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1
Xu, Bingan. "Lime chemistry in the Bayer process." Thesis, Xu, Bingan (1991) Lime chemistry in the Bayer process. PhD thesis, Murdoch University, 1991. https://researchrepository.murdoch.edu.au/id/eprint/52725/.
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A fundamental study of the kinetics and mechanism of lime chemistry in the Bayer process has been undertaken. To simplify the study and avoid interference from impurities, experiments were carried out in relatively pure systems. Calcium hydroxide and calcium oxide, the solid reactants, were used in two different forms: rotating discs and powders. The former gives the most useful mechanistic information, while the latter most closely approximates industrial practice. The structure and composition of the surface was also investigated using a variety of techniques including scanning electron microscopy.
The dissolution of calcium hydroxide in water has been investigated under a variety of conditions. A study of the dissolution of rotating calcium hydroxide discs at low rotation speeds (<250 rpm) showed that the reaction rate increased with increasing rotation speed and temperature but decreased when the solution contained either calcium ions or hydroxide ions. It was concluded that the dissolution of calcium hydroxide under these circumstances is controlled by the diffusion of calcium ions and hydroxide ions away from the calcium hydroxide surface. Using the Levich equation for mass transfer from a rotating disc and assuming that the dissolution step prior to slow diffusion from the surface is at equilibrium, it is possible to estimate the dissolution rate. Rates calculated in this way agree well with the measured rates.
At high rotation speeds the reaction becomes controlled by the speed of the dissolution process itself.
For powdered calcium hydroxide samples, it was found that the dissolution process can be approximated by the "shrinking sphere" model and that the associated rate constant behaves similarly to that for a rotating disc under conditions of diffusion control.
An investigation of the slaking of calcium oxide discs in water and solutions containing Ca2+ or OH- ions showed that the slaking process has the same behaviour as that for calcium hydroxide the diffusion discs, i.e. of Ca2+ or OH- ions away from the surface is also the rate-determining step when the reaction is slow. Therefore, the theory proposed for the dissolution of Ca(OH)2 discs applies to the slaking reactions. However , when the reaction rate is fast enough, the entire slaking process becomes chemically controlled. The similarity of the results obtained using both Ca(0H)2 discs and CaO discs indicates that the reaction of calcium oxide with water to form calcium hydroxide is not the rate-determining step.
It was found that the slaking of powdered calcium oxide also follows the shrinking sphere model proposed for the dissolution of calcium hydroxide particles. The rate of slaking depended on the size of the calcium oxide particles and the calcination conditions (temperature and time) under which the calcium oxide was formed from calcium carbonate. The presence of Ca2+ ions and OH- ions causes a reduction in the slaking rate similar to that observed for rotating disc samples under the same conditions, suggesting that the reaction mechanism is the same for both powdered and disc samples.
The slaking of both powdered CaO and rotating CaO disc samples in sodium carbonate solution is controlled by the deposition of calcium carbonate on the dissolving surface. This results in a reduction in the dissolution rate of the calcium hydroxide or calcium oxide, and a reduction in the rate of precipitation of calcium carbonate on the surface. Before the blocking layer of calcium carbonate is formed, the loss of carbonate ions from solution is at least partially diffusion controlled.
A study of the slaking of CaO in sodium aluminate solution was also conducted. The experimental results show that calcium aluminate precipitates on the reacting CaO surface, leading to a reduction in the dissolution rate of Ca(OH)2. The experimental results also suggest that the precipitation of calcium aluminate is chemically controlled while the slaking reaction remains diffusion controlled. Under competitive reaction conditions, the rate of CaCO3 formation is faster than that of Ca3Al2O5.
2
Lee, Mei-yin. "The mechanism of gibbsite crystal growth in Bayer liquor." Thesis, Curtin University, 1998. http://hdl.handle.net/20.500.11937/759.
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Although the precipitation of aluminium trihydroxide as gibbsite, via the Bayer process has been widely studied, the mechanism of crystal growth is poorly understood. This work focus on the morphology of gibbsite and the relative growth rates of individual crystal faces.Initial work was carried out to characterize aluminium trihydroxide and it was found that bayerite, another polymorph, precipitated at temperatures below 50 [degrees] C and its morphology depended on the method of precipitation. Gibbsite however, precipitated above this temperature and its morphology depended on the type of alkali aluminate solutions used. The method of precipitation does not affect the morphology, only the size of the precipitate formed. The morphology of gibbsite can be altered by the addition of organic compounds which are known to inhibit gibbsite precipitation. Some of these compounds were found to selectively inhibit the growth of individual crystal faces, thus altering the overall morphology of gibbsite. Boehmite, a polymorph of aluminium hydroxide, can be produced by partial dehydration of gibbsite at 300T. The morphology of boehmite consisted of diamond shaped crystals.The influence of cation incorporation on the morphology of gibbsite was studied experimentally and computationally (molecular modelling). These studies showed that there is a linear relationship between the amount of cation incorporated and atomic radii and between the amount of cation incorporated and the defect energy calculated. The equilibrium morphology of gibbsite predicted in the absence of media matched the morphology of gibbsite grown slowly from sodium aluminate, implying that the amount of sodium incorporation is low in these crystals.The growth rates of individual crystal faces were measured in situ, and found to be a function of supersaturation squared for the prismatic faces, possibly indicating that E growth occurs by spiral growth mechanism. The growth of the basal face was found to follow the spiral growth mechanism below a relative supersaturation of 0.815 and the birth and spread mechanism above this level. The activation energies and kinetic coefficients for the individual prismatic faces were also determined.Growth rate dispersion was observed in these microscopic studies, but the question of size dependency remains unanswered.The overall growth rates of gibbsite crystal, determined using rapid dynamic light scattering, was found to be an exponential function of supersaturation indicative of a birth and spread growth mechanism.
3
Kenyon, Nicola Jane. "Investigation of scale formation in the Bayer process." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494464.
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4
Jamieson, Evan John. "Development and utilisation of Bayer process by-products." Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/198.
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The Bayer Process is the hydrometallurgical treatment of bauxite ore for the extraction of alumina. This thesis reports on the development and utilisation of key by-products including:• Carbonated Red Mud and Alkaloam® - produced from the fine bauxite residue commonly termed red mud• Red Sand™ - manufactured from coarse bauxite residue• Red Lime™ - a by-product of liquor causticisation• Bayer-derived geopolymers - a cement replacement made from processed Bayer liquor.
5
Perron, Alexandre. "Mesure de vitesse dans une solution électrolytique à force ionique élevée par une méthode électrochimique /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2003. http://theses.uqac.ca.
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6
Armstrong, Jennifer Ann. "The investigation of scale formation in the Bayer process." Thesis, Loughborough University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251012.
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7
Péloquin, Guy. "Modélisation mathématique de la décantation de boue rouge /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2003. http://theses.uqac.ca.
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8
Lee, Mei-yin. "The mechanism of gibbsite crystal growth in Bayer liquor." Curtin University of Technology, School of Applied Chemistry, 1998. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10719.
Full textAbstract:
Although the precipitation of aluminium trihydroxide as gibbsite, via the Bayer process has been widely studied, the mechanism of crystal growth is poorly understood. This work focus on the morphology of gibbsite and the relative growth rates of individual crystal faces.Initial work was carried out to characterize aluminium trihydroxide and it was found that bayerite, another polymorph, precipitated at temperatures below 50 [degrees] C and its morphology depended on the method of precipitation. Gibbsite however, precipitated above this temperature and its morphology depended on the type of alkali aluminate solutions used. The method of precipitation does not affect the morphology, only the size of the precipitate formed. The morphology of gibbsite can be altered by the addition of organic compounds which are known to inhibit gibbsite precipitation. Some of these compounds were found to selectively inhibit the growth of individual crystal faces, thus altering the overall morphology of gibbsite. Boehmite, a polymorph of aluminium hydroxide, can be produced by partial dehydration of gibbsite at 300T. The morphology of boehmite consisted of diamond shaped crystals.The influence of cation incorporation on the morphology of gibbsite was studied experimentally and computationally (molecular modelling). These studies showed that there is a linear relationship between the amount of cation incorporated and atomic radii and between the amount of cation incorporated and the defect energy calculated. The equilibrium morphology of gibbsite predicted in the absence of media matched the morphology of gibbsite grown slowly from sodium aluminate, implying that the amount of sodium incorporation is low in these crystals.The growth rates of individual crystal faces were measured in situ, and found to be a function of supersaturation squared for the prismatic faces, possibly indicating ++that E growth occurs by spiral growth mechanism. The growth of the basal face was found to follow the spiral growth mechanism below a relative supersaturation of 0.815 and the birth and spread mechanism above this level. The activation energies and kinetic coefficients for the individual prismatic faces were also determined.Growth rate dispersion was observed in these microscopic studies, but the question of size dependency remains unanswered.The overall growth rates of gibbsite crystal, determined using rapid dynamic light scattering, was found to be an exponential function of supersaturation indicative of a birth and spread growth mechanism.
9
Tromans, Andrew J. "Solution chemistry of some dicarboxylate salts of relevance to the Bayer process /." Access via Murdoch University Digital Theses Project, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040730.140604.
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10
Normandin, Mélanie. "Étude sur la clarification d'une suspension de boue rouge et de liqueur Bayer par floculation /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
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Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2005.La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en ingénierie. CaQQUQ Bibliogr.: f. 128-131. Document électronique également accessible en format PDF. CaQQUQ
11
au, A. Tromans@chem murdoch edu, and Andrew John Tromans. "Solution Chemistry of some Dicarboxylate Salts of Relevance to the Bayer Process." Murdoch University, 2001. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040730.140604.
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This thesis deals with certain aspects of the solution chemistry of the simple dicarboxylate anions: oxalate, malonate and succinate, up to high concentrations. These ions are either significant impurities in the concentrated alkaline aluminate solutions used in the Bayer process for the purification of alumina, or are useful models for degraded organic matter in industrial Bayer liquors. Such impurities are known to have important effects on the operation of the Bayer process.
To develop a better understanding of the speciation of oxalate (the major organic impurity in Bayer liquors) in concentrated electrolyte solutions, the formation constant (Log£]) of the extremely weak ion pair formed between sodium (Na+) and oxalate (Ox2{) ions was determined at 25 oC as a function if ionic strength in TMACl media by titration using a Na+ ion selective electrode. Attempts to measure this constant in CsCl media were unsuccessful probably because of competition for Ox2{ by Cs+.
Aqueous solutions of sodium malonate (Na2Mal) and sodium succinate (Na2Suc) were studied up to high (saturation) concentrations at 25 oC by dielectric relaxation spectroscopy (DRS) over the approximate frequency range 0.1 T £h/GHz T 89. To complement a previous study of Na2Ox, formation constants of the Na+-dicarboxylate ion pairs were determined and they were shown to be of the solvent-shared type. Both the Mal2{ and Suc2{ ions, in contrast to Ox2{, were also shown to possess large secondary hydration shells
Apparent molal volumes (Vf) and heat capacities at constant pressure (Cpf) of aqueous solutions of Na2Ox, Na2Suc, Na2Mal and K2Ox were determined at 25 oC up to their saturation limits using vibrating tube densitometry and flow calorimetry. These data were fitted using a Pitzer model. The adherence of Vf and Cpf of various Na+ and K+ salts to Young¡¦s rule was examined up to high concentrations using the present and literature data. Young¡¦s rule was then used to estimate hypothetical values of Cpf and Vf for the sparingly soluble Na2Ox at high ionic strengths, which are required for the thermodynamic modelling of Bayer liquors.
The solubility of Na2Ox in various concentrated electrolytes was measured, at temperatures from 25 oC to 70 oC in media both with (NaCl, NaClO4, NaOH) and without a common ion (KCl, CsCl, TMACl). The common ion effect was found to dominate the solubility of Na2Ox. The solubility of calcium oxalate monohydrate (CaOxªH2O) was also determined. The solubilities of both Na2Ox and CaOxªH2O in media without a common ion increased with increasing electrolyte concentration, except in TMACl media, where they decreased.
The solubility of Na2Ox was modelled using a Pitzer model assuming the Pitzer parameters for Na2SO4 and minimising the free energy of the system. The data were modelled successfully over the full concentration and temperature range of all the electrolytes, including ternary (mixed electrolyte) solutions.
12
Tromans, Andrew John. "Solution chemistry of some dicarboxylate salts of relevance to the Bayer process." Thesis, Tromans, Andrew John (2001) Solution chemistry of some dicarboxylate salts of relevance to the Bayer process. PhD thesis, Murdoch University, 2001. https://researchrepository.murdoch.edu.au/id/eprint/371/.
Full textAbstract:
These ions are either significant impurities in the concentrated alkaline aluminate solutions used in the Bayer process for the purification of alumina, or are useful models for degraded organic matter in industrial Bayer liquors. Such impurities are known to have important effects on the operation of the Bayer process. To develop a better understanding of the speciation of oxalate (the major organic impurity in Bayer liquors) in concentrated electrolyte solutions, the formation constant (Log Beta) of the extremely weak ion pair formed between sodium (Na+) and oxalate (Ox2-) ions was determined at 25 degrees C as a function if ionic strength in TMACl media by titration using a Na+ ion selective electrode. Attempts to measure this constant in CsCl media were unsuccessful probably because of competition for Ox2 by Cs+.
Aqueous solutions of sodium malonate (Na2Mal) and sodium succinate (Na2Suc) were studied up to high (saturation) concentrations at 25 degrees C by dielectric relaxation spectroscopy (DRS) over the approximate frequency range 0.1 less-equal v/GHz less-equal 89. To complement a previous study of Na2Ox, formation constants of the Na+-dicarboxylate ion pairs were determined and they were shown to be of the solvent-shared type. Both the Mal2- and Suc2- ions, in contrast to Ox2-, were also shown to possess large secondary hydration shells.
Apparent molal volumes (V[phi]) and heat capacities at constant pressure (Cp[phi]) of aqueous solutions of Na2Ox, Na2Suc, Na2Mal and K2Ox were determined at 25 degrees C up to their saturation limits using vibrating tube densitometry and flow calorimetry. These data were fitted using a Pitzer model. The adherence of V[phi] and Cp[phi] of various Na+ and K+ salts to Young's rule was examined up to high concentrations using the present and literature data. Young's rule was then used to estimate hypothetical values of CpV[phi] and V[phi] for the sparingly soluble Na2Ox at high ionic strengths, which are required for the thermodynamic modelling of Bayer liquors.
The solubility of Na2Ox in various concentrated electrolytes was measured, at temperatures from 25 degrees C to 70 degrees C in media both with (NaCl, NaClO4, NaOH) and without a common ion (KCl, CsCl, TMACl). The common ion effect was found to dominate the solubility of Na2Ox. The solubility of calcium oxalate monohydrate (CaOx.H2O) was also determined. The solubilities of both Na2Ox and CaOx.H2O in media without a common ion increased with increasing electrolyte concentration, except in TMACl media, where they decreased. The solubility of Na2Ox was modelled using a Pitzer model assuming the Pitzer parameters for Na2SO4 and minimising the free energy of the system. The data were modelled successfully over the full concentration and temperature range of all the electrolytes, including ternary (mixed electrolyte) solutions.
13
Tromans, Andrew John. "Solution chemistry of some dicarboxylate salts of relevance to the Bayer process." Tromans, Andrew John (2001) Solution chemistry of some dicarboxylate salts of relevance to the Bayer process. PhD thesis, Murdoch University, 2001. http://researchrepository.murdoch.edu.au/371/.
Full textAbstract:
These ions are either significant impurities in the concentrated alkaline aluminate solutions used in the Bayer process for the purification of alumina, or are useful models for degraded organic matter in industrial Bayer liquors. Such impurities are known to have important effects on the operation of the Bayer process. To develop a better understanding of the speciation of oxalate (the major organic impurity in Bayer liquors) in concentrated electrolyte solutions, the formation constant (Log Beta) of the extremely weak ion pair formed between sodium (Na+) and oxalate (Ox2-) ions was determined at 25 degrees C as a function if ionic strength in TMACl media by titration using a Na+ ion selective electrode. Attempts to measure this constant in CsCl media were unsuccessful probably because of competition for Ox2 by Cs+.
Aqueous solutions of sodium malonate (Na2Mal) and sodium succinate (Na2Suc) were studied up to high (saturation) concentrations at 25 degrees C by dielectric relaxation spectroscopy (DRS) over the approximate frequency range 0.1 less-equal v/GHz less-equal 89. To complement a previous study of Na2Ox, formation constants of the Na+-dicarboxylate ion pairs were determined and they were shown to be of the solvent-shared type. Both the Mal2- and Suc2- ions, in contrast to Ox2-, were also shown to possess large secondary hydration shells.
Apparent molal volumes (V[phi]) and heat capacities at constant pressure (Cp[phi]) of aqueous solutions of Na2Ox, Na2Suc, Na2Mal and K2Ox were determined at 25 degrees C up to their saturation limits using vibrating tube densitometry and flow calorimetry. These data were fitted using a Pitzer model. The adherence of V[phi] and Cp[phi] of various Na+ and K+ salts to Young's rule was examined up to high concentrations using the present and literature data. Young's rule was then used to estimate hypothetical values of CpV[phi] and V[phi] for the sparingly soluble Na2Ox at high ionic strengths, which are required for the thermodynamic modelling of Bayer liquors.
The solubility of Na2Ox in various concentrated electrolytes was measured, at temperatures from 25 degrees C to 70 degrees C in media both with (NaCl, NaClO4, NaOH) and without a common ion (KCl, CsCl, TMACl). The common ion effect was found to dominate the solubility of Na2Ox. The solubility of calcium oxalate monohydrate (CaOx.H2O) was also determined. The solubilities of both Na2Ox and CaOx.H2O in media without a common ion increased with increasing electrolyte concentration, except in TMACl media, where they decreased. The solubility of Na2Ox was modelled using a Pitzer model assuming the Pitzer parameters for Na2SO4 and minimising the free energy of the system. The data were modelled successfully over the full concentration and temperature range of all the electrolytes, including ternary (mixed electrolyte) solutions.
14
FROTA, Luis Eduardo Medeiros. "Avaliação do uso de diferentes fontes de bauxita no processo de produção de óxido de alumínio." Universidade Federal de Campina Grande, 2012. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/256.
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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.
15
Sipos, Gabriella. "The mechanisms of action of sodium oxalate seed stabiliser molecules under Bayer conditions." Thesis, Curtin University, 2001. http://hdl.handle.net/20.500.11937/1922.
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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.
16
Smith, Fraser O. "Discontinuous flow analyser for process chemical analysis." Thesis, Queensland University of Technology, 1999.
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17
Wu, Fei. "Aluminous goethite in the bayer process and its impact on alumina recovery and settling." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/1954.
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Aluminium substituted goethite present in the Bayer process is closely related to settling problem and reduction of alumina recovery. The finer particle size and larger specific surface area of Al-substituted goethite compared with those of hematite contribute to the negative effects to the Bayer circuit.The project aims to improve the settling performance and recover alumina from aluminous goethite by hydrothermal transformation of Al-goethite to hematite/Al-hematite in the Bayer digestion process.A hypothesis of the solubility limit in goethite-diaspore solid solution (Al-goethite) has been developed through the characteristic study on synthetic Al-goethite. The mechanism of Al for Fe substitution has presumably been considered to be a partial Al substitution in the core of goethite structure with the remainder forming a surface diaspore coating.The thermal transformation of goethite to hematite does not change the goethite structure until temperature 600°C since the phase change happens in the temperature range of 300 to 400°C. On the other hand, the study of hydrothermal transformation of goethite suggests that 230°C is the sensitive reaction temperature. Hematite seeding is beneficial to the transformation while alumina content is an inhibitor.Natural aluminous goethite in the Bayer digestion performs differently due to the effects of impurities in the bauxite on the process. The presence of anatase adversely affects the transformation through the reaction with caustic to form into sodium titanate, which forms a film-like coating on the surface of goethite to prevent further transformation. However, adding CaCO3 directly to the digestion zone at 250°C can largely improve the transformation of Al-goethite to hematite by consuming anatase with CaCO3 to prevent the formation of sodium titanate. It is noted that the adding point of CaCO3 is crucial to the enhancement.A near completion of hydrothermal transformation of aluminous goethite to hematite has been achieved through the addition of CaCO3 directly to the digestion zone at 250ºC within 30 minutes. The extent of Al substitution in the original goethite from 25 mol% reduces to 5~6 mol% in hematite. More importantly, alumina recovery increased by 20% and the settling rate greatly improves as a result of the transformation of Al-goethite to hematite.
18
Tabassum, Rasheed, and tabassum rasheed@svt com au. "Scale growth study in a concentric reducer: Measurement of instantaneous velocity using Particle Image Velocimetry." Central Queensland University. School of Advance Technology and Processes, 2005. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20060720.095421.
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Gibbsite scale growth in pipe fittings is a major problem for an alumina refinery. A recent
investigation into the scale growth mechanism at an alumina refinery found almost 60 % more
scale growth in a reducer when compared with the connecting straight pipe sections for similar
flow conditions.
Scale growth occurs where liquor (supersaturated solutions) come in contact with solid surfaces
and it is affected by the liquor flow velocity besides other physical and chemical parameters. The
present work is dedicated to study the hydro-dynamical aspects of the mechanism of scale
growth. In particular, the role of the phenomenon of turbulent bursting, stream wise and cross
stream fluctuating velocity components (Ux and Uy) was investigated as the flow moves through
the reducer. Particle Image Velocimetry (PIV) technique was used to get a full view of the
reducer and the readings close-to-the-wall of the reducer at Reynolds number of 27,000 and
44,000 upstream which corresponds to Reynolds number of 41,500 and 66,000 downstream of
the reducer respectively.
The results showed an increase in cross stream and a decrease in magnitude of stream wise
fluctuating velocity components, whereby we presume that the increased cross stream fluctuating
velocity component increases the frequency of impacts of the scaling particles on the wall thus
initiating excessive scale growth in the reducer when compared with the connecting straight pipe
sections, for similar flow conditions.
19
Sipos, Gabriella. "The mechanisms of action of Sodium oxalate seed stabiliser molecules under Bayer conditions /." Curtin University of Technology, School of Applied Chemistry, 2001. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=12616.
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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.
20
Brady, James Peter. "An examination of the applicability of hydrotalcite for removing oxalate anions from Bayer process solutions." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/46165/1/James_Brady_Thesis.pdf.
Full textAbstract:
Hydrotalcite and thermally activated hydrotalcites were examined for their potential as methods for the removal of oxalate anions from Bayer Process liquors. Hydrotalcite was prepared and characterised by a number of methods, including X-ray diffraction, thermogravimetric analysis, nitrogen adsorption analysis and vibrational spectroscopy. Thermally activated hydrotalcites were prepared by a low temperature method and characterised using X-ray diffraction, nitrogen adsorption analysis and vibrational spectroscopy. Oxalate intercalated hydrotalcite was prepared by two methods and analysed with X-ray diffraction and for the first time thermogravimetric analysis, Raman spectroscopy and infrared emission spectroscopy. The adsorption of oxalate anions by hydrotalcite and thermally activated hydrotalcite was tested in a range of solutions using both batch and kinetic adsorption models.
21
Jones, Alan. "Production and utilisation of Bayer Process Red Sand™ for construction and its beneficiation by magnetic separation." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/393.
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The extraction of alumina from bauxite produces a high volume by-product which is stored in secure impoundments. In Western Australia, typically half of the by-product has a particle size in excess of 90 microns and is called Red Sand™ by Alcoa of Australia Limited (Alcoa). This coarse fraction is unique to Western Australia due to the high quartz content of bauxite from the Darling Range. Alcoa has three Western Australian refineries and this coarse fraction represents a potential resource of up to 20,000 tonnes per day.Red Sand™ currently requires storage in large and expensive impoundment sites due to the entrained sodium hydroxide. This is both an expensive cost upon the production facility as well as a wasted resource to the community. A variety of uses for coarse bauxite residues have now been evaluated. Primarily, Red Sand™ has been deemed to have physical properties suitable for use as construction sand because it is little different from fine crushed rock (which it actually is). Some of the uses now evaluated include use as a general fill material, in concrete, use in geopolymers, for topdressing of turf, for drainage improvement of turf, as lower sub-grade base in road construction and as the valuable sub-base in road construction. The normal use of sand in Western Australia is about 9 million tonnes per annum. Significant infrastructure projects, however, could require several multiples of this; whereas the production of Red Sand™ could be as high as 20 million tonnes per annum. Clearly new markets for this material will be required to take advantage of this unutilised resource if it is to be fully commercialised.One method for opening markets and improving product value is to apply magnetic separation techniques. Magnetic separation of Red Sand™ has yielded a material that may be suitable for iron production and another that may be suitable for concrete manufacture. Other fractions appear to have new opportunities but are not covered here. Initial separations tended to provide a band of sand that resists separation and totals about 30% of total volume. Operational parameters and investigations were required to reduce or remove this fraction.This thesis looked at the assessment of sand sources and the production of clean sand for various applications. This was an iterative process as the production of clean sand (Red Sand™) ultimately required a process that would allow subsequent magnetic separation if required. The production of clean sand was tested in the laboratory and then on a 10t/hr pilot plant. Product from this plant was then used in the construction of a trial section of road.Assessments were also made on the magnetic separation products to remove alumina, both for recovery to the alumina process, but also to improve product quality of the high iron fraction.
22
Boivin, Alain. "Étude expérimentale sur le compactage de la boue rouge dans un décanteur semi-industriel /." Thèse, Chicoutimi : [Rimouski : Université du Québec à Chicoutimi ;. Université du Québec à Rimouski], 2004. http://theses.uqac.ca.
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Thèse (M.Eng.) -- Université du Québec à Chicoutimi, programme extensionné à l'Université du Québec à Rimouski, 2003.Bibliogr.: f. [189-195]. Document électronique également accessible en format PDF. CaQCU
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Kurucak, Abdurrahman. "Flow Sheet Optimization By The Concept Of Sustainable Development: Alumina Industry." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611680/index.pdf.
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In this study, effects of changes in various parameters of the Bayer process on the amount of &ldquored mud&rdquo
, which has many environmental drawbacks, were examined in accordance with the principles of &ldquo
sustainable development&rdquo
. The production process of SeydiSehir Aluminum Plant is modeled as a case study. First a steady-state mass balance calculation is carried out by incorporating sequential modular approach. Then a model of the Bayer process digester is programmed and several simulations are carried out using this model. Results of the mass balance calculation revealed that changes in the extent of the digestion reaction, which is a function of temperature and caustic concentration, and washing efficiency may have a 2.07% decrease on the amount of red mud produced,which implies nearly 10,000 tons of decline per annum, while amount of hydrate produced is increased by 4.52%. A 7.40 % decrease on the amount of red mud produced on dry basis per kg of hydrate was found to be achievable. Optimum operating temperature for the digester was calculated as 277.3 °
C.
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Jayalatharachchi, Vishakya. "Understanding desilication products in bauxite refinery residues." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/101127/1/Vishakya_Jayalatharachchi_Thesis.pdf.
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This research developed standard methods for quantifying and identifying alkali compounds in red mud, with a particular focus on desilication compounds. X-ray diffraction and infrared spectroscopy were used as they are relatively accessible and fast characterisation techniques for industry to use. This research is of particular importance as it will enable better predictions to be made on the suitability/stability of red mud in land rehabilitation programs.
25
Jitsangiam, Peerapong. "Performance, evaluation, and enhancement of red sand for road bases, embankments, and seawall fills." Thesis, Curtin University, 2007. http://hdl.handle.net/20.500.11937/1733.
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Australia produces approximately 40% of the world’s bauxite and over 30% of the world’s alumina. Each year, about 25 million tonnes of bauxite residue is produced in Australia, requiring storage and maintenance. The construction and operation of such large impoundment areas is costly. During the extraction of alumina from bauxite ore using the Bayer process, a fine residue is produced called Red Mud. In West Australia, Darling Range bauxite deposits contain high levels of quartz which result in a coarse residue fraction also being produced. This fraction has been termed Red Sand with a typical particle size in excess of 90 microns. Typically, red mud and red sand are produced in almost equal quantity. Processing of red sand can neutralise the residual caustic and lower the salt content as required. Magnetic separation is also possible to produce a high silica fraction having low iron oxide content. The sustainable use of coarse bauxite residues for road construction is an attractive option with a high potential for large volume reuse.This study focuses on whether red sand is a viable option for use as a road base, embankment fills and as seawall fills in Western Australia. Red sand comes from bauxite ore, a product of intense tropical weathering. Hence, there are various physical properties resulting from the weathering process. Thus it is necessary to fully understand the characterisation of red sand with respect to its engineering properties in the initial part of this research. To satisfy minimum requirements of road bases, a soil stabilisation technique (a Pozzolanic- Stabilised Mixture, PSM) was used. The intent of this stabilisation technique was to use Western Australia’s by-products as stabilising materials. A Pozzolanic - Stabilised Mixture consisting of Class F fly ash (a by-product from a coal power station) and activators (the byproduct from the quicklime manufacturing in terms of lime kiln dust) were employed to develop pozzolanic activity. Once the appropriate mixture of red sand, fly ash, and activators was established (based on a maximum dry density and a value of unconfined compressive strength), a set of laboratory tests were performed which included a triaxial compressive strength test, a resilient modulus test, and a permanent deformation test.Comparisons were made between the stabilised red sand and the conventional road base material in Western Australia (crushed rock added with 2% General Purpose (GP) Portland Cement named Hydrated Cemented Treated Crushed Rock Base, HCTCRB). As for the use of red sand for embankments, the representative stabilised red sand (from red sand for road bases) was used to be an alternative fill embankment material. A testing program to evaluate the important properties of stabilised red sand for embankments including permeability, compressibility and strength was undertaken. The permeability, compressibility, and strength of the representative type of red sand were examined to assess the suitability of red sand as seawall fill. The application of red sand and stabilised red sand on three structures (road bases, embankments and seawalls) is also discussed.
26
Torres, Armando Antonio de Oliveira. "Modelagem do processo Bayer utilizando o software comercial Aspen Plus." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267614.
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Orientador: Maria Regina Wolf MacielDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: O Processo Bayer é definido como uma tecnologia para a produção de óxido de alumínio (Ah03), principal matéria prima para a produção de Alumínio. Este processo transforma o minério de bauxita em alumina Ah03, utilizando soda cáustica e vapor gerado por caldeiras. Os sub processos que compõem o processo Bayer são a Moagem, Digestão, Filtração, Troca Térmica, Precipitação, Calcinação e Evaporação. Utilizando os dados da Refinaria de Poços de Caldas e trabalhando no Laboratório de Desenvolvimento de Processos de Separação da Faculdade de Engenharia Química da Unicamp, foi desenvolvido um método que utiliza os modelos existentes no software Aspen Plus para compor o "Modelo do Processo Bayer".O principal objetivo deste trabalho foi inter-relacionar os modelos do Aspen Plus para representar a Refinaria de Poços de Caldas, simulando o balanço de massa e energia do processo Bayer. A simulação foi conduzi da utilizando o módulo do simulador para sistemas eletrolíticos, considerando o estado dos componentes em seu modo verdadeiro, para melhor representar a não idealidade da solução. O licor do processo Bayer é uma solução eletrolítica, em que a água é o solvente e os demais componentes da mistura, NaOH, NaAlOz, NazCO3 estão completamente dissociados em íons como Na+, AlOz-, CO3-z, e OH-. As operações unitárias utilizadas do software para construir o "Modelo do Processo Bayer" foram o reator estequiométrico, tanques de "flash", lavadores simples, decantadores de contra corrente, misturadores, aquecedores e condensadores. O processo Bayer é controlado através do monitoramento das concentrações alcalina (TA), cáustica (TC) na unidade de equivalente g NazCO3 por litro de licor, como também a concentração de alumina em g AlzO3 por litro de licor. Foi necessário desenvolver uma metodologia que transformasse estas concentrações para expressões na base em massa para os compostos NaOH, NaAlOz, NazCO3 e água. A equação de densidade do Aspen Plus apresentou um desvio de 15% quando tentou-se obter os volumes e massas da solução. Foi necessária a utilização de uma outra equação de densidade (Equação de Russel) para desenvolver o método de transformação das concentrações de solução em massa. Comparando-se este método com dados analíticos, encontrou-se desvios da ordem de 1 %, demonstrando grande precisão do método. A entrada de dados para as simulações foram provenientes de amostras e análises químicas do licor e medidas de fluxo, temperatura e pressão do processo produtivo. Com os resultados da simulação do "Modelo do Processo Bayer", as massas dos íons Na+, AL02-, C03-2, e OH- são obtidas, as quais são transformadas em concentrações nas bases TA, TC e AhO3, para que seja possível a comparação entre os resultados do modelo e os dados analíticos de cada sub processo. Os desvios entre os resultados dos modelos de cada sub processo e as concentrações de planta estiveram entre O e 3 %. F oram utilizados fatores de ajuste para representar o sub processo da digestão e a evaporação natural dos tanques de processo para aumentar a precisão do modelo. O "Modelo do Processo Bayer" apresentou baixos desvios da realidade quando foram comparadas com as concentrações da solução cáustica da planta e as geradas pelo modelo. Foi observado o grande potencial de utilização nas seguintes atividades: Planejamento operacional e estimativa do custo de produção da alumina de acordo com o consumo de soda, bauxita e energia. Controle de volume da planta. Predizer as concentrações cáusticas do licor; Diferenças e perdas de energia em aquecedores; Identificação de anonnalidades no processo
Abstract: (AlzO3), main raw material to produce Aluminum. This process transforms Bauxite ore in a white sand alumina (AlzO3), using Caustic Soda and Steam from the Boilers. The sub processes that represent a Bayer Refinery are Grinding, Digestion, Filtration, Heat Exchange, Precipitation, Ca1cination and Evaporation. Using the Poços de Caldas Refinery data, and working at the Separation Process Development Laboratory at Campinas State University, a method to link the models in Aspen Plus software, to build up the Bayer process was developed. The main objective of this work was to interrelate the models from the Aspen Plus to represent the Poços de Caldas Refinery, to simulate the Energy and Mass Balances from the Bayer Process. Simulation for Electrolyte Systems were performed, with true components and to represent the non-ideality ofthe liquid solution, the NRTL thermodynamic model was used to get the activity coefficients in order to calculate the vapor-liquid phase equilibria. The Bayer liquor is an electrolyte solution, in which water is the solvent and the components from the mixture, NaOH, NaAlO2, Na2CO3 are completely dissociated in ions as Na+, AlO2-, CO3-Z and OH-. The unit operations used from the software to build up the Bayer process are: Stoichometric Reactor, Flash Tank, Single Wash, Counter Current Decanter, Mixers, Heaters and Condensers. The Bayer process is controlled by following the alkaline, caustic and alumina concentrations in equivalent unit (g Na2CO3 per liquor liter). A methodology to transform this concentration expression in mass of NaOH, NaAlOz, Na2CO3 and water was necessary to be developed. The density equation from the Aspen Plus gave 15% of error when it was tried to calculate the volumes or the masses. Another equation (Russell equation) was, then, used to develop the method to transform the concentration number in mass. Comparing with analytical data, the error were about 1 %, giving a good accuracy to the translated method. Samples and chemical analyses, flows, temperature and pressure measurements are the inputs for the model from the planto The outputs from the "Bayer Model" in Na+, AIO2-, CO3-and OR mass, were transformed in TA, TC and AhO3 concentrations (Alkaline, Caustic and Alumina concentration) to compare with the results of the analytical plant that were collected in the outlets from each sub processo Each sub processes was runned and the outputs plant concentrations were compared with the results from Aspen giving deviations between O and 3%. Fitting factors in the reactor to represent the digestors were used. The natural evaporation that occurs in the tanks was necessary to be considered in the model to increase its accuracy. The Bayer Model developed can be used to: Control the plant volume. Predict liquor concentration and find ilegal dilution in the process. Carry out an operating plan and to estimate the alumina cash cost according to the consumption of Soda, Bauxite and Energy Proceed with mass and energy balances and lost in the heaters. So, using the models from Aspen Plus for Electrolyte System, it is possible to build up a "Bayer Process Model" to represent a Plant with deviation between O to 3%. With this accuracy, the model can predict the energy and mass balances and the solution concentrations from the plant liquor. The density equation from Russell is necessary to be used to get the accuracy commented to translate the liquor concentration (TA, TC and AhO3) to the NaOH, NaAlO2, Na2CO3 and Water
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
27
Escobar, Eduardo Marchioni. "Determinação simultanea, em linha, da concentração de soda caustica e de alumina em solução de aluminato de sodio do processo bayer de produção de oxido de aluminio." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248534.
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Orientador: Marcia Miguel Castro FerreiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Mestrado
Físico-Química
Mestre em Química
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Garcia, Marta Cristina Suarez. "Modificação do resíduo de bauxita gerado no processo Bayer por tratamento térmico." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-13062013-121328/.
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A lama vermelha é o resíduo gerado pela Indústria do Alumínio. Assim como outros resíduos industriais apresenta características complexas com inúmeras dificuldades de manipulação, além de ser um material perigoso pela sua baixa granulometria e alcalinidade. É um resíduo com potencial poluidor alto, agravado pela forma de disposição vulnerável geralmente adotada, sendo esta a disposição do resíduo em lagoas projetadas para esta finalidade. O estudo e desenvolvimento de alternativas sustentáveis para a utilização da lama vermelha devidamente tratada como matérias-primas de outros processos são tendências importantes e necessárias no contexto mundial de preservação do meio ambiente. O objetivo deste estudo é compreender o comportamento da lama vermelha sob a influência de diferentes temperaturas de tratamento térmico. Baseados nos efeitos de redução de área e transformações de fases, característicos dos processos térmicos, adotou-se um foco de análise voltado para a redução pH e dos íons livres. A identificação dos pHs adequados de análise da concentração de íons solúveis foi feita com base nas curvas de mobilidade eletroforética e condutividade. Os resultados obtidos para as amostras calcinadas mostraram queda do pH inicial das dispersões e da concentração dos íons solubilizados. Esse efeito pode ser atribuído a redução de área e a incorporação de íons à estrutura, o que assegura ao resíduo menor reatividade.Red mud is the waste generated by Aluminium Industry, like other industrial wastes, has complex features with several difficulties in handling, as well as being a hazardous material because of its low particle size, alkalinity and high amount generated. It is a waste with high pollution potential, compounded by the vulnerability of the disposition generally adopted, usually in lagoons designed for this purpose. The study and development of sustainable alternatives for the use of properly treated red mud, as raw material of other processes, are important tendencies and necessaries in the global context of environmental preservation. However, this work deals the thermal treatment as method to modify the characteristics of the waste, suggesting the reduction of alkalinity with the lower leaching of alkaline ions. This approach can be a discarding alternative most reliable and safe for the environment. The objective of this study is understand the red muds behavior using thermal treatment. Based on the reduction effects of the area and phase transformations characteristic of thermal process, the analysis was taken observing the reduction of free ions and pH. Identification of correct pH of analyse of soluble ions concentration was based at mobility electrophoretic and conductivity graphics. The results of calcined samples showed reduction of initial pH and the concentration of soluble ions. This effect could be assigned to the area reduction and ions incorporation at structure, which ensures the residue lower reactivity.
29
QUARESMA, Danielly da Silva. "Estudo hidrometalúrgico de compostos de titânio proveniente do resíduo do processo Bayer." Universidade Federal do Pará, 2012. http://repositorio.ufpa.br/jspui/handle/2011/3420.
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Estudos realizados no resíduo do processo Bayer, lama vermelha, para reciclagem desse material têm sido intensificados por suas características físico-químicas. O resíduo é constituído por inúmeros óxidos, destes se destaca o óxido de ferro em teores acima de 30% em peso e óxido de titânio em concentrações acima de 5% em peso. Este trabalho estuda a possibilidade de extrair óxido de ferro, objetivando a concentração de compostos de titânio. A extração foi realizada através do processo de calcinação da lama vermelha a 900°C seguida de lixiviação ácida com concentração de H2SO4 a 20% e 30% em volume a 60°C, 80°C e 90°C, com retirada de uma alíquota a cada 30 minutos. Durante o processo de lixiviação, foi observada extração intensa dos compostos de ferro, resultando no aumento da concentração de titânio na lama vermelha, verificado em todos os experimentos, com destaque para os que foram realizados a 90°C e H2SO4 a 30% em v/v, onde houve extração de 95% de ferro e concentração de até 14% de titânio considerando o balanço de massa global. Diante dos dados obtidos, a lama vermelha torna-se um material interessante para ser utilizado como fonte alternativa para obtenção de minerais de titânio, os quais são encontrados na natureza com um percentual em torno de 8%.
Studies performed in the Bayer process residue, red mud, for recycling this material has been intensified by their physicochemical characteristics. The residue has several oxides, these stands out the iron oxide content above 30% by weight and titanium oxide at concentrations above 5% by weight. This work studies the possibility of extracting iron oxide, aiming at concentration of titanium compounds. The extraction was carried through process of calcination of red mud at 900°C followed by acid leaching with concentration of H2SO4 at 20% and 30% by volume at 60°C, 80°C and 90°C, with removal of an aliquot every 30 minutes. During the leaching process, there was intense extraction of iron compounds, resulting in an increased concentration of titanium at the red mud. This was found in all experiments, especially those which were performed at 90°C and H2SO4 at 30% v/v, where was a extraction of 95% iron and concentration of up to 14% titanium considering the global mass balance. From the data obtained, the red mud becomes an interesting material to be used as an alternative source of minerals titanium, which are found in nature with a percentage of around 8%.
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REIS, André Wilson da Cruz. "Caracterização mineralogica do agregado obtido a partir da lama vermelha do processo bayer." Universidade Federal do Pará, 2014. http://repositorio.ufpa.br/jspui/handle/2011/7707.
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As atividades industriais cada vez mais geram uma grande quantidade de resíduos e subprodutos, sendo armazenados no meio ambiente, apresentando características físico-químicas que podem na maioria das vezes serem reutilizadas. A lama vermelha, resíduo do processo Bayer, vem sendo estudada para o uso na produção de agregados sintéticos, que tem como finalidade substituir os agregados naturais utilizados na construção civil. Este trabalho estuda as características físico-químicas e mineralógicas dos agregados sintetizados a partir da mistura da lama vermelha, argila, areia e carvão vegetal em 4 composições, variando as quantidades de lama vermelha e argila. As matérias primas foram pré-tratadas e analisadas por fluorescência de Raios-X, difração de Raios-X, Análise térmica e granulométrica. As amostras foram calcinadas a 1200ºC por 4 horas. Em seguida submetidas a análises por difratometria de Raios-X, fluorescência de Raios-X, análise térmica diferencial e microscopia eletrônica de varredura para caracterização e testes físicos. Para o estudo da observação de mullita no agregado sintético foram confeccionados corpos de prova embutidos em resina e adição de HF a 5% por 3 e 4 minutos. O material após a sinterização apresentou, massa especifica aparente média abaixo de 2 g\cm3, fases cristalinas principais por DRX quartzo e hematita e pode ser observada a presença de mullita a partir do tratamento com HF.
The industrial activities increasingly generate a lot of waste and by-products being stored in the environment, with physicochemical characteristics which can most often be reused. The red mud residue from the Bayer process, is being studied for use in the production of synthetic aggregates, which aims to replace natural aggregates used in construction. This work studies the physical, chemical and mineralogical characteristics of the aggregates synthesized from a mixture of red mud, clay, sand and charcoal in 4 compositions, varying amounts of red mud and clay. The raw materials were pretreated and analyzed by X-ray fluorescence, X - ray diffraction, thermal and particle size analysis. The samples were calcined at 1200 °C for 4 hours. Then subjected to analysis by X-ray diffraction, X- ray fluorescence, differential thermal analysis and scanning for characterization and physical tests electron microscopy. For the study of the observation of synthetic mullite aggregate specimens embedded in resin, and adding 5% HF for 3 to 4 minutes were made. The material presented after sintering, apparent specific gravity average below 2 g\cm3 main crystalline phases by XRD quartz and hematite and the presence of mullite from the HF treatment can be observed.
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Avelar, Angela Nair. "Influência da mineralogia na etapa de separação da lama vermelha no processo Bayer." Programa de Pós-Graduação em Engenharia Mineral. Departamento de Engenharia de Minas, Escola de Minas, Universidade Federal de Ouro Preto, 2011. http://www.repositorio.ufop.br/handle/123456789/2349.
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Neste trabalho foi realizado um estudo de caracterização mineralógica em amostras bauxitas de forma a permitir uma melhor quantificação das espécies de ferro presentes nos minérios originais e nas lamas vermelha obtidas a partir da digestão alcalina em escala de laboratório. Esta caracterização permitiu identificar um correlação entre a composição mineralógica e o desempenho na etapa de sedimentação da lama vermelha. As amostras utilizadas nesse trabalho são provenientes de Trombetas (Mineração Rio do Norte) e de Paragominas (Mineração Paragominas S.A.) localizadas no Pará também uma amostra de Gana. Os ensaios de digestão alcalina foram realizados a 145°C e pressão de 5,0 Kgf/cm 2 . Tanto as amostras iniciais quanto as lamas geradas na digestão foram caracterizadas por microscopia ótica, microscopia eletrônica de varredura, análise termogravimétricas, análises químicas, difração de raios X e espectroscopia Mössbauer A quantificação das fases majoritárias existentes em todas as amostras foi realizada com a combinação dos resultados obtidos por estas técnicas. A espectroscopia Mössbaue possibilitou a comprovação da existência de dois tipos de goethita nas amostras iniciais Para algumas amostras ocorreu a conversão de goethita para hematita. Observou-se um correlação linear satisfatória (R 2 ~0.90, n = 9) entre a velocidade de sedimentação e o teores de goethita com maiores substituições isomórficas e/ou menores tamanhos d partícula. Desta forma, sugere-se que a presença desse tipo de goethita tem efeito negativo na velocidade de sedimentação. ____________________________________________________________________________________________________
ABSTRACT: A mineralogical characterization of several bauxites was undertaken in order in order to improve the quantification of all iron-bearing species occurring in the beneficiated ores and in the red mud obtained from the alkaline digestion tests carried out on laboratory scale. A correlation between the mineralogical composition and the settling rate of red mud was derived. The samples used in this work were from Trombetas (MRN) and Paragominas (Mineração Paragominas S.A.) located in the Para State and one sample from Ghana. The alkaline digestions were done at 145°C and pressure of 5.0 kgf/cm 2 . Both the initial samples and the red mud generated in these digestions were characterized by optical microscopy, scanning electron microscopy, thermogravimetric analysis, chemical analysis, X-ray diffraction and Mössbauer spectroscopy. The quantification of the major phases was made by combining the results obtained by these techniques. The Mössbauer results allowed the identification of two types of goethite in the initial samples. For some samples it was observed the conversion of goethite to hematite during the digestion. A satisfactory linear correlation (r 2 ~ 0.90, n =9) between the red mud settling and the concentration of goethite with higher isomorphic substitutions and / or smaller particle sizes was observed. Thus, it is suggested that the presence of this type of goethite has a negative effect on the settling rate.
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Chen, Zhao. "Bayesian and Empirical Bayes approaches to power law process and microarray analysis." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000430.
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Grosso, Andrea. "Tailing del Processo Bayer: analisi dell'alcalinità e studio del processo industriale di filtropressatura al fine di ridurne l'impatto ambientale." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3912/.
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Eisenbarth, Thomas [Verfasser], and Bernhard [Akademischer Betreuer] Bauer. "Semantic Process Models: Transformation, Adaptation, Resource Consideration / Thomas Eisenbarth. Betreuer: Bernhard Bauer." Augsburg : Universität Augsburg, 2014. http://d-nb.info/1077703414/34.
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Hogan, Matthew Charles. "Process issues in redox biocatalysis : cyclohexanone monooxygenase catalysed chiral lactone syntheses." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325655.
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Hubbard, Rebecca Allana. "Modeling a non-homogeneous Markov process via time transformation /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9607.
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Baier, Thomas [Verfasser], and Mathias [Akademischer Betreuer] Weske. "Matching events and activities : preprocessing event logs for process analysis / Thomas Baier ; Betreuer: Mathias Weske." Potsdam : Universität Potsdam, 2015. http://d-nb.info/1217939040/34.
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van, der Wilk Mark. "Sparse Gaussian process approximations and applications." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288347.
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Many tasks in machine learning require learning some kind of input-output relation (function), for example, recognising handwritten digits (from image to number) or learning the motion behaviour of a dynamical system like a pendulum (from positions and velocities now to future positions and velocities). We consider this problem using the Bayesian framework, where we use probability distributions to represent the state of uncertainty that a learning agent is in. In particular, we will investigate methods which use Gaussian processes to represent distributions over functions. Gaussian process models require approximations in order to be practically useful. This thesis focuses on understanding existing approximations and investigating new ones tailored to specific applications. We advance the understanding of existing techniques first through a thorough review. We propose desiderata for non-parametric basis function model approximations, which we use to assess the existing approximations. Following this, we perform an in-depth empirical investigation of two popular approximations (VFE and FITC). Based on the insights gained, we propose a new inter-domain Gaussian process approximation, which can be used to increase the sparsity of the approximation, in comparison to regular inducing point approximations. This allows GP models to be stored and communicated more compactly. Next, we show that inter-domain approximations can also allow the use of models which would otherwise be impractical, as opposed to improving existing approximations. We introduce an inter-domain approximation for the Convolutional Gaussian process - a model that makes Gaussian processes suitable to image inputs, and which has strong relations to convolutional neural networks. This same technique is valuable for approximating Gaussian processes with more general invariance properties. Finally, we revisit the derivation of the Gaussian process State Space Model, and discuss some subtleties relating to their approximation. We hope that this thesis illustrates some benefits of non-parametric models and their approximation in a non-parametric fashion, and that it provides models and approximations that prove to be useful for the development of more complex and performant models in the future.
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Santos, Hugo Henrique Kegler dos. "Procedimentos sequenciais Bayesianos aplicados ao processo de captura-recaptura." Universidade Federal de São Carlos, 2014. https://repositorio.ufscar.br/handle/ufscar/4494.
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Previous issue date: 2014-05-30Financiadora de Estudos e Projetos
In this work, we make a study of the Bayes sequential decision procedure applied to capture-recapture with fixed sample sizes, to estimate the size of a finite and closed population process. We present the statistical model, review the Bayesian decision theory, presenting the pure decision problem, the statistical decision problem and the sequential decision procedure. We illustrate the theoretical methods discussed using simulated data.
Neste trabalho, fazemos um estudo do procedimento de decisão sequencial de Bayes aplicado ao processo de captura-recaptura com tamanhos amostrais fixados, para estimação do tamanho de uma população finita e fechada. Apresentamos o modelo estatístico, revisamos a teoria de decisão bayesiana, apresentando o problema de decisão puro, o problema de decisão estatística e o procedimento de decisão sequencial. Ilustramos os métodos teóricos discutidos através de dados simulados.
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Ravet, Alexandre. "Introducing contextual awareness within the state estimation process : Bayes filters with context-dependent time-heterogeneous distributions." Thesis, Toulouse, INSA, 2015. http://www.theses.fr/2015ISAT0045/document.
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Ces travaux se focalisent sur une problématique fondamentale de la robotique autonome: l'estimation d'état. En effet, la plupart des approches actuelles permettant à un robot autonome de réaliser une tâche requièrent tout d'abord l'extraction d'une information d'état à partir de mesures capteurs bruitées. Ce vecteur d'état contient un ensemble de variables caractérisant le système à un instant t, comme la position du robot, sa vitesse, etc. En robotique comme dans de nombreux autres domaines, le filtrage bayésien est devenu la solution la plus populaire pour estimer l'état d'un système de façon robuste et à haute fréquence. Le succès du filtrage bayésien réside dans sa relative simplicité, que ce soit dans la mise en oeuvre des équations récursives de filtrage, ou encore dans la représentation simplifiée et intuitive du système au travers du modèle de Markov caché d'ordre 1. Généralement, un filtre bayésien repose sur une description minimaliste de l'état du système. Cette représentation simplifiée permet de conserver un temps d'exécution réduit, mais est également la conséquence de notre compréhension partielle du fonctionnement du système physique. Tous les aspects inconnus ou non modélisés du système sont ensuite représentés de façon globale par l'adjonction de composantes de bruit. Si ces composantes de bruit constituent une représentation simple et unifiée des aspects non modélisés du système, il reste néanmoins difficile de trouver des paramètres de bruit qui sont pertinents dans tous les contextes. En effet, à l'opposé de ce principe de modélisation, la problématique de navigation autonome pose le problème de la multiplicité d'environnements différents pour lesquels il est nécessaire de s'adapter intelligemment. Cette problématique nous amène donc à réviser la modélisation des aspects inconnus du systèmes sous forme de bruits stationnaires, et requiert l'introduction d'une information de contexte au sein du processus de filtrage. Dans ce cadre, ces travaux se focalisent spécifiquement sur l'amélioration du modèle état-observation sous-jacent au filtre bayésien afin de le doter de capacités d'adaptation vis-à-vis des perturbations contextuelles modifiant les performances capteurs. L'objectif principal est donc ici de trouver l'équilibre entre complexité du modèle et modélisation précise des phénomènes physiques représentés au travers d'une information de contexte. Nous établissons cet équilibre en modifiant le modèle état-observation afin de compenser les hypothèses simplistes de bruit stationnaire tout en continuant de bénéficier du faible temps de calcul requis par les équations récursives. Dans un premier temps, nous définissons une information de contexte basée sur un ensemble de mesures capteurs brutes, sans chercher à identifier précisément la typologie réelle de contextes de navigation. Toujours au sein du formalisme bayésien, nous exploitons des méthodes d'apprentissage statistique pour identifier une distribution d'observation non stationnaire et dépendante du contexte. cette distribution repose sur l'introduction de deux nouvelles composantes: un modèle destiné à prédire le bruit d'observation pour chaque capteur, et un modèle permettant de sélectionner un sous-ensemble de mesures à chaque itération du filtre. Nos investigations concernent également l'impact des méthodes d'apprentissage: dans le contexte historique du filtrage bayésien, le modèle état-observation est traditionnellement appris de manière générative, c'est à dire de manière à expliquer au mieux les paires état-observation contenues dans les données d'apprentissage. Cette méthode est ici remise en cause puisque, bien que fondamentalement génératif, le modèle état-observation est uniquement exploité au travers des équations de filtrage, et ses capacités génératives ne sont donc jamais utilisées[...]Prevalent approaches for endowing robots with autonomous navigation capabilities require the estimation of a system state representation based on sensor noisy information. This system state usually depicts a set of dynamic variables such as the position, velocity and orientation required for the robot to achieve a task. In robotics, and in many other contexts, research efforts on state estimation converged towards the popular Bayes filter. The primary reason for the success of Bayes filtering is its simplicity, from the mathematical tools required by the recursive filtering equations, to the light and intuitive system representation provided by the underlying Hidden Markov Model. Recursive filtering also provides the most common and reliable method for real-time state estimation thanks to its computational efficiency. To keep low computational complexity, but also because real physical systems are not perfectly understood, and hence never faithfully represented by a model, Bayes filters usually rely on a minimum system state representation. Any unmodeled or unknown aspect of the system is then encompassed within additional noise terms. On the other hand, autonomous navigation requires robustness and adaptation capabilities regarding changing environments. This creates the need for introducing contextual awareness within the filtering process. In this thesis, we specifically focus on enhancing state estimation models for dealing with context-dependent sensor performance alterations. The issue is then to establish a practical balance between computational complexity and realistic modelling of the system through the introduction of contextual information. We investigate on achieving this balance by extending the classical Bayes filter in order to compensate for the optimistic assumptions made by modeling the system through time-homogeneous distributions, while still benefiting from the recursive filtering computational efficiency. Based on raw data provided by a set of sensors and any relevant information, we start by introducing a new context variable, while never trying to characterize a concrete context typology. Within the Bayesian framework, machine learning techniques are then used in order to automatically define a context-dependent time-heterogeneous observation distribution by introducing two additional models: a model providing observation noise predictions and a model providing observation selection rules.The investigation also concerns the impact of the training method we choose. In the context of Bayesian filtering, the model we exploit is usually trained in the generative manner. Thus, optimal parameters are those that allow the model to explain at best the data observed in the training set. On the other hand, discriminative training can implicitly help in compensating for mismodeled aspects of the system, by optimizing the model parameters with respect to the ultimate system performance, the estimate accuracy. Going deeper in the discussion, we also analyse how the training method changes the meaning of the model, and how we can properly exploit this property. Throughout the manuscript, results obtained with simulated and representative real data are presented and analysed
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Sun, Yaguang [Verfasser], and Bernhard [Akademischer Betreuer] Bauer. "Mining High-Quality Business Process Models from Real-Life Event Logs / Yaguang Sun ; Betreuer: Bernhard Bauer." Augsburg : Universität Augsburg, 2018. http://d-nb.info/115333903X/34.
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SOUZA, José Antônio da Silva. "Estudo e avaliação do uso de resíduos do processo Bayer como matéria-prima na produção de agregados sintéticos para a construção civil." Universidade Federal do Pará, 2010. http://repositorio.ufpa.br/jspui/handle/2011/4050.
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A grande quantidade de resíduos sólidos, oriundos da indústria de mineração e metalurgia, constitui um sério problema sócio-ambiental. As características físicoquímicas destes resíduos despertam grande interesse para outras indústrias. A indústria cerâmica pode ser uma interessante consumidora da maioria deste material, para suprir a grande escassez das reservas de matérias-primas atual. Neste contexto, este trabalho mostra os estudos realizados para a reciclagem da lama vermelha, como matéria-prima na produção de agregado sintético, visando à construção civil. A lama vermelha, principal rejeito industrial da fabricação de alumina, mostrou-se um insumo de grande interesse na fabricação de diferentes tipos de agregado para ser utilizado na produção de concreto, para a construção civil. Pelas suas características físico-químicas e a grande quantidade que é produzida anualmente (cerca de 10.000.000 t em duas fábricas, só no Norte do Brasil). Estudos realizados neste trabalho mostram a possibilidade de fabricação de agregados, com diferentes propriedades e possibilidades de aplicação, na indústria da construção civil. Estas propriedades dependem do controle de parâmetros, como o teor de sílica livre e argila, a granulometria e a temperatura de sinterização. Tais variáveis permitem controlar perfeitamente a formação de fase vítrea que é a responsável pelas propriedades dos agregados como: porosidade, resistência mecânica e densidade. Este material pode ser utilizado em concreto convencional ou em concretos especiais, para atender a demanda da construção civil.
The large amount of solid waste coming from mines and metallurgical industries became a serious social-environmental problem. The physical and chemical features of this material can raise a great interest in other industries. The ceramic industry might be a great costumer for most of this material, since it can supply the current lack of raw material. The red mud, main industrial residue of the alumina manufacturing, has been a very interesting input for several kinds of aggregates manufacturing used for the concrete production in civil engineering. In this context, this paper deals with studies concerning the red mud recycling to be applied as raw material for the synthetic light aggregate production to be used as an alternative material in the civil construction industry. This is because of its physical-chemical features and the large amount annually produced (around 10 million tons within two factories in the North of Brazil). The studies completed in this work show the feasibility of aggregates manufacturing, with different properties and possibilities. These properties depend on the parameters control such as content of free silica and clay, and the sintering temperature. Such variables allow to perfectly controlling the glassy phase formation which is responsible for the aggregate properties such as: porosity, mechanical resistance and density. This material can be used for conventional or special concretes to supply the civil engineering needs.
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Hwang, Beom Seuk. "Semiparametric Bayesian Joint Modeling with Applications in Toxicological Risk Assessment." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366327467.
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Costa, Eliardo Guimarães da. "Tamanho amostral para estimar a concentração de organismos em água de lastro: uma abordagem bayesiana." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-05072018-164225/.
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Metodologias para obtenção do tamanho amostral para estimar a concentração de organismos em água de lastro e verificar normas internacionais são desenvolvidas sob uma abordagem bayesiana. Consideramos os critérios da cobertura média, do tamanho médio e da minimização do custo total sob os modelos Poisson com distribuição a priori gama e binomial negativo com distribuição a priori Pearson Tipo VI. Além disso, consideramos um processo Dirichlet como distribuição a priori no modelo Poisson com o propósito de obter maior flexibilidade e robustez. Para fins de aplicação, implementamos rotinas computacionais usando a linguagem R.Sample size methodologies for estimating the organism concentration in ballast water and for verifying international standards are developed under a Bayesian approach. We consider the criteria of average coverage, of average length and of total cost minimization under the Poisson model with a gamma prior distribution and the negative binomial model with a Pearson type VI prior distribution. Furthermore, we consider a Dirichlet process as a prior distribution in the Poisson model with the purpose to gain more flexibility and robustness. For practical applications, we implemented computational routines using the R language.
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Gill, Hardeep. "The Effect of Aluminium Industry Effluents on Sediment Bacterial Communities." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23423.
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The goal of this project was to develop novel bacterial biomarkers for use in an industrial context. These biomarkers would be used to determine aluminium industry activity impact on a local ecosystem. Sediment bacterial communities of the Saguenay River are subjected to industrial effluent produced by industry in Jonquière, QC. In-situ responses of these communities to effluent exposure were measured and evaluated as potential biomarker candidates for exposure to past and present effluent discharge. Bacterial community structure and composition between control and affected sites were investigated. Differences observed between the communities were used as indicators of a response to industrial activity through exposure to effluent by-products. Diversity indices were not significantly different between sites with increased effluent exposure. However, differences were observed with the inclusion of algae and cyanobacteria. UniFrac analyses indicated that a control (NNB) and an affected site (Site 2) were more similar to one another with regard to community structure than either was to a medially affected site (Site 5) (Figure 2.4). We did not observe a signature of the microbial community structure that could be predicted with effluent exposure. Microbial community function in relation to bacterial mercury resistance (HgR) was also evaluated as a specific response to the mercury component present in sediments. Novel PCR primers and amplification conditions were developed to amplify merP, merT and merA genes belonging to the mer-operon which confers HgR (Table 5.6). To our knowledge, the roles of merP and merT have not been explored as possible tools to confirm the presence of the operon. HgR gene abundance in sediment microbial communities was significantly correlated (p < 0.05) to total mercury levels (Figure 3.4) but gene expression was not measurable. We could not solely attribute the release of Hg0 from sediments in bioreactor experiments to a biogenic origin. However, there was a 1000 fold difference in measured Hg0 release between control and affected sites suggesting that processes of natural remediation may be taking place at contaminated sites (Figure 3.7). Abundance measurements of HgR related genes represent a strong response target to the mercury immobilized in sediments. Biomarkers built on this response can be used by industry to measure long term effects of industrially derived mercury on local ecosystems. The abundance of mer-operon genes in affected sites indicates the presence of a thriving bacterial community harbouring HgR potential. These communities have the capacity to naturally remediate the sites they occupy. This remediation could be further investigated. Additional studies will be required to develop biomarkers that are more responsive to contemporary industrial activity such as those based on the integrative oxidative stress response.
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Do, Van-Cuong. "Analyse statistique de processus stochastiques : application sur des données d’orages." Thesis, Lorient, 2019. http://www.theses.fr/2019LORIS526/document.
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Les travaux présentés dans cette thèse concernent l'analyse statistique de cas particuliers du processus de Cox. Dans une première partie, nous proposons une synthèse des résultats existants sur le processus power-law (processus d'intensité puissance), synthèse qui ne peut être exhaustive étant donné la popularité de ce processus. Nous considérons une approche bayésienne pour l'inférence des paramètres de ce processus qui nous conduit à introduire et à étudier en détails une distribution que nous appelons loi H-B. Cette loi est une loi conjuguée. Nous proposons des stratégies d'élicitation des hyperparamètres et étudions le comportement des estimateurs de Bayes par des simulations. Dans un deuxième temps, nous étendons ces travaux au cas du processus d’intensité exponentielle (exponential-law process). De la même façon, nous définissons et étudions une loi conjuguée pour l'analyse bayésienne de ce dernier. Dans la dernière partie de la thèse, nous considérons un processus auto-excité qui intègre une covariable. Ce travail est motivé, à l'origine, par un problème de fiabilité qui concerne des données de défaillances de matériels exposés à des environnements sévères. Les résultats sont illustrés par des applications sur des données d'activités orageuses collectées dans deux départements français. Enfin, nous donnons quelques directions de travail et perspectives de futurs développements de l'ensemble de nos travauxThe work presented in this PhD dissertation concerns the statistical analysis of some particular cases of the Cox process. In a first part, we study the power-law process (PLP). Since the literature for the PLP is abundant, we suggest a state-of-art for the process. We consider the classical approach and recall some important properties of the maximum likelihood estimators. Then we investigate a Bayesian approach with noninformative priors and conjugate priors considering different parametrizations and scenarios of prior guesses. That leads us to define a family of distributions that we name H-B distribution as the natural conjugate priors for the PLP. Bayesian analysis with the conjugate priors are conducted via a simulation study and an application on real data. In a second part, we study the exponential-law process (ELP). We review the maximum likelihood techniques. For Bayesian analysis of the ELP, we define conjugate priors: the modified- Gumbel distribution and Gamma-modified-Gumbel distribution. We conduct a simulation study to compare maximum likelihood estimates and Bayesian estimates. In the third part, we investigate self-exciting point processes and we integrate a power-law covariate model to this intensity of this process. A maximum likelihood procedure for the model is proposed and the Bayesian approach is suggested. Lastly, we present an application on thunderstorm data collected in two French regions. We consider a strategy to define a thunderstorm as a temporal process associated with the charges in a particular location. Some selected thunderstorms are analyzed. We propose a reduced maximum likelihood procedure to estimate the parameters of the Hawkes process. Then we fit some thunderstorms to the power-law covariate self-exciting point process taking into account the associated charges. In conclusion, we give some perspectives for further work
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Santos, Evaldo Gondim dos. "O processo tornado vis?vel: metafic??o par?dica e narrativa policial em O Xang? de Baker Street." PROGRAMA DE P?S-GRADUA??O EM ESTUDOS DA LINGUAGEM, 2016. https://repositorio.ufrn.br/jspui/handle/123456789/22676.
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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
Nesta tese ? discutido e analisado como a metafic??o par?dica, a saber, o processo que torna a fic??o vis?vel pela repeti??o com diferen?a, potencializa a cria??o de uma narrativa policial diferente no romance O Xang? de Baker Street (1995), de J? Soares. A pesquisa ? estabelecida a partir de leituras que tratam, sobretudo, da metafic??o par?dica, da escrita autopoi?tica, do humor enquanto arte das superf?cies, bem como da fabula??o de mundos por vir, fazendo uso de conceitos da filosofia da diferen?a em Deleuze e Guattari e da cr?tica liter?ria, principalmente, em Linda Hutcheon, Blanchot e Foucault, tais como: m?quina autopoi?tica, humor, fabula??o, metafic??o, par?dia, espa?o liter?rio e obra. No plano de composi??o, o romance do humorista brasileiro torna a sua realidade ficcional vis?vel pelo parodiar de obras liter?rias e historiogr?ficas, sobretudo as narrativas policiais doylianas e as que retratam o Rio Janeiro no final do s?culo XIX. Nesse sentido, desenvolve-se, nesta obra, uma escrita que se mant?m em si mesma, desloca significa??es e flagra sua realidade ficcional. No heterocosmo soareano, a narrativa se apresenta como num espa?o de uma biblioteca. O apelo da obra se encontra na convoca??o de estere?tipos apresentados em livros sobre a capital do imp?rio dos tr?picos, no final do segundo reinado, bem como em narrativas policiais. A repeti??o com diferen?a de livros e obras p?e em questionamento imagens arraigadas, abrindo espa?o para o ?flagrante delito? da fabula??o de mundos, que se constituem na superf?cie da escrita e que n?o se reduzem a sedimenta??es.
This thesis discusses and analyzes as the parodic metafiction, namely, the process that makes fiction visible by repetition with difference, enhances the creation of a different detective narrative in the novel A Samba for Sherlock (1995), by J? Soares. The research is established by readings which take into account mainly the parodic metafiction, the autopoietic writing, the humor as the art of surfaces, as well as the fabulation of worlds to come, making use of concepts of the philosophy of difference in Deleuze and Guattari and literary criticism, especially in Linda Hutcheon, Blanchot and Foucault such as autopoietic machine, humor, fabulation, metafiction, parody, space of literature and work. In the plane of composition, the novel of the Brazilian humorist makes its fictional reality visible, parodying literary and historiographical works, mainly the Doylian detective narratives, and work related to the Rio de Janeiro of the late nineteenth century. In this sense, this work develops a writing that remains in itself, displaces significations and sees its fictional reality. In Soares?s heterocosm, the narrative brings together the space of a library. The appeal of the work is in the convening of stereotypes presented in books on the capital of the empire of the tropics at the end of the second reign, as well as on detective narratives. The repetition with difference of books and works call into question deep-rooted images, making room for fabulation ?in flagrante delicto? of worlds that constitute the writing surface and not reduce itself to sedimentation.
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Solmi, Stefania. "Studio di nuovi processi catalitici per la sintesi di acido adipico." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5740/.
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L’acido adipico (AA) è un importante intermedio chimico prodotto in quantità pari a circa tre milioni di tonnellate annue, i cui usi riguardano principalmente la produzione di Nylon-6,6. Tutti i processi industriali odierni per la produzione dell’AA hanno in comune lo stadio finale di ossidazione con acido nitrico dell’ultimo intermedio di sintesi, che in genere è una miscela di cicloesanolo e cicloesanone (KA Oil). Esistono diversi problemi riguardanti questo processo, come la pericolosità che deriva dall’uso di acido nitrico concentrato. Dal punto di vista ambientale, il problema principale riguarda la produzione di protossido di azoto e di altri ossidi di azoto durante l’ultima fase di ossidazione con HNO3, per questo motivo, tutte le aziende che producono AA devono essere munite per legge di sistemi di abbattimento quantitativi o di recupero degli ossidi di azoto, che però risultano essere molto incisivi sul costo del processo. A livello industriale, quindi, il problema riguarda principalmente la sostenibilità economica, ma poiché queste procedure hanno un prezzo in termini di materiali ed energia, si ha anche un forte legame con la sostenibilità ambientale. Gli studi riguardanti nuovi processi per la produzione di AA sono numerosi; alcuni hanno portato a vie più “green”, ma solo pochi esempi sono veramente sostenibili dal punto di vista sia ambientale che economico. Il presente lavoro di tesi è diviso in due parti, entrambe riguardanti vie di sintesi alternative per la produzione di AA. La prima parte riguarda lo studio del secondo passaggio di una via di sintesi in due step che parte da cicloesene e che ha come intermedio l’1,2-cicloesandiolo.Sono stati provati catalizzatori eterogenei a base di nanoparticelle di Au supportate su MgO per il cleavage ossidativo in fase liquida del diolo con O2 in ambiente basico. La seconda parte invece riguarda il processo di sintesi dell’AA a partire da cicloesanone mediante l’ossidazione con perossido di idrogeno a e- caprolattone e la successiva ossidazione ad AA. Nello specifico, è stato studiato il meccanismo di reazione del primo passaggio in quanto evidenze sperimentali ottenute nel corso di lavori precedenti avevano dimostrato la presenza di un cammino di reazione differente da quello tipico per un’ossidazione di Baeyer-Villiger. In questa parte, si è studiato l’effetto di alcuni catalizzatori eterogenei a base di acidi di Lewis sui prodotti ottenuti nel primo stadio ossidativo.
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Bakhtiari, Koohsorkhi Alireza. "Analysis of the Dirichlet Process Mixture Model with Application to Dialogue Act Classification." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28503/28503.pdf.
Full textAbstract:
La reconnaissance des intentions de l’utilisateur est l’un des problèmes les plus difficiles
dans la conception des systèmes de dialogues. Ces intentions sont généralement codés
en termes d’actes de dialogue, où un rôle fonctionnel est attribué à chaque énoncé d’une
conversation. L’annotation manuelle des actes de dialogue est généralement coûteuse
et prends du temps, il y a donc un grand intérêt à plutôt annoter automatiquement des
corpus de dialogue.
Dans ce mémoire, nous proposons une approche non paramétrique bayésienne pour
la classification automatique des actes de dialogue. Nous utilisons les mélanges par
processus de Dirichlet (DPMM), dans lesquels chacune des composantes est déterminée
par une distribution de Dirichlet-multinomial. Deux nouvelles approches pour
l’estimation des hyperparamètres dans ces distributions sont introduites. Les résultats
de l’application de ce modèle au corpus DIHANA montre que la DPMM peut récupérer
le nombre réel d’étiquettes en haute précision.Recognition of user intentions is one of the most challenging problems in the design of dialogue systems. These intentions are usually coded in terms of Dialogue Acts (Following Austin’s work on speech act theory), where a functional role is assigned to each utterance of a conversation. Manual annotation of dialogue acts is both time consuming and expensive, therefore there is a huge interest in systems which are able to automatically annotate dialogue corpora. In this thesis, we propose a nonparametric Bayesian approach for the automatic classification of dialogue acts. We make use of the Dirichlet Process Mixture Model (DPMM), within which each of the components is governed by a Dirichlet-Multinomial distribution. Two novel approaches for hyperparameter estimation in these distributions are also introduced. Results of the application of this model to the DIHANA corpus shows that the DPMM can successfully recover the true number of DA labels with high precision
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Ruyt, M. Rayner de. "Estudio de las condicionantes ambientales intervenientes en el proceso de regeneración de bosque nativo alterado en la cuenca inferior del rio Baker : 47°35 - 47°51 latitud sur (coordenadas referenciales)." Tesis, Universidad de Chile, 2009. http://www.repositorio.uchile.cl/handle/2250/115743.
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