In the extraction of iron, hot air is introduced into the blast furnace through?

Analysis of the Question

The question asks for the specific component of a blast furnace used to inject hot air into the furnace during the extraction of iron from its ore (usually haematite, $Fe_2O_3$).

Concept Explanation

In the metallurgy of iron, a blast furnace is used to reduce iron ore into molten iron. The process requires a very high temperature, which is achieved by blowing a "blast" of hot air into the bottom of the furnace. This air reacts with coke (carbon) to produce heat and carbon(II) oxide, which acts as the reducing agent.

The structure of a blast furnace includes specific openings near the base, known as tuyeres (pronounced twee-yairs). These are nozzles through which the preheated air is forced into the furnace at high pressure to ensure efficient combustion of the coke.

Step-by-Step Solution

1. Identify the process: The extraction of iron involves the blast furnace process.
2. Understand the role of air: Hot air is essential for the combustion of coke to provide the heat and the reducing gas ($CO$) required for the reaction.
3. Locate the entry point: The design of a blast furnace features specific ports or nozzles located around the lower part of the furnace stack.
4. Evaluate the options: • Valves are used to control the flow of gases or liquids but are not the specific name for the furnace nozzles. • Open-hearths refer to a different type of furnace used in steelmaking, not the entry point for air in a blast furnace. • Arcs refer to electric arc furnaces, which use electricity rather than a blast of air for heating. • Tuyeres are the specific nozzles through which the hot blast of air enters the furnace.

Conclusion

Based on the design and operation of a blast furnace, the hot air is introduced through the tuyeres.

Exam Tip: When studying metallurgy, always visualize the diagram of the blast furnace. Remember that "tuyeres" are the "nozzles" at the bottom—think of them as the "tuyere-tires" (nozzles) that keep the furnace breathing!