Application limits of fireclay bricks: in which of the following metallurgical processes are fireclay (acidic) bricks never used due to severe chemical attack?

Introduction / Context:
Refractory selection hinges on slag chemistry. Acidic refractories such as fireclay and silica withstand acidic slags but are rapidly corroded by basic slags rich in CaO, FeO, and alkalis. Choosing the wrong brick chemistry for a furnace campaign can cause catastrophic wear and unplanned outages.

Given Data / Assumptions:

• Fireclay bricks are acidic/neutral in behavior.
• Lead blast furnaces generate aggressive basic slags.
• Coke oven walls commonly employ silica at the hot face; fireclay is used in ancillary zones.

Concept / Approach:
Basic slags dissolve silica and aluminosilicates. Therefore, acidic fireclay bricks are incompatible with basic iron- or lead-smelting slags and must be replaced with basic refractories (e.g., magnesite, dolomite, or carbon-bonded systems) in those zones. While fireclay may appear in some auxiliary structures, it is never used where the basic slag directly impinges, such as the working linings of a lead blast furnace.

Step-by-Step Solution:

Verification / Alternative check:
Metallurgical texts prescribe basic refractories for lead and copper smelting furnaces; coke ovens use silica for walls with fireclay in other components, validating the selection.

Why Other Options Are Wrong:

• Beehive coke oven: fireclay is used in certain parts.
• Coke oven walls: hot face is silica, but fireclay is used elsewhere; “never used” does not apply to the entire plant.
• Zinc roaster: material compatibility varies; statement “never” is too strong.
• Glass tank checkers: fireclay may be used in checkerworks depending on service.

Common Pitfalls:
Assuming brick compatibility without analyzing slag basicity index; confusing hot-face brick with backup/insulating layers.

Final Answer:
Lead blast furnace