Charging an iron blast furnace: which device is commonly used to charge raw materials (burden) at the top?

Introduction / Context:
Blast furnaces are charged with alternating layers of coke, sinter/pellets, and fluxes. The charging system must deliver heavy burdens to the furnace top reliably while coordinating with the bell/valve (or bell-less) distribution mechanism to control burden profile.

Given Data / Assumptions:

• Large, continuous steelmaking blast furnace.
• Burden consists of coarse, heavy solids.
• Traditional charging systems considered.

Concept / Approach:
Skip hoists (skip cars on inclined tracks) historically transport burdens to the furnace top where they are tipped into the receiving hopper. While modern furnaces often use conveyor/bell-less top systems, the classic and widely referenced method is the skip hoist. Bucket elevators and screw conveyors are less suited to the very coarse, heavy, and abrasive burden at the required tonnages and heights.

Step-by-Step Solution:
Identify traditional device for hefty, coarse burden → skip hoist.Exclude bucket elevator/screw conveyor due to wear and capacity considerations.

Verification / Alternative check:
Historical blast furnace layouts depict dual skip hoists feeding a double-bell charging system.

Why Other Options Are Wrong:
Bucket elevator: susceptible to rapid wear with huge lumps and tonnages.Screw conveyor: impractical for very coarse, high-throughput charging up steep inclines.

Common Pitfalls:
Confusing modern belt/bell-less tops with historical exam standards; skip hoist remains the canonical answer.

Final Answer:
Skip hoist