The blast furnace is a counter-current heat exchanger used to smelt iron from iron ore for steel production. Reactions inside reduce iron oxides to molten iron and separate impurities into a slag. The furnace operates at over 1500°C, using coke as the reducing agent and limestone as a flux. Key reactions include the reduction of iron oxides to iron and carbon monoxide, and the removal of impurities like sulfur. The process produces molten iron, known as pig iron, and a slag byproduct. The composition of the pig iron depends on the burden chemistry and furnace operating temperature.

2. I. Blast furnace is a counter current heat and mass
exchanger in which reduction and smelting of
metallic mineral takes place.

3. Chemistry
• Elements lying at top of
reactivity series are
more reactive than
elements lying below
them in series.
Thermodynamics
• From Ellingum diagram
: A metal/element that
forms stabler oxide
(lower line) would replace
metal from less stable
oxide (upper line).

4. The Reactivity Series
potassium
sodium
calcium
magnesium
aluminium
zinc
iron
copper
gold
(carbon)
Increasingreac
Metals above carbon must be
extracted using electrolysis.
Metals below carbon
can be extracted from the ore by reduction
using carbon, coke, or charcoal.
Gold and silver often do not need to
be extracted. They occur native.
The reactivity of a metal
determines the method of
extraction.
lead
silver

5. 1)Free energy vs
temperature plot.
2)Gives stability of
oxides.
3) Oxides lying at
lower positions
are more stable
than oxides lying
at top positions.

6. Iron ore: iron bearing
materials ,provides iron to hot
metal.
Coke: Reductant , fuel, provides
permeability to bed.
Limestone: acts as flux.
Others: Manganese ore, coal dust,
coal tar, pellets, sinter …….
Iron Ore
Sinter
L
i
m
e
st
o
n
e
Coal Dust

7.  Hearth Dia.=8-9 m.
 Bosh Dia.=9-10 m
 Hearth Height=3-3.5
m.
 Bosh Height=3-4 m.
 Throat Diameter=5.5
-6.5 m.
 Stack Height=18-20 m.
 Overall Useful Height
= 30-32 m.
 Working Height = 21-
24 m .
B
S
P

9. • Decomposition of carbonates other than that of Ca.
• Vaporization of moisture.
• Carbon Deposition, 2CO = CO2 + C
• Haematite to Magnetite; 3Fe2O3 + CO = 2Fe3O4 + CO2
• Magnetite to Wustite; Fe3O4 + CO = 3FeO + CO2
• Water-Gas Shift Reaction; CO + H2O = CO2 + H2

10. • Endothermic calcinations of limestone : CaCO3= CaO + CO2
• Endothermic direct reduction of FeO : FeO + C = Fe + CO
• Endothermic direct reduction of SiO2 : SiO2 + 2C = Si +2CO
• Endothermic direct reduction of P2O3 : PO3 +5C = 2P + 5CO
• Endothermic sulphur removal : FeS + CaO +C = CaS +Fe + CO
• Exothermic combustion of carbon : C+ O2 (air) = CO2
• Exothermic reduction of CO2 : CO2 + C = 2CO
• Endothermic reduction of moisture in blast : C + H2O = CO +H2 ( >1000 C)⁰

12. • Temperature of hearth zone is about 1500 – 1550 C.⁰
• The reactions occuring in this zone are electrochemical in nature :
1. [Mn ] = (Mn2+
) + 2 e-
[ anodic reaction ]
2.( Fe 2+
) + 2e-
= [ Fe] [cathodic reaction ]
Hence,
[Mn ] +( FeO ) = ( MnO) + [Fe ]
[Mn] +( Fe 2+
) = ( Mn2+
) + [ Fe ] .

13. Metal (pig iron).
Slag
Gas
The quality of slag and
metal produced depends
mainly on the burden
chemistry and temperature
at which furnace is
operated.
• Pig iron composition:
o carbon = 3.5 – 4.2 %
oSilicon = 0.5 - 2.5%
oManganese = 0.5 – 1.5 %
oPhosphorous = 0.04 – 2.0 %
oSulphur = 0.04 – 0.15 % ..

14. Cast House - BSP