Volatilization of Refractory Silica in Hydrogen Water Vapour Gas Streams
Palmer Technologies Pty. Ltd., 4151 Coorparoo DC, Queensland, Australia
Revision
Volume 4, Issue 4, Pages 63 -70
Abstract
The volatilization of silica (SiO2) from refractory concrete in steamhydrogen environments has been studied extensively and reaction thermodynamics are also well published. This research has shown that silica volatilization occurs over a wide range of temperatures and that at temperatures less than 980 °C the dominant species is Si(OH)4 and at temperatures above approximately 1000 °C the dominant species formed is SiO. By using a reaction kinetics approach it is shown that the rate of silica volatilization can be reasonably well calculated from refractory used in industrial processes. Analysis of refractory samples from an ammonia transfer line shows that shows that the loss of silica occurs from the aggregate and not the matrix.
Keywords
refractory, volatilization, silica, reduction
References
[1] Wright, R.E.; Wolff, H.I.: Refractory problems in production of hydrogen by pyrolysis of natural gas. J. Am. Ceram. Soc. 31 (1948) [2] 31–38
[2] Day, D.E.; Gac, F.D.: Stability of refractory castables in steam-N2 and steam-CO atmospheres at 199 °C. Am. Ceram. Soc. Bull. 56 (1977) [7] 644–648
[3] Jacobson, N.S.; et al.: Thermodynamics of gas phase species in the Si-O-H System. J. Chem. Thermodynamics 37 (2005) [10] 1130–1137
[4] Crowley, M.S.: Hydrogen-silica reactions in refractories. Am. Ceram. Soc. Bull. 46 (1967) [7] 679– 682
[5] Crowley, M.S.: Hydrogen-silica reactions in refractories, Part II. Am. Ceram. Soc. Bull. 49 (1970) [5] 527–530
[6] Gardner, R.A.: The kinetics of silica reduction in hydrogen. J. of Solid State Chem. 9 (1974) 336– 344
[7] Tso, S.T.; Pask, J.A.: Reaction of silicate glasses and mullite with hydrogen gas. J. Am. Ceram. Soc. 65 (1982) [8] 383–387
[8] Davis, R.F.; Aksay, I.A.; Pask, J.A.: Decompos-ition of mullite. J. Am. Ceram. Soc. 55 (1972) [2] 98– 101
[9] Sacks, M.D.; et al.: Corrosion and mechanical behaviour correlations with composition and microstructure of aluminium silicate refractories. J. Am. Ceram. Soc. 58 (1979) [7]
[10] Gardner, R.A.; Buchanan, R.C.: High temperature loss of silica from zircon and refractory silicates. J. Electrochem. Soc. 122 (1975) [2] 205–210
[11] Misra, A.K.: Thermodynamic analysis of chemical stability of ceramic materials in hydrogen-containing atmospheres at high temperatures. NASA Contractor Rept. No. 4271. National Aeronautics and Space Administration, Cleveland, OH, 1990.
[12] Crowley, M.S.: Hydrogen steam reactions in refractories. AIChE 75th National Meeting Detroit, June 3–6, 1973
[13] Robinson, R.C.; Smialek, J.L.: SiC recession caused by SiO2 scale volatility under combustion conditions, I: Experimental results and empirical model. J. Am. Ceram. Soc. 82 (1999) [7] 1817–1825
[14] Opila, E.J.; Hann, R.E.: Paralinear oxidation of CVD SiC in water vapour. J. Am. Ceram. Soc. 80 (1997)
1] 197–205
[15] Opila, E.J.; et al.: SiC recession caused by SiO2 scale volatility under combustion conditions, II: Thermodynamics and gaseous-diffusion model. J. Am. Ceram. Soc. 82 (1999) [7] 1826–1834
[16] Opila E.J.: Oxidation and volatilization of silica formers in water vapour. J. Am. Ceram. Soc. 86 (2003) [8] 1238–1248
[17] Johnson, R.C.; Crowley, M.S.: State of the art refractory linings for hydrogen reformer vessels. UNITECR 2005
[18] Robbins, C.R.; Mauer, F.A.: Chemical degradation of castable refractories in coal gasification process environments. J. Mater. for Energy Sys-tems 3 (1981) [6] 32–42
[19] Herbell, T.P.; Hull, D.R.; Garg, A.: Hot hydrogen exposure degradation of the strength of mullite. http://gltrs.grc.nasa.gov/Citations.aspx?id= 3459
[20] Fox, D.S.; Opila, E.J.; Hann, R.E.: Paralinear oxidation of CVD SiC in simulated fuel-rich combustion. J. Am. Ceram. Soc. 83 (2000) [7] 1761–1767
[21] Tso, S.T.; Pask, J.A.: Reaction of fused silica with hydrogen gas. J. Am. Ceram. Soc. 65 (1982) [9] 457
[22] Cheng, M.-C.; Cutler, I.B.: Vaporization of silica in steam atmosphere. J. Am. Ceram. Soc. 62 (1979)
11–12] 593–596
Copyright
Göller Velag GmbH
