RESIDENCE TIME DISTRIBUTION IN A SERIES OF THREE TANKS WITH BYPASS AND BACK-MIXING. APPLICATION TO MULTISTAGE FLUIDIZED-BED

Abstract

The theoretical and experimental study of the solid RTD in a perforated-plate 3-stage fluidized-bed (i.e. with distributors holes larger than particles diameter) is presented. Two models are proposed: a 1-parameter model, which is the classical cascade-of-reactors model; and a 2-parameter model, established considering the column as a succession of identical contactors, with solid bypass and back flow. First a parametric theoretical study is done. Then, the parameters values are estimated in both models fitting the RTD experimental curve. Both models give very satisfying results, although the 2-parameter one appears to be slightly better in the first part of the RTD curve

It is found from the theoretical study that the 2-parameter (back-mixing and bypass ratios) model can be applied to a lot of systems, as long as the experimental RTD curve does not oscillate and the curve remains lower than 1.

KEYWORDS:

• Multistage
• Residence time distribution
• Mixing
• Fluidized bed