The portion of the blast furnace below its widest cross-section is called:
🔬 Understanding the Anatomy of a Blast Furnace
A blast furnace is a massive, vertically oriented furnace used for smelting iron ore. It is not a uniform cylinder but has a specific shape with several distinct zones, each with a unique name and function. The widest point of the furnace is known as the belly.
The question asks to identify the section located below this widest point (the belly). Understanding the layout from top to bottom is key to answering correctly.
⚖️ Detailed Analysis of Blast Furnace Zones (Top to Bottom)
Let's examine the different parts of the furnace in the order that the raw materials travel.
(d) Throat
Location: The very top of the furnace.
Function: This is the opening where the raw materials (iron ore, coke, and limestone) are charged into the furnace.
(b) Stack
Location: The long, upper, conical section of the furnace, extending from the throat down to the belly.
Function: As the raw materials descend through the stack, they are preheated by the rising hot gases from the combustion zone below. Initial chemical reduction of the iron ore also begins here.
(c) Bosh
Location: An inverted conical section located directly below the widest part (the belly) and above the hearth.
Function: This is the hottest part of the furnace. Hot air ("blast") is injected through nozzles called tuyeres in this zone, leading to intense combustion of the coke. The final melting of the iron and slag occurs here.
Conclusion: This is the correct answer as it is the section located below the widest cross-section.
(a) Hearth
Location: The cylindrical base or crucible at the very bottom of the furnace.
Function: This is the collection zone. The molten pig iron and the lighter molten slag collect here in two separate layers before being tapped off.
💡 Study Tips for Blast Furnace Anatomy
- Visualize the Shape: Picture the furnace as a tall structure that is narrow at the top (Throat), widens out (Stack), reaches its widest point (Belly), narrows again (Bosh), and then becomes a cylinder at the bottom (Hearth).
- Remember the Order (Top to Bottom): Throat → Stack → Belly → Bosh → Hearth.
- Bosh is Below the Belly: The key landmark is the "belly" (the widest part). The Bosh is the section immediately below it.