What is a common material for the bed in a fluidized bed boiler?

In a fluidized bed boiler, the most common material used for the bed is typically sand. Sand is ideal for this application because it has the right particle size and density to allow efficient fluidization when air or gas is passed through the bed. This creates a suspended state where the solid particles behave like a fluid, allowing for effective heat transfer and combustion of fuels.

Using crushed rocks, while theoretically possible, is less efficient because the larger and irregular shapes may not fluidize as uniformly as sand does. Steel can withstand high temperatures, but it is generally used in structural components rather than as a bed material because it lacks the necessary properties for effective fluidization. Brick can be used in some applications but is more common for construction and support rather than as the fluidized bed material due to its weight and lack of fluidization properties.

Therefore, sand is the preferred choice for achieving the optimal functioning of a fluidized bed boiler due to its ability to easily fluidize and provide excellent thermal properties.