Dab tsi yog Qhov Kev Tshawb Fawb Txog Kev Ncaj Ncees Thickness rau 316 Stainless Steel Circulation Heaters hauv 20% Monoethylene Glycol Dej daws ntawm 110℃Hauv qab 4 Bar Siab?

Qhov kev lag luam yooj yim- tawm hauv cov voj voog glycol siab

Monoethylene glycol (MEG) raws li kaw- lub tshuab cua sov yog siv los ua cov dej khov tiv thaiv cov cua sov hloov pauv hauv cov chaw sab nrauv, kev teeb tsa lub hnub ci thermal thiab cov txheej txheem kev lag luam cua sov qhov twg qhov kub thiab txias nyob hauv qab khov. Kev daws 20% ntawm MEG hauv dej muaj kev tiv thaiv los ntawm kev tawg mus txog li -8℃nrog rau qhov tsim nyog viscosity thiab lub peev xwm kub. Lub 316 stainless hlau ncig cov cua sov hauv xws li kev daws teeb meem ntawm 110℃thiab 4bar system siab, yog nyob rau hauv ib qho kev txhoj puab heev tab sis feem ntau ua haujlwm. Glycol daws yog oxidised maj mam los tsim cov organic acids (glycollic thiab oxalic acids) ntawm qhov kub thiab txias, uas txo cov pH ntawm nruab nrab mus txog 5-6 lub sij hawm. Cov pa oxygen hauv thawj zaug tuaj yeem ua rau muaj kev cuam tshuam hauv zos kom txog thaum nws tau noj los ntawm kev ua haujlwm nrog glycol, lossis raug tshem tawm los ntawm lub tank nthuav dav. Hauv daim ntawv thov no, sheath thickness tsis yog hais txog kev muaj sia nyob siab corrosion, tab sis yog hais txog kev tswj hwm qhov sib npaug ntawm lub siab ncaj ncees, thermal efficiency, thiab lub sij hawm ntev tsis kam mus rau kev loj hlob degradation uas tshwm sim ntau xyoo ntawm kev ua haujlwm tas mus li.

Yam tsawg kawg nkaus tus qauv phab ntsa thiab lub nkoj siab xav tau

Lub hoop kev nyuaj siab nyob rau hauv ib tug ncig lub rhaub sheath yog sib piv me me ntawm kev khiav hauj lwm siab ntawm 4 bar. Rau ib tug raug raj ntawm 12 hli sab nraud txoj kab uas hla thiab 1.2 hli phab ntsa thickness, qhov kev nyuaj siab ntawm lub puab nto nyob rau hauv lub siab yuav xam tau siv lub nyias- phab ntsa lub tog raj kheej mis σ=P⋅ri/tσ=P⋅ri​/t qhov twg PP yog lub ntsuas siab (4 bar lossis 0.4 MPa) sab hauv peb mm rau phab ntsa 1.2 hli) thiab tt yog phab ntsa thickness. Qhov no muab qhov kev ntxhov siab ntawm kwv yees li 1.6 MPa, uas yog qhov tsis tseem ceeb piv rau 316 stainless hlau yield zog ntawm ib ncig ntawm 200 MPa ntawm chav tsev kub thiab 150 MPa ntawm 110 degree. Nrog rau kev nyab xeeb ntawm 5 a 0.5 hli phab ntsa yuav theoretically tuav lub siab. Txawm li cas los xij, cov lej rau cov hlab ntsha siab, piv txwv li, ASME Boiler thiab Pressure Vessel Code, qhia qhov tsawg kawg nkaus phab ntsa thicknesses rau cov neeg kho tshuab lub zog, xov kev sib koom, thiab kev tiv thaiv corrosion. Lub sheath ntawm cov cua kub cua nrog threaded los yog flanged sib txuas yuav tsum muaj peev xwm tiv tsis tau tsuas yog nyob rau hauv lub siab, tab sis kuj installation torques thiab pressures los ntawm thermal expansion. Phab ntsa thickness<1.0 mm may risk thread stripping or tube collapse upon assembly. Thus the minimal structural thickness for a 316 stainless steel circulation heater in a 4 bar glycol service is in the region of 1.0-1.2 mm. This thickness is driven more by mechanical handling and connection integrity than by pressure containment.

Corrosion Allowance thiab Glycol Degradation - Lub Sij Hawm Ntev

Hauv cov kev daws teeb meem kub MEG qhov kev pheej hmoo corrosion tseem ceeb yog qhov qeeb ntawm cov organic acids ntawm thermal oxidation. Nyob rau hauv lub xub ntiag ntawm cov pa yaj, uas yog ze li ntawm ib lub voj voog tsis ntev los no tau ntim los yog ua tsis zoo, cov glycol decomposes ntawm qhov kub thiab txias tshaj 90℃los tsim glycollic acid, oxalic acid thiab formic acid. Cov kua qaub no tuaj yeem ua rau cov yeeb yaj kiab tsis zoo ntawm 316 stainless hlau thiab txo cov pH. Laboratory xeem ntawm 316 stainless hlau nyob rau hauv 25 % MEG ntawm 110℃nyob rau hauv aerated xwm txheej qhia zoo ib yam corrosion tus nqi ntawm 0.02 mus rau 0.05 mm nyob rau hauv ib xyoos, nrog me ntsis siab dua tus nqi (0.05 mus rau 0.10 mm ib xyoos twg) nyob ze cov kua-vapor interface cheeb tsam uas cov pa concentration siab tshaj. Yog li kev tiv thaiv corrosion ntawm 0.5-1.0 hli thaum lub neej tsim ntawm kaum xyoo yog qhov ua tau zoo. Thaum lub sij hawm ntawd phab ntsa ntawm 1.2 hli yuav poob txog 0.2-0.5 hli, tawm 0.7-1.0 hli-tseem structurally txaus, tab sis nrog me ntsis margin rau xws li contingencies xws li huab cua nkag los yog localized warming. Lub phab ntsa 1.5-1.8 hli muab kev tiv thaiv corrosion zoo dua thaum nyob hauv thermally npaum. Ntau insidious yog qhov muaj peev xwm ntawm kev ua phem rau ntawm cov flanges gasketed los yog nyob rau hauv scale deposits. Cov khoom tawg ntawm glycol tuaj yeem polymerize rau hauv cov nplaum nplaum uas tuav cov kua qaub ntawm cov hlau. Hauv cov kab nrib pleb zoo li no, pH hauv zos tuaj yeem txo qis rau 3-4 thiab tus nqi corrosion tuaj yeem ncav cuag 0.2-0.5 hli hauv ib xyoos. Qhov ntxiv phab ntsa tuab muab qhov kev nyab xeeb ntau dua tiv thaiv qhov tsis paub meej qhov tob ntawm crevice nres.

Thermal Efficiency thiab cuam tshuam ntawm phab ntsa Thickness ntawm Glycol cua sov

Monoethylene glycol solutions have a lower thermal conductivity and a higher viscosity than water that further decreases the heat transmission from the sheath to the fluid. This difficulty is compounded by a thick wall of stainless steel. The convective heat transfer coefficient for 20 % MEG at 110 C is in the range of 800-1200 W/m2-K for turbulent flow (Re>4000). Qhov no tsawg dua qhov dej uas yog 1500-2500 W/m2-K. Li no lub sheath thermal kuj yog ib feem ntau dua ntawm tag nrho cov thermal circuit tshaj nws yuav nyob rau hauv dej. Ua ob npaug ntawm phab ntsa tuab ntawm 12 hli txheej kab ntawm lub raj los ntawm 1.2 hli mus rau 1.8 hli ua rau kom cov khoom siv hluav taws xob nce li 50% thiab txo qis tag nrho cov cua sov hloov mus los ntawm 15-20% nyob rau hauv tib qhov chaw tso dej. Qhov tseem ceeb tshaj plaws, cov phab ntsa tuab yuav tsum muaj qhov kub siab dua sheath saum npoo rau tib lub zog nkag. Watt ceev rau cov cua kub cua sov feem ntau yog 8-10 W / cm 2 ntawm lub plhaub. Ib phab ntsa 1.2 hli hauv 110℃MEG daws tuaj yeem ua kom lub plhaub kub ntawm 135-140 degree. Ib phab ntsa 1.8 hli yuav nyob rau hauv qhov kub ntawm 155-165C. Glycol oxidation yog nrawm heev ntawm qhov kub siab tshaj 150 degree. Tus nqi ntawm glycol decomposition txog ob npaug rau txhua 10oC nce siab tshaj 120oC. Qhov no tso cai rau cov phab ntsa tuab los siv los muab kev tiv thaiv corrosion, tab sis cov phab ntsa tuab tuaj yeem ua rau qhov kub thiab txias hauv zos ntawm cov kua-sheath interface, yog li indirectly accelerating corrosion nws yog txhais tau tias yuav tiv taus. Qhov kev tawm tswv yim ntawm tus kheej no txhais tau hais tias hauv kev xyaum rau glycol cov kev pab cuam thinner phab ntsa tsis tsuas yog siv tau zoo dua tab sis kuj tseem tuaj yeem tiv taus corrosion ntau dua vim lawv khaws cov sheath txias dua.

Cov lus pom zoo rau Thickness rau cov kev pabcuam sib txawv

Cov txheej txheem tuab hauv qab no siv rau lub voj kaw 20% MEG system ntawm 110 ºC thiab 4 bar raws li kev tsim qauv thiab kwv yees cov pa oxygen. Tus nqi corrosion yog tsawg heev (0.01-0.02 hli hauv ib xyoos) rau lub kaw lus kaw kom zoo nrog lub tank nthuav dav uas npog nrog nitrogen thiab nrog cov pa yaj uas khaws cia tsawg dua 100 ppb. Lub thickness ntawm 1.2-1.5 hli muab lub neej kaum xyoo nrog ntau cov paj. Cov phab ntsa nyias kuj pab ua kom cov tawv nqaij qis qis, uas tseem txo qis glycol. Rau lub kaw lus qhib, nyob rau hauv uas huab cua yog kos los ntawm lub vented expansion tank thiab thaum yaj oxygen nyob rau hauv saturation theem (kwv yees li 1 mus rau 2 ppm ntawm 110 degree), tus nqi corrosion nce mus rau 0.05 mus rau 0.10 hli ib xyoo. Nws tau pom tias lub thickness yog 1.6-1.8 hli los muab kev tiv thaiv corrosion ntawm 0.5-1.0 hli rau 10 xyoo. Tab sis cov phab ntsa tuab no yuav tsum tau ua ke nrog qis dua watt ntom ntom, tsis pub tshaj 6-7 W / cm 2, txhawm rau tswj qhov kub ntawm qhov qis dua 150℃. 2.0 hli thickness tej zaum yuav tsim nyog rau cov tshuab raug rov ua cov txheej xwm qhuav lossis yog tias cov glycol tsis tau rov qab thiab cov kua qaub ntau dua, txawm hais tias nyob rau theem no lub tshav kub raug nplua yog ntau heev. Nyob rau hauv qhov xwm txheej no, txoj hauv kev tsim nyog es tsis yog ua kom lub thickness ntawm cov hlau yog hloov cov hlau mus rau ntau dua corrosion resistant alloy xws li 316Ti los yog 317L los yog ntxiv ib pob corrosion inhibitor rau glycol.

Tshaj Thickness: Tsim cov yam ntxwv ntawm qhov system cuam tshuam rau lub neej kev pabcuam tiag

Phab ntsa thickness tsuas yog ib qho tseem ceeb hauv lub neej ntev glycol rhaub. Qhov tseem ceeb tshaj plaws yog tswj cov pa oxygen. Kho qhov loj me ntawm lub tank nthuav dav nrog nitrogen daim pam lossis diaphragm tshem tawm cov pa oxygen thiab txo qis tus nqi corrosion los ntawm ib qho kev txiav txim ntawm qhov loj, ua kom siv cov phab ntsa thinner, thermally ntau dua. Qhov thib ob yog qhov ceev watt. Lub tshuab cua sov ntev dua lossis ntau lub tshuab cua sov kom txo tau qhov ntom ntom ntom ntom rau 6 W / cm2 los yog tsawg dua yuav ua rau lub tsho kub qis dua 140℃txawm tias muaj 1.8-mm phab ntsa, txo qis glycol oxidation. Qhov thib peb yam yog qhov ceev ntawm cov kua. Cov khoom siv hluav taws xob yuav tsum tau muab tso rau hauv ib ntu ntawm cov yeeb nkab uas qhov dej ntws tawm tsawg kawg yog 1.5-2.0 m / sec kom ntseeg tau tias muaj cua sov sib kis thiab tiv thaiv kom tsis txhob muaj qhov kub thiab txias. Qhov thib plaub yog qhov zoo thiab kev saib xyuas ntawm glycol. Rau kev pabcuam kub kub, siv cov tshuaj inhibited glycol (cov tshuaj tiv thaiv kab mob thiab cov tshuaj antioxidants) kom ntev lub neej ntawm cov kua dej thiab txo cov kua qaub. Kev ntsuas pH tsis tu ncua thiab khaws cia alkalinity nrog kev hloov cov kua dej thaum pH poob qis dua 6 tiv thaiv cov xwm txheej hnyav acidic xav tau cov phab ntsa loj.

Xaus: Kev Tshawb Fawb Tsim Thickness rau Kev Pabcuam Glycol

The sheath thickness for 316 stainless steel circulation heaters in 20% MEG at 110°C and 4 bar should not be at the extremes. Very thin walls, below 1.0 mm, are not appropriate, as they lack the mechanical resilience for threaded connections and do not give sufficient corrosion allowance for a decade of operation. Very thick walls (>2.0 mm) yog qhov tsis zoo, vim tias lawv ua rau qhov kub thiab txias rau hauv qhov ntau ntawm glycol oxidation accelerates, tsim cov kua qaub heev uas tawm tsam cov hlau. Cov kev tshawb fawb tau lees paub ntau yam yog 1.4-1.8 hli rau feem ntau cov ntawv thov kev lag luam, nrog rau tus lej tseeb yog kev ua haujlwm ntawm txoj kev tswj cov pa oxygen thiab watt ntom. Rau cov txheej txheem nitrogen-pam nrog lub tank tsim kom tsim nyog, 1.4-1.5 hli yog qhov zoo tagnrho tuab, txaus nyias los tswj cov sheath kub hauv qab 140℃ntawm 8 W / cm2 tab sis tuab txaus kom muaj kev tiv thaiv corrosion ntawm 0.3-0.4 hli dhau kaum xyoo. Rau lub kaw lus qhib ua pa ambient cua 1.7-1.8 hli yog haum tab sis tsuas yog rau ib tug qis watt ceev ntawm 6 W / cm 2 los yog hauv qab no. Cov kws kho tsheb yuav tsum qhia txog qhov xav tau ntawm cov pa oxygen, qhov siab tshaj plaws tso cai sheath kub thiab qhov xav tau watt ceev. Qhov no txhawb kev sib tham los ntawm qhov yooj yim qhov ntev mus rau tag nrho cov txheej txheem engineering tshwj xeeb uas khi cov phab ntsa thickness rau corrosion kuj thiab thermal kev ua tau zoo nyob rau hauv pressurized glycol cua sov loops.