Förbättrad processtyrning av ljusbågsugnar genom utveckling av mätteknik – Slutrapport

Erik Sandberg, Christoffer Schmidt, Dan Sandström, Nils Andersson, Anders Tilliander, Johan Björkvall

This project has focused on improving process control of the EAF in three areas; time for charging scrap baskets, time of transition between melting phase and refining phase and time for temperature measurement. To provide a basis for improved control, four different measurement techniques (harmonic current distortions, sound, light and vibrations) have been developed and tested. The project's main thesis is that these measurements will provide sufficient information to reduce the power-on time by an average of 2.9% for the scrap-based Swedish steel industry (5% for the initial recipient plant Outokumpu Stainless).

To achieve the improved control, soft sensors for meltdown degree and steel temperature based on the developed measuring techniques have developed. New control strategies have also been developed based on the soft-sensor signals. The measurement techniques for harmonic current distortions and sound, and the integration of these signals in the soft-sensors into existing systems, have been realized within the project. Although promising, vibration measurements require more maintenance than the sound measurements while providing similar though noisier information.

Light measurements could not be carried out at industrial scale due to practical problems with the installation, but the measurements in pilot scale were promising. Soft sensors and control strategies were tested in a final industrial trial campaign. None of the tested control strategies had statistically significant effect (95% confidence level) on the power-on time. However, the control strategy for charging of baskets resulted in reduction of the average power-on time by 44 seconds per heat (1.55% of 47.62 minutes or 36% of the estimated potential at the test-plant). The potential for further improvements is deemed high by continued development of soft sensors, techniques for measuring light and adjusting the control strategies.