Mechanical processes for recycling of End-of-Life Tyres

The extensive growth of End-of-Life Tyres (ELTs) has raised significant environmental concerns, making ELTs recycling a crucial strategy in mitigating their impact on the environment. ELTs recycling process begins with complex mechanical processes aimed at size reduction of rubber material and the rubber production at various sizes. Mechanical recycling processes not only generate a variety of useful products for most applications but also serve as the foundation for subsequent chemical and thermal processes in ELTs recycling. This paper aims to review the status of research and development related to mechanical processes for recycling ELTs. It provides a comprehensive overview of mechanical processes and techniques used in ELTs recycling, examining essential input variables, performance indicators and their relationships. To produce powders smaller than 0.8 mm, a mechanical recycling system typically involves multiple grinding stages and various particle separation methods. In most shredding processes, the produced particle sizes range from 100 mm to 200 mm. To achieve better shredding performance, an optimal configuration includes multiple rotational shafts, fewer than three cutting edges, and operation at temperatures below −70 °C. Grinding processes can generate granulates smaller than 2 mm, with cryogenic and wet grinding techniques capable of producing particle sizes <0.1 mm. Cryogenic grinding achieves the smallest expected particle size of 0.075 mm with a distribution below 0.1 mm. A future work could focus on developing a thorough relationship between multiple input and output parameters for further design and optimization of the mechanical recycling of ELTs. By integrating advanced engineering knowledge with a good combination of latest technology, an optimum ELTs recycling plan is developed to efficiently extract the reusable materials of ELTs and convert the additional material into reusable forms like energy, hydrogen etc.