Components in a Dense-Phase Fluidized Bed

Bed components in a dense-phase fluidized bed include the gas distributor, cyclone, dipleg, heat exchanger, expanded section, and baffles, as shown in Fig. 9.4. The basic function of each component in a fluidized bed is described in the following. 

The cyclone separates solid particles from the outlet gas. Several cyclones may be combined to form a multistage cyclone system. More than one multistage cyclone system can be placed inside or outside the bed. Other types of gas-solid separators (e.g., filters) are also used for gas-solid separation although the cyclone is most widely adopted in fluidized beds. The dipleg/standpipe returns the particles separated by the cyclone into the dense bed. The outlet of a dipleg may be located in the freeboard or immersed in the dense bed. 

The heat exchanger removes generated heat from or adds required heat to the fluidized bed by a cooling fluid or heating fluid. Heat exchangers can either be immersed in the dense bed or be placed both in the dense bed and in the freeboard, which is the region above the dense bed. Possible erosion and corrosion of heat exchangers require special attention. 

The expanded section reduces the linear gas velocity in the freeboard so that settling of the particles carried by the fluidizing gas can be efficiently achieved. The expanded section 

Dense-phase fluidization can also be conducted in the presence of force fields other than a gravitational field. Such force fields include vibrational, acoustic, centrifugal, and magnetic fields. Operations with applications of these fields are known, respectively, as vibrofluidized beds [Mori et al., 1992], acoustic fluidized beds [Montz et al., 1988 Chirone et al., 1992], 

---