Postmortem analyses of salvaged conventional silica bricks from glass production furnaces

The microstructure, phase content, and thermal conductivity of salvaged con ventional silica bricks from float glass and TV-panel glass production furn aces were examined as a function of position through the brick, and compare d with the original, unaltered brick materials. The silica brick from the f loat glass furnace was in service for approximately 10 years while that for the TV-panel glass furnace was for approximately 6 1/2 years. The microstr ucture and phase content in both salvaged bricks showed gradients, from tri dymite at the bricks' cold-face ends, to cristobalite at their hot-face end even though both bricks were an initial mixture of tridymite and cristobal ite to begin with. The thermal conductivity of both bricks had increased as a consequence of these phase and microstructural changes. A thermal analys is model predicted that such changes would result in an increase in the bri cks' cold-face temperature and heat content during service. The initially-p roduced temperature gradients and environment caused microstructural change s in the silica brick; however, the cause-and-effect relationship between t emperature/environment and microstructural changes in the brick likely beca me mutually reversible once the microstructural changes initiated and the t hermal conductivity of the brick started to change as a consequence.