Kev tuav cov roj chlorine ntub dej los yog kua bromine yog qhov tsis yooj yim heev -cov halogens no tawm tsam ntau cov hlau thiab tuaj yeem nkag mus lossis kev ntxhov siab -pua qee cov fluoropolymer. PVDF (polyvinylidene fluoride) tau tshwm sim los ua cov khoom siv rau kev sib hloov cua sov hauv cov kev pabcuam nruj heev vim nws qhov sib xyaw ua ke ntawm kev tiv thaiv thiab lub zog. Rau cov txheej txheem engineers tsim cov bromine rov qab units, chlorine drying systems, los yog tshuaj tua kab mob sib cuag tso tsheb hlau luam, PVDF tshav kub exchangers muab ib tug txaus siab tshuav nyiaj li cas ntawm tshuaj compatibility thiab txhua yam robustness uas feem ntau surpasses ib txwm PTFE-raws li kev daws teeb meem.
Tshuaj Resistance ntawm PVDF nyob rau hauv Halogen Environments
PVDF yog ib nrab -crystalline fluoropolymer uas muaj CH₂ thiab CF₂ pab pawg. Cov qauv no muab kev tiv thaiv zoo rau oxidizing cov neeg ua haujlwm, suav nrog cov chlorine ntub dej, chlorine dioxide, hypochlorites, thiab kua bromine. Tsis zoo li lwm cov fluoropolymers, PVDF tsis pom qhov permeation tseem ceeb lossis kev ntxhov siab tawg thaum raug rau cov halogens raws li kev ua haujlwm zoo.
Cov kev paub dhau los ua pov thawj tias PTFE tuaj yeem raug kev puas tsuaj los ntawm kev nkag mus rau hauv lub sijhawm ntev - cov tshuaj chlorine ntub dej. Chlorine molecules maj mam diffuse los ntawm PTFE matrix, uas yuav ua rau blistering los yog delamination nyob rau hauv lub tshav kub exchanger hlab. PVDF's denser crystalline qauv thiab qis dua ntim txo halogen permeation tus nqi los ntawm qhov kev txiav txim ntawm qhov loj lossis ntau dua. Yog li ntawd,PVDF tshav kub exchanger chlorine bromine kev pabdaim ntawv thov tau loj hlob tsis tu ncua hauv chlor-alkali nroj tsuag, bromine extraction chaw, thiab dej kho tshuab.
Qhov Kev Pab Cuam Tshaj Plaws Tshaj Plaws thiab Kev Cuam Tshuam
PVDF tuav nws halogen tsis kam mus txog qhov siab tshaj plaws kev pabcuam kub ntawm kwv yees li 135℃(275℃F). Hauv qhov no, PVDF tiv taus cov roj chlorine ntub dej (saturated nrog dej vapor) thiab kua bromine yam tsis muaj degradation. Ntawm qhov kub siab tshaj 135 degree, PTFE tseem nyob ruaj khov (txog 260 degree), tab sis rau feem ntau ntawm cov tshuaj chlorine thiab bromine txheej txheem -uas ua haujlwm qis dua 120℃-PVDF yog tag nrho txaus.
Concentration txwv yog dav. PVDF tiv thaiv cov chlorine ntub dej los ntawm cov kab mus txog 100% roj theem, muab cov dej noo tam sim no (cov roj chlorine qhuav tuaj yeem hnov mob nrog PVDF ntawm qhov kub siab). Rau bromine, PVDF tuav cov kua bromine, dej bromine, thiab bromine vapor nyob rau hauv qhov kub txwv.
Mechanical Strength Advantages Tshaj PTFE
Ib qho txiaj ntsig tseem ceeb yog PVDF lub zog zoo dua qub piv rau PTFE. Cov lus hauv qab no qhia txog kev sib piv:
| Khoom | PTFE | PVDF |
|---|---|---|
| Tensile zog (MPa) | 20–30 | 40–55 |
| Flexural Modulus (MPa) | 500–700 | 2000–2500 |
| Elongation ntawm tawg (%) | 250–400 | 20–50 |
| Hardness (Shore D) | 50–60 | 70–80 |
| Abrasion tsis kam | Tsawg | Nruab nrab mus rau siab |
PVDF yog qhov muaj zog thiab ruaj khov. Qhov no tso cai rau cov khoom siv hluav taws xob sib txawv nrog cov phab ntsa nyias nyias- feem ntau 0.5-1.0 hli rau PVDF piv rau 1.0-2.0 hli rau PTFE. Cov phab ntsa nyias txhais kom qis dua thermal kuj thiab txhim kho cov cua sov hloov coefficient. Lub plhaub PVDF-thiab- raj kub exchanger tuaj yeem ua tiav tag nrho cov cua sov hloov coefficients 15-25% siab dua li qhov sib npaug ntawm PTFE chav tsev, piv txwv li tib lub geometry.
Lub zog siv tshuab siab dua kuj ua rau muaj kev ntsuas siab dua. PTFE heat exchangers feem ntau txwv rau 3-5 bar (45-75 psi) vim yog creep thiab txias txaus. PVDF cov khoom siv hluav taws xob niaj hnub ua haujlwm 8-10 bar (115-145 psi), thiab nrog cov khoom siv ntxiv, txog li 15 bar. Qhov no ua rau PVDF haum rau cov ntawv thov uas cov kab siab muaj nruab nrab tab sis tshaj PTFE lub peev xwm.
Abrasion kuj yog lwm qhov sib txawv. Nyob rau hauv cov kev pab cuam uas lub tshav kub exchanger pom tshem tawm cov khib nyiab, muaju (xws li, ntsev nyob rau hauv chlor-alkali brine), los yog turbulent flow nrog entrained hais, PTFE hlab erode kuj sai heev. PVDF lub siab dua hardness thiab abrasion tsis kam ua rau lub neej ntev ntev.
Kev siv tswv yim hauv kev ua Halogen
Chlorine Drying Systems
Hauv kev tsim cov tshuaj chlorine, cov chlorine ntub dej los ntawm cov hlwb electrolysis dhau los ntawm lub tshuab ziab khaub ncaws (feem ntau yog sulfuric acid). Cov txheej txheem ziab yog exothermic, yuav tsum tau txias. PVDF heat exchangers yog dav siv los ua chlorine coolers ua ntej los yog tom qab ziab. Lawv tiv thaiv ob qho tib si chlorine ntub dej (sab sauv ntawm ziab) thiab cov tshuaj chlorine qhuav nrog cov dej noo (kem hauv qab), hos hlau yuav corrode sai.
Bromine rov qab los ntawm Brine
Bromine extraction los ntawm seawater los yog ntsev pas dej brines koom nrog oxidation ntawm bromide rau bromine siv chlorine gas, ua raws li los ntawm chav stripping. Lub resulting bromine vapor yog condensed thiab purified. PVDF heat exchangers ua cov condensers thiab cov khoom txias hauv cov kev pabcuam no. Cov ntaub ntawv tshaj tawm qhia txog kev pabcuam lub neej tshaj 10 xyoo hauv bromine rov qab units, whereas PTFE heat exchangers nyob rau tib qhov chaw qhia permeation - cuam tshuam tsis ua hauj lwm tom qab 3-5 xyoo.
Bleach thiab Hypochlorite Txias
Sodium hypochlorite (bleach) decomposes ntawm qhov kub thiab txias, tso pa oxygen thiab cua sov. PVDF heat exchangers txias cov tshuaj hypochlorite thaum lub sij hawm tsim khoom kom muaj kev ruaj ntseg. PTFE kuj tsim nyog, tab sis PVDF lub zog siab dua tso cai ntau dua, tus nqi - tsim tau zoo.
Limitations thiab Compatibility ciam teb
PVDF tsis yog kev hloov pauv thoob ntiaj teb rau PTFE. Nws raug tawm tsam los ntawm cov kuab tshuaj muaj zog polar, suav nrog:
Ketones (acetone, methyl ethyl ketone)
Esters (ethyl acetate, butyl acetate)
Qee cov ethers (tetrahydrofuran)
Fuming sulfuric acid (ntau tshaj 100% H₂SO₄)
Concentrated hot caustic (above 80 °C and >20% NaOH)
Hauv cov cheeb tsam no, PTFE tseem yog cov khoom nyiam. Tsis tas li ntawd, PVDF tsis tuaj yeem siv nrog cov roj chlorine qhuav ntawm qhov kub siab (siab tshaj 135 degree) lossis nrog cov tshuaj chlorine trifluoride. Rau cov kev pab cuam tshaj 135℃los yog xav tau universal tshuaj tiv thaiv, PTFE tshav kub exchangers tseem tus qauv.
Compatibility Table: PTFE vs. PVDF nyob rau hauv Halogen thiab lwm yam tshuaj
Cov lus hauv qab no muab cov lus qhia dav dav rau cov khoom siv hluav taws xob sib txawv. Ratings: E=Zoo heev, G=Zoo (me me nres), F=Ncaj ncees (limited service), X=Tsis pom zoo.
| Tshuaj | Nco ntsoov | Kub | PTFE | PVDF |
|---|---|---|---|---|
| Chlorine, ntub dej (gas) | Saturated | Mus txog 100 degree | E | E |
| Chlorine, ntub dej (gas) | Saturated | 100-135 degree | E | G |
| Chlorine, qhuav | 100% gas | Mus txog 100 degree | E | F¹ |
| Bromine, kua | 100% | Mus txog 100 degree | E | E |
| Bromine, kua | 100% | 100-135 degree | E | G |
| Bromine dej | Saturated | Mus txog 100 degree | E | E |
| Chlorine dioxide | Aqueous | Txog li 80 degree | E | E |
| Sodium hypochlorite | 15% | Txog li 50 degree | E | E |
| Hydrochloric acid | 37% | Mus txog 100 degree | E | E |
| Sulfuric acid, fuming | >100% | 25 degree | E | X |
| Acetone | 100% | 25 degree | E | X |
| Ethyl acetate hmoov | 100% | 25 degree | E | X |
| Sodium hydroxide | 50% | 80 degree | E | F² |
¹ Qhuav chlorine ntawm qhov kub siab tshaj 100℃yuav ua rau degradation ntawm PVDF. Siv PTFE hloov.
² PVDF tuaj yeem siv tau rau kev sib tshuam lossis qis -concentration caustic tab sis tsis yog rau kev ua haujlwm siab - kub, siab - kev pabcuam siab.
Tsim kev xav rau PVDF Heat Exchangers
Thaum qhia txog aPVDF tshav kub exchanger chlorine bromine kev pabdaim ntawv thov, ntau yam yuav tsum tau saib xyuas:
Tube phab ntsa thickness:Txawm hais tias PVDF lub zog, qhov tsawg kawg nkaus thickness ntawm 0.8 hli raug pom zoo rau kev pabcuam halogen los muab kev nyab xeeb ntawm cov npoo tiv thaiv permeation thiab mechanical puas.
Gaskets thiab seals:Siv PTFE lossis perfluoroelastomer (FFKM) gaskets. PVDF gaskets zoo li nkag. EPDM thiab FKM tsis sib xws nrog halogens.
Kev poob siab:Cov raj nyias nyias tso cai rau qhov nrawm dua, tab sis kev yaig- corrosion tsis yog ib qho kev txhawj xeeb nrog PVDF. Kev nrawm mus txog 3 m / s tau txais ntawm lub raj sab.
Thermal expansion:PVDF muaj ib coefficient ntawm thermal expansion kwv yees li 8 npaug ntawm carbon hlau. Cov qauv siv hluav taws xob sib txawv yuav tsum ua kom haum rau qhov sib txawv ntawm qhov nthuav dav ntawm lub voj voog, hauv qab, lossis cov ntawv ntab raj.
Sib piv nrog Lwm Cov Fluoropolymer Alternatives
ETFE (ethylene tetrafluoroethylene) thiab ECTFE (ethylene chlorotrifluoroethylene) kuj tau siv hauv kev pabcuam halogen. Ob leeg muaj zog txhua yam ntawm PTFE thiab PVDF, nrog rau cov tshuaj tiv thaiv me ntsis hauv qab PTFE tab sis saum PVDF rau qee cov kuab tshuaj. Txawm li cas los xij, PVDF feem ntau yog tus nqi ntau dua - ua haujlwm tau zoo thiab yooj yim dua muaj nyob rau hauv cov ntaub ntawv hloov hluav taws xob (plhaub- thiab - raj, coil, immersion). Rau bromine thiab ntub chlorine tshwj xeeb, PVDF cov ntaub ntawv ntev ua rau nws muaj ntug.
Xaus
PVDF tshav kub exchangers sau ib qho tseem ceeb niche nyob rau hauv halogen kev pab cuam qhov twg lawv tshwj xeeb tsis kam mus rau ntub chlorine thiab kua bromine, ua ke nrog superior mechanical zog, outperform PTFE. Cov phab ntsa nyias nyias, kev ntsuas siab dua, kev ua kom zoo dua qub, thiab qis permeation tus nqi ua rau PVDF tus nqi -kev xaiv zoo thiab txhim khu kev qha rau chlor-alkali, bromine rov qab, thiab cov txheej txheem tshuaj tua kab mob hauv qab 135 degree. Txawm li cas los xij, kev xaiv cov khoom yuav tsum muaj kev nkag siab ntxaws txog cov txheej txheem chemistry-xws li muaj cov kuab tshuaj polar solvents, fuming acids, lossis siab -kub qhuav chlorine- qhov twg PTFE tseem tsim nyog. Rau feem ntau ntawm cov tshuaj chlorine thiab bromine tshav kub hloov cov dej num, PVDF muaj qhov sib npaug ntawm kev ua tau zoo thiab kav ntev.
