M. Tech. Industrial Engineering / The ability to respond to changes and uncertainty in production demands currently constitutes a crisis in small and medium scale mining industries in South Africa. The case study of various mining and mineral processing site visits which was carried out revealed that the existing conventional screening methods are not scalable or able to be integrated and have limited processing capacity, which constitutes a high production cost on a long-term basis. In view of this, the Reconfigurable Vibrating Screen machine was designed and manufactured with the intension of eliminating these challenges faced by small and medium scale mining industries. The newly developed vibrating screen utilizes the concept of re-configurability, making it simple to attain full capacity processing production on the same machine. The design of a reconfigurable vibrating screen is based on the idea of enhancing the processing capacity by adjustable width and length of the screen structure with regard to the desired processing output.

M. Tech. Industrial Engineering / The Reconfigurable Vibrating Screen is a newly designed beneficiation machine to be used for mineral particle separation in mines and quarries with adjustable screen capacity and structure in order to respond to changes in production and quantity demand required by the customers. In order to increase the durability, availability, reliability and maintainability of a reconfigurable vibrating screen, an effective method is required to functionally appraise and improve its working condition. The aim of this study is to develop a tool for functionally assessing reconfigurable vibrating screens and existing vibrating screens.

FAPEMIG - Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Petrobrás - Petróleo Brasileiro S.A / Os fluidos de perfuração são substâncias injetadas no poço cuja principal função é trazer à superfície os cascalhos de rocha produzidos durante a perfuração. A separação e a reutilização do fluido de perfuração são de suma importância para que se atenda às exigências da legislação ambiental em relação ao descarte de resíduos. Além disso, é imprescindível a recuperação do fluido utilizado por questões de redução de custos da etapa de perfuração. O objetivo do presente estudo foi desenvolver um modelo matemático para a separação entre cascalho e fluido de perfuração por peneiras vibratórias com base nos princípios da dinâmica newtoniana e da lei de conservação de massa. Para tanto a tela da peneira foi considerada um leito empacotado de espessura muito fina e com inclinação ascendente. Correlações para a queda de pressão foram analisadas e uma nova correlação foi proposta com base em metodologias indicadas na literatura. O comportamento do fluido foi avaliado para a variação nos seguintes parâmetros: viscosidade plástica, tensão limite de escoamento, coeficiente de escoamento, inclinação da tela e força-g. O modelo não se mostrou sensível a variações na tensão limite de escoamento do fluido. Os demais parâmetros mostraram significativa influência sobre o comprimento de tela molhada. Os resultados obtidos estão de acordo com o relatado pela literatura e mostram que o modelo desenvolvido é adequado para a descrição do processo de peneiramento vibratório. / Drilling fluids are substances injected into the well whose main function is to suspend drilled solids, remove them from the well bore and release them at the surface. Separation and reuse of drilling fluids is of great importance to fulfill the requirements of environmental legislation regarding waste disposal. In addition, it is essential to recover the drilling fluid in order to reduce costs of the drilling process. The objective of the present study was to develop a mathematical model based on the principles of Newtonian dynamics and the law of mass conservation for the process of removal of drilled cuttings from drilling fluid using vibrating screens. For this purpose, the sieve screen was considered to be a very thin packed bed and tilted upward. Pressure drop correlations were analyzed and a new correlation was proposed based on methodologies indicated in the literature. The behavior of the fluid was evaluated for the variation in the following parameters: plastic viscosity, yield stress, flow coefficient, tilt of the screen and g factor. The model was not sensitive to variations in the yield stress of the fluid while other parameters showed a significant influence on wet screen length. Obtained results are in agreement with the reported ones in the literature and show that the developed model is suitable for the description of the process of vibrating screening. / Dissertação (Mestrado)