凝结水过冷度产生的原因分析

凝结水过冷度产生的原因分析摘要:本文从各个方面分析了凝结水过冷度产生的原因及其对机组运行经济性、安全性的影响,从凝汽器的设计、改造、检修以及运行维护几个方面,提出了减小凝结水过冷度的对策,从而提高机组运行的经济性和安全性。Abstract:thispaperanalyzedfromvariousaspectsthecausesofthecondensatesupercoolingdegreeanditsimpactonunitoperationefficiency,safety,fromthedesignofthecondenser,modification,overhaulandoperationmaintenanceaspects,andputsforwardthemeasurestoreducethecondensatesupercoolingdegree,soastoimprovetheeconomicbenefitofunitoperationandsafety.关键词:凝汽器;过冷度;经济性;安全性Keywords:thecondenser;Supercoolingdegree;Economy;security1、引言1,theintroduction凝汽器是凝汽式汽轮机的主要辅助设备,是汽轮机组系统的重要组成部分,它工作性能的好坏直接影响着整个机组的热经济性和安全性。而凝汽器运行状态的优劣集中表现在以下三个方面:是否保持在最佳真空、凝结水的过冷度是否最小以及凝结水的品质是否合格。其中凝结水的过冷度越大,说明被冷却水带走损失的热量越多,而这部分热损失要靠锅炉多燃烧燃料来弥补,从而导致整个热力系统热经济性降低。而且过冷度越大,凝结水中的含氧量也越多,从而加速了相关管道、设备的腐蚀速度。因此需从各个方面对凝汽水过冷度加以重视并采取措施使其减到最小,以此来提高机组运行的经济性和安全性。Condenserisamainauxiliaryequipmentofcondensingsteamturbine,steamturbineunitsystemisanimportantpartofitsworkperformanceisgoodorbaddirectlyaffectsthethermalefficiencyoftheentireunit,andsecurity.Andadvantagesanddisadvantagesofthecondenserrunningstatusinthefollowingthreeaspects:whethertomaintainthebestvacuum,minimumofcondensatesupercoolingdegreeandwaterqualityisqualified.Ofcondensatesupercoolingdegree,thegreatertheinstructionswastakenawaybycoolingwaterthemoreheatloss,andthispartoftheheatlosswilldependontheboilerburningmorefueltomakeupfor,resultinginreducedthewholethermalsystemthermalefficiency.Andthegreaterthedegreeofsupercooling,is,themoreoxygenincondensate,whichacceleratedthecorrosionrateofrelatedpipingandequipment.Thereforeneedfromallaspectsonthesodasupercoolingdegreeofattentionandtakemeasurestominimize、凝结水过冷度的定义和表示方法2,thedefinitionofcondensatesupercoolingdegreeandthesaidmethod2.1定义2.1definitions凝结水过冷度表征了凝汽器热水井中凝结水的过度冷却程度,凝汽器热水井出口凝结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。Condensatesupercoolingdegreeofcharacterizationoftheovercoolingofthecondensateinthecondenserhotwell,thecondenserhotwellexportwatertemperatureandthecondenserintheexhauststeampressurecorrespondingtothesaturationtemperaturedifferencethatiscalledthedegreeofsupercooling.2.2表示方法2.2representationmethod温度形式:Temperatureoftheform:Δtn=ts-tcΔtn=ts-tc式中:Δtn—凝结水过冷度;Type:Δtn-condensatesupercoolingdegree;ts—凝汽器绝对压力下的饱和温度;Tsofthecondenserundertheabsolutepressureofsaturatedtemperature;tc—凝汽器热井中凝结水温度。Tc-thecondensatetemperatureinthecondenserhotwell.3、过冷度产生的原因3,thecauseofsupercoolingdegree凝汽器运行中产生凝结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,一般主要原因有以下几个。Producedintheoperationofthecondensercondensatesupercooledphenomenonincondenserdesignmightbetheproblem,alsomaybeimproperoperation,generallyhasthefollowingseveralmainreasons.3.1凝汽器内管束排列不好3.1withinthecondensertubebundlearrangementisnotgood在旧式结构的凝汽器上,凝结水过冷度可能很大。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置过密和排列不当,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,引起凝汽器内部绝对压力从凝汽器入口到抽气口逐渐降低,使得凝汽器大部分区域的蒸汽实际凝结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部分集中在上部冷却管束处,蒸汽所凝结的水通过密集的管束,又在冷却水管外侧形成一层水膜,又起到再冷却凝结水的作用,加之排汽不能回热热水井中凝结水,进一步加剧了凝结水的过冷却。Intheoldstructureofthecondenser,thecondensatesupercoolingdegreecouldbelarge.Thesecondenserareoftenaregenerative,condensertubebundlearrangementduetothecoolingwaterinsidetoocloseandimproperarrangement,makethesteamgasmixtureinthecenterofthetubebundletothecondensersteamandlowerwhenthereisabigresistance,absolutepressureinsideacondenserfromcondenserinlettograduallyreducebleedingpoint,makesmuchofthecondenserofthesteamcondensestemperatureislowerthanactualsaturationtemperatureattheentranceofthecondenser,formedthedegreeofsupercooling.Thiscausedasteamloadatthesametimemostlyintheuppercoolingtubebundle,steamcondensationwaterthroughdensebundles,andformalayerofwaterfilmontheoutsideofthecoolingwater空气漏入凝汽器或抽气器工作不正常3.2airleakageintothecondenserorejectordoesn'tworkproperly机组运行过程中,处于真空状态下的汽轮机的排汽缸、凝汽器以及低压给水加热系统等部分,若有不严密处,则会造成空气漏入;另一方面,抽气器工作不正常,不能及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凝结气体增加,这不仅会在冷却水管的表面形成传热不良的空气膜,降低传热效果,增加传热端差;同时还使得凝汽器内的汽气混合物中空气成分的增高,造成空气分压提高、蒸汽分压降低,而凝结水是在对应蒸汽分压的饱和温度下冷凝,所以此时凝结水温度必然低于凝汽器压力下的饱和温度,因而产生了凝结水的过冷却。Unitoperationintheprocess,underavacuumofsteamturbineexhaustcylinder,condenserandlowpressurefeedwaterheatingsystem,iftherearenottight,itwillcauseairleakageintothe;Ejectorwork,ontheotherhand,isnotnormal,notinatimelymannertothecondenserleakageintotheair.Withinthesetwoaspectsmakesthecondenserstockpiledon'tcondensegassuchasairincreases,thiswillnotonlyonthesurfaceofcoolingwater