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Title:ŠTUDIJA VPLIVA OBRATOVALNIH POGOJEV IN PREDČIŠČENJA NA MAŠENJE MEMBRANE PRI ULTRAFILTRACIJI HLADILNO MAZALNIH SREDSTEV
Authors:Križan Milić, Janja (Author)
Simonič, Marjana (Mentor) More about this mentor... New window
Goršek, Andreja (Co-mentor)
Files:.pdf DR_Krizan_Milic_Janja_2014.pdf (2,79 MB)
MD5: D53F3F84FB563C9292720ED1C1F3A24F
 
Language:Slovenian
Work type:Dissertation (m)
Typology:2.08 - Doctoral Dissertation
Organization:FKKT - Faculty of Chemistry and Chemical Engineering
Abstract:Raziskava v okviru doktorske disertacije temelji na preučevanju vpliva različnih dejavnikov na mašenje membrane med ultrafiltracijo hladilno mazalnih sredstev. Eden od možnih načinov preprečevanja oziroma omejevanja mašenja membrane in posledično zmanjševanje gostote volumskega toka je nadzor obratovalnih pogojev. Zato smo v prvem delu doktorske naloge preučevali relativni vpliv štirih procesnih parametrov (pH, koncentracije olja v emulziji, φ, transmembranskega tlaka, Δp, in temperature, T) na treh nivojih in določali kombinacijo obratovalnih pogojev, pri katerih je bila dosežena največja gostota volumskega toka ter najmanjše mašenje keramične membrane. V raziskavi so predstavljeni in obravnavani rezultati poskusov filtracije, ki so bili vnaprej določeni s Taguchijevim načrtom poskusov. Z metodo analize variance (ANOVA) smo statistično ovrednotili delež vpliva procesnih parametrov na vrednost optimizacijskega kriterija, ki je bil v našem primeru gostota volumskega toka. Poskusi ultrafiltracije modelne emulzije rezalnega olja so bili izvedeni na pilotni ultrafiltracijski napravi s keramično membrano, integrirano v cevni modul. Med poskusi smo spremljali gostoto volumskega toka permeata v odvisnosti od časa ultrafiltracije. Na podlagi rezultatov kemijskih analiz smo določali učinkovitost odstranjevanja posameznih komponent pri določenih procesnih pogojih. Optimalne pogoje ultrafiltracije, ki zagotavljajo najvišjo gostoto volumskega toka, smo dosegli pri Δp = 5 bar, pH = 7, φ = 0,5 v/v % in T = 45 °C. pH emulzije je imel največji vpliv na učinkovitost odstranjevanja organskih onesnažil. Površinske in strukturne lastnosti membrane so pomembne za njihovo prepustnost, ki definira zmogljivost filtracijske naprave, ter igrajo ključno vlogo v povezavi z mašenjem membrane. Na splošno velja pravilo − bolj je površina membrane hidrofilna, manj se maši. Tudi elektrostatični pojavi, ki jih pogosto ovrednotimo z zeta potencialom membrane, imajo vpliv na pojav mašenja. V drugem delu raziskave smo preučevali ultrafiltracijo rezalnega olja s tremi različnimi polimernimi membranami (regenerirana celuloza (RC), poliakrilonitril (PAN) in polieterimid (PEI)). Gostoto volumskega toka v odvisnosti od časa ultrafiltracije smo preučevali na dveh različnih napravah s čelnim in prečnim pretokom. Glede na meritve zmanjšanja gostot volumskega toka smo določili mehanizme mašenja membran z uporabo modelov po Hermi-ji in modificiranega indeksa mašenja membran (MFI). Površinske lastnosti uporabljenih membran smo določali z merjenjem stičnega kota in pretočnega potenciala. Med tremi različnimi testiranimi materiali ultrafiltracijskih membran smo dobili najboljše rezultate pri uporabi membrane iz močno hidrofilne regenerirane celuloze pri prečni pretočni filtraciji. Prevladujoči mehanizem, ki se pojavlja pri mašenju membran z rezalnimi olji, v glavnem ustreza modelu filtrnega kolača. V tretjem delu doktorske naloge smo problem mašenja membran reševali s predčiščenjem oljne emulzije. Preučevali smo uporabnost elektrokoagulacije v nadgradnji sistema ultrafiltracije. S predobdelavo smo želeli znižati delež organskega onesnaženja in izboljšati proces ultrafiltracije. Uporabili smo modelne emulzije rezalnega olja z različnimi koncentracijami olja v vodi. Pri poskusih elektrokoagulacije smo uporabili aluminijeve elektrode, poskuse ultrafiltracije pa smo izvedli v laboratorijski celici s prečnim pretokom z uporabo ploščate membrane iz regenerirane celuloze. Ugotovili smo, da predčiščenje z elektrokoagulacijo bistveno izboljša gostoto volumskega toka pri ultrafiltraciji emulzije rezalnega olja. Prav tako se zmanjša mašenje membrane in upornost sloja filtrnega kolača. Ireverzibilno mašenje membrane popolnoma izgine po 30 min elektrokoagulacije. Z elektrokoagulacijo se poveča velikost delcev v emulziji in izboljša odstranjevanje rezalnega olja do 10 %.
Keywords:hladilno mazalna sredstva, ultrafiltracija, keramična membrana, elektrokoagulacija, predčiščenje, mehanizmi mašenja
Year of publishing:2014
Publisher:J. Križan Milić]
Source:[Maribor
UDC:628.349:66.087.5:542.816(043.3)
COBISS_ID:273712128 New window
NUK URN:URN:SI:UM:DK:HXFUURB7
Views:1686
Downloads:156
Metadata:XML RDF-CHPDL DC-XML DC-RDF
Categories:KTFMB - FKKT
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Secondary language

Language:English
Title:Study of the influence of different process parameters and pre-treatment on membrane fouling by ultrafiltration of cutting oils
Abstract:The context of the doctoral dissertation is based on the study of various factors on the membrane fouling during the ultrafiltration of metalworking fluids. One of the possible ways to prevent the membrane fouling and consequent flux reduction is by controlling the operating conditions. Therefore, in the first part of the doctoral thesis Taguchi experimental design methodology was used to determine the optimal combination and relative importance of process parameters influencing the ultrafiltration (UF) of cutting oil emulsions. Four parameters, including pH, oil concentration, transmembrane pressure and temperature, were researched at three levels. The highest flux was used as optimization criterion. In order to reduce the number of experiments, the Taguchi method was applied. Analysis of variance (ANOVA) was used to determine the most significant parameters affecting the optimization criterion. Filtration experiments were performed in cross-flow operation at total recycle condition in a lab-scale plant. The ceramic UF membrane was employed in the tubular type module. During the experiments permeate flux was measured. Based on the results of the chemical analysis, the retention of individual components was calculated. The optimum conditions of UF providing the highest flux were found at Δp = 5 bar, pH = 7, and φ = 0,5 v/v % and T = 45 °C. The pH of emulsion had the greatest impact on the removal efficiency of organic compounds. The surface and structural properties of the membrane are very important for their permeability (which defines the capacity of filtration device) and play a crucial role in determining the fouling resistance property of the membranes. It is a general rule that hydrophilic materials are less sensitive to adsorption when compared to hydrophobic ones. Also, electrostatic phenomena, often quantified by the membrane zeta potential, influence permeate flux and the fouling behaviour. In the second part of the study, the ultrafiltration of the cutting oil with three different polymeric membranes (regenerated cellulose (RC), polyacrylonitrile (PAN) and polyetherimide (PEI)) was studied. The permeate flux in dependence of ultrafiltration time was studied using two devices with cross-flow and dead-end flow. According to permeate flux reduction fouling mechanisms using Hermia’s model and modified membrane fouling index (MFI) were determined. Also, physical parameters as contact angle and streaming potential of membranes were analysed. The tests showed that among the three different UF membrane materials, regenerated cellulose showed the best performance in terms of the water flux and fouling tendency, due to its good hydrophilicity, in cross-flow operation. The dominant fouling mechanism was the cake layer formation model followed by the intermediate blocking model. In the third part of the doctoral thesis we solved the problem of membrane fouling by pre-treatment of oily emulsion. The aim of the pre-treatment was to reduce the organic fraction and to improve the ultrafiltration performance. Electrocoagulation and ultrafiltration experiments were carried out with cutting oil solutions at different concentrations. Electrocoagulation experiments were performed with aluminium electrodes. Ultrafiltration experiments were performed in a lab-scale cross-flow cell using flat sheet regenerated cellulose membrane. Electrocoagulation as a pre-treatment considerably improved the overall flux in UF of cutting oils. It also reduced fouling and cake layer resistance. Irreversible fouling was eliminated completely after 30 minutes of pre-treatment by electrocoagulation. Electrocoagulation increased the size of particles/droplets and improved removal of cutting oil up to 10 %.
Keywords:metalworking fluid, ultrafiltration, ceramic membrane, electrocoagulation, pre-treatment, fouling mechanisms


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