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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
631

Concept development to extract sodium sulfate from an aqueous solution

Selander, André January 2021 (has links)
Now when the interest is increasing to reach a sustainable infrastructure, one possibility SCA is experimenting with is the possibility to produce renewable hydrocarbons from black liquor which can be extracted from a Kraft process. However, when extracting the black liquor, a lot of sodium-based compounds are removed from the recovery process and when hydrocarbons are produced in SCA’s biorefinery, these compounds are caught in an aqueous solution. The aqueous solution is received at 50°C, and the sodium-based compounds are mainly sodium sulfate and sodium carbonate, where the solution do also contain organic compounds and a solvent that is used in the biorefinery.  This thesis focused on building a concept to extract sodium sulfate from the aqueous solution. The thesis did also include if any additional preparatory work needs to be done to the solution before extracting sodium sulfate. Finally, a flow chart that maps the energy needed for the process was created.  The method that was used was crystallisation by cooling the solution. By cooling the solution, sodium sulfates solubility decreases which will result in that sodium sulfate falls out of the solution as crystals. It was determined that the solvent that the solution contains should be extracted if the solvents boiling temperature is below 100°C. Further, by cooling the solution under stirring to 15°C with a residence time of 3 hours, unwanted compounds can be extracted. By later cooling the solution under stirring to 5°C with a residence time of 1 hour, it gave sodium sulfate decahydrate (Na2SO4·10H2O) with small amounts of organic compounds. By removing the water, the dry product reached a purity of 94wt% sodium sulfate with a yield of 12% (mass of dry product/mass of aqueous solution). This result reached the specific objectives that were set at the start of this thesis, which was to reach a purity of 90wt% sodium sulfate with a yield of 5%.  The energy intensity for evaporating the solvent is expected to be high. It highly depends on which solvent is used. However, this process can use the lowest quality of steam that is available from the pulp mill. It is expected that the cooling will require high amounts of cooling water and a high investment cost for the heat exchanger. Yet, this is a vital part of the process to reduce the need for coolers which is powered by electricity. / Nu när intresset ökar, för att nå en hållbar infrastruktur, så experimenterat SCA med möjligheten att producera förnybara kolväten från svartlut som kan extraheras från en sulfatprocess. Vid extrahering av svartluten tas dock mycket natriumbaserade föreningar bort från återvinningsprocessen och när kolväten produceras i SCA:s bioraffinaderi fastnar dessa föreningar i en vattenlösning. Den lösningen tas emot vid 50°C och de natriumbaserade föreningarna är huvudsakligen natriumsulfat och natriumkarbonat, där lösningen också innehåller organiska föreningar och ett lösningsmedel som används i bioraffinaderiet. Denna avhandling fokuserade på att bygga ett koncept för att extrahera natriumsulfat från vattenlösningen. Avhandlingen omfattade också om ytterligare förberedande arbete måste göras av lösningen innan man extraherar natriumsulfat. Slutligen skapades ett flödesschema som kartlägger den energi som behövs för processen. Metoden som bestämde sig för att användas var kristallisering genom kylning av lösningen. Genom att kyla lösningen minskar lösligheten av natriumsulfater vilket leder till att natriumsulfat faller ut ur lösningen som kristaller. Det bestämdes att lösningsmedlet som lösningen innehåller skulle extraheras om lösningsmedlets koktemperatur är under 100°C. Vidare, genom att kyla lösningen under omrörning till 15°C med en uppehållstid på 3 timmar, kan oönskade ämnen extraheras. Genom att senare kyla lösningen under omrörning till 5°C med en uppehållstid på 1 timme gav natriumsulfatdekahydrat (Na2SO4·10H2O) med små mängder organiska föreningar. Genom att avlägsna vattnet nådde den torra produkten en renhet av 94 vikt% natriumsulfat med ett utbyte av 12% (massa torr produkt/massa vattenlösning). Detta resultat nådde de specifika mål som sattes i början av denna avhandling, vilket var att nå en renhet av 90 vikt% natriumsulfat med ett utbyte på 5%. Energiintensiteten för att förånga lösningsmedlet förväntas vara hög. Det beror mycket på vilket lösningsmedel som används. Denna process kan dock använda den lägsta ångkvaliteten som finns tillgänglig från massafabriken. Det förväntas att kylningen kommer att kräva stora mängder kylvatten och höga investeringskostnader för värmeväxlaren. Ändå är detta en viktig del av processen för att minska behovet av kylare som drivs av elektricitet.
632

Percolated Si:SiO2 Nanocomposites: Oven- vs. Millisecond Laser-induced Crystallization of SiOx Thin Films

Schumann, E., Hübner, R., Grenzer, J., Gemming, S., Krause, M. 07 May 2019 (has links)
Three-dimensional nanocomposite networks consisting of percolated Si nanowires in a SiOx matrix, Si:SiO2, were studied. The structures were obtained by reactive ion beam sputter deposition of SiOx (x~0.6) thin films at 450 °C and subsequent crystallization using conventional oven as well as millisecond line focus laser annealing. Rutherford backscattering spectrometry, Raman spectroscopy, X-ray diffraction, cross-sectional and energy-filtered transmission electron microscopy were applied for sample characterization. While oven annealing resulted in a mean Si wire diameter of 10 nm and a crystallinity of 72 % within the Si volume, almost single-domain Si structures with 30 nm in diameter and almost free of amorphous Si were obtained by millisecond laser application. The structural differences are attributed to the different crystallization processes: Conventional oven tempering proceeds via solid state, millisecond laser application via liquid phase crystallization of Si. The 5 orders of magnitude larger diffusion constant in the liquid phase is responsible for the three times larger Si nanostructure diameter. In conclusion, laser annealing offers not only significantly shorter process times but moreover a superior structural order of nano-Si compared to conventional heating.
633

Minimization of chemical's release from a large-scale pharmaceutical industry : By optimization of the crystallization process / Minimering av utsläpp av kemikalier från en storskalig läkemedelsfabrik : Genom optimering av kristallisationsprocessen

Rahn, Cecilia January 2021 (has links)
The presence of active pharmaceutical ingredients (APIs) and other chemicals in wastewater has caused concerns in recent years due to its potential risk to the environment and society. Thus, the aim of the study is to investigate ways to minimize the release of chemicals from a large-scale pharmaceutical industry to an industrial wastewater treatment plant. The large-scale industry that is studied is located at Cambrex Karlskoga AB and the process that is investigated is the production of the intermediate R1-MR2E, from a carboxylic acid and an alcohol through an esterification. The investigations are performed by modifying a HPLC-UV method and mapping the release of the carboxylic acid and R1-MR2E as well as examining possible ways of minimizing the release by optimization of the crystallization of the recirculation of the carboxylic acid and of the product R1-MR2E. The method used in the investigation is mostly the modified HPLC-UV method. The optimizations are performed by examining the effect of the maturation time on the crystallization of the recirculated carboxylic acid, and by investigating the effect that a concentrated solution has on the pH of crystallization. The results indicate a possibility to remove the washing water of the recirculated carboxylic acid in order to minimize the release of the compound and R1-MR2E without affecting the quality of R1-MR2E. The results also show that a minimized amount of solvent can be used in the crystallization of R1-MR2E without affecting the process. / Förekomsten av aktiva läkemedelsingredienser (API) och andra kemikalier i avloppsvatten har orsakat stor oro de senaste åren på grund av dess potentiella risk för miljö och samhälle. Syftet med studien är därmed att undersöka sätt att minimera utsläppet av kemikalier från en storskalig läkemedelsindustri till ett industriellt reningsverk. Den storskaliga industrin som studeras är Cambrex Karlskoga AB och processen som undersöks är produktionen av intermediatet R1-MR2E, från en karboxylsyra och en alkohol genom en esterifiering. Undersökningarna utförs genom att modifiera en HPLC-UV metod och kartlägga utsläppet av karboxylsyran och R1-MR2E, samt genom att undersöka möjliga sätt att minimera utsläppet genom optimering av kristalliseringen vid återcirkulation av karboxylsyran och av produkten R1-MR2E. Metoden som används i undersökningarna är mestadels den modifierade HPLC-UV metoden. Optimeringarna utförs genom att undersöka effekten som mognadstiden har på kristallisationen av den återcirkulerade karboxylsyran och genom att undersöka effekten som en koncentrerad lösning har på kristallisationens pH. Resultatet indikerar en möjlighet att avlägsna tvättvattnet vid återcirkulering av karboxylsyran för att minimera utsläppet av föreningen och R1-MR2E utan att påverka kvaliteten på R1-MR2E. Resultatet visar även att en minimerad mängd lösningsmedel kan användas i kristallisationen av R1-MR2E utan att påverka processen.
634

Preparation of a Flavonol Specific Glucosyltransferase found in Grapefruit and Site-Directed Mutants for Protein Crystallization

Birchfield, Aaron 01 May 2019 (has links)
This research was designed to determine the conditions necessary to remove c-myc and 6x-His tags from a flavonol specific glucosyltransferase found in grapefruit (CP3GT) using thrombin in preparation for crystallization. X-ray crystallography of CP3GT crystals may elucidate structural features that account for flavonol specificity in some glucosyltransferase enzymes. A thrombin cleavage site was inserted into WT CP3GT and one mutant. Recombinant CP3GT was expressed in yeast and purified. Optimal conditions for thrombin digestion were explored. Digestion with 100U of thrombin for 2 hours at 4o C was optimal for removing tags from CP3GT. Storage at 4o C for 2 hours resulted in approximately 70% retention of activity. The effect of thrombin treatment on CP3GT activity was tested. Purified CP3GT protein with and without tags was tested for activity with the flavonol quercetin. Data showed no significant difference in overall activity between tagged and native protein.
635

Effect of High Intensity Ultrasound on the Crystallization Behavior of Interesterified Fats

Kadamne, Jeta Vijay 01 May 2018 (has links)
The process of partial hydrogenation produces trans fats and the fats that undergo this process are called partially hydrogenated fats (PHF). Clinical studies have shown a strong association between PHF and coronary heart diseases. In 2015 The U.S. Food and Drug Administration removed the Generally recognized as safe or "GRAS" status of PHF. These fats were used in confectionary, margarines, shortenings, doughnuts, cookies, cakes, etc. The PHF serve a function in food by providing a higher shelf life and a desired harder structure due to their higher melting point. Hence, the food industry is currently looking for PHF alternatives which serve the function but have no harmful health effects. One of the alternatives to replace PHF is to use interesterified fats that have a low level of saturation that makes them healthier. However, these new fats are too soft with restricted use in many food applications. In this study, we explored the use of high intensity ultrasound (HIU) to improve the functional properties of interesterified fats and make them harder. Our study showed that HIU formed small crystals in these fats and increased their viscosity. The results from this study on the flavor release from the interesterified fats showed that the physical structure and hence the amount of solid fat in the sample affected its flavor perception. The solid fats had higher flavor perception than the liquid fat samples. The goal of this study is to improve the functionality of the interesterified fats using HIU and understand the flavor release from these fats to make substitution in food products easier.
636

Modélisation et simulation de l’encrassement des échangeurs de chaleur pour eaux géothermales / Modelling and simulation of the fouling of heat exchangers used with geothermal water

Cazenave, Florian 08 October 2019 (has links)
Dans le cadre de la thématique consacrée à la transition énergétique, le Laboratoire de Thermique Energétique et Procédés (LaTEP) travaille sur la géothermie profonde. Cette thèse se focalise sur l’étude de l’encrassement des échangeurs de chaleur de surface et plus spécifiquement sur la modélisation et la simulation de l’évolution d’un dépôt. L’encrassement conduit à des pertes d’efficacité et nécessite la mise en place de moyens de prévention ou de nettoyage, entraînant d’importants surcoûts. Le modèle général proposé décrit des réactions hétérogènes entre deux phases multi-constituantes, l’une liquide et l’autre solide. La phase liquide est une solution contenant des ions dilués dans un solvant, tandis que le solide est composé de constituants immobiles. L’électro-migration des espèces est prise en compte dans la description. L’interface entre les deux phases est le siège de multiples réactions hétérogènes. Les conditions aux limites faisant intervenir la vitesse de l’interface permettent le couplage complet entre les deux domaines. Ce modèle général est ensuite appliqué au cas particulier de l’encrassement d’un tube par formation de sels et résolu à l’aide de Comsol Multiphysics. La simulation d’un cas simplifié d’encrassement par le sulfate de baryum a permis d’analyser la phénoménologie de la croissance du dépôt et de mettre en évidence les effets des évolutions de la solubilité et de la cinétique via la chute de température dans le tube, ainsi que de la mobilité radiale des espèces par diffusion qui limite la croissance. L’électro-migration participe significativement au transport mais n’influence pas l’épaisseur du dépôt. L’hypothèse d’une réaction de cristallisation de la barytine instantanément équilibrée conduit à une forte surestimation de l’encrassement. La composition de l’eau est ensuite complexifiée afin d’étudier l’influence de la présence du chlorure de sodium à 1 mol.L-1, puis d’ions strontium et ainsi la co-précipitation de barytine et de célestine. / In the framework of the theme devoted to the energy transition, the “Laboratoire de Thermique Energétique et Procédés” (LaTEP) is working on deep geothermal energy. This thesis focuses on the study of the fouling phenomenon of surface heat exchangers and more specifically on the modelling and the simulation of the evolution of a deposit. Fouling leads to loss of efficiency and requires means of prevention and cleaning, leading to huge over-costs. The proposed general model describes heterogeneous reactions between two multi-component phases, one liquid and the other solid. The liquid phase is a solution containing ions diluted in a solvent, while the solid is composed of immobile constituents. Transport by electro-migration is taken into account in the description. At the interface between the two phases, multiple heterogeneous reactions occur. The boundary conditions involves the interface’s velocity and allow a complete coupling between the two domains. This general model is then applied to the particular case of fouling of a pipe by salt formation and is solved using Comsol Multiphysics. Simulation of a simplified case of fouling from barium sulfate allowed an analysis of the phenomenology of the deposit growth. It highlights the effects of changes in solubility and kinetics caused by the temperature drop in the tube, as well as the effect of radial mobility of the species by diffusion, limiting the growth. Electro-migration contributes significantly to transport but does not influence the thickness of the deposit. The hypothesis of an instantly balanced barite crystallization reaction leads to an overestimation of the fouling. In a second time, more species are added to the water’s composition in order to study the influence of the presence of sodium chloride at 1 mol.L-1. Finally, the addition of strontium ions leads to co-precipitation of barite and celestine.
637

Desenvolvimento de vitrocerâmico utilizando escória de fundição /

Leme, Thariany Sanches January 2019 (has links)
Orientador: Agda Eunice de Souza Albas / Resumo: Neste trabalho, vidro e material vitrocerâmico foram obtidos a partir de uma composição baseada no diagrama ternário SiO2-Al2O3-CaO, utilizando escória de ferro fundido, provenientes de empresas de fundição, e, cal hidratada (comercial). A escória foi caracterizada através de: espectrometria de fluorescência de raios X (FRX), para determinar sua composição química; difratometria de raios X (DRX), para a identificação das fases cristalinas e análise térmica (TG), para evidenciar as reações térmicas associadas à desidratação e decomposição dos compostos presente no material. O vidro foi obtido através do processo de fusão/resfriamento (melt-quenching), fundido na temperatura de 1450°C. Foram caracterizados através de: calorimetria exploratória diferencial (DSC), para determinar as temperaturas de transição vítrea e de cristalização e difratometria de raios X (DRX), para identificar a sua estrutura amorfa. O estudo da cinética de cristalização do vidro foi realizado através de métodos cinéticos não isotérmicos baseados na descrição teórica formulada por Johnson-Mehl-Avrami (JMA). Estes métodos descrevem os processos de nucleação e cristalização utilizando dados provenientes da curva de DSC. O estudo cinético teve início com a obtenção do material vitrocerâmico tratado termicamente à 900ºC por 1,5h e identificação das fases cristalinas formadas, utilizando DRX. Considerando a formação de três fases cristalinas, os parâmetros cinéticos foram determinados a partir dos ajustes dos d... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work, glass and glass-ceramic materials were obtained from a composition based on the ternary diagram SiO2-Al2O3-CaO using cast iron slag from foundry companies and hydrated lime (commercial). The slag was characterized by: X-ray fluorescence (XRF) to determine its chemical composition; X-ray diffractometry (XRD), to the crystalline phases identification and thermal analysis (TG), to show the thermal reactions associated with dehydration and decomposition of the compounds present in the material. The glass was obtained by melt quenching at 1450°C. They were characterized by differential scanning calorimetry (DSC) to determine glass transition and crystallization temperatures and X-ray diffraction (XRD) to identify their amorphous structure. The study of crystallization kinetics was performed by non-isothermal kinetic methods based on the theoretical description formulated by Johnson-Mehl-Avrami (JMA). These methods describe the nucleation and crystallization processes using data from the DSC data. The kinetic study began by obtaining heat-treated glass-ceramic material, at 900ºC for 1.5h, and identifying the crystalline phases formed using XRD. Considering three crystalline phases formation, the kinetic parameters were determined from the DSC data adjustments by the Kissinger, Augis-Bennett, and Matusita and Sakka methods. The best fit resulted in three crystallization peaks. The activation energy (Ea) of the crystallization process was obtained using the Kissinger an... (Complete abstract click electronic access below) / Mestre
638

Synthesis and Characterization of Novel Telechelic High Performance Polyester Ionomers

Kang, Huaiying 04 December 2001 (has links)
Novel poly(ethylene isophthalate) (PEI) and poly(ethylene terephthalate) (PET) polymers containing terminal units derived from sodio 3-sulfobenzoic acid (SSBA) were synthesized using catalyzed melt polymerization techniques. Various concentrations of the ionic end group, SSBA, were successfully incorporated in a telechelic fashion. For comparison, polyesters containing telechelic alkyl groups with controllable molecular weights were also synthesized. Furthermore, ionic copolymers of dimethyl isophthalate and trans-cyclohexane dicarboxylate, dimethyl isophthalate and dimethyl terephthalate were synthesized to study the influences of polarity and rigidity of the polymer chain backbone on material properties. Novel branched polyester ionomers using trimellitic anhydride were also prepared. In addition to modifying the polymer compositions, PET ionomers were blended with zinc stearate to investigate the effect of plasticizer on the melt processibilty of the ionomers. FTIR spectroscopy, which was used to quantify the sulfonate end groups for all of the ionomers, indicated an absorbance peak for the S-O stretching mode between 600-700 cm⁻¹. ¹H NMR spectroscopy was used to confirm the structure of the ionic and non-ionic polyesters, as well as to verify the presence of the terminal groups. By systematically varying the chemical structure of these ionomer model systems (i.e., altering the contents of ionic functional groups), detailed characterizations were carried out, wherein the ionic interactions/aggregations in the ionomers were found to play an important role in the resulting material properties. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements were performed to study the effects of ionic groups and oligomer composition on the thermal properties of the polyesters. The glass transition temperatures of the ionomers revealed that the ionic interaction helped to maintain the structural integrity of the polymer chains, thus limiting their mobility. The dilute solution viscosity behavior of the ionomers exhibited upward curvature, which is a key characteristic of an ionomer. In PEI ionomers, the ionic aggregates formed at lower temperatures (<150 °C), while at higher temperatures (>150 °C), the ionic aggregations dissociated and behaved similarly to oligomers with lower molecular weights. Dodecanol was used as an effective end-capper to control the molecular weight of the non-ionic polyesters. In addition to telechelic ionic PEI and PET homopolymers, copolymers of poly(ethylene isophthalate-co-trans-1,4-cyclohexane dicarboxylate) (PEI-co-trans-CHDC) and poly(ethylene isophthalate-co-terephthalate) (PEIT) telechelic ionomers were also synthesized and characterized. Introducing trans-1,4-cyclohexane dicarboxylate into PEI ionomers decreased the polarity and packing regularity of the polymer chains. Also, the kinked-structure of dimethyl isophthalate reduced the regularity of the polymer chains in PET ionomers, thus reducing their propensity for rapid crystallization. Crystallization kinetics were studied for both ionic and alkyl telechelic polyesters, and resulting data revealed that the nature of the endgroup had a dramatic effect on crystallization from the melt state. The catalyst residue in the polymers also affected the crystallization rate for both ionic and non-ionic polyesters. With regard to the ionomers, antimony catalyst interacted with ionic aggregates, further increasing the crystallization rate. Branched PEI and PET ionomers showed an increase in melt strength. After blending with zinc stearate, the melt viscosity of the PET ionomers dropped dramatically. / Master of Science
639

Vývoj nových druhů plynotěsných a vodotěsných povrchových úprav / RESEARCH OF NEW TYPES GAS AND WATER-TIGHTNESS SURFACE TREATMENTS

Bohuš, Štěpán January 2013 (has links)
The work deals with the development of new types of gas and waterproof tight coatings based on secondary crystallization of cement, using industrial waste as secondary raw material in the formulation of new recipes.
640

The Approach to Characterizing Three <i>S</i>-Adenosyl-L-Methionine-Dependent Methyltransferases from <i>Mycobacterium tuberculosis</i>

Loarer, Gwendal January 2018 (has links)
No description available.

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