Thermodynamic Analysis of Alumina Refractory Corrosion by Sodium or Potassium Hydroxide in Glass Melting Furnaces

Abstract

In this paper the high-temperature corrosion of Al 2 O 3 refractories by MOH͑g͒ (M ϭ Na, K) found in the combustion atmospheres of typical air-and oxygen-fired glass-melting furnaces is examined using thermodynamic equilibrium calculations. These hydroxide species are considered to be the primary reactive alkali species since their partial pressures are significantly larger than those of M͑g͒, the next most abundant gas-phase alkali-containing species expected in typical furnace atmospheres. Thermochemical simulations show that corrosion of ␣-alumina by NaOH͑g͒ at typical furnace p NaOH͑g͒ of around 200 ppm under oxy/fuel-fired conditions is unlikely as long as the refractory temperature exceeds 1564 K. For KOH͑g͒ at 200 ppm, the temperature of the refractory must exceed 1515 K to avoid corrosion. Under air-fired conditions, p NaOH͑g͒ is considerably lower ͑40-80 ppm͒; at 50 ppm, corrosion is thermodynamically unfavorable at temperatures above 1504 K. For KOH͑g͒ at furnace levels of ϳ50 ppm, temperatures must be above 1458 K. The paper also presents a re-evaluation of the thermodynamic and phase equilibrium properties of the Na 2 O-Al 2 O 3 and K 2 O-Al 2 O 3 binary systems to develop accurate and self-consistent thermodynamic data. The data for MAl 9 O 14 ͑␤-alumina͒ and M 2 Al 12 O 19 (␤Љ-alumina) are particularly critical since these phases are likely products of the corrosion of alumina refractories by MOH vapors in glass melting furnaces.

Thermodynamic Optimization of Lithia–Alumina

“…It has also been shown that in spite of its simplicity, the associate species model can accurately predict the activities of components in metastable glass phases 4,5 . The databases developed using the associate species approach have found utility in waste glass modeling 4,5,8 and in understanding corrosion in refractories 9,10 …”

Corrosion of Ceramic Materials for Allothermal Circulating Fluidized Bed Gasification

“…[34,35]. Korund eignet sich insbesondere aufgrund seiner guten Stabilität gegen Alkaliangriff für die Vergasung von Biomasse [36]. Auch in der Literatur hat sich der erfolgreiche Einsatz von korund-und mullitbasierten Filterkerzen bestätigt [37 -39].…”

Dynamic and static corrosion of alpha-alumina bonded refractory in contact with molten soda-lime-silica (SLS) glass

“…Hence, the refractory materials that are in contact with glass at elevated temperatures must have excellent chemical and mechanical stability [2]. Alumina is one of the most important refractory materials in glass furnaces due to its high melting point, good mechanical properties such as high hardness, high compressive strength, high elastic modulus and, good chemical and thermal stability [3][4][5][6][7][8].…”