Abstract

he main reasons of applying insulating ceramics as furnace linings are related to energy costs and environmental concerns. From the emission point of view, most industrial furnaces operate in the infrared wavelength range (0.7 to 100 micra) where the thermal transmission by radiation is the major mechanism for the total effective thermal conductivity. This information is fundamental to design the composition and the microstruture of insulating ceramic materials. Commercial Al2O3-SiO2 and Al2O3-ZrO2-SiO2 linings present high porosity (70 to 85 vol%), but densify during use due to silica based binders. An alternative could rely on plain Al2O3 insulating lining, however it presents lower thermal shock resistance and higher thermal conductivity. In this work, alumina-based refractory foams with low thermal conductivity values (0.25 to 1.0 W/mK), high porosity (70 to 84 vol%), good compressive strength and high resistance to thermal shock were applied as insulating lining in a glass melting furnace operating at 1700oC. The performance of the insulating refractory was evaluated considering the energy consumed by the heating elements and the cycled thermal shock resistance. Power consumption indicated lower values when using foamed ceramic lining compared to the commercial ones. Additionally, the foamed ceramics performed very well under severe thermal shock conditions (DT=1700oC).