Investigation on Electrostatic Charging and Its Effect on Mixing of Binary Particles in a Vibrating Bed

The vibrating bed is widely applied in various industrial areas for drying, mixing, and segregation of granular materials. Triboelectrification becomes unavoidable due to frequent collisions and friction between particles and between particles and the wall, which will greatly affect the performance of the vibrating bed. In our study the triboelectrification model under the framework of the discrete element method was implemented to simulate the triboelectrification process, as well as the effect of electrostatic forces on the hydrodynamics of spherical particles and cylindrical particles. The numerical results showed that the triboelectrification could become stronger with increasing solid loading or bed diameter, and decreasing particle size. At low vibrating frequencies or amplitudes, the triboelectrification for cylindrical particles was stronger than that for spherical particles, while at high vibrating frequencies or amplitudes the triboelectrification for spherical particles became stronger. The repulsive or attractive electrostatic forces among particles could help improve the mixing between spherical particles and cylindrical particles. With the increasing vibrating frequencies and amplitudes, the mixing between spherical particles and cylindrical particles was improved and then approached a plateau. Due to strong triboelectrification between solid particles and the wall, the particles could attach to the wall due to attractive electrostatic forces from the wall, and form rings in the vibrating bed, which might deteriorate the mixing in the vibrating bed. These results may help us get insight in the triboelectrification of the vibrating bed and provide guidance in improving its performance by virtue of electrostatics.