Mineral liberation as the main purpose of comminution in ore beneficiation is not applied in the design of comminution machines or even often neglected in designing comminution circuits. In addition, other factors critical for comminution efficiency such as fracture energy, and particle fragmentation are rarely considered. The current study investigates the combined effects of particle textural properties and process operational conditions on the fragmentation of bed particle. In particular, the influence of ore texture and loading displacement rate (as the material and machine properties) on particle specific fracture energy, breakage mode, liberation, and fragmentation was studied. The results indicate that ore textures with coarsest grain sizes and lower quantities of cleavage minerals have the least amount of fracture energy. In terms of fragmentation, a lower displacement rates results in higher quantities of the fragmented particles compared to the higher displacement rate. Among studied ore textures, two types of hematite ore textures which had the coarsest grain sizes had lower liberation in finer size fractions. Overall, the outcomes show that the displacement rate and ore texture can affect the specific fracture energy, particle fragmentation, mineral liberation, and breakage mode at different degrees.

Understanding and optimizing the comminution process in terms of mineral liberation, fragmentation, and fracture energy are aligned with sustainable approaches and overall international goals of green solutions. This study investigates the combined effect of material properties (ore textural features) and process factors (displacement rate) on mineral liberation, fracture energy, and fragmentation. For achieving this aim, multivariate data analysis tools are used to examine the fragmentation by compression of multiple layers of iron oxide minerals in a particle bed. The results indicate that ore textural features distinctively influence particle fragmentation, mineral liberation, and fracture energy and the ore textural effects are more pronounced compared to displacement rate.

Within mineral comminution, the product properties (such as particle size distribution and mineral liberation characteristics) along with process efficiency are affected by material related and process environment factors. Understanding and optimizing these factors leads to designing and developing an energy-efficient process with a specified product. A better understanding of interactions between comminution environments and ore properties is the fundamental approach to improve the breakage process. This could lead to achieving a desired product particle size and liberation with the least energy consumption. It can even be used for designing new or improving the performance of comminution machines. In this doctoral thesis, breakage fundamentals are analyzed and set against the principles of various comminution machines: (i) Loading mechanism is defined as the physical action that is applied to a particle or several particles to introduce mechanical stress. (ii) The resulting pattern of the particle failure is referred to as breakage mechanism. (iii) The breakage mode defines the particle breakage and its dependence on ore texture and mineral liberation. To date, most of the research has addressed fragmentation and energy consumption within the comminution system. While optimizing these two factors is used as the approach to have an efficient process, improving mineral liberation is the other approach. In this regard, promoting the breakage mode to preferential in phase and phase boundary breakage could help to increase the liberation degree. According to the literature, mechanical stress is one of the factors controlling mineral liberation. While mechanical stresses are related to the comminution environment, ore texture is related to the particle's inherent characteristics. The thesis aims to identify ore textural micro features and combine them with micro-static and micro-dynamic processes as the key to achieve the most efficient process in terms of mineral liberation, fracture energy, and particle fragmentation. In the first stage of the work, iron oxide ore from the Malmberget mine in Northern Sweden was used and various ore textures were characterized on micro-level to attain the qualitative and quantitative features. These features were not only used for distinguishing textures but were also used later for data interpretation. In the second stage, two distinct ore textures were selected to investigate single particle breakage through four‐dimensional deformation and two‐dimensional crack quantification. The former method determines the breakage mode by quantifying internal deformation and strain in a three-dimensional volume of in-situ X-ray computed micro-tomography measurements. In the latter method, two-dimensional scanning electron microscopy - backscattered electron was used to quantify cracks based on the type of breakage mode. In addition, X-ray computed micro-tomography three-dimensional imaging was used in order to track the propagated cracks in the third dimension. Moreover, magnetite grains cracks were studied qualitatively based on optical microscopy images in order to identify and characterize the propagated cracks. In the third stage, multiple layers of particles of three hematite and three magnetite ore textures were fragmented at two displacement rates. The attained data in terms of breakage mode, liberation distribution, fragmented particles, and fracture energy were compared and their relation to micro-processes and micro-ore features were evaluated. In the fourth stage, multivariate data analysis was applied for finding and predicting patterns in mineral liberation, fracture energy, and fragmentation connected to ore texture features and displacement rate. Moreover, a comparison of ore textural features was also done to find the strongest factors. Finally, the optimal conditions to have the lowest fracture energy and highest liberation were investigated.

Dry grinding as an alternative to wet grinding is one of Sweden's strategic research areas to promote dry beneficiation. However, dry grinding has remained unpopular due to its higher specific energy consumption (Ec), wider particle size distribution (PSD), difficult material handling, and purported effects on downstream processes. In this work, the effects of the new additives (Zalta™ GR20–587, Zalta™ VM1122, and Sodium hydroxide) employed as grinding aids (GA) on dry grinding and product characteristics of a magnetite ore were studied in light of possible downstream effects. The grinding efficiency of Magnetite increased after using GAs in comparison without the GAs; however, an optimal dosage exists for each of the chemical additives investigated. Comparing to grinding without GA, Zalta™ VM1122, a viscosity modifier was selected as the most effective GA where by using this GA; the Ec decreased by 31.1% from 18.0 to 12.4 kWh/t, the PSD became narrower and finer (the P₈₀ decreasing from 181 to 142 µm), and the proportion of the particles (38–150 µm) increased from 52.5 to 58.3%. Zalta™ VM1122 resulted in increased surface roughness and minimum microstructural defects. Further, it was found that Zalta™ VM1122 resulted in similar zeta potentials and pH values for the product compared to grinding without GA. These comparable product properties are advantageous as they minimize any potential negative effects on all possible downstream processes such as flotation.

Grinding aids (GAs) have been an important advent in the comminution circuits. Over the last few decades, in order to address the high energy consumption and scarcity of potable water for mineral processing, chemical additives have become a promising alternative. Using GAs can have some advantages such as enhancing grinding efficiency, reducing water usage, improving material flowability, and narrowing the particle size distribution of the grinding products. A study on the effect of GAs on size reduction units is crucial for the beneficiation value chain of minerals and the impact on downstream processes. However, our understanding of the effects of these materials on the particle size reduction is quite limited. This article analyses the literature, which used GAs and provides a comprehensive review of their applications in the ore beneficiation processes. The outcomes of this investigation indicated that the current understanding on the mechanism of GA effects focuses only on their impacts on the product fineness and size distribution, and neglecting the aspect of energy expended and physicochemical environment. The application of GAs is mainly for rationalisation of energy where the type of reagent, pH, and ionic strength of the grinding environment is important. Gaps in knowledge of GAs are discussed in the context of addressing their use in the mineral industry, considering the mechanism of their effect, effect on grinding efficiency, and effect on the downstream processes. Addressing these gaps will pave the way for the application of GAs in improving size reduction efficiencies, which ultimately reduces environmental impacts.

Mineral liberation and size reduction are the most critical steps before mineral separation. Several investigations showed that mineral liberation degree could be affected by ore texture and/or loading mechanisms. However, varied definitions have been used for the breakage fundamentals as the leading cause of mineral liberation. This review identifies the breakage fundamentals and analyzes them in terms of process and ore breakage behavior. It is highlighted that the breakage fundamentals are essential for optimizing of comminution environments and designing the comminution machines. Three main areas of breakage processes in regard to fundamentals of breakage are classified and addressed as “Loading mechanism”, “Breakage mechanism”, and “Breakage mode”. Despite the fact that many advances have been made in the design of the comminution machines; still, the combined effect of breakage fundamentals and ore properties such as ore texture in a quantitative manner is not fully understood. In this regard, this study identifies and discusses the material and process factors influencing the breakage phenomenon. This potentially paves the way for improving the comminution environment concerning a particular ore type.

In comminution, particle breakage starts with crack induction and propagation. The path of cracks defines the breakage mode, e.g. preferential in phase 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 minerals breakage mode. By knowing minerals breakage mode it is possible to identify the factors which affect minerals liberation and optimizing these factors in order to liberate minerals even in coarser size fractions. 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 analyze 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 consequently mineral liberation.

 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.

In comminution, particle breakage starts with crack initiation and propagation. For investigating crack formation behavior, the description by displacement fields can be applied. Ore texture and operational conditions such as loading mechanisms will affect the crack formation. This study aims at investigating the effects of ore texture and loading displacement rate on particle deformation. The objective is to describe the spatial displacement fields in the ore textures. In order to obtain these, in-situ compression loading with different displacement rates were conducted, followed by X-ray computed micro-tomography and Digital Volume Correlation (DVC). The outcomes showed that DVC has the potential to predict crack formation for describing mineral liberation.

Water scarcity dictates to limit the use of water in ore processing plants particularly in arid regions. Since wet grinding is the most common method for particle size reduction and mineral liberation, there is a lack of understanding about the effects of dry grinding on downstream separation processes such as flotation. This manuscript compiles various effects of dry grinding on flotation and compares them with wet grinding. Dry grinding consumes higher energy and produces wider particle size distributions compared with wet grinding. It significantly decreases the rate of media consumption and liner wear; thus, the contamination of pulp for flotation separation is lower after dry grinding. Surface roughness, particle agglomeration, and surface oxidation are higher in dry grinding than wet grinding, which all these effects on the flotation process. Moreover, dry ground samples in the pulp phase correlate with higher Eh and dissolved oxygen concentration. Therefore, dry grinding can alter the floatability of minerals. This review thoroughly assesses various approaches for flotation separation of different minerals, which have been drily ground, and provides perspectives for further future investigations.