Dej ntws los ntawm daim nyias nyias nyob rau hauv siab, tab sis cov ntsev thiab cov organic teeb meem tsis tuaj yeem hla thiab raug daig ntawm daim nyias nyias. Lub solute "sau" rau ntawm daim nyias nyias muaj qhov siab ntau dua li cov dej ntws ntau; Qhov no yog qhov concentration polarization. Kev tsim ntawm cov ciam teb txheej no muaj kev cuam tshuam rau lub system.
Hauv cov txheej txheem rov qab osmosis, qhov piv ntawm cov ntsiab lus ntawm cov kua nplaum ntawm daim nyias nyias mus rau qhov concentration hauv cov dej ntws ntau yog txhais tau tias yog qhov concentration polarization. Hauv kev xyaum ua engineering, feem ntau yog tswj hwm hauv qab 1.2. Txawm li cas los xij, thaum qhov pub channel raug thaiv lossis tus nqi ntws qis, tuaj yeem yooj yim nce mus rau 1.4 lossis txawm 1.5. Qhov no txhais tau hais tias ntsev concentration ntawm daim nyias nyias yog 40% -50% siab tshaj qhov ntsev concentration ntawm cov concentrate peb ntsuas.
Piv txwv li, nrog cov dej tsis zoo, thaum cov concentration ntsev ntau yog 5000 mg / L, cov concentration hauv cheeb tsam ntawm daim nyias nyias tuaj yeem ncav cuag 7000-7500 mg / L. Osmotic siab yog ncaj qha proportional rau salinity - rau txhua txhua 1000 mg / L nce nyob rau hauv salinity, lub osmotic siab nce los ntawm kwv yees li 0.07 MPa (0.7 bar).
Ib qho 2500 mg / L nce nyob rau hauv qhov chaw concentration ua rau muaj ze li ntawm 0.18 MPa (1.8 bar) hauv osmotic siab. Rau brackish dej membrane systems khiav hauj lwm ntawm 1.0-1.2 MPa, qhov no txhais tau hais tias 15% -18% ntawm lub net tsav siab yog absorbed los ntawm concentration polarization.
Quantification ntawm permeate flow rate thiab desalination tus nqi:
Raws li daim nyias nyias cov ntaub ntawv qhia txog kev siv tshuab (siv DuPont FilmTec series ua piv txwv), nrog rau 15% txo tus nqi pub noj thiab nce ntawm 1.2 mus rau 1.4, qhov system permeate flow rate yuav txo qis los ntawm 12% -18% hauv hom kev siab tas mus li. Qhov no tsis yog vim cov membrane fouling, tab sis theej lub zog tsav tsheb raug offset.
Hais txog desalination tus nqi, rau txhua txhua 0.1 nce nyob rau hauv, NaCl permeability nce li ntawm 20% -30%. Thaum lub desalination tus nqi ntawm ib txwm brackish dej membrane yog 99.5%, permeate conductivity yog kwv yees li 10-15 µS / cm.
Thaum cov concentration polarization hnyav, qhov permeate conductivity tuaj yeem nce mus rau 30-50 µS/cm. Rau ib-theem rov qab osmosis system nrog lub txaj sib xyaw, qhov no tuaj yeem txhais tau tias lub txaj sib xyaw ua ke yog compressed los ntawm 72 teev mus rau tsawg dua 24 teev, ob npaug acid thiab alkali noj.
Scale Risk:
Langerile Saturation Index (LSI) ntawm calcium carbonate feem ntau yog tsim los kom qis dua 1.8 (nrog rau cov nplai inhibitors). Concentration polarization tsub kom qhov concentration ntawm daim nyias nyias, ua rau qhov tseeb LSI tus nqi 0.5-1.0 siab dua cov dej ntws ntau.
Nyob rau hauv ib qhov dej khib nyiab rov siv dua qhov project, bulk concentrate LSI yog 1.6. Ntxiv cov nplai inhibitors yuav tsum muaj kev nyab xeeb raws li kev tsim, tab sis thaum lub sijhawm ua haujlwm, qhov sib txawv ntawm qhov sib txawv ntawm lub davhlau ya nyob twg daim nyias nyias tau nce ntawm 10 psi mus rau 25 psi hauv peb lub hlis. Dissection qhia calcium carbonate crystals rau ntawm daim nyias nyias, nrog ib tug ntsuas nto LSI siab li 2.4-2.7, ib tug ncaj txim ntawm ciam teb txheej concentration buildup.
Sulfate scale yog txawm ntau rhiab heev. Cov khoom solubility (Ksp) ntawm calcium sulfate yog kwv yees li 2.4 × 10⁻⁵ (25 degree). Thaum cov concentration polarization yog 1.4, cov khoom ion saum npoo tuaj yeem yooj yim tshaj Ksp los ntawm 1.2-1.5 zaug, ua rau cov khoom siv lead ua. Thaum cov pob zeb ua kom dej nag, tshuaj ntxuav feem ntau xav tau kev ncig rau 6-8 teev lossis ntau dua, thiab kev tu ib leeg tuaj yeem txo tus nqi desalination los ntawm 0.5% -1%.
Tswj cov qauv rau kev khiav hauj lwm parameter:
Nyob rau hauv cov txheej txheem tsim cov txheej txheem membrane, qhov kawg concentration ntws tus nqi yog qhov tseem ceeb tswj qhov taw qhia. Rau 8-nti daim nyias nyias cov ntsiab lus, cov concentration ntws ntawm ib chav tsev feem ntau tsis tsawg dua 3.6 m³ / h.
Thaum tus nqi ntws qis qis dua 3.0 m³ / h, lub membrane nto shear quab yuam txo los ntawm kwv yees li 250-300 s⁻¹ mus rau ib ncig ntawm 150 s⁻¹, uas ua rau muaj kev nce ntxiv hauv thaj tsam txheej tuab.
Cov ntaub ntawv ntsuas qhov tseeb qhia tau hais tias ntawm lub sijhawm no, tus nqi yuav dhia los ntawm qhov qub 1.15-1.2 mus rau ntau dua 1.35, thiab qhov system desalination tus nqi yuav pom qhov txo qis hauv 1-2 lub lis piam.
Rov qab Rate thiab Concentration Polarization:
Rau ib zaug xwb -theem rov qab osmosis system, nce tus nqi rov qab los ntawm 50% mus rau 75% nce tus nqi ntawm cov membrane kawg los ntawm kwv yees li 0.1-0.15. Qhov no yog vim li cas cov tshuab feem ntau yog tsim los nrog ob lossis peb theem, nrog rau txhua theem tus nqi rov qab tswj tau ntawm 40% -50%. Tus nqi rov qab tag nrho yog nce los ntawm kev ntxiv ntau theem, es tsis yog los ntawm kev nyem tawm tus nqi rov qab ntawm ib theem.
Ntau qhov kev ua haujlwm raug xwm txheej tshwm sim vim tias, raws li lub tswv yim ntawm "tsim dej ntau," tus nqi rov qab tau nce los ntawm 75% mus rau 80%, uas ua rau qhov kawg ntawm tus nqi siab tshaj 1.5, ua rau scaling tswb nyob rau hauv ib lub hlis.