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27 Cards in this Set
- Front
- Back
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In a nuclear power plant that uses uranium, the heat energy is released by a process |
Fission |
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The steam generator or boiler is a major part of the many systems that comprise a steam power plant. A typical pulverized-coal-fired utility power plant is shown schematically in the figure. The major systems of this power plant can be identified as |
1. Coal receipt and preparation2. Coal combustion and steam generation3. Environmental protection4. Turbine generator and electric production5. Condenser and feedwater system6. Heat rejection, including the cooling tower |
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Coal-fired power plant |
utilizes pulverized coal firing where example of a mediumsizedmodern pulverized-coal-fired boiler is shown in the figure and incorporates low NOx burners to meet current emission requirements on nitrogen oxides. |
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OIL- AND GAS-FIRED BOILERS |
has declined except for certain areas of the world where these otherwise critical fuels are readily available and low in cost. |
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Steam consideration |
The reheat steam cycle is used on most fossil fuel–fired utility plants. In this cycle, highpressuresuperheated steam from the boiler passes through the high-pressure portion of the turbine, where the steam reduces in pressure as it rotates the turbine, and then this lower pressure steam returns to the boiler for reheating. |
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Boiler feedwater |
When water is obtained from sources that are either on or below the surface of the earth, it contains, in solution, some scale-forming materials, free oxygen, and in some cases, acids |
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INDUSTRIAL AND SMALL POWER PLANTS |
Various industries require steam to meet many of their needs: heating and air conditioning;turbine drives for pumps, blowers, or compressors; drying and other processes; water heating; cooking; and cleaning. |
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BUBBLING FLUID BED (BFB) BOILER. |
the air velocity in the bed is maintained low enough that the material that comprises the bed (e.g., fuel, ash, limestone, and sand), except for fines, is held in the bottom of the unit, and the solids do not circulate through the rest of the furnace enclosure. |
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CIRCULATING FLUID BED (CFB) BOILER. |
provides an alternative to stoker or pulverized coal firing. In general, it can produce steam up to 2 million lb/h at 2500 psig and 1000°F. It is generally selected for applications with high-sulfur fuels, such as coal, petroleum coke, sludge, and oil pitch, as well as for wood waste and for other biomass fuels such as vine clippings from large vineyards. |
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The advantages of a CFB boiler are reduced capital and operating costs that result primarily from the following: |
• It burns low-quality and less costly fuels.• It offers greater fuel flexibility as compared with coal-fired boilers and stoker-fired boilers.• It reduces the costs for fuel crushing because coarser fuel is used as compared with pulverized fuel.• Fuel sizing is slightly less than that required for stoker firing.• It has lower capital costs and lower operating costs because additional pollution control equipment, |
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The quality x of steam |
may be expressed either as a percentage or as a decimal. As most calculations involve the use of steam quality ex-pressed as a decimal, it will always be so used in this work. |
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The total enthalpy of a pound of wet steam reckoned above 32 F, is |
have= hf + xhfg |
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When the quality of steam is expressed decimally, the specific volume vow of wet saturated steam may be computed as |
vave = vf + x(vg— vf) (134) |
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The dryness or quality of saturated steam is determined by |
means of some type of steamcalorimeter. There are two general types of steam calorimeters: the separating and the throttling or superheating instruments. |
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was formed by the decomposition of vegetation that grew in prehistoric forests. At that time the climate was favorable for very rapid growth. |
Coal |
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the first product in the formation of coal and consists of partially decomposed plant and mineral matter. |
Peat |
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the lowest ranking of coal with a heating value of less than 8300 Btu/lb and a moisture content as high as 35 percent. |
Lignite |
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These coals are non-coking; i.e., they have minimal swelling on heating and have a relatively high moisture content of 15 to 30 percent. They are high in volatile matter and thus ignite easily. Theyalso have less ash and burn cleaner than lignite |
Bitominous |
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This is the highest ranked coal. It has the highest contentof fixed carbon, ranging from 86 to 98 percent. It has a low volatile content, which makes it a slow-burning fuel. Its moisture content islow at about 3 percent, and its heating value can be as high as 15,000 Btu/lb. |
Anthracite |
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These are the products that remain after the more volatile hydrocarbons have been extracted. The removal of these hydrocarbons lowers the flash point and makes the oil safe for handling andburning. |
Residual oil |
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This is the material as it comes from the oil well without subsequent processing. Sometimes, because of exposure to the weather or for other reasons |
Crude petroleum |
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These are obtained by fractional distillation and are of a consistency between kerosene and lubrication oils. Fuel oil produced in this manner does not contain the heavy tar residue found in others. The light grades of fuel oils are produced in this manner. |
Distillate oil |
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These are mixtures of two or all of the above, in proportions to meet the desired specifications |
Blended oils |
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usually occurs in the same region as petroleum |
Natural gas |
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is an analysis of the composition of fuel which gives, on mass basis, the relative amounts of moisture content, volatile matter, fixed carbon and ash. |
Proximate analysis |
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is an analysis of the composition of fuel which gives, on mass basis, the relative amounts of carbon, hydrogen, oxygen, nitgrogen, sulphur, ash and moisture. |
Ultimate analysis |
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Specific gravity |
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