Investigation on the interaction mechanism during co-pyrolysis of waste tire and coal for resource recovery and fossil carbon reduction

The synergistic thermal conversion of waste tire and coal is an effective approach to achieve the resource recovery of waste tire and the reduction and substitution of coal. However, the complexity of co-pyrolysis system, especially different rubbers in waste tire, hinders the understanding of pyrolysis mechanism. Therefore, this work employed an infrared-heated fixed-bed reactor to investigate the interaction behaviors of different rubbers with coal, and synergistic effects during co-pyrolysis were revealed through analysis of product yields, tar compositions and char properties. Results showed that more tar and less char and water were produced in co-pyrolysis between coal and different rubbers than individual coal pyrolysis. Besides, tar formation was easily affected by softening and melting of rubber during co-pyrolysis. More light tar was generated and its formation was promoted. The distribution of tar components presented lower content of phenols and long-chain aliphatic hydrocarbons, but the contents of alicyclic hydrocarbon and mono-ring aromatic hydrocarbon were boosted during co-pyrolysis in comparison with individual coal pyrolysis. In addition, obvious coating phenomenon over co-pyrolysis char varied with the reactivity of rubber, and the interactions between volatiles released from coal and waste tire pyrolysis were affected by coating phenomenon, and the inorganic components contained in coal or waste tire contributed to the enhancement of interaction of waste tire with coal. The possible reaction route between coal and waste tire was proposed, which will provide a basis for resource utilization of waste tire and coal.