PET Bottle Recycling Line: High-Efficiency Recycling Washing Systems (500-6000kg/h)

Polyethylene Terephthalate (PET) is a semi-crystalline thermoplastic polyester widely used in beverage packaging due to its excellent transparency, barrier properties, and mechanical strength.

In the context of recycling, a key parameter for PET is Intrinsic Viscosity (IV). The IV value of virgin bottle-grade PET typically ranges between 0.78 and 0.85 dl/g. However, during the recycling process, the IV value diminishes due to thermal degradation and hydrolysis. To achieve high-value "Bottle-to-Bottle" utilization, the recycling process must minimize IV degradation and ensure the IV value of the final flakes remains above 0.70 dl/g. -- (Why do Bottle-to-Bottle recycling programs require a PET SSP system?)

The primary challenge in recycling arises not from PET itself, but from the complex matrix of co-existing contaminants. This includes:

(PVC) Labels and Bottles: PVC degrades at PET processing temperatures (approx. 270°C), releasing hydrochloric acid which corrodes equipment and causes PET degradation and yellowing. Industry standards typically require PVC content to be below 30 ppm.
(PP/PE) Caps and Gaskets: With melting points and densities lower than PET, incomplete separation leads to haze and deteriorated mechanical properties in the recycled material.
Adhesives and Organic Residues: Residual hot melt glue, oil, and sugars, if not thoroughly washed, will carbonize during extrusion, forming black specks.

All of the above issues should be addressed during the PET bottle recycling production line stage.

Overview of Mechanical Recycling Process

Mechanical recycling refers to the process of restoring waste plastics into pure flakes through physical means (sorting, crushing, washing, and separation) to remove contaminants. Compared to chemical recycling, mechanical recycling is characterized by low energy consumption, high technical maturity, and significant economic benefits.

A standard PET bottle recycling line typically includes the following core modules: Pre-treatment (De-baling and impurity removal), Size Reduction (Crushing), Washing (Cold wash, Hot wash, Friction wash), Sorting (Density separation, Hydrocyclone, Optical sorting), and Drying & Packaging.

De-baling Technology

Post-consumer PET bottles are typically baled into high-density compressed bales to facilitate transportation. The De-baler (or Bale Opener) serves as the starting point of the production line.

Mechanical Principle: De-balers utilize low-speed, high-torque rotors to physically break apart the compressed bales. Boxin Machinery’s equipment features a unique "dual/quad-shaft design" specifically optimized for ultra-high-density bales, capable of thoroughly breaking down the bales into individual bottles.

Process Objective: Achieving "Singulation." Only when bottles are separated individually can subsequent optical sorters and manual sorting platforms effectively identify and remove impurities.

Energy Efficiency Considerations: Although the de-baling process operates at low rotational speeds, it involves extreme load fluctuations. Advanced control systems automatically adjust the feed conveyor speed based on the motor current load to achieve load-adaptive control.

Trommel Screening for Impurity Removal

The material stream following de-baling is contaminated with significant quantities of dirt, stones, metals, and even glass. The trommel screen utilizes rotational centrifugal force and gravity to perform physical screening.

Screening Mechanism: Bottles tumble forward within the drum, while impurities smaller than the screen apertures (typically 50mm)—such as caps, stones, and broken glass—fall through and are discharged.

Importance: This step is critical for protecting downstream crusher blades, as hard foreign objects can cause blade chipping, thereby significantly increasing maintenance costs.

Label Removal Technology

With the prevalence of full-body Shrink Sleeve Labels, traditional washing methods encounter significant challenges. These labels typically tightly encase the bottle body, and their constituent materials (PVC, PETG, OPS) possess densities similar to PET, rendering separation in sink-float tanks difficult.

Efficiency Metrics: High-performance label removers can achieve removal rates of 80%-90% for compressed bottles and 90%-95% for loose bottles.

Necessity: Removing labels prior to crushing significantly reduces the generation of paper pulp and microplastics during downstream washing stages, thereby alleviating the load on water treatment systems.

Manual Sorting

While optical sorting systems possess a high degree of automation, manual sorting remains critical for eliminating items potentially missed by machinery. This module serves as the final quality control checkpoint prior to the crushing process. It operates in conjunction with metal detectors and manual inspection platforms to remove any residual off-color bottles, multi-layer bottles, or metal contaminants that bypassed automatic sorting.

Advantages of Wet Crushing

Modern recycling lines universally adopt the wet crushing process, which involves injecting water into the crushing chamber.

Friction Cleaning Effect: The high-speed rotating rotor (approx. 450-600 RPM) not only cuts the plastic but also drives the water to generate intense turbulence. This hydraulic shear action washes away sand and dirt the instant new surfaces are created, serving as an effective pre-wash.

Thermal Control and Lubrication: The cutting process generates significant frictional heat. The presence of water provides cooling and lubrication, preventing PET from melting and clumping due to localized overheating (Anti-melting), while simultaneously reducing the generation of fines.

Blade Protection: The flushing action of the water reduces direct contact between the blades and abrasive impurities (such as sand), thereby extending the service life of the knives.

Cold Washing Process

Cold washing utilizes ambient temperature water to perform physical rinsing.

Applicable Scenarios: Primarily used for processing lightly contaminated bottles (e.g., purified water bottles) or for non-food-grade applications with lower cleanliness requirements, such as the production of Polyester Staple Fiber (PSF) and strapping bands.

Energy Efficiency Advantages: The primary benefit is energy conservation. Eliminating the need to heat large volumes of water significantly reduces Operating Expenses (OPEX) and carbon emissions.

Limitations: Cold water cannot effectively remove oils, stubborn hot melt adhesives, or specific chemical residues. Furthermore, it fails to eliminate pathogens, rendering it unsuitable for food-grade rPET production.

Hot Washing Process

Temperature: Typically maintained at 85°C - 90°C. This exceeds the softening point of common hot melt adhesives, facilitating their detachment from the flake surface.

Chemical Agents: Caustic Soda (NaOH) is added at a concentration of 1-2%. The highly alkaline environment hydrolyzes grease, breaks adhesive chemical bonds, and etches a micron-level surface layer of the polymer to thoroughly remove deep-seated contaminants. Additionally, industrial detergents are added to emulsify oils.

Residence Time: To ensure sufficient chemical reaction, the material typically requires a residence time of 30-45 minutes within the hot washing tank.

High-Speed Friction Washing

Mechanical Scrubbing: Strips softened adhesive residues and paper pulp, and removes residual chemical agents.

Dewatering & Impurity Removal: Dirty water and fine impurities are discharged through the screen mesh under centrifugal force, while the flakes are conveyed to the subsequent process.

Sink-Float Separation Tank

This is the most fundamental and widely used separation technique, utilizing the density of water (1.0 g/cm³) as the medium.

PET: Density approx. 1.33-1.40 g/cm³; sinks in water.

Polyolefins (PP/PE): Density approx. 0.90-0.96 g/cm³; floats in water.

Equipment Design: The tank is typically a longitudinal trough (e.g., 6 meters long). Top-mounted rollers or paddle wheels skim off floating caps and labels, while a bottom screw conveyor discharges the settled PET flakes.

Process Control: Precise control of water levels and turbulence is mandatory. Excessive currents may cause sinking PET to be entrained in the floating layer, resulting in yield loss. Conversely, insufficient agitation may prevent PET trapped within caps from sinking. Boxin Machinery’s equipment features an automatic discharge function to minimize manual intervention.

Mechanical Dewatering + Thermal Drying

Drying Objective: Final moisture content must be controlled below 1%, or even below 0.5%, to prevent hydrolysis during subsequent extrusion, which leads to a sharp decline in IV value.

Centrifugal Dewaterer: Prior to thermal drying, a high-speed rotating centrifuge (approx. 2200 RPM) is utilized to remove surface free water. Centrifugal force expels moisture through a screen mesh, reducing moisture content to approximately 2%-3%.

Pipeline Dryer: Flakes are suspended in a hot air stream and traverse a pipeline tens of meters long (e.g., 15m length, 159mm diameter). The hot air ensures full contact with the flakes, instantly evaporating moisture.

Winnowing (Elutriation)

Utilizes a Z-classifier or Zig-zag separator to remove contaminants via an upward airflow. This process extracts lightweight impurities such as dust, residual label fragments, and fibers, leaving behind purified PET flakes.

Optical Sorting

Modern production lines are typically equipped with Color Sorters and Material Sorters at the final stage.

Technology: Utilizes visible light and Near Infrared (NIR) technology.

Function: Detects and ejects off-color flakes (e.g., yellowed or multicolored flakes) and non-PET materials (e.g., PVC flakes, metals).

Objective: Ensures the total impurity content of the final product meets industry standards.

Production Line Technical Specifications and Capacity Planning

Model	Input Capacity (kg/h)	Installed Power (kW)	Water Consumption (m³/h)	Required Area (L*W)	Target Application
BXC-1000	1000	~280	3-4	50m x 6m	Fiber / Strapping
BXC-2000	2000	~450	5-6	70m x 6m	Sheet / Fiber / Bottle-to-Bottle
BXC-3000	3000	~680	8-10	90m x 8m	Sheet / Fiber / Bottle-to-Bottle
BXC-5000	5000+	~1100	12-15	Custom Layout	Mega Factory

Comparison of Resource Consumption and Configuration Parameters for PET Recycling Washing Lines.

Note: Installed power includes the power of all motors and electrical heating elements. The actual operating power is typically 60%-70% of the installed power.

Finished Product Quality Standards

A high-quality recycling line should be capable of producing rPET flakes that meet the following specifications:

Moisture Content: < 1.0%
Total Impurity Content: ≤ 150 ppm
PVC Content: ≤ 30 ppm
Metal Content: ≤ 10 ppm
pH Value: 7.5 ± 0.5 (Neutral, indicating thorough rinsing of caustic solution)
Flake Size: > 85% within the 3-12mm range

Global Manufacturer Case Studies and Technology Approaches

Sorema (Italy):

Customization and High Purity Sorema represents the European philosophy of high-end customized engineering, placing special emphasis on high-quality "Bottle-to-Bottle" output.

Technical Features: Places extreme importance on pre-treatment; its dry delabeling technology effectively reduces the load on subsequent washing steps. Its water treatment systems are specifically designed by its subsidiary, Teknodepurazioni Aquae, ensuring wastewater discharge compliance or reuse.

Herbold Meckesheim (Germany):

Technical Features: The Hydrocyclone is its flagship technology, maintaining stable separation performance even at extremely high throughputs. Its "building block" modular design allows clients to progressively add equipment as business grows (e.g., upgrading from cold wash to hot wash).

Boxin Machinery (China):

High Cost-Performance and Automation

Technical Features: Offers complete turnkey projects ranging from 500kg/h to 5000kg/h. Characterized by high integration, covering not only core washing equipment but also solutions for filling optical sorting blind spots, automatic chemical dosing systems, and even downstream pelletizing lines.

(Learn more about PET bottle recycling line factories)

Conclusion

The construction of a PET bottle recycling line is a systematic engineering endeavor that demands a perfect balance between the limits of physical separation and the efficacy of chemical cleaning.

For enterprises seeking to enter or upgrade within this sector, the core decision-making logic must always revolve around the "End Application":

High-End Bottle-to-Bottle: If the target is food-grade regeneration, significant Capital Expenditure (CAPEX) must be invested to establish a complete production line featuring hot washing, optical sorting, and high-performance water treatment.
Fiber-Grade Market: If the target is the fiber market, a more cost-effective cold washing solution may be considered.

FAQ & Expert Tips: Most Common Buyer Questions

Straight Answers to the Questions You Might Be Hesitant to Ask

Can a PET bottle recycling line produce Food-Grade rPET flakes?

Yes, but it requires the configuration of a Hot Washing module and an SSP (Solid State Polycondensation) system. The standard Boxin BXA Series recycling line utilizes high-temperature chemical washing (85°C-90°C) to effectively strip adhesives and oils, maintaining total impurities within 100 ppm. To achieve FDA/EFSA food-grade compliance, downstream extrusion pelletizing and SSP equipment must be integrated to eliminate Volatile Organic Compounds (VOCs) and restore Intrinsic Viscosity (IV)..

What are the primary differences between the 1000kg/h and 3000kg/h recycling lines?

Aside from capacity, the main distinctions lie in the level of automation and water treatment capability. 1000kg/h Line: Typically employs semi-automatic de-baling, with water consumption of approx. 4-5 tons/hour and installed power of approx. 300kW. Suitable for small to medium-sized facilities. 3000kg/h Line: Standard configuration includes fully automatic Optical Sorting and a closed-loop water treatment system. Water consumption is 6-8 tons/hour with installed power of approx. 600kW. This scale is better suited for large-scale recycling plants aiming for economies of scale.

How much water can the Boxin recycling line's water circulation system save?

Our closed-loop filtration system achieves a water recycling rate of >90%. By integrating sedimentation tanks, Dissolved Air Flotation (DAF) units, and filtration devices, the production line only requires replenishment for minor losses due to evaporation and product carry-over. For a 3000kg/h line, actual fresh water consumption can be controlled within 1-1.5 tons per ton of product.

How to Choose Between Hot Washing and Cold Washing?

The selection depends on the end application. Cold Washing: Utilizes ambient temperature water and friction washing. Suitable for producing low-end Staple Fiber or strapping bands. It features low energy consumption but cannot remove oils or adhesives. Hot Washing: Utilizes steam heating up to 90°C with the addition of NaOH (Caustic Soda). Suitable for producing Filament, Sheet, or Bottle-to-Bottle recycling. It thoroughly eliminates oils and sterilizes the material, making it a prerequisite for high-end recycling.

What Are the Key Components of a PET Bottle Recycling Line?