Raws li kev sib xyaw tshwj xeeb ntawm Sulfate -Txo cov kab mob (SRB) suav thiab Kub Ua 316 Stainless Steel Heater Sheath Tsim Microbially Influenced Corrosion (MIC) Pitting hauv Dej Stagnant

Biogenic sulfide mechanism rau pitting ntawm nruab nrab kub

Microbially cuam tshuam corrosion (MIC) los ntawm sulfate-txo cov kab mob (SRB) tuaj yeem ua rau pitting ntawm 316 stainless hlau sheathed hluav taws xob cua sov cov hlab ua haujlwm nyob rau hauv tsis tu ncua los yog qis- dej ntws nrog cov organic loads siab xws li cov dej txias ntauwd, cov khoom siv hluav taws xob tiv thaiv, lossis cov dej tuav dej, txawm tias nyob rau theem chloride (<100 ppm) below those at which conventional pitting would not be expected. Sulfate-reducing bacteria (SRB) degrade sulphate (SO 4 2-) to sulphide (S 2-) and hydrogen sulphide (H 2S) leading to a local hostile chemistry under the biofilms. At 30-40°C (ideal SRB growth range) SRB counts >10^3 hlwb/mL muab pitting tus nqi ntawm 0.2-0.5 hli/xyoo. Ntawm 50-60℃(qhov siab kawg ntawm qhov ntsuas kub rau ntau hom SRB), suav ntau tshaj 104-105 hlwb / mL yog xav tau rau qhov sib npaug ntawm pitting. Ntawm qhov kub siab tshaj 70℃qhov kev ua SRB txo qis thiab qhov phom sij ntawm MIC tsawg heev. Daim ntawv no ntsuas SRB suav thiab ntsuas qhov kub thiab txias rau MIC pitting pib ntawm 316 sheaths hauv dej khov.

Yuav ua li cas SRB ua rau pitting.

Sulfate-txo cov kab mob (xws li Desulfovibrio, Desulfotomaculum) vam meej nyob rau hauv anaerobic los yog microaerophilic chaw, feem ntau nyob rau hauv biofilms ntawm hlau nto. Hauv biofilm, SRB hloov sulphate rau sulfide thiab metabolise organic molecules (lactate, acetate). Cov sulphide ua ke nrog cov txheej txheem passive ntawm 316 los tsim chromium oxide (Cr2O3) rau chromium sulphide (Cr2S3) uas tsis yog{10}} tiv thaiv. Tus nqi ntawm cov txheej txheem cathodic yog nce los ntawm hydrogen sulphide, thiab cov hlau nyob rau hauv cov deposit yog sai corroded. Qhov no ua rau thaj chaw pitting, feem ntau capped los ntawm "dub crust" ntawm hlau sulfide (FeS) saum lub qhov. SRB pitting feem ntau yog nrawm (0.2-1 mm / xyoo) thiab tshwm sim hauv cov dej uas yuav suav tias tsis yog corrosive rau 316.

Quantification ntawm SRB-induced pitting thresholds hauv dej tseem

Cov kev pib pitting thiab kev nthuav tawm hauv qab no tau txais los ntawm kev soj ntsuam kev soj ntsuam (dej 50 ppm sulphate, 50 ppm chloride, pH 7.0) nrog inoculated SRB (Desulfovibrio vulgaris) nyob rau hauv chaw nres tsheb.

SRB Cell Count (cells/mL) Biofilm Formation Sijhawm ntawm 30℃(hnub) Kub (degree) Pitting Initiation Sijhawm (hnub) Pitting Rate (mm/yr) Lub Sijhawm rau Perforation (1.5 hli phab ntsa) Pom zoo rau Kev Pabcuam Dej Tsis Txaus<10 None Any >365 <0.02 >75 xyoo Yes
10-10² 30-60 30-40 180-300 0.02-0.05 30-75 xyoo Yog 10²-10³ 20-40 30-40 90-180 0.05-0.15 10-30 xyoo Txais
10³-10⁴ 10-20 30-40 30-90 0.15-0.40 4-10 xyoo Marginal 10⁴-10⁵ 5-10 30-40 15-30 0.40-0.80 2-4 xyoo Tsis pom zoo
10⁵-10⁶ 3-7 30-40 7-15 0.80-1.50 1-2 xyoo Tsis tau10⁶<5 30-40 <7 >1.50 <1 year Not acceptable
10³-10⁴ 20-40 50-55 90-180 0.05-0.15 10-30 xyoo Txais
104-105 10-20 50-55 45-90 0.15-0.30 5-10 xyoo Marginal
10⁵-10⁶ 5-15 50-55 20-45 0.30-0.60 2.5-5 yrsNot recommend10⁶<10 50-55 <20 >0.60 <2.5 years Unacceptable
Any Any >70 Tsis muaj SRB kev loj hlob<0.02 >75 xyoo Yes
Ib Ib<10 Reduced activity <0.05 >30 xyoo Yes
Cov nyhuv ntawm dej chemistry ntawm SRB pitting hnyav

Qhov pib rau SRB suav yog cuam tshuam los ntawm cov ntsiab lus sulphate thiab cov organic carbon.

Sulphate Concentration (ppm) Organic Carbon Availability (ppm BOD) SRB suav rau Pitting Initiation (cells/mL) Pom Zoo Ua Haujlwm<10 Any >10⁶ (tsis zoo) Tsis txhawj
10-50 <10 >10⁵ Saib
10-50 10-100 >10⁴ Biocide kho tau pom zoo 50-200<10 >10⁴ Acceptable 50-200 10-100 >10³ Biocide pom zoo 200-500<10 >10³ Monitor 200-500 10-100 >10² Biocide necessary >500 >100 >10¹ Muaj kev pheej hmoo siab, kho dej
Cov Lus Qhia Tshwj Xeeb rau Kev Pabcuam Dej Tuag

Cov txheej txheem tswj SRB hauv qab no tau npaj rau 316 lub tshuab cua sov hauv cov ntawv thov dej tsis tu ncua nyob ntawm qhov kub thiab txias.

Dej Kub Kub Stagnation Lub Sijhawm SRB Tswj Txoj Kev Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Lij Tshaj Tawm<30°C <1 month None <104 5-10 years <30°C >1 lub hlis Biocide txhua 2 lub lis piam<103 8-12 years 30-50°C <1 week None <103 8-12 years
30-50°C >1 lub lis piam Biocide txhua lub lim tiam<10² 10-15 years 50-60°C Any Occasional biocide <10⁴ (natural suppression) 10-15 years >Any None Any (no growth) >15 xyoo ntawm 60 degree
Txhua yam nrog dej kho.Chlorination, ib qho (0.5-1 ppm residual)<10² >15 xyoo
SRB Pitting Identification nyob rau hauv teb

Rau MIC ntawm SRB, ib tug yuav tsum xav tias pitting ntawm 316 lub rhaub dej nyob rau hauv cov dej uas tsis muaj chlorides (<100 ppm). Features include:

Dub, adhering sulphide crust (FeS) dhau qhov pits, rotten qe tsw (H₂S) thaum cuam tshuam

Pits nquag hemispherical nyob rau hauv cov duab, nrog "nceb" los yog "khob" morphology

Pits nrog ib txheej biofilm slime nyob ib ncig ntawm lawv (dawb, grey los yog ntsuab)

Cov dej ntau SRB suav> 103-104 hlwb / mL (los ntawm kev rov ua dua lossis ATP tsom xam)

Sulphate txo: txo cov sulphate thiab kev loj hlob ntawm sulfide thoob plaws hauv lub cev

Kev lees paub yuav yog los ntawm polymerase saw cov tshuaj tiv thaiv (PCR) lossis cov khoom siv SRB kab lis kev cai (xws li API kuaj strips) thiab tuaj yeem txheeb xyuas Desulfovibrio lossis lwm yam genera ntawm SRB. Rau qhov kev ua tsis tau zoo li no, kev kho mob yog los siv cov kev kho mob biocide (xws li . 100-200 ppm sodium hypochlorite lossis 50-100 ppm glutaraldehyde, txhua lub lim tiam) lossis hloov mus rau ntau MIC-resistant alloy xws li titanium lossis Alloy 625.

Xaus: Tswj ntawm SRB Kev Ua Haujlwm kom tsis txhob MIC Pitting

316 stainless hlau encased heaters qhia pitting nyob rau hauv cov dej stagnation nrog SRB suav ntau tshaj 10 3-10 4 hlwb/mL ntawm 30-40℃nyob rau hauv 30-90 hnub nrog rau tus nqi ntawm 0.2-0.8 mm/xyoo. Thaum kub tshaj 60-70 degree, SRB kev ua haujlwm yog inhibited thiab MIC kev pheej hmoo tsawg. Cov kws tsim qauv qhia txog 316 sheaths rau lub tank tiv thaiv hluav taws, cov dej txias ntauwd lossis cov dej ntws qis qis yuav tsum saib xyuas SRB suav thiab kev kho biocide yuav tsum tau siv thaum suav txog 10³ hlwb / mL. Rau cov tshuab uas muaj teeb meem SRB tsis tu ncua, hloov kho rau titanium lossis ua kom qhov kub siab tshaj 60℃(qhov ua tau) tshem tawm qhov kev pheej hmoo. Ntawm no peb muab lub moj khaum uas cuam tshuam txog SRB suav thiab qhov kub thiab txias rau qhov ntsuas pitting pib lub sijhawm thiab cov nqi nthuav tawm, tso cai rau cov neeg yuav khoom tsim cov phiaj xwm kho dej kom tiv thaiv microbially induced corrosion nyob rau hauv qhov kev pab cuam.