The Development of BOF Slag Modification Technique in CSC

by Yao-Hung Tseng, Yu-Chen Lee, Bor-Liang Sheu

Publisher - China Steel Corporation, Kaohsiung, Taiwan (R.O.C.)

Category - Engineering & IT

It has been a challenge for steel companies worldwide to recycle and utilize BOF slag. The volumetric expansion of BOF slag, caused by the existence of f-CaO/MgO in slag, restricts the utilization of BOF slag. To effectively diminish the volumetric expansion of BOF slag, the core technology, namely, hot stage BOF slag modification (HBM), is developed by CSC (China Steel Corporation). By treating BOF slag with HBM, f-CaO/MgO of BOF slag reacts with silica to form calcium/magnesium silicates so that the volumetric expansion of the slag is inhibited. Through our QC examination, it is found that modified slag with nearly zero volumetric expansion can be obtained if a successful modification of BOF slag is applied. At present, the successful rate of the BOF slag modification is steadily higher than 96% after refining several experimental parameters during HBM operation. The modified slag, which shows good volumetric stability, is a suitable raw material for road construction, concrete-based materials as well as asphalt concrete aggregates, etc. Several applications for modified slag utilization, such as pavement bricks, concrete-based revetment blocks and tetrapods, etc. are developed. Good performances of these slag-based products are revealed in the field test and outdoors. In addition to conventional uses, novel applications of modified slag (e.g. ceramic tiles and high value-added functional materials) are being developed. Based on these results, we believe that the development of BOF slag modification technique in CSC will show promise for the utilization and reuse of BOF slag.

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