Bench-scale tests to determine mechanisms of charge generation due to particle–particle and particle–wall contact in binary systems of fine and coarse particles

Bench-scale methods were utilized to determine changes in electrostatic charges and their mechanisms for various coarse and fine particles as they came into contact with each other and/or their containing vessel walls. Techniques included shaking tests and particle-copper plate contacting experiments. Electrostatic behaviour of coarse particles (glass beads and polyethylene) and fine particles (Larostat 519, glass beads and silver-coated glass beads) were investigated. Shaking tests resulted in charge separation in which the fine particles acquired significant positive charges, opposite to those carried by the large particles. In copper-plate contacting tests, charge transfer occurred between the fines and the copper plate with fines carrying away almost all of the initial charges on the plate followed by further charge separation. Charge separation was found to be the dominant charging mechanism between the coarse particle and copper plate, with the particles becoming negatively charged.