Blast Furnace Burden — Typical Proportions by Weight The charge (burden) fed to a blast furnace typically consists of calcined iron ore, coke, and limestone in approximately which ratio by weight?

Introduction / Context:
The blast furnace burden must supply iron units, fuel, and flux in balanced proportions to achieve efficient smelting. Typical textbook ratios provide a baseline for understanding material balances, although modern plants optimize these values based on ore quality, sinter/basicity, and pulverized coal injection (PCI).

Given Data / Assumptions:

• Classical burden comprising calcined ore (or sinter/pellets), coke as fuel and permeable support, and limestone as flux.
• Approximate, illustrative ratio used for teaching purposes.

Concept / Approach:
Ore provides Fe2O3/Fe3O4; coke supplies carbon for reduction and heat; limestone (CaCO3) decomposes to CaO for slag formation, capturing silica and other impurities. A common illustrative mix is roughly 8:4:1 (ore:coke:limestone) by weight, reflecting the dominant mass share of iron units, the substantial but lesser fuel requirement, and a smaller flux portion sufficient to achieve target basicity of the slag.

Step-by-Step Solution:
Identify roles: ore → iron, coke → fuel/reductant/structure, limestone → flux.Recall the didactic ratio: 8 (ore) : 4 (coke) : 1 (limestone).Select the option matching this ratio exactly.Hence, choose option with “8, 4, 1.”

Verification / Alternative check:
Metallurgy texts often present this 8:4:1 ratio to introduce burden composition before detailing real-plant adjustments (sinter/pellet chemistry, PCI rates, flux additions).

Why Other Options Are Wrong:

• Swapped or exaggerated proportions do not reflect iron unit dominance or realistic flux levels.
• Equal parts ignore practical mass balances for reduction and slag formation.

Common Pitfalls:
Assuming fixed ratios across all plants; in practice, burden composition is optimized continuously based on feed chemistry and operational goals.

Final Answer:
calcined ore (8 parts), coke (4 parts), limestone (1 part)