Atmospheric fluidized-bed combustion balance-of-plant reference manual

Atmospheric fluidized-bed combustion (AFBC) power plants have achieved commercial acceptance in outputs up to 250 MWe and continue to be developed at larger sizes. The AFBC process differs from conventional pulverized coal power plants in three main ways: Sulfur capture is achieved as part of the combustion process by feeding calcium-based sorbents directly to the furnace. Combustion is maintained at temperatures well below those at which thermal NO[sub x] is generated. AFBC boilers are inherently low-NO[sub x] burners. The large thermal mass of fluidized bed material in the boiler allows firing of high-ash and high-moisture fuels for which there is no good combustion alternative. AFBC boilers differ from conventional PC boiler plants in several significant ways including expanded material handling systems, additional combustion air handling equipment and more rugged materials of construction to survive the aggressive high-velocity, high-solids loadings conditions inside the boiler. This reference manual describes the ways that AFBC boilers differ from conventional PC boilers. The objective is to provide utility engineers with information and guidelines with which they can prepare specifications and evaluate proposals, and to allow them to anticipate AFBC maintenance activities.