Zugl.: Aachen, Techn. Hochsch., Diss., 2008

No description available.

Zugl.: Wien, Univ., Habil-Schr., 2002.

In der Erzindustrie findet ein Umdenken statt. Der Einsatz der bewährten aber energieineffizienten Sturzmühlen zur Mittel- und Feinzerkleinerung wird hinterfragt. In der Zementindustrie hat bereits ein vergleichbarer Technologiewandel stattgefunden. In diesem Bereich haben sich vor allem Wälzmühlen auf Grund ihrer Vorteile durchgesetzt. Diese Maschinen stellen auch für die Mahlung von Erzen eine Alternative zu konventionellen Sturzmühlen dar. In der Dissertation werden die Ergebnisse von systematisch durchgeführten Mahlversuchen mit einer Wälzmühle im Pilotmaßstab vorgestellt. Ziel der Untersuchungen mit drei verschiedenen Erzen war es den Einfluss ausgewählter konstruktiver und betrieblicher Parameter auf wichtige Zielgrößen wie Produktfeinheit, Energiebedarf und Verschleiß mit Hilfe von Regressionsmodellen zu quantifizieren und damit die Grundlage für eine Optimierung der Mahlanlage für den neuen Anwendungsbereich zu schaffen.

Buzwagi Gold Mine (BGM) is operated by Acacia Mining and located in the Lake Victoria Goldfields of central Tanzania. The mine commenced its operation since April 2009 and treats a sulphide copper-gold ore to produce gold in form of doré bars and a concentrate containing gold, copper and silver. The BGM comminution circuit includes a primary crushing stage with a gyratory crusher and a two grinding circuits using a Semi-Autogenous Grinding (SAG) mill and a ball mill. The SAG mill circuit also includes a single-deck screen and a cone crusher while the ball mill circuit utilizes hydrocyclones. Currently, the grinding circuits are inefficient in achieving the aspired product fineness of xP,80 = 125 μm even at low to normal throughputs (450-600 t/h). An evaluation and optimization study of the circuit performance was conducted to improve the product fineness through circuit surveys, experimental lab work and simulations. In three full scale sampling campaigns, size distributions and solids contents of the samples were determined at selected points in the circuit. Further, several types of breakage tests were conducted; standard Bond tests to determine ore grindability and work indices, batch grinding tests to determine parameters for breakage and selection functions , and standard ball mill tests for mineral liberation characterization by an automated mineral liberation analyzer (MLA).The tests were conducted in a size range from 0.063 to 2 mm. Then, mass balance of the circuit was calculated and the models for mills, screens and hydrocyclones were employed in MODSIM (version 3.6.24). Firstly, simulations were conducted to optimize the existing plant. Several options were evaluated such as reduction of SAG screen aperture, adjustment of cyclone feed solids content and reduction of vortex finder and apex diameters. Moreover, simulations were also evaluated for a possible modification of the existing circuit and include; partial splitting of the cyclone underflow back to SAG mill, introduction of a second classification stage as well as introduction of a second ball mill. The evaluation of breakage tests and survey data revealed the following; the Bond work index obtained for the current ore ranges between 17.20 - 18.70 kWh/t compared to 14.50 - 16.50 kWh/t which was estimated during plant design.This indicates a change in hardness of the ore during the last 7 years. Harder ore means more energy requirement for an efficient operation, the consequence of which is increased costs. Thus, a periodic review of the ore hardness for ongoing mining operation is recommended. This will help in establishing better blends as well as prediction of appropriate tonnages for the existing ore types, so as to be efficiently treated by the available plant design. The work indices of the ore blends treated during survey were correlated with their quartz content and showed a strong linear relationship (R2= 0.95). Therefore, the work index for the BGM ore could be predicted based on known quartz content of the material. Further, the model could be used as a control tool for monitoring hardness variation of the SAG mill feed. The mineral liberation studies indicated that the valuable phase (pyrite-pyrrhotite) could be liberated at relatively coarser particle sizes (200-400 µm). This implies that, there could be no problem with the efficiency of the gravity circuit for the BGM operation, where the gold contained in pyrite-pyrrhotite could be easily concentrated. However, the efficiency of flotation and cyanidation processes will still require finer feed. In overall, the liberation characteristics of the ore blends treated during survey showed minor differences. The Bond efficiency factors of 48-61 % were obtained for the BGM grinding circuit, indicating an inefficient operation. This suggests that the operation could achieve targets by lowering the throughput. Further, the SAG mill circuit was characterized by fluctuating feed size of between xF,80 =102 to 185 mm. A need for control of the feed size as well as blending ratios was recommended for an efficient operation in terms of throughput and final product size. This could be achieved through closer monitoring of the primary crusher performance and proper control of the ratios for the SAG mill feeders drawing the ore from the stockpile. The ball mill grinding efficiency was poor and could be indicated by the fraction < 125 µm of only 5-9 % or xP, 80 : >400 µm in the mill discharge. This was deemed due to poor hydrocyclone performance which was characterized by higher feed solids content, coarser overflow xP,80: >200 µm as well as cut sizes, xT : > 200 µm. An improvement of product fineness up to 327 µm could be achieved during the simulation and optimization of the existing design. This could be achieved by modification of the operating conditions such as reduction of SAG screen aperture from 12 mm to 10 mm, reduction of vortex finder from 280 mm to 270.3 mm, reduction of apex diameter from 150 mm to 145.6 mm as well as adjustment of the cyclone feed solids content from 66.7 to 67.1 %. Based on this result, it was concluded that the current equipment could not achieve the target product quality (i.e. xP,80 = 125 µm ). Further simulations based on flowsheet modification options showed that a second ball mill (series configuration) can help to achieve the desired product fineness as well as an increase of throughput from 618 t/h to 780 t/h. Although the circulating load increases to approximately 500 % in this configuration, it is outweighed by the benefits. Importantly, this option is cost intensive and hence may be considered as a long term solution and especially after cost-benefit analysis. Finally, the results based on optimization of the existing design is recommended as short term solution for improvement of the BGM operation. Although the fineness achieved is still low (i.e. xP,80 = 327 µm) compared to the target (i.e. xP,80 = 125 µm), this gives additional advantage in the sense that, also better hydrocyclone performance is achieved in terms of overflow product (xP,80 = 105 µm vs. > 240 µm) , cut size (xT =133.1 µm vs. > 220 µm) and circulating load (CL =350 %). The improved overflow fineness will contribute to improved efficiency for the downstream processes.

In der Erzindustrie findet ein Umdenken statt. Der Einsatz der bewährten aber energieineffizienten Sturzmühlen zur Mittel- und Feinzerkleinerung wird hinterfragt. In der Zementindustrie hat bereits ein vergleichbarer Technologiewandel stattgefunden. In diesem Bereich haben sich vor allem Wälzmühlen auf Grund ihrer Vorteile durchgesetzt. Diese Maschinen stellen auch für die Mahlung von Erzen eine Alternative zu konventionellen Sturzmühlen dar. In der Dissertation werden die Ergebnisse von systematisch durchgeführten Mahlversuchen mit einer Wälzmühle im Pilotmaßstab vorgestellt. Ziel der Untersuchungen mit drei verschiedenen Erzen war es den Einfluss ausgewählter konstruktiver und betrieblicher Parameter auf wichtige Zielgrößen wie Produktfeinheit, Energiebedarf und Verschleiß mit Hilfe von Regressionsmodellen zu quantifizieren und damit die Grundlage für eine Optimierung der Mahlanlage für den neuen Anwendungsbereich zu schaffen.

Buzwagi Gold Mine (BGM) is operated by Acacia Mining and located in the Lake Victoria Goldfields of central Tanzania. The mine commenced its operation since April 2009 and treats a sulphide copper-gold ore to produce gold in form of doré bars and a concentrate containing gold, copper and silver. The BGM comminution circuit includes a primary crushing stage with a gyratory crusher and a two grinding circuits using a Semi-Autogenous Grinding (SAG) mill and a ball mill. The SAG mill circuit also includes a single-deck screen and a cone crusher while the ball mill circuit utilizes hydrocyclones. Currently, the grinding circuits are inefficient in achieving the aspired product fineness of xP,80 = 125 μm even at low to normal throughputs (450-600 t/h). An evaluation and optimization study of the circuit performance was conducted to improve the product fineness through circuit surveys, experimental lab work and simulations. In three full scale sampling campaigns, size distributions and solids contents of the samples were determined at selected points in the circuit. Further, several types of breakage tests were conducted; standard Bond tests to determine ore grindability and work indices, batch grinding tests to determine parameters for breakage and selection functions , and standard ball mill tests for mineral liberation characterization by an automated mineral liberation analyzer (MLA).The tests were conducted in a size range from 0.063 to 2 mm. Then, mass balance of the circuit was calculated and the models for mills, screens and hydrocyclones were employed in MODSIM (version 3.6.24). Firstly, simulations were conducted to optimize the existing plant. Several options were evaluated such as reduction of SAG screen aperture, adjustment of cyclone feed solids content and reduction of vortex finder and apex diameters. Moreover, simulations were also evaluated for a possible modification of the existing circuit and include; partial splitting of the cyclone underflow back to SAG mill, introduction of a second classification stage as well as introduction of a second ball mill. The evaluation of breakage tests and survey data revealed the following; the Bond work index obtained for the current ore ranges between 17.20 - 18.70 kWh/t compared to 14.50 - 16.50 kWh/t which was estimated during plant design.This indicates a change in hardness of the ore during the last 7 years. Harder ore means more energy requirement for an efficient operation, the consequence of which is increased costs. Thus, a periodic review of the ore hardness for ongoing mining operation is recommended. This will help in establishing better blends as well as prediction of appropriate tonnages for the existing ore types, so as to be efficiently treated by the available plant design. The work indices of the ore blends treated during survey were correlated with their quartz content and showed a strong linear relationship (R2= 0.95). Therefore, the work index for the BGM ore could be predicted based on known quartz content of the material. Further, the model could be used as a control tool for monitoring hardness variation of the SAG mill feed. The mineral liberation studies indicated that the valuable phase (pyrite-pyrrhotite) could be liberated at relatively coarser particle sizes (200-400 µm). This implies that, there could be no problem with the efficiency of the gravity circuit for the BGM operation, where the gold contained in pyrite-pyrrhotite could be easily concentrated. However, the efficiency of flotation and cyanidation processes will still require finer feed. In overall, the liberation characteristics of the ore blends treated during survey showed minor differences. The Bond efficiency factors of 48-61 % were obtained for the BGM grinding circuit, indicating an inefficient operation. This suggests that the operation could achieve targets by lowering the throughput. Further, the SAG mill circuit was characterized by fluctuating feed size of between xF,80 =102 to 185 mm. A need for control of the feed size as well as blending ratios was recommended for an efficient operation in terms of throughput and final product size. This could be achieved through closer monitoring of the primary crusher performance and proper control of the ratios for the SAG mill feeders drawing the ore from the stockpile. The ball mill grinding efficiency was poor and could be indicated by the fraction < 125 µm of only 5-9 % or xP, 80 : >400 µm in the mill discharge. This was deemed due to poor hydrocyclone performance which was characterized by higher feed solids content, coarser overflow xP,80: >200 µm as well as cut sizes, xT : > 200 µm. An improvement of product fineness up to 327 µm could be achieved during the simulation and optimization of the existing design. This could be achieved by modification of the operating conditions such as reduction of SAG screen aperture from 12 mm to 10 mm, reduction of vortex finder from 280 mm to 270.3 mm, reduction of apex diameter from 150 mm to 145.6 mm as well as adjustment of the cyclone feed solids content from 66.7 to 67.1 %. Based on this result, it was concluded that the current equipment could not achieve the target product quality (i.e. xP,80 = 125 µm ). Further simulations based on flowsheet modification options showed that a second ball mill (series configuration) can help to achieve the desired product fineness as well as an increase of throughput from 618 t/h to 780 t/h. Although the circulating load increases to approximately 500 % in this configuration, it is outweighed by the benefits. Importantly, this option is cost intensive and hence may be considered as a long term solution and especially after cost-benefit analysis. Finally, the results based on optimization of the existing design is recommended as short term solution for improvement of the BGM operation. Although the fineness achieved is still low (i.e. xP,80 = 327 µm) compared to the target (i.e. xP,80 = 125 µm), this gives additional advantage in the sense that, also better hydrocyclone performance is achieved in terms of overflow product (xP,80 = 105 µm vs. > 240 µm) , cut size (xT =133.1 µm vs. > 220 µm) and circulating load (CL =350 %). The improved overflow fineness will contribute to improved efficiency for the downstream processes.

Diese Forschung zielt darauf ab, den Einsatz realistischer Mineralmikrostrukturen in Mineralverarbeitungssimulationen Simulationen von Aufbereitungsprozessen zu ermöglichen. Insbesondere Zerkleinerungsprozesse, wie z.B. das Brechen und Mahlen von mineralischen Rohmaterialien, werden stark von der mineralischen Mikrostruktur beeinflusst, da die Textur und die Struktur der vielen Körner und ihre mikromechanischen Eigenschaften das makroskopische Bruchverhalten bestimmen. Ein Beispiel: Stellen wir uns vor, wir haben ein mineralisches Material, das im Wesentlichen aus Körnern zweier verschiedener Mineralphasen, wie Quarz und Feldspat, besteht. Wenn die mikromechanischen Eigenschaften dieser beiden Phasen unterschiedlich sind, wird sich dies wahrscheinlich auf das makroskopische Bruchverhalten auswirken. Unter der Annahme, dass die Körner eines der Minerale bei geringeren Belastungen brechen, ist es wahrscheinlich, dass sich ein Riss durch einen Stein dieses Materials durch die schwächeren Körner ausbreitet. Tatsächlich ist dies eine wichtige Eigenschaft für die Erzaufbereitung. Um wertvolle Mineralien aus einem Erz zu gewinnen, ist es wichtig, sie aus dem kommerziell wertlosen Material, in dem sie vorkommen, zu befreien. Dazu ist es wichtig zu wissen und zu verstehen, wie das Material auf Korngrößenebene bricht. Um diesen Bruch simulieren zu können, ist es wichtig, realistische Modelle der mineralischen Mikrostrukturen zu verwenden. Diese Studie zeigt, wie solche realistischen zweidimensionalen Mikrostrukturen auf der Grundlage der quantitativen Mikrostrukturanalyse am Computer erzeugt werden können. Darüber hinaus zeigt die Studie, wie diese synthetischen Mikrostrukturen dann in die gut etablierte Diskrete-Elemente-Methode integriert werden können, bei der der Bruch von mineralischem Material auf Korngrößenebene simuliert werden kann.:List of Acronyms VII List of Latin Symbols IX List of Greek Symbols XV 1 Introduction 1 1.1 Motivation for using realistic microstructures in Discrete Element Method (DEM) 1 1.2 Possibilities for using realistic mineral microstructures in DEM simulations . 4 1.3 Objective and disposition of the thesis . . . . . . . . . . . . . . . . . . . . 7 2 Background 9 2.1 Discrete Element Method (DEM) . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.1 Fundamentals of the Discrete Element Method (DEM) . . . . . . . . 9 2.1.2 Applications of DEM in comminution science . . . . . . . . . . . . . 21 2.1.3 Limitations of DEM in comminution science . . . . . . . . . . . . . . 26 2.2 Quantitative Microstructural Analysis . . . . . . . . . . . . . . . . . . . . . 29 2.2.1 Fundamentals of the Quantitative Microstructural Analysis . . . . . . 29 2.2.2 Applied QMA in mineral processing . . . . . . . . . . . . . . . . . . 49 2.2.3 Applicability of the QMA for the synthesis of realistic microstructures 49 3 Synthesis of realistic mineral microstructures for DEM simulations 51 3.1 Development of a computer-assisted QMA for the analysis of real and synthetic mineral microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 3.1.1 Fundamentals of the computer-assisted QMA . . . . . . . . . . . . 53 3.1.2 The requirements for the false-color image. . . . . . . . . . . . . . 54 3.1.3 The conversion of a given real mineral microstructure into a false-color image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.1.4 Implementation of the point, line, and area analysis . . . . . . . . . 59 3.1.5 Selection of appropriate QMA parameters for analyzing two-dimensional microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.1.6 Summary of the principles of the adapted Quantitative Microstructural Analysis (QMA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3.2 Analysis of possible strategies for the microstructure synthesis . . . . . . . . 71 3.3 Implementation of the drawing method . . . . . . . . . . . . . . . . . . . . 76 3.3.1 Drawing of a single grain . . . . . . . . . . . . . . . . . . . . . . . 77 XVIII List of Greek Symbols 3.3.2 Drawing of multiple grains, which form a synthetic microstructure . . 81 3.3.3 Synthesizing mineral microstructures consisting of multiple phases . 85 3.4 The final program for microstructure analysis and synthesis . . . . . . . . . 89 3.4.1 Synthesis and analysis of an example microstructure . . . . . . . . . 90 3.4.2 Procedure for generating a realistic synthetic microstructure of a given real microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4 Validation of the synthesis approach 103 4.1 Methodical considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 4.1.1 The basic idea of the validation procedure . . . . . . . . . . . . . . 103 4.1.2 The experimental realizations . . . . . . . . . . . . . . . . . . . . . 108 4.2 Basic indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 4.2.1 Considerations for the basic indenter test . . . . . . . . . . . . . . . 109 4.2.2 Realization and evaluation of the real basic indenter test . . . . . . . 114 4.2.3 Realization and evaluation of the simulated basic indenter test . . . 127 4.2.4 Conclusions on the basic indenter test . . . . . . . . . . . . . . . . . 138 4.3 Extended indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 4.3.1 Basic considerations for the extended indenter test . . . . . . . . . . 139 4.3.2 Realization and evaluation of the real extended indenter test . . . . 142 4.3.3 Realization and evaluation of the simulated extended indenter test . 154 4.3.4 Conclusions on the extended indenter test . . . . . . . . . . . . . . 171 4.4 Particle bed test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 4.4.1 Basic considerations for the particle bed test . . . . . . . . . . . . . 173 4.4.2 Realization and evaluation of the real particle bed test . . . . . . . . 176 4.4.3 Realization and evaluation of the simulated particle bed test . . . . . 188 4.4.4 Conclusions on the particle bed test . . . . . . . . . . . . . . . . . . 203 5 Conclusions and directions for future development 205 6 References 211 List of Figures 229 List of Tables 235 Appendix 237 / This research aims to make it possible to use realistic mineral microstructures in simulations of mineral processing. In particular, comminution processes, such as the crushing and grinding of raw mineral materials, are highly aff ected by the mineral microstructure, since the texture and structure of the many grains and their micromechanical properties determine the macroscopic fracture behavior. To illustrate this, consider a mineral material that essentially consists of grains of two diff erent mineral phases, such as quartz and feldspar. If the micromechanical properties of these two phases are diff erent, this will likely have an impact on the macroscopic fracture behavior. Assuming that the grains of one of the minerals break at lower loads, it is likely that a crack through a stone of that material will spread through the weaker grains. In fact, this is an important property for ore processing. In order to extract valuable minerals from an ore, it is important to liberate them from the commercially worthless material in which they are found. For this, it is essential to know and understand how the material breaks at grain-size level. To be able to simulate this breakage, it is important to use realistic models of the mineral microstructures. This study demonstrates how such realistic two-dimensional microstructures can be generated on the computer based on quantitative microstructural analysis. Furthermore, the study shows how these synthetic microstructures can then be incorporated into the well-established discrete element method, where the breakage of mineral material can be simulated at grain-size level.:List of Acronyms VII List of Latin Symbols IX List of Greek Symbols XV 1 Introduction 1 1.1 Motivation for using realistic microstructures in Discrete Element Method (DEM) 1 1.2 Possibilities for using realistic mineral microstructures in DEM simulations . 4 1.3 Objective and disposition of the thesis . . . . . . . . . . . . . . . . . . . . 7 2 Background 9 2.1 Discrete Element Method (DEM) . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.1 Fundamentals of the Discrete Element Method (DEM) . . . . . . . . 9 2.1.2 Applications of DEM in comminution science . . . . . . . . . . . . . 21 2.1.3 Limitations of DEM in comminution science . . . . . . . . . . . . . . 26 2.2 Quantitative Microstructural Analysis . . . . . . . . . . . . . . . . . . . . . 29 2.2.1 Fundamentals of the Quantitative Microstructural Analysis . . . . . . 29 2.2.2 Applied QMA in mineral processing . . . . . . . . . . . . . . . . . . 49 2.2.3 Applicability of the QMA for the synthesis of realistic microstructures 49 3 Synthesis of realistic mineral microstructures for DEM simulations 51 3.1 Development of a computer-assisted QMA for the analysis of real and synthetic mineral microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 3.1.1 Fundamentals of the computer-assisted QMA . . . . . . . . . . . . 53 3.1.2 The requirements for the false-color image. . . . . . . . . . . . . . 54 3.1.3 The conversion of a given real mineral microstructure into a false-color image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.1.4 Implementation of the point, line, and area analysis . . . . . . . . . 59 3.1.5 Selection of appropriate QMA parameters for analyzing two-dimensional microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.1.6 Summary of the principles of the adapted Quantitative Microstructural Analysis (QMA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3.2 Analysis of possible strategies for the microstructure synthesis . . . . . . . . 71 3.3 Implementation of the drawing method . . . . . . . . . . . . . . . . . . . . 76 3.3.1 Drawing of a single grain . . . . . . . . . . . . . . . . . . . . . . . 77 XVIII List of Greek Symbols 3.3.2 Drawing of multiple grains, which form a synthetic microstructure . . 81 3.3.3 Synthesizing mineral microstructures consisting of multiple phases . 85 3.4 The final program for microstructure analysis and synthesis . . . . . . . . . 89 3.4.1 Synthesis and analysis of an example microstructure . . . . . . . . . 90 3.4.2 Procedure for generating a realistic synthetic microstructure of a given real microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4 Validation of the synthesis approach 103 4.1 Methodical considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 4.1.1 The basic idea of the validation procedure . . . . . . . . . . . . . . 103 4.1.2 The experimental realizations . . . . . . . . . . . . . . . . . . . . . 108 4.2 Basic indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 4.2.1 Considerations for the basic indenter test . . . . . . . . . . . . . . . 109 4.2.2 Realization and evaluation of the real basic indenter test . . . . . . . 114 4.2.3 Realization and evaluation of the simulated basic indenter test . . . 127 4.2.4 Conclusions on the basic indenter test . . . . . . . . . . . . . . . . . 138 4.3 Extended indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 4.3.1 Basic considerations for the extended indenter test . . . . . . . . . . 139 4.3.2 Realization and evaluation of the real extended indenter test . . . . 142 4.3.3 Realization and evaluation of the simulated extended indenter test . 154 4.3.4 Conclusions on the extended indenter test . . . . . . . . . . . . . . 171 4.4 Particle bed test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 4.4.1 Basic considerations for the particle bed test . . . . . . . . . . . . . 173 4.4.2 Realization and evaluation of the real particle bed test . . . . . . . . 176 4.4.3 Realization and evaluation of the simulated particle bed test . . . . . 188 4.4.4 Conclusions on the particle bed test . . . . . . . . . . . . . . . . . . 203 5 Conclusions and directions for future development 205 6 References 211 List of Figures 229 List of Tables 235 Appendix 237

The underlying research that resulted in this doctoral dissertation was performed at the Division of Economic Geology and Petrology of the Department of Mineralogy, TU Bergakademie Freiberg between 2011 and 2014. It was the primary aim of this thesis to develop and test novel applications for the technology of ‘Automated Mineralogy’ in the field of economic geology and geometallurgy. A “Mineral Liberation Analyser” (MLA) instrument of FEI Company was used to conduct most analytical studies. This automated system is an image analysis system based on scanning electron microscopy (SEM) image acquisition and energy dispersive X-ray spectrometry which can be used to determine both quantitative mineralogical data and mineral processing-relevant parameters. The analyses can be conducted with unconsolidated and solid rocks but also with ores and products of the mineral processing and recycling industry. In consequence of a first-time broadly-based and comprehensive literature review of more than 1,700 publications related to all types of automated SEM-based image analysis systems several trends in the publication chronicle were observed. Publications related to mineral processing lead the field of automated mineralogy-related publications. However, this is with a somewhat smaller proportion than expected and with a significant decrease in share between around 2000 and 2014. The latter is caused by a gradual but continuous introduction of new areas of application for automated mineralogical analysis such as the petroleum industry, petrology or environmental sciences. Furthermore, the quantity of automated mineralogy systems over time was carefully assessed. It is shown that the market developed from many individual developments in the 1970s and 1980s, often conducted from research institutes, e.g., CSIRO and JKMRC, or universities, to a duopoly - Intellection Pty Ltd and JKTech MLA - in the 1990s and 2000s and finally to a monopoly by FEI Company since 2009. However, the number of FEI’s competitors, such as Zeiss, TESCAN, Oxford Instruments, and Robertson CGG, and their competing systems are increasing since 2011. Particular focus of this study, published in three research articles in peer-reviewed international journals, was the development of suitable methodological approaches to deploy MLA to new materials and in new contexts. Data generated are then compared with data obtained by established analytical techniques to enable critical assessment and validation of the methods developed. These include both quantitative mineralogical analysis as well as methods of particle characterisation. The first scientific paper “Use of Mineral Liberation Analysis (MLA) in the Characterization of Lithium-Bearing Micas” deals with the field of mineral processing and describes the characterisation of lithium-bearing zinnwaldite mica - as potential natural resource for lithium - by MLA as well as the achievement of mineralogical association data for zinnwaldite and associated minerals. Two different approaches were studied to comminute the samples for this work, conventional comminution by crusher as well as high-voltage pulse selective fragmentation. By this study it is shown that the MLA can provide mineral data of high quality from silicate mineral resources and results very comparable to established analytical methods. Furthermore, MLA yields additional relevant information - such as particle and grain sizes as well as liberation and grade-recovery data. This combination of quantitative data cannot be attained with any other single analytical method. The second article “Characterisation of graphite by automated mineral liberation analysis” is also located in the field of mineral processing. This research article is the first published contribution on the characterisation of graphite, an important industrial mineral, by MLA respectively an automated mineralogy-related analytical method. During this study graphite feeds and concentrates were analysed. By this study it is shown that it is possible to gather statistically relevant data of graphite samples by MLA. Furthermore, the MLA results are validated by quantitative X-ray powder diffraction as well as particle size determinations by laser diffraction and sieve analysis. The third research paper “Nature and distribution of PGE mineralisation in gabbroic rocks of the Lusatian Block, Saxony, Germany” deals with the scientific field of geoscience. In this study it is shown that it is possible to obtain a significant body of novel mineralogical information by applying MLA analysis in a region previously regarded as being well-studied. The complex nature and relatively large distribution of the occurring platinum group minerals (PGM) is well illustrated by this contribution. During previous light microscopic studies and infrequent electron microprobe measurements only a handful isolated PGM grains were identified and characterised. In this investigation, using the samples of previous studies, 7 groups of PGM and 6 groups of associated tellurides as well as in total more than 1,300 mineral grains of both mineral groups were identified. Based on the data obtained, important insight regarding mineral associations, mineral paragenesis and the potential genesis of the PGM is obtained. Within this context, the value of MLA studies for petrological research focused on trace minerals is documented. MLA yields results that are both comprehensive and unbiased, thus permitting novel insight into the distribution and characteristics of trace minerals. This, in turn, is immensely useful when developing new concepts on the genesis of trace minerals, but may also give rise to the development of a novel generation of exploration tools, i.e., mineralogical vectors towards exploration akin to currently used geochemical vectors. The present dissertation shows that automated mineralogy by using a Mineral Liberation Analyser is able to deliver a unique combination of quantitative data on mineralogy and several physical attributes that are relevant for ore geology and mineral processing alike. It is in particular the automation and unbiasedness of data, as well as the availability of textural data, size and shape information for particles and mineral grains, as well as mineral association and mineral liberation data that define major advantages of MLA analyses - compared to other analytical methods. Despite the fact that results are obtained only on 2-D polished surfaces, quantitative results obtained compare well/very well to results obtained by other analytical methods. This is attributed mainly due to the fact that a very large and statistically sound number of mineral grains/particles are analysed. Similar advantages are documented when using the MLA as an efficient tool to search for and characterise trace minerals of petrological or economic significance. / Die Forschung die der vorliegenden kumulativen Dissertation (‚Publikationsdissertation‘) zugrunde liegt wurde im Zeitraum 2011-2014 am Lehrstuhl für Lagerstättenlehre und Petrologie des Institutes für Mineralogie der TU Bergakademie Freiberg durchgeführt. Das primäre Ziel dieser Arbeit war es neue Einsatzmöglichkeiten für die Technik der Automatisierten Mineralogie im Gebiet der Lagerstättenkunde und Geometallurgie zu entwickeln und zu testen. Im Mittelpunkt der wissenschaftlichen Studien stand die analytische Nutzung des Großgerätes „Mineral Liberation Analyser“ (MLA) der Firma FEI Company. Dieses automatisierte System ist ein Bildanalysesystem und basiert auf der Erfassung von Rasterelektronenmikroskopiebildern und energiedispersiver Röntgen-spektroskopie. Mit Hilfe der MLA-Analysetechnik lassen sich sowohl statistisch gesichert quantitative mineralogisch relevante als auch Aufbereitungsprozess-relevante Parameter ermitteln. Die Analysen können sowohl an Locker- und Festgesteinen als auch an Erzen und Produkten der Aufbereitungs- und Recyclingindustrie durchgeführt werden. Infolge einer erstmaligen, breit angelegten und umfassenden Literaturrecherche von mehr als 1.700 Publikationen im Zusammenhang mit allen Arten von automatisierten REM-basierten Bildanalysesystemen konnten verschiedene Trends in der Publikations¬historie beobachtet werden. Publikationen mit Bezug auf die Aufbereitung mineralischer Rohstoffe führen das Gebiet der Automatisierte Mineralogie-bezogenen Publikationen an. Der Anteil der Aufbereitungs-bezogenen Publikationen an der Gesamtheit der relevanten Publikationen ist jedoch geringer als erwartet und zeigt eine signifikante Abnahme des prozentualen Anteils zwischen den Jahren 2000 und 2014. Letzteres wird durch eine kontinuierliche Einführung neuer Anwendungsbereiche für die automatisierte mineralogische Analyse, wie zum Beispiel in der Öl- und Gasindustrie, der Petrologie sowie den Umweltwissenschaften verursacht. Weiterhin wurde die Anzahl der Systeme der Automatisierten Mineralogie über die Zeit sorgfältig bewertet. Es wird gezeigt, dass sich der Markt von vielen einzelnen Entwicklungen in den 1970er und 1980er Jahren, die oft von Forschungsinstituten, wie z. B. CSIRO und JKMRC, oder Universitäten ausgeführt wurden, zu einem Duopol - Intellection Pty Ltd und JKTech MLA - in den 1990er und 2000er Jahren und schließlich seit 2009 zu einem Monopol der FEI Company entwickelte. Allerdings steigt die Anzahl der FEI-Konkurrenten, wie Zeiss, TESCAN, Oxford Instruments und Robertson CGG, und deren Konkurrenzsysteme seit 2011. Ein Schwerpunkt der drei von Experten begutachteten und in internationalen Fachzeitschriften publizierten Artikel dieser Studie war die Entwicklung eines geeigneten methodischen Ansatzes um die MLA-Technik für neue Materialien und in neuem Kontext zu verwenden. Die erzeugten Daten wurden mit Daten die von etablierten analytischen Techniken gewonnen wurden verglichen, um eine kritische Bewertung und Validierung der entwickelten Methoden zu ermöglichen. Dazu gehören sowohl quantitative mineralogische Analysen als auch Methoden der Partikelcharakterisierung. Der Schwerpunkt der Studie zum ersten Fachartikel „Use of Mineral Liberation Analysis (MLA) in the Characterization of Lithium-Bearing Micas“ liegt im Gebiet der Aufbereitung mineralischer Rohstoffe. Er beschreibt die Charakterisierung von Zinnwaldit-Glimmer - einem potentiellen Lithium-Rohstoff - durch die MLA-Technik sowie das Erringen von Mineralverwachsungsdaten für Zinnwaldit und assoziierter Minerale. Dabei wurden zwei unterschiedliche Wege der Probenzerkleinerung des Rohstoffes untersucht. Zum einen erfolgte eine konventionelle Zerkleinerung der Proben mittels Brecher und Mühle, zum anderen eine selektive Zerkleinerung durch Hoch¬spannungsimpulse. Es konnte aufgezeigt werden, dass die automatisierte Rasterelektronen¬mikroskopie-basierte Bildanalyse mittels MLA von silikatischen Rohstoffen Mineral¬informationen von hoher Güte zur Verfügung stellen kann und die Ergebnisse gut vergleichbar mit etablierten analytischen Methoden sind. Zusätzlich liefert die MLA weitere wertvolle Informationen wie zum Beispiel Partikel-/Mineralkorngrößen, Aussagen zum Mineralfreisetzungsgrad sowie Gehalt-Ausbring-Kurven des Wertstoffes. Diese Kombination von quantitativen Daten kann mit keiner anderen analytischen Einzelmethode erreicht werden. Der zweite Fachartikel „Characterisation of graphite by automated mineral liberation analysis“ ist ebenfalls im Fachgebiet der Aufbereitung mineralischer Rohstoffe angesiedelt. Während dieser Studie wurden Edukte und Produkte der Aufbereitung von Graphit-Erzen untersucht. Der vorliegende Artikel ist der erste in einer internationalen Fachzeitschrift publizierte Beitrag zur Charakterisierung des Industrieminerals Graphit mittels MLA-Technik bzw. einer Analysenmethode der Automatisierten Mineralogie. Mit der Studie konnte gezeigt werden, dass es möglich ist, auch mit der MLA statistisch relevante Daten von Graphitproben zu erfassen. Darüber hinaus wurden die Ergebnisse der MLA-Analysen durch quantitative Röntgenpulverdiffraktometrie sowie Partikelgrößen-bestimmungen durch Laserbeugung und Siebanalyse validiert. Der dritte Fachartikel „Nature and distribution of PGE mineralisation in gabbroic rocks of the Lusatian Block, Saxony, Germany“ ist im Gegensatz zu den ersten beiden Artikeln im Gebiet der Geowissenschaften angesiedelt. In dieser Studie wird gezeigt, dass es möglich ist mittels MLA-Analyse eine signifikante Anzahl neuer Daten von einem eigentlich schon gut untersuchten Arbeitsgebiet zu gewinnen. So konnte erst mit der MLA die komplexe Natur und relativ große Verbreitung der auftretenden Platingruppenelement-führenden Minerale (PGM) geklärt werden. Während früherer lichtmikroskopischer Analysen und einzelner Elektronenstrahlmikrosonden-Messungen konnten nur eine Handvoll weniger, isolierter PGM-Körner nachgewiesen und halbquantitativ charakterisiert werden. In der vorliegenden Studie konnten nun, an den von früheren Studien übernommenen Proben, 7 PGM-Gruppen und 6 assoziierte Telluridmineral-Gruppen mit insgesamt mehr als 1.300 Mineralkörnern beider Mineralgruppen nachgewiesen werden. Auf der Grundlage der gewonnenen Daten wurden wichtige Erkenntnisse in Bezug auf Mineralassoziationen, Mineralparagenese und zur möglichen Genese der PGM erreicht. In diesem Zusammenhang wurde der Wert der MLA-Studien für petrologische Forschung mit dem Fokus auf Spurenminerale dokumentiert. Die MLA liefert Ergebnisse, die sowohl umfassend und unvoreingenommen sind, wodurch neue Einblicke in die Verteilung und Charakteristika der Spurenminerale erlaubt werden. Dies wiederum ist ungemein nützlich für die Entwicklung neuer Konzepte zur Genese von Spurenmineralen, kann aber auch zur Entwicklung einer neuen Generation von Explorationswerkzeugen führen, wie zum Beispiel mineralogische Vektoren zur Rohstofferkundung ähnlich wie derzeit verwendete geochemische Vektoren. Mit der vorliegenden Dissertationsschrift wird aufgezeigt, dass Automatisierte Mineralogie mittels Mineral Liberation Analyser eine einzigartige Kombination an quantitativen Daten zur Mineralogie und verschiedene physikalische Attribute, relevant sowohl für die Lagerstättenforschung als auch für die Aufbereitung mineralischer Rohstoffe, liefern kann. Im Vergleich zu anderen etablierten analytischen Methoden sind es insbesondere die Automatisierung und Unvoreingenommenheit der Daten sowie die Verfügbarkeit von Gefügedaten, Größen- und Forminformationen für Partikel und Mineralkörner, Daten zu Mineralassoziationen und Mineralfreisetzungen welche die großen Vorteile der MLA-Analysen definieren. Trotz der Tatsache, dass die Ergebnisse nur von polierten 2-D Oberflächen erhalten werden, lassen sich die quantitativen Ergebnisse gut/sehr gut mit Ergebnissen anderer Analysemethoden vergleichen. Dies kann vor allem der Tatsache zugeschrieben werden, dass eine sehr große und statistisch solide Anzahl von Mineralkörnern/Partikeln analysiert wird. Ähnliche Vorteile sind bei der Verwendung der MLA als effizientes Werkzeug für die Suche und Charakterisierung von Spurenmineralen von petrologischer oder wirtschaftlicher Bedeutung dokumentiert.

The Per Geijer iron oxide-apatite deposits are important potential future resources for Luossavaara-Kiirunavaara Aktiebolag (LKAB), which has been continuously mining magnetite/hematite ores in northern Sweden for almost 130 years. The Per Geijer deposits reveal a high phosphorus content and vary from magnetite-dominated to hematite-dominated ores, respectively. The high phosphorus concentration of these ores results from highly elevated content of apatite as gangue mineral. Reliable, robust, and qualitative characterization of the mineralization is required as these ores inherit complex mineralogical and textural features. The precise mineralogical information obtained by optical microscopy, SEM-MLA and Raman improves the characterization of ore types and will benefit future processing strategies for this complex mineralization. The different approaches demonstrate advantages and disadvantages in classification, imaging, discrimination of iron oxides, and time consumption of measurement and processing. A comprehensive mineral-chemical dataset of magnetite, hematite and apatite obtained by electron microprobe analysis (EPMA) and LA-ICP-MS from representative drill core samples is presented. Magnetite, four different types of hematite and five types of apatite constitute the massive orebodies: Primary and pristine magnetite with moderate to high concentrations of Ti (∼61–2180 ppm), Ni (∼11–480 ppm), Co (∼5–300 ppm) and V (∼553–1831 ppm) indicate a magmatic origin for magnetite. The presence of fluorapatite and associated monazite inclusions and disseminated pyrite enclosed by magnetite with high Co:Ni ratios (> 10) in massive magnetite ores are consistent with a high temperature (∼ 800°C) genesis for the deposit. The different and abundant types of hematite, especially hematite type I, state subsequent hydrothermal events. Chromium, Ni, Co and V in both magnetite and hematite have low concentrations in terms of current product regulations and thus no effect on final products in the future. In terms of a possible future hematite product, titanium seems to be the most critical trace element due to very high concentrations in hematite types I and IV, of which type I is most abundant in zones dominated by hematite. Further interest on other products is generated due to the high variability of hematite and apatite in some of these ores. Information obtained from comminution test works in the laboratory scale can be utilized to characterize ore types and to predict the behavior of ore during comminution circuit in the industrial scale. Comminution tests with a laboratory rod and ball mill of 13 pre-defined ore types from the Per Geijer iron-oxide apatite deposits were conducted in this study. The highest P80 values were obtained by grinding in the rod mill for 10 minutes only (step A). Grinding steps B (25 min ball mill) and C (35 min ball mill) reveal very narrow P80 values. Ore types dominated by hematite have significantly higher P80 values after the primary grinding step (A), which indicates different hardness of the ore types. P80 values are generally lowest after the secondary grinding step C ranging between 26 µm (ore type M1a) and 80 µm (ore type H2a). Generally, Fe content increases in the finer particle size classes while CaO and P contents decrease. The influence of silica or phosphorus seems to be dependent on the dominant iron oxide. Magnetite-dominated ore types are more likely to be affected in their comminution behavior by the presence of the silicates. Contrary, hematite-dominant ore types are rather influenced by the presence of apatite. The difference in the degree of liberation of magnetite and hematite between ore types depends rather on size fractions than the amount of gangue in the ore. Davis tube data indicates that magnetite can be separated from gangue quite efficiently in the magnetite-dominated ore types. Contrary to magnetite ore, hematite-dominated ore types cannot be processed by DT. It is favored to use strong magnetic separation in order to achieve a desirable hematite concentrate. The magnetic material recovered by DT is most efficiently separated at an intensity current of 0.2 A, whereas above 0.5 A the separation process is neglectable. Based on comminution and magnetic separation tests a consolidation to eight ore types is favored which supports possible future mining of the Per Geijer deposits.:Contents ABSTRACT ……………………………………………………………………… I CONTENTS ……………………………………………………………………… II LIST OF FIGURES AND TABLES ……………………………………………… IV LIST OF ABBREVIATIONS ……………………………………………… V 1 INTRODUCTION ……………………………………………………… 1 1.1 Background and motivation of study ……………………………… 2 1.2 Previous and current work on the Per Geijer deposits ……………… 3 1.3 The need for mineral processing and in-situ ore description ……………… 4 1.4 General and generic aspects on iron oxide apatite deposits ……………… 5 Chapter A 2 REGIONAL GEOLOGY ………………………………………………. 7 2.1 Local geology of the Kiruna area ……………………………………… 7 2.2 Geology of the Per Geijer deposits ……………………………………… 9 3 METHODOLOGY ……………………………………………………… 12 3.1 Core sampling and preparation ……………………………………… 12 3.2 SEM – MLA in-situ ore ……………………………………………… 14 3.3 Electron Probe Microanalyses (EPMA) ……………………………… 15 3.3.1 Iron oxide measurements ……………………………………… 15 3.3.2 Apatite measurements ……………………………………… 15 3.4 In-situ LA-ICP-MS ……………………………………………………… 16 3.5 Whole-rock geochemistry ……………………………………………… 18 3.5.1 Exploration drill core assays ……………………………… 18 3.5.2 Chemical assays of rock chips ……………………………… 18 4 RESULTS ……………………………………………………………… 19 4.1 Pre-definition of ore types ………………………………...……………. 19 4.2 Mineralogy of in situ ore ……………………………………………… 21 4.2.1 Ore Type M1a ……………………………………………… 21 4.2.2 Ore Type M1b ……………………………………………… 22 4.2.3 Ore Type M2a ……………………………………………… 23 4.2.4 Ore Type M2b ……………………………………………… 25 4.2.5 Ore Type HM1b ……………………………………………… 26 4.2.6 Ore Type HM2a ……………………………………………… 27 4.2.7 Ore Type HM2b ……………………………………………… 28 4.2.8 Ore Type H1a ……………………………………………… 29 4.2.9 Ore Type H1b ……………………………………………… 30 4.2.10 Ore Type H2a ……………………………………………… 31 4.2.11 Ore Type H2b ……………………………………………… 32 4.2.12 Comparison of ore types ……………………………………… 33 4.3 Geochemistry of in situ ore types ……………………………… 36 4.3.1 Whole-rock chemical assays of drill cores ……………………… 36 4.3.2 Whole-rock geochemistry of rock chips ……………………… 39 4.4 Mineral chemistry of iron oxides ……………………………………… 42 4.4.1 Iron oxides and associated minerals ……………………………… 42 4.4.2 Mineral chemistry of magnetite from Per Geijer ……………… 43 4.4.3 Mineral chemistry of hematite from Per Geijer ……………… 47 4.5 Mineral chemistry of apatite ……………………………………… 51 4.5.1 Apatite and associated minerals ……………………………… 51 4.5.2 Mineral chemistry of apatite from Per Geijer ……………… 53 Chapter B 5 COMMINUTION TESTS ……………………………………………… 58 5.1 Methodology of comminution tests ……………………………………… 59 5.1.1 Sampling for comminution tests ……………………………… 59 5.1.2 Comminution circuit ……………………………………………… 61 5.1.3 Energy consumption calculation ……………………………… 62 5.1.4 SEM – MLA ……………………………………………………… 64 6 MAGNETIC SEPARATION TESTS ……………………………… 65 6.1 Methodology of magnetic separation by Davis magnetic tube ……… 66 6.2 Davis magnetic tube tests for characterization of the Per Geijer ore types 66 6.3 Separation analysis based on the Henry-Reinhard charts .……………... 67 7 RESULTS OF COMMINUTION OF ORE TYPES ……………………… 69 7.1 General characteristics of magnetite-dominated ore types ……………… 69 7.2 General characteristics of hematite-dominated ore types ……………… 72 7.3 General characteristics of magnetite/hematite-mixed ore types ……… 75 7.4 General characteristics of low-grade ore types ……………………… 77 7.5 Mineral liberation characteristics of magnetite-dominated ore types 79 7.6 Mineral liberation characteristics of hematite-dominated ore types 83 7.7 Mineral liberation characteristics of magnetite/hematite-mixed ore types 87 7.8 Mineral liberation characteristics of low-grade ore types ……………… 90 7.9 Total energy consumption of ore types from the Per Geijer deposits 94 8 RESULTS OF MAGNETIC SEPARATION OF ORE TYPES ……… 95 8.1 Magnetic separation of magnetite-dominated ore types ……………… 95 8.2 Magnetic separation of hematite-dominated ore types ……………… 96 8.3 Magnetic separation of magnetite/hematite-mixed ore types ……………… 97 8.4 Magnetic separation of low-grade ore types ……………………………… 98 8.5 Henry-Reinhard charts ……………………………………………… 99 9 DISCUSSION ……………………………………………………… 101 9.1 Mineralogy of the in-situ ore types from the Per Geijer deposits ……… 101 9.2 Geochemistry of the in-situ ore types from the Per Geijer deposits ……… 103 9.3 Mineral chemistry of iron oxides from the Per Geijer deposits ……… 105 9.4 Mineral chemistry of apatite from the Per Geijer deposits ……………… 114 9.5 Comminution of ore types from Per Geijer ……………………… 119 9.6 Magnetic separation of ore types from Per Geijer ……………………… 120 9.7 Issues with process mineralogy of in-situ and grinded ore types ……… 121 10 CONCLUSIONS ……………………………………………………… 128 11 IMPLICATIONS FOR FUTURE WORK ……………………………… 131 12 REFERENCES ……………………………………………………………… 134