Silica bricks are acidic refractory materials consisting of scaled quartz, square quartz and a small amount of residual quartz and glass phases. These raw materials are mixed, shaped, dried and roasted in a furnace at 1400-1430℃.
Silica bricks are acidic refractories with a silica content of over 94% and a true density of 2.38 g/cm3. They are resistant to acidic slag erosion and have high high temperature strength. It has a load softening temperature of 1620～1670℃, which is not deformed in long-term use at high temperature. 600℃ and above, generally no crystalline transformation. Lower temperature expansion coefficient. Higher thermal shock resistance.
Silica bricks are mainly used in the partition wall of carbonization and combustion chamber of coke oven, heat storage chamber and slag chamber of steel blast furnace, even heat furnace, glass melting kiln and ceramic firing kiln, also used in the high temperature bearing part of hot blast furnace and acid blast furnace roof.
Physical and chemical indicators of general silica bricks
| Item | GZ-96 | GZ-95 | GZ-94 |
| SiO2, %, ≥ | 96 | 95 | 94 |
| Fe2O3, %, ≤ | 1.0 | 1.2 | 1.4 |
| Apparent porosity, %, ≤ | 22(24) | ||
| Normal temperature compressive strength, MPa, ≥ | 35(30) | kg/pcs,＜20Kg | |
| 30(25) | kg/pcs, ≥20Kg | ||
| 0.2MPa Load softening temperature, ≥ | 1660 | 1650 | 1640(Colloidal silica1620) |
| True Density, g/cm3, ≤ | 2.34 | 2.35 |
Silica bricks for coke ovens
A coke oven is a complex, long term continuous use thermal equipment. Its purpose is to dry distill coal by heating it to 950-1050℃ under the condition of air isolation, so as to obtain coke and other by-products. Silica bricks have become the main refractory material for coke ovens because of their good thermal conductivity, high load softening temperature, good high temperature mechanical strength and stable high temperature volume change, refractoriness, small residual expansion, and strong resistance to acid slag erosion.
Silica bricks for coke ovens are used in all major parts of coke ovens: heat storage chamber wall, ramp, carbonization chamber bottom, furnace wall and roof.
The use of silica bricks for coke ovens can increase the temperature of combustion chamber, shorten the coking time, increase the production capacity of coke oven and prolong the age of coke oven, so modern large coke ovens are mainly built with silica bricks.
| Item | Silica bricks for coke oven | Silica bricks for coke oven |
| Furnace bottom, furnace wall | Other | |
| SiO2, %, ≥ | 94.5 | 94 |
| Al2O3, %, ≤ | 1.2 | 1.5 |
| Fe2O3, %, ≤ | 1.2 | 1.5 |
| CaO, %, ≤ | 3.0 | 3.0 |
| Na2O+K2O, %, ≤ | 0.35 | 0.35 |
| Apparent porosity, %, ≤ | 22 | 24 |
| Normal temperature compressive strength, MPa, ≥ | 35 | 28 |
| 0.2MPa Load softening temperature, ℃, ≥ | 1650 | |
| True Density, g/cm3, ≥ | 2.33 | 2.34 |
| Reburn line change, %, 1450℃x2h | 0-0.2 | |
| Coefficient of thermal expansion 1000℃, %, ≤ | 1.28 | 1.3 |
Silicon bricks for glass kilns
Silica brick is the most used and important brick type in float glass kiln. For large glass kilns, silica bricks are mainly used in the melting section and the working section of the kiln roof swan, chest wall and front and rear end walls, heat storage room top swan and heat storage room upper partition wall, etc.
The SiO2 content of silica bricks for glass kilns is 96-98%. Its density is 2.35-2.38g/cm3. It has high structural strength at high temperature, such as high load softening temperature (1640~1700℃) and low creep rate. After absorbing a small amount of alkali components in addition to very slight fusion corrosion, and doesn’t reduce the structural strength of the kiln roof.
Silica bricks for glass kilns have the following characteristics.
① High temperature volume stability.
② Slight contamination of the glass liquid.
③ Chemical erosion resistance.
④ Small bulk density, can reduce the weight of the furnace body.
| Item | Unit | KBG-96a | KBG-96b | KBG-95 | |
| SiO2 | ≥ | % | 96 | 96 | 95 |
| FeO3 | ≤ | % | 0.6 | 0.8 | 1.0 |
| Melting index，Al2O3+2R2O3 | ≤ | % | 0.5 | 0.7 | - |
| Apparent porosity | ≤ | % | 21 | 22 | 22 |
| True Density | ≤ | g/cm3 | 2.34 | 2.34 | 2.34 |
| 0.2MPa Load softening temperature | ≥ | ℃ | 1680 | 1670 | 1670 |
| Normal temperature compressive strength | ≥ | MPa | 40 | 35 | 30 |
| re-burn line change. 1450℃*2h | ≤ | % | +0.2 | +0.2 | +0.2 |
Silica bricks for hot blast furnaces
Product characteristics of silica bricks for hot blast furnace.
1、Under long-term high temperature and high load conditions, the volume is stable and the high temperature creep rate is low, and it can be used continuously for 1 or 2 blast furnaces.
2、Good thermal shock resistance above 600 degrees, adapt to the change of hot blast furnace temperature and keep the masonry intact.
3, chemical resistance is better than clay bricks and general high alumina bricks.
4、The thermal conductivity of silica bricks for hot blast furnace is greater than clay bricks and high alumina bricks, which is good for storing and releasing heat in a short time.
| Item | Vault and furnace wall tiles | Checker bricks |
| SiO2 % ≥ | 95 | 95 |
| Al2O3 % ≤ | 1.0 | 1.0 |
| Fe2O3 % ≤ | 1.2 | 1.2 |
| Apparent porosity % ≤ | 22 | 24 |
| Normal temperature compressive strength MPa ≥ | 40 | 30 |
| 0.2MPa Load softening temperature℃ ≥ | 1650 | 1650 |
| True Density g/cm3 ≥ | 2.33 | 2.34 |
| 0.2MPCreep rate % 1550℃ 0-50h ≤ | 0.8 | 0.8 |
| Coefficient of thermal expansion 1000℃ % ≤ | 1.26 | 1.26 |
Semi-silica brick
Semi-silica brick is a kind of quartz clay brick, which is an aluminous silicate refractory product with alumina content of 15-30%. It is generally made of refractory clay containing quartz sand, chlorite clay or tailings of kaolinite beneficiation as raw material. Its refractoriness is 1670 ℃, the load softening point is not less than 1250 ℃. Semi-silica bricks have better resistance to rapid cold and heat than silica bricks, and the volume stability is better than silica bricks. It is mainly used as the refractory layer of steel drum lining and steel pouring system. In addition, it can also be used for hot furnace roof, heat storage chamber lattice brick, iron furnace lining, various kiln furnace bottom and flue and other parts.
| Name | Fire resistance，℃ | Bulk density，g/cm3 | Apparent porosity，% | Normal temperature compressive strength，MPa | Load softening temperature（T6.6），℃ | AI2O3，% | SiO2，% | Fe2O3，% |
| Semi-silica brick | 1630-1650 | 2.10 | 18 | 29 | 1490 | 21.59 | 76.58 | 0.83 |
