Improvement of the selectivity in electrostatic separation by surface modification

静电分离基本上是一种利用目标材料的导电性差异的方法。然而，表面电导率在环境中容易受到各种因素的影响，特别是湿度，因此该方法在日本还没有被广泛采用。在本研究开发的方法中，通过添加表面活性剂处理和电解液喷雾两种前处理方法来解决这一问题。首先通过实验确定了理论基础，然后在每个阶段明确了如下边界条件：1)表面活性剂的种类和浓度，干燥条件，2)电解液的种类和浓度，雾化器和样品的配置，样品体积，颗粒表面的水分含量等。在表面活性剂处理阶段，尝试并证实了喷雾方法的有效性，以使工艺更可行。程序采用电荷方法模拟电场，计算了重力、离心力、摩擦力、静电力和阻力。通过改变电极结构(轴线和距离)、施加电压等条件进行了实验验证，模拟中考虑了静电电极而不考虑电晕电极。

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.