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Numerical Study of the Gas Flow and Heat Transfer during Electromagnetic Stirring and Post Combustion in EAFs
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The effect of electromagnetic stirring on scrap melting and post combustion in two different electric arc furnaces (EAFs) have been studied using numerical modelling. The effect of electromagnetic stirring on melting of a piece of scrap located at the eccentric bottom tapping (EBT) region of an EAF has been studied. The results were compared to a condition in which the only source term for momentum transfer was buoyancy. It was shown that the use of electromagnetic stirring can contribute to a better heat transfer rate at the melt–scrap interface. The Grashof and Nusselt number for both electromagnetic stirring and natural convection were estimated, and were compared with those estimated in previous studies. The post combustion (PC) inside a duct system of an EAF has been studied considering combustion of hydrogen and carbon monoxide. The aim was to study the effect of air leakage through the airgap and fan power on post combustion of the off–gas leaving the furnace. Furthermore, to see how much uncombusted can be captured after the air gap. It was shown a higher off-gas mass flow rate and a higher power of the outlet fan led to a higher combustion of CO and H2. Moreover, a backward modeling of the flow was done to estimate the off–gas composition at the furnace outlet. The post combustion inside the same EAF used in the previous part has been studied. The domain consists of the fluid region above the melt bath. The oxy fuel reactions and combustion of CO were taken into account. The oxy-fuel reactions in a both simplified and a more accurate form (JC) were studied. The results showed less combustion of CO in the latter form. Using the results of the off–gas composition at the outlet, an attempt was made to estimate the flow rate of CO arising from the bath. Different flow rates of CO from the melt and air flow rate through the roof were assumed. In both burner mode and burner + lancing mode, the calculated concentration of CO2 was higher than that calculated in the previous part. The reason could be that the dissociation of CO2 to CO and O2 at high temperatures, and the de-post combustion of CO2 due to the reaction with carbon in the melt and in the electrodes were not considered.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2014. , x, 40 p.
Keyword [en]
EMS, EAF, post combustion, heat transfer, duct system
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-157484ISBN: 978-91-7595-379-3 OAI: oai:DiVA.org:kth-157484DiVA: diva2:770087
Presentation
2014-12-17, Sal Sefström M131, Brinellvägen 23, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20141211

Available from: 2014-12-11 Created: 2014-12-09 Last updated: 2017-03-02Bibliographically approved
List of papers
1. Mathematical Modeling of Scrap Melting in an EAF Using Electromagnetic Stirring
Open this publication in new window or tab >>Mathematical Modeling of Scrap Melting in an EAF Using Electromagnetic Stirring
2013 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 1, 48-55 p.Article in journal (Refereed) Published
Abstract [en]

Numerical modeling has been used to investigate the influence of electromagnetic stirring on melting of a single piece of scrap in an eccentric bottom tapping (EBT) electric arc furnace (EAF). The heat transfer and fluid flow in the melt for both conditions with and without electromagnetic stirring were studied. The buoyancy and electromagnetic forces were considered as the source terms for momentum transfer in the studied conditions. The enthalpy-porosity technique was applied to track the phase change of a scrap piece defined in the EBT region of the furnace. Different scrap sizes, preheating temperatures, stirring directions and force magnitudes were considered, and the heat transfer coefficient was estimated from the heat transfer rate at the melt-scrap interface. The results showed that electromagnetic stirring led to a reduced melting time and an increased heat transfer coefficient by a factor of four. The results for Nusselt number versus Grashof number for natural convection and Reynolds number for electromagnetic stirring were compared with those obtained through correlations from previous studies.

Keyword
EAF, electric arc furnace, mathematical model, electromagnetic stirring
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-120321 (URN)10.2355/isijinternational.53.48 (DOI)000315834700007 ()2-s2.0-84873822898 (Scopus ID)
Note

QC 20130404

Available from: 2013-04-04 Created: 2013-04-04 Last updated: 2017-12-06Bibliographically approved
2. Modeling of post combustion inside the off-gas duct system of the Ovako electric arc furnace
Open this publication in new window or tab >>Modeling of post combustion inside the off-gas duct system of the Ovako electric arc furnace
2014 (English)In: CDF 2014: 10th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, SINTEF, Trondheim, Norway, 17-19 June 2014, Proceedings, 2014Conference paper, Published paper (Refereed)
Abstract [en]

In order to study the post combustion (PC) inside the duct system of an electric arc furnace (EAF), a three-dimensional computational fluid-dynamics (CFD) model was developed. The reactions between the off gas species (oxygen and hydrogen) and oxygen which leaked into the duct, through the air gap, was considered. The off-gas composition, the off –gas velocity and the outlet pressure were considered as parameters affecting the PC. The results showed that there was a considerable amount of the uncombusted CO to be captured. The highest CO concentration was found at the central part of the duct. The results also showed that a higher off-gas mass flow rate and a higher power of the outlet fan led to a higher combustion of CO and H2. An off-gas analysis probe was then installed after the air gap, where the tip of the probe was placed according to the predicted high CO concentration area found in the simulations. Thereafter, the measured off-gas composition was used to predict the off-gas composition at the outlet of the EAF.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-157541 (URN)
Conference
10th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, SINTEF, Trondheim, Norway, 17-19 June 2014
Note

QC 20141211

Available from: 2014-12-11 Created: 2014-12-11 Last updated: 2014-12-11Bibliographically approved
3. Modeling of Post Combustion in Ovako electric arc furnace (EAF)
Open this publication in new window or tab >>Modeling of Post Combustion in Ovako electric arc furnace (EAF)
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-157542 (URN)
Note

QC 20141211

Available from: 2014-12-11 Created: 2014-12-11 Last updated: 2014-12-11Bibliographically approved

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