Physical screening method
Physical screening is one of the commonly used impurity removal methods in the processing of Recycled PE particles. By screening the crushed waste plastics through screens with different apertures, larger impurities such as stones and metal fragments can be effectively separated. This method is simple and easy, low cost, and can quickly remove most obvious impurities. For example, in the primary screening stage, a screen with a larger aperture can be used to remove larger block impurities, and then a screen with a smaller aperture can be used for further screening to improve the screening accuracy and ensure the purity of Recycled PE particles. In addition, equipment such as vibrating screens can be used to stratify the material on the screen through vibration, which is more conducive to the separation of impurities and PE particles and improves the screening effect.
Flotation method
The flotation method mainly uses the difference in surface properties of different substances to remove impurities. For some impurities with a density similar to PE but different surface properties, such as paper, plastic labels, etc., they can be separated by flotation. During the flotation process, the crushed waste plastics are mixed with water and an appropriate amount of flotation agent is added. The flotation agent will attach to the surface of the impurity, changing its surface properties so that it can float on the water, while the PE particles sink to the bottom, separating the impurities from the PE particles. This method is effective in removing light impurities, but attention should be paid to the selection and amount of flotation agents used to avoid environmental pollution.
Magnetic separation method
Magnetic separation is suitable for removing magnetic impurities in waste plastics, such as iron filings, iron nails, etc. Through the magnetic field generated by the magnetic separation equipment, the magnetic impurities will be adsorbed on the surface of the magnetic separation equipment, while the non-magnetic PE particles will not be affected, thereby achieving the removal of impurities. The magnetic field strength of the magnetic separation equipment can be adjusted according to actual needs to achieve the best magnetic separation effect. Generally speaking, first removing larger magnetic impurities through a strong magnetic field, and then further removing fine magnetic particles through a weak magnetic field can improve the efficiency and accuracy of magnetic separation and ensure that the content of magnetic impurities in Recycled PE particles meets the requirements.
Chemical cleaning method
The chemical cleaning method uses chemical agents to react with impurities to dissolve or convert impurities into separable substances, thereby achieving the purpose of removing impurities. For example, organic impurities such as oil and ink on the surface of waste plastics can be cleaned with organic solvents or surfactants. Organic solvents can dissolve impurities such as oil and remove them from the surface of PE particles; surfactants can disperse impurities in water through emulsification and then remove them by washing. In addition, for some inorganic impurities, such as rust, acid can be used for cleaning, but when using chemical cleaning methods, attention should be paid to the selection and use conditions of chemical agents to avoid damage to PE particles. At the same time, the wastewater after cleaning should be properly treated to reduce pollution to the environment.
