Polyvinyl chloride cooperates with biomass to assist in directional conversion N and Cl as NH₃ and HCl to prepare clean fuel by low temperature microwave heating

This work proposed an innovative integrated process to produce clean fuel. Waste polyvinyl chloride (PVC) was co-pyrolysis with biomass as a hydrogenation agent to enhance the conversion N of biomass to NH₃ in the gaseous product by microwave heating. This work demonstrated the conditions suitable for the co-pyrolysis of PVC and the biomass (straw and rice husk, respectively) process based on the denitrification and dechlorination effects including indexes of N and Cl removal ratio and NH₃ and HCl production ratio. The mass ratio of PVC to biomass (PVC: biomass), microwave heating power, active carbon (AC), and the pyrolysis temperature turned out to be significant factors for N and Cl removal and PVC: biomass and AC were also positive for converting N and Cl to NH₃ and HCl. The optimum operating conditions were PVC: biomass 1:9, microwave heating power 500 W, active carbon 1.6 g, and heating temperature 300 °C. The mechanism could be primarily related to the volumetric and selective heating advantage of microwave heating, being attributed to producing abundant H radicals from PVC and promoting the hydrogenation reaction of biomass to remove N as NH₃. Moreover, the denitrification and dechlorination effect differences between microwave heating and electric heating were studied to explore the microwave non-thermal heating effect. The amount of the N removal ratio and the NH₃ production ratio by microwave heating was almost 5%–10% higher. The amount of the Cl removal ratio and the HCl production ratio was almost 10% and 7% higher than that by electric heating. The pyrolysis reaction enhancement and the better denitrification and dechlorination effect of microwave heating could be a result of specific microwave non-thermal effects in addition to the thermal effect, containing more uniform heat distribution and selective heating characteristics. The present work may provide a new viewpoint for the clean utilization of biomass and chlorinated plastic waste as a fuel and avoid HCl corrosion when treating the chlorinated plastic waste.