| 1. |
- Bai, Haitong, 1986-, et al.
(författare)
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Effect of swirling flow tundish submerged entry nozzle outlet design on multiphase flow and heat transfer in mould
- 2019
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Ingår i: Ironmaking & steelmaking. - : TAYLOR & FRANCIS LTD. - 0301-9233 .- 1743-2812.
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Tidskriftsartikel (refereegranskat)abstract
- Effect of a swirling flow SEN (submerged entry nozzle) outlet design on the multiphase flow and heat transfer in a mould was investigated by using numerical simulation. It was found that different SEN outlet designs could form different flow patterns and temperature distributions on the upper of the mould. The enlarged outlet SEN design had an effect to decrease the horizontal velocity of liquid steel flowing out the SEN outlet, reducing the steel flow velocity towards the solidification front. Although a higher velocity was found near the slag/steel interface with the enlarged outlet SEN, but the turbulent kinetic energy was lower. The reason was that less circulation flows were formed in the region of the mould top. The weak horizontal flow towards the solidification front with the enlarged outlet SEN induced lower wall shear stresses, at the same time it also formed a lower temperature distribution near the solidified shell.
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| 2. |
- Bölke, Kristofer, et al.
(författare)
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Physical Modeling Study on the Mixing in the New IronArc Process
- 2018
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Ingår i: Steel Research International. - : WILEY-V C H VERLAG GMBH. - 1611-3683 .- 1869-344X. ; 89:7
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Tidskriftsartikel (refereegranskat)abstract
- IronArc is a newly developed technology for pig iron production with the aim to reduce the CO2 emission and energy consumption, compared to a conventional blast furnace route. In order to understand the fluid flow and stirring in the IronArc reactor, water modeling experiments are performed. Specifically, a down scaled acrylic plastic model of the IronArc pilot plant reactor is used to investigate the mixing phenomena and gas penetration depth in the liquid bath. The mixing time is determined by measuring the conductivity in the bath, after a sodium chloride solution is added. Moreover, the penetration depth is determined by analyzing the pictures obtained during the experimental process by using both a video camera and a high speed camera. The results show that the bath movements are strong and that a circular movement of the surface is present. The mixing in the model for the flow rate of 282 NLmin(-1) is fast. Specifically, the average mixing times are 7.6 and 10.2s for a 95% and a 99% homogenization degree, respectively. This is 15% and 18% (per degree of homogenization) faster compared to the case when using 3 gas inlets and the same flow rate.
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| 3. |
- Chen, Chao, et al.
(författare)
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A Model Study of Inclusions Deposition, Macroscopic Transport, and Dynamic Removal at Steel–Slag Interface for Different Tundish Designs
- 2016
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 47:3, s. 1916-1932
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents computational fluid dynamics (CFD) simulation results of inclusions macroscopic transport as well as dynamic removal in tundishes. A novel treatment was implemented using the deposition velocity calculated by a revised unified Eulerian deposition model to replace the widely used Stokes rising velocity in the boundary conditions for inclusions removal at the steel–slag interface in tundishes. In this study, the dynamic removal for different size groups of inclusions at different steel–slag interfaces (smooth or rough) with different absorption conditions at the interface (partially or fully absorbed) in two tundish designs was studied. The results showed that the dynamic removal ratios were higher for larger inclusions than for smaller inclusions. Besides, the dynamic removal ratio was higher for rough interfaces than for smooth interfaces. On the other hand, regarding the cases when inclusions are partially or fully absorbed at a smooth steel–slag interface, the removal ratio values are proportional to the absorption proportion of inclusions at the steel–slag interface. Furthermore, the removal of inclusions in two tundish designs, i.e., with and without a weir and a dam were compared. Specifically, the tundish with a weir and a dam exhibited a better performance with respect to the removal of bigger inclusions (radii of 5, 7, and 9 μm) than that of the case without weir and dam. That was found to be due to the strong paralleling flow near the middle part of the top surface. However, the tundish without weir and dam showed a higher removal ratio of smaller inclusions (radius of 1 μm). The reason could be the presence of a paralleling flow near the inlet zone, where the inclusions deposition velocities were much higher than in other parts.
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| 4. |
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| 5. |
- Lundkvist, Nicholas, et al.
(författare)
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A Physical Modeling Study on Slag Behavior in the AOD Converter Process
- 2018
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Ingår i: Steel Research International. - : WILEY-V C H VERLAG GMBH. - 1611-3683 .- 1869-344X. ; 89:6
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Tidskriftsartikel (refereegranskat)abstract
- A water/oil physical model is built up to investigate the slag behavior under the side gas-blowing condition of an AOD process. The critical side-blowing air flow rates for the top oil entrainment and emulsification are investigated. In addition, the oil entrainment with the existence of solid particles is studied. Specifically, the influences of the tuyere size, oil viscosity, oil thickness, and volume fraction of solid particles in oil on the mixing phenomena are studied. It is found that oil viscosity is an important factor for the initial oil entrainment and emulsification. Oil thickness only has a slight influence on these phenomena. The critical air flow rate for both initial oil entrainment and emulsification increases slightly with an increased tuyere size from 2.0 to 3.2 mm. Empirical equations have been proposed to predict the critical air flow rate for the initial oil entrainment and emulsification. Furthermore, solid particles in oil are found to increase the critical air flow rate for an initial entrainment. This may be due to the increase of oil viscosity when solid particles exist in oil. In addition, a new model is developed to predict the oil viscosity when solid particles exist inside it.
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| 6. |
- Ni, Peiyuan, et al.
(författare)
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A Kinetic Model of Mass Transfer and Chemical Reactions at a Steel/Slag Interface under Effect of Interfacial Tensions
- 2019
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Ingår i: ISIJ International. - : IRON STEEL INST JAPAN KEIDANREN KAIKAN. - 0915-1559 .- 1347-5460. ; 59:5, s. 737-748
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Tidskriftsartikel (refereegranskat)abstract
- A new kinetic model was developed to predict the dynamic change of the interfacial oxygen content and the steel/slag interfacial tension. This model mainly describes the following interfacial physicochemical phenomena: i) Silica decomposition and oxygen adsorption at the interface, ii) Oxygen and aluminum reactions at the interface, iii) Oxygen desorption from the interface, iv) Silica mass transfer from the slag to the interface, v) Dissolution of the formed alumina into the slag and its transfer in slag and vi) Blockage on the silica mass transfer, to come in contact with the steel, by the accumulation of the formed alumina at the interface. With this model, the dynamic changes of the interfacial oxygen contents under different aluminum contents in steel and different slag viscosities were predicted. Overall, the interfacial oxygen content was found to increase with a decreased aluminum content and a decreased slag viscosity. Furthermore, the aluminum reaction rate can significantly influence the interfacial oxygen content as well as the interfacial tension. In addition, the model captured the fast increase of the interfacial tension after passing the minimum value point for the system of a high -Al content steel and a low viscous slag, which is in agreement with the experimental observations. Furthermore, a parameter study was carried out to show the influence of various parameters on the dynamic interfacial phenomena.
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| 7. |
- Ni, Peiyuan
(författare)
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A Study on Particle Motion and Deposition Rate : Application in Steel Flows
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Non-metallic inclusions in molten steel have received worldwide attention due to their serious influence on both the steel product quality and the steel production process. These inclusions may come from the de-oxidation process, the re-oxidation by air and/or slag due to an entrainment during steel transfer, and so on. The presence of some inclusion types can cause a termination of a casting process by clogging a nozzle. Thus, a good knowledge of the inclusion behavior and deposition rate in steel flows is really important to understand phenomena such as nozzle clogging. In this thesis, inclusion behaviors and deposition rates in steel flows were investigated by using mathematical simulations and validation by experiments.A ladle teeming process was simulated and Ce2O3 inclusion behavior during a teeming stage was studied. A Lagrangian method was used to track the inclusions in a steel flow and to compare the behaviors of inclusions of different sizes. In addition, a statistical analysis was conducted by the use of a stochastic turbulence model to investigate the behaviors of different-sized inclusions in different nozzle regions. The results show that inclusions with a diameter smaller than 20 μm were found to have similar trajectories and velocity distributions in the nozzle. The inertia force and buoyancy force were found to play an important role for the behavior of large-size inclusions or clusters. The statistical analysis results indicate that the region close to the connection region of the straight pipe and the expanding part of the nozzle seems to be very sensitive for an inclusion deposition.In order to know the deposition rate of non-metallic inclusions, an improved Eulerian particle deposition model was developed and subsequently used to predict the deposition rate of inclusions. It accounts for the differences in properties between air and liquid metals and considers Brownian and turbulent diffusion, turbophoresis and thermophoresis as transport mechanisms. A CFD model was firstly built up to obtain the friction velocity caused by a fluid flow. Then, the friction velocity was put into the deposition model to calculate the deposition rate.For the case of inclusion/particle deposition in vertical steel flows, effects on the deposition rate of parameters such as steel flow rate, particle diameter, particle density, wall roughness and temperature gradient near a wall were investigated. The results show that the steel flow rate/friction velocity has a very important influence on the rate of the deposition of large particles, for which turbophoresis is the main deposition mechanism. For small particles, both the wall roughness and thermophoresis have a significant influence on the particle deposition rate. The extended Eulerian model was thereafter used to predict the inclusion deposition rate in a submerged entry nozzle (SEN). Deposition rates of different-size inclusions in the SEN were obtained. The result shows that the steel flow is non-uniform in the SEN of the tundish. This leads to an uneven distribution of the inclusion deposition rates at different locations of the inner wall of the SEN. A large deposition rate was found to occur at the regions near the SEN inlet, the SEN bottom and the upper region of two SEN ports.For the case of an inclusion/particle deposition in horizontal straight channel flows, the deposition rates of particles at different locations of a horizontal straight pipe cross- section were found to be different due to the influence of gravity and buoyancy. For small particles with a small particle relaxation time, the gravity separation is important for their deposition behaviors at high and low parts of the horizontal pipe compared to the turbophoresis. For large particles with a large particle relaxation time, turbophoresis is the dominating deposition mechanism.
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| 8. |
- Ni, Peiyuan, 1987-, et al.
(författare)
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A study on the nonmetallic inclusion motions in a swirling flow submerged entry nozzle in a new cylindrical tundish design
- 2018
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 49:2, s. 723-736
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Tidskriftsartikel (refereegranskat)abstract
- Different sizes and shapes of nonmetallic inclusions in a swirling flow submerged entry nozzle (SEN) placed in a new tundish design were investigated by using a Lagrangian particle tracking scheme. The results show that inclusions in the current cylindrical tundish have difficulties remaining in the top tundish region, since a strong rotational steel flow exists in this region. This high rotational flow of 0.7 m/s provides the required momentum for the formation of a strong swirling flow inside the SEN. The results show that inclusions larger than 40 µm were found to deposit to a smaller extent on the SEN wall compared to smaller inclusions. The reason is that these large inclusions have Separation number values larger than 1. Thus, the swirling flow causes these large size inclusions to move toward the SEN center. For the nonspherical inclusions, large size inclusions were found to be deposited on the SEN wall to a larger extent, compared to spherical inclusions. More specifically, the difference of the deposited inclusion number is around 27 pct. Overall, it was found that the swirling flow contains three regions, namely, the isotropic core region, the anisotropic turbulence region and the near-wall region. Therefore, anisotropic turbulent fluctuations should be taken into account when the inclusion motion was tracked in this complex flow. In addition, many inclusions were found to deposit at the SEN inlet region. The plotted velocity distribution shows that the inlet flow is very chaotic. A high turbulent kinetic energy value of around 0.08 m2/s2 exists in this region, and a recirculating flow was also found here. These flow characteristics are harmful since they increase the inclusion transport toward the wall. Therefore, a new design of the SEN inlet should be developed in the future, with the aim to modify the inlet flow so that the inclusion deposition is reduced.
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| 9. |
- Ni, Peiyuan, et al.
(författare)
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Application of a swirling flow producer in a conventional tundish during continuous casting of steel
- 2017
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 57:12, s. 2175-2184
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Tidskriftsartikel (refereegranskat)abstract
- A swirling flow producer was designed for a conventional tundish in order to produce a swirling flow in the SEN driven by the steel flow potential. CFD simulations were carried out to investigate the flow phenomena in the new tundish system. The results show that a swirling flow in the tundish SEN was successfully obtained. The swirl number of the obtained steel flow inside the SEN can reach a value of 1.34, with a tangential velocity of around 2.8 m/s. The possibility of slag entrainment at the top of the tundish was estimated by analyzing the steel flow characteristics near the top surface. The calculated Weber Number is around 0.3 outside the cylinder, which indicates a low possibility of slag entrainment. A high value of shear stress was found on the SEN wall. This is due to the rotational steel flow in SEN. Also, non-metallic inclusions were tracked in the fully developed steel flow field. It was found that the number of inclusions that touch the top surface increases with an increased inclusion size. Small size inclusions mainly move into the cylinder from the left side of tangential inlet. Therefore, methods like installing a dam at the tundish bottom may be helpful to change the inclusion trajectories to move towards the top of the tundish.
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| 10. |
- Ni, Peiyuan, et al.
(författare)
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Deposition of particles in liquid flows in horizontal straight channels
- 2016
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Ingår i: International Journal of Heat and Fluid Flow. - : Elsevier. - 0142-727X .- 1879-2278. ; 62, s. 166-173
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Tidskriftsartikel (refereegranskat)abstract
- A flow in a horizontal channel is an important method for the transport of materials, products and/or waste gases/liquids. The deposition of particles in a horizontal channel may clog the flow path. The purpose of this paper is to extend the use of a developed Eulerian deposition model to liquid flows in horizontal straight channels to predict the particle deposition rate. For a horizontal pipe, the deposition rates may differ greatly along a cross section, due to the influences of gravity and buoyancy. The current deposition model is first applied to air flows to enable a comparison with available experimental data. Then, the model is applied to liquid flows in horizontal straight pipes. The effects of gravity, buoyancy, water flow rates, wall roughness, particle size and temperature difference in the near-wall boundary layer on the deposition rate have been studied and explained. The results show that the deposition rates of particles increase with an increased flow rate. The gravity separation has a large influence on the deposition of large particle at high and low parts of the horizontal pipe in some flows. Moreover, both the wall roughness and thermophoresis have a significant influence on the deposition rate of small particles. In addition, the roughness also shows an important influence on the large particle deposition at the top of the investigated pipe, due to that a large value of roughness can make the deposition location somewhat far away from the wall, where a stronger turbophoresis exists. The intensity of the turbophoresis relative to the gravity separation before a particle is reaching the deposition location is important for the large particle deposition when the gravity separation play a negative role on the deposition rate. (C) 2016 Elsevier Inc. All rights reserved.
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| 11. |
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| 12. |
- Ni, Peiyuan, et al.
(författare)
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Mathematical Modelling Study of Dynamic Composition Change of Steel and Mold Flux in Continuous Casting of Steel
- 2019
-
Ingår i: ISIJ International. - : IRON STEEL INST JAPAN KEIDANREN KAIKAN. - 0915-1559 .- 1347-5460. ; 59:11, s. 2024-2035
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Tidskriftsartikel (refereegranskat)abstract
- A kinetic model was developed to describe multicomponent reactions and mass transfer at the steel/molten flux interface under the effect of the interfacial tension. This model mainly describes the following interfacial physicochemical phenomena: i) Silica decomposition and oxygen adsorption at the interface, ii) Oxygen and titanium reactions at the interface, iii) Oxygen and aluminum reaction at the interface, iv) Silica mass transfer from the flux bulk to the interface, and v) Dissolution of the formed titanium dioxide and alumina into the flux and its transfer in flux. With this model, the dynamic changes of the mold flux composition, steel composition, interfacial oxygen content and interfacial tension for different mold flux compositions were predicted. Overall, the dynamic composition changes of the mold fluxes in a casting mold were reproduced. The basicity of the mold flux shows a large influence on the dynamic change of its composition. The initial composition change of the mold flux is fast when the flux with a high basicity was used, compared with the case of the mold flux with a low basicity. The interfacial oxygen content and the interfacial tension were found to reach a constant value after the steel/flux reaches a metastable state. In addition, the interfacial adsorption of oxygen due to the interfacial tension effect was found to significantly accelerate the dynamic change process of the steel/mold flux system.
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| 13. |
- Ni, Peiyuan, et al.
(författare)
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Non-Metallic Inclusion Behaviors in a New Tundish and SEN Design Using a Swirling Flow during Continuous Casting of Steel
- 2016
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Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X.
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Tidskriftsartikel (refereegranskat)abstract
- The behaviors of non-metallic inclusions in a new tundish and SEN design enabling a swirling flow are investigated by using a Lagrangian particle tracking scheme. The results show that 99% of both Al2O3 and Ce2O3 inclusions are removed from both the top surface and the other tundish walls with a "trap" boundary condition, while only around 60% are removed from the top surface of tundish for a "reflect" boundary condition at the other tundish walls. Large size non-metallic inclusions of different densities show a large difference under a "reflect" boundary condition at tundish walls, due to a high buoyancy of light inclusions. In the swirling flow SEN, a much smaller number of large Al2O3 inclusions touches the wall compared to Ce2O3 inclusions. This is due to that they have larger deviations from the steel flow path compared to heavy Ce2O3 inclusions, due to the centripetal force. For small size inclusions, the centripetal separation is not effective neither for the light Al2O3 inclusions nor for the heavy Ce2O3 inclusions in the current swirling flow SEN with a swirl number of 0.4. Light Al2O3 inclusions larger than 40μm can be influenced by the current centripetal force.
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| 14. |
- Ni, Peiyuan, 1987-, et al.
(författare)
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Numerical and Physical Study on a Cylindrical Tundish Design to Produce a Swirling Flow in the SEN During Continuous Casting of Steel
- 2017
-
Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 48:5, s. 2695-2706
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Tidskriftsartikel (refereegranskat)abstract
- A new tundish design was investigated using both water model experiments and numerical simulations. The results show that the Reynolds Stress Model simulation results agree well with the Particle Image Velocimetry-measured results for water model experiments. A strong swirling flow in the Submerged Entry Nozzle (SEN) of the new tundish was successfully obtained, and the tangential velocity in the region near SEN inlet could reach a value of around 3.1 m/s. A high value of the shear stress was found to exist on the SEN wall, due to the strong swirling flow inside the SEN. This large shear stress leads to the dissipation of the rotational momentum of the steel flow. Thus, the maximum tangential velocity of the steel flow decreases from 3.1 m/s at around the SEN inlet to 2.2 m/s at a location close to the SEN outlet. In addition, the near-wall region has a high pressure, which is larger than the atmospheric pressure, due to the centrifugal effect. The calculated swirl number, with the value of around 1.6 at SEN inlet, illustrates that the current design can produce a similar strong swirling flow compared to the swirl blade method and the electromagnetic stirring method, while this is obtained by simply changing the steel flow path in tundish instead of using additional device to influence the flow.
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| 15. |
- Ni, Peiyuan
(författare)
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Numerical Study on Steel Flow and Inclusion Behavior during a Ladle Teeming Process
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inclusions in molten steel have received worldwide concern due to their serious influence on both the steel product quality and the steel production process. These inclusions may come from the deoxidation process, reoxidation by air and/or slag due to an entrainment during steel transfer, and so on. They can break up a casting process by clogging a nozzle. A good knowledge on both steel flow and inclusion behavior is really important to understand nozzle clogging, as well as to take some possible measures to alleviate clogging. In this thesis, steel flow and inclusion behavior during a teeming process were investigated by mathematical simulations with verification by pilot-plant experiments.Firstly, steel flow phenomena during a ladle teeming process were studied. Different turbulence models, including the low Reynolds number k-ɛ model and the realizable k-ɛ model both with an enhanced wall treatment (EWT) and a standard wall function (SWF), were used to simulate this process. All of these turbulence model predictions generally agreed well with the experimental results. The velocity distributions in the nozzle were also predicted by these turbulence models. A large difference of the boundary-layer velocity predicted with these two near wall treatment methods was found. At the late stage of the teeming process, the drain sink flow phenomena were studied. The combination of an inclined ladle bottom and a gradually expanding nozzle was found to be an effective way to alleviate a drain sink flow during teeming.Then, inclusion behavior during a teeming stage was studied. A Lagranian method was used to track the inclusions in steel flow and compare the behaviors of different-size inclusions. In addition, a statistical analysis was conducted by the use of a stochastic turbulence model to investigate the behaviors of different-size inclusions in different nozzle regions. Inclusions with a diameter smaller than 20μm were found to have a similar trajectory and velocity distribution in the nozzle. However, inertia force and buoyancy force were found to play an important role for the behavior of large-size inclusions or clusters. The statistical analysis results indicate that the regions close to the connection between different angled nozzle parts seem to be very sensitive for an inclusion deposition.
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| 16. |
- Ni, Peiyuan, 1987-, et al.
(författare)
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Numerical study on the influence of a swirling flow tundish on multiphase flow and heat transfer in mold
- 2018
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- The effect of a new cylindrical swirling flow tundish design on the multiphase flow and heat transfer in a mold was studied. The RSM (Reynolds stress model) and the VOF (volume of fluid) model were used to solve the steel and slag flow phenomena. The effect of the swirling flow tundish design on the temperature distribution and inclusion motion was also studied. The results show that the new tundish design significantly changed the flow behavior in the mold, compared to a conventional tundish casting. Specifically, the deep impingement jet from the SEN (Submerged Entry Nozzle) outlet disappeared in the mold, and steel with a high temperature moved towards the solidified shell due to the swirling flow effect. Steel flow velocity in the top of the mold was increased. A large velocity in the vicinity of the solidified shell was obtained. Furthermore, the risk of the slag entrainment in the mold was also estimated. With the swirling flow tundish casting, the temperature distribution became more uniform, and the dissipation of the steel superheat was accelerated. In addition, inclusion trajectories in the mold also changed, which tend to stay at the top of the mold for a time. A future study is still required to further optimize the steel flow in mold.
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| 17. |
- Ni, Peiyuan, et al.
(författare)
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On the deposition of particles in liquid metals onto vertical ceramic walls
- 2014
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Ingår i: International Journal of Multiphase Flow. - : Elsevier BV. - 0301-9322 .- 1879-3533. ; 62, s. 152-160
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Tidskriftsartikel (refereegranskat)abstract
- The deposition of non-metallic particles in liquid-metal flows is a serious industrial problem because the build-up of particles on ceramic walls clogs the flow path and interrupts the production, and this leads to large economic losses. This paper is an effort to extend the current state-of-the-art knowledge of particle deposition in air in order to predict particle deposition rates in liquid-metal flows using an improved Eulerian deposition model and considering Brownian and turbulent diffusion, turbophoresis and thermophoresis as transportation mechanisms. The model was used to predict the rate of deposition of particles in an air flow, and the predictions were compared to published measurements to demonstrate its performance. The model was then modified to take into account the differences in properties between air and liquid metals and thereafter applied to liquid-metal flows. Effects on the deposition rate of parameters such as steel flow rate, particle diameter, particle density, wall roughness and temperature gradient near the wall were investigated. It is shown that the steel flow rate has a very important influence on the rate of deposition of large particles, for which turbophoresis is the main deposition mechanism. For small particles, both wall roughness and thermophoresis have a significant influence on the particle deposition rate. Particle deposition rates under various conditions were successfully predicted.
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| 18. |
- Ni, Peiyuan, et al.
(författare)
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Simulations of the LadleTeeming Process and Verification With Pilot Experiment
- 2013
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 84:3, s. 276-287
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Tidskriftsartikel (refereegranskat)abstract
- The ladle teeming process was investigated by 2D axis-symmetrical mathematical models and a pilot-plant experiment. Different turbulence models, including the low Reynolds number k-epsilon model and the realizable k-epsilon model both with an enhanced wall treatment (EWT) and a standard wall function (SWF), were used to simulate this process. All of these turbulence model predictions generally agreed well with the experimental results. The velocity distributions in the nozzle were also predicted by these turbulence models. At the late stage of the teeming process, the drain sink flow phenomenon was studied. The combination of an inclined ladle bottom and a gradually expanding nozzle was found to be an effective way to alleviate a drain sink flow.
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| 19. |
- Ni, Peiyuan, et al.
(författare)
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Study on Slopping Prevention in the BOF Steelmaking Process
- 2017
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Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 88:8
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Tidskriftsartikel (refereegranskat)abstract
- A new method of preventing slopping is proposed in this paper, by simply blowing gas at the top of the foam surface. The physical experiment results show that the foam height can be effectively decreased by the top blowing air. The maximum decrease of the foam height can reach around 70 mm with an initial foam height of 145 mm in the current setup, around a 48% decrease. The first 40 mm of the foam height is easy to destroy with a low flow rate from the top. However, it is increasingly difficult for a further decrease in the foam height. Different types of nozzles show a large difference in the role of destroying the foam. The air flow velocity from the nozzle outlet is found to be the key factor for a decreased foam height. Overall, three foam destruction mechanisms are proposed. When the top air flow velocity is small, the drag and pressure destruction mechanisms are the main reasons for the decrease in foam height. However, when a large top air flow velocity is used, the coalescence and breakup mechanisms due to a high turbulence and the shear force on gas bubble shape deformation become important.
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| 20. |
- Ni, Peiyuan, et al.
(författare)
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The development of an eulerian deposition model in liquid metal flows and its application on nozzle clogging during continuous casting of steel
- 2015
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Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 439-442
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Konferensbidrag (refereegranskat)abstract
- An Eulerian deposition model was developed and used to predict the deposition rates of non-metallic inclusions in liquidmetal flows. Effects of parameters such as particle diameter, wall roughness and temperature gradient near the wall on the deposition rates were investigated. Thereafter, the modified Eulerian model was used to calculate the deposition rate of non-metallic inclusions in a tundish nozzle. Furthermore, the deposition rates of different-size inclusions in the SEN were predicted and compared. The results show that both the wall roughness and thermophoresis have a significant influence on the deposition rate of small particles. For larger inclusions, turbophoresis is the main deposition mechanism. In addition, an uneven distribution of the inclusion deposition rates at the inner wall of the SEN was observed. A large deposition rate was found at the regions near the SEN inlet, the SEN bottom and the upper region of two SEN ports.
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| 21. |
- Ni, Peiyuan, et al.
(författare)
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The Use of an Enhanced Eulerian Deposition Model to Investigate Nozzle Clogging During Continuous Casting of Steel
- 2014
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 45:6, s. 2414-2424
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Tidskriftsartikel (refereegranskat)abstract
- Nozzle clogging caused by the build-up of non-metallic inclusions on ceramic walls is a serious industrial problem during continuous casting of steel. The current theoretical study uses the extended Eulerian model to predict the inclusion deposition rate in a submerged entry nozzle (SEN). The model considers Brownian and turbulent diffusion, turbophoresis, and thermophoresis as transportation mechanisms. First, the steel flow in a tundish was simulated using a three-dimensional CFD model. The obtained flow parameter in a SEN was then put into the Eulerian deposition model to predict the deposition rate of non-metallic inclusions. Thereafter, the deposition rates of different-size inclusions in the SEN were predicted and compared. The result shows that the steel flow is non-uniform in the SEN of the tundish. This leads to an uneven distribution of the inclusion deposition rates at different locations of the inner wall of the SEN. In addition, large size inclusions among the size of inclusions considered show a large deposition rate, due to the strong effect of turbophoresis.
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| 22. |
- Ni, Peiyuan, et al.
(författare)
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Transport and Deposition of Non-Metallic Inclusions in Steel Flows- A Comparison of Different Model Predictions to Pilot Plant Experiment Data
- 2017
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Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 88:12
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Tidskriftsartikel (refereegranskat)abstract
- Inclusion behavior during a ladle teeming process is investigated. A Lagrangian method is used to track different-size inclusions and to compare their behaviors in steel flows, solved by the realizable k-epsilon model with SWF (Standard Wall Function), realizable k-epsilon model with EWT (Enhanced Wall Treatment), and RSM (Reynolds Stress Model). The results show that inclusion tracking based on the realizable k-epsilon model with SWF to predict the steel flow does not agree with the data fromplant experiments. The predicted number of inclusions touching the wall shows almost no dependence on inclusion size. This is due to that the boundary layer is not resolved. The inclusion deposition predicted using the realizable k-epsilon model with EWT and the RSM model to predict the steel flow generally agrees with the experimental observations. However, the large size inclusion deposition is over-predicted when using the realizable k-epsilon model with EWT. More specifically, the prediction for 20 mu m inclusions is three times larger than that with the RSM. This is due to that this model cannot calculate the anisotropic turbulence fluctuations. In summary, the turbulence properties in the near-wall boundary layer are found to be very important for a good prediction on inclusion deposition.
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| 23. |
- Ni, Peiyuan, et al.
(författare)
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Turbulent Flow Phenomena and Ce2O3 Behavior during a Steel Teeming Process
- 2013
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 53:5, s. 792-801
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Tidskriftsartikel (refereegranskat)abstract
- Steel flow phenomena and Ce2O3 inclusion behavior are presented in this paper. A three-dimensional model was developed to describe the steel flow phenomena and the inclusion behavior during a teeming process. The Kim-Chen modified k-ɛ turbulent model was used to simulate the turbulence properties and the Height-of-Liquid model was used to capture the interface between gas and steel. A Lagranian method was then used to track the inclusions and to compare the behaviors of different-size inclusions in the steel flow. In addition, a statistical analysis was carried out by the use of a stochastic turbulence model to investigate the behaviors of different-size inclusions at different nozzle regions. The results show that the steel flow was the most turbulent at the connection part of the straight pipe part and the expanding part of the nozzle. All inclusions with a diameter smaller than 20 μm were found to have a similar trajectory and velocity distribution in the nozzle. However, inertia force and buoyancy force were found to play an important role for the behaviors of large-size inclusions/clusters. The statistical analysis results indicate that the regions close to the connection region between different angled nozzle parts seem to be very sensitive with respect to deposition of inclusions.
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| 24. |
- Niu, L., et al.
(författare)
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Fluidized-bed chlorination rates of Kenya rutile ore
- 2014
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Ingår i: Xiyou jinshu cailiao yu gongcheng. - 1002-185X. ; 43:6, s. 1377-1380
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Tidskriftsartikel (refereegranskat)abstract
- The thermodynamics and kinetics of natural rutile carbochlorination have been investigated in a fluidized-bed. Thermodynamic analysis of this system reveals that when C is excess in the solid phase, TiCl4 and CO are the only two stable products in the chemical equilibrium compositions system, and the increase of the ratio of C to TiO2 has little effect on the product composition. At high temperature, the reaction with CO as the product is the dominant reaction. This paper proposed a reaction rate model, and got a rutile chlorination rate formula, which is more consistent with experimental data. For the TiO2-C-Cl2 system, the reaction rate is dependent on both size and density of natural rutile. From 900 to 1000°C, the apparent activation energy is 10.569 kJ/mol. In this temperature range, mass diffusion is the main reaction controlling step. The expression of the chlorine reaction rate in the C-Cl2 system was obtained, and it depends on the degree of reaction, Cl2 concentration and the size of coke.
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| 25. |
- Niu, Li-Ping, et al.
(författare)
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Mechanism of fluidized chlorination reaction of Kenya natural rutile ore
- 2014
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Ingår i: Rare Metals. - : Springer Science and Business Media LLC. - 1001-0521 .- 1867-7185. ; 33:4, s. 485-492
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the thermodynamics and kinetics of nature rutile carbochlorination in a fluidized-bed were investigated. The thermodynamic calculations of TiO2-C-Cl-2 system show that when C is excess in the solid phase, titanium tetrachloride and carbon monoxide can exist stably. At high temperature, the reaction with CO as the product is the dominant reaction. The appropriate reaction conditions are as follows: reaction temperature of 950 A degrees C, reaction time of 40 min, carbon ratio of 30 wt% of rutile, natural rutile particle size of -96 mu m, petroleum coke size of -150 mu m, and chlorine flow of 0.036 m(3)center dot h(-1). Under the above conditions, the reaction conversion rate of TiO2 can reach about 95 %. This paper proposed a reaction rate model, and got a rutile chlorination rate formula, which is generally consistent with the experimental data. For the TiO2-C-Cl-2 system, the reaction rate is dependent on the initial radius of rutile particle, density, and the partial pressures of Cl-2. From 900 to 1,000 A degrees C, the apparent activation energy is 10.569 kJ center dot mol(-1), and the mass diffusion is found to be the main reaction-controlling step. The expression for the chlorine reaction rate in the C-Cl-2 system is obtained, and it depends on the degree of reaction, the partial pressure of Cl-2, and the size of rutile particle.
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| 26. |
- Ternstedt, Patrik, 1979-, et al.
(författare)
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A physical modelling study to determine the influence of slag on the fluid flow in the AOD converter process
- 2018
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Ingår i: Ironmaking & steelmaking. - : Taylor & Francis. - 0301-9233 .- 1743-2812. ; 45:10, s. 944-950
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Tidskriftsartikel (refereegranskat)abstract
- A 1:4.6 scale physical model of a production argon oxygen decarburisation (AOD) converter was used to study the influence of top slag on the AOD process. Specifically, the gas penetration depth, fluid flow and slag behaviour under different nozzle diameters, nozzle numbers and gas flow rates were studied. The results show that the relative gas penetration depth generally increases linearly with an increased gas flow rate and a decreased nozzle size. Furthermore, the slag thickness increases linearly with an increased gas flow rate. In addition, the open-eye size was found to increase exponentially with an increased gas flow rate. Overall, three kinds of fluid flow patterns were found in the experiments: (i) a counter-clockwise rotation, (ii) a clockwise rotation and (iii) a double circulation with the plume in the middle of the converter. A counter-clockwise rotation was most common for the current experimental conditions.
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| 27. |
- Wang, Jiahao, et al.
(författare)
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Effect of gas blowing nozzle angle on multiphase flow and mass transfer during RH refining process
- 2023
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Ingår i: International Journal of Minerals, Metallurgy and Materials. - : Springer Nature. - 1674-4799 .- 1869-103X. ; 30:5, s. 844-856
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Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional mathematical model was developed to investigate the effect of gas blowing nozzle angles on multiphase flow, circulation flow rate, and mixing time during Ruhrstahl-Heraeus (RH) refining process. Also, a water model with a geometric scale of 1:4 from an industrial RH furnace of 260 t was built up, and measurements were carried out to validate the mathematical model. The results show that, with a conventional gas blowing nozzle and the total gas flow rate of 40 L center dot min(-1), the mixing time predicted by the mathematical model agrees well with the measured values. The deviations between the model predictions and the measured values are in the range of about 1.3%-7.3% at the selected three monitoring locations, where the mixing time was defined as the required time when the dimensionless concentration is within 3% deviation from the bath averaged value. In addition, the circulation flow rate was 9 kg center dot s(-1). When the gas blowing nozzle was horizontally rotated by either 30 degrees or 45 degrees, the circulation flow rate was found to be increased by about 15% compared to a conventional nozzle, due to the rotational flow formed in the up-snorkel. Furthermore, the mixing time at the monitoring point 1, 2, and 3 was shortened by around 21.3%, 28.2%, and 12.3%, respectively. With the nozzle angle of 30 degrees and 45 degrees, the averaged residence time of 128 bubbles in liquid was increased by around 33.3%.
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| 28. |
- Wang, Jiahao, et al.
(författare)
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Study on Multiphase Flow Characteristics During RH Refining Process Affected by Nonradial Arrangement of Gas-Blowing Nozzle
- 2023
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 94:12
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Tidskriftsartikel (refereegranskat)abstract
- Bath stirring, degassing, and decarburization in steel refining are strongly related to flow behaviors. The bubble plume produced in Ruhrstahl–Heraeus (RH) up-snorkel plays an important role during refining, since it not only acts as a bubble pump, but also provides the reaction interface. Herein, it is aimed to form a new flow pattern in the up-snorkel by using a nonradially arranged gas-injection nozzle to enhance the 260 ton RH refining process. The results show that an upward spiral steel flow is produced, when nonradial gas-injection nozzles are used in the up-snorkel. Meanwhile, some bubbles moved toward the center region of the up-snorkel, which may be caused by the centripetal effect in a rotational steel flow. This leads to a more uniform bubble distribution on the cross section of the snorkel, compared to that of the conventional case. Specifically, the circulation flow rate is increased by about 18.0%, and the mixing time are shortened by about 26.2% (criteria of ±5%), compared to that of the conventional case. In addition, the inclusion removal rate is increased by 0.5%, 4.8%, and 11.3% for the inclusion size of 20, 50, and 100 μm, respectively, compared to the conventional radial nozzle case.
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