La-Mont Boiler — Circulation Method In a La-Mont water-tube boiler, the circulation of water and steam through the evaporator tubes is primarily:

Introduction / Context:
The La-Mont boiler is a notable high-pressure water-tube unit designed to prevent film boiling and overheating of evaporator tubes through vigorous circulation. Understanding its circulation principle explains its suitability for higher heat fluxes and rapid load changes compared with natural circulation designs.

Given Data / Assumptions:

• Water-tube geometry with a steam–water separator or drum.
• External circulation pump recirculates water through the evaporator tubes.
• Operation at pressures where natural buoyancy may be insufficient for required mass flux.

Concept / Approach:
La-Mont boilers employ a high-capacity recirculation pump to force water through the evaporator circuit at rates several times the steam generation rate. This stabilizes tube wall temperature, avoids local dry-out, and improves heat transfer. The forced flow also enables uniform distribution among parallel tube circuits.

Step-by-Step Solution:
Identify hardware: circulation pump, downcomers, risers, separator.Trace flow: pump drives water through evaporator tubes; mixture returns to separator; steam is separated while water recycles.Conclude: circulation is forced, not natural.

Verification / Alternative check:
La-Mont is categorically listed among forced-circulation boilers alongside Benson (once-through) and Velox types in standard boiler classifications.

Why Other Options Are Wrong:

• Natural circulation: would rely on buoyancy only; La-Mont explicitly uses a pump.

Common Pitfalls:
Confusing La-Mont with drum-type natural circulation boilers because both may include a separator drum; the critical distinction is the circulation pump.

Final Answer:
forced