| 1. |
- Dahlin, Anders, et al.
(författare)
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Influence of ladle slag additions on BOF process performance
- 2012
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 378-385
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Tidskriftsartikel (refereegranskat)abstract
- A plant trial has been performed, with recycling of ladle slag to the LD converter at SSAB EMEA, Lulea, Sweden. The effect of ladle slag addition on the slag and steel composition, together with the slag weight, was investigated with sampling both during the blow and at blow end. The addition of ladle slag resulted in an increase in slag weight between 1 and 2 t throughout the blow and an increase of 3 wt-% in the slag Al2O3 content. This indicated that the ladle slag melted during the initial stages of the blow and enhanced the early slag formation. Lime additions were reduced with 3.5 kg t(-1) liquid steel without drawbacks on the phosphorus or sulphur refining. Heats with added ladle slag had an increase in blowing time with similar to 4% and an increased tendency for slopping. However, this can be handled by different lance and addition programmes.
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| 2. |
- Dahlin, Anders, et al.
(författare)
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Influence of ladle slag additions on BOF process under production conditions
- 2012
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 318-326
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Tidskriftsartikel (refereegranskat)abstract
- The influence of recycled ladle slag on the basic oxygen furnace (BOF) process under production conditions was investigated in plant trials. More specifically, 25 heats with ladle slag additions and 23 heats without ladle slag additions were studied. Both steel and slag samples were collected, from which the chemical compositions were determined. In addition, several process parameters were monitored. Overall, it was found that recirculation of ladle slag during normal production conditions works fine. On the positive side, it was seen that the steel quality concerning the phosphorus and sulphur contents of liquid steel has, in accordance with previous studies, not been affected by the ladle slag additions. Furthermore, no major differences in the slag composition occur when the recycling of ladle slag to BOF is performed. Finally, in comparison to previous studies, the increased tendency for slopping when adding ladle slag could be eliminated with a change in the lance schedule. However, on the negative side, it was seen that the addition of ladle slag leads to an increased blowing time due to lower iron ore additions. Moreover, the slag weight at tapping increased due to an increased weight of added slag formers.
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| 3. |
- Samuelsson, Peter, et al.
(författare)
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Use of Physical Modelling to Study How to Increase the Production Capacity by Implementing a Novel Oblong AOD Converter
- 2017
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Ingår i: Ironmaking and Steelmaking: Processes, Products and Applications. - 0301-9233.
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Tidskriftsartikel (refereegranskat)abstract
- There is no known example of an AOD converter with oblong cross sections in the literature. Changing the geometry of the converter vessel, from the traditional circular cross sections, to increase converter volume could potentially influence the performance of the converter and in particular the decarburisation rate. Due to physical limitations in an existing melt shop the only available way to increase the tapped weight and hence the productivity was to consider a modified converter cross section, namely an oblong cross section. A change in cross section could potentially influence the decarburisation performance and in the worst case counteract the intended increase in productivity. In order to study the feasibility of implementing an oblong converter, physical modelling was used to establish whether it would be suitable to change the AOD geometry from a circular cross section to a novel oblong cross section to increase the converter volume and thus the productivity. Specifically, the aim was to use physical modelling to study the fluid flow of the proposed converter configuration (geometry and number of tuyeres) and the potential influence on the decarburisation rate. Two water models linearly scaled down to a 1:4.6 dimension in comparison to a production converter were employed using water containing ???? and gas injected through six or eight tuyeres as fluids. In the model one tuyere was used for injection of ??2 gas, while air was injected through the remaining five or seven tuyeres. The reaction of ??2 and ???? (??2 + 2???? ⇄ ??&??3 + ?2?) was indirectly measured by detecting the pH value of the water in the model. The purpose of the model was to simulate the decarburisation part of the converter process as any prolongation of the decarburisation will defeat the purpose of increasing the productivity. The mixing time is considered to be a good indicator of the decarburisation as the kinetics will be diffusion controlled in the latter parts of the process. According to our experience, the thermodynamics of decarburisation will not be dependent on the converter shape. The following three converter figurations were studied: i) a circular converter with six tuyeres, ii) an oblong converter with six tuyeres, and iii) an oblong converter with eight tuyeres. The mixing time, defined as the time to reach 95% of the final ??2 concentration, can be used to evaluate the different converter configurations. The average ??2 concentrations based on several experiments, calculated based on pH measurements in the water, differed by less than 5% between the circular and oblong models after 165 s of injection of air and ??2. The results also showed that no difference in mixing time could be found when using 6 and 8 tuyeres, respectively in the oblong model. In fact, the ??2 concentrations in the oblong model differed by less than 2% after 165 s of injection of air and ??2 between six and eight tuyeres. Based on the findings, it has been observed that the influence of converter geometry on mixing time is small, it was concluded that decarburisation rate is likely to be the same irrespectively of converter geometry. Thus it is possible to construct an oblong converter to increase the productivity.
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| 4. |
- Akbarnejad, Shahin, et al.
(författare)
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Effect of Batch Dissimilarity on Permeability of Stacked Ceramic Foam Filters and Incompressible Fluid Flow : Experimental and Numerical Investigation
- 2022
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 12:6, s. 1001-
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Tidskriftsartikel (refereegranskat)abstract
- Ceramic foam filters (CFFs) are used to remove inclusions and/or solid particles from molten metal. In general, the molten metal poured on the top of a CFF should reach a certain height to form the pressure (metal head) required to prime the filter. For estimating the required metal head and obtaining the permeability coefficients of the CFFs, permeability experiments are essential. Recently, electromagnetic priming and filtration of molten aluminum with low and high grades of CFF, i.e., 30, 50 and 80 pore per inch (PPI) CFFs, have been introduced. Since then, there has been interest in exploring the possibility of obtaining further inclusion entrapment and aluminum refinement by using electromagnetic force to prime and filter with stacked CFFs. The successful execution of such trials requires a profound understanding concerning the permeability parameters of the stacked filters. Such data were deemed not to exist prior to this study. As a result, this study presents experimental findings of permeability measurements for stacks of three 30, three 50 and three 80 PPI commercial alumina CFFs from different industrial batches and compares the findings to numerically modelled data as well as previous research works. Both experimental and numerical findings showed a good agreement with previous results. The deviation between the experimentally and numerically obtained data lies in the range of 0.4 to 6.3%.
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| 5. |
- Andersson, Margareta, et al.
(författare)
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Some Aspects on Grain Refining Additions with Focus on Clogging during Casting
- 2006
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 46:6, s. 814-823
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Tidskriftsartikel (refereegranskat)abstract
- Some ideas of how to study optimum conditions for implementation of grain refining in liquid steel processing with focus on how to avoid clogging are discussed. It is assumed that the inclusions most beneficial for grain refining are known from studies by physical metallurgists. The challenge for a process metallurgist is how to provide a homogeneous distribution of grain refiners at the onset of solidification. Four different ways of providing information to succeed with this are discussed. Thermodynamic modeling can be used to predict what additions to make to create potential grain refiners, if relevant thermodynamic data is available. Mathematical fluid-flow modeling can be used to study where to add potential grain refiners. It is discussed that the tundish is the most appropriate reactor to add grain refiners, since enough time is given to a complete mixing of the grain refiner into the steel before the steel enters the mold. By using the scanning laser microscopy technique it is possible to study which potential grain refiners has the lowest attraction forces between each other. This is important in order to minimise growth of inclusions when they collide during transport in the tundish, which can lead to the formation of larger inclusions that do not serve as useful grain refiners. Finally, it is suggested that laboratory experiments are carried out in order to study the tendency for nozzle clogging, before the use of grain refiners is tested in industrial scale.
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| 6. |
- Andersson, Nils, et al.
(författare)
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Fundamental decarburisation model of AOD process
- 2013
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:5, s. 390-397
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Tidskriftsartikel (refereegranskat)abstract
- A mathematical fluid flow model of gas injection in an argon–oxygen decarburisation (AOD) converter process has been coupled with a high temperature thermodynamic model. The current model is a further enhancement of an earlier developed three-dimensional, three-phase model, to also include some thermodynamics of the process. The model is based on fundamental transport equations and includes separate solutions for the steel, slag and the gas phases and their coupling by friction. The AOD model has been used to predict the first injection stage of decarburisation in an AOD converter. The predictions have been found to agree well with the corresponding results from an industrial process control model. One of the important observations from the simulations was that large concentration gradients of carbon exist in the AOD at an early stage and as the first injection step approaching its end the carbon gradients diminish. Also, the results show, in accordance with theory, that the local decarburisation rate is decreased at elevated pressures.
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| 7. |
- Andersson, Nils, et al.
(författare)
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Investigating the effectof slag on decarburization in an AOD converter using a fundamental model
- 2013
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 84:2, s. 169-177
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Tidskriftsartikel (refereegranskat)abstract
- A high-temperature thermodynamics model has been coupled with a fundamental mathematical model describing the fluid flow, where boundary conditions were chosen based on data for an industrial AOD converter. Using this model, the effect of both slag phases (a liquid part and a solid part) on the decarburization was studied. More specifically, the separation of chromium oxide to liquid slag as well as the effect of the amount of rigid top slag (solid)on the decarburization was investigated. The liquid slag was considered with respect to the uptake of chromium oxide, while the rigid top slag was only considered with respect to the increase of the metallostatic pressure in the steel melt. The results suggest that separation of chromium oxide to liquid slag results in a decreased decarburization rate. The same conclusion can be drawn with respect to the amount of solid top slag.
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| 8. |
- Andersson, Nils, et al.
(författare)
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Preliminary investigation of influence of temperature on decarburisation using fundamental AOD model
- 2013
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:7, s. 551-558
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Tidskriftsartikel (refereegranskat)abstract
- A high temperature thermodynamics model was earlier coupled with a fundamental mathematical model describing the fluid flow in an argon–oxygen decarburisation (AOD) converter and was initially validated for an idealised temperature description. More specifically, a linear average temperature relation was used such that the temperature would be isolated from other effects such as reactions and mixing. Thereafter, the effect of the starting temperature on the decarburisation was studied. The purpose is to provide some initial knowledge about how temperature affects the decarburisation in an AOD converter. The results suggest that the thermodynamic limit for carbon concentration after reaching the carbon removal efficiency (CRE) maxima is vertically translated downwards at higher temperatures. Furthermore, when plotting the mass ratio between CO and CO2, there is an indication of a point that may relate to a CRE maximum.
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| 9. |
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| 10. |
- Andersson, Nils Å. I., et al.
(författare)
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An in-Depth Model-Based Analysis of Decarburization in the AOD Process
- 2012
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 83:11, s. 1039-1052
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Tidskriftsartikel (refereegranskat)abstract
- A previously reported flow and reaction model for an argon-oxygen decarburization converter was extended to also include a thermodynamic description. An in-depth study of the model results has been conducted to answer how concentrations of elements and species in the converter at different locations change with time. This may contribute to the understanding of the mechanisms of the refining procedure in the argon-oxygen decarburization process. The refining procedure includes several step-wise changes of an injected gas composition to higher and higher inert gas ratio, called step changes. A step change leads to a decreased partial pressure of carbon monoxide and maintains the decarburization at a higher efficiency. The results shows early and late concentration profiles for the first injection step and suggests a way to determine when a step change should be made. Moreover, the step change could be determined by calculating the carbon concentration profiles and deciding when the carbon concentration gradients start to diminish.
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