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A theoretical study of the effect of ladle-slag additions on the BOF process
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A Case study has been performed using the commercial Multi‐Phase equilibrium (MPE) software. The aim was to study the effect on the energy balance of an industrial BOF converter when recycling of ladle slag is made to the process. A reference simulation was made with typical process parameters of an industrial converter without the addition of ladle slag. The energy penalty of recycling ladle slag to the process was found to be 1728 MJ. Moreover, five different options to obtain an energy balance in the converter were studied. The results showed that either the scrap weight could be decreased by 1.5t, or the iron‐ore addition could be reduced with 380 kg. These two solutions offered consistent metallurgical performance in the process, but had drawbacks due to a decreased yield and an increased blowing time respectively. It was also found that the chemical energy released from the process could be increased, by oxidizing FeO or adding FeSi. However, this had negative effects on the process time as well as the steel quality. The most beneficial way for the BOF process to compensate for the energy loss is to reduce the tapping temperature with 12°C. This will also have positive effects on the phosphorus removal in the process. The results also showed that 200 kg per heat of burnt lime could be saved thanks to the recirculation of ladle slag. However, concluding remarks on the environmental and economical effect of the different options to compensate for the energy penalty needs to be assessed by a Life Cycle Analysis in the future to which this study can act as a useful guide.

 

Keyword [en]
Energy balance, simulation, ladle slag, recycling, BOF
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-33300OAI: oai:DiVA.org:kth-33300DiVA: diva2:414319
Note
QS 2011Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2011-05-03Bibliographically approved
In thesis
1. Influence of Ladle-slag Additions on BOF-Process Parameters
Open this publication in new window or tab >>Influence of Ladle-slag Additions on BOF-Process Parameters
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The influence of ladle-slag additions on the BOF-process performance were investigated in plant trials. The aim of the study was to recycle ladle slag from secondary steelmaking to the LD-converter to save lime and improve the slag formation. More specifically, two plant trial campaigns covering in total 83 heats, whereof 47 with ladle-slag additions and 36 without ladle-slag additions, were performed.

 Slag and steel sampling of the process were performed at tapping as well as during blowing at 15, 35, and 65% of the total blowing time. During the first campaign, ladle slag was added through the chute and lime reductions were made manually to correct for the ladle-slag addition.

 In the second campaign, a development of the approach was made to suite a normal production practice. More specifically, the ladle slag was added through the weight-hopper system and implemented in the process-control system. In this way, the lime additions were reduced automatically by approximately 260 kg per heat. Moreover, the heat balance was compensated with a reduction in the iron-ore consumption. Additionally, the lance program was modified and the lance was lowered in the initial stages of the blow.

 On the positive side, it was found that no demerits in the metallurgical performance of the process occur when ladle slag is recycled to the BOF-process. Furthermore, only slight affections on the slag composition were found, mainly with respect to the Al2O3 and FeO-content. In addition, the ladle slag was shown to melt during the initial stages of the blow. This contributed to an increased slag weight both during the blow and at tapping. However, a negative effect on the blowing time was experienced during the trials. Although, this effect was more pronounced during the first campaign and could be reduced with a controlled heat balance during the second campaign.

 

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xii, 28 p.
Keyword
BOF, slag formation, ladle slag, recycling, steel, composition, energy
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-33270 (URN)978-91-7415-961-5 (ISBN)
Presentation
2011-05-04, Sal B1, KTH, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20110503Available from: 2011-05-03 Created: 2011-05-02 Last updated: 2011-05-03Bibliographically approved

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