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首页 8_KilnSys烧成工艺.ppt

8_KilnSys烧成工艺.ppt

8_KilnSys烧成工艺.ppt

上传者: zhouck1999 2017-09-08 评分 5 0 147 20 669 暂无简介 简介 举报

简介:本文档为《8_KilnSys烧成工艺ppt》,可适用于工程科技领域,主题内容包含**烧成工艺烧成工艺KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingI符等。

**烧成工艺烧成工艺KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**烧成工艺简介工艺简介:各种窑型说明窑内各工艺带目的mdash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。KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIReviewofthekilnssystemsandthepyroprocessingzonesIntroductiontoProcessusedasabasiswithanexpectationtobetterunderstandthedetailsReviewofthekilnssystemsandthepyroprocessingzonesIntroductiontoProcessusedasabasiswithanexpectationtobetterunderstandthedetails**烧成工艺窑型湿法窑WSK,PLD,SEA,(RMDK,K)半干法窑法国Lafarge干法窑STC,BFD,KAM,ALP,SCK,EXSK,JPAK,BTH预热器窑WHL,(Demopolis),BTH,JPAK分解窑EXSK,RMD,SCKII,(Balcones)KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIITheprocessofmanufacturingclinkerisincarriedoutinoneofthesekilntypes**烧成工艺窑热耗KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThewetkilnsingeneralconsumetwiceasmuchheatthanamodernprecalcinerFollowsthehistoricaldevelopmentoftechnologyDifferencebetweenPreheaterandPrecalcinernotaslargeaspeopleoftenthink**烧成工艺回转窑长度KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIILookingatwhathappensintherotarykilnitself,fromtheinlettothedischargehellipimpactonthekilnlengthchaindensity:=mThekilnlengthcanbereducedifthecalcinationisachievedoutsidethekiln**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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIITheprimarydriverforrotarykilnadvancementhasbeentoincreasekilnoutputwhileloweringcapitalcostsThisisimportantinkilndesignandequipmentselectionOperationalpersonnelneedtounderstandtheresultingadvantages,disadvantagesandinherentconstraintsinordertogetthemostoutoftheexistinginstallations**烧成工艺湿法工艺进料以泥浆状进入窑湿度含量达到增加的脱水带要求湿法窑比干法窑长需要更多的燃料KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIISincetheadditionalmoistureistoberemovedsoanadditionalzoneisrequiredtodriveoffthemoistureThesekilnswereutilizedmoreintheolddays,sincethefuelpriceswerenothighTheyprovidedamainbenefitofveryuniformrawmixforthekilnbecauseofbetterblendingAlsotheregionwithwetclimatealreadyhadhighmoistureinthematerial,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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**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。KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThereisnosemidryprocesskilnintheLafargeNorthAmericaplantsEfficientprocessintermsoffuelconsumptionUsefulforplaceswithhighmoisturerawmaterialsSincekilnexitgasespassthroughthefeed,thedustwastingislowDuetopartlycalcinedfeed,thekilnlengthrsquosshorterUniformsizeoftheclinkerisamainadvantageControllingbedthicknessinthecoolerrequirescloseattentionThehotkilngasesflowthroughapproxcmdeepbedofpelletsonthegratesThepelletsmusthavesomemechanicalstrength,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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThefeedentersthekilnindrypowerformCountercurrentflowformaterialandhotgasesSincetheexitgaseshavehighamountofheat,drykilncanbeusedtogeneratepowerLongdryplantsarenowencounteringcombustionemissionissues(egLimitedSOXscrubbing,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)KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThegasesenterthechainsatatemperatureofapproximatelydegCandleavethekilnataboutdegCMaterialentersthechainswithatemperatureofdegCandemergesthechainsectionwithatemperatureofdegCChainsarehighmaintenanceitem,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SAx链条SA粉尘产生总是一种限制因素链带加快气体速度粉尘量=kV湿法窑ndash有捕获粉尘的可能性塑性带中的泥浆流动问题干法窑ndash限制粉尘产生捕获能力差一致的链条密度KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIDustgenerationandtrappingareimportantissuesinkilnchaindesignOftentheamountofchainsthatcanbeaddedispracticallylimitedbytheamountofdustthatisgeneratedandwhichmustthenbehandledbythedustreturnsystemTheslurryinawetkilnoffersmorepossibilitytotrapgenerateddust,althoughslurryflowproblems(plasticzone)oftencausebackspillingandlimitproductionInadrykiln,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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThepreheatingofthekilnfeedisdoneoutsidetherotarykilnInawetordrykiln,thetotalamountofheatfordecarbonationmustbetransferredtothefeedwithintherotarykilnitselfSincetheavailablesurfaceareaforheattransferisverysmallandheattransferisinefficient,sothekilnsarelongandwideAdrykilnforexamplerequiresapproxmtoachievecalcinationandfeedtakesmorethananhourtotravelthroughthissectionIntheprecalkilns,thesameisachievedinlessthanaminuteInpreheaterkiln,thefeediscalcineduptointhepreheattower,theheatrequiredinthekilnismuchlessThisresultsinhigherproductionfortheequalsizekilns**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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIICountercurrentflowoccursintherotarykiln,whilecocurrentoccursflowpatterninsidecyclones**烧成工艺旋风筒KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIBothcountercurrentandcocurrentflowsexitforthetowerkilnsExplainhowtwodifferentflowsexistinthepreheaterandprecalcinersExplainhowheatexchangetakesplaceinthecyclonesandducts**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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIPrecalcinersareessentiallysuspensionpreheaterkilnsthatareequippedwithasecondaryfiringsystemtoofthetotalfuelisfiredattheprecalcinerAirneededforthecombustionofthisfuel:eithercomesfromthekilnitselforitissuppliedbytheenormousexcesswastegasfromtheclinkercoolerbymeansofatertiaryairductSupplyoffuelisdividedbetweentwofiringpointsThecombustionairforthepreheaterburnerconsistingofexhaustairfromclinkercoolercomesthroughthekilnoraseparateductResidencetimeinthekiln:minutes**烧成工艺带分解炉的级预热器KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIExplainthedifferentstepsinthepreheaterandprecalcinerkilnsHeatexchangedependsondurationofcontactCyclonersquosseparate,ductsforheatexchangeOutlettemperaturetypicalforstagesstagespossibleifnotmuchheatneededforrawdrying**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(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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIISincethecalcinationisachievedveryquicklyanduptooutsidethekiln,thekilnsizeisverysmallandrequiresmuchlessheatforthetotalprocess(moreefficientandquickcalcination)SmallerkilnswithlessheatinputinthekilnmeansincreasedrefractorylifeandlessoverallmaintenancewithhigherreliabilityandstabilityTheprocessisespeciallyadvantageouswhenrelativelylowgradefuelswithlowcalorificvalueandorhighcontentofinertmatterhavetobeused(charcoal,lignite,wastefuels,tires,etc),asthesecanbefiredinthecalcineratrelativelylowtemperaturesbelowdegCsufficeforobtainingtherequiredcalcination**烧成工艺)燃料分布)停留时间)空气烟气流场设计)生料燃料空气混合均匀分解炉的性能KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIEvenfueldistributionforevenheatprofileisimportantTheresidencetimeofthefuelmustbeenoughtoensurecompletecombustionwithgoodamountofairneededforcombustionTheuniformityofrawmix,fuelfinenessandpropermixingareessentialrequirementsWithunevenfueldistribution,thethermalprofilewilloftenchange,asaresultthevolatilecyclewillnotstabilizeandthebuildupformationwillspreadalloverThermalchangesalsopromoteharderandstablebuildupsWithlessthenrequiredretentiontime,unburntfuelparticlewillmixintheloadcausingmorevolatilizationForagoodcombustionintheprecalciner,thelaquoTraquorulesshouldbeadheredtot=combustionTime:Temperature,Turbulence,fineness(Tenuity),oxygenconTent*(*adaptedfromFrenchTrules)Temperatureintheprecalciner:AhightemperatureimprovescombustionandsignificantlyreducesNOxemissions(hotcoreprecalciner)itisgovernedbytertiaryairtemperaturewhichshouldbemaximized,precalcinerdesign,kilnfeedandfueldistributionTimeofcombustion:AlongtimeprocessimprovescombustionperformanceTheoxygencontent:CombustionshouldpreferablybeignitedintertiaryairbeforeitismixedwiththekilnexhaustandasufficientairexcessshouldbeusedforgoodcombustionHowever,forreducingtheNOxemissionlevelstagecombustionshouldbeinitiallywithoutairandthenterminatedupstreamfromthelowercyclonewithexcessairTurbulence:Toimprovethecombustionkinetics,itisnecessary,asforthemainburnerpipe,toinsurerapidmixingoffuelandcombustionagentTenuity:Thefuelshouldbewellpreparedandoftheproperfineness,sometimesbetterthanforthemainburnerpipeIffinenessisnotsufficient,solidunburntsinthekilninletmaterialincreasetherisksofvolatilizationinthekilnThecombustionqualityintheprecalcinerisimportantonaccountof:volatilizationrisksassociatedwiththepresenceofunburntsolids,heatlossesfromgaseousunburnts,possiblereductionofNOxemissions**烧成工艺干法窑湿法窑热分布KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThegastemperaturecurvediffersfromthematerialtemperatureinthetwoendothermiczones:waterevaporationanddecarbonizationTheplateauinthematerialcurveindicatesthatthereistheabsorptionofheatTheheatprofileshaveadifferentcoatinglengthtokilnlengthratio(precalcinerwetprocess)However,afterconcentratingontheactuallengthofthekilncoveredbythecoating,inalldifferenttypeofkilnprocessesisaboutthesame,iemForwetkilnsthetempdifferencebetweentheairandthematerialisthehighestatthefeedendsincethefeedenterswetBecauseofthedifferenceinthespheatofthematerialandair,theairtemperatureislowerthenclinkerattheexitTheoretically,theprofileisapproximatelythesameinclinkeringzoneforallthekilnstypes**烧成工艺预热器窑预分解窑热分布KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIInaPreheaterkiln,materialentersthekilnapproximatelycalcined,versesaPrecalcinerwhichisuptocalcinedThetransitionzone,betweenthecalciningandclinkeringzonecanvaryconsiderablyforkilntypes(PrecalcinerminSinglestagepreheatermin)ThelongertheresidencetimeleadstoreducedclinkerreactivitybecauseofthegrowthofbeliteandfreelimecrystalsGranulationandldquosinteringrdquomaybeimpededrequiringhigherburningtemperature**烧成工艺窑内带的划分)游离水蒸发)黏土化合水的脱水)分解)烧成)冷却KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**烧成工艺蒸发(degC)degC:HO(l)热量HO(g)H=kJmol湿法窑KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**烧成工艺脱水(degC)degC:黏土脱结晶水SiObullAlObullHO加热SiObullAlOHOH=kJmoldegC:碳酸镁分解MgCO加热MgOCOH=kJmol有机物与硫化物的蒸发、氧化FeSOFeOSOdegC:碳酸钙分解degC纯状态由于不纯和酸性环境出现较早KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**烧成工艺分解带(degC)C黏土矿物分解为氧化物AlObullSiOAlOSiO黏土氧化物固相反应CaO,SiO,AlOCA,CA,CS,CSCC,CSdegC碳酸钙快速分解CaCOCaOCOH=kJmol游离石灰与SiO反应CaOSiOCaOSiOH=kJmol游离石灰然后与氧化铝和铁反应CaOAlO,FeOCaOAlO,CaOFeOKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIAtdegCcalcitedecomposesfastBecauseofitsdecompositionpressureatthistemperaturefreelimestartstoreactFirstwithsilicatoformCS,ndwithAlOandthenwithFeODecarbonationisveryheatconsuming(endothermic)FormationofCSisexothermic**烧成工艺分解速度材料温度决定CaCO至CO分解的分压气体温度控制热交换:物料向SiO、FeO、AlO的分解CO分压CaCO的分解压力和燃烧气体压力的总量KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIICaOCaOCOPressureequilibriumthelowerthepressure,thequickerthereaction**烧成工艺分解带(degC)在degC游离CaO与SO化合生成CaSOCaOSOCaSOSO影响复盐形成CaONaO,KONaSO,KSO,KSONaSO如果碱金属过剩NaOCANaCAKOCSKCSKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIAnhydritereactswithalkaliesfromclaystoformalkalisulfatesIfenoughSOisnotpresent,thenalkaliescombinewithcalciumtoformhigheralkalicompoundsAtlowtemperatureregions,thesealkalisulfatesandchloridescondenseandactasfluxestoproduceringsIntermediatestepsCaOSOOCaSO=withfreelimeinthematerialthatentersthekiln,thepreheaterkilnisabletotrapmoreSOinthegasthanthelongdrykiln(ifenoughO)**烧成工艺硫碱反应(degC)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(KSONaSO)双盐:硫酸钾镁钙、钾石膏流动性问题NaCA凝固时间短、需水量大强度发展慢KCS表现如CS但是化合稳定不形成CS更低的CS(强度)、更高的fCaO(凝固时间)KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIAchangeinthealkalibalanceduetokilncyclingmaychangetheclinkerqualitywithoutbeingdetectedbychemicalanalysisCyclinginakilncancauseswingsinSOlevelsformtoAhourcompositemaynotshowadrasticswing,whenwearegoingfromanundersulfatedtoaoversulfatedclinkerAlkalisreactwithsilicatesinaggregatesandcauseexpansionproblemsinconcreteCompoundswhichcancausebuildupsarethealkalichorides(KCl,NaCl),spyrrite(CSCaCO)andsulfosyprrite(CSCaSO)TheseareformedataboutC**烧成工艺窑操作员观察:烧成带开始上过渡带(min)放热,烧成反应开始与燃烧相似反应开始称为ldquo亮点rdquoldquo亮点rdquo物料温度上升地非常快肉眼观察烧成带和火焰材料在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度角翻转KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIITakenfromkilnoperatortrainingcourse**烧成工艺烧成带(degC)degCB矿(CS)彻底形成CaOSiOCaOSiOH=kJmolCA,CaO成为CACAF固熔CaOAlOFeOCAFH=kJmoldegCCA和CAF熔解形成液相。碱,SO的挥发RSO,CaSO加热RO,CaOSOO如果是还原条件:FeOFeOOdegCCaOCSCSH=kJmol液相存在会促进也是固固反应。KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIReactionBeliteiscompletelyformedliquidatdegC=AFM(Mgo)KNIfmoreO,lessSO(volatilization)R=KorN(alkalies)Thefluxistheliquidsolutionthatlowerstheburningtemperaturerequiredforthereaction(CS)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米或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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**烧成工艺冷却带(degC)degCtodegCCS结晶生成的szligCS如果缓慢冷却CS会分解为CS,CaO(双折射)碱性硫酸盐从熔体中凝固CA与CAF结晶熔化的硫酸盐结晶KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**烧成工艺相图KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**烧成工艺吸热(kJkg熟料))生料从加热到degC)黏土脱水)材料从deg加热到degC)degC分解)分解的材料从deg加热到degC)熔化加热放热)脱水黏土结晶)形成熟料相)熟料从degC冷却到degC)气体从degC冷却到degC生产公斤熟料需要的热量窑内的反应热量KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**烧成工艺总结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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingII**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mdash窑入口。窑头:窑熟料出口。烧成带:窑的最高温度区。CS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KilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIReviewofthekilnssystemsandthepyroprocessingzonesIntroductiontoProcessusedasabasiswithanexpectationtobetterunderstandthedetailsReviewofthekilnssystemsandthepyroprocessingzonesIntroductiontoProcessusedasabasiswithanexpectationtobetterunderstandthedetailsKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIITheprocessofmanufacturingclinkerisincarriedoutinoneofthesekilntypesKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThewetkilnsingeneralconsumetwiceasmuchheatthanamodernprecalcinerFollowsthehistoricaldevelopmentoftechnologyDifferencebetweenPreheaterandPrecalcinernotaslargeaspeopleoftenthinkKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIILookingatwhathappensintherotarykilnitself,fromtheinlettothedischargehellipimpactonthekilnlengthchaindensity:=mThekilnlengthcanbereducedifthecalcinationisachievedoutsidethekilnKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIITheprimarydriverforrotarykilnadvancementhasbeentoincreasekilnoutputwhileloweringcapitalcostsThisisimportantinkilndesignandequipmentselectionOperationalpersonnelneedtounderstandtheresultingadvantages,disadvantagesandinherentconstraintsinordertogetthemostoutoftheexistinginstallationsKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIISincetheadditionalmoistureistoberemovedsoanadditionalzoneisrequiredtodriveoffthemoistureThesekilnswereutilizedmoreintheolddays,sincethefuelpriceswerenothighTheyprovidedamainbenefitofveryuniformrawmixforthekilnbecauseofbetterblendingAlsotheregionwithwetclimatealreadyhadhighmoistureinthematerial,solessworkwasneededKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThereisnosemidryprocesskilnintheLafargeNorthAmericaplantsEfficientprocessintermsoffuelconsumptionUsefulforplaceswithhighmoisturerawmaterialsSincekilnexitgasespassthroughthefeed,thedustwastingislowDuetopartlycalcinedfeed,thekilnlengthrsquosshorterUniformsizeoftheclinkerisamainadvantageControllingbedthicknessinthecoolerrequirescloseattentionThehotkilngasesflowthroughapproxcmdeepbedofpelletsonthegratesThepelletsmusthavesomemechanicalstrength,otherwisetheybreakandchokethegratesKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThefeedentersthekilnindrypowerformCountercurrentflowformaterialandhotgasesSincetheexitgaseshavehighamountofheat,drykilncanbeusedtogeneratepowerLongdryplantsarenowencounteringcombustionemissionissues(egLimitedSOXscrubbing,limitedabilitytoreduceNOx)AnumberofkilnsseemtobeletoperatingwithpooroperatorcontrolpracticesKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThegasesenterthechainsatatemperatureofapproximatelydegCandleavethekilnataboutdegCMaterialentersthechainswithatemperatureofdegCandemergesthechainsectionwithatemperatureofdegCChainsarehighmaintenanceitem,andrequireconstantattentionKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIDustgenerationandtrappingareimportantissuesinkilnchaindesignOftentheamountofchainsthatcanbeaddedispracticallylimitedbytheamountofdustthatisgeneratedandwhichmustthenbehandledbythedustreturnsystemTheslurryinawetkilnoffersmorepossibilitytotrapgenerateddust,althoughslurryflowproblems(plasticzone)oftencausebackspillingandlimitproductionInadrykiln,fromexperience,thetrendistouniformdensityKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIThepreheatingofthekilnfeedisdoneoutsidetherotarykilnInawetordrykiln,thetotalamountofheatfordecarbonationmustbetransferredtothefeedwithintherotarykilnitselfSincetheavailablesurfaceareaforheattransferisverysmallandheattransferisinefficient,sothekilnsarelongandwideAdrykilnforexamplerequiresapproxmtoachievecalcinationandfeedtakesmorethananhourtotravelthroughthissectionIntheprecalkilns,thesameisachievedinlessthanaminuteInpreheaterkiln,thefeediscalcineduptointhepreheattower,theheatrequiredinthekilnismuchlessThisresultsinhigherproductionfortheequalsizekilnsKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIICountercurrentflowoccursintherotarykiln,whilecocurrentoccursflowpatterninsidecyclonesKilnSystemReviewProcessEngineeringTrainingProgramPyroprocessingIIBothcountercurrentandcocurrentflowsexitforthetowerkilnsExplainhowtwodiffer

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