oxide + carbon → metal + oxide of carbon
NEET / JEE foundation Why carbon monoxide wins as the reducing agent at the top of the furnace, and the idea of a reduction taking place in steps. Fe2O3 → Fe3O4 → FeO → Fe
Quick check - the blast furnace 0 / 8

8 / 8
For revisionTheory, method and exam tips

What this shows

Iron is below carbon in the reactivity series, so it can be extracted from its ore by reduction with carbon. In the blast furnace the ore is hematite, mainly iron(III) oxide. Coke is the fuel and, through carbon monoxide, the reducing agent. Limestone is there to remove the sandy impurity as slag. Hot air is blown in near the bottom; the solids work their way down while the hot gases rise through them.

Fe2O3 + 3CO → 2Fe + 3CO2

The raw materials

  • Hematite, Fe2O3: the source of the iron.
  • Coke, almost pure carbon: burns to heat the furnace and makes the carbon monoxide.
  • Limestone, CaCO3: removes the silicon dioxide (sand) impurity.
  • Hot air, blown in through the tuyeres: supplies the oxygen for the coke to burn.

The reactions, in order

  1. Coke burns in the hot air: C + O2 → CO2. This is exothermic and keeps the furnace hot.
  2. Carbon dioxide meets more hot coke: CO2 + C → 2CO.
  3. Carbon monoxide reduces the ore: Fe2O3 + 3CO → 2Fe + 3CO2.
  4. Limestone decomposes in the heat: CaCO3 → CaO + CO2.
  5. Calcium oxide removes the sand as slag: CaO + SiO2 → CaSiO3.

What you should see

  • Layers of ore and coke sinking slowly while gas streams upward through them.
  • The ore darkening and turning metallic as it loses oxygen on the way down.
  • White-hot coke at the tuyeres, where the air blast hits it.
  • Two liquids in the hearth: slag on top, molten iron underneath, tapped off separately.

Where marks are lost

  • Naming carbon as the main reducing agent in the equation. The mark scheme wants carbon monoxide: Fe2O3 + 3CO → 2Fe + 3CO2.
  • Saying limestone "removes impurities". Say what it removes: it forms calcium oxide, which reacts with silicon dioxide to make calcium silicate (slag).
  • Getting the layers the wrong way round. Slag is less dense, so it floats on top of the iron.
  • Mixing up oxidation and reduction. Iron(III) oxide loses oxygen and is reduced; carbon monoxide gains oxygen and is oxidised.

Questions students ask

Why is the air blown in hot?
Hot air makes the coke burn faster and hotter, so less coke is needed to keep the bottom of the furnace above the melting point of iron. The air is heated in the tall stoves beside the furnace.
Where does the carbon dioxide from the reduction go?
It rises with the other gases and leaves at the top as waste gas, together with nitrogen from the air and some unused carbon monoxide.
Is the iron from the furnace pure?
No. It is pig iron, about 4% carbon, which makes it brittle. Most of it is taken straight to a steelmaking furnace, where oxygen burns the extra carbon off.
Why do the equations for slag count as neutralisation?
Calcium oxide is a basic oxide and silicon dioxide is an acidic oxide. They react together to give a salt, calcium silicate.

Try these next

Written for Cambridge IGCSE Chemistry 0620 and CBSE Class 10. Lumps, molecules and the cut-away are drawn for clarity, and the process runs much faster than a real furnace. Temperatures are typical of a working furnace; tonnages are for this model hearth.