Coal stack ash

Miller, V. R., E. L. Wehry, and G. Mamantov, Photochemical Transformation of Pyrene Vapor Deposited on Eleven Subfractions of a High-Carbon Coal Stack Ash, Environ. Toxicol. Chem., 9, 975-980 (1990). 

Chemical Reactivity of Polycyclic Aromatic Compounds Adsorbed on Coal Stack Ash... 

The photochemical reactivity of anthracene, phenanthrene, pyrene, benzo[a]pyrene, and benz[a]anthracene is examined. Each aromatic hydrocarbon was adsorbed onto the surface of each of a variety of coal stack ashes. 

Mauldin RF, Vienneau JM, Werhy EL, Mamantov G. Supercritical fluid extraction of vapour deposited pyrene from carbonaceous coal-stack ash. Talanta 1990 37 1031-1036. 

Yokley, R. A., A. A. Garrison, E. L. Wehrly, and G. Mamantov. 1986. Photochemical transformation of pyrene and benzo[a]pyrene vapor-deposited on eight coal stack ashes. Environ. Sci. Technol. 20 86-90. 

The bulk of the samples for this study came from TVA s Allen Steam Plant at Memphis, Tenn. The sampling points (Figure 4) included inlet air, coal, bottom ash, precipitator inlet, and outlet at the 268-ft stack level. During the 2-week sampling period the unit was operated under steady state conditions at 240 MW (12) with a uniform coal supply so that a mass balance might be established for a number of elements. All the coal from southern Illinois was washed and crushed so that 90% was less than 4 mesh. Nominal coal analysis indicated the following composition 9.5% moisture, 34% volatiles, 43% fixed carbon, 13% ash, and 3.4% sulfur. 

The second program, funded by the U.S. Bureau of Mines, is concerned with the fate of the various toxic trace elements present when coal is burned in power plants. Coals and ashes from experimental combustors and power plants are collected and chemically analyzed. Comparing the amount of a trace element in a coal with the amount found in the ash resulting from the combustion of that coal allows us to determine the maximum amount of that element that could be emitted into the environment via the power plant stacks. 

The results of the mass balance are summarized in Table VI. The ratio of the mercury found in the gas stream to the amount of mercury released from the coal but not recovered in the ash is given in the third column. The average of this ratio is 1.19, with a standard deviation of 0.24. Within one standard deviation unit there is not a significant difference between the measured ratio and the expected ratio of 1.0. Therefore, based on 14 ratios at one plant, there is not a statistically significant difference between the total mercury found in the stack gas and the amount expected in the stack gas from the coal and ash determinations. Dual tests 13 and 14 showed close ratios of 0.88 and 0.95. 

The two highest ratios, from tests 3 and 7, showed the greatest deviation from the expected norm of 1.0. Results from these tests showed a larger amount of mercury in the stack gas stream than was expected from the coal and ash analysis. These two tests were the first two tests... 

Organic compounds in the various effluents from the efficient combustion of coal at power plants do not appear to be an environmental problem. This conclusion is based on interpretation of results obtained during a four-year study of samples of stack gas and fly, grate and stack ashes from the combustion of coal alone and of mixtures of coal and refuse-derived fuel. 

Kimble, B. J., and Gross, M. L. (1980). Tetrachlorodibenzo-dioxin quantitation in stack-collected coal fly ash. Science 207, 59-61. 

Hock JL and Lichtman D (1982) Studies of surface layers on single particles of in-stack coal fly ash. Environ Sci Technol 16 423-427. 

LD Hansen, D Silberman, GL Eisher, DJ Eatough. Chemical speciation of elements in stack-collected, respirable-size, coal fly ash. Environ Sci Tech 18 181-186, 1984. 

Apparentiy the addition of SO2 to the analysis enabled refinement of the coal combustion factor. The newer non-secondary sulfate coal plant emission numbers comport better with known percentages of coal fly ash in ambient air. Coal fly ash (CFA), mainly composed of aluminosihcates with calcium or sodium, iron, and trace materials, is the major primary PM2.5 coal plant stack emission (CFA atmospheric concentrations typically are in the tens of ng/m, up to 200 ng/m, depending on the number of coal plants in the region). The use of temperature, differentiated EC and OC fractions allowed differentiation of diesel and gasoline emissions, and also caused the contributions of other factors to change (e.g., wood smoke). 

Griest, W. H. L. A. Harris, 1985. Microscopic identification of carbonaceous particles in stack ash from pulverised-coal combustion. Fuel. 64 821-826. 

FGD materials Derived from a variety of processes used to control sulfur emissions from boiler stacks. These systems include wet scrubbers, spray dry scrubbers, sorbent injectors, and a combined sulfur oxide (SOx) and nitrogen oxide (NOx) process. Sorbents include lime, limestone, sodium-based compounds, and high-calcium coal fly ash. 

Element Symbol Coal Bottom ash Precipitated ash Bag ash Stack ash... 

Low levels of cresols are constantly emitted to the atmosphere in the exhaust from motor vehicle engines using petroleum based-fuels (Hampton et al. 1982 Johnson et al. 1989 Seizinger and Dimitriades 1972). Cresols have been identified in stack emissions from municipal waste incinerators (James et al. 1984 Junk and Ford 1980) and in emissions from the incineration of vegetable materials (Liberti et al. 1983). Cresols have also been identified as a component of fly ash from coal combustion (Junk and Ford 1980). Therefore, coal- and petroleum-fueled electricity-generating facilities are likely to emit cresols to the air. The combustion of wood (Hawthorne et al. 1988, 1989) and cigarettes (Arrendale et al. 1982 Novotny et al. 1982) also emits cresols to the ambient air. Cresols are also formed in the atmosphere as a result of reactions between toluene and photochemically generated hydroxy radicals (Leone et al. 1985). 

Coles DG, Ragaini RC, Ondov JM, et al. 1979. Chemical studies of a stack fly ash from a coal-fired power plant. Environ Sci Technol 13 455-459. 

QueHee SS, Finelli VN, Fricke FL, et al. 1982. Metal content of stack emissions, coal and fly ash from some eastern and western power plants in the USA as obtained by ICP-AES. Int J Environ Anal Chem 13 1-18. 

Figure 7. Comparison of mass and elemental composition of fly ash sampled in the stack of a coal-burning power plant, and bulk hopper fly ash, collected while warm on the same day, later resuspended at Davis...

Goodarzi, F., Peel, W. P., Huggins, F. E., Brown, J. R., Charland, J.-P. Percival, J. 2002. Chemical and mineralogical characteristics of milled coal, ashes, and stack-emitted material from unit no. 5, Battle River coal-fired power station, Alberta, Canada. Geological Survey of Canada Bulletin, 570, 148 p. 

Methods and technology were developed to analyze 1000 samples/yr of coal and other pollution-related samples. The complete trace element analysis of 20-24 samples/wk averaged 3-3.5 man-hours/sample. The computerized data reduction scheme could identify and report data on as many as 56 elements. In addition to coal, samples of fly ash, bottom ash, crude oil, fuel oil, residual oil, gasoline, jet fuel, kerosene, filtered air particulates, ore, stack scrubber water, clam tissue, crab shells, river sediment and water, and corn were analyzed. Precision of the method was 25% based on all elements reported in coal and other sample matrices. Overall accuracy was estimated at 50%. 

A series of mercury mass balances was obtained at a coal-fired power plant by comparing the volatile and particulate mercury in the stack gas stream to the mercury initially in the coal, corrected for the mercury adsorbed and retained by the various ashes. These data were used to determine the fate of the mercury in the combustion process and to check the accuracy of the volatile mercury sampling procedure (gold amalgamation). The bottom ash had the lowest mercury concentration of the ash samples collected, and the mercury concentration increased as one proceeded through the ash collection system from the initial mechanical ash to the electrostatic ash. The mercury recovered in the various ashes represented about 10% of the total mercury introduced in the raw coal. 

Evaluating the quantitative effect of these factors on the volatile mercury concentration requires determining how much of the initial mercury found in the coal is 1. not volatilized from the coal during combustion, 2. recovered in the various ash collection mechanisms by some adsorption phenomena, and 3. released to the atmosphere. With this information, a mercury mass balance can be calculated in which the amount of mercury consumed during the combustion process is compared with the amount in the stack gas and the various ashes. During this study, this was accomplished by comparing the stack gas concentration with the amount of mercury initially in the coal, corrected for the amounts recovered in the ashes. Differences between these two values would represent adsorption and/or desorption onto and off the walls of the ducts and stack and any significant contribution from the ambient air used in the combustion process. 

Mercury Mass Balance. The mass balance consisted of comparing the amount of mercury in the stack gas stream with the amount in the coal minus that mercury recovered in the ash. In obtaining this balance it was assumed that the walls of the stack and the duct work did not affect the mercury concentration in the gas stream. The author felt that this was a correct assumption only if ... 

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