Coal Fired Power Plants

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... 

Utilities and industrial power plant fuel-fired boilers coal - pulverized coal - cyclone cole - stoker oil wood - bark bagasse fluid coke... 

What an amazing process this is One could compare it to the burning of coal to make electricity. In a coal-fired power plant, coal is burned to boil water. Steam runs turbines that make electricity, but when the coal burns up, it s gone. 

Converting coal to electric power appears, on paper, to be a relatively simple process. In most coal-fired power plants, coal is crushed into fine powder and fed into a combnstion nnit where it is burned. Heat from the burning coal is nsed to generate steam that is nsed to spin one or more turbines to generate electricity. 

The cost of coal is of some concern, more so in places ofher fhan in fhe United States. It has been reported that the world-wide average price of coal increased from about 60/ton at the beginning of 2007 to 120/ton at the end of 2007. That tremendous increase has not been the case in the United States. Still at 30 to 40/ton (typical cost for western coal delivered to fhe Midwest or east), the fuel cosf for generating power in coal-fired plants in the... 

Fig. 12. Costs as a function of plant size for (—) coal-fired steam plants and (-) early MHD power plants where x corresponds to the EGAS reference...

Conceptual designs of two repowered existing coal-fired plants in the United States, the Montana Power Company s Corette plant in Billings, Montana, and Gulf Power s Schofi plant, in Sneads, Florida are described in References 150 and 151. 

Lower power ratings of reactors provide greater dexibiUty for a utihty to add power generation to a system (19). The AP600 uses prefabricated modules to shorten the constmction time. Thus constmction and operating costs are expected to be competitive with coal-fired plants. 

In 1956, the world s first commercial nuclear power plant started operation in England. By the 1960s, many nuclear power plants were built worldwide. At the end of the twentieth century, nuclear generating plants are used widely by U.S. electric utiHties. Since 1984, these plants have provided the second largest share of total U.S. electricity generation, 21% of annual GW-h generated, behind coal-fired power plants (see Nuclearreactors). 

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. 

A primary concern in coal-fired power generation is the release of air pollutants. Limits on SO2 output, 0.52 g/MJ equivalent of coal input to a new plant, have been estabflshed. Eor a bituminous coal of 27.9 MJ/kg there is thus an upper limit of 0.72% sulfur content. Relatively few coals can meet this requirement. The U.S. Department of Energy indicated recoverable reserves of 420 x 10 t in 1987 (2) that were categorized by sulfur content 33.5% had 0.6% S or less, 15.4% had between 0.61% and 0.83% S, 16.1% had between 0.84 and 1.67% S, 12.4% had between 1.68 and 2.50% S, and 22.6% had more than 2.5% S. The lowest sulfur coal, 86%, is found west of the Mississippi River, mainly in Montana and Wyoming, quite distant from the electric power demand centers in the East. A trend to utilization of the western coals has developed. 

In 1983 there were 116 flue-gas desulfurization (FGD) systems in service, representing 47 gigawatts-electric of power generation capacity (66). As of 1992, more than 150 coal-fired boilers in the United States operated with FGD systems. The total electrical generating capacity of these plants has risen to 72 gigawatts (67). FGD processes are classified into (/) wet-throwaway, (2) dry-throwaway, (J) wet-regenerative, and (4) dry-regenerative processes (68). 

Water Consumption and Effluent Characterization. Another advantage of CGCC power generation is derived from lower water requirements. Because more than half of the power generated in a CGCC plant comes from the gas turbine, the water requirement is only 70—80% of that required for a coal-fired power plant, where all of the power is generated from steam turbines. 

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