High temperature effects on the dense phase properties of gas fluidized beds

This paper reports some of the results obtained from an extensive experimen tal campaign aimed to study the influence of temperature on the fluidizatio n behaviour of solid materials. The fluidization behaviour of a wide range of materials was investigated from ambient conditions up to 650 degreesC. T he aim of this work was to highlight the conditions under which the role of the hydrodynamic forces (HDFs) or interparticle forces (IPFs) were dominan t, in order to make predictable the fluidization behaviour at elevated temp eratures. To this end, the fluidization behaviour of three fresh FCC cataly sts was studied. An E-cat FCC catalyst, which contained process residuals, was examined without performing pre-treatments prior to fluidization tests. Furthermore, a highly porous silica catalyst was doped with increasing amo unt of potassium acetate (KOAc), 1.7, 7 and 10 wt.%. and a sample of glass ballotini was doped with 0.1 wt.% of KOAc. This was done in the attempt of modifying their surface characteristics. thus triggering changes in their f luidization behaviour with increasing temperature. The measured pressure dr op across the bed and deaeration tests was used to highlight changes in the fluidization behaviour as a function of temperature. The standardized coll apse time (SCT) was obtained from the collapse profiles and was used to dis tinguish between systems of powders dominated by HDFs and IPFs. Results obt ained from analytical techniques such as thermomechanical analysis (TMA), G as Chromatography Mass Spectrometry analysis (GCMS) and scanning electron m icroscope (SEM) are also discussed. these techniques were used to investiga te physical changes in the particles with increasing temperature. (C) 2001 Elsevier Science B.V. All rights reserved.