Exclusive application of carbon refractories: in which of the following furnace zones are carbon blocks used essentially as the standard lining?

Introduction / Context:
Carbon refractories provide unique benefits—low wettability by hot metal and strong resistance to many slags—making them the go-to choice for certain high-duty zones. The question asks for the zone where carbon is essentially the standard lining.

Given Data / Assumptions:

• Focus on where carbon blocks are “exclusive” or standard.
• Consider contact with molten iron and slag.
• Longevity and chemical compatibility are critical.

Concept / Approach:
The blast furnace hearth contains molten iron and slag at very high temperatures. Carbon blocks excel here due to non-wetting behavior and chemical compatibility. By contrast, coke oven walls and regenerators predominantly use silica and fireclay; soaking pits/portions of cement kilns rely on other refractory families, not bulk carbon linings.

Step-by-Step Solution:
Identify the zone with prolonged molten metal contact → BF hearth.Confirm carbon’s advantages (non-wetting, chemical stability) for hearth service.Exclude other listed zones where silica/alumino-silicates are standard.

Verification / Alternative check:
BF lining designs universally specify carbon blocks in the hearth region, with safety/backup layers outside.

Why Other Options Are Wrong:
Coke ovens/regenerators: silica/fireclay dominate.Soaking pits/cement kilns: other refractory types are standard.

Common Pitfalls:
Generalizing carbon use beyond the BF hearth where its benefits are unique.

Final Answer:
Hearth of blast furnace