Spouted operating characteristics

The liquid holdup characteristics of a countercurrent, three-phase spouted-bed column are studied by Vukovic et al.141 They found that the total liquid holdup increased with the gas flow rate. Both the total and dynamic liquid holdups were comparable to those obtained in cocurrent-upflow three-phase fluidized-bed columns operating with similar gas and liquid flow conditions. 

Scale-up data of conventional SBDs are well known, but the relations cannot be applied to MSB dryers with inert packing due to different hydro-dynamical and drying characteristics. Therefore, the drying mechanism itself, effects of various process and operational parameters, and the relevant relationship had to be investigated in more detail. Important dimensions as well as geometric, physical, and hydro-dynamical characteristics of equipment and of the particles forming the spouted bed are summarized in Table 15.3 [18-20]. 

The principle of operation, basic design, and process characteristics for most common types of dryers with inert carriers are well described in easily accessible literature. These are the vibrated fluid bed dryer and the fluid bed dryer in its conventional and two-chamber configurations (Kudra and Mujumdar, 1995 Erdesz and Ormos, 1986), spouted bed dryer (Re and Freire, 1989), jet-spouted bed dryer (Markowski, 1992), pneumatic dryer (Blasco et al., 1996), rotary dryer (Limaverde et al., 2000), impinging stream dryer (Kudra and Mujumdar, 1989), dryer with a vertical inner conveyor screw (Pallai et al., 1995), etc. Therefore, here we present less common configurations that are interesting from research and applications points of view. 

Some typical fluid bed granulation equipment and a few of their main characteristics are given in Fig. 1. The conventional fluid bed granulator (Fig. la) can be operated in either top (as shown) or bottom spray mode. The bed is usually tapered, as shown, to improve solid circulation. The spouted bed granulator (Fig. lb) is somewhat different in that it has no distributor and that there is a calibrated gap between the nozzle and the bottom of the spout that allows discharge of granulated material. It is common industrial practice to combine the two fluid beds presented so far... 

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