| 1. |
- Dahlin, Anders, et al.
(author)
-
Influence of ladle slag additions on BOF process performance
- 2012
-
In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 378-385
-
Journal article (peer-reviewed)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.
(author)
-
Influence of ladle slag additions on BOF process under production conditions
- 2012
-
In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 318-326
-
Journal article (peer-reviewed)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. |
- Andersson, Nils, et al.
(author)
-
Fundamental decarburisation model of AOD process
- 2013
-
In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:5, s. 390-397
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Journal article (peer-reviewed)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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| 4. |
- Andersson, Nils, et al.
(author)
-
Investigating the effectof slag on decarburization in an AOD converter using a fundamental model
- 2013
-
In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 84:2, s. 169-177
-
Journal article (peer-reviewed)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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| 5. |
- Andersson, Nils, et al.
(author)
-
Preliminary investigation of influence of temperature on decarburisation using fundamental AOD model
- 2013
-
In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:7, s. 551-558
-
Journal article (peer-reviewed)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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| 6. |
- Andersson, Nils Å. I., et al.
(author)
-
An in-Depth Model-Based Analysis of Decarburization in the AOD Process
- 2012
-
In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 83:11, s. 1039-1052
-
Journal article (peer-reviewed)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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| 7. |
- Ersson, Mikael, et al.
(author)
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Dynamic modelling of steel, slag and gas during initial blowing in a top-blown converter
- 2011
-
In: Steel Grips - Journal of Steel and Related Materials. - 1611-4442 .- 1866-8453. ; :9, s. 41-47
-
Journal article (peer-reviewed)abstract
- A coupling between computational fluid dynamics (CFD) and thermodynamics has recently been done. In the current model improvement, a more realistic model was developed, where the numbers of gas species and slag phases were increased. For each simulation the transport of momentum, energy and mass of species as well as the thermodynamic equilibrium in each cell containing at least two phases was treated. Read how this calculation procedure can handle dynamic simulations of interaction between an oxygen gas jet, a melt and a slag. How is the agreement between the predicted rate of decarburization and experimental data? Which findings were achieved from the simulation of four cases varying the temperature, the dissolved carbon content and the dissolved oxygen content?
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| 8. |
- Gauffin, Alicia, et al.
(author)
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KTH Steel Scrap Model : Iron and Steel Flow in the Swedish Society 1889–2010
- 2013
-
In: Journal for Manufacturing Science and Production. - : Walter de Gruyter GmbH. - 2191-0375 .- 2191-4184. ; 13:1/2, s. 47-54
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Journal article (peer-reviewed)abstract
- KTH Steel Scrap Model calculates material flows of iron and steel in the Swedish society based on statistics, mass balance and mass flow analysis and industry knowledge. The material flows of iron and steel were calculated for external scrap consumption, internal scrap, domestic steel scrap arising and net flow of iron and steel into the Swedish society. Model output on external steel scrap consumption and domestic steel scrap arising was compared to an earlier analysis done by Jernkontoret for the timeline 1980–2009. The results show that mass balance calculations are area wise corresponding to consumption figures based on trade statistics. In addition the difference in trend is assumed to be mainly due to stocking effect. Furthermore it is shown that mass balance and mass flow models could be used as a tool to calculate apparent scrap consumption based on crude steel production figures by process type.
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| 9. |
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| 10. |
- Hallgren, Line, et al.
(author)
-
A First Attempt to Implement a Swirl Blade in Production of Ingots
- 2010
-
In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:12, s. 1763-1769
-
Journal article (peer-reviewed)abstract
- Plant trials were carried out to test if it would be possible to place a ceramic swirl blade in the runner channel during filling of ingots The initial experiments showed that no production disturbances were found More specifically no problems with unusual refractory wear or cracks in the refractory were found Thus it was concluded that the use of swirl blade has a potential in the future to be used to influence the initial filling conditions Also mathematical modeling was done in order to illustrate how it was possible to improve the layout of the runner system in order to increase the potential for use of swirl for the current plant conditions The results showed that the meniscus was not dampened as much when the swirl blade is positioned in a horizontal direction in the runner channel compared to the results of a previous physical modeling study where the swirl blade was placed in a vertical direction just before the steel entered the mold However if a horizontally positioned swirl blade is used in combination with an inlet with an angle of 15 degrees the hump height at the initial filling stage can be lowered from 100 to 58 mm compared to a case without a swirl blade This illustrates the potential to apply mold powder closer to the bottom without risking reoxidation due to reactions with steel and mold powder
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| 11. |
- Hallgren, Line, 1978-
(author)
-
A Study of the Initial Mould Filling during Up-hill Ingot Casting
- 2012
-
Doctoral thesis (other academic/artistic)abstract
- The fluid flow in the mould during up-hill teeming is of great importance for the quality of the cast ingot and thereby the quality of the final steel products. At the early stage of the filling of an up-hill teeming mould, liquid steel flows with a high velocity from the runner into the mould. The resulting turbulence on the meniscus can lead to entrainment of mould flux. The entrained mould flux might subsequently end up as defects in the final product. It is therefore very important to get a less turbulent and more stable inlet flow in the entrance region of the mould, to minimize the interactions between the steel and the mould flux. It has been acknowledged recently that a swirling motion, induced using a helix shaped swirl blade in the submerged entry nozzle, is remarkably effective to control the fluid flow pattern in both the slab and billet type continuous casting moulds. The focus in this thesis is the effect of a swirling flow, generated through a helix shaped swirl blade inserted into the runner system of the up-hill casting system, as a new method of reducing the deformation of the rising surface and the unevenness of the flow during filling of the up-hill teeming mould. The study covers a theoretical part, including mathematical modelling and water modelling experiments. Moreover, a part with some novel plant trials to test the swirling technology at the steel plants of Ovako bar in Hofors and Scana steel in Björneborg. The swirl blade has two features: (1) to generate a swirling flow in the entrance nozzle and (2) to suppress the uneven flow developed after flowing through a bend. Water modelling was used to assert the effect of the swirl blade on rectifying of tangential and axial velocities in the filling tube for the up-hill teeming and also to verify the results from the numerical calculations. The effect of swirl in combination with a diverged nozzle was also investigated in a similar way, i. e. with water model trials and numerical calculations. The earlier studies, using water as a fluid, have shown that the placement of a swirl blade in the vertical part of the runner channel, at the entrance to the mould, will be beneficial for a calm initial filling of the ingot during casting. Later, the plant trials were carried out to test if it would be possible to place a ceramic swirl blade in the runner channel during filling of ingots and to investigate the effect of a widening of the entry nozzle. Because of constrains of the current design of the runner systems at the steel plants it was not possible to place the swirl blade at the entrance. Instead, the swirl blade was placed in the horizontal part of the runner system. The initial experiments with swirl blade in the runner showed that no production disturbances were found. More specifically, no problems with unusual refractory wear or cracks in the refractory were found. Also, the mould powder consumption was found to decrease when using the swirl blade in combination with an inlet with a 6° diverged nozzle. Thus, it was concluded that the use of swirl blade has a potential in the future to be used to influence the initial filling conditions in a positive way. In addition to the plant trials with swirl blade, separate trials of changing the inlet angle from 1.7° to 6° or 10° showed that the widened inlet area resulted in a decrease in mould powder consumption. However, the decrease was not to the same extent as for the case with swirl blade.
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| 12. |
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| 13. |
- Kasedde, Hillary, et al.
(author)
-
A State of the Art Paper on Improving Salt Extraction from Lake Katwe Raw Materials In Uganda
- 2012
-
Reports (other academic/artistic)abstract
- The characteristics of Katwe salt lake are briefly discussed. The lake is the largest of the eight saline lakes in the Katwe-Kikorongo volcanic field and is a major source of salt production in Uganda. Today, salt production at the lake is carried out using traditional and artisanal mining methods. Attempts to mechanize the production of domestic and commercial grade salt at the lake were unsuccessful due to the use of a wrong technology. In this paper, the most common available technologies for salt extraction from brine are described. These are divided into four broad categories, namely thermal, membrane, chemical and hybrid processes. A review of the state of the art, previous research and developments in these technologies is presented. A detailed analysis of the processes used was done based on studies reported in the literature. From the analysis, it was observed that thermal salt production processes, especially distillation and solar evaporation have the highest share in installed capacities worldwide. Membrane technologies such as Electro-dialysis, Reverse Osmosis and chemical technologies have not found wide application in the commercial salt industry. Electro-dialysis and Reverse Osmosis have been used mainly as pre-concentration processes for subsequent thermal processes. Prospects for application of hybrid systems for salt production through integration of thermal desalting processes should be investigated for better performance efficiencies and recoveries at the salt lake.
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| 14. |
- Kasedde, Hillary, et al.
(author)
-
Characterization of brines and evaporites of Lake Katwe, Uganda
- 2014
-
In: Journal of African Earth Sciences. - : Elsevier BV. - 0899-5362 .- 1464-343X. ; 91, s. 55-65
-
Journal article (peer-reviewed)abstract
- Lake Katwe brines and evaporites were investigated to determine their chemical, mineralogical and morphological composition. 30 brine samples and 3 solid salt samples (evaporites) were collected from different locations of the lake deposit. Several analytical techniques were used to determine the chemical composition of the samples including Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), Inductively Coupled Plasma-Sector Field Mass Spectrometry (ICP-SFMS), ion chromatography, and potentiometric titration. The mineralogical composition and morphology of the evaporites was determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Physical parameters of the lake brines such as density, electrical conductivity, pH, and salinity were also studied. The results show that the lake brines are highly alkaline and rich in Na+, Cl-, CO32-, SO42-, and HCO3- with lesser amounts of K+, Mg2+, Ca2+, Br-, and F- ions. The brines show an intermediate transition between Na-Cl and Na-HCO3 water types. Among the trace metals, the lake brines were found to be enriched in B, I, Sr, Fe, Mo, Ba, and Mn. The solid salts are composed of halite mixed with other salts such as hanksite, burkeite and trona. It was also observed that the composition of the salts varies considerably even within the same grades.
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| 15. |
- Kasedde, Hillary, et al.
(author)
-
Mineral recovery from Lake Katwe brines using isothermal evaporation
- 2013
-
In: International Mine Water Association Annual Conference 2013. - : IMWA International Mine Water Association. - 9780615793856 ; , s. 855-860
-
Conference paper (peer-reviewed)abstract
- Lake Katwe is a saline lake within the East African Rift system in Western Uganda, with a rich source of mineral salts. The present work aims at evaluating possibilities of future salt extraction from the lake deposit. An isothermal evaporation experiment was conducted on the lake brines. The precipitated salts were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. Various economic salts such as thenardite, gypsum, mirabilite, burkeite, hanksite, anhydrite, trona, halite, nahcolite, thermonatrite, and soda ash precipitate from the lake brines. The experiments also reveal the sequence of mineral salt precipitation in the order sulfates→chlorides→carbonates.
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| 16. |
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| 17. |
- Safavi Nick, Reza, et al.
(author)
-
A mathematical model of the solid flow behavior in a real dimension blast furnace : Effects of the solid volume fraction on the velocity profile
- 2013
-
In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 84:10, s. 999-1010
-
Journal article (peer-reviewed)abstract
- A mathematical model based on the continuum mechanic concept has been developed to describe the profile of solid particles in a blast furnace with respect to the in-furnace conditions and characteristics, e.g., the shape and size of the deadman. The Navier-Stokes differential equation for multi-phase multi-dimensional space has been used to describe the behavior of existing phases. The equation has been modified to make it possible to describe the dual nature of the solid phase in the system by applying the concept of the solid surface stress to characterize the inter-granular surface interactions between particles. Since different phases co-exist in a blast furnace, the volume fraction plays an important role in a blast furnace. Therefore, the influence of three different packing densities (0.68, 0.71, and 0.74, respectively) on the profile of the flow in the upper part of a furnace down to the tuyeres level has been studied. It is shown that an increase in the volume fraction of the solid phase lead to a decrease in magnitude of the velocity. The decrease in the magnitude of the velocity due to an increase in the solid volume fraction will increase the resident time of the particles inside a blast furnace. In addition, it is shown that the solid phase velocity magnitude decreases from the throat to the belly of the furnace for the studied conditions. However, after belly the velocity magnitude increases.
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| 18. |
- Safavi Nick, Reza, et al.
(author)
-
Mathematical Model of Solid Flow Behavior in a Real Dimension Blast Furnace
- 2013
-
In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 53:6, s. 979-987
-
Journal article (peer-reviewed)abstract
- A mathematical model based on the continuum mechanic concept has been developed to describe the profile of solid particles in an industrial scale blast furnace with respect to the in-furnace conditions and its characteristics such as the shape and size of the deadman. The Navier-Stokes differential equation for multi-phase multi-dimensional space has been used to describe the behavior of existing phases. The surface stress tensor has been defined as an extra term and added to the Navier-Stokes equation to describe the particle-particle interactions. This extra term in the Navier-Stokes equation behave as a breaking force when the particles are sliding down. It is shown that the particles change their profile from a V-shape to a W-shape due to the characteristics of the deadman. Moreover, the velocity magnitude is higher at the outer surface of the deadman for higher grid-slabs in this region than the near-wall cells. However, the situation changes as solid particles moving to even lower level of grid-slabs at the outer surface of the deadman in comparison to near-wall cells. It has also been shown that an increase in the magnitude of the effective pressure reduces the velocity magnitude of descending particles.
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| 19. |
- Safavi Nick, Reza, 1977-
(author)
-
Mathematical Model of the Solid Flow Behavior in a Real Dimension Blast Furnace
- 2012
-
Licentiate thesis (other academic/artistic)abstract
- A mathematical model based on the continuum mechanic concept has been developed to describe the profile of solid particles in an industrial scale blast furnace. The focus is the in-furnace conditions and its characteristics such as the shape and size of the deadman. The Navier-Stokes differential equation for multi-phase multi-dimensional space has been used to describe the behavior of existing phases. The equation has been modified to make it possible to describe the dual nature of the solid phase in the system. This has been done by applying the concept of the solid surface stress to describe the intergranular surface interactions between particles. More specifically, this term is added as an extra term to the Navier-Stokes equation to describe the particle-particle interactions. This extra term in behave as a breaking force when the particles are sliding down in the furnace. During the descending movement in the furnace it is shown that the particles change their profile from a V-shape to a Wshape, due to the characteristics of the deadman. Moreover, the velocity magnitude is higher at the outer surface of the deadman for higher grid-slabs in this region than the near-wall cells. However, the situation changes as solid particles moving to even lower levels of the grid-slabs at the outer surface of the deadman in comparison to near-wall cells. It has also been shown that an increase in the magnitude of the effective pressure reduces the velocity magnitude of descending particles. Furthermore, since different phases co-exist in a blast furnace, the volume fraction plays an important role in the blast furnace. Therefore, the influence of three different packing densities (0.68, 0.71 and 0.74 respectively) on the profile of the flow through the upper part of the blast furnace from the throat to the tuyeres level has been studied. It is shown that an increase in the volume fraction of the solid phase lead to a decrease in the velocity magnitude. This decrease is due to an increase in the solid volume fraction, which will increase the resident time of the particles inside a blast furnace. In addition, it is shown that the velocity magnitude of the solid phase decreases from the throat to the belly of the furnace, for the studied conditions. However, after belly the velocity magnitude increases again.
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| 20. |
- Steneholm, K., et al.
(author)
-
Removal of hydrogen, nitrogen and sulphur from tool steel during vacuum degassing
- 2013
-
In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:3, s. 199-205
-
Journal article (peer-reviewed)abstract
- The removal of hydrogen, nitrogen and sulphur during vacuum degassing of a tool steel grade was studied. Both slag and steel samples were collected before and after vacuum treatment for 10 heats. From these, the chemical compositions of steel and slag were determined. Thereafter, the removal rates of sulphur, hydrogen and nitrogen were calculated. For sulphur and hydrogen only first order reaction models were considered. However, for nitrogen both first order and second order kinetic models were studied. The results showed that the removal of hydrogen and nitrogen can be described with first order reaction models. However, the removal rate of sulphur follows the equilibrium sulphur content at all stages during the vacuum degassing. It is also clear that after 10 min of degassing the hydrogen and nitrogen removal is more or less finished for the studied steel grade. However, the sulphur refining can still be carried out for longer times to reach lower values.
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| 21. |
- Swartling, Maria, et al.
(author)
-
Experimentally determined temperatures in blast furnace hearth
- 2010
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In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 37:1, s. 21-26
-
Journal article (peer-reviewed)abstract
- In this study temperature measurements have been carried out at blast furnace no. 2 at SSAB Oxelosund. The temperature was measured in the hearth lining and at the outer surfaces of the hearth wall and bottom. The lining temperature was measured using permanently installed thermocouples and surface temperatures were measured using a hand held thermocouple. The aims of the study were to find a correlation between lining and surface temperatures as well as to find a method to determine the surface temperature based on readings from lining thermocouples. The overall conclusion is that the bottom and wall surface temperatures can be determined based on lining temperatures.
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| 22. |
- Swartling, Maria, et al.
(author)
-
Heat Transfer Modelling of a Blast Furnace Hearth
- 2010
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In: STEEL RES INT. - : Wiley. - 1611-3683. ; 81:3, s. 186-196
-
Journal article (peer-reviewed)abstract
- This paper describes the development of a heat transfer model with the purpose of studying the heat flows in the hearth of an operating blast furnace. Temperature profiles were calculated for a period of time to study the transition from steady blast furnace operation to an unsteady period, and back to a steady period. This total time period had the highest lining temperatures registered since the beginning of the current campaign. It was concluded that no part of the lining had an inner temperature higher than the critical temperature of 1150 degrees C. Thus, no refractory could have been in direct contact with slag or iron. The corner between the wall and the bottom was identified to be the most sensitive part of the lining. It is suggested that thermocouples are installed in this area, to improve the temperature control.
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| 23. |
- Swartling, Maria, et al.
(author)
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Interpretation of Tap Induced Cyclic Temperatures in the Blast Furnace Lining
- 2012
-
In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 83:7, s. 695-704
-
Journal article (peer-reviewed)abstract
- The thermal behavior of the blast furnace hearth was studied using modeling. The focus was the effect of the size and shape of the taphole clay layer around the taphole. Four different cases have been calculated: one reference case and three cases with different taphole clay layer geometries. It was found that the calculated peak-to-peak amplitudes of the lining temperatures during the tap cycles at the location of a thermocouple can be approximated as a linear function of the taphole clay layer thicknesses for all calculated cases. Modeling was also done where both the 90th and the 10th percentile of the observed peak-to-peak values of the studied tap cycles were included to describe the behavior of the operating furnace. The taphole region can be divided into three categories based on how well the model can describe the measured process data: below, at, and above taphole level. Below the taphole level, the measured lining temperature variations are smaller than for the calculated results. At the taphole level, the model can describe the behavior well. Above the taphole level the measured lining temperature variations are larger than for the calculated results. It was concluded that in order to make a more accurate heat transfer model of the taphole region, the presence of a skull build-up below the taphole, erosion above the taphole, and the bath level variations need to be taken into account.
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| 24. |
- Swartling, Maria, et al.
(author)
-
Short-term Lining Temperature Changes during Tapping in a Blast Furnace
- 2010
-
In: Steel Research International. - : Wiley. - 1611-3683. ; 81:9, s. 724-734
-
Journal article (peer-reviewed)abstract
- The following paper presents a three-dimensional heat transfer model of the blast furnace hearth. The model has been developed with the objective of studying the short term changes in lining temperature during regular tappings. It is based on the actual conditions of Blast Furnace No. 2 at SSAB Oxelosund in Sweden. The model was evaluated and analysed using thermocouple data from the operating furnace. The study showed that a layer of tap clay around the tap hole had a significant effect on the heat transfer by reducing the heat variations in the lining. More specifically, a layer of 10-15 cm gave the best correlation between calculated and thermocouple data. A simulation was performed where the melt temperature and the tap cycle duration was based on process data from the operating furnace. Moreover, the size of the area subjected to changes due to the regular tappings was defined. It was found to be the region within an angle of 13 degrees from the tap hole, 0.9 m above and 0.8 m below the tap hole.
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| 25. |
- Ternstedt, PAtrik, 1979-, et al.
(author)
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Mixing Time in a Side-Blown Converter
- 2010
-
In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:5, s. 663-667
-
Journal article (peer-reviewed)abstract
- The mixing time in a side-blown converter was studied using physical modelling. Water was used to simulate steel and a KCI tracer was added during the experiments. Thereafter, the mixing time was determined experimentally by measuring the electrical conductivity in the water bath. Experiments were done for two bath diameters of 200 mm and 300 mm, respectively. Furthermore, for gas flow rates between 30 cm(3)/s and 800 cm(3)/s as well as bath heights ranging from 106 to 314 mm. The mixing times were also calculated based on an expression involving the Strouhal and Reynolds numbers. The experimentally determined mixing times were found to be within +/- 20% of the theoretical values, which is considered to be good in physical modelling. Overall, the mixing time was found to be influenced by the gas flow rate and the vessel diameter, but not by the bath height.
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| 26. |
- Tilliander, Anders, et al.
(author)
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A Three-Dimensional Three-Phase Model of Gas Injection in AOD Converters
- 2014
-
In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 85:3, s. 376-387
-
Journal article (peer-reviewed)abstract
- A mathematical model of gas injection in the AOD converter process has been developed by augmentation of an earlier developed three-dimensional two-phase model to the slag phase and an industrial relevant geometry including six nozzles. The model is based on fundamental transport equations and includes separate solution of the steel and the gas phases and their coupling by friction as well as the slag phase. The 3D 3-phase (steel, slag, and gas) AOD model has been used to predict fluid flow, turbulence, and bubble characteristics as well as fluid-slag dispersion. In addition, two different gas flow rates have been simulated which resulted in quite different flow pattern. This new findings opens up for future investigations of gas-metal reactions in the AOD converter, which are of key interest from an industrial point of view.
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| 27. |
- Zhang, Zhi, et al.
(author)
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A Numerical Study of Swirl Blade Effects in Uphill Teeming Casting
- 2010
-
In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:12, s. 1756-1762
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Journal article (peer-reviewed)abstract
- The initial filling period during ingot casting was studied theoretically The motivation was that it is crucial to achieve a preferred flow pattern which can lead to a smooth filling condition particularly during the initial teeming stage In this study a twist-tape swirl blade was applied in a mathematical model to create a swirl flow in the inlet of the mold The swirl blade was set vertically lust beneath the inlet which was made of a gradually divergent cross section area The results showed that combinations of the inlet swirl flow and mold with gradually divergent bottom contributes to 0 Inlet flow passes along the wall of the mold ii) the formation of a very uniform velocity distribution within only 6s after the molten steel filled into the mold and 10 No formation of a hump on the free surface of the mold during the entire filling times These phenomena will ensure that the mold flux is spread onto the surface of liquid steel evenly Besides the stable surface also prevents the mold flux from being dispersed into the molten steel
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| 28. |
- Zhang, Zhi, et al.
(author)
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Mathematical Modelling of Water Sampler Filling
- 2010
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In: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 81:2, s. 112-122
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Journal article (peer-reviewed)abstract
- Steel samples taken from ladles or tundishes during the steel making process can be of significant importance when monitoring the inclusion size and distribution. In order to preserve the original size and distributions of inclusions in the extracted samples, it is important to avoid their collisions and coagulations inside samplers during filling. Thus, it is necessary to investigate the flow during a sampling process to make sure that this is minimized. In addition, it is important to study the turbulence characteristics, since it is known to influence the inclusion growth. This study presents mathematical modelling of sampler filling using water as a media and experimental results for verification. The study focuses on a lollipop-shaped sampler since it is one of the most common in the industry. The sampler is filled from an inlet pin located at the bottom centre of the main body. In addition, two different turbulence models, the realizable k-ε model and Wilcox k-ω model, were used to study the flow pattern in the sampler. The predictions were compared to experimental results obtained by Particle Image Velocimetry (PIV) measurements. It was found that the flow field predictions using the Wilcox k-ω model agreed best with the flow field obtained by PIV measurements. Furthermore, it was illustrated that the Wilcox k-ω model can be used for predictions of the different flow regions as well as the positions of the centres of vortexes which are located near the free surface. Thus, it is concluded that the Wilcox k-ω model can be used in the future to predict the filling of steel samplers.
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| 29. |
- Zhang, Zhi, 1982-
(author)
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On the Study of a Liquid Steel Sampling Process
- 2010
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Doctoral thesis (other academic/artistic)abstract
- The liquid steel sampling method is one of the commonly used procedures in monitoring the steelmaking process. Besides it can be used for analyzing the dissolved alloys, hydrogen content and oxygen content, it can be also employed to monitor the inclusion characteristics at the steelmakings. Here, a crucial point is that the steel sampler should be filled and the metal solidifies without changing the inclusion characteristics. Therefore, the objective of this work is to fundamentally understand the liquid steel sampling process by means of analyzing and modeling the two-phase flow during the sampler filling process, and verifying the mathematical model by using the experimental data. The present dissertation presents an experimental and theoretical study of the filling process of both the lollipop-shaped sampler and the rectangular-shaped sampler. Firstly, a physical modeling by using a water model has been carried out to fundamentally investigate the flow pattern inside the sampler vessels during its filling. The flow patterns were obtained by a PIV system. Then, a mathematical model has been built to theoretically understand the phenomena. The commercial CFD code was used. Here, different turbulence model have been compared between the realizable k-ε turbulence model and Wilcox k-ω turbulence model. It concludes that the Wilcox k-ω turbulence model agrees well with the PIV measurements.HH Thus, the preferred it was further employed to predict the turbulent flow inside the production lollipop-shaped sampler fillings. It is important to find that the average collision volume in the production steel sampler without solidification at filling is about 30 times higher than that in a ladle furnace. In the end, the whole sampling system was modeled. The initial solidification during the filling was taken into account. Focus was on the influence of the initial solidification on the inclusion concentrations. A discrete phase model was used to simulate the movement of inclusions in the liquid steel. Some selected different sized primary inclusions that exist in the ladles at a steelmaking process were simulated. The same method of studying the filling procedure of the lollipop-shaped sampler was further applied to comprehensively investigate the rectangular-shaped sampler.
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| 30. |
- Zhang, Zhi, et al.
(author)
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Simulation of the Filling of a Liquid Steel Sampler
- 2010
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In: Steel Research International. - : Wiley. - 1611-3683. ; 81:9, s. 749-758
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Journal article (peer-reviewed)abstract
- Steel samples extracted from the ladle furnace in liquid state are vital to monitor the steel making process in the iron & steel industries. The main function of the steel sample is to exam whether the steel is at the aimed composition for elements that dissolve in steel. In addition, more interest is arising to determine the inclusion characteristics in steel samples, in order to monitor the development throughout the process. However, the molten steel sampling is a process involving multi-phenomena such as a high temperature, a fast solidification, reoxidation of steel and a highly turbulent flow pattern. Therefore, mathematical simulations have been carried out to fundamentally study the sampler filling process. The Wilcox k-ω turbulence model was employed to predict the turbulent flow. The calculated results show that flow patterns inside the sampler can be classified into three distinct flow regions: the vortex flow region close to the free surface, the lower horizontal flow region and the middle vertical flow region. From the flow and turbulence data, the inclusion particle collision volume rate was calculated to study the influence of turbulent flow on the inclusion growth in the sampler during fillings. It is shown that the collision volume in the sampler is much higher than that found in the ladle furnace, where the steel sampling normally takes place. This is due to the high turbulence energy dissipation rate in the samplers compared to the ladles.
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| 31. |
- Zhang, Zhi, et al.
(author)
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Simulation of the Steel Sampling Process
- 2010
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In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:12
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Journal article (peer-reviewed)abstract
- This work presents a theoretical study of the liquid steel sampling process in the iron &steel industry. As a continuous research with the previous work, the initial solidification duringthe sampler filling was taken into account. The liquid steel sampling procedure, which ismainly used to monitor whether the steel is at the correct composition during the steelmaking,can also be applied to examine the inclusion size characteristics. Focus was on the influence ofthe initial solidification on the inclusion concentrations. The whole sampling system wasmodeled in order to obtain a simulation result which is realistic from an industrial perspective.Argon-protected sampling was the focus in the simulations. A discrete phase model was usedto simulate the movement of inclusions in the liquid steel. Inclusions were injected from theinlet pin of the lollipop-shaped sampler. Some selected different sized primary inclusions thatexist in the ladles during a steelmaking process were simulated. The conclusion from this workis that turbulent flow patterns within the sampler mold will change because of the spaceshrinkage due to the solidification. This, in turn, will also affect the inclusion dispersions. Itconcludes that the preferred position for detecting inclusions is the bottom region, except thebottom surface. It estimates that the mean deviation between the calculated result and the initialconcentration for all inclusions in these regions is within 10%.
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