| 1. |
- Abdul Abas, Riad, et al.
(författare)
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Studies on Graphitisation of Blast Furnace Coke by X-ray Diffraction Analysis and Thermal Diffusivity Measurements
- 2005
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 77:11, s. 763-769
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Tidskriftsartikel (refereegranskat)abstract
- High temperature XRD and thermal diffusivity experiments were employed to investigate the degree of graphitisation in blast furnace coke. The experiments were conducted between room temperature and 1473 K. X-ray diffraction studies were carried out in order to monitor the degree of graphitisation in the coke samples from the same campaign. In these cases, the degree of graphitisation was followed by the changes in the vertical dimension. The degree of graphitisation was found to be dependent on temperature. On the other hand, the graphitisation at each temperature was instantaneous, even at as low a temperature as 973 K and no dependency on time could be noticed. The thermal diffusivities of the coke samples taken from deeper level of the experimental blast furnace were measured using the laser-flash technique. The results from these measurements showed that thermal diffusivities increased with the degree of graphitisation, which in turn, can be affected by the level in the blast furnace at which the coke sample was taken. The present results indicate that the degree of graphitisation as followed by X-ray diffraction analysis as well as thermal diffusivities can be used to trace the thermal history of coke. DSC measurements show that the heat capacity of the coke increases with temperature towards the heat capacity of graphite, which could be due to the increasing the graphitisation degree of the coke.
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| 2. |
- 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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| 3. |
- Brandberg, Jenny, et al.
(författare)
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Water capacity model of Al2O3-CaO-MgO-SiO2 quaternary slag system
- 2007
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 78:6, s. 460-464
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Tidskriftsartikel (refereegranskat)abstract
- The focus of the present work was to develop a water capacity model for the quaternary slag system Al2O3-CaO-MgO-SiO2. In the model, a silicate melt was considered to consist of two ion groupings, viz. cation grouping and oxygen ion. The water capacity of a melt is supposed to depend on the interactions between the cations in the presence of oxygen ions. These interactions were determined on the basis of the experimentally measured water solubility data. Only binary interactions were employed in the model. For the system CaO-SiO2, disagreement in the literature data was found. Since the interaction between Ca2+ and Si4+ would play an important role, experiments were carried out to determine the water capacities of some CaO-SiO2 slags. For this purpose a thermogravimetric method was employed. Iso-lines of water capacities at constant MgO contents were predicted by the model and compared with the experimental data from literature. The model calculations agreed well with the experimental results.
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| 4. |
- Eriksson, Robert, et al.
(författare)
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An experimental study of the velocity field during filling of an ingot mould
- 2003
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 74:7, s. 423-430
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Tidskriftsartikel (refereegranskat)abstract
- In the present study the velocity field in a 1:3 scale water model of a 4.2-tonne ingot mould was determined using Laser Doppler Anemometry (LDA). The velocity was measured in the horizontal and vertical directions at several different locations along the centre plane of the model. The effect of different volumetric flow rates and water temperatures was also investigated. The reproducibility of the measurements was found to be satisfactory, since the mean velocity at any measurement location had an average difference of around 10% between two fillings. The effect of different volumetric flow rates showed that while decreasing the flow rate, the mean velocity at the bottom turned from an upward direction to a downward direction. At the top of the model the difference between the mean velocities for the different flow rates was less pronounced. An influence of the temperature on the mean velocity could be observed. However, further studies are required to verify this result.
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| 5. |
- Fredriksson, Patrik, et al.
(författare)
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Thermodynamic activities of FeO in some binary FeO-Containing slags
- 2004
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:4, s. 240-246
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Tidskriftsartikel (refereegranskat)abstract
- In the present investigation, experimental measurements of the thermodynamic activities of iron oxide in the Al2O3-FeO, CaO-FeO and FeO-SiO2 systems were performed in the temperature range 1823-1873 K by using gas equilibration technique. The molten slag, kept in a Pt-crucible was brought to equilibrium with a gas mixture of known oxygen partial pressure. A part of the Fe from the FeO was reduced during the equilibration and got dissolved in the Pt phase. The samples were quenched after the required equilibration time and the slag phase as well as the platinum crucible was subjected to chemical analysis. The activities of FeO in the slag were calculated from the experimental data using thermodynamic information on the Fe-Pt binary metallic system generated and assessed earlier. The experimental results are compared with earlier thermodynamic studies of the slag systems. Reassessment with the KTH slag model is performed and the results are compared with other thermodynamic models, viz. F*A*C*T(TM) and Thermo-Calc(TM) respectively. The experimental activities predicted by the KTH slag model are in good agreement with the experimental data available in the literature. A general agreement between the various models is also observed.
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| 6. |
- Fredriksson, Patrik, et al.
(författare)
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Thermodynamic activities of FeO in some ternary FeO-containing slags
- 2004
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:6, s. 357-365
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Tidskriftsartikel (refereegranskat)abstract
- Thermodynamic data concerning FeO-containing slags is of importance in ladle refining of steel. With a view to generate a set of reliable and self-consistent thermodynamic data for these slags, experimental determination of the activities of iron oxide in the Al2O3-FeO-SiO2, CaO-FeO-SiO2 and FeO-MgO-SiO2 systems was carried out using the gas equilibration method involving CO-CO2-Ar gas mixtures in the temperature range 1823-1923 K. The slag samples kept in Pt crucibles were quenched after the equilibration and subjected to chemical analysis. The thermodynamic activities of FeO in the slags were calculated from the experimental data. The results are incorporated into a thermodynamic description of silicate melts developed in the present laboratory. The model is based on a Temkin-Lumsden approach and is able to compute the thermodynamics of higher order systems from the lower order ones. The model was updated with the present results and iso-activity contours of FeO in the three component systems are presented at 1873. The capacity of the model to predict the thermodynamic activites in four-, five-, and six-component slags is demonstrated in the case of steelmaking slags.
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| 7. |
- Persson, Mikael, et al.
(författare)
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A Thermodynamic Approach to a Density Model for Oxide Melts
- 2007
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 78:4, s. 290-298
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Tidskriftsartikel (refereegranskat)abstract
- In an attempt to estimate the densities of complex slags, a model based on the thermodynamics ofslags developed earlier by the present authors is extended to ternary and multi-component systemsin the present work. The molar volumes of ternary and higher order systems were derived from therelative integral molar enthalpies of mixing of the corresponding slags. The higher order of slagsystems has been predicted by using the parameters from the related binary sub-systems, whichhave been evaluated earlier. Comparisons of calculated results with experimental data on molarvolumes available in literature show a satisfying agreement for a number of systems, within the limitsof experimental uncertainties. The model presents a promising method to compute the molar volumeof slag systems where no experimental data is available using the abundance of thermodynamicdata available. The model would also enable the generation of density data for slags containingAl2O3, CaO, FeO, MgO, MnO, and SiO2 compatible with the corresponding thermodynamic data.
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| 8. |
- Persson, Mikael, et al.
(författare)
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Estimation of molar volumes of some binary slags from enthalpies of mixing
- 2007
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 0177-4832. ; 78:2, s. 102-108
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to interlink the thermo chemical and thermo physical properties of slags, the present work was undertaken to derive the molar volumes of complex slags from the enthalpies of mixing of the corresponding slags. As a first step, binary systems of the following oxides were investigated; Al2O3, CaO, FeO, MgO, MnO, and SiO2. An empirical correlation was derived between the enthalpies of mixing and molar volumes. A comparison of the computed results on the basis of the above relationship with the experimental data on molar volumes available in literature shows that the agreement between the calculated results and measured densities is satisfactory in the case of most of the binary systems, within the limits of experimentally uncertainties. The advantage of the present approach is that it would enable prediction of molar volumes of slags that are compatible with the thermodynamic data available.
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| 9. |
- Söder, Mats, et al.
(författare)
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Inclusion growth and removal in gas stirred ladles
- 2004
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:2, s. 128-138
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Tidskriftsartikel (refereegranskat)abstract
- A static modelling approach was used to study the growth and removal of inclusions during gas stirring in a ladle. A mathematical model of a gas-stirred ladle was used to predict the data necessary to calculate growth and removal of inclusions. Results indicated that inclusion growth resulting from laminar shear collisions is negligible in comparison with growth from turbulent and Stokes collisions. Furthermore, the need for a model describing inclusion flotation by spherical-cap bubbles was identified. Since the existing models presented in the literature are only valid for spherical bubbles, a model for the removal of inclusions by spherical-cap bubbles was developed. Inclusion removal to the slag, refractory and by bubble flotation was compared. The mechanism determined to be responsible for the removal of the majority of inclusions larger than 25 μm was Stokes flotation and for the majority of the smaller inclusions, bubble flotation by spherical-cap bubbles (assuming plane contact between the inclusion and the bubble).
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| 10. |
- Wu, Liushun, et al.
(författare)
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The effect of solid particles on liquid viscosity
- 2011
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 82:4, s. 388-397
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Tidskriftsartikel (refereegranskat)abstract
- The viscosities of solid-liquid mixtures were experimentally determined for silicon oil-paraffin system at room temperature and solid-liquid oxide mixture at steelmaking temperature. The use of oil-paraffin systems was to confirm the results of high temperature measurements, the experimental conditions being very difficult to control. The silicon oil- paraffin mixtures behaved Newtonian until the particle fraction reached 0.15. At this fraction, the mixture started deviate from Newtonian flow; though some average values could still be collected with very high uncertainty. Liquid-2CaO.SiO2 mixtures and liquid-MgO mixtures were studied at steelmaking temperature with carefully prepared particle fractions and well controlled conditions. Liquid-2CaO.SiO2 mixture behaved Newtonian even when the particle fraction reached 0.1. The results of both room temperature measurements and steelmaking temperature measurements were used to examine the applicability of the existing models. Einstein-Roscoe equation was found to be the only model applicably for the systems studied. No modification of the model parameter was found necessary, though the particles were not spherical.
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