Fluidized-bed furnaces operate in quite a different manner from fixed-bed furnaces and have a number of advantages associated with them. Fluidized-bed combustion uses silica sand (lime stone, dolomite, or other noncombustible materials) for bed material, keeps fuel and sand in furnace in boiling state with high-pressure combustion air, and burns through thermal storage and heat transmission effect of sand. It is suitable for high-moisture fuel or low-grade fuel. The typical operating temperatures are lower than fixed-bed systems. Depending on the blowing air velocity, fluidizing-bed systems can be further divided into Bubbling Fluidized-Bed (BFB) and Circulating Fluidized-Bed (CFB).