Materials and Products of Pyrolysis
Overview of input materials and resulting products from the pyrolysis process
Input Materials
End-of-life tyres are a durable and often problematic waste stream, but they can be fully recovered through pyrolysis. Before entering the reactor, they must be mechanically shredded into smaller fractions to ensure uniform heating and efficient decomposition. The process produces pyrolysis oil (equal in quality and purity to oil from plastics, but darker and with a stronger odour), syngas, carbon black, and steel, which is directly recyclable in the metallurgical industry.
Mixed or contaminated plastics that cannot be mechanically recycled are ideal feedstock for pyrolysis. They must first be shredded into smaller pieces, improving heat transfer and conversion efficiency. The resulting oil has the same quality as tyre-derived oil, but it is lighter in colour and almost odourless. In addition to oil, pyrolysis of plastics provides syngas that powers the unit and only minimal solid residues.
RDF is produced from selected high-calorific fractions of municipal waste (such as textiles, paper, and plastics). As with tyres and plastics, shredding is required to prepare the material for the reactor. Pyrolysis of RDF generates oil and syngas, reducing landfill volumes while replacing fossil fuels.
Products of Pyrolysis
Tyre-derived pyrolysis oil is chemically similar to plastic-derived oil and can be used in industrial boilers, marine fuels, or chemical feedstock. Its darker colour and odour come from higher aromatic and sulphur compounds, but desulphurisation makes it suitable for higher-value petrochemical uses.
Plastic-derived oil has the same properties and applications as tyre-derived oil but is lighter in colour and nearly odourless. Its lower sulphur content makes refining easier, and it is particularly suitable as a petrochemical feedstock for producing fuels and chemicals.
Syngas is a combustible mixture of hydrogen, methane, and carbon monoxide. Its primary role is to fuel the unit itself, making the process energy self-sufficient. Any surplus syngas can be used in cogeneration units to produce electricity and heat, increasing the economic value of the system. The exact composition depends on the feedstock and operating conditions, so it is always purified before use.
Carbon black is primarily produced from tyre feedstock and is a valuable raw material for the rubber and plastics industries, as a reinforcing filler and pigment. Recovered carbon black can replace virgin material made from fossil resources after further treatment, contributing to both emission reduction and resource conservation.
Typical Yields from Pyrolysis of 1 Ton of Material
During the processing of one ton of input material in a pyrolysis unit, approximately 40–45% of pyrolysis oil, about 35% of carbon black, around 20% of syngas, and in the case of tire processing an additional 5% of steel are produced. These outputs may vary slightly depending on the composition of the feedstock and operating conditions, but the given values represent the typical distribution of products from the pyrolysis process.