Spinel bricks for highly stressed roofs in glass melting furnaces

Abstract

New challenges are raised to the refractory materials in the crown and superstructure of oxy-fuel fired glass melting furnaces in comparison to air-fuel fired glass melting furnaces. In glass melting furnaces which are oxy-fuel fired the water steam partial pressure above the melt increases very strongly. In the case of soda-lime-silica glass melts together with the water steam partial pressure the alkaline hydroxide partial pressure increases with a factor of three in comparison to an air-fuel firing system. This leads to an aggressive action on the refractory lining in the crown and superstructure. After extensive thermodynamic calculations and laboratory tests a pure spinel refractory material (MgO ∙ AI2O3) was developed for the application in the crown and superstructure of oxy-fuel fired glass melting furnaces. The chemical and physical properties as well as the results of corrosion tests under oxy-fuel conditions of this direct-bonded fused spinel material will be discussed. Because of the high corrosion resistance to alkaline attack and the excellent behaviour of the creeping under load even at a temperature of 1650 °C, this spinel material can be proposed for the successful application as crown and superstructure refractory for oxy-fuel fired glass melting furnaces.