Analysis of Phase Separator Design Criteria Using Computational Fluid Dynamics

Gravitational phase separation is a common unit operation found in most large-scale chemical processes. The need for phase separation can arise e.g. from product purification or protection of downstream equipment. In gravitational phase separation, the phases separate without the application of an external force. This is achieved in vessels where the flow velocity is lowered substantially compared to pipe flow. If the velocity is low enough, the denser phase settles towards the bottom of the vessel while the lighter phase rises. To find optimal configurations for gravitational phase separator vessels, several different geometrical and internal design features were evaluated based on simulations using OpenFOAM computational fluid dynamics (CFD) software. The studied features included inlet distributors, vessel dimensions, demister configurations and gas phase outlet configurations. Simulations were conducted as single phase steady state calculations. For comparison, additional simulations were performed as dynamic single and two-phase calculations. The steady state single phase calculations provided indications on preferred configurations for most above mentioned features. The results of the dynamic simulations supported the utilization of the computationally faster steady state model as a practical engineering tool. However, the two-phase model provides more truthful results especially with flows where a single phase does not determine the flow characteristics.

Laimentimen merkitys metallien neste-nesteuutossa

Työssä tutkittiin korkean leimahduspisteen laimentimien vaikutusta uuton tehokkuuteen ja turvallisuuteen. Kirjallisuusosa sisältää katsauksen uuttolaitoksilla tapahtuneista suuronnettomuuksista, staattisen sähkön aiheuttamista vaaroista uuttolaitoksilla ja kaupallisesti saatavista laimentimista. Lisäksi kirjallisuusosassa tarkastellaan hiilivetyjen molekyylirakenteen vaikutusta niiden leimahduspisteeseen, haihtuvuuteen, viskositeettiin ja liuotinominaisuuksiin. Kokeellisessa osassa tutkittiin uuton tehokkuutta kuvaavia ominaisuuksia, joita olivat sekoituksen pisarakoko, faasien selkeytymisnopeus,uuton ja takaisinuuton kinetiikka, orgaanisen faasin viskositeetti ja tiheys. Uuttoliuosten turvallisuusominaisuuksia tutkittiin mittaamalla synteettisten uuttoliuosten ja laimentimien leimahduspisteitä sekä sähköisesti varattujen laimentimien relaksaatioaikoja. Korkean leimahduspisteen laimentimena käytettiin Orfom SX 11-laimenninta. Vertailukohteena käytettiin Shellsol D70- ja Escaid 100- laimentimia. Malliuuttona käytettiin kuparin uuttoa hydroksioksiimireagensilla happamasta sulfaattiliuoksesta. Kokeissa havaittiin, että korkean leimahduspisteen laimentimen viskositeetti oli huomattavasti suurempi kuin Shellsol D70- laimentimella. Korkea viskositeetti hidasti faasien selkeytymistä uutossa, mutta sillä ei ollut vaikutusta uuton kinetiikkaan tai sekoituksen aiheuttamaan pisarakokoon. Uuttoliuoksen reagenssipitoisuudella havaittiin olevan vaikutusta uuttoliuoksen leimahduspisteeseen, mutta uuttoliuoksen latausasteella ei havaittu olevan vaikutusta. Sähköisesti varattujen laimentimien varauksien relaksaatioajoissa oli hieman eroja, mutta relaksaatioajat olivat kaikilla laimentimilla liian pitkiä staattisen sähkön aiheuttaman vaaran poistamiseksi.

Validation Studies of Thermal-hydraulic Code for Safety Analysis of Nuclear Power Plants

This thesis gives an overview of the validation process for thermal hydraulic system codes and it presents in more detail the assessment and validation of the French code CATHARE for VVER calculations. Three assessment cases are presented: loop seal clearing, core reflooding and flow in a horizontal steam generator. The experience gained during these assessment and validation calculations has been used to analyze the behavior of the horizontal steam generator and the natural circulation in the geometry of the Loviisa nuclear power plant. The cases presented are not exhaustive, but they give a good overview of the work performed by the personnel of Lappeenranta University of Technology (LUT). Large part of the work has been performed in co-operation with the CATHARE-team in Grenoble, France. The design of a Russian type pressurized water reactor, VVER, differs from that of a Western-type PWR. Most of thermal-hydraulic system codes are validated only for the Western-type PWRs. Thus, the codes should be assessed and validated also for VVER design in order to establish any weaknesses in the models. This information is needed before codes can be used for the safety analysis. Theresults of the assessment and validation calculations presented here show that the CATHARE code can be used also for the thermal-hydraulic safety studies for VVER type plants. However, some areas have been indicated which need to be reassessed after further experimental data become available. These areas are mostly connected to the horizontal stem generators, like condensation and phase separation in primary side tubes. The work presented in this thesis covers a large numberof the phenomena included in the CSNI code validation matrices for small and intermediate leaks and for transients. Also some of the phenomena included in the matrix for large break LOCAs are covered. The matrices for code validation for VVER applications should be used when future experimental programs are planned for code validation.

Epäpuhtaudet sinkin uutossa

Työssä tutkittiin metalli- ja anioniepäpuhtauksien myötäuuttautumista sinkin mukana di(2-etyyliheksyyli)fosforihappoalla (D2EHPA). Laboratoriokokeissa selvitettiin pH:n vaikutusta metalliepäpuhtauksien uuttautumiseen pH-alueella -O, l... 3 sekä pesujen vaikutusta sinkillä ladatun orgaanisen faasin metallipitoisuuksiin. Kokeita tehtiin sekä synteettisillä että autenttisilla prosessiliuoksilla. Anionikokeissa tutkittiin raudan ja sinkin vaikutusta kloridin ja fluoridin uuttautumiseen. Synteettisillä liuoksilla tehdyissä kokeissa tutkittiin kadmiumin, koboltin, nikkelin, kuparin sekä antimonin uuttautumista sinkkisulfaattiliuoksesta. Kokeissa havaittiin D2EHPA:n uuttavan sinkkiä selvästi em. metalleja paremmin. Sinkki uuttautui sulfaattiliuoksesta lähes täydellisesti tasapaino-pH:n ollessa yli 2,3. Sinkin jälkeen muista metalleista uuttautui eniten kadmium ja järjestyksessä sitten kupari, koboltti ja nikkeli. Epäpuhtausmetallien myötäuuttautumista lisääntyi uuton tasapaino-pH:n kasvaessa ja väheni sinkkilatauksen kasvaessa. Kahdella peräkkäisellä pesuaskeleella, joissa ensimmäinen pesuliuos sisälsi 5 g/L rikkihappoa ja toinen sekä 15 g/L rikkihappoa että 5 g/L sinkkiä saatiin kaikkien epäpuhtausmetallien pitoisuudet jäämään alle 3 mg/L. Antimonin uuttokokeissa huomattiin antimonin uuttautuvan täydellisesti D2EHPA:lla pH:sta riippumatta pH-alueella0...3. Prosessiliuoksilla tehdyissä kokeissa todettiin D2EHPA:n pystyvän tehokkaasti erottamaan sinkin magnesiumista ßzn,Mg ˜107 ja kadmiumista ßzn,cd ˜106. Havaittiin myös, että mitä suurempi sinkki- ja rautalataus orgaanisessa faasissa on sitä vähemmän magnesiumia ja kadmiumia uuttautuu. Ensimmäisessä pesussa saatiin sekä kadmiumin että magnesiumin pitoisuudet putoamaan keskimäärin 0,1 mg/L eli 30 alkuperäisestä pitoisuudesta. Toisella pesuaskeleella ei enää ollut vaikutusta kadmiumin ja magnesiumin pitoisuuksiin orgaanisessa faasissa. Kokeissa havaittiin myös, että D2EHPA:n latausasteen ylittäessä 0,7 alkaa sinkki-D2EHPA-kompleksit polymeroitua ja faasit eivät enää selkeytyneet helposti. Anionikokeissa huomattiin, ettei D2EHPA uuttanut kloridi tai fluoridi sinkin tai raudan mukana. D2EHPA:n havaittiin myös itsessään sisältävän hieman kloridia.

Nikkelin takaisinuutto karboksyylihappoon perustuvasta uuttoreagenssista

Työssä tutkittiin typpihapon soveltuvuutta nikkelin takaisinuuttoon. Tarkoituksena oli selvittää, millä typpihapon konsentraatioilla orgaaninen faasi, joka koostuu Versatic 10 uuttoreagenssista ja alifaattisesta laimentimesta, alkaa nitrautua tai hapettua ja mitkä ovat mahdolliset sivureaktiot. Lisäksi tutkittiin rikkihapon ja eräiden orgaanisten aineiden kontaminaation vaikutusta uuttoliuokseen. Kirjallisuusosassa kartoitetaan mahdollisten nitrautumisreaktioiden mekanismit, sekä kuvataan laimentimen, uuttoreagenssin ja mahdollisten reaktiotuotteiden ominaisuuksia, sekä niiden mahdollisessa muodostumisessa syntyviä riskejä. Orgaanisen faasin kestotesteissä tutkittavia muuttujia olivat typpi- ja rikkihapon konsentraatio, sekoitusaika, lämpötila, avoin tai suljettu astia sekä vieraiden aineiden kontaminaatio. Kontaminaatiota aiheuttavien orgaanisten materiaalien funktionaaliset ryhmät olivat hydroksi-, karbonyyli- ja amiiniryhmät, joiden lisäksi tutkittiin syklisen yhdisteen kontaminaatiota. Analyyseissä käytettiin FT-IR- spektroskopiaa, jolla tutkittiin reagenssin funktionaalisen ryhmän reaktioita ja uusien ryhmien muodostumista, sekä seurattiin selkeytyksessä erottumattomien typpiyhdisteiden määrää ja laatua orgaanisessa faasissa. Uuttofaasin koostumuksen muutosta seurattiin myös mittaamalla leimahduspisteen muutosta.

Process intensification: From optimised flow patterns to microprocess technology

This thesis is focused on process intensification. Several significant problems and applications of this theme are covered. Process intensification is nowadays one of the most popular trends in chemical engineering and attempts have been made to develop a general, systematic methodology for intensification. This seems, however, to be very difficult, because intensified processes are often based on creativity and novel ideas. Monolith reactors and microreactors are successful examples of process intensification. They are usually multichannel devices in which a proper feed technique is important for creating even fluid distribution into the channels. Two different feed techniques were tested for monoliths. In the first technique a shower method was implemented by means of perforated plates. The second technique was a dispersion method using static mixers. Both techniques offered stable operation and uniform fluid distribution. The dispersion method enabled a wider operational range in terms of liquid superficial velocity. Using dispersion method, a volumetric gas-liquid mass transfer coefficient of 2 s-1 was reached. Flow patterns play a significant role in terms of the mixing performance of micromixers. Although the geometry of a T-mixer is simple, channel configurations and dimensions had a clear effect on mixing efficiency. The flow in the microchannel was laminar, but the formation of vortices promoted mixing in micro T-mixers. The generation of vortices was dependent on the channel dimensions, configurations and flow rate. Microreactors offer a high ratio of surface area to volume. Surface forces and interactions between fluids and surfaces are, therefore, often dominant factors. In certain cases, the interactions can be effectively utilised. Different wetting properties of solid materials (PTFE and stainless steel) were applied in the separation of immiscible liquid phases. A micro-scale plate coalescer with hydrophilic and hydrophobic surfaces was used for the continuous separation of organic and aqueous phases. Complete phase separation occurred in less than 20 seconds, whereas the separation time by settling exceeded 30 min. Fluid flows can be also intensified in suitable conditions. By adding certain additives into turbulent fluid flow, it was possible to reduce friction (drag) by 40 %. Drag reduction decreases frictional pressure drop in pipelines which leads to remarkable energy savings and decreases the size or number of pumping facilities required, e.g., in oil transport pipes. Process intensification enables operation often under more optimal conditions. The consequent cost savings from reduced use of raw materials and reduced waste lead to greater economic benefits in processing.

Magnetic and transport properties of LaMnO3+δ, La1-xCaxMnO3, La1-xCaxMn1-yFeyO3 and La1-xSrxMn1-yFeyO3

Interest to hole-doped mixed-valence manganite perovskites is connected to the ‘colossal’ magnetoresistance. This effect or huge drop of the resistivity, ρ, in external magnetic field, B, attains usually the maximum value near the ferromagnetic Curie temperature, TC. In this thesis are investigated conductivity mechanisms and magnetic properties of the manganite perovskite compounds LaMnO3+, La1-xCaxMnO3, La1-xCaxMn1-yFeyO3 and La1- xSrxMn1-yFeyO3. When the present work was started the key role of the phase separation and its influence on the properties of the colossal magnetoresistive materials were not clear. Our main results are based on temperature dependencies of the magnetoresistance and magnetothermopower, investigated in the temperature interval of 4.2 - 300 K in magnetic fields up to 10 T. The magnetization was studied in the same temperature range in weak (up to 0.1 T) magnetic fields. LaMnO3+δ is the parent compound for preparation of the hole-doped CMR materials. The dependences of such parameters as the Curie temperature, TC, the Coulomb gap, Δ, the rigid gap, γ, and the localization radius, a, on pressure, p, are observed in LaMnO3+δ. It has been established that the dependences above can be interpreted by increase of the electron bandwidth and decrease of the polaron potential well when p is increased. Generally, pressure stimulates delocalization of the electrons in LaMnO3+δ. Doping of LaMnO3 with Ca, leading to La1-xCaxMnO3, changes the Mn3+/Mn4+ ratio significantly and brings an additional disorder to the crystal lattice. Phase separation in a form of mixture of the ferromagnetic and the spin glass phases was observed and investigated in La1- xCaxMnO3 at x between 0 and 0.4. Influence of the replacement of Mn by Fe is studied in La0.7Ca0.3Mn1−yFeyO3 and La0.7Sr0.3Mn1−yFeyO3. Asymmetry of the soft Coulomb gap and of the rigid gap in the density of localized states, small shift of the centre of the gaps with respect to the Fermi level and cubic asymmetry of the density of states are obtained in La0.7Ca0.3Mn1−yFeyO3. Damping of TC with y is connected to breaking of the double-exchange interaction by doping with Fe, whereas the irreversibility and the critical behavior of the magnetic susceptibility are determined by the phase separation and the frustrated magnetic state of La0.7Sr0.3Mn1−yFeyO3.

Recovery and refining of manganese as by-product from hydrometallurgical processes

The consumption of manganese is increasing, but huge amounts of manganese still end up in waste in hydrometallurgical processes. The recovery of manganese from multi-metal solutions at low concentrations may not be economical. In addition, poor iron control typically prevents the production of high purity manganese. Separation of iron from manganese can be done with chemical precipitation or solvent extraction methods. Combined carbonate precipitation with air oxidation is a feasible method to separate iron and manganese due to the fast kinetics, good controllability and economical reagents. In addition the leaching of manganese carbonate is easier and less acid consuming than that of hydroxide or sulfide precipitates. Selective iron removal with great efficiency from MnSO4 solution is achieved by combined oxygen or air oxidation and CaCO3 precipitation at pH > 5.8 and at a redox potential of > 200 mV. In order to avoid gypsum formation, soda ash should be used instead of limestone. In such case, however, extra attention needs to be paid on the reagents mole ratios in order to avoid manganese coprecipitation. After iron removal, pure MnSO4 solution was obtained by solvent extraction using organophosphorus reagents, di-(2-ethylhexyl)phosphoric acid (D2EHPA) and bis(2,4,4- trimethylpentyl)phosphinic acid (CYANEX 272). The Mn/Ca and Mn/Mg selectivities can be increased by decreasing the temperature from the commonly used temperatures (40 –60oC) to 5oC. The extraction order of D2EHPA (Ca before Mn) at low temperature remains unchanged but the lowering of temperature causes an increase in viscosity and slower phase separation. Of these regents, CYANEX 272 is selective for Mn over Ca and, therefore, it would be the better choice if there is Ca present in solution. A three-stage Mn extraction followed by a two-stage scrubbing and two-stage sulfuric acid stripping is an effective method of producing a very pure MnSO4 intermediate solution for further processing. From the intermediate MnSO4 some special Mn- products for ion exchange applications were synthesized and studied. Three types of octahedrally coordinated manganese oxide materials as an alternative final product for manganese were chosen for synthesis: layer structured Nabirnessite, tunnel structured Mg-todorokite and K-kryptomelane. As an alternative source of pure MnSO4 intermediate, kryptomelane was synthesized by using a synthetic hydrometallurgical tailings. The results show that the studied OMS materials adsorb selectively Cu, Ni, Cd and K in the presence of Ca and Mg. It was also found that the exchange rates were reasonably high due to the small particle dimensions. Materials are stable in the studied conditions and their maximum Cu uptake capacity was 1.3 mmol/g. Competitive uptake of metals and acid was studied using equilibrium, batch kinetic and fixed-bed measurements. The experimental data was correlated with a dynamic model, which also accounts for the dissolution of the framework manganese. Manganese oxide micro-crystals were also bound onto silica to prepare a composite material having a particle size large enough to be used in column separation experiments. The MnOx/SiO2 ratio was found to affect significantly the properties of the composite. The higher the ratio, the lower is the specific surface area, the pore volume and the pore size. On the other hand, higher amount of silica binder gives composites better mechanical properties. Birnesite and todorokite can be aggregated successfully with colloidal silica at pH 4 and with MnO2/SiO2 weight ratio of 0.7. The best gelation and drying temperature was 110oC and sufficiently strong composites were obtained by additional heat-treatment at 250oC for 2 h. The results show that silica–supported MnO2 materials can be utilized to separate copper from nickel and cadmium. The behavior of the composites can be explained reasonably well with the presented model and the parameters estimated from the data of the unsupported oxides. The metal uptake capacities of the prepared materials were quite small. For example, the final copper loading was 0.14 mmol/gMnO2. According to the results the special MnO2 materials are potential for a specific environmental application to uptake harmful metal ions.

Kullan uutto kloridiliuoksista

Työssä tutkittiin kullan neste-nesteuuttoa kloridiliuoksista kirjallisuustutkimuksen ja laboratoriokokeiden avulla. Uuttoreagenssina käytettiin Outotecin kehittämää kullanuuttoreagenssia. Teoreettisessa osassa tarkastellaan kullan käyttäytymistä happamissa vesiliuoksissa, jotka sisältävät kloridia ja bromidia. Lisäksi työssä käsitellään kultakloridiyhdisteiden käyttöturvallisuutta. Teollisuudessa vuonna 2012 käytettäviä neste-nesteuuttoon perustuvia kullan talteenottomenetelmiä esitellään lyhyesti. Kirjallisuusosassa käsitellään myös joidenkin teollisesti käytettävien polymeeristen rakennemateriaalien ominaisuuksia. Kokeellisessa osassa määritettiin kullanuuttoreagenssin fysikaalisia ominaisuuksia, kuten sen tiheys, viskositeetti, liukoisuus veteen sekä faasien selkeytyminen uuttoprosessissa. Tuloksista havaittiin, että eri modifiointiaineet vaikuttavat huomattavasti kullanuuttoliuoksen fysikaalisiin ominaisuuksiin. Kullan uuttoa tutkittiin pienen mittakaavan laboratoriokokein käyttämällä synteettisiä kultaa sisältäviä lähtöliuoksia. Kokeissa tutkittiin lähtöliuoksen happopitoisuuden ja bromidipitoisuuden, sekä uuttoreagenssin modifiointiaineiden vaikutuksia kullan uuttotasapainoon. Lisäksi tutkittiin joidenkin epäpuhtausmetallien myötäuuttautumista. Materiaalitutkimuksissa tarkasteltiin kullanuuttoreagenssin ja autenttisen kullan halidiliuoksen vaikutuksia polymeerimateriaaleihin pitkäaikaisessa kontaktissa. Uuttoliuosten havaittiin aiheuttavan turpoamaa sekä pinnan pehmenemistä joissakin teollisissa muoveissa.

Tislauskolonnin pohjaosan likaantumisen vähentäminen sisärakenteita muuttamalla

Tässä työssä tutkittiin pohjaöljy-yksikössä sijaitsevan tislauskolonnin pohjaosan likaantumista ja likaantumisen vähentämistä kolonnin sisärakenteita muuttamalla. Tislauskolonnin likaantuminen aiheutuu raskaista molekyyleistä, asfalteeneistä, joita pohjaöljy sisältää. Pohjaöljyä krakattaessa kevyemmiksi tisleiksi asfalteenien liukoisuus pienenee. Asfalteenimolekyylit alkavat lopulta yhdistyä, minkä seurauksena muodostuu asfalteenejä sisältävä hiilimäinen mesofaasi. Radikaalireaktioiden kautta mesofaasista muodostuu koksia. Mesofaasi tarttuu tiukasti tislauskolonnin sisärakenteiden pinnoille aiheuttaen koksaantumista. Koksaantumisen seurauksena strippausvälipohjina käytettävien suihkupohjien tislausteho huononee. Koksaantumisen johdosta suihkupohjien ja kolonnin pohjaosan tukkeentumisen riski kasvaa. Suihkupohjien likaantumista pyritään vähentämään muuttamalla suihkupohjat sileiksi välipohjiksi ilman patolevyjä ja reikiä. Tällä tavoin saadaan neste virtaamaan vapaasti välipohjalta toiselle, mikä vähentää mesofaasin ja koksin muodostumista. Likaantumista voitaisiin myös vähentää tuomalla jäähdytyskiertopalautus välipohjille, minkä avulla neste saadaan jäähtymään nopeammin alle lämpökrakkautumislämpötilan, mikä vähentää koksaantumista. Kolonnin pohjaosassa sijaitsevan pohjaseulan likaantumista voitaisiin vähentää harventamalla pohjaseulan tankoja, mikä vähentää koksin tarttumapinta-alaa. Likaantumisen online-seurantaa saadaan parannettua lisäämällä pintalämpötilamittauksia järjestelmällisesti samoille korkeuksille kolonnin vastakkaisille puolille.

Influence of stationary phase and eluent properties on chromatographic separation of carbohydrates

In this thesis, the sorption and elastic properties of the cation-exchange resins were studied to explain the liquid chromatographic separation of carbohydrates. Na+, Ca2+ and La3+ form strong poly(styrene-co-divinylbenzene) (SCE) as well as Na+ and Ca2+ form weak acrylic (WCE) cation-exchange resins at different cross-link densities were treated within this work. The focus was on the effects of water-alcohol mixtures, mostly aqueous ethanol, and that of the carbohydrates. The carbohydrates examined were rhamnose, xylose, glucose, fructose, arabinose, sucrose, xylitol and sorbitol. In addition to linear chromatographic conditions, non-linear conditions more typical for industrial applications were studied. Both experimental and modeling aspectswere covered. The aqueous alcohol sorption on the cation-exchangers were experimentally determined and theoretically calculated. The sorption model includes elastic parameters, which were obtained from sorption data combined with elasticity measurements. As hydrophilic materials cation-exchangers are water selective and shrink when an organic solvent is added. At a certain deswelling degree the elastic resins go through glass transition and become as glass-like material. Theincreasing cross-link level and the valence of the counterion decrease the sorption of solvent components in the water-rich solutions. The cross-linkage or thecounterions have less effect on the water selectivity than the resin type or the used alcohol. The amount of water sorbed is higher in the WCE resin and, moreover, the WCE resin is more water selective than the corresponding SCE resin. Theincreased aliphatic part of lower alcohols tend to increase the water selectivity, i.e. the resins are more water selective in 2-propanol than in ethanol solutions. Both the sorption behavior of carbohydrates and the sorption differences between carbohydrates are considerably affected by the eluent composition and theresin characteristics. The carbohydrate sorption was experimentally examined and modeled. In all cases, sorption and moreover the separation of carbohydrates are dominated by three phenomena: partition, ligand exchange and size exclusion. The sorption of hydrophilic carbohydrates increases when alcohol is added into the eluent or when carbohydrate is able to form coordination complexes with the counterions, especially with multivalent counterions. Decreasing polarity of the eluent enhances the complex stability. Size exclusion effect is more prominent when the resin becomes tighter or carbohydrate size increases. On the other hand,the elution volumes between different sized carbohydrates decreases with the decreasing polarity of the eluent. The chromatographic separation of carbohydrateswas modeled, using rhamnose and xylose as target molecules. The thermodynamic sorption model was successfully implemented in the rate-based column model. The experimental chromatographic data were fitted by using only one adjustable parameter. In addition to the fitted data also simulated data were generated and utilized in explaining the effect of the eluent composition and of the resin characteristics on the carbohydrate separation.

Modeling of electrolyte sorption – from phase equilibria to dynamic separation systems

In this thesis, general approach is devised to model electrolyte sorption from aqueous solutions on solid materials. Electrolyte sorption is often considered as unwanted phenomenon in ion exchange and its potential as an independent separation method has not been fully explored. The solid sorbents studied here are porous and non-porous organic or inorganic materials with or without specific functional groups attached on the solid matrix. Accordingly, the sorption mechanisms include physical adsorption, chemisorption on the functional groups and partition restricted by electrostatic or steric factors. The model is tested in four Cases Studies dealing with chelating adsorption of transition metal mixtures, physical adsorption of metal and metalloid complexes from chloride solutions, size exclusion of electrolytes in nano-porous materials and electrolyte exclusion of electrolyte/non-electrolyte mixtures. The model parameters are estimated using experimental data from equilibrium and batch kinetic measurements, and they are used to simulate actual single-column fixed-bed separations. Phase equilibrium between the solution and solid phases is described using thermodynamic Gibbs-Donnan model and various adsorption models depending on the properties of the sorbent. The 3-dimensional thermodynamic approach is used for volume sorption in gel-type ion exchangers and in nano-porous adsorbents, and satisfactory correlation is obtained provided that both mixing and exclusion effects are adequately taken into account. 2-Dimensional surface adsorption models are successfully applied to physical adsorption of complex species and to chelating adsorption of transition metal salts. In the latter case, comparison is also made with complex formation models. Results of the mass transport studies show that uptake rates even in a competitive high-affinity system can be described by constant diffusion coefficients, when the adsorbent structure and the phase equilibrium conditions are adequately included in the model. Furthermore, a simplified solution based on the linear driving force approximation and the shrinking-core model is developed for very non-linear adsorption systems. In each Case Study, the actual separation is carried out batch-wise in fixed-beds and the experimental data are simulated/correlated using the parameters derived from equilibrium and kinetic data. Good agreement between the calculated and experimental break-through curves is usually obtained indicating that the proposed approach is useful in systems, which at first sight are very different. For example, the important improvement in copper separation from concentrated zinc sulfate solution at elevated temperatures can be correctly predicted by the model. In some cases, however, re-adjustment of model parameters is needed due to e.g. high solution viscosity.

Studies of Liquid-liquid Separation in Fibre Coalescer

This thesis focuses on fibre coalescers whose efficiency is based on the surface properties/characteristics. They have the ability to preferentially wet or interact with one or more of the fluids to be separated. Thus, the interfacial phenomena governing the separation efficiency of the coalescers is investigated depending on physical factors such as flowrates, phase ratios and coalescer packing density. Design of process equipment to produce and separate of the emulsions was carried out.The experimentation was carried out to test the separation efficiency of the coalescing medias, namely fibreglass, polyester I and polyester II. The performances of the coalescing medias were assessed via droplet size information. In conclusion, the objectives (design of process equipment and experimentation) were achieved. Fibre glass was the best coalescing media, next was polyester I and then finally polyester II. Droplets sizes increased with decreased flowrates and increased packing density of the coalescer. Phase ratio had effect on the droplet sizes of the feed but had no effect on the coalescence of droplets of the feed.