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Characterization of ore texture crack formation and liberation by quantitative analyses of spatial deformation
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.ORCID iD: 0000-0002-6284-5792
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.ORCID iD: 0000-0002-5979-5608
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0001-7395-3302
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
(English)In: Article in journal (Refereed) Submitted
Abstract [en]

In comminution, particle breakage starts with crack induction and propagation. The path of cracks defines the breakage mode, e.g. preferential breakage or phase boundary breakage. For investigating crack formation behavior, the description by displacement fields can be applied. The displacement fields of the mineral phases can then be used to understand breakage mode and liberation. Ore texture and operational conditions such as loading mechanisms will affect the system. One of the ore texture aspects is the ore texture heterogeneity, which is a complex quantity comprising mineral heterogeneity, geometrical heterogeneity, weak grain boundaries, and micro-cracks. This study aims at investigating the effects of ore texture and loading displacement rate on breakage mode and liberation. The approach is to describe the spatial displacement fields in different ore textures. In order to obtain these, in-situ compression loading tests with different displacement rates were conducted, followed by X-ray computed micro-tomography (XCT) and Digital Volume Correlation (DVC). In addition, the resulting cracks from ore breakage were analyzed and quantified in order to predict the breakage mode. Moreover, XCT imaging was used for tracking the propagated cracks in the third dimension. For identifying mineral phases, automated scanning electron microscopy (SEM) complemented by energy dispersive spectroscopy was applied. The outcomes showed that both ore texture and loading mechanism should be considered for describing crack formation and mineral liberation.

National Category
Geosciences, Multidisciplinary
Identifiers
URN: urn:nbn:se:ltu:diva-78065OAI: oai:DiVA.org:ltu-78065DiVA, id: diva2:1414722
Available from: 2020-03-15 Created: 2020-03-15 Last updated: 2020-03-20
In thesis
1. Effects of loading mechanisms and texture on ore breakage: A multidimensional study
Open this publication in new window or tab >>Effects of loading mechanisms and texture on ore breakage: A multidimensional study
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

 In comminution machines, the product properties (particle size distribution, mineral liberation characteristics) and process consumables (energy for size reduction, wear) are affected by various parameters. On the one hand, understanding and optimizing these parameters can provide an energy efficient process and a specified product. On the other hand, a fundamental understanding of the breakage process can even be used for designing new or improved comminution machines. In this thesis, breakage fundamentals are analyzed and set against the principles of various comminution machines. The study of the breakage fundamentals is crucial for a better understanding of the effect of different comminution environments on ore types and their textures in order to achieve a desired product size and liberation. This work defines three main areas of breakage processes with breakage fundamentals, namely “loading mechanism”, “breakage mechanism” and “breakage mode”. The “loading mechanism” is defined as the physical action that is applied to a particle or several particles in order to introduce mechanical stress. The resulting pattern of the particle failure is named “breakage mechanism”. Finally, the “breakage mode” defines the particle breakage in terms of being random or non‐random. Non‐random breakage depends on the ore texture, which can be categorized as preferential breakage and phase boundary breakage. Promoting the breakage mode to the phase boundary breakage could help to increase the liberation degree. Various studies have assessed the effect of ore texture and operational parameters on mineral liberation. While ore texture is related to the particle inherent characteristics, operational conditions such as loading mechanism are related to the comminution environment. In all these investigations, little attempt has been made to explore the combined effects of loading mechanism and quantitative ore texture features on breakage mode and mineral liberation. In addition, a lack of fundamental understanding of the breakage process and mineral liberation can be seen. Accordingly, a more fundamental study of the causes behind the effects of loading mechanism and texture is required in order to optimize the comminution process in terms of mineral liberation. The objective of this work is, therefore, to investigate the effects of different loading mechanisms on particle breakage and breakage mode. In order to achieve this goal, work has started with using two methods including three‐dimensional deformation and two‐dimensional crack quantification. The former method involved X‐ray computed micro‐tomography (XCT) imaging and Digital Volume Correlation (DVC) measurements which determiners the breakage mode in terms of being random or non-random. Whereas the latter was done using an image processing code in MATLAB to quantify cracks in terms of random and non-random breakage (preferential or phase boundary) from Scanning Electron Microscopy (SEM) images. In addition, XCT 3D imaging was used in order to track the propagated cracks in the third dimension. Moreover, phase boundary breakage in magnetite grains was studied qualitatively based on optical microscopy images in order to identify and characterize the propagated cracks.

Place, publisher, year, edition, pages
Luleå University of Technology, 2020
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords
Breakage mechanism, Loading mechanism, Ore texture, Liberation, Comminution
National Category
Geosciences, Multidisciplinary Metallurgy and Metallic Materials
Research subject
Mineral Processing
Identifiers
urn:nbn:se:ltu:diva-78068 (URN)978-91-7790-554-7 (ISBN)978-91-7790-555-4 (ISBN)
Presentation
2020-05-11, F1031, Luleå, 13:00 (English)
Opponent
Available from: 2020-03-16 Created: 2020-03-15 Last updated: 2020-04-21Bibliographically approved

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Semsari Parapari, ParisaParian, MehdiForsberg, FredrikRosenkranz, Jan

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