8_KilnSys烧成工艺

*-*烧成工艺烧成工艺KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺简介 工艺简介：各种窑型说明窑内各工艺带 目的—增进理解：各种窑型的益处与局限窑型选择、熟料化学和工艺控制之间的交互作用 你能够成为水泥回转窑的烧成工艺专家。KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIReviewofthekilnssystemsandthepyro-processingzones.IntroductiontoProcessusedasabasiswithanexpectationtobetterunderstandthedetails.Reviewofthekilnssystemsandthepyro-processingzones.IntroductiontoProcessusedasabasiswithanexpectationtobetterunderstandthedetails.*-*烧成工艺窑型湿法窑WSK,PLD,SEA,(RMDK1,K2)半干法窑法国Lafarge干法窑STC,BFD,KAM,ALP,SCK,EXSK4,JPAK1,BTH预热器窑WHL,(Demopolis),BTH,JPAK2分解窑EXSK5,RMD,SCKII,(Balcones)KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIITheprocessofmanufacturingclinkerisincarriedoutinoneofthesekilntypes.*-*烧成工艺窑热耗KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThewetkilnsingeneralconsumetwiceasmuchheatthanamodernpre-calciner.Followsthehistoricaldevelopmentoftechnology.DifferencebetweenPre-heaterandPre-calcinernotaslargeaspeopleoftenthink.*-*烧成工艺回转窑长度KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIILookingatwhathappensintherotarykilnitself,fromtheinlettothedischarge….impactonthekilnlength/chaindensity:200=60m.Thekilnlengthcanbereducedifthecalcinationisachievedoutsidethekiln.*-*烧成工艺窑型评估降低每吨熟料的投资费用主要的考虑因素降低热耗次要的考虑因素最大的利益是从湿法到干法环境问题新窑设计中的考虑因素 操作：在理解工艺制约的同时，充分利用其优势KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIITheprimarydriverforrotarykilnadvancementhasbeentoincreasekilnoutputwhileloweringcapitalcosts.Thisisimportantinkilndesignandequipmentselection.Operationalpersonnelneedtounderstandtheresultingadvantages,disadvantagesandinherentconstraintsinordertogetthemostoutoftheexistinginstallations.*-*烧成工艺湿法工艺 进料以泥浆状进入窑 湿度含量达到40% 增加的脱水带要求湿法窑比干法窑长 需要更多的燃料KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIISincetheadditionalmoistureistoberemovedsoanadditionalzoneisrequiredtodriveoffthemoisture.Thesekilnswereutilizedmoreintheolddays,sincethefuelpriceswerenothigh.Theyprovidedamainbenefitofveryuniformrawmixforthekilnbecauseofbetterblending.Alsotheregionwithwetclimatealreadyhadhighmoistureinthematerial,solessworkwasneeded.*-*烧成工艺湿法工艺产量小无规模经济节约产量(除数)小---固定成本热耗高浪费燃料工艺强项代用垃圾燃料代用生料选择性高砖使用寿命低烧成带中热负荷高KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺半干法工艺回转炉篦子加热机工艺或立波尔窑窑出口气体通过粒状料层部分分解的生料进入窑调节窑非常困难。KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThereisnosemidryprocesskilnintheLafargeNorthAmericaplants.EfficientprocessintermsoffuelconsumptionUsefulforplaceswithhighmoisturerawmaterialsSincekilnexitgasespassthroughthefeed,thedustwastingislowDuetopartlycalcinedfeed,thekilnlength’sshorterUniformsizeoftheclinkerisamainadvantageControllingbedthicknessinthecoolerrequirescloseattention.Thehotkilngasesflowthroughapprox.15-20cmdeepbedofpelletsonthegrates.Thepelletsmusthavesomemechanicalstrength,otherwisetheybreakandchokethegrates*-*烧成工艺干法工艺窑尾高温运行典型的，在进料端有链条带适合联合余热发电问题燃烧排放受操作者控制习惯影响KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThefeedentersthekilnindrypowerform.Countercurrentflowformaterialandhotgases.Sincetheexitgaseshavehighamountofheat,drykilncanbeusedtogeneratepower.Longdryplantsarenowencounteringcombustionemissionissues(eg.LimitedSOXscrubbing,limitedabilitytoreduceNOx).Anumberofkilnsseemtobeletoperatingwithpooroperatorcontrolpractices*-*烧成工艺链条链条带在窑内较短的长度中提供大的表面面积 如果没有链条带，热耗就会很高，但是可以回收利用(Alpena)KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThegasesenterthechainsatatemperatureofapproximately800°Candleavethekilnatabout450°C.Materialentersthechainswithatemperatureof50°Candemergesthechainsectionwithatemperatureof730°C.Chainsarehighmaintenanceitem,andrequireconstantattention.*-*烧成工艺链条设计优化设计：降低热耗及粉尘量增加链条，热耗得到改善粉尘是重要的热交换机理粉尘量S.A.2x链条S.A.粉尘产生总是一种限制因素链带加快气体速度粉尘量=kV2湿法窑–有捕获粉尘的可能性塑性带中的泥浆流动问题干法窑–限制粉尘产生捕获能力差一致的链条密度KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIDustgenerationandtrappingareimportantissuesinkilnchaindesign.Oftentheamountofchainsthatcanbeaddedispracticallylimitedbytheamountofdustthatisgeneratedandwhichmustthenbehandledbythedustreturnsystem.Theslurryinawetkilnoffersmorepossibilitytotrapgenerateddust,althoughslurryflowproblems(plasticzone)oftencausebackspillingandlimitproduction.Inadrykiln,fromexperience,thetrendistouniformdensity.*-*烧成工艺干法长窑竞争性强如果整个工艺（设备）得到优化投资成本特别低合理的热耗不是预分解炉也非湿工艺不便使用废燃料挥发周期必须得到核查与控制BTH,JPA有过烧的趋势烧成带长，质量低KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺预热器窑进料被预热并部分分解在旋风筒中由窑气进行热交换机理在旋风器中，悬浮的冷的材料与高温气体换热旋风筒阻塞窑气中的碱、硫、氯的浓度高常常需要旁路KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThepreheatingofthekilnfeedisdoneoutsidetherotarykiln.Inawetordrykiln,thetotalamountofheatfordecarbonationmustbetransferredtothefeedwithintherotarykilnitself.Sincetheavailablesurfaceareaforheattransferisverysmallandheattransferisinefficient,sothekilnsarelongandwide.Adrykilnforexamplerequiresapprox.45mtoachieve90%calcinationandfeedtakesmorethananhourtotravelthroughthissection.Intheprecalkilns,thesameisachievedinlessthanaminute.Inpreheaterkiln,thefeediscalcinedupto35%inthepreheattower,theheatrequiredinthekilnismuchless.Thisresultsinhigherproductionfortheequalsizekilns.*-*烧成工艺逆流及同流换热低温流体出口温度能超过高温流体的出口温度理想的是，要求长热交换器低温与高温气流体在出口温度接近常常快一些在入口温差大KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIICountercurrentflowoccursintherotarykiln,whileco-currentoccursflowpatterninsidecyclones.*-*烧成工艺旋风筒KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIBothcountercurrentandco-currentflowsexitforthetowerkilns.Explainhowtwodifferentflowsexistinthepreheaterandprecalciners.Explainhowheatexchangetakesplaceinthecyclonesandducts.*-*烧成工艺燃烧空气预分解经过窑（AT）经过独立管道（AS）任一或任一或在预热器内(在线)在独立的容器内(离线)预分解窑KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIPrecalcinersareessentiallysuspensionpreheaterkilnsthatareequippedwithasecondaryfiringsystem.50to70%ofthetotalfuelisfiredattheprecalciner.Airneededforthecombustionofthisfuel:eithercomesfromthekilnitselforitissuppliedbytheenormousexcesswastegasfromtheclinkercoolerbymeansofatertiaryairduct.Supplyoffuelisdividedbetweentwofiringpoints.Thecombustionairforthepreheaterburnerconsistingofexhaustairfromclinkercoolercomesthroughthekilnoraseparateduct.Residencetimeinthekiln:40-60minutes*-*烧成工艺带分解炉的4级预热器KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIExplainthedifferentstepsinthepreheaterandprecalcinerkilns.Heatexchangedependsondurationofcontact.Cyclone’sseparate,ductsforheatexchangeOutlettemperaturetypicalfor4stages5stagespossibleifnotmuchheatneededforrawdrying.*-*烧成工艺预分解窑的优点回转窑尺寸更小窑热负荷低耐火材料使用寿命延长生产能力高（10000吨/天）窑运行更稳定独立的分解燃料控制分解采用低级燃料停机次数少（稳定,耐火材料使用寿命）增加现有预热器窑的生产能力挥发问题更容易控制KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIISincethecalcinationisachievedveryquicklyandupto90%outsidethekiln,thekilnsizeisverysmallandrequiresmuchlessheatforthetotalprocess(moreefficientandquickcalcination).Smallerkilnswithlessheatinputinthekilnmeansincreasedrefractorylifeandlessoverallmaintenancewithhigherreliabilityandstability.Theprocessisespeciallyadvantageouswhenrelativelylow-gradefuelswithlowcalorificvalueand/orhighcontentofinertmatterhavetobeused(charcoal,lignite,wastefuels,tires,etc.),asthesecanbefiredinthecalcineratrelativelylowtemperaturesbelow900°Csufficeforobtainingtherequiredcalcination.*-*烧成工艺1) 燃料分布2) 停留时间3) 空气-烟气流场设计4) 生料/燃料/空气混合均匀分解炉的性能KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIEvenfueldistributionforevenheatprofileisimportant.Theresidencetimeofthefuelmustbeenoughtoensurecompletecombustionwithgoodamountofairneededforcombustion.Theuniformityofrawmix,fuelfinenessandpropermixingareessentialrequirements.Withunevenfueldistribution,thethermalprofilewilloftenchange,asaresultthevolatilecyclewillnotstabilizeandthebuild-upformationwillspreadallover.Thermalchangesalsopromoteharderandstable-build-ups.Withlessthenrequiredretentiontime,unburntfuelparticlewillmixintheloadcausingmorevolatilization.Foragoodcombustionintheprecalciner,the«5T»rulesshouldbeadheredto.5t=combustionTime:Temperature,Turbulence,fineness(Tenuity),oxygenconTent*(*adaptedfromFrench%Trules)Temperatureintheprecalciner:AhightemperatureimprovescombustionandsignificantlyreducesNOxemissions(hot-coreprecalciner);itisgovernedby;tertiaryairtemperaturewhichshouldbemaximized,precalcinerdesign,kilnfeedandfueldistribution.Timeofcombustion:Alongtimeprocessimprovescombustionperformance.Theoxygencontent:Combustionshouldpreferablybeignitedintertiaryairbeforeitismixedwiththekilnexhaustandasufficientairexcessshouldbeusedforgoodcombustion.However,forreducingtheNOxemissionlevelstagecombustionshouldbeinitiallywithoutairandthenterminatedupstreamfromthelowercyclonewithexcessair.Turbulence:Toimprovethecombustionkinetics,itisnecessary,asforthemainburnerpipe,toinsurerapidmixingoffuelandcombustionagent.Tenuity:Thefuelshouldbewellpreparedandoftheproperfineness,sometimesbetterthanforthemainburnerpipe.Iffinenessisnotsufficient,solidunburntsinthekilninletmaterialincreasetherisksofvolatilizationinthekiln.Thecombustionqualityintheprecalcinerisimportantonaccountof:volatilizationrisksassociatedwiththepresenceofunburntsolids,heatlossesfromgaseousunburnts,possiblereductionofNOxemissions.*-*烧成工艺干法窑湿法窑热分布��KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThegastemperaturecurvediffersfromthematerialtemperatureinthetwoendothermiczones:waterevaporationanddecarbonization.Theplateauinthematerialcurveindicatesthatthereistheabsorptionofheat.Theheatprofileshaveadifferentcoatinglengthtokilnlengthratio(45-60%precalciner;12-20%wetprocess).However,afterconcentratingontheactuallengthofthekilncoveredbythecoating,inalldifferenttypeofkilnprocessesisaboutthesame,i.e.20-30m.Forwetkilnsthetemp.differencebetweentheairandthematerialisthehighestatthefeedendsincethefeedenterswet.Becauseofthedifferenceinthesp.heatofthematerialandair,theairtemperatureislowerthenclinkerattheexit.Theoretically,theprofileisapproximatelythesameinclinkeringzoneforallthekilnstypes.*-*烧成工艺预热器窑预分解窑热分布��KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIInaPreheaterkiln,materialentersthekilnapproximately40%calcined,versesaPrecalcinerwhichisupto95%calcined.Thetransitionzone,betweenthecalciningandclinkeringzonecanvaryconsiderablyforkilntypes(Precalciner-5min;Singlestagepreheater-15min).Thelongertheresidencetimeleadstoreducedclinkerreactivitybecauseofthegrowthofbeliteandfree-limecrystals.Granulationand“sintering”maybeimpededrequiringhigherburningtemperature.*-*烧成工艺窑内带的划分1) 游离水蒸发2) 黏土化合水的脱水3) 分解4) 烧成5) 冷却KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺蒸发(100-400°C)100-400°C: H2O(l)+热量H2O(g) H=+44.2kJ/mol湿法窑�KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺脱水(350-650°C)350-650°C:黏土脱结晶水 2SiO2•Al2O3•2H2O+加热2SiO2•Al2O3+2H2O H=+274kJ/mol400°C:碳酸镁分解 MgCO3+加热MgO+CO2 H=+120kJ/mol有机物与硫化物的蒸发、氧化 FeS2+O2Fe2O3+SO3550°C:碳酸钙分解900°C纯状态由于不纯和酸性环境，出现较早KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺分解带(600-1200°C)600-900C黏土矿物分解为氧化物 Al2O3•SiO2Al2O3+SiO2黏土氧化物固相反应 CaO,SiO2,Al2O3CA,C12A7,CS,C2S.CC,C2S850-900°C碳酸钙快速分解 CaCO3CaO+CO2 H=+474kJ/mol游离石灰与SiO2反应 2CaO+SiO22CaO.SiO2 H=-143kJ/mol游离石灰然后与氧化铝和铁反应 2CaO+Al2O3,Fe2O32CaO.Al2O3,2CaO.Fe2O3KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIAt900°Ccalcitedecomposesfast.Becauseofitsdecompositionpressureatthistemperaturefreelimestartstoreact.FirstwithsilicatoformC2S,2ndwithAl2O3andthenwithFe2O3.Decarbonationisveryheatconsuming(endothermic).FormationofC2Sisexothermic.*-*烧成工艺分解速度材料温度决定CaCO3至CO2分解的分压气体温度控制热交换:物料向SiO2、Fe2O3、Al2O3的分解CO2分压CaCO3的分解压力和燃烧气体压力的总量KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIICaO3CaO+CO2Pressureequilibrium-thelowerthepressure,thequickerthereaction.*-*烧成工艺分解带(600-1200°C)在850-900°C游离CaO与SO3化合生成CaSO4 CaO+SO3CaSO4SO3影响复盐形成CaO+Na2O,K2ONa2SO4,K2SO4,3K2SO4.Na2SO4如果碱金属过剩 Na2O+C3ANaC8A3 K2O+C2SKC23S12KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIAnhydritereactswithalkaliesfromclaystoformalkalisulfates.IfenoughSO3isnotpresent,thenalkaliescombinewithcalciumtoformhigheralkalicompounds.Atlowtemperatureregions,thesealkalisulfatesandchloridescondenseandactasfluxestoproducerings.IntermediatestepsCaO+SO2+1/2O2CaSO4=withfreelimeinthematerialthatentersthekiln,thepreheaterkilnisabletotrapmoreSO2inthegasthanthelongdrykiln(ifenoughO2).*-*烧成工艺硫碱反应(850-900°C)碱平衡的改变可能改变质量挥发循环在熟料样中通常不被注意不稳定的凝固时间、强度、流动性问题形成结皮、结圈3(K2SO4.Na2SO4)双盐:硫酸钾镁钙、钾石膏流动性问题NaC8A3凝固时间短、需水量大强度发展慢KC23S12表现如C2S;但是化合稳定，不形成C3S更低的C3S(强度)、更高的f-CaO(凝固时间) KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIAchangeinthealkalibalanceduetokilncyclingmaychangetheclinkerqualitywithoutbeingdetectedbychemicalanalysis.CyclinginakilncancauseswingsinSO3levelsform0.5to2.5%.A2-4hourcompositemaynotshowadrasticswing,whenwearegoingfromanundersulfatedtoaoversulfatedclinker.Alkalisreactwithsilicatesinaggregatesandcauseexpansionproblemsinconcrete.Compoundswhichcancausebuildupsarethealkali-chorides(KCl,NaCl),spyrrite(2C2S.CaCO3)andsulfo-syprrite(2C2S.CaSO4).Theseareformedatabout800C.*-*烧成工艺窑操作员观察:烧成带开始上过渡带(5-15min)放热,烧成反应开始与燃烧相似反应开始，称为“亮点”“亮点”物料温度上升地非常快肉眼观察烧成带和火焰材料在5-6英尺之内从黑变白随着烧成的进展出现熔化物料开始黏附在砖上和窑皮上然后，开始45度角翻转KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIITakenfromkilnoperatortrainingcourse.*-*烧成工艺烧成带(1200-1450°C)1200°CB-矿(C2S)彻底形成 2CaO+SiO22CaO.SiO2 H=-125kJ/molC12A7,CaO成为C3AC4AF固熔 4CaO+Al2O3+Fe2O3C4AF H=-50.4kJ/mol1250-1300°CC3A和C4AF熔解形成液相。碱,SO3的挥发 R2SO4,CaSO4+加热R2O,CaO+SO2+1/2O2如果是还原条件:Fe2O32FeO+1/2O21310-1450°C CaO+C2SC3S H=-125kJ/mol液相存在会促进;也是固-固反应。KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII Reaction1-Beliteiscompletelyformed %liquidat1400°C=2.95A+2.25F+M(Mgo)+K+N IfmoreO2,lessSO2(volatilization);R=KorN(alkalies)Thefluxistheliquidsolutionthatlowerstheburningtemperaturerequiredforthereaction(C3S).Mineralizersarecompoundsaddedinextremelysmallamountstoincreasethespeedofthereactionsandthuslowertheburningtemperaturewithoutappreciablyincreasingtheliquidcontent.*-*烧成工艺终点：很难精确界定烧成带结束的位置大概在距离窑出料口2-3米或15英尺处取决于物料在烧成带中的温度燃烧器的位置很重要有一个通常的规定，窑皮的前端为烧成带终点。 窑操作员观察:烧成带终点KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺冷却带(1400-1250°C)1400°Cto1250°C-C2S结晶生成的ß-C2S如果缓慢冷却C3S会分解为C2S,CaO(双折射)碱性硫酸盐从熔体中凝固C3A与C4AF结晶熔化的硫酸盐结晶KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺相图KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺 吸热 (kJ/kg熟料)1) 生料从20加热到450°C 7142) 黏土脱水 1683) 材料从450°加热到900°C 8204) 900°C分解 19955) 分解的材料从900°加热到1400°C 5256) 熔化加热 105 4327放热1) 脱水黏土结晶 422) 形成熟料相 4203) 熟料从1400°C冷却到20°C 15124) 气体从900°C冷却到20°C 588 2562生产1公斤熟料需要的热量 1765窑内的反应热量KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺 总结 初级经济法重点总结下载党员个人总结TXt高中句型全总结.doc高中句型全总结.doc理论力学知识点总结pdf 窑系统设计降低投资成本每个系统都有其优势和劣势热负荷为重要参数热输入分解-产量烧成-质量复杂的反应解释运行中的反应对质量的重要影响KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingII*-*烧成工艺一次空气： 经燃烧器引入的燃烧空气。二次空气： 来自邻近工艺的燃烧空气。三次空气： 有代表性的是，来自熟料冷却机的气体。从不邻近燃烧器的工艺中某处引进的燃烧空气。其特点是高温熟料冷却机的气体在分解炉中使用,窑尾： 窑的进料端—-窑入口。窑头： 窑熟料出口。烧成带： 窑的最高温度区。C3S在这里形成。.分解带： 窑/预热塔区域.熟料冷却带： 位于窑前端，熟料出窑之前在此冷却到一定程度。熟料快速冷却： 熟料冷却机内，熟料的快速空气冷却。窑尾引风机：引风机，用于抽吸窑内气体。窑皮： 窑耐火材料上形成，起保护耐火材料和窑绝热作用。挥发： 高温情况下，化学成分的蒸发。术语词汇KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIKilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIKilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIReviewofthekilnssystemsandthepyro-processingzones.IntroductiontoProcessusedasabasiswithanexpectationtobetterunderstandthedetails.Reviewofthekilnssystemsandthepyro-processingzones.IntroductiontoProcessusedasabasiswithanexpectationtobetterunderstandthedetails.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIITheprocessofmanufacturingclinkerisincarriedoutinoneofthesekilntypes.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThewetkilnsingeneralconsumetwiceasmuchheatthanamodernpre-calciner.Followsthehistoricaldevelopmentoftechnology.DifferencebetweenPre-heaterandPre-calcinernotaslargeaspeopleoftenthink.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIILookingatwhathappensintherotarykilnitself,fromtheinlettothedischarge….impactonthekilnlength/chaindensity:200=60m.Thekilnlengthcanbereducedifthecalcinationisachievedoutsidethekiln.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIITheprimarydriverforrotarykilnadvancementhasbeentoincreasekilnoutputwhileloweringcapitalcosts.Thisisimportantinkilndesignandequipmentselection.Operationalpersonnelneedtounderstandtheresultingadvantages,disadvantagesandinherentconstraintsinordertogetthemostoutoftheexistinginstallations.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIISincetheadditionalmoistureistoberemovedsoanadditionalzoneisrequiredtodriveoffthemoisture.Thesekilnswereutilizedmoreintheolddays,sincethefuelpriceswerenothigh.Theyprovidedamainbenefitofveryuniformrawmixforthekilnbecauseofbetterblending.Alsotheregionwithwetclimatealreadyhadhighmoistureinthematerial,solessworkwasneeded.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIKilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThereisnosemidryprocesskilnintheLafargeNorthAmericaplants.EfficientprocessintermsoffuelconsumptionUsefulforplaceswithhighmoisturerawmaterialsSincekilnexitgasespassthroughthefeed,thedustwastingislowDuetopartlycalcinedfeed,thekilnlength’sshorterUniformsizeoftheclinkerisamainadvantageControllingbedthicknessinthecoolerrequirescloseattention.Thehotkilngasesflowthroughapprox.15-20cmdeepbedofpelletsonthegrates.Thepelletsmusthavesomemechanicalstrength,otherwisetheybreakandchokethegratesKilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThefeedentersthekilnindrypowerform.Countercurrentflowformaterialandhotgases.Sincetheexitgaseshavehighamountofheat,drykilncanbeusedtogeneratepower.Longdryplantsarenowencounteringcombustionemissionissues(eg.LimitedSOXscrubbing,limitedabilitytoreduceNOx).AnumberofkilnsseemtobeletoperatingwithpooroperatorcontrolpracticesKilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThegasesenterthechainsatatemperatureofapproximately800°Candleavethekilnatabout450°C.Materialentersthechainswithatemperatureof50°Candemergesthechainsectionwithatemperatureof730°C.Chainsarehighmaintenanceitem,andrequireconstantattention.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIDustgenerationandtrappingareimportantissuesinkilnchaindesign.Oftentheamountofchainsthatcanbeaddedispracticallylimitedbytheamountofdustthatisgeneratedandwhichmustthenbehandledbythedustreturnsystem.Theslurryinawetkilnoffersmorepossibilitytotrapgenerateddust,althoughslurryflowproblems(plasticzone)oftencausebackspillingandlimitproduction.Inadrykiln,fromexperience,thetrendistouniformdensity.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIKilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIThepreheatingofthekilnfeedisdoneoutsidetherotarykiln.Inawetordrykiln,thetotalamountofheatfordecarbonationmustbetransferredtothefeedwithintherotarykilnitself.Sincetheavailablesurfaceareaforheattransferisverysmallandheattransferisinefficient,sothekilnsarelongandwide.Adrykilnforexamplerequiresapprox.45mtoachieve90%calcinationandfeedtakesmorethananhourtotravelthroughthissection.Intheprecalkilns,thesameisachievedinlessthanaminute.Inpreheaterkiln,thefeediscalcinedupto35%inthepreheattower,theheatrequiredinthekilnismuchless.Thisresultsinhigherproductionfortheequalsizekilns.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIICountercurrentflowoccursintherotarykiln,whileco-currentoccursflowpatterninsidecyclones.KilnSystemReviewProcessEngineeringTrainingProgram-PyroprocessingIIBothcountercurrentandco-currentflowsexitforthetowerkilns.Explainhowtwodiffer