| 1. |
- Andersson, Annika, et al.
(författare)
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A study of some elemental distributions between slag and hot metal during tapping of the blast furnace
- 2004
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:5, s. 294-301
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the distribution of elements between slag and hot metal from a blast furnace through calculation of distribution coefficients from actual production data. First, samples of slag and hot metal tapped from a commercial blast furnace were taken continually at 10-minute intervals for a production period of 68 hours. Distribution coefficients of manganese, silicon, sulphur and vanadium were then calculated from the results of the sample analyses. A major conclusion drawn from examination of the results was that the behaviour of the studied elements was as could be expected when approaching the equilibrium reactions from thermodynamic theory. The distributions of the elements in the slag-metal system showed clear tendencies which did not appear to be influenced by the operational conditions of the furnace. For example, for manganese, vanadium and sulphur, it was found that a higher basicity led to a decreased distribution coefficient L-Mn and L-V, but an increased L-S, which is according to theory. Another observed relationship was that slag basicity increased with an increased carbon content in the hot metal, which indicated that SiO2 was reduced to [Si] when the oxygen potential decreased. Furthermore, it was found that sulphur and silica behaviour likened that of acidic slag components, while the manganese oxide and vanadium oxide behaviour was similar to that of basic slag components.
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| 2. |
- Andersson, A. J., et al.
(författare)
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Use of an optimisation model for the burden calculation for the blast furnace process
- 2004
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 33:3, s. 172-182
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Tidskriftsartikel (refereegranskat)abstract
- The aim of a burden calculation in the blast furnace process is to compute the amounts of burden materials to be charged for obtaining desired hot-metal and slag composition. Burden calculations are normally based on trial-and-error instead of optimisation. In this study, the use of an optimisation model for a typical blast furnace operation is presented. The yield factors of some components, such as Mn, Si, S, P and V, used in the model have been determined. The more common distribution coefficients have also been studied. Both the yield factor and distribution coefficient values were generally good and showed stable behaviour for repeated periods under similar operational conditions. In this study, the model was found to be an excellent tool for determining burden material amounts and hot-metal and slag compositions for a blast furnace under steady and normal operation conditions. Using an optimising burden calculation model is time efficient, because it demands only 1 calculation procedure instead of a couple calculations as in the case with a trial-and-error method.
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| 3. |
- Andersson, Annika J., et al.
(författare)
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Variation in hot metal and stag composition during tapping of blast furnace
- 2004
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 31:3, s. 216-226
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Tidskriftsartikel (refereegranskat)abstract
- To determine the quality of the hot metal and the thermal conditions inside the blast furnace, the composition of the hot metal and slag must be known. Obtaining representative metal and slag samples during tapping is thus highly important to blast furnace operation. The study covered in the present report focused on hot metal and slag composition variation during tapping from a commercial blast furnace. From the results, optimal sampling time points for obtaining elemental concentrations that can be taken as representative for the whole tapping sequence were identified. It was furthermore concluded, that the reliability of hot metal composition data is significantly improved by averaging elemental concentrations determined from two samples, each taken at a particular time point. One sampling, however, was found to be adequate for slag. Results from the study also showed a fairly strong correlation between amounts of silicon and carbon, sulphur and carbon, and silicon and sulphur in the hot metal, while a weaker correlation between hot metal temperature and each of these elements was observed.
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| 4. |
- Almcrantz, M., et al.
(författare)
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Determination of inclusion characteristics in the Asea-SKF process using the modified spark-induced OES technique as a complement in studying the influence of top slag composition
- 2005
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 76:9, s. 624-634
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Tidskriftsartikel (refereegranskat)abstract
- The spark-induced modified optical emission spectroscopy (OES) technique developed by Ovako Steel makes it possible to rapidly determine inclusion characteristics in steel samples. In earlier investigations using the modified spark-induced OES technique for steel samples taken from billets, predicted oxygen contents agreed well with results from conventional melt extraction analyses. In this investigation, samples taken during ladle treatment in an ASEA-SKF ladle furnace were analysed using the modified OES technique. When comparing the results with inclusion characteristics determined by conventional analysis, similar trends were found. Plant trials were also carried out where three different top slag compositions were used. The purpose was to evaluate if the modified OES technique can be used to study the effect of changes in the refining operation on inclusion characteristics. Results indicated that the modified OES technique could be used to determine the effect of a changed slag composition on the inclusion characteristics in the steel. Since the modified OES method provides rapid feedback of inclusion characteristics, it has the potential of being used for faster optimisation of ladle refining operations.
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| 5. |
- Andersson, Margareta A. T., et al.
(författare)
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A thermodynamic and kinetic model of reoxidation and desulphurisation in the ladle furnace
- 2000
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 40:11, s. 1080-1088
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Tidskriftsartikel (refereegranskat)abstract
- A thermodynamic and kinetic model of reoxidation and desulphurisation in the ladle furnace has been developed by using a two-dimensional fluid-flow model combined with equations expressing the thermodynamics of reoxidation and desulphurisation. More specifically ladle vacuum treatment of a gas-stirred ladle has been simulated. In order to describe the activities of the oxide components of the slag, expressions by Ohta and Suito(1)) were adopted. The thermodynamic model describes the slag/metal equilibria between Al, Si, O, Mn and S in the molten steel and Al2O3, SiO2, FeO, MnO and S in the slag. A fluid dynamic model that considers the slag, steel and argon phases derives the kinetics. Results from an isothermal calculation have been heuristically compared with industrial plant data and they show good agreement. The model results have also revealed that the reduction of silica plays a part in aluminium loss during ladle treatment.
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| 6. |
- Andersson, Margareta A. T., et al.
(författare)
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Optimisation of ladle slag composition by application of sulphide capacity model
- 2000
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 27:4, s. 286-293
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Tidskriftsartikel (refereegranskat)abstract
- The sulphur distribution ratio for ladle slags at Ovako Steel AB has been determined by calculating the sulphide capacity using the Royal Institute of Technology (KTH) model and the alumina activity via an empirical expression suggested by Ohta and Suite, and by using the well established theories for sulphur refining. A parameter study was carried out based on plant data from a previous study on desulphurisation, The effect of carbon and aluminium in the steel, the temperature of the steel, and alumina and lime in the slag on the sulphur distribution ratio was investigated, it was shown that the Al2O3/CaO ratio had the largest influence on the conditions studied, and that when it increased the sulphur distribution ratio decreased. Based on these results, new plant trials were carried out, in which the alumina content in the slag was changed. The calculated sulphur distribution ratios for these trials were found to be in good agreement with experimentally determined sulphur distribution ratios. It is concluded that the present approach can be used to optimise multicomponent ladle slags with respect to sulphur refining. I&S/1493.
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| 7. |
- Andersson, Margareta A.T., et al.
(författare)
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Slag-metal reactions during ladle treatment with focus on desulphurisation
- 2002
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 29:3, s. 224-232
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Tidskriftsartikel (refereegranskat)abstract
- Within several cooperative projects, KTH (Royal Institute of Technology), Ovako Steel AB, and MEFOS have investigated the desulphurisation of bearing steel during vacuum degassing. The work includes thermodynamic calculations of the slag-metal equilibrium, CFD modelling of slag-metal reactions, and plant trials. Results from the various studies are presented and discussed in this paper. Models for predicting slag properties (sulphide capacity, viscosity, and oxide activities) in liquid slags as functions of slag composition and temperature have been used for the calculation of data which have been employed in static and dynamic modelling of sulphur refining. The results from static modelling show that the method allows fast and easy evaluation of the theoretical desulphurisation conditions during degassing at Ovako Steel AB, as well as theoretical determination of the parameters that have the greatest influence on the equilibrium sulphur distribution. The conclusion from dynamic modelling is that the vacuum degassing operation can be described dynamically with the present knowledge of sulphide capacity, sulphur distribution, viscosity, and oxide activities of ladle slags if this knowledge is combined with fluid flow modelling to derive the overall kinetics. The presented model approaches have been found useful in understanding the sulphur refining process at Ovako Steel AB. The dynamic modelling concept is also believed to have potential for dynamic descriptions of other slag-metal reactions in steelmaking.
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| 8. |
- Andersson, Margareta A.T., et al.
(författare)
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The influence of different calcium-based additions on desulphurisation and inclusion characteristics
- 2001
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 30:3, s. 127-135
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Tidskriftsartikel (refereegranskat)abstract
- The size, distribution, and composition of inclusions during the desulphurisation and deoxidation steps were studied in laboratory experiments. 3 different calcium-based desulphurisation mixtures were used. The number of inclusions and composition of inclusions were then determined using optical microscopy and scanning electron microscopy, respectively. The results show that 2 of the 3 proposed desulphurisation mixtures managed to render lower and roughly equivalent inclusion counts. The results also show that the composition of the inclusions in all 3 samples varied from the beginning to the end of the desulphurisation process. A desulphurisation mixture consisting of Al, CaO, CaCO3 and CaSi produced the overall best results with respect to desulphurisation and inclusion characteristics.
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| 9. |
- Doostmohammadi, Hamid, et al.
(författare)
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Effect of EAF Slag Carryover on Slag-metal Equilibrium Calculations for Ladle Degassing Process
- 2009
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Ingår i: EPD CONGRESS 2009, PROCEEDINGS. - 9780873397322 ; , s. 695-702
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Konferensbidrag (refereegranskat)abstract
- During the tapping of liquid steel from Electric Arc Furnace (EAF), some slag is carried over into the ladle. High levels of FeO and MnO in slag carryover increase the oxygen activity in steel melt leading to oxide inclusion formation during the ladle treatment. The demand on cleaner steels requires minimization of carryover slag. In this work, the effect of EAF slag carryover on ladle slag-steel equilibrium calculations for a hot working tool steel was studied. Steel and slag sampling were done in Uddeholm Tooling AB in Sweden. XRF and OES techniques were used to determine chemical composition of samples. The quantity of slag carryover was calculated based on a mass balance followed by thermodynamic calculations on metal-slag equilibrium using Thermo-Calc software. The agreement between predictions and experimentally determined compositions was good. This leads to the development of a prediction method for optimizing the production of other tool steel grades.
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| 10. |
- Ekengard, J., et al.
(författare)
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Distribution of metal droplets in top slags during ladle treatment
- 2008
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 35:8, s. 575-588
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Tidskriftsartikel (refereegranskat)abstract
- The investigation focused on the mixing of the metal and slag phases during ladle refining from the point of tapping the EAF to casting. Steel droplet distributions were determined for slag samples taken at different stages in the ladle refining process at two different steel plants in Sweden. The droplet distributions were determined using light optical microscopy and classification according to the standard SS111116. Sample analysis results showed the slag samples taken before vacuum degassing to contain the greatest concentration of steel droplets. The total interfacial area between the steel droplets and slag was determined to be 3-14 times larger than the projected flat interfacial area between the steel and slag. The effects of slag viscosity and reactions between steel and slag on metal droplet formation in slag were also considered.
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| 11. |
- Ekengard, Johan, et al.
(författare)
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Theoretical study of equilibrium reactions between metal droplets and slag
- 2007
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Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 78:2, s. 109-116
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Tidskriftsartikel (refereegranskat)abstract
- The dispersion of metal droplets in slag was investigated through analysis of slag samples taken during ladle refining at Scana Steel in Bjorneborg, Sweden. The chemical composition of steel droplets found in the ladle slag was determined for five industrial-scale heats. Possible reactions occurring between the steel droplets and slag were identified, as were differences in steel-droplet and steel-bulk composition. Three different slag models were used to calculate the activities of oxide components (Al2O3 and SiO2) in the slag. These results were then used in the dilute-solution model, whereby oxygen activities in the steel droplets were calculated and compared with measured oxygen activities in the steel bulk. Significant differences were found in the comparison of both the calculated and measured oxygen activities and the steel bulk and droplet compositions.
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| 12. |
- Gustavsson, Joel, et al.
(författare)
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A thermodynamic study of silicon containing gas around a blast furnace raceway
- 2005
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 45:5, s. 662-668
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium conditions for silicon transfer from ash to the liquid metal phase via SiO gas have been discussed by several authors. However, no published calculations have been found using the most modern thermodynamic models available. Since there are major differences in the results of calculations using different thermodynamic models and the models are continuously being improved, new equilibrium calculations on SiO and SiS gas formation have been performed using the recently developed models. Different ingoing compositions of coke ash, coal powder ash and blast air were used in the calculations. The compositions chosen represent blast furnace no. 3 at SSAB in Lulea, Sweden. Temperature was found to be the major factor influencing the equilibrium silicon level in the gas phase. At low temperatures (below 1 600 degrees C the total gas pressure was also seen to influence the silicon content in the gas phase. The main reason for this is that below 1 600 degrees C, the amount of liquid slag at equilibrium increases with the total gas pressure. Liquid slag contains large amounts of silica that then can not be found in the gas phase. Higher carbon activity is usually expected to result in higher SiO gas levels in the blast furnace. The equilibrium calculations show that increased carbon activity increases the amount of silicon in the gas phase at temperatures up to about 1 600 degrees C, but that at higher temperatures SiC is formed that decreases the equilibrium silicon level in the gas phase.
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| 13. |
- Gustavsson, Joel, et al.
(författare)
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Comparison of calculated equilibrium and operation data for blast furnace with focus on silicon
- 2009
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 36:5, s. 341-353
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of reactions involving blast furnace hot metal, slag and gas at equilibrium was carried out. Performed calculations were based on estimated total gas pressures, measured temperatures and hot metal and slag compositions. Calculated element contents of liquid phases were found to be very similar to their corresponding values determined through measurement when formation of the gas phase was suppressed. This resulted in higher equilibrium CO partial pressures compared to the measured total gas pressure in the bustle ring. When only equilibrium conditions were considered, the predicted amount of silicon was much higher than the measured. A comparison of activity coefficients of elements in the hot metal using different calculation models was also carried out. Two different models based on dilute solutions were compared with the TCFe3 database developed for the software Thermo-Calc, which can handle higher alloying concentrations. Considerably different calculation results were found among the different models studied.
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| 14. |
- Gustavsson, J., et al.
(författare)
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Effect of selected model parameters on predicted RAFT data
- 2002
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 31:5, s. 328-341
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Tidskriftsartikel (refereegranskat)abstract
- A new raceway adiabatic flame temperature (RAFT) model has been developed where the effect of injected BOF slag has been considered. A parameter study was performed to evaluate the influence of (i) coke temperature factor, (ii) degree of silica reduction, (iii) coal powder burning degree, (iv) reduction degree of some components in injected BOF slag when leaving raceway, (v) enthalpy of coke burning and (vi) Cp value of coke. The coke burning enthalpy was found to have the largest influence on the absolute value of RAFT. In Swedish blast furnaces, the RAFT is usually kept relatively constant by adjusting the oxygen content in the blast. Therefore, the exchange ratios between the oxygen content in blast and the injected material to retain RAFT were predicted. The burning degree of coal powder was found to have the largest influence when coal powder was evaluated. Silica and silicon carbide reduction was found to have the largest influence when a change of BOF slag rate was evaluated.
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| 15. |
- Steneholm, Karin, et al.
(författare)
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Change of inclusion characteristics during vacuum degassing of tool steel
- 2006
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Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 77:6, s. 392-400
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Tidskriftsartikel (refereegranskat)abstract
- The inclusion characteristics were studied during vacuum degassing by interrupting the operation at five different times after the start of operation. Slag and steel samples were collected and thereafter assessed with respect to steel and slag composition, total oxygen content, size distribution of inclusions and chemical composition of inclusions. The main conclusion is that the number of inclusions in the different size classes as well as the total oxygen content seem to reach a minimum value after around ten minutes of vacuum degassing. Furthermore, it seems to be a consistent trend that, during vacuum degassing, the top slag influences the inclusion composition.
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| 16. |
- Steneholm, Karin, et al.
(författare)
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Effect of top slag composition on inclusion characteristics during vacuum degassing of tool steel
- 2007
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Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 78:7, s. 522-530
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Tidskriftsartikel (refereegranskat)abstract
- The focus of the study was to investigate the effect of the chemical composition of the top slag on the inclusion chemical composition during vacuum treatment of a plastic mould tool steel. Sampling was done before and after vacuum degassing. The chemical composition of the inclusions was determined by using SEM combined with EDX. The results showed that several inclusion compositions were found before vacuum degassing, while only one main composition of inclusions was present after vacuum degassing. Furthermore, the composition of the top slag was found to have a great influence on the composition of the inclusions found in samples taken after vacuum degassing. The present study also shows that the vacuum degassing effectively reduces the number of inclusions in steel. Finally, the thermodynamic calculations of the activities using Wagner's equation were found to predict a lower oxygen activity value than the calculations made using the Thermo-Calc software.
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| 17. |
- Sterneland, J., et al.
(författare)
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Comparison of iron ore reduction in experimental blast furnace and laboratory scale simulation of blast furnace process
- 2003
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 30:4, s. 313-327
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Tidskriftsartikel (refereegranskat)abstract
- The reduction of iron ore pellets in an experimental blast furnace has been surveyed by dissection of the blast furnace. Results of the dissection, as well as some results of measurements taken in the blast furnace interior during operation, have been compared with those of previously conducted laboratory reduction, softening and melting tests using the same type of pellets. The aim of the work was to compare laboratory testing with results from an experimental blast furnace. The high temperature phenomena occurring when reducing olivine iron ore pellets, with limited softening and a short temperature range of the melting process resulting in a thin cohesive zone, were found to be the same in laboratory tests and in the experimental blast furnace. The reduction process down through the burden of the experimental blast furnace, however, was not identical to that in the reduction, softening and melting experiments. The differences obtained were found to arise from different reducing conditions. Therefore, it was concluded that simulation of the reduction occurring in the blast furnace can be conducteded on a laboratory scale, provided that the experimental conditions are carefully chosen for the specific blast furnace process to be simulated. Information about the internal state of the blast furnace can be obtained from the experimental blast furnace.
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