Influence of particle size, fluidization velocity and relative humidity on fluidized bed electrostatics

The influence of particle size, d(p), fluidization velocity, U-r, and relative humidity, RH, on the degree of electrification reached by a fluidized bed of glass beads has been studied. The static electrification of the bed was measured by means of the potential difference observed between an electric probe and the metallic distributor. The effect of relative humidity appears to be complex and is connected with the quality of fluidization - bubbling or slugging - existing in the bed. A characteristic curve for electrification vs. humidity has been proposed that consists of five zones. The results show that when the value of the relative humidity is lower than a critical value (RH(c)), the static electrification of the bed cannot be measured accurately because the adhesion of particles to the probe leads to irreproducible voltage values. Also, the degree of electrification increases with particle size and air velocity. The relationship between the average solid circulation velocity and electrification is studied.