Determining process conditions for online monitoring of temperature and carbon content in the electric arc furnace to optimize end point control (MELTCON) : final report

Due to the high heating power of the electric arc furnace, precise end point control of the EAF refining process is essential for efficient melt processing. The evolution of the steel bath temperature was measured during the EAF refining phase using a novel fibre optical measurement system based on the DynKonTemp® technique developed by BFI. This measurement system was applied at the high productivity furnace of Ferriere Nord producing construction steels and the furnace of Saarschmiede Freiformschmiede producing high quality forging steel grades. Fibre optical online measurement of the carbon content in the melt failed due to the low signal to background relation of the thermal excited transition. The continuous liquid steel temperature measurements were also used to optimize the performance of dynamic EAF process models. The dynamic process models for melt temperature and carbon content were validated by conventional thermocouple measurements and chemical analysis of steel samples. In addition, to interpret the measurement results, the processes of both steel shops were simulated using computational fluid dynamics calculations. Fluid flow and distribution of steel bath temperature and carbon content were modelled to determine optimal measurement time, minimum measurement duration, and influence of the measurement position. Based on the analysis of the liquid steel temperature evolution, more reliable set points for energy input and temperature control are determined. Thus, the combined use of offline CFD calculations, online dynamic process modelling, and fibre optical inline measurement leads to enhanced EAF end point control.