Crushing is a harsh process and production units are subjected to wear and failure over time which will reduce the overall performance of the plant. To achieve optimum process performance, both time dependant process dynamics and operating conditions should be taken into account. In this paper the aim is to create a framework for simulating the process from a more operational perspective to evaluate process performance and process optimum for different operational scenarios. The objective is to model and simulate the discrete phenomena that can cause the process to alter performance and implement it with dynamic process simulations. A method for combining discrete probability simulations with time-continuous simulations for process evaluation and optimization is presented. The proposed framework demonstrates a systematic approach to evaluate the process performance and locating optimum process configuration, for a given condition. The developed models can be used to optimize different aspects of the operation depending on the defined objective function and the system boundaries. Optimization of process throughput by manipulating configuration of both the grizzly and the crushers, as well as the time between calibrations has been illustrated in this paper. Adjusting the process continuously and calibrating it at the appropriate time can have major benefits when it comes to the process availability and utilization, increasing performance by 4.1-9.3 % in these cases. Evaluation of process robustness with regards to different maintenance strategies and process variation gave an indication of the process and unit performance under a long operating period. By combining discrete and dynamic simulation, a higher simulation fidelity can be achieved to provide a more operational perspective to the optimization and process analysis.

Crusher models presented in research is calibrated using experimental data. This approach is everyday praxis and is made in many different ways. One method is to use two different compression tests. The single-particle breakage test (SPB) and the inter-particle breakage test (IPB). Models for predicting the breakage energy and size distribution for the SPB test and also to show the correlation between the SPB and IPB test is presented. The results show that Weibull analysis and Rosin-Rammer distributions are a successful way to model both energy and size distribution for SPB and IPB based compression crushing. The number of experiments conducted in both SPB and IPB tests can be drastically reduced by testing the lowest and highest compression ratio values used in the original SPB and IPB tests. The results also show a strong correlation between the SPB and IPB tests when evaluating the relationship between the consumed breakage energy and the coefficient of variance. The energy model is compared with Bond Work Index (BWI), and it was shown that the model parameter C shows a good correlation with BWI. A full-scale validation of a cone crusher is made, presenting a calculation scheme for addressing the use of the IPB and SPB models for predicting the size distribution.

The modelling of breakage in compression breakage has traditionally been done using population balance modelling, and the research has been developed over the last decades into advanced dynamic models. This paper presents a model for predicting particle size distribution and energy consumption. The particle size distribution model is derived using a first-order differential equation for how the coefficient of variance depends on the compression length. The coefficient of variance model is combined with a bimodal Weibull distribution to predict the cumulative size distribution. The power consumption is modelled in a similar way using Weibull analysis to determine the relationship between power consumption and the coefficient of variance.

Aggregate quality is of great importance, and in this context it is essential to understand how various process parameters influence the product quality characteristics. Thus, there is a need for aggregate producers to improve their process knowledge. Research has led to an improved understanding of how different process parameters affect the outcomes of specific comminution processes. In aggregate production, breakage models are one example of such a research result. These models have been refined over the years. The breakage models that have been presented to date can accurately predict the size distribution of aggregates. On the other hand, they cannot normally predict any other material characteristics such as shape and strength. This thesis outlines the research to date, which has focused on a frequently discussed quality parameter, namely the shape of the product. Knowledge of various methodologies is required to measure this parameter. A novel method for measuring the shape of fine aggregates is presented. The rheology test, the methodology of which was originally based on a New Zealand standard, can be correlated with other data to measure particle shape in accordance with the F-aspect method. The correlation between these methods is very good, and since the rheology test is easy to use, it is suitable for a quarry or a basic test facility. The cone crusher is the most commonly used tertiary stage crusher today. One of its great advantages is that it produces a relatively low amount of fines. However, it only produces acceptable particle shapes for certain fraction sizes. The vertical shaft impact crusher (VSI) creates particles of a very satisfactory shape across all fractions, including fine aggregate, as confirmed by studies using the aforementioned rheology test. This thesis presents two models for predicting shape in crushed aggregate from a cone crusher. The first model is empirical, and my conclusion is that there are four dominating parameters affecting shape: the average feed size, the closed side setting (CSS), throw and eccentric speed. To further investigate how compressive breakage affects particle shape, an inter-particle breakage model is introduced. This model simulates a specific crushing stage inside the crusher. Simulation results show that the outcome from a crushing event can be predicted with good accuracy. A VSI model for describing particle size and shape is presented in this work. It is proposed that the dominating breakage mechanism in a VSI equipped with a rock box is of abrasive character. Abrasive breakage can appropriately shape all particle sizes, assuming the crusher is operated at a proper velocity. The empirical cone crusher model and the VSI models are combined in a mathematical simulation in order to determine how a crushing plant should be operated to maximise both yield and aggregate quality. The results show that there exists a set of rules to determine the crusher and screen settings that will achieve the best performance in terms of product yield and quality requirements.

Coarse comminution test-work and modeling are powerful tools in the design and optimization of mineral processing plants and provide information on energy consumption. Additional information on mineral liberation characteristics can be used for assessing the potential of pre-concentration stages or screens in the plant design. In ores of high-value metals (e.g., Ta, W), standard techniques—such as the mineralogical quantification of grain mounts by quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) or chemical analysis by X-ray fluorescence (XRF) can be challenging, due to the low relative abundance of such valuable minerals. The cost of QEMSCAN is also a limiting factor, especially considering the large number of samples required for the optimization of coarse comminution. In this study, we present an extended analytical protocol to a well-established mechanical test of interparticle breakage to improve the assessment of coarse mineral liberation characteristics. The liberation of ore minerals is a function of the rock texture and the difference in size and mechanical properties of the valuable minerals relative to gangue minerals and they may fraction in certain grain sizes if they behave differently during comminution. By analyzing the bulk-chemistry of the different grain size fractions produced after compressional testing, and by generating element by size diagrams, it is possible to understand the liberation characteristics of an ore. We show, based on a case study performed on a tantalum ore deposit, that element distribution can be used to study the influence of mechanical parameters on mineral liberation. This information can direct further mineralogical investigation and test work

Screens are an important production unit in crushing plants. The performance of the screen is essential to the performance of the crushing plant. In this paper a mechanistic model of a banana screen is described and a novel model for screen deck configuration is presented. The developed model can be used for optimization of a screen so that it has the best possible performance with respect to different feeding conditions, in order to obtain a desired separation. The simulation results were compared to full scale test data and the conclusions from this comparison is that the screen model needs further parameters to handle the necessary screen deck configuration. An initial static model was derived to explain how the screen deck configuration will affect the screen efficiency. The modification of the screen deck parameters resulted in a better correlation both regarding size distribution and predicted capacity.

There is an increasing demand to optimize performance and profit of comminution circuits. Research in this area has resulted in the development of numerous optimization tools, and recent research has shown that the quality aspects of the production have a great influence on the optimization results. The quality, cost, profit and capacity of a product are influenced by several parameters, and in order to control all of these parameters it is necessary to use some sort of optimization algorithm. In this paper, a novel approach to apply e.g. cost, revenue, capacity and quality in order to perform a multi objective optimization with the ability to handle dynamic variations of a comminution is presented. The problem with optimizations in general is that the objective function used for optimization is reduced in complexity in order to save computational time. In a comminution process performance varies with time and in order to perform a correct optimization the objective function used must be able to handle this type of dynamic behavior. The process has a given set of constraints that represents the conditions normal in these type of comminution applications. The first step in this paper is to identify if the range of the constraints can cause undesirable production costs when reaching for a given product property. In this step a dynamic response model is described that will be able to address the difficulties with optimizing dynamic systems. The next step in the optimization is the definition of the multi-objective optimization formulation including constraints for the optimization. Evaluating the result of the optimization in combination with a strategy for relaxing constraint can show how to increase overall productivity and still reach certain product properties. The conclusions made in this work are that multi objective optimization is essential when optimizing a comminution circuit against multiple objectives.

Modelling and simulations for mineral processing plants have been successful in replicating and predicting predefined scenarios of an operating plant. However, there is a need to explore and increase the potential of such simulations to make them attractive for users. One of the tools to increase the attractiveness of the simulations is through applying optimization schemes. Optimization schemes, applied on mineral processing simulations, can identify non-intuitive solutions for a given problem. The problem definition itself is subjective in nature and is dependent on the purpose of the operating plant.The scope of this paper is to demonstrate two optimization schemes: Multi-Objective Optimization (MOO) using a Genetic Algorithm (GA) and Multi-Disciplinary Optimization (MDO) using an Individual Discipline Feasible (IDF) approach. A two stage coarse comminution plant is used as a case plant to demonstrate the applicability of the two optimization schemes. The two schemes are compared based on the problem formulations, types of result and computation time. Results show that the two optimization schemes are suitable in generating solutions to a defined problem and both schemes can be used together to produce complementary results.

A fundamental understanding of the factors influencing particle shape is of central importance for optimisation of the output quality from crushing plants for aggregate production. The literature reports that the wear on and setting of a cone crusher influence particle shape, The fact that wear on and the setting of a cone crusher influence particle shape is considered common knowledge and is also reported in the literature. To date, no mathematical model for predicting particle shape has been presented. A novel model capable of predicting aggregate shape is presented in this paper. The particle flakiness model has two parameters: the average particle size of the feed and the closed side setting (CSS) of the crusher. A common method used for controlling the process flow in a crushing plant is also demonstrated. Detailed process knowledge is important in order to minimize the circulating load whilst still maximizing product quality. The model shows that the flakiness of the product can be estimated with knowledge of the following two parameters: CSS and the average particle size of the feed. Additional investigations are needed to improve the precision of the model.

Natural gravel has traditionally been the main choice of material for Swedish concrete manufacturers. However, due to the fact that natural gravel also acts as a fresh water filter, the deposits are limited. The obvious question is how to compare machine made and natural gravel in terms of particle shape, rheology and other material characteristics. This paper will present some methods and results that demonstrate performance of different machine made rock materials. Particle shape characteristics were assessed from flow measurements in a standard cone. The vertical shaft impact crusher (VSI) produces gravel that is a good alternative to natural gravel. The quality of the material and the particle shape seem to meet concrete producers’ demands.

There is increasing demand to optimise yield and increase capacity of crushing plants. Research in this area has resulted in the development of numerous optimisation tools, and resent research has shown that the quality aspects of production have great influence on the optimisation results. The quality and capacity of a product is influenced by several parameters, and in order to control all these parameters it is necessary to use some sort of optimisation software. In this paper, a novel approach to analyse parameters influence on product capacity and quality is presented. As an example a cone crusher and a vertical shaft impact crusher (VSI) is simulated in a tertiary stage. The simulation shows how capacity and product quality for a range of products will be affected when a parameter is changed. The paper also shows how wear will affect product capacity and quality.

The vertical shaft impact (VSI) crusher is a commonly-used machine in aggregate production. A comprehensive understanding of the physical phenomena that influence the power consumption and the particle output of the device are essential to enable development of protocols that minimize energy consumption during rock crushing. While natural gravel has traditionally been the main choice of material for Swedish concrete manufacturers, the number of deposits is limited due to its role as a fresh water filter. It is therefore essential to achieve a product size distribution of aggregate that is on the same order as that of natural gravel to enable its use in concrete production. This work aims to present a model that predicts capacity, power and particle size distribution in a VSI crusher.

There is increasing demand to optimise performance and profit of crushing plants. Research in this area has resulted in the development of numerous optimisation tools, and resent research has shown that the quality aspects of production have great influence on the optimisation results. The quality, cost, profit and capacity of a product is influenced by several parameters, and in order to control all of these parameters it is necessary to use some sort of optimisation software. In this paper, a novel approach use the parameters cost, profit, capacity and quality in order to perform a multi objective optimization of a crushing plant is presented. As an example a tertiary crushing stage consistent of a cone crusher and a vertical shaft impact crusher (VSI) is used as base for the designed objective function. The process has a given set of constraints that represents the conditions normal in these type of crushing applications. The first step in this paper is to identify if the range of the constraints can cause undesirable production costs when reaching for a given product property. The next step in the optimization shows how a strategy for relaxing constraint can increase overall productivity and still reach certain product properties. The conclusions made in this work are that multi objective optimization is essential when optimizing crushing plant production against multiple objectives. Relaxation of constraints can increase the overall performance of the crushing plant.

Material modelling within a crushing plant is closely dependent on both manual and automatic operations as well as a close follow up on the utilization of the plant performance from a management perspective. The desire to fully be able to utilize the crushing plant with respect e.g. to material handling is limited due to the lack of possibility to fully observe actions within the process. There are large quantities of data that can be monitored in the crushing plant SCADA system. However the data collected are governed by the quantity of actual sensors in the process. The aim with this paper is to propose a method for how-to pre-process the automatically gathered SCADA data in order to fill up dynamic models for process simulations. There is a fundamental need to increase the resolution of how the crushing plant behaves. This will be structured as a framework for analysing and suggesting model improvements that will increase the utilization and decrease both manual operations and give better performance when controlling the process.

There is increasing demand to optimise yield and increase capacity of crushing plants. Research in this area has resulted in the development of numerous optimisation tools, and recent research has shown that the quality aspects of production have great influence on the optimisation results. The quality and capacity of a product is influenced by several parameters, and in order to control all of these parameters it is necessary to use some sort of optimisation software. In this paper, a novel approach to analyse the parameters product capacity and quality is presented. As an example a cone crusher and a vertical shaft impact crusher (VSI) is simulated in a tertiary stage. The simulation shows how capacity and product quality for a range of products will be affected when a parameter is changed. The paper also shows how wear will affect product capacity and quality.

In process control of crushing plants the traditional control is focused on stability control of single machines and not on controlling material utilization. The reason for this is that the use of material property models is not that well known. The material models describe properties as e.g. capacity over time for a given product and this may depend on many parameters and dynamic effects in the process. Due to this it is complicated to model and thus a methodology is needed to solve this problem. In this paper a novel method for modeling the current effect that the production units have on the material presented. The paper presents a methodology how to use process data from SCADA system to analyze and suggest dynamic material model properties in real time.

The machine parameters of throw and eccentric speed affect the particle shape. Their influence on particle shape is however not fully investigated. Preliminary tests on a full-scale crusher had shown certain trends in regard to the flakiness of the product (Fig. 1). These effects were investigated in detail by means of a series of piston-and-die tests, followed by modelling of the laboratory data. An empirical model of a crusher was developed which links the product size distribution and the shape of the particles to operating parameters. The simulator produced trends which were similar to the full-scale data. The throw and eccentric speed affects the utilised compression acting on the rock/rock-bed. This paper presents a method suitable for characterizing the compressive breakage behaviour of rock materials during form conditioned compression. In this method, size reduction is primarily related to geometric compression. The method provides a complete description of the breakage characteristics of the tested rock material when compressive crushing is employed. The results can be used for modelling and simulation purposes in the design of crushing equipment or crushing plants. A novel approach to optimise form conditioned crushing in order to achieve an acceptable particle size and shape is presented. The paper concludes that inter-particle breakage in combination with high compression ratio is beneficial for the particle shape. The full scale tests support this since an increase in throw improves particle shape for particles subjected to inter-particle breakage. © 2009 Elsevier Ltd. All rights reserved.

There is increasing demand to optimise yield and increase capacity of crushing plants. Research in this area has resulted in the development of numerous optimisation tools, and resent research has shown that the economic aspects of production have great influence on the optimisation results. The profitability of a product is influenced by several parameters, and control of all these parameters is necessary to use some sort of optimisation software. In this paper, we present a case study of a typical crushing plant, with the goal of reducing the number of crusher while keeping the plant capacity and quality. By reducing the number of crusher the plant will need less maintenance which will decrease the operating costs. The article presents a method to combine crushing plant simulation and optimisation with quality and economic considerations in order to successfully study alternative configurations of the plant.

Research in warehouse optimization has gotten increased attention in the last few years due to e-commerce. The warehouse contains a waste range of different products. Due to the nature of the individual order, it is challenging to plan the picking list to optimize the material flow in the process. There are also challenges in minimizing costs and increasing production capacity, and this complexity can be defined as a multidisciplinary optimization problem with an IDF nature. In recent years the use of parallel computing using GPGPUs has become increasingly popular due to the introduction of CUDA C and accompanying applications in, e.g., Python. 

In the case study at the company in the field of retail, a case study including a system design optimization (SDO) resulted in an increase in throughput with well over 20% just by clustering different categories and suggesting in which sequence the orders should be picked during a given time frame. 

The options provided by implementing a distributed high-performance computing network based on GPUs for subsystem optimization have shown to be fruitful in developing a functioning SDO for warehouse optimization. The toolchain can be used for designing new warehouses or evaluating and tuning existing ones. 

Optimization is a pivotal point in distinguishing the competitiveness between industries that are developing, designing and operating products and processes. Mineral processing is an industry which operates various sub-processes and produces one or several products. The sub-processes involved are dynamic in nature and differs in discipline of operation. These dynamic sub-processes are sequentially integrated forming a mineral processing system. Currently, the developed simulations for the mineral processing systems have the potential to be used to design, operate and control mineral processing plants to an increased extent, but need broader optimization strategies to integrate multiple sub-processes involved.<br />The scope of this research is to demonstrate application of multi-disciplinary optimization (MDO) architectures into a mineral processing simulation. A case study consisting of two sub-processes of comminution and classification circuits to produce aggregate products is used to demonstrate the application of MDO architectures. The MDO architectures are compared based on problem formulation, computational resources required and validity of the results. The optimization results using MDO architectures can be used to illustrate trade-offs between different sub-processes within the considered scope. The application of MDO architectures can facilitate the linking mathematical models of various disciplines such as comminution, and liberation in mineral processing simulation.

There has been continuous development going over the past 40 years related to the creation of models and simulation techniques to predict the behaviour of equipment and processes in minerals processing. At the same time, application of optimization theory into such modelling and simulation schemes has been applied to generate knowledge to improved performances of the equipment and processes. Different optimization techniques have been applied to design and configure different equipment and processes, yet there are no well-established formulations to reproduce the results. The research is scattered and focused on the need and application of the specific equipment or process not utilizing the optimization’s full potential. The aim of this paper is to highlight the trends in development of optimization schemes in minerals processing. By understanding the state of the art in application of optimization theory into mineral processing will further pave the possibility to develop utility in this field. The paper presents two classification schemes: State of Development Stage and State of Application Area as a basis to classify research within optimization related to mineral processing. In order to make smart and strategic decisions in minerals processing operations, it is required to further develop optimization techniques into modelling and simulation schemes to extract the relevant information. The classification schemes can be useful in defining the future focus area for research and development.

In today’s automotive industry there is a growing demand for more fuel efficient vehicles and reduced development times. These trends are driven by stricter environmental regulations, a growing environmental awareness, and increasing technological development and competitiveness. Finding an optimized and balanced component that fulfils the requirements in an early phase of the product development is a prerequisite for enabling more competitive lead times, costs, weights and minimizing the risk for late design changes. The aim with this paper is to show a process capturing CAE driven development for an early stage development of components in a complex system. The process utilizes structural optimization techniques to generate knowledge, optimize and balance packaging volumes of adjacent components in complex systems. The paper also highlight the organizational challenges and technical challenges involving the use of structural optimization for realizing the process completely. The paper will illustrate the simultaneous use of topology and shape optimization to generate knowledge for the optimized design volume for multiple adjacent components linked together. The linking of the multiple component is carried out using morphing technique and the design space between the multiple components is dynamic in nature during simulation. The mesh in one component is allowed to change according to the mesh of the other component during the simulation. The result from the simultaneous topology and shape optimization simulation generates the knowledge if it is feasible to change design volume to meet the weight and performance targets. The process also indicates how much performance increase is possible if the design volume is allowed to change and thus generating a trade-off between the components performance. The new process has a potential to be extended to other conflicting scenarios in adjacent components which exists in early stages of development process especially, cases involving conflicting structural requirements in various industries.

This paper aims at demonstrating the applicability of video learning in CDIO based project courses and at evaluating to what extent it benefits students. The courses are Machine Elements (PPU210), Product Planning - Needs and Opportunities (PPU085) and Engineering Design and Optimization (PPU190) in the Mechanical Engineering programme at Chalmers University of Technology. The research was carried out by first creating a set of videos for selected topics in three courses. In total, 22 videos were created including topics such as “Benchmarking”, “SWOT”, and “Prototype lab equipment instructions”. The learning outcomes of the video lectures were mapped to the CDIO syllabus. A blended learning environment was developed, i.e. the videos were utilised as additional support alongside existing learning activities. The videos were then used in the courses and the students’ feedbacks collected through a dedicated questionnaire, the regular course evaluation survey, and in student-teacher group meetings during and after the courses. The collected data was analysed to produce inferences about the applicability and utility of the video lectures. The resulting analysis shows the students’ preferences regarding the evaluated video lectures and instructions. The students find videos more appealing compared to traditional lectures. One of the main benefits highlighted is the possibility of watching the videos in parallel to the design-build-test project execution rather having the classroom lecture only. This helps in reinforcing concepts, and results in less dependency on supervisors during the project execution. Videos proved to be suitable for creating a blended learning environment and improved the perceived learning experience for the students. In order to maximize student satisfaction and interaction with the videos, the videos should be short and closely aligned to the other learning activities. The paper also suggests future improvements to be carried out for video-based learning in the courses, and proposes an easy adaptable way for teachers to develop video material.

In recent year, cutting tool manufacturers are moving towards improving the robustness of the positioning of an insert in the tool body interface. Increasing the robustness of the interface involves designs with both chamfered and serrated surfaces. These designs have a tendency to over-determine the positioning and cause instabilities in the interface. Cutting forces generated from the machining process will also plastically deform the interface, consequently, altering the positioning of the insert. Current methodologies within positioning and variation simulation use point-based contacts and assume linear material behaviour. In this article, a first order reliability-based design optimization framework that allows robust positioning of surface-to-surface-based contacts is presented. Results show that the contact variation over the interface can be limited to pre-defined contact zones, consequently allowing successful positioning of inserts in early design phases of cutting tool designs.

Locating schemes, used to position parts during manufacturing, are usually designed in such a way that the response from the system is minimized. This implies that the position of the fasteners and/or welds are known in an assembly. Today there exist numerous of methods aiming to find an optimal set of locating points to increase the stability of an assembly, for both rigid and compliant parts. However, various industrial applications use surface-to-surface contacts to constrain certain degrees of freedom. This can lead to designs sensitive to geometric and load variations. As the complexity of the surfaces increases, difficulties of allocating geometric tolerances arise. An approach to control this is to keep the contact locations statistically stable. In this paper a methodology is presented where the First-Order reliability Method (FORM) is applied for numerical data, retrieved through Finite Element Analysis (FEA), to ensure that statistically stable contact location are achieved for two bodies with surface-to-suface contact. The FEA data represents how much of the total stress that lies within a given area, sW. The data is continuous and therefore it is assumed that the gradient can be calculated numerically with small steps. The objective function is to maximize sW for n variables. The data set is simulated through Finite Element Analysis using the commercial software Ansys and the results is illustrated on a case study from the machining industry.

Screening is a key unit operation for the large-scale separation of materials. There are certain different machine parameters and variables that affect the process of screening. The Discrete Element Method (DEM) is a suitable method to analyze parameters and variables. The main benefit of using the DEM for simulating the screening process is that, as a contact model, it provides the possibility of tracking each particle in the material flow and all collisions between particles and between particles and boundaries.

There are different types of materials used for screening media, such as rubber and polyurethane, which are used in modular systems as a panel, and such as steel, which are used as a wire in the mesh. This paper presents how different materials used in screen decks affect the screening process. The materials’ strength and elasticity have been examined in order to study how the aperture will change in different materials and how different shapes of the aperture and material of screening media affect the screening performance by analyzing the effect on material flow.

Banana screening is an important size classification component. The screens are characterized by a high capacity for separation. The operation of screening usually takes place after crushing operation. The shape of the banana screens causes the feed material to flow rapidly and the result will be faster screening rate. The difference between banana screens and other screens is that in banana screens the screen cut size varies with the changing slope of the decks. There are number of factors that affect screening operation like inclination of discharge, open area, thickness of deck and feed rate. The aim of this paper is to simulate the screener deck with the help of DEM Simulation and to analyze different parameters that affect screener operation efficiency and optimizing the screener so that it has the best performance during the wear life of the screen media. The one deck banana screen are simulated, the result show when the value of deck thickness and deck slope increase the probability of particles passage through the apertures will be decrease.

Screening is an important process in size classification of granular materials. It is a complex process due to the collision between particles and also a number of different operational parameters that effect the screening process. The aim of this paper is to evaluate screening performance in one of the LKAB crushing platforms.

In this work an industrial vibration screen has been simulated by using Discrete Element Method (DEM). The simulations were validated with data from experiments and the screening performance has been analyzed by changing the parameters such as feeding rate.

The result shows that DEM simulation is an effective tool for understanding the process of screening and because of the contact model between individual particles and particles and geometries the result is comparable with real process. It is shown that by increasing the feeding rate to 100 ton/h the screening efficiency can be improved by 20 percent.

Screening is a key unit operation for the large-scale separation of materials. There are a number of different machine parameters and variables which affect the process of screening. The Discrete Element Method (DEM) is a suitable method to analyze all parameters and variables. The main benefit of using DEM for simulating the screening process is that as a particle contact model it gives the possibility to track each particle in the flow and all collisions between particles and between particles and boundaries.<br />There are a number of different materials commonly used for screen media such as rubber and polyurethane which are used in modular systems as a panel and steel is usually used as steel wire mesh but sheet metal can also be used. This paper presents how different materials used in screen decks affect the screening process. The strength and elasticity has been examined in order to study how the aperture will change with different materials and also how different shapes of the aperture and the material of screen media affect the screening performance by analyzing different material flow.

Banana screens are popular and frequently used in minerals processing. The screens are characterized by a high separation capacity and low maintenance need. The operation of screening usually takes place after crushing operation. The banana screens have multiple panels with variable slope which enables the feed material to flow rapidly resulting in a high screening rate. The difference between banana screens and other screens is that in banana screens the screen cut size varies with the changing slope of the decks. There are a number of factors affecting the screening operation; the deck panel slope progression, screen deck material, aperture shape, vibrational motion, open area, thickness of deck, feed rate and material properties. The aim of this paper is to simulate the screening performance by using the Discrete Element Method (DEM) and to analyse different motions that affect screening operation efficiency. Three decks with different slopes have been used and two different motions, linear and elliptical, have been evaluated at one feed rate. Figure 1 shows the overview of DEM simulation of screening process. Design of Experiment (DoE) has been used to evaluate the factors that control the value of parameters. The results show that the classification efficiency can be evaluated by conventional comparison between the feed particle size distribution and each of the product streams. The resolution of the model also enables the calculation of a critical efficiency criteria position along the screen deck. This position can be used to define a screening robustness factor. The passage probability and stratification behaviour can also be evaluated.

Control systems for cone and gyratory crushers were first introduced during the early 60ths. The common opinion is that if these systems are able to compensate for the wear of the crushing liners the production yield can be increased with 20-25%. Over the years these types of systems have been widely used but the theory behind the principles have not been thoroughly scientifically scrutinized and presented. Of special interest is the capability to protect the crushers from long term overloading commonly defined as fatigue.

Gyratory and cone crushers are regaining interest and are becoming more frequently used in order to create more energy efficient comminution circuits. A typical example is found in coarse comminution circuits were HPGRs are used as a first milling stage. In this case the preparation of a suitable feed with a well-defined width of the particle size distribution and a controlled top size are of high importance. In turn, this emphasizes the importance of a stable and controlled operation of the preceding crushing stages. Control systems for cone and gyratory crushers were first introduced during the early 60ths. The common opinion is that if these systems are able to compensate for the wear of the crushing liners the production yield can be increased with 20-25%. Over the years these types of systems have been widely used but the theory behind the principles have not been thoroughly scientifically scrutinized and presented. Of special interest is the capability to protect the crushers from long term overloading commonly defined as fatigue. With developments in electronics and plant control the crusher control systems have become more refined over the years. Though, there are sometimes conflicting interests in the control strategies between process requirements and crusher protection. In the paper an overview of the challenges, opportunities and existing control systems for cone and gyratory crushers is presented. A requirement specification for a system that is possible to fully integrate into modern plant control systems is outlined.

The interest and need for compressive crushing in gyratory, cone and HPGR crushers are increasing since ores become more competent and more difficult to break. Compressive crushing is energy efficient as a consequence of the crushing principle and the imposed stress-state. The stress variations can be described by stress amplitudes and it is a known fact that many different materials, components and machines suffer from cyclic loading which shortens the service lifetime. This phenomena is explained by density variations of the particle beds in the equipment which in turn originates from particle segregation and feeding alignment. The phenomena is often called fatigue and the consequence is premature breakdowns and a relatively shorter lifetime than expected. In this paper, a previously developed theory for lifetime assessment of cone crushers will be used as a foundation for evaluation of full-scale operating cone crushers in minerals processing plants. Lifetime is calculated as a consequence of the load spectrum. The data shows that improper feeding conditions will substantially decrease the lifetime of the crusher equipment leading to excessive operating costs. An adequate control system should be able to recognise the hazardous lifetime decreasing overloads and to warn the operator. There are sometimes conflicting interests in the control strategies between production yield (process requirements) and crusher protection.

VSI crushers are established comminution machines often used for size reduction and to improve the sphericity of rock particles. Data collection and experimental observation inside VSI crushers remains difficult, leading to lack of understanding of the full extent of the particle dynamics inside a VSI crusher. The aim of this paper is to attempt to characterize the probability of collision of particles in relation to their distance from the rotor. By comparing the number of collisions at a given location with the overall amount of collisions, the probability of a collision event related to the distance a particle has travelled from the rotor can be estimated. The result is an increased understanding of VSI crushers and the particle collision behaviour inside of a VSI crushing chamber.

The increasing restrictions on natural aggregates have led to a demand for effective production of artificial sand and gravel. VSI crushers are established comminution machines often used in order to improve the sphericity of particles. Due to the difficulty in data collection, the full extent of the particle dynamics inside a VSI crusher has remained unexplored. The aim of this paper is to use DEM simulations to model a full-scale crusher, generate a realistic material flow and make a number of crusher tests with different rotor tip speeds. Each particle’s collision energy compared to its size will provide a spectrum which can be related to the probability of breakage. This will show how increasing rotational speed affects collisions and the impact energy of particles inside the crusher. The result is an increased understanding that can allow optimization and modeling of VSI crushers with higher accuracy.

There is an increasing demand to simulate and optimize the performance and profit ofcomminution circuits, especially in low-grade ore processing, as is the case with critical metalsminerals. Recent research has shown that the optimization result is greatly influenced by qualityaspects of the products, such as cost, profit, and capacity. This paper presents a novel approach toperforming a multi-objective technical and economic analysis of tantalum ore processing to increasethe production of critical metals minerals. The article starts with mineral composition analysis tohighlight the potential of strategies for balancing the process layout for maximized production. Theintroduction of a combined technical and economic analysis presents the possibility of improving theprofit by rearranging the mass flow given the rock’s mineral composition. Results show that selectivecomminution can improve process capacity by 23% and decrease production cost by 10% for thepresented case.

Due to the raising global demand for rare earth minerals there is an increased need for development of more efficient extraction processes of such materials. Comminution models commonly predict size reduction with the focus on a single component, but few models integrate the mineral composition. This paper focuses on defining a multi component model, combining the size reduction and the mineral liberation. In this study, compressive breakage and liberation analysis experiments were conducted on a Tantalum ore. The work is divided into two stages, firstly the methodology of fitting measured data into a size reduction model, and secondly the multi component modelling where the liberation results are integrated into the size reduction model. Results from the work show that in order to address multi component modelling it is necessary to focus on dominating factors such as dominating quantities of different minerals. It was also seen that the model can be used for determining the choice of compression ratio in crushing for optimizing liberation.

Due to the raising global demand for rare earth minerals there is an increased need for development of more efficient extraction processes of such materials. Comminution models commonly predict size reduction with the focus on a single component, but few models integrate the mineral composition. This paper focuses on defining a multi component model, combining the size reduction and the mineral liberation. In this study, compressive breakage and liberation analysis experiments were conducted on a Tantalum ore. The work is divided into two stages, firstly the methodology of fitting measured data into a size reduction model, and secondly the multi component modelling where the liberation results are integrated into the size reduction model. Results from the work show that in order to address multi component modelling it is necessary to focus on dominating factors such as dominating quantities of different minerals. It was also seen that the model can be used for determining the choice of compression ratio in crushing for optimizing liberation.

Nowadays there are numerous tungsten applications and uses, due to this the global demand for tungsten has increased the extraction and production of this rare earth mineral. The liberation of tungsten is achieved by using comminution equipment, e.g. crushers, there is a lack of knowledge how tungsten is liberated by means of compressive breakage. Even though it is possible to use find comminution models for explaining the size reduction, there is also need to implement a mineral liberation model into theses comminution models. This paper will focus on a fundamental model that combine and integrate the size reduction with the mineral liberation in early stages of the breakage process. This work focuses on analysing the liberation characteristics that occur by means of interparticle breakage. The work includes two parts, firstly the integration of the measured data into a size reduction model, and secondly a reflexion and understanding of the liberation and fracture mechanism during the breakage. Results from the work show that in order to address multi component modelling it is necessary to focus on controlling factors such as dominating quantities of different minerals, breakage mechanism in different bounded minerals and how this is connected with the liberation of them. It also was observed that the model could be used for determining the choice of the compression ratio in crushing for optimising liberation.

In this study, an analytical perspective is used to develop a fundamental model of a jaw crusher. Previously, jaw crushers were modelled in regard to certain aspects, for example, energy consumption (Legendre and Zevenhoven, 2014) or kinematics (Oduori et al., 2015). Approaches to date have been mainly property specific. In this work a physical modelling approach has been used to derive the modules, which are based on established facts of comminution machines, from the literature. A modelling methodology mainly inspired by Evertsson has been applied (Evertsson, 2000). The modules are divided into kinematics, flow, breakage, capacity, pressure and power. Each module has been derived and tested decoupled from the other modules to provide increased transparency of the module and its behaviour. The results of the modelling are presented for a baseline case of one industrial-scale jaw crusher and compared to manufacturer data. Future work will include validation and DEM simulations.

Given the increasing global demand for rare metals, there is a need for the development of fundamental predictive models to improve extraction processes. Comminution models commonly predict particle size reduction based on the compressive breakage behaviour; however, few of them include mineral concentration or mineral liberation at a coarse scale. This paper focuses on developing a model to predict the mineral concentration of rare metals as a function of the particle size distribution after a cycle of the compression crushing process. In this study, compressive breakage and geochemical analysis experiments were conducted on four different rare metal ores of tantalum and tungsten. The work is divided into two stages: the methodology of modelling particle size and modelling concentration by selecting a bimodal Weibull distribution for calibration. A novel model for simulating the concentration of rare metals as a function of the compression ratio is presented.

In order to design competitive products that meet today’s challenges, future engineers need knowledge and experience in applying and integrating optimization theory in the engineering design process. The Chalmers course Engineering Design and Optimization addresses this need and was developed and first offered in the fall semester of 2013. This paper provides a detailed account of the course development experiences, teaching methods and course evaluations using CDIO Standards. It also includes a discussion of the learning objectives, required resources, instructional processes and student assessments. The course is analyzed to see to what extent the course aim is satisfied and highlight areas of improvement. Three projects are carried out in groups of two students. The projects are a cantilever design-build-test exercise, a redesign project that involves material selection, and a multi disciplinary design project of an engine component using multi-physics software. The assignments are assessed with respect to both engineering criteria as well as reporting and communication. The course is believed to be novel in the way optimization theory and tools are taught as an integrated learning experience with engineering design and physical prototyping. The course has had a great impact on the students’ choice of master’s thesis project. The number of optimization-focused master thesis projects has increased from two or three to around 15 annually. Several of these projects are multidisciplinary and joint projects between departments of Applied Mechanics and Product & Production Development. The course has also initiated a valuable partnership with industry on optimization that now has grown to a network with 20 industrial and academic members.

Cooperative vehicles are no longer fiction. A key factor is the ability for vehicles to exchange information with their environment. The shared information can be used to realize new functionalities, from virtual traffic lights to emergency braking, thus with potential to increase safety and efficiency of vehicle systems. However, external information has inherent uncertainties and this poses a threat to safety. In this paper we will discuss how to handle these uncertainties by use of dynamic safety contracts. We propose an extension to AUTomotive Open System Architecture (AUTOSAR) which consists of a safety manager which actively enforces the safety rules described in such safety contract. We also propose to integrate the architecture of an Intelligent Transport System (ITS) station tightly to AUTOSAR. It is our hypothesis that such architecture provides a viable platform for run time safety assessment. Future research work is to evaluate what kind of safety assessments our system can be able to handle.

An ITS represents a Cyber-Physical System (CPS), which will involve information exchange at operational level as well as potential explicit collaboration between separate entities (systems of systems). Specific emphasis is required to manage the complexity and safety of such future CPS. In this paper we focus on model-based approaches for these purposes for analyzing and managing safety throughout the lifecycle of ITS. We argue that: (1) run-time risk assessment will be necessary for efficient ITS; (2) an information centric approach will be instrumental for future ITS to support all aspects of safety management – a “safety loop”; (3) a formal basis is required to deal with the large amounts of information present in an ITS. We elaborate these arguments and discuss what is required to support their realization.