Fossil fuel steam plants

Conventional steam generation plants or more modern cogeneration steam plants (Fig. 8.17) consist of many sections operating at different temperatures and pressures  

In such plants, there are special corrosion problems in each of these sections. There are also special problems associated with exposure to hot combustion gases. The materials used in high-temperature steam and water include steels, stainless steels, and 

City water Treated Raw water tank water tank 

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Fossil Fuel-Fired Plants. In modem, fossil fuel-fired power plants, the Rankine cycle typically operates as a closed loop. In describing the steam—water cycle of a modem Rankine cycle plant, it is easiest to start with the condensate system (see Fig. 1). Condensate is the water that remains after the steam employed by the plant s steam turbines exhausts into the plant s condenser, where it is collected for reuse in the cycle. Many modem power plants employ a series of heat exchangers to boost efficiency. As a first step, the condensate is heated in a series of heat exchangers, usually sheU-and-tube heat exchangers, by steam extracted from strategic locations on the plant s steam turbines (see HeaT-EXCHANGETECHNOLOGy). 

The increasing number of atomic reactors used for power generation has been questioned from several environmental points of view. A modern atomic plant, as shown in Fig. 28-3, appears to be relatively pollution free compared to the more familiar fossil fuel-fired plant, which emits carbon monoxide and carbon dioxide, oxides of nitrogen and sulfur, hydrocarbons, and fly ash. However, waste and spent-fuel disposal problems may offset the apparent advantages. These problems (along with steam generator leaks) caused the plant shown in Fig. 28-3 to close permanently in 199T. 

Utility operators may choose from several technologies to generate electricity, although the most common approach is via the use of high-temperature, fossil fuel boiler plants. In this case, the boiler (steam generator) itself may be of several different design types. 

When hydrogen is burned in a combustion chamber instead of a conventional boiler, high-pressure superheated steam can be generated and fed directly into a turbine. This could cut the capital cost of a power plant by one half. While hydrogen is burned, there is essentially no pollution. Expensive pollution control systems, which can be almost one third of the capital costs of conventional fossil fuel power plants are not required. This should also allow plants to be located closer to residential and commercial loads, reducing power transmission costs and line losses. 

Nuclear power plants generate electricity in much the same way fossil fuel power plants do. Water is heated to create steam that can be used to turn electricity-generating fur bines. The fundamental difference between these two types of power pi ants i s th e fuel used to h eat th e water. A fossil fuel plant burns fossil fuel, such as coal or petroleum, but a nuclear plant, such as the one shown in this chapter s opening photograph, uses the heat created by nuclear fission to heat the water. 

In many ways, the design of a nuclear power plant and that of a fossil fuel burning power plant are very similar. In both cases heat from a reaction is used to generate steam. The steam is then used to drive turbines that produce electricity. In a typical fossil fuel power plant, the chemical combustion of coal, oil, or gas generates the heat, whereas in a nuclear power plant, a nuclear fission reaction generates the heat. Because of the hazardous radioactive fuels and fission products present at nuclear power plants, a dense concrete structure is usually built to enclose... 

If we compare for the two kinds of power plants we find that the fossil fuel power plant has about 40% higher efficiency, i.e. the amount at "reject heat" is up to 40% higher for the typical nuclear power plant ((0.50—0.30)/0.50). This lower effici icy is a consequence of the lower steam temperature of the nuclear reactor. However, in the last 10 years considerable development has taken place with respect to coolant, cladding and fuel stability, and inertness, allowing considerably higher fuel temperatures, cf. Ch. 21. 

The electric power industry uses three types of fossil fuel power plants coal-fired steam, gas turbine, and combined cycle power plants. The most common and widely used is the pulverized coal-fired steam power plant. Fuel oil can be used in place of... 

In many respects, a nuclear power plant is similar to a conventional fossil fuel power plant. In this type of plant, a fossil fuel (coal, oil, natural gas) is burned, and the heat is used to boil water, which, in turn, is used to make steam. 

Evans, Robert L. Fueling Our Future An Introduction to Sustainable Energy. New York Cambridge University Press, 2007. Looks at energy supply and demand and how to reduce reliance on fossil fuels. Leyzerovich, Alexander S. Steam Turbines for Modern Fossil-fuel Power Plants. Lilburn, Ga. Fairmont Press, 2008. Closely examines the engineering and operating properties of modern steam turbines in fossil fuel power plants. 

Recommended Practice for Fire Protection for Fossil-Fueled Steam and Combustion Turbine Electric Generating Plants, Report No. NFPA 850, National Fire Protection Association, Quincy, MA, 1990. 

The major challenge to PAFC systems is the high cost of materials the high platinum content is particularly costly and represents 10% to 15% of the total PAFC system costs. Other material costs and processing costs also contribute to making the first cost of the PAFC system considerably greater than the average fossil-fueled steam turbine power plant. 

Leyzerovich, A.S. (2008) Steam Turbines for Modem Fossil-Fuel Power Plants, Fairmont Press, Lilbum. 

Tremmel, A. and Hartmann, D. (2004) Efficient steam turbine technology for fossil fuel power plants in economically and ecologically driven markets. VGB PowerTech, 84 (11), 38-43. 

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