Cov kws sau ntawv tau tshuaj xyuas lub zog tshiab cov lus qhia tshwj xeeb ib zaug thiab ib zaug ntxiv, uas cov neeg tsim qauv feem ntau xaiv 304 lossis 316 stainless hlau rau condenser thiab auxiliary heat exchanger tubing.Rau ntau, lub sij hawm stainless hlau conjures ib qho aura ntawm invincible corrosion, thaum qhov tseeb, stainless hlau tej zaum yuav yog qhov phem tshaj kev xaiv vim hais tias lawv yog susceptible rau ob peb cov dej txias, availability. d nrog cov cua txias ua haujlwm ntawm lub voj voog siab, lub peev xwm stainless hlau tsis ua haujlwm mechanisms tau nthuav dav. Hauv qee qhov kev siv, 300 series stainless hlau tsuas yog muaj sia nyob rau lub hlis, qee zaum tsuas yog lub lis piam, ua ntej ua tsis tiav.Qhov tsab xov xwm no tsom rau yam tsawg kawg ntawm cov teeb meem uas yuav tsum tau txiav txim siab thaum xaiv cov khoom siv condenser raj los ntawm kev kho dej.Lwm yam tsis tau tham hauv daim ntawv no tab sis qhov uas ua lub luag haujlwm rau kev xaiv cov khoom siv hluav taws xob, cov khoom siv hluav taws xob thiab cov khoom siv hluav taws xob.
Ntxiv 12% los yog ntau dua chromium rau hlau ua rau cov hlau ua ib txheej oxide txuas ntxiv uas tiv thaiv cov hlau hauv qab.Li no lub sij hawm stainless hlau.Thaum tsis muaj lwm cov ntaub ntawv alloying (tshwj xeeb yog npib tsib xee), carbon hlau yog ib feem ntawm pawg ferrite, thiab nws chav tsev cell muaj lub cev-centered cubic (BCC) qauv.
Thaum npib tsib xee ntxiv rau cov hlau sib tov ntawm qhov sib xyaw ntawm 8% lossis siab dua, lub xov tooj ntawm tes yuav muaj nyob rau hauv lub ntsej muag-centered cubic (FCC) qauv hu ua austenite, txawm nyob hauv qhov kub thiab txias.
Raws li pom nyob rau hauv Table 1, 300 series stainless hlau thiab lwm yam stainless steels muaj ib tug nickel cov ntsiab lus uas tsim ib tug austenitic qauv.
Austenitic steels tau ua pov thawj tias muaj txiaj ntsig zoo hauv ntau daim ntawv thov, suav nrog cov khoom siv rau kev kub siab superheater thiab reheater tubes hauv lub hwj chim boilers.The 300 series tshwj xeeb yog feem ntau siv los ua cov khoom siv rau cov kub kub exchanger tubes, nrog rau cov chav da dej condensers.Txawm li cas los xij, nws yog nyob rau hauv cov ntawv thov uas muaj ntau yam tsis pom kev tsis ua haujlwm.
Qhov teeb meem tseem ceeb ntawm cov hlau tsis muaj steel, tshwj xeeb tshaj yog cov khoom nrov 304 thiab 316, yog qhov kev tiv thaiv oxide txheej feem ntau raug puas tsuaj los ntawm impurities hauv dej txias thiab los ntawm cov crevices thiab deposits uas pab concentrate impurities.Ntxiv mus, nyob rau hauv kaw tej yam kev mob, sawv ntsug dej yuav ua tau rau microbial kev loj hlob, uas metabolic byproducts yuav ua rau heev puas tsuaj rau hlau.
Ib qho dej txias tsis huv, thiab ib qho nyuaj tshaj plaws los tshem tawm kev lag luam, yog chloride.This ion tuaj yeem ua rau muaj ntau yam teeb meem hauv cov tshuab hluav taws xob, tab sis nyob rau hauv condensers thiab auxiliary heat exchangers, qhov teeb meem tseem ceeb yog cov chlorides hauv cov concentration txaus tuaj yeem nkag mus thiab rhuav tshem cov txheej txheem oxide tiv thaiv ntawm cov hlau tsis huv, ua rau thaj tsam corrosion, piv txwv li pitting.
Pitting yog ib qho ntawm feem ntau insidious cov ntaub ntawv ntawm corrosion vim tias nws tuaj yeem ua rau phab ntsa nkag thiab cov khoom siv tsis ua haujlwm nrog cov hlau me me.
Chloride concentrations tsis tas yuav siab heev ua rau pitting corrosion nyob rau hauv 304 thiab 316 stainless hlau, thiab rau huv si qhov chaw yam tsis muaj deposits los yog crevices, qhov kev pom zoo siab tshaj plaws chloride concentrations yog tam sim no suav hais tias yog:
Ntau yam tuaj yeem ua tau yooj yim tsim cov tshuaj chloride ntau tshaj cov lus qhia no, feem ntau thiab hauv thaj chaw hauv cheeb tsam.Nws tau dhau los ua qhov tsawg heev uas yuav tsum xub xav txog ib zaug-los ntawm kev ua kom txias rau cov chaw tsim hluav taws xob tshiab.Feem ntau yog tsim nrog cov yees txias, los yog qee zaus, cua txias condensers (ACC).Rau cov cua txias yees, cov concentration ntawm impurities hauv tshuaj pleev ib ce muaj peev xwm "txog 5 lub voj voog nrog chloride". Kev sib xyaw ua ke, thiab cov ntsiab lus chloride ntawm cov dej ntws yog 250 mg / l.Qhov no ib leeg yuav tsum tau txiav txim siab 304 SS. Ntxiv rau, nyob rau hauv cov nroj tsuag tshiab thiab uas twb muaj lawm, muaj kev xav tau ntau ntxiv los hloov cov dej tshiab rau cov nroj tsuag recharge.Ib qho kev xaiv yog cov dej khib nyiab hauv nroog.Table 2 piv cov kev soj ntsuam ntawm plaub cov khoom siv dej tsis zoo nrog rau plaub qhov dej khib nyiab.
Saib xyuas kom muaj cov tshuaj chloride ntau ntxiv (thiab lwm yam impurities, xws li nitrogen thiab phosphorus, uas tuaj yeem ua rau kom muaj kab mob microbial nyob rau hauv lub tshuab ua kom txias).Rau qhov tseem ceeb ntawm txhua qhov dej grey, txhua qhov kev ncig hauv cov cua txias yuav tshaj li cov chloride txwv tau pom zoo los ntawm 316 SS.
Cov kev sib tham yav dhau los yog raws li qhov muaj peev xwm corrosion ntawm cov khoom siv hlau.Fractures thiab sediments dramatically hloov zaj dab neeg, raws li ob qho tib si muab qhov chaw uas impurities tuaj yeem mloog zoo.Ib qho chaw rau cov neeg kho tshuab tawg hauv condensers thiab cov khoom siv hluav taws xob zoo sib xws yog ntawm cov raj-rau-tube ntawv junctions.Sediment nyob rau hauv lub raj tuaj yeem tsim cov kab nrib pleb ntawm cov sediment ib cheeb tsam ntawm nws tus kheej. nyob ntawm ib txheej oxide txuas ntxiv rau kev tiv thaiv, cov deposits tuaj yeem tsim cov chaw tsis zoo uas tig cov hlau seem rau hauv anode.
Cov kev sib tham saum toj no qhia txog cov teeb meem uas cov neeg tsim khoom cog feem ntau tsis xav txog thaum qhia cov condenser thiab auxiliary heat exchanger tube cov ntaub ntawv rau cov haujlwm tshiab.Lub hlwb hais txog 304 thiab 316 SS qee zaum tseem zoo li "qhov ntawd yog qhov peb ib txwm ua" yam tsis xav txog qhov tshwm sim ntawm qhov kev ua li ntawd. Cov ntaub ntawv hloov pauv yog muaj los daws cov nroj tsuag tam sim no.
Ua ntej sib tham txog lwm yam hlau, lwm cov ntsiab lus yuav tsum tau hais luv luv.Ntau zaus, 316 SS lossis 304 SS ua tau zoo thaum lub sijhawm ua haujlwm ib txwm, tab sis ua tsis tiav thaum lub zog hluav taws xob. Feem ntau, qhov tsis ua haujlwm yog vim qhov tsis zoo ntawm cov condenser lossis cov khoom siv hluav taws xob ua rau cov dej nyob hauv cov raj.Qhov ib puag ncig no muab cov xwm txheej zoo rau kev loj hlob ntawm microorganisms. de lub tubular hlau.
Cov txheej txheem no, hu ua microbially induced corrosion (MIC), paub tias ua kom puas stainless hlau kav thiab lwm yam hlau nyob rau hauv lub lis piam.Yog hais tias lub tshav kub exchanger tsis tuaj yeem ntws, kev txiav txim siab loj yuav tsum tau muab rau cov dej ntws los ntawm lub tshav kub hloov pauv thiab ntxiv biocide thaum lub sijhawm txheej txheem. hauv Champaign, IL nthuav tawm ntawm 39th Electric Utility Chemistry Symposium.)
Rau qhov hnyav ib puag ncig uas tau hais los saum toj no, nrog rau qhov hnyav hnyav xws li dej tsis huv lossis dej hiav txwv, lwm yam hlau tuaj yeem siv los tiv thaiv cov impurities.Peb pawg alloy tau ua pov thawj tiav, kev lag luam ntshiab titanium, 6% molybdenum austenitic stainless hlau thiab superferritic stainless hlau.Cov alloys no kuj yog MIC titanium resistant rau cov qauv zoo heev. thiab tsis tshua muaj elastic modulus ua rau nws raug rau cov neeg kho tshuab puas tsuaj.Qhov no alloy yog zoo tshaj plaws haum rau tshiab installation nrog muaj zog tube kev pab txhawb nqa qauv.Ib qho zoo heev lwm txoj kev yog lub super ferritic stainless hlau Sea-Cure®.Cov muaj pes tsawg leeg ntawm cov khoom no yog qhia hauv qab no.
Cov hlau yog siab chromium tab sis tsis tshua muaj npib tsib xee, yog li nws yog ferritic stainless hlau es tsis yog austenitic stainless hlau.Vim nws cov ntsiab lus tsis tshua muaj nickel, nws raug nqi ntau dua li lwm cov alloys.Sea-Cure lub siab zog thiab elastic modulus tso cai rau cov phab ntsa thinner dua lwm cov ntaub ntawv, ua rau kev txhim kho cua sov.
Cov khoom zoo ntawm cov hlau no tau pom nyob rau ntawm "Pitting Resistance Equivalent Number" daim ntawv qhia, uas, raws li lub npe qhia, yog cov txheej txheem sim siv los txiav txim siab qhov tsis kam ntawm ntau yam hlau rau pitting corrosion.
Ib qho ntawm cov lus nug feem ntau yog "Dab tsi yog cov ntsiab lus chloride siab tshaj plaws uas ib qib tshwj xeeb ntawm cov hlau tsis muaj peev xwm zam tau?"Cov lus teb sib txawv.Cov ntsiab lus suav nrog pH, qhov kub thiab txias, muaj thiab hom kev puas tsuaj, thiab lub peev xwm rau cov kab mob lom neeg.A lub cuab yeej tau ntxiv rau ntawm txoj cai axis ntawm daim duab 5 los pab nrog qhov kev txiav txim siab no.Nws yog nyob ntawm nruab nrab pH, 35 ° C ntws dej feem ntau pom muaj nyob rau hauv ntau BOP thiab condensation daim ntaub ntawv (kom tiv thaiv kev tso nyiaj ntawm daim duab 5). intersected nrog rau qhov tsim nyog slash.Qhov siab tshaj plaws chloride pom zoo tuaj yeem txiav txim siab los ntawm kev kos kab kab rov tav ntawm txoj cai axis. Feem ntau, yog tias cov hlau yuav raug txiav txim siab rau cov ntawv siv dej khib nyiab lossis dej hiav txwv, nws yuav tsum muaj CCT siab tshaj 25 degrees Celsius raws li ntsuas los ntawm G 48 xeem.
Nws yog tseeb hais tias cov super ferritic alloys sawv cev los ntawm Sea-Cure® feem ntau haum rau txawm seawater applications.Muaj lwm yam txiaj ntsig rau cov ntaub ntawv no uas yuav tsum tau hais txog.Manganese corrosion teeb meem tau raug soj ntsuam rau 304 thiab 316 SS tau ntau xyoo, suav nrog ntawm cov nroj tsuag raws tus dej Ohio. Tsis ntev los no, cov cua kub sib txawv ntawm cov nroj tsuag raws Mississippi thiab Missouri muaj teeb meem zoo. corrosion mechanism tau raug txheeb xyuas raws li manganese dioxide (MnO2) reacting nrog oxidizing biocide los tsim hydrochloric acid nyob rau hauv lub deposit.HCl yog dab tsi yeej tawm tsam hlau.[WH Dickinson thiab RW Pick, "Manganese-Dependent Corrosion nyob rau hauv lub fais fais fab kev lag luam";nthuav tawm ntawm 2002 NACE Lub Rooj Sib Tham Txhua Xyoo Corrosion, Denver, CO.] Ferritic steels tiv taus qhov kev txhim kho corrosion.
Xaiv cov ntaub ntawv qib siab dua rau cov condenser thiab cov cua kub exchanger tubes tseem tsis tau hloov pauv rau kev kho dej kom zoo chemistry tswj.As tus sau Buecker tau piav qhia hauv tsab xov xwm dhau los ntawm lub zog hluav taws xob engineering, ib qho kev tsim thiab ua haujlwm tshuaj kho mob yog tsim nyog los txo qhov peev xwm rau scaling, corrosion, thiab fouling.Polymer chemistry yog tshwm sim los ntawm kev siv hluav taws xob ntau dua rau kev siv tshuaj tiv thaiv kab mob thiab kev tiv thaiv corrosion. Cov cua txias ntauwd systems.Controlling microbial contamination tau thiab tseem yuav yog ib qho teeb meem tseem ceeb.Thaum oxidative chemistry nrog chlorine, tshuaj dawb, los yog cov tebchaw zoo sib xws yog lub hauv paus ntawm kev tswj cov kab mob microbial, cov kev kho mob ntxiv tuaj yeem txhim kho kev ua haujlwm ntawm cov kev kho mob.Ib qho piv txwv yog stabilization chemistry, uas yuav pab ua kom muaj kev sib txuas ntawm cov dej hauv cov dej thiab cov chlorine ua kom zoo dua. , supplemental feed nrog non-oxidizing fungicides tej zaum yuav muaj txiaj ntsig zoo hauv kev tswj cov kab mob microbial.Qhov tshwm sim yog tias muaj ntau txoj hauv kev los txhim kho kev ruaj khov thiab kev ntseeg siab ntawm cov hluav taws xob cog hluav taws xob hloov hluav taws xob, tab sis txhua qhov system sib txawv, yog li ceev faj kev npaj thiab kev sab laj nrog cov kws tshaj lij kev lag luam yog qhov tseem ceeb rau kev xaiv cov ntaub ntawv thiab cov txheej txheem tshuaj.Muaj cov kab lus no yog sau los ntawm cov khoom siv los ntawm kev siv dej, tab sis qhov kev txiav txim siab ntawm cov khoom siv los ntawm kev txiav txim siab, peb tsis muaj kev txiav txim siab. yog nce thiab khiav.Qhov kev txiav txim zaum kawg ntawm kev xaiv cov khoom yuav tsum tau ua los ntawm cov neeg ua haujlwm cog raws li ntau yam uas tau teev tseg rau txhua daim ntawv thov.
Txog Tus Sau: Brad Buecker yog Senior Technical Publicist ntawm ChemTreat.Nws muaj 36 xyoo ntawm kev paub hauv lossis koom nrog kev lag luam fais fab, feem ntau ntawm nws hauv chav tsim hluav taws xob chemistry, kev kho dej, kev tswj huab cua thiab hauv Nroog Dej, Lub Teeb & Lub Hwj Chim (Springfield, IL) thiab Kansas City Power & Light Company yog nyob rau ntawm La Cygnewater chaw nres tsheb, Kans vis dis aus thiab kev ua haujlwm ntawm ob xyoos. .Buecker tuav BS hauv Chemistry los ntawm Iowa State University nrog rau kev ua haujlwm ntxiv hauv Fluid Mechanics, Energy thiab Materials Equilibrium, thiab Advanced Inorganic Chemistry.
Dan Janikowski yog Tus Thawj Saib Xyuas Kev Lag Luam ntawm Plymouth Tube.Rau 35 xyoo, nws tau koom nrog hauv kev tsim cov hlau, tsim thiab sim cov khoom siv tubular xws li tooj liab alloys, stainless hlau, nickel alloys, titanium thiab carbon steel.Tau nrog Plymouth Metro txij li xyoo 2005, Janikowski tuav ntau txoj haujlwm laus ua ntej dhau los ua Tus Thawj Saib Xyuas Kev Lag Luam hauv 201.