Identify the example of a shaft furnace from the following industrial units commonly discussed in metallurgical operations.

Introduction / Context:
Shaft furnaces are vertical reactors in which burden descends by gravity while gases flow counter-currently. Recognizing equipment types by flow pattern and geometry is key in process selection and design.

Given Data / Assumptions:

• Focus on typical heavy-industry units: LD converter, glass tank, blast furnace, soaking pit.
• Definition: shaft furnace has tall shaft, descending solids, ascending gas.

Concept / Approach:
The blast furnace is the archetype of a shaft furnace: iron ore, coke, and fluxes descend; hot blast gas ascends, enabling counter-current heat and mass transfer. Other listed units have different geometries and flow patterns (e.g., LD converter is a basic oxygen steelmaking vessel with top/bottom blown oxygen; glass tank is a pool-type melter; soaking pit reheats ingots in a pit/box configuration).

Step-by-Step Solution:
1) Recall shaft furnace features: vertical, packed burden, counter-flow.2) Map each option: blast furnace matches; others do not.3) Select ‘‘blast furnace’’.

Verification / Alternative check:
Textbook classifications consistently cite the blast furnace as a classic counter-current shaft furnace.

Why Other Options Are Wrong:
L.D. converter: Basic oxygen converter; not a shaft reactor.glass melting tank: Pool melting; horizontal bath and flame, not shaft.soaking pit: Box-type reheating; no counter-current gas–solid contact.

Common Pitfalls:
Confusing tall geometry of some vessels with true shaft-furnace operation.

Final Answer:
blast furnace