Airflow Electrostatic Composite Separation Technology For Waste Circuit Board Crushed Materials

With the progress of science and technology,the update speed of electronic products is speeding up,and the electronic products that are eliminated are called electronic waste.As we all know,electronic waste is one of the largest solid waste in China.If it is not treated,it will damage and affect the surrounding environment and human health.Moreover,the printed circuit board in the electronic waste has a high recycling value.The printed circuit board contains a lot of metal copper,a small amount of precious metals and some harmful and toxic substances.The content of these metals in the tons of printed circuit board is quite amazing,even dozens or even hundreds of times higher than the content of natural mineral resources.These resources cannot be wasted in vain,and need to be using scientific methods to extract it for reuse.In this paper,based on the traditional high-voltage electrostatic separation,air flow is added,and the self-made air flow electrostatic separation equipment is used to separate the mixed materials after the broken circuit board.Firstly,the charge area,electrostatic area and the force of particles in the fluid are analyzed theoretically.Secondly,the electric field simulation software Ansoft is used to analyze the corona electric field and electrostatic field.The results show that when the number of corona electrodes is m=3,the corona voltage is U₁=25kv,and the distance between the corona electrode and the earth electrode is L=55mm,the corona field strength reaches the maximum.At the same time,the size and shape of the positive and negative pole have no effect on the electrostatic field strength.Under this parameter,the movement of particles in the sorting bin is simulated and analyzed by using the coupling of the discrete element simulation software EDEM and the finite element simulation software ANSYS.It is preliminarily concluded that when the applied corona voltage U₁=20kv,the positive and negative pole voltage U₂=25kv,the air flow velocity v=1.0m/s-1.5m/s is the best air flow electrostatic sorting parameter.Finally,the waste circuit board was broken.It was found that when the material was broken to the particle size of-5+1mm,the metal and non-metal particles had been completely separated.Under this particle size,there would be no over breaking phenomenon of non-metal particles,resulting in a large number of non-metal powder destructive sorting behavior,which is also different from the traditional roller high-voltage electrostatic separator.The orthogonal experimental method is used to analyze the self-made high-voltage electrostatic separation equipment.At the laboratory level,it is found and determined that when the corona voltage U₁=20kv-25kv,the positive and negative voltage U₂=30kv,it is the best electrostatic separation parameter,which is basically consistent with the simulation data and the comprehensive separation efficiency of materials is almost the same.Based on the high-voltage electrostatic separation parameters,a vertical upward air flow is added.Through the experiment,it can be seen that for the particles with small particle size,when the air flow velocity is less than 1.0m/s,the materials can enter the separation bin smoothly for separation.For the particles with large particle size,when the air flow velocity is less than 1.5m/s,the materials can enter the separation bin smoothly for separation.The comprehensive separation efficiency of small particle and large particle is higher than that of pure electrostatic separation,and under the same parameters,the comprehensive separation efficiency of small particle is better than that of large particle.