However, the composition of MSW varies significantly from one project to another. Plastic content, impurity levels, material size and feedstock composition can all differ. For plastic recycling companies, the key challenge is to recover plastics from mixed MSW and prepare them to meet the feed requirements of downstream chemical recycling systems.

To address different feedstock conditions, Harden Machinery offers three pre-treatment solutions for recovering plastics from MSW for chemical recycling. From fine shredding of pre-sorted plastic feedstock to screening and separation of mixed MSW, and multi-stage processing of complex waste streams, Harden helps customers select the right process configuration for their needs.

Solution 1: Fine Shredding for Pre-Sorted, Plastic-Rich Feedstock

Suitable feedstock: Plastic-rich materials that have already undergone preliminary sorting and contain relatively few impurities.

If the feedstock already has a high plastic content and meets the basic cleanliness requirements of the downstream chemical recycling system, there may be no need for complex screening and separation equipment.

In this case, the main objective of pre-treatment is to control particle size and ensure the output meets the feeding requirements of downstream equipment.

Process flow:

Pre-Sorted Plastic Feedstock → Single-Shaft Fine Shredding → Plastic Feedstock with the Required Particle Size

Key benefits:

• Avoids unnecessary processing stages.

• Controls the particle size of the plastic output.

• Prepares plastic feedstock for downstream chemical recycling equipment.

Solution 2: Screening and Separation of Mixed MSW Before Fine Shredding

Suitable feedstock: Mixed municipal solid waste containing plastics and other waste materials, where plastic fractions need to be recovered.

When the feedstock consists of mixed MSW that has not been sufficiently sorted, fine shredding alone cannot effectively remove impurities and may increase the processing burden on downstream equipment.

A better approach is to screen and separate the mixed materials first, then fine-shred the recovered plastic fraction to achieve the required particle size.

Process flow:

Mixed Municipal Solid Waste (MSW) → Screening + Wind Shifting → Separation by Particle Size and Material Density → Plastic Fraction Recovery → Single-Shaft Fine Shredding → Pre-Treated Plastic Feedstock

Key benefits:

• Recovers plastic fractions from mixed MSW.

• Removes some non-plastic contaminants.

• Improves plastic particle size consistency for downstream chemical recycling.

Solution 3: Multi-Stage Shredding and Separation for Complex MSW

Suitable feedstock: Complex MSW containing large and irregular materials, lightweight plastics, and contaminants such as metals, glass and stones.

For MSW with a complex composition and high impurity levels, basic screening and wind separation alone may not be sufficient to meet the target feedstock requirements.

These projects require a more comprehensive, multi-stage pre-treatment system. Depending on the material composition, the process can combine primary shredding, metal separation, screening, wind shifting and fine shredding to progressively remove contaminants and recover plastic fractions.

Process flow:

Complex MSW → Twin-Shaft Primary Shredding → Metal Separation → Screening → Wind Shifting → Single-Shaft Fine Shredding → Pre-Treated Plastic Feedstock

Key benefits:

• Reduces the size of bulky and irregular materials through primary shredding.

• Removes some contaminants through metal separation, screening and wind shifting.

• Further controls the particle size of the plastic output.

• Handles MSW streams with more complex compositions.

4. What Are the Differences Between the Three Solutions?

Different MSW feedstocks require different pre-treatment processes. Harden provides flexible system configurations based on feedstock complexity and the requirements of downstream chemical recycling systems.

It is important to note that screening and wind shifting separate materials based mainly on particle size and physical properties. They cannot fully identify or distinguish different plastic types.

For plastics that require specific control, such as PVC, additional identification and sorting measures should be selected according to the requirements of the downstream chemical recycling process.

5. Different Feedstock, Different Process Configuration

There is no single pre-treatment process suitable for every MSW chemical recycling project.

Already-sorted plastic feedstock: Focus on fine shredding and particle size control.

Mixed MSW: Screen and separate the materials first, then fine-shred the recovered plastic fraction.

Complex MSW: Use multi-stage shredding and separation to recover plastics and remove more contaminants.

Harden develops different levels of pre-treatment solutions based on MSW composition, impurity levels, processing capacity and downstream feed requirements.

From individual shredding machines to complete pre-treatment systems, Harden helps plastic recycling companies optimise plastic recovery and feedstock preparation, providing more suitable material for downstream chemical recycling.