Pyrolysis oil is a product obtained from the pyrolysis of waste plastics, rubber tires, or oil sludge under oxygen-free conditions. It serves as an alternative to conventional fuels in industrial heating systems and can also be upgraded into valuable products like non-standard diesel or naphtha. So, how can we assess the quality of pyrolysis oil? And why is this evaluation important? Read on for more information.
Key Indicators of Pyrolysis Oil Quality
To evaluate the quality of pyrolysis oil, multiple indicators must be considered. The following section outlines these key indicators based on the oil’s physical properties and chemical characteristics.
Physical Properties
Chemical Indicators
The physical characteristics of pyrolysis oil offer a straightforward way to assess its quality. Many of these properties can be observed or measured directly, providing quick insights into the oil’s usability and stability. Key aspects include:
Appearance and Color
Pyrolysis oil with a clear, amber to brown color generally indicates effective separation of oil from impurities during production. Such clarity suggests fewer suspended solids like soot or char particles. Conversely, oil that appears cloudy, dark brown, or black often contains contaminants such as uncondensed tars, residual char, or water droplets. These impurities can negatively affect combustion efficiency and downstream processing.
Viscosity
Viscosity measures the oil’s resistance to flow. If pyrolysis oil is too viscous, it will not atomize properly in burners, leading to poor combustion and increased deposits. Maintaining a balanced viscosity ensures efficient fuel spray and consistent flame characteristics.
Density
Density reflects the composition of the oil, including the ratio of light to heavy hydrocarbons. Typical pyrolysis oil density ranges from 0.80 to 0.95 g/cm³. Higher density often indicates a greater proportion of heavy fractions or residual solids, which may require additional refining or blending to achieve a smooth use.
Water Content
Water is a critical contaminant in pyrolysis oil. Excess moisture lowers the oil’s heating value and may cause corrosion in combustion chambers and storage tanks. It also affects ignition and flame stability. The ideal water content for pyrolysis oil is below 0.05%, which can be monitored using Karl Fischer titration or similar precise laboratory methods.
Beyond physical appearance, chemical indicators help reveal the internal composition and potential contaminants in the oil. These factors play a critical role in determining combustion behavior, emissions, and processing suitability. The following indicators are particularly important:
Odor
A typical pyrolysis oil has a mild hydrocarbon-like smell, resembling light fuel oil. However, a strong, pungent, or unpleasant odor usually signals the presence of sulfur compounds or chlorinated hydrocarbons. These substances not only impact air quality when burned but can also cause corrosion and damage in engines or industrial boilers.
Ash and Impurities
Ash content and solid impurities result from incomplete feedstock conversion or inadequate filtration. High ash levels can clog fuel nozzles and damage equipment. Removing solids through filtration or centrifugation before use is necessary to protect combustion systems and maintain performance.
Factors Influencing Oil Quality
Several variables in the pyrolysis process directly impact the quality of the resulting oil. Understanding these factors is essential for producing stable, clean, and high-value pyrolysis oil. Key influences include:
Type of Feedstock
The composition of the input material determines the chemical makeup of the oil. Clean polyethylene (PE) or polypropylene (PP) plastic often yields lighter, low-sulfur oil. In contrast, rubber tires contain more sulfur and carbon black, leading to heavier oil with higher impurity levels. Mixed or contaminated feedstock increases variability and reduces predictability in oil quality.
Pyrolysis Temperature
Pyrolysis temperature plays a critical role in determining the quality of the oil produced. For most feedstocks like waste tires and plastics, temperatures between 350–450°C are commonly used to maximize oil yield. The optimal range varies depending on the material’s composition and desired product characteristics.
Residence Time
The residence time in the reactor depends on the feedstock. For materials like waste tires and plastics, an optimal duration of 8–10 hours ensures sufficient thermal cracking. Longer exposure may lead to secondary reactions, degrading valuable oil fractions and increasing the formation of gas or solid residues.
Condensation and Cooling System
Efficient condensation systems, especially multi-stage or zoned cooling, can better separate light and heavy oil fractions. This helps reduce tar carryover and ensures a cleaner, more uniform product.
Importance of Pyrolysis Oil Quality
Operational Efficiency and Equipment Protection
High-quality pyrolysis oil ensures stable and complete combustion, which reduces carbon deposits, prevents nozzle blockage, and minimizes wear on burners and piping systems. In contrast, oil with high water content, ash, or heavy impurities can cause incomplete combustion, clogging, or corrosion, leading to higher maintenance costs and operational downtime.
Upgrading Potential and Economic Value
Cleaner pyrolysis oil can be further refined into non-standard diesel, naphtha, or other petrochemical intermediates through distillation or catalytic upgrading. These refined products have higher market value and are in demand across various industries. Poor-quality oil, on the other hand, limits such downstream processing opportunities.
Compliance and Market Acceptance
Low-sulfur, low-contaminant oils made from pyrolysis plant are more likely to meet emission regulations and industrial fuel standards. Ensuring consistent oil quality enhances buyer confidence and facilitates entry into regulated or high-value markets.
Producing ISCC-Certified Oil with Beston Pyrolysis Equipment
Beston Group pyrolysis machines are capable of producing oil that meets ISCC (International Sustainability and Carbon Certification) standards. ISCC-certified pyrolysis oil signifies compliance with global sustainability, traceability, and greenhouse gas reduction criteria. It enhances the oil’s credibility in the international market, making it more attractive for eco-conscious industries and fuel refiners.
To improve the quality and value of the oil, Beston pyrolysis plant integrate several key systems:
Condensation System
A condenser efficiently separates light and heavy oil fractions. It reduces tar content, improves oil clarity, and increases the yield of usable light oil.
Plastic Catalytic System
Catalysts accelerate the cracking of long-chain polymers, reduce the formation of undesirable compounds (wax), and promote the generation of lighter, cleaner oil with better combustion properties.
Distillation System
By refining raw pyrolysis oil through a distillation unit, higher-value end products such as non-standard diesel and naphtha can be extracted. These fractions have improved stability, higher calorific value, and broader application in transportation and chemical industries.
Toward Cleaner and Certified Pyrolysis Oil
In summary, assessing and improving pyrolysis oil quality is essential for safe application, economic value, and environmental compliance. With ongoing advancements in pyrolysis technology and quality control systems, producers are achieving cleaner, more consistent outputs. This progress is paving the way for pyrolysis oil to become a key contributor to the circular economy and the global shift toward sustainable fuels.
