Improvement of process control and refractory performance of the AOD converter

An AOD process observation system, which covers the on-line calculation of the carbon content and the melt temperature, has been developed by BFI and applied at one of the AOD converters of TKN Bochum within a preceding ECSC project [9]. Decarburisation was observed from a carbon balance based on measured off-gas values. Due to inaccuracies in the input values of this balance calculation, the standard deviation of the modelling error for the final carbon content was with 0.09 % unacceptable high. The same was true for the energy balance to calculate the melt temperature. Here the error standard deviation regarding the final temperature was 38 K. This process observation system was subject of improvement and extension regarding the control of nitrogen within the project presented in this report. Concerning AOD refractory wear performance, within a previous ECSC project [19] the wear mechanisms due to the back-attack phenomena in the tuyere area and due to the thermal stress caused by blowing interruptions were studied. The analysis of the wear mechanisms were to be extended to all relevant mechanisms, in order to built a comprehensive refractory wear model. Its development and validation with the help of a method for an on-line measurement of the refractory wear are described within the report of this project.