Plastic pollution has become a global environmental challenge, and efficient recycling is key to overcoming this challenge. As the core of the plastic recycling industry chain, advanced plastic waste sorting and recycling equipment is transforming mixed waste plastics into high-value renewable resources through intelligent and automated technologies. Guoxin Machinery will systematically analyze the entire process of plastic waste sorting and recycling.
I. What is Plastic Waste?
Plastic waste is mainly divided into post-consumer waste (such as beverage bottles, packaging bags, and appliance casings) and post-industrial waste (scrap materials from the production process). They usually exist in mixed forms, and the main types include:
PET: Commonly found in beverage bottles.
HDPE: Shampoo bottles, milk jugs.
PVC: Pipes, windows, and door profiles.
LDPE/LLDPE: Plastic bags, films.
PP: Takeout containers, automotive parts.
PS: Foam packaging, disposable tableware.
The primary task of efficient recycling is to accurately separate these plastics of different materials, colors, and shapes.
II. Principles of Plastic Sorting
Modern sorting technologies are primarily based on the differences in the physical properties of materials to achieve automated, high-precision separation:
1. Near-Infrared (NIR) Spectroscopy Sorting: The mainstream technology. Utilizing the different absorption and reflection spectra of near-infrared light by different plastics, a probe scans the material and instantly identifies the material (e.g., distinguishing PET from HDPE), then separates them using high-pressure air jets. High precision and speed.
2. Color Sorting (Visible Light Sorting): Using a high-definition camera to identify the color of the material, often used to separate different colors of the same type of plastic (e.g., transparent and blue PET bottle flakes), increasing the value of recycled materials.
3. Density Separation (Air/Water Separation): Utilizing the density differences of plastics. Air separators separate films and heavy bottles using airflow; flotation tanks separate different plastics by adjusting the water flow density (e.g., separating PP from PET).
4. Electrostatic Separation: Suitable for crushed mixed plastic powders, utilizing the differences in the triboelectric charge of different plastics to achieve separation in an electric field.
III. Plastic Waste Recycling Process
1. Front-end Pre-processing:
Bag Breaking and Loose Packaging: Unpacking waste materials.
Coarse Crushing: Crushing large materials into smaller sizes.
Screening: Removing dust, broken glass, and other impurities using trommel screens, vibrating screens, etc., and grading by size.
2. Core Sorting Stage:
Magnetic Separation and Eddy Current Separation: First, removing ferrous and non-ferrous metals.
First-stage NIR Sorting: Typically using “positive” or “reverse” sorting based on material to extract target plastics (e.g., all PET bottles).
Air Sorting(Air Density Separator): Separating lightweight films, labels, etc.
Second-stage Fine Sorting: Further sorting similar materials by color (e.g., transparent PET, green PET).
Optical Sorting (Foreign Object Removal): Identifying and removing residual non-target materials.
3. Back-end Processing:
Fine Shredding and Washing: Shredding the sorted, clean plastic sheets to standard sizes and performing hot washing and friction cleaning to remove stains and label adhesive.
Dehydration and Drying: Removes moisture.
Intelligent Packaging: Packages clean plastic fragments for easy transport to the pelleting plant.
IV. Plastic waste recycling promotes economic circulation
1. Improved Recycling Rate and Purity: Automated sorting significantly reduces human error and costs, allowing more low-value mixed waste plastics to enter the recycling system, producing single-category fragments with a purity of 95%-99%.
2. Guaranteed Recycled Material Quality: High-purity recycled fragments are a prerequisite for producing high-quality recycled plastic pellets (RPET, rHDPE, etc.). These pellets can be widely used in:
Food-grade Applications: Recycled PET can be used to manufacture new bottles and fibers.
High-end Packaging: Cosmetic bottles, detergent bottles.
Engineering and Building Materials: Pipes, pallets, outdoor furniture.
3. Formation of a Closed-Loop Economy: A closed loop of “waste plastic collection → intelligent sorting → cleaning and pelletizing → high-value product remanufacturing” is established, reducing dependence on virgin resins and lowering carbon emissions.