| 1. |
- Davydenko, Arkadiy, et al.
(författare)
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Direct Reduction of Fe, Ni and Cr from Oxides of Waste Products Used in Briquettes for Slag Foaming in EAF
- 2019
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Ingår i: Materials. - : MDPI. - 1996-1944. ; 12:20
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Tidskriftsartikel (refereegranskat)abstract
- Environmental aspects and the sustainable manufacturing of steels require producers to pay more and more attention to the efficient utilization of materials and waste products during steelmaking. This study is focused on the evaluation of possibilities for the recovery of metals (such as Fe, Ni and Cr) from waste products used for slag foaming in the Electric Arc Furnace (EAF) process. Two types of industrial briquettes were produced by mixing mill-scale from the hot rolling of stainless steels with anthracite and pet-coke, respectively. Thereafter, an assessment of the metal reduction processes in briquettes at high temperatures (1500 degrees C) was made by using laboratory thermo-gravimetric reduction experiments in an argon atmosphere. The amounts of metal, slag and gas obtained from the briquettes were estimated. In addition, the velocity and time for the removal of metal droplets from the liquid slag depending on the size of the metal droplets was estimated. It was found that up to 97% of metal droplets can be removed from the slag during the first 30 min. Moreover, results showed that most of the Cr, Ni and Fe (up to 93-100%) can be reduced from oxides of these metals in briquettes at 1500 degrees C. Moreover, the anthracite and pet-coke in the investigated briquettes have similar reduction capabilities. It was found that up to 330 kg of Fe, 28 kg of Ni and 66 kg of Cr per ton of added briquettes can be recovered from waste products by the industrial application of those briquettes for slag foaming in EAF.
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| 2. |
- Deng, Zhiyin, et al.
(författare)
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Study on the blocking of ladle well due to sintering of filler sand
- 2015
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Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 529-532
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Konferensbidrag (refereegranskat)abstract
- The present work aimed at a mechanism study of blocking of ladle well by filler sand. Laboratory experiments were carried out using two different chromite based filler sands technically proven. The interaction between the liquid steel and the sand was also studied by using steels containing different contents of Mn and Al. The reaction between the silica phase and the chromite phase was found to be the main mechanism for the sintering of sand. The reaction resulted in a liquid oxide phase, which became the binding phase between the solid oxide grains. The size of silica phase was found to have great impact on the formation of the liquid oxide phase. Faster formation of the liquid oxide phase would lead to more serious sintering of the sand. It was found that the presence of liquid steel enhanced considerably the sintering of the sand and even increased the amount of liquid phase. Higher temperature and longer holding time would make the sintering of the sand more seriously.
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| 3. |
- Glaser, Bjoern, et al.
(författare)
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Fluid Flow and Heat Transfer in the Ladle during Teeming
- 2011
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 82:7, s. 827-835
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Tidskriftsartikel (refereegranskat)abstract
- A two dimensional axisymmetric model was developed to predict the heat flux in a steelmaking ladle during the teeming process. The model predicts dynamically the flow fields in both liquid phase and gas phase along with the movement of the liquid upper surface. The model also predicts the temperature distributions in the liquid metal, gas phase and all layers in the ladle wall. Industrial measurements using infrared radiation camera inside the ladle after teeming and at the wall outside the ladle during the whole process were carried out. The model predictions were found to be in agreement with the measured data. It was found that the heat transfer to the surrounding atmosphere and the conductivity of the highly insulating layer were the most important factors for the heat loss. The decrease of the thickness of the working lining was found to have limited effect on the total heat flux.
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| 4. |
- Kazemi, Mania, et al.
(författare)
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Study on Direct Reduction of Hematite Pellets Using a New TG Setup
- 2014
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 85:4, s. 718-728
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Tidskriftsartikel (refereegranskat)abstract
- A new thermogravimetric setup was developed to study direct reduction of iron oxide under well-controlled experimental conditions. Pure and industrial hematite samples were isothermally reduced by hydrogen and carbon monoxide gaseous mixtures. Influences of gas composition, gas flow rate, and temperature on reduction were investigated. Reduction rates obtained using the new setup were higher compared to conventional thermogravimetric method. This difference was due to the time required to replace the inert gas with the reactant gas in the conventional method, which led to lower reduction rate at the initial stage. Carbon deposited on the surface of the pellets at relatively high gas flow rates and at low temperatures. The presence of pure iron and high carbon potential in the gas phase were the cause for carbon deposition. Study of partially reduced samples illustrated that the outer layer of pellet with high iron content thickened as reduction proceeded inside the pellet. Closure of micro-pores and formation of dense iron phase in this layer decelerated diffusion of reactant and product gases, and led to decrease of reduction rate at later stages of reaction. At lower temperatures, this effect was coupled with carbon deposition. Therefore, the reduction was seriously hindered.
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| 5. |
- Liu, Yu, et al.
(författare)
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Decarburization in an Electric Arc Furnace using Coupled Fluid dynamics and Thermodynamics
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A coupled method of Fluid dynamics and Thermodynamics, named as Multi-zone Reaction Model, was established to simulate the flow pattern with bottom oxygen injection in a 145t electric arc furnace. The simulated maximum hot spot temperature and decarburization rate in the refining phase were compared against the data measured in the industrial operation. Moreover, the physical modeling was carried out to study the effect of nozzle size on the flow characteristics in the reaction zone. The results show, under high flow rates, the effect of nozzle size on the flow field in the reaction zone of the plume area can be neglected. The decarburization rate and hot spot temperature predicted by the modeling are consistent with the industrial measurements. The maximum hot spot temperature gradually decreases during the refining phase. The oxygen flow rate has a significant influence on the decarburization rate, hot spot temperature and average steel temperature. In terms of combined injection of O2 and inert argon gas, for a certain O2 flow rate, the decarburization rate increases due to the efficient mass transfer of carbon in the molten steel. Furthermore, for the replacement of argon using CO2, it is demonstrated that as the ratio of CO2 mass fraction increases from 0% to 40%, the maximum hot spot temperature decrease with the value of 570K, and the increment rate of average steel temperature, and the decarburization rate in the molten steel decrease with the ratio of 68%, and 81%, respectively. The endothermic reaction of CO2 with the molten steel results in a temperature drop in the plume above the hot spot zone.
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| 6. |
- Liu, Yu, 1990-
(författare)
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Thermodynamics and Kinetics in Metallurgical Processes - with a Special Focus on Bubble Dynamics
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gas stirring is commonly used in the steelmaking processes to reinforce chemical reactions, kinetic transfer, and inclusion removal, etc. This dissertation concentrates on multiphase flows with gas bubbling to study fluid dynamics and thermodynamics in metallurgical processes. A study of bubble behavior has been carried out using a multiscale approach as follows: Prototype scale (macro) → Plume scale → Single bubble scale → Reaction scale (micro).Initially, previous works on physical modeling and mathematical modeling in relation to the gas bubbling in the ladle have been reviewed. From that, several aspects that can be improved were found:For physical modeling, such as mixing and homogenization in ladles, the general empirical rules have not been analyzed sufficiently;The mathematical models focusing on inclusion behaviors at the steel-slag interface need to be improved;The phenomena governing the transfer of elements, vacuum degassing, and the combination of fluid dynamics and thermodynamics, such as in desulfurization, need to be investigated further.The kinetics transfer with regards to temperature and element homogenization is one of the most extensive research fields in steel metallurgy. For the analysis on prototype scale, the optimal plug configuration has been studied for a 50t ladle. For stirring using bottom-blowing, a separation angle between dual plugs of 160 degree is mostly recommended, and the optimal dual-plug radial position is around 0.65R. Moreover, the influence of the tracer’s natural convection on its homogenization pattern cannot be neglected, especially for ‘soft bubbling’ conditions using low gas flow rates.Subsequently, in studies of the statistical behavior of gas bubbling in the plume, mathematical modeling using an Euler-Euler approach and an Euler-Lagrange approach have been compared. With respect to the bubble coalescence and breakup, the Euler-Lagrange approach is more accurate in predicting the flow pattern for gas injection using a porous plug. With regards to the effect of plug design on the statistical behavior of gas bubbling, gas injection using a slot plug promotes kinetic reactions close to the open eye due to the concentrated plume structure, and gas bubbling using a porous plug promotes a good inclusion removal because of the increased amount of bubbles.Focusing on single bubble behavior, under the same flow rate, as the top gauge pressure is reduced, the bubble diameter increases and the bubble generation frequency decreases. During the bubble ascent, a large bubble gradually reaches stable conditions by means of shedding several small bubbles. In a steel-argon system, under a flow rate in the range of 5.0(mL‧min-1)STP to 2000(mL‧min-1)STP, the bubble diameter is in the range of 6.0mm to 20.0mm. Under laminar conditions, the maximum bubble width is 65mm when the surrounding pressure is 0.2bar, and the steady bubble width is around 58mm under a pressure of 2.0bar.Finally, a coupling method, named Multi-zone Reaction Model, has been developed to predict the conditions in the EAF refining process. Using a combined injection of O2 and argon, and the same injected mass of O2, the decarburization rate increases due to an efficient kinetic mass transfer of carbon in the molten steel. Furthermore, using CO2 to replace argon, as the ratio of the CO2 content in the injection increases, the maximum hot spot temperature, the increment rate of average temperature, and the decarburization rate decrease dramatically.The research step from multiphase fluid dynamics to its coupling with high temperature thermodynamics is a large advancement in this study. Moreover, the research process using open source software to replace the commercial software is also an important technical route. This can help the transparent development of future modules for reacting flow in metallurgical processes.
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| 7. |
- Martinsson, Johan
(författare)
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A Study of the Behavior of Foaming Slag in Steelmaking
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis presents a fundamental study on some aspects regarding foaming slag. In today’s society, the requirements on environmental impact and energy consumption are increasing. It is essential for the steel industry to better understand the fundamentals of their processes to be able to develop both the process but also process control to reach the demands. In this work, the basic BOF furnace is the main focus, even though foaming slag may also occur in some electric arc furnaces. The BOF is a chaotic process with the purpose to decarburize and dephosphorize hot metal from the blast furnace. The foaming slag plays a profound role in the kinetics of the reactions, maintains the temperature in the furnace and protects the lining material of the furnace.The first part of the thesis includes a study of the structure of different foams and some viscosity measurements. Both room temperature and high temperature experiments are conducted. It is shown that the apparent viscosity of a foam is not only depending on the dynamic viscosity of the liquid phase and the gas fraction of the foam, but also the surface tension of the liquid and the bubbles size of the foam. The foam appears to show a shear thinning non-Newtonian behavior with apparent viscosities up to 5 times as high as for the pure liquid. The reason is found in the structure of the foams.The behavior of particles falling through foams generated from different sugar solutions is studied in the second part of the thesis. The particle behavior differs a lot depending on the size and density of the particle, and the viscosity and surface tension of the liquid phase. Some particles get stuck in the foam, some heavy particles fall through the foam crushing the bubbles in its path, and some particles fall slowly in a zick-zack pattern towards the bottom. The residence time is also measured, and a semi-empirical model is developed to describe the apparent velocity of the particles falling in a zick-zack pattern.The decarburization is the source of the foam in the furnace, and is studied in the third part of the thesis. Pig iron is dropped into liquid slag and the reaction rate is studied by quenching of samples at different times. Small droplets are decarburized faster than big droplets, and the incubation time of the reaction is found to play a big role in the decarburization process for different slag compositions.ivThe last part of the thesis is a comparison of lime dissolution in liquid versus foaming BOF slags. The controlling dissolution mechanism in liquid slag is the removal of interfacial layers of calcium silicates. In the foam on the other hand, the contact area between liquid slag and lime seem to be the controlling mechanism. In total, the rate seem to be similar in some liquid and foaming slag compositions while in others, the lime is dissociated into small pieces in the foaming slag due to the chaotic environment in the experiment.
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| 8. |
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| 9. |
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| 10. |
- Martinsson, Johan, et al.
(författare)
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The structure of foaming BOF-converter slag
- 2019
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Ingår i: Ironmaking & steelmaking. - : TAYLOR & FRANCIS LTD. - 0301-9233 .- 1743-2812. ; 46:8, s. 777-781
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Tidskriftsartikel (refereegranskat)abstract
- The structure of foaming synthetic BOF-converter slags was studied by freezing the foam and using ocular examination. The foams were generated by CO gas formed due to the reaction between FeO in the slag and carbon in the hot metal. The character of the foams varied a lot with slag composition. Slag with lower viscosity resulted in foams with small gas bubbles, while slag having high viscosity resulted in very big bubbles.
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