Combustion generation

Pollutant Formation and Control in Flames Key combustion-generated air pollutants include nitrogen oxides (NOJ, sulfur oxides (principally SO9), particulate matter, carbon monoxide, and unburned hydrocarbons. 

The combustion-flow interactions should be central in the computation of combustion-generated flow fields. This interaction is fundamentally multidimensional, and can only be computed by the most sophisticated numerical methods. A simpler approach is only possible if the concept of a gas explosion is drastically simplified. The consequence is that the fundamental mechanism of blast generation, the combustion-flow interaction, cannot be modeled with the simplified approach. In this case flame propagation must be formalized as a heat-addition zone that propagates at some prescribed speed. 

Experimental research during the last decade (Section 4.1) has shown clearly that deflagrative combustion generates blast only in those portions of a quiescent vapor cloud which are sufficiently obstructured and/or partially confined (Zeeuwen et al. 1983 Harrison and Eyre 1987 Harris and Wickens 1989 Van Wingerden 1989a). 

Operability analysis and control system synthesis for an entire chemical plant Mathematical modeling of transport and chemical reactions of combustion-generated air pollutants... 

Combustion-generated noise is a problem in itself. However, if an acoustic wave can interact with the combustion zone, so that the heat release rate is a function of the acoustic pressure, q = f p ), then Equation 5.1.14 describes a forced oscillator, whose amplitude can potentially reach a high value. The condition for positive feedback was first stated by Rayleigh [23] ... 

W.C. Strahle. On combustion generated noise. J. Fluid Mech., 49 399-414,1971. 

Czuczwa JM, Hites RA (1984) Environmental fate of combustion-generated polychlorinated dioxins and furans. Environ Sci Technol 18(6) 444-450. doi 10.1021/es00124a010... 

Smoke abatement from the thermal reduction batch processor (TRBP) smoking rooms and the measurement and management of carbon monoxide and other products of incomplete combustion generated in these rooms. (These processes were not adequately addressed in the EDP.)... 

This chapter seeks not only to provide better understanding of the oxidation processes of nitrogen and sulfur and the processes leading to particulate (soot) formation, but also to consider appropriate combustion chemistry techniques for regulating the emissions related to these compounds. The combustion— or, more precisely, the oxidation—of CO and aromatic compounds has been discussed in earlier chapters. This information and that to be developed will be used to examine the emission of other combustion-generated compounds thought to have detrimental effects on the environment and on human health. How emissions affect the atmosphere is treated first. 

In earlier sections of this chapter, the role that particulates play in a given environmental scenario was identified. This section will be devoted exclusively to combustion-generated particulates whose main constituent is carbon. Those carbonaceous particulates that form from gas-phase processes are generally referred to as soot, and those that develop from pyrolysis of liquid hydrocarbon fuels are generally referred to as coke or cenospheres. 

Similar to liquid ramjets, ducted rockets take in air from the atmosphere through an air-intake attached to the front end of the combustor. However, in contrast to liquid ramjets, the fuel components used for ducted rockets are fuel-rich pyrolants composed of fuel and oxidizer components. The products of incomplete combustion generated by a pyrolant in a gas generator burn with the air introduced from the atmosphere in the combustor.Ii- As in the case of liquid ramjets, the thrust of ducted rockets is generated by the momentum difference between the exhaust gas from the combustor and the air taken in from the atmosphere. 

The results presented here suggest a new mechanism of toxicity for PM 5 based on sustained hydroxyl radical generation by the semiquinone radicals present in PM 5. Because a substantial fraction of the fine particles in the atmosphere arises from combustion sources (9), it is possible that the deleterious health effects associated with PM2 5 can be at least partially ascribed to radicals associated with combustion-generated particulate matter. 

The physical and chemical complexity of primary combustion-generated POM is illustrated in Fig. 10.1 (Johnson et al., 1994), a schematic diagram of a diesel exhaust particle and associated copollutants. The gas-phase regime contains volatile (2-ring) PAHs and a fraction of the semivolatile (3- and 4-ring) PAHs. The particle-phase contains the remainder of the semivolatile PAHs ( particle-associated ) along with the 5- and 6-ring heavy PAHs adsorbed/absorbed to the surface of the elemental carbon spheres that constitute the backbone of the overall diesel soot particle. Also present is sulfate formed from oxidation of sulfur present in the diesel fuel and gas- and particle-phase PACs. 

As an example, we saw earlier, replacing the CH2 group in the parent PAH 7//-benz[de]anthracene, XII, by a keto group, C=0, gives 7//-benz[de]anthracen-7-one, XIII (benzanthrone). It is well known as a major O-PAC in combustion-generated emissions and ambient air (see Table 10.4) and the 3-nitro derivative,... 

TABLE 10.5 Structures, Common Names, Empirical Formulas, and Molecular Weights for Selected Sulfur-Containing Mono- and Polycyclic Aromatic Compounds (S-PACs) in Ambient Air e and Combustion-Generated Emissions, , d... 

Examples of common names and structures of several S-PACs and nitro-S-PACs identified in combustion-generated emissions (including tobacco smoke condensate) and ambient air are given in Table 10.5. 

Box 10.9), a new class of mutagenic compounds was discovered, the nitroarenes. Within a short time, they were identified as directly mutagenic copollutants present along with well-known promutagenic PAHs in combustion-generated emissions and distributed worldwide in urban ambient air (see Section D). 

The toxicology-based conclusion that the minimum concentration for 2-nitrofluoranthene to be an important human cell mutagen is 1 p.g/g, coupled with air quality sampling data showing its concentrations in respirable particles sampled from ambient air can in fact reach 10 pg/g, provides a useful example of a productive symbiotic interaction between atmospheric chemists and toxicologists. Such interactions are essential for reliable risk assessments of air pollution and human health effects of complex combustion-generated mixtures of gases and particles. 

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