Formation mechanism of the protective layer in a blast furnace hearth

Ke-xin Jiao^1,2，Jian-liang Zhang^1,2，Zheng-jian Liu^1,2，Meng Xu³，Feng Liu^1,2

1. School of Metallurgical and Ecological Engineering,University of Science and Technology Beijing2. State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing3. Shougang Research Institute of Technology

摘 要：A variety of techniques, such as chemical analysis, scanning electron microscopy-energy dispersive spectroscopy, and X-ray diffraction, were applied to characterize the adhesion protective layer formed below the blast furnace taphole level when a certain amount of titanium-bearing burden was used. Samples of the protective layer were extracted to identify the chemical composition, phase assemblage, andistribution. Furthermore, the formation mechanism of the protective layer was determined after clarifying the source of each componenFinally, a technical strategy was proposed for achieving a stable protective layer in the hearth. The results show that the protective layemainly exists in a bilayer form in the sidewall, namely, a titanium-bearing layer and a graphite layer. Both the layers contain the slag phaswhose major crystalline phase is magnesium melilite（Ca₂Mg Si₂O₇） and the main source of the slag phase is coke ash. It is clearly determinethat solid particles such as graphite, Ti（C,N） and Mg Al₂O₄ play an important role in the formation of the protective layer, and the key factofor promoting the formation of a stable protective layer is reasonable control of the evolution behavior of coke.

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