Variable nozzle height in AOD converter

Purpose and goal

The purpose of the pre-study was to investigate if variable nozzle height can be used to achieve shorter decarburization times in the AOD converter and a decreased use of natural resources. This was due to internal reports that an old converter has a shorter decarburization time compared to a new one. The study thus aimed to give conditions for a future improvement of the decarburization during stainless steelmaking by using variable reaction pressure (nozzle height).

Expected results and effects

The results show that there is a noticable difference between a new and an old converter in terms of decarburization efficiency. This was seen by less oxygen was used to achieve the same final carbon content. The stirring on the other hand was seen to become worse for an old converter. This points to that the system is mainly controlled by thermodynamics rather than kinetics, which in turn gives good opportunities for further implementation of the results in the industry.

Planned approach and implementation

In the study there were an analysis of plant data from two stainless steel plants, water modeling of stirring conditions as well as mathematical modeling of the stirring conditions. The results showed a good possibility to use variable nozzle height in the AOD converter. This leads to good conditions to continue research in nozzle placements and changed blowing schemes in order to increase productivity and decrease use of natural resources.