Rheology of spinel sludge in molten glass

Abstract

, and NiO [1-4]. Itnucleates virtually instantaneously and grows rapidly[5]. Spinel is harmless when it precipitates in glassduring cooling. It does not cause cracking nor does itreduce glass durability [6]. However, spinel can causeserious problems in glass melters. Formation of spinelsludge at the melter bottom or precipitation of spinel inthe melter overflow can obstruct the discharge of glassand shorten the melter lifetime [7]. Economic concernsmay require an increase in the loading factor of thewaste in glass. At a certain level of waste loading, spinelprecipitates in the melter. If some fraction of spinelsettles and accumulates at the melter bottom, aperiodical removal of spinel sludge may be considered.Construction of melters with inclined bottoms andbottom drains has been proposed [8]. The knowledge ofrheological behavior of precipitated spinel sludge isimportant for an advanced melter design. In this work,we produced spinel sludge in the laboratory and studiedits behavior using a rotating spindle viscometer.EXPERIMENTAL PARTWe used three glasses (table 1). The baseline glass(SS-A) had high concentrations of Fe