Experimental Methods for Measurement of Umf
Méthod 1: Measure of total pressure drop through the bed
The method consists of measuring the evolution of the bed pressure drop between the bottom and top of the column as a function of superficial gas velocity.
Figure 3 –Behaviour of curve Dp versus U0to a bed with medium particles and uniform size (Kunii and Levenspiel, 1991)
Method 2: Measure of average differential pressure between two levels of the bed. The minimum fluidization velocity can also be determined with the aid of measure of differential pressure between two pressure tappings located within the bed, distant from L as a function of the superficial gas velocity at the decreasing velocity (Tannous et al. 1994). The relationship can be represented by:
(Glass beads, dp=1500mm, Dc=0,192m, Ms=13kg, Ho=0,30m)
Method 3: Adimensional standard deviation of pressure drop fluctuations. It can be seen by evolution of standard deviation, which, for fixed beds, this magnitude is zero. This increases, then with the superficial gas velocity for fluidized beds (Tannous et al. 1994). The Umf can be defined as the velocity corresponding to intersection of the growing linear part of curve with the axes of the velocity. (Tannous et al., 1994).
(Glass Beads, dp=1500mm, Dc=0,192m, Ms=13kg, Ho=0,30m)
Evolution of the dimensional standard deviation of total pressure drop fluctuations.