As moagens autógena (AG) e semiautógena (SAG) mostram-se como opções cada vez mais consideradas na seleção de novos circuitos de cominuição. A flexibilidade de operação, assim como a combinação de grandes capacidades de processamento e altas relações de redução obtidas, são algumas das vantagens destes circuitos. Este trabalho procurou descrever o método utilizado na condução de ensaios de moagem semiautógena em escala piloto e de caracterização tecnológica, empregando o minério de ouro da Rio Paracatu Mineração S/A (RPM). A moagem semiautógena foi investigada considerando diferentes condições de operação e às especificidades do minério da RPM. Foram conduzidos 69 ensaios em planta piloto que permitiram o estudo do efeito das variáveis de operação sobre parâmetros de moagem SAG, como taxa de processamento, consumo energético específico, qualidade do produto, entre outros. As informações obtidas na campanha de ensaios em planta piloto e nos trabalhos de caracterização das amostras mostraram-se consistentes e fundamentaram o dimensionamento e projeto do circuito de Expansão da RPM, com capacidade de processamento adicional de 41 Mtpa. / The autogenous (AG) and semi-autogenous (SAG) mills have increasingly been considered options in the selection of new comminution circuits. The flexibility of the operation, as well as the combination of high processing capacity and high reduction rates obtained, are some of the advantages of these circuits. This study sought to describe the method used in conducting semi-autogenous grinding pilot plant and technological characterization, using the gold ore from the Rio Paracatu Mineração S/A (RPM) mine. The semi-autogenous grinding was investigated considering different operating conditions and specific characteristics of the ore from the Rio Paracatu Mineração mine. Were conducted 69 tests in a pilot plant that enabled the study of the effects of the operating variables of the SAG grinding parameters such as processing rates, specific energy consumption, product quality, among others. Information obtained in the test campaign of the pilot plant and the characterization work of the samples were consistent and supported the design and project of the circuit of the expansion of the Rio Paracatu Mineração mine, with additional processing capacity of 41 Mtpy.

The objective of this thesis is to investigate the principles of laboratory-scale particle bed comminution in a piston-die-press. The feed materials used in this investigation are quartz and calcite which were stage-crushed and dry screened to produce 3.35 x 2.36, 2.36 x 1.7, 1.7 x 1.18, 1.18 x 0.85, and minus 0.85mm size fractions. First, these narrow size fractions (excluding minus 0.85mm fraction) were comminuted under different pressures to determine the baseline for energy utilization. Then, these size fractions and minus 0.85mm size fraction were proportionately mixed to produce feeds of three different size distributions having three different Gates-Gaudin-Schuhmann (GGS) size distribution moduli (m=0.5, 0.7, and 0.9), and comminuted under different bed pressures of appropriate magnitudes to generate a reasonable range of specific breakage energy inputs. As a result of the experiments carried out, it can be concluded that higher amounts of fines were obtained from calcite samples than quartz at all narrow-range size fractions and distribution moduli. Furthermore, experimental results showed that the feed material having the widest size distribution (m = 0.5) showed more resistance to size reduction when compared with narrow-size fractions, which led to increase in energy consumption due to the presence of higher amounts of fines. Tests samples with distribution moduli of 0.7 and 0.9 showed higher resistance to size reduction than narrow-size samples, but the reduction ratios achieved with the size distributed samples were higher than those achieved with the narrow-size samples. In addition, by using t-curves (t50 and t10) the amounts of breakage of different samples were compared. Consequently, the distribution modulus of 0.9 gave better breakage results in terms of expended energy and amount of breakage than all narrow-size fractions, especially for the relatively soft mineral calcite.

A cada dia aumenta a preocupação com relação às condições de exposição ocupacional dos trabalhadores, nos mais diversos setores, tanto em nível da análise dos postos de trabalho quanto das implicações legais decorrentes destas. No presente estudo, sobre as atividades desenvolvidas em instalações de britagem, objetivou-se criar um modelo para analisar, avaliar e propor melhorias para o funcionamento destas instalações, com ênfase na saúde e em segurança dos trabalhadores. Utilizou-se para tal uma metodologia compreendendo: visitas in loco, questionários, análise dos postos de trabalho e da vivência, ou seja, do conhecimento dos envolvidos na operação. Como resultado, obteve-se um modelo que considera os diversos fatores intervenientes na implantação de instalações de britagem (ligando os fatores relacionados aos aspectos: técnicos, jurídicos e ocupacionais). Foram verificadas especificamente possíveis melhorias a serem introduzidas na empresa, bem como, de forma mais ampla, a constatação do descaso ou desconhecimento das empresas quanto aos diversos aspectos que norteiam esta atividade, aspectos psicossociais e comportamentais dos trabalhadores. / Day after day we are becoming more and more concerned about workers´ occupational exposition conditions in several sectors from workplace analysis level to their legal implications. In the present study about activities developed in crushing plant facilities we targeted the creation of a model to analyze, assess and propose improvements for these facilities functions focused on health and on workers’ safety. Therefore, we used a methodology which comprehends the following: in loco visits, questionnaires, workplace analysis, its life mode, that is, the knowledge of the ones involved in the operation. As a result we obtained a model which considers the several interfering factors in the implementation of crushing plant facilities (linking factors related to occupational, juridical and technical aspects). We verified specifically possible improvements to be introduced in the company as well as, in a broader scope, we realized a neglect or ignorance of companies regarding the several aspects which rule this activity such as worker´s psychosocial and behavioral aspects.

A cada dia aumenta a preocupação com relação às condições de exposição ocupacional dos trabalhadores, nos mais diversos setores, tanto em nível da análise dos postos de trabalho quanto das implicações legais decorrentes destas. No presente estudo, sobre as atividades desenvolvidas em instalações de britagem, objetivou-se criar um modelo para analisar, avaliar e propor melhorias para o funcionamento destas instalações, com ênfase na saúde e em segurança dos trabalhadores. Utilizou-se para tal uma metodologia compreendendo: visitas in loco, questionários, análise dos postos de trabalho e da vivência, ou seja, do conhecimento dos envolvidos na operação. Como resultado, obteve-se um modelo que considera os diversos fatores intervenientes na implantação de instalações de britagem (ligando os fatores relacionados aos aspectos: técnicos, jurídicos e ocupacionais). Foram verificadas especificamente possíveis melhorias a serem introduzidas na empresa, bem como, de forma mais ampla, a constatação do descaso ou desconhecimento das empresas quanto aos diversos aspectos que norteiam esta atividade, aspectos psicossociais e comportamentais dos trabalhadores. / Day after day we are becoming more and more concerned about workers´ occupational exposition conditions in several sectors from workplace analysis level to their legal implications. In the present study about activities developed in crushing plant facilities we targeted the creation of a model to analyze, assess and propose improvements for these facilities functions focused on health and on workers’ safety. Therefore, we used a methodology which comprehends the following: in loco visits, questionnaires, workplace analysis, its life mode, that is, the knowledge of the ones involved in the operation. As a result we obtained a model which considers the several interfering factors in the implementation of crushing plant facilities (linking factors related to occupational, juridical and technical aspects). We verified specifically possible improvements to be introduced in the company as well as, in a broader scope, we realized a neglect or ignorance of companies regarding the several aspects which rule this activity such as worker´s psychosocial and behavioral aspects.

A etapa de cominuição é a operação que mais consome energia de forma ineficiente. Pequenos ganhos de eficiência podem impactar significativamente nos custos operacionais da planta. Durante as décadas passadas, foram atingidas melhoras consideráveis na eficácia dos processos não apenas pela otimização integrada das etapas de cominuição, mas também pelo desenvolvimento de tecnologias que permitem o uso mais eficiente da energia. Entre elas está a Prensa de Rolos de Alta Pressão (PRAP, em inglês High Pressure Griding Rolls - HPGR). Uma campanha experimental em planta piloto foi conduzida para avaliar o desempenho da prensa de rolos (PR) em diferentes configurações de circuito. No total, foram conduzidos 18 ensaios em circuito fechado com peneira, com recirculação parcial do produto da PR e recirculação do produto das bordas. Este estudo apresenta os resultados de tal campanha e as análises contemplam: A comparação do desempenho da PR em diferentes configurações do circuito em termos do consumo de energia, da capacidade do circuito e da granulometria do produto. A avaliação do impacto da eficiência de classificação e da carga circulante no desempenho da PR em circuitos fechados. As análises conduzidas compararam o desempenho da PR a partir dos índices de desempenhos do equipamento e do circuito (capacidade específica, relação de redução e potência específica) que foram obtidos através das variáveis de processo como a vazão mássica, o P50 das distribuições granulométricas dos fluxos e o consumo de potência. Porém, dependendo do índice avaliado, uma configuração é mais vantajosa que a outra. Portanto, foi estabelecido um indicador que relacione as três variáveis de processo (capacidade, consumo de potência e granulometria) para determinar o circuito mais energeticamente eficiente. / Comminution is the most energy-intensive and energy-inefficient operation. A small gain in comminution efficiency can have a large impact on the operating cost of a plant. During the last decade, there have been considerable improvements in comminution efficiency not only due to the optimal design of grinding systems and operating variables that enable more efficient use of existing comminution devices, but also due to the development of comminution devices with the ability to enhance energy utilization. One such recognized technology which addresses most of these issues is the highpressure grinding roll (HPGR). A pilot scale test program was conduct in order to evaluate the size reduction performance of HPGR operating in different circuit configurations. In total, eighteen pilot-HPGR locked cycle tests were performed to simulate the HPGR performance in closed circuit with a screen, product recycle and edge recycle. This work provides the results from the pilot scale HPGR test program. The analysis reported herein includes: A comparison of different circuit configurations of HPGR operation in terms of energy consumption and product fineness. An evaluation of the impact of classification efficiency and circulating load on the performance of closed HPGR circuits. Analyses conducted compared the HPGR performance based onequipment and circuits indexes (specific capacity, reduction ratio and specific power) that were obtained through process variables such as flow rate, the P50 of the particle size distribution and power consumption. However, depending on the index evaluated, a configuration is more advantageous than the other. Therefore, an indicator was established that relates the three process variables (capacity, power consumption and particle size) to determine the most energy efficient circuit.

As moagens autógena (AG) e semiautógena (SAG) mostram-se como opções cada vez mais consideradas na seleção de novos circuitos de cominuição. A flexibilidade de operação, assim como a combinação de grandes capacidades de processamento e altas relações de redução obtidas, são algumas das vantagens destes circuitos. Este trabalho procurou descrever o método utilizado na condução de ensaios de moagem semiautógena em escala piloto e de caracterização tecnológica, empregando o minério de ouro da Rio Paracatu Mineração S/A (RPM). A moagem semiautógena foi investigada considerando diferentes condições de operação e às especificidades do minério da RPM. Foram conduzidos 69 ensaios em planta piloto que permitiram o estudo do efeito das variáveis de operação sobre parâmetros de moagem SAG, como taxa de processamento, consumo energético específico, qualidade do produto, entre outros. As informações obtidas na campanha de ensaios em planta piloto e nos trabalhos de caracterização das amostras mostraram-se consistentes e fundamentaram o dimensionamento e projeto do circuito de Expansão da RPM, com capacidade de processamento adicional de 41 Mtpa. / The autogenous (AG) and semi-autogenous (SAG) mills have increasingly been considered options in the selection of new comminution circuits. The flexibility of the operation, as well as the combination of high processing capacity and high reduction rates obtained, are some of the advantages of these circuits. This study sought to describe the method used in conducting semi-autogenous grinding pilot plant and technological characterization, using the gold ore from the Rio Paracatu Mineração S/A (RPM) mine. The semi-autogenous grinding was investigated considering different operating conditions and specific characteristics of the ore from the Rio Paracatu Mineração mine. Were conducted 69 tests in a pilot plant that enabled the study of the effects of the operating variables of the SAG grinding parameters such as processing rates, specific energy consumption, product quality, among others. Information obtained in the test campaign of the pilot plant and the characterization work of the samples were consistent and supported the design and project of the circuit of the expansion of the Rio Paracatu Mineração mine, with additional processing capacity of 41 Mtpy.

A cada dia aumenta a preocupação com relação às condições de exposição ocupacional dos trabalhadores, nos mais diversos setores, tanto em nível da análise dos postos de trabalho quanto das implicações legais decorrentes destas. No presente estudo, sobre as atividades desenvolvidas em instalações de britagem, objetivou-se criar um modelo para analisar, avaliar e propor melhorias para o funcionamento destas instalações, com ênfase na saúde e em segurança dos trabalhadores. Utilizou-se para tal uma metodologia compreendendo: visitas in loco, questionários, análise dos postos de trabalho e da vivência, ou seja, do conhecimento dos envolvidos na operação. Como resultado, obteve-se um modelo que considera os diversos fatores intervenientes na implantação de instalações de britagem (ligando os fatores relacionados aos aspectos: técnicos, jurídicos e ocupacionais). Foram verificadas especificamente possíveis melhorias a serem introduzidas na empresa, bem como, de forma mais ampla, a constatação do descaso ou desconhecimento das empresas quanto aos diversos aspectos que norteiam esta atividade, aspectos psicossociais e comportamentais dos trabalhadores. / Day after day we are becoming more and more concerned about workers´ occupational exposition conditions in several sectors from workplace analysis level to their legal implications. In the present study about activities developed in crushing plant facilities we targeted the creation of a model to analyze, assess and propose improvements for these facilities functions focused on health and on workers’ safety. Therefore, we used a methodology which comprehends the following: in loco visits, questionnaires, workplace analysis, its life mode, that is, the knowledge of the ones involved in the operation. As a result we obtained a model which considers the several interfering factors in the implementation of crushing plant facilities (linking factors related to occupational, juridical and technical aspects). We verified specifically possible improvements to be introduced in the company as well as, in a broader scope, we realized a neglect or ignorance of companies regarding the several aspects which rule this activity such as worker´s psychosocial and behavioral aspects.

This work deals with the study of limestone and corundum dry milling using attritor-type stirred mill in a batch mode. There were stearin and polyethylene glycol used as surfactants and spherical shaped steel grinding elements used for the experimental part of the work. The main idea was to examine behavior of the selected grinding stock type within a long-term grinding forces exposure in selected conditions of ultrafine dry milling leading up to the submicron area. Characterization of samples was performed by laser granulometry, X-ray powder diffraction analysis, flame atomic absorption spectroscopy, objective color determination and electrokinetic potential measurement. Experimetaly measured data implies that in all cases there was a re-agglomeration of the grinding stock particles occurring, although in different stages of the disintegration process and in mutually various degree. The analysis results denote that a larger erosion of the crystal structures with the associated increase of the amorphous phase in the submicron particle size took place in the grinding stock.

A grinding mill circuit forms a crucial part in the energy-intensive comminution process of extracting valuable metals and minerals from mined ore. The ability to control the grinding mill circuit is of primary importance to achieve the desired product specification with regards to quality and production rate. In order to achieve control objectives an accurate dynamic model of the milling circuit is required. Phenomenological models are preferred over linear-time-invariant models since the latter cannot describe the non-linear behaviour of the process. However, the available phenomenological models of grinding mill circuits are usually complex, use large parameter sets and are mostly aimed towards steady-state design of grinding mill circuits. This study investigates simplified non-linear dynamic models of grinding mill circuits suitable for process controller design. In the first part of this study, the number of size classes in a cumulative rates model of a grinding mill circuit is reduced to determine the minimum number required to provide a reasonably accurate model of the circuit for process control. Each reduced size class set is used to create a non-linear cumulative rates model which is linearized to design a linear model predictive controller. The accuracy of a model is determined by the ability of the corresponding model predictive controller to control important process variables in the grinding mill circuit as represented by the full non-linear cumulative rates model. The second part of the study validates a simple and novel non-linear model of a run-of-mine grinding mill circuit developed for process control and estimation purposes. This model is named the Hulbert-model and makes use of the minimum number of states and parameters necessary to produce responses that are qualitatively accurate. It consists of separate feeder, mill, sump and hydrocyclone modules that can be connected to model different circuit configurations. The model uses five states: rocks, solids, fines, water and steel balls. Rocks are defined as too large to be discharged from the mill, whereas solids, defined as particles small enough to leave the mill, consist of out-of-specification coarse ore and in-specification fine ore fractions. The model incorporates a unique prediction of the rheology of the slurry within the mill. A new hydrocyclone model is also presented. The Hulbert-model parameters are fitted to an existing plant’s sampling campaign data and a step-wise procedure is given to fit the model to steady-state data. Simulation test results of the model are compared to sampling campaign data of the same plant at different steady-state conditions. / Dissertation (MEng)--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted

Background: Complex proximal humerus fractures with metaphyseal comminution remain challenging regarding reduction and stability. In most fracture patterns the hard bone of the bicipital groove remains intact. In this case series, we describe a novel technique of hybrid double plate osteosynthesis of complex proximal humerus fractures with metaphyseal comminution. Methods: In randomly chosen shoulder specimens and synthetic bones, pilot studies for evaluation of the feasibility of the technique were performed. Between 4/2010 and 1/2012 10 patients underwent hybrid double plate osteosynthesis. Seven patients (4 male, 3 female, mean age was 50 years (range 27–73)) were available for retrospective analysis. Based on plain radiographs (anterior-posterior and axial view), the fractures were classified according to the Orthopaedic Trauma Association classification (OTA) and by descriptive means (head-split variant (HS), diaphyseal extension or comminution (DE)). Results: Follow-up radiographs demonstrated complete fracture healing in six patients and one incomplete avascular necrosis. None of the patients sustained loss of reduction. Three patients where reoperated. The medium, not adapted, Constant score was 80 Points (58–94). Patients subjective satisfaction was graded mean 3 (range: 0–6) in the visual analog scoring system (VAS). Conclusion: The technique of hybrid double plate osteosynthesis using the bicipital groove as anatomic landmark may re-establish shoulder function after complex proximal humerus fractures in two dimensions. Firstly the anatomy is restored due to a proper reduction based on intraoperative landmarks. Secondly additional support by the second plate may provide a higher stability in complex fractures with metaphyseal comminution.