MW机组凝结水含氧量超标的危害和预防

600MW机组凝结水含氧量超标的危害和预防600MWunitscondensateoxygencontentofthehazardsofexcessiveandprevention１Condensateofdissolvedoxygenisoneofthemainindicatorsofthechemicalsupervision，600MWunitscondensatedissolvedoxygencontenthigherdissolvedoxygen，becausealotofexcessiveorlong-termfailure,Itwillacceleratethecondensatepipelineandequipmentcorrosion,andmakecondensatcontainsironoxideions,causinggalvaniccorrosion，Heattransferdeterioration,untiltheoccurrenceofboilertube,andcrewsafetyandeconomicoperationofunits.凝结水溶解氧是化学监督的主要指标之一,特别是600M机组对凝结水溶解氧含量有更高的要求.因为溶解氧大幅度超标或长期不合格，会加速凝结水管道及设备的腐蚀，并使凝结水中含有氧化铁离子，引起电化腐蚀，使传热恶化，直至发生锅炉爆管，严重威胁机组安全、经济运行。凝结水溶解氧存在的原因：1.真空系统不严密，进入凝结器的漏量大；2.有溶解氧含量较高的补水或回收水大量进入凝结器；Condensateofdissolvedoxygenreasonsfortheexistence:1.vacuumsystemisnottight,alotofairtoenterthecondenser;2.higherlevelsofdissolvedoxygenreplenishwaterorrecycledwaterenterthecondenser针对上述原因，从以下方面进行防范和处理：Fortheabovereasons,fromthefollowingaspectspreventandtreatment:运行中真空系统的查漏以氦介质检漏为主。方法是在运行真空泵出口布置氦介质检漏装置，利用专用的喷枪在所有负压系统的阀门、法兰、管道焊缝、排大气口等处喷氦气，然后观察1-2分钟，如果检测点有泄露，检漏装置就会发出报警，泄漏量越大，报警数值就越大，即使很微量的泄露，也能检测出来。并且这种方法灵活，不受时间限制，消除漏点后随时可以检测溶解氧的变化。缺点是工作量大，耗时长。1.真空系统的查漏1.vacuumsystemleakrunningvacuumsystemleakismainlyheliummediumLeak.runningvacuumpumpoutletlayouttheheliummediumleakdetectiondevices,withadedicatedgunsprayheliumtoallnegativepressuresystemvalves,flanges,pipeweldsandexclusiveatmospheremouthetc,thenobservedfor1-2minutes,ifitdetectssomeleakage,andtheleakdetectiondevicewillalarm,thegreatertheamountofleakage,thegreaterthealarmvalue,evenaverysmallamountofleakagecanbedetected.themethodisflexible,withouttimelimit,aftereliminatetheleak，atanytimethechangeofdissolvedoxygencanbedetected.Thedrawbackisthelargeamountofwork,time-consuminglong灌水查漏。方法是：凝结器灌水至末级叶片下100mm高度，然后查漏处理。需要注意的是灌水过程中有专人监视水位，防止水位过高进入汽轮机。但这种方法必须停机后才能进行。Condenserirrigationtothelaststagebladesunder100mmheight,thenleaktohandle.Shouldbenotedthatthereissomeonetomonitorthewaterlevel,inordertopreventthehighwaterlevelentertheturbineintheirrigationprocess.However,thismethodmustbeshutdownafter.Thepurposeofirrigationleak2.凝结水泵系统的改造Condensatepumpsealwaterinsteadoftwo:closedwaterandcondensatepumpoutletself-sealingwater凝结水泵密封水水源改为两路：闭式水和凝结泵出口自密封水。凝结水泵进口滤网顶部增加排空气管路2.CondensatepumpsystemtransformationIncreaseexhaustairlineatthetopofcondensatepumpinletfilter3.对加入凝结水的回收水进行处理热力系统内漏进入凝结器内的非正常疏水。该疏水进入凝结器导致热负荷增加，汽阻增大，造成凝结器内空气分压的提高，从而凝结水的含氧量增加。因此查出阀门泄露并及时更换内泄阀门是一项长期的工作低加等热力系统的正常疏水。方法是维持低加正常水位，防止无水位运行或常开危急疏水运行，另外加强对疏水系统阀门法兰的检漏，尽可能减少空气的漏人3.Joincondensaterecycledwatertreatmentnormaldrainlowpressureheaterofthermalsystem.themethodistomaintainthethelowpressureheaternormallevel,topreventthenolevelorlong-timeopenacriticaldrainvalverunning,inadditiontostrengtheningthevalveflangeleakdetectionofdrainsystem,inordertominimizeairleakage.theabnormaldrainleakageofthermalsystemleakintocondenser.thedrainenteringcondenserthatheatloadincreases,andthesteamresistanceincreases,resultetoraisethebranchpressureofairinthecondenser,andraisethewateroxygencontentofcondenser,thereforedetectvalveleaksandtimelyreplacementtheleakingvalveisalong-standingwork.4．凝补水系统的改造凝补水是除盐水。除盐水的含氧量很高，需要进行深度除氧。一般的说，凝补水直接补入热井，没有利用凝结器的真空除氧作用，除盐水补水口应接在6.9米的7、8号低加侧，经充分雾化后增大凝补水与排汽的接触面积，从而减少凝结水的含氧量。4.CondensatereplenishmentsystemtransformationCondensatereplenishmentisdemineralizedwater,theoxygencontentofdemineralizingwaterisveryhigh,itneeddepthtoremoveoxygn.Condensatereplenishmentdirectlyintothehotwell,nomakefullusevacuumremovallingoxygnroleofcondenser,replenishmentpointofdemineralizingwatershouldpickthe6.9m7,8lowpressureheaterside,afterfullyatomizedtoincreasecontactingareaofcondensatereplenishmentwithexhaust,therebyreducetheoxygencontentofthecondensate.案例分析:上海吴泾发电有限责任公司2*300MW机组运行中凝结水溶解氧时有超标( 标准 excel标准偏差excel标准偏差函数exl标准差函数国标检验抽样标准表免费下载红头文件格式标准下载 控制＜30ug/L),2010年12月份#1机组进行B级检修时发现:给水泵、省煤器腐蚀严重，同时发现锅炉内部也有一定结垢和腐蚀。经过排查发现:凝结泵自密封阀门开度小于10%时凝补水会进入凝结水中，导致凝结水含氧量升高。另外排查发现:真空系统漏点多集中在凝结器管阀和凝结水泵入口管阀等处，空气的漏入导致凝结水含氧量升高。上述问题解决后凝结水溶解氧合格率达到100%，平均化验值达到21ug/L.CaseStudy:ShanghaiWujingPowerCompany2*300MWunit:duringoperationitoftencanbefindexcessivebydissolvedoxygenofcondensate(standardcontrol<30ug/L).when#1unitBtypeoverhaul:severecorrosionforthefeedwaterpumpsandeconomizer,atthesametimefindsomescaleandcorrosioninsidetheboiler.Afterinvestigationfound:thecondensatereplenishmententercondensatewhengraduationofcondensatePumpself-sealingvalveislessthan10%,resulttoincreaseoxygencontentofcondensateAnotherinvestigationfound:vacuumsystemleakagepointsaremoreconcentratedinthecondenserpipevalveandcondensatepumpinletpipevalveetc.,reasonofairleakagecausetoincreaseoxygencontentofcondensate.2013年3月22日Afteraboveproblemresolves,dissolveoxygenofcondensatepassingrateare100%,theaveragelaboratoryvalues​​are21ug/L.