The Manufacturing Process of Silica Bricks

Silica brick is a kind of acidic refractory mainly composed of tridymite, cristobalite and a small amount of residual quartz and glass phase. It features good resistance to acid slag and good creep resistance. Its manufacturing process is similar to that of the fireclay brick.

Silica brick is made of silica containing more than 96% SiO2 , with addition of mineralizing agent (such as iron scales, lime) and binder (such as molasses, sulfite pulp waste), by  kneading, shaping, drying and calcining. The raw materials are crushed and then mixed evenly according to the formulation. Then the raw materials are shaped into the desired shape. After shaping, the products are dried in the tunnel kiln at about 120 ℃ and then fired at 1500℃. 

 

Generally, silica and waste silica bricks are washed and then crushed with the jaw crusher and cone crusher. The crushed raw materials are then screened with the vibrating screen. Then different raw materials are accurately weighed according to the formulation and mixed with mineralizing agent (such as iron scales, lime) and binder (such as molasses, sulfite pulp waste). 

 

Mineralizing agent is added to absorb the stress generated by the volume change. It can accelerate the conversion from quartz to phosphorus quartz and cristobalite but not significantly reduce its refractoriness and prevent excessive expansion and the formation of cracks. 

 

The shaping of silica bricks is complex, due to the shaping characteristics of the blank and the complexity of the shape. The blanks are hard barren materials with poor binding and plasticity. There are two shaping methods: hand shaping and machine shaping. Mass-produced products with simple shapes can adopt machine shaping. These products have denser structure and less pores. 

 

After shaping, the products are dried in the tunnel kiln at about 120 ℃ and then fired at 1500℃. A phase change occurs in the firing process, accompanied with a large volume change. Therefore the firing of silica bricks is more difficult. 

 

Silica brick can be widely used in coke oven, hot blast furnace, glass furnce and carbon furnace. In glass industry, it is mainly employed to build the doghouse crown, suspended wall of channel, top crown and inlet sealing. In metallurgy industry, it is adopted as the nozzle brick.