| The recycling of end-of-life vehicles has become an unavoidable problem for countries around the world.Due to the improvement of safety requirements,the performance of auto parts is excellent,and its reasonable recycling will produce huge economic and social benefits.As one of the important raw materials for automobiles,automotive polymers are widely used in automotive interior and exterior parts and functional parts.In China’s ELV recycling system,the polymer exists in the form of disassembly mixture or crushing residue,which is composed of a variety of polymer mixtures.Different polymers have different compositions and properties.How to efficiently and cleanly separate polymer mixtures is the key to the high value-added recycling of polymers for end-of-life vehicles.Based on the high-voltage electrostatic separation technology,the theoretical and experimental research on the charging and separation of polymer particles for vehicles is carried out on the basis of the friction barrel electrostatic separation equipment.The research contents and conclusions are as follows:Firstly,the motion model of polymer particles in the charging process is established.By analyzing the force of polymer particles in a rotating cycle of the friction barrel type charge device,the motion equation of the particles relative to the fin in a rotating cycle and the motion equation of the particles after leaving the fin are derived.The EDEM simulation software is used to simulate and analyze the single particle motion cycle and the particle swarm full cycle motion.The simulation results are consistent with the theoretical results.Secondly,based on the motion model,the contact model between the particle and the friction bucket and the particle charge model are established,so as to obtain the factors that have a great influence on the particle charge.The friction charge sequence of common vehicle polymer particles was measured by charge pre-experiment.Finally,taking polyamide(PA),polypropylene(PP)and polyethylene(PE)as the research objects,the interaction between various influencing factors and the optimal charging parameters were determined by single factor experiment and response surface experiment.The charging time is 71 s,the friction barrel speed is 36 rpm and the friction barrel tilt angle is 12 °.Finally,the motion model of charged polymer particles in the two-stage free fall electrostatic field is established,and the motion trajectory of polymer particles is simulated by Matlab and Comsol.Based on the motion model and simulation calculation,a separation purity prediction method is proposed by exploring the charge-mass ratio distribution of PA,PP and PE mixed polymer particles after charging under the optimal charging parameters.The purity of the separation experiment is basically the same as the predicted purity.After that,the response surface experiment was used to obtain the optimal separation parameters of the secondary high-voltage electrostatic field.The electric field voltage is 45 KV,the electrode spacing is 160 mm and the electrode inclination angle is 15 °.Under the optimal charge parameters and separation parameters,the purity of PA,PP and PE is 94.864 %,84.432 % and88.957 %,respectively.In summary,the paper has carried out theoretical and experimental research on the friction barrel electrostatic separation equipment from the aspects of charging and separation.Through theoretical exploration,the paper analyzes the motion and charging mechanism of polymer particles,constructs its motion and charging model in the friction barrel,and then analyzes the dynamic characteristics of particles in the secondary high-voltage electrostatic field.On the basis of theoretical research,the optimal charge parameters and separation parameters of PA,PP and PE particles in the friction barrel electrostatic separation equipment are obtained through experiments.The research provides a reference for the clean and efficient separation of polymer particles for vehicles. |
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