Tuzsizlantirish sho'r suv isitgichlarida (ko'p bosqichli chaqnash) 120 daraja havosizlangan sho'r suv bilan 2-darajali titanning devor qalinligi vodorodning shikastlanishini oldini oladi?

Ko'p bosqichli fleshli (MSF) tuzsizlantirish sho'r suv isitgichlari 110-120 daraja haroratda havosizlangan sho'r suv (erigan kislorod) bilan ishlaydi.<20 ppb). Deaeration is required to prevent corrosion of the carbon steel components, but it provides a reducing environment for titanium. The passive layer of titanium is less stable in high temperature chloride brine without oxygen and hydrogen can be absorbed from water reduction ( 2H 2 O + 2e − → H 2 + 2OH − ) . Hydrogen absorption causes brittle hydride (TiH₂) formation, leading to hydrogen damage-cracking and embrittlement without significant wall weakening. In this article the minimal wall thickness to avoid hydrogen damage over a typical 10 years campaign of a desalination plant is established.

Deaeratsiyalangan sho'r suvda vodorodning shikastlanish mexanizmi
Gazlangan sho'r suvda titan yuzasida kislorod kamayadi, bu potentsial olijanoblikni saqlaydi va vodorod evolyutsiyasini oldini oladi. Gazsizlangan sho'r suvda (kislorod<20 ppb) the cathodic reaction is shifted to water reduction. Atomic hydrogen formed at the surface may permeate into the titanium lattice Hydrogen atoms concentrate in areas of tensile stress (welds, tube bends, inflated tube ends). Titanium hydride precipitates when the local concentration surpasses the solid solubility (about 150 ppm at 120°C). Hydride platelets are brittle and microcracking occurs. Such process results in crack propagation followed by tube perforation or fracture due to further hydrogen absorption.

Vodorodning yutilish tezligi harorat, sho'r kimyo va titan yuzasining holatiga bog'liq. MSF sho'r suvida vodorodni 120 daraja (70 000 - 80 000 ppm Cl-, havosizlangan) 0,05-0,15 ppm/soat 2-darajali so'riladi.

Vodorod konsentratsiyasining muhim vaqti
Vodorodning dastlabki darajasi 30-50 ppm (2-darajali tavlangan) dan boshlab, kritik 150 ppm chegarasiga erishish muddati: zarur bo'lgan assimilyatsiya=100-120 ppm. 0,10 ppm/soat, vaqt=100 / 0.10=1,000 soat, o'rta diapazonda assimilyatsiya tezligini faraz. Soatiga 0,15 ppm, vaqt=100/{0.15=667 soat.

Bunday qisqa vaqt oralig'i (1-2 oy) shuni ko'rsatadiki, 2-daraja 120 daraja havosizlangan sho'r suvda tezda mo'rtlashadi. Biroq, amalda MSF sho'r suv isitgichlari qoldiq kislorod (10-20 ppb) bilan gazsizlangan sho'r suvdan foydalanadi va ko'pincha xloramin yoki boshqa qo'shimchalar tufayli titan yuzasida ozgina oksidlovchi sharoitlarda ishlaydi. Haqiqiy o'simliklarda so'rilish tezligi soatiga 0,01-0,05 ppm ni tashkil qiladi, shuning uchun kritik konsentratsiyaga erishish uchun 2000-10000 soat (3-12 oy) kerak bo'ladi. Bu hali uzoq muddatli xizmat uchun juda sekin.

Yumshatishning devor qalinligi
Hech qanday devor qalinligi vodorod emilimi uchun hech qanday to'siq emas. Vodorod titanda devor qalinligidan mustaqil ravishda tarqaladi. Qalinroq devorlar teshilishdan oldin gidrid yorilishiga qarshi turish uchun ko'proq material beradi. Gidrid hosil bo'lgach, yoriqlar devor bo'ylab harakatlanadi. Devor qanchalik qalinroq bo'lsa, yorilish shunchalik uzoqroq bo'ladi.

2-darajali gazsizlangan sho'r suvda 120 daraja haroratda devor qalinligi va vodorod shikastlanishi (yutilish boshlanganidan keyin) teshilish vaqti o'rtasidagi bog'liqlik juda chiziqli:

Devor qalinligi (mm) Gidrid yorilishi boshlanishigacha bo'lgan vaqt (oylar) Boshlanishdan perforatsiyagacha bo'lgan vaqt (oylar Umumiy xizmat muddati (oylar))
0,9 mm 3-6 1-2 4-8 1.2 mm 3-6 2-3 5-9 1.65 mm 3-6 3-5 6-11 2.0 mm 3-6 4-6 7-12
2,5 mm 3-6 5-8 8-14
Hech qanday devor qalinligi 10 yil umr bermaydi, chunki vodorodning emishi to'xtatilmaydi. Qalinligi qanday bo'lishidan qat'i nazar, yorilish bir necha oy ichida boshlanadi. Qalin devorlar teshilishni kechiktiradi, ammo buzilishning oldini olmaydi.

Boshqa variantlar
Devor qalinligining oshishi uzoq umr ko'rmaydi, shuning uchun boshqa qadamlar talab qilinadi:

Kislorod, qoldiq: erigan kislorod 50 ppb dan katta bo'lishi kerak (karbonli po'latning korroziyasini cheklash uchun 200 ppb dan kam). Bu kislorodning katodik reaktsiyasini kamaytiradi. Bu vodorod evolyutsiyasini bostiradi.

Xloramin yoki boshqa oksidlovchilardan foydalaning: katod oksidlovchi sifatida harakat qilish uchun sho'r suvga 0,5-2 ppm xloramin qo'shing.

7-sinfga ko'tarilish: Palladiy (0,12-0,25%) kislorodning juda past konsentratsiyasida ham kislorodning kamayishini katalizlaydi va vodorodning so'rilishini bostiradi. 7-darajali havosizlangan sho'r suvda 120 daraja vodorodni o'zlashtiradi<0.005 ppm per hour, providing 10+ year life.

* Katodik himoya teskari: potentsialni kislorodni kamaytirish oralig'iga o'tkazish uchun titanni yanada olijanob metallga (platina yoki oltin) biriktiring. MSF isitgichlari uchun amaliy emas.

MSF sho'r suv isitgichlari uchun dastur matritsasi
Brin holati erigan kislorod (ppb) Tavsiya etilgan titan darajasidagi devor qalinligi Kutilayotgan xizmat muddati
Havosizlangan (odatiy MSF)<20 ppb Grade 7 1.2-1.65 mm 10-15 years
Xloramin qo'shilishi bilan havosizlanadi<20 ppb + 1 ppm ClO2- Grade 2 or Grade 7 1.65 mm 8-12 years (Grade 2)
Kislorodning kamligi (bezovta holati) 20-50 ppb Darajasi 2 2.0 mm 3-5 yil
Aerated (maintenance bypass) >200 ppb darajasi 2 1.65 mm 10+ yil (garchi uglerodli po'lat korroziyaga uchrasa ham)
2-darajali titan MSF tuzsizlantirish sho'r suv isitgichlari uchun 120 daraja havosizlangan sho'r suv (kislorod) bilan mos kelmaydi.<20 ppb) regardless of wall thickness. Hydride cracking 6-12 months; perforation 6-14 months depending on wall thickness due to hydrogen absorption. This service requires grade 7 titanium (Ti-0.15Pd). Standard 1.2-1.65 mm wall gives 10-15 year life. The higher cost of Grade 7 is offset by the lack of hydrogen damage. If Grade 2 must be used (e.g., existing plant), keep dissolved oxygen above 50 ppb or add chloramine to suppress hydrogen evolution. Specify seamless tubing for new MSF plants, pickled finish, Grade 7. "Don't just use wall thickness as a shield against hydrogen damage in deaerated high temperature brine. Perform annual hydrogen monitoring using sacrificial Grade 2 coupon analysis for hydrogen content and replace heaters if the hydrogen content exceeds 100 ppm (below the critical threshold of 150 ppm) to avoid an unexpected failure.