(303c) Reaction Engineering Routes to Waste Gasification for Sustainable Living Environments

Concern over “green,” or environmentally friendly, technologies has risen considerably over the past decade. Thus, over the past 50 years, metropolitan areas have realized a need for waste disposal alternatives as landfills approach capacity and take up valuable land space. Although newer technology has made incinerators more efficient, there is an increasing interest in formulating more ‘green’ gasification options as alternatives to incinerators.

Gasification converts organic and carbonaceous materials into a combination of gaseous products known as “syngas,” or synthetic gas. This research focuses on advancing the current knowledge of a catalytic gasification process as a potential in-situ resource utilization and waste management system. With significance in a variety of engineering applications, this research is of particular relevance towards municipal waste management and as in-situ resource utilization alternative for advancing space exploration.

The catalytic gasification reaction mechanism evolves through a multi-phase reaction mechanism. The process is initiated by a liquid phase oxidation reactions of long chain polymers. The liquid phase oxidation reactions produce carbon monoxide, carbon dioxide, and water. Current long chain polymers being studied in the catalytic gasification mechanism are focused on cellulose and polyethylene as model substrates. The oxidation reactions are complemented by two gas phase reactions: the Water Gas Shift and the Sabatier reaction, the main stages in the pathway of producing hydrogen and methane.

Gasification experiments 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 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.

Analysis of the liquid and solid reaction residues, along with the gaseous products, enabled the characterization of the gasification kinetic pathway. 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.

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.

The results will be presented along with a preliminary extension for a continuous gasification process, which clearly illustrate the potential of catalytic gasification as a sustainable waste management alternative.