EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

When the scrap charge in EAF melts, the heat transfer between the arc and side panels increases until slag foaming is started or arc length is reduced. However, the slag accumulated on the side panels acts as a kinetic barrier between the arc and cooling water. Previously, only estimates of the cause of slag has been obtained due to lack of reference measurement. In this work side panel cooling water temperature gradient is compared to optical emission spectrum gathered with optical fibers through EAF roof. The data used in the analysis was obtained from simultaneous measurement of three EAF hot-spot optical emission spectra conducted at Outokumpu Stainless Oy, Tornio Works, EAF 2 in 2015. The time delay between thermal and optical signals was analysed with cross-correlation method and signal change detection. The delays were calculated for over 100 heats to estimate the length and variation of the delay caused by the accumulated slag. The results from the different methods were evaluated to find the most accurate description of time delay. The results indicate that cross-correlation method gives the most stable results. The average delay calculated with the cross-correlation method was approximately 80 seconds in the upper and 100 seconds in the lower panels.