Why is PVC Plastic Not Suitable for Pyrolysis Treatment?

Why is PVC Plastic Not Suitable for Pyrolysis Treatment?

PVC (polyvinyl chloride) plastic poses a series of severe environmental, safety, and technical challenges during pyrolysis, making it a typical plastic category unsuitable for this process. The core reasons are as follows:

1. Releases Toxic Hydrogen Chloride (HCl) Gas

PVC contains approximately 56% chlorine, which is released as large amounts of hydrogen chloride gas during pyrolysis:

This highly corrosive gas severely corrodes furnace bodies, pipelines, and other equipment components, significantly shortening service life and increasing maintenance costs.

If discharged untreated, HCl contributes to acid rain, contaminating soil and water sources and damaging ecosystems.

It also irritates the human respiratory tract, causing acute poisoning such as pulmonary edema, posing major safety risks.

2. Generates Persistent Organic Pollutants (POPs) Like Dioxins

At pyrolysis temperatures between 300–800°C, chlorine reacts readily with organic compounds to form dioxins, extremely toxic substances:

Dioxins are highly carcinogenic and teratogenic, resist degradation in the environment, and bioaccumulate in the food chain, posing long-term threats to ecosystems and human health.

Even with exhaust treatment systems, controlling dioxins within safe limits requires extremely high costs, increasing environmental investment and project risks.

3. Poor-Quality Products That Are Hard to Utilize

Pyrolysis oil from PVC has high chlorine content, making it highly corrosive and unstable, rendering it unsuitable for direct use as fuel oil:

Refining it to meet standards requires additional dechlorination processes, substantially raising production costs.

Pyrolysis residues (carbon black) also contain chlorine, making them difficult to recycle and usually requiring disposal as hazardous waste, further increasing costs and environmental burdens.

4. Extremely High Environmental Compliance Costs

Treating HCl and dioxins demands complex exhaust purification systems (e.g., scrubbers, activated carbon adsorption, catalytic decomposition units), with equipment and operational costs far exceeding those of regular plastic pyrolysis projects:

Even with these investments, projects face strict regulatory scrutiny and the risk of emissions violations, severely reducing economic viability and sustainability.