The spout-fluid bed is a very successful modification to the conventional spouted bed. It reduces some limitations of spouting and fluidization by combining features of spouted and fluidized beds. In spout-fluid beds, in addition to supplying spouting fluid through the central nozzle, auxiliary fluid is introduced through a porous or perforated distributor surrounding the central orifice. Compared with spouted beds, spout-fluid beds obtain better gas–solid contact and mixing in the annular dense region and reduce the likelihood of particle agglomeration, dead zones, and sticking to the wall or base of the column. However, the hydrodynamics of spout-fluid beds are more complex than those of conventional spouted beds. This chapter briefly presents up-to-date information on the fundamentals and applications of spout-fluid beds without draft tubes, based on the limited reported work.
Flow regimes and flow regime map
Different flow regimes occur in a spout-fluid bed when the central spouting gas flowrate and the auxiliary gas flowrate are adjusted. A schematic representation of familiar flow regimes is presented in Figure 6.1. These are the fixed bed (FB), internal jet (IJ), spouting with aeration (SA), jet in fluidized bed with bubbling (JFB), jet in fluidized bed with slugging (JFS), and spout-fluidizing (SF) regimes.