Investigation of scientific basics of Selective Comminution concerning mineralogical and technological properties of raw materials

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More and more new developed deposits are characterized by a complex mineralogical composition and lower contents of valuable components. The mineral grains are often smaller, more intergrown and the valuable elements are located in larger variety of ore minerals. For a sufficient liberation, the ores must be ground to a smaller product particle size. The energy requirement for comminution increases with a smaller product particle size in a highly progressive manner. This energy requirement could be significantly reduced by Selective Comminution.Selective Comminution leads either to a preferred crack propagation and fracture along the grain boundaries and thus allows a high degree of liberation with a large particle size. Or it produces a preferential crack propagation and fracture in one or several components. This results in a particle size-dependent distribution of the components. The separation of valuable and waste can be achieved with a subsequent classification. Thus, Selective comminution is, in combination with a simple classification, a very efficient separation process.A quantitative description of the ores and its constituents is an essential basis for the purposeful design of comminution machines and beneficiation processes. Mineralogical properties of the important ore and rock forming minerals are well documented. Knowledge on comminution properties of individual minerals, however, is low and the properties of grain boundaries are hardly investigated. The aim of the research project is therefore to systematically investigate the properties and the comminution behavior of the minerals and especially the grain boundaries. In order to investigate the interaction of mineralogical properties and crack propagation under mechanical stress, a testing device will be constructed with a polarization ore microscope comprising an interchangeable indenter.The testing device allows the development of a suitable indenter for the reliable generation of Palmqvist cracks. On the basis of the Palmqvist cracks, the mechanical properties of the grain boundaries are investigated. Parallel to this, various mineralogical methods such as computer tomography and Quantitative Microstructural Analysis are used. Experimental investigations on Selective comminution accompany the research project and are used for correlations between the measured properties on the micro level and the Selective comminution behavior in the macro level. The research project provides methods for the reliable quantitative determination of the comminution behavior of the minerals as well as methods for the science-based selection of comminution machines and the purposeful design of the comminution processes in ore beneficiation.