DEVELOPMENT OF SANDWICHED FLUIDIZED BEDS

Multistage fluidized beds suffer from possible clogging problems of the intermediate gas distributors. This may be avoided by superposing Geldart's class A and B fluidized layers (sandwiched fluidized beds); the A layer acting as a gas redistributor. This is only possible if the mixing between A and B layers is very low. The non-mixing of multisolid gas-fluidized systems (segregation) is known to be strongly dependent on the gas velocity and also on the characteristics of the particles (density, size, ) and may be assessed by empirical correlations, like the one proposed by Rowe and Nienow (1976). In the present work, it is shown that the representation of iso-mixing curves on a dimensionless chart “size ratio versus density ratio”, leads to straightforward design of “sandwiched fluidized beds”. The sensitivity of the iso-mixing curves to the system parameters has been investigated numerically. A two dimensional bed has been used successfully to check experimentally the validity of the present approach f...