Technical Paper
REFRACTORIES ENGINEER
THE
[3] Tassot, P, Bachmann E, Johnson RC: The influence of reducing atmospheres on monolithic refractory linings for petrochemical service, UNITECR, Cancun, Mexico, 2001, Proc. Vol. II, pp. 858- 871.
[4] Shiang L et al: Influence of hydrogen on CO corrosion resistance of gunning material in blast furnace, 43th International Colloquium on Refractories, Aachen, Germany 2000, pp. 185-189.
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CO- und Abriebbeanspruchung, 40th International Colloquium on Refractories, Aachen, Germany 1997, pp. 185-189.
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Fig. 3: Castable prisms after CO resistance test (ASTM C288) 200h at 500°C
Based on the works [12] conducted by Lafarge Aluminates on CO resistance the following guidelines on maximum limits of iron and iron oxide in castable have been established:
- -
metallic iron (250ppm) free iron oxide (0.2%)
CONCLUSION:
CO-resistance is a critical feature that is essential in refractories for several industries including petrochemical. DRI, coal gasification, blast furnace and aluminium. The reaction is catalysed by metallic iron as well as iron oxide present in the refractories. Metallic iron catalyses the reaction more dominantly than iron oxides. The latter is often present in solid solution together with other oxides. Therefore, total iron content and more importantly its free iron part should be reduced to save refractories from CO-attack. For monolithic refractories, the iron content of the whole composition should be considered instead of only one component. Products from same clinker chemistry can show significantly different CO-resistance due to their specific method of crushing or milling. CAC 70 with lower iron oxide (around 0.2%) and free iron content offers a wider choice of aggregates than CAC 50 with higher iron oxide content (around 1.5%) and free iron. The correct selection of aggregate is important as their CO-resistance shows a clear link with total iron % and aggregates constitute major part of the composition.
REFERENCE:
[1] Baxendale S: Testing of refractory materials in Refractories Handbook. Ed. Schacht C., Marcel Dekker, New York. pp 452-453.
[2] Bartha P, Koehne V, Kurjat J: Carbon disintegration in refractory building materials, T. I. Z, vol. 97 no.7, 1973, p 244-7.
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