Physical Modeling Evaluation on Refining Effects of Ladlewith Different Purging Plug Designs

Fangguan Tan, Zhu He,* Shengli Jin, Liping Pan, Yawei Li, and Baokuan Li

1. Introduction

To meet the demands for high-quality steel, ladle refining is per-formed widely, which is used for temperature and compositionhomogenization, decarburization, desulphurization, and inclu-sion removal. In a typical secondary refining technique, argongas is blown into the molten steel from the bottom of the ladlefurnace through purging plugs. Bubbles are successively formedat the exit of the purging plugs, rise upward entraining the sur-rounding molten steel into their wakes, turn horizontally at thebath surface, push the slag layer to the periphery of the ladle, and

escape from the bath surface into theatmosphere.[1,2] Meanwhile, the inclusionsare attached to the rising bubbles and comeup to the slag layer with the bubbles.[3–5]

Nevertheless, the rising bubbles form aturbulent bubble plume, and the resultingslag eye causes the reoxidation of liquidsteel. Intense interactions occur betweenthe slag and molten steel because the over-lying slag is pushed to the side.[6] It iswidely known that the bubble size and itsmotion affect momentum, heat, and masstransfer in gas–liquid bubble flow.[7–9]

In addition, finer bubbles have a high prob-ability for inclusions attachment due totheir larger gas/liquid interfacial area,which is determinant to the quality ofsteel.[10] Therefore, bubbles play an impor-

tant role in the flow field, which affects not only the mixing timethat was usually applied for representing the chemical efficiency,but also inclusion removal rate that determines the cleanliness ofsteel liquid, and slag eye where slag entrapment and mass trans-fer always occurs.

Major process variables, such as gas flow rate, plug position,bath height, and slag layer, relevant to gas stirred ladle metal-lurgy, have been deeply studied, and their influences are nowknown with a considerable level of accuracy.[11,12] For instance,Conejo et al. explored the influences of the slag thickness,nozzle position, and the number of nozzles on mixing time.[13]

The effect of the nozzle diameter on the mixing has also beeninvestigated.[14] These results indicate the effect of the nozzleon mixing time. Moreover, to model the inclusion removal, acriterion applicable for a water model has been suggested, basedon which different sizes of inclusions can be represented by theparticle-to-liquid density ratio.[15] After that, certain studies haveestablished computational approaches and water model systemsto investigate the inclusion removal mechanism.[3–5,10] It hasbeen shown that the bubble size can be controlled by optimizedstructural of purging plug for higher inclusion removal rate andlower entrapment rate. In addition, to investigate the behavior ofthe slag layer, the relations between the slag eye area and oper-ating conditions were explored using a physical model.[16] Caoand Nastac developed a transient numerical model to simulateslag entrapment in a bottom gas stirring ladle.[7] It can be con-cluded that the variations in the main controlling parameters(bubble size and gas flow rate) and their potential impact onthe multiphase fluid flow and mass transfer characteristics(turbulent intensity, mass transfer rate, slag eye area, flow patterns,and so on) in gas-stirred ladles were quantitatively determinedto ensure the proper increase in the ladle refining efficiency.

Dr. F. Tan, Prof. Z. He, L. Pan, Prof. Y. LiThe State Key Laboratory of Refractories and MetallurgyWuhan University of Science and TechnologyWuhan 430081, ChinaE-mail: hezhu@wust.edu.cn

Dr. F. Tan, Prof. Z. He, L. Pan, Prof. Y. LiNational-Provincial Joint Engineering Research Center of HighTemperature Materials and Lining TechnologyWuhan University of Science and TechnologyWuhan 430081, China

Dr. S. JinChair of CeramicsMontanuniversität LeobenA-8700 Leoben, Austria

Prof. B. LiSchool of MetallurgyNortheastern UniversityShenyang 110819, China

The ORCID identification number(s) for the author(s) of this articlecan be found under https://doi.org/10.1002/srin.201900606.

DOI: 10.1002/srin.201900606

Circular slits are introduced in purging plugs for alleviating the stress concen-tration to prolong their service life. Herein, the effects of slits with differentgeometries on the mixing time, inclusion removal rate, and slag eye area arestudied by water model method. Experimental results show that the inclusionremoval rate decreases with increasing slit angle for the gas flow rate of less than6.02 NLmin�1. Moreover, with slit diameter increases, the mixing time andinclusion removal rate decrease when a gas flow rate is less than 5.26 NLmin�1.The slag eye area increases with increasing slit diameter, and the slit angle has apositive influence on the formation of the slag eye. Finally, the optimization of themixing time and inclusion removal rate for less consumption of stirring energyand less slag entrapment indicates that the smaller the slag eye area is, the betterthe refining effect is.

FULL PAPERl

www.steel-research.de

steel research int. 2020, 1900606 1900606 (1 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Recently, the model developed by Tan et al.[17] shows thatthe stress concentration of purging plug with rectangular slitsis directly related to its failure in service, whereas the stressconcentration of purging plug with circular slits was alleviatedsignificantly.[18] However, a comprehensive understanding ofthe metallurgical effect of this type of purging plug is stillrequired for effective process control and possible process opti-mization. In addition, one factor governing the bubble plumecharacteristics that can affect metallurgical effect is the geometryof the slits or orifices.[19–22]

As a consequence, herein, we adopted a physical model to fur-ther investigate the refining effect of purging plugs with differentslit geometries, i.e., the slit angles and diameters. To explore theinfluence of slit angle on the refining effect, purging plugs withtwo sets of slit angles for circular slits were used, and theircorresponding effects for different diameters were compared.Furthermore, three kinds of purging plugs with circular slitsof different diameters were prepared to investigate the effectof slit diameter on the refining effect.

2. Physical Modeling

2.1. Apparatus

A water model was established with transparent acrylic glass,at a reduced scale of ðλÞ 1∶5 of the industrial ladle nominalcapacity of 150 tons. Table 1 shows the detailed physicaldimension of both the actual purging plug and the scale model.Three experimental systems were designed to measure themixing time (Figure 1), inclusion removal rate (Figure 2),and slag eye area (Figure 3). In these systems, the liquidsteel and slag layer were simulated with water and bean oil,respectively. Instead of argon, N2 was blown into ladle throughthe purging plug, which was assembled at 0.5R (where R isthe radius of the model bottom). The operating conditionsused in water ladle and the material properties are shown inTable 2.

Instead of slit diameter, the slit number was reduced to ensurea 1:5 scale slit area for the water model considering the limit ofmanufacturing accuracy. Consequently, the gas-blown area ofthe purging plug was reduced to 20% of that of the prototype.Figure 4 shows a cross-sectional view of the purging plugprepared for the water model experiments and illustrates thediagram of slit angles. Table 3 shows the purging plugs with

different slit diameters and angles that were used to investigatethe impact of slit diameter and angles on the refining effect in thewater model experiment.

Table 1. Dimensions of reference purging plug for water model andprototype for practical usage.

Water model Prototype

Type of slit Circular Circular

Number of slits 28 150

Argon blowing area [mm2] 24 120

Size of slit ϕ ¼ 0:55mm ϕ ¼ 0:55mm

Diameter of top surface [mm] 25.4 125

Diameter of bottom surface [mm] 37.6 185

Height [mm] 71.1 350

Figure 1. Schematic of the water model system for measuring the mixingtime.

Figure 2. Schematic of the water model system for the inclusionremoval rate.

Figure 3. Schematic of the water model system for the slag eye area.

www.advancedsciencenews.coml

www.steel-research.de

steel research int. 2020, 1900606 1900606 (2 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

2.2. Similarity Criterion

To characterize the plume flow field in ladle metallurgy, a modi-fied Froude number, based on the similarity of kinetics, has beenapplied to determine the gas flow rate in the water model.[23]

However, Krishnapisharody and Irons[24] demonstrated thatthe modified Froude number is not appropriate enough todescribe flow development in ladles. Therefore, to model theplume and ladle hydrodynamics, they proposed an effectivedimensionless ratio, which deduced from the similarity

parameters of the plume. This dimensionless ratio in the proto-type is equal to that in the water model, and can be defined as

Gp ¼ρAg

2

ρst2

UAg2

gHp(1)

UAg ¼QAg

Sp(2)

For the water model

Gm ¼ ρNg2

ρw2

UNg2

gHm(3)

UNg ¼QNg

Sp(4)

Gm ¼ Gp (5)

λ ¼ Hm=Hp (6)

where G is the dimensionless ratio, U is the initial velocity, H isthe height, ρ is the density, g is the gravitational acceleration, Qis the gas flow rate, and S is the area of blowing. The subscriptsp, m, Ng, Ag, and st represent the prototype, water model, nitro-gen, argon, and liquid steel, respectively.

In actual metallurgy, the argon pressure is variable becausethe gas temperature would increase when it is injected into thegas supply network. Therefore, the relationship between the gasflow rate, temperature, and pressure is defined as[16]

QAg ¼T0

T in·Pin

P0Q 0

Ag (7)

where P0 and Pin are the standard atmospheric pressure(101 kPa) and the pressure at the gas inlet (Pin ¼ P0 þ ρst gh),respectively. T0 and T in are the room temperature (25 �C) and thesteel temperature (1600 �C), respectively, and Q 0

Ag is the gas flowrate, which was the actual flow rate at the gas inlet of the purgingplug immediately after ejection from the gas supply network.

Thus, the gas flow rate for the experiment can be obtainedusing Equation (8), which was deduced from the aforementionedequation. The gas flow rates for the experimental operation andin actual ladle metallurgy are shown in Table 4.

QNg ¼ 0:00752Q Ag (8)

To quantify the inclusion removal rate, it is assumed that theinclusions rise to the slag eye with the Stokes’ velocity, consider-ing the size range of inclusions in the ladle. The velocity of therising inclusions in the steel ladle can be divided into twocomponents, the rising velocity (V r;p) and the fluid velocity(V f ;p). For accurate simulation, the corresponding velocities,

Table 2. Dimensions of the ladle and material properties for water model.

Parameters Values Material properties Values

Top diameter [mm] 660 Water density [kg m�3] 1000

Bottom diameter [mm] 600 Water viscosity [kg m�1 s�1] 0.001

Liquid depth [mm] 500 Oil density [kg m�3] 900

Slag layer thickness [mm] 40 Oil viscosity [kg m�1 s�1] 0.058

Top diameter of plug [mm] 25 Gas density [kg m�3] 1.138

Bottom diameter of plug [mm] 37 Gas viscosity [kg m�1 s�1] 1.663� 10�5

Saturated (NaCl) [kg m�3] 1.205 Polystyrene density [kg m�3] 996

Inclusion density [kg m�3] 3500 Steel liquid density [kg m�3] 7020

Figure 4. Purging plugs for water model experiments. a) Cross-sectionalview and b,c) top view showing circular slits of different diameters.

Table 3. Purging plugs with various slit geometries and number.

Purging plug Number of slits Angle of slits Diameter [mm]

O-#28-02�-25 28 2 0.25

O-#28-00�-25 28 0 0.25

O-#28-02�-55 28 2 0.55

O-#28-00�-55 28 0 0.55

O-#50-02�-80 50 2 0.8

O-#50-02�-60 50 2 0.6

O-#50-02�-40 50 2 0.4

Table 4. Gas flow rates for water model experiment and actual ladlemetallurgy.

Value

Steel–argon system [NLmin�1] 93 300 400 500 600 700 800 900 1000

Water model system [NLmin�1] 0.7 2.26 3.01 3.76 4.51 5.26 6.02 6.78 7.51

www.advancedsciencenews.coml

www.steel-research.de

steel research int. 2020, 1900606 1900606 (3 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

V r;m and V f ;m, in the water model should follow Equation (9),which is based on the Froude criterion[14]

V f ;m

V f ;p¼ V r;m

V r;p¼

ffiffiffi

λp

(9)

The Stokes’ velocities for the rising inclusions in the watermodel and the prototype can be defined as

V r;m ¼ 2R2s;mgðρw � ρs;mÞ

9μw(10)

V r;p ¼2R2

s;pgðρst � ρs;pÞ9μst

(11)

where Rs,m is the diameter of the inclusions in the water model,Rs,p is the diameter of inclusions in the prototype, subscript srepresents the inclusions, μw is the molecular viscosity of thewater model, and μst is the molecular viscosity of the prototype.

Note that the particle-to-liquid density ratio in the watermodel is not equal to the inclusion-to-liquid density ratioof the material chosen for this experiment. Therefore, accord-ing to Equation (9)–(11) and based strictly on the Froudesimilarity criterion, the relationship of the inclusion sizeswith the prototype and the water model can be expressed byEquation (12).

Rs;m

Rs;p¼ λ0:25

2

6

4

�

1� ρs;pρst

�

�

1� ρs;mρw

�

3

7

5

0.5

(12)

Equation (12) implies that different sizes of inclusions can bemodeled by varying the particle-to-liquid density ratio.[15]

2.3. Experimental Section

Figure 1 shows the schematic of the water model system formeasuring the mixing time using the electric conductivitymethod, in which the saturated NaCl solution was dropped intothe ladle as a tracer. First, N2 gas was blown into the water modelthrough the slits of the purging plug, and the conductivityelectrode was placed at the position termed the “dead zone”where the flow rate of molten steel is less than 0.01m s�1, whichwas obtained from a numerical simulation (data not shown).When the flow field of the water model was stabilized, 150mLsaturated NaCl solution was dropped into the ladle from the slageye. Meanwhile, the electric conductivity meters DDSJ308F(REX, INESA, China) automatically detected the electricconductivity value every 0.1 s. The time taken to attain a stablevalue was the mixing time, which is deduced based on 95%homogenization.[12,25] Every measurement was conductedthree times.

The apparatus was established, referring to previousresearch,[26] which was applied for measuring the inclusionremoval rate (Figure 2). According to Equation (12), and polysty-rene (PS) particles of diameter 125–160 μm are used to simulateactual inclusions of diameter �50 μm.[27] The properties of thewater and PS particles are shown in Table 1. In this experiment,6 g PS particles were premixed with water, and then the

water–particle mixture was poured into empty water ladle.Meanwhile, the mixture was stirred in the clockwise and coun-terclockwise direction by paddle at a certain speed. Then, themixture water supply was stopped when the free surface reachedthe top of the ladle. At this moment, PS particles evenly sus-pended in the water model when the ladle is full of water–particlemixture. In addition, the time between the homogenizationand the beginning of the experiments was kept constant.Subsequently, water and gas were then injected into the modelat certain flow rates using the pump, and the water supply causedan overflow of the mixture from the top of the ladle. After 30 s,the PS particles were filtered from the overflowing water, thendried and weighed to calculate the inclusion removal rate ηaccording to Equation (13).[26,28] For improving the accuracyof measurement, every set of experiments was repeated threetimes.

η ¼ ωd

ω0(13)

where ωd is the weight of filtered particles, and ω0 is the weightof particles that were suspended in the water model.

Figure 3 shows the water model for exploring the slag eye area.A high-speed camera was used to capture the boundariesbetween oil and water under certain conditions. When the flowfield of the water model was stabilized, the high-speed camerabegan capturing images at 15 frames s�1. Due to the unsteadynature of the slag eye area, three images were chosen from everyexperiment, and the average slag eye area was evaluated fromthese images following the threshold technique.[29] In addition,the experiment was repeated five times for each operatingcondition.

3. Results and Discussion

3.1. The Behavior of Bubbles and Gas Plume

Figure 5 shows the bubble plume region for a gas flow rate of4.51 NLmin�1 with slit angles of 0� and 2�. The standard devia-tion is depicted as error bars. It can be observed that the smallerbubbles are successively formed at the exit of the purging plugsand then rise upward. Furthermore, Figure 5 also shows that theslit angle affects the initial size of the ejected bubble, which is

Figure 5. Gas plume: a) slit angle: 2�; b) slit angle: 0�—for a gas flow rateof 4.51 NLmin�1.

www.advancedsciencenews.coml

www.steel-research.de

steel research int. 2020, 1900606 1900606 (4 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

consistent with previous research.[21] Subsequently, the conicalgas plume is formed when nitrogen gas is injected into theladle. As shown in Figure 6, with the rising of bubbles, the latterwill catch up with the former, and coalesce into a larger bubble.The angle of the gas plume formed by the purging plug with aslit angle of 2� is smaller compared with the purging plug with aslit angle of 0�, which was marked by the red line, as shown inFigure 5. This phenomenon can be explained as follows: whenthe slit angle increases, the trajectory of ejected bubbles is easierto cross. As a result, the angle of the gas plume is smaller. Inaddition, the cross-trajectory of ejected bubbles also increasesthe probability of bubble collision and coalescence, which leadsto the formation of more large bubbles and greater consump-tion of the stirring energy. Accordingly, the mean size of thebubbles from the purging plug with a large slit angle wasincreased.

3.2. Effects on Mixing Time

Figure 7 shows the influence of the slit angle on the mixingtime, in which purging plugs with two different slit anglesand diameters were considered under different gas flow rates.It appeared that with increasing the gas flow rate, the mixingtime decreased, and for a larger slit diameter, a significantlyshorter mixing time can be obtained when the gas flow ratewas moderate. For a larger gas flow rate, the influence of slit

diameter was negligible. Although the slit angle was changedfrom 0� to 2�, the mixing time increased when the diameter ofslits is 0.25 mm, but the mixing time decreased when thediameter of slits is 0.55 mm. It was indicated that the influenceof slit diameter is more significant than that of a slit angleon the evolution of the flow field. Moreover, when the gasflow rate exceeded 6.02 NLmin�1, the slope of the mixing timecurve decreased and approached zero (Figure 7). This phenom-enon is attributed to the consumption of the stirring energyto form a larger slag eye once the gas flow rate reaches a criticalvalue.[30]

Figure 8 shows the evolution of the mixing time with respectto the gas flow rate to further analyze the effect of purgingplugs with varying circular slit diameters. The mixing timedecreased rather rapidly when the gas flow rate was less than4.51 NLmin�1. Meanwhile, the mixing time decreased withincreasing diameter of the circular slit. This may be a conse-quence of the effective increase in the blown area for the samegas flow. As has been previously reported, stirring energy is acrucial factor during molten mixing in the ladle, and mainlydepends on the gas flow rate.[1] Figure 8 also shows that thedifference in the mixing time for different slit diameters is insig-nificant when the gas flow rate is larger than 3.01 NLmin�1;this trend agrees well with the previous research.[14,31] This islikely due to the consumption of the stirring energy, which pro-longed the mixing time.[17]

Figure 6. Coalescence of bubbles (slit angle: 0�, gas flow rate: 4.51 NLmin�1).

Figure 8. Influence of purging plugs with different slit diameters on themixing time.

Figure 7. Influence of purging plugs with different slit angles and diam-eters on the mixing time.

www.advancedsciencenews.coml

www.steel-research.de

steel research int. 2020, 1900606 1900606 (5 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

3.3. Effects on Inclusion Removal Rate

Figure 9 shows the inclusion removal rates as a function of gasflow rates for the purging plugs with two slit angles and slit diam-eters. With increasing gas flow rates in a certain range, the inclu-sion removal rate increased. As reported in previous research,[10]

the finer bubbles possess a larger gas/interfacial area and higherattachment probability of the inclusions to bubbles, which lead toan increasing inclusion removal rate. As mentioned previously,an increase in the slit angle is accompanied by a higher proba-bility of bubble collision, and the bubble size will grow largerwhile rising. Therefore, when the slit angle was changed from0� to 2�, and the diameter was the same, the inclusion removalrate decreased. However, it is shown in Figure 9 that the inclu-sion removal rate reached a maximum at 5.26 NLmin�1 gas flowrate. This phenomenon can be explained as follows. As reportedin previous research, the bubble size has a V-shaped relationshipwith the gas flow rate at the same slit diameter.[10] Furthermore,finer bubbles processed high attachment probability of inclu-sions to bubbles. As a result, the inclusion removal rate reacheda maximum at 5.26 NLmin�1 gas flow rate because the bubblesize is smallest at this time.

Figure 10 shows the changes in the inclusion removal rate forpurging plugs with different slit diameters with 50 slits. It showsthat when the gas flow rate reached a critical value, the inclusionremoval rate decreased instead of further increased. This is pos-sible because the bubble size will gradually increase with the gasflow rate in a certain range.[21] Moreover, with increasing the slitdiameter, the inclusion removal rate decreased; this is more pro-nounced for a low gas flow rate. In reference to a previous inves-tigation, there is a V-shaped relationship between the bubble sizeand orifice diameter, where the turning point is located at an ori-fice diameter of 0.25mm.[19] The slit diameters used in the pres-ent diagram were larger than the diameter at the turning point.Consequently, the bubble size increases with increasing slitdiameter. The increase in bubble size reduced the inclusionremoval rate, as shown in Figure 9 and 10.

3.4. Effects of the Slag Eye Area

Figure 11 shows the changes in the slag eye area for purgingplugs with different slit angles and slit diameters. The slageye area increased with the gas flow rate, as was also reportedin a previous study.[32] As shown in Figure 5 and 6, an increasein the slit angle may lead to a higher probability of collisions andcoalescence/breakup of bubbles, and a smaller plume angle.Therefore, the slit angle has a positive influence on the formationof the slag eye area, which is consistent with the results shown inFigure 11. Furthermore, considering the dissipation of the stir-ring energy by the ladle wall and the behavior of the slag layer,[33]

the difference among the slag eye areas decreases with increas-ing gas flow rate. In addition, although the slit diametergrows, the impact of the slit angle on the slag eye area decreases.

Figure 9. Comparison of inclusion removal rates for purging plugs withdifferent slit angles and diameters.

Figure 10. Comparison of inclusion removal rates for purging plugs withdifferent slit diameters.

Figure 11. Effects of the slit angles on the slag eye area.

www.advancedsciencenews.coml

www.steel-research.de

steel research int. 2020, 1900606 1900606 (6 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This is likely attributed to the larger bubble, which brings about aweaker turbulence in the ladle.[7]

Figure 12 shows the relationship between the slit diameter ofthe purging plug and the slag eye area when the slit number is50. When the gas flow rate increased, the slag eye area increasedsignificantly, which is because the input energy is dissipated dueto slag emulsification, generating slag droplets.[34,35] It should benoted that, for cases in Figure 12, the gas flow rate in each slit isdiminished due to the increased slit number and the enlarged slitdiameter. As a consequence, although the slit diameter increases,the discrepancy of the slag eye area in Figure 12 is not apparentwhile the gas flow rate is the same. As known, when gas is blowninto melt steel, the overlying slag is pushed away by floating bub-bles, resulting in the formation of an exposed eye in the ladle.This eye leads to higher heat losses, reoxidation of the moltensteel, and slag entrapment. Nevertheless, the homogeneity ofthe chemical constituents and the temperature shall be main-tained.[36] It can be concluded that the reduction of the slageye area and mixing time, and increase in inclusion removal ratecannot be achieved at the same operation condition in practicalityprocess. Thus, the slit diameter, slit angle, and gas flow rate needto be optimized to achieve the excellent performance of the refin-ing effect in further study.

4. Conclusion

In summary, a physical model was used to investigate the influ-ences of purging plugs with different slit angles (0� and 2�) andslit diameters on the mixing time, inclusion removal rate,and slag eye area. The following conclusions can be drawn:1) When the gas flow rate was less than 6.02 NLmin�1 andthe diameter of the slits was 0.55mm, the increase in the slitangle had a positive influence on the mixing time; however,the inclusion removal rate decreased with increasing the slitangle. 2) When the diameter of the slits was increased, the mix-ing time was shortened, and the inclusion removal ratedecreased for a gas flow rate of less than 5.26 NLmin�1.

3) The slag eye area increased with increasing slit diameter,and the increase in the slit angle had a positive influence onthe formation of the slag eye. 4) For a better mixing time andinclusion removal rate, the smaller the slag eye area is, the lesserthe stirring energy will be consumed, and the lesser the slagentrapment will be.

Therefore, despite the nozzle position and separation angle,changing the slit angle could also optimize the flow field andthereby shorten the mixing time and decrease the inclusionremoval rate. Varying the diameter of the circular slits, in thisstudy, is a novel approach to control the bubble size for excellentrefining.

AcknowledgementsThis work was financially supported by the National Natural ScienceFoundation of China (grant no. 51974211) and the Special Project ofCentral Government for Local Science and Technology Development ofHubei Province (grant nos. 2019ZYYD003 and 2019ZYYD076).

Conflict of InterestThe authors declare no conflict of interest.

Keywordscircular slits, purging plugs, refining effects, slit angles, water modelexperiments

Received: November 19, 2019Revised: March 9, 2020

Published online:

[1] T. Haiyan, G. Xiaochen, W. Guanghui, W. Yong, ISIJ Int. 2016, 56, 2161.[2] D. Mazumdar, J. W. Evans, Metall. Mater. Trans. B 2004, 35, 400.[3] X. Guo, J. Yu, X. Ren, D. Xue, W. Xuan, Y. Zhong, Z. Ren, Ironmaking

Steelmaking 2018, 45, 648.[4] Y. J. Kang, L. Yu, D. Sichen, Ironmaking Steelmaking 2007, 34, 253.[5] L. Zhang, S. Taniguchi, K. Matsumoto, Ironmaking Steelmaking 2002,

29, 326.[6] Q. N. Hoang, M. A. Ramírez-Argáez, A. N. Conejo, B. Blanpain,

A. Dutta, JOM 2018, 70, 2109.[7] Q. Cao, L. Nastac, Metall. Mater. Trans. B 2018, 49, 1388.[8] S. V. Komarov, M. Sano, ISIJ Int 1998, 38, 1045.[9] H. Duan, L. Zhang, B. G. Thomas, A. N. Conejo,Metall. Mater. Trans.

B 2018, 49, 2722.[10] L. Zhang, J. Aoki, B. G. Thomas,Metall. Mater. Trans. B 2006, 37, 361.[11] K. B. Owusu, T. Haas, P. Gajjar, M. Eickhoff, P. Kowitwarangkul,

H. Pfeifer, Steel Res. Int. 2019, 90, 1800346.[12] R. González-Bernal, G. Solorio-Diaz, A. Ramos-Banderas,

E. Torres-Alonso, C. A. Hernández-Bocanegra, R. Zenit, Steel Res.Int. 2018, 89, 1700281.

[13] A. N. Conejo, S. Kitamura, N. Maruoka, S. J. Kim,Metall. Mater. Trans.B 2013, 44, 914.

[14] M. S. C. Terrazas, A. N. Conejo,Metall. Mater. Trans. B 2015, 46, 711.[15] Y. Sahai, T. Emi, ISIJ Int. 1996, 36, 1166.[16] Z. Liu, L. Li, B. Li, ISIJ Int. 2017, 57, 1971.[17] F. Tan, Z. He, S. Jin, H. Cai, B. Li, Y. Li, H. Harmuth, Steel Res. Int.

2019, 90, 1900213.

Figure 12. Effects of the slit diameters on the slag eye area.

www.advancedsciencenews.coml

www.steel-research.de

steel research int. 2020, 1900606 1900606 (7 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

[18] F. Tan, Z. He, S. Jin, H. Cai, B. Li, Y. Li, ISIJ Int. 2020, unpublished.[19] J. Yuan, Y. Li, N. Wang, Y. Cheng, X. Chen, Metall. Mater. Trans. B

2016, 47, 1649.[20] J. Xie, X. Zhu, Q. Liao, H. Wang, Y.-D. Ding, Int. J. Heat Mass. Tran.

2012, 55, 3205.[21] C. Liu, B. Liang, S. Tang, E. Min, Chin. J. Chem. Eng. 2013, 21, 1206.[22] S. D. Bari, A. J. Robinson, Exp. Therm. Fluid. Sci. 2013, 44, 124.[23] M. A. S. C. Castello-Branco, K. Schwerdtfeger, Metall. Mater. Trans. B

1994, 25, 359.[24] K. Krishnapisharody, G. A. Irons,Metall. Mater. Trans. B 2013, 44, 1486.[25] H. Tang, J. Liu, S. Zhang, X. Guo, J. Zhang, Ironmaking Steelmaking

2019, 46, 405.[26] M. Kawabata, Y. Tsukaguchi, J. Kang, K. Hayashi, A. Tomiyama, ISIJ

Int. 2019, 59, 209.

[27] T. Merder, M. Warzecha, P. Warzecha, J. Pieprzyca, A. Hutny, SteelRes. Int. 2019, 90, 1900193.

[28] H. Arai, PhD Thesis, Tohoku University, 2010.[29] X. D. Xu, G. Brooks, W. Yang, S. Curic, Ironmaking Steelmaking 2010,

37, 620.[30] Y. Kishimoto, Y. Sheng, G. A. Irons, J.-S. Chang, ISIJ Int. 1999, 39, 113.[31] A. N. Conejo, R. Mishra, D. Mazumdar, Metall. Mater. Trans. B 2019,

50, 1490.[32] K. Krishnapisharody, G. A. Irons, Metall. Mater. Trans. B 2006,

37, 763.[33] D. Mazumdar, R. I. L. Guthrie, Metall. Mater. Trans. B 2010, 41, 976.[34] S. Chatterjee, K. Chattopadhyay,Metall. Mater. Trans. B 2016, 47, 508.[35] L. T. Khajavi, M. Barati, ISIJ Int. 2010, 50, 654.[36] K. Krishnapisharody, G. A. Irons,Metall. Mater. Trans. B 2015, 46, 191.

www.advancedsciencenews.coml

www.steel-research.de

steel research int. 2020, 1900606 1900606 (8 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim