Orientador: Teresa Massako Kakuta Ravagnani / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-14T23:59:28Z (GMT). No. of bitstreams: 1 Domenico_MicheleDi_M.pdf: 2117165 bytes, checksum: 3837c602b224622b3736355d2e6b6e1c (MD5) Previous issue date: 2010 / Resumo: Com o propósito de aumentar a eficiência no processo de destilação convencional, e conseqüentemente diminuir o consumo excessivo de energia, inúmeras alternativas foram propostas na literatura. Uma destas metodologias, denominada paradestilação, é baseada na divisão da corrente gasosa em duas partes iguais no fundo de uma coluna de separação. Para este esquema de fluxo, uma divisória é colocada centralmente em toda a altura da coluna, e a corrente líquida contata, em estágios alternados, ambas as correntes do vapor. As vantagens deste processo incluem um aumento no número de estágios e uma diminuição na queda de pressão por unidade de altura da coluna convencional. Apesar das vantagens apresentadas em trabalhos computacionais, faz-se necessário o estudo experimental envolvendo os dois tipos de colunas sob as mesmas condições de operação. Assim, este trabalho apresenta um estudo comparativo entre uma coluna de destilação e outra de paradestilação, contendo respectivamente, 4 e 6 pratos perfurados, dotados de vertedores circulares. Para tanto, as colunas foram construídas de acordo com as recomendações de dimensionamento da literatura, de modo a fornecerem uma mesma eficiência de separação. Os experimentos foram realizados utilizando uma mistura de etanol-água, à pressão atmosférica e em condições de refluxo total e parcial. A comparação entre os processos foi realizada através da análise do comportamento hidrodinâmico e da eficiência de pratos de Murphree, avaliando-se parâmetros como a velocidade superficial da fase vapor, limites operacionais, tipo e altura da dispersão formada sobre o prato e perfil de composição da fase líquida ao longo das colunas. Verificou-se que as colunas de destilação e paradestilação apresentam uma faixa de operação muito semelhante. Sob condições de refluxo parcial, a coluna alternativa é menos sensível a uma variação na razão de refluxo. Ainda, as eficiências de Murphree foram fortemente influenciadas pelas propriedades do sistema destilante, composição da fase líquida e velocidades das fases líquida e gasosa. Os maiores valores de eficiência foram encontrados sob condições de refluxo total e em baixas velocidades da fase vapor. / Abstract: In order to increase the operation efficiency of conventional distillation and therefore reduce the excessive energy consumption, several techniques have been proposed in the literature. One of these methods, called parastillation, is based on the division of the vapor phase into two equal parts at the bottom of a separation column. For this configuration, an axial partition run the full height of the column, and the whole falling liquid stream contacts alternatively on a stage-by-stage basis with both parts of the vapor. The advantages of this process also include an increase in the number of stages and a decrease in pressure drop per unit of column height. Despite of the advantages presented in computational works, experimental studies involving distillation and parastillation columns operating under the same conditions are necessary. Therefore, this work presents a comparative study between a distillation and a parastillation column, using six and four sieve trays, respectively, with circular downcomers. The columns were assembled in agreement to the recommendations of literature design, in order to provide the same separation efficiency. The experiments were conducted using an ethanol-water system at atmospheric pressure and under total and partial reflux conditions. The comparison between the processes was carried out by analyzing the hydrodynamic behavior and the Murphree tray efficiency, evaluating parameters such as vapor phase velocity, operating limits, type and height of the dispersion formed above the trays and liquid composition profile along the columns. It was found that the distillation and parastillation columns have similar operating range. Under partial reflux conditions, the alternative column presented a lower sensitivity to a modification of the reflux ratio. In addition, the Murphree efficiency appears to be strongly dependant on system properties, composition of the liquid phase and vapor and liquid flow rates. The higher values of efficiency were found under total reflux conditions and at low vapor velocities. / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

M. Tech. / The separation of minerals such as coal, diamonds and others have involved the use of a heavy medium. The heavy medium separation technique, used in the diamond industry as a primary concentrator, is a physical process that separates minerals of different specific densities based on their relative movement and resistance to motion in a viscous fluid. It is made up of a suspension of finely ground solid particles constituting a stable suspension. There is a wide range of materials that are used to prepare suspension media in Heavy Medium Separation (HMS), but Ferrosilicon has found a wider usage. Major demand for dense medium Ferrosilicon powder is from the diamond industry which accounts for 77 percent of milled sales. In HMS, either dynamic or static separators can be used, even though; dynamic separators are widely used because they give higher separation efficiencies. A number of accounts have been reported on the effects of stability and viscosity to the medium. It is, however, observed that the effect of ore mineralogy, which is a major contributing factor during ore and medium interaction, during separation, has not been properly taken into account, apart from the fact that ore mineralogy form a basis for HMS efficiency. The literature, however, does not cover a thorough investigation of the relationship between the recovery of diamond bearing ores and stability of Ferrosilicon grades media, as a function of physicochemical properties of ferrosilicon. Eight samples of Ferrosilicon, four milled and four atomized were used to prepare media to recover value from kimberlitic ore, alluvial ore and synthetic ore in a laboratory set-up HMS. Both Ferrosilicon and ore samples were characterized with the following techniques before use: XRD, XRF, SEM-EDAX and Screening, to investigate physico-chemical properties of ferrosilicon and ore mineralogy. The used Ferrosilicon was also characterized to investigate any v changes as Ferrosilicon medium interacted with the ores. Settling tests were performed on each Ferrosilicon grade to investigate media stability before and after recovery exercise. The stability of the media was then related to the recovery of each ore. In-circuit sample of ferrosilicon was collected from Letšeng diamonds to compare any changes with Ferrosilicon used in the laboratory, and also used to study the effects of contamination on the degradated medium. All recovery results were done in a static HMS, but in practice dense medium cyclones are widely used. The screening characterization technique revealed that there was a loss of finer particles size fraction, predominant in sieves 75 microns and 45 microns and that loss was highest with atomized grades than milled ferrosilicon grades. Minimal changes in density and chemical compositions were observed for each ferrosilicon grade. The loss of the finer fraction was found to effect changes in the settling rate of each ferrosilicon grade differently, hence changes in the stability of their media. The efficiency (Ep) of separation was found to vary with each grade of Ferrosilicon used, accompanied by a shift in cut point density indicating the influence of grade on the separation efficiency. The effects of medium stability on recovery for both ores showed that although both ores percentage recoveries differ, the trend of medium stability to recovery, with each Ferrosilicon grade, is the same. However, the recovery was found to be more dependent on the density of the medium, as the effects of loss of finer particle size fraction did not show any significant contribution to recovery, but rather on the medium loss. The mineralogy of the ores also had been observed to give a minimal or no contribution to the separation efficiency, if related to recovery. Milled Ferrosilicon is further recommended over atomized Ferrosilicon, based on cost and stability. The highest loss of atomized Ferrosilicon could escalate the operating costs and affect the stability of the medium. It should be remembered that the purchasing costs of atomized grades is higher than that of milled grades.

Magister Scientiae - MSc / Over the past 40 years, research pertaining to membrane technology has lead to the development of a wide range of applications including beverage production, water purification and the separation of dairy products. For the separation of gases, membrane technology is not as widely applied since the production of suitable gas separation membranes is far more challenging than the production of membranes for eg. water purification. Hydrogen is currently produced by recovery technologies incorporated in various chemical processes. Hydrogen is mainly sourced from fossil fuels via steam reformation and coal gasification. Special attention will be given to Underground Coal Gasification since it may be of great importance for the future of South Africa. The main aim of this study was to develop low temperature CsHSO4/SiO2 composite membranes that show significant Idea selectivity towards H2:CO2 and H2:CH4. / South Africa

Orientador: Francisco Maugeri Filho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-04T01:27:34Z (GMT). No. of bitstreams: 1 Santos_TihanyMoritaAnterodos_D.pdf: 818442 bytes, checksum: c034c03d154eadb3c1ed625f0144e680 (MD5) Previous issue date: 2004 / Resumo: O xilitol é um açúcar-álcool com ampla utilização na indústria alimentícia, porém mesmo sendo numerosos os estudos sobre a sua produção a partir da fermentação de hidrolisados hemicelulósicos, poucos são os trabalhos que tratam da sua separação e purificação. O objetivo principal deste trabalho é, portanto, desenvolver uma metodologia de separação do xilitol dos compostos remanescentes no meio fermentado obtido por fermentação do hidrolisado de bagaço de cana-de-açúcar por Candida guilliermondii. Inicialmente, ensaios conduzidos com as zeólitas Na86X, Baylith 415 e Baylith WE 894 em diferentes formas catiônicas permitiram constatar a maior eficácia das zeólitas NaWE e BaWE na adsorção do xilitol e posteriormente, o uso de colunas de leito fixo empacotadas com estas duas zeólitas em diferentes granulometrias, a 30 e 50 ºC, revelou que a separação do xilitol foi superior com o uso da zeólita BaWE com partículas de 53-125 µm a 50 ºC. Estas condições foram empregadas na determinação da constante de equilíbrio deste composto usando a resposta a pulsos cromatográficos, sendo o valor obtido igual a 1,03. Os efeitos da temperatura, da velocidade superficial e da razão volume de pulso/volume de leito (Vp/Vl) sobre a separação do xilitol foram investigados através de análise estatística de experimentos delineados por um planejamento fatorial 23, que revelou que a condição mais favorável para separar o xilitol envolve o uso de temperatura de 80 ºC, velocidade superficial de 0,5 cm.min-1 e Vp/Vl igual a 0,2. O emprego de etanol e acetona em diferentes concentrações como eluentes permitiu concluir, após avaliação das eficiências obtidas e do custo dos mesmos, que o etanol a 30 % é o eluente mais adequado para ser utilizado na separação do xilitol. Após a determinação dos parâmetros de separação em meio sintético, iniciaram-se os testes com meio fermentado, obtido da fermentação de hidrolisado de bagaço de cana-de-açúcar com Candida guilliermondii. Dentre as metodologias empregadas na destoxificação deste meio, o uso de resinas de troca iônica foi o mais eficiente, permitindo obter maiores parâmetros fermentativos. A avaliação da separação do xilitol obtido por fermentação foi realizada variando-se o número de colunas e o volume do pulso e os melhores resultados foram obtidos utilizando-se 2 e 3 colunas de zeólita BaWE alimentadas com volume de pulso igual a 8 % do volume do leito. Apesar das eficiências de separação terem sido superiores com 3 colunas, verificou-se que a porcentagem de xilitol nas frações enriquecidas e a quantidade recuperada deste poliol foram somente ligeiramente superiores às obtidas em sistema com 2 colunas (0,5 e 2,1 % superiores, respectivamente). Além deste fato, o sistema de 2 colunas contribuiu para uma eluição mais rápida dos compostos e requereu menor volume de eluente. Estas observações permitiram concluir que dentre os sistemas experimentais avaliados, o composto por 2 colunas de zeólita BaWE com altura total de leito de 89 cm, alimentadas com volume de pulso igual a 8 % do volume do leito, a 80 ºC e 0,5 cm.min-1 conduziu a uma melhor separação do xilitol. Nestas condições obteve-se uma fração com 97,28 % de xilitol, 0,84 % de arabinose, 0,82 % de xilose e 0,54 % de arabitol e eficiências de separação de 3,17 e 2,72 com relação a arabinose e a xilose, respectivamente / Abstract: Xylitol is a sugar alcohol with large utilization in food industry. Nevertheless, although there are numerous studies on its production from the fermentation of hemicellulosic hydrolysates, there are few works dealing with its separation and purification. The principal aim of this work is, therefore, to develop a methodology for xylitol separation from the compounds remaining in the fermented medium, which was obtained by fermentation with Candida guilliermondii in sugar cane bagasse hydrolysate. Initially, assays were conducted with the zeolites Na86X, Baylith 415 and Baylith WE 894 in different cationic forms, which permitted us to observe a higher effectiveness of zeolites NaWE and BaWE in the xylitol adsorption, and later, the use of fixed bed columns packed with these two zeolites in different granulometries, at 30 and 50 ºC, revealed that the xylitol separation was better when 53-125 µm BaWE zeolite particles at 50 ºC were utilized. These conditions were also employed for determining the equilibrium constant of this compound using the chromatographic pulse response technique, the value obtained being equal to 1.03. The effects of temperature, superficial velocity and pulse volume/bed volume ratio (Vp/Vl) on the xylitol separation were investigated by means of statistical analysis of experiments described by a 23 factorial design, which showed that the most favorable conditions for this separation are: temperature of 80 ºC, superficial velocity of 0.5 cm.min-1 and Vp/Vl of 0.2. The use of ethanol and acetone at different concentrations as eluents enabled us to conclude, after an evaluation of their costs and of the efficiencies obtained, that ethanol at 30 % is the most suitable eluent for xylitol separation. After determining the parameters of separation in synthetic medium, tests were performed with fermented medium obtained from fermentation of sugar cane bagasse hydrolysate with Candida guilliermondii. Of the methodologies employed for detoxification of this medium, the use of ion-exchange resins proved the most effective, giving higher fermentative parameters. The separation of xylitol obtained from fermentation was evaluated by varying the number of columns and the pulse volume, the best results being attained with 2 and 3 columns of zeolite BaWE fed with a pulse volume equal to 8 % of bed volume. Although the separation efficiencies were enhanced by using 3 columns, it was observed that the amount of xylitol in the enriched fractions and its recovered amount were only slightly higher than those obtained using 2 columns (0.5 and 2.1 % higher, respectively). In addition, the 2-column system contributed to a more rapid elution of the compounds and required a lower eluent volume. It can therefore be concluded that, of the experimental systems that were evaluated, the one composed of two columns of zeolite BaWE with a bed 89 cm in total height and fed with a pulse volume equal to 8 % of bed volume, at 80 ºC and 0.5cm.min-1, led to a better xylitol separation. Under these conditions, the fraction obtained contained 97.28 % xylitol, 0.84 % arabinose, 0.82 % xylose and 0.54 % arabitol, and the efficiencies of xylitol separation from arabinose and xylose were 3.17 and 2.72 respectively / Doutorado / Engenharia de Alimentos / Doutor em Engenharia de Alimentos

No description available.

Thesis: M.S., Massachusetts Institute of Technology, Department of Chemical Engineering, 1982 / Bibliography: leaves 59-60. / by Willie K. Chan. / M.S. / M.S. Massachusetts Institute of Technology, Department of Chemical Engineering

Methods for the analysis of surfactants and proteins by Capillary Electrophoresis (CE) were investigated. Several modifications of the system to achieve detection and separation of these analytes were examined. These modifications included buffer additives, sample additives and surface treatment and modification of the fused silica capillary. For the analysis of anionic surfactants, the addition of an anionic IN absorbing compound to the buffer was investigated to achieve indirect detection of the non-absorbing surfactants. The effect on detection sensitivity and separation efficiency of the absorbing ion was examined. These parameters were affected by differences in the electrophoretic mobilities of the analytes in comparison to the absorbing ion. The use of organic modifiers was also investigated to minimize micelle formation of the surfactants which leads to zone spreading. For the analysis of serum and urine proteins, the use of high pH buffers was investigated to minimize solute/capillary surface interactions and achieve separation. At high pH's the proteins are negatively charged; therefore, they should be repelled by the negatively charged fused silica surface. To improve reproducibility of migration times of the proteins the addition of polyvinyl alcohol to the sample was also investigated. The polyvinyl alcohol improved reproducibility by reversibly covering the active sites on the capillary surface to minimize protein interactions. Migration time reproducibility was also improved by optimizing the capillary cleaning procedure. Lastly, the addition of methyl cellulose to the buffer to work as a dynamic molecular sieving medium was investigated to improve resolution. Analyte/ capillary surface interactions are a major limitation in CE especially for the analyses of proteins. The use of coated capillaries to eliminate these interactions has been widely investigated. However, reproducibility and degree of surface deactivation with these coating can be poor. In this work hydrothennal treatment of the fused silica capillary surface prior to deactivation was examined. Hydrothennal treatment was used to produce a homogenous surface prior to coating which leads to the production of more highly deactivated, reproducible columns. The effects of the treatment were studied by coating the surface with a silane and examining the influence of the coating on electroosmotic flow and analyte adsorption. / Ph. D.

The present study addresses a systematic evaluation of the effect of crosslinking via terminal maleimide units on the gas transport properties through a dense polymer film of amorphous Poly(Arylene Ether Ketones) or PEK. The methodology for the preparation of crosslinked maleimide terminated PEK (or MIPEK) films from several blend ratios of different molecular weights of MIPEK is discussed in detail. The primary focus of this work has been to investigate the influence of different degrees of crosslinking on gas permeabilities and selectivities, with an objective of producing a highly selective membrane. It has been demonstrated that crosslinking markedly decreases the permeation of methane, without changing the values for molecules such as helium. / Master of Science

M.S.

Thesis (M.Tech.) / The electrochemical refining of copper was investigated at different temperatures, distances between electrodes, different levels of overvoltage, current density, metal impurities, smootheners, electrode-active area and concentration of electrolyte using the parallel-plate model. The purpose of the investigation was to evaluate the effect of smootheners, impurities and other factors on the recovery of copper from solutions. The results showed that the metal impurities, with more negative oxidation potentials, did not affect the electro-deposition of copper whilst metals with oxidation potentials close and equal to that of copper reduced the current efficiency. The current density increased with the increase in temperature, overvoltage and concentration of electrolyte. The increase in overvoltage and current density above limiting values produced increased rates of deposition resulting in efficiencies greater than 100% to be attained. The increase in the limiting current density at concentration below 10.8g/L produced low values of current efficiency ranging from 100 to 30%. The 2 and 3cm distance between electrodes produced stable efficiencies of between 92-100% and 96-100% respectively. The temperature was found to have indirect effect on the current efficiency but direct effect on the dissociation of electrolyte in solution, current density and overvoltage. An increase of 20cm2 of electrode active area reduced the current efficiency by about 40%. The increase in concentration of electrolyte produced an increase in the current density and efficiency ranging from 75-100%. The use of smootheners; thiourea and EDTA (Ethylenediaminetetraacetic acid) reduced the current density and current efficiency (100>CE>30%). However increased concentration of Kglue, B-glue and G-Arabic in conjunction with EDTA or thiourea and NaCl improved the current efficiency even at increased levels of overvoltage to levels of 96-100%, 100% and 90-100% respectively. Therefore, the presence of impurities, the use of high current densities, inadequate distance between electrodes, and too low concentration of electrolyte and the absence of glue disadvantaged the recovery process while the presence of K-glue and B-glue reduced the inhibition effects of thiourea and EDTA and thus improved the recovery of copper from solutions.