Dab tsi yog Qhov Siab Tshaj Lij Tshaj Lij Tshaj Tawm rau Titanium Qib 7 Sheath Heater Submerged nyob rau hauv 15% Sulfuric Acid ntawm 90℃kom tsis txhob muaj qhov kub hauv zos -Induced Corrosion?

Kev kub siab hauv kev ua haujlwm sulfuric acid yog qhov nyuaj rau cov khoom siv cua sov titanium. Qib 7 titanium (Ti-0.15Pd) muaj qhov zoo corrosion kuj nyob rau hauv 15% H2SO4 ntawm 90 deg C nyob rau hauv cov xwm txheej zoo tib yam immersion, tab sis lub zos chemistry tau hloov zoo heev los ntawm qhov muaj qhov kub. Nyob rau ntawm titanium sheath nto, lub hauv paus boiling ntawm cov sulfuric acid tov yog pom tau hais tias ntawm cov hlau -kua interface thaum tshav kub flux mus txog ib tug tseem ceeb tus nqi. Boiling ua rau cov kua qaub nyob ze ntawm qhov chaw sov thiab ua rau lub zos kub siab tshaj li ntawm 90 degree, thiab tuaj yeem hloov tus cwj pwm corrosion ntawm passive mus rau active. Qhov tshwm sim yog kev quab yuam nrawm pom raws li lub nplhaib ntawm corrosion ntawm vapor{17}}kua interface lossis raws li pitting tam sim ntawd hauv qab ua npuas npuas. Kab lus no txiav txim siab qhov siab tshaj plaws uas tso cai rau cov cua sov rau Qib 7 titanium sheath heaters hauv 15% sulfuric acid ntawm 90℃kom tsis txhob muaj qhov kub hnyiab vim yog corrosion.

Corrosion txheej txheem tshwm sim los ntawm boiling
Sulfuric acid yog ib qho uas tsis yog -azeotropic tov uas nws lub boiling point nyob ntawm nws cov concentration. Rau 15% H₂SO₄ ntawm atmospheric siab lub boiling point yog hais txog 103 degree. Cov npuas vapor yog nucleated ntawm qhov tsis zoo ntawm qhov chaw thaum lub tshuab cua sov sheath qhov kub siab tshaj qhov kub kub hauv zos. Cov npuas tsim ua rau cov yeeb yaj kiab ua kua nruab nrab ntawm nws thiab qhov chaw kub kom evaporate, tsom rau cov sulfuric acid hauv txheej nyias. Cov concentration tuaj yeem nce los ntawm 15% mus rau 30-50% hauv milliseconds los ntawm npuas nucleation thiab lub zos kub ntawm cov hlau nto hauv qab npuas nce mus txog qhov kub ntawm cov phab ntsa, feem ntau 5-20 ° C saum toj no qhov kub kub.

In sulfuric acid, the passive-active transition of Grade 7 titanium is observed at a critical combination of concentration and temperature. Grade 7 is passive in 15% acid at 90 C with corrosion rate of less than 0.05 mm per year. In 30% acid at 100°C the corrosion rate increases to 0.5-1.0 mm/year. In 40% acid at 110°C, the rate is >5mm / xyoo. Lub boiling -induced concentration txheej hauv zos tsim cov aggressive tej yam kev mob precisely, ua rau ib tug sai hlau poob ntawm cov npuas nucleation qhov chaw.

Thaum tshav kub kub Flux Threshold Determination
Qhov tseem ceeb ntawm cov hluav taws kub kub (CHF) rau nucleate boiling ntawm 15% sulfuric acid ntawm 90℃yog qhov xwm txheej uas cov vapor npuas tsim muaj zog txaus los txhawb nqa cov txheej txheem acid. Nyob rau hauv CHF, cov npuas tshwm sim ib ntus thiab tawm mus sai, tso cai rau cov txheej txheem sib xyaw ua ke rau hauv cov khoom ua ntej kev xeb loj heev pib. Saum toj no CHF, qhov npuas ceev nce, coalescence tshwm sim thiab ib tug nruam vapor zaj duab xis yuav tsim (hloov mus rau zaj duab xis boiling). Cov teebmeem no ua kom cov concentration thiab corrosion.

Cov kev tshawb fawb soj ntsuam nrog Qib 7 titanium xeem sojntsuam rau hauv 15% H2SO4 ntawm 90℃qhia qhov tshwm sim sai ntawm corrosion ntawm tshav kub fluxes tshaj 35 kW / m2. Corrosion tus nqi ntawm 25 kW / m2 yog tsawg dua 0.05 hli / xyoo. Ntawm 35 kW / m2 tus nqi nce mus rau 0.10 mm / xyoo, tseem siv tau rau feem ntau daim ntawv thov. Ntawm 45 kW / m2 tus nqi nce mus rau 0.35 mm / xyoo. Tus nqi siab tshaj 0.8 hli ib xyoo ntawm 55 kW / m² thiab pom lub nplhaib corrosion tshwm sim ntawm vapor{21}}kua interface. Kev nrawm nrawm hauv zos perforates phab ntsa 1.65 hli hauv 1000 teev ntawm 65 kW / m{sup 2}.

The maximum permissible heat flux for safe long term (>5 xyoo) kev ua haujlwm yog 40 kW / m². Rau cov ntawv thov nrog lub neej kev pab ntawm 2-3 xyoos, 50 kW / m2 raug tso cai. Yog tias tus nqi siab dua 60 kW / m², Qib 7 titanium tsis tsim nyog, tsis hais txog phab ntsa thickness.

Mitigating Factors thiab Application Matrix
Kev khiav hauj lwm qhov chaw & lub tshuab rhaub cua sov siab tshaj plaws tso cua sov Flux (kW / m2) Kev Cia Siab Corrosion Mechanism Pom Zoo Phab Ntsa Thickness
Vertical orientation, tag nrho submerged, zoo ntuj convection 40 kW / m² (nruam) Uniform passive corrosion<0.05 mm/year 1.2-1.65 mm
Siab raus dej, kab rov tav alignment, zoo convection 35 kW / m² Tsawg boiling concentration nyob rau saum npoo 1.65 hli
Ib nrab submerged (vapor{0}}kua interface tam sim no) 25 kW/m2 Meniscus nplhaib corrosion 2.0 mm los yog tiv thaiv ib nrab submersion
Agitated tank (mechanical los yog huab cua sparging) 50 kW / m² Npuas tawg los ntawm agitation, txo concentration 1.2-1.5 hli
Tsis tshua muaj kev ncig, stagnant tank 30 kW / m2Bubble ntev boosts nres 1.65 hli
Txhua qhov kev pab cuam nrog nto fouling / scaling 25 kW / m2 Fouling tsub kom lub cheeb tsam ntawm qhov kub thiab txias 2.0 hli Tswv yim tsim tswv yim
Qhov siab tshaj plaws tso cai rau cov cua sov ua haujlwm tas mus li yam tsis muaj qhov kub hnyiab rau Qib 7 titanium sheath rhaub rau hauv 15% sulfuric acid ntawm 90℃yog 40 kW / m^2. Qhov kub kub no ua rau qhov kub ntawm ib ncig ntawm 8-10℃saum toj no cov kua kub kub, ua kom cov hlau saum npoo qis dua 100℃thiab txwv lub zog tsav rau vapor npuas nucleation. Cov kws kho tsheb yuav tsum tau ua kom cov cua sov hauv cheeb tsam es tsis txhob siv watt ceev kom tau txais cov cua sov uas xav tau hauv qhov kev txwv no. Tib lub zog tag nrho tuaj yeem muab tau los ntawm kev siv hluav taws xob qis dua los ntawm kev siv lub tshuab hluav taws xob ntev dua lossis ntau lub taub me me hauv tandem. Nug rau qhov ntsuas qhov hluav taws xob ntawm lub qhov hluav taws xob (tag nrho lub zog muab faib los ntawm thaj chaw submerged sheath) thaum koj xaj lub rhaub, thiab xyuas kom tseeb tias nws tsis ntau tshaj 40 kW / m2. Hauv cov kab ke uas tsis zoo los yog qhov twg ib nrab submersion tsis tuaj yeem zam tau, txo qis qhov tso cai rau 25-30 kW / m2 lossis xaiv lwm txoj kev cua sov xws li chav sparging.