Hazardous Air Pollutants Abstracts

C.A. Miller, R.K. Srivastava, and J.V. Ryan, "Emissions of Organic Hazardous Air Pollutants from the Combustion of Pulverized Coal in a Small-Scale Combustor," Environmental Science and Technology, Vol. 28, pp. 1150-1158, 1994.

Emissions of Organic Hazardous Air Pollutants from the Combustion of Pulverized Coal in a Small-Scale Combustor

C. Andrew Miller U.S. Environmental Protection Agency Air and Energy Engineering Research Laboratory, MD-65 Research Triangle Park, NC 27711 Ravi K. Srivastava Jeffrey V. Ryan Acurex Environmental Corporation P.O. Box 13109 Research Triangle Park, NC

Abstract
The emissions of hazardous air pollutants (HAPs) from the combustion of pulverized coal have become an important issue in light of the requirements of Title III of the 1990 Clean Air Act Amendments, which impose emission limits on 189 compounds and compound classes. Although previous field and laboratory studies have examined the emissions of some HAPs from coal combustion sources, no work has been done to evaluate the emissions of a broad range of these compounds, particularly in the case of organics. Therefore, a study was conducted at the U.S. Environmental Protection Agency's Air and Energy Engineering Research Laboratory to characterize emissions of 76 organic HAPs in the flue gases from the combustion of pulverized coal in a small-scale down-fired combustor. The combustor was operated under different conditions to simulate baseline, high excess air firing, and nitrogen oxide (NO_x) controls by combustion modifications. Samples were extracted near the combustor exit, upstream of any pollution control equipment. Data collected indicate that relatively low levels of organic HAPs are present in the flue gases for any of the combustion conditions; however, several compounds were present that have not been reported in previous studies. To the extent these small-scale tests accurately simulate full-scale units, estimates based on these experiments indicate that the total HAP emissions from a large utility power plant are not likely to increase significantly due to installation of combustion modification techniques for NO_x control.

"Effects of Changing Coals on the Emissions of Metal Hazardous Air Pollutants from the Combustion of Pulverized Coal," C.A. Miller, EPA-600/R-95-106, July 1995

Effects of Changing Coals on the Emissions of Metal Hazardous Air Pollutants from the Combustion of Pulverized Coal

C. Andrew Miller U.S. Environmental Protection Agency Air Pollution Prevention and Control Division Research Triangle Park, NC 27711

Abstract
A series of tests were conducted at the U.S. Environmental Protection Agency's National Risk Management Research Laboratory, Air Pollution Prevention and Control Division (APPCD), formerly the Air and Energy Engineering Research Laboratory, to evaluate the effects of changing coals on the emissions of metal hazardous air pollutants (HAPs) from coal-fired boilers. The tests were conducted on a small scale combustor, and samples were taken prior to any pollution control equipment to allow application of different control efficiencies to the uncontrolled emissions. Six different coals were burned in APPCD's Innovative Furnace Reactor (IFR) under the same combustion conditions, and each coal was sampled for 10 metals: antimony, arsenic, beryllium, cadmium, chromium, lead, manganese, nickel, selenium, and mercury. Each of these metals is on the list of 189 compounds and compound classes listed as HAPs under Title III of the 1990 Clean Air Act Amendments. The results of the tests showed that changes in the uncontrolled emissions tended to correlate well with the corresponding changes in the as-fed metal content of the coals in the cases of mercury, selenium, and arsenic. For beryllium, chromium, manganese, and nickel, changes in the uncontrolled emissions with different coals did not correlate well with the changes in the as-fed trace metal contents. The remaining three metals, antimony, cadmium, and lead, did not show conclusive results when comparing emissions to as-fed trace metal contents. The factor that determines the degree of correlation between the as-fed trace metal concentration and the uncontrolled stack emissions appears to be the vapor pressure of the metal. Metals that have high vapor pressures tend to exhibit strong correlations between the as-fed metal concentration in the coal and the uncontrolled emissions, while metals with low vapor pressures tend to show a much weaker correlation. In summary, the study illustrates that predictions of metal emissions based only on the trace metal content of the coal do not yield accurate results in all cases. Such predictions cannot be used with any confidence for refractory metals, but do have some degree of validity for the more volatile metals of interest. Based on average emission factors (in lb/10⁶ Btu), the Illinois coals had higher emissions of arsenic, beryllium, cadmium, lead, and selenium than did the western coals, while the western coals had higher emissions of chromium, manganese, and nickel. Antimony and mercury emissions were similar for both coals. These results must be carefully interpreted, however, given the limited scope of testing and the fact that the tests were conducted on a small scale unit.

Comparisons of the small scale results with U.S. Department of Energy (DOE) field data show that the highest measured full scale emissions tend to be lower than the small scale results, with the exception of mercury, which was higher in the DOE field data. This is in contrast to the data taken from a full scale test using one of the coals used in this study. In this case, measurements upstream of any pollution control equipment showed the small scale results to be 30-50% lower than the full scale emissions for manganese, nickel, and selenium, with the remaining emissions being similar between the two tests. The correlation between full scale and small scale emissions remains unclear in general. However, trends seen in the small scale tests are expected to be similar to trends from the full scale testing, to the degree that similar changes in coals are made.

"Trace Metal Transformation Mechanisms during Coal Combustion," W.P. Linak and J.O.L. Wendt, Fuel Processing Technology, V. 39, pp. 173-198, 1994.

Trace Metal Transformation Mechanisms During Coal Combustion

William P. Linak Combustion Research Branch, MD-65 Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency Research Triangle Park, NC 27711 Jost O.L. Wendt Department of Chemical Engineering University of Arizona Tucson, AZ 85721

Abstract
Mechanisms governing the fate of trace metals during coal combustion are reviewed, and new theoretical results interpreting existing data are presented. Emphasis is on predicting the size segregated speciation of trace metals in pulverized coal fired power plant effluents. This facet, which determines how trace metals originally in coal, impact the environment, is controlled by fuel composition and combustion conditions.

Multicomponent equilibrium calculations are used to predict vaporization/condensation temperatures for antimony, arsenic, beryllium, cadmium, chromium, lead, mercury, nickel, and selenium compounds in coal combustion flue gases, for a representative Illinois No. 6 coal. Experimental data show that equilibrium provides a good guide on the effect of chlorine on the partitioning of pure nickel, cadmium, and lead salts, introduced separately into a gaseous turbulent diffusion flame within an 82 kW combustor. Metal nuclei coagulation mechanisms are examined using existing computer codes, and these predict that coagulation did not allow condensed metal nuclei to be scavenged by existing coal ash particles. Rather, literature data on trace metal enrichment on small particles are consistent with processes of reactive scavenging of metals by larger particles, and it is suggested that these processes might be exploited further to convert these metals into environmentally benign forms.

P.M. Lemieux, "Pilot-Scale Evaluation of the Potential for Emissions of Hazardous Air Pollutants from Combustion of Tire-Derived Fuel," U.S. Environmental Protection Agency

Pilot-Scale Evaluation of the Potential for Emissions of Hazardous Air Pollutants from Combustion of Tire-Derived Fuel

Paul M. Lemieux U.S. Environmental Protection Agency Air and Energy Engineering Research Laboratory Research Triangle Park, NC 27711 Prepared for: U.S. Environmental Protection Agency Office of Research and Development Washington, DC 20460

Abstract
Experiments were conducted in a 73 kW (250,000 Btu/hr) rotary kiln incinerator simulator to examine and characterize emissions from incineration of scrap tire material. The purpose of this project is not to generate statistically defensible emission factors for the controlled combustion of scrap tire material. Rather, the purpose of this project is to generate a profile of target analytes for full-scale stack sampling efforts, and, where possible, give insight into the technical issues and fundamental phenomena related to controlled combustion of scrap tires. Wire-free crumb rubber sized to less than 0.64 cm (less than 1/4 in) was combusted at two different feed rates, two different temperatures, and at three different kiln oxygen concentrations. Along with continuous emissions monitoring for oxygen (O₂), carbon dioxide (CO₂), carbon monoxide (CO), nitric oxide (NO), sulfur dioxide (SO₂), and total hydrocarbons (THCs), samples were taken to examine volatile and semi-volatile organics, polychlorinated p-dibenzodioxins and dibenzofurans (PCDD/PCDF), and metal aerosols. In addition, a continuous polycyclic aromatic hydrocarbon (PAH) analyzer was used in all the tests. Samples were analyzed with an emphasis on the 189 hazardous air pollutants (HAPs) listed in the 1990 Clean Air Act Amendments (CAAA), but other compounds were also identified where possible.

Results indicate that, if burned in a steady-state mode, TDF combustion will result in very low emissions of CO, THCs, volatile and semi-volatile organics, and PCDD/ PCDF. Metal emissions were also very low, with the exception of arsenic (As), lead (Pb), and zinc (Zn). Uncontrolled stack concentrations of As and Pb were 37.16 and 65.96 µg/Nm³, respectively. Uncontrolled Zn emissions were considerably higher, at 35,465 µg/Nm³. Results also indicate that organic emissions can increase significantly when TDF is fired in a non-steady mode. The continuous PAH analyzer appeared to track transient operation well, and gave concentration results in the same range as those derived using EPA standard semi-volatile organic sampling methodologies. Overall, it appears that, with the exception of zinc, potential emissions from TDF combustion are not significantly different from emissions from combustion of conventional fossil fuels, when burned in a well-designed and well-operated combustion device. If unacceptable particulate loading occurs due to zinc emissions, then the emissions would have to be controlled by an appropriate particulate control device.

"Characterization of Air Toxics from an Oil-Fired Firetube Boiler," C.A. Miller, J.V. Ryan, and T. Lombardo, Journal of the Air & Waste Management Association, Vol. 46, pp. 742-748, 1996;

Characterization of Air Toxics from an Oil-Fired Firetube Boiler

C. Andrew Miller U.S. Environmental Protection Agency Air Pollution Prevention and Control Division Research Triangle Park, NC 27711 Jeffrey V. Ryan Tony Lombardo Acurex Environmental Corporation P.O. Box 13109 Research Triangle Park, NC 27709

Abstract
Tests were conducted on a commercially available firetube package boiler running on #2 through #6 oils to determine the emissions levels of hazardous air pollutants from the combustion of four fuel oils (a #2 oil, a #5 oil, a low sulfur #6 oil, and a high sulfur #6 oil). Measurements of carbon monoxide, nitrogen oxides, particulate matter, and sulfur dioxide stack gas concentrations were made for each oil. Flue gases were also sampled to determine levels of volatile and semivolatile organic compounds and of metals. Analytical procedures were used to provide more detailed information regarding the emissions rates for carbonyls (aldehydes and ketones), and polycyclic aromatic hydrocarbons (PAHs) in addition to the standard analyses for volatile and semi-volatile organics. Metals emissions were greater than organic emissions for all oils tested, by an order of magnitude. Carbonyls dominated the organic emissions, with emission rates more than double the remaining organics for all four oils tested. Formaldehyde made up the largest percentage of carbonyls, at roughly 50% of these emissions for three of the four oils, and approximately 30% of the carbonyl emissions from the low sulfur #6 oil. Naphthalene was found to be the largest part of the PAH emissions for three of the four oils, with phenanthrene being greatest for the #2 fuel oil. The flue gases were also sampled for polychlorinated dibenzodioxins and polychlorinated dibenzofurans; however, inconsistent levels were found between repeat tests. For the boiler tested, no single hazardous air pollutant (HAP) was emitted at a rate which would require control under Title III of the Clean Air Act Amendments of 1990. The fuel emitting the largest amount of HAPs was the high sulfur #6 oil, which had a total HAP emission rate of less than 100 lb (45 kg)/year, based on operation for a full year at a firing rate of 1.25 x 10⁶ Btu/hr (50% load of the unit tested).

The emissions of hazardous air pollutants (HAPs) from the combustion of pulverized coal have become an important issue in light of the requirements of Title III of the 1990 Clean Air Act Amendments, which impose emission limits on 189 compounds and compound classes. Although previous field and laboratory studies have examined the emissions of some HAPs from coal combustion sources, no work has been done to evaluate the emissions of a broad range of these compounds, particularly in the case of organics. Therefore, a study was conducted at the U.S. Environmental Protection Agency's Air and Energy Engineering Research Laboratory to characterize emissions of 76 organic HAPs in the flue gases from the combustion of pulverized coal in a small-scale down-fired combustor. The combustor was operated under different conditions to simulate baseline, high excess air firing, and nitrogen oxide (NO_x) controls by combustion modifications. Samples were extracted near the combustor exit, upstream of any pollution control equipment. Data collected indicate that relatively low levels of organic HAPs are present in the flue gases for any of the combustion conditions; however, several compounds were present that have not been reported in previous studies. To the extent these small-scale tests accurately simulate full-scale units, estimates based on these experiments indicate that the total HAP emissions from a large utility power plant are not likely to increase significantly due to installation of combustion modification techniques for NO_x control.

"Hazardous Air Pollutants from the Combustion of an Emulsified Heavy Fuel Oil in a Firetube Boiler," C.A. Miller, EPA-600/R-96-019, 1996.

Hazardous Air Pollutants from the Combustion of an Emulsified Heavy Fuel Oil in a Firetube Boiler

C. Andrew Miller U.S. Environmental Protection Agency National Risk Management Research Laboratory (MD-65) Research Triangle Park, NC 27711

Abstract
Emissions of criteria and hazardous air pollutants (HAPs) were measured from the combustion flue gases of a #6 fuel oil, both with and without an emulsifying agent, in a 2.5 mmBtu/hr firetube boiler, with the purpose of determining the impacts of the emulsifier on HAP emissions. The flue gases of the boiler were sampled and analyzed for both metal and organic HAPs, and the effects of the emulsification on criteria emissions such as carbon monoxide (CO), nitrogen oxides (NO_x), and particulate matter (PM) were also measured. Measured in pounds per million British thermal units, the emulsified oil showed a decrease in the CO emission factor of 24%, a decrease of 35% in the NO_x emission factor, and a decrease of 37% in the PM emission factor compared to emission factors measured from burning the base oil (i.e. the same #6 oil without the emulsifying agent). Emissions of sulfur dioxide (SO₂) and metals were essentially unchanged for the emulsified oil compared to the base oil. Emissions of total organic HAPs from the emulsified oil were 29% lower than for the base oil. No polychlorinated dibenzodioxins or polychlorinated dibenzofurans were detected in the flue gases of either oil. There was a notable shift in the particle size distribution toward smaller size ranges for the emulsified oil compared to the base oil, although it is currently unclear whether the reduction in total particulate emissions results in an overall reduction in emissions of smaller (less than 2.5 micron) particles. Additional work is planned to provide quantitative information on the differences in size distributions and the total mass emissions for the different particle size ranges.

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