| 1. |
- Andersson, Anton, et al.
(author)
-
Characterization and Upgrading of a Low Zinc-Containing and Fine Blast Furnace Sludge : A Multi-Objective Analysis
- 2017
-
In: ISIJ International. - : The Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 57:2, s. 262-271
-
Journal article (peer-reviewed)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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| 2. |
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| 3. |
- Andersson, Anton, et al.
(author)
-
Characterization of Blast Furnace Sludge and Upgrading Using Physical Separation and Leaching
- 2017
-
Conference paper (peer-reviewed)abstract
- The on-site sinter plants of the Swedish ore based steel industry are all closed. Instead of using sinter, the blast furnaces (BF) operate on iron ore pellets and the major part of the recycling of in-plant residues is realized via cold bonded briquettes charged to the BF. Cost of raw materials and energy continuously drives the work towards an increased recycling of in plant residues. The major part of the zinc entering the BF leaves through the top gas ending up in the BF dust and sludge. The recycling of all the BF dust back to the BF leaves the BF sludge as the main bleed of zinc out of the system. In order to utilize the iron and carbon content of the sludge, means to remove zinc is required prior to recycling via the briquette. In the present work, blast furnace sludge has been characterized. Using the characterization as standpoint, different operations for zinc removal was suggested and studied in laboratory scale. Zinc was successfully removed using a hydrometallurgical and physical separation route, respectively. A successful dezincing operation would enable the recycling of the sludge. This would improve the material- and energy efficiency and substantially decrease the amount of sludge being landfilled.
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| 4. |
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| 5. |
- Andersson, Anton
(author)
-
Recycling of Blast Furnace Sludge within the Integrated Steel Plant : Potential for Complete Recycling and Influence on Operation
- 2019
-
Doctoral thesis (other academic/artistic)abstract
- Ore-based steelmaking generates various residues including dust, sludges, scales and slags. Internal and external recycling has allowed for 68-90 % of the dust, sludges and scales to be recycled. However, several residues are landfilled despite containing elements valuable as raw material in the production of steel. One such residue is the blast furnace (BF) sludge which has a chemical composition dominated by iron and carbon. In 2008, the annual worldwide landfilling of BF sludge was estimated to 8 million metric tons in dry weight. Furthermore, as the iron production via the BF route has increased significantly since 2008, the landfilling of BF sludge could be even higher as of today. Thus, the potential to reclaim valuable iron and carbon while improving the raw material efficiency is substantial.Traditionally, in-plant recycling of residues generated in the integrated steel plant is conducted via the sinter or, in the case of pellet-based BFs, via cold-bonded briquettes and injection in the BF tuyeres. The challenges in recycling BF sludge via these routes are the fine particle size distribution, the high water content and the zinc content. Of these challenges, the latter is the main concern as too high zinc loads in the BF lead to increased reductant rates, reduced lining life of carbon-based bricks and scaffold formation, which may disturb the process. The challenge regarding zinc has previously been addressed by pretreating the sludge, generating a low-zinc and high-zinc fraction where the former has been recycled to the BF via the sinter or cold-bonded pellets. Although pretreatment and recycling of the low-zinc fraction have been achieved in industrial scale, the reported sludges are generally coarse in size and high in zinc. Furthermore, recycling of pretreated BF sludge to the BF utilizing cold-bonded briquettes has not been reported and the internal recycling of the high-zinc fraction has not been considered.In the present thesis, newly produced BF sludge with a fine particle size distribution and low zinc content was characterized finding that a majority of the zinc was present in weak acid soluble phases and that the finest fraction of the sludge carried most of the zinc. Based on these findings, the BF sludge was pretreated using sulfuric acid leaching, hydrocycloning and tornado treatment, respectively. Sulfuric acid leaching was the most effective method in selectively separating zinc from the iron, carbon and solids. However, both hydrocycloning and tornado treatment were successful in generating a fraction low in zinc.The low-zinc fraction of the tornado-treated BF sludge was incorporated in cold-bonded briquettes and tested for strength, swelling and intrinsic reducibility. Furthermore, the briquettes were charged as basket samples in the LKAB Experimental Blast Furnace (EBF) in order to study the behavior in actual BF conditions. The results suggested that the low-zinc fraction of the BF sludge could be added to the briquettes without negatively affecting the performance of the briquettes in the BF. The results were confirmed in industrial-scale trials where non-treated BF sludge was added to cold-bonded briquettes in an amount that would facilitate complete recycling of the low-zinc fraction. Charging these briquettes to the BF did not induce any negative effects on the process or the hot metal (HM) quality.The high-zinc fraction of the tornado-treated BF sludge was added in self-reducing cold-bonded agglomerates and studied in technical-scale smelting reduction experiments aiming at recycling to the HM desulfurization plant. The experiments suggested that melt-in problems could be expected when using either briquettes or pellets. Nonetheless, industrial-scale trials were performed aiming to study the feasibility of recycling cold-bonded briquettes to both the HM desulfurization plant and basic oxygen furnace (BOF). These trials suggested that a substantial amount could be recycled without affecting the final quality of the steel. However, additional experiments were identified to be required in order to enable 100 % recycling of the high-zinc fraction of the tornado-treated BF sludge.Based on the results from the experimental work, a holistic concept to completely recycle the BF sludge within the integrated steel plant was suggested.
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| 6. |
- Andersson, Anton, et al.
(author)
-
Upgrading of Blast Furnace Sludge and Recycling of the Low-Zinc Fraction via Cold-bonded Briquettes
- 2019
-
In: Journal of Sustainable Metallurgy. - : Springer. - 2199-3823 .- 2199-3831. ; :3, s. 350-361
-
Journal article (peer-reviewed)abstract
- Depending on the operation of the blast furnace (BF), the main outlet of zinc from the furnace is more or less via the BF dust and sludge. As the dust is recycled to the BF, the sludge has to be de-zinced prior to recycling to prevent the accumulation of zinc in the BF. De-zincing and recycling of the low-zinc fraction via sinter have been reported. However, no research con-cerning recycling of upgraded BF sludge via cold-bonded briquettes has been performed. In the present study, a fine-grained BF sludge with low zinc content, generated by a BF operating on a ferrous burden of 100% pellets, was upgraded using the tornado process. The process simultaneously dried and separated the BF sludge into a high-zinc and a low-zinc fraction. The feasibility of recycling the low-zinc fraction to the BF using cold-bonded briquettes was studied on a laboratory-scale BF shaft simulator. On comparison with a reference briquette, the experiments indicated that 10 wt% of the upgraded BF sludge can be added to the briquette without negatively affecting the reducibility. Higher additions were found to render the briquette less reduced compared to the reference under test conditions corresponding to the central part of the BF. The strength of the briquettes was not compromised with the addition of the upgraded BF sludge, and a decision to study the briquettes in the LKAB experimental blast furnace was made in order to evaluate the behavior under actual BF conditions.
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| 7. |
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| 8. |
- Andersson, Charlotte, et al.
(author)
-
The need for fundamental measurements for a sustainable extraction of metals
- 2011
-
In: Mineral Processing and Extractive Metallurgy. - 0371-9553 .- 1743-2855. ; 120:2, s. 199-204
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Journal article (peer-reviewed)abstract
- The increased need for efficient material processing and efficient utilisation of more complex raw materials and the need for recycling or reusing byproduct and waste streams, are all increased challenges in material processing. To cope with these challenges, there is a need for new basic physical and thermodynamic data. The present paper gives four examples, as well as preliminary data, of areas where increased knowledge of fundamental parameters will increase the possibility for a sustainable extraction of metals. The examples include measurement of solubility of pure individual slag minerals, determination of distribution of leachable elements between different mineralogical phases in slag, influence of alumina on liquidus temperature of a copper slag and thermal diffusivity measurements in magnetite based iron ore pellets, all important in different ways to increase the sustainability of the respective materials involved
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| 9. |
- Awe, Samuel Ayowole, et al.
(author)
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Dissolution kinetics of tetrahedrite mineral in alkaline sulphide media
- 2010
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In: Hydrometallurgy. - : Elsevier BV. - 0304-386X .- 1879-1158. ; 103:1-4, s. 167-172
-
Journal article (peer-reviewed)abstract
- The present study investigates the dissolution kinetics of tetrahedrite in aqueous alkaline sodium sulphide solutions. Effect of reaction temperature, mineral particle size, sodium sulphide and sodium hydroxide concentrations on antimony and arsenic dissolution rate from tetrahedrite were studied. It was found that the rate of reaction increases with increase in reaction temperature, sodium sulphide concentration, and sodium hydroxide concentration and with decrease in mineral particle size. The kinetic study indicates that the rate of tetrahedrite leaching in the lixiviant under selected conditions is chemically controlled through the particle surface reaction. The estimated activation energies were found to be 81 kJ/mol and 75 kJ/mol, respectively, for antimony and arsenic dissolution from tetrahedrite, which are in agreement with the values of activation energies reported for the chemically controlled reaction process
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| 10. |
- Awe, Samuel Ayowole, et al.
(author)
-
Elimination and recovery of antimony from copper resources
- 2013
-
Conference paper (peer-reviewed)abstract
- In a response to the recent growth in the global demand for copper products, mining industries have intensified in their mining operations. Unfortunately, the grade of copper ore concentrates mined today is declining due to the intensive mining of the relatively high grade copper resources. Therefore, future copper ore deposits to be mined are likely to be richer in impurity elements like antimony and arsenic which attract smelter’s penalty if the content of these impurities is too high. It is however imperative to selectively eliminate and recover the antimony impurity of the copper concentrates in an environmentally friendly process with a view of upgrading the concentrates for a pyrometallurgical processing.This paper discusses the alkaline sulphide hydrometallurgical technology to selectively solubilize antimony impurity from a copper concentrate. The effect of sodium sulphide and sodium hydroxide concentrations, leaching time and leaching temperature on antimony dissolution will be examined. Furthermore, antimony recovery as a marketable product from simulated pregnant leach liquor through electrodeposition will be discussed. Various experimental factors that influence antimony deposition from alkaline sulphide electrolyte are reported.
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| 11. |
- Awe, Samuel Ayowole, et al.
(author)
-
Wise process routes for varying feedstock in base metal extraction
- 2011
-
In: Proceedings, European Metallurgical Conference EMC 2011. - Germany : GDMB. - 9783940276391 ; , s. 1315-1322
-
Conference paper (peer-reviewed)abstract
- In Sweden, there are several large but low-grade ore deposits that have not been extracted so far. The main reason is presence of impurities such as arsenic and antimony that increase the overall cost of the process and make the extraction uneconomical. In-depth experimental studies, plant data and theoretical modelling and innovations are needed to develop new techniques for an efficient use of the resources. Besides, recycling of metals from end of life scrap and metal containing waste, e.g. waste electric and electronic equipment (WEEE), is an important part of a metal production plant. Most of these secondary raw materials contain mixtures of different metals together with various plastics and ceramics that may adversely affect products and by-products of the metallurgical opera-tion. Therefore, a thorough study on how to control possible changes of properties is required. The aim of the research is to develop an optimum combination of hydro- and pyro- metallurgical path-ways to bleed out impurities from the metal extraction chain and/or convert them into valuable by-products. The first part of the current paper focuses on impurity removal from a complex copper concentrate as an upgrading stage. It is shown that by selective dissolution of tetrahedrite in alkaline sulphide solution, antimony and arsenic would be eliminated and the concentrate can be treated in pyro-metallurgical processes. In the second part of the paper, influences of one of the most common and significant compounds that is included in most of the secondary raw materials, alumina Al2O3, on properties of a copper production slag are explained. Results show that increased alumina content of the slag will cause formation of a new phase and rises the liquidus temperature, while its leaching properties are not adversely affected.
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| 12. |
- Babanejad, Safoura, et al.
(author)
-
High-Temperature Behavior of Spent Li-Ion Battery Black Mass in Inert Atmosphere
- 2022
-
In: Journal of Sustainable Metallurgy. - : Springer Nature. - 2199-3823 .- 2199-3831. ; 8, s. 566-581
-
Journal article (peer-reviewed)abstract
- The increased demand for Li-ion batteries has prompted the scientific community to improve recycling routes in order to reuse the valuable materials in batteries. After their end-of-life, the batteries are collected, discharged, and mechanically disintegrated, generating plastic and metallic streams that are recycled directly; this leaves behind a small particle size fraction known as black mass (BM). BM is composed mainly of graphite and Li-metal complex oxides. Pyrometallurgy is a route known for recycling of BM, in which identifying the BM’s behavior at high temperatures is essential. In this study, two types of BM are characterized in two fractions of 150–700 µm and smaller than 150 µm. The thermal behavior of the BM is studied with thermal analysis techniques. The analyses demonstrate that the mineralogical and morphological properties of the two fractions do not significantly differ, while the amounts of C and organic materials might vary. When the BM was thermally treated, the binders decomposed until a temperature of 500 ℃ was reached, where the volatilization of hydrocarbons was observed, although F mostly persisted in the BM. The Li-metal oxide was partially reduced to lower oxides and Li carbonate at ⁓ 600 ℃, and the main mass loss was caused by carbothermic reduction immediately thereafter. As the products of this process, metallic Co and Ni phases were formed, and part of the graphite remained unreacted. Regarding the Li behavior, it was observed that in the presence of Al, AlLiO2 is the most likely composition to form, and it changes to LiF by increasing the F concentration in the composition.
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| 13. |
- Björkman, Bo, et al.
(author)
-
Dust forming mechanisms in the copper converting process
- 1996
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In: Second International Symposium on Extraction and Processing for the Treatment and Minimization of Wastes, 1996. - Warrendale, Pa : Minerals, Metals & Materials Society. - 0873393694 ; , s. 105-114
-
Conference paper (peer-reviewed)abstract
- A controlled dust generation whereby the dust generated would be enriched with specific metals would considerably facilitate the possibilities of recovering metals from such dusts. A basic understanding of the dust forming mechanisms is of fundamental importance to achieve a controlled dust generation. The present study deals with dust formation in a copper converting process. Dust samples collected from various places in the gas cleaning system were characterised for chemical and mineralogical composition using chemical analysis as well as microprobe analysis. Thermodynamic calculations were used to predict the formation of chemically formed dust at various temperatures and amounts of leakage air to the gas system. The results show that a separation of mechanically formed dust, e.g. SiO sub 2 , Cu and chemically formed dust, e.g. Pb, Zn, As, Bi, could, to some extent, be obtained due to their different particle sizes. A selective condensation of Pb, Zn and As at a various temperatures could, according to thermodynamic calculations, be possible at high temperature. A selective condensation of metals requires an airtight gas cleaning system or a gas cleaning system with a limited amount of leakage air in order to maintain the desired temperature level.
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| 14. |
- Björkman, Bo, et al.
(author)
-
Kinetics of Impurity Elimination During Roasting
- 1994
-
In: Extraction and processing for the treatment and minimization of wastes, 1994. - Warrendale, Pa : Minerals, Metals & Materials Society. - 0873392612 ; , s. 825-842
-
Conference paper (peer-reviewed)abstract
- Four different arsenic containing dusts from the Boliden plant, Boliden Mineral AB, Sweden have been examined. A kinetic study of the arsenic elimination was performed in a laboratory scale roasting furnace for roasting furnace ESP dust and smelting furnace ESP dust. Characterisation and thermodynamic calculations were carried out to determine the mineralogy, and the stability of compounds in the dusts studied. The characterisation methods used were chemical analysis, X-ray diffraction analysis and microprobe analysis. It was found in the experiments that a high degree of As elimination was obtained for roasting furnace ESP dust and a low degree for smelting furnace ESP dust. Derived kinetic models are given. A prediction of the As-elimination for settling furnace dust and converter ventilation dust is presented
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| 15. |
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| 16. |
- Björkman, Bo, et al.
(author)
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Recycling of Steel
- 2014
-
In: Handbook of recycling. - Waltham, Mass : Elsevier. - 9780123965066 ; , s. 65-83
-
Book chapter (peer-reviewed)abstract
- Steel is perhaps the most important construction material in the world, providing services for the well-being of mankind. An increased demand for steel services creates demand for steel consumption, and the lifetime of the products in use determines the recycling potential and the need for replacement. At the same time the steel sector contributes 9% to global energy consumption and process-related carbon emissions. This is a figure that is very much dependent on the amount of steel recycled, because production of steel from recycled material can be carried out with much less energy and CO2 emissions.Considering volume, steel is already the most recycled metal, and there is a well-functioning business structure for the recycling of steel. Currently about 40% of the steel produced comes from recycled material. If and when the increase in world consumption of steel decreases, there will be numerous possibilities of producing a large amount of the steel from recycled scrap.Based on the existing process technology for scrap sorting and steel processing and on what is known about scrap quality, possible limitations and possible actions, the chapter discusses possibilities to reach a truly sustainable steel recycling. The greatest challenge for the steel and scrap processing industry to obtain long term sustainable steel recycling is perhaps the question of scrap quality and the need to avoid quality losses when recycling steel. As the share of steel produced from ore has increased in the last decade, accumulation of tramp elements has not been an issue of high importance recently, but it is an issue that has to be tackled in the future.
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| 17. |
- Björkman, Bo, et al.
(author)
-
Waste reduction through process optimization and development
- 1996
-
In: JOM. - 1047-4838 .- 1543-1851. ; 48:3, s. 45-49
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Journal article (peer-reviewed)abstract
- In this article, the possibilities of optimizing metallurgical processes based on minimization for waste reduction and application requirements for the reuse of waste products are discussed together with the possibilities of treating existing waste in direct connection with the process involved. Some results from ongoing projects on controlled dust generation and an outline of an ongoing research program are also described.
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| 18. |
- Brämming, Mats, et al.
(author)
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BOF Process Control and Slopping Prediction Based on Multivariate Data Analysis
- 2016
-
In: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X. ; 87:3, s. 301-310
-
Journal article (peer-reviewed)abstract
- In a complex industrial batch processes such as the top-blown BOF steelmaking process, it is a complicated task to monitor and act on the progress of several important control parameters in order to avoid an undesired process event such as "slopping" and to secure a successful batch completion such as a sufficiently low steel phosphorous content. It would, therefore, be of much help to have an automated tool, which simultaneously can interpret a large number of process variables, with the function to warn of any imminent deviation from the normal batch evolution and to predict the batch end result. One way to compute, interpret, and visualize this "batch evolution" is to apply multivariate data analysis (MVDA). At SSAB Europe's steel plant in Luleå, new BOF process control devices are installed with the purpose to investigate the possibility for developing a dynamic system for slopping prediction. A main feature of this system is steelmaking vessel vibration measurements and audiometry to estimate foam height. This paper describes and discusses the usefulness of the MVDA approach for static and dynamic slopping prediction, as well as for end-of-blow phosphorous content prediction. Multivariate data analysis (MVDA) methods have been applied on the top-blown BOF steelmaking process, with the main aim to create industrially applicable static (i.e., prior to blow), as well as dynamic in-blow batch models for predicting the slopping probability. The MVDA approach has also been investigated in regard to in-blow prediction of end-of-blow phosphorous content.
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| 19. |
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| 20. |
- Brämming, Mats, et al.
(author)
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Characterization of Slag‐Metal Emulsion and Its Impact on Foaming Behavior and Slopping in the LD Process
- 2019
-
In: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 90:2
-
Journal article (peer-reviewed)abstract
- In the Basic Oxygen Steelmaking (BOS) process, a heterogeneous emulsion‐solid mix will form, consisting of an emulsion of liquid slag and metal droplets, in which 2nd phase particles of undissolved fluxes and solid in‐blow precipitates are suspended. When the carbon in the metal droplets reacts with iron oxide, small bubbles of CO gas are formed. If the upward movement of these bubbles is obstructed by the physical properties of the emulsion‐solid mix, foaming will occur. Certain process conditions may lead to an excessive foam growth, in the worst case forcing foam out of the vessel. This undesired process event is known as “slopping”. Extensive studies during recent decades have shown that emulsion characteristics strongly connected to foaming are: viscosity, surface tension, and density. The extent of foaming is also dependent on bubble size; foaming increasing with smaller bubble size. However, investigations into the influence of the mineralogy and morphology of the emulsion‐solid mix on foaming in basic oxygen steelmaking are scarce. In this work, samples from trials in a 6‐tonne pilot plant BOS vessel are examined by XRD and with SEM for the determination of emulsion‐solid mix mineralogy and morphology at different stages of the oxygen blow. The study confirms the importance of tight process control in order to minimize the emulsion‐solid mix apparent viscosity and, hence, the foam height, but this without over‐oxidizing the liquid slag phase, which would result in increased gas generation within the slag‐metal emulsion.
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| 21. |
- Engström, Andreas
(author)
-
Reduction Annealing Synthesis of Nanostructured Carbide and Nitride Particulate Composites
- 2014
-
Licentiate thesis (other academic/artistic)abstract
- This thesis covers reduction-annealing synthesis of nanostructured SiC-TiCN and SiC-TiC particulate composite powders. These were characterized by X-ray diffraction and electron microscopy. In the SiC-TiC powder it was found that TiC could be added in certain amounts by reducing controlled amounts of titanium chloride source followed by a suitable annealing. A transmission electron microscopy showed that TiC formed polyhedrons and SiC formed rods. This was in agreement with a trend towards these crystal shapes, regardless of synthesis method, as found in the literature. In the SiC-TiCN particulate powder, nitration was achieved at low nitrogen concentration. In a scanning electron microscopy study it was seen that SiC formed elongated crystals, while TiCN formed polyhedrons. A gradual nitration of TiC into TiCN was proposed. Nitration was promoted by a high reactivity of TiC and an integrated nitrogen surplus over titanium and carbon amount during annealing.
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| 22. |
- Engström, Fredrik, et al.
(author)
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A study of the solubility of pure slag minerals
- 2013
-
In: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 41, s. 46-52
-
Journal article (peer-reviewed)abstract
- Large amounts of oxidic by-product are annually produced by the steel industry worldwide. By far the largest in volume is slag, generated from different stages of steel production. In order to avoid landfilling, steelmakers usually try to process the slag into useful resources that can be used externally. However, leaching of different metals can sometimes be a problem. Since steel slags are a mixture of numerous types of minerals, the solubility of each mineral will affect the outcome of the leachability. The aim of this study was to investigate how six common slag minerals behave during dissolution. Mayenite (Ca12Al14O33), merwinite (Ca3MgSi2O8), akermanite (Ca2MgSi2O7), gehlenite (Ca2Al2SiO7), γ-dicalcium silicate (γ-Ca2SiO4) and tricalcium aluminate (Ca3Al2O6) were synthesized and their dissolution was evaluated through titration using HNO3 at constant pH. Acidic to alkaline pHs (4, 7 and 10) were selected to investigate the solubility of the minerals under conditions comparable to those prevailing in newly produced slags, and one pH value, representing acid conditions. It can be concluded that all six minerals behave differently when dissolving and that the rate of dissolution is generally slower at higher pH values, which are normal in the case of steelmaking slags. At pH 10, the solubility of merwinite, akermanite and gehlenite is considered low. The dissolution of γ-Ca2SiO4 is not affected in the same way as the other minerals when the pH is changed.
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| 23. |
- Engström, Fredrik, et al.
(author)
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Ageing investigation of steel slags from EAF (Electric Arc Furnace) processes
- 2008
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In: REWAS 2008. - : Minerals, Metals & Materials Society. - 9780873397261 ; , s. 353-358
-
Conference paper (peer-reviewed)abstract
- Large amounts of by-products are generated by the Swedish steel industry each year. The EAF-process generates about 400 000 ton of slag, from which 80% is deposit. An alternative to deposit is to use slag as road construction material. However, metal content in the slag can be a problem, due to the leaching. The aim of this work was to investigate how stable these materials are when ageing and kept outside. Five different EAF-slags from domestic steel plants were used in this study. The materials were characterised after 0, 6, 12, 18 and 24 month to evaluate the ageing process. Scanning electron microscope (SEM), x-ray diffraction pattern (XRD) and a standard test for leaching were used. The changes in behaviour differ between the five materials. The total leachability decreases with time for all samples. CaCO3 is formed on slag surfaces as CaO reacts with moister and CO2 in the air.
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| 24. |
- Engström, Fredrik, et al.
(author)
-
Crystallization behaviour of some steelmaking slags
- 2010
-
In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 81:5, s. 362-371
-
Journal article (peer-reviewed)abstract
- The present study was aimed at highlighting the final properties of two different steelmaking slags which undergo different cooling rates. The experiments were conducted in laboratory scale using an induction furnace. One of the slags originates from an electric arc furnace (EAF) (high-alloyed) and the second slag from a basic oxygen furnace (BOF). The treatment of the slag included re-melting along with different cooling rates. The material collected from the tests was characterized through X-ray diffraction, scanning electron microscopy as well as thermodynamic calculations which were compared with experimental results, for confirmation. The results indicate that both the EAF and BOF slags show increased reactivity with water, as well as a decrease in crystal size when rapid cooling is applied. The wüstite-type solid solution (Mg,Fe,Mn)O varies in composition depending on the cooling conditions. Metastable Ca3SiO5 was found in the rapidly- cooled BOF slag.
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| 25. |
- Engström, Fredrik, et al.
(author)
-
Leaching Behavior of Aged Steel Slags
- 2014
-
In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 85:4, s. 607-615
-
Journal article (peer-reviewed)abstract
- Large amounts of slag are generated by the Swedish Steel Industry each year. The Electric Arc Furnace process generates about 200 000 ton of slag per annum, from which approximately 40% is deposited. An alternative to deposit is to use slag as road construction material. However, leaching of metals from the slag can be a reason to limit slag use in road construction. The aim of this work was to investigate how stable these materials are when aged, in an environment open to seasonable weather conditions, with respect to leaching and mineralogy. Three different EAF-slags from domestic steel plants were used in this study. The materials were characterized after 0, 6, 12, 18, and 24 months to evaluate the ageing process. The analytical techniques that were used to evaluate the effect of ageing are scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and a standard test for leaching. The changes in ageing behavior differ between the three materials. The conductivity and the pH decreases with time for all samples. The leaching of calcium, chromium as well as aluminum decreases with time while the leaching of magnesium increases. CaCO3 was formed on slag surfaces as CaO reacts with moisture and CO2 from the air.
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| 26. |
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| 27. |
- Feng, Yan, et al.
(author)
-
Characterization and evaluation of the pozzolanic activity of granulated copper slag modified with CaO
- 2019
-
In: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 232, s. 1112-1120
-
Journal article (peer-reviewed)abstract
- GCS, granulated copper slag, is currently utilized in cement and concrete with a low rate, due mainly to its low pozzolanic activity. The present study was thus performed by first mixing the GCS with CaO, and then melting and water-granulating the GCS-CaO mixtures, as to enhance the reactivity of GCS. Blended cements were formulated by replacing 30 wt. % of the cement, PC, with the modified GCS. The addition of CaO in GCS increased the release rates of heat from the early-age hydration of the blended cement pastes. The pastes with CSC20, the GCS of the highest CaO content (19.5%), acquired higher compressive strengths than those for the PC and other PC-GCS pastes at both 28 and 90 days of curing. The GCS richer in CaO consumed more calcium hydroxide for the formation of calcium silicate hydrates, with SEM micrographs showing a microstructure of more gel phases and less pores in PC-GCS paste. These results indicate that the modification by addition of CaO is an effective way to achieve a high reactivity for the GCS. It may then be possible to utilize the modified GCS as a high-quality supplementary cementitious material to enhance the sustainability for both copper and cement industries.
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| 28. |
- Feng, Yan, et al.
(author)
-
Mechanical Activation of Granulated Copper Slag and Its Influence on Hydration Heat and Compressive Strength of Blended Cement
- 2019
-
In: Materials. - Basel, Switzerland : MDPI. - 1996-1944. ; 12:5
-
Journal article (peer-reviewed)abstract
- Mechanical activation of granulated copper slag (GCS) is carried out in the present study for the purposes of enhancing pozzolanic activity for the GCS. A vibration mill mills the GCS for 1, 2, and 3 h to produce samples with specific surface area of 0.67, 1.03 and 1.37 m²/g, respectively. The samples are used to replace 30% cement (PC) to get 3 PC-GCS binders. The hydration heat and compressive strength are measured for the binders and derivative thermogravimetric /thermogravimetric analysis (DTG/TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are used to characterize the paste samples. It is shown that cumulative heat and compressive strength at different ages of hydration and curing, respectively, are higher for the binders blending the GCS milled for a longer time. The compressive strength after 90 d of curing for the binder with the longest milling time reaches 35.7 MPa, which is higher than the strength of other binders and close to the strength value of 39.3 MPa obtained by the PC pastes. The percentage of fixed lime by the binder pastes at 28 days is correlated with the degree of pozzolanic reaction and strength development. The percentage is higher for the binder blending the GCS with longer milling time and higher specific surface area. The pastes with binders blending the GCS of specific surface area of 0.67 and 1.37 m²/g fix lime of 15.20 and 21.15%, respectively. These results together with results from X-ray diffraction (XRD), FTIR, and SEM investigations demonstrate that the mechanical activation via vibratory milling is an effective method to enhance the pozzolanic activity and the extent for cement substitution by the GCS as a suitable supplementary cementitious material (SCM).
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| 29. |
- Haapakangas, Juho, et al.
(author)
-
Coke Reactivity in Simulated Blast Furnace Shaft Conditions
- 2016
-
In: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 47:4, s. 2357-2370
-
Journal article (peer-reviewed)abstract
- Despite the fact that H2 and H2O are always present in the gas atmosphere of a blast furnace shaft, their role in the solution-loss reactions of coke has not been thoroughly examined. This study focuses on how H2 and H2O affect the reaction behavior and whether a strong correlation can be found between reactivity in the conditions of the CRI test (Coke Reactivity Index) and various simulated blast furnace shaft gas atmospheres. Partial replacement of CO/CO2 with H2/H2O was found to significantly increase the reactivity of all seven coke grades at 1373 K (1100 °C). H2 and H2O, however, did not have a significant effect on the threshold temperature of gasification. The reactivity increasing effect was found to be temperature dependent and clearly at its highest at 1373 K (1100 °C). Mathematical models were used to calculate activation energies for the gasification, which were notably lower for H2O gasification compared to CO2 indicating the higher reactivity of H2O. The reactivity results in gas atmospheres with CO2 as the sole gasifying component did not directly correlate with reactivity results in gases also including H2O, which suggests that the widely used CRI test is not entirely accurate for estimating coke reactivity in the blast furnace.
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| 30. |
- Hofgren, Caisa, 1952, et al.
(author)
-
Cognitive screen and employment long-term after infratentorial stroke
- 2022
-
In: Acta Neurologica Scandinavica. - : Hindawi Limited. - 0001-6314 .- 1600-0404. ; 145:5, s. 610-618
-
Journal article (peer-reviewed)abstract
- Objectives: Motor problems are well-described neurological deficits that occur commonly after an infratentorial ischemic stroke. However, the brain stem and cerebellum are also part of the neural interconnections responsible for cognition, emotions, and behavioral responses. We lack studies on long-term cognitive outcomes and patient employment after an infratentorial stroke. In the present study, we described and compared long-term poststroke cognitive outcomes and employment between patients that experienced infratentorial and supratentorial ischemic strokes. Materials and Methods: We included consecutive patients that experienced an acute ischemic stroke at <= 58 years of age. Patients were classified according to the stroke location. At seven years poststroke, surviving participants were assessed for neurological deficits (National Institutes of Health Stroke Scale [NIHSS]), functional outcome (modified Rankin Scale [mRS]), cognitive function Barrow Neurological Institute Screen (BNIS), and employment. Results: Among 141 participants, 25 (18%) had infratentorial and 116 (82%) had supratentorial strokes. At the 7-year poststroke follow-up, there was no significant difference in BNIS total scores; with a median of 43 (IQR 40.5-46) and 41 (IQR 38-46) in the infratentorial and supratentorial groups, respectively. This result indicated that cognitive dysfunction occurred frequently in both groups. Similar employment rates were observed in the infratentorial (48%) and supratentorial (55%) groups. Both groups had a median NIHSS score of 0 and a median mRS score of 2 at the 7-year follow-up. Conclusion: Patients who survived an infratentorial or supratentorial ischemic stroke had similar rates of long-term cognitive dysfunction and difficulties in returning and/or remaining at work.
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| 31. |
- Isaksson, Jenny, et al.
(author)
-
Improved Settling Mechanisms of an Industrial Copper Smelting Slag by CaO Modification
- 2023
-
In: Journal of Sustainable Metallurgy. - : Springer Nature. - 2199-3823 .- 2199-3831. ; 9:3, s. 1378-1389
-
Journal article (peer-reviewed)abstract
- A significant source of copper losses from pyrometallurgical copper extraction is attributed to dissolved and entrained copper in discarded slag. Entrained copper can be recovered via pyrometallurgical slag cleaning in a settling furnace, where the slag viscosity and copper droplet size distribution (CDSD) are critical parameters. Reduced copper losses suggest improved raw material efficiency, and the slag becomes a more environmentally safe byproduct. In this study, iron silicate slags from a smelting furnace are industrially CaO modified in a fuming furnace to contain a CaO content between 8 and 18 wt.%. The viscosity of slags with and without CaO modifications is evaluated in the temperature range from 1423 to 1723 K. The influences of the CaO modifications on the CDSD, slag matrix copper content, and total copper content were determined. The results show that the slag viscosity decreases with increasing CaO concentrations in the slag. In addition, the copper content decreases in the slag phase, and the CDSD shifts to contain relatively larger droplets. The effect of CaO slag modification reveals a linear relationship between the overall copper recovery and viscosity, which increased from 63 to 88% when the viscosity in the respective batch was 0.51 and 0.25 Pa·s.
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| 32. |
- Isaksson, Jenny, et al.
(author)
-
Improved Settling Properties of Iron Silicate Slag by CaO Modifications
- 2023
-
Conference paper (other academic/artistic)abstract
- One of the most significant sources of copper losses from pyrometallurgical copper extraction is attributed to dissolved and entrained copper in the discarded slag. The entrained copper can be recovered via pyrometallurgical slag cleaning in a settling furnace. Reduced copper losses mean increased smelter profits by improved raw material efficiency, and, in addition, the slag will become a more environmentally safe by-product. One way to increase the copper recovery during the settling process is to modify the slag to improve the properties that decrease copper solubility and slag viscosity. In this study, iron silicate slag was modified using CaCO3 on an industrial scale to evaluate its effect on the settling process. More specifically, the changes in settling were related to the modifications and measurements of slag viscosity and copper droplet size distributions in the slag. The trial was evaluated by comparing the copper content in different batches, the size distribution of copper-containing droplets using automated scanning electron microscopy, and performing rheological studies using a high-temperature rheometer. The results showed that increasing the CaO content of the slag by modification with CaCO3 has a positive effect on the settling process and is thus a possible method to improve the industrial settling process of valuable metals in slag.
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| 33. |
- Isaksson, Jenny, et al.
(author)
-
Industrial Slag Cleaning of Reduced Iron Silicate Slag - Effect of Process Parameters and Slag Modification
- 2022
-
In: Proceedings of Copper 2022 international conference. ; , s. 22-40
-
Conference paper (peer-reviewed)abstract
- During primary copper sulfide smelting and converting, one of the main copper losses is to the slag, which decreases the overall copper recovery. To decrease the copper losses, which are mechanically entrained or dissolved, a slag cleaning route can be used. At the Boliden Rönnskär smelter in Sweden, the slag from the smelting furnace is treated under reducing conditions in a fuming furnace and then tapped into an electric settling furnace where the copper is separated from the slag under the action of gravity. A trial was conducted in the settling furnace at the Rönnskär smelter to increase the knowledge of the copper content in slag and how the process parameters temperature and settling time influence the final slag copper content. The slag was also modified with CaO, to enhance the slag properties for an increased settling velocity and thus decreased copper content. The trial was evaluated by collecting multiple samples of the ingoing and outgoing slag and then compare the slag copper content in the samples. The results showed that the copper content increased with increasing temperature and decreased when the slag was modified with CaO, both parameters had a more pronounced effect compared to the settling time. The slag was also characterized showing that copper was associated with spinels and bubbles, which hinders the settling.
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| 34. |
- Isaksson, Jenny, et al.
(author)
-
Influence of process parameters on copper content in reduced iron silicate slag in a settling furnace
- 2021
-
In: Metals. - : MDPI. - 2075-4701. ; 11:6
-
Journal article (peer-reviewed)abstract
- During the pyrometallurgical extraction of copper, a significant fraction of this metal is lost with discard slag, which decreases profits and overall copper recovery. These copper losses can be reduced by using a settling furnace, in which suspended droplets containing copper separate from slag under the influence of gravity. An industrial trial was conducted in a settling furnace to increase the knowledge of the effect of temperature and settling time on the copper content of slag, and thus enhance the settling process to increase copper recovery. Slag samples were collected from four sample points: the ingoing and outgoing slag stream, within the furnace during settling, and the granulated slag. The chemical composition of the slag samples was analyzed and compared between batches with different temperatures and settling times. The appearance of copper and its associated phases were analyzed using a scanning electron microscope with an energy‐dispersive X‐ray spectroscopy detector (SEM‐EDS). The results indicated that the outgoing slag copper content increased with an increase in temperature, and it was also concluded to be influenced by the attachment of copper to spinels and gas bubbles. The results indicate that regulating the settling furnace temperature to a lower interval could increase copper recovery.
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| 35. |
- Isaksson, Jenny, et al.
(author)
-
Interactions of Crucible Materials With an FeOx–SiO2–Al2O3 Melt and Their Influence on Viscosity Measurements
- 2023
-
In: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Nature. - 1073-5615 .- 1543-1916. ; 54:6, s. 3526-3541
-
Journal article (peer-reviewed)abstract
- Viscosity is a critical parameter during metal extraction, influencing the settling of valuabledroplets, slag handling, and mass transfer. The viscosity of oxide melts can be measured withhigh-temperature rheometers. During such measurements, interactions between the crucible andthe oxide system can change the chemical composition, melt structure, and thus the viscosity.For increased reliability of viscosity measurements, the influence of crucible and spindlematerials on viscosity must be studied. In this study, the viscosity of a syntheticFeOx–SiO2–Al2O3 melt was measured using the rotating spindle technique and three differentcrucible and spindle materials (Mo, Fe, and Ni) to determine the interactions with the melt andthe influence on viscosity. The interaction was evaluated by comparing the post-experimentalchemical analyses, the Fe/Fe2+/Fe3+ content, visual observations, and using scanning electronmicroscopy–energy dispersive spectroscopy (SEM–EDS). The results showed that all thecrucibles partially dissolved into the melt, affecting the melt structure, composition, and, thus,the viscosities. The viscosity data obtained using the Mo setup interacted the least with the melt,was the most stable, and with the best reproducibility.
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| 36. |
- Isaksson, Jenny
(author)
-
Settling Mechanisms of Valuable Metal Droplets in Iron Silicate Slag
- 2023
-
Doctoral thesis (other academic/artistic)abstract
- A significant source of copper losses from pyrometallurgical copper extraction is attributed to dissolved and entrained copper in discarded slag. Entrained copper can be recovered via pyrometallurgical slag cleaning in a settling furnace where the droplets settle under gravity. Reduced copper losses suggest improved raw material efficiency, and the slag becomes a more environmentally safe byproduct as it contains less copper and its associated elements. The copper content in the discarded slag often equals or is higher than in the copper ore, implying that the copper slag is a valuable secondary resource for copper.The settling velocity of droplets and, thus, the metal recovery depends on the slag viscosity, copper droplet size distribution, dissolved copper content, and density difference between the slag phase and the copper droplets. The process parameters, temperature and settling time, theoretically affect the copper recovery, where an extended settling time means that droplets have a longer time to settle, and the temperature affects the viscosity, where a higher temperature means a lower viscosity and thus a higher settling rate. However, the temperature also affects the copper solubility; therefore, the overall effect of temperature on the copper recovery during industrial settling processes is unknown. Modifying the slag composition is another option to alter the viscosity and copper solubility. CaO has experimentally been shown to affect both factors in iron silicate slag positively and is thus a potential modifier for increased copper recovery in a settling process. However, there is a knowledge gap regarding the industrial CaO slag modification in a settling process and the effect on copper droplet size distribution, dissolved copper content, copper recovery, and the relationship between recovery and viscosity. Further research is necessary to bridge the knowledge gap and explore the potential benefits of CaO slag modification for improved copper recovery.Within the scope of this thesis, an industrial trial was conducted with the identified factors, temperature, settling time, and CaO slag modification to gain knowledge of the effect on the industrial settling process. The trial was evaluated by performing a slag characterization focusing on the appearance of copper and its associated elements and phases, copper droplet size distribution, slag matrix copper content, and investigating the slag copper content, copper recovery, and slag viscosity. The results showed that the copper droplets were mainly copper matte and speiss and were primarily associated with the slag phase and occasionally with a chromium-rich spinel and bubbles, which can hinder the settling. The results suggested that the viscosity and slag matrix copper content decreased when the slag was modified with CaO, and the copper droplet size distribution shifted to contain larger droplets. The CaO modification resulted in a higher copper recovery, revealing a linear relationship between the overall recovery and the viscosity.A crucible and spindle material with minimum interaction and influence on viscosity had to be identified to perform the viscosity measurement. Iron silicate slags are the dominating slag used during pyrometallurgical copper extraction of Cu-Fe-S concentrates. The dissolution of the crucible and spindle material into the melt is often analyzed and reported. However, the influence on viscosity is rarely investigated and reported. Three crucibles were studied, Mo, Ni, and Fe, concluding that Mo was preferable for viscosity measurements as it interacted the least with the melt and gave the most stable measurements with the highest reproducibility. Mo was thus the crucible choice for viscosity measurements of the industrial slag with and without CaO modifications. Based on the results from the industrial trial and the experimental evaluation, it was concluded that it is difficult to see an effect of regulating the temperature and settling time in the settling furnace process. It was, however, possible to increase the copper recovery by industrial CaO slag modification, which contributes to an increased raw material efficiency and, thus, a more sustainable pyrometallurgical copper extraction.
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| 37. |
- Isaksson, Jenny, et al.
(author)
-
Settling of copper phases in lime modified iron silicate slag
- 2021
-
In: Metals. - : MDPI. - 2075-4701. ; 11:7
-
Journal article (peer-reviewed)abstract
- Copper in discarded slag decreases the profits and copper recovery during the pyrometallurgical extraction processes. The copper losses to slag can be reduced by using a settling furnace, in which mechanically entrained copper droplets separate from the slag under the action of gravity. The settling rate of entrained droplets can be increased by modifying the slag composition and, thus, the slag properties, which are known to influence the settling rate. The knowledge of industrial CaO slag modification in a reduced iron silicate slag with a Fe/SiO2 ratio close to unity is limited. An industrial trial was thus conducted in an electric settling furnace, where the slag had been pretreated in a fuming furnace, to investigate the effect of CaO slag modification on the final slag copper content. Slag samples were collected from the ingoing and outgoing slag and from within the furnace of batches modified with CaO up to about 16 wt %. The trial was evaluated by comparing the final slag copper content and the copper recovery in the settling furnace. The results indicate that the settling becomes more efficient with the CaO modification as the final slag copper content decreased with increasing CaO content.
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| 38. |
- Isaksson, Jenny
(author)
-
Slag Cleaning of a Reduced Iron Silicate Slag by Settling : Influence of Process Parameters and Slag Modification on Copper Content
- 2021
-
Licentiate thesis (other academic/artistic)abstract
- During the pyrometallurgical extraction of copper, a significant part of the copper is lost with discard slag, which decreases profits, overall copper recovery, and efficiency of raw material usage. Smelting furnace slag usually has a copper content that is close to or higher than that of copper ores. The investigation of copper losses to slag is thus a task of practical significance, as the ore grades are depleting. Slag cleaning, e.g., a settling furnace, can reduce copper losses to slag as the mechanically suspended copper-containing droplets separate from slag under the action of gravity and can hence be recovered. An industrial trial was conducted in an electric settling furnace with slag originating from an electric smelting furnace and processed in a zinc fuming furnace. The trial was conducted to increase the understanding of copper losses to slag and how the process parameters temperature and settling time influence the slag copper content. The obtained slag samples were also evaluated to gain better insights as to the settling mechanism and, if any, factors that hinder the copper phases from settling. Slag modification with CaO was also evaluated to investigate how the modification influences the settling of copper phases and, thus, the final slag copper content. Samples collected during the industrial trial were the basis for the evaluation in the current work. The samples came from batches with varying temperatures, settling times, and CaO content collected at four different sample positions. Instrumental techniques, including XRF, FAAS, ICP-SFMS, and SEM-EDS, were used to analyze the chemical compositions of the samples and the appearance of copper and associated phases. The results indicated that the copper content of outgoing slag increased with increasing temperature in the evaluated interval. The copper content was also concluded to be more strongly affected by the temperature compared to the settling time. Regulating the temperature to the lower temperature interval in the settling furnace could thus decrease the final slag copper content. During the slag characterization, it was found that suspended copper-containing phases were hindered from settling, due to the attachment to solid phases and gas bubbles in the slag. By controlling and minimizing the presence of the bottom buildup and thus solid phases in the slag, the copper content can be decreased. The results indicated that the CaO slag modification decreased the final slag copper content, and can thus be used as a modifier for increased settling.
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| 39. |
- Kero Andertun, Jakob, et al.
(author)
-
Characterisation and leaching behavior of CaO-modified iron-silicate slag produced in laboratory and industrial scales
- 2021
-
In: Canadian metallurgical quarterly. - : Taylor & Francis. - 0008-4433 .- 1879-1395. ; 60:4, s. 294-305
-
Journal article (peer-reviewed)abstract
- Water-granulated CaO-modified iron-silicate slags have shown beneficial properties for cement applications. To further evaluate potential applications, the leaching properties must be understood. Therefore, this study aims to characterise and assess the metal leaching of iron-silicate slags (2.6% CaO) modified with lime (CaO, up to 20 wt.%) produced on both laboratory and industrial scales. The granulated samples showed amorphous contents for the studied CaO range. Generally, the metal content of the samples decreased with the increasing CaO content. Batch leaching tests were conducted on the slags, and the metal leaching and CaO content of the slag were strongly correlated. The leaching of Zn and Cu decreased with the increasing CaO content in the slag. Overall, the slags with 12–13% CaO exhibited minimal leaching of Zn, Cu, Ni, and Sb. These findings indicate that CaO influences the properties of the slag and can suppress metal leaching from water-granulated iron-silicate slags.
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| 40. |
- Kero Andertun, Jakob, et al.
(author)
-
Characterisation and leaching behaviour of granulated iron silicate slag constituents
- 2022
-
In: Canadian metallurgical quarterly. - : Taylor & Francis. - 0008-4433 .- 1879-1395. ; 61:1, s. 14-23
-
Journal article (peer-reviewed)abstract
- Due to increased copper production and the associated environmental consequences, copper production processes need to be improved, considering the impact of their byproducts, among others slag. This study investigated the leaching of individual constituents of iron silicate slag from a copper smelter. This was done by characterising granulated samples of its constituents – glass, matte, speiss – to determine their leaching contribution. It was observed that leaching in distilled and deionised water without pH regulation achieved various natural pH for the constituents. At natural pH, glass (Cu, Zn) and speiss (Ni, Sb) contributed to leaching. Static pH titrations showed the increased leaching of Zn, Cu, Ni, As, and Sb with decreasing pH. The results showed that, an iron silicate slag consisting of glass, matte and speiss, contributes to leaching as follows: matte – Cu and Ni, speiss – Cu, Ni, As, and Sb. Zn leaching is similar among the constituents.En raison de l’augmentation de la production de cuivre et des conséquences environnementales associées, on a besoin d’améliorer les processus de production du cuivre, tenant compte de l’impact de leurs sous-produits, parmi lesquels les scories. Cette étude a examiné la lixiviation des constituants individuels des scories de silicate de fer provenant d’une fonderie de cuivre. Ceci a été accompli en caractérisant les échantillons granulés de ses constituants –verre, matte, smaltite–pour déterminer leur contribution à la lixiviation. On a observé que la lixiviation dans de l’eau distillée et désionisée sans régulation du pH atteignait divers pH naturels pour les constituants. Au pH naturel, le verre (Cu, Zn) et la smaltite (Ni, Sb) contribuaient à la lixiviation. Les titrages de pH statique ont montré une augmentation de la lixiviation du Zn, Cu, Ni, As et Sb avec une diminution du pH. Les résultats ont montré que les scories de silicate de fer composées de verre, de matte et de smaltite contribuent à la lixiviation comme suit: matte–Cu et Ni, smaltite–Cu, Ni, As et Sb. La lixiviation du Zn est similaire parmi les constituants.
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| 41. |
- Kero Andertun, Jakob
(author)
-
Leaching of water-granulated iron silicate slags and their compounds : A study of synthetic and industrial slag systems
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- Copper smelter slag is a residue product of the pyrometallurgical extraction of copper. Due to its physical properties, the iron silicate type of copper smelter slag has many possible application areas, e.g., different aggregates and abrasives. During the copper-making process, some copper becomes distributed in the slag; therefore, copper recovery from the slag is commonly done through slag treatment processes. Despite treatment, copper-containing inclusions can remain in the final slag. In order to secure the environmental properties of slags containing inclusions, the leaching mechanisms needs to be understood, which is the focus of the thesis presented.Synthetic and industrial iron silicate slags have been studied with respect to the impact of the slag constituent’s oxide (glass), sulfide (matte) and metalloids (speiss) on leaching as well as the impact of chemical composition (ZnO and CaO content). The synthetic slags are melted in laboratory furnaces. The industrial slags have undergone a Zn-fuming and settling process (including CaO additions for some slags) to recycle and reduce the zinc content and further separate copper-containing inclusions such as sulfide (matte) and metalloid (speiss) species. The materials investigated in the thesis are solidified using water granulation.All materials are characterized by their chemical compositions and mineralogy. Further, industrial slag constituents are investigated regarding their leaching contribution. Syntheticiron silicate (oxide) is investigated regarding the influence of ZnO content and granulation temperature on Zn leaching. CaO-modified industrial iron silicate slags are investigated regarding the leaching of specific elements (e.g., Cu, Zn, Ni, As, Sb). The leaching tests examine the effect of pH, oxidation and time using water leaching, acid and oxidating leaching and dynamic leaching methods.Characterizing the slag constituents shows that the glass mainly contains amorphous iron silicate. The matte contains mainly copper sulfides, and speiss contains copper metalloids. The leaching results show that the glass contributes to Cu and Zn leaching at pH 8.4, and the speiss contributes to Ni and Sb leaching at pH 7.8. Further, the leaching contribution of matte and speiss increased with decreasing pH. The main leaching elements from the matte and speiss include Cu, Ni, As and Sb.Characterization of the ZnO-modified iron silicate shows that Zn is mainly distributed in glass and partly in fayalite. Further, the Zn leaching increases with granulation temperature, ZnO content in the glass and decreasing pH.Characterization of CaO-modified slags shows that up to 20 wt.% CaO dissolves into the glass phase. An increased CaO content resulted in increased Ca leaching, yielding higher pH. Leaching of Zn, Cu, Ni and Sb was on the other hand shown to decrease. Further, long-term leaching studies confirm increasing pH and Ca leaching. In contrast, the leaching of Cu, Zn and Ni showed a peak after a certain time, which was lowered with increasing CaO content in the slags. The leaching of As and Sb increased with increasing leaching time, but the increase diminished with increasing CaO content in the slags. A lower pH and an oxidating environment increased the leaching of Zn, Cu and Ni.The summarized results from this thesis indicate that the glass contributes to Zn leaching while copper-containing inclusions matte and speiss contribute to the leaching of Cu, Ni, As and Sb. The leaching of elements from the copper-containing inclusions matte and speiss can be limited by ensuring a pH buffer preventing acidification, for example, by CaO modification. CaO modifications decrease the slag leaching resistance, which contributes to increasing pH in the leachate by Ca-dissolution and hence decreased leaching of copper-containing inclusions in the slag. Also, the Zn leaching from the slag decreased with increasing pH in the leachate.
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| 42. |
- Kero Andertun, Jakob, 1991-, et al.
(author)
-
Long-Term Leaching Effects on CaO-Modified Iron Silicate Slag
- 2022
-
In: Minerals. - : MDPI. - 2075-163X. ; 12:11
-
Journal article (peer-reviewed)abstract
- Granulated iron silicate slag, a by-product of pyrometallurgical copper extraction, has excellent properties for construction applications. Slag modification with CaO enhances the application properties regarding pozzolanic reactivity, potentially extending slag use in the future. The slags’ short-term leaching behavior has already been investigated with promising results, while the long-term leaching effects are less studied. Therefore, this study aims to determine the long-term leaching effects on CaO-modified iron silicate slags. The CaO-modifications were conducted during full-scale slag treatment operation. The slags were characterized and leached, and the remaining slags were investigated regarding the formation of secondary phases. The long-term leaching of main and trace elements was determined over 30 days using a dynamic leaching method corresponding to an extended time period. The leaching tests showed increased leaching of the main slag elements (Si, Ca). Zn and Cu showed peak leaching after four days of leaching, and the leaching of As and Sb decreased with the increasing CaO content in the samples. After dynamic leaching, secondary phases formed on the Cu-containing inclusions on the sample surfaces. Independent of the CaO content, the leaching of Cu was increased when subjected to external acidic and oxidating conditions using static pH titration at pH 5 in dilute nitric acid.
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| 43. |
- Kero Andertun, Jakob, et al.
(author)
-
The Effect of Zn Content and Granulation Temperature on Zn Leaching in an Fe-Saturated (FeXZn(1−X))2SiO4 System
- 2022
-
In: Minerals. - : MDPI. - 2075-163X. ; 12:6
-
Journal article (peer-reviewed)abstract
- The zinc in the fayalite slag of copper smelters, in which Zn-containing raw materials are used, is mainly found to be in oxidic phases, such as glassy iron silicate. During the slag water granulation process, the molten slag is heated, whereby the granulated slag achieves varying granulation temperatures. Therefore, in this study, we aimed to characterize and assess the leaching behavior of a synthesized Fe-saturated (FeX,Zn(1−X))2SiO4 system to understand the dependance of the zinc leaching behavior on the parameters of the ZnO content (1–10 wt.%) and granulation temperature (1300 or 1400 °C). It was found that the Zn leaching increased with the increasing Zn content and granulation temperature, using both batch and static pH leaching methods. Zn leaching was further increased at pH 5 using diluted nitric acid under oxidation conditions. Among the oxides in the samples—fayalite, spinel, and glass—glass was found to contribute to Zn leaching, owing to its weathering during pH-titration.
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| 44. |
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| 45. |
- Larsson, Mikael, et al.
(author)
-
Improved energy and material efficiency using new tools for global optimisation of residue material flows
- 2006
-
In: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:2, s. 127-137
-
Journal article (peer-reviewed)abstract
- Residue materials generated in the metallurgical industry have gained an increasing importance, both from the points of view of energy and material supply. A joint process integration model for the integrated steel plant system is developed and used in this paper. It takes into account both residue materials and energy recirculation for the system. The potential for increased recirculation and the effect on the system from an environmental point of view is presented, and implementations and practical experiences are discussed. The model developed can serve as a benchmark for different steelmaking operations and constitute a basis for the continuous work involved in material, energy, environment or economic analyses for the steel production system.
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| 46. |
- Lehner, Theo, et al.
(author)
-
Converting and refining : experience in ferrous and non-ferrous metallurgy
- 2009
-
In: Supplemental proceedings, TMS 2009 138th annual meeting & exhibition. - Warrendale, Pa : Minerals, Metals & Materials Society. ; , s. 53-69
-
Conference paper (peer-reviewed)abstract
- Converting and refining play a central role in the extraction of metals. Sweden has a long tradition as an experimental play ground for metallurgists, chemists and alchemists, developing new methods and technologies. Presenters of papers are usually happy in recording successful developments. But reporting failures can be as great a value as the former. In the paper experiments and experience in process development are illustrated, differences between ferrous and non-ferrous developments are highlighted and industrial learning curves are discussed.
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| 47. |
- Lennartsson, Andreas, et al.
(author)
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Characterisation of buildup in an electric furnace for smelting copper concentrate
- 2015
-
In: Canadian metallurgical quarterly. - 0008-4433 .- 1879-1395. ; 54:4, s. 477-484
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Journal article (peer-reviewed)abstract
- The results from a characterization of buildup in an electric smelting furnace for treating copper-rich feed material at the Boliden Rönnskär smelter in Sweden are presented. The aim of the work was to obtain better knowledge about the mechanisms behind the formation of the buildup. Samples from the buildup were taken during the rebuilding of the furnace. The samples were characterized using chemical and mineralogical techniques. The buildup consists mainly of different phases such as spinel, matte, olivine and metalloids and has a complex and varying mineralogy, which indicates that the buildup is not formed under equilibrium conditions.
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| 48. |
- Lennartsson, Andreas, et al.
(author)
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Development of a model for copper converting
- 2013
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In: Canadian metallurgical quarterly. - 0008-4433 .- 1879-1395. ; 52:4, s. 422-429
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Journal article (peer-reviewed)abstract
- Building on previous work reported in the literature, a dynamic model of the operation of the Peirce-Smith Converter has been developed to describe the distribution of the major elements present. The fundamental principle of the model was a thermodynamic calculation. The situation of non-equilibrium conditions was considered by dividing the converter into different zones linked by predefined flow parameters. The model was verified against actual converter plant data, with the simulated results for the major elements being in good agreement with the plant data. The agreement between plant and calculated data for Pb, and Zn was not as good and more work is required regarding this aspect.
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| 49. |
- Lennartsson, Andreas, 1980-, et al.
(author)
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Large-Scale WEEE Recycling Integrated in an Ore-Based Cu-Extraction System
- 2018
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In: Journal of Sustainable Metallurgy. - : Springer. - 2199-3823 .- 2199-3831. ; 4:2, s. 222-232
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Journal article (peer-reviewed)abstract
- At Boliden’s Rönnskär smelter, WEEE is smelted in a Kaldo process and the black copper, together or without the slag, is charged to the PS converter. This process route has proven to be a viable way to obtain a high WEEE smelting capacity in an originally ore-based process system. Experience shows that the slag in the PS converter is usually not fully liquid, and the amount of solids present in the slag increases due to introduction of slag and black copper from WEEE smelting. The effect of increased content of Al2O3 and Cr in the slag on the liquidus temperature has been calculated using FactSage both for the converter slag and for the slag in the electric smelting furnace. The potential of changed slag chemistry is discussed. The consequences of the applied praxis on the removal of Antimony in the converter have been modeled using SimuSage.
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| 50. |
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