Corrosion Behavior of SiC and Si3N4 by Alkali Gas

초록

Studies of effective furnace cooling technology and refractory materials have extended the lifetime of a blast furnace to more than 15 years. On the other hand, the replacement of refractories in the blast furnace results in considerable cost and time loss for stopping the blast furnace operation. Various kinds of refractories are used inside a blast furnace, and SiC-based refractories, which are resistant to abrasion and thermal shock, are used in the area where frequent friction of charged materials occurs. However, these SiC-based refractories are quite vulnerable to an oxidizing atmosphere and alkali gases, and it is difficult to prevent corrosion by alkali gases generated from the impurities of the raw materials only by controlling the composition of the refractories and raw materials. Therefore, this study was carried out to investigate the alkali gas corrosion behavior of the blast furnace refractory as a fundamental study. Experimental results showed that the SiC and Si3N4 refractories used in the bosh part of the blast furnace were corroded by alkali gas even in an inert atmosphere. The alkali corrosion progressed gradually with time, and the alkali element and numerous pores and liquid precipitates were observed in the section of the corrosion layer. It was confirmed that the alkali gas corrosion reaction occured according to the well-defined conventional reaction mechanism. In addition, it was found that the corrosion rate of the SiC castable was 30 times faster than that of the SiC brick.

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