Besides using oxygen lances and tuyeres, operators can reduce electrical demands by improving stirring of the melt, which helps heat transfer, says Michael Chiariello, marketing director of the Danieli Group in Udine, Italy. Steelmakers also can save on electricity by charging DRI, which doesn't take as much power to melt as scrap, Burda says. A pilot Comelt plant, constructed primarily to test the idea of slanted electrodes, is operating in Linz, Austria. A conveyor belt charges the scrap through a side door in the preheating shaft. An electrode-control system automatically moves the electrodes forward or back depending on prevailing arc conditions.
Operators also can slue the electrodes left or right and change their inclination.
The inclined electric arcs, which are up to about three feet long, extend into the charge toward the electrode axis. Hot process gases stream to the middle of the scrap pile and then upward through the column of scrap in the furnace and in the preheating shaft. The Comelt furnace's off-gas preheats the scrap column. The EAF is totally enclosed, which allows collection of almost all fumes, Voest-Alpine says. Comelt's operating-noise level is lower than that of conventional furnaces by up to 15 dBA, and the energy needed for gas cleaning is lower, the company says.