A Transient Discrete Element Method-Based Virtual Experimental Blast Furnace Model

Hou, Q.F., E, D.Y., Kuang, S.B., Yu, A.B., 2020. A Transient Discrete Element Method-Based Virtual Experimental Blast Furnace Model. Steel Research International, 2000071. https://doi.org/10.1002/srin.202000071

A Transient Discrete Element Method‐Based Virtual Experimental Blast Furnace Model

Qinfu Hou  Dianyu E  Shibo Kuang  Aibing Yu

Abstract

Intensive heat and mass transfer between continuum fluids and discrete particulate materials occur in the current working‐horse blast furnace (BF) ironmaking process. To optimize the operation, its energy efficiency and sustainability, discrete particle models are very helpful when they are incorporated with flow, heat and mass transfer, and chemical reaction models. Herein, a transient discrete element method‐based virtual BF model is developed through scaling. The scaled model simulates the process significantly faster and makes it practical to track the whole process of iron ore reduction from burden charge to the cohesive zone (CZ). The model is applied to an experimental BF and the predictions are tested against available experimental results and those of computational fluid dynamics models. The results demonstrate that the scaled virtual BF model can reasonably predict in‐furnace flow state, temperature distribution, iron ore reduction, and the characteristics of the CZ. The particle‐scale BF model provides detailed information of particle motion, temperature, and chemical reactions, enabling fundamental understanding and further optimization and control of the process. The scaled BF model can be extended to study the effects of raw material properties and operation parameters on BF performance.

Relevant publications:

Hou, Q.F., E, D.Y., Kuang, S.B., Yu, A.B., 2020. A process scaling approach for CFD-DEM modelling of thermochemical behaviours in moving bed reactors. Fuel Processing Technology 202, 106369.

Hou, Q.F., E, D.Y., Kuang, S.B., Li, Z.Y., Yu, A.B., 2017. DEM-based virtual experimental blast furnace: A quasi-steady state model. Powder Technology 314, 557-566.

[Paper online: Powder Technology] DEM investigation of heat transfer in a drum mixer with lifters

DEM investigation of heat transfer in a drum mixer with lifters

Qiang Xie, Zuobing Chen, Qinfu Hou, Aibing Yu, Runyu Yang

http://dx.doi.org/10.1016/j.powtec.2016.09.022

Abstract

Rotating drums are widely used in industries to handle and process particulate materials and heat transfer is often involved in these processes. This work numerically investigated heat transfer inside a drum mixer by coupling the discrete element method (DEM) with a conductive heat transfer model. The mixer was fitted with different types of lifters and rotated at various speeds so their effects on heat transfer characterised by heat transfer coefficient (HTC) could be investigated. The simulation results showed that the specific HTC of the particle flow increased with increasing rotating speed but decreased with the number and height of the lifters. While all types of lifters sped up heat transfer, the straight lifers were more efficient than the arc shape lifters. To better understand the mechanisms of heat transfer, the specific HTC was linked to the particle-wall contact area and dynamic behaviour of particles. The change of lifter configuration, i.e. lifter height, number and shape, mainly affected the particle-wall contact area while the change of mixer rotating speed affected particle mixing behaviour.

[SRI paper] Three-dimensional DEM Study of Coal Distribution in the Melter Gasifier of COREX

A paper online in Steel Research Int.Three-dimensional DEM Study of Coal Distribution in the Melter Gasifier of COREXYang You, Qin-Fu Hou*, Zhi-Guo Luo,Hai-Feng Li, Heng Zhou, Ren Chen and Zong-Shu ZouLink: http://onlinelibrary.wiley.com/doi/10.1002/srin.201500481/abstract

Abstract

COREX is one of the commercialized smelting reduction ironmaking processes. It mainly includes two reactors: a reduction shaft and a melter gasifier (MG). Lump coal is used in the MG to generate reducing agents, and hence its distribution plays an important role in determining the temperature distribution and the reduction of iron ores. To understand the formation of burden profiles, a three-dimensional discrete element method (DEM) model is established and validated against experimental tests. The effects of key operational parameters such as the chute angle and the rotational speed are investigated, and the underlying mechanisms in the formation of an asymmetrical pile are analyzed. The results show that the asymmetrical pile is intrinsic to the discharge system due to the outward motion of lump coal. The results also reveal a significant size segregation of lump coal along the radial direction. Small particles tend to accumulate in the inner side of the pile while the large ones have large fractions in the outer side. The effect of the rotational speed is minor within the range from 3 to 12 rpm. These findings are helpful for the control and optimization of the MG to improve its energy efficiency.

[Aiche J. Paper] Discrete Particle Modeling of Lateral Jets into a Packed Bed and Micromechanical Analysis of the Stability of Raceways

Discrete Particle Modeling of Lateral Jets into a Packed Bed and Micromechanical Analysis of the Stability of Raceways

Authors: Q.F. Hou, D.Y. E, A.B. Yu

http://onlinelibrary.wiley.com/doi/10.1002/aic.15358/full

Abstract

Gas jets are often used to promote heat and mass transfer by forming raceways or circulating regions in a packed bed. Such an operation is common and critical in many processes. Multiple raceways can interact and be affected by the formation of different flow zones. This work develops a multiscale model to examine the formation and the stability of raceways and the underlying micromechanics. Four states are observed in the fluidized flow regime. More fundamentally, a critical bed width for the observation of different flow zones and states is found through numerical simulations and a theoretical analysis. Finally, the complicated transitions between different flow states are examined at a bed scale, and two general trends of the averaged solid velocity are found. The findings from the multiscale model are useful both scientifically for the understanding of state transitions and practically for the design and the operation of relevant chemical reactors. 

Review: Particle Scale Study of Heat Transfer in Packed and Fluidized Beds

A review is available online in Advances in Chemical Engineering. It is considered very useful for those researchers who want to study heat transfer from the particle scale.

Link: http://www.sciencedirect.com/science/article/pii/S0065237715000071

Particle Scale Study of Heat Transfer in Packed and Fluidized Beds

Qinfu Hou*, †, Jieqing Gan*, Zongyan Zhou*, Aibing Yu*

doi:10.1016/bs.ache.2015.10.006

Abstract

Understanding and modeling coupled flow and heat transfer in a particulate system at a particle scale is a rapidly developing research area, in connection with the development of discrete particle simulation techniques and computer technology. The approach based on the discrete element method plays an important role in this area. This approach can provide detailed dynamic information of particulate systems, such as realistic packing structure, transient/static deformation, and relative velocities between fluid and individual particles. The information is directly related to the prediction of thermal behavior. In this chapter, the development of this approach in our laboratory is briefly reviewed, together with the discussion of different case studies. It is concluded that this particle scale approach is effective for studying the coupled fluid flow and heat transfer in particulate systems, although further developments are necessary to be generally applied to industrial processes.

Keywords

Discrete particle simulation; Computational fluid dynamics; Heat transfer; Fluidized bed; Packed bed

An essay of myself in SCIENCE is online!

One essay of MYSELF is online in <SCIENCE> website, selected as one of top essays on postdoc mechanisms from over 300 submissions by Science.

Sounds great!

http://www.sciencemag.org/content/349/6243/24/suppl/DC1

Given the fast increasing number of postgraduates and the decreasing period to finish a research degree (e.g., 3 years for a Ph.D. degree in many Australian universities) it becomes essentially important that a transition period should be there between formal academic and postgraduate to further advance their professional skills. It might be helpful to promote their development by establishing some small funds for them to apply. Right now, although the salary is relatively high for many postdocs in Australia, compared to those in the United States and Europe, the future is not optimistic for postdocs because there is currently only one funding scheme for them (with success rate 14.3% for 2015, which is quite low given that postdocs from the world will apply and research in Australia is not leading in many areas). Many postdocs and early academics (lecturer/senior lecturer) are contemplating or attracted to leaving Australia. There is definitely something that Australian government can do to retain or improve its research capacity to enhance its innovative capability for the challenging economics.
Qinfu Hou
Department of Chemical Engineering, Monash University, Clayton, VIC, 3800, Australia.
E-mail: qinfu.hou@monash.edu

There are some printed.

Postdocs reimagined

In April, we asked young scientists if the idea of the postdoc position is obsolete. If so, what should replace it, and if not, how can it be improved? We received a record response of more than 300 submissions. About a third of respondents felt that postdocs are indeed obsolete. The rest deemed them necessary, if imperfect. Many felt that creating a permanent staff scientist position, with full salary and benefits, would help the plight of postdocs, either by replacing the postdoc entirely or by serving as a long-term option after the completion of a postdoc. Others suggested that a system in which postdocs had dedicated funding and were not beholden to a PI would foster more creativity and minimize exploitation. Tailoring postdocs to a broader array of career paths was another common theme. Many responses reflected the feeling that postdocs deserve more respect and recognition. A sample of the responses describing these and other ideas can be found below. To allow for as many voices as possible, in some cases we have printed excerpts of longer submissions (indicated by ellipses) and lightly copyedited original text for clarity. To read the complete versions, as well as many more, go to http://scim.ag/NG15R. Follow Science's NextGen VOICES survey on Twitter with the hashtag #NextGenSci.

Previous post about reseachers in Australia
http://qfhou.blogspot.com.au/2011/10/academics-unhappy-in-australia.html

CFD-DEM Study of Heat Transfer in the Reduction Shaft of Corex 【featured paper online】

CFD-DEM Study of Heat Transfer in the Reduction Shaft of Corex

Qinfu Hou*, Jian Li and Aibing Yu

This article is featured on the Cover.

http://onlinelibrary.wiley.com/doi/10.1002/srin.201400367/abstract

Corex is a promising iron making process beside blast furnace. Using a combined approach of computational fluid dynamics and discrete element method transient heat transfer of gas?solid flow in reduction shaft of Corex is investigated. The effects of discharge rate and burden profiles are discussed. Useful information for the scaling of a discrete particle model is provided.

Abstract

Keywords: Corex; discrete element method; reduction shaft; burden profile; heat transfer

Corex has a great potential to produce hot metal economically and environmentally friendly. Reduction shaft (RS) for the direct reduction of iron ore is one of the two major reactors in Corex. This work uses a two-dimensional slot model to investigate the thermal behavior of the gas?solid flow in the RS by a combined computational fluid dynamics and discrete element method approach. The general heat transfer characteristics are firstly examined. The complicated transient gas?solid and heat transfer phenomena are demonstrated in the RS process. Then, the effects of discharge rate and two common burden profiles are investigated qualitatively. The results show a linear relation between the steady state bed temperature and discharge rate, which could be helpful for the construction of a reliable scaled down discrete particle model of the RS. The difference between the temperature distributions for two burden profiles is illustrated, which indicates that the control of burden profile could be an effective method to improve energy efficiency. These findings should be useful for the control and optimization of the RS operation.

[paper online] Gas-solid flow and heat transfer in fluidized beds with tubes: Effects of material properties and tube array settings

Gas-solid flow and heat transfer in fluidized beds with tubes: Effects of material properties and tube array settings

http://www.sciencedirect.com/science/article/pii/S0032591015002326

Q.F. Hou, , Z.Y. Zhou, A.B. Yu

doi:10.1016/j.powtec.2015.03.028

Highlights
*Heat transfer and gas-solid flow in fluidized beds with tubes are investigated.
*Different mechanisms are revealed for non-cohesive and cohesive particles.
*The uniformity of particle velocities and temperatures is analysed.
*Complicated variation of heat transfer is demonstrated for different array settings.
*Microscopic local porosity and contact number are linked to macroscopic behaviours.

Abstract
The effects of material properties and tube array settings on gas-solid flow and heat transfer characteristics in fluidized beds with tubes are investigated by the combined approach of computational fluid dynamics and discrete element method, incorporated with heat transfer models. First, the effect of material properties is illustrated by considering cohesive and non-cohesive powders with different particle sizes. The contributions of different heat transfer mechanisms are discussed at two tube temperatures. Significant differences of gas-solid flow between cohesive and non-cohesive powders are observed. The results reveal that conductive heat transfer between a fluidized bed and a tube is dominant for small cohesive particles while convective heat transfer is dominant for large non-cohesive particles. Then, the uniformity of particle velocity and temperature fields is analyzed. It is shown that material properties and gas velocity affect the uniformity of particle velocity and temperature in a complicated manner. Finally, the effect of tube array settings is examined in terms of two geometrical parameters for both in-line and staggered settings. Complicated gas-solid flow and heat transfer characteristics are observed. An effort is made to link macroscopic observations to microscopic information such as local porosity and contact number between fluidized particles and tubes. The findings should be helpful for the optimization of operation and design of fluidized systems with tubes.

Paper: Modeling the Gas-solid Flow in the Reduction Shaft of COREX

Modeling the Gas-solid Flow in the Reduction Shaft of COREX

By:Hou, QF (Hou, Qin-Fu)^[ 1 ] ; Samman, M (Samman, Mohammed)^[ 1 ] ; Li, J (Li, Jian)^[ 2 ] ; Yu, AB (Yu, Ai-Bing)^[ 1 ]

ISIJ INTERNATIONAL

Volume: 54

 

Issue: 8

 

Pages: 1772-1780

Published: 2014

Abstract

COREX is a promising alternative to blast furnace ironmaking. It includes two main reactors: a reduction shaft (RS) for the direct reduction of iron ore and a melter gasifier for the melting reduction of directly reduced iron. This work uses a two-dimensional slot model to investigate the gas-solid flow in the RS by a combined computational fluid dynamics and discrete element method approach. The three-dimensional flow of cohesive solids is then examined for three RS designs by the discrete element method. The effects of gas flow, the stickiness between particles, the rotational speed of screws, and different designs are depicted in terms of gas-solid flow pattern, overall bed pressure drop and solid flowrate. The results show that the effect of gas flow is insignificant on gas-solid flow pattern due to the small gas-solid interaction forces under the considered conditions. Solid flow varies in a complex manner with the rotational speed of screws and the sticking force, and a correlation is formulated for predicting the solid flowrate based on the simulated results. It is also shown that the effect of geometrical design on solid flow is complicated and significant. Caution should be taken for any changes in the design. The findings should be useful for the design, control and optimization of the RS operation.

Keywords

Author Keywords:COREX; discrete element method; reduction shaft; screw feeder; sticking force

Full text available at https://www.jstage.jst.go.jp/article/isijinternational/54/8/54_1772/_article if you have access.

[powder technology paper online] DEM study of the flow of cohesive particles in a screw feeder

http://www.sciencedirect.com/science/article/pii/S0032591014000710

Highlights
Interparticle cohesion significantly affects solid flow in screw feeders.
Three flow regimes of cohesive particles in a screw feeder are identified.
The mechanism underlying the effect of interparticle cohesion is depicted.
The effects of some factors are quantified based on the DEM simulation.
Methods to reduce the effect of interparticle cohesion are discussed.
Abstract
Screw feeders are widely used in various industries to transfer granular materials at relatively precise rates. The performance can be affected by many factors such as the shape and size of particles, and the design of a screw and associated charging container. Some of these factors are difficult to investigate experimentally, including, for example, the cohesion between particles. In this work, a numerical model is developed by means of the discrete element method to study the flow of cohesive particles in screw feeders. In the model, the magnitude of the cohesive force is assumed, but it can be related to the van der Waals attraction for fine particles or the capillary force for wet particles. Based on the simulated results, a correlation for the prediction of solid flowrate is formulated as a function of the magnitude of cohesive force and the rotational speed of a screw. The mechanisms are then depicted in terms of contact forces and their spatial and temporal distributions. Three flow regimes, namely, continuous, intermittent and stable arch, are identified based on the standard deviation of solid flowrate in a screw feeder. Possible methods to reduce the effect of cohesive force on solid flow are discussed, in the study of the effects of the screw length in the associated charging container as well as the container design. The findings should be useful for the design and operation of screw feeders.

关于静电除尘器的多孔板流动的一个合作文章（纯CFD）in press

这篇文章对通过多孔板的气体流动进行了详细的分析，得出的结论对一些应用于多孔板的模型有一定的参考意义（比如porous jump condition）。指出压降的产生不是局限于孔内，而是由于孔后的涡造成主要的压力降。在数值模拟这类结构时，还是要仔细考虑在什么范围内考虑多孔板的压降。

Guo, B.Y., Q.F.Hou, Yu, A.B., Li, L.F. & Guo, J. (2012). Numerical Modelling of the Gas Flow through Perforated Plates. Chemical Engineering Research and Design.

http://www.sciencedirect.com/science/article/pii/S0263876212004224

[Paper online] Micromechanical modeling and analysis of different flow regimes in gas fluidization

Micromechanical modeling and analysis of different flow regimes in gas fluidization
Q.F. Hou, Z.Y. Zhou, A.B. Yu
Abstract
The micromechanics of different particle-fluid flow regimes, such as fixed, expanded and fluidized beds, in gas fluidization is investigated for group A and B powders. To establish the connection between macroscopic and microscopic descriptions of complex particle-fluid flows, focus is given to the following two aspects: the formation of a stable expanded bed in relation to the interparticle cohesive, sliding and rolling frictional forces, and the correlation between coordination number (CN) and porosity (ε). The method employed is the combined approach of three-dimensional (3D) discrete element method (DEM) and two-dimensional (2D) computational fluid dynamics. The results show that compared to 2D DEM, 3D DEM is more reliable in investigating the micromechanics of granular media, although both can capture key features of different flow regimes. The roles of various forces between particles and between particles and fluid are examined, and the origin of different flow regimes is discussed. It is shown that the cohesive force is critical to the formation of a static expanded bed, while the sliding and rolling frictional forces also play a role here. The criterion for bed expansion is analyzed at bulk and particle scales, and the deficiency at a bulk scale is identified. CN, as a key measure of local structure, is analyzed. It is found that the CN-ε relationship for group A powders has a transitional point between the expanded and fluidized bed flow regimes at a bulk scale, unlike group B powders. A new phase diagram is established in terms of CN-ε relationship that has two branches representing expanded and fluidized (bed) states, which corresponds to the one in terms of interparticle forces.

Highlights
► Flow regimes such as fixed, expanded and fluidized beds are numerically reproduced.
► The effects of various forces is analysed corresponding to different flow regimes.
► The contacts among particles and associated flow structures are studied in details.
► A new phase diagram is established to describe the flow regimes.

Keywords
Fluidization; Computational fluid dynamics; Discrete element method; Granular materials; Microstructure; Simulation

http://www.sciencedirect.com/science/article/pii/S0009250912005568?v=s5

Paper online: Computational study of the effects of material properties on heat transfer in gas fluidization

Ind. Eng. Chem. Res., 2012, 51 (35), pp 11572–11586

ABSTRACT

Heat transfer characteristics of different powders in gas fluidization are investigated by means of a combined approach of discrete element method and computational fluid dynamics. First, the heat transfer characteristics in three flow regimes of group A powders are examined. Then, the effects of the Hamaker constant and particle size, both related to the van der Waals force, are investigated in detail. The results confirm that the convective heat transfer is dominant, and radiative heat transfer becomes important when the bed temperature is high. However, conductive heat transfer also plays a role depending on the flow regimes and material properties. Significant effects of the Hamaker constant and particle size are observed under certain conditions. Finally, an effort is made to quantify the effects of the Hamaker constant, particle size and inlet gas velocity. The findings should be useful for better understanding and predicting the heat transfer in gas fluidization.

Keywords: fluidization; heat transfer; mathematical modeling; multiphase flow; cohesive force; discrete element method

Link:  http://pubs.acs.org/doi/abs/10.1021/ie3015999

Snapshots showing heating process of particles by hot air uniformly injected at the bed bottom in different flow regimes: (a) fixed bed (u_f/u_mf = 0.5); (b) expanded bed (u_f/u_mf = 1.4); and (c) fluidized bed (u_f/u_mf = 6.0). Particles are colored by their dimensionless temperatures.

A brief review paper of averaging methods in press: linking micro- and macro-properties of particulate flows

Linking discrete particle simulation to continuum process modelling for granular matter: Theory and application
H.P. Zhu^a, Z.Y. Zhou^b, Q.F. Hou^b and A.B. Yu^b, , 
In Press, Corrected Proof, Available online 12 June 2011

^a School of Engineering, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia

^b Laboratory for Simulation and Modelling of Particulate Systems, School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia

Received 8 September 2010;  

revised 11 January 2011;  

accepted 11 January 2011.  

Available online 12 June 2011. 

Abstract

Two approaches are widely used to describe particle systems: the continuum approach at macroscopic scale and the discrete approach at particle scale. Each has its own advantages and disadvantages in the modelling of particle systems. It is of paramount significance to develop a theory to overcome the disadvantages of the two approaches. Averaging method to link the discrete to continuum approach is a potential technique to develop such a theory. This paper introduces an averaging method, including the theory and its application to the particle flow in a hopper and the particle-fluid flow in an ironmaking blast furnace.

Zhu, H.P., Zhou, Z.Y., Hou, Q.F., Yu, A.B., 2011. Linking discrete particle simulation to continuum process modelling for granular matter: Theory and application. Particuology 9, 342-357.

A heat transfer paper in AIChE Journal is online

Computational study of heat transfer in a bubbling fluidized bed with a horizontal tube

1. Q.F. Hou, 
2. Z.Y. Zhou, 
3. A.B. Yu^,†

DOI: 10.1002/aic.12700

Keywords:

• Discrete particle simulation;
• Heat transfer;
• Fluidization;
• Horizontal tube

Abstract

A combined approach of discrete particle simulation and computational fluid dynamics is used to study the heat transfer in a fluidized bed with a horizontal tube. The approach is first validated through the good agreement between the predicted distribution and magnitude of local heat transfer coefficient with those measured. Then, the effects of inlet fluid superficial velocity, tube temperature and main particle properties such as particle thermal conductivity and Young's modulus are investigated and explained mechanistically. The relative importance of various heat transfer mechanisms is analysed. The convection is found to be an important heat transfer mode for all the studied conditions. A large convective heat flux corresponds to a large local porosity around the tube, and a large conductive heat flux corresponds to a large number of particle contacts with the tube. The heat transfer is enhanced by the increase of particle thermal conductivity while it is little affected by Young's modulus. Radiative heat transfer becomes increasingly important as the tube temperature is increased. The results are useful for temperature control and structural design of fluidized beds. © 2011 American Institute of Chemical Engineers AIChE J, 2011.

ISIJ 2005 paper: Comparison between standard and renormalization group k-epsilon models in numerical simulation of swirling flow tundish.

Q. Hou, Z. Zou. Comparison between standard and renormalization group k-epsilon models in numerical simulation of swirling flow tundish. ISIJ Int. 45(2005) 325-330.
http://dx.doi.org/10.2355/isijinternational.45.325
Because of the introduction of a cylindrical swirling chamber into a neotype tundish, the Swirling Flow Tundish (SFT), the numerical simulation becomes difficult for this kind of tundish by the standard two-equation k-epsilon turbulence model. So another kind of k-epsilon turbulence model, the Renormalization Group (RNG) k-epsilon turbulence model derived from the theory of renormalization group, was adopted and compared with the standard one. Both of these two kinds of turbulence models were used to simulate the flow patterns in SFT on staggered grid systems based on Finite Volume Method (FVM) with SIMPLER algorithm for steady 3D and incompressible Newtonian turbulent flows. The comparison of simulation results from these two models shows that the RNG k-epsilon turbulence model for SFT leads quicker convergence than the standard one. Unsymmetrical flow patterns were obtained and the grid independence of this mathematical model for SFT was also discussed. The theoretical analyses of forces on particle, turbulent kinetic energy distribution and lower flow velocity behind dam and weir show that there will be a good effect for non-metal inclusion aggregation and separation with the swirling chamber.

A co-authored paper in Chinese Science Bulletin (CSB): Averaging method of particulate systems

H. P. Zhu, Q. F. Hou, Z. Y. Zhou, A. B. Yu. Averaging method of particulate systems and its application to particle-fluid flow in a fluidized bed. Chin Sci Bull 54(2009) 4309-4317.

http://dx.doi.org/10.1007/s11434-009-0500-0

ABSTRACT: A particulate system can be described through the discrete approach at the microscopic level or through the continuum approach at the macroscopic level. It is very significant to develop the method to link the two approaches for the development of models allowing a better understanding of the fundamentals of particulate systems. Several averaging methods have been proposed for this purpose in the past, but they mainly focused on cohesionless particle systems. In this work, a more general averaging method is proposed by extending it for cohesionless particle systems. The application of the method to the particle-fluid flow in a gas fluidized bed is studied. The density, velocity and stress of this flow are examined. A detailed discussion has been conducted to understand the dependence of the averaged variables on sample size.

Publication in 2008 ISIJ (Click this title for link)

ISIJ Int., Vol. 48 (2008) No. 6, pp. 787-792, ISSN 0915-1559

Modelling of Inclusion Motion and Flow Patterns in Swirling Flow Tundishes with Symmetrical and Asymmetrical Structures

http://dx.doi.org/10.2355/isijinternational.48.787
Swirling flow tundish (SFT) has recently been developed as a new type of tundish. Its key mechanism is forming swirling flow to enhance inclusion removal from steel for high quality slab casting. This is achieved by guiding the liquid steel into the tundish through the tangential inlet of a cylindrical swirling chamber (SC). This can restrain and alleviate the turbulence of the impact zone. SC has been settled into two types of tundishes-originally symmetrical and asymmetrical. To understand the fundamentals, physical and mathematical modellings of this new process have been conducted in this work. Physical modellings are carried out with the utilization of an asymmetrical one-strand 1 : 2.5 and a symmetrical two-strand 1 : 3 scale models. The internal flow is measured by digital particle image velocimetry (DPIV). Numerical modelling is carried out in line with the physical modelling to examine the details of the flow patterns and rotational effect caused by the SC. The trajectories of non-metallic inclusion particles are also studied by discrete phase model (DPM) within the commercial CFD package environment, FLUENT. The mathematical model proposed is validated by comparing the predicted and measured residence time distribution and velocity fields. The results show that both originally symmetrical and asymmetrical flow fields have been changed to asymmetrical ones after setting SC into it. And the results show that the flow is slower behind the dam and weir. Examinations of the trajectories of inclusion particles suggest that the inclusion removal capacity of the SFT is higher than the tundish with a turbulence inhibitor (TI). From the separation ratio results, it can be seen that SFT has higher ability to remove small inclusion particles than a tundish with TI, which is of great significance especially for production of high-quality steel.