阐述凝结水过冷度的定义和表示方法

阐述分散水过冷度的定义和表示方法2.1定义definitions分散水过冷度表征了凝汽器热水井中分散水的过度冷却程度,凝汽器热水井出口分散水温度与凝汽器在排汽压力下对应的饱和温度之差即称为过冷度。Characterization of condensate supercoolingdegreearetheovercoolingofthecondensateinthecondenserhotwell,thecondenserhotwellexportwatertemperatureandthecondenserintheexhauststeampressurecorrespondingtothesaturationtemperaturedifferencethatisreferredtoasthedegreeofsupercooling.表示方法2.2representationmethod温度形式:Temperatureoftheform:δtn=ts-tcThedeltatn=ts-tc式中:δtn—分散水过冷度;“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxType:thedeltatn-condensatesupercoolingdegree;ts—Ts-condenserundertheabsolutepressureofsaturatedtemperature;tc—凝汽器热井中分散水温度。Tc-thecondensatetemperatureinthecondenserhotwell.3、过冷度产生的缘由3,thecauseofsupercoolingdegree凝汽器运行中产生分散水过冷却现象可能是凝汽器设计中的问题,也可能是运行不当而产生的,一般主要缘由有以下几个。Producedintheoperationofthecondensercondensatesupercooledphenomenonmaybeaprobleminthedesignofthecondenser,alsomaybeimproperoperation,generallyhasthefollowingseveralmainreasons.“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjx3.1凝汽器内管束排列不好withinthecondensertubebundlearrangementisnotgood在旧式构造的凝汽器上,分散水过冷度可能很大。这些凝汽器通常均为非回热式的,凝汽器内由于冷却水管束布臵过密和排列不当,使汽气混合物在通往凝汽器的管束中心和下部时存在很大的汽阻,引起凝汽器内部确定压力从凝汽器入口到抽气口渐渐降低,使得凝汽器大局部区域的蒸汽实际分散温度要低于凝汽器入口处的饱和温度,形成了过冷度。这同时造成了蒸汽负荷大局部集中在上部冷却管束处,蒸汽所分散的水通过密集的管束,又在冷却水管外侧形成一层水膜,又起到再冷却分散水的作用,加之排汽不能回热热水井中分散水,进一步加剧了分散水的过冷却。Intheoldstructureofthecondenser,thecondensatesupercoolingdegreecouldbelarge.Thecondenserisusuallyarenotregenerative,condenserinsideduetoimpropercoolingwatertubebundlearrangementtoocloseandarrangement,makethesteamgasmixtureinthecenterofthetubebundletothecondensersteamandlowerwhenthereisabigresistance,absolutepressureinsidea“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxcondenserfromcondenserinlettothepumpintakereducedgradually,makesmuchofthecondenserofsteamcondensationtemperatureislowerthanactualsaturationtemperatureattheentranceofthecondenser,formedthedegreeofsupercooling.Thiscausedasteamloadatthesametimemostlyin the upper cooling tube bundle, steamcondensationwaterthroughdensebundles,andformalayerofwaterfilmontheoutsideofthecoolingwaterpipe,alsohavetheeffectofcoolingthecondensateagain,combinedwiththeexhauststeamcan”tbacktohotWellsinthecondensate,furtherexacerbatingtheovercoolingofthecondensate.空气漏入凝汽器或抽气器工作不正常theairleakageintothecondenserorejectordoesn”tworkproperly缸、凝汽器以及低压给水加热系统等局部,假设有不严密不能准时地把凝汽器内漏入的空气抽走。这两方面使得凝汽器内积存的空气等不分散气体增加,这不仅会在冷“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjx气成分的增高,造成空气分压提高、蒸汽分压降低,而分散水是在对应蒸汽分压的饱和温度下冷凝,所以此时分散水温度必定低于凝汽器压力下的饱和温度,因而产生了分散水的过冷却。Unitoperationintheprocess,underavacuumofsteamturbineexhaustcylinder,condenserandlowpressurefeedwaterheatingsystem,iftherearenottight,itwillcauseairleakageintothe;Ejectorwork,ontheotherhand,isnotnormal,notinatimelymannertothecondenserleakintotheair.Accumulatedwithinthesetwoaspectsmakesthecondenseroftheairandcondensationgasincreases,thiswillnotonlyonthesurfaceofcoolingwaterpipeformbadairheattransferfilm,reducetheheattransfereffect,increasetheheattransferenddifference;Alsomakethesteamcondenserinthehighergasmixtureofaircomposition,increasecausedbyairpressure,steampartialpressureisreduced,andthecondensateisincorrespondingtothepartialpressureofsaturatedsteamcondensingtemperature,“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxsoatthispointthecondensatetemperaturemustbelowerthanthesaturationtemperatureofthecondenserpressure,thusproducedtheovercoolingofthecondensate.分散水水位过高thecondensatewaterlevelistoohigh运行过程中,由于分散水泵真空局部漏入空气或其它故障,使凝汽器热井中分散水水位过高,漂浮了下部使分散水再次被冷却,过冷度必定增大。Operationprocess,becauseofthecondensatepumpvacuumpartleakintotheairorotherfault,thecondensateinthecondenserhotwellwaterlevelistoohigh,coveredthebottomofthecoolingwaterpipe,coolingwaterandtakeawaypartoftheheatofthefrozenwater,makewateriscooledagain,degreeofsupercoolingisboundtoincrease.冷却水漏入分散水内coolingwaterleakageintothewater分散水硬度增大的现象发生。“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxInsidethecondensercoolingwaterpipeburst,resultinginwaterleakageintothewater,lowerthewatertemperature,super-cooling degreeincrease,accompaniedbythephenomenonofwaterhardnessincreaseoccurredatthistime.凝汽器冷却水入口温度和流量的影响condensercoolingwaterinlettemperatureandflowrate现代电站凝汽器通常为回热式的,具有合理设计的管束构造,汽阻微小,在额定的设计工况下运行时,分散水过冷度实际可为零。在这种状况下,分散水过冷度主要受凝汽设备运行工况因素的影响,其中最重要的因素是凝汽器冷却水的入口温度和流量。Modernpowerplantcondenserforregenerative,usuallyhaveabundlestructureofreasonabledesign,steamresistancesmall,underthedesignconditionsofratedrunning,thecondensatesupercoolingdegreecanbezero.Inthiscase,thecondensatesupercoolingdegreeismainlyinfluencedbycondensingequipmentoperationconditionfactors,oneofthemostimportantfactoristhecondensercoolingwaterinlettemperature“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxandflowrate.试验与运行阅历说明,在肯定的蒸汽负荷下,当冷却水入口温度降低或流量增加时,细石混凝土泵凝汽器压力降低,真空增加,进入热井的分散水的过冷度将增大。Testandoperationexperienceshowthatunderacertainloadofthesteam,whenthecoolingwaterinlettemperaturedecreaseorincreasetraffic,condenserpressure,vacuum,inhotwellofthecondensatesuper-coolingdegreewillincrease.蒸汽负荷的影响theinfluenceofsteamload凝汽器蒸汽负荷的大小对分散水过冷度也有肯定的影响。依据前苏联вти的试验结果,对于汽流向心式凝汽器,随着蒸汽负荷的提高,过冷度增大;而对于汽流向侧式凝汽器,蒸汽负荷上升时,过冷度减小。对于旧起过冷度增加。Condensersteamloadonthesizeofthecondensatesuper-coolingdegreehasacertaininfluence.AccordingtotheformerSovietunionkindguideтиtestresults,forsteamflowtotheheart“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxtypecondenser,withtheimprovementofthesteamload,super-coolingdegreeincreased;Forthesteamflowtothelateraltypecondenser,steamloadincreases,thedegreeofsupercooling.Foroldnonregenerativecondenser,steamloadreduced,will inevitably cause super-cooling degreeincrease.将温度较低的补充水直接补入凝汽器的热水井Add3.7willbeaddedcoolerwaterdirectlyintothecondenserhotwell机组在运行过程中,由于锅炉排污等缘由,导致工质在循环过程中产生了汽水损失,因此为了满足汽轮机补充水补入的位臵有除氧器和凝汽器两种方案,假设承受况时凝汽器中分散水温度可达十几摄氏度。这样将温度较低的补充水直接补入凝汽器的热水井,并且在补充水流量较大时,势必会造成分散水温度的降低,致使过冷度增加。Unitsintheprocessofoperation,duetoreasonssuchasboilerblowdown,causeworkingsubstance“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxproducedsodalossinthecirculationprocess,soinordertomeettheneedsofthesteamturbineinletsteamquantity,mustaddintothesodamediumcirculationsysteminatimelymanner.Supplementwateraddthelocationofthedeaeratorandcondensercoagulationtwoplans,ifaddcondenserdesign,make-upwaterinwintertemperatureislowerthanthedesignworkingconditionofthecondensateinthecondensertemperaturecanbeuptotendegreesCelsius.Suchlowtemperatureaddsupplementarywaterdirectlyintothecondenserhotwell,andtosupplementthewaterflowisbig,willcausethecondensatetemperatureisreduced,thesupercoolingdegreeincrease.4、过冷度对机组运行经济性和安全性的影响4,thesupercoolingdegreeofimpactontheeconomyandsafetyoftheequipmentoperation4.1对机组运行经济性的影响“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjximpactonunitoperationeconomicalefficiency凝汽器过冷度会增加冷源损失,引起作功力量的损失,降低系统的热经济性。Condensersupercoolingdegreecanincreasethecoldsourceloss,causethelossofworkability,reducethethermalefficiencyofthesystem.n154.9/470,当分散水过冷却度增加2℃时,蒸汽等效焓降削减0.457kj/kg,机组效率相对降低0.051%,电厂标准煤耗0.198g/kw.h。假设该机组年运行小时数为7500h,那么,一台该型号机组每年多耗标煤为147.6t,相当于每年多支出燃料本钱3.1万元。可见,分散水过冷度对因此实行各种措施降低分散水过冷度是格外必要和有意义的。A4.9/470typesteamturbineofn15calculationresultsshowthatwhenthecondensatesupercooleddegreeincrease2℃,thenewsteamtoreduce0.457kj/kgofequivalententhalpydrop,theunitefficiencyrelativelyreduced0.051%,thestandardcoalconsumptionofpowerplantby0.198g/kw.H.Assumethattheunitannualoperationhoursis7500“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxh,so,onethemodelunitsannuallymoreBiaoMeiconsumptionis147.6t,equivalenttomorethanayearspendingonfuelcosts31000yuan.Visible,thecondensatesupercoolingdegreehasdistincteffectontheeconomicoperationoftheunit,cannotbeignoredisanindicator,sototakevarious measures toreducethe condensatesupercooling degree isverynecessary andmeaningful.对机组运行安全性的影响4.2impactonunitoperationsafety分散水过冷度的存在会威逼机组运行的安全性和牢靠性。分散水温度过低,即分散水水面上的蒸汽分压含量增加,由于溶于分散水的气体量和热井水面上气体的分压力成正比。因此假设分散水消灭过冷度,则其含氧量增加,这将导致凝汽器内换热管、低加及相关管道阀门腐蚀加剧,以致降低设备的使用寿命,不利于机组的安全运行。这同时也加重了除氧器的工作负担,使除氧的给水管道和锅炉省煤器管,引起泄漏和爆管。据统计,2023年某电厂凝汽器冷却水管腐蚀造成的泄漏,使“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjx达5次。可见,分散水过冷度的存在对机组运行安全性极为不利。Thecondensatesupercoolingdegreetherewillendangerthesafetyandreliabilityoftheequipment operation. Condensation watertemperaturewaslow,thepartialpressureofthesteamcondensatewater,gaspartialpressureincreases,madethegasdissolvedinthewatercontentincreases,becauseinthecondensategasamountandhotwellwatersurfaceisdirectlyproportionaltothepartialpressureofthegas.Soifappearscondensatesupercoolingdegree,theoxygencontentincreases,thiswillleadtothecondenserheatexchangetube,lowcorrosionintensifiesandrelatedpipelinevalve,soastoreducetheservicelifeofequipment,isnotconducivetothesaferunningoftheunit.Italsoaddstothedeaerator”sworkburden,makethedeaeratingeffectofdeaerator,seriouscorrosionathightemperaturewhentheyworkundertheenvironmentofwatersupplypipesandboiler“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxeconomizertubes,leakageanddetonationtube.Accordingtostatistics,in2023acertainpowerplantcondensercoolingwaterpipecorrosioncausedbytheleak,thewaterhardnessishigh,forcingthecrewcutoutputloadingleakfrequencyupto5times.Visible,theexistenceofcondensatesupercoolingdegreeofunitoperationtothedetrimentofsecurity.5、削减分散水过冷度的对策5,toreducethecondensatesupercoolingdegreeofcountermeasures通过上述对分散水过冷度产生缘由及其对机组运行经济性和安全性的影响的分析可以看到,分散水过冷度的存在威逼着机组运行的安全性和牢靠性,同时也会降低机组运行的经济性。因此须从设计、改造、检修以及运行维护等各个环节对其实行有效措施,以期降低分散水过冷度,提高机组运行的经济性和安全性。Bytheabovereasonsofcondensatesupercooling“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxdegreeanditseffectontherunningefficiencyandsecurityanalysiscansee,thecondensatesupercoolingdegreeoftheexistenceofthethreattothesafetyandreliabilityoftheequipmentoperation,alsocanreducetherunningefficiency.Somustbefromthedesign,modification,maintenance,andoperationmaintenanceandsooneachlinktotakeeffectivemeasures,inordertoreducethecondensatesupercoolingdegree,improvetheeconomicbenefitofunitoperationandsafety.5.1设计中所实行的对策designcountermeasurestakenin在冷却水管束设计中改进管束的布臵,在管束构造中适当留有足够宽的蒸汽通道,这除了可以保证汽流均匀进入管束各区域外,还可保证局部排汽可直接通应使抽气口位臵离开分散水远一些,以削减分散水过冷度;theimprovementinthedesignofcoolingwatertubebundletubebundlearrangement,properinthevascularbundleshaveenoughwidesteamchannel,inadditiontothiscanensureuniformsteamflow“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxintothetubebundledistrictoutside,stillcanensuresomeexhauststeamcanpassdirectlytothecondensingobjectsbottom,heatingwater,reducethecondensatesupercoolingdegree;Alsoshouldmakethebleedingpointlocationawayfromthecondensatefaraway,inordertoreducethecondensatesupercoolingdegree;从凝汽器入口至抽气口的路径应力求直接,且有足够的流通面积,蒸汽进入管束的流速不超过40m/s～50m/s,蒸汽沿程阻力尽量小,以削减汽阻,降低分散水的过冷度;fromthecondensertothepathoftheentrancetothesuctionportdirectly,andhaveenoughcirculationarea,theflowrateofthesteamintothetubebundleisnotmorethan40m/s~50m/s,steamon-wayresistancesmall,asfaraspossibletoreducethesteamresistance,reducethecondensatesupercoolingdegree;合理选择凝汽器内的淋水装臵,优化设计循环冷却水量;selectionofcondenserinthewaterspraydevice,theoptimaldesignofcirculatingcooling“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxwater;汽轮机排汽口与凝汽器的连接承受柔性连接,theexhaustmouthconnectedtothecondenserofthesteamturbineadoptsflexibleconnection,inordertopreventconfusingcauseairleakageintotheoperationofinflation;对于排入凝汽器的各种疏水、补充水、再循环水水位,最好接至分散器上部蒸汽空间,并装折流档板,防止冲刷冷却水管,以除掉这些水源中的空气,削减对分散水溶氧及对过冷度的影响;forintothecondenserofhydrophobic,replenishwaterandcirculatingwaterandotheradditionalfluid,connecttothelocationofthecondensermustbehigherthanthatofthecondensatewaterlevel,thebestupperconnectedtothecondensersteamspace,andbaffleplate,“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxtopreventscourcoolingwaterpipe,inordertogetridofthewaterintheair,toreduceacrosscoldwaterdissolvedoxygenandthedegreeofinfluence;利用锅炉连续排污对补充水进展加热,以削减补入凝汽器的补充水对分散水的过冷却。一般凝汽器的补充水箱与除氧器、连续排污扩容器布臵在同一平台处,因此可在补充水箱内加装一组管式换热器,由连续排污7675(6)usingtheboilercontinuoussewageformake-upwaterforheating,inordertoreducetheaddedwateraddcondenserovercoolingofthecondensate.Generaladditionaltankcondenseranddeaerator,continuousblowdownflashtankarrangedonthesameplatform,thuscansupplementthetankequippedwithasetofpipeheatexchanger,thecontinuousblowdownflashtankraisesthetube,thedomesticsewageasheatsource,heatexchangerintointurn(76)(on75)supplementedbyheatingthewater,andthenintothegutter.改造中所实行的对策“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxreformcountermeasurestakenin旧式凝汽器通常均为非回热式的,冷却管束通道很窄,汽阻很大,可达1.3～2.0kpa,这本身就可使过冷度5℃～10是改造凝汽器冷却管束构造。如:Oldcondenserareusuallynonregenerative,coolingtubebundlechannelisverynarrow,steamresistanceisverybig,canreach1.3~2.0kpa,thatinitselfcanmakethesupercoolingdegreereach5℃to10℃.Fortheseoldcondenser,thecondensatesupercoolingdegreehaslittletodowithworkingcondition,eliminatethesupercoolingphenomenonistheonlyeffectivemeasurestotransformthecondensercoolingtubebundlestructure.Suchas:撤除一局部冷却水管(削减一局部冷却面积),让排汽可深入到冷却面中部,并留有足够的宽度,但不穿通,使蒸汽能沿着冷却面作均匀的安排,并使分散水加热到排汽温度;Part(1)thedemolitionofpartofthecoolingwaterpipe(reducecoolingarea),allowtheexhauststeam“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxintothecentralcoolingsurface,andhadenoughwidth,butnotthrough,canmakesteamalongthecoolingsurfaceoftheuniformdistribution,andmakesthewaterheatedtosteamdischargetemperature;inthecoolingbundlesreasonabledecoratesomecatchmentanddrainageelement;限制管束中汽流流速,使其尽可能不超过40m/s～50m/s。(3)bundleZhongQiflowvelocity,sothatitisnotasmuchaspossibleformorethan40m/s~50m/s.检修中所实行的对策maintenancecountermeasurestakenin对真空系统进展灌水查漏,重点检查凝汽器喉部、低压抽汽管路、低压缸轴封蒸汽进出管道焊口、低凝汽器水位计接头处、疏水扩容器焊接处、与热井连接的真空系统阀门等部位,并修补泄漏处;thevacuumsystemforwaterleak,checkthecondenserthroat,lowpressuresteamextraction“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxpipe,lowpressurecylinderinandoutofthepipejointandlowpressureshaftsealsteamcylinderflangejointsurface,thermalWells,condensatepipelineflangejointwelds,condenserwaterlevelgauge,jointdrainflashtankwelding,vacuumsystem,whichisconnectedwithhotwellvalveandotherparts,andrepairtheleak;检查凝汽器内的淋水装臵;checkthetubeinthecondenserwaterdevice;对凝汽器水位调整器和轴封压力调整器进展检修;theregulatorandshaftsealwaterlevelinthecondenserpressureregulatorformaintenance;对抽真空系统进展检修,保证抽气设备的正常工作,以便运行时可准时抽出凝汽器内不分散气体。(4)thevacuumsystemformaintenanceandrepair,thenormalworkoftheextractionequipment,sothattheruntimecantimelytakeoutinsidethecondensercondensategas.运行中所实行的对策intheoperationoftheadoptedcountermeasures保证真空局部的严密性“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjxensurevacuumrigor保证真空局部的严密性,防止空气漏入,同时正确配臵抽气器。这不仅是为了维持凝汽器内的高真空度,也是防止分散水过冷的有效措施之一。投运行轴封压力调整器,并将轴封压力掌握在规定值内,以防止空气从轴封漏入,影响凝汽器真空。Ensurepartvacuumrigor,preventleakageintotheair,atthesametimecorrectconfigurationofejector.Thisisnotonlytomaintainahighvacuumdegreewithinthecondenser,itisalsooneoftheeffective measures to prevent condensatesupercooling. Run forshaft sealpressureregulator,andshaftsealpressurecontrolwithinthespecifiedvalue,inordertopreventtheairfromtheshaftsealleakage,affectthecondenservacuum.对分散水水位及水质的监视与掌握ofcondensatewaterlevelandwaterqualitymonitoringandcontrol为了消退运行中分散水水位过高而造成的分散水过冷却现象,一方面除了要求运行人员对分散水水位严格监视外,另一方面可通过装设分散水水位自动调整器“:///“://“://tastdmp/“://tastdmp“://taflmy/“://taflmy“://tastjx/“://tastjx可以利用分散水泵本身的运行特性,承受凝汽器低水位运行的方式。Inordertoeliminatethecondensateintheoperationofthecondensatesupercooledphenomenoncausedbywaterlevelistoohigh,ontheonehand,inadditiontotherequiredoperatingpersonneltothecondensatewateroutsidethestrictsupervision,ontheotherhandcanfurnishthecondensatewaterautomaticregulator