Bern Klein


Relevant Degree Programs


Graduate Student Supervision

Doctoral Student Supervision

Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.

Development of a comprehensive HPGR model using large experimental data sets (2021)

Mining activities, particularly the crushing and grinding process, are energy intensive and energy inefficient. To meet the increasing demand in raw materials, mining companies need to focus more on energy efficiency that can enhance the operating profitability and meet the society demands for reduced carbon footprint. The High Pressure Grinding Roll (HPGR) is an important energy-efficient comminution technology with potential to significantly reduce energy consumption in the mining industry. However, a wider adoption of the HPGR is considered slow. The goal of this research is to increase the accessibility of HPGR technology for all mining companies and their projects. A key outcome is the development of a comprehensive simulator incorporating empirical and semi-empirical models for HPGR equipment sizing, circuit design, and process simulation. Empirical models for predicting key HPGR sizing parameters were developed based on large pilot HPGR tests conducted at the University of British Columbia (UBC). The predictions are primarily driven by feed material characteristics and HPGR operating conditions. This approach enables the sizing and selection of HPGR for cases with no specific HPGR characterization test work. Typically, mining projects would undergo different study phases for project evaluation. A framework incorporating empirical models and small scale Piston-die Press Testing (PPT) data was proposed, which aimed at providing a low-cost option for HPGR evaluation while meeting the specific requirements per each study phase. Case studies were presented to demonstrate the use of empirical models and some specific HPGR characterization test work under the proposed framework to support different stage of studies. Advances have also been made in addition to the semi-empirical model developed by Davaanyam (2015) that enhanced the capacity of HPGR modeling and simulation. At last, a comprehensive HPGR simulator was developed for HPGR evaluation integrating HPGR empirical models, semi-empirical models and phenomenological models. Overall, the development of a comprehensive and reliable HPGR model and simulator provides an easier access to mining companies who may benefit from the HPGR technology. Ultimately, it is hopeful that increased number of HPGR installations can be promoted and greater energy savings can be realized.

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The assessment of mineralogical properties and hydrological or physicochemical controls on the drainage chemistry of mine waste rock (2020)

Mining exploitation produces a substantial amount of waste rock that, when exposed to water and oxygen, may liberate metals and acidity in mine drainage. Waste rock and mine drainage should therefore be carefully managed to avoid the propagation of harmful elements in the environment. Proper management strategies include geochemical characterization of waste rock, water quality monitoring, long-term predictions, and thorough knowledge of mobility controls of solutes in mine waste. This study investigates the relationship between waste rock weathering, processes controlling mineral reactivity or solute mobility, and drainage chemistry in field barrel kinetic tests or within the full-scale waste-rock pile. The main findings of this work are that: 1) Waste rock reactivity, evaluated from mineral liberation and association indices that are calculated from automated mineralogy data, complements bulk geochemistry and lithological characterization and improves drainage quality predictions; 2) Mechanisms of secondary mineral precipitation, sorption, surface passivation and galvanic reactions are linked to potential mobilization or inhibition of metals in the drainage data; 3) Mineralogical composition and weathering patterns are interrelated with hydrological responses, providing an initial qualitative indication of hydrological and geochemical processes controlling drainage chemistry in field barrels; 4) Reactive transport modeling provides site-specific calibrated mineral weathering rates illustrating the control of hydrological, physicochemical, and mineralogical processes on drainage chemistry; 5) High-resolution sampling and analyses of waste rock weathering and drainage of reactive zones within the waste-rock pile reveal high degrees of physicochemical heterogeneity that can hardly be described by static laboratory testing or sensor measurements alone. Overall, this thesis is facilitating the interpretation of waste-rock reactivity using waste-rock quantitative mineralogical evaluations; providing mineralogical perspectives on geochemical and hydrological processes; expanding the identification of mechanisms affecting metal mobility from waste-rock drainage; and, providing information to achieve more accurate drainage prediction models. As improvements are made to the automation of mining operations at large scales, more information can be gathered cost-effectively. This novel mineralogical approach, adding new perspectives on weathering processes impacting mine drainage, could therefore be applied to other mine sites, ultimately allowing for the optimization of waste-rock management as well as long-term drainage predictions.

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Cave-to-Mill: mine and mill integration for block cave mines (2019)

Population growth and economic development are expected to increase future global copper demand. The depletion of significant near-surface deposits and advances in detecting deeply buried ore has led to the mining industry progressively exploring further below the surface to discover new copper deposits. Accordingly, block and panel cave mining methods are being increasingly proposed as they allow massive, deeply situated ore-bodies to be mined economically. To improve the productivity of a mining method that will be used to excavate a growing proportion of global copper supply, an integrated mine and mill approach for planning and operating block cave mines, termed Cave-to-Mill, was developed. Key distinguishing features of cave mining, in comparison to other mining methods, are the uncertainty in the size of rock being fed to the mill and the lack of selectivity. As part of the Cave-to-Mill framework, fragmentation and sensor-based sorting studies were carried out at the New Afton block cave mine to investigate opportunities to improve overall productivity.Cave fragmentation is a key cave-to-mill parameter as it has implications on the productivity of both mining and milling processes. Fragmentation measurements of drawpoint muck, comminution tests and calibrated mill models were used to assess the impact of variations in feed size and hardness on New Afton mill performance. Analysis of historical mine and mill data showed that mill feed size and subsequently mill throughput are sensitive to the areas being mucked within the cave. A sensor-based ore sorting study, incorporating bulk and particle sorting systems, showed that rock from the New Afton copper-gold porphyry deposit is amenable to prompt gamma neutron activation analysis, and to X-Ray fluorescence sensors. A conceptual flowsheet, where both technologies are used as separate unit operations, was evaluated. It was found that the sorting concept demonstrated an improvement in the net smelter return of excavated material. Results from the study were used to develop a method to design and evaluate a block cave for the case where sensor-based sorting systems are included in the flowsheet.

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Piston Press Test Procedures for Predicting Energy-Size Reduction of High Pressure Grinding Rolls (2015)

High Pressure Grinding Rolls (HPGR) have been used for over 20 years, however the technology has not received wide industry acceptance despite reports of substantial energy advantages. One barrier is that full and fair consideration cannot be given to HPGR-based comminution circuits for early-stage mining projects, because industry standard tests require large sample sizes for evaluation of the technology. The main objective of the research was to develop methodologies, requiring small sample quantities, to predict the energy–size reduction performance of HPGRs. A key outcome is the development of three piston press testing procedures that require significantly less sample than standard HPGR evaluation methods. One method, referred to as the direct calibration methodology, involves calibrating results of piston press tests against pilot-scale HPGR tests. This methodology was developed primarily for situations where HPGR test data is only available for a composite sample and the energy requirements of individual geometallurgical units within a deposit are to be determined.To address the case where HPGR test results are not available, a second method was developed which relies only on piston press testing and empirical equations that were determined from a database of pilot-scale HPGR results. The simulation-based methodology was also developed to be able to assess the impact of changes in HPGR operation or circuit configuration on comminution performance. An existing energy–breakage model was adopted and modified for application to particle-bed comminution. The three methodologies were compared by applying them to samples from a copper-gold deposit in central British Columbia. Through utilization of these methodologies, the energy–size reduction performance of the HPGR technology can be predicted with small sample requirements which can be applied to a broad range of ore types and provide a stronger statistical basis for the process design. During development of the methodologies, significant research outcomes resulted. Controlled piston press and HPGR pilot tests on the same samples confirmed that normalized product PSDs of the respective equipment can be regarded as equivalent. Furthermore, data from particle-bed comminution tests was used to determine master curves describing breakage appearance functions for the compression mode of breakage.

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Improving Operation and Performance of Continuous Variable Discharge Concentrator (2014)

Continuous discharge centrifugal concentrators have been in use for more than 20 years but their technological advantages have not yet been fully exploited due to limited fundamental understanding of the technology and lack of operating strategy to efficiently adjust the multiple interacting variables to improve performance. In addition there is no mechanism for scale up and the existing laboratory procedures have limitations for predicting metallurgical response. This thesis focuses on two main goals. Firstly to develop a gravity amenability laboratory scale test procedure and secondly to develop a procedure for tuning CVD variables to improve operational performance with the aim of increasing application.A novel optimization approach, code named NNREGA, integrating artificial neural networks, regression and a genetic algorithm, was developed and tested for tuning CVD operating variables to simultaneously maximize gold recovery and grade from a polymetallic flotation tailing. An optimum operating line was generated using a Pareto genetic algorithm. Results show that the procedure provides an efficient way of exploring the design space to learn the relationship between interacting variables and outputs and is capable of predicting an improvement in CVD performance. By generating the operating curves, the procedure provides a basis for CVD scale up. It also allows for continuous improvement and can be used as part of an operating strategy with potential to integrate into machine logic control.A Gravity Release Analysis procedure, which consists of rougher, scavenger and four incremental cleaner laboratory scale Knelson concentrator stages was developed to characterize ore amenability to CVD concentration. The procedure was used to quantify gravity recoverable gold bearing sulphides in flotation tails from a massive sulphide ore and an epithermal gold vein ore. Results show good correlation between the laboratory procedure and CVD, with the laboratory procedure results forming an upper limit for the CVD. Thus, the Gravity Release Analysis procedure can be used to predict potential CVD application and to benchmark operating machines. Based on the Gravity Release Analysis procedure, a mechanism of quantifying gravity amenability and gravity kinetics, the gravity release index, was introduced. The index can be used to quantify the relative abundance of different gravity recoverable mineral species in an ore.

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Quantifying, reducing and improving mine water use (2013)

Water is vital to the mining industry; mines can require substantial amounts of water and are often located in some of the driest places on earth. Reducing water withdrawals and improving mine water use are key strategic requirements for moving toward a more sustainable mining industry. Mine water requirements often have significant technical, economic, environmental and political implications. This thesis quantifies global mine water withdrawals and discusses methods of improving mine water use by reducing water withdrawals and water-related energy consumption.The thesis is composed of four main sections. First, two methods are proposed to calculate global mining water withdrawals by commodity. One method is based on the amount of water required to process a tonne of ore and the other is based on the amount of water required to produce a tonne of concentrate. A large database was created, compiling data regarding ore production, commodity production, commodity prices, and mine water withdrawals between 2006 and 2009. The study estimates that global water withdrawals range from 6 to 8 billion m3 per annum. Second, the thesis presents a case study on the challenges faced and lessons learned during the design, start-up and modification of the water systems of a large copper mine site. Third, the thesis identifies multiple mine water reduction, reuse and recycle strategies that have been implemented around the world. A model is developed and used to show the potential impact of these strategies. The results of the modelling show how a hypothetical mine could reduce water withdrawals from 0.76 m³/t to 0.20 m³/t of ore processed or lower. In particular, the combination of ore pre-concentration and filtered tailings disposal reduced water consumption by over 74% of the base case. Finally, this thesis describes and demonstrates a method of determining the lowest energy option for a mine water network. The method uses a linear programming algorithm to compare options for matching water sources with consumers at mine sites. An example illustrates the method and shows how mine water system energy requirements can be reduced by over 50%.

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The effect of stirred mill operation on particles breakage mechanism and their morphological features (2011)

Stirred milling is a grinding tool that is used extensively for mineral liberation, in order to achieve successful downstream processing such as flotation or leaching. The focus of this research is to understand the effect of different operating parameters on particle breakage mechanism. Operating parameters could be summarized as stress intensity on the particles which are varied by changing the mill’s agitator speed, and different ground material properties such as extreme hard/low density minerals like quartz versus soft/high density minerals like galena. Grinding performance is assessed by analysing particle size reduction and energy consumption. Breakage mechanism is evaluated using the state of the art morphological analysis and liberation. Finally, theoretical evaluation of particles flow, types of forces and energy distribution across the mill are investigated using Discrete Element Modelling (DEM). It is observed that breakage mechanisms are affected by the type of mineral and stress intensities (agitator speed) in the mill. For example, galena, the soft/high density mineral, reaches its grinding limit very fast at high agitator speed and specific energy consumption increases exponentially with the increase of the agitator speed. On the other hand, for quartz, the hard/low density mineral, the breakage rate is very slow at low agitator speed and the specific energy consumption increases linearly with the increase of the agitator speed. Fracture mechanism of the particles is also a function of the agitator speed and type of mineral. At high agitator speed, galena fractures mostly along the grain boundaries, whereas quartz breaks across the grains, which is abrasion. The morphology observation is confirmed by the DEM model, which conveyed that at higher agitator speed, the normal forces were higher than tangential forces on the galena particles compared to the ceramic grinding media particles. The core of this research is the morphology analysis, which is a novel approach to studying particle breakage mechanisms. More work is recommended in the field of morphology with other types of minerals to confirm the findings of this research. 3D liberation analysis was introduced in this research; a correlation to the conventional liberation methodology would be a major addition to the industry.

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Pipe flow of homogeneous slurry (2008)

The objective of this Thesis is to devise a system for the "rheology-based design" of non-settling (homogeneous) slurry pipelines that is more conducive to application by practicing engineers without impairing its accuracy or utility for research purposes. The cornerstone is the development of a new rheological model and constitutive equation for homogeneous slurry based on the aggregation/deaggregation of the suspended mineral particles. This “yield plastic” model is shown to describe a family of models that includes the Newtonian, Bingham plastic and Casson models as special cases. It also closely approximates the results of many consistency models, including power law, yield power law, Cross and Carreau-Yasuda.The yield plastic model is then used to develop design equations to determine the pressure-gradient of laminar and turbulent pipe flow. A relative energy dissipation criterion is proposed for the laminar-turbulent transition and shown to be consistent with currently used transition models for Newtonian and Bingham fluids. Finally, a new dimensionless group (the “stress number”) is proposed that is directly proportional to the pressure-gradient and independent of the velocity. When the design equations are presented graphically in terms of the stress number and the plastic Reynolds number, the resulting “design curve diagram” is shown to be a dimensionless (pressure-gradient vs. velocity) pipe flow curve. The net result is that the hydraulic design of homogeneous slurry systems only requires the use of a single constitutive equation and three engineering design equations. The results are presented in a conceptually easy form that will foster an intuitive understanding of non-Newtonian pipe flow. This will assist engineers to understand the impact of slurry rheology when designing, operating and troubleshooting slurry pipelines and, in the future, other slurry related processes.

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Master's Student Supervision

Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.

Optimizing beneficial productivity in open pits using shovel-based sorting systems (2022)

The purpose of this study is to develop a model to assess the economic value delivered by deploying a new ore sorting solution in an open pit environment. ShovelSenseTM is a technology based on x-ray fluorescence sensors mounted on the bucket of the shovels in order to execute the ore sorting at the mining face in real time. This is a different application of the technology that was previously used in the mining industry on conveyors belts.The model was built using two steps. The first stage of this study was built using ExtendSim, a discrete event simulation software. This technology is widely used in the mining industry mainly modeling hauling and mineral processing systems. What was modeled in ExtendSim is a conventional open pit based on a shovel-truck system that has three possibilities or destinations (waste dump, heap leach and mill) to send the material extracted from the mine, where the destinations are constrained by a COG. Furthermore, the DES model is capable of reading the information coming from a resource block model via a text file.The second stage takes the outputs produced in the simulation (tonnage and grade distribution per destination) and applies a set of recoveries, metal prices and operating costs in order to model the economic case.The value delivered by the technology is estimated by running two sets of data in the form of block models, where one set is influenced by the technology and the other is not. Ultimately, the economic assessment compares the two options to determine which delivers the most benefit. Finally, the comparison shows a substantial economic value delivered by deploying ShovelsenseTM into the open pit operation analysed in this study. Furthermore, the unlocked value by the technology is the result of optimizing the material assignation to the different destinations in the system.

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Adoption of extended reality (xr) for enhancement of human capital in the mining workforce of the future (2021)

Industry and society are at the beginning stages of the 4th Industrial Revolution or in the case of mining, known as Mining 4.0. Among the multitude of drivers of the new revolution, automation and digitization will transform the nature of human capital within the mining industry. Skill polarization will occur with a reduction in repetitive, low skilled jobs while high skilled programming and engineering jobs will increase. This polarization will benefit those with degrees and access to education in urban areas while the local remote and Indigenous communities will face greater challenges in getting employment in the mines which will increasingly be run by complex smart integrated systems. Extended Reality (XR) encompasses Virtual (VR), Augmented (AR), and Mixed (MR) realities and these methods could provide learning benefits, remote learning/collaboration, and translate to considerable cost and time savings if used for the training of new workers or for the up-skilling of current employees. Despite the benefits of XR methods, there is limited adoption within the mining industry. In order to understand the reasons behind the lack of adoption, a Comprehensive Literature Review was conducted to identify experts and a cross sectional survey was designed and distributed. The research questions attempted to be answered were: what are the perceived advantages/disadvantages, barriers, and timeline for XR adoption? Results indicate that mining company management misunderstands the usage of XR, hardware for XR methods needs more development and software should be more available for companies. The timeline for adoption seems to be 1-3 years for VR, and 3-5 years for AR/MR methods, and recommendations were provided for implementation.

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Assessment and modelling of quaternary and quinary HPGR performance for iron ore applications (2021)

The complexity degree of a mining plant’s comminution circuit is critical for allowing the processing of low-grade iron ore deposits. Considering that the comminution stage is responsible for most of the energy consumption in a mineral processing plant, the pursuit of energy-efficient technologies is a major challenge of the mining industry. The High Pressure Grinding Rolls (HPGR) have been applied for over 20 years and is widely recognized in terms of energy savings. However, the limited access to industry and academic studies about the HPGR performance and the lack of a widely industry accepted bench-scale laboratory test for sizing and modelling HPGRs are major hindrances that must be addressed in order to promote the machine acceptance and implementation.The research's main objectives were to evaluate the HPGR amenability to comminute iron ore in a two-stage HPGR circuit and extend the applicability of Davaanyam’s (2015) Direct Calibration and Database-Calibrated methodologies for predicting the energy consumption and size reduction of HPGRs through laboratory-scale piston-press tests. The HPGR performance and modelling evaluation for quaternary and quinary applications were supported by a combination of laboratory-scale testing, pilot-scale testing and modelling work.Results obtained from the research showed that the HPGR is suitable for comminuting iron ore in open circuit quaternary and closed circuit quinary applications. The performance evaluation revealed a strong linear relationship between the machine’s specific pressing force and net specific energy consumption. The size reduction also increased linearly with the increase of the pressing force. The ore moisture content revealed to be detrimental to the HPGR’s throughput at high concentrations but did not impact the performance in terms of size reduction. The Direct Calibration methodology was successfully applied to iron ore for quaternary applications, but the current Database-Calibrated regression models resulted in poor energy-size reduction predictions. because the variable levels for the quaternary application extended beyond the ones used for developing the current regression models. The results indicate that the database needs to be extended to finer sizes, higher moisture levels and possibly ore types.

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Laser Induced Breakdown Spectroscopy to quantify penalty elements in iron ore (2021)

Producing mines and new projects are forced to mine lower grade and more complex ores. As a consequence, there is an increased need to monitor penalty elements. The penalty elements are the constituents that reduce the quality, and therefore the value of the concentrate. Many of these constituents are low atomic number elements that are not adequately detected with most existing sensors. The case study evaluated in this work, is an operating iron mine where silicon, aluminum, potassium, phosphorus, and sulfur are penalty elements.Real-time ore monitoring and Sensor-Based Sorting utilize different analytical techniques that serve as sensors. Many of the more studied and used analytical techniques, such as ICP (Inductively Coupled Plasma), XRD (X-Ray Diffraction), XRF (X-Ray Fluorescence), PGNAA (Prompt Gamma Neutron Activation Analysis), or XRT (X-ray Transmission), require long scanning times, time-consuming sampling procedures or cannot detect low atomic number elements.Laser Induced Breakdown Spectroscopy (LIBS) is a proven analytical technique that can analyze all elements in the periodic table in real-time. It had advanced significantly since its conception when it was a fragile laser technology. Especially after 2012 and 2021, LIBS received much attention when NASA successfully used it on the Mars rover to analyze soils and rocks at a distance. In this thesis, the experiments were done with crushed Run of Mine iron ore material to investigate the reconciliation between the bulk analysis by conventional techniques (assay) versus surface analysis provided by LIBS. Univariate and multivariate models achieved between 88 to 99% correlation with the assay results. The challenges presented during this research can be explained by low signal-to-noise ratios, self-absorption phenomena, low concentration of the element of interest, and the available low energy LIBS setup used in the study. The results presented indicate that LIBS can be used to accurately perform monitoring and sorting of crushed iron ore, with multiple economic and environmental advantages. Supplementary materials available at:

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Size classification and dewatering for fine HPGR comminution circuit (2021)

High-pressure grinding roll (HPGR)-based circuits are increasingly applied to replace the semi-autogenous grinding (SAG) mill circuits due to their higher energy efficiency and lower operating cost. A novel HPGR circuit is proposed to replace conventional ball mills and extend the energy benefits for final grinding before the flotation or leaching circuit. However, the typical moisture of the ball mill feed is 20–35%, while the highest acceptable feed moisture to the HPGR is ~10%. Therefore, replacing the ball mill with HPGR technology requires a size classification and dewatering system. The purpose of this thesis was to assess the applicability of a variety of size classification and dewatering technologies to a novel HPGR comminution circuit. A ranking system was developed to identify the size classification and dewatering technologies with the most potential for the proposed circuit. The ranking matrix was developed using criteria essential for selecting equipment—with weighting factors assigned for each criterion. The ranking results for size classification equipment showed that the screw classifier scored the highest, followed by the high-frequency screens and the Derrick® Stack Sizer®. Based on the ranking results, test work was conducted to evaluate the capabilities of the selected equipment to process the material for the novel circuit. As a result, the size classification using the screen or screw obtained efficiencies of over 85%. For the dewatering equipment ranking, the dewatering screw scored the highest, followed by the pan filter and the dewatering screen. Based on the ranking results, test work was conducted with these three selected pieces of equipment. The vacuum filtration and the screw could achieve a moisture content below 10%. Therefore, both technologies were suitable for the novel circuit.With the ranking and test results, three combinations of equipment were suggested for the novel HPGR circuit for fine grinding: 1- Screens, follow by screw dewatering 2- Screws, follow by dewatering screw, and 3- Single-stage of screw classifier. The three proposed circuits could achieve the target moisture (less than 10%), but only the first to can achieve the target fine content (less than 5%).

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A power based approach for the selection and comparison of ball mill liners (2018)

Current technology and simulation software used in the mining industry fail to factor in the effect of liner type and wear on ball mill grinding efficiency and throughput. This thesis provides a comprehensive analysis of key mill operating parameters and addresses the following key research question: how does liner type, lifter face angle, and liner wear affect mill grinding efficiency?The hypothesis is a lifter’s face angle drive a ball mill’s grinding efficiency and throughput independently of the type of liner used. To test this hypothesis, plant data and the profile and lifter face angle of the three most widely used liners are analyzed in terms of mill power draw using Morrell’s model C and MillTraj®.Results show the mill ball charge shoulder angle is strongly affected by the liner lifter’s face angle and that Morrell’s Model C could be improved by including a correction parameter that reflects the power draw of a mill along the service life of its liner. The correction parameter is to reflect the effect of wear on the shoulder angle. Results show that mill grinding efficiency decreases as the liner wears but that efficiency can still be maintained by adjusting the mill speed. The operating work index was found to be an effective tool for identifying increased grinding inefficiency along the liner’s service life.Further research is required to include a wear parameter that indicates the liner profile in Morell’s Model C power equations. It is also necessary to carry out additional research on variable speed drivers (VSD) for mill motors, which could potentially pay back the cost of adding a VSD on ball mills due to the increased grinding efficiency.

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Development of a tower mill model using hardgrove mill tests (2018)

The gravity-induced low speed stirred milling technology, commonly referred to as tower mills, are widely used for fine grinding due to their high energy efficiency compared to conventional tumbling mills. Moreover, the lower operating cost, shorter installation period and simpler operating strategy make it attractive for many mines. Researchers have attempted to develop an ore characterization method and mathematical models for tower mills. However, there is no well-established universal fine material characterization method for both the grindability assessment and modeling of tower mills.In this study, a modified Hardgrove mill fine material characterization method was developed for the tower mill grindability assessment. The test result was integrated into the fmat breakage model, which incorporates both the effect of specific energy and particle size. Several industrial tower mill grinding circuit surveys were conducted to provide the information regarding the operating conditions and grinding product size distribution. The ore breakage model, the size specific energy level model, internal classification model and tower mill power models were integrated into a mass-size balance model to simulate the tower mill performance. A sensitivity analysis was conducted to simulate the tower mill performance under varied stirrer speed and media charge.Results obtained from the model and simulation work show that the developed model is capable of predicting the tower mill grinding product size distribution with adequate accuracy. The sensitivity analysis indicated a new opportunity to control the tower mill performance by adjusting the stirrer speed rather than by the conventional media addition strategy.

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Development of operation strategies for variable speed ball mills (2018)

Mineral processing productivity relates to a range of operating parameters, including production rate, product grind size, and energy efficiency. Variations in ore properties and operating conditions change the comminution dynamics, resulting in a constant deviation from operational goals. Although most processing facilities currently use fixed speed grinding mills, variable speed drive is considered to provide an important control variable that can contribute to achieving operational objectives.This thesis examines variable speed ball mill performance under changing operating conditions to recommend operating conditions for the Copper Mountain Mine. JK SimMet, a very powerful predictive tool, was used to estimate grinding circuit performance and mill power consumption. Samples and operating data were collected directly from the Copper Mountain Mine to build a calibrated model. Appearance (breakage distribution) functions of different geo-samples were measured and used to predict plant performance under different ore property variations.The results indicate that higher mill speed and lower ball load operating strategies are preferable with respect to energy savings in variable speed ball mill operations. Ore characteristic variations at the Copper Mountain Mine are significant and can cause large oscillations within mill operations. Thus, ore blending in Copper Mountain should be done carefully and cautiously. However, in combination with traditional optimization methods, ball mill grinding speed can be used to control energy input and offset the influences of ore variability. Optimum ball mill operating conditions can be determined based on circuit design and operating dynamics for any given run-of-mine ore.

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Surface XRF mapping for intraparticle heterogeneity assessment and particle grade estimation (2018)

Sensor-based sorting is perceived as a feasible solution for some of the most critical aspects of mineral processing. There are two basic classes of sensors, 1. those that measure a property characteristic of the bulk of a particle; and 2. those that measure a property of the surface of a particle. For the second class, the surface measurement is then correlated to the bulk property of interest. The correlation does not only depend on how well the sensors can analyze the surface, but also on how well the surface correlates to the volume of the rock. The correlation is even more complex since only part of the rock surface is scanned by an actual sorter. Thus, the heterogeneity within each particle, defined as intraparticle heterogeneity, is an important variable to be characterized. The main objective of this work was to design and develop a method for rock surface mapping to assess intraparticle heterogeneity and to evaluate the correlation between surface grade and bulk grade for run of the mine or primary crushed rocks. The XRF mapping technique developed, and the procedure selected to analyze the mapping data, were described and applied to two porphyry copper ore samples. According to an univariate statistical analysis, for the samples analyzed, copper and iron data distributions did not follow either normal or lognormal distribution. Median and median absolute deviation were proposed as the best parameters to summarize the surface grade and the intraparticle heterogeneity, respectively. The median value of the surface grade data showed the best correlation to the bulk grade of the rock for both elements.For the copper ore used in this work, with mainly vein type mineralization, the one-dimensional heterogeneity assessment showed a high degree of intraparticle heterogeneity. This characteristic of the ore might generate poor reproducibility in the results of an XRF sorter when sensing only one face of each rock. The variogram was evaluated as a measure of heterogeneity in two dimensions. Two-color mapping method was selected to display the data collected in the XRF mapping for both samples analyzed.

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Validation of methodologies for sizing a high pressure grinding roll (2018)

Currently, there is no standard recognized bench-scale laboratory test for sizing or modelling a high pressure grinding roll (HPGR) in hard rock mining. As a result, metallurgical studies are prohibitively expensive and not economical for early-stage projects. To be adopted as a standard industry test for the HPGR, a bench scale test must: 1) use the same breakage mechanism as an HPGR, 2) produce results that are reproducible by independent metallurgical laboratories, and 3) apply to full-scale HPGR in a non-proprietary manner for engineering design.In 2015, the Piston Press test Database Calibrated and Direct Calibration methodologies were developed at the NBK Institute of Mining Engineering at the University of British Columbia. These methodologies can calibrate Piston Press test results to the HPGR performance using a UCS machine to define energy breakage relationships. This thesis developed a multi-stage program for facilitating the transfer of these methodologies to industry. This program formalized Piston Press test into a standard operating procedure by examining the effects of moisture, sample preparation, and material porosity. The results of the program demonstrated the Piston Press test to be reproducible. In addition, the results validated the Piston Press test Database Calibrated and Direct Calibration methodologies for a full-scale HPGR closed circuit.The program results indicate that an increase of moisture 1.5% to 5% during high-pressure compression breakage results in improved reduction ratio performance and has a negligible effect on the specific energy consumption of the sample. Material porosity was found to be an indicator of ore amenability to high-pressure compression breakage. Duplicate test-work conducted at UBC and at an independent laboratory demonstrated the Piston Press test is reproducible and can be adapted to varying piston press machine configurations. Both the Database Calibrated and Direct Calibrated methodologies are suitable for simulating full-scale HPGR. The simulation methods developed in this research can be easily applied and adopted by industry.

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Amenability of low-grade ore deposits to sensor-based ore sorting (2017)

With sensor-based ore sorting attracting more attention among the industry leaders, and in an effort to show the potential for sensor-based ore sorting technology, this research takes a particle sorting approach and looks at sorting low-grade and waste rock stockpiles to concentrate the misplaced mineralized rocks and generate value.The results from the optical sensor showed that where there was a visual distinction between the mineralized and gangue material, this sensor managed to identify each group well. Despite using a multivariate linear regression (MLR) analysis, the electromagnetic sensor did not predict the grades effectively.The X-Ray Transmission (XRT) sensor performed quite well for both base metal and gold samples. One recurring problem was the presence of iron minerals such as pyrite that, due to their relatively high atomic density, tarnished the sorting results.With elemental distinguishing capabilities, the X-Ray Fluorescence (XRF) sensor boasts great potential for ore sorting. Both single and multivariate linear regression analysis were used to analyse the results from the XRF sensor. Although, while overall satisfactory results were obtained from the XRF sensor, sensor capabilities in actual dynamic sorting cases need to be assessed.Recommendations for future work can be on different aspects of this work. One would be to try to improve the static, bench-top testing facilities so they represent dynamic sorting scenarios better, such as use of a conveyor-type platform where rocks can pass under a sensor. If a similar study is to be performed, it is highly suggested to focus the efforts on one mine, one size fraction (preferably -50 mm +37.5 mm) with a larger number of particles.In terms of continuation of this work, it would be best to take these tests to the next level and perform bulk sorting tests to determine how these bench-scale tests correlate with bulk dynamic sorting results. Also, a detailed economic analysis based on these results would yield valuable results.

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Linking the fracture intensity of an in situ rock mass to block cave mine fragmentation (2017)

Prediction of cave fragmentation has been one of the biggest concerns for caving operation, since the inadequate assessment can potentially result in loss of project value and safety. The spatial variability of the natural fracture network holds significant implications with respect to block cave mine fragmentation. In this thesis, an in situ fragmentation model is generated, based on Discrete Fracture Network (DFN) models. The volumetric fracture intensity value (P₃₂), derived from the DFN model, is used as an indicator of the rock mass’ structural character, and it provides a direct link to rock mass fragmentation. Major structures were included in the model in a deterministic manner, and the spatial variability of the fracture intensity was analyzed to derive a geostatistical model of rock mass fragmentation. The fragmentation ‘block model’ was then superimposed onto a PCBC draw schedule model, in an attempt to link fragmentation and height of draw.Poor data can potentially compromise DFN analysis, and may result in flawed validation and understanding. At the same time, it is important to define clear and objective methodologies, when analyzing field data, and when deriving input for DFN models. Piecewise Linear Interpolation and recreation of the conceptual DFN model are both used to study the influence of fracture intensity interval length and role of human uncertainty, on the final DFN-derived 3D spatial model. The results show that interval lengths are related to a resolution that can be effectively used in large-scale 3D continuum models, to represent the Representative Elementary Volume (REV) for the rock mass. A digital image processing technique is applied in order to assess caved ore fragmentation. Validation of this method has been gained from the study of lab experiments. Furthermore, a conversion factor for relating 1D image-based measurement to 3D objects is calculated, since the DFN-based in situ fragmentation model yields volumetric size distribution, whereas image processing techniques yield equivalent spherical diameters. Finally, by using the above-mentioned input data analyses, this thesis investigates the possible links between natural fragmentation, secondary fragmentation, height of draw, and observed over-sized material and hang-up.

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Study of New Afton ore heterogeneity and its amenability to sensor based ore sorting (2017)

With extraction of low-grade and high throughput deposits, elimination of tonnes of uneconomic material is highly desired to reduce energy consumption and water usage in the mine/mill production cycle. Even though technologies such as sensor-based sorting has wide application for pre-concentration purposes, effectiveness of sorter systems and key parameters for sortability of a material are still in the developmental stage. Number of factors such as grade variability, mineralogical alteration and ore blending scenarios during material handling will significantly affect contents of a material resulting in unforeseen changes in downstream processes. For these reasons, the ‘ore heterogeneity’ parameter is studied to evaluate sortability of an ore material under varying mine production scenarios.Production data, drillhole data and representative drawpoint samples were provided from the New Afton copper-gold mine located near Kamloops, BC. The New Afton mine utilizes the block caving method for extraction of ore from the copper-gold alkali-porphyry deposit.The distribution heterogeneity (DH) parameter is estimated for the data sets and the quantity of potentially removable material ahead of delivery to mill is studied. The DH is defined by variation of grade of a group of samples that constitute a lot, i.e. a group being an equal tonnage of material drawn from a drawpoint and the lot being the drawpoint. With this approach, the DH is analyzed across drawpoints, vertically within a drawpoint and along drill holes with changing vertical intervals of 0.5m – 10m. The DH values are compared with copper grades and an inverse relationship is found. This finding indicated that sortability of ore material can be defined by a heterogeneity parameter, especially the information can be obtained earlier from drillcore samples. The drillcore information can indicate a measure of heterogeneity and related copper grade of an in-situ material in advance of assay samples or sensor detection where a certain degree of mixing has occurred.Overall, 27% of the sample data from the New Afton historical production record has grades less than 0.4% Cu, which is the current cut-off grade, and it correlates with relatively high heterogeneity and presents an opportunity for sorting and feed grade upgrade.

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Predicting HPGR performance and understanding rock particle behavior through DEM modelling (2014)

High pressure grinding rolls (HPGR) are becoming an increasingly popular energy efficient solution for comminution of hard rock ores. A significant barrier to the increased adaptation of HPGRs is the current requirement for large amounts of sample for pilot testing.The primary objective of the research was to develop a DEM based computer model for an HPGR to analyze the particle behavior in the unit and to predict its sizing information. EDEM, a DEM based software, was used to model the pilot scale HPGR unit and single particle compression test was used to evaluate the particle breakage and then used as an input parameter for the simulations. The results obtained from the simulation were then validated with the results from the pilot scale tests.Results obtained from the simulation suggested that a DEM-based model can be used to identify the pressure/force distribution profile for an HPGR roll surface that can then be used to design the appropriate piston geometry to match the HPGR pressure profile. Also, the developed HPGR model was used to estimate the critical sizing information for certain samples and machine operating conditions. The model generated similar trends as the pilot scale test with a lower magnitude of m-dot and specific energy consumption primarily due to the absence of a packed particle bed.The HPGR model, combined with powerful computers and larger sample masses for simulation, can be used as a procedure to size and select an industrial HPGR unit and to analyze the equipment behavior under various operating conditions and feed characteristics.

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Scale-Up and Operations of a Vertical Stirred Mill (2014)

Stirred media mills are relatively new to mining industry, and several new technologies have been developed such as the VXPmill (vertical stirred mill). There is little technical understanding of optimizing and scaling-up of the VXPmill. This thesis addresses both of these issues and therefore supports commercial applications of this vertical stirred mill. Stirred media mills are influenced by a great number of operating variables. A study was conducted to understand the influence of mill speed, feed particle size and, slurry density and rheology on the VXPmill performance. For scale-up, a study was conducted to compare the batch recycle and the pendulum testing procedures. A scale-up demonstration study was also done utilizing the pilot-scale (VXP10) mill and the full-scale (VXP2500) mill to validate the procedure.The following are the main findings from this work:There is an optimum tip speed such that if too high (12 m/s) results in energy losses due to mechanical friction and heat. If too low (3 m/s) there are insufficient stresses to promote breakage. The optimum tip speed was found to be about 7 m/s.Feed particle size is an important variable when predicting the energy-size reduction relationship. A coarser feed requires more energy than a finer feed to achieve the same grind size. The batch recycle testing procedure overestimates the energy consumption as compared to the pendulum test over a broad range of grind sizes. Therefore, it should not be used for scale up applications. However, the pendulum test can be used to predict energy requirements for scale-up.By utilizing the VXP10 mill, the stress intensity of grinding beads and specific energy input control the grind size for the comminution of feldspars-quartz ore. At optimum stress intensity, the energy utilization is maximum. For the effective and accurate scaling-up of stirred media mills, it is extremely important that both the pilot-scale and the full-scale mills are operated at relatively similar operating conditions, and treating similar material of the same feed particle size. However, both mills should be operated at their optimal flow rates.

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Comparison of HPGR - ball mill and HPGR - stirred mill circuits to the existing AG/SAG mill - ball mill circuits (2013)

In the past 20 years, the energy-efficient comminution technologies, including high pressure grinding rolls (HPGR) and high speed stirred mill, have been developed and adopted in the hard-rock mining operation in order to reduce the energy consumption and improve the process performance. The combination of HPGR and stirred mill in a single flowsheet without tumbling mills has been demonstrated to be technically feasible. This research focused on the energy and cost comparisons of the existing AG/SAG ball mill circuits with two proposed comminution circuits, including an HPGR - ball mill circuit and a novel HPGR - stirred mill circuit.The main objective of this research was to advance the understanding of the potential benefits of the proposed HPGR stirred mill-based comminution circuits for low-grade, high -tonnage base metal operation. Samples and operating data were collected directly from the existing SAB/AGBC/SABC circuits to establish a base case for comparison. To support the base case, the existing circuits were fitted and simulated using a JK SimMet® model. Specific energy requirements for the proposed HPGR - ball mill circuit and HPGR - stirred mill circuit were determined from a pilot-scale HPGR and stirred mill test, in association with a JK SimMet® simulation.Results obtained from the research showed that the HPGR - ball mill circuit and HPGR - stirred mill circuit achieved a substantial reduction in energy, with considerable cost advantage over the existing SAB/AGBC/SABC circuits.

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Development of a Laboratory Scale Procedure for Predicting Throughput of High Pressure Grinding Rolls (2012)

The throughput capability of a high pressure grinding roll (HPGR), a critical process parameter, has been found to heavily depend on the sample type being processed. Existing HPGR test methods require the use of pilot machines and large sample quantities to assess the throughput characteristics of a certain ore type. Addressing the need for a laboratory scale HPGR test, a laboratory procedure was proposed to assess the throughput capability of mineral samples. Existing procedures were adopted from the fields of terramechanics and soil mechanics, and used as a basis for predictive HPGR throughput models. The applicability of the proposed tests was assessed through the comparison of predicted throughput with observed values from pilot HPGR testing. Results showed that outcomes of the proposed laboratory scale tests were statistically significant when used for the prediction of HPGR throughput. Primarily, the frictional properties of feed samples, as characterized by a direct shear box test, were found to be of particular significance. An approach to modelling the pressure profile which occurs on the HPGR roller surface was also proposed for potential use in a force-based model. Based on the results, an approach to HPGR testing requiring a reduced amount of sample was presented. Further work on characterizing the frictional properties of mineral samples was recommended. Analysis of HPGR outcomes indicated that strong relationships exist between power, throughput and roll gap, hence holistic approaches to HPGR modelling may be most appropriate for future predictive models.

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Technical amenability study of laboratory-scale sensor-based ore sorting on a Mississippi Valley type lead-zinc ore (2012)

Automatic sensor-based sorting is a clean preconcentration technique that can be used to separate valuable ore rock from waste rock based on the difference of the detected physical properties. This research evaluated the amenabilities of a Mississippi Valley type lead-zinc ore sample from Pend Oreille Mine to X-ray Fluorescence Sorting, X-ray Transmission Sorting, Optical Sorting and Microwave-Infrared Sorting using laboratory-scale bench-top sensing systems. A methodology for laboratory-scale quick evaluation of the amenability of an ore sample to automatic sensor-based sorting using bench-top sensor systems was generated as reference for future study.The preliminary testwork results showed that the two X-ray methods exhibited the best sorting results. About 37.7%~52.8% of the feed mass could be rejected as waste while above 95% of the lead and zinc was recovered in the product. The sorting feed (-37.5+26.5 mm) could be upgraded by a factor of 1.5~2. The optical sorting method seemed not as effective as the X-ray methods. Only 18.8% of the sorting test feed (-37.5+26.5 mm) was rejected to maintain above 95% metal recovery in the product. The test feed was upgraded by a factor of 1.2. Microwave-Infrared sorting results demonstrated that carbonate gangue mineral does not heat when exposed to microwave heating, while lead-zinc bearing sulfide does. Factors such as particle size, heating time and quantity of particles being heated at a time would influence microwave heating of rocks. Sorting feed of -19+13.2 mm presented the best segregation results after 10s of microwave heating. Above 95% of lead and zinc was recovered in a mass yield of 70% to the product. The test feed was upgraded by a factor of 1.4.The preconcentrate of X-ray Fluorescence sorting had a bond work index 12% smaller than that of the feed ore. The overall metal (lead and zinc) recoveries and grades in the flotation products were also improved after XRF sorting. The costs of both the grinding and the flotation reagent could also be reduced due to the reduction of the feed mass by rejecting the dolomitic gangue minerals up to 50%.

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A pilot-scale examination of a novel high-pressure grinding roll/stirred mill comminution circuit for hard-rock mining (2011)

The mining industry will be faced with new challenges as the need to develop lower grade ore deposits expands to meet the rising demand for raw resources. Low-grade deposits require a substantially increased tonnage to achieve adequate metal production and have caused the consumption of energy in mining practices such as comminution to rise dramatically. If improvements could be made in the processes employed for metal extraction, the mining industry could remain sustainable for future generations. This research focused on the development of a novel comminution circuit design to addresses these issues. The circuit design incorporated two, known energy efficient technologies, the High Pressure Grinding Roll (HPGR) and the horizontal high-speed stirred mill, and examined the technical feasibility of a circuit operating without the need for a tumbling mill.The main objectives of this research were to setup pilot-scale research equipment and develop the design criteria necessary to operate an HPGR / stirred mill circuit. Testing consisted of using a copper-nickel sulphide ore from Teck Limited’s Mesaba deposit to evaluate a circuit comprised of two stages of HPGR comminution followed by stirred mill grinding. To evaluate the potential energy benefits of this novel circuit arrangement, energy consumption related to comminution was calculated for the circuit using power draw readings off the main motor and the throughput recorded during testing. To provide a basis for comparison, the energy requirements for two conventional circuits, a cone crusher / ball mill and an HPGR / ball mill, were determined through HPGR pilot-scale testing, Bond grindability testing and JK SimMet® flowsheet simulation.Results from this research showed that operating the first-stage HPGR in open circuit and the second stage in closed circuit with a 710µm screen, resulted in a circuit energy requirement of 14.85kWh/t, a reduction of 9.2 and 16.7% over the HPGR / ball mill and cone crusher / ball mill circuits, respectively. To assist in future HPGR / stirred mill studies, a refined testing procedure was developed with a reduced sample commitment and the ability to perform an energy comparison with a Semi-Autogenous Grinding (SAG) mill / ball mill circuit.

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Assessment of waste rock weathering characteristics at the Antamina mine based on field cells experiment (2010)

The weathering behaviour of waste rock is being evaluated using field cell experiments at the Antamina Mine. The results presented here are a component of a larger study that is being conducted in Antamina, whose objective is to understand the geochemical and hydrological behaviour exhibited by different waste rock types, and their potential operational and post-closure impacts on the environment, in order to identify and implement prevention/mitigation measures. The waste rock is currently classified into three classes based on metal (zinc, arsenic) and sulfide contents: reactive (A), slightly reactive (B), and non-reactive (C). This thesis presents the analysis only of Class B marble and hornfels material. Particle size was measured through the standard sieving method and Elutriation techniques, and surface area through geometrical estimation and the BET methods. The data gathered was correlated with chemical assay results and complemented with the mineralogical and mineral availability for leaching data obtained using a Mineral Liberation Analyzer. Minerals containing copper, lead, and zinc, and all sulfide minerals were examined. Seven field kinetic cells were installed with samples having particles of less than 10 cm in diameter. Metal leaching, elemental production rates and release rate trends from two years of data are presented. The relationship between mineral availability and field cells drainage data was investigated. A refined waste rock classification system for Class B was recommended including the incorporation of lithology, mineralogy, mineral availability for leaching, and sulfur-sulfide content.The diopside marble samples were found to be coarser than the black marble and gray hornfels samples. Large surface were reported in the black marble, this was because a relatively higher proportion of clay minerals were found in this sample.Acid-base accounting testing reported that all samples were non-acid generating. However, Cu, Pb, Zn, and Sb were reported in higher concentrations in the leachate from the field cells. Solid phase concentrations of these elements were found to increase as the size fractions decreased, but in two diopside samples, Cu, Pb and Zn minerals were available for leaching in high proportion from the coarse particles. The main sources of these elements were chalcopyrite, galena, and sphalerite.

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