High Temperature Reactions Caused by Alkalis in Mullite-Corundum Based Refractory Bricks

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Refractory bricks were used in lab scale tests to investigate reactions with deposit materials and alkalis. Alkalis were added as they are known to act corrosively in industrial kilns. Alkalis originate from additives and binders in the pellets and from fly ash in the burner coal. Alkalis react with mullite in the lining, and form feldspathoid minerals, which accelerate degradation of the lining.

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CONCLUSIONS

•K reacts with the brick in the range 850 to 950°C

•K and Na react with the brick in the range 600 to 925°C

•Feldspathoids begin to form at around 850°C

•Nepheline forms at higher temperatures than kalsilite

•Hematite reacts with neither the alkalis nor with the brick

•The deposit material melts in the presence of Na but only sinters in the presence of K

•Na feldspathoid forms mainly in the corroded layer

•K feldspathoids form beneath the corroded layer

•Kaliophilite forms only in solid state brick reactions