When conventional recycling is not practical, plastic pyrolysis offers another potential route for recovering resources from suitable waste plastics.

Through shredding, pre-treatment and pyrolysis, selected plastic-rich waste streams can be converted into pyrolysis oil and other hydrocarbon products, supporting the recovery of value from waste plastics.

The Process: Shredding → Pyrolysis → Oil Condensation

Step 1: Shredding and Pre-treatment — Preparing Plastics for Pyrolysis

Lightweight plastics from MSW often contain tangled films, mixed materials and contaminants. Without proper pre-treatment, these materials can cause inconsistent feeding and affect downstream process stability.

Harden Machinery's plastic pre-treatment system is designed to shred lightweight plastics, including films and flexible plastics, reducing material size and breaking up tangled bundles. Combined with appropriate screening and separation equipment, the process can help remove contaminants such as stones, metals and food residues.

The result is a more manageable, consistently sized feedstock that supports smoother feeding into the pyrolysis reactor.

Step 2: Oxygen-Limited Pyrolysis — Breaking Down Plastic Polymers

Plastics such as polyethylene (PE) and polypropylene (PP) contain long polymer chains made primarily of hydrocarbons.

In a sealed pyrolysis reactor, suitable pre-treated plastics are heated under oxygen-free or tightly controlled oxygen-limited conditions. At temperatures typically around 400–550°C, depending on the feedstock and process design, the polymer chains break down into smaller molecules, producing hydrocarbon vapours and gases.

Unlike combustion, pyrolysis relies on thermal decomposition rather than burning the plastics in air.

Step 3: Condensation — Recovering Pyrolysis Oil

The vapours produced during pyrolysis are directed into a condensation system, where condensable compounds cool and form liquid products known as pyrolysis oil.

Non-condensable gases may be recovered for use as process fuel, subject to appropriate gas treatment and safety requirements. Solid residues are collected separately for further treatment or disposal.

Depending on its composition and quality, the recovered oil may undergo further refining for potential use as an industrial fuel or chemical feedstock.

Why Is Shredding Important for Plastic Pyrolysis?

Plastic pyrolysis is not simply a matter of heating waste plastics to produce oil. Effective pre-treatment is a key step in preparing suitable feedstock for stable downstream processing.

Proper shredding and separation can help to:

• Break up tangled plastic films and reduce material size.

• Remove some contaminants before they enter the pyrolysis process.

• Improve feedstock consistency and feeding stability.

• Prepare plastic-rich material to meet downstream particle-size requirements.

Harden Machinery: Plastic Pre-treatment Solutions for Chemical Recycling

Harden Machinery Machinery Ltd. specialises in solid waste shredding, screening and pre-treatment solutions.

For plastic recycling and chemical recycling projects, Harden Machinery provides integrated equipment solutions designed to prepare waste plastics before pyrolysis.

By combining shredding and separation technologies, Harden Machinery helps operators improve feedstock preparation and connect the waste handling stage with downstream pyrolysis processes.

From waste plastics to prepared feedstock, Harden Machinery helps make the first step towards resource recovery more efficient and reliable.