Experimental observations of fluidized beds at high temperatures
Paola Lettieri1, David Newton1, John G.Yates2
1 BP Chemicals Ltd., Poplar House, Chertsey Road, Sunbury on Thames, Middlesex, TW16 7LL,
2Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK
The objective of this paper is to report some experimental observations on the effect of temperature on the fluidization of three fresh FCC catalysts and an equilibrium (E-cat) FCC. The bed collapse test was used as a quantitative test to characterise the fluidization quality of these materials with increasing temperatures. It provides a sensitive and discriminating means of assessing the changes in the materialsí responses between low and high temperature fluidization. The standardised collapse time, SCT, was calculated from the collapse profiles and the experimental values obtained for the FCC catalysts are reported in this paper. The fluidization quality of the fresh FCC catalysts improved with increasing temperature, as indicated by the increase in SCT values. On the other hand, the standardised collapse time of the E-cat FCC decreased with increasing temperature as the catalyst became less aeratable. Changes of the surface properties of this material occurred on increasing temperature. The flow behaviour of the E-cat catalyst was compared with fluidization of a Group C material. The aeratability of this latter material decreased exponentially, due to the dominant role of the interparticle forces over the hydrodynamic forces, with increasing temperature. The use of classical concepts such as the non bubbling ratio, umb/umf, to describe fluidization at low and high temperatures is discussed. Experimental umb/umf values obtained for the fresh FCC catalysts are compared with predictions.