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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.
51

Avaliação de técnicas de separação combinadas para a purificação de xilose visando a obtenção de bioprodutos / Evaluation of combined separation techniques for the xylose purification aiming a production of bioproducts

Magacho, Ana Luísa Ferreira 17 February 2009 (has links)
O presente trabalho teve como objetivo avaliar o uso combinado de processos de separação, visando a adequação do substrato rico em xilose (hidrolisado de bagaço de cana) para a obtenção de produtos por via fermentativa. Foram estudados processos como coagulação e precipitação seletiva de impurezas coloidais, separação com membranas de microfiltração e ultrafiltração e resinas de troca iônica, tendo como ponto de partida o hidrolisado concentrado 5,56 vezes (hidrolisado H1). Na avaliação dos ensaios de coagulação e precipitação foi utilizado planejamento fatorial fracionado, o qual auxiliou o estudo da performance de agentes coagulantes (policloreto de alumínio e polieletrólito aniônico), em diferentes concentrações, pHs e temperaturas. Como variável resposta foi determinado a redução de compostos fenólicos, resultando numa diminuição final de 32,67% e num modelo matemático que representa os parâmetros envolvidos no processo:[C. Fenólicos] = 13,82 + 4,54xpH + 0,03xPAC - 0,58xpH2 + 0,19xPAC2 - 0,25xpHxPAC. Após a determinação das melhores condições experimentais desta etapa, aplicou-se este modelo numa escala 36 vezes maior, resultando em uma diminuição de 10,49% destes contaminantes, produzindo o hidrolisado H2. Este hidrolisado foi percolado por resinas, e assim, determinou-se a série de resinas de troca iônica mais eficiente (série I: Amberlyst 15Wet, Amberlite FPA98, Amberlite 252Na e Amberlite IRA96). Esta etapa proporcionou uma redução de 96,29% no índice de cor, 98,72% dos compostos fenólicos, 74,19% do hidroximetilfurfural, 55,56% de furfural e 52,03% de ácido acético, utilizando um volume de leito de 20 mL, por coluna de resina. O hidrolisado H2, também, foi utilizado para a determinação do melhor modo de permeação por membranas de separação. Neste caso, optou-se em utilizar somente a membrana de ultrafiltração. A permeação do hidrolisado H2 por esta membrana resultou no hidrolisado H3, e em reduções de 12,50% de ácido acético, 33,00% de compostos fenólicos e 54,29% no índice de cor. Assim, o hidrolisado H3 foi percolado pela série de resinas mais eficiente, obtendo ao final uma diminuição de 63,29% do ácido acético, 75,86% de furfural, 77,78% de hidroximetilfurfural e 88,09% dos compostos fenólicos, promovendo uma redução de 90,90% no índice de cor. A seguir, o hidrolisado purificado foi submetido a fermentações para a produção de xilitol e etanol. Essas bioconversões foram aptas a produzir 0,250g/L.h de xilitol e 0,265g/L.h de etanol além de apresentarem rendimentos de 0,68g/g de xilitol por xilose consumida e 0,30g/g de etanol por xilose consumida. Estes resultados indicam a boa fermentabilidade do hidrolisado tratado pelo processo combinado proposto. / This study evaluated the combined use of separation processes, seeking the adequacy of the substrate rich in xylose (hydrolysate of sugar cane bagasse) in the attainment of products from fermentative processes. During this research processes as coagulation and precipitation of selective colloidal impurities, microfiltration and ultrafiltration membranes separations and ion exchange resins were studied, taking as its starting point a hydrolysate concentrate 5.56 times (hydrolysate H1). During the tests of coagulation and precipitation a fraction factorial design was applied, which helped the study of coagulating agents performance (aluminum polychloride and anionic polyelectrolyte) in different concentrations, pH and temperatures. The response variable utilized was phenolic compounds reduction resulting in a drop of 32.67% and the mathematical model that represents the parameters involved in the process was: [C. Fenólicos] = 13.82 + 4.54 xpH + 0.03 xPAC - 0.58 xpH2 + 0.19 xPAC2 - 0.25 xpHxPAC. After determining the best experimental conditions of this step, this model was applied on a scale 36 times greater resulting in a decrease of 10.49% on contaminants, producing the hydrolysate H2. This hydrolysate was percolated through resins and determined the sequence of ion exchange resins more efficient; Serie I (Amberlyst 15Wet, Amberlite FPA98, Amberlite 252Na and Amberlite IRA96). This step reduced 96.29% in the index of color, 98.72% of phenolic compounds, 74.19% of hydroxymethylfurfural, 55.56% of furfural and 52.03% acetic acid, using a bed volume of 20 mL for each resin column. The hydrolysate H2 also was used to determine the best way of membranes permeation. In this case, opted to use only the ultrafiltration membrane. The permeation of the hydrolysate H2 through membrane resulted the hydrolysate H3, and showed reductions of 12.50%, 33.00% and 54.29% in acetic acid, phenolic compounds and index of color, respectively. Thus, the hydrolysate H3 was percolated through the resins series more efficient, obtaining a decrease of 63.29% of acetic acid, 75.86% of furfural, 77.78% of hydroxymethylfurfural and 88.09% of phenolic compounds, promoting a reduction of 90.90% in the index of color on the finish treatment. So this hydrolysate purified was subjected to fermentations for the production of xylitol and ethanol. These bioconversions were able to produce 0.250 g/L.h of xylitol and 0.265g/L.h of ethanol and showed xylitol yield from xylose of 0.68g/g and ethanol yield from xilose of 0.30g/g in ethanol. Theses results indicate the good fermentability of the hydrolysate treated by proposed combined process.
52

Lokal provtagning och analys på rökgaskondensat för driftövervakning av tungmetallrening med jonbytarmassor

Olofsson, Emelie January 2020 (has links)
I värme- och kraftvärmeverk förbränns olika typer av bränslen för produktion av el och fjärrvärme. Vid förbränningen bildas rökgaser som innehåller föroreningar, till exempel tungmetaller, från bränslet. Anläggningarna har ofta krav på utsläpp både via rökgaserna och avloppsvatten. Rökgaserna renas därmed genom olika tekniker var av en vanlig teknik är rökgaskondensering. Vid rökgaskondenseringen bildas en vätska, kallad rökgaskondensat, som delvis innehåller tungmetaller från bränslet. Rökgaskondensatet måste renas innan det kan lämna anläggningen och det görs bland annat med tungmetalljonbytare. Jonbytarmassan i tungmetalljonbytarkolonnerna behöver bytas ungefär två gånger per driftsäsong då den inte längre kan binda mer tungmetaller. Detta är en kostnad för värme- och kraftvärmeverken som de vill minimera. I denna studie undersöktes om lokal provtagning och analys på ett kraftvärmeverk av ett antal utvalda tungmetaller i rökgaskondensat är en bra metod för att optimering av reningssteget med tungmetalljonbytare. Samt om detta kan säkerställa att miljökraven för tungmetaller i det renade rökgaskondensatet uppfylls. Med optimering avses att jonbytarmassornas fulla kapacitet utnyttjas, d.v.s. att byten av jonbytarmassor kan reduceras utan att riskera otillåtna halter av tungmetaller i de renade rökgaskondensatet till följd av att jonbytarmassorna använts för länge. Även tiden som behöver avsättas för lokal provtagning och analys dokumenterades. I dagsläget sker analyser hos ackrediterade laboratorium där det tar drygt två veckor att få resultatet och under väntetiden kan mycket på anläggningen förändras. En verifiering av resultaten från studien gjordes mot resultat från ett sådant. I denna studie undersöktes lokal provtagning och analys med mätinstrumentet FREEDD som bygger på tekniken kvartskristall mikrobalans (QCM-teknik). Andra alternativ för lokal analys har inte undersökts här.  Resultatet visade att det i dagsläget är svårt att med lokal provtagning optimera reningssteget med jonbytarmassor samt kontrollera utsläppen av tungmetaller via det renade rökgaskondensatet. Korrigeringar hos mätinstrumentet och provpunkterna behöver göras för att få pålitligt resultat. Tiden som behöver avsättas för provtagning och analys beror på vilken metall som ska analyseras då tiden för preparering av prov varierar. Men om det kan möjliggöra att anläggningarna kan använda jonbytarmassorna längre samt får kontroll på utsläppen via det renade rökgaskondensatet kan det vara lönsamt att avvara den tiden. / In heating and combined heat and power plants, different types of fuels are burned to produce electricity and district heating. During the combustion flue gases containing pollutants, such as heavy metals, are formed from the flue. The plants have requirements for low emissions, both from the flue gases and the wastewater. The flue gases are purified by various techniques and a common technique is flue gas condensation. During the flue gas condensation, a liquid called flue gas condensate, is formed, which partly contains heavy metals from the flue. The flue gas condensate must be cleaned before it can leave the plant. A step in the purification of the flue gas condensate is usually heavy metal ion-exchanger. The ion-exchange mass in the heavy metal ion-exchange columns needs to be changed approximately twice per operating season as it no longer has room to bind more heavy metals. This is an expensive cost for the heating and combined heat and power plants that they want to minimize. This study investigated whether local sampling and analysis at a cogeneration plant of a number selected heavy metals in flue gas condensate is a good method for optimizing the purifications step with heavy metal ion-exchangers. And if this can ensure that the environmental requirements for the heavy metals in the purified flue gas condensate are met. Optimization means that the full capacity of the ion-exchange masses is utilized, i.e. that the exchange of ion-exchange masses can be reduced without risking unauthorized levels of heavy metals in the purified flue gas condensate as a result of the ion exchange masses being used for too long.  The time needed for local sampling and analysis was also documented. At present, analyzes are done at accredited laboratories where it takes over two weeks to get the result and during that time much can be changes at the plant. A verification of the result of the study was also made against the result of an accredited laboratory. In this study, local analysis was made with the measuring instrument FREEDD which is based on quartz crystal microbalance (QCM-technology). Other options for local sampling and analysis have not been investigated. The result showed that, in the present, it is difficult to optimize the purification step with ion-exchange masses and check emissions of heavy metals with the purified flue gas condensate. To obtain reliable result, corrections to the measuring instrument and test points need to be made. The time that needs to be set aside for sampling and analysis depends on the metal, as the time for sample preparation varies.  But if it can enable the plants to use the ion-exchange masses longer and gain control of the emissions of heavy metals with the purified flue gas condensate, it can be profitable to save that time.
53

Résine échangeuse d’ions en mode biologique pour l’enlèvement de matières organiques naturelles des eaux de surface

Liu, Zhen 08 1900 (has links)
La matière organique naturelle (MON) est omniprésente dans les eaux de surface. Bien que l’exposition à la MON via l’eau potable soit commune et ne soit pas associée à des effets directs sur la santé humaine, la MON peut avoir des impacts négatifs sur la production d’eau potable, tels que la contribution aux goûts et odeurs, le développement du biofilm dans les systèmes de distribution et la formation de sous-produits de désinfection. La résine échangeuse d’ions en mode biologique (en anglais : Biological ion exchange, BIEX) est un processus prometteur pour l’enlèvement de la MON des eaux de surface. Il s’agit d’opérer la résine échangeuse d’ions dans un réacteur à lit fixe avec une régénération peu fréquente de sorte qu’une communauté microbienne peut se développer sur la surface de résine et ainsi contribuer à l’enlèvement de la MON par biodégradation. Néanmoins, les mécanismes de l’enlèvement de la MON dans le BIEX et la faisabilité de son application dans l’usine de production d’eau potable demeurent inconnus. Ainsi, l’objectif de cette thèse est 1) de comprendre et favoriser l’application du BIEX pour l’enlèvement de la MON des eaux de surface et 2) de résumer les stratégies qui peuvent alléger la gestion de la saumure engendrée par la régénération de résines. Les résines en forme chlorure et bicarbonate ont été d’abord évaluées pour l’application du BIEX où le pilote de BIEX a été alimenté par l’eau de surface pendant 9 mois sans régénération. Les résultats ont démontré que l’échange d’ions est le mécanisme dominant pour le BIEX, i.e., la MON échange avec les ions préchargés (i.e., chlorure et bicarbonate) et les ions préretenus (i.e., sulfate). En plus, les résines colonisées ont été prélevées du pilote et testées en laboratoire où les résines colonisées ont été mises en contact avec les composés de modèles (i.e., micropolluants organiques). Les résultats ont démontré que la biodégradation contribuait à l’enlèvement de micropolluants organiques sur les résines colonisées, mais le degré de biodégradation dépend des caractères de micropolluants organiques et la communauté microbienne sur les résines. Ensuite, le BIEX a été évalué en parallèle du charbon actif biologique (CAB) en filtration secondaire dans l’usine de production d’eau potable de Sainte-Rose. Les résultats ont démontré que bien que le BIEX ait réalisé un enlèvement du carbone organique dissous (COD) plus élevé par rapport à celui du CAB, il a une perte de charge plus significative et le rétrolavage de BIEX s’avère être plus complexe par rapport à celui de CAB. Finalement, une revue de littérature a été menée afin d’identifier les stratégies sur l’opération de résine et la gestion de saumure, et ainsi d’alléger la gestion de la saumure engendrée par la régénération de résines échangeuses d’ions. En somme, cette thèse permet de comprendre les mécanismes de l’enlèvement de la MON dans le BIEX, évaluer la faisabilité de son application dans l’usine de production d’eau potable ainsi qu’identifier les stratégies qui peuvent alléger la gestion de la saumure engendrée par la régénération de résines échangeuses d’ions. / Natural organic matter (NOM) is ubiquitous in surface water. Although the exposure to NOM via drinking water is common and is not associated with direct effects on human health, NOM can cause negative impacts on drinking water treatment, such as contribution to taste and odors, development of biofilms in distribution systems and formation of disinfection by-products. Biological ion exchange (BIEX) is a promising process for the removal of NOM from surface waters. It involves operating the ion exchange resin in a fixed bed reactor with infrequent regeneration so that a microbial community can develop on the resin surface and thus contribute to the removal of NOM by biodegradation. However, the mechanisms for the removal of NOM in BIEX and the feasibility of its application in the drinking water plant remain unknown. Therefore, the general objective of this thesis is 1) to understand and promote the application of BIEX for the removal of NOM from surface water and 2) to summarize the strategies that can alleviate the management of the brine generated by the regeneration of resins. Chloride and bicarbonate-form resins were first evaluated for the BIEX application where the BIEX pilot was fed with surface water for 9 months without regeneration. The results demonstrated that ion exchange is the dominant mechanism in BIEX, i.e., NOM exchanges with preloaded ions (i.e., chloride and bicarbonate) and pre-retained ions (i.e., sulfate). In addition, the colonized resins were harvested from the pilot and tested in the laboratory where the colonized resins were in contact with the model compounds (i.e., organic micropollutants). The results demonstrated that biodegradation contributes to the removal of organic micropollutants on colonized resins, but the extent of biodegradation depends on the characteristics of the organic micropollutants and the microbial community on the resins. Then, BIEX was evaluated in parallel with biological activated carbon (BAC) at the second-stage filtration of the Sainte-Rose drinking water treatment plant. The results demonstrated that although BIEX achieved higher dissolved organic carbon (DOC) removal compared to BAC, it had a more significant pressure drop and the backwash of BIEX filters was proved to be more complex compared to that of BAC. Finally, a literature review was carried out to identify strategies on resin operation and brine management, and thus alleviate the management of the brine generated by the regeneration of ion exchange resins. Overall, this thesis allows understanding the mechanisms for the removal of NOM in BIEX, evaluating the feasibility of its application in drinking water production plants as well as identifying the strategies that can alleviate the management of the brine generated by the regeneration of ion exchange resins.

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