Yuav Ua Li Cas Kub Concentrated Sodium Acetate Solution (20-40%) ntawm 80-120℃Hloov Qhov Tseem Ceeb Quartz Sheath Phab Ntsa Thickness rau Dyeing Auxiliary thiab Buffer System Heaters?

Kub Sodium Acetate Attack ntawm Fused Silica Tsav los ntawm Me Hydrolysis

Sodium acetate (CH3COONa) is a common chemical used in the dyeing of textiles (as a pH buffer and auxiliary), food preservation, pharmaceutical manufacture and as a chemical for heating pads (sodium acetate trihydrate). Working temperatures are 80-120°C in dyeing baths, buffer system heaters and evaporators, and standard industrial concentrations are 20-40% by weight in aqueous solution. Quartz immersion heaters are typically selected for sodium acetate service because to the high chemical purity of quartz (precluding the contamination of metal ions that can damage dyeing or pharmaceutical operations) and its exceptional resilience to most salt solutions. However, heated concentrated sodium acetate is slightly corrosive to fused silica, not by direct attack of the salt, but by hydrolysis. The conjugate base of acetic acid (pKa 4.76) is the acetate ion, CH3COO-, which hydrolyzes in water: CH3COO- + H2O CH3COOH + OH-. At higher temperatures this equilibrium is shifted in favor of the formation of hydroxide ions , and the solution becomes somewhat alkaline . A solution of sodium acetate 30% at 25 °C has a pH of about 8.5 to 9.0. At 100°C the pH can rise to 9.5-10.0 due to enhanced hydrolysis and alteration of the dissociation constants. The hydroxide ions formed assault the silica network in the same way as dilute caustic: SiO2 + 2OH- ->SiO3(2-) + H2O. Tsis tas li ntawd cov acetate ions tuaj yeem tsim cov complexes nrog silicon, tab sis cov no tsis muaj zog. Kev tshawb fawb soj ntsuam cov txiaj ntsig ntawm sodium acetate concentration (20-40%), kub (80-120 degree) thiab tshuaj pH ntawm qhov sib txawv corrosion ntawm fused silica. Qhov xav tau quartz sheath phab ntsa thickness rau cov kev pab cuam lub sij hawm (5,000 mus rau 20,000 teev) nyob rau hauv textile dyeing thiab buffer system cua sov yog muab los thiab lub thermal txim ntawm cov phab ntsa loj nyob rau hauv no high density ntsev tov yog tham.

Hydroxide Mediated Corrosion ntawm Fused Silica hauv Kub Sodium Acetate: Corrosion Kinetics

Hydroxide ions tshwm sim los ntawm hydrolysis ntawm acetate yog lub luag hauj lwm rau corrosion ntawm quartz nyob rau hauv kub sodium acetate. Ntawm 25 degree, qhov dej tsis tu ncua yog K_h=K_w/K_a=1e-14/1.8e-5=5.6e-10. Cov pH rau sodium acetate yog xam raws li hauv qab no. Rau 30% sodium acetate tov (~ 3.7 M), pH ntawm 25C yog ~ 9.4 . [ OH- ]=sqrt ( K_h * C )=sqrt ( 5.6e-10 * 3.7 )=7 sqrt (M-2.=4.34 pH=9.66 K_w nce mus txog 5.5e-13 ntawm 100℃thiab K_a rau acetic acid hloov (me ntsis nce), yog li qhov kev suav ua nyuaj, txawm hais tias pH feem ntau nce mus rau 9.5-10.0. Ntawm pH 9.5-10.0, OH⁻ concentration yog 10⁻⁴ txog 10⁻⁵ M, txaus los tsim qeeb tab sis pom quartz corrosion.

Qhov kev sim ntawm purity siab fused quartz nyob rau hauv 30% sodium acetate ntawm 95℃qhia tau hais tias tus nqi sib xws ntawm 0.00005-0.0001 mm / hr. Ntawm 120℃(nyob rau hauv siab, piv txwv li nyob rau hauv lub siab dyeing tshuab) tus nqi nce mus rau 0.0002-0.0004 mm / hr. Ntawm 80℃tus nqi tsawg dua 0.00003 mm / h. Hauv qhov sib piv, 0.001 M NaOH (pH 11) ntawm 95℃corrodes quartz ntawm 0.005 mm / teev, ob qhov kev txiav txim siab ceev dua. Tus nqi qis qis yog vim lub xeev tsis tshua muaj zog ntawm OH⁻ hauv sodium acetate daws. Lub 2.0 hli quartz sheath nyob rau hauv 30% sodium acetate ntawm 95℃yuav poob 0.00008 mm / teev × 25,000 teev=2.0 hli nyob rau hauv lub neej ntawm txog 25,000 teev (2.8 xyoo). Ib phab ntsa 1.5 hli muab 18,750 teev (2.1 xyoo). Yog li ntawd quartz yog qhov ruaj khov nyob rau hauv kub sodium acetate thiab tsis tshua muaj corrosion tsis tshua muaj teeb meem lub neej. Lub 2.0 hli phab ntsa ntawm 120℃tseem muab 5,000 rau 10,000 teev (7 mus rau 14 lub hlis) ntawm kev siv uas yog siv tau rau ntau daim ntawv thov kev lag luam.

Dawb acetic acid (siv rau kev hloov kho pH hauv cov tshuab tsis sib haum) txo tus nqi corrosion. Acetic acid slows lub hydrolysis ntawm acetate (kev ua ion feem ntau) thiab yog li txo qis OH⁻ concentration. Ntawm pH 7-8 (xws li hauv sodium acetate-acetic acid buffer) tus nqi corrosion tseem tsawg, qis dua 0.00002 mm/hr. Txawm li cas los xij, yog tias muaj kab mob sib kis (xws li sodium hydroxide) ua rau kev daws teeb meem los ua alkaline ntau dua, tus nqi corrosion nce ntxiv rau qhov OH- concentration. pH 7-9 tsis zoo rau quartz durability.

Localized Crystallization thiab Pitting ntawm Sodium Acetate

Sodium acetate yog soluble hauv dej heev (46 g / 100 mL ntawm 20 degree, nce nrog kub). Txawm li cas los xij, nyob rau hauv evaporative tej yam kev mob (xws li, nyob rau saum npoo ntawm cov kua, los yog nyob rau hauv rhuab saum toj no cov kua kab) sodium acetate crystallize raws li lub trihydrate los yog anhydrous ntsev. Cov khoom siv lead ua no tsis tua quartz tab sis tuaj yeem tsim kom muaj zog insulating nplai ntawm quartz nto. Cov nplai txwv tsis pub hloov cov cua sov thiab ua rau lub hauv paus quartz khiav kub dua, uas tuaj yeem ua rau muaj kev cuam tshuam hauv zos (txawm hais tias tus nqi corrosion twb tsawg heev). Qhov tseem ceeb tshaj, cov nyhuv thermal rwb thaiv tsev yuav ua rau muaj kev ntxhov siab thermal thiab ua tau quartz tawg yog tias qhov ntsuas tsis sib npaug. Tsis tas li ntawd, sodium acetate trihydrate melts ntawm 58 degree, yog li ntawd nyob rau hauv ib tug kub system cov muaju yuav yaj thiab re{11}}crystallize rau txias, ua rau mechanical kev nyuaj siab ntawm lub quartz nto. Lub polished quartz nto tiv thaiv crystallization thiab periodic tu nrog dej kub dissolves lub teev.

Lub cheeb tsam meniscus yog thaj tsam ntawm kev mob siab heev crystallization. Raws li cov dej evaporates cov sodium acetate yuav ntau concentrated. Cov tshuaj ua supersaturated thiab crystals tsim. Cov qib kua ruaj khov lossis vapor shield inhibits meniscus-crust formation. Nyob rau hauv daim ntawv thov dyeing qhov twg cov kua theem hloov (xws li thaum ntxiv ntaub), ib tug rhuab qaum sheath (tshaj li 100 degree) inhibits crystallization txij li thaum lub sodium acetate tseem molten los yog cov dej evaporates tsis tsim ib tug khoom crust.

Kev cuam tshuam ntawm phab ntsa thickness ntawm kev pab cuam lub neej ntawm kub sodium acetate heaters

Txij li cov nqi ntawm cov khoom tsis sib xws yog qhov tsawg (0.00005-0.0004 mm / teev) qhov kev tiv thaiv corrosion xav tau rau 5-10 xyoo khoom siv lub neej tsuas yog 0.005-0.04 hli. Phab ntsa tuab, yog li ntawd, tsis yog txiav txim siab los ntawm kev tiv thaiv corrosion, tab sis los ntawm cov khoom siv dag zog, kev tiv thaiv siab (qhov cuam tshuam) thiab tiv thaiv thermal shock thiab kev puas tsuaj thaum tuav. Txheem phab ntsa thicknesses ntawm quartz heaters (1.5 mus rau 2.0 mm) yog ntau tshaj li txaus rau kev siv sodium acetate. Nce phab ntsa thickness rau 3.0-4.0 hli muab tsis muaj corrosion kom zoo dua, tsuas yog nce thermal kuj thiab hnyav. Rau cov ntawv thov uas suav nrog kev rov ua kom sov dua (xws li, cov tshuab dyeing batch uas lub tshuab rhaub cua sov thiab txias txhua hnub), cov phab ntsa tuab tuaj yeem tiv taus thermal stress cracking, tab sis qhov txiaj ntsig me me vim quartz twb tau tiv taus thermal shock . 1.5-2.0 hli phab ntsa yooj yim ua tau raws li qhov yuav tsum tau muaj siab (feem ntau.<10 bar) of pressurized dyeing systems running at 120 o C.

Rau cov tshuab tsis nrog cov circulating thiab lim dej kom huv si sodium acetate tov lub thinnest practicable phab ntsa (1.5 hli) yog pom zoo rau qhov zoo tshaj plaws tshav kub kis tau tus mob.

Thermal Penalty of Nce Phab Ntsa Thickness hauv Sodium Acetate Solutions

Piv txwv li, 30% sodium acetate daws ntawm 95℃qhia thermal conductivity ntawm 0.55-0.60 W / (m·K) qis dua li cov dej ntshiab. Qhov ceev 1.10-1.15 g / cm3, viscosity 1.0-1.5 cP. Hauv agitated dyeing machines lossis buffer tanks convective heat transfer coefficients nyob rau hauv thaj tsam ntawm 600-1,200 W / (m²·K). Rau phab ntsa 1.5 hli, R_cond=0.00109 m 2 ·K/W; rau phab ntsa 3.0 mm, R_cond=0.00217. R_boundary=0.00125 , h=800 W/m^2.K . Tag nrho cov kev tiv thaiv rau 1.5 mm=0.00234 → U=427 W / (m2.K) Rau 3.0 mm=0.00342 → U=292 W / (m2.K) 32% txo. Qhov ntawd yog lub txim hnyav. Phab ntsa yuav tsum tsis txhob ua kom tuab dua vim qhov no tsis muaj kev tiv thaiv corrosion ntxiv. Qhov zoo tshaj plaws phab ntsa thickness yog qhov tsawg kawg nkaus uas muab cov neeg kho tshuab muaj zog txaus, feem ntau 1.5-2.0 hli.

Scenario-Raws li Quartz Sheath Phab Ntsa Thickness Xaiv Matrix rau Kub Sodium Acetate Service

Daim ntawv thov Scenario & Kev khiav hauj lwm Parameters Core Rationale nrog Quantified Trade-Tawm phab ntsa Thickness pom zoo
Textile dyeing tsis (30% sodium acetate, 95 degree, pH 8, nruam ncig, 1 xyoo tu) 1.5-2.0 hli, qib txheem, nplaim polished Corrosion npaum li cas<0.00008 mm/hour → 2.0 mm offers >25,000 teev (2.8 xyoo). Nplaim taws-polish txo qis kev ua raws li siv lead ua. U ≈ 450 W / (m²·K)
Pressure dyeing machine (120°C, 20% sodium acetate, pH 7.5, batch cycles, 5 bar) 1.5 – 2.0 mm, annealed Rate ~0.0003 mm/hr → 2.0 mm gives >6,600 teev (9 lub hlis). Batch cycled annealed quartz yog resistant rau thermal stress. U ≈ 400 W / m 2K .
Sodium acetate evaporator (40% concentration, 105 degree, crystallization, ntxuav txhua lub lim tiam) 2.0 hli, raws li - kos Corrosion tsis tseem ceeb. Thickness ntawm phab ntsa siv rau txhua yam muaj zog thaum ntxuav. U ≈ 380 W / (m²·K)
Buffer system High pH (>9.5 los ntawm kev ua qias tuaj) 2.0 hli, saib pH tus nqi nce mus rau 0.001 mm / hr ntawm pH 10. 2.0 hli muab 2000 teev. Tswj pH kom qis dua 9.
Tsawg kub sodium acetate (80 degree, 25%, kev ua zaub mov) 1.5 hli, txheem qib Corrosion insignificant (<0.00003 mm/hour). The thin wall maximizes the heat transfer. Life >30,000 teev
Kev Hloov Tsim Ntxiv rau Cov Kub Sodium Acetate Heaters

Phab ntsa tuab yog tam sim no txaus tab sis peb txoj kev siv los ua kom lub neej ntawm quartz rhaub . 1. pH tswj: qhov concentration ntawm cov hydroxide dawb yog suppressed los ntawm kev sib ntxiv ntawm cov ntim me me ntawm acetic acid los yog sodium acetate raws li xav tau los tswj cov tshuaj sodium acetate ntawm pH 7-9. Lub pH maub los siv cov lus tawm tswv yim kuj tseem tuaj yeem tiv thaiv alkaline excursions uas yuav ua rau kom corrosion. Thib ob, kev tu ncua sij hawm: immersion ntawm lub rhaub rau hauv dej kub deionized (los yog mus rau hauv cov kua qaub acetic acid) rau 1-2 teev dissolves sodium acetate crystals thiab restores tshav kub hloov efficiency. Ib txoj kev tu txhua hli yuav tiv thaiv kev tsim cov nplai. Thib peb, vapor-qhov chaw cua sov: lub tshuab cua sov tau muab tso rau ntawm lub quartz sheath saum cov kua kab kom tswj tau qhov kub ntawm qhov kub siab tshaj 100℃thiab tiv thaiv kom tsis txhob muaj crystallization ntawm sab sauv sheath. Xwb ib chav rhuab vapor shield tuaj yeem ua haujlwm. Plaub, polished nto: nplaim polished quartz nto minimizes adherence ntawm siv lead ua thiab tej nplai yog yooj yim dua tshem tawm thaum tu.

Xaus: Quartz Phab Ntsa Thickness Specification rau Kub Sodium Acetate nrog kev ntseeg siab hauv kev ua haujlwm ntev

Quartz immersion heaters yog tshwj xeeb tshaj yog zoo yoog rau kub concentrated sodium acetate kev pab cuam ntawm 80-120℃nrog uniform corrosion tus nqi <0.0004 mm / teev nyob rau hauv lub pH 7-9 ntau yam ntxwv ntawm cov kev daws teeb meem. Txheem phab ntsa thicknesses ntawm 1.5-2.0 hli ua rau kev pab cuam lub neej ntawm 10,000-25,000 teev (1-3 xyoos), nyob ntawm qhov kub thiab txias. Corrosion plays lub luag haujlwm me me hauv kev ua tsis tiav. Qhov teeb meem kev saib xyuas loj tsis yog corrosion tab sis kev tsim- ntawm sodium acetate crystals ntawm quartz nto uas yuav txwv tsis pub hloov hluav taws xob. Kev tu lub sijhawm, vapor-chaw cua sov thiab cov kua dej khov kho muab kev tswj xyuas zoo tshaj plaws ntawm crystallization. Cov phab ntsa tuab (3.0-4.0 hli) tsis muab cov txiaj ntsig corrosion thiab muaj tus nqi thermal ntawm 30-35% thiab yog li tsis pom zoo. Rau cov tshuab siab lossis rau cov ntawv thov raug thermal cycling, annealed quartz nrog 1.5-2.0 hli phab ntsa muaj qhov tshwj xeeb ruaj khov. Thaum txiav txim tus nqi rau sodium acetate heaters, thov qhia kom meej concentration, kev khiav hauj lwm kub, pH ntau, kwv yees crystallization zaus thiab tu niaj hnub. Qhov no tso cai rau cov chaw tsim khoom los qhia qhov zoo tshaj plaws phab ntsa thickness, feem ntau yog 1.5 mus rau 2.0 hli, rau lub zog txuag, kev ua haujlwm ntev hauv textile dyeing, tsis siv tshuab thiab lwm yam kev siv sodium acetate.