Unwanted Aggregation in Fluidized Beds

Using the dilatometer technique, a small sample of powder (about 1 -2 grams) is heated at constant rate in the apparatus depicted schematically in Fig. 43. Dilatation of the sample is measured by a linear voltage transducer (LVDT) contraction of the sample indicates particle-particle surface flattening and defines the minimum softening point ox sintering temperature, Ts. In 

It was also shown both theoretically and experimentally (Tardos et al., 1985a,b) that there is a strong correlation between the excess temperature above the minimum sintering point, T-Ts, and the excess gas velocity above minimum fluidization conditions (measured below the sintering point) U-lJm required to maintain fluidization. A general correlation was developed between the excess temperature and the excess gas velocity, which takes the form 

There is a significant difference in the form of Eq. (46) for amorphous and crystalline materials (Compo et al., 1987 and 1990) for the first group, a slight increase in temperature above minimum sintering results in a significant increase in excess gas velocity as can be seen in both, the value of the 

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