OCR Text |
Show - 3 - Introduction Halogenated hydrocarbons constitute a major fraction of the global hazardous-waste stream. In the U.S. alone, it is estimated that over 20% of the wastes contain chlorinated hydrocarbons [1]. Incineration is an attractive technique for the detoxification of these wastes. Despite widespread use of combustion as a means for disposal, the limitations of incineration are not well understood. To elucidate these limitations, various studies have focused on parameters such as poor atomization, flame quenching by cold surfaces, poor mixing, incinerator residence times, fuel structure, etc. similar to studies which attempt to minimize emissions from conventional hydrocarbon-fired systems (e.g., [2-12]). Nevertheless, studies indicate that simple premixed flames are capable of destroying typical halogenated compounds to a degree which is not routinely attainable in practical, state-of-the-art, incinerators without the use of post-flame processes, such as afterburners [11,12]. This seems to indicate that the essential features of halogenated hydrocarbon flames which lead to this behavior have not been addressed. Observations on the macroscopic structure of chlorinated hydrocarbon flames presented here may shed light on some of the underlying phenomena which control emissions from the incineration of halogenated hydrocarbons. Mixtures of chlorinated C2 - hydrocarbons, ethylene, hydrogen, and chlorine are reacted with mixtures of oxygen and nitrogen in a Bunsen burner - type premixed flame. The level of oxygen is varied to examine the effect of oxygen enrichment. Under certain conditions, these fuels exhibited a peculiar double-flame structure. The observed behavior of these double flames may have profound implications to incineration emissions as well as incinerator operation. Two-Stage Premixed Flames Premixed trichloroethylene flames are known to exhibit two consecutive reaction zones (two-stage flames) [13]. These two-stage flames have been interpreted to consist of an initial reaction lone in which the carbon of the trichloroethylene is first oxidized to CO followed by a delayed second stage reaction zone in which the CO is oxidized to C02 [14]. The second flame is essential not only for the bum-out of CO but also paramount to the effective destruction of remaining chlorohydrocarbons as |