Danieli Automation HIREG PLUS--Electrode regulation in Electric Arc Furnace for improving energy efficiency

摘要

The use of Electric Arc Furnaces (EAF) for steelmaking has grown dramatically in recent years. The capacity of furnaces varies from as few as 30 tonnes to as much as 400 tonnes (CMP, 1987). Steelmaker's reasons for adopting this process route is its lower investment cost combined with a more flexible product mix. EAFs usually include furnaces for low and medium-alloyed steels, specialty steels, and stainless steels, with a combination of various raw materials such as scrap, pig iron, hot metal, and DRI/HBI. These are charged in batch or continuous mode. Batch charging may involve small interruptions during recharging of scrap in a heat. The entire operation can be divided into three stages -boring, melting and refining. For efficient melting, the electrodes should bore through the scrap to form a liquid metal pool. The electric arc must be lengthened by increasing the voltage to maximum power. Then, the arc length is changed so that the shorter arc will deliver a major portion of its heat to the metal below the electrode. Chemical treatment of steel continues under low power conditions (Hocine, 2008). The current changes dramatically during boring and melting operations. This is due to scrap surface irregularities and collapsing masses around the graphite electrodes. Hence, the state of equivalent electric circuit shifts among short-circuit, open-circuit, and nonlinear behavior.