(25b) Characterizing Catalytic Waste Gasification - Effects of Substrate and Catalyst
AIChE Annual Meeting
Sunday, November 13, 2016 - 3:48pm to 4:06pm
The experiments performed examine gasification dynamics for different substrates promoted by different catalysts. It utilizes a high pressure batch scale reactor which allows examining controlled multi-phase catalytic isothermal oxidation of solid and melting substrates in the presence high purity air. The reaction time was varied between 2 and 24 hours and a preliminary overall kinetic model was formulated based on conversion, selectivity, and yield determinations. The studied substrates, Polyethylene and Cellulose, are both long chain organic polymers, and make up a substantial portion of both space and municipal waste composition. Although similar in nature, these substrates exhibit marked differences as it pertains to gasification, and were therefore selected as model substrates. Namely, cellulose contains oxygen as part of its molecular structure, while polyethylene does not. Since the technology investigated is aimed at working to relatively low temperatures (below 350 oC), cellulose remains as a solid particulate at the investigated reaction temperature while polyethylene melts.
Following the reaction phase, both the liquid and solid reaction residues, along with the gaseous products, are collected for characterization and analysis. Gas quantification is performed using a Gas Chromatograph. While thermal characterization (DSC) and Scanning Electron Microscopy (SEM) are used to characterize solid and liquid residuals.
Preliminary results suggest that catalytic gasification provides potential control for the liquid-phase oxidations. Under appropriate conditions, oxidation was found to follow the incomplete oxidation pathway which resulted in significant yields of hydrogen and methane, which are potentially high value products as they can be used for energy recovery.
Comparisons between the gasification rates for the two substrates are drawn. Similarly, comparative studies of different catalysts are also presented. The results are used in conjunction with a kinetic model for the gas-phase to formulate a methodological model for the gasification of solid waste. The results will be presented along with a preliminary extension for a continuous gasification process.