| 1. |
- Bonechi, L., et al.
(författare)
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BLEMAB European project : muon imaging technique applied to blast furnaces
- 2022
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Ingår i: Journal of Instrumentation. - : IOP Publishing. - 1748-0221. ; 17:04, s. C04031-
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Tidskriftsartikel (refereegranskat)abstract
- The BLEMAB European project (BLast furnace stack density Estimation through on-line Muon ABsorption measurements), evolution of the previous Mu-Blast European project, is designed to investigate in detail the capability of muon radiography techniques applied to the imaging of a blast furnace???s inner zone. In particular, the geometry and size of the so called ???cohesive zone???, i.e. the spatial zone where the slowly downward moving material begins to soften and melt, that plays an important role in the performance of the blast furnace itself. Thanks to the high penetration power of the natural cosmic ray muon radiation, muon transmission radiography represents an appropriate non-invasive methodology for imaging large high-density structures such as blast furnaces, whose linear size can be up to a few tens of meters. A state-of-the-art muon tracking system, whose design profits from the long experience of our collaboration in this field, is currently under development and will be installed in 2022 at a blast furnace on the ArcelorMittal site in Bremen (Germany) for many months. Collected data will be exploited to monitor temporal variations of the average density distribution inside the furnace. Muon radiography results will also be compared with measurements obtained through an enhanced multipoint probe and standard blast furnace models.
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| 2. |
- Boström, M., et al.
(författare)
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Understanding ice and water film formation on soil particles by combining density functional theory and Casimir-Lifshitz forces
- 2023
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 108:12
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of ice and water on soil particles play crucial roles in environmental and technological processes. Understanding the fundamental physical mechanisms underlying their formation is essential for advancing scientific knowledge and engineering practices. Herein, we focus on the role of the Casimir-Lifshitz force, also referred to as dispersion force, in the formation and behavior of thin films of ice and water on soil particles at 273.16 K, arising from quantum fluctuations of the electromagnetic field and depending on the dielectric properties of interacting materials. We employ the first-principles density functional theory (DFT) to compute the dielectric functions for two model materials, CaCO3 and Al2O3, essential constituents in various soils. These dielectric functions are used with the Kramers-Kronig relationship and different extrapolations to calculate the frequency-dependent quantities required for determining forces and free energies. Moreover, we assess the accuracy of the optical data based on the DFT to model dispersion forces effectively, such as those between soil particles. Our findings reveal that moisture can accumulate into almost micron-sized water layers on the surface of calcite (soil) particles, significantly impacting the average dielectric properties of soil particles. This research highlights the relevance of DFT-based data for understanding thin film formation in soil particles and offers valuable insights for environmental and engineering applications.
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| 3. |
- Franklin White, Jesse, 1971-, et al.
(författare)
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Towards Bio-carbon Substitutes in the Manufacture of Electrodes and Refractories for the Metallurgical Industries : A Science and Technology Review
- 2023
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Ingår i: Advances in Pyrometallurgy. - Cham : Springer Nature. ; , s. 151-152
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Konferensbidrag (refereegranskat)abstract
- The unique structural versatility and chemical and thermophysical properties of carbon make it essentially irreplaceable for non-reductant uses in many high-temperature metallurgical processes. At present, bio-carbon substitutes are not technically feasible for large-scale use in electrode and refractory materials that are vital consumables in the steel, aluminum, and non-ferrous metal industries. Carbon electrodes of all types (including Soderberg, prebaked, and anodes/cathodes for Al) as well as carbon lining pastes are all similar in that they are comprised of a granular carbon aggregate and a carbon-based binder. Similarly, refractories such as MgO-C utilize both natural (mined) graphite and carbon-based binders. Replacements of fossil materials with equivalent bio-carbon substitutes have the potential to dramatically reduce the carbon footprints of these products. However, there are still considerable materials engineering challenges that must be surmounted. The properties of bio-carbon materials and technological obstacles are explored, including catalytic graphitization and development of bio-pitch materials.
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| 4. |
- Frosin, C., et al.
(författare)
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Exploring the potential of muon radiography for blast furnace assessments: advancements in non-invasive imaging and structural analysis
- 2024
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Ingår i: Journal of Instrumentation. - : IOP Publishing. - 1748-0221. ; 19:2
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Tidskriftsartikel (refereegranskat)abstract
- The BLEMAB European project (BLast furnace stack density Estimation through online Muon ABsorption measurements), the evolution of the previous Mu-Blast European project, is designed to investigate in detail the capability of muon radiography techniques applied to the imaging of the inner zone of a blast furnace. In particular, the goal of this collaboration is to characterize the internal region (so-called cohesive zone) where the slowly downward-moving material begins to soften and melt, which plays an important role in the performance of the blast furnace itself. In this contribution, we describe the state-of-the-art of the muon tracking system which is currently being developed and installed at a blast furnace on the ArcelorMittal site in Bremen (Germany). Moreover, we will present the GEANT4 simulation framework devised for this application together with the simulation results. Finally, we will show the possible contribution of multiple scattering effects to such peculiar applications.
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| 5. |
- Khadhraoui, S., et al.
(författare)
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A new approach for modelling and control of dephosphorization in BOF converter
- 2018
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Ingår i: La Metallurgia Italiana. - : Associazione Italiana di Metallurgia. - 0026-0843. ; 110:11-12, s. 5-16
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Tidskriftsartikel (refereegranskat)abstract
- In the BOF process, the accurate control of Phosphorous removal up to ultra-low values is very important to ensure a high quality of the end–product. This has proven to be associated with several challenges, leading to a preferred usage of high priced low P iron ores. Thus, in the scope of the European BOFdePhos project, important thermodynamic and kinetic aspects of the dephosphorisation reaction such as the effect of solid phases on Phosphorous distribution and lime dissolution in a foamy slag were investigated. It was found that BOF slags are heterogeneous during a large period of the blow and also at the end of blow in most cases. The type and amount of solid phases is strongly affected by temperature and minor oxides content such as MgO-, MnO- and Al2O3-content. The consideration of solid phases formation in the slag, especially the P dissolving C2S_C3P phase, is crucial for a successful modelling and control of dephosphorisation. However, most of the Phosphorous distribution equations available in the literature were developed for homogeneous slags. Thus, a new approach for thermodynamic modelling of the P-distribution between a heterogeneous slag and liquid iron covering the total blowing period in converter was developed and incorporated in a kinetic dephosphorisation model. It was found that while the P distribution in a fully liquid slag was a strong function of temperature, CaO- and FeO-content, the P distribution in a heterogeneous slag depended further on temperature but also on the amount of solid phase as well as the basicity of the liquid slag phase. Even though the C2S_C3P phase can dissolve high amount of Phosphorous, the P-dissolution in the solid phase in the industrial process is associated with strong kinetic limitations. New strategies for the enhancement of dephosphorization control in the BOF converter, focusing on using the potential of the solid phase in removing Phosphorous, were developed.
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| 6. |
- Lu, Yu-Chiao, 1995-
(författare)
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Application of Hydrochar for Low-CO2 Emission Steel Production
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Steel is an indispensable material of the modern society and yet the production of steel is one of the largest anthropogenic CO2 emission sources on the planet. The conventional blast-furnace-basic-oxygen-furnace (BOF) process is responsible for generating 85% of the steel industry’s total CO2 emissions, which is the result of a high coal consumption rate for the reduction of iron ores and for providing the heat necessary for the high-temperature process. In order to meet the climate goal set by the Paris Agreement, the iron and steel industry must drastically decrease its CO2 emissions and aim at achieving net-zero emissions by 2050. Bioenergy is a form of renewable energy, and if it is managed sustainably throughout its life cycle, it can be considered carbon-neutral. Replacing fossil fuels with biofuels consumed during the steelmaking processes is one way to decrease CO2 emissions. However, this approach has not been widely adopted by steelmakers over the world due to the high price and the limited availability of wood-based biofuels. Hydrochar is a coal-like solid material that is produced from the hydrothermal carbonization (HTC) of biomass. It has attracted great interest from steelmakers due to its coal-like properties and the fact that it can be produced from a wide range of organic waste streams that can be found in almost every country. Previous studies focused on the use of hydrochar for the blast furnace process. This thesis therefore examines the potential use of hydrochar in the direct-reduction-electric-arc-furnace (DR-EAF) process, and particularly in two applications where the use of fossil coal is difficult to abate—the coal-based direct reduction of iron ore and the carburization of liquid steel in the EAF. This thesis begins with a characterization study of a hydrochar produced from lemon peel waste (LPH) and its comparison with a fossil reference material (anthracite) and two bio-reference materials (charcoal). The results reveal that LPH is a highly volatile material that is characterized by a low fixed carbon content and a medium calorific value. The volatile matter of LPH consists of gas, tar, and aqueous liquids, and contains approximately half of the total carbon and energy content of LPH. On the contrary, charcoal, anthracite, and the pyrolyzed char of LPH (PLPH) hardly emit any volatiles and are stable up to a high temperature (1200 °C). These materials are characterized by high fixed carbon contents and high calorific values, which makes them ideal fuel, carburizers, and reducing agents. On the other hand, LPH seems to be more efficient when it is applied in areas where its volatile matter content could be utilized to an advantage, such as to provide heating energy and to reduce metal oxides. Next, two hydrochars (produced from lemon peel and rice husk) were tested for coal-based direct reduction and their performance were compared to that of anthracite. Hematite-carbon mixtures prepared with varying fixed-carbon-to-oxygen ratios (C/O) were heated in nitrogen atmosphere up to 1100 °C for direct reduction. The hematite in briquettes with molar C/O ratios greater than 1.0 were completely reduced to metallic iron, whereas briquettes with C/O ratios equal to 0.4-0.5 were reduced by 63-86%. It was confirmed that the volatile matter released by the carbonaceous materials and the organic binder reduced hematite up to a maximum of 35% but the utilized fractions of the volatile matter were quite low (12-56%). As a result, the reduction of hematite was dominated by carbothermic reduction which involved fixed carbon. Thus, the efficiency of a carbonaceous material as a reducing agent for the coal-based direct reduction processes is still predominantly determined by its fixed carbon content. Then, LPH was tested for carburization of liquid iron in a laboratory setup under an inert atmosphere and its performance was compared with that of charcoal. Iron-carbon briquettes, which have higher apparent densities than the carbonaceous material itself, were utilized as carburizers with an aim to improve the carbon’s penetration depth in the liquid iron. The briquettes were experimented in two different ways to simulate the carbon addition practices in an EAF. With the first method, the briquettes were slowly heated from room temperature up to 1600 °C, which simulates the loading of carbon into an EAF at the beginning of a heat via a scrap bucket. With the second method, briquettes were directly charged into a pool of liquid iron. The results reveal that the carburization yield is predominantly determined by the fixed carbon content of the carbonaceous material, and when a more aggressive carbon addition method (e.g. direct charging) was used, there were additional carbon losses which lowered the yield. In the final part of the thesis, two types of hydrochars (those produced from orange peel and green waste) and an anthracite were applied for carburization tests in a pilot-scale EAF. Carbonaceous materials were either top-charged into the EAF at the beginning of a heat, or injected as powder via a lance directly into liquid steel after scrap meltdown. The results show that hydrochar and anthracite has a similar carburization yield (based on fixed carbon) when the same carbon addition method was used, and the carburization yields achieved by top-charging were higher than that achieved by lance injection. Based on the results obtained in this thesis, three main conclusions are drawn. Firstly, hydrochar can completely replace fossil coal as a reducing agent for the direct reduction of iron ores and as a carburizing agent in the EAF process. However, it is more efficient to use pyrolyzed hydrochar than to use pristine hydrochar since the fixed carbon content of the material mostly determines its substitution ratio for anthracite. Secondly, some negative impact of the ash content of hydrochar has been identified in this study. For example, the reduction rate of hematite-carbon composite mixture is lowered by the hindering effect of ash on carbothermic reduction. Furthermore, ash increases the slag volume and decreases the slag’s basicity in the EAF. Hydrochars produced from fruit peel wastes (lemon peel, orange peel) have lower ash contents than hydrochars produced from plant wastes (rice husk, green waste) and are more suitable to be applied directly in steelmaking processes. Lastly, the substitution of anthracite with charcoal or hydrochar lowers the total amount of sulfur introduced into the EAF. The increase in the amount of phosphorous introduced into the EAF resulting from the addition of hydrochar can be resolved either by controlling the amount of hydrochar added, or by lowering the phosphorous content of hydrochar through additional impurity reduction treatment following the HTC process, which should be investigated in future studies.
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| 7. |
- Lu, Yu-Chiao, et al.
(författare)
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Comparison of Hydrochar and Anthracite as Reducing Agents for Direct Reduction of Hematite
- 2024
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Ingår i: ISIJ International. - Tokyo, Japan : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 64:6, s. 978-987
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Tidskriftsartikel (refereegranskat)abstract
- The substitution of fossil coal with biocarbon in the metallurgical processes can help to decrease fossil CO2 emissions. Biocarbon’s characteristics, such as high volatile matter contents and high reactivities with CO2, are beneficial for increasing the reduction degrees and reduction rates of iron oxides in carbon composite agglomerates (CCA). This study compared the reduction of hematite by of two types of carbonaceous materials (CM): hydrochar (high-volatile biocarbon) and anthracite (a low-volatile coal) in the form of CCA. CM, hematite, and binder (starch) were mixed together to obtain mixtures with C/O molar ratios equal to 0.4–1.2. The mixtures were reduced non-isothermally in nitrogen atmosphere up to 1003 K or 1373 K. Up to 1003 K, the volatiles released from CMs and starch reduced hematite by 18–35%. Between 1003 K and 1373 K, both hydrochars (produced from lemon peels and rice husks) reacted with iron oxides more rapidly than anthracite below 1360 K, when the samples had C/O ratios in the range of 1.0–1.2. In this temperature range, rice husk hydrochar promoted a slower reaction with iron oxides than lemon peel hydrochar, which was possibly influenced by its higher ash content which decreased the rate of Boudouard reaction. Samples with C/O ≥ 1.0 achieved complete reduction at 1373 K, regardless of the type of CM used, whereas samples with C/O equal to 0.4–0.5 achieved 63–86% reduction. It can be concluded from this study that hydrochar can fully substitute anthracite for direct reduction of iron oxide to decrease fossil CO2 emissions during ironmaking processes.
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| 8. |
- Martinsson, Johan, et al.
(författare)
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Lime Dissolution in Foaming BOF Slag
- 2018
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Nature. - 1073-5615 .- 1543-1916. ; 49:6, s. 3164-3170
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes the dissolution mechanisms of lime into liquid and foaming slags relevant to the BOF process. Two different master slags are employed, representing two different periods of the converter process: an early stage where the FeO content is fixed to 45 wt pct, and a later stage where the FeO content is fixed to 25 wt pct. For these master slags, the ratio between CaO/SiO2 is varied to examine the effect of basicity on lime dissolution. Calcium silicates are formed and peeled off, or partially peeled off, from the interface between the lime cube and the slag in all cases. The main difference for the dissolutions in pure liquid slag and foaming slag is the controlling step for dissolution. In liquid slag, the controlling mechanism is the removal of the calcium silicate layers, while in foaming slag, the controlling mechanism is the contact area between the lime and the liquid slag phase of the foam. The strong convection in the foam enhance the dissolution process, in some cases, the lime even dissociates into small pieces.
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| 9. |
- Rigas, Konstantin, et al.
(författare)
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Investigations on Vibrational Interpretations of Bubbles in Metal-Making Processes
- 2023
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Nature. - 1073-5615 .- 1543-1916. ; 54:4, s. 2105-2120
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Tidskriftsartikel (refereegranskat)abstract
- Vibration measurements were carried out using highly sensitive accelerometers in an experimental ladle integrated into the LIMMCAST (Liquid Metal Model for Steel Casting) facility at HZDR. The model is operated with liquid Sn–40 wt pctBi alloy at 200 °C, whose physical properties are close to those of molten steel. Three accelerometers were attached to the outer wall of the LIMMCAST vessel to record the vibrations caused by the argon bubble flow in the liquid metal at different process parameters. The results obtained at the liquid metal experiments differ from those reported for water models where the relationship between root mean square (RMS) value of the vibration amplitude and the gas flow rate follows different curve shapes. Furthermore, the results of vibration measurements in the LIMMCAST model are compared with vibration measurements in a steel plant during vacuum degassing. The comparison of the RMS data shows a fairly good agreement. This indicates that the vibrations in both the industrial process and the laboratory model are caused by the same physical mechanisms, and thus, the vibration behavior in an industrial steelmaking ladle can be reproduced quite well by suitable liquid metal models. These studies on bubble flows can help to improve the understanding of industrial stirring processes and thus contribute to a better process control.
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| 10. |
- Safavi Nick, Reza, et al.
(författare)
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Mathematical Modelling of Desulphurisation of Raw Iron by Powder Injection in a Ladle
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The current study has investigated the particles profile of the SSAB Luleå ladle in the sulfur refining station. The study has modeled the particles using the passive scalar transport concept where the buoyancy force is manually coded.The study suggest that increase in the number of ports from two (current set up) to four with the same material feeding rate will distribute the particles more evenly into the bath. Moreover, the study also suggests that positioning the lance at the bottom of the ladle, while the lance has only two jet ports similar to the current practice, will produce rather similar particle distribution at the upper region of the domain. The study shows a practical benefit of positioning the lance at the bottom of the ladle can be the residence time of the particles and elimination of stagnant zone below the lance in normal operation. Finally, the study shows that activating the porous plug will result in an asymmetrical profile.The simulation suggested that this asymmetrical behaviour is not affecting the distribution profile of the particles in region around the lance but the magnitude. Furthermore, the model seems to suggest that the number of particles in zones below the lance on either side is three orders of magnitude larger than the reference case while the profiles of these zones are rather similar to the reference case. Furthermore, in the case of zone immediately below the lance, the profiles seem to behave rather differently on different side of the porous plug while in case of zone in front of it the profiles are very similar but with a slight difference in the magnitude.
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