Blast furnace scale — typical overall height What is the approximate overall height of a modern blast furnace used for hot metal (pig iron) production, measured from hearth to top works?

Introduction / Context:
The geometric scale of a blast furnace controls residence time, burden distribution, gas–solid contact, and thermal efficiency. A sense of typical dimensions is helpful for understanding capital costs, throughput, and why burden descent and gas flow patterns matter.

Given Data / Assumptions:

• Question asks for an approximate height, not an exact value.
• Conventional large furnaces are considered, not small pilot or mini blast furnaces.
• Height is measured from the hearth region up to the throat/top.

Concept / Approach:
Traditional and many modern large blast furnaces fall in the 30–35 m range for the working stack and top assembly, though some high-capacity plants may exceed this. Options of 10 m or 20 m are too small for industrial ironmaking; 40 m can occur but is above the “typical” textbook value. Therefore, 30 m is a reasonable approximation.

Step-by-Step Solution:

Verification / Alternative check:
Industry descriptions and plant tours frequently cite heights near 30–35 m, with total structure heights sometimes higher when including top charging equipment.

Why Other Options Are Wrong:

• 10 m and 20 m: far below typical industrial scale.
• 40 m or 50 m: possible in some designs but not the standard “approximate” figure taught in fundamentals courses.

Common Pitfalls:
Confusing furnace shell height with total building height; mixing up blast furnaces with smaller cupolas used in foundries.

Final Answer: