Can waste tires and waste plastics be mixed and pyrolyzed in one furnace?

In the field of waste resource utilization, pyrolysis technology has gained increasing favor among investors due to its efficiency and environmental friendliness. However, many clients, when dealing with waste materials, often face a common question: they have both waste tire raw materials and waste plastic raw materials at hand. To save time and improve processing efficiency, they naturally wonder: "Since both are waste materials processed through pyrolysis, can they be combined and fed into the same furnace for one-time treatment?"

Waste tire/plastic pyrolysis process

DOING Company clearly states: The answer is "No," waste tires and waste plastics cannot be mixed and pyrolyzed in the same furnace.

Today, DOING Company, with its years of industry experience and professional expertise, will provide an in-depth analysis of why these two raw materials—waste tires and waste plastics—must be "treated separately" and the severe consequences that mixed pyrolysis can entail, helping you gain a comprehensive understanding of this issue.

I. Technical Core Analysis — Why Can't They Be Mixed?

Although waste tires and waste plastics are both high-molecular organic compounds and can be converted into valuable energy through pyrolysis technology, their chemical structures, physical properties, and pyrolysis behaviors exhibit fundamental differences. It is precisely these differences that dictate why they cannot be mixed and pyrolyzed in the same furnace. Here is a detailed technical analysis:

1. Significant Differences in Physical Form and Heat Transfer

Waste Tires: Waste tires are primarily composed of natural rubber and synthetic rubber, containing large amounts of carbon black, steel wire, and other fillers. They are characterized by high density and slow heat conductivity. Inside the pyrolysis reactor, tire pieces require the tumbling action of the furnace and sufficient friction to effectively absorb heat. The pyrolysis process is relatively slow, and the resulting oil generally has a higher proportion of heavy components, alongside carbon black and steel wire residues.

Waste tire pretreatment

Waste Plastics: Waste plastics, such as PE, PP, especially plastic films, have a low specific gravity and fast pyrolysis speed. Upon heating, they rapidly melt, forming a highly viscous liquid.

Waste plastic material

Risks of Mixing: When lightweight waste plastics encounter heavy waste tire pieces, due to density differences, plastic fragments will float on top of or entangle with the tire pieces. The heat within the furnace is first rapidly absorbed by the lightweight plastics, causing them to melt. This leads to localized overheating in the reactor, even resulting in 'scorching' or burning, while the tire fragments at the bottom have not yet been sufficiently heated. This uneven heating will not only significantly reduce the overall oil yield but also lead to incomplete pyrolysis and low-quality products because the tires fail to reach the temperature and time required for complete decomposition.

2. Conflicts in Chemical Reactions and Raw Material Characteristics

Waste Tires: Waste tires belong to cross-linked rubber. Their molecular structure requires a stable and sustained high temperature to gradually break down. The pyrolysis process is relatively gentle, with oil and gas as the main products, and carbon black and steel wire as the final residues.

Final products of waste tire pyrolysis

Waste Plastics: During pyrolysis, waste plastics first undergo a rapid melting process, becoming extremely viscous.

Risks of Mixing: Imagine a scenario where the viscous plastic melt coats the surface of waste tire fragments. It acts like a thick 'insulating layer,' not only severely impeding heat transfer into the tires but also blocking the microporous channels through which oil and gas are released from tire pyrolysis. This mixture will form large clumps of agglomerated material or coke blocks inside the reactor. This not only prevents the pyrolysis reaction from proceeding effectively but can also directly block the reactor's gas outlet, cause pressure buildup in the equipment, and even lead to severe coking inside the reactor, resulting in irreversible damage to the pyrolysis machine.

3. Challenges in Discharge and Slagging

Waste Tires: The solid residues after waste tire pyrolysis are primarily carbon black and steel wire. These materials have a relatively loose structure and can typically be smoothly discharged through the pyrolysis machine's automatic slagging system.

\DOING waste pyrolysis machine discharge systems

Waste Plastics: If not completely pyrolyzed, pure plastics can also form coke blocks or waxy substances.

Risks of Mixing: However, when the carbon black residues from waste tires are mixed with the viscous melt of waste plastics, the situation becomes entirely different. They will form hard, highly viscous blocks resembling 'asphalt mixed with gravel' . These blocks will not only firmly adhere to the inner wall of the pyrolysis reactor, making cleaning extremely difficult, but will also clog the slag discharge port, rendering the slagging system ineffective. This means the equipment cannot operate continuously, and each cleaning will consume significant labor, material resources, and time, severely impacting production efficiency and economic benefits.

II. List of Specific "Troubles"

Beyond the technical issues mentioned above, mixed pyrolysis directly impacts your production and profitability:

Oil Quality Compromise: The oil produced from mixed pyrolysis is neither pure tire oil nor qualified plastic oil. Instead, it's an unstable 'hodgepodge' of inconsistent quality. It often has a high acid value, numerous impurities, and unstable sulfur and wax content. This leads to sharply increased post-processing costs and makes it difficult to meet market demands for the oil products, significantly reducing the commercial value and sales profit of the finished oil.

Common tire pyrolysis oil and plastic pyrolysis oil

Pipe Clogging Risk: Waxy components are easily produced during plastic pyrolysis. These waxy substances tend to condense and solidify in the condenser pipelines when cooled. Once mixed with ash from tires or pyrolyzed carbon black, they form even more stubborn, sticky blockages. This can severely clog condensers and other pipelines, not only affecting production efficiency but also potentially causing pressure buildup in the equipment, leading to safety hazards.

Shortened Equipment Lifespan: Localized overheating and uneven heating resulting from mixed pyrolysis accelerate the aging and fatigue of the reactor's main body material. Additionally, acidic gases that might be produced during plastic pyrolysis can accelerate reactor corrosion, severely shortening the lifespan of the pyrolysis machine.

III. DOING's Recommended Solutions

For the sake of your production safety, product quality, and the long-term stable operation of your pyrolysis machine, DOING Company has the following recommendations:

Batch Processing: DOING Company advises clients to adopt a batch processing approach: pyrolyze waste tires first, and after the reactor has been cleaned, then process waste plastics. While this might require a bit more time, it fundamentally ensures your production safety, the purity of your pyrolysis oil, and the long-term stable operation of your pyrolysis machine. In the long run, it is the most economical and efficient choice.

Professional Equipment Support: As a professional manufacturer of waste tire and plastic pyrolysis machine, DOING Company can recommend and customize specially designed pyrolysis machine types based on your specific raw materials (whether whole tires, tire rubber powder, or various PP/PE plastics). For example, for highly viscous plastics, we have special coke removal designs to ensure each raw material can be processed efficiently and safely under optimal conditions.

DOING waste plastic pyrolysis machine wax removal system

In conclusion, for the sake of your production safety, the quality of your finished oil, and the long-term stable operation of your pyrolysis machine, it is imperative to pyrolyze waste tires and waste plastics separately.

DOING Company is always committed to providing clients with the most professional and reliable pyrolysis solutions. If you have any questions regarding raw material classification, equipment selection, or pyrolysis processes, please feel free to contact DOING's technical team. We will provide you with a one-on-one raw material analysis report and customized processing solutions to help you achieve the maximum value from waste resource utilization!