Prediction of minimum fluidization velocity of gas–solid fluidized beds by pressure fluctuation measurements — Analysis of the standard deviation methodology

We analyze here an experimental method for the evaluation of Umf in gas fluidized beds, based on pressure fluctuation measurements in which Umf is determined by the relationship between the standard deviation of pressure measurements and fluid velocity [M. Puncochar, J. Drahos, J. Cermak, K. Selucky, Evaluation of minimum fluidizing velocity in gas fluidized bed from pressure fluctuations, Chem. Eng. Commun. 35 (1985) 81–87]. This was tested in four different particles: Sand, Microcrystalline Cellulose, FCC and Alumina using two circular plexiglass columns with internal diameters of 0.11 m and 0.14 m as the experimental apparatus. Validation of the method was made by comparing our Umf results with those obtained by the fluid-dynamic curve. The experimental data revealed that: (1) the valid range of fluid velocity in the method employed by us is broader than those observed by other authors; (2) the method is suitable for both Geldart A and B solids. Influence of probe location and type of pressure measurement (either absolute or differential) were also analyzed and discussed.