燃煤循環流化床鍋爐外文翻譯

1、<p><b>　　英文文獻翻譯</b></p><p><b>　　1；文獻原文</b></p><p>　　(1)Coal-Fired, Circulating Fluidized-Bed Boilers in Action</p><p>　　Electric utilities burning coal

2、continue to search for cost-effective ways to increase electricity generation while still meeting increasingly stringent emission standards. Over the last several years, fluidized-bed combustion has emerged as a viable o

3、ption. One company with significant experience in the area of industrial and utility boiler design has developed a compact atmospheric internal recirculation circulating fluidized-bed (IR-CFB) boiler for commercial appli

4、cation.</p><p>　　Performance data for Babcock & Wilcox IR-CFB installations at Southern Illinois University (SIU) and an industrial facility in India are reported in a recent paper prepared by S. Kavidas

5、s and Mikhail Maryamchik of Babcock & Wilcox (Barberton, Ohio),C. Price of SIU (Carbondale, Illinois), and A. Mandal of Kanoria Chemicals & Industries Ltd. (Renukoot, India). The paper, entitled “B&W’s IR-CFB

6、 Coal-Fired Boiler Operating Experiences,” was presented at the Fifteenth Annual International Pittsburgh </p><p>　　IR-CFB Boiler Design</p><p>　　In a fluidized-bed boiler, crushed coal is intro

7、duced into a furnace containing a bed of either an inert material (like sand or crushed limestone) or dolomite. Pressurized air, fed into the bottom of the furnace, blows upward through the bed and causes the coal and be

8、d materials to “fluidize” in a highly turbulent, suspended state. Figure 1 profiles a typical IR-CFB furnace, demonstrating the change in bed density with increasing height. The turbulence of the fluidized-bed system all

9、ows prolonge</p><p>　　A circulating fluidized bed captures the solids carried out of the furnace and returns them to the primary combustion chamber. This recycling feature increases the fuel residence time i

10、n the furnace, which increases combustion efficiency. The Babcock & Wilcox IR-CFB boiler provides two stages of solids recirculation, maximizing fuel burnout and sulfur capture. Also, design</p><p>　　vel

11、ocities at the furnace exit are relatively low, which significantly reduces erosion of the upper furnace and primary solids separator.</p><p>　　Unique Design Features</p><p>　　One of the feature

12、s of Babcock & Wilcox’s IR-CFB design is the use of a U-beam solids separation system. As shown in Figure 2, the U-beam system consists of rows of U-shaped vertical rods attached to the roof of the furnace that inter

13、rupt the flow of the gases exiting the furnace. Two rows of U-beams are placed inside the furnace itself, and four rows of U-beams are installed behind the furnace rear wall plane. The in-furnace U-beams capture about 75

14、% of the solids, which slide down the length o</p><p>　　The IR-CFB furnace is made of gas-tight membrane enclosure water-cooled walls with studded tubing spaced every four inches. The lower furnace walls (up

15、 to a height of 7.3 meters [24 ft]) are protected with an ultra high-strength, abrasion-resistant, low-cement refractory material less than 1 inch in thickness, which is placed over the studs protruding from the cooling

16、tubes. A band of metal spray is typically applied to further protect against erosion at the point where the refractory material e</p><p>　　Other beneficial characteristics of the IR-CFB boiler design include

17、:</p><p>　　* Use of in-furnace surfaces (division and wing walls) for furnace temperature control;</p><p>　　* Gravity fuel feed and simplified secondary ash recycle system;</p><p>　

18、　* Absence of hot expansion joints, allowing significantly reduced maintenance; </p><p>　　* Smaller footprint, which allows retrofit inside existing structural steel.</p><p>　　Operating Experien

19、ce at Two Installations</p><p>　　The IR-CFB design has been installed at two locations—one at SIU in Carbondale, Illinois, and the second at the Kanoria Chemicals & Industries Ltd. (Kanoria) site in Renu

20、koot, India. The SIU installation is a 35-megawatt (MW) boiler that burns high-sulfur, low-ash Illinois coal, while the 81-MW Kanoria unit uses low-sulfur, high-ash coal. The SIU boiler has a crushed limestone</p>

21、<p>　　bed to combat the higher sulfur content of the fuel, while the Kanoria boiler uses a sand bed.</p><p>　　SIU Unit data</p><p>　　The SIU boiler is located close to the Old Ben II coal

22、mine in southern Illinois. The plant was completed in 1996 and started operation in mid-1997. Performance testing was completed in September 1997. Table 1 shows the design and performance data for the SIU boiler.</p&g

23、t;<p>　　Raw coal, delivered by truck, is moved by drag chain conveyor to a crusher. A 24-hour capacity silo stores the pulverized coal. The coal is introduced into the furnace by one gravimetric feeder through the

24、 side wall. Two 60-MMBtu/hr gas-fired, over-bed burners and two 25-MMBtu/hr gas-fired, in-bed lances provide heat for startup. A multi-cyclone dust collector is used as a secondary solids separator (downstream from the U

25、-beams). The overall solids collection efficiency exceeds 90% and solids co</p><p>　　The bed material is periodically drained from the furnace to control bed solids build-up and to remove any oversized mater

26、ial. The SIU unit has a single 8-inch diameter drain pipe to remove the bed, which is cooled with a screw ash cooler using recirculated plant water supply.</p><p>　　Cold startup to 100% maximum continuous ra

27、ting (MCR) can be achieved within five hours and the observed boiler dynamic load response is 5%–6% per minute. A boiler turndown of 5:1 has been achieved without auxiliary fuel (a turndown ratio of 3.5:1 to 4:1 is guara

28、nteed). Further, all major equipment has performed reliably while meeting or surpassing permitted emissions. A soot blower installed at the horizontal convection pass floor has experienced plugging with ash and residual

29、moisture. While th</p><p>　　Kanoria Unit Data</p><p>　　The Kanoria facility is located within the state of Utter Pradesh, India, in close proximity to the Singaroli coal mine. The boiler was con

30、structed in 1996 and began commercial operation in February 1997. Performance testing continued until September 1997. Design and performance data for the Kanoria boiler are also shown in Table 1.</p><p>　　In

31、 contrast to the Illinois coal, the Kanoria fuel is erosive, low in sulfur, and high in ash.</p><p>　　Crushed coal is introduced via two volumetric drag chain feeders through the front wall of the furnace. T

32、wo 60-MMBtu/hr oil-fired over-bed burners provide heat for startup. Solids collected by the U-beams are reinjected by gravity into the furnace at four locations. The Kanoria unit uses an electro-static precipitator for f

33、inal particulate control. Bed draining is accomplished through two bed drain pipes and ash coolers; fine material is returned to the furnace, while oversize particles are dive</p><p>　　The observed boiler ef

34、ficiency of 88.8% is higher than originally anticipated and combustion efficiency has exceeded 99%,due to very low unburned carbon and low flue gas outlet temperatures. However, the erosive nature of the fuel initially c

35、aused tubing leaks in the water-cooled furnace wall, which have been remedied by applying additional metal spray at the refractory interface and adjusting the interface angle. Also, furnace temperature exceeded design<

36、;/p><p>　　value on several occasions due to insufficient upper furnace inventory caused by failures of the first fields of the electrostatic precipitator and the ash conveying system. Adjustments to the precipi

37、tator rectifier and the ash silo backpressure have solved these problems.</p><p>　　In summary, two examples of IR-CFB boilers are successfully operating at 100% MCR with varying fuel types. IR-CFB appears re

38、liable and incorporates several very low-maintenance features that reduce operating costs. </p><p>　?。?）Why Build a Circulating Fluidized Bed Boiler</p><p>　　to Generate Steam and Electric Power

39、</p><p><b>　　Abstract</b></p><p>　　In Asia, demand for electric power continues to rise steeply due to population growth, economic development, and progres-sive substitution of alter

40、nate technology with clean forms of energy generation. Atmospheric circulating fluidized bed (CFB) echnology has emerged as an environmentally acceptable technology for burning a wide range of solid fuels to generate ste

41、am and electricity power. CFB, although less than 20 years old, is a mature technology with more than 400 CFB boilers in operation wo</p><p>　　Electric utilities and Independent Power Producers must now sele

42、ct a technology that will utilize a wide range of low-cost solid fuels, reduce emissions, reduce life cycle costs, and provide reliable steam generation for electric power generation.Therefore, CFB is often the preferred

43、 technology. Even though pulverized coal (PC) fired boilers continue to play a major role worldwide, they have inherent issues such as fuel inflexibility,environmental concerns and higher maintenance costs.</p>&l

44、t;p>　　This paper discusses the benefits of CFB boilers for utility and industrial applications. Specific emphasis is given to B&W’s nternal Recirculation CFB (IR-CFB) technology, CFB technology comparisons, PC vs.

45、 CFB technology, emissions benefits,and economics including maintenance cost and boiler reliabilty.</p><p>　　Introduction</p><p>　　Babcock & Wilcox (B&W) is a leading global supplier of

46、industrial/utility boilers and has supplied more than 700 units totaling more than 270,000 MWe. Many of B&W’s CFB boiler design features have been adapted from vast experience designing and building boilers of all ty

47、pes and sizes for industrial and electric utility applications. B&W’s design is an inherently compact, distinctive internal recirculation fluidized bed (IR-CFB) boiler featuring U-Beam solids separators. The furnace

48、and convectio</p><p>　　To date, B&W, including B&W joint ventures and licenseecompanies, has sold 16 CFB boilers worldwide, shown in Table 1.B&W offers IR-CFB boilers up to 175 MWe, both reheat a

49、nd</p><p>　　non-reheat, with full commercial guarantees and warranties. The IR-CFB boiler is simple in configuration and compact, requires a smaller boiler foot print, has minimal refractory, requires low ma

50、intenance, features quick startup, and provides high avail-ability.</p><p>　　The modern way of burning solid fuels requires fuel flex-ibility and reliable technology, plus good combustion efficiency with low

51、 emissions. CFB technology is well suited for a wide range of sold fuels. CFB technology is proven, mature and competitive.</p><p>　　What is CFB technology? </p><p>　　CFB technology utilizes the

52、 fluidized bed principle in which crushed (6 –12 mm x 0 size) fuel and limestone are injected into the furnace or combustor. The particles are suspended in a stream of upwardly flowing air (60-70% of the total air) which

53、 enters the bottom of the furnace through air distribution nozzles.The balance of combustion air is admitted above the bottom of the furnace as secondary air. While combustion takes place at 840-900 C, the fine particles

54、 (<450 microns) are elutr</p><p>　　Designers and power plant operators have vast experience in PC-fired boiler design and operations. Adapting and under-standing CFB technology by those familiar w

55、ith the PC environment requires time. CFB technology brings the capability of designs for a wide range of fuels from low quality to high quality fuels, lower emissions, elimination of high maintenance pulverizers, low au

56、xiliary fuel support and reduced life cycle costs.A PC vs. IR-CFB comparison is given in Table 2.</p><p>　　The combustion temperature of a CFB (840-900 C) is much lower than PC (1350-1500 C) which results in

57、 lower Nox for-mation and the ability to capture SO2 with limestone injection in the furnace. Even though the combustion temperature of CFB is low, the fuel residence time is higher than PC, which results in good combust

58、ion efficiencies comparable to PC. The PC pulverizers, which grind the coal to 70% less than 75 microns, require significant maintenance expenses. These costs are virtually elimina</p><p>　　CFB is a fuel-dri

59、ven and flexible technology</p><p>　　CFB can be the technology of choice for several reasons.The CFB can handle a wide range of fuels such as coal, waste coal, anthracite, lignite, petroleum coke and agricul

60、tural waste,with low heating value (>1500 kcal/kg), high moisture content (< 55%), and high ash content (< 60%). The fuel flexibility provides use of opportunity fuels where uncertainty of fuel supply exists and

61、 economics are an issue. If a CFB boiler is designed for coal, the same boiler can be used to burn lignite or petroleum</p><p>　　Environmental benefits of CFB technology</p><p>　　The CFB combust

62、ion process facilitates steam generation firing a wide range of fuels while meeting the required emissions such as sulfur dioxide (SO2 ) and nitrogen oxides (NO x) even more effectively than World Bank guidelines, as sho

63、wn in Table 3.</p><p>　　The major environmental benefit of selecting CFB technology is the removal of SO2 (90-95%) and NOx (emission is less than 100 ppm) in the combustion process without adding postcombust

64、ion cleaning equipment such as wet or dry flue gas desulfurization (FGD) systems and selective catalytic reduction (SCR) systems. When the limestone is injected into the furnace,the following reactions occur.</p>

65、<p>　　* Oxidation of sulfur S+O2 --> SO2</p><p>　　* Limestone is calcined to form calcium oxide</p><p>　　CaCO3--> CaO + CO2 –425 kcal/kg (of CaCO3 )</p><p>　　* S

66、ulfur dioxide gas reacts with solid CaO</p><p>　　SO2+ 1/2 O2 + CaO --> CaSO4 (Solid) +3740 kcal/kg (of S)</p><p>　　The resulting calcium-sulfate-based ashes are chemically stable and are eas

67、ily disposed. This ash can be used as raw material for cement manufacturing, soil stabilization, concrete blocks, road base, structural fills, etc. Limestone injection is required for fuels with sulfur greater than >0

68、.5%. Lime (CaO) and unburned carbon content must be considered in re-use applications, depending on the fuel being fired.</p><p>　　NOx present in flue gas generally comes from two sources:the oxidation of ni

69、trogen compounds in the fuel (fuel NOx) and reaction between the nitrogen and oxygen in the combustion air (thermal NOx ). With low temperature and staged combustion,the oxidation of fuel nitrogen is suppressed resulting

70、 in very low NOx emissions. NOx emissions are <100 ppm with CFB.</p><p>　　CO and hydrocarbon emissions in the CFB boiler are well controlled. In recent years, financial institutions have pushed the power

71、project developers to meet the World Bank emissions requirements. Therefore obtaining the project permit is less difficult with CFB technology.</p><p>　　Design features of B&W IR-CFB Boiler technology<

72、;/p><p>　　B&W IR-CFB technology is very comparable to PC-fired boilers in arrangement. The IR-CFB boiler design consists of the following major systems, shown in Fig. 1. The main CFB boiler components are:&

73、lt;/p><p>　　* Boiler furnace</p><p>　　* Furnace bottom air distributor and nozzles</p><p>　　* Primary solids separators and recirculation system</p><p>　　* Secondary solid

74、s separators and recirculation system</p><p>　　* Pendant superheater / reheater</p><p>　　* Economizer and horizontal tubular air heater</p><p>　　* Air assisted gravity fuel /limesto

75、ne feed system</p><p>　　Boiler Furnace</p><p>　　The furnace cross section is selected based on flue gas superficial velocity. B&W typically uses furnace depths of 3.7 m,4.6 m and 5.4 m, depe

76、nding on the unit size. The furnace enclosure is made of gas-tight membrane water-cooled walls having 63.5 mm or 76 mm tube diameters on 102 mm centers. The furnace primary zone is reduced in plan area cross section to p

77、rovide good mixing and promote solids entrainment at low load.The auxiliary startup burners, fuel feed points and secondaryash re-injectio</p><p>　　A thin layer of refractory is applied on all lower furnace

78、walls,including the lower portion of the division walls and wing wall nose to protect against corrosion and erosion. An ultra high strength abrasion-resistant low cement alumina refractory 16-25 mm thick is applied over

79、a dense pin studded pattern. B&W has patented a RDZTM reduced diameter zone feature that elimihas nates erosion concern at the furnace interface. The furnace temperature is precisely controlled by maintaining proper

80、inven</p><p>　　Air Distrbutors and Nozzles</p><p>　　The furnace bottom air plenum or wind box is made of water-cooled panels or casing depending on startup air temperature. Bubble caps are fitte

81、d on the water-cooled distributor floor panels as shown in Fig. 2. The bubble caps are designed to distribute air uniformly, prevent the back sifting of solids at low load operation, and create good turbulence for fuel /

82、sorbent mixing in the primary zone. The bubble caps are spaced 102 mm x 117 mm with 60-70% of total combustion air admitted through the bo</p><p>　　Primary Solids Separators</p><p>　　The solids

83、separation system is a key element of any CFB boiler design. The B&W separation system is designed for the life of the unit without replacement, influencing life cycle costs.The B&W IR-CFB has a two stage primary

84、 solids separator as shown in Fig. 3, comprised of in-furnace U-Beam separators and external U-Beam separators. The in-furnace U-Beams (two rows) are able to collect nearly 75% of the solids. The remaining solids are col

85、lected by the four rows of external U-Beams and are disch</p><p>　　Secondary Solids Separator</p><p>　　The multicyclone dust collector (MDC) is located in the convective pass either upstream or

86、downstream of the economizer.The MDC typically has a top inlet and top outlet as shown in Fig. 5. The MDC tube diameter is normally 229 mm arranged over the second pass entire cross section. The MDC provides outstanding

87、retainment of fine particles up to 50 microns. The MDC collection tubes and spin vanes have high hardness (550 BHN), designed for longer life and easy replacement duringplanned outages.</p><p>　　The small qu

88、antities of fines which escape from the external U-Beams are collected by the MDC. The collected fines are stored in the MDC hopper. Variable speed rotary feeders or inclinedscrews are used to control the ash recycle flo

89、w rate from the hopper. Precise furnace temperature control is achieved by adjusting the speed of the rotary feeders or inclined screws, taking the temperature signal from the furnace.</p><p>　　The superheat

90、er may consist of vertical pendant type primary and secondary banks, located in the convection pass, as well as surface in the furnace in the form of superheater wing walls. An attemperator is used to control the final s

91、team temperature over the design load range. The flue gas velocities are relatively low and selected by considering the dust loading and ash erosivity of the fuel. When required, the reheater is located in the convection

92、 pass, and steam bypass is recommended to contr</p><p>　　Economizer and Horizontal Tubular air heater</p><p>　　The economizer is designed with tubes running front to back in an in-line arrangeme

93、nt. Flue gas velocities used consider the dust loading and ash erosivity of the fuel. If the MDC is located upstream of the economizer, higher velocities are used and both the economizer and the air heater are located in

94、 an in-line arrangement to minimize ash fouling. The air heater is located after the MDC and the economizer. The flue gas is outside the tubes and air is passed through the tubes. A hopper is provi</p><p>　　

95、Air-Assisted Gravity Fuel/Limestone Feed System</p><p>　　Fuel handling and feeding is one of the major challenges in CFB boiler operation, especially with waste fuels because of high fines and moisture conte

96、nt. The crushed fuel (6-12 mm x 0) is stored in the silo, usually located in front of the boiler as shown in Fig. 6. Fuel is fed to the boiler via down spout from silo discharge to feeder and a series of feeders and grav

97、ity feed chutes. The fuel chute will have at least a 65 degree angle from horizontal. Primary air is used to sweep the fuel into t</p><p>　　The limestone handling and feeding system is relatively simple comp

98、ared to the fuel feed system. Limestone is fed either pneumatically or mechanically into the CFB boiler. The pneumatic system feeds the limestone directly into the furnace through furnace openings in the front and rear w

99、alls. In the mechanical system, the limestone is fed into the discharge end of the fuel feeders via rotary feeders. The limestone falls by gravity down the fuel feed chute with the fuel into the furnace,and is a f</p&