Physical-chemical interactions during contact between molten glass and refractories

Abstract

The physical-chemical interactions at contact of molten glass with refractories in a glassmaking furnace, mostly electricity melted baddeleyite -corundum (bacor), are examined. Three basic interactions are discussed: surface phenomena, chemical interactions, and transport phenomena.Glassmaking and the preparation of molten glass for molding are conducted in refractory tanks and feeders. High temperatures and complicated physical-chemical interactions in the contact zone destroy the refractory masonry and result in the appearance of different types of flaws on the molded glass articles.In what follows the interaction of glass melts, having the most common compositions (sheet glass, glass containers), with baddeleyite-corundum (bacor) refractory melting tank of a glassmaking furnace is examined.The characteristic features of the contact phases are: -the glass melt at high temperatures is a chemically active ionized liquid with high viscosity and surface tension, exhibiting nonuniformity of the composition, properties, and structure;-the structure of the refractory materials is represented by microparticles of the crystalline phase, cemented by a refractory glassy phase; the rough surface of refractories has the capability of adsorbing various compounds from gases, vapors, and liquids; as a result of the nonuniformity of the composition, properties, and structure of the refractory materials, they breakdown nonuniformly in a glassmaking furnace.The interaction of the molten glass with the refractories of a glassmaking tank determines the service life of the glassmaking furnace and the quality of the glass. This is mainly due to the quality of the refractory materials but the character of the interaction is determined by complicated complex processes occurring at the interphase boundary, including:-chemical interaction; -surface phenomena; -transport phenomena. These processes result in the formation of a "meso-layer" with thickness~10 -3 m. Marked surface, chemical, and ionic-diffusion phenomena are observed in the direct contact zone (thickness~10 -5 m). As the thickness of the "mesolayer" increases, the convective components of the transport phenomena begin to manifest together with shearing deformations.Ordinarily, works devoted to the corrosion of refractory materials examine the overall interaction picture, which is associated with the glass stability of refractories of the glass-making furnaces. Individual components of the interaction of refractories and the molten glass have also been studied. The key information on these directions is contained in [1 -6]. CHEMICAL INTERACTIONSThe tanks of glassmaking furnaces are constructed from baddeleyite (bacor) refractory beams. The chemical composition of bacor is close to the eutectic region of the ternary system Al 2 O 3 -ZrO 2 -SiO 2 [7] (Fig. 1). The structure of bacor is characterized by aggregate concretions of baddeleyite and corundum crystals, which largely determine the resistance of refractories to glass melts. However, when melted refractories are prepared t...