Natural draft furnaces — identification Which of the following is operated as a natural-draft furnace under typical service?

Introduction / Context:
Draft supplies combustion air and removes flue gases. Furnaces may use natural draft (chimney effect) or mechanical draft (forced/induced fans). Recognizing which units traditionally rely on natural draft is a common fundamentals question.

Given Data / Assumptions:

• Standard industrial practice without special retrofits.
• Power boilers typically employ fans to control excess air and emissions.
• Blast furnace stoves are tall regenerative heaters connected to stacks providing natural draft.

Concept / Approach:
Natural draft depends on hot flue gas density differences in a tall stack. Hot-blast stoves have substantial stack height and operate cyclically (heat/checker and blast phases) with natural draft sufficient for combustion air/flue evacuation. Modern power plant boilers predominantly use forced and induced draft fans for precise control and environmental compliance.

Step-by-Step Solution:
Identify units with tall stacks and historical reliance on chimney effect: blast furnace stoves.Eliminate power boilers: mechanical draft is standard for control and efficiency.Sintering furnaces often use fans for process control; not typical natural-draft exemplars.

Verification / Alternative check:
Plant layouts show hot-blast stoves adjacent to blast furnaces with integral stacks providing natural draft during the heating cycle.

Why Other Options Are Wrong:

• Power plant boilers: induced/forced draft fans are standard.
• Sintering furnace: generally employs controlled airflow with fans.

Common Pitfalls:

• Assuming all tall-stack units are natural draft; many modern systems still use fans for precise control.

Final Answer:
Blast furnace stoves (hot-blast stoves)