Analysis of wall fouling and electrostatic charging in gas-solid fluidized beds

Abstract

This research study focuses on wall fouling and electrostatic charging in gas–solid fluidized beds. Experiments were conducted with glass bead particles with different mass median diameters in an acrylic column at different humidity levels. The coverage ratio of particles on a wall was measured with two different methods. To obtain the local coverage ratio, the number of particles was counted with digital image processing. To achieve the required average coverage ratio, all the particles which adhered to the wall were weighed. The electrostatic charges of these particles and in the dense phase of the fluidized beds were measured individually with the use of a Faraday cup combined with a vacuum device. The surface potential of the wall was also measured with an electrostatic potential meter. The coverage ratio of the particles was high at low humidity because of the electrostatic attraction that was affected considerably by the surface potential of the wall compared with the surface charge density of the particles. The relationship between the wall fouling and electrostatic charging could be explained based on (a) the charge that the wall provided to the particles according to the triboelectric charging and (b) the number of particles that acquired the charge.