The Foundations of Chemistry

Slag

Heated air ~ 900°C

Molten iron

Reducing

zone Gases riseSolids descend

Hot gases used

to preheat air

Flue gas (CO, CO 2 )

Charge of ore, coke, and limestone

200 °C

700 °C

1200 °C

2000 °C

3Fe 2 O 3 + CO → 2Fe 3 O 4 + CO 2

CaCO 3 → CaO + CO 2

Fe 3 O 4 + CO → 3FeO + CO 2

C + CO 2 → 2CO

FeO + CO → Fe + CO 2

Impure iron melts

Molten slag forms

Silicates and phosphates reduced

2C + O 2 → 2CO

Processing of recycled Al now accounts for more than half of the production of this metal.
Recycling of aluminum drink cans is now so successful that more than two thirds of this
aluminum is used to produce new cans. The typical time elapsed from collection of cans
until new ones made from the same aluminum appear on supermarket shelves is only a
few weeks.

IRON

The most desirable iron ores contain hematite, Fe 2 O 3 , or magnetite, Fe 3 O 4. As the avail-
able supplies of these high-grade ores have dwindled, taconite, which is magnetite in very
hard silica rock, has become an important source of iron. The oxide is reduced in blast
furnaces (Figure 22-8) by carbon monoxide. Coke mixed with limestone (CaCO 3 ) and
crushed ore is admitted at the top of the furnace as the “charge.” A blast of hot air from
the bottom burns the coke to carbon monoxide with the evolution of more heat.

22-7

22-7 Iron 911

In Fe 3 O 4 , the formal oxidation state of

iron is ^83 . Two thirds of the Fe atoms

are in the 3 state and the other one

third are in the 2 state. The formula

is sometimes written as Fe 2 O 3 
FeO.

Figure 22-8 A schematic drawing

of a blast furnace for reduction of

iron ore.