Worldwide, 1878 million tonnes of steel are currently produced each year. About 70% of this is produced through the basic oxygen furnace (BOF) process, also called the converter process.

During this process, oxides (= the slag), that float on top of the metal bath, are formed. This slag plays an important role during this process. This is because of its influence in three different areas.

Firstly, the slag phase will influence the refining (purification) of the steel phase. As many impurities as possible are removed from the liquid hot metal. Secondly, this slag phase will interact with the refractory wall of the converter. This interaction can have both a negative and a positive impact on the service life of the wall. And thirdly, the slag phase affects the formation of foam during the melting process. Uncontrolled foaming is detrimental and should be kept to a minimum.

Despite recognition of the general importance of this phase, the exact mechanisms remain unknown. To understand the role of the slag and the effect of slag composition, it is important to be able to study the change of slag composition during the process.

"In my PhD, I investigated the role of the slag phase in the converter using thermodynamic models. I combined different modelling techniques to simulate both the slag and steel composition during the process and at the end of the process", she explains.

The results of the thermodynamic models were verified with industrial measurements and data sets. Finally, two completely different models were developed to simulate the change of slag composition during the process. One model with the aim of predicting to investigate new areas of operation and one non-predictive model for retrospective use.

"Thanks to these thermodynamic models, steel can be produced in an even more controlled and efficient way in the future," concludes Lotte.

Read a more detailed summary or the entire PhD

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PhD Title: Thermodynamic Investigation of Converter Slag Characteristics with Industrial Validation

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Contact: Lotte De Vos, Inge Bellemans, Kim Verbeken  

Lotte De Vos graduated with highest distinction as Master of Sustainable Materials Engineering at the University of Ghent in 2017. In September of that year, she started her PhD in cooperation with ArcelorMittal Gent. For this, she obtained a personal financing through a Baekeland mandate (VLAIO).

During her PhD, Lotte was involved in several teaching activities. Her research resulted in several A1 publications and was presented at several international conferences.

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Editor: Jeroen Ongenae - Final editing: Ilse Vercruysse - Illustrator: Roger Van Hecke