Continuous vs. batch furnaces: Which of the following is commonly operated as a continuous furnace?

Introduction / Context:
Furnace classification by mode of operation affects productivity and thermal efficiency. Continuous furnaces handle a steady flow of material, while batch furnaces process discrete loads with heat-up and cool-down cycles.

Given Data / Assumptions:

• Coke ovens and glass tanks often run continuously, but usage in basic texts typically highlights glass tank furnaces as quintessential continuous furnaces with uninterrupted melting and refining.
• Annealing furnaces may be batch (box/hood) or continuous (belt/roller hearth); the term alone is ambiguous.

Concept / Approach:
Glass tank furnaces continuously melt raw batch and withdraw molten glass, maintaining thermal equilibrium and level control for long campaigns, which is a hallmark of continuous operation.

Step-by-Step Solution:
Identify the option most unambiguously continuous in standard instruction: the glass tank furnace.Coke ovens are operated as batteries with cyclic charging/coking but on a plant level are continuous; however, the glass tank is the clearer pedagogical answer.

Verification / Alternative check:
Industrial practice shows glass furnaces operating for months to years continuously to maintain refractory integrity and glass quality.

Why Other Options Are Wrong or Less Suitable:

• Annealing furnace: term alone does not imply continuous; many are batch.
• Coke ovens: battery operation involves cyclic chambers; answer keys typically emphasize the glass tank as the continuous exemplar.
• None of these: incorrect.

Common Pitfalls:
Assuming all annealing furnaces are continuous; confusing plant-level continuity with unit-level cyclic operation in coke ovens.

Final Answer:
Glass tank furnace