Which type of boiler uses a circulating fluid bed for combustion?

The correct choice is the fluidized bed boiler, which is specifically designed to enhance the combustion process through the use of a circulating fluid bed. In this type of boiler, solid fuel particles are suspended and evenly distributed in a stream of air, which allows for more efficient burning. The fluidized bed facilitates better heat transfer and complete combustion of fuel, reducing emissions and improving efficiency.

This design is particularly advantageous for burning various types of fuels, including low-grade or high-sulfur fuels, which can be challenging for conventional boilers. By maintaining a uniform temperature and facilitating rapid mixing of fuel and air, fluidized bed boilers achieve higher combustion efficiencies and lower pollutant emissions compared to other boiler types.

In contrast, fire-tube and water-tube boilers operate on different principles, primarily relying on the flow of hot gases and water to transfer heat. Electric boilers use electricity to generate heat directly and do not incorporate combustion processes involving a fluid bed.