Nyob rau hauv Zero-Liquid-Tshuaj evaporator kho siab-Chloride (100,000 ppm) Brine ntawm 120℃, Yuav Ua Li Cas Qhov Kev Pom Zoo ntawm Oxygen Tswj Lub Passivation Stability ntawm Titanium Sheath?

Kev lag luam tseem ceeb- tawm hauv titanium rhaub tsim rau kub brine evaporators
Hauv xoom- kua- tso tawm (ZLD) cov evaporators, cov dej khib nyiab hauv kev lag luam yog nyob ze ze rau qhov dej kom tsim cov brines nrog chloride concentrations txog 100,000-150,000 ppm ntawm qhov kub thiab txias ntawm 100{18}}120 degree. Lub immersion rhaub siv nyob rau hauv qhov kev pab cuam no zoo dua titanium vim nws zoo heev corrosion kuj nyob rau hauv cov tshuaj chloride. Cov xwm txheej hnyav no, txawm li cas los xij, sim cov kev txwv ntawm titanium's passivity. Nyob rau hauv dej ntsev (19,000 ppm Cl⁻ ntawm 30 degree) titanium yog indefinitely passive, tab sis nyob rau hauv lub xub ntiag ntawm 100, 000+ ppm chlorides ntawm 120 degree, lub passive titanium dioxide txheej yog nyob rau hauv ib tug mob qhov twg nws stability yog tseem ceeb nyob rau hauv lub concentration ntawm cov pa yaj b. Hauv cov xwm txheej oxygenated cov zaj duab xis passive tus kheej- kho sai thiab titanium sheath (1.0 mm) ntawm nyias phab ntsa tuab tuaj yeem muab kev pabcuam ntau xyoo - xyoo. Cov zaj duab xis passive tsis ua rau muaj cov pa oxygen tshaib plab lossis deaerated thiab ceev hauv zos pitting thiab hydrogen absorption tuaj yeem tshwm sim thiab ua txhaum lub phab ntsa 2.5 hli hauv ib hlis. Oxygen ua haujlwm raws li cathodic depolarizer thiab hloov lub peev xwm corrosion mus rau hauv cheeb tsam passive. Qhov kev soj ntsuam no hais txog kev sib raug zoo ntawm cov pa oxygen-passivity, thiab muab cov lus qhia rau phab ntsa tuab raws li kev ua haujlwm ntawm kev ua haujlwm ntawm cov pa oxygen nyob rau hauv ZLD evaporator kev pabcuam.

Mechanical Integrity Impact: Deearated thiab Aerated Conditions rau Passivation
Titanium yog passivated los ntawm ib tug ruaj khov TiO2 zaj duab xis uas yog tsis tu ncua repassivated nyob rau hauv aerated chloride daws nyob rau hauv siab kub. Cov tshuaj tiv thaiv cathodic ntawm cov zaj duab xis passive yog qhov txo qis ntawm cov pa oxygen (O₂ + 2H₂O + 4e⁻ → 4OH⁻). Qhov tsim nyog dissolved oxygen theem kom muaj kev vam meej ntawm Qib 2 titanium hauv 100,000 ppm chloride brine ntawm 120℃yog qhov kev txiav txim ntawm 0.5 ppm. Ntawm qhov chaw pib no, qhov muaj peev xwm corrosion tseem nyob siab tshaj qhov pitting muaj peev xwm (~+300 mV vs. Ag/AgCl), thaum tus nqi corrosion tsis zoo yog qis dua 0.01 hli / xyoo. Hauv qab 0.5 ppm oxygen cov tshuaj tiv thaiv cathodic hloov mus rau qhov txo cov dej (2H2O + 2e- → H2 + 2OH-), ua hydrogen ntawm qhov chaw. Lub peev xwm corrosion hloov mus rau hauv thaj chaw nquag thiab cov tshuaj chloride ions tuaj yeem nkag mus rau cov yeeb yaj kiab tsis txaus ntseeg. Nyob rau hauv cov xwm txheej deearated (oxygen <0.1 ppm) ntawm 120 degree, ntsuas pitting tus nqi siab -chloride brine yog 0.5-1.0 mm ib xyoo, qhia tias phab ntsa 1.5 hli tuaj yeem perforate hauv 18-36 lub hlis. Qhov tseem ceeb tshaj, cov hydrogen tsim nyob rau hauv cathodic qhov chaw tsiv mus rau hauv titanium lattice thiab ua rau embrittlement, uas induces cracking ua ntej pitting perforation. Yog li ntawd, cov neeg kho tshuab kev ncaj ncees ntawm lub sheath yog nyob ntawm tsis tsuas yog nyob rau ntawm phab ntsa thickness, tab sis kuj nyob rau hauv lub xub ntiag ntawm txaus yaj oxygen los txhawb lub cathodic cov tshuaj tiv thaiv uas ua rau cov titanium nyob rau hauv ib tug passive lub xeev.

Kev cuam tshuam ntawm Kev Ua Haujlwm Thermal: Oxygen Depletion ntawm Qhov Kub Kub
The temperature differential across the titanium sheath causes a local oxygen concentration gradient. The solubility of dissolved oxygen diminishes as brine is heated over the sheath surface. At bulk brine temperatures of 120 °C the equilibrium oxygen solubility at 1 atm is ~2 ppm. At the titanium surface, the local oxygen solubility is reduced to around 1.5 ppm, where it may reach 125-130°C due to electrical resistance through the wall. This difference is generally not enough to result in loss of passivity. However, the surface temperature can be higher than 140 C when the heater works with high power density (>3.5 W/cm 2 ) or with thick wall (>1.8 mm), where oxygen solubility is less than 1 ppm. Even at these temperatures, a bulk oxygen content of 2 ppm may not be enough to keep the sheath surface passive. Finite element modeling of oxygen transport indicates that a 1.2 mm wall at a surface temperature of 128°C consumes oxygen at the cathodic surface at a rate that can be sustained by diffusion from the bulk if the bulk concentration is greater than 1.5 ppm. A 2.0 mm wall at a surface temperature of 142°C necessitates a bulk oxygen concentration of >3 ppm uas feem ntau tsis ua tau hauv deaerated ZLD evaporators. Yog li, cov phab ntsa nyias nyias tsis tsuas yog ua kom cov cua sov kis tau zoo xwb, tab sis kuj txo qhov kub ntawm qhov chaw, ua kom lub plhaub hauv qis dua thiab ntau dua oxygen tau txais kev kub ntxhov.

Synthesis of the Trade-off: Oxygen Concentration as a Multiplier of Phab Ntsa Thickness
Cov matrix hauv qab no qhia tau hais tias titanium phab ntsa tuab rau ZLD evaporator rhaub rau 100,000 ppm chloride brine ntawm 120℃nyob ntawm seb qhov kev txiav txim siab yaj oxygen concentration nyob rau hauv recirculating brine kwj.

Dissolved Oxygen nyob rau hauv Bulk Brine (ppm ntawm 120 degree) Titanium Phab ntsa Thickness Cov lus qhia (Qib 2) Predicted Stability thiab Lifetime of Passive FilmCore Engineering Rationale 2.0 ppm (ua tiav aerated, qhib evaporator nrog cua sparging) 1.0 mm - 1.2 mm Excellent > 5 xyoos Oxygen concentration yog siab dua qhov tseem ceeb. Stable passive zaj duab xis. Nyias phab ntsa txhim kho cov cua sov hloov thiab txo qhov kub ntawm qhov chaw. Kev tiv thaiv corrosion ntawm 0.05 hli / xyoo muab kev nyab xeeb tsis pub dhau.
1.0 - 2.0 ppm (moderate aeration, semi- kaw kaw lus) 1.4 mm - 1.6 mm Zoo; 3 - 5 xyoos Oxygen nce mus txog qhov tseem ceeb. Lub phab ntsa tuab muab qhov kev tiv thaiv corrosion rau qhov khib nyiab rau hauv oxygen. Nruab nrab phab ntsa thickness muab kev sib haum xeeb ntawm thermal kev ua tau zoo thiab passivation margin.
Cov pa oxygen tsawg, de- aerated pub, tsis tshua muaj cua ingress 0.5 - 1.0 ppm 1.8 mm - 2.0 mm Marginal; 2 - 3 xyoos Oxygen tsuas yog siab dua qib tseem ceeb. Qhov txaus ntshai ntawm pitting yog siab. Cov phab ntsa tuab xav tau rau kev tiv thaiv corrosion. Pom zoo rau kev saib xyuas hydrogen embrittlement. Kev khiav ntawm qib oxygen no tsis zoo.
< 0.5 ppm (deaerated, e.g. closed loop with oxygen scavengers)Not recommended (any thickness) Unstable; < 18 months Passivity is not sustainable. Pitting and hydrogen embrittlement will occur independent of wall thickness Reintroduction of oxygen or other material (such as titanium-palladium Grade 7 or zirconium) is necessary.
Oxygen Management and Grade Selection Engineering Beyond the Wall
ZLD evaporator tsim tau ua haujlwm nyob rau hauv qis qis oxygen <1 ppm. Peb cov kev daws teeb meem ntxiv tau pom tias yuav rov qab tau titanium passivity yam tsis tas yuav tsum muaj cov phab ntsa tuab. Ua ntej, bubbling cua los yog oxygen mus rau hauv lub brine recirculation voj yuav coj cov pa concentration mus txog 2-3 ppm, uas yog feem ntau txaus txawm rau nyias -walled titanium heaters. Cua sparging nqi zog tsawg dua piv rau kev hloov cov cua sov ntau zaus. Qhov thib ob, kev hloov pauv ntawm Qib 2 mus rau Qib 7 titanium (Ti-0.15% Pd) txo qis cov pa oxygen tseem ceeb rau kev ua haujlwm ntawm 0.5 ppm mus rau tsawg dua 0.1 ppm. Lub xub ntiag ntawm palladium ua haujlwm raws li cathodic catalyst, tso cai rau kev txo qis ntawm hydrogen mus rau qis dua qhov muaj peev xwm thiab ua rau muaj kev hloov pauv ntawm qhov muaj peev xwm corrosion mus rau ntau yam txawm tias nyob rau hauv deaerated brines. Cov ntaub ntawv teb los ntawm ZLD evaporators qhia tau tias Qib 7 titanium nrog 1.2 hli phab ntsa tuab tuaj yeem muaj sia nyob hauv brines nrog qis li 0.2 ppm oxygen rau 6-8 xyoo, thaum Qib 2 titanium tsis nyob hauv tsawg dua 2 xyoo. Thib peb, kev siv sodium hydroxide pab tswj cov pH me ntsis alkaline (8.5–9.5) uas ua kom cov yeeb yaj kiab tsis muaj zog thiab txo qis qhov xav tau oxygen. Rau Qib 2 ntawm pH 9 qhov tsim nyog oxygen concentration txo mus rau 0.2 ppm, tso cai rau cov phab ntsa thinner txawm nyob rau hauv ib feem ntawm deaerated systems.

Cov ntsiab lus: Nyias - Phab ntsa Titanium rhaub hauv High Chloride Brine Ua tiav los ntawm Oxygen Control
Hauv ZLD evaporator kho 100,000 ppm chloride brine ntawm 120 degree, oxygen yog qhov tseem ceeb cuam tshuam rau titanium sheath passivation stability thiab phab ntsa thickness xav tau. Cov pa roj carbon monoxide 1.0-1.2 hli phab ntsa Qib 2 titanium rhaub muab lub neej ua haujlwm ntau xyoo ntawm cov pa oxygen ntau dua 2 ppm. Nrog cov pa oxygen ntawm 0.5 mus rau 2 ppm, phab ntsa tuab yuav tsum tau nce mus rau 1.5 mus rau 2.0 hli kom suav nyiaj rau corrosion vim tias muaj kev phom sij ntau ntxiv ntawm pitting. Tsis muaj qhov tseeb Qib 2 phab ntsa tuab uas yuav muab lub neej txaus hauv qab 0.5 ppm oxygen. Cov lus teb yog ob qho tib si kom rov ua dua cov pa oxygen (air sparging) lossis hloov mus rau qib 7 titanium nrog palladium uas yuav nyob twj ywm txawm tias nyob hauv cov xwm txheej deearated. Cov lus qhia tshwj xeeb rau ZLD evaporator installation tshiab yog tsim los rau ib qho kev ua kom cov pa oxygen concentration tsawg kawg yog 2 ppm los ntawm kev tswj huab cua sparging thiab tom qab ntawd qhia Qib 2 titanium nrog 1.2 hli phab ntsa tuab. Qhov kev sib xyaw ua ke no muab qhov siab tshaj plaws hloov mus rau qhov kub, qhov tsawg kawg nkaus tus nqi ntawm cov khoom siv thiab lub rhaub lub neej ntawm 5+ xyoo. Thaum nrhiav ib qho kev tsocai, muab qhov kwv yees qib ntawm cov pa oxygen (ppm) thiab pH ntawm cov brine ntawm kev ua haujlwm kub, vim tias cov kev ntsuas no tseem ceeb dua rau lub neej cua sov dua li phab ntsa tuab.