Coal-fired utility plants

Until 20 years ago coal-fired utility plants were considered a triumph of modern technology for generating heat and electricity at reasonable costs. As of 1989, 2,777 billion kilowatt-hours of electrical power were generated in the United States, of which 56% was produced by burning coal, 19% from nuclear plants, 9.5% from hydroelectric sources, 9.5% from burning natural gas and the remaining 6% from petroleum, geothermal and other sources. 

A study by DRI/McGraw Hill Electricity Service, an economic analysis firm, estimated that of the 1,300 coal-fired utility plants in the USA, about 800 would be affected. Approximately 450 would probably switch from high to low sulphur coal, while 133 would opt to retrofit scrubbers. Of the remaining 217 plants, DRI expected that most would utilise embryonic clean coal technologies (Wall Street Journal. June 14, 1989). The interviews conducted in the US, however, indicate that this may be a substantial overestimate of the market for clean coal technologies. 

The scientific press seemed confused by all this. In an editorial on acid rain in July 1983, Science asserted that"... there is wide disagreement among sincere people as to. . . who is responsible, and how the problem should be ameliorated. . . People in the northeast United States take the position that coal-fired utility plants in the Midwest are a principal source of the acid in the rain that has been falling on them. .. A large number of studies, however, have shown that the Northeast is itself responsible for a large share of its own pollution. Indeed, everyone who drives an automobile is a contributor to acid rain." ... 

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... 

According to [4], two coincineration routes can be utilized with good energy recovery coincineration in coal-fired thermoelectric plants and coincineration in cement furnaces to replace fossil fuels, which in the Brazilian case is generally petroleum coke (petcoke). The substitution in power plants is up to 10% and in cement plants up to 30% by weight. The calorific power of the SRF in the study by [4] is 18 MJ/kg or 4,300 kcal/kg, which corresponds to 6% of the calorific power of coal. 

Co-burning is a commercially available, ex situ technology for the treatment of nonhazardous tar and tar-contaminated soils from former manufactured gas plant (MGP) sites. The process burns MGP waste with coal in existing utility boilers at coal-fired power plants. 

Ondov, J.M., Biermann, A.H., "Physical and Chemical Characterization of Aerosol Emissions from Coal-Fired Power Plants." in Environmental and Climatic Impact of Coal Utilization, J.J. Singh and A. Deepak, Eds., (Academic Press, New York) 1979. 

About 53 percent of the electricity produced in the United States comes from coal-burning utilities. Only about 20 percent of U.S. electricity comes from nuclear power plants. Wby do Americans tend to oppose nuclear power plants more than coal-fired power plants ... 

While the development of flue gas clean-up processes has been progressing for many years, a satisfactory process is not yet available. Lime/limestone wet flue gas desulfurization (FGD) scrubber is the most widely used process in the utility industry at present, owing to the fact that it is the most technically developed and generally the most economically attractive. In spite of this, it is expensive and accounts for about 25-35% of the capital and operating costs of a power plant. Techniques for the post combustion control of nitrogen oxides emissions have not been developed as extensively as those for control of sulfur dioxide emissions. Several approaches have been proposed. Among these, ammonia-based selective catalytic reduction (SCR) has received the most attention. But, SCR may not be suitable for U.S. coal-fired power plants because of reliability concerns and other unresolved technical issues (1). These include uncertain catalyst life, water disposal requirements, and the effects of ammonia by-products on plant components downstream from the reactor. The sensitivity of SCR processes to the cost of NH3 is also the subject of some concern. 

The second reason for environmental projections is the significance of control costs. For example, proposed acid rain legislation could cost utilities and their customers billions of dollars. Before this money is spent, it is important to be able to evaluate the effects that controls may have on emissions, on employment, in different regions of the country, and the like. A large share of S02 emissions are from older, dirtier, coal-fired power plants. If these plants are retiring in a few years, it may not make economic sense to spend millions or billions of dollars to retrofit them with controls. On the other hand, if such plants will be operating for many years to come, the benefits may be considered worth the expense. 

Power from a new coal-fired power plant will cost 5 to 6.4 cents per kWh and 4 to 5.7 cents per kWh for a gas-fired plant, and 4.6 to 6.5 cents per kWh for a nuclear plant, according to UNIPEDE, the European Utility Association. 

Selenium may also be found in wastewater streams of coal-fired power plants, ore refineries, and industrial plants (e.g., selenium rectifier production) where selenium is utilized. Stack and quench waters in industry may contain 14 Jgkg Se (New-... 

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