Minimum fluidization velocity determination in dielectrical material fluidized beds by electrostatic charge transfer measurement

One of the main parameters of material powder characterisation is the minimal fluidization velocity. This gas velocity defines the threshold between the fixed state and fluidized one. When this threshold is reached, the particle vibrations appear with layer expansion. For this gas velocity (U_g), the particles are totally in suspension and the bed behaves as a fluid. Several experimental methods are used to determine this velocity, the most classic is the method recommended by Richardson (1971). This paper presents a new method named electrofluidodynamics. This method is based in the electrical current generated on two electrodes, produced by collisions and frictions between themselves and electrodes. The electrical current variation is linked to the agitation degree of the material, which depends of the gas velocity. The current generated is measured at each stage of defluidization. The current variation observation allows us thus to determine the threshold value. The results obtained are compared with the Richardson classic method