Originally designed for sinter feed grinding, the Carajas grinding circuit includes two ball mills in parallel lines in a closed configuration with cyclones. The ground product is further deslimed in hydrocyclone for achieving the final specifications regarding size distribution and surface area. In this process, there is a significant amount of high grade material, not recovered due to overgrind. Ore characterization was here selected for predicting the grinding circuit performance, which in turn was the basis for optimization. The aim of this work is the characterization of the main Carajas ore types as well as the development of a method that includes these characteristics for predicting the grinding circuit performance. Laboratory grinding tests and samplings in the industrial circuit were carried out to predict the grinding circuit performance. The grinding test results were used to set operational conditions in which the laboratory better represented the industrial circuit. Results from industrial sampling and characterization were the basis for fitting the mathematical models. The fitted model was an excellent resource for the prediction of the grinding circuit performance as well as for the grinding test. To assess the grinding performance, products size distribution and surface area were evaluated. Moreover, simulations of the grinding circuit indicated the potential of some ore types. The derived methods were validated as tools for predicting the grinding circuit performance and for operational optimization.
ResumoO modelo de misturador perfeito (PMM) leva em conta, tanto as características do equipamento, como as do minério. As características do minério são representadas pela função distribuição de quebra. Tal função pode ser determinada através de um método laboratorial proposto pelo JKMRC ou de funções padronizadas. O presente trabalho descreve o processo de modelagem matemática do circuito de moagem de Carajás, utilizando o software JKSimMet. Como resultado, foi possível avaliar a qualidade do ajuste do modelo em dois cenários: 1) utilizando a função distribuição de quebra-padrão do programa; 2) utilizando a função distribuição de quebra determinada para a alimentação do circuito de moagem. A partir desta análise, determinou-se, no ajuste do PMM e, em particular, na função taxa de quebra ou cinética de fragmentação, a infl uencia da função distribuição. Palavras-chave:Moagem, modelagem, minério de ferro. Abstract The perfect mixing model (PMM) is based on parameters derived from
ResumoEmpregando-se o método descrito na Parte 1 desse artigo, foram realizadas caracterizações quanto à fragmentação dos principais tipos de minério de Carajás, provenientes das frentes de lavra das minas N4 e N5. A partir das características
With many of the world's richest ore deposits already depleted, deposits with complex mineralogy, higher competence and lower grades are now being targeted and mining projects have progressively increased in scale. The mechanical constraints, processing performance and cost limitations of conventional processing technologies when applied to high-throughput low grade resources are becoming increasingly apparent, motivating engineers to investigate practices such as selective blasting, pre-concentration, preweakening, selective grinding and design of circuits that can be actively controlled to respond to variable feed characteristics. Provided the ore is amenable to these processes, they have the potential to deliver improved efficiency and can help in absorbing process instabilities caused by ore variability.In order to confidently simulate circuits in which these processing strategies can be applied and quantify their potential benefits, a configurable simulation interface called the Model Developers' Kit (MDK) developed at the JKMRC has been used. It features a multicomponent modelling and simulation engine that allows dealing with multiple components in the feed, accommodating different competencies of ores, utilising physical separation opportunities and tracking the grade reporting along the different potential processing routes.Three case studies were selected for the development of methodologies for exploiting multi-component characteristics of ores in the modelling and simulation of comminution and separation circuits in MDK and to trial the ability of different circuit designs to respond to variable stream properties.For each case study, component types were selected based on the characteristics of the selected ores, multi-component models were fitted to industrial measured data, followed by simulation of circuit design scenarios aimed at optimising grinding and separation efficiencies. These methodologies demonstrate the behaviour of individual components and quantify the performance of various flowsheets that treat mixtures of minerals or processing streams with different competencies and ores with preferential deportment of high-grade material after crushing and grinding stages. These simulations demonstrate that the composition and properties of multi-component systems can be used advantageously to improve circuit performance and energy efficiency.ii Declaration by authorThis thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis.I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the com...
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