Modeling charge transfer and induction in gas–solid fluidized beds

A simple mechanistic model is developed by applying the method of images to distinguish induced and transferred charges, assuming circular bubbles with charged particles around their surfaces. The simulation shows that the trace of induced charge vs. time is insensitive to the thickness of the layer of charged particles at the bubble surface with a uniform charge density distribution. However, charge transfer during a collision of particles surrounding the rising bubble with a probe is a strong function of the particle velocity profile. Experiments in which single bubbles were injected into an acrylic two-dimensional column showed that 321 μm glass beads, fluidized by air, were charged positively. The model with uniform charge on the surface of the bubble gives better predictions of the charge and voltage outputs than when opposite charges are assumed at the front and rear of the bubble as in previous work, but significant improvements are needed to eliminate discrepancies between the predictions and experimental measurements.