Combustion sources

Following the movement of airborne pollutants requires a natural or artificial tracer (a species specific to the source of the airborne pollutants) that can be experimentally measured at sites distant from the source. Limitations placed on the tracer, therefore, governed the design of the experimental procedure. These limitations included cost, the need to detect small quantities of the tracer, and the absence of the tracer from other natural sources. In addition, aerosols are emitted from high-temperature combustion sources that produce an abundance of very reactive species. The tracer, therefore, had to be both thermally and chemically stable. On the basis of these criteria, rare earth isotopes, such as those of Nd, were selected as tracers. The choice of tracer, in turn, dictated the analytical method (thermal ionization mass spectrometry, or TIMS) for measuring the isotopic abundances of... 

The emissions from combustion processes may be predicted to some extent if the variables of the processes are completely defined. Figure 6-7 indicates how the emissions from a combustion source would be expected to vary with the temperature of the reaction. No absolute values are shown, as these will vary greatly with fuel type, independent variables of the combustion process, etc. 

Standard sampling trains are specified for some tests. One of these standards is the system specified for large, stationary combustion sources (4). This train was designed for sampling combustion sources and should not be selected over a simpler sampling train when sampling noncombustion sources such as low-temperature effluents from cyclones, baghouses, filters, etc. (5). 

Pollutant Loading Pollutant loading is dependent upon the control effectiveness for fine PM of the primary PM control system. Fine PM may, in some cases, comprise up to 90 percent of the total mass of PM emissions from a combustion source, and many primary control technologies have relatively low collection efficiencies for fine PM. 

Other Considerations The fine fraction of PM emissions from a combustion source often contains cadmium and other metals. Use of a condensation scrubber to capture fine PM may provide an effective method of reducing the emission of metals. 

For PM control from combustion sources, the tlue gas enters a coagulation area (e.g., ductwork, a chamber, or a cyclone) to reduce the number of ultrafine particles, and then a gas conditioner to cool the gas to a suitable temperature and saturation state. This is generally accomplished by means of a waste heat recovery heat exchanger to reduce the temperature of the flue gas or by spraying water directly into the hot flue gas stream. 

EPA, 1996b. U.S. EPA, Office of Air Quality Planning and Standards, "Chemical Recovery Combustion Sources at Kraft and Soda Pulp Mills," EPA-453/R-96-012, Research Triangle Park, NC, October, 1996. 

One of the more significant classes of compounds resulting from and emitted by combustion sources include polycyclic aromatic hydrocarbons (PAHs) these species serve as nuclei for the formation of soot particles. Past studies have concluded that 85% of... 

Organophosphate Ester Hydraulic Fluids. Populations with potentially high exposures to organophosphate ester hydraulic fluids include aircraft mechanics and other mechanics repairing and maintaining hydraulic equipment designed to operate near combustion sources that require fire resistant hydraulic fluids. 

Pex, P.P.A.C. and Y.C. van Delft, Silica membranes for hydrogen fuel production by membrane water gas shift reaction and development of a mathematical model for a membrane reactor, in Carbon Dioxide Capture for Storage in Deep Geologic Formations—Results from the C02 Capture Project Capture and Separation of Carbon Dioxide from Combustion Sources, eds., D. Thomas, and B. Sally, Vol. 1, Chapter 17, 2005. 

Note that the chemical dimensions do not yield such robust "markers", or tracers, as the isotopic dimensions. For a given combustion source, for example, one is apt to find chemical--but not isotopic—fractionation varying significantly with time, particle size, particle history (differential volatilization or reaction), etc. The ratio K/Fe, for example, was quite different in the fine and coarse fractions from a slash burn (1.5 vs. 0.3) [33] and Pb/Br, which has been popular as an automobile exhaust tracer, varies with the "age" of urban particles [22]. 

Contemporary Carbon Combustion Source Contributions to Urban Air Particulate Levels Using C-14 Measurements, to be published in Env. Sci. Tech., 1981. 

These quasi-static pressures are determined by the total heat energy in the explosive and/or combustible source, the volume of the enclosure, the vent area and the vent panel configuration, the mass per unit area of vent covers, and the initial ambient conditions within the enclosure. 

Fiedler 1999). An overview of combustion sources known to generate and emit PCDD/PCDFs (Fiedler, 1999) is presented in Table 2. 

Murr LE, Soto KP (2005) A TEM study of soot, carbon nanotubes, and related fullerene nanopol-yhedra in common fuel-gas combustion sources. Mater Characteriz. 55 50-65. 

Murr LE, Bang JJ, Esquivel EV, Guerrero PA, Lopez A (2004) Carbon nanotubes, nanocrystal forms, and complex nanoparticle aggregates in common fuel-gas combustion sources and the ambient air. J Nanopart Res 6 241-251. 

Historically, the sulfur oxides have long been known to have a deleterious effect on the atmosphere, and sulfuric acid mist and other sulfate particulate matter are well established as important sources of atmospheric contamination. However, the atmospheric chemistry is probably not as well understood as the gas-phase photoxidation reactions of the nitrogen oxides-hydrocarbon system. The pollutants form originally from the S02 emitted to the air. Just as mobile and stationary combustion sources emit some small quantities of N02 as well as NO, so do they emit some small quantities of S03 when they bum sulfur-containing fuels. Leighton [2] also discusses the oxidation of S02 in polluted atmospheres and an excellent review by Bulfalini [3] has appeared. This section draws heavily from these sources. 

Nitric oxide is the primary nitrogen oxide emitted from most combustion sources. The role of nitrogen dioxide in photochemical smog has already been discussed. Stringent emission regulations have made it necessary to examine all possible sources of NO. The presence of N20 under certain circumstances could, as mentioned, lead to the formation of NO. In the following subsections the reaction mechanisms of the three nitrogen oxides of concern are examined. 

Adsorption of nitric and sulfuric acids on ice particles provides the sol of the nitrating mixture. An important catalyst of aromatic nitration, nitrous acid, is typical for polluted atmospheres. Combustion sources contribute to air pollution via soot and NO emissions. The observed formation of HNO2 results from the reduction of nitrogen oxides in the presence of water by C—O and C—H groups in soot (Ammann et al. 1998). As seen, gas-phase nitration is important ecologically. 

Sidhu S, Gullet B, Striebich R, Klosterman JR, Contreras J, DeVito M (2005) Endocrine disrupting chemical emissions from combustion sources diesel particulate emissions and domestic waste open bum emissions. Atmos Environ 39 801-811... 

Carbon monoxide, carbon dioxide, sulfur dioxide, hydrogen cyanide, particulates, nitrogen dioxide, benzoapryene, etc. from combustion sources including gas ranges, dryers, water heaters, kerosene heaters, fireplaces, wood stoves, garage, etc. Aminos from humidification equipment ... 

Berwick M, Leaderer BP, Stowijk JA, et al. 1989. Lower respiratory symptoms in children exposed to nitrogen dioxide from unvented combustion sources. Environment International 15(l-6) 369-373. 

EPA. 1987b. Human exposure to mutagens from indoor combustion sources. Research Triangle Park, NC U.S. Environmental Protection Agency, Health Effects Research Laboratory. Report no. EPA/600/D-87/144. 

Leaderer BP, Zagraniski RT, Berwick M, et al. 1986. Assessment of exposure to indoor air contaminant from combustion sources Methodology and application. Am J Epidemiol 124(2) 275-289. 

Tucker WG. 1987. Characterization of emissions from combustion sources Controlled studies. Atmos Environ 21(2) 281-284. 

Legislative restrictions on pollutant emissions have motivated the combustion community to seek new low-emission combustion techniques that are practical industrial energy sources. However, to meet the needs in most industrial applications, a combustion source needs to be able to maintain low-emission output over a range of heat release rates, occupy minimal volume, and have low operating costs per unit energy produced. One would like to maximize the turn-down ratio, volumetric heat release, and overall thermal efficiency while minimizing NOa , CO, and hydrocarbon emission levels. The ultra-low NO, emission performance of the CSC has been previously documented by the authors and its... 

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. 

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