| Summary: | 博士 === 國立臺灣大學 === 環境工程學研究所 === 93 === Combustion has long been a common alternative for the ultimate disposal of solid and hazardous wastes. In Taiwan, there are 21 regional incinerators developed to manage more than 90% of municipal solid wastes (MSWs). In addition, there are more than four thousands small size incinerators in commercial and industrial sectors for disposal of various industrial wastes and organic solvent. Unfortunately, the dioxin-like compounds emitted in flue gas and present in the solid residues generated after combustion process have become a very sensitive environmental problem.
Owing to catalytic destruction of chlorinated compounds is one of the key methods in reducing pollutant emissions. Therefore, the aims of this project were focus on the development of novel catalyst, furthermore, for the purpose of utilizing waste materials to suppress chlorinated compounds formation. If feasible, this would achieve waste reuse and enhance combustion efficiency in general, and reduce dioxin emission in particular. Consequently, this study was undertaken to evaluate the performance of the regenerated iron oxide for oxidizing carbon monoxide and suppressing PCDD/F formation in a pilot-scale incinerator.
Ferric iron sludge is commonly generated in metal removal facilities, after the preparation of dewatered, heated (800 oC for 4 hrs), and ground into smaller particles. The regenerated ferric oxide particles were then used as the oxidation catalyst to destroy CO formation during the combustion of three chlorinated solvents and to suppress dioxin formation in flue gas in a real waste solvent.
In the presence of catalyst, the combustion efficiency (ratio of CO2 to the sum of CO2 and CO) for chlorobenzene was more than 98% at 850 oC in a pilot scale incinerator. The destruction and removal efficiencies of chlorobenzene, 2,4-dichlorophenol and trichlorofluoroethane were more than six nines. In the absence of catalysts, the flue gas emission from a real waste could not meet the regulatory dioxin standard of 0.1 ng-TEQ/Nm3 even with the powdered activated carbon injection. The use of catalyst at either 100 or 300 g/hr, however, was able to meet the emission standard.
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