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| 2. |
- Martinsson, Johan, et al.
(författare)
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A Semi-Empirical Model of Particle Velocity in Foam
- 2018
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 58:7, s. 1368-1370
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Tidskriftsartikel (refereegranskat)abstract
- A semi-empirical model was developed to predict the apparent velocity of particles falling through foams. Different foams were generated from liquids with different viscosities and surface tensions. Particles with different sizes and densities were dropped into the foam and average velocities were calculated. Based on the experimental work, the semi-empirical model was derived from an energy balance between buoyancy, drag and the energy needed for the particles to deform the bubbles in their path.
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| 3. |
- 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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| 4. |
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| 5. |
- Martinsson, Johan, et al.
(författare)
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Decarburization of Pig Iron in Synthetic BOF Converter Slag
- 2019
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Ingår i: ISIJ International. - : IRON STEEL INST JAPAN KEIDANREN KAIKAN. - 0915-1559 .- 1347-5460. ; 59:1, s. 46-50
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents a study on the decarburization of pig iron droplets in synthetic BOF slag. The effects of droplet size and slag composition were studied. The results show evidently that the decarburization is very fast in general. One gram of pig iron is mostly decarburized within one minute. The reaction is shown to be faster when many small droplets were employed instead of one big droplet with equal total mass. This is explained by the bigger interfacial area between the liquid slag and the pig iron of the many small particles. It is also interesting to see that the decarburizing reaction in the slag having lower dynamic viscosity and higher FeO activity is slower than in the slag with higher viscosity and lower FeO activity. The slower reaction could be explained by the longer incubation time in this slag.
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| 6. |
- Martinsson, Johan, et al.
(författare)
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Impact of Solid Particles and Liquid Droplets on Foams - Cold Model and High Temperature Experiments
- 2022
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 62:1, s. 104-111
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Tidskriftsartikel (refereegranskat)abstract
- In order to obtain a realistic view of the foam in metallurgical slag, high temperature experiments where the foaming heights of FeO-CaO-SiO2-MgO slags containing precipitated MgO center dot FeO particles were measured. The foaming height slightly increased when small amounts of particles were present in the slag, but decreased to half height already when approximately 8 vol% particles were present in the liquid phase of the foam. To help the understanding, the foaming heights of silicone oil and food oil containing liquid insoluble droplets and non-reacting particles were also studied at room temperature. In these experiments, insoluble oil droplets were found to stabilize the foam, increasing the foaming height, while the addition of water droplets or solid particles had very little effect on foaming height. In line with the literature, it is believed that the interfacial energy between the droplets or particles and the bulk liquid as well as the interfacial energy between the droplets or particles and gas plays an important role. When the interfacial energy between the different phases becomes too high, the foaming height decreases, while when it's low enough, the foaming height increases.
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| 7. |
- 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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| 8. |
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| 9. |
- Martinsson, Johan, et al.
(författare)
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Study on apparent viscosity of foaming slag – Cold model and high temperature experiments
- 2017
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Ingår i: Advances in Molten Slags, Fluxes, and Salts. - Cham : Springer International Publishing AG. - 9783319486253 ; , s. 431-438
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Konferensbidrag (refereegranskat)abstract
- The apparent viscosities of foaming silicon oil and foaming slag was measured. In both studies, the rotating cylinder method was used for the measurements. Additionally, the movement of particles in foaming silicon oil and the behavior of pig iron droplets in foaming slag was investigated. An increase of the apparent viscosity compared to the dynamic viscosity could be observed. The apparent viscosities decreased with increasing rotation speed of the spindle. The moving particles in the foaming silicon oil gave reasonable information regarding the behavior of particles and droplets in foam. This information are needed to get a better understanding of the behavior of iron droplets in foaming slag. After high temperature experiments, the pig iron droplets were collected and analyzed. Conclusions were made regarding mass transfer between foaming slag and iron droplets.
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