Numerical Modeling of Dehydrogenation and Denitrogenation in Industrial Vacuum Tank Degassers

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.advisor Louhenkilpi, Seppo, Prof., Aalto University, Department of Materials Science and Engineering, Finland Yu, Shan 2014-09-24T09:00:13Z 2014-09-24T09:00:13Z 2014
dc.identifier.isbn 978-952-60-5839-9 (electronic)
dc.identifier.isbn 978-952-60-5838-2 (printed)
dc.identifier.issn 1799-4942 (electronic)
dc.identifier.issn 1799-4934 (printed)
dc.identifier.issn 1799-4934 (ISSN-L)
dc.description.abstract Hydrogen and nitrogen are inescapable elements in all commercial steel products and the presence of dissolved hydrogen and nitrogen in liquid steel can cause various problems in most of the final products. In general, the reduction of these elements in liquid steel is required in most steelmaking companies, where vacuum treatment is typically applied to remove these impurities. The main focus of this thesis work has been put on investigating the dehydrogenation and/or denitrogenation behavior in a number of operational vacuum tank degassers (VTD) from different industrial plants. A literature review on various investigations and modeling techniques in the related field was firstly presented in this report. Based on the developed theories and methods that are relatively separate in the open literature, an integrated computational fluid dynamics (CFD) model was built to better understand the degassing process on an industrial scale and more importantly, for accurate predictions that are of considerable importance to industrial process operators. The CFD model consists of two sub-routines for calculating multiphase flows and species transportations, respectively. The commercial CFD package of ANSYS FLUENT was adopted and augmented by various user-defined functions. As for the multiphase sub-model, the standard k-epsilon equations were extended by adding extra source terms to consider the impact of gas injections on turbulence quantities. The sub-model was validated by using literature data for an aqueous system whose similarity represented one of the industrial VTDs studied in this work. With the extended k-epsilon equations, deviations from measured data of axial liquid velocity and turbulent kinetic energy were lower than 13 % and 18 % respectively, whereas the deviations were about 30 % and 85 % with the standard equations. For mass transfer calculations, two fundamental expressions that have been commonly employed to compute mass transfer coefficient in gas-liquid systems were assessed. Comparisons with process data showed that the eddy-cell correlation provides a better prediction under the studied conditions. The versatility of the CFD model was further demonstrated by performing extensive simulations to cover the effect of gas flow rate, initial element (i.e., hydrogen and nitrogen) content and steel compositions on final element content and degassing rate. For hydrogen removal, deviations from measured data in different industrial plants were ranged between 6 % and 14 % and for nitrogen removal, the deviations were generally lower than 13 %. en
dc.format.extent 59 + app. 68
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Aalto University en
dc.publisher Aalto-yliopisto fi
dc.relation.ispartofseries Aalto University publication series DOCTORAL DISSERTATIONS en
dc.relation.ispartofseries 131/2014
dc.relation.haspart [Publication 1]: Shan Yu and Seppo Louhenkilpi: Numerical Simulation of Dehydrogenation of Liquid Steel in the Vacuum Tank Degasser, Metallurgical and Materials Transactions B, 44 (2013), pp. 459-468. DOI: 10.1007/s11663-012-9782-8
dc.relation.haspart [Publication 2]: Shan Yu, Jyrki Miettinen and Seppo Louhenkilpi: Numerical Study on the Removal of Hydrogen and Nitrogen from the Melt of Medium Carbon Steel in Vacuum Tank Degasser, Materials Science Forum, 762 (2013), pp. 253-260. DOI: 10.4028/
dc.relation.haspart [Publication 3]: Shan Yu, Jyrki Miettinen and Seppo Louhenkilpi: Modeling Study of Nitrogen Removal from the Vacuum Tank Degasser, Steel Research International, DOI: 10.1002/srin.201300262.
dc.relation.haspart [Publication 4]: Shan Yu, Jyrki Miettinen, Lei Shao and Seppo Louhenkilpi: Mathematical Modeling of Nitrogen Removal from the Vacuum Tank Degasser, accepted for publication in Steel Research International.
dc.subject.other Metallurgy en
dc.title Numerical Modeling of Dehydrogenation and Denitrogenation in Industrial Vacuum Tank Degassers en
dc.type G5 Artikkeliväitöskirja fi Kemian tekniikan korkeakoulu fi School of Chemical Technology en
dc.contributor.department Materiaalitekniikan laitos fi
dc.contributor.department Department of Materials Science and Engineering en
dc.subject.keyword CFD en
dc.subject.keyword dehydrogenation en
dc.subject.keyword denitrogenation en
dc.subject.keyword vacuum tank degasser en
dc.identifier.urn URN:ISBN:978-952-60-5839-9
dc.type.dcmitype text en
dc.type.ontasot Doctoral dissertation (article-based) en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.contributor.supervisor Louhenkilpi, Seppo, Prof., Aalto University, Department of Materials Science and Engineering, Finland
dc.opn Saxén, Henrik, Prof., Åbo Akademi University, Finland 2014-08-26
dc.contributor.lab Metallurgy en
dc.contributor.lab Metallurgia fi
dc.rev Fabritius, Timo, Professor, University of Oulu, Finland
dc.rev Jönsson, Pär, Professor, KTH Royal Institute of Technology, Sweden 2014-10-03

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