Emission fired power plant

Emissions control systems play an important role at most coal-fired power plants. For example, PC-fired plants sited in the United States require some type of sulfur dioxide control system to meet the regulations set forth in the Clean Air Act Amendments of 1990, unless the boiler bums low sulfur coal or benefits from offsets from other highly controlled boilers within a given utiUty system. Flue-gas desulfurization (FGD) is most commonly accomphshed by the appHcation of either dry- or wet-limestone systems. Wet FGD systems, also referred to as wet scmbbers, are the most effective solution for large faciUties. Modem scmbbers can typically produce a saleable waUboard-quaUty gypsum as a by-product of the SO2 control process (see SULFURREMOVAL AND RECOVERY). 

Also, wood fuel is low in sulfur, ash, and trace toxic metals. Wood-fired power plants emit about 45% less nitrogen oxides, NO, than coal-fired units. Legislation intended to reduce sulfur oxides, SO, and NO emissions may therefore result in the encouragement of wood-burning or cofiring wood with coal. 

Major sources for emissions of SO, and NO, m the United States are presented in Figures 3 and 4 respectively. Approximately two-thirds of the SO, emissions are from electric utilities. Efforts to reduce SO, emissions both nationally and regionally have focused on electric utilities. The CAAA of 1990 have stipulated a reduction of 9.1 million metric tons (10 million short tons) of SO, below 1980 levels, with most of this reduction coming from coal-fired power plants. Implementation of Phase I reductions (199.5-2000) has been successful and has resulted in an 18 percent decline in SO, emissions from electric utilities, compared with 1990 SO, emissions. There has been a 16 percent decline in SO, for this time period when all sources are considered. Phase 2 of the CAAA, which is designed to reduce SO, emissions from electric utilities by another 20 percent... 

In the future, if the criterion for selecting new generating capacity was solely fuel cost, coal will be the number one choice. But the much greater costs of coal-fired plants (primarily to meet local and federal emission standards), as well as the potential of tighter standards, will make gas more attractive in many cases. And although natural gas prices may rise, the fuel costs per kilowatt-hour for gas-fired power plants should remain unchanged as efficiency gains offset the rise in fuel prices. 

Reductions in U.S. mercuiy emissions from medical and municipal waste incinerators and other industrial sectors have already occurred. Additional emission reductions from some coal-fired power plants have also already begun as co-benefits from technologies used to control SO2 and NO emissions. These mercury emissions from power plants are, however, expected to be reduced further over the next few decades. Meanwhile, changes in mercuiy emissions in other parts of the world may also affect some U.S. ecosystems. 

Table 4. Cost estimates of alternative mitigation technologies in the power generation sector compared to baseline pulverized coal-fired power plant and natural gas Combined Cycle with Gas Turbine (CCGT) power stations and the potential reductions in C02 emissions to 2020 [14]...

In the energy sector, coal-fired power plants contribute 54% of C02 emissions, and gas-fired power plants contribute 40%. In 2009, C02 emission from fossil fuels is estimated to increase by 113% compared to the year 2000. Each kWh of electricity of Vietnam contributes 0.52 kg C02 emission. The contribution of each sector to the total emissions in Vietnam through the years is shown in Fig. 9. 

Emissions of silver from coal-fired power plants may lead to accumulations in nearby soils (Fowler and Nordberg 1986). Silver in soils is largely immobilized by precipitation to insoluble salts and by complexation or adsorption by organic matter, clays, and manganese and iron oxides (Smith and Carson 1972). 

Exposure of humans and wildlife to arsenic may occur through air (emissions from smelters, coal-fired power plants, herbicide sprays), water (mine tailings runoff, smelter wastes, natural mineralization), and food (especially seafoods). 

Considering the composition of petroleum and petroleum products (Speight, 1994, 1999), it is not surprising that petroleum and petroleum-derived chemicals are environmental pollutants (Loeher, 1992 Olschewsky and Megna, 1992). The world s economy is highly dependent on petroleum for energy production, and widespread use has led to enormous releases to the environment of petroleum, petroleum products, exhaust from internal combustion engines, emissions from oil-fired power plants, and industrial emissions where fuel oil is employed. 

Ahlberg M, Berghem L, Nordberg G, et al. 1983. Chemical and biological characterization of emissions from coal- and oil-fired power plants. Environ Health Perspect 47 85-102. 

Mustonen R, Jantunen M. 1985. Radioactivity of size fractionated fly-ash emissions from a peat-and oil-fired power plant. Health Phys 49 1251-1260. 

A typical, modem, coal-fired power plant emits 25 pg nickel per Megajoule (MJ) of power produced, compared with 420 pg/MJ for an oil-fired plant (Hasanen et al. 1986). The nickel concentration in stacks emissions from a modem coal-fired power plant with an electrostatic precipitator was 1.3 pg/m (Lee et al. 1975). High-sulfur eastern coal has a higher nickel content than low-sulfur western coal, so power plants using eastern coal emit more nickel than those using western coal (QueHee et al. 1982). 

From a public health point of view, the concentration of nickel associated with small particles that can be inhaled into the lungs is of greatest concern. The nickel content of aerosols from power plant emissions is not strongly correlated with particle size (Hansen and Fisher 1980). In one modem coal plant, 53% and 32% of nickel in emissions were associated with particles <3 and <1.5 pm in diameter, respectively (Sabbioni et al. 1984). Other studies found that only 17-22% of nickel emissions from coal-fired power plants were associated with particles of >2 pm, and that the mass medium diameter (MMD) of nickel-containing particles from a plant with pollution control devices was 5. 4 pm (Gladney et al. 1978 Lee et al. 1975). In one study, 40% of the nickel in coal fly ash was adsorbed on the surface of the particles rather than being embedded in the aluminosilicate matrix (Hansen and Fisher 1980). Surface-adsorbed nickel would be more available than embedded nickel. 

Gas-Zero Emissions Plant (ZEP). Alstom Power s Cas-ZEP project explores methods to capture the CO2 as it is produced in a natural gas-fired power plant without substantial reductions in plant efficiencies. 

Hopke, et al. (4) and Gaarenstroom, Perone, and Moyers (7) used the common factor analysis approach in their analyses of the Boston and Tucson area aerosol composition, respectively. In the Boston data, for 90 samples at a variety of sites, six common factors were identified that were interpreted as soil, sea salt, oil-fired power plants, motor vehicles, refuse incineration and an unknown manganese-selenium source. The six factors accounted for about 78 of the system variance. There was also a high unique factor for bromine that was interpreted to be fresh automobile exhaust. Large unique factors for antimony and selenium were found. These factors may possibly represent emission of volatile species whose concentrations do not oovary with other elements emitted by the same source. 

Gladney, E. S. Trace Elemental Emissions from Coal-Fired Power Plants A Study of the Chalk Point Electric Generating Station, Ph.D Thesis, University of Maryland, 1974. 

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