The Blast Furnace
A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron. It is a large, vertical furnace that is used to extract iron from its ore. The furnace operates by continuously feeding a charge of iron ore, coke (a fuel derived from coal), and limestone (a fluxing agent) into the top of the furnace. The materials descend through the furnace, and the iron is extracted at the bottom, while the waste gases and byproducts are released through the top.

The Parts of a Blast Furnace
A blast furnace is made up of several distinct sections, each with its own purpose and function. These sections include the hearth, stack, bosh, and throat, among others. Each section plays a critical role in the overall operation of the furnace.

The Hearth
The hearth is the bottom part of the blast furnace where the molten iron and slag are collected. It is the widest cross-section of the furnace and is typically lined with refractory materials to withstand the high temperatures and corrosive environment. The hearth provides a space for the molten iron to accumulate and be tapped off periodically.

The Stack
The stack refers to the vertical portion of the blast furnace above the widest cross-section, extending up to the top. It is responsible for providing the necessary height for the furnace and allows for the proper flow of gases and materials. The stack is typically made of steel and is lined with refractory materials to protect it from the harsh conditions inside the furnace.

The Bosh
The bosh is the portion of the blast furnace below its widest cross-section, located between the hearth and the stack. It has a tapered shape, narrowing as it ascends towards the stack. The bosh is where the iron ore, coke, and limestone mixture begins to melt and react, forming liquid slag and molten iron. It is a critical section for the smelting process, as it allows for the proper distribution and mixing of the materials.

The Throat
The throat is the narrowest section of the blast furnace, located at the top of the bosh. It acts as a transition between the bosh and the stack, allowing the gases and materials to flow smoothly from one section to another. The throat also helps maintain the appropriate pressure inside the furnace, ensuring efficient operation.

Conclusion
In summary, the portion of the blast furnace below its widest cross-section is called the bosh. It is a critical section where the iron ore, coke, and limestone mixture begins to melt and react, forming liquid slag and molten iron. The bosh allows for the proper distribution and mixing of the materials, facilitating the smelting process in the blast furnace.