Study On Tribocharging Characteristics In Fluidized Bed And Electrostatic Separation Of End Of Life Passenger Vehicle

Under the dual pressure of energy shortage and environmental degradation,it is necessary to effectively recycle retired passenger cars.After dismantling the high utilization value parts and five major assemblies of retired passenger cars,the mixture after shearing,crushing and separation is called automotive crushing residue.The mixture contains a large number of plastic particles,which are traditionally disposed of in landfills and incinerators,causing serious environmental hazards and a huge waste of resources.Mixed plastic particle sorting is an important way to achieve its high value-added recycling.China’s automotive plastic polymer electrostatic sorting is still in its infancy,electrostatic sorting charge mechanism and its motion characteristics and other basic research needs to be carried out.The thesis takes retired passenger car plastics as the research object and carries out the research on their charging characteristics under fluidized bed charging device and the motion characteristics of charged particles in high voltage electrostatic field,the main research contents are as follows:(1)Study of the charge and motion characteristics of particles in fluidized beds.A model for the motion of plastic particles in a fluidized bed is analyzed based on the conservation of momentum and energy equations and Newton’s law of motion satisfied by the gas-solid two-phase medium in the fluidized bed.Further,based on the soft ball collision model,the inter-particle and particle-wall collision mechanisms in the fluidization process were characterized,and the action of fluid on plastic particles was explored based on the traction model.After that,the force model of the particles was further constructed by exploring the force characteristics of the particles in the fluidized bed.Finally,the equations of motion of the particle in the electric field are established based on the simplified force model of the particle.(2)Particle fluidization state simulation and charge study.Based on coupled CFD-DEM,numerical simulation of the designed fluidized bed chamber structure under different return plate angles,particle fluidization gas phase velocity and air pressure magnitude and other states,the simulation shows that when the return plate angle is 45 degrees can effectively reduce the overflow particle mass,the proportion of particle overflow is 1.6%.Simulation also shows that when the fluidized air velocity is6m/s-8m/s,the particles are better distributed in the electric field action area,which is convenient for sorting.In addition,the optimal charge time for fluidization of plastic particles in two groups of ABS,PP,PA and PE,PP,PVC was verified by experiment for 6 min.(3)Experimental study of particle swarm fluidization sorting.Based on the COMSOL Multiphysics simulation platform,the sorting trajectories of two groups of mixed particles ABS,PP,PA and PE,PP,PVC commonly found in passenger cars were simulated,and the voltage range of the two groups of particles sorted was 25KV-45 KV.On the basis of simulation,an experimental platform is established for the fluidized bed charge and high pressure sorting of plastic particles from end-of-life vehicles.Based on the response surface method,the fluidized charge electrostatic sorting experiments of the retired passenger car plastic pellet clusters were carried out,and the sorting optimization experiments were conducted for two groups of pellets.After optimization,the plastic sorting purity and recovery rate can reach more than 90%.In summary,to realize the green separation of retired passenger car hybrid polymer fluidized charging and high pressure electrostatic separation,the research on particle swarm fluidized charging and electrostatic separation is carried out to explore the inter-particle charge transfer behavior during fluidization,establish the particle fluidized charging sequence,and further investigate the effects of different wind speed,charging time,electric field distribution and other parameters on the electrostatic separation effect,so as to improve the recycling rate of retired passenger cars in China,which will provide basic theoretical and methodological support for improving the recycling rate of retired passenger cars and the high value-added resource recycling of retired passenger car urban minerals.