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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Contribution to the capacity determination of semi-mobile in-pit crushing and conveying systems

Ritter, Robert 04 January 2017 (has links) (PDF)
As ore grades decline, waste rock to ore ratios increase and mines become progressively deeper mining operations face challenges in more complex scenarios. Today´s predominant means of material transport in hard-rock surface mines are conventional mining trucks however despite rationalisation efforts material transportation cost increased significantly over the last decades and currently reach up to 60% of overall mining. Thus, considerations and efforts to reduce overall mining costs, promise highest success when focusing on the development of more economic material transport methods. Semi-mobile in-pit crusher and conveyor (SMIPCC) systems represent a viable, safer and less fossil fuel dependent alternative however its viability is still highly argued as inadequate methods for the long term projection of system capacity leads to high uncertainty and consequently higher risk. Therefore, the objective of this thesis is to develop a structured method for the determination of In-pit crusher and conveyor SMIPCC system that incorporates the random behaviour of system elements and their interaction. The method is based on a structured time usage model specific to SMIPCC system supported by a stochastic simulation. The developed method is used in a case study based on a hypothetical mine environment to analyse the system behaviour with regards to time usage model component, system capacity, and cost as a function of truck quantity and stockpile capacity. Furthermore, a comparison between a conventional truck & shovel system and SMIPCC system is provided. Results show that the capacity of a SMIPCC system reaches an optimum in terms of cost per tonne, which is 24% (22 cents per tonne) lower than a truck and shovel system. In addition, the developed method is found to be effective in providing a significantly higher level of information, which can be used in the mining industry to accurately project the economic viability of implementing a SMIPCC system.
52

Evaluating the effects of radio-frequency treatment of rocks: textural changes and implications for rock comminution

Swart, Arthur James 12 1900 (has links)
D. Tech. (Engineering, Department Electronic Engineering, Faculty of Engineering and Technology), Vaal University of Technolog / Ore, from a mining operation, goes through a process that separates the valuable minerals from the gangue (waste material). This process usually involves crushing, milling, separation and extraction where the gangue is usually discarded in tailings piles. Current physical methods used for crushing of rocks in the mineral processing industry result in erratic breakages that do not efficiently liberate the economically valuable minerals. Research studies have found that the rock comminution and mineral liberation can be enhanced through various electrical treatment techniques, including pulsed power, ultrasound and microwave. These electrical treatment techniques each have their own advantages and disadvantages which are discussed in this dissertation. However, this research proposes a new technique in an attempt to improve the rock comminution process. The main purpose of this research is to evaluate the effect that RF power exerts on rock samples, with particular focus on textural changes. Four valuable scientific contributions to the fields of metallurgical and electrical engineering were made in this regard. Firstly, a new technique for the treatment of rock samples using RF heating is substantiated. The effect of RF power on textural changes of the rocks is evident in their surface temperature rise, where the RF heating of dole-rite (JSA) and marble (JSB, JS 1 and JS2) resulted in surface temperatures of approximately 100 °C within two minutes of treatment. A particle screening analysis of particles obtained form a swing-pot mill of both the untreated (not exposed to RF power) and treated (exposed to RF power) rock samples were performed to ascertain if the treated samples' size had changed. Two samples (JSA and JSD) revealed a notable change in their particle size distribution. The fact that the percentage of larger sized particles increased (from 38 J..Lm to 90 J..Lffi as seen in Chapter 6) suggests that the rock was strengthened rather than weakened. Secondly, an innovative coupling technique (using a parallel-plate capacitor with dimensions of 28 x 47 mm) to connect rock samples to high powered RF electronic equipment is described. The feasibility of this technique is confirmed by repeated correlated measurements taken on a vector voltmeter and network analyser. Low SWR readings obtained from an inline RF Wattmeter in a practical setup also proves the viability of the matching network used in the coupling technique. Thirdly, anoriginal coupling coefficient (81.58 x 10-3) for the parallel-plate capacitor is presented. This value may be used in similar sized capacitors to determine the specific heat capacity of dielectric materials. However, the value of the coupling coefficient was only verified for seven (relatively dark in surface colour) out of the ten rock samples. Therefore, this coupling coefficient may hold true for all dark coloured rock samples, as it represents the coupling of energy between the parallel-plate capacitor and the rock sample. Finally,this research defines the mathematical models for 10 rock samples for the VHF range of frequencies (30 - 300 MHz), providing unique phase angle to resonance equations for each sample. These equations can be used with each specific rock to determine the resonating frequency where the maximum current flows and the minimum resistance is present. Evaluating the effects of RF power treatment on rocks has brought to light that mineral grain boundaries within specified rock samples are not significantly weakened by RF treatment. This was firstly confirmed by the similar electrical properties of the untreated and treated samples, where consistent values for the resonating frequency were obtained from the network analyser. Secondly, the SEM analysis of the untreated and treated rock samples revealed no significant changes in the form of fractures or breakages along the mineral grain boundaries. Photomicrographs of the thin sections of all ten rock samples were used in this analysis. The particle size distribution of both samples further revealed no weakening or softening of the rock, as the percentage of smaller sized particles did not increase in the treated samples. It may therefore be stated that treating rock samples with RF power within the VHF range will not significantly improve rock comminution and mineral liberation.
53

Crime d'honneur, crime d'horreur ? : les homicides en Corse dans la seconde moitié du XIXe siècle : pratiques, autorités et représentations / Crime of honour, crime of horror ? : Corsican criminality in the second 19th century : practices, authorities and representations

Parsi, Caroline 17 June 2014 (has links)
À partir de sources inédites et exceptionnelles, à savoir les dossiers de procédure de plus de quatre cents affaires jugées aux Assises par le président Vincent de Caraffa (fonds privé conservé aux Archives de Bastia), nous proposons d’étudier la criminalité corse au second XIXe siècle, dans l’interaction des pratiques et de leur appréciation. La réalité insulaire fait état d’un impressionnant niveau de criminalité et montre que les violences reposent souvent (mais pas systématiquement) sur l’honneur. Les contemporains ne sont pas indifférents face à l’ampleur excessive et à la nature particulière des homicides, qu’il s’agisse des vendettas ou du banditisme, en Corse. Leurs discours, ceux des autorités comme ceux des simples citoyens, ceux des continentaux comme ceux des insulaires, sont loin d’être uniformes, mais tous concourent à la construction d’un « cas corse » à la fin du XIXe siècle. Or, l’idée d’une singularité absolue des pratiques criminelles du département peut pourtant être fortement relativisée, au regard de l’existence d’autres espaces violents et d’autres sociétés à honneur en France et en Méditerranée. S’il n’est donc pas véritablement attesté par les faits, le « cas corse » n’en existe pas moins, puisqu’il est présent dans les imaginaires du temps. / Using hitherto unseen and exceptional sources, namely the files from procedures of more than four hundred cases that were judged in a criminal Court by Judge Vincent de Caraffa (private collection in Bastia archives), we shall endeavour to study Corsican criminality in the second 19th century, in the interplay of its practices and their perception. The island reality demonstrates an impressive crime rate and shows that violence often – but not consistently – lies on honour. Corsican and French people in the 19th century could not be indifferent to the excessive scope and the particular nature of homicides – such as vendettas and banditry – in Corsica. Their speeches, those of the authorities as those of ordinary citizens, continentals or islanders, are far from being identical but they all contribute to the construction of a « Corsican case » at the end of the 19th century. Yet, the idea of an absolute singularity of criminal practices in Corsica may strongly be qualified as regards the existence of other more violent areas and other honor societies in France and in the Mediteranean Basin. If it is not truly proved by facts, the « Corsican case » nonetheless remains true, since it has been present in collective minds for a long time.
54

Sistema para simulação dinâmica de circuitos de britagem. / System for dynamic simulation of crushing circuits.

Deliberato Neto, Octávio 17 December 2007 (has links)
A produção de brita para construção civil na região metropolitana de São Paulo (RMSP) é uma tarefa desafiadora: de um lado, as crescentes pressões da sociedade e das questões ambientais e, de outro, os baixos preços e parâmetros de qualidade impostos pelo mercado fazem a indústria de agregados perseguir, cada vez mais, custos de operação baixos que se traduzam em vantagem competitiva. Seja na otimização de intalações existentes, seja em novos projetos de instalações, vem se acentuando o uso de simuladores de circuitos de britagem. A automação das instalações produtoras de agregados da RMSP também se mostra como uma tendência irreversível. Neste contexto, este trabalho apresenta um simulador dinâmico de circuitos de britagem, desenvolvido para auxiliar as tarefas de otimização, automação e mesmo projeto de instalações produtoras de agregados. AggXtream, um novo simulador dinâmico de circuitos de britagem, foi desenvolvido com os mais modernos modelos matemáticos de britagem atualmente disponíveis, e traz consigo um conjunto de rotinas de calibração desses modelos que utiliza técnicas de inteligência artificial. / The production of aggregates for civil construction in the metropolitan region of São Paulo (RMSP) is a challenging task: from one side, growing pressures of society and environmental issues and, from another, low prices and quality standards demanded by the market make the aggregate industry pursue, even more, low operating costs that turn into competitive advantage. Either in the optimization of existing plants or new projects, the use of simulators of mineral comminution circuits is becoming widespread. The automation of RMSPs aggregates operations has also become an irreversible trend. Within this context, the present work describes the development of a dynamic simulator for crushing circuits, aiming to be used in the optimization, automation and project of aggregates plants. AggXtream, a new dynamic simulator of crushing circuits, has been built with the most modern mathematical models of crushing currently available. It also incorporates model calibration routines that use artificial intelligence techniques.
55

Prehospital omvårdnad vid risk för crush syndrom

Jonsson, Uno January 2012 (has links)
Sammanfattning. Bakgrund:Crush syndrome eller traumatisk rahbdomyolys är vanligt vid större naturkatastrofer som tex jordbävningar. Det kan också uppkomma när personer utsätts för tryck mot musklerna vid tex stroke, intoxikationer, byggnadsras, industriolyckor. Inom ambulanssjukvården i Sverige har vi inte någon behandlingsplan för detta tillstånd och därför kan det finnas en risk att dessa patienter inte får rätt omvårdnad. Syfte:Studiens syfte var att belysa ambulanssjuksköterskans omvårdnad vid risk för Crush syndrome. Metod:En litteraturstudie gjordes för att granska redan publicerat forskningsmaterial. Sökningarna gjordes i databaserna Cinahl och Pubmed. Fem artiklar inkluderades och innehållet analyserades med manifest innehållsanalys. Resultat:De patienter som riskerar att få Crush syndrom har följande symtom: skada på muskelmassa, förlängd kompression, komprimerad lokal cirkulation, puls >120 och onormal urinfärg. Den viktigaste omvårdnadsåtgärden som kan vara livräddande för personen är insättande av intravenös kristalloid vätska samtidigt som personen losstages. Den vätska som rekommenderas är vanlig natriumklorid. Klinisk implikation:Ett förslag på omvårdnadsplan presenteras. Nyckelord:crush syndrome, prehospital care, prehospital omvårdnad, klämsklador, muskelskador, / Abstrakt. Background: Crush syndrome or traumatic rehbdomyolys is common in major natural disaster such as earthquakes. It can also arise when people are exposed on the muscle at such stroke, poisoning, structural collapse, industrial accidents. In prehospital care in Sweden we have no treatment plan for this condition and therefore it may be a risk that these patients not receiving the proper care. Purpose:The aim of this study was to illuminate the ambulance nurses care at risk of Crush syndrome. Method:A literature review was done to examine already published research material. The searches was made in the databases Cinahl and Pubmed. Five articles were included and the contents analyzed by manifest content analysis. Results:The patients who are at risk of Crush syndrome has the following symptoms: damage to the muscle mass, prolonged compression, compressed local circulation, heart rate > 120 and abnormal urine color. The most important nursing action that can be lifesaving is initiation of  intravenous crystalloid fluid while the person being detached. The fluid recommended is the usual sodium chloride. Clinical implication: A proposal for the nursing care plan are presented. Keywords:crush syndrome, prehospital care, crushing, muscle damage,
56

On the crushing of honeycomb under axial compression

Wilbert, Adrien 15 February 2011 (has links)
This thesis presents a comprehensive study of the compressive response of hexagonal honeycomb panels from the initial elastic regime to a fully crushed state. Expanded aluminum alloy honeycomb panels with a cell size of 0.375 in (9.53 mm), a relative density of 0.026, and a height of 0.625 in (15.9 mm) are laterally compressed quasi statically between rigid platens under displacement control. The cells buckle elastically and collapse at a higher stress due to inelastic action. Deformation then first localizes at mid-height and the cells crush by progressive formation of folds; associated with each fold family is a stress undulation. The response densifies when the whole panel height is consumed by folds. The buckling, collapse, and crushing events are simulated numerically using finite element models involving periodic domains of a single or several characteristic cells. The models idealize the microstructure as hexagonal, with double walls in one direction. The nonlinear behavior is initiated by elastic buckling while inelastic collapse that leads to the localization observed in the experiments occurs at a significantly higher load. The collapse stress is found to be mildly sensitive to various problem imperfections. For the particular honeycomb studied, the collapse stress is 67% higher than the buckling stress. It was also shown that all aspects of the compressive behavior can be reproduced numerically using periodic domains with a fine mesh capable of capturing the complexity of the folds. The calculated buckling stress is reduced when considering periodic square domains as the compatibility of the buckles between neighboring cells tends to make the structure more compliant. The mode consisting of three half waves is observed in every simulation but its amplitude is seen to be accented at the center of the domains. The calculated crushing response is shown to better resemble measured ones when a 4x4 cell domain is used, which is smoother and reproduces decays in the amplitude of load peaks. However, the average crushing stress can be captured with engineering accuracy even from a single cell domain. / text
57

Avaliação da influência do tamanho de partícula sobre as propriedades de carvões coqueificáveis e de coques produzidos em escala de laboratório

Flores, Ismael Vemdrame January 2014 (has links)
Atualmente a decrescente disponibilidade de carvões de excelente qualidade e seus preços elevados levam as coquerias a utilizarem carvões mais baratos e consequentemente com propriedades inferiores. Ao mesmo tempo, ocorre à necessidade de se manter as elevadas especificações de qualidade exigidas para o coque pelos altos-fornos. Nesse contexto, independente da escolha dos carvões a serem utilizados, o controle granulométrico dos carvões e misturas, realizado durante a britagem, pode manter ou até melhorar a qualidade do coque a ser produzido. O presente estudo teve como objetivo geral avaliar de que forma as propriedades dos carvões variam em relação a suas principais frações granulométricas após a cominuição, e estudar qual o efeito de diferentes distribuições de tamanhos de partículas sobre as propriedades de coques produzidos em escala de laboratório. Para isso, dois carvões coqueificáveis individuais e uma mistura foram amostrados, separados em frações granulométricas e caracterizados. Após a caracterização das matérias-primas, foram confeccionados coques em escala de laboratório, a partir de diferentes misturas de granulometrias para os carvões individuais amostrados. A caracterização dos coques foi realizada segundo análise imediata, textura, reatividade ao CO2 em termobalança, resistência a frio em tambor tipo I e microresistência. Os resultados obtidos da caracterização das matérias-primas mostraram que a cominuição dos carvões leva a concentrações de cinzas, matéria volátil e composição maceral em diferentes frações granulométricas produzindo alterações nas propriedades coqueificantes das frações granulométricas. O resultado da caracterização dos coques mostrou que cada carvão apresenta uma distribuição de tamanhos de partículas mais adequada, que irá gerar um coque de boa qualidade. Em termos de reatividade ao CO2, uma grande quantidade de partículas finas nas misturas levou a um aumento da reatividade dos coques produzidos. Além disso, a resistência mecânica foi mínima para as misturas grosseiras, enquanto uma mistura mais fina tendeu a produzir coques de resistência mecânica superior. / Nowadays, the decreasing availability of excellent quality coals and their high prices lead cokemakers to use cheaper coals, consequently with inferior properties. At the same time, there is the need to maintain the high coke quality specifications required for the blast furnace. In this context, independent of the choice of coal to be used, the particle size control of coals and blends, created during crushing, can maintain or even improve the quality of coke to be produced. The present study had as main objective to assess how the properties of coals vary in relation to its particle size fractions after crushing, and study what effect different particle size distributions can cause on the properties of coke produced in laboratory scale. Thus, two individual coking coals and a blend were sampled, separated into particle size fractions and characterized. After the characterization of raw materials, cokes were made on a laboratory scale, from blends of different particle sizes for an individual coals. The characterizations of cokes were done by proximate analysis, texture, thermobalance CO2 reactivity, cold strength in a CSR drum, and microstrength. The results of the characterization of raw materials showed that the comminution of coal leads to concentrations of ash, volatile matter and macerals on different size fractions, causing changes in coking properties of size fractions. The results of the characterization of the cokes showed that each coal used has a more suitable particle size distribution which will generate a good quality coke. In terms of CO2 reactivity, a large amount of small particles in the blend led to an increase of coke reactivity. Furthermore, the mechanical strength of cokes was sharply affected by coarse particle, while a blend with high fine proportion produced a coke with high mechanical strength.
58

Aplicação de areia de britagem de rochas basálticas na fabricação de concreto de cimento Portland

Viero, Edison Humberto 17 June 2010 (has links)
Na produção de concreto estrutural, apesar dos avanços tecnológicos, ainda se utilizam de materiais in natura, o que vem ocasionando problemas ambientais e econômicos a cadeia produtiva. Um dos problemas está associado à extração de areia do leito de rios, motivo pelo quais os profissionais envolvidos com a tecnologia do concreto vêm buscando alternativas ao uso dessa areia na produção de concreto estrutural. Uma alternativa que vem sendo estudada, pela grande disponibilidade, é o uso de uma areia produzida a partir da cominuição de rochas, chamada de areia de britagem. Na região de Caxias do Sul existem grandes reservas de rochas de origem basáltica (Riodacitos), a partir das quais é possível se produzir esse tipo de areia. Neste trabalho foi avaliada a viabilidade de se substituir à areia natural por areia de britagem de rochas basálticas produzidas em cinco empresas mineradoras localizadas na região de Caxias do Sul. O estudo foi desenvolvido em três etapas: na primeira foram avaliadas as características das areias decorrentes da mineralogia e petrografia das rochas e do processo de fabricação nas mineradoras; na segunda etapa foram avaliadas as propriedades do concreto através do método de dosagem EPUSP/IPT; na terceira etapa, para comprovar a eficiência do método de dosagem, foram produzidos traços específicos para cada tipo de areia. Os resultados de caracterização demonstraram que as areias de britagem possuem características diferentes das da areia natural e que apenas duas das cinco areias avaliadas apresentam propriedades que permitem a sua utilização em concreto estrutural. As propriedades decorrentes do processo de fabricação, como a presença de material pulverulento, forma e textura dos grãos provocaram um aumento no teor de argamassa, o que influenciou diretamente no proporcionamento dos materiais constituintes. Os resultados para a avaliação das propriedades do concreto demonstraram que, para um mesmo traço, a resistência a compressão axial e o módulo de elasticidade são menores nos concretos produzidos com areias de britagem. Corrigindo-se os teores de argamassa e produzindo-se traços específicos para cada tipo de areia é possível produzir concretos com resistências desejadas. Apesar das diferenças encontradas nas propriedades das areias foi comprovado que as areias de britagem estudadas podem ser utilizadas na produção de concreto estrutural de cimento Portland, substituindo totalmente à areia natural. / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-03T20:43:28Z No. of bitstreams: 1 Dissertacao Edison Humberto Viero.pdf: 1978943 bytes, checksum: fab5a6668b1624ae95d901331299a4d3 (MD5) / Made available in DSpace on 2014-06-03T20:43:28Z (GMT). No. of bitstreams: 1 Dissertacao Edison Humberto Viero.pdf: 1978943 bytes, checksum: fab5a6668b1624ae95d901331299a4d3 (MD5) / Despite the technological advances on the structural concrete production, in natura materials are still used. This fact has been causing environmental and economic problems to the manufacturing chain. One of the problems is related to the sand extraction from riverbeds, this is the reason why professionals involved with concrete technology are searching for alternatives to the use of this type of sand in the structural concrete manufacturing. One alternative that is being studied in various parts of the country, because its large availability is a sand produced from the rocks´ comminution, called crushing sand. In the Caxias do Sul region there are large reservations of basaltic rocks origin (Riodacitos), from which it is possible to produce this type of sand. In this work, it was evaluated the feasibility of substitute natural sand for crushing sand from basaltic rocks produced in five mining companies located at Caxias do Sul region. The study was developed in three stages: on the first one, the features of the sand that arises from rocks´ mineralogy and petrography and from the mining manufacturing process were evaluated; on the second the concrete properties through the EPUSP/IPT dosage method were evaluated; on the third they were produced specific trace to each type of sand in order to verify the efficiency of the dosage method. The characterization results established that the crushing sand have different features IF compared with natural sand and that Just two out of Five evaluated sands presented properties that allow its use in structural concrete. The properties arising from the fabrication process, for example the presence of powder material, the grains´ shape and texture caused the raise of the plaster content, which influenced directly on the constituents materials proportioning. The results of the concrete properties evaluation showed that, for the same trace, the resistance to axial compression and the elasticity module are smaller in the concretes produced with crushing sand. If the plaster content is corrected and the specific traces are produced for each type of sand it is possible to produce concretes with desired resistance. In spite of the differences found on the sand properties it was proven that the crushing sand produced at the Caxias do Sul region can be used on the portland cement structural concrete production, replacing totally the natural sand used.
59

Avaliação da influência do tamanho de partícula sobre as propriedades de carvões coqueificáveis e de coques produzidos em escala de laboratório

Flores, Ismael Vemdrame January 2014 (has links)
Atualmente a decrescente disponibilidade de carvões de excelente qualidade e seus preços elevados levam as coquerias a utilizarem carvões mais baratos e consequentemente com propriedades inferiores. Ao mesmo tempo, ocorre à necessidade de se manter as elevadas especificações de qualidade exigidas para o coque pelos altos-fornos. Nesse contexto, independente da escolha dos carvões a serem utilizados, o controle granulométrico dos carvões e misturas, realizado durante a britagem, pode manter ou até melhorar a qualidade do coque a ser produzido. O presente estudo teve como objetivo geral avaliar de que forma as propriedades dos carvões variam em relação a suas principais frações granulométricas após a cominuição, e estudar qual o efeito de diferentes distribuições de tamanhos de partículas sobre as propriedades de coques produzidos em escala de laboratório. Para isso, dois carvões coqueificáveis individuais e uma mistura foram amostrados, separados em frações granulométricas e caracterizados. Após a caracterização das matérias-primas, foram confeccionados coques em escala de laboratório, a partir de diferentes misturas de granulometrias para os carvões individuais amostrados. A caracterização dos coques foi realizada segundo análise imediata, textura, reatividade ao CO2 em termobalança, resistência a frio em tambor tipo I e microresistência. Os resultados obtidos da caracterização das matérias-primas mostraram que a cominuição dos carvões leva a concentrações de cinzas, matéria volátil e composição maceral em diferentes frações granulométricas produzindo alterações nas propriedades coqueificantes das frações granulométricas. O resultado da caracterização dos coques mostrou que cada carvão apresenta uma distribuição de tamanhos de partículas mais adequada, que irá gerar um coque de boa qualidade. Em termos de reatividade ao CO2, uma grande quantidade de partículas finas nas misturas levou a um aumento da reatividade dos coques produzidos. Além disso, a resistência mecânica foi mínima para as misturas grosseiras, enquanto uma mistura mais fina tendeu a produzir coques de resistência mecânica superior. / Nowadays, the decreasing availability of excellent quality coals and their high prices lead cokemakers to use cheaper coals, consequently with inferior properties. At the same time, there is the need to maintain the high coke quality specifications required for the blast furnace. In this context, independent of the choice of coal to be used, the particle size control of coals and blends, created during crushing, can maintain or even improve the quality of coke to be produced. The present study had as main objective to assess how the properties of coals vary in relation to its particle size fractions after crushing, and study what effect different particle size distributions can cause on the properties of coke produced in laboratory scale. Thus, two individual coking coals and a blend were sampled, separated into particle size fractions and characterized. After the characterization of raw materials, cokes were made on a laboratory scale, from blends of different particle sizes for an individual coals. The characterizations of cokes were done by proximate analysis, texture, thermobalance CO2 reactivity, cold strength in a CSR drum, and microstrength. The results of the characterization of raw materials showed that the comminution of coal leads to concentrations of ash, volatile matter and macerals on different size fractions, causing changes in coking properties of size fractions. The results of the characterization of the cokes showed that each coal used has a more suitable particle size distribution which will generate a good quality coke. In terms of CO2 reactivity, a large amount of small particles in the blend led to an increase of coke reactivity. Furthermore, the mechanical strength of cokes was sharply affected by coarse particle, while a blend with high fine proportion produced a coke with high mechanical strength.
60

Sistema para simulação dinâmica de circuitos de britagem. / System for dynamic simulation of crushing circuits.

Octávio Deliberato Neto 17 December 2007 (has links)
A produção de brita para construção civil na região metropolitana de São Paulo (RMSP) é uma tarefa desafiadora: de um lado, as crescentes pressões da sociedade e das questões ambientais e, de outro, os baixos preços e parâmetros de qualidade impostos pelo mercado fazem a indústria de agregados perseguir, cada vez mais, custos de operação baixos que se traduzam em vantagem competitiva. Seja na otimização de intalações existentes, seja em novos projetos de instalações, vem se acentuando o uso de simuladores de circuitos de britagem. A automação das instalações produtoras de agregados da RMSP também se mostra como uma tendência irreversível. Neste contexto, este trabalho apresenta um simulador dinâmico de circuitos de britagem, desenvolvido para auxiliar as tarefas de otimização, automação e mesmo projeto de instalações produtoras de agregados. AggXtream, um novo simulador dinâmico de circuitos de britagem, foi desenvolvido com os mais modernos modelos matemáticos de britagem atualmente disponíveis, e traz consigo um conjunto de rotinas de calibração desses modelos que utiliza técnicas de inteligência artificial. / The production of aggregates for civil construction in the metropolitan region of São Paulo (RMSP) is a challenging task: from one side, growing pressures of society and environmental issues and, from another, low prices and quality standards demanded by the market make the aggregate industry pursue, even more, low operating costs that turn into competitive advantage. Either in the optimization of existing plants or new projects, the use of simulators of mineral comminution circuits is becoming widespread. The automation of RMSPs aggregates operations has also become an irreversible trend. Within this context, the present work describes the development of a dynamic simulator for crushing circuits, aiming to be used in the optimization, automation and project of aggregates plants. AggXtream, a new dynamic simulator of crushing circuits, has been built with the most modern mathematical models of crushing currently available. It also incorporates model calibration routines that use artificial intelligence techniques.

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