Plastic Pyrolysis Process

In order to recycle waste plastics in a green and profitable way, Beston has developed plastic waste pyrolysis plant, which refers to converting waste plastic into fuel oil and carbon black through high temperature plastic pyrolysis process.

Plastic Pyrolysis Process
Plastic Pyrolysis Process

Principle: Plastic Pyrolysis Technology

Plastic pyrolysis is the thermal degradation of plastic waste at different temperatures (280–400°C)  in the absence of oxygen, to produced liquid oil. It involves the molecular breakdown of larger plastic molecules into smaller molecules of oil gas and carbon by using heat.

What is Plastic Pyrolysis

Plastic Pyrolysis Process Steps

Plastic pyrolysis is a process that involves the thermal decomposition of plastic waste to produce fuel or other valuable products. Here are the general steps involved in plastic pyrolysis:

1. Plastic pretreatment

  • Shredding: Plastic waste is shredded into smaller pieces to increase the surface area for better heat transfer during the subsequent pyrolysis process.
  • Drying: The shredded plastic is then dried to remove moisture content. Moisture can interfere with the pyrolysis efficiency.

2. Pyrolysis:

The dried and shredded plastic is then fed into a pyrolysis reactor, where it undergoes a thermochemical decomposition process in the absence of oxygen. The plastic is heated to high temperatures, typically ranging from 300 to 800 degrees Celsius, causing it to break down into various gaseous, liquid, and solid products.

3. Condensation:

The gaseous products produced during pyrolysis, such as hydrocarbons and other volatile compounds, are passed through a condensation system. This system cools the gases, causing them to condense into liquid products. The condensed liquids can include pyrolysis oil or bio-oil, which can be further processed for various applications.

4. Dedusting:

After condensation, the remaining gases may still contain fine particulate matter and impurities. A dedusting or filtration system is employed to remove these particles from the gas stream. This step is essential to ensure that the released gases meet environmental standards and to prevent the release of pollutants.

5. Collection:

The final step involves collecting the end products of the pyrolysis process. These products may include:

  • Pyrolysis oil or bio-oil: A liquid fuel that can be used for heating or as a feedstock for producing chemicals.
  • Gases: Depending on the process, gases such as syngas may be collected and utilized for energy production.
  • Char or solid residue: The remaining solid material after pyrolysis, which may have applications as a carbon source or for other uses.

Plastic Waste Pyrolysis Process

Raw Materials: Waste Plastic Types

The success of the plastic pyrolysis process hinges on the careful selection of raw materials – the waste plastic. Different types of plastics have distinct chemical compositions, affecting the efficiency and output of the pyrolysis process. The following introduces several common waste plastics suitable for pyrolysis and two types that are not suitable for pyrolysis.

PE, PP, PS, ABS – Recommended to produce pyrolysis oil

  • Recommended for their high oil yield during decomposition.

PVC – Not suitable for pyrolysis

  • Contains chlorine, and during decomposition, it releases hydrogen chloride, which can corrode pipes and equipment.
  • Combustion of decomposed PVC can release carcinogenic dioxins.

PET – Not suitable for pyrolysis

  • Does not yield oil during decomposition.
  • Releases oxygen during the decomposition process, posing a safety hazard.

Select Plastic for Pyrolysis

Results: Plastic Pyrolysis Oil and Different Oil Yield

The primary product of plastic pyrolysis plant is liquid fuel, often in the form of pyrolysis oil, which can be used as an alternative to traditional fossil fuels or further refined to diesel or gasoline.

Plastic Pyrolysis Oil and Oil Yield

Involved Device: Plastic Pyrolysis Plant

Executing the plastic pyrolysis process requires a specialized apparatus – the plastic pyrolysis plant. This plant typically encompasses a feed system, a pyrolysis reactor, a combustor, a condensation system, a dedusting system, and units for the collection of final products. Beston Group has designed three types of plastic pyrolysis equipment: skid-mounted-type, batch-type, and continuous-type. These machines are engineered to withstand high temperatures and maintain an oxygen-free environment, ensuring the success of the pyrolysis process.

BLJ-3 Model Batch Pyrolysis Plant

BLJ-6&10 Model Batch Pyrolysis Plant

Skid-mounted type:
  • Model: BLJ-3;
  • Capacity: 1-3t/d;
  • Compact design and small floor space;
  • Easy to transport, install and migrate;
  • Low labor cost (1-2 workers enough).
Batch Type:
  • Model: BLJ-6/10/16;
  • Capacity: 4-6t/d; 8-10t/d; 12-16t/d;
  • Small land occupied;
  • Short ROI cycle;
  • No special requirements for raw materials.
Semi-continuous type:
  • Model: BLL-16;
  • Capacity: 8t/d (only for rubber powder);
  • Automatic feeding and discharging;
  • Added water-cooled discharge system;
  • High Oil Yield than batch type.
Continuous Type:
  • Model: BLL-30;
  • Capacity: 4-6t/d; 8-10t/d; 12-16t/d;
  • Automatic feeding and discharging;
  • Continuous work for 3-6 days;
  • Intelligent PL control& IOT monitoring.

Several Influence Factors

Several factors influence the efficiency and outcome of the plastic pyrolysis process. These include temperature control within the reactor, the residence time of the plastic in the reactor, the type of catalyst used (if any), and the design of the Plastic Pyrolysis Plant. Proper optimization of these factors is essential for maximizing the yield of valuable end products and minimizing environmental impact.

Tire material properties

The chemical composition, additives, moisture content, and size of the tires can result in different types and properties of pyrolysis products.

Residence time

The residence time affects the extent of the pyrolysis reactions. Balancing residence time is important – too short may result in incomplete conversion, while too long may lead to the formation of undesirable by-products.

Temperature control

The temperature within the reactor plays a crucial role in determining the efficiency of plastic pyrolysis. Generally, higher temperatures facilitate faster reactions, but there’s a balance because extremely high temperatures may lead to undesired side reactions or energy inefficiencies. The optimal temperature for plastic pyrolysis is 300-400℃.

Pyrolysis reactor design

The reactor design should facilitate efficient heat transfer, mixing of the feedstock, and collection of products. Factors such as the type of reactor (fixed bed, fluidized bed, etc.) and the configuration of heating elements are important.

Catalysts

Some processes use catalysts to enhance the pyrolysis reactions. Catalysts can increase the yield of desired products, reduce the operating temperature, and influence the selectivity of the reaction pathways.

Optimizing these factors can maximize the recovery of valuable resources while minimizing the environmental impact, promoting a circular economy for plastics.

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