(695c) Coupling Effects of Mass Transfer and Chemical Kinetics during the Co-Pyrolysis of Cellulose and High Density Polyethylene

The increasing amount of municipal solid waste (MSW) causes growing environmental concern for the humanity. Growing global population needs to secure food, energy and water resources, and with decreasing amount of available land, landfills of the waste do not constitute a long-term solution. Biomass and plastics are two of the most dominant components of MSW, and a method that can concurrently convert both waste streams into energy or useful products will be beneficial for humanity. Pyrolysis is one of the simplest ways to convert waste into high-value products. When biomass is pyrolyzed alone, however, it forms pyrolysis oil with high oxygen content, which causes low heating value, thermal instability and corrosiveness. Plastic wastes, which are rich in hydrogen and low in oxygen, could be helpful for enhancing the quality of pyrolytic oil. Many studies have shown that co-pyrolysis of biomass and plastics provides oil with higher yields and caloric value than the one produced from biomass pyrolysis alone. Despite this promise, mixed results regarding their interactions are reported in the literature, and the fundamental interactions between biomass and plastics during co-pyrolysis are still not well understood. As a result, there is a need to unravel the interactions between biomass and plastics at the molecular level. In our work, the coupling effects of the mass transfer and chemical kinetics during cellulose/plastics co-pyrolysis is studied to explain the contradictory results in the literature. An experimental apparatus was constructed to allow fast pyrolysis of cellulose, high density polyethylene (HDPE), and their mixtures. The samples with different mixing patterns but same compositions were reacted. The differences of the product yields were observed, suggesting a competition between the intraphase diffusion and interphase diffusion of the biomass-derived molecules.