Abstract:
Although boron (B) is well known as one of the effective elements to prevent slag dusting [1], there is the possibility that B concentration and its leaching amount of steelmaking slag exceed the limit of environmental standards [2]. Therefore, it is important to understand the leaching behavior of B in slag. There are, however, few reports on the behavior and mechanism of B leaching from slag.
The leaching behavior of steelmaking slag, modified by B-containing flux, has been reported [3]. Although the effect of the particle size was investigated in the publication, the effect of the component condition of the slag on the leaching behavior of B has not been understood.
In this study, the leaching test has been performed using the steelmaking slag with a different basicity. In addition, the chemical structure of B in slag before leaching has been analyzed by solid-state 11B NMR and FIB-TOF-SIMS.
The leaching amount of B decreased with increasing slag basicity and calcium (Ca) concentration in water. The effect of slag basicity should be related to the leaching amount of Ca because the slag with higher basicity increases free-CaO and Ca concentration in water. From NMR and FIB-TOF-SIMS results, B is found to coexist primarily with Ca in the slag. Consequently, it is considered that B leaches with Ca. The slag with higher basicity decreases the leaching amount of B due to the common-ion effect by calcium.
References:[1] A. Seki, Y. Aso, M. Okubo, F. Sudo and K. Ishigaki : Kawasaki Steel Giho, 18(1986), pp. 20-24.
[2] T. Sasaki : Nippon Steel & Sumitomo Metal Technical Report, 109(2015), pp. 189-194.
[3] K. Kakimoto, F. Noguchi, N. Sakamoto, S. Sato and S. Kawada : CAMP-ISIJ, 18(2005), p.285.
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