Plumes, particulate stack

Based on a limited amount of test data, it appears that the units may not be able to meet specific local air pollution codes. Particulate stack plumes are visible, especially when operation requires an accelerated loading schedule to lower primary combustion temperatures. 

Examples of the need for multimedia models are found in contemporary problem areas. Polynuclear aromatic hydrocarbons and metals are emitted into the atmosphere as trace impurities with the products of coal combustion. The organics have low vapor pressure and partially condense on emitted particulates in a stack plume. The particulates are transferred to the soil by dry deposition, rainout or washout. The metals manifest... 

The emphasis in the present work is on leachates derived from fly ash disposal, but it must not be forgotten that fine ash particles may escape from power plants. The transport and dispersion of particulate emissions from tall stacks has been actively researched over the last 20-30 years. A review by Carras (1995) records that plumes have been observed to remain as coherent units up to distances of at least 1800 km and thus deposit pollution far from source. However, maximum particulate surface loadings are likely to be found adjacent to old power plants with limited fine-particle fly ash entrapment. Evans et al. (1980) estimated that in a period of 23 years the cumulative stack ash load at a distance of 1.7 km from an 83 MW... 

Although the details are beyond the scope of this book, health problems can be caused by solids and liquids suspended in water (for example, in waste-tailings streams) or in air (for example, in stack-emission plumes). Specific potential hazards have been associated with a diverse spectrum of colloidal materials, including synthetic chemicals, coals, minerals, metals, pharmaceuticals, plastics, and wood pulp. Limits for human exposure for many particulate, hazardous materials are published [504,505],... 

The burning uranium heated the graphite, which also burned to release CO and CO,. About 2x10 Ci of gaseous iodine, which represented 12% of the available iodine inventory, were released into the atmosphere from the stack. The filter removed the particulate iodine (20 to 50x10 Ci). The radioactive plume was detected as far away as Germany and Norway. 

The public, unfortunately, sometimes concludes that all the emissions they perceive are pollution. Natural gas could appear to the public to be a greater pollutant than either oil or coal when, in fact, the emissions are just water vapor. The sulfur content of coal and oil can be released as sulfur dioxide to the atmosphere, and the polluting capacities of coal and oil are much greater than natural gas when all three are being burned properly. The sulfur contents as delivered to the consumers are as follows natural gas, 4 x 10 % (as added mercap-tans) number 6 fuel oil, up to 2.6% and coal, from 0.5 to 5%. In addition, coal may release particulate matter into the stack plume. 

Field studies of S02 oxidation have been performed mostly in the downwind regions of sufficiently isolated sources. The favored objects were stacks of electric power plants, whose plumes often are identifiable at distances up to 300 km from the source, and larger cities. S02 and particulate sulfate were measured and the data were analyzed in terms of the concentration ratio (S04-)/(S02) + (S04 ) as a function of time or a combination of wind speed and distance. Sampling was done mostly by aircraft, although urban plumes have also been studied by ground-based measurements. Table 10-11 presents results from a variety of such investigations. 

Recently, the application of short term bio-assays to a variety of emission and ambient particulate samples has demonstrated that other compounds than PAH, most likely PAH-derivatives, can be responsable for a major part of the observed biological activity of the extracts. These results have forced us to widen our interest to the field of particulate polycyclic organic matter (POM), which besides hetero-atomic PAH (polycyclic aromatic compounds, PAC, containing nitrogen or sulfur) may also contain oxidized, nitrated, or sulfonated derivatives of PAH, formed in exhausts, emission stacks, plumes or during transport through the atmosphere. 

For this noncatalytic NO reducing process, NH3 must be injected at a 2-to-l molar ratio (based on the flue-gas NO concentration). Therefore, there is some shp of NH3 that does not react completely and can potentially cause odors. Also, fine particulate emissions that create a visible plume can be formed from the reaction of NH3 and HCl (a soUd-fuel combustion byproduct) downwind of the stack. Therefore, it is important to keep the NO injection rate to the minimum necessary. 

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