Fluidization and elutriation of iron oxide particles.: A study of attrition and agglomeration processes in fluidized beds

Elutriation is a way of separating particles by means of fluidodynamic forces as well as a very common method to generate solid aerosols to be used for many different purposes. In this work, a study of the elutriation of different size iron oxide particles from a fluidized bed has been carried out in order to determine the elutriation rate constants and the magnitude of the attrition and agglomeration processes in a fluidized bed of this sort of powder, which can be considered as C-type in Geldart's particle classification. The fluidized bed was formed by a mixture of sand and iron oxide particles. Sand particles were much bigger than iron oxide particles and the weight of the latter particles, which were elutriated was very small compared with the initial weight in the bed so that the weight of the bed could be considered as a constant. Theory about elutriation and its application to study the iron oxide behaviour and to determine the elutriation rate constants are presented. Experimental results showed the importance of attrition and agglomeration in iron oxide powders. The smallest iron oxide particles were not those most easily elutriated from fluidized beds of mixed size particles. These particles may be agglomerated between them or with larger sand particles. Elutriation results were compared with previous literature and it was found that a correlation similar in form to Yagi and Aochi's correlation fits the experimental results quite well. (C) 2000 Elsevier Science S.A. All rights reserved.