热能与动力工程专业英语翻译Ch 02 教案

29-29-10Chapter2Boiler其次章锅炉Airheater空预器Anchor支座，固定Anhydrousammonia无水氨Anthracite无烟煤Atomized雾化Austenitic奥氏体钢Auxialiary关心机械Axis轴Bagasse甘蔗渣Baretube光管Bark树皮Beam梁，横梁Bituminouscoal烟煤Blade叶片Blast鼓风Blowdown排污Boiler锅炉Bulk大块的Burnerzone燃烧器区域Butane丁烷Calcination煅烧Capacity出力Carbonsteel碳钢Cerium铈Chromium铬

Commissioning试运行Compressor压缩机、压气机Condenser凝汽器Containment反响堆安全壳Convection对流Coolant制冷剂Coordinated坐标，定位Corten低合金耐腐蚀钢Counterflow逆流〔换热器〕Creepstrength蠕变强度Criterion标准Criticalpressure临界压力Culm煤屑Cyclonefurnace旋风炉Debris残骸、有机残留物Decane癸烷Decay分解Deposited沉积，沉淀的Deterioration恶化Dieseloil柴油Differential差动，微分Distillate馏出物Distortion变形Divisionwall分隔墙，双面水冷壁Drainage疏水CirculatingfluidizedbedCFB 循环流化Drum汽包床锅炉Coalchar 煤焦Cogenerator热点联产机组Combustion燃烧

Dwelltime保存时间Economizer省煤器Embrittlement脆性，脆化Equalization均衡，平衡Erosive侵蚀的，腐蚀的Ethane乙烷Evaluate评估，评价Evaporate蒸发Excessair Extendedsurface扩展受热面Fatigue疲乏Feedwater给谁Ferrite铁素体Fin鳍片，肋片Flange法兰Fluegas烟气Fouling沾污Furnace炉膛Generator发电机Geological地质的Girth环形Govern掌握、调整Gravity重力Header联箱，集箱Helical螺旋状的Helium氦Heterogeneous不均匀的Hopper斗，料斗Husk壳，外壳Hydraulic水力的，液压的Ignite点火Impurity杂质Inert惰性Inferior低级的，劣质的Ingredients成分

Ingress进口，入口In-line顺列Inorganic无机的Ion离子Jurisdiction权限Lignite褐煤Lime石灰Limestone石灰石Lowalloy低合金钢Low-volatile低挥发分的Margin裕量，安全系数Matrix矩阵Membrane膜Methane甲烷Mill磨煤机Molecule分子Molten熔化Nitricoxide氮氧化物Nonpressure非承压的Nontoxic无毒的Organisms有机体Oxidation氧化Peat泥煤Pendantssuperheatplaten悬吊式屏式过热器Pentane戊烷Petrochemical石油化工制品Petroleum石油制品Plasmaspraycoating等离子喷涂Platen屏Polymer聚合物Pores气孔，小孔Porosity多空的Potassium钾Prandtlnumbers普朗特数Prefabricated预制的Premiumfuel优质燃料Pressureloss压力损失Primaryair一次风Propane丙烷Proximateanalysis工业分析Pulp纸浆Pyrites黄铁矿Radius半径，范围Rareearthelement稀土元素Recuperator间壁式换热器Regenerator回热器，蓄热器Regulate掌握，调整Repercussions反响Reservoirs储气罐Residualefueloil渣油Resonant共振Retract缩回Reynoldsnumber雷诺数Rigid刚性的，严密地Rollers辊子Scale水垢，Seal密封Sedimentary沉积Serpentinetube蛇形管Shale页岩Silica二氧化硅Silt淤泥Single-phase单相Skincasing外护板Slag结渣

Slurry水煤浆Sodium钠Solvents溶剂Sootblower吹灰器Sourgas含硫气体Specification规格Stableignition稳定着火Stantonnumber斯坦顿数Saturated饱和的Straw稻草Steamlineblowing蒸汽管路吹灰Steams茎，杆Stresscorrosion应力腐蚀Structuralformula构造式Stud双头螺栓Subbituminous贫煤，次烟煤Suction真空，负压Sulphur硫Superheater过热器Swamp沼泽Sweetgas无硫气Switchgear配电装置，开关装置Temperature-entropy温熵图Tenacious黏的Thermodynamics热力学Tubebundles管束Tubular管状的Turbine汽轮机Velocity速度Verticalspidlemill中速磨，立轴磨Vessel容器Viscosity黏度Volumetricexpansion体膨胀Vulnerable易损的，薄弱的Wear磨损Welded焊接Yttrim釔AbbreviationsAFBC常压流化床燃烧AFCO燃料自动切断AFWC给水自动切断ASME美国机械工程师协会ATM标准大气压BFP锅炉给水泵BUT按钮BWC锅炉水浓度BYP旁路CFBB循环流化床锅炉MCR最大连续蒸发量DAS数据采集系统

DEH数字电液系统DNB偏离核态沸腾FDF送风机FGD烟气脱硫FSSS炉膛安全检测保护系统HRB回热锅炉IDF引风机IGCC整体煤气化联合循环LMTD对数平均温差MFT主燃料切断MUF锅炉补给水NWL正常水位OFA火上风，燃尽风PFBC增压流化床燃烧SSC刮板除渣机TGA热重UBC未燃烧WFGD湿法烟气脱硫2.1IntroductionBoilersuseheattoconvertwaterintosteamforavarietyofapplications.Primaryamongtheseareelectricpowergenerationandindustrialprocessheating.Steamhasbecomeakeyresourcebecauseofitswideavailability, advantageouspropertiesandnon toxic nature. The steam flow rates and operating conditions can dramatically;from1000lb/h(0.1kg/s)inoneprocessusetomorethan10millionlb/h(1260kg/s)inlargeelectricpowerplant;fromabout14.7psi(1bar)and212ºFinsomeheatingapplicationstomorethan4500psi(310bar)and1100ºF(593℃)inadvancedcyclepowerplant.SSC具有有利的参数和无毒特性，因此蒸汽作为一种关键的工质〔资源〕被广泛地应用。蒸汽流量和运行参数的变化很大：从某一过程里1000磅/小时〔0.126kg/s〕到大型电厂超过10×106小时1260kg/，压力从一些加热应用的14.7/i〔1.0135ba212〔10℃〕到先进循环电厂的4500/i310ba1100〔59℃。Modernboilerscanbeclassifiedbyvariouscriteria.Theseincludeenduse,firingmethod,operatingpressure,fuelandcirculationmethod.环方式。Utilityboilersareusedprimarilytogenerateelectricityinlargecentralpowerstations.Theyaredesignedtooptimizeoverallthermodynamicefficiencyatthehighestpossibleavailability.Akeycharacteristicofnewerunitsistheuseofareheatersectiontoincreaseoverallcycleefficiency.机组的关键特性是利用再热器提高整个循环效率。Avarietyofadditionalsystemsalsoproducesteamforpowerandprocessapplications.Thesesystemsusuallytakeadvantageoflowcostorfreefuels,acombinationofpowercyclesandprocess,andrecoveryofwasteheatinordertoreduceoverallcosts,examplesoftheseinclude:各种附加的系统也产生蒸汽用于发电及其他过程应用料，联合动力循环和过程，以及余热回收，以削减总费用。这些例子包括：Gasturbinecombinedcycle(CC)useadvancedgasturbineswithheatrecoverysteamgeneratoraspartofabasecycletousewasteheatrecoveryandincreasethermalefficiency.燃气轮机联合循环C用余热并提高热效率。IntegratedGasificationCombinedCycle(IGCC)addsacoalgasifiertotheCCtoreducefuelcostandminimizeairborneemissions.整体煤气化联合循环IGC：在CC排放降到最低。Pressurized Fluidized-bed Combustion (PFBC) includes higher pressurecombustionwithgascleaningandexpansionofthecombustionproductsthroughagasturbine.增压循环流化床燃烧PFB并通过燃气轮机做功。Blastfurnacehoodheatrecovgeernyeratessteamusingthewasteheatfromablastfurnace.高炉排烟热量回收：利用高炉余热产生蒸汽。Solarsteamgeneratorusesconcentratorstocollectandconcentratesolarradiationandgeneratesteam.太阳能蒸汽发生器：利用集热器收集太阳辐射热产生蒸汽。DevelopmentofUtilityBoilerThemodern660MWcoal-firedboilerhassome6000tonsofpressurepartswhichinclude500kmoftubing,3.5kmofintegralpipingand30,000tubebuttwelds.Itistheculmination25页ofsomefiftyyearsdevelopmentandwhilethebasicconceptofpulverizedfuelfiringintoafurnacelinedwithevaporatortubes,withthecombustiongasesthenpassing over convection superheater and heat recovery surface, has remainedunchanged,theadvancementofsteamconditions,increasesinunitsizeandthepropertiesofthefuelfiredhaverequiredmajorchangesinmaterialsemployed,fabricationtechniquesandoperatingprocedures.2.2电站锅炉的进展660MW6000500千米的受热面管材，3.53000050行程序上相应进展。IntheyearsimmediatelyfollowingthesecondWorldWar,iswascustomarytoinstallinapowerstation,agreaternumberofboilersthanturbines,theboilersfeedingarangetowhichtheturbineswereconnected.Thisarrangementreflectedtheinferioravailabilityofboilerscomparedwithturbinesbutincreaseinboileravailabilityinthelate1940sledtotheacceptanceofunitizedboilersandturbines.Thechangetounitized boiler and turbine allowed reheat to become practical and, with availabilityofhightemperaturesteels,therefollowedacontinuousadvanceinsteamingconditionstothecurrentstandardcycleof2400lbf/in2(165.5bar),568℃withreheatto568℃.Totakefulladvantageofthemoreadvancedsteamconditionsandtoobtaintheeconomiesofsize,thenextfifteenyearsalsosawatwenty-foldincreaseinunitsize.2400lbf/i〔165.5ba56℃和56℃再热的标准循环。为充分利用更高的蒸汽参数和获得更大的经济性，在接下来的15年，机组20倍。Autility normally procures plant from specialist manufactures who haveresponsibility for design, manufacture, erection and commissioning. While themanufacturescarryoutdevelopmentofmanufacturingprocessandcontinuouslyupdatetheirdesignmethods,andchangeinoperationconditionsandsizenecessarilyresultsinanewplantbeingofaprototypenature.Whilesomenewfeaturescanbetestedinadvanceofconstructiontheonlyrealtestofanewboilerdesignisinoperationandwithitsassociatedturbineandgenerator.Thecommercialsuccessofanewdesignisprovedoverthewholeprojectedlifeofpowerstationandutility,therefore,hastobalancetheimmediateeconomicadvantagesofanewdesignintermsofimprovedefficiency,reducedcapitalcosts,etc.againsttheriskofpooravailability,needformajormodifications,etc.,whichmightresultfromanewdevelopment.Autilitynormallypurchasesplantagainstgeneratingneedsandtherepercussionsofpoorinitialavailabilityarenotonlybeingunabletomeetloaddemandbutalsohavingtousecostlyplantto makeuptheshortfall. Thisperiodofmajoradvancein steamcycleandunitsizethereforerequiredquiteexceptionalinteractionwithmanufacturersindesignandfabricationareaanddevelopmentofoperationandmaintenancetechniquestoensurethattheeconomicgainsdidnotproveillusory.然一些的特性可以在安装前进展测试套运行后进展的。一个的设计获得商业成功需要通过电站在整个设计寿命中的使用来证且最初可用性较低的影响不仅不能满足负荷需求，还需要使用昂贵设备以弥补缺乏。因此，在对蒸汽循环及机组容量进展较大改进的时期，必需和厂商在设计、制造领域，以及运行、维护技术领域亲热合作，以保证经济利益的牢靠。2.3FuelandcombustionThefuelsusedinmostboilersarecoal,naturalgasandoil.However,duringthepastfewdecades,nuclearenergyhasalsobeguntoplayamajorroleinatleasttheelectricpowergenerationarea.Also,anincreasingvarietyofbiomassmaterialsandprocessbyproductshavebecomeheatsourcesforsteamgeneration.Theseincludepeat,woodandwoodwasters,straw,coffeeground,cornhusks,coalminewastes(culm)[煤屑],wasteheatfromsteelmaking26页furnacesandevensolarenergy.燃料及燃烧热源。这些包括泥煤、木材及木材废弃物、麦秆、咖啡渣、玉米秆、煤矿废弃物〔煤屑、炼钢炉废热甚至太阳能。ThedominantfuelinmodernU.S.centralstationsiscoal,eitherbituminous,sub-bituminousorlignite.Whilenaturalgasorfueloilmaybethefuelofchoiceforselectedfuturefossilfuelpowerplants,coalexpectedtocontinueitsdominantroleinsupplyingenergytonew,basepowerutilitypowerstationboilers.是将来化石燃料电厂的燃料选择，但对于带根本负荷的电站，煤仍将是主要的锅炉燃料。CoalclassificationAcoalclassificationsystemisneededbecausecoalisaheterogeneoussubstancewithawiderangeofcomposition andproperties.Theproperties ofatypicalChinacoalareshowedintable2-1.Coalsaretypicallycalssifiedbyrank.Thisindicatestheprogressivealterationinthecoalificationprocessfromlignitetosubitiminous,bituminousandanthracitecoals.Therankindicatesacoalsgeologicalhistorycharacteristics.煤的分类

页〕2-1的大小：从褐煤到贫煤、烟煤以及无烟煤。煤阶说明白煤的地质历史和主要特性。ThesystemusedintheU.S.forclassifyingcoalbyrankwasestablishedbytheAmericanSocietyforTestingandMaterials(ASTM).ASTMclassificationisasystemwhichusesthevolatilematterandfixedcarbon(FC)resultsfromtheproximateanalysisandtheheatingvalueofthecoalasrankingcriteria.Thissystemaidsinidentifyingcommercialusesofcoalsandprovidesbasicinformationregardingcombustioncharacteristics.〔ASTM〕工业分析所确定的挥发分和固定碳的含量以及煤的发热量作为分类标准确定煤的商业使用价值，并供给关于煤燃烧特性的根本信息。CombustionsystemsThecombustionoffossilfuelswithinaboilerforsteamraisingpurposeshasbeenpractised for many years. However,within the past two decades techniqueshavebeenconsiderablyrefinedinordertoreduceatmosphericemissionsandpollutiontopracticableminimum.燃烧系统将大气排放和污染降到可行的最低程度，燃烧技术得到了很大程度的提高。OilcombustionsystemsOilisburnedinallutilityboiler,incoalboilertoignitethecoalburners,towarmuptheboilerandraisepressurebeforecoalisadmitted,andinoilfiredboilersasthemainload27fuel.Ingeneral,theoilisresidualFuelOilof3500sec.to6500sec.viscosity.Inordertoburneffectivelythisoilmustbeheatedto120-130℃anddividedoratomizedintoverysmalldroplets.油燃烧系统而在燃油锅炉中则作为主要负荷燃料。一般地，燃油都是粘度在3500sec6500sec120~130℃并被良好地分散或雾化成很小的微滴。Theuseofthisoil,cheaperthannormaldistillate(diesel/gasoiletc.)causesproblems,amongstthem,acidsmutsanddustemissions.Thesmutproblemiscausedbythesulfurcontentoftheoil,whichmaybeupto3%.Intheearly1960stheutilityundertookanintensivedevelopmentprogramonoilburnerdesign,whichwasaimedatremovingtheproblemsofoilfiredemissions.Thisresultedinanoilburner, StandardBurner”whichreducedemissionsofcarbonatverylowexcessairlevels.Considerableworkwasalsodoneinordertoensurethatburnerinaboilerreceivedthesameamountofair,andthecurrentoperatinglevelforexcessairinanoilfiredunitis2%.燃用渣油，要比一般的馏分油〔柴油，汽油等〕廉价，但又带来一些问题：时可高达3%。在20世纪60年月早期，人们对油燃烧器设计进展了深入争论和2%。CoalcombustionsystemsCoalburnershavebeendevelopedinasimilarfashiontotheoilburners,andconsiderableemphasisisplaceduponfeedingeachburnerwithcarefullyregulatedamountsofcoalandoil.Allcoalfiredboilersintheutilityfirepulverizedcoal(producedbymilling)whichisveryfinelydividedcoalcarriedtotheburneronastreamofair(primaryair).Thedesigneffortdirectedatflowequalizationhasproducedboilerswhichcanbeoperatedatlowerexcessairlevelsthanpreviously,andthushaveincreasedoverallefficiencywithoutincreasingunburnedcarbonlevelsintheash.煤燃烧系统煤燃烧器的进展模式同油燃烧器类似量。实际中全部的燃煤锅炉都是燃烧煤粉〔由磨煤机生产，这些煤粉经过很好的粉碎，然后由空气流〔一次风〕在较低的过量空气水平下运行，并在不增加飞灰含碳量水平的状况下提高了总的效率。This,whencombinedwiththedevelopmentoflowNOxburnerswillresultinreducedgaseousemissioninlinewithEECdirectivesandisthemainobjectiveoftwoboilerconversions(bothcomplete)toestablishtheleveltowhichNOxmaybereducedintheexhaustfrom500MWcoalfiredboilers.ANOxreductiondevelopmenttrialisproposedonathirdboilerdesign,这样，结合低NOx燃烧器的开发，就使气体排放到达欧共体的标准，这也是两代锅炉转换〔已完成〕的主要目的，即设定500MW燃煤锅炉可能到达的NOx的开拓性试验。Thearrangementofcoal-firedsystemcomponentsmustbedeterminedaccordingtoeconomicfactorsaswellastheattributesofthecoal.Theperformanceintermsofproductfineness,milloutlettemperature,andair-coalratiomustallbedeterminedaspartofoverallcombustionsystemdesign.煤燃烧系统部件的布置必需依据经济因素和煤的性质来确定性能参数，煤粉细度、磨煤机出口温度、空煤比等都必需到达要求。LowNOxcombustionsystemsThefactorsaffectingNOxaretheproportionofnitrogenchemicallycombinedwiththefuel,peakflametemperature,theavailableoxygenintheflameandtheresidencetimeofthegaseswithinthesystem.Someofthecoalboundnitrogenisreleasedasvolatilesasthechemicalstructureofthecoalbreaksdownonenteringthefurnace.Nitricoxideproducedfrom atmosphericnitrogenas“thermalNOx”canbelimitedbyminimizingresidencetimesathightemperature,whichlimitingtheamountofoxygenavailabletothefuelduringthecombustionstageresultsintheproductionofharmlessnitrogenratherthanNOx.NOX燃烧系统影响NOx被释放出来。由大气中的氮生成的一氧化氮即“热力型NOx”可以通过削减烟气在高温区域的停留时间而得到掌握，这样就会掌握燃烧阶段中可用氧量，最终生成的是无害氮而不是NOx。Sincecoalfiringrequiressomeexcessoxygeninthecombustionzonetoachievetotalcarbonburnoutandnitrogenfreecoal isunavailable,NOxreductionhasto performedbyboilerandburnerdesign.由于煤在燃烧区的燃烧需要肯定的过量氧气以便使全部的碳燃尽获得的，因此NOx28GascombustionsystemsNaturalgashasbeenfiredatpowerstationsformainloadpurposes.However,gashasnotbeenavailabletotheutilityforsomeyearsnowanditisnotenvisagedthat,asapremiumfuel,itwilleverbeavailableagaininanyquantity.Propaneiswidelyusedinignitersfortheoilburnersinbothmainoilandcoalfiredboilers.自然气燃烧系统人们没有正视这样的事实，即自然气作为一种优质燃料将会重得到大量应用。丙烷常常作为一种点火剂，广泛地应用于燃油锅炉和燃煤锅炉中的油燃烧器。Fluidized-bedcombustionAvariationonPCcombustionisfluidizedbedcombustioninwhichcoalisburnedwithairinafluidbed,typicallyacirculatingfluidizedbed(CFB).CFBsarebestsuitedtolow-costwastefuelsandlow-qualityorlowheatingvaluecoals.Crushedcoalandlimestonearefedintothebed,wherethelimestoneundergoescalcinationtoproducelime(CaO).Thefluidizedbedconsistonlyoflime,withafewpercentcoalandrecirculatedcoalchar.Thebedoperatesatsignificantlylowertemperatures, about 427℃(800ºF), which thermodynamically favors low NOxformationandSO2capturebyreactionwithCaOtoformCaSO4.Thesteamcyclecanbesubcriticalandpotentiallysupercritical,aswithPCcombustion,andgeneratingefficienciesaresimilar.TheprimaryadvantageofCFBtechnologyisitscapacitytocaptureSO2inthebed,anditsflexibilitytoawiderangeofcoalproperties,includingcoalswithlowheatingvalue,highashcoalsandlow volatilecoals,andchangesincoaltypeduringoperation.Severallignite-burningCFBunitshavebeenconstructedrecently,andCFBsarewellsuitedtoco-firingbiomass.2.3.3流化床燃烧流化床燃烧是煤粉燃烧方式的一种床中，典型的是循环流化床。循环流化床最适合于燃烧低本钱废弃燃料、低品质或低热量煤，煤焦在其中循环。运行中的床温很低，只有427℃(800℉)，在这个温度下的热力学环NOxSOCaO反响生成CaSO2 4是它在床中捕获SO的力量和它对煤质的广泛适应性，其中包括低热量煤、高灰分煤和低挥2台燃烧褐煤的循环流化床机组。ThemostcommonlyusedcirculatingfluidizedbedcombustorisshowninFig.2-1.Coalandcoalcharareburnedwhilethecoal,coalchar,coalashandsorbentarecarriedupthroughthefurnaceby combustionair.Thesolidmaterialsareseparatedfromthefluegasin2-1循环流化床锅炉设计布置实例29页thecycloneandpassthroughaconvectivesectionwhereheatistransferredtoboiler tubes generating high-pressure steam. Additional steam is generatedbyremovingheatfromthehotsolidsinthefluidizedbedheatexchangesectionbeforetheyarereturnedtothefurnace.Therearenoboilertubesinthelowerfurnacebecausetherapidmovingsolidscauseexcessiveerosion.NOxismanagedthroughlow temperature and staged injection of the combustion air.SOx emission controlledviathelimesorbentinthebed.Thissavessignificantcapitalforfluegascleanup,butlowSOxemissionrequirelow-sulfurcoal,andNOxemissionsarelimitedbycombustionchemistry.Extremelylowemissionslevelswouldrequiretheadditionoffluegasclean-upunitswiththeattendantcostincrease.ThelargestCFBunitis330MWeinChina,and600MWunitshavebeendesigned,butnounitofthissizehasbeenbuilt.如图2-1所示，目前最常用的流化床技术是循环流化床燃烧技术。煤和煤焦SOx排放通过床中石灰脱硫剂掌握。SOx排放需要燃烧低硫分煤，并PulverizingSystemThe development and growth of coal pulverization closely parallels thedevelopmentofpulverizedcoal-firingtechnology.Inordertoachieveefficientcombustionintheboilerfurnacethecoalleavingtheburnermustbesizedsothatitcanburnrapidlyandthismeansthatitmustbeintheformofsmallparticlesthatcanquicklybeheateduptoignitiontemperatureandgetreadyaccesstothecombustionair.Thejobofthepulverizersistogrindthefeedcoaldowntoasuitablesizefortheabovepurposes.Earlysystemsusedball-and-tubepulverizerstogrindcoalandholdingbinstotemporarilystorethecoalbeforefiring.Evolutionofthetechnologytoeliminatethebinsanddirectfirethecoalpneumaticallytransportedfromthepulverizers required more responsive and reliable grinding equipment. air-sweptpulverizersmetthisneed.制粉系统能被快速加热到着火温度并和空气良好混合的牢靠性有很高的要求。Onpressurizedpulverizingsystemstheprimaryairfanwhichprovidesthepulverizedfueltransportmediumissituatedbeforethepulverizerandtherehandlecleanairandisnotsubjecttoerosivewearasisanexhaustfan.Thisisthechiefadvantageofthepulverizingsystem,howeverthepulverizerdoesneedsealingairwhichisusuallyprovidedbyaseparatefanatapressurehigherthanthatofthepulverizerinterior.由单独风机供给高于磨煤机内部压力的密封空气。Adisadvantageofthepressuretypepulverizeristhatitmustbeabsolutelyairtightinordertoavoidpulverisedfuelleakagetotheatmosphere.Converselythestandardofsealingonasuctionpulverizerneednotbesohigh,butitmustnotbeallowedtodeterioratetoofarastheinwardsleakage,beingcoldair,willmakeitdifficulttodrythewettercoals.Thisleakageairisalsounmeasuredasregardsitsquantity,andifexcessiveundercertainconditionsproducesahighair/coalratiowhichmaybeexplosiveshouldtherebeanignitionsource.正压磨煤机的一个缺点是它必需完全由空气密封以避开煤粉泄露到大气中。相对来说，/Verticalair-sweptpulverizersTherollerpassesoveralayerofgranularmaterial,compressingitagainstamovingtable.Themovementoftherollercausesmotionbetweenparticles,whiletherollerpressure30页createscompressiveloadsbetweenparticles.Motionunderappliedpressurewithintheparticlelayercauseattrition(particlebreakupbyfriction)whichisthedominantsizereductionmechanism.Thecompressedgranularlayerhasacushioninginfluencewhichreducesgrindingeffectivenessbutalsoreducestherateofrollerweardramatically.Whenworkingsurfacesinagrindingzoneareclosetogether,nearthedimensionsofsingleproductparticles,wearisincreasedbythreebodycontact(roller,particleandtable).Wearratescanbethreebodycontact hasalsobeenobservedinoperatingmillswhensignificantamountsofquartsbearingrockarepresentinsizesequaltoorgreaterthanthegrindinglayerthickness.中速磨〔煤粒依靠摩擦力裂开，这就是磨煤机的工作原理。耐磨层具有缓冲作用，虽然降低了磨的效率，个部件〔磨辊，颗粒，磨盘〕间的磨损就会大大增加，磨损速率会是正常磨煤机的100倍。当带有石英的石头尺寸等于或大于磨层厚度时，也会在运行中发生三部件接触的磨损。Asgrindingproceeds,fineparticlesareremovedfromtheprocesstopreventexcessivegrinding,powerconsumptionandwear.Fig.2-2presentsasimplifiedMPSverticalpulverizer,showingtheessentialelementsofaverticalair-sweptdesign.Atableisturnedfrombelowandrollers,calledtires,rotateagainstthetable.Rawcoalisfedintothemillfromaboveandpassesbetweentherollersandtherotatingtable.Eachpassageoftheparticlesundertherollersreducesthesizeofcoal.Thecombinedeffectsofcentrifugalforceanddisplacementofthecoallayerbytherollersspillspartlygroundcoalofftheoutsideedgeofthetable.Anupwardflowofairfluidizesandentrainsthiscoal.随着磨煤的进展，为了防止过度磨制和降低能耗及磨损，磨好的煤粉从磨煤机中排出。2-2MPS的煤粉挤出磨盘边缘，由上升的空气流流化并携带这些煤粉。2-2磨煤机内部的颗粒循环Thepointwhereairisintroducedisoftencalledtheairportring,nozzleringorthroat.Risingairflow,mixedwiththecoalparticles,creastesafluidizedparticlebedjustabovethethroat.Theairvelocityislowenoughsothatitentrainsonlythesmallerparticlesandpercolateswiththemthroughthebed.Theair-solidsflowleavingthebedformstheinitialstageofsizeseparationorclassification.Thepreheatedairstreamalsodriesthecoaltoenhancethecombustionprocess.煤粒离开流化床形成了第一步的分别。预热的空气同时枯燥煤粉以保证煤粉的有效燃烧。Verticalpulverizersareeffectivedryingdevices.Coalwithmoisturecontentupto40%havebeensuccessfullyhandledinverticalmills.Highermoisturelevelsarepossible,buttheprimaryairtemperatureneededwouldrequiredspecialstructurematerialsandwouldincreasethechanceofpulverizerfires.Apracticalmoisturelimitis40%,byweight,requiringairtemperatureto750ºF(398℃).立式中速磨是有效的枯燥装置。即使煤中水分到40%也能在中速磨中很好地得到枯燥，了磨煤机着火的可能。实际运行的水分最大值是40〔质量，此时要求一次风温高达750℉。Astheair-solidsmixtureflowsupward,theflowareaincreaseandvelocitydecreasesreturninglargerparticlesdirectlytothegrindingzone.Thefinalstageofsizeseparationis31页providedbytheclassifierlocatedatthetopofthepulverizer.Thisdeviceisacentrifugalseparator.Thecoal-airmixtureflowsthroughopeningsangledtoimpartspinandinducecentrifugalforce.Thecoarserparticlesimpacttheperimeter,comeoutofsuspensionandfallbackintothegrindingzone.Thefinerparticlesremainsuspendedintheairmixtureandexittothefuelconduits.上升进入煤粉管。LowspeedpulverizersTheoldestpulverizerdesignstillinfrequentuseistheballandtubemill.Thisisahorizontalcylinder,partlyfilledwithsmalldiameterballs(Fig.2-3).Thecylinderislinedwithwearresistantmaterialcontouredtoenhancetheactionofthetumblingballsandtheballsfill25%to30%ofthecylindervolume.Therationalspeedis80%ofthatatwhichcentrifugalforcewouldovercomegravityandcausetheballstoclingtotheshellwall.Grindingiscausedbythetumblingactionwhichtrapscoalparticlesbetweenballsastheyimpact.2-3典型的钢球磨制粉系统低速磨2530以抑制重力时速度的80%，这样可以使钢球贴在筒体的内壁上。通过筒体转动时钢球的碰撞来实现煤粉的磨制。Ball-and-tubemillsmaybeeithersingleordoubleended.Intheformer,airandcoalenterthroughoneendandexittheopposite.Doubleendedmillsarefedcoalandairateachendandground-driedcoalisextractedfromeachend.Inbothtypes,classifiersareexternaltothemillandoversizematerial isinjectedbacktothemillwiththerawfeed.Ball-and-tubemillsdonotdevelopthefluidizedbedwhichischaracteristicofverticalmillsandthepoormixingofairandcoallimitsthedryingcapability.Whencoalwithmoistureover20%mustbegroundinball-and-tubemills,auxiliaryequipment,usuallycrusherdryers,mustbeused.筒式钢球磨不具有类似立式磨的流化床特点力量。假设筒式钢球磨要磨的煤中水分高于20%，就必需使用关心的枯燥装置，比方裂开干燥机。Ball-and-tube mills have largely been supplanted by vertical air-sweptpulverizersfornewboilers.Theytypicallyrequirelargerbuildingvolumeandhigherspecificpowerconsumptionthantheverticalair-sweptpulverizres.Theyarealsomoredifficulttocontrolandhavehighermetal wearrates.Theyare,however,wellsuitedforgrindingextremelyabrasive,lowmoistureanddifficultmaterialsuchaspetroleumcoke.Theirlongtimemakesthemeffectiveforfinegrinding.32页的停留时间可以实现有效的磨制。PulverizingsystemsPulverizersarepartoflagersystems,normallyclassifiedaseitherdirect-firedorstorage.Indirectfiring,coalleavingeachmillgoesdirectlytothecombustionprocess.Theair,evaporatedmoistureandthethermalenergywhichenteredthemill,alongwiththegroundcoal,allbecomepartofthecombustionprocess.Storagesystemsseparatethegroundcoalfromtheair,evaporatedmoistureand thethermalenergypriortothecombustionprocess.Storedgroundcoalistheninjectedwithnewtransportairtothecombustionprocess.Binstoragesystemsareseldomusedinsteamgenerationtoday,butarestillusedwithspecialtechnologiessuchascoalgasificationandblastfurnacecoalinjection.Ofthe1000orsoMPSpulverizersinserviceintheU.S.morethan90%areusedindirect-firedsystems.制粉系统中的煤粉由的一次风输送到燃烧设备。目前生产蒸汽的过程中很少承受中储式制粉系统，但是很多特别的场合仍旧需要，比方煤气化和高炉投煤。目前在美国运行的中速磨大约有100099%以上的是直吹式系统。Theessentialelementsofadirect-firedsystemare:Arawcoalfeederthatregulatesthecoalflowfromasiloorbunkertothepulverizer.Aheatsourcethatpreheattheprimaryairforcoaldrying.Apulverizer(primaryair)fanthatistypicallylocatedaheadofthemill(pressurizedmill)asablower,orafterthemill(suctionmill)asanexhauster.Apulverizer,configuredaseitherapressurizedorsuctionunit.Pipingthatdirectsthecoalandprimaryairfromthepulverizertotheburners.Burnerswhichmixthecoalandbalanceofcombustionair,andControlandregulatingdevices.直吹式系统的主要部件有：给煤机，通过煤仓调整进入磨煤机的给煤量。热源，用来预热枯燥煤粉的一次风一次风机，典型的状况是作为鼓风机布置于磨煤机之前〔正压系统位于磨煤机之后〔负压系统〕磨煤机，作为正压系统或负压系统的主体局部。管路，把煤和一次风从磨煤机输送到燃烧器燃烧器，混合煤粉和平衡燃烧空气掌握和调整装置Thesecomponentscanbearrangedinseveralwaysonprojecteconomics.Withpressurizedpulverizers,thechoicemustbemadebetweenhotprimaryairfanswithadedicatedfanforeachmill,orcoldfanslocatedaheadofadedicatedairheaterandahotairsupplysystemshavealowercapitalcostbecauseadedicatedprimaryairheaterisnotrequired.Coldfansystemshaveloweroperatingcostswhich,onlargersystems,mayoffsetthehigherinitialcost.是承受热一次风风机〔每个磨一个风机，还是承受冷风风机〔布置在特定的空气加热器前面。热风输送系统初始投资费用较低，由于不需要特定的空气加热器。对大型机组而言，冷风风机系统具有较低的运行费用，可以补偿较高的初始投资。Theterminologyforair-sweptpulverizersreferstotheairintroducedfordryingandtransportasprimaryair.Controlofprimaryairisofvitalimportancetoproperpulverizersystemoperation.