New Standard for Cleaner Production in the Plastic Recycling Industry

--PWI Core Technology of Solid-Liquid Separation System

Core pain points in the plastic recycling industry: Wastewater from the crushing and cleaning process is particularly typical, as the wastewater in the plastic recycling industry contains complex suspended solids, and Sludge Treatment costs are high.

I. Classification Overview of Plastics:

The most basic classification of plastics can be made based on their behavior after being heated. Differences in chemical composition determine their different properties. The core of chemistry lies in the fact that the performance differences of different plastics stem from their monomer units and molecular chain structures.

"Thermoplastic" and "thermosetting" plastics are distinguished based on their behavior after being heated. The underlying principle of this classification lies in the differences in their internal molecular structures and behaviors when heated.

The scientific principle behind this can be understood through a good analogy:

· Thermoplastics → Butter or ice cubes: melt when heated and harden when cooled, and this process can be repeated (physical change).

· Thermosetting plastics → Eggs or cakes: They change from a liquid to a solid state when heated, but once solidified, they will not return to a liquid state when reheated, only charring (chemical change).

II. Summary of the Recycling Principles of Plastics:

1. Principle of recyclability of thermoplastics:

Precisely because this process is a purely physical change without any chemical reactions occurring, the molecular chains themselves remain intact. Therefore, in theory, you can melt, cool, remelt, and recool a piece of thermoplastic (such as a plastic water bottle) indefinitely. This achieves mechanical recycling - that is, reshaping it into new products through heating and melting.

Common examples: polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polystyrene (PS). The vast majority of plastics in daily life are thermoplastic.

Principle of recyclability of thermosetting plastics (traditional mechanical recycling):

· Cannot be reshaped: because it does not melt when heated, you cannot reshape it into a new form using traditional heating methods.

· Stable chemical structure: makes it difficult to be decomposed back into its original monomers.

· Therefore, thermosetting plastics cannot be recycled through simple melting and re-granulation. They are usually crushed and used as fillers, or processed through energy recovery (incineration for power generation), but the most common outcome is still landfill.

Common examples: Epoxy resin (AB glue, circuit board), phenolic resin (electrical switch, pot handle), polyurethane (PU) foam (sofa sponge, insulation), unsaturated polyester resin (automobile parts).

Therefore, the weak intermolecular forces of thermoplastics make them easy to recycle, while the strong covalent bond network structure of thermosetting plastics endows them with excellent properties such as high strength and heat resistance, but also sacrifices recyclability.

III. PWI - Core Technology of Solid-Liquid Separation System

a.Lamellar Clarifier + Dissolved Air Flotation System - Physical Sedimentation:

After passing through the coagulant and flocculant dosing system, the wastewater from the plastic recycling, crushing, and cleaning process uses a treatment process mainly composed of VMC Lamellar Sedimentation + Dissolved Air Flotation System（DAF） to remove most of the suspended solids in the wastewater. Through the Lamellar Sedimentation Tank equipped with inclined plates/tubes to improve sedimentation efficiency, the preliminary solid-liquid separation is quickly and efficiently completed, ensuring that most of the clean water can be reused. The supernatant flows back to the production process by gravity, significantly reducing fresh water consumption.

b.High-Efficiency Automatic Filter Press - Core Filtration:

Derived from Germany's advanced rapid solid-liquid separation technology, the equipment features a unique quick-opening and enclosed design, integrating a series of operations such as automatic pressure filtration, filter plate vibration, valve opening and closing, material pump start and stop, material detection, and fault alarm. According to customer requirements and operating conditions, functions such as automatic liquid collection drip trays, electric vibrating plates for auxiliary cake discharge, and filter plate and cloth spray cleaning are customized to provide customers with a new type of sludge dewatering equipment that is more efficient, cleaner, safer, and smarter. It reduces the moisture content of sludge to an extremely low level (e.g., from over 98% to 40%-50%), forming low-volume, high-dryness sludge cakes, significantly reducing sludge weight and subsequent disposal costs.

Value Summary: PWI's system enables customers to achieve comprehensive value enhancement in "water conservation, energy savings, cost reduction, emission reduction, and easy disposal" by providing new, more efficient, cleaner, safer, and smarter sludge dewatering equipment.