Improvement of the selectivity in electrostatic separation by surface modification

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Electrostatic separation is basically a method in which the difference in the electric conductivity of targeted materials is utilized. However, surface conductivity is easily influenced by various factors in the circumstances especially humidity, then the method has not been widely adopted in Japan. In the method developed in this study, this problem will be dissolved by adding the two kind of pretreatment methods, 1) surfactant treatment and 2) electrolyte solution spraying. Theoretical background was at first made sure experimentally, then the following boundary conditions are clarified in each stage, such as 1) species and concentration of surfactant, drying conditions, 2) species and concentration of electrolyte solution, configuration of atomizer and sample, sample volume, water content of particle surface, etc. Spray method in the stage of surfactant treatment was tried and confirmed effective for making more feasible process.Simulation program was created for obtaining particle behavior in the electrostatic separation. Charge ^<*****> method was used for simulating electric field and gravitational, centrifugal, frictional, electrostatic, and drag forces were calculated in the program. The simulation was validated in the experiments by changing conditions of electrodes configuration (axes and distance), voltage applied, etc. Electrostatic electrode was took into account but not corona electrode in the simulation.