1、英文文献翻译 1；文献原文 (1)Coal-Fired, Circulating Fluidized-Bed Boilers in Action Electric utilities burning coal continueto search for cost-effective ways toincrease electricity generation whilestill meeting increasingly stringent emissionstandards. Over the last several years,fluidized-bed combustion has e
2、merged as aviable option. One company with significant experience in the area of industrial andutility boiler design has developed a compact atmospheric internal recirculation circulating fluidized-bed (IR-CFB) boiler forcommercial application. Performance data for Babcock & WilcoxIR-CFB installatio
3、ns at Southern IllinoisUniversity (SIU) and an industrial facility inIndia are reported in a recent paper preparedby S. Kavidass and Mikhail Maryamchik ofBabcock & Wilcox (Barberton, Ohio),C. Price of SIU (Carbondale, Illinois), andA. Mandal of Kanoria Chemicals & Industries Ltd. (Renukoot, India).
4、The paper, entitled B&Ws IR-CFB Coal-Fired BoilerOperating Experiences, was presented atthe Fifteenth Annual International Pittsburgh Coal Conference, held September 1418, 1998 inPittsburgh, Pennsylvania. IR-CFB Boiler Design In a fluidized-bed boiler, crushed coal isintroduced into a furnace contai
5、ning a bedof either an inert material (like sand orcrushed limestone) or dolomite. Pressurizedair, fed into the bottom of the furnace, blowsupward through the bed and causes the coaland bed materials to fluidize in a highlyturbulent, suspended state. Figure 1 profilesa typical IR-CFB furnace, demons
6、trating thechange in bed density with increasingheight. The turbulence of the fluidized-bedsystem allows prolonged contact betweenthe air and the particles of coal, resulting inmore complete combustion at a lower temperature than older systems (which reducesnitrogen oxides). If sorbent material such
7、 aslimestone is used as bed material, emissionsof sulfur dioxide are likewise reduced due toconversion to calcium sulfate. Further, because combustion occurs at a lower temperature, the process is relatively insensitiveto the type of fuel burned. This allows theuse of alternative fuels such as coal
8、waste,biomass fuels, petroleum coke, and otherlower British thermal unit (Btu) material. A circulating fluidized bed captures thesolids carried out of the furnace and returnsthem to the primary combustion chamber.This recycling feature increases the fuel residence time in the furnace, which increase
9、scombustion efficiency. The Babcock &Wilcox IR-CFB boiler provides two stagesof solids recirculation, maximizing fuelburnout and sulfur capture. Also, design velocities at the furnace exit are relativelylow, which significantly reduces erosion ofthe upper furnace and primary solids separator. Unique
10、 Design Features One of the features of Babcock & Wilcoxs IR-CFB design is the use of a U-beamsolids separation system. As shown in Figure 2, the U-beam system consists of rowsof U-shaped vertical rods attached to theroof of the furnace that interrupt the flow ofthe gases exiting the furnace. Two ro
11、ws ofU-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% of thesolids, which slide down the length of thebeams back into the combustion chamber.The remaining solid particles captured in theex
12、ternal U-beams are collected in a particlestorage hopper, which is periodically emptied back into the furnace forreburning.Theflue gas velocity across the U-beams isaround 8 meters/second (26.5 ft/sec) or less,producing a relatively low gas-side pressuredrop (less than 1 inch of water column) ascomp
13、ared to conventional cyclone-typeseparators (6 to 10 inches of water column). The IR-CFB furnace is made of gas-tightmembrane enclosure water-cooled wallswith studded tubing spaced every fourinches. The lower furnace walls (up to aheight of 7.3 meters 24 ft) are protectedwith an ultra high-strength,
14、 abrasion-resistant, low-cement refractory material lessthan 1 inch in thickness, which is placedover the studs protruding from the coolingtubes. A band of metal spray is typicallyapplied to further protect against erosion atthe point where the refractory material ends.The very thin application of r
15、efractory material means faster startup and less maintenance cost. Other beneficial characteristics of the IR-CFB boiler design include: * Use of in-furnace surfaces (division andwing walls) for furnace temperature control； * Gravity fuel feed and simplified secondary ash recycle system； * Absence o
16、f hot expansion joints, allowingsignificantly reduced maintenance； * Smaller footprint, which allows retrofitinside existing structural steel. Operating Experience at Two Installations The IR-CFB design has been installed attwo locationsone at SIU in Carbondale, Illinois, and the second at the Kanor
17、iaChemicals & Industries Ltd. (Kanoria) sitein Renukoot, India. The SIU installation is a35-megawatt (MW) boiler that burns high-sulfur, low-ash Illinois coal, while the 81-MW Kanoria unit uses low-sulfur, high-ashcoal. The SIU boiler has a crushed limestone bed to combat the higher sulfur content o
18、fthe fuel, while the Kanoria boiler uses a sandbed. SIU Unit data The SIU boiler is located close to the OldBen II coal mine in southern Illinois. Theplant was completed in 1996 and startedoperation in mid-1997. Performance testingwas completed in September 1997. Table 1shows the design and performa
19、nce data forthe SIU boiler. Raw coal, delivered by truck, is movedby drag chain conveyor to a crusher. A24-hour capacity silo stores the pulverizedcoal. The coal is introduced into the furnaceby one gravimetric feeder through the sidewall. Two 60-MMBtu/hr gas-fired, over-bed burners and two 25-MMBtu
20、/hr gas-fired, in-bed lances provide heat for startup.A multi-cyclone dust collector is used as asecondary solids separator (downstreamfrom the U-beams). The overall solids collection efficiency exceeds 90% and solidscollected in the cyclone are returned to thefurnace via an air fluidized conveyor.
21、Abaghouse provides final particulate control. The bed material is periodically drainedfrom the furnace to control bed solids build-up and to remove any oversized material.The SIU unit has a single 8-inch diameterdrain pipe to remove the bed, which iscooled with a screw ash cooler using recirculated
22、plant water supply. Cold startup to 100% maximum continuous rating (MCR) can be achieved withinfive hours and the observed boiler dynamicload response is 5%6% per minute. Aboiler turndown of 5:1 has been achievedwithout auxiliary fuel (a turndown ratio of3.5:1 to 4:1 is guaranteed). Further, all maj
23、orequipment has performed reliably whilemeeting or surpassing permitted emissions.A soot blower installed at the horizontalconvection pass floor has experienced plugging with ash and residual moisture. Whilethe boiler can operate successfully withoutthe soot blower, more investigation isneeded to ov
24、ercome this operational glitch. Kanoria Unit Data The Kanoria facility is located within thestate of Utter Pradesh, India, in close proximity to the Singaroli coal mine. The boilerwas constructed in 1996 and began commercial operation in February 1997. Performance testing continued until September19
25、97. Design and performance data for theKanoria boiler are also shown in Table 1. In contrast to the Illinois coal, the Kanoriafuel is erosive, low in sulfur, and high in ash. Crushed coal is introduced via two volumetric drag chain feeders through the front wallof the furnace. Two 60-MMBtu/hr oil-fi
26、redover-bed burners provide heat for startup.Solids collected by the U-beams are reinjected by gravity into the furnace at fourlocations. The Kanoria unit uses an electro-static precipitator for final particulate control. Bed draining is accomplished throughtwo bed drain pipes and ash coolers； finem
27、aterial is returned to the furnace, whileoversize particles are diverted to the ashdisposal system. The observed boiler efficiency of 88.8%is higher than originally anticipated andcombustion efficiency has exceeded 99%,due to very low unburned carbon and lowflue gas outlet temperatures. However, the
28、erosive nature of the fuel initially causedtubing leaks in the water-cooled furnacewall, which have been remedied by applyingadditional metal spray at the refractory interface and adjusting the interface angle.Also, furnace temperature exceeded design value on several occasions due to insufficient u
29、pper furnace inventory caused by failures of the first fields of the electrostaticprecipitator and the ash conveying system.Adjustments to the precipitator rectifier andthe ash silo backpressure have solved theseproblems. In summary, two examples of IR-CFBboilers are successfully operating at 100%MC
30、R with varying fuel types. IR-CFB appears reliable and incorporates several verylow-maintenance features that reduce operating costs. （ 2） Why Build a Circulating Fluidized Bed Boiler to Generate Steam and Electric Power Abstract In Asia, demand for electric power continues to rise steeplydue to population growth, economic development, and progres-sive substitution of alternate technology
