ABSTRACT
If a gas passes upward through a bed of particles, the bed is fixed at low gas velocities, but when the velocity is increased further, the particles separate from each other and are supported by the gas, then the bed starts fluidizing. In the fluidized bed, the particles contact with the gas at high efficiency, and temperature is kept uniform because of good mixing of the particles. The features have been utilized for industrial applications1; the first use of the fluidized bed as a large-scale reactor was Winkler’s coal gasifier in 1926. Since the 1940s the fluidized bed had played an important role for fluid catalytic cracking using a combination of a reactor and a catalyst regenerator. Recently a circulating fluidized bed, as shown in Figure 20.1, has been widely used as a boiler for solid fuel and waste.
