Question

Metallurgical coke acts mainly as

• A. Oxidizing agent
• B. Catalyst
• C. Reducing agent
• D. Flux

Hint:

The coke rate in modern blast furnaces is a key performance metric. Minimizing it through the injection of auxiliary fuels through the tuyeres reduces both steel production costs and carbon dioxide emissions.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the primary chemical role played by metallurgical coke in the extraction of iron within a blast furnace.

Step 2: Key Formula or Approach:
Inside the blast furnace, hematite (\( \text{Fe}_2\text{O}_3 \)) must be reduced to metallic iron.
Coke reacts with oxygen to generate carbon monoxide gas:
\[ 2\text{C} + \text{O}_2 \rightarrow 2\text{CO} \]
This carbon monoxide then acts as the primary gaseous reducing agent to reduce iron oxides:
\[ \text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2 \]

Step 3: Detailed Explanation:

• Three Roles of Coke: Metallurgical coke plays three vital roles in the blast furnace:
1.

Chemical Role (Reducing Agent): It reacts to produce CO, which serves as the reducing agent. Carbon from coke also directly reduces silicon, manganese, and phosphorus in the hearth.
2.

Thermal Role (Fuel): The combustion of coke at the tuyere level provides the high temperatures required for endothermic reactions and melting of iron and slag.
3.

Physical Role (Permeable Support): Coke is the only material that remains solid and strong in the high-temperature cohesive zone of the blast furnace. It provides a highly permeable grid that supports the raw materials while allowing gases to rise and liquid iron/slag to drain.

• Analysis of Other Options:
- Coke is not an oxidizing agent (Option A); its purpose is to remove oxygen, not supply it.
- It is a reactant consumed in large quantities, not a catalyst (Option B).
- Fluxes (Option D, like limestone) are added to remove ash and form slag, which is a different chemical function.


Step 4: Final Answer:
Hence, metallurgical coke acts mainly as a reducing agent, corresponding to Option (C).