Modelling of a surface-absorption fixed-bed solar-driven reactor for waste plastics pyrolysis

The use of concentrated solar energy to drive high-temperature chemical reactions can markedly reduce carbon emissions and enable the fixation of solar energy. In this study, a fixed-bed solar-driven reactor employing a SiC tube packed with Al₂O₃ porous media is proposed for the solar pyrolysis of waste plastics. In a solar simulator setup, a multi-physics coupled solar-heat-flow-reaction model for continuous feeding is developed, incorporating detailed thermodynamic and kinetic models for ex-situ pyrolysis. Thermal protection using a quartz glass tube and stainless-steel foil raises reactor temperature by about 186 °C. Reducing pore size increases oil yield from 38.2 wt% to 46.2 wt%, while porosity has little effect. Higher solar power raises gas yield but oil yield peaks at 44.81 wt% at a simulator power input of 2.2 kW; solar-to-fuel efficiency keeps increasing. Higher feeding rate slightly improves oil yield (32.22 wt% to 41.42 wt%) and raises solar-to-fuel efficiency to 6.59%. Scaling up the system by a factor of 50 in feeding rate, with its structural dimensions enlarged proportionally, remains feasible and substantially enhances the solar-to-fuel efficiency. This study provides new physical models for the application of solar energy, paving the way for the future development of efficient and scalable solar-driven waste-to-fuel systems.