冷卻水系統(tǒng)計(jì)算專題培訓(xùn)課件

冷卻水系統(tǒng)計(jì)算ContentCoolingTower&MassBalanceConcentrationRate(CR)L.S.I.pHadjustmentwithAcidCoolingTowerTypeFunctionofCoolingTowersremoveheatfromprocessoperationHVAC,industrial,powergenerationmostlybyevaporation(80%)partiallybysensibleheatloss(20%)contacthotwaterwithcoolerairalsoactasairscrubberscorrosionandfoulingproblemsTowerDesignConsiderationsheatload,supplytemperatureneededlocation,wetbulbcostwaterqualityandavailabilityfootprint,othertowersmaterialsfilltypeCoolingTowerHeatTransferMechanismsSensibleHeat顯熱Sensibleheatisheatenergytransferredbetweenthewaterdropletsandairwhenthereisadifferenceintemperaturebetweenthem.LatentHeat潛熱LatentHeatofVaporizationistheheatenergyremovedbyevaporatingasmallpercentageofrecirculatedtowerwater.Eachpoundofwaterevaporatedremovesapproximately1,000Btuintheformofheat.ReviewofBasicCoolingTower

DefinitionofTermsCoolingTowerWaterBalanceCoolingTowerTermsRange

TheDifferencebetweentheHotWaterTemperatureandtheColdWaterTemperatureApproachTheDifferencebetweentheColdWaterTemperatureandtheAmbientorInletWetBulbTemperatureWetBulbtemperatureofairsaturatedwithwatermeasuredbypsychrometercalculatedfrompsychrometricchartat100%RH,wetbulb=drybulbwetbulbislowestpossiblecoolingtemperatureatlowRH,coldwatertemperaturecanbelessthandrybulbtemperaturePsychrometersCOOLINGTOWERTERMSHOTWATERTEMPERATURECOLDWATERTEMPERATUREDRYBULBTEMPERATUREWETBULBTEMPERATURERANGETAPPROACHDeterminedbyHumidityHeatExchangeQ=8.33xRxdeltaTxCpR=waterrecirculation,gpmdeltaT=temperaturedropacrosstower,FQ=heatexchangedordissipatedacrosstower,Btu/min (1Ton=200Btu/min)Cp=specificheatofwater,1Btu/lb-FEvaporationneedabout1000Btu/lbtoevaporatewateratambientconditionsE=RxdeltaTxCpxf/1000f=evaporationfactornormallyuse0.8or80%WaterEvaporatedfromtheCirculatingWaterintotheAtmospherebytheCoolingTowerTowerDriftD=F2xRBD=BDc+D+LR=waterrecirculation,gpmD=towerdrift,gpmF2=drifteliminatorefficiencyfactor(0.005%to0.1%,use0.01%ifunknown)BD=totalblowdown,gpmBDc=controlledblowdown,gpmL=leakage,gpmWaterlostfromtheTowerasLiquidDropletsEntrainedintheExhaustAir.DriftisIndependentofWaterLostbyEvaporationCyclesofConcentrationmostcoolingfromevaporationaswaterevaporates,saltsremaininsystemsaltconcentration(ppm)increasesinrecirculatingwatercycles(ofconcentration)referstoincreasedconcentration(ppm)ofsaltsinrecirculatingwater濃縮倍數(shù)CR定義：濃縮倍數(shù)是指循環(huán)水中的鹽離子濃度與補(bǔ)充水中的鹽離子濃度的比值。也代表了水在系統(tǒng)中的循環(huán)次數(shù)。循環(huán)水處理的主要目的之一是維持盡可能高的濃縮倍數(shù)，以提升水的再利用率cyclesofconcentrationrefertothedegreethatthetotaldissolvedsolidsinthemakeupwaterhavebeenconcentratedintherecirculatingwaterofanevaporativeheatingorcoolingwatersystem.CyclesofConcentration4L2L1L4L2L1L4L2L1L100mg/4L=25mg/L(makeup)100mg/2L=50mg/L2X100mg/1L=100mg/L4XIncreasingtheCyclesQ.HowdoesincreasingcyclesinthetoweraffecttheEvaporationRate?A.Itdoesn’t.Theheatloadhasnotchanged.ItaffectsonlyBDandMUrates.CR的計(jì)算方法根據(jù)水量根據(jù)水質(zhì)20CR的計(jì)算方法Conductivity-Therelativeconductivitylevelsareusuallyagoodindicatorofthecyclesexceptwhere:Lowmakeupconductivityislow(<100μmhos).(<50μmhos,severe)significantlikelihoodofcalciumcarbonatescaleforming(MA>Hardness,cond.<300umhos)largeamountsofsulfuricacidbeingusedforpHcontrol21CR的計(jì)算方法Chlorides-Therelativechloridelevelscanbeagoodindicatorofthecyclesexceptwhere:Themakeupchloridelevelislow(<10ppm).Oxidizingbiocidesareused.22CR的計(jì)算方法Silica-Therelativesilicalevelscanbeagoodindicatorexceptwhere:Themakeupsilicalevelislow(<4ppm).Themakeupsilicalevelishigh23CoC的計(jì)算實(shí)例Inthewateranalysisabove,allthreeofthekeytestparametersusedtomonitorcycles(inblue)indicatethatabout5cyclesarebeingmaintained.24CalciumCycles≈ActualCyclesCalciumisnotprecipitating.Notegoodagreementbetweencyclesasdeterminedbytherelativeconductivity,chloride,andsilicalevels.CalciumCycles?TrueCyclesCalciumisprecipitating.Relativesilicaandchloridelevelsarethebestindicatorsofcycles.Thelowerthanexpectedconductivitycyclesareprobablyduetogrossprecipitationofdissolvedsolids.CalciumCycles?TrueCyclesCalciumisbeingre-dissolved.Relativeconductivityandsilicalevelsarethebestindicatorsofcycles.Makeupchloridesleveltoolowforaccuratemeasurement.Ifanoxidizingbiocideisbeingusedasthisexampleshows,therelativechloridelevelisevenmoreunreliableformonitoringcycles.CyclesofConcentrationTypically,magnesiumisthebestiontousewhencalculatingcyclesofconcentrationHowever,underconditionsofhighsilica(>40mg/L)andhighpH(>7.8),thereisahighprobabilityofmagnesiumsilicateprecipitationUndertheseconditions,cyclesofconcentrationcanbestbedeterminedbyaveragingtheconcentrationratiocalculatedbasedonseveralionsinboththemakeupandtheconcentratedwater.28CyclesofConcentrationTypically,magnesiumisthebestiontousewhencalculatingcyclesofconcentrationHowever,underconditionsofhighsilica(>40mg/L)andhighpH(>7.8),thereisahighprobabilityofmagnesiumsilicateprecipitationUndertheseconditions,cyclesofconcentrationcanbestbedeterminedbyaveragingtheconcentrationratiocalculatedbasedonseveralionsinboththemakeupandtheconcentratedwater.29CyclesofConcentrationForanyionconcentrationinthetowerthatislessthantheexpectedvalue(makeupconcentrationtimesCR)bymorethan10%,thepotentialforprecipitationofmineralscaleshouldbeconsidered.calculatedcalciumandmagnesiumCRcanbeeffectivelyusedtodeterminewhetherthetoweris“inbalance”.CalciumCRthatis10%lessthanmagnesiumCRwarrantsinvestigation.30CalciumandmagnesiumCRshowingprecipitationofcalciumcarbonate31FlowVsCyclesIfweincreasedCOCfrom3.0to5.0time,howmanypercentageofwaterwillbesaved?Ifcurrentchemicaldosingrateis100ppm,andwhenCOCisincreasedto5time,chemicaldosingratewillbealsoincreasedto120ppm.Howmanypercentageofchemicalwillbesaved?TheImpactofBlowdownandCyclesControl33CoolingTowerTermsHoldingTimeIndex(HTI)

TheHoldingTimeIndex,alsocalledtheHalf-Life,isameasureofhowmuchtimeittakestodiluteachemicalthathasbeenaddedtoanevaporativesystemto50%ofitsoriginalconcentration.HOLDINGTIMEINDEX01234567891001020304050TimeConcentration-ppmImportanceofHTIMatchTreatmentProgramstoHTIHighLevelsofBiocidecouldbeDischargedfromaSystemwithaShortHTIiftheBiocidehasalongkilltime.BiocideLevelscouldbeDepletedVeryRapidlyinaSystemwithaLongHTIiftheBiocidehasashortkilltime.HighHTIcanStressCorrosionandScaleInhibitorsandDispersants,ReducingtheirEffectiveness.ImportanceofHTIMatchTreatmentProgramstoHTIHTIinexcessof48to72hourscanresultinsignificantdegradationofinhibitorsHoldingTimeIndexHBiocideAisaBetterChoiceforSystemswithShortHTIHBiocideBisaBetterChoiceforSystemswithLongHTI001010202030304040505060607070808090901001000010102020303040405050606070708080909010010000661212181824243030363642424848HoldingTimeIndexHoldingTimeIndexBiocidePersistenceBiocidePersistenceConc.(ppm)Conc.(ppm)BiocideABiocideABiocideBBiocideBIsothiazoline6hoursGlutaraldehyde2hoursDBNPA0.5hoursCoolingSystemWorkshopTheCoolingSystemMaterialBalanceAmbientAirSolidsBuildUpEvaporationMakeupDelta-TWarmMoistAirBlowdownAircompressors,vacuumpumps,oilcoolers,etc.RecirculationRate41基本概念之定義(一)1)補(bǔ)水量--MU(m3/hr)M=make-up

由于蒸發(fā)、排污、泄漏造成循環(huán)水損失，而補(bǔ)充到系統(tǒng)中的水量稱為補(bǔ)水量。2)蒸發(fā)量--E(m3/hr)E=evaporation

在敞開式循環(huán)水系統(tǒng)中，冷的循環(huán)水經(jīng)換熱變?yōu)闊崴祷氐嚼鋮s塔中，通過(guò)蒸發(fā)達(dá)到冷卻。在這過(guò)程中造成水損失，稱之為蒸發(fā)量。3)風(fēng)吹損失量--D(m3/hr)

由于風(fēng)夾帶水滴到大氣中，造成的水量損失，稱之為風(fēng)吹損失量。424)排污量--BD(m3/hr)

blowdownrate,includesleakage

從系統(tǒng)中不斷排出一定量水，以保持系統(tǒng)中離子濃 度的要求，稱之為排污量。5)溫差--T (C)

temperaturedropthroughthetower

冷卻塔入口溫度和水池出口溫度之差。6)循環(huán)水量--RR(m3/hr)

RR=recirculationrate

系統(tǒng)中單位時(shí)間內(nèi)循環(huán)水的量。7)濃縮倍數(shù)--CR=cyclesofconcentration

指補(bǔ)給水與排污水的濃度比。基本概念之定義(二)438)保有水量--HC(m3)HoldingCapacityorSystemVolume

指冷卻塔、水池、換熱器、管道、設(shè)備保有水量的總和。9)循環(huán)周期--RT(分鐘/周期)

循環(huán)水水在冷卻水系統(tǒng)中循環(huán)一周所需時(shí)間。10)半衰期--HTI(hr)HoldingTimeIndex

該計(jì)算數(shù)值表示系統(tǒng)中化學(xué)品或補(bǔ)給水減少到初始值的 50%所需時(shí)間。11)總?cè)芄?-TDS(ppm)

水中含可溶物質(zhì)量總和?；靖拍钪x(三)4412)腐蝕率(mm/a或mpy,mdd)

指示金屬的腐蝕速度。通常用掛片來(lái)測(cè)試。13)污垢沉積速率(mg/月/cm2)

表明循環(huán)水系統(tǒng)中污泥沉積和結(jié)垢的綜合趨勢(shì)。14)碳酸鈣飽和指數(shù)--LSI

該指數(shù)用來(lái)確定CaCO3的成垢趨勢(shì)。

LSI=pH-pHs>0 成垢趨勢(shì)

LSI=pH-pHs=0 中性

LSI=pH-pHs<0 有腐蝕趨勢(shì)基本概念之定義(四)45CoolingTowerEvaporationRateE=0.85%ofRRforevery5.6oCoftemperaturedrop,orE=ΔTxRRx0.00153EvaporationRateRuleofThumbEvaporationRateOldRuleE=1.0%ofRRforevery5.6oCoftemperaturedrop,or1.78%forevery10oC.46CoolingTowerEvaporationRateE=RR×(0.0018)×△T×(%Load)RR=3GPM/RT=0.68m3/h/RTVolume=

10

Gallon/RTor0.038m3/RTAnotherwayforHVACsystemExample:Given:500RTChiller,50%loadingFind:E,RR,V47CyclesofConcentration=Make-up BlowdownMake-up=Blowdown*+EvaporationRateMake-up=EvaporationRatexCycles (Cycles–1)HTI=0.7xSystemVolume BlowdownCoolingTowerCalculations*Blowdownincludeallwaterlosses,i.e.,driftandsystemleakage48濃縮倍數(shù)：CR=MU/BD 或

CR=循環(huán)水電導(dǎo)率/補(bǔ)充水電導(dǎo)率補(bǔ)給水量：MU=E×[CR/(CR－1)] 或

MU=BD+E+D排污水量：BD=E/(CR－1)循環(huán)周期：RT=HC/RR半衰期：HTI=0.693×(HC/BD)49BasicCoolingTowerCalculationsEvaporationMakeUpBlowdownE=evaporationRR=recirc.rateCR=conc.rateMU=makeupBD=blowdown0.085%=heatfact.說(shuō)明：RR=1,100(m3/hr)InletTemp.=40(C)

BasinTemp.=30(C)

塔池尺寸=18m*12m*1.8m水深=1.2m管道內(nèi)直徑=500mm管道長(zhǎng)度=400m計(jì)算實(shí)例–Team#1EvaporationRecirc.RateMakeUpBlowdown51求解：蒸發(fā)量--E(m3/hr)

排污量—BD補(bǔ)水量--MU保有水量—HC半衰期—HTI計(jì)算實(shí)例–Team#1EvaporationRecirc.RateMakeUpBlowdown52說(shuō)明：RR=1,000(m3/hr)InletTemp.=40.5(C)

BasinTemp.=29.5(C)

塔池尺寸=20m*10m*1.6m水深=1.2m管道內(nèi)直徑=500mm管道長(zhǎng)度=500m計(jì)算實(shí)例–Team#2EvaporationRecirc.RateMakeUpBlowdown

MakeupWaterCoolingWaterCRRatioConductivity@25.0oC,us/cm:1005005.0CaHardness(asCaCO3),ppm:22622.8MgHardness(asCaCO3),ppm:12363.0Silica(asSiO2),ppm:9273.0Chloride(asCl-),ppm:15724.8Sulfate(asSO42-),ppm10828.253求解：蒸發(fā)量--E(m3/hr)

排污量—BD補(bǔ)水量--MU保有水量—HC半衰期—HTI計(jì)算實(shí)例–Team#2EvaporationRecirc.RateMakeUpBlowdown54解答：CR=3.3蒸發(fā)量E=0.85%*1,100*(40-30)5.6=16.7(m3/hr)排污量BD=16.7/(3.3-1)=7.3(m3/hr)補(bǔ)水量MU=16.7+7.3=24(m3/hr)保有水量HC=18*12*1.2+3.14*(0.5*0.5)/4*400=259.2+78.5=337.7(m3)半衰期HTI=0.693*337.7/7.3=32hr計(jì)算實(shí)例（解答）–Team#1EvaporationRecirc.RateMakeUpBlowdown55解答：CR=3.0蒸發(fā)量E=0.85%*1,000*(40.5-29.5)5.6=16.7(m3/hr)排污量BD=16.7/(3.0-1)=8.35(m3/hr)補(bǔ)水量MU=16.7+8.35=25(m3/hr)保有水量HC=20*10*1.2+3.14*(0.5*0.5)/4*500=240+98=338(m3)半衰期HTI=0.693*338/8.35=28hr計(jì)算實(shí)例（解答）–Team#2EvaporationRecirc.RateMakeUpBlowdown56如果我們把濃縮倍數(shù)從3.0倍提高到5.0倍,可以節(jié)省多少水(m3/hr)，節(jié)省的百分比是多少?水價(jià)是3.5元/噸，則一年可以節(jié)省多少費(fèi)用？當(dāng)前（3.0倍濃縮）的緩蝕阻垢劑加藥量是100ppm。濃縮倍數(shù)提高到5.0時(shí)，加藥量需要提高到120ppm。藥劑的用量是增加了，還是減少了？每年會(huì)增加（或減少）多少公斤？如果藥劑單價(jià)是33元/公斤，則，增加（減少）的費(fèi)用是多少？計(jì)算實(shí)例#3–濃縮倍數(shù)的影響57藥劑耗量計(jì)算分散劑和緩蝕阻垢劑的藥劑耗量計(jì)算可通過(guò)排污量的計(jì)算值進(jìn)行估算： 單位小時(shí)耗量=排污量藥劑濃度/1000 =藥劑耗量(公斤/小時(shí))非氧化性殺菌劑的藥劑耗量計(jì)算公式為： 每次耗量=系統(tǒng)保有水量藥劑濃度/1000 =藥劑耗量(公斤/次)氧化性殺菌劑的藥劑耗量計(jì)算公式為： 單位小時(shí)耗量=循環(huán)水量藥劑濃度/1000 =藥劑耗量(公斤/小時(shí))58L.S.I.-LangelierSaturationIndexpHs=(9.3+A+B)-(C+D)LSI=pH–pHs（實(shí)際水質(zhì)）LSI=pHest–pHs（預(yù)估水質(zhì)）L.S.I的所反映的碳酸鈣趨勢(shì)實(shí)例計(jì)算LSI&Inhibitor如果LSI過(guò)高，如>2.5，甚至3.0，有什么辦法？AcidDosageCalculation1ppmof98%H2SO4reducesMal