What is the by-product that is formed by melting Pig iron at 1500°C?
🔬 Understanding the Production of Pig Iron
The question refers to the process of creating pig iron, which is the raw iron produced in a blast furnace. This high-temperature process (around 1500°C) is designed to separate pure iron from the impurities found in iron ore.
The Process: Iron ore (containing iron oxides and impurities like silica and alumina) is heated with a fuel (coke) and a flux (limestone). The intense heat melts the iron, and the limestone combines with the impurities to form a molten, glass-like substance that is lighter than the iron. This substance is the primary by-product.
⚖️ Detailed Analysis of Industrial By-products
It's important to distinguish between the different by-products mentioned, as they originate from very different industrial processes.
(c) Blast furnace slag
Origin: This is the direct by-product of producing pig iron in a blast furnace. The limestone (flux) reacts with the silica and alumina impurities from the iron ore to form a molten slag. Because it is less dense than the molten iron, it floats on top and can be easily separated.
Conclusion: This is the correct answer as it is the specific by-product from the process described.
(a) Surkhi
Origin: Surkhi is not a by-product of an industrial process but a manufactured material. It is made by grinding up burnt clay bricks into a fine powder. It is used as a pozzolanic material in lime mortars and concrete.
Conclusion: Incorrect, as it is derived from bricks, not iron production.
(b) Fly ash
Origin: Fly ash is a by-product of burning pulverized coal in coal-fired electric and steam generating power plants. It is the fine, powdery particulate matter that is carried away in the flue gas.
Conclusion: Incorrect, as it comes from thermal power plants, not blast furnaces.
(d) Silica fume
Origin: Silica fume is an ultra-fine powder collected as a by-product of the production of silicon and ferrosilicon alloys in electric arc furnaces.
Conclusion: Incorrect, as it comes from the silicon industry, not the primary iron-making process.
💡 Study Tips for Industrial By-products
- Blast Furnace makes Blast Furnace Slag: The name of the process is in the name of the by-product. This is the most direct association.
- Fly Ash Flies: Think of fly ash as the fine ash that "flies" up the chimneys of a coal power plant.
- Surkhi is from Soil (Clay): Surkhi comes from burnt clay bricks, which are made from soil.
- Silica Fume is from Silicon: This is another direct association. The production of silicon metal creates silica fume.