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Mathematical and Physical Simulations of BOF Converters
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.ORCID iD: 0000-0001-6212-7662
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The purpose of this study is to develop mathematical models to explore the mixing and its related phenomena in converter bath. Specifically, first, a mathematical model of a physical model converter, which was scaled down to 1/6th of a 30 t vessel, was developed in this study. A number of parameters were studied and their effects on the mixing time were recorded in a top blown converter. Second, a mathematical model for a combined top-bottom blown was built to investigate the optimization process. Then, a side tuyere was introduced in the combined top-bottom blown converter and its effects on the mixing and wall shear stress were studied. Moreover, based on the above results, the kinetic energy transfer phenomena in a real converter were investigated by applying the mathematical models.

A simplified model, in which the calculation region was reduced to save calculation compared to simulations of the whole region of the converter, was used in the mathematical simulation. In addition, this method was also used in the simulation of real converters. This approach makes it possible to simulate the Laval nozzle flow jet and the cavity separately when using different turbulence models.

In the top blown converter model, a comparison between the physical model and the mathematical model showed a good relative difference of 2.5% and 6.1% for the cavity depth and radius, respectively. In addition, the predicted mixing time showed a good relative difference of 2.8% in comparison to the experimental data. In an optimization of a combined top-bottom blown converter, a new bottom tuyere scheme with an asymmetrical configuration was found to be one of the best cases with respect to a decreased mixing time in the bath. An industrial investigation showed that the application effects of the new tuyere scheme yield a better stirring condition in the bath compared to the original case. Furthermore, the results indicated that the mixing time for a combined top-bottom-side blown converter was decreased profoundly compared to a conventional combined top-bottom blown converter. It was found that the side wall shear stress is increased by introducing side blowing, especially in the region near the side blowing plume.

For a 100 t converter in real, the fundamental aspects of kinetic energy transfer from a top and bottom gas to the bath were explored. The analyses revealed that the energy transfer is less efficient when the top lance height is lowered or the flowrate is increased in the top blowing operations. However, an inverse trend was found. Namely, that the kinetic energy transfer is increased when the bottom flowrate is increased in the current bottom blowing operations. In addition, the slag on top of the bath is found to dissipate 6.6%, 9.4% and 11.2% for the slag masses 5, 9 and 15 t compared to the case without slag on top of the surface of the bath, respectively. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xii, 47 p.
Keyword [en]
BOF, physical model, mathematical model, mixing time, kinetic enregy
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-175462ISBN: 978-91-7595-714-2 (print)OAI: oai:DiVA.org:kth-175462DiVA: diva2:861142
Public defence
2015-11-06, M3, Brinellvägen 68, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20151015

Available from: 2015-10-15 Created: 2015-10-15 Last updated: 2015-10-15Bibliographically approved
List of papers
1. Mathematical and physical simulation of a top blown converter
Open this publication in new window or tab >>Mathematical and physical simulation of a top blown converter
Show others...
2014 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 2, 273-281 p.Article in journal (Refereed) Published
Abstract [en]

A mathematical model of a top blown converter, which was based on a physical model of a 30 t vessel, was developed in this study. A simplified model consisting of the converter was used in the mathematical simulation. With the simplified model, it is possible to run a large number of tracer calculations within a short time, compared to solving for the entire flow evolution each time. A cavity depth and radius comparison has been done between the physical model and the mathematical model, which showed a good relative difference of 2.5% and 6.1% for the cavity depth and radius, respectively. The velocity change in the bath of the converter was monitored by setting several monitoring points in the physical model. A fully developed flow field was assumed to occur when the fluctuations in these points were small or periodic. It took approximately 25 s to get a developed flow field. In addition, the predicted mixing time showed a good relative difference of 2.8% in comparison to the experimental data. A simplified model consisting of the converter has been used in the mathematical simulation. The comparison between the physical model and the mathematical model shows that the simplified top blown model can successfully be used to calculate long-time simulations, and the mixing time calculations in frozen field can save a large amount of time compared to the simulation time using a transient flow field.

Keyword
converter, mixing time, cavity, simplified model, top blown
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-142979 (URN)10.1002/srin.201300310 (DOI)000331948200011 ()2-s2.0-84893635768 (Scopus ID)
Note

QC 20140314

Available from: 2014-03-14 Created: 2014-03-14 Last updated: 2017-12-05Bibliographically approved
2. Optimization of Combined Blown Converter Process
Open this publication in new window or tab >>Optimization of Combined Blown Converter Process
2014 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, no 10, 2255-2262 p.Article in journal (Refereed) Published
Abstract [en]

A 1/6th scaled down physical model was used to study and optimize the stirring condition of a 30 t converter. A number of parameters were studied and their effects on the mixing time were recorded. A new bottom tuyere scheme with an asymmetrical configuration was found to be one of the best cases with respect to a decreased mixing time in the bath. Mathematical modeling was employed to study the flow field characteristics caused by the new tuyere scheme. In the mathematical model, a comparison between the existing and the new tuyere setups was made with regards to the mixing time and turbulence in the bath. In addition, a new volumetric method for calculating the mixing time was applied. The results showed that, on average, a 23.1% longer mixing time resulted from the volumetric method compared to the standard method where discrete point are used to track the mixing time. Furthermore, an industrial investigation was performed to check the effects of the new tuyere scheme in a converter by analyzing the [O], [C] and [P] contents in the bath. The results showed that the application effects of the new tuyere scheme yield a better stirring condition in the bath compared to the original case.

Keyword
Combined blown, Converter, Industrial experiment, Mixing time, Optimized scheme
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-150640 (URN)10.2355/isijinternational.54.2255 (DOI)000343741200016 ()2-s2.0-84908473652 (Scopus ID)
Note

QC 20141121. Updated from manuscript to article in journal. Previous title: "Optimization of the Combined Blown Converter Process".

Available from: 2014-09-08 Created: 2014-09-08 Last updated: 2017-12-05Bibliographically approved
3. Numerical and Physical Simulations of a Combined Top-Bottom-Side Blown Converter
Open this publication in new window or tab >>Numerical and Physical Simulations of a Combined Top-Bottom-Side Blown Converter
2015 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, no 11, 1328-1338 p.Article in journal (Refereed) Published
Abstract [en]

In this study, a side tuyere was introduced to investigate how it is possible to lower the mixing time and to avoid problems of a reduced stirring when using the application of slag splashing process in the combined top and bottom blown converter. Both physical and mathematical models were applied to study the flow in the bath. Specifically, the effects of a side-blowing gas jet on the bath stirring intensity was studied. The results indicate that the mixing time for a side blown converter is decreased profoundly compared to a conventional combined top and bottom blown converter. Overall, the mathematical model showed similar trends and a good agreement with that of the physical modeling data. Furthermore, the shear stress at the wall in the top-bottom-side (TBS) converter was considered, since the furnace lining is important when side blowing is used in the converter. It was found that the side wall shear stress is increased by introducing side blowing, especially in the region near the side blowing plume. Three side tuyeres with different locations in the same level did not show any obvious effects on the mixing of the bath, but showed apparent differences in the shear stress and the oscillation of the bath. Overall, the results showed that the mathematical model can be used to design the configuration of the metallurgical vessels when it is necessary to consider the oscillation and the shear stress of the bath.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2015
Keyword
side tuyere, converter, mathematical model, mixing time, shear stress
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-175464 (URN)10.1002/srin.201400376 (DOI)000363679600011 ()2-s2.0-84945469118 (Scopus ID)
Note

QC 20151120

Available from: 2015-10-15 Created: 2015-10-15 Last updated: 2017-12-01Bibliographically approved
4. Numerical Simulations of the Kinetic Energy Transferin the Bath of a BOF Converter
Open this publication in new window or tab >>Numerical Simulations of the Kinetic Energy Transferin the Bath of a BOF Converter
2016 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 1, 434-445 p.Article in journal (Refereed) Published
Abstract [en]

The paper focuses on the fundamental aspects of the kinetic energy transfer from a top andbottom gas injection to the bath of the basic oxygen furnace (BOF) by applying a mathematicalmodel. The analyses revealed that the energy transfer is less efficient when top lance height islowered or the flowrate is increased in the top blowing operations. However, an inverse trendwas found that the kinetic energy transfer is increased when the bottom flowrate is increased forthe current bottom blowing operation conditions. The kinetic energy transfer index resultsindicated that the energy transfer for the bottom blowing is much more efficient than that of thetop blowing operations. To understand the effects of the upper buoyant phase on the energydissipation of the bulk liquid in the bath, different mass and physical properties of slag and foamwere considered in the bottom blowing simulations. The slag on top of the bath is found todissipate by 6.6, 9.4, and 11.2 pct for slag mass values of 5, 9, and 15 t compared to the casewithout slag atop the surface of the bath, respectively. The results showed that the kinetic energytransfer is not largely influenced by the viscosity of the upper slag or the foaming phases.

Place, publisher, year, edition, pages
Springer, 2016
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-175465 (URN)10.1007/s11663-015-0465-0 (DOI)000368692300040 ()2-s2.0-84958160131 (Scopus ID)
Note

QC 20160210

Available from: 2015-10-15 Created: 2015-10-15 Last updated: 2017-12-01Bibliographically approved

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