University of Oulu

Electric arc characterisation and furnace process monitoring with optical emission spectroscopy and image analysis

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Author: Pauna, Henri1,2
Organizations: 1University of Oulu Graduate School
2University of Oulu, Faculty of Technology, Process Engineering, Process Metallurgy (MET)
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 32.5 MB)
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Language: English
Published: Oulu : University of Oulu, 2020
Publish Date: 2020-10-20
Thesis type: Doctoral Dissertation
Defence Note: Academic dissertation to be presented with the assent of the Doctoral Training Committee of Technology and Natural Sciences of the University of Oulu for public discussion in the Auditorium L5, on October 30th, 2020, at 12 o'clock noon.
Tutor: Professor Timo Fabritius
Professor Marko Huttula
Doctor Matti Aula
Reviewer: Professor Jianhua Liu
Associate Professor Anders Tilliander
Opponent: Associate Professor Valentina Colla
Kustos: Professor Timo Fabritius


Electric arc furnaces (EAFs) and ladle furnaces (LFs) are the main recycling units for scrap metal. With lower CO₂ emissions than traditional ore-based steelmaking, the importance of EAFs can be expected to increase in the future. Increasing steel production rates and demand for high-quality and special steels require innovative process control systems to be developed for the steel industry. However, the harsh conditions inside the furnaces set strict requirements for durability and viable data acquisition methods for online measurement systems.

In this thesis, the applicability of optical emission spectroscopy (OES) as an online measurement system for industrial EAFs and LFs is discussed, based on the results from pilot-scale and industrial EAFs, and an industrial LF.

The electric arc has been characterised with OES, plasma diagnostics, and image analysis in the pilot-scale EAF measurements. These studies highlighted the influence of slag composition on the overall properties of the electric arc, the electrical parameters of the furnace, and the arc length{voltage relation. The majority of the atomic emission lines in the electric arc OES spectra were observed to originate from the slag components.


In the industrial EAF campaign, high alloyed steel grade was observed to have high-quality arc spectra within 30 mins before tapping and higher radiative heat transfer compared with the carbon steel grade. The spectra from the carbon steel grade, on the other hand, were used to observe how spectra evolve during slag foaming. Additionally, the molten bath surface temperature was estimated from the OES spectra. The slag composition was evaluated with OES in the industrial LF campaign, indicating that the CaF₂, MgO, and MnO content of the slag could be evaluated from the spectra.

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Osajulkaisut / Original papers

Osajulkaisut eivät sisälly väitöskirjan elektroniseen versioon / Original papers are not included in the electronic version of the dissertation.

  1. Pauna, H., Willms, T., Aula, M., Echterhof, T., Huttula, M., & Fabritius, T. (2019). Pilot-scale AC electric arc furnace plasma characterization. Plasma Research Express, 1(3), 035007.

    Rinnakkaistallennettu versio / Self-archived version

  2. Pauna, H., Willms, T., Aula, M., Echterhof, T., Huttula, M., & Fabritius, T. (2020). Electric Arc Length-Voltage and Conductivity Characteristics in a Pilot-Scale AC Electric Arc Furnace. Metallurgical and Materials Transactions B, 51(4), 1646–1655.

    Rinnakkaistallennettu versio / Self-archived version

  3. Pauna, H., Aula, M., Seehausen, J., Klung, J.-S., Huttula, M., & Fabritius, T. (2020). Optical Emission Spectroscopy as an Online Analysis Method in Industrial Electric Arc Furnaces. Steel Research International, 2000051.

    Rinnakkaistallennettu versio / Self-archived version

  4. Pauna, H., Aula, M., Seehausen, J., Klung, J.-S., Huttula, M., & Fabritius, T. (2020). Industrial Ladle Furnace Slag Composition Analysis with Optical Emissions from the Arc. ISIJ International, 60(9), 1985–1992.

    Rinnakkaistallennettu versio / Self-archived version

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Series: Report series in physical sciences
ISSN: 1239-4327
ISSN-L: 1239-4327
ISBN: 978-952-62-2731-3
ISBN Print: 978-952-62-2730-6
Issue: 136
Type of Publication: G5 Doctoral dissertation (articles)
Field of Science: 114 Physical sciences
215 Chemical engineering
Copyright information: © University of Oulu, 2020. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.