Detection and closed-loop control of foaming slag for AC electric arc furnaces

Foaming slag is a useful item for high-power electric arc furnace operation. It helps to achieve high productivity as well as acceptable wear. Feeding of fine coal, which is necessary for foaming, is usually based on an operation-diagram or it is done manually. Either the rigid diagram nor the subjective human control really meets the operation conditions of the furnace. That's why Ispat Hamburger Stahlwerke and Institute for Automation of Helmut-Schmidt-University together developed a closed-loop foaming slag control. First step was to find an objective signal, which describes the slag level; second step was to design the corresponding control algorithm. Both will be explained.