Application of plastic trash sorting technology in separating waste plastic mulch films from impurities

Abstract: Plastic film mulching technique has been using widely in China because of it's notable features such as raising temperature,inhibiting weed growth,promoting crop maturity and increasing production. A large number of used plastic mulch films which have not be recycled and accumulated in the soil year after year and results serious waste plastic mulch film pollution. Recycled waste plastic mulch films twined each other with other impurities and makes the mulch film utilization becomes difficult. Some recycled waste plastic mulch films has been stacked or burned on field ridge freely which leads secondary pollution.Thus, the waste plastic mulch film pollution problems should be cracked from it's beginning.Agricultural waste plastic mulch film and impurities separation technology is key links during mechanized mulch films recycling and reusing. Waste plastic mulch film as a valuable renewable resource and be important part of plastic production which comes from waste plastic mulch film by separation process. Effective recycling and reusing of waste plastic mulch film can improve economic benefits and even what's more is that it can decrease the secondary pollution probability which caused by improper waste plastic mulch film handling. Some documents shows that the thickness of plastic mulch film used in foreign countries is generally above 0.12mm which keep the tensile strength of plastic mulch film be good enough and promote the rolling recycling machine development.Waste plastic mulch film is clean and complete which recycled by rolling recycling machine and it can be reused directly.At present, there is no relevant report about technology and equipment for waste plastic mulch film separation at abroad.The thickness of the plastic mulch film used generally in China between 0.004-0.008mm which leads the tensile strength not good enough after harvesting season and can not be recycled by rolling way. The only way which can recycling waste plastic mulch film by recycling machine based on tooth type collector which collect everything including plastic film and stalk,root and so on. Some related documents shows that the separation technology of waste plastic mulch film in China carried out in recent years.The technology development still be in primary stage and related device just remain in laboratory research condition. There is little available technology and experience can be used for reference.Therefore, the difference and similarity between city life plastic trash and agricultural waste plastic mulch film have been analyzed based on different separation methods and related equipment all over the world in this paper. All those work can provide theoretical basis and scientific basis for separation processing after waste plastic mulch film recycling. According to present documents statistic shows, conventional plastic trash sorting methods as follow: wind separation, hydraulic cyclone separation, friction electrostatic separation and separation based on light and so on. It's difficult to separate waste plastic mulch film with other agricultural impurities such as stalk,dust and so on by conventional plastic separation methods because of the characteristic of city plastic trash is different from agricultural waste plastic mulch film such as impurity composition, ingredient ratio, water content. Conventional plastic trash separation method can not be used in agricultural waste plastic mulch film separation process. The only thing which wen can take it into waste plastic mulch film separation is the plastic sorting method. Based upon existing method and equipment, related plastic trash sorting method can be probed and machine can be invented which suitable for field waste plastic mulch film recycling industry. Bench test proved that air separation method combined with screening will be the main development trend of separate waste plastic mulch film from impurities in China.