Polycyclic Aromatic Hydrocarbon (PAH) Formation from Combustion and Gasification of Tires: Mechanistic understanding and reduction potential

摘要

Solid waste combustion and gasification has a potential for use as an alternative fuel to be used in distributed power applications. Due to the heterogeneity of the fuel it is imperative that a full understanding of the mechanism of degradation is obtained. This will ensure proper combustion and gasification design yielding the highest efficiency with the least emissions. While the major reaction sequences have been studied and identified, there is nearly no understanding of how soot precursors, such as PAH, form and react during the decomposition processes. The waste focused on for this research effort is tires. Experimental work has been carried out to characterize the thermal decomposition of the major constituents of tires and actual tire filings using Thermo-Gravimetric Analysis (TGA) in various atmospheres; 100% N_2, air, and oxygen-lean and rich air. It can be shown that the structure of the material plays a role in the amounts and types of PAHs formed. A quantitative mechanism is developed to describe the evolution of PAH in the different atmospheres during decomposition. The identities and absolute concentrations of 60 major and minor species have been established. In addition, a catalyst has been used not only to mitigate the generation of pollutants, but also to find a suitable catalyst and optimal operation condition for the prevention of air pollutants. These measurements supply information on the identities and levels of hazardous air pollutants, and provide useful data for the development and validation of detailed reaction mechanisms describing their origin and fate.