Common SiO2 Series Refractories Used In the Glass Furnaces

With the development of new refractories, the quality of the refractories has been continuously improved, which promotes the high temperature melting technology in the glass industry. The common SiO2 refractories used in the glass furnace include white afrodite and silica brick. 

The white afrodite is a kind of natural quartz refractory bonded with kaolinite. The white afrodite with gray color, dense and hard structure and no impurities and stripes is better. Its main crystal phases are quartz and kaolinite with obvious layered structure and anisotropy. Its refractoriness is between 1650-1730℃. 

 

The expansion of the white afrodite is different from that of the silica brick. It has the biggest expansion coefficient at 700-800℃ and is most likely to burst. 

 

The white afrodite, after burned, has an increased softening temperature under load and strength, low residual expansion and stable volume and an improved thermal shock. So, it is used as a refractory in the middle and small size furnaces. 

 

The silica brick is a refractory with a SiO2 as the main composition. It is made of high pure and dense quartz and a small amount of lime. The clinker is waste silica brick powder. Its composition is 94%-98% SiO2, 1.5%-3.5% CaO, 0.2%-2% Al2O3, 0.3%-3% Fe2O3 and 0-0.5% R2O. 

Its main mineral phases are tridymite and cristobalite as well as a small amount of residual quartz and glass phase. The transformation of crystal phases in the silica bricks is accompanied with volume changes. The biggest thermal expansion occurs below 300℃, so when preheating the furnaces it should be paid attention to. When the temperature is above 700℃, it will not damage the furnace.

 

The thermal stability of the silica brick is bad. The 850℃ silica brick can only withstand once or twice rapid cooling in the water with being damaged. Silica brick is an acid refractory, so it has good resistance to the acid slags, but bad resistance to alkali slags and erosion by glass liquid. 

 

Since silica brick has high softening temperature under load and bad resistance to R2O in the glass liquid, it is used in crowns, head walls and breast walls of the cooling zone, but is not suitable to the sidewall in direct contact with glass liquid.