Extraction of Iron from Hematite

• Iron is extracted in a large container called a blast furnace from its ore, hematite
• Modern blast furnaces produce approximately 10,000 tonnes of iron per day
• Diagram showing the carbon extraction of iron

  A) iron

  B) Fe2O3

  C) coke

  D) carbon

  E) limestone

  F) CaCO3

  G) waste gases

  H) Waste gases

  I) CaO

  J) CO2

  K) 2Fe(III)

  L) 3CO2(g)

  M) 2CO(g)

  N) CO2 (g)

  O) air

  P) air

  Q) slag

  R) CaSiO3(l)

  S) iron

  T) iron oxide

  U) FeO3(s)

  V) impurities

  W) silicon dioxide

  X) SiO2 (s)

  
• Carbon extraction of iron

  • The raw materials: iron ore (hematite), coke (an impure form of carbon), and limestone are added into the top of the blast furnace
  • Hot air is blown into the bottom
• Zone 1 in the blast furnace

  • Coke burns in the hot air forming carbon dioxide
  • The reaction is exothermic so it gives off heat, heating the furnace
  • carbon + oxygen → carbon dioxide
• Zone 2

  • At the high temperatures in the furnace, more coke reacts with carbon dioxide forming carbon monoxide
  • Carbon dioxide has been reduced to carbon monoxide
  • carbon + carbon dioxide → carbon monoxide
• Zone 3 (1)

  • Carbon monoxide reduces the iron(III) oxide in the iron ore to form iron
  • This will melt and collect at the bottom of the furnace, where it is tapped off
  • iron(III) oxide + carbon monoxide  →  iron + carbon dioxide
  • Limestone (calcium carbonate) is added to the furnace to remove impurities in the ore
  • The calcium carbonate in the limestone thermally decomposes to form calcium oxide
  • calcium carbonate → calcium oxide + carbon dioxide
• Zone 3 (2)

  • The calcium oxide formed reacts with the silicon dioxide, which is an impurity in the iron ore, to form calcium silicate
  • This melts and collects as a molten slag floating on top of the molten iron, which is tapped off separately
  • calcium oxide + silicon dioxide →  calcium silicate
• Zone 1 equations

  • The burning of carbon (coke) to provide heat and produce carbon dioxide:
  • C (s)  +  O2 (g)  →  CO2 (g)
• Zone 2 equations

  • The reduction of carbon dioxide to carbon monoxide:
  • CO2 (g)  +  C (s)  →  2CO (g)
• Zone 3 equations

  • The reduction of iron(III) oxide by carbon monoxide:
  • Fe2O3 (s)  +  3CO (g)  →  2Fe (I)  +  3CO2 (g)
  • The thermal decomposition of calcium carbonate (limestone) to produce calcium oxide:
  • CaCO3 (s)  →  CaO (s)  +  CO2 (g)
  • The formation of slag: CaO (s)  +  SiO2 (s)  →  CaSiO3 (l)