DEMIN - Departamento de Engenharia de Minas

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/510

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2012 - 201912020 - 20221

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Tem arquivos: SimAssunto: search.filters.subject.Granular media

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Agora exibindo 1 - 2 de 2
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    On bed porosity of multisized spheroidal particles.
    (2022) Prado, Diogo Rodrigues; Luz, José Aurélio Medeiros da; Milhomem, Felipe de Orquiza; Paracampos, Marcos Paulo Salomão
    In numerous instances of engineering the problem to quantify the porosity of polydisperse systems arises. Despite its great importance, the theoretical predictability of the bed porosity is still problematic. In the field of ceramics, classically, Furnas' studies on porosity are quoted, where he has studied void fraction resulting from blending two distinct particle sizes in various proportions. Less often, ternary diagrams plotting porosity isovalues for spherical particles beds are used to characterize ternary mixtures of distinct monosized particulate systems (usually in ceramics industry). Although similar studies using polydisperse systems have been conducted, a lot of improvement is yet to be achieved. This article falls in this context and aims at contributing to this field of technical and economic impact. Synthetic samples with controlled particle size distribution were used. The resulting porosity of those glass beads random packs (mimicking several size distributions described by Rosin–Rammler equation) has been experimentally determined under a standardized compaction level. The main result was to obtain an equation for the porosity forecast for bead beds inside spheroidal containers, as a function of the sharpness parameter, n, from Rosin–Rammler distribution. An accurate extrapolation to systems well described by the Whiten sigmoidal distribution was achieved as well. A generalization of the Ergun equation is presented at the end of the article, as an application example.
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    Modelling of binary mixture comminution.
    (2012) Sudário, Flávia Emery Pereira; Luz, José Aurélio Medeiros da
    This paper treats on grindability differences of mineral mixtures to achieve a preliminary selective particle size contrast by comminution in order to improve further sorting operation. Quartz and calcite had been chosen as example of binary system. The theoretical basis for this work was inspired by the optimization study carried out by Ray and Szekely (1973), through an algebraic model based on evolution of log-normal distribution of particle size during comminution. On the other hand, the present work has described grindability differences through the classical Rosin-Rammler size distribution. The study of the evaluation of binary mixture differences was realized by sieving analyses and the estimation of Rosin-Rammler sharpness and median diameter. An objective function was conceived stressing the relationship between the expended energy in the grinding process and the optimum residence time. It is possible to use the results as a background for grinding optimization system, since that the penalty function inside objective function can be adequately calibrated as far as technical and economic impacts on further sorting separations are concerned.