Swelling effect on the microwave pyrolysis of waste car tires

Swelling can change the mechanical properties and structural characteristics of waste car tires (WCTs), so that the rubber molecular chain stretching, porousness becomes larger, which is conducive to improving the mass transfer effect and pyrolysis efficiency. Based on the modification characteristics of swelling, the swelling effects of different swelling agents, temperatures, tire types, and particle sizes were investigated. The results showed that coal tar can effectively swell WCTs, and the higher temperature and smaller particle size, contribute to better swelling. When the temperature is 40°C and the particle size is 1 × 1 cm, the equilibrium mass absorption rate of WCTs can reach up to 1.67 g/g, and the swelling effect is the best. In addition, combined with the unique microwave advantages, the swelling rate was further accelerated, WCTs reached swelling saturation 58.5 h earlier than in natural swelling. Moreover, the swelling effect on the three-phase product output of microwave pyrolysis of WCTs was investigated. After swelling treatment, we achieved the deeper pyrolysis degree of WCTs and the yield of pyrolysis oil was relatively increased by about 39.2%, while the yield of both gases and solids decreased. © 2023 Wiley Periodicals LLC.