In the plastic recycling industry, the plastic recycling and washing line, as the core link connecting front-end pretreatment and back-end granulation, bears the heavy responsibility of deep cleaning and homogenization of crushed plastic scraps. Through the organic integration of processes such as mechanical crushing, friction washing, sorting and impurity removal, and dehydration and drying, it transforms waste plastic scraps containing oil, labels, mud, and other impurities into raw materials with a cleanliness level meeting the requirements for re-granulation or reprocessing. This is a key guarantee for achieving high-value recycling of plastics.
The process flow of a plastic recycling and washing line typically begins with crushing and refining. Plastic scraps (particle size mostly between 10–50 mm) from the front-end shredding or crushing equipment first enter a secondary crusher or grinding mill to further reduce the particle size to 2–10 mm, increasing the specific surface area and improving the contact and removal efficiency of contaminants from the plastic surface during subsequent washing. At this stage, the type of blade and screen aperture must be selected according to the material characteristics to avoid increased dust or energy consumption due to over-crushing.
The next step is the friction cleaning stage, the core functional area of the washing line. The crushed material is conveyed to a high-speed rotating friction cleaner or a spiral-propelled cleaning tank. Under the combined action of mechanical agitation and water flow, intense friction occurs between the plastic particles and between the particles and the tank walls, causing ink, adhesives, grease, and fine sand adhering to the surface to detach. To enhance the cleaning effect, an appropriate amount of environmentally friendly cleaning agent can be added, and precise control of water temperature and pH promotes the emulsification and dispersion of stains. The friction cleaner is equipped with a grading screen that can separate suspended light impurities (such as pulp and fine sand) from settled heavy impurities (such as metal and glass shards) in real time, reducing secondary pollution.
The sorting and impurity removal process follows immediately, aiming to further improve the purity of the material. The crushed material, after friction washing, enters a rinsing tank or eddy current separator. Utilizing the differences in density and buoyancy between different materials, residual lightweight impurities (such as foam particles and paper scraps) are separated from the plastic granules. For materials containing metal inserts, magnetic separators or eddy current separators can be introduced to adsorb or repel ferromagnetic and non-ferrous metal impurities. Some high-end crushing and washing lines are also equipped with optical sorting units, using near-infrared or visible light recognition technology to sort materials online (PE, PP, PET, etc.), creating conditions for subsequent classification and granulation.
Dehydration and drying is the final stage of the crushing and washing line and a crucial prerequisite for ensuring granulation quality. The wet material undergoes a screw dewatering machine or centrifugal dewatering machine to remove most of the free water, and then enters a hot air dryer or steam dryer to reduce the moisture content to below 0.5%. The drying process requires strict control of temperature and time to prevent heat-sensitive plastics (such as PVC) from overheating and decomposing to produce harmful gases, while ensuring uniform drying of the granule surface to avoid clumping that could affect subsequent conveying and melting.
The design and operation of plastic recycling washing lines must fully consider material compatibility, energy consumption and water resource utilization efficiency, and environmental compliance. For lightweight, buoyant materials like films, flattening and pre-washing devices can be added to reduce floating accumulation in the washing tank. For highly oily industrial materials, multi-stage countercurrent washing and hot water spraying can be used to improve decontamination efficiency and reduce cleaning agent usage. Modern washing lines generally incorporate closed-loop water circulation systems, using sedimentation tanks, filtration devices, and water quality monitoring to achieve water resource reuse and reduce wastewater discharge. Exhaust gas collection and purification devices ensure the effective treatment of volatile organic compounds generated during washing and drying.
From an industrial value perspective, plastic recycling washing lines significantly improve the cleanliness and consistency of recycled plastics, bringing their performance indicators close to virgin materials, thereby expanding their application space in high-requirement fields such as food packaging, medical products, and automotive parts. Simultaneously, through system integration and intelligent control, washing lines can achieve dynamic optimization of production capacity and energy consumption, reducing unit processing costs and enhancing the market competitiveness of recycled plastics.
In summary, the plastic recycling and washing line, with its core processes of crushing and refining, friction washing, sorting and impurity removal, and dehydration and drying, constitutes an indispensable refining link in the plastic recycling chain. Its efficient, clean, and low-consumption operation not only ensures the quality of recycled plastics but also promotes the plastic recycling industry towards high-quality and sustainable development, providing solid technical support for global plastic pollution control and resource conservation.