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Steam-induced volatilization of silica from refractories
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1989
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Description:"The Bureau of Mines conducted a study to determine the loss in weight of silica (SiO2) volatilization from low-alumina Al203 refractories used as hot face liner materials in such process equipment as coal gasifiers, synthesis gas transfer lines, and ammonia plant secondary reformers. Small specimens of 80- and 40-pct-Al2O3 brick and 95-pct-SiO2 brick were exposed to steam in high-pressure furnaces at pressures of up to 1,000 deg and temperatures up to 1,400 deg C for periods ranging up to 120 h. Weight losses from the 40-pct-A12O3 brick after 40 h of exposure were highest, 2.75 pct at 1,400 deg C and 1,00 psig. The rate of weight loss had dropped to near zero after 80 h of exposure at all temperatures. No relationship between total silica content of the specimen and weight loss could be established nor did scanning electron microscopic examination of the specimens before and after exposure identify specific regions (e.g., surface) suffering a disproportionate share of the silica loss. It was concluded that minor silica volatilization is likely to occur, if at all, at temperatures of less than 1,000 deg C and pressures below 1,000 psig, and that low-alumina refractories should be used as dry-ash coal gasifier hot face linings." - NIOSTHTIC-2
NIOSHTIC no. 10005453
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