Reduction in the blast furnace

Coke makes the gas that takes the oxygen

1. Iron ores and extraction of iron

2. Who takes the oxygen?

Roasted iron ore is iron oxide. To get iron, the oxygen must be removed. The blast furnace is fed with coke, a form of carbon.

Pick the right answer

Predict: in the book's equations, what takes the oxygen from

Fe2O3 Fe X_{2} O X_{3}

A. Solid coke, directly
B. Carbon dioxide, $CO2 CO X_{2}$
C. Carbon monoxide, CO, made from the coke
D. Oxygen from the air

Explanation

Carbon monoxide, CO, made from the coke, takes the oxygen:

3CO + Fe2O3 \to 2Fe + 3CO2 3 CO + Fe X_{2} O X_{3} 2 Fe + 3 CO X_{2}

above 700 °C. In

CO2 CO X_{2}

carbon already holds two oxygen atoms, and oxygen from the air would add oxygen instead of removing it.

3. Reduction of iron ores

Ore dressing → Reduction of iron ores
Reduction of iron ores → Iron production

Extraction of iron from its ores: three stages (book p.17-18)

Reduction of iron ores

The reduction of iron oxides to iron, by one of two methods depending on the reducing agent.

Method (a): carbon monoxide from coke, in the blast furnace. Method (b), the Midrex furnace, comes next.

4. Coke makes carbon monoxide

Coke

A solid fuel made from coal. It is mostly carbon.

C(s) + O2(g) \to[Δ] CO2(g) C (s) + O X_{2} (g) Δ CO X_{2} (g)

CO2(g) + C(s) \to[Δ] 2CO(g) CO X_{2} (g) + C (s) Δ 2 CO (g)

Coke burns to

CO2 CO X_{2}

. The

CO2 CO X_{2}

meets more hot coke and becomes CO.

5. CO reduces the ore

3CO(g) + Fe2O3(s) →[higher than 700\,^C] 2Fe(s) + 3CO2(g)

Substance	Oxygen	So it is
CO	gains O → CO₂	oxidized: the reducing agent
Fe₂O₃	loses O → Fe	reduced

The book's condition: higher than 700 °C.

6. Why 3 CO?

Each CO takes one oxygen atom. Add CO molecules to one

Fe2O3 Fe X_{2} O X_{3}

CO molecules 0

O removed 0

O still on the iron 3

Balance the equation

Now balance it yourself.

CO(g) + Fe2O3(s) \to Fe(s) + CO2(g) □ CO (g) + □ Fe X_{2} O X_{3} (s) □ Fe (s) + □ CO X_{2} (g)

Balanced equation

3CO(g) + Fe2O3(s) \to 2Fe(s) + 3CO2(g) 3 CO (g) + Fe X_{2} O X_{3} (s) 2 Fe (s) + 3 CO X_{2} (g)

Explanation

3 C, 2 Fe and 6 O on each side.

7. Coke or CO?

Coke, C → CO₂ (burns in O₂)
CO₂ → CO (+ more hot coke)
CO → Fe₂O₃ → 2Fe (takes the O)

Coke is the source; CO takes the oxygen

Contrast:

CO2 CO X_{2}

is not a reducing agent here. Its carbon has already gained all the oxygen it takes in these reactions.

8. Check yourself

Pick the right answer

Exam question: "Explain the role of coke in the blast furnace." Which answer gets full marks?

A. It reduces $Fe2O3 Fe X_{2} O X_{3}$ directly to iron.
B. It burns to $CO2 CO X_{2}$ , which reduces the ore.
C. It burns to $CO2 CO X_{2}$ ; with more coke this gives CO, which reduces the ore.
D. It removes sulphur and phosphorus from the ore.

Explanation

Coke burns to

CO2 CO X_{2}

, and

CO2 CO X_{2}

reacts with more coke to give CO, which reduces the ore:

3CO + Fe2O3 \to 2Fe + 3CO2 3 CO + Fe X_{2} O X_{3} 2 Fe + 3 CO X_{2}

. So coke is the source of CO, the reducing agent.

Fill in the blanks

New case:

CuO + CO \to[Δ] Cu + CO2 CuO + CO Δ Cu + CO X_{2}

. The reducing agent is _____ and the substance reduced is _____.

Explanation

CO gains oxygen (reducing agent); CuO loses oxygen (reduced).

9. Summary

$C + O2 \to CO2 C + O X_{2} CO X_{2}$ , then $CO2 + C \to 2CO CO X_{2} + C 2 CO$ .
$3CO + Fe2O3 \to 2Fe + 3CO2 3 CO + Fe X_{2} O X_{3} 2 Fe + 3 CO X_{2}$ , higher than 700 °C.
CO is the reducing agent; coke is its source.

Back to the hook: can you explain why CO, not

CO2 CO X_{2}

, reduces the ore?

Reveal

CO2 CO X_{2}

, carbon already holds two oxygen atoms, so it cannot take one more. CO can still gain an oxygen atom:

3CO + Fe2O3 \to 2Fe + 3CO2 3 CO + Fe X_{2} O X_{3} 2 Fe + 3 CO X_{2}

Concepts in this lesson