n the annual report for 1990 we described the experimental setup developed for characterizing group A powders at room temperature; results were reported on the influence which mean particle size and addition of fines fraction had on bed expansion, Umf, Umb, deaeration rates and times, and bubble sizes. It is generally assumed that if tests are conducted at high temperature, the powder behaviour will be predicted simply by using the appropriate physical properties of the gas, adjusted for temperature, in correlations based on data gathered at room temperature with different gases. However, it is our hypotheses that interparticle forces play a major role in the behaviour of group A powders, particularly these which are at the finer end of the group, and that temperature will alter these forces. Thus, the powder behaviour change at high temperature may not be predicted by hydrodynamics effects alone.
Temperature effects on incipient fluidization velocity Umf and bed voidage at incipient fluidization point and bubble sizes have been extensively studied on group B and group D powders. In this work, temperature effects on some fluidization characteristics of group A powders are reported: these are incipient fluidization velocity mf, and the voidage of loosely settled bed cS, incipient bubbling U velocity Umb, and bed expansion.