Bevel-helical speed reducer B4 sideType H Hollow shaft with keyway Type K Hollow B4HH-20-C

Flender/Flender Gear Units/Bevel-helical speed reducer B4

tions for easily uidizable materials.In the latter type, the particles are vigorously mixed in the bed, maintaining uniform tem- perature, and the inlet particles are dried up quickly under dispersed conditions. The ratio of bed length to its width for well-mixedtype uidized bed dryer is equal to or lessthan 1, and this is generally suitable for those particles that are difcult to uidize (. Because of broader distribution of residence time, drying results are seldom uniform, com- pared with plug-ow type. plug-ow uidized bed dryer is more commonly used for grain drying than is the well-mixed type. 4.3.6 Spouted Bed DryingThe spouted bed dryer is particular design of uidized bed dryer. Coarse solids too large to uidize can be handled in spouted bed. Its applicability has been well recognized for granular materials with diameters that are generally above 5 mm (.., grains). In this type of dryer, high-velocity air is allowed to enter through centrally located nozzle ina conical-base, vertical chamber (Fig. . The zone of fast-moving particles at the centercreates spout, and the grains (or granular materials) move downward at slower rate surrounding the central spout. Thus, the downward-moving grains generally receive thecountercurrent-moving air at the annular zone. The initial drying takes place at higher rate in the central spout, but the later drying in the annular bed is relatively mild. Fig. 7 Schematic of uidized bed grain-drying system. 1 Das and Chakraverty Fig. 8 Schematic of spouted bed. An empirical correlation between the minimum supercial uid velocity Vs(/) through the bed necessary for spouting in 3- to 1-in.diameter column can be obtained as follows (: Vs/H1/H2dp dc/H2/H2do dc/H2.3/H2gl(/H1a) /H2/2 ( where dpis the particle diameter (); dcis the column (bed) diameter (); d0is the uid inlet nozzle diameter (); lis the bed height (); sis the density of solid (kg/m; and ais the density of uid (kg/m. The classic spouted bed dryer as de