Flame soot generated from

Validation of the methodology used for components that could not be detected in extracts of particle samples was obtained by extraction of surrogate samples. The surrogate sample for PAHs was soot generated from an air-starved methane flame. The positive results obtained from this soot sample have been reported elsewhere (13). The surrogate sample for dioxins was an incinerator ash obtained from Dow Chemical Company. Results obtained from analysis of extracts of this ash sample were 50% of the published values for the tetra-, hexa-, hepta- and octachloro- isomers (14). This agreement substantiated the validity of the analytical protocol used to screen the effluent samples for dioxin compounds. 

Figure 1. The photoacoustic spectrum of airborne soot generated from a propane-Ot flame using a tunable dye laser light source. This figure is adapted from Figure...

The ratio of the light extinction coefficient of flame-generated smoke to the mass concentration of soot in the smoke is approximately constant and equal to os = 8.7 1.1 m2/g.64 The implication of this nearly universal value is that the soot yield, i.e., the mass of soot generated per mass unit of fuel burnt, can be estimated from light extinction measurements as follows ... 

Electrodeposition Tests. White oil solutions of the above dis-persants were tested for charging of carbon black particles generated from the soot of a toluene flame. A hundred volts... 

As die composition of diesel particulates (e.g. fi action of adsorbed hydrocarbons) depends upon many motor characteristics as engine load, speed, and various temperatures, it is difficult to collect batches of soot with constant properties. Tlierefore, we choose to work with printex-U (a flame soot supplied by Degussa AG) as a model soot. Properties of tliis model soot and diesel particulates collected from a one cylinder direct injected diesel engine (Yanmar L90E diesel generator set) are listed in Table 1. 

Mere destruction of the original hazardous material is not, however, an adequate measure of the performance of an incinerator. Products of incomplete combustion can be as toxic as, or even more toxic than, the materials from which they evolve. Indeed, highly mutagenic PAHs are readily generated along with soot in fuel-rich regions of most hydrocarbon flames. Formation of dioxins in the combustion of chlorinated hydrocarbons has also been reported. We need to understand the entire sequence of reactions involved in incineration in order to assess the effectiveness and risks of hazardous waste incineration. 

One of the earliest detailed diagnostic efforts on sooting of diffusion flames was that of Wagner et al. [86-88], who made laser scattering and extinction measurements, profile determinations of velocity by LDV, and temperature measurements by thermocouples on a Wolfhard-Parker burner using ethene as the fuel. Their results show quite clearly that soot particles are generated near the reaction zone and are convected farther toward the center of the fuel stream as they travel up the flame. The particle number densities and generation rates decline with distance from the flame zone. The soot formation rate appeared to... 

EXHAUST FLOW. The exhaust flow system has perhaps the least stringent requirements of all the parts of the FID. Yet even here a variety of possible problems have been uncovered. It is necessary not only to get the gases out of the detector, but also the heat generated, and in the case of large samples or heavy column loadings, soot and silica. The soot is a problem if particles of it occasionally fall back into the flame,giving spikes. The bleed from a silicon-coated column burns to silica which can... 

Dirty Flames. At this point one could well ask so what happens in real combustors which are turbulent, soot and particle laden and are highly luminous By the end of this morning s session you should be convinced that CARS can be applied to these systems. I don t want to steal all of Alan Eckbreth s slides so I will show only two more. Figure 13 shows the BOXCARS spectrum of N- with a computer fit to a temperature of 2000°K in a laminar sooting propane diffusion flame (12). Figure 14 shows the vertical temperature profile for this same flame system. It should be pointed out that care must be taken under these conditions to account for the laser interaction with carbon in the flame which can generate laser induced Swan Band emission from C2-... 

The oxidation of soot in fuel-rich premixed flames proceeds through hydroxyl attack, with one atom of carbon removed by each OH radical hitting the surface of the soot. The absolute level and composition dependence of the disappearance rate of soot show that OH is the important species. The oxidation was followed experimentally by laser light scattering from soot particles generated in one flame and passed directly into the gas supply of a larger hydrogen/air flame controlled at 1700-2200 K. 

Kinetic studies in flames require a well defined environment, and particular attention was given to the design of the birnier (Figure 1). Soot was generated in a primary burner following Fenimore and Jones (3), and the soot-laden gases were cooled and injected into the base of a secondary burner. Both primary and secondary burners were constructed from spaced hypodermic tubing, and the tubes for the observa-... 

The stmcture of products from sooting benzene/oxygen flames has also been studied in this context. It turned out that the sooty film precipitating on the cool parts of the apparatus consists of tubular and onion-like carbon species. Still the product obtained is rather inhomogeneous, so for the time being, combustion methods are no effective means of generating carbon onions. 

Butler and Crossley (102) studied the reactivity of PAH, naturally present on soot particles, generated in a flame from an eth-ylene-air burner, in a reaction chamber with ambient air containing 5-10 ppm of sulfur dioxide or a mixture of nitrogen oxides. While exposure of up to three months to SO did not yield any significant loss of PAH, degradation by NO occurred readily and resulted in half lives varying between 7 and 30 days (for benzo(a)-pyrene and phenanthrene respectively),in correspondence with the order of reactivity for electrophilic substitution of aromatic systems. 

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