熱能與動力工程專業(yè)英語翻譯CH02教案

1、Chapter2Boiler第二章鍋爐29-9Airheater空預(yù)器Anchor支座，固定Anhydrousammonia無水氨Anthracite無煙煤Atomized霧化Austenitic奧氏體鋼Auxialiary輔助機(jī)械A(chǔ)xis軸Bagasse甘蔗渣Baretube光管Bark樹皮Beam梁，橫梁Bituminouscoal煙煤Blade葉片Blast鼓風(fēng)Blowdown排污Boiler鍋爐Bulk大塊的Burnerzone燃燒器區(qū)域Butane烷Calcination煨燒Capacity出力Carbonsteel碳鋼Cerium制iChromium銘Circulatingflui

2、dizedbedCFB循環(huán)流化床鍋爐Coalchar煤焦Cogenerator熱點聯(lián)產(chǎn)機(jī)組Combustion燃燒Commissioning試運行Compressor壓縮機(jī)、壓氣機(jī)Condenser凝汽器Containment反應(yīng)堆安全殼Convection對流Coolant制冷劑Coordinated坐標(biāo)，定位Corten低合金耐腐蝕鋼Counterflow逆流（換熱器）Creepstrength蠕變強(qiáng)度Criterion標(biāo)準(zhǔn)Criticalpressure臨界壓力Culm煤屑Cyclonefurnace旋風(fēng)爐Debris殘骸、有機(jī)殘留物Decane癸烷Decay分解Deposited沉積，

3、沉淀的Deterioration惡化Dieseloil柴油Differential差動，微分Distillate偏出物Distortion變形Divisionwall分隔墻，雙面水冷壁Drainage疏水Drum汽包Dwelltime保留時間Economizer省煤器Embrittlement脆性，脆化Equalization均衡，平衡Erosive侵蝕的，腐蝕的Ethane乙烷Evaluate評估，評價Evaporate蒸發(fā)Excessair過量空氣Extendedsurface擴(kuò)展受熱面Fatigue疲勞Feedwater給誰Ferrite鐵素體Fin鰭片，肋片F(xiàn)lange法蘭Fluega

4、s煙氣Fouling沾污Furnace爐膛Generator發(fā)電機(jī)Geological地質(zhì)的Girth環(huán)形Govern控制、調(diào)節(jié)Gravity重力Header聯(lián)箱，集箱Helical螺旋狀的Helium氮Heterogeneous不均勻的Hopper斗，料斗Husk殼，外殼Hydraulic水力的，液壓的Ignite點火Impurity雜質(zhì)Inert惰性Inferior低級的，劣質(zhì)的Ingredients成分Ingress進(jìn)口，入口In-line順列Inorganic無機(jī)的Ion離子Jurisdiction權(quán)限Lignite褐煤Lime石灰Limestone石灰石Lowalloy低合金鋼Low

5、-volatile低揮發(fā)分的Margin裕量，安全系數(shù)Matrix矩陣Membrane膜Methane甲烷Mill磨煤機(jī)Molecule分子Molten熔化Nitricoxide氮氧化物Nonpressure非承壓的Nontoxic無毒的Organisms有機(jī)體Oxidation氧化Peat泥煤Pendantssuperheatplaten懸吊式屏式過熱器Pentane戊烷Petrochemical石油化工制品Petroleum石油制品Plasmaspraycoating等離子噴涂Platen屏Polymer爽合物Pores氣孔，小孔Porosity多空的Potassium鉀Prandtlnu

6、mbers普朗特數(shù)Prefabricated預(yù)制的Premiumfuel優(yōu)質(zhì)燃料Pressureloss壓力損失Primaryair一次風(fēng)Propane丙烷Proximateanalysis工業(yè)分析Pulp紙漿Pyrites黃鐵礦Radius半徑，范圍Rareearthelement稀土元素Recuperator間壁式換熱器Regenerator回?zé)崞?，蓄熱器Regulate控制，調(diào)節(jié)Repercussions反應(yīng)Reservoirs儲氣罐Residualefueloil渣油Resonant共振Retract縮回Reynoldsnumber雷諾數(shù)Rigid剛性的，緊密地Rollers輯子Sca

7、le水垢,Seal密封Sedimentary沉積Serpentinetube蛇形管Shale頁巖Silica二氧化硅Silt淤泥Single-phase單相Skincasing外護(hù)板Slag結(jié)渣Slurry水煤漿Sodium鈉Solvents溶劑Sootblower吹灰器Sourgas含硫氣體Specification規(guī)格Stableignition穩(wěn)定著火Stantonnumber斯坦頓數(shù)Saturated飽和的Straw稻草Steamlineblowing蒸汽管路吹灰Steams莖,桿Stresscorrosion應(yīng)力腐蝕Structuralformula結(jié)構(gòu)式Stud雙頭螺栓Subbit

8、uminous貧煤，次煙煤Suction真空，負(fù)壓Sulphur硫Superheater過熱器Swamp沼澤Sweetgas無硫氣Switchgear配電裝置，開關(guān)裝置Temperature-entropy溫燧圖Tenacious黏的Thermodynamics熱力學(xué)Tubebundles管束Tubular管狀的Turbine汽輪機(jī)Velocity速度Verticalspidlemill中速磨,立軸磨Vessel容器Viscosity黏度Volumetricexpansion體膨脹Vulnerable易損的，薄弱的Wear磨損Welded焊接Wingwall屏式凝渣管Yttrim&LA

9、bbreviationsAFBC常壓流化床燃燒AFCO燃料自動切斷AFWC給水自動切斷ASME美國機(jī)械工程師協(xié)會ATM標(biāo)準(zhǔn)大氣壓BFP鍋爐給水泵BUT按鈕BWC鍋爐水濃度BYP旁路CFBB循環(huán)流化床鍋爐MCR最大連續(xù)蒸發(fā)量DAS數(shù)據(jù)采集系統(tǒng)DEH數(shù)字電液系統(tǒng)DNB偏離核態(tài)沸騰FDF送風(fēng)機(jī)FGD煙氣脫硫FSSS爐虺安全檢測保護(hù)系統(tǒng)HRB回?zé)徨仩tIDF引風(fēng)機(jī)IGCC整體煤氣化聯(lián)合循環(huán)LMTD對數(shù)平均溫差MFT主燃料切斷MUF鍋爐補(bǔ)給水NWL正常水位OFA火上風(fēng)，燃盡風(fēng)PFBC增壓流化床燃燒SSC刮板除渣機(jī)TGA熱重分析儀UBC未燃燒WFGD濕法煙氣脫硫24IntroductionBoilersus

10、eheattoconvertwaterintosteamforavarietyofapplications.Primaryamongtheseareelectricpowergenerationandindustrialprocessheating.Steamhasbecomeakeyresourcebecauseofitswideavailability,advantageouspropertiesandnontoxicnature.Thesteamflowratesandoperatingconditionscanvarydramatically;from10(X)1b/h(0.1kg/s

11、)inoneprocessusetomorethan10millionIb/h(1260kg/s)inlargeelectricpowerplant;fromabout14.7psi(1bar)and212°Finsomeheatingapplicationstomorethan4500psi(3lObar)and1100°F(593)inadvancedcyclepowerplant.1.1 能介SSC鍋爐利用熱量使水轉(zhuǎn)變成蒸汽以進(jìn)行各種利用。其中主要是發(fā)電和工業(yè)供熱。由于蒸汽具有有利的參數(shù)和無毒特性，因此蒸汽作為一種關(guān)鍵的工質(zhì)(資源)被廣泛地應(yīng)用。蒸汽流量和運行參數(shù)的變

12、化很大：從某一過程里1000磅/小時(O.126kg/S)到大型電廠超過10X106磅/小時(1260kg/s),壓力從一些加熱應(yīng)用的力.7磅/ii?(I.O135bar)212F(100)到先進(jìn)循環(huán)電廠的4500磅/id(310bar)HOOF(593C)。Modemboilerscanbeclassifiedbyvariouscriteria.Theseincludeenduse,firingmethod,operatingpressure,fuelandcirculationmethod.現(xiàn)代鍋爐可根據(jù)不同的標(biāo)準(zhǔn)分類。這些包括最終用途、燃燒方式、運行壓力、燃料和循環(huán)方式。Utilityb

13、oilersareusedprimarilytogenerateelectricityinlargecentralpowerstations.Theyaredesignedtooptimizeoverallthermodynamicefficiencyatthehighestpossibleavailability.Akeycharacteristicofnewerunitsistheuseofareheatersectiontoincreaseoverallcycleefficiency.大型中心電站的電站鍋爐主要用來發(fā)電。它們經(jīng)過優(yōu)化設(shè)計，可達(dá)到最高的熱效率。新機(jī)組的關(guān)鍵特性是利用再熱器提

14、高整個循環(huán)效率。Avarietyofadditionalsystemsalsoproducesteamforpowerandprocessapplications.Thesesystemsusuallytakeadvantageoflowcostorfreefuels,acombinationofpowercyclesandprocess,andrecoveryofwasteheatinordertoreduceoverallcosts,examplesoftheseinclude:各種附加的系統(tǒng)也產(chǎn)生蒸汽用于發(fā)電及其他過程應(yīng)用。這些系統(tǒng)常常利用廉價或免費燃料，聯(lián)合動力循環(huán)和過程，以及余熱回收

15、，以減少總費用。這些例子包括：Gasturbinecombinedcycle(CC)useadvancedgasturbineswithheatrecoverysteamgeneratoraspartofabasecycletousewasteheatrecoveryandincreasethermalefficiency.燃?xì)廨啓C(jī)聯(lián)合循環(huán)(CC)：先進(jìn)的燃?xì)廨啓C(jī)，將余熱鍋爐作為基本循環(huán)的一部分，以利用余熱并提高熱效率。integratedGasificationCombinedCycle(IGCC)addsacoalgasifiertotheCCtoreducefuelcostandmini

16、mizeairborneemissions.整體煤氣化聯(lián)合循環(huán)(IGCC)：在CC基礎(chǔ)上增加煤氣化爐，以降低燃料費用并將污染排放降到最低。PressurizedFluidized-bedCombustion(PFBC)includeshigherpressurecombustionwithgascleaningandexpansionofthecombustionproductsthroughagasturbine.增壓循環(huán)流化床燃燒(PFBC)：在更高壓力下燃燒，包括燃?xì)鈨艋?，以及燃燒產(chǎn)物膨脹并通過燃?xì)廨啓C(jī)做功.Blastfurnacehoodheatrecoverygeneratesste

17、amusingthewasteheatfromablastfurnace.高爐排煙熱量回收：利用高爐余熱產(chǎn)生蒸汽。Solarsteamgeneratorusesconcentratorstocollectandconcentratesolarradiationandgeneratesteam.太陽能蒸汽發(fā)生器：利用集熱器收集太陽輻射熱產(chǎn)生蒸汽。1.2 DevelopmentofUtilityBoilerThemodem660MWcoal-firedboilerhassome6000tonsofpressurepartswhichinclude500kmoftubing,3.5kmofinteg

18、ralpipingand30,000tubebuttwelds.Itistheculmination教材25頁ofsomefiftyyearsdevelopmentandwhilethebasicconceptofpulverizedfuelfiringintoafurnacelinedwithevaporatortubes,withthecombustiongasesthenpassingoverconvectionsuperheaterandheatrecoverysurface,hasremainedunchanged,theadvancementofsteamconditions,in

19、creasesinunitsizeandthepropertiesofthefuelfiredhaverequiredmajorchangesinmaterialsemployed,fabricationtechniquesandoperatingprocedures.1.3 電站鍋爐的發(fā)展現(xiàn)代660MW燃煤鍋爐有大約6000噸的壓力部件，其中包括500米的受熱面管材，3.5米連接管，和3(XXX)個管接頭焊口。這是經(jīng)過大約50年發(fā)展的成果，并形成了至今未變的基本概念，即燥粉在布置有蒸發(fā)管束的爐膛內(nèi)燃燒，然后煙氣通過對流過熱器和熱回收表面。蒸汽參數(shù)的提高，機(jī)組容量的增大及燃料燃燒特性改進(jìn)都要求

20、在材料、制造技術(shù)和運行程序上相應(yīng)發(fā)展。IntheyearsimmediatelyfollowingthesecondWorldWar,iswascustomarytoinstallinapowerstation,agreaternumberofboilersthanturbines,theboilersfeedingarangetowhichtheturbineswereconnected.Thisarrangementreflectedtheinferioravailabilityofboilerscomparedwithturbinesbutincreaseinboileravailabi

21、lityinthelate1940sledtotheacceptanceofunitizedboilersandturbines.Thechangetounitizedboilerandturbineallowedreheattobecomepracticaland,withtheavailabilityofhightemperaturesteels,therefollowedacontinuousadvanceinsteamingconditionstothecurrentstandardcycleof2400Ibf/in2(165.5bar),568withreheatto568C.Tot

22、akefulladvantageofthemoreadvancedsteamconditionsandtoobtaintheeconomiesofsize,thenextfifteenyearsalsosawatwenty-foldincreaseinunitsize.二戰(zhàn)后的一些年里，在電廠安裝鍋爐的數(shù)量多于汽輪機(jī)是很常見的，鍋爐提供蒸汽到母管然后到汽機(jī)。這種布置反應(yīng)了鍋爐的可用性低于汽輪機(jī)。四十年代后期，隨著鍋爐可用性的提高，鍋爐和汽機(jī)開始可以相互配套使用°這一變化使再熱變得可行，而且隨著高溫鋼材可用性的提高，蒸汽參數(shù)不斷變化，達(dá)到了當(dāng)前的24001bf7in2(165.5bar

23、),568和568c再熱的標(biāo)準(zhǔn)循環(huán)。為充分利用更高的蒸汽參數(shù)和獲得更大的經(jīng)濟(jì)性，在接下來的15年，機(jī)組容量又增加了20倍。Autilitynormallyprocuresplantfromspecialistmanufactureswhohaveresponsibilityfordesign,manufacture,erectionandcommissioning.Whilethemanufacturescarryoutdevelopmentofmanufacturingprocessandcontinuouslyupdatetheirdesignmethods,andchangeinoper

24、ationconditionsandsizenecessarilyresultsinanewplantbeingofaprototypenature.Whilesomenewfeaturescanbetestedinadvanceofconstructiontheonlyrealtestofanewboilerdesignisinoperationandwithitsassociatedturbineandgenerator.Thecommercialsuccessofanewdesignisprovedoverthewholeprojectedlifeofpowerstationanduti

25、lity,therefore,hastobalancetheimmediateeconomicadvantagesofanewdesignintermsofimprovedefficiency,reducedcapitalcosts,etc.againsttheriskofpooravailability,needformajormodifications,etc.,whichmightresultfromanewdevelopment.Autilitynormallypurchasesplantagainstgeneratingneedsandtherepercussionsofpoorin

26、itialavailabilityarenotonlybeingunabletomeetloaddemandbutalsohavingtousecostlyplanttomakeuptheshortfall.Thisperiodofmajoradvanceinsteamcycleandunitsizethereforerequiredquiteexceptionalinteractionwithmanufacturersindesignandfabricationareaanddevelopmentofoperationandmaintenancetechniquestoensurethatt

27、heeconomicgainsdidnotproveillusory.電站設(shè)備一般向負(fù)責(zé)設(shè)計、制造、建設(shè)和調(diào)試的專業(yè)廠商購得。同時生產(chǎn)廠商實施生產(chǎn)過程的發(fā)展，不斷修正設(shè)計方法，改變必要的運行參數(shù)和容量，從而形成新電廠的原型。雖然一些新的特性可以在安裝前進(jìn)行測試，但一個新設(shè)計鍋爐的真正測試是和汽輪發(fā)電機(jī)組配套運行后進(jìn)行的。一個新的設(shè)計獲得商業(yè)成功需要通過電站在整個設(shè)計壽命中的使用來證明。因此，需要平衡考慮由效率提高、投資成本減少等帶來的直接經(jīng)濟(jì)效益，與新設(shè)計機(jī)組可能產(chǎn)生的可靠性低和需要大的改進(jìn)等風(fēng)險。公用事業(yè)公司般依靠發(fā)電需求購買設(shè)備，并且最初可用性較低的影響不僅不能滿足負(fù)荷需求，還需要使用品貴

28、設(shè)備以彌補(bǔ)不足。因此，在對蒸汽循環(huán)及機(jī)組容量進(jìn)行較大改進(jìn)的時期，必須和廠商在設(shè)計、制造領(lǐng)域，以及運行、維護(hù)技術(shù)領(lǐng)域密切合作，以保證經(jīng)濟(jì)利益的可靠。1.4 FuelandcombustionThefuelsusedinmostboilersarecoal,naturalgasandoil.However,duringthepastfewdecades,nuclearenergyhasalsobeguntoplayamajorroleinatleasttheelectricpowergenerationarea.Also,anincreasingvarietyofbiomassmaterialsa

29、ndprocessbyproductshavebecomeheatsourcesforsteamgeneration.Theseincludepeat,woodandwoodwasters,straw,coffeeground,comhusks,coalminewastes(culm)煤屑,wasteheatfromsteelmaking教材26頁furnacesandevensolarenergy.2. 3燃料及燃燒大部分鍋爐以煤、天然氣和石油作為燃料。然而，在過去的兒十年里，至少在發(fā)電領(lǐng)域核能開始扮演一個主要角色。同樣，不斷增加的各種生物質(zhì)和工業(yè)副產(chǎn)品也成為生產(chǎn)蒸汽的熱源。這些包括泥煤、木

30、材及木材廢棄物、麥稈、咖啡渣、玉米稈、煤礦廢棄物(煤屑)、煉鋼爐廢熱甚至太陽能。ThedominantfuelinmodemU.S.centralstationsiscoal,eitherbituminous,sub-bituminousorlignite.Whilenaturalgasorfueloilmaybethefuelofchoiceforselectedfuturefossilfuelpowerplants,coalexpectedtocontinueitsdominantroleinsupplyingenergytonew,basepowerutilitypowerstation

31、boilers.現(xiàn)代美國中心電站以煤作為主要燃料，使用煙煤、次煙煤或褐煤。雖然天然氣和燃油也許是未來化有燃料電廠的燃料選擇，但對于帶基木負(fù)荷的新電站，燥仍將是主要的鍋爐燃料。231CoalclassificationAcoalclassificationsystemisneededbecausecoalisaheterogeneoussubstancewithawiderangeofcompositionandproperties.ThepropertiesofatypicalChinacoalareshowedintable2-1.Coalsaretypicallycalssifiedbyr

32、ank.Thisindicatestheprogressivealterationinthecoalificationprocessfromlignitetosubitiminous,bituminousandanthracitecoals.Therankindicatesacoal'sgeologicalhistoryandcharacteristics.表21(27頁)3. 3.1煤的分類由于煤是一種不均勻的物質(zhì)，且其組成和特性變動很大，所以建立煤的分類系統(tǒng)是很必要的。中國煤的性質(zhì)如表2-1所示。以煤階進(jìn)行燥的分類是典型的做法。這表現(xiàn)為煤化程度的大小：從褐煤到貧燥、煙煤以及無煙煤。

33、煤階表明了煤的地質(zhì)歷史和主要特性。ThesystemusedintheU.S.forclassifyingcoalbyrankwasestablishedbytheAmericanSocietyforTestingandMaterials(ASTM).ASTMclassificationisasystemwhichusesthevolatilematterandfixedcarbon(FC)resultsfromtheproximateanalysisandtheheatingvalueofthecoalasrankingcriteria.Thissystemaidsinidentifying

34、commercialusesofcoalsandprovidesbasicinformationregardingcombustioncharacteristics.現(xiàn)在美國應(yīng)用的煤分類標(biāo)準(zhǔn)是由美國材料試驗學(xué)會(ASTM)建立的。其分類是通過煤的I：業(yè)分析所確定的揮發(fā)分和固定碳的含量以及煤的發(fā)熱量作為分類標(biāo)準(zhǔn)。這套系統(tǒng)目的在于確定媒的商業(yè)使用價值，并提供關(guān)于煤燃燒特性的基本信息。4. 3.2CombustionsystemsThecombustionoffossilfuelswithinaboilerforsteamraisingpurposeshasbeenpractisedformanyy

35、ears.However,withinthepasttwodecadescombustiontechniqueshavebeenconsiderablyrefinedinordertoreduceatmosphericemissionsandpollutiontopracticableminimum.2.3.2燃燒系統(tǒng)鍋爐內(nèi)化石燃料燃燒以產(chǎn)生蒸汽的技術(shù)已成熟多年。然而，在過去的二十多年中，為了將大氣排放和污染降到可行的最低程度，燃燒技術(shù)得到了很大程度的提高。OilcombustionsystemsOilisburnedinallutilityboiler,incoalboilertoignit

36、ethecoalburners,towarmuptheboilerandraisepressurebeforecoalisadmitted,andinoilfiredboilersasthemainload教材27頁fuel.Ingeneral,theoilisresidualFuelOilof3500sec.to6500sec.viscosity.Inordertobumeffectivelythisoilmustbeheatedto120-130anddividedoratomizedintoverysmalldroplets.油燃燒系統(tǒng)所有的電站鍋爐都燃用油,在燃煤鍋爐中點燃煤粉,在媒進(jìn)

37、入爐膛之前加熱爐膛并升壓,而在燃油鍋爐中則作為主要負(fù)荷燃料。一般地，燃油都是玷度在3500sec到6500sec的殘渣燃料油。為了有效的燃燒，這些油必須被加熱到120130并被良好地分散或霧化成很小的微滴。Theuseofthisoil,cheaperthannormaldistillate(diesel/gasoiletc.)causesproblems,amongstthem,acidsmutsanddustemissions.Thesmutproblemiscausedbythesulfurcontentoftheoil,whichmaybeupto3%.Intheearly1960st

38、heutilityundertookanintensivedevelopmentprogramonoilburnerdesign,whichwasaimedatremovingtheproblemsofoilfiredemissions.Thisresultedinanoilburner,“theStandardBurner“whichreducedemissionsofcarbonatverylowexcessairlevels.Considerableworkwasalsodoneinordertoensurethatburnerinaboilerreceivedthesameamount

39、ofair,andthecurrentoperatinglevelforexcessairinanoilfiredunitis2%.燃用渣油，要比一般的儲分油(柴油，汽油等)便宜，但又帶來一些問題：酸性污染物和粉塵的排放。酸性污染問題是由石油中的硫產(chǎn)生的，硫分的含量有時可高達(dá)3%。在20世紀(jì)60年代早期，人們對油燃燒器設(shè)計進(jìn)行了深入研究和開發(fā)，目的在于解決燃油的排放問題。由此誕生了一種油燃燒器“標(biāo)準(zhǔn)燃燒器”，它可以在非常低的過量空氣系數(shù)下減少碳排放。為保證鍋爐中每個燃燒器獲得同樣多的空氣也做了大量的工作。目前油燃燒過量空氣系數(shù)運行水平為2%oCoalcombustionsystemsCoalb

40、urnershavebeendevelopedinasimilarfashiontotheoilburners,andconsiderableemphasisisplaceduponfeedingeachburnerwithcarefullyregulatedamountsofcoalandoil.Allcoalfiredboilersintheutilityfirepulverizedcoal(producedbymilling)whichisveryfinelydividedcoalcarriedtotheburneronastreamofair(primaryair).Thedesign

41、effortdirectedatflowequalizationhasproducedboilerswhichcanbeoperatedatlowerexcessairlevelsthanpreviously,andthushaveincreasedoverallefficiencywithoutincreasingunbumedcarbonlevelsintheash.燥燃燒系統(tǒng)燥燃燒器的發(fā)展模式同油燃燒器類似，而且重點放在準(zhǔn)確控制每只燃燒器燥和油的供給量。實際中所有的燃煤鍋爐都是燃燒煤粉(由磨煤機(jī)生產(chǎn))，這些燥粉經(jīng)過很好的粉碎，然后由空氣流(一次風(fēng))送入燃燒器。同以前相比，在流動平衡上的設(shè)

42、計成果現(xiàn)在已能使鍋爐在較低的過量空氣水平下運行，并在不增加飛灰含碳量水平的情況下提高了總的效率。This,whencombinedwiththedevelopmentoflowNOXburnerswillresultinreducedgaseousemissioninlinewithEECdirectivesandisthemainobjectiveoftwoboilerconversions(bothcomplete)toestablishtheleveltowhichNOXmaybereducedintheexhaustfrom500MWcoalfiredboilers.ANOXreduc

43、tiondevelopmenttrialisproposedonathirdboilerdesign,汶樣，結(jié)合低NOx燃燒器的開發(fā)，就使氣體排放達(dá)到歐共體的標(biāo)準(zhǔn)，這也是兩代鍋爐轉(zhuǎn)換(已完成)的主要目的，即設(shè)定500MW燃煤鍋爐可能達(dá)到的NOx排放水平。在第三代鍋爐的設(shè)計中進(jìn)行了進(jìn)一步降低NOx的開拓性試驗。Thearrangementofcoal-firedsystemcomponentsmustbedeterminedaccordingtoeconomicfactorsaswellastheattributesofthecoal.Theperformanceintermsofproduct

44、fineness,milloutlettemperature,andair-coalratiomustallbedeterminedaspartofoverallcombustionsystemdesign.燥燃燒系統(tǒng)部件的布置必須根據(jù)經(jīng)濟(jì)因素和煤的性質(zhì)來確定。作為整個燃燒系統(tǒng)設(shè)計的性能參數(shù)，煤粉細(xì)度、磨煤機(jī)出口溫度、空煤比等都必須達(dá)到要求。LowNOXcombustionsystemsThefactorsaffectingNOXaretheproportionofnitrogenchemicallycombinedwiththefuel,peakflametemperature,theava

45、ilableoxygenintheflameandtheresidencetimeofthegaseswithinthesystem.Someofthecoalboundnitrogenisreleasedasvolatilesasthechemicalstructureofthecoalbreaksdownonenteringthefurnace.Nitricoxideproducedfromatmosphericnitrogenas"thermalNOx“canbelimitedbyminimizingresidencetimesathightemperature,whichli

46、mitingtheamountofoxygenavailabletothefuelduringthecombustionstageresultsintheproductionofharmlessnitrogenratherthanNOX.低NOx燃燒系統(tǒng)影響NOx生成的因素包括燃料含氮量、火焰峰值溫度、火焰中的可用氧量以及氣流在鍋爐系統(tǒng)中的停留時間。當(dāng)煤進(jìn)入爐膛其化學(xué)結(jié)構(gòu)被破壞時，一些煤中的化合氮就作為揮發(fā)分被釋放出來。由大氣中的輒生成的一氧化氮即“熱力型NO.，可以通過減少煙氣在高溫區(qū)域的停留時間而得到控制，這樣就會控制燃燒階段中可用氧量，最后生成的是無害氮而不是NOxoSincecoalf

47、iringrequiressomeexcessoxygeninthecombustionzonetoachievetotalcarbonburnoutandnitrogenfreecoalisunavailable,NOXreductionhastobeperformedbyboilerandburnerdesign.因為煤在燃燒區(qū)的燃燒需要一定的過量氧氣以便使所有的碳燃盡,且不含氮的煤是難以獲得的，因此NOx的減少必須依靠鍋爐和燃燒器的設(shè)計來完成。教材28頁GascombustionsystemsNaturalgashasbeenfiredatpowerstationsformainload

48、purposes.However,gashasnotbeenavailabletotheutilityforsomeyearsnowanditisnotenvisagedthat,asapremiumfuel,itwilleverbeavailableagaininanyquantity.Propaneiswidelyusedinignitersfortheoilburnersinbothmainoilandcoalfiredboilers.天然氣燃燒系統(tǒng)天然氣曾經(jīng)作為電廠主要燃料。然而一些年來，沒有太多的天然氣可供電廠使用，并且人們沒有正視這樣的事實，即天然氣作為一種優(yōu)質(zhì)燃料將會重新得到大量

49、:應(yīng)用。丙烷常常作為一種點火劑，廣泛地應(yīng)用于燃油鍋爐和燃燥鍋爐中的汕燃燒器。23.3Fluidized-bedcombustionAvariationonPCcombustionisfluidizedbedcombustioninwhichcoalisburnedwithairinafluidbed,typicallyacirculatingfluidizedbed(CFB).CFBsarebestsuitedtolow-costwastefuelsandlow-qualityorlowheatingvaluecoals.Crushedcoalandlimestonearefedintothe

50、bed,wherethelimestoneundergoescalcinationtoproducelime(CaO).Thefluidizedbedconsistonlyoflime,withafewpercentcoalandrecirculatedcoalchar.Thebedoperatesatsignificantlylowertemperatures,about427(800°F),whichthermodynamicallyfavorslowNOXformationandSO2capturebyreactionwithCaOtoformCaSO4.Thesteamcyc

51、lecanbesubcriticalandpotentiallysupercritical,aswithPCcombustion,andgeneratingefficienciesaresimilar.TheprimaryadvantageofCFBtechnologyisitscapacitytocaptureS02inthebed,anditsflexibilitytoawiderangeofcoalproperties,includingcoalswithlowheatingvalue,highashcoalsandlowvolatilecoals,andchangesincoaltyp

52、eduringoperation.Severallignite-burningCFBunitshavebeenconstructedrecently,andCFBsarewellsuitedtoco-firingbiomass.2.3.3流化床燃燒沆化床燃燒是燥粉燃燒方式的一種，采用這種燃燒方式時煤在空氣中的燃燒發(fā)生在流化床中，典型的是循環(huán)流化床。循環(huán)流化床最適合于燃燒低成本廢棄燃料、低品質(zhì)或低熱量煤。將煤粒和布灰布投入到床中，布灰布在床內(nèi)煨燒成石灰。流化床中主要是石灰和少量的煤，煤焦在其中循環(huán)。運行中的床溫很低，只有427(800T),在這個溫度下的熱力學(xué)環(huán)境有利于減少NOx的形成和捕集SM

53、使之與CaO反應(yīng)生成CaSCU對于煤燃燒，蒸汽循環(huán)可以是亞臨界，也可能是超臨界，它們具有相近的發(fā)電效率。循環(huán)流化床技術(shù)的最大的優(yōu)點是它在床中捕捉S02的能力和它對煤質(zhì)的廣泛適應(yīng)性，其中包括低熱量燥、高灰分燥和低揮發(fā)分煤，并且在運行中可以改變煤種。循環(huán)流化床鍋爐適合與生物質(zhì)共燃，最近就新建了幾臺燃燒褐燥的循環(huán)流化床機(jī)組。ThemostcommonlyusedcirculatingfluidizedbedcombustorisshowninFig.2-1.Coalandcoalcharareburnedwhilethecoal,coalchar,coalashandsorbentarecarrie

54、dupthroughthefurnacebycombustionair.Thesolidmaterialsareseparatedfromthefluegasin圖2-1循環(huán)流化床鍋爐設(shè)計布置實例教材29頁thecycloneandpassthroughaconvectivesectionwhereheatistransferredtoboilertubesgeneratinghigh-pressuresteam.Additionalsteamisgeneratedbyremovingheatfromthehotsolidsinthefluidizedbedheatexchangesectio

55、nbeforetheyarereturnedtothefurnace.Therearenoboilertubesinthelowerfurnacebecausetherapidmovingsolidscauseexcessiveerosion.NOXismanagedthroughlowtemperatureandstagedinjectionofthecombustionair.SOXemissioniscontrolledviathelimesorbentinthebed.Thissavessignificantcapitalforfluegascleanup,butlowSOXemiss

56、ionrequirelow-sulfurcoal,andNOXemissionsarelimitedbycombustionchemistry.Extremelylowemissionslevelswouldrequiretheadditionoffluegasclean-upunitswiththeattendantcostincrease.ThelargestCFBunitis33OMWeinChina,and600MWunitshavebeendesigned,butnounitofthissizehasbeenbuilt.如圖2所示，目前最常用的流化床技術(shù)是循環(huán)流化床燃燒技術(shù)。煤和煤焦

57、燃燒的同時，空氣攜帶煤、煤焦、煤灰和脫硫劑通過爐膛。固體材料通過旋風(fēng)分離器從煙氣中分離出來，然后通過對流煙道部分，煙氣把熱量傳給爐管以產(chǎn)生高壓蒸汽。另一部分蒸汽是由流化床中的高溫固體在返回爐膛前放出熱量產(chǎn)生的。爐膛內(nèi)固體快速運動會引起過量的磨損，因此爐膛底部不安裝爐管。通過低燃燒溫度和空氣分級燃燒來控制NOx的生成。SOx排放通過床中石灰脫硫劑控制。這些為煙氣凈化節(jié)省了大筆的投資，但是低的SOx排放需要燃燒低硫分煤，并且NOx的排放受燃燒反應(yīng)的限制。極低的排放需要額外的煙氣凈化設(shè)備，同時會增加相應(yīng)的維護(hù)成本。在中國最大的流化床鍋爐是33OMWe,設(shè)計最大的鍋爐是600MWe,但是還沒有投建。2

58、.4PulverizingSystemThedevelopmentandgrowthofcoalpulverizationcloselyparallelsthedevelopmentofpulverizedcoal-firingtechnology.Inordertoachieveefficientcombustionintheboilerfurnacethecoalleavingtheburnermustbesizedsothatitcanbumrapidlyandthismeansthatitmustbeintheformofsmallparticlesthatcanquicklybeheateduptoignitiontemperatur