Zugl.: Kampen, Theolog. Univ., Diss., 2006

Thèses (M.Sc.A.)--Université de Sherbrooke (Canada), 2001. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Thèses (M.Sc.A.)--Université de Sherbrooke (Canada), 2002. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Diss.--Westfälische Wilhelms-Universität zu Münster, 2001. / Bibliogr. p. 379-397.

Dissertation--Universität zu Köln, 2005. / Bibliogr. p. 367-385.

Submitted by Dilene Paulo (dilene.fatima@ufcg.edu.br) on 2018-02-05T15:39:20Z No. of bitstreams: 1 LUIS EDUARDO MEDEIROS FROTA – DISSERTAÇÃO PPGEQ 2012.pdf: 1801644 bytes, checksum: 1d91f3ec19c316106682f868684e0357 (MD5) / Made available in DSpace on 2018-02-05T15:39:20Z (GMT). No. of bitstreams: 1 LUIS EDUARDO MEDEIROS FROTA – DISSERTAÇÃO PPGEQ 2012.pdf: 1801644 bytes, checksum: 1d91f3ec19c316106682f868684e0357 (MD5) Previous issue date: 2012-05-16 / O Oxido de alumínio, Al2O3, comumente chamado de alumina se trata de um composto químico de ampla utilização na indústria estando presente em pastas de dente, tinta, aditivos para tratamento de água dentre outros. Porém sua principal utilização é na indústria do Alumínio onde representa a principal material prima para a obtenção deste metal. A maior parte do Oxido de alumínio produzido no mundo hoje tem como fonte primária a Bauxita. O Alumínio está presente nesse minério na forma de óxi-hidroxidos de alumínio onde os principais são: gibbsita Al(OH)3, diasporo AlO(OH) e boehmita AlO(OH). O processo de refino para obtenção da Alumina a partir da Bauxita mais comumente aplicado atualmente é o processo Bayer no qual o minério é atacado com uma solução cáustica a base de hidróxido de sódio (NaOH) a fim de solubilizar o Alumínio para posterior recristalização. As várias etapas do processamento do minério são definidas e ajustadas em virtude das peculiaridades da bauxita utilizada como, por exemplo, composição química, granulometria e composição mineralógica. Bauxitas com características diferentes pedem processamento diferenciado. Com a demanda por alumina crescente, novas fontes de Bauxita necessitam ser exploradas e uma preocupação é que tipo de mudanças um minério de uma nova fonte pode causar ao processo. Este trabalho teve como objetivo avaliar a bauxita proveniente de uma nova fonte seus impactos no processo servindo como embasamento para tomada de decisão sobre a viabilidade da abertura de uma nova mina e um aumento de capacidade de processamento por parte da Refinaria. Caracterização química e simulação do processo Bayer em bancada mostraram que o material proveniente da nova fonte de bauxita não apresenta diferenças significativas em relação ao minério já utilizado embasando assim os investimentos para abertura e uma mina com capacidade de 4 milhões de toneladas de minério por ano e um aumento de capacidade de produção na refinaria de 2 milhões de toneladas de alumina ao ano. / The aluminum oxide, Al2O3, commonly called alumina it is a compound widely used in chemical industry and is present in toothpastes, ink, water treatment additives and others. However aluminum industry is the principal client where is the main raw material for production of this metal. Most of the aluminum oxide produced today has Bauxite as the main source. The aluminum is present in this ore as oxi-hydroxides which are the main: gibbsita Al(OH)3, diasporo AlO(OH) and boehmita AlO(OH). The refining process for obtaining alumina from bauxite most commonly is the Bayer Process where ore is attacked with a caustic solution based on sodium hydroxide (NaOH) in order to solubilize the aluminum subsequent to recrystallization. The various steps of ore processing are set and adjusted based on the characteristics used as, eg, chemical, mineralogical composition and particle size. Bauxites with different characteristics require different processing. With the increasing demand for alumina, new bauxite sources need to be explored and to know what kind of changes new ore source could require is fundamental. This work aimed to evaluate possible impacts caused by a new source and use this information to evaluate a new mine operation and increase processing capacity at Refinery. Chemical characterization and reproduction of some stages of the Bayer process in bench showed that material from the new source of bauxite does not differ significantly in relation to the first ore confirming investments for opening a anew mine with a capacity of 4 million tons per year supporting production increase refinery production capacity of 1,5 million tons of alumina per year.

Sodium oxalate is one of the many organics present in Bayer liquor. Due to its limited solubility, sodium oxalate can co-precipitate with alumina trihydrate during precipitation. This can have detrimental effects on the final product quality, especially if it occurs in the initial stages of precipitation.Quaternary amine type cationic surfactants can prevent sodium oxalate co-precipitation and increase the tolerable concentration of sodium oxalate in Bayer liquor. Their action is via the inhibition of nucleation or/and the inhibition of crystal growth. This study presents work detailing the effect of quaternary amines on sodium oxalate crystal growth in Bayer liquor.A series of quaternary amines were tested and classified as strong, medium or weak crystal growth inhibitors in plant liquor. The octadecyltrimethylammonium bromide was found to be the most effective under plant conditions.Results will show that while quaternary amines inhibit crystal growth in Bayer liquor, they have no effect on crystallization in synthetic liquor. It has been postulated that the presence of certain organic molecules is required for quaternary amines to crystallization and therefore stabilize the liquor. The inhibition of oxalate crystal growth in Bayer process liquors is due to the plant organics present, and the stabilizing effect of quaternary amines is the result of an interaction between quaternary amines and plant humic material on the oxalate surface. A series of organics, anionic macromolecules and anionic surfactants, have been tested to simulate the behaviour of plant humates, and their inhibitory effect on sodium oxalate crystal growth has been measured.A method for the analysis of the strongest quaternary amine has been adopted, improved and modified in order to fulfil experimental conditions.The CMC of quaternary amines has been determined in liquor. Surface tension ++ / measurements revealed relationships between certain liquor components and quaternary amines.Adsorption isotherms of quaternary amines have been successfully generated in Bayer liquor. Investigations with quaternary amines and plant humics reveal a synergy between the two. Co-adsorption of quaternary amines and plant humates onto the oxalate surface has been found, and the effect of the components on the adsorption behaviour will be discussed. The inhibitory effect and the adsorbed amount of components have been compared. Results revealed a relationship between the amount of plant humates on the surface and the crystal growth inhibition.The nature of the adsorption has been investigated with confocal laser scanning microscopy. These results will show that humic material adsorbs at the edges and in the corners of the crystals. In the presence of quaternary amines, the humic material occupies the main crystal faces as well. The nucleation of sodium oxalate from humic solution and from a mixture of humates and quaternary amine resulted in crystals with different morphology.Fourier Transform Infrared Attenuated Total Reflection Spectroscopy investigations will present the adsorption of quaternary amine on oxalate, and will indicate that the adsorption is pH dependent.

Precipitation of gibbsite from supersaturated caustic aluminate solutions has been investigated extensively due to its central role in the commercial Bayer plant, for extracting the alumina compound from bauxite. The primary focus of Bayer process simulation and optimisation is to help maximise the product recovery and the production of a product crystal size distribution (CSD) that meets the product specification and improves downstream process performance. The product CSD is essentially determined by the nucleation, growth and agglomeration kinetics, which occur simultaneously during the precipitation process. These processes are still poorly understood, owing to the high complexity of their mechanisms and of the structure of the caustic aluminate solutions. This research focuses on the modelling and kinetics estimation aspects of simulating gibbsite precipitation. Population balance theory was used to derive different laboratory gibbsite precipitator models, and the discretised population balance models of Hounslow, Ryall & Marshall (1988) and Litster, Smit & Hounslow (1995) were employed to solve the resulting partial integro-differential equations. Gibbsite kinetics rates were determined from literature correlation models and also estimated from the CSD data using the, so-called, differential method. Modelling of nonstationary gibbsite precipitation systems showed that error propagated with the precipitation time scale. The main contribution to the observed error was found to be from the uncertainties in the kinetic parameter estimates, which are estimated from experimental data and used in the simulation. This result showed that care is required when simulating the CSD of non-stationary precipitators over longer time scales, and methods that produce precise estimates of the kinetics rates from the experimental data need to be used. / Kinetics estimation study from repeated batch gibbsite precipitation data showed that the uncertainty in the experimental data coupled with the error incurred from the kinetic parameter estimation procedure used, resulted in large uncertainties in the kinetics estimates. The influences of the experimental design and the kinetics estimation technique on the accuracy and precision of estimates of the nucleation, growth and agglomeration kinetics for the gibbsite precipitation system were investigated. It was found that the operating conditions have a greater impact on the uncertainties in the estimated kinetics than does the precipitator configuration. The kinetics estimates from the integral method, i.e. non-linear parameter optimisation method, describe the gibbsite precipitation data better than those obtained by the differential method. However, both kinetics estimation techniques incurred significant uncertainties in the kinetics estimates, particularly toward the end of the precipitation runs where the kinetics rates are slow. The uncertainties in the kinetics estimates are strongly correlated to the magnitude of kinetics values and are dependent on the change in total crystal numbers and total crystal volume. Batch gibbsite precipitation data from an inhomogeneously-mixed precipitator were compared to a well-mixed precipitation system operated under the same operating conditions, i.e. supersaturation, seed charge, seed type, mean shear rate and temperature. / It was found that the gibbsite agglomeration kinetic estimates were significantly different, and hence, the product CSD, but the gibbsite growth rates were similar. It was also found that a compartmental model approach cannot fully account for the differences in suspension hydrodynamics, and resulted in unsatisfactorily CSD predictions of the inhomogeneously-mixed precipitator. This is attributed to the coupled effects of local energy dissipation rate and solids phase mixing on agglomeration process.

Detta dokument beskriver hur man kan använda kameramodulen TRDB DC2 från Terasic tillsammans med ett utvecklingskort DE2 för Alteras FPGA-kretsar. Kamerabilder överförs från kameramodulen till en VGA-skärm. VGA-bilden har en upplösning på 640 x 480 pixlar och 10bitars upplösning på färgerna. Systemet presterar maximalt 15 bilder per sekund och det är själva bildsensorn som sätter den begränsningen, man kan bla ändra exponeringstid och frysa bilden om man så vill. Hela projektet är skrivet i VHDL och arbetet är gjort i Quartus 6.0 från Altera. VHDL-koden är skriven i första hand för att vara lättförståelig och enkel att modifiera, några större ansträngningar för att minimera hårdvara eller på annat sätt effektivisera konstruktionen har inte gjorts.

<p>Detta dokument beskriver hur man kan använda kameramodulen TRDB DC2 från Terasic tillsammans med ett utvecklingskort DE2 för Alteras FPGA-kretsar. Kamerabilder överförs från kameramodulen till en VGA-skärm. VGA-bilden har en upplösning på 640 x 480 pixlar och 10bitars upplösning på färgerna. Systemet presterar maximalt 15 bilder per sekund och det är själva bildsensorn som sätter den begränsningen, man kan bla ändra exponeringstid och frysa bilden om man så vill. Hela projektet är skrivet i VHDL och arbetet är gjort i Quartus 6.0 från Altera. VHDL-koden är skriven i första hand för att vara lättförståelig och enkel att modifiera, några större ansträngningar för att minimera hårdvara eller på annat sätt effektivisera konstruktionen har inte gjorts.</p>