Multiphysical Modeling Approach for Basic Oxygen Steelmaking Process

Ari Kruskopf

Multiphysical Modeling Approach for Basic Oxygen Steelmaking Process

Julkaisun otsikon käännös: Multifysikaalinen työkalu teräskonvertteriprosessiin

Ari Kruskopf

Kemian tekniikan ja metallurgian laitos

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Primäärimetallurgiassa teräksen konvertointi on tärkeä prosessivaihe. Teräksen konvertoinnissa hiili ja muutamia muita alkuaineita poistetaan metallisulasta puhaltamalla happea sulan päälle. Konvertterissa käytetään yleensä romua metallisulan jäähdyttämiseen. Monissa konverttereissa metallisulaa sekoitetaan inertillä kaasulla, joka puhalletaan pohjasuuttimien kautta. Konvertterin prosessimalleilla pyritään ennustamaan lämpötilan ja koostumuksen kehitystä metalli- ja kuonafaaseissa prosessin aikana. Prosessimallit ovat yleensä hyvin yksinkertaisia ja ne laskevat prosessin tilaa reaaliaikaisesti. Reaaliaikaisuus on tärkeää prosessin säätämisen kannalta. Tämän työn tarkoitus oli parantaa teräskonvertterin tärkeimpien ilmiöiden numeerista mallinnusta ja saavuttaa samalla reaaliaikainen laskenta. Tässä väitöstyössä kehitettiin uusia algoritmeja ja numeerisia menetelmiä neste/kaasu kaksifaasi-virtaukseen, useiden faasien välisiin kemiallisiin reaktioihin, sekä kiinteän romun sulamiseen. Kehitetyt mallit on jaettu kolmeen alikategoriaan, jotka on validoitu erikseen. Lisäksi työssä on muodostettu teoreettinen pohja alimallien yhdistämiseksi yhdeksi kokonaismalliksi. Kaikki alimallit kykenevät reaaliaikaiseen laskentaan. Työssä kehitettyjä mallinnuskonsepteja voidaan soveltaa myös muihin pyrometallurgisiin korkealämpötilaprosesseihin.Romun sulamismalli kehitettiin tässä työssä 1-dimensioiseksi. Mallin tavoitteena oli ennustaa metallisulan jähmettyminen kylmän romun pintaan sekä näin muodostuneen jähmeän kuoren ja perusmateriaalin sulaminen. Kyseiset faasimuutokset otetaan huomioon liikkuvalla numeerisella laskentahilalla. Romun sulamismalli validoitiin vertaamalla laskentatuloksia mittauksiin, jotka oli tehty upokkaassa kolmelle eri metallisulan lämpötilalle. Tulokset olivat hyvin sopusoinnussa mittausten kanssa. 2-dimensioinen numeerinen kaksifaasivirtausmalli kehitettiin laskemaan kaasun pohjapuhalluksen vaikutuksia metallisulan virtauskenttään ja sen sekoittumiseen. Algoritmin tarkoituksena on säilyttää geometrian nesteen kokonaismassa ja samalla saavuttaa laskentatulos tehokkaasti. Malli validoitiin vertailemalla tuloksia kolmen vesimallin mittauksiin. Yksi näistä vesimalleista oli verrattavissa teollisuusmittakaavan teräskonvertteriin.Kemiallisten reaktioiden malli kehitettiin laskemaan termodynaaminen tasapaino bulkkifaasienväliselle rajapinta-alueelle, jota kutsutaan reaktiotilavuudeksi. Prosessissa tapahtuvien kemiallisten reaktioiden eteneminen lasketaan sitten bulkkifaasien ja reaktiotilavuuden välisen aineensiirron kautta. Tasapainolaskenta mahdollistaa myös mahdollisten kiinteiden kuonakomponenttien erkautumisen ennustamisen. Malli validoitiin vertaamalla tuloksia mittauksiin, jotka oli tehty teollisuuskokoluokan teräskonvertterissa. Vertailut samanaikaisesti kirjallisuuden mallien tuloksiin paljastivat, että väitöstyön malli ennusti tarkemmin metallisulan hiilipitoisuuden sekä kuonan pääkomponenttien kehityksen puhallusajan funktiona.

Julkaisun otsikon käännös	Multifysikaalinen työkalu teräskonvertteriprosessiin
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Gasik, Michael, Vastuuprofessori Louhenkilpi, Seppo, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-7794-9
Sähköinen ISBN	978-952-60-7795-6
Tila	Julkaistu - 2018
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

teräskonvertteri
virtausdynamiikka
numeerinen mallinnus
monifaasivirtaus

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-7795-6Lisenssi: Määrittelemätön

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@phdthesis{4ff041c8fb934ad8988fbea550be9591,

title = "Multiphysical Modeling Approach for Basic Oxygen Steelmaking Process",

abstract = "In primary metallurgy, the converter process is an important stage in the production of steel from iron ore. The aim of the process is to remove carbon and several minor elements from iron melt by blowing oxygen on top of the melt. The scrap is used mainly to lower the furnace temperature. In a typical converter the iron bath is mixed by inert gas injection through nozzles placed at the bottom of the furnace.Converter process models aim to predict the temperature and compositional changes in the metal and slag phases during the oxygen blow. Process models are usually very simple and compute the results in real time. Real time capability is important for online process control use. The purpose of this thesis is was to improve the numerical modelling of the phenomena that takes place inside the steel converter, with an eye towards real-time applicability. The thesis developed new algorithms and numerical methods for computing gas/liquid two-phase flow, chemical reactions between multiple phases, as well as scrap melting. The models for these three phenomena were divided into three sub-models, which were tested independently. A theoretical basis for combining the sub-models was developed too. All of the models were developed to work in real-time. The approximations used are readily applicable to many other high temperature processes. The scrap melting model was developed to work in 1-D. The main idea was to predict the crust formation when liquid iron solidifies on the cold scrap, and then the melting of the solid material. The phase changes in the solid material are taken into account with a moving numerical grid. The scrap melting model was validated against melting measurements done in a crucible for three different melt temperatures. The numerical results compared well with the measurements.The 2-D two-phase computational fluid dynamics model was developed to predict the flow field and mixing of the iron melt due to the bottom gas stirring. The algorithm was developed to conserve liquid mass with computational economy, which was a feature missing in the literature. The model was validated with three different water models, one of which was similar to an industrial-scale steel converter. The chemical reaction model was based on computing chemical thermodynamic equilibrium via the Gibbs energy minimisation procedure for a reaction volume, which exists in the interfacial region of the main phases. The evolution of the chemical reactions are then determined by the mass transfer between the reaction volume and the bulk phases. Computing the equilibrium allows the modelling of simultaneous reactions and predict possible saturation of the components. The model was validated against measurements done in an industrial-scale steel converter. Accuracy was improved over existing literature models.",

keywords = "steel converter, CFD, numerical modeling, ter{\"a}skonvertteri, virtausdynamiikka, numeerinen mallinnus, monifaasivirtaus, steel converter, CFD, numerical modeling",

author = "Ari Kruskopf",

year = "2018",

language = "English",

isbn = "978-952-60-7794-9",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "5",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Multiphysical Modeling Approach for Basic Oxygen Steelmaking Process

AU - Kruskopf, Ari

PY - 2018

Y1 - 2018

N2 - In primary metallurgy, the converter process is an important stage in the production of steel from iron ore. The aim of the process is to remove carbon and several minor elements from iron melt by blowing oxygen on top of the melt. The scrap is used mainly to lower the furnace temperature. In a typical converter the iron bath is mixed by inert gas injection through nozzles placed at the bottom of the furnace.Converter process models aim to predict the temperature and compositional changes in the metal and slag phases during the oxygen blow. Process models are usually very simple and compute the results in real time. Real time capability is important for online process control use. The purpose of this thesis is was to improve the numerical modelling of the phenomena that takes place inside the steel converter, with an eye towards real-time applicability. The thesis developed new algorithms and numerical methods for computing gas/liquid two-phase flow, chemical reactions between multiple phases, as well as scrap melting. The models for these three phenomena were divided into three sub-models, which were tested independently. A theoretical basis for combining the sub-models was developed too. All of the models were developed to work in real-time. The approximations used are readily applicable to many other high temperature processes. The scrap melting model was developed to work in 1-D. The main idea was to predict the crust formation when liquid iron solidifies on the cold scrap, and then the melting of the solid material. The phase changes in the solid material are taken into account with a moving numerical grid. The scrap melting model was validated against melting measurements done in a crucible for three different melt temperatures. The numerical results compared well with the measurements.The 2-D two-phase computational fluid dynamics model was developed to predict the flow field and mixing of the iron melt due to the bottom gas stirring. The algorithm was developed to conserve liquid mass with computational economy, which was a feature missing in the literature. The model was validated with three different water models, one of which was similar to an industrial-scale steel converter. The chemical reaction model was based on computing chemical thermodynamic equilibrium via the Gibbs energy minimisation procedure for a reaction volume, which exists in the interfacial region of the main phases. The evolution of the chemical reactions are then determined by the mass transfer between the reaction volume and the bulk phases. Computing the equilibrium allows the modelling of simultaneous reactions and predict possible saturation of the components. The model was validated against measurements done in an industrial-scale steel converter. Accuracy was improved over existing literature models.

AB - In primary metallurgy, the converter process is an important stage in the production of steel from iron ore. The aim of the process is to remove carbon and several minor elements from iron melt by blowing oxygen on top of the melt. The scrap is used mainly to lower the furnace temperature. In a typical converter the iron bath is mixed by inert gas injection through nozzles placed at the bottom of the furnace.Converter process models aim to predict the temperature and compositional changes in the metal and slag phases during the oxygen blow. Process models are usually very simple and compute the results in real time. Real time capability is important for online process control use. The purpose of this thesis is was to improve the numerical modelling of the phenomena that takes place inside the steel converter, with an eye towards real-time applicability. The thesis developed new algorithms and numerical methods for computing gas/liquid two-phase flow, chemical reactions between multiple phases, as well as scrap melting. The models for these three phenomena were divided into three sub-models, which were tested independently. A theoretical basis for combining the sub-models was developed too. All of the models were developed to work in real-time. The approximations used are readily applicable to many other high temperature processes. The scrap melting model was developed to work in 1-D. The main idea was to predict the crust formation when liquid iron solidifies on the cold scrap, and then the melting of the solid material. The phase changes in the solid material are taken into account with a moving numerical grid. The scrap melting model was validated against melting measurements done in a crucible for three different melt temperatures. The numerical results compared well with the measurements.The 2-D two-phase computational fluid dynamics model was developed to predict the flow field and mixing of the iron melt due to the bottom gas stirring. The algorithm was developed to conserve liquid mass with computational economy, which was a feature missing in the literature. The model was validated with three different water models, one of which was similar to an industrial-scale steel converter. The chemical reaction model was based on computing chemical thermodynamic equilibrium via the Gibbs energy minimisation procedure for a reaction volume, which exists in the interfacial region of the main phases. The evolution of the chemical reactions are then determined by the mass transfer between the reaction volume and the bulk phases. Computing the equilibrium allows the modelling of simultaneous reactions and predict possible saturation of the components. The model was validated against measurements done in an industrial-scale steel converter. Accuracy was improved over existing literature models.

KW - steel converter

KW - CFD

KW - numerical modeling

KW - teräskonvertteri

KW - virtausdynamiikka

KW - numeerinen mallinnus

KW - monifaasivirtaus

KW - steel converter

KW - CFD

KW - numerical modeling

M3 - Doctoral Thesis

SN - 978-952-60-7794-9

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Multiphysical Modeling Approach for Basic Oxygen Steelmaking Process

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Tutkimusalat

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