Experimental and Numerical Studies of the Fluidization and Electrostatic Characteristics of Non-Spherical Particles in a Pseudo-2D Fluidized Bed

Electrification is a common phenomenon in a gas-solid fluidized bed that involves intensive collisions and interactions between particles with each other and particles with the wall. There have been extensive studies of the mechanism of triboelectrification in particle systems using experimental and numerical methods. However, these studies focus mostly on spherical particles and investigations into non-spherical particle are scarce. It is challenging to quantify directly the electrostatic characteristics of non-spherical particles in a fluidized bed because of the high number and complex behaviors of particles in the bed. In addition, the charge transferred between the particles is difficult to measure accurately. In this study, by conducting experiments with single grains in a sliding process, the charges transferred between different materials are quantified. In the sliding experiments a range of 3D printed regular non-spherical particles with different shapes and surface areas are used. The effects of sphericity, material properties, ambient temperature and relative humidity on the charge generation of non-spherical particles are investigated. In addition, a new dynamic model for the electrification of non-spherical particles is established using the above parameters. In order to verify the established model, the fluidization of non-spherical particles was carried out in a pseudo-2D fluidized bed. Rice grains and mung beans were used as test material. To evaluate the hydrodynamic and electrostatic characteristics in the fluidized bed, digital imaging and electrostatic sensing techniques are applied. Moreover, computational fluid dynamics and discrete element modeling (CFD-DEM) method, which includes the new electrification model, is used to simulate the fluidization process. Non-spherical particles are represented by the multi-sphere model in the DEM method. The simulation results show more detailed information about charge characteristics and particle distribution in the whole bed. Besides, the relationship between the electrostatics and the hydrodynamics of particles is investigated. A close agreement between the experimental results and numerical simulation data on the characteristics of electrostatics and hydrodynamics is observed. The results confirm that the new dynamic model for the electrification of non-spherical particles is capable of simulating the electrostatic phenomena in the fluidized bed with a maximum error of 4%.