2018 Volume 58 Issue 10 Pages 1943-1952
To recover valuable elements such as Fe or P from steelmaking slag and to modify the slag composition, a molten slag reduction process (IBX process: Iron Bath for X) has been developed. So far, pilot and commercial scale test operations have been carried out and it has been clarified that closed-type DC arc furnaces are desirable for the slag reduction process with hot slag charging. In the present work, issues and solutions of the actual operation are discussed. One issue is the optimization of the material feeding method. A hollow electrode, top lance, and injection pipe method were tested in the same furnace and the performance of each was investigated. The second issue is slag boiling and solidification at hot slag charging. To establish stable operation, use of a bottom block to avoid the formation of an emulsion at slag charging and off-gas combustion for heating the slag were proposed and tested. Finally, thermal aspects were discussed and the required energy consumption was estimated to show the effect of hot slag charging. Through these studies, it was confirmed that stable operation of slag reduction with hot slag charging can be attained in closed-type DC arc furnace, representing a great step for realizing of complete utilization process of BOF slag.