Fossil-fired plants

Since the early 1960s, advanced steam conditions have not been pursued. In the 1960s and early 1970s there was little motivation to continue lowering heat rates of fossil-fired plants due to the expected increase in nuclear power generation for base-load application and the availability of relatively inexpensive fossil fuel. Therefore the metallurgical development required to provide material X for advanced steam conditions was never undertaken. 

Modem fossil-fired plants typically have capacities from 300 to 900 MW 600 MW is the approximate average for U.S. utilities (Miller and Allen, 1985). Some plants have been built with capacities of 1300 MW. Steam conditions... 

I.A. Johnston, S. Westaway, A Review of the Factors Influencing the Selection of Desulfurisation Process of Large Fossil-fired Plant , Proc. International Lime Congress, Berlin, 1994. 

If a large power station is needed in the future, it could be made up of multiple small units each being added as the need arises. This is not unlike the manner in which fossil-fired plants were originally built with multiple smaller units. 

In the longer term, however, a resumption of economic growth will increase electricity demand and will probably lead to new orders for nuclear power plants even in countries where ordering has now been suspended, if the main problems associated with nuclear power can be resolved, i.e. construction times kept under control and thereby also costs. Under the same conditions the fact that in a few years old fossil fired plants and the first nuclear power plants have to be replaced may also bring new orders. There is also a growing awareness of the need to reduce emissions of sulphur oxides and other pollutants from fossil fuel plants, and one means of doing this is to include more nuclear plants in the energy mix. 

The market for electricity generation is shared by fossil-fired (coal, oil, gas), nuclear, hydroelectric and other (geothermal, etc.) plants. In general, most readily accessible hydroelectric sites in the size ranges under discussion have already been developed in OECD countries, so in essence SMPRs and MPRs will have to compete for market share against fossil-fired plants, especially coal-fired ones of conventional and advanced designs. 

All systems that are important to safeguard plant safety, are protected by the concrete vessel. The rest of the plant can be built as a conventional fossil-fired plant. 

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. 

Although the petrochemical and metals industries were the primai y focus of the toxic air pollutants legislation, approximately forty of these substances have been detected in fossil power plant flue gas. Mercury, which is found in trace amounts in fossil fuels such as coal and oil, is liberated during the combustion process and these emissions may be regulated in the future. EPA issued an Information Collection Request (ICR) that required all coal-fired plants to analyze their feed coal for mercury and chlorine. Since these data will be used in making a regulatory decision on mercury near the end ot the year 2000, it is critical that the power industry provide the most accurate data possible. 

Fossil-fuel-fired boilers, 23 216 Fossil fuel plants, combined cycle,... 

The importance of chemistry to the nuclear power industry is now well recognized. Chemical control in water circuits is an accepted part of the operating requirements of nuclear generating stations, as it is for modern fossil-fired stations. While there have been major advances in knowledge of the chemistry of aqueous systems at temperatures above lOQoC, there is still a need for further work. As we improve our understanding of thermodynamics and kinetics of solid-aqueous reactions and the effect of radiation on them, we can expect further advances in controlling radiation fields in reactor circuits and in minimizing iron deposition in GS plants. 

Figure 12 shows the quantity of CO2 emitted into the atmosphere from two geothermal power plants in Iceland and how it compares with CO2 emission from fossil fuel plants. At Krafla, the quantity of C02 emitted per MW-year (MWy) is 8401, which is only about 10% of that from a typical coal-fired power plant (8760 t/MWy, Armannsson Kristmannsdottir 1992). The... 

Last year China added 96 gW of new coal-burning power plants—without any C02 cleanup—to its electricity-generating capacity. Today, China is building almost two fossil-fired power plants a week. In 2006, she added 114 gW to her fossil-generating capacity. Last year she burned 2.7 billion tons of coal. This is 75% of the quantity that was projected for 2020. Since 1990, American emissions rose by 18%, whereas Chinese emissions increased by 77%. Because the Chinese economy is three times as "carbon intensive" as the American, dollar for dollar more reduction could be achieved if investments were made to reduce Chinese, instead of American, power plant emissions. 

Figure 4. Exergy (and energy) flow diagram for a conventional fossil-fired steam power plant (negative numbers are exergy consumptions). ...

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