| 1. |
- Chipakwe, Vitalis, et al.
(författare)
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Effects of Chemical Additives on Rheological Properties of Dry Ground Ore - a Comparative Study
- 2022
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Ingår i: Mineral Processing and Extractive Metallurgy Review. - : Taylor & Francis. - 0882-7508 .- 1547-7401. ; 43:3, s. 380-389
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Tidskriftsartikel (refereegranskat)abstract
- It is well documented that chemical additives (grinding aid “GA”) during grinding can increase mill throughput, reduce water and energy consumption, narrow the particle size distribution of products, and improve material flowability. These advantages have been linked to their effects on the rheology, although there is a gap in understanding GA effectiveness mechanism on the flow properties. The present study aims to fill this gap using different GAs (Zalta™ GR20-587, Zalta™ VM1122, and sodium hydroxide) through batch grinding experiments of magnetite ore and addressing the mechanisms of their effects on the rheology by an FT4 Powder Rheometer as a unique system. Experimental results showed that GA improved grinding efficiency (energy consumption and product fineness), which were well-correlated with basic flow energy, specific energy, aerated basic flow energy, and aerated energy. Moreover, the rheometry measurement showed strong linear correlations between basic flow energy, specific energy, and the resulting work index when GAs was considered for grinding, which confirmed the effect of GA on ground particles’ flowability. Zalta™ VM1122, a polysaccharide-based grinding aid, showed the best performance with 38.8% reduction of basic flow energy, 20.4% reduction of specific energy, 24.6% reduction of aerated basic flow energy, and 38.3% reduction of aerated energy. It also showed the strongest correlation between the grinding parameters and flow parameters (r > 0.93). The present investigation shows a strong indication that the predominant mechanism of GAs is based on the alteration of rheological properties and identify Zalta™ VM1122 as the best GA.
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| 2. |
- Alakangas, Lena, et al.
(författare)
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Project: Improve Resource Efficiency and Minimize Environmental Footprint
- 2016
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Annan publikation (populärvet., debatt m.m.)abstract
- The REMinE project is organized in five work packages that comprise: detailedcharacterization and risk assessment of the mine wastes selected (WP2), identification of new processing methods for mine waste (WP3), characterization and risk assessment of the remaining residuals (WP4), outlining business opportunities and environmental impact in a conceptual model for sustainable mining (WP5). The project comprises case studies of historical mine wastes from three different European countries, namely Portugal, Romania and Sweden. The interdisciplinary research collaboration in this project is innovative in the sense that separation of minerals and extraction of metals not only are basedon technical and economic gain but also considers the environmental perspective.
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| 3. |
- Andersson, Anton, et al.
(författare)
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Characterization and Upgrading of a Low Zinc-Containing and Fine Blast Furnace Sludge : A Multi-Objective Analysis
- 2017
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Ingår i: ISIJ International. - : The Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 57:2, s. 262-271
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Tidskriftsartikel (refereegranskat)abstract
- Ore-based steelmaking generates a variety of residues including dusts, sludges and slags. Recycling of these residues within the process or via other applications is essential for sustainable production from both environmental and economic aspects. In blast furnace (BF) ironmaking, there are generally two residues leaving the gas cleaning equipment; namely, BF dust and BF sludge. Traditionally, the dust is recycled via the sinter or, in the case of pellet based BF, via cold bonded agglomerates and injection. As the main output of zinc from the BF is the top gas, the sludge has to be dezinced prior to recycling to prevent accumulation of zinc in the furnace. Although dezincing of BF sludge has been successfully accomplished using e.g., hydrocycloning, the studied sludges are generally coarse sized and high in zinc. Furthermore, information is lacking regarding the efficiency of separation of different hydrocyclone setups. In the present work, hydrocycloning of a fine sludge, with low zinc content, generated by a pellet based BF has been studied. The gas cleaning equipment used to produce the sludge was running a primary aerocyclone and a scrubber. A characterization of the sludge has been conducted together with an evaluation of the separation efficiency of the hydrocyclone in order to assess the hydrocyclone performance and limitations. Furthermore, the dezincing using the hydrocyclone has been compared to that of sulfuric acid leaching. The results suggest that 51 to 93% of the sludge can be recycled depending on the demand on zinc removal and the chosen dezincing route.
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| 4. |
- Bergamo, Pedro A. de S.
(författare)
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On the use of immersive technologies in the professional education of mineral processing
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the advance of technology, many educators started implementing immersive technologies like simulators and gamified learning applications to improve the trainings of process operators. However, it is noted that the minerals sector is significantly behind other industries, for instance, the chemical industry, especially when it comes to the evaluation of these types of trainings. Understanding how new technologies and concepts can improve the creation and evaluation of operator trainings, would perhaps create solutions for the lack of skilled operators in the mining sector, which is partly related to the challenge of evaluating time-dependent skills. In this scenario, this research aims to access the use of immersive technologies to increase the creation of operator talent in the minerals industry. In this context, an EU-funded network called “metalintelligence” exists. Its aim is to provide innovative research and equip a new generation of leaders in the minerals processing field providing lasting novel technological and training methods to build capacity in this growing area thus further establishing the EU’s leadership position in minerals processing. Hypothetically, the research in this field, backed by strong case studies, could provide valuable hints on how the trainings of operators could be made more efficient by using new technologies and concepts such as modelling and simulation and gamification. The study conducted within this thesis project can be divided into four parts, starting with a systematic review of how immersive technologies such as virtual reality (VR), educational games and simulation-based trainings have been used to teach different topics related to mining and mineral processing operations during the last 20 years. The current applications are mostly focused on hazard awareness and specific maneuvers of mining equipment, while only a few are related to the operation and management of the control rooms in mineral processing plants. During the review, it was noted that most papers found in the literature focus on the technical description of their solutions but fail to present an evaluation of the application by experts in the field. The review also found that further benefits can be achieved by employing tools like cloud solutions and gamification as these technologies can help with the collection of user data and improve the validation of technology-enhanced trainings. In the second part of this thesis, a case study is presented on how the current trainings of mineral process operators can benefit from immersive technologies. It involves the development and evaluation of a simulator-based training for froth flotation. The training was delivered to a group of operators at a greenfield process site and the analysis of the trainees’ evaluations were collected and discussed based on the first two levels of the Kirkpatrick evaluation model, a broadly used evaluation model. The reaction evaluation showed a strong satisfaction and a high learning perception from the trainees, while the learning evaluation, gathered with the help of the simulator, showed several weak spots in the training, especially when it came to teaching performance calculations. The disparity between the reaction and learning evaluations raises serious questions about evaluating trainings solely on the trainees’ feedback and goes against some principles of established evaluation methods such as Kirkpatrick’s. The third part of this study comprises the development of a training solution called “Minfloat”. It is an educational game developed in Unity3D focused on teaching the basic process behavior of froth flotation to operators and university students. It also describes the attempts to create a light-weight simulator core that could be run on a mobile device. After first testing a short-cut model, a model based on first principles was programmed and linked to the user interface. The game also includes an intelligent tutoring system (ITS) which presents concepts, examples, and questions pertinent to flotation performance calculations to the user. The principles of user experience (UX) design were used to produce assets (e.g., boxes, buttons, containers, and graphs) that could be re-used by other training developers, therefore promoting modularity, in a way that developers could use those to create their own educational games. The current game could be extended to basically every aspect of flotation, as also other mineral processes. In addition, the modules (such as assets, ITS, and graphs) could be re-used by other Unity3D developers to create trainings for topics in practically every process industry. The fourth and last part of the study involved the development of a questionnaire aiming to evaluate “Minfloat” in terms of overall quality, didactic efficacy, and inspiring character, besides having a better understanding of the target audience and outlook of the solution. To develop this questionnaire, the history of evaluation frameworks such as Kirkpatrick’s ‘Four levels’, Phillips’s ‘return on investment (ROI) based evaluation’ and Scriven’s ‘Goal-free evaluation’ are introduced to help clarifying the steps involved in assessing and evaluating a gamified educational solution like “Minfloat”.The questionnaire was applied to 25 experts in the minerals industry to access key aspects of the game-based training described earlier. From the results, three key lessons can be taken. The first is that users were, in general, satisfied with the game in terms of quality, efficacy and inspiring character. Second, users thought that the main target of the game should be university students, although novice industrial operators could also benefit from it. Third, the use of this short questionnaire, combined with the use of online forms, is a powerful tool for researchers who need a fast and efficient way to evaluate important aspects of a game and get feedback in written form.By analyzing the four parts of this research, some clear concluding benefits of the use of immersive technologies in operator training can be outlined. The first is that new engines such as Unity3D united with modelling and simulation, were proven to be powerful tools to create efficient, inspiring and non-expensive educational solutions for the process industry. Being a free software for personal or small companies, there is a big chance that, in the near future, engineering students will start using it to create their own educational trainings, and compete with larger companies which currently dominate that training market. Another contribution from this research is an evaluation form that provides training developers a way to get feedback for their application, improve their games or simulation-based trainings and produce more comprehensive articles about education in the minerals industry.The next step for this research would be to develop similar kinds of applications for other mineral beneficiation units and methods, such as comminution and hydrometallurgy. The game presented could even be expanded to teach the operation of an entire mineral processing plant. This way, university students and novice operators could learn and understand, in an inspiring way, important aspects of this type of operations, including material characterization, reagent usage, operational parameter setting, equipment design as well as financial and holistic operations of mineral processes. This development could revolutionize the teaching of mineral processes, the same way simulators leveled up the training of flight operators. However, this revolution will only occur if those immersive technologies are guided by the light of a proper and inexpensive evaluation, which will make sure that the technologies developed by academia are resonating in the same wavelength as the solutions of the industrial sector. Another aspect that immersive technologies could help with, is the declining rates of students entering university courses like mineral industry and geoscience. Digitalization solutions like the one described could help to inspire more students to choose a career in those fields, helping with the development of societies and their increasing needs for minerals.
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| 5. |
- Bru, Kathy, et al.
(författare)
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Comparative laboratory study of conventional and Electric Pulse Fragmentation (EPF) technologies on the performances of the comminution and concentration steps for the beneficiation of a scheelite skarn ore
- 2020
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Ingår i: Minerals Engineering. - : Elsevier. - 0892-6875 .- 1872-9444. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- Electric Pulse Fragmentation (EPF) is an innovative technology that uses High-Voltage Pulsed Power (HVPP) for the selective comminution of a material. This paper aims to compare a beneficiation flowsheet including an EPF treatment in the comminution circuit to a conventional pathway where the EPF step was replaced by a series of jaw crushers. Tests were performed on a skarn ore containing scheelite as the main mineral of interest. This ore is characterized by a fine-grained mineralogy and represents a challenge to conventional comminution processing, requiring fine grinding to liberate the valuable minerals. Fine grinding has high energy requirements and generates large amounts of fines which can result in losses of the target mineral due to their removal before the concentration processes, especially in this case since scheelite is a brittle material.Comparison of EPF treatment to mechanical crushing with a similar product size P80 (i.e. 80% passing size) showed that the EPF treatment led to a significant increase in WO3 content and distribution in the 0/250 µm size fraction suggesting a pre-concentration aspect to EPF treatment. Moreover, a marked improvement of the grindability of the ore treated at a discharged energy of 9.1 kWh/t was observed with values of 10.6 kWh/t compared to 14.5 kWh/t when conventional treatment was used. Subsequent grinding and concentration steps confirmed the positive impacts of the fragmentation selectivity and pre-weakening effect of the EPF treatment. In particular, a reduction in fines production was observed after ball milling and a better concentrate grade was achieved for a similar recovery rate when an EPF treatment was included in the comminution pathway compared to the conventional one. These results confirm the potential of the EPF treatment for improving the performances of the beneficiation processes of this scheelite-bearing skarn ore.
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| 6. |
- Chelgani, Saeed Chehreh, et al.
(författare)
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A comparative study on the effects of dry and wet grinding on mineral flotation separation : a review
- 2019
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Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854 .- 2214-0697. ; 8:5, s. 5004-5011
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Forskningsöversikt (refereegranskat)abstract
- Water scarcity dictates to limit the use of water in ore processing plants particularly in arid regions. Since wet grinding is the most common method for particle size reduction and mineral liberation, there is a lack of understanding about the effects of dry grinding on downstream separation processes such as flotation. This manuscript compiles various effects of dry grinding on flotation and compares them with wet grinding. Dry grinding consumes higher energy and produces wider particle size distributions compared with wet grinding. It significantly decreases the rate of media consumption and liner wear; thus, the contamination of pulp for flotation separation is lower after dry grinding. Surface roughness, particle agglomeration, and surface oxidation are higher in dry grinding than wet grinding, which all these effects on the flotation process. Moreover, dry ground samples in the pulp phase correlate with higher Eh and dissolved oxygen concentration. Therefore, dry grinding can alter the floatability of minerals. This review thoroughly assesses various approaches for flotation separation of different minerals, which have been drily ground, and provides perspectives for further future investigations.
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| 7. |
- Chipakwe, Vitalis, et al.
(författare)
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A comparative study on the effect of chemical additives on dry grinding of magnetite ore
- 2020
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Ingår i: South African Journal of Chemical Engineering. - : Elsevier. - 1026-9185. ; 34, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- Dry grinding as an alternative to wet grinding is one of Sweden's strategic research areas to promote dry beneficiation. However, dry grinding has remained unpopular due to its higher specific energy consumption (Ec), wider particle size distribution (PSD), difficult material handling, and purported effects on downstream processes. In this work, the effects of the new additives (Zalta™ GR20–587, Zalta™ VM1122, and Sodium hydroxide) employed as grinding aids (GA) on dry grinding and product characteristics of a magnetite ore were studied in light of possible downstream effects. The grinding efficiency of Magnetite increased after using GAs in comparison without the GAs; however, an optimal dosage exists for each of the chemical additives investigated. Comparing to grinding without GA, Zalta™ VM1122, a viscosity modifier was selected as the most effective GA where by using this GA; the Ec decreased by 31.1% from 18.0 to 12.4 kWh/t, the PSD became narrower and finer (the P80 decreasing from 181 to 142 µm), and the proportion of the particles (38–150 µm) increased from 52.5 to 58.3%. Zalta™ VM1122 resulted in increased surface roughness and minimum microstructural defects. Further, it was found that Zalta™ VM1122 resulted in similar zeta potentials and pH values for the product compared to grinding without GA. These comparable product properties are advantageous as they minimize any potential negative effects on all possible downstream processes such as flotation.
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| 8. |
- Chipakwe, Vitalis, et al.
(författare)
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A critical review on the mechanisms of chemical additives used in grinding and their effects on the downstream processes
- 2020
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Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854 .- 2214-0697. ; 9:4, s. 8148-8162
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Forskningsöversikt (refereegranskat)abstract
- Grinding aids (GAs) have been an important advent in the comminution circuits. Over the last few decades, in order to address the high energy consumption and scarcity of potable water for mineral processing, chemical additives have become a promising alternative. Using GAs can have some advantages such as enhancing grinding efficiency, reducing water usage, improving material flowability, and narrowing the particle size distribution of the grinding products. A study on the effect of GAs on size reduction units is crucial for the beneficiation value chain of minerals and the impact on downstream processes. However, our understanding of the effects of these materials on the particle size reduction is quite limited. This article analyses the literature, which used GAs and provides a comprehensive review of their applications in the ore beneficiation processes. The outcomes of this investigation indicated that the current understanding on the mechanism of GA effects focuses only on their impacts on the product fineness and size distribution, and neglecting the aspect of energy expended and physicochemical environment. The application of GAs is mainly for rationalisation of energy where the type of reagent, pH, and ionic strength of the grinding environment is important. Gaps in knowledge of GAs are discussed in the context of addressing their use in the mineral industry, considering the mechanism of their effect, effect on grinding efficiency, and effect on the downstream processes. Addressing these gaps will pave the way for the application of GAs in improving size reduction efficiencies, which ultimately reduces environmental impacts.
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| 9. |
- Chipakwe, Vitalis
(författare)
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Application of Chemical Additives in Minerals Beneficiation – Implications on Grinding and Flotation Performance
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The application of chemical additives, known as grinding aids (GAs), dates to 1930 in the cement industry. Unlike the cement industry, where the use of GAs is in the final processing step, it could be one of the first processing steps in ore beneficiation. Further to grinding performance, the successful application of GAs requires understanding the effect on ground products and possible interaction of the GAs in view of downstream processes. Understanding and controlling any GA-separation reagent interactions is critical to ensure that the required downstream process efficiency and integrity of the entire value chain are maintained. In this thesis, the effect of selected chemical additives on dry grinding performance and product properties is investigated. Second, the effect of the additives on surface properties and pulpchemistry, together with the resulting behavior in subsequent froth flotation separation, is investigated.The use of environmentally benign and sustainable alternatives to conventional surfactants is growing within mineral processing. To this end, a polysaccharide-based grinding aid (PGA) (natural polymer) together with a polyacrylic acid-based grinding aid (AAG) (synthetic polymer) were used as grinding aids. The effect of PGA and AAG at varying concentrations was investigated with respect to energy consumption, particle size distribution, BET surface area, roughness, and rheology. The resulting grinding parameters were correlated with the measured rheology indices from the automated FT4 powder rheometer. Moreover, the effect of the GAs on the flotation of quartz from magnetite was investigated using an artificial mixture ore. Zeta potentials, stability measurement, adsorption test, and FTIR analyzes were performed to understand the mechanisms of surface interaction and adsorption.The grinding results indicated that the application of GAs reduced energy consumption by up to 31.1 % and gave a finer-uniform product size, higher specific surface area, and increased surface roughness compared to grinding without. Further studies on powder rheology indicated that the GAs used resulted in improved material flowability compared to grinding without additives. There was a strong correlation (r > 0.93) between the grinding and the flow parameters. Flotation tests on pure samples illustrated that PGA has beneficial effects on magnetite depression (with negligible impact on quartz floatability) through reverse flotation separation. The benefits were further confirmed by the flotation of the artificial mixture in the presence of PGA. The PGA adsorption mechanism was mainly through physical interaction based on UV-Vis spectra, zeta potential tests, Fourier transform infrared spectroscopy (FT-IR), and stability analyses. Additionally, single mineral flotation tests indicated that AAG enhanced quartz collection with minimal effect on magnetite. Mixed mineral flotation revealed that, by using AAG, comparable metallurgical performance could be achieved at a lower collector dosage. The zeta potentials and stability measurements showed that AAG shifts the potential, thus improving the stability and dispersion of the suspension. Adsorption tests revealed that AAG adsorbed on both quartz and magnetite, with the former having a higher capacity. Fourier transform infrared spectroscopy showed that the interaction between AAG and the minerals occurs via a physical interaction.The findings illustrate that GAs improved grinding efficacy at optimum dosage and enhanced product properties. Furthermore, the predominant mechanism of GAs is based on the alteration of rheological properties. Importantly, the feasibility of using GAs to improve grinding performance has been demonstrated with secondary beneficial effects on flotation.
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| 10. |
- Chipakwe, Vitalis, et al.
(författare)
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Beneficial effects of a polysaccharide-based grinding aid on magnetite flotation: a green approach
- 2022
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Grinding is the most energy-intensive step in mineral beneficiation processes. The use of grinding aids (GAs) could be an innovative solution to reduce the high energy consumption associated with size reduction. Surprisingly, little is known about the effects of GAs on downstream mineral beneficiation processes, such as flotation separation. The use of ecofriendly GAs such as polysaccharide-based materials would help multiply the reduction of environmental issues in mineral processing plants. As a practical approach, this work explored the effects of a novel polysaccharide-based grinding aid (PGA) on magnetite's grinding and its reverse flotation. Batch grinding tests indicated that PGA improved grinding performance by reducing energy consumption, narrowing particle size distribution of products, and increasing their surface area compared to grinding without PGA. Flotation tests on pure samples illustrated that PGA has beneficial effects on magnetite depression (with negligible effect on quartz floatability) through reverse flotation separation. Flotation of the artificial mixture ground sample in the presence of PGA confirmed the benefits, giving a maximum Fe recovery and grade of 84.4 and 62.5%, respectively. In the absence of starch (depressant), PGA resulted in a separation efficiency of 56.1% compared to 43.7% without PGA. The PGA adsorption mechanism was mainly via physical interaction based on UV–vis spectra, zeta potential tests, Fourier transform infrared spectroscopy (FT-IR), and stability analyses. In general, the feasibility of using PGA, a natural green polymer, was beneficial for both grinding and reverse flotation separation performance.
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