THE USE OF HUMIDITY AND TEMPERATURE PROFILES IN OPTIMIZING THE SIZE OF FLUIDIZED-BED IN A COATING PROCESS

The distribution of the gas humidity and temperature is an important f actor influencing the process of coating particles in a fluidized bed. Reported are profiles based on experimental results for a top spray p articulate coating using a single non-submerged spray nozzle. The prof iles indicate that during the process,pockets of low temperature and h igh humidity are formed deep inside the bed. Associated with these poc kets are regions of high temperature and humidity fluctuations. The pr ofiles also show that the lowest gas temperature is located at the top most part of the bed directly below the nozzle. The region of low temp erature extends inwards giving rise to one of the two general shapes f ormed by the profile. Also, inside the bed, a region with highest gas temperature is formed, with its general shape depending on the shape o f the temperature profile. The areas of the bed below the highest temp erature region have a stable and constant gas temperature and humidity . The shape of the profiles are used to reveal the net circulation pat tern of the particles. Using the profiles, four different zones with d ifferent coating functions were also identified. From the size of the zones, an optimum bed size for the given operating conditions can be d educed. (C) 1998 Elsevier Science S.A. All rights reserved.