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Silica Brick

Product: Silica Brick

Category:  Sintered Refractories

Application:  glass, metallurgy, Steelmaking, and other industries

Item Code:  A2401/A2402

What is silica Brick?

Silica brick is a type of acidic refractory brick that contains at least 94% oxide silica (SiO2). It consists mainly of squamous quartz, cristobalite, and a small amount of residual quartz and glass phase. The true density is 2.35/cm3. Silica refractory is resistant to acidic slag erosion and has a higher high-temperature strength. The load softening starting temperature is 1620~1670 °C.

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Advantages of Sintered Silica Firebrick

Good acid corrosion resistance

Good thermal conductivity

Good thermal expansion coefficient

High volume stability under long-term high-temperature

Low potential to creep

High softening temperature under load

Relatively cheap

Application of silica refractory

Silica bricks with different properties are variable in their applications.

Glass Industry: the crown of a molten pool in a glass kiln

Coke oven: Partition wall between carbonization chamber and combustion chamber

steelmaking open-hearth furnace:  regenerator and slag chamber

ceramic firing kilns and other kilns: vaults and other load-bearing parts

High-temperature load-bearing parts of hot blast furnaces and acidic open-hearth furnace tops.

Silica refractory brick specification

Item CodeGZ-96GZ-95GZ-94BG-96ABG-96BBG-95ABG-95B
Chemical CompositionSiO2%96959496969595
Fe2O31.01.21.40.81.01.21.2
Melt Index (Al2O3+2R2O)
unit Weight<20kg
unit Weight≥20kg
///
0.5
0.6



0.7
0.7


RUL 0.2MPa166016501640
(Cementing Silica 1620)
1680167016601650
AP%22(24)
CCS
unit Weight<20kg unit Weight≥20kg
MPa
35(30)
30(25)
True Densityg/cm32.342.352.342.35
Application FieldsMetallurgical IndustryGlass Furnace Industry
Data in brackets are indicators of handmade bricks.
The technical requirements of bricks that are hand-shaped and with a weight over 40kg shall be agreed upon by both parties.

Chemical composition of silica bricks

The mineral phase composition of silica bricks is mainly tridymite and cristobalite, with a small amount of quartz and glass. Tridymite, cristobalite, and residual quartz have large volume changes due to changes in crystal form at low temperatures, so the thermal stability of silica bricks at low temperatures is very poor. During use, heat and cool slowly below 800°C to avoid cracks. Therefore, it is not suitable to be used in kilns with sudden temperature changes below 800°C.

Manufacturing of the silica refractory brick

The production of silica bricks mainly goes through mixing, shaping, drying, and then firing in a kiln at 1400–1430 °C.

When preparing silica brick mud, a certain amount of waste silica brick is usually added to the ingredients. The purpose is to reduce the expansion and stress generated when the product is fired, reduce the occurrence of cracks, and improve the yield. The amount added is related to the shape and weight of the brick. For special-shaped bricks weighing less than 25kg, 20% can be added; for special-shaped bricks weighing more than 25kg, 30% can be added; and for special-shaped silica bricks, 30% can be added. When adding waste silica bricks, you should pay attention to this problem. Adding too much will reduce the refractoriness and mechanical strength of the product and increase its porosity. Therefore, the amount of waste bricks added should not be too much.

The binding agents used in making silica bricks include sulfite pulp waste liquid and lime milk. When milk of lime is used as a binder, it acts as a plasticizer. Milk of lime increases the strength of the bricks during the drying process and becomes a mineralizing agent during firing, promoting the transformation of quartz. Lime should contain a large amount of active CaO, undecomposed CaCO3, and MgCO3, which should not exceed 5%, and Al2O3+Fe2O3+SiO2 should not exceed 5%. When large particles of underburned Ca-CaO and overburned lime are contained, molten holes will occur in the product, affecting the quality of the product. When making ingredients, the amount of lime added should be converted into CaO. The amount added varies depending on the product and usually fluctuates between 1.5 and 2.5%. For example, to produce coke oven silica bricks, the CaO addition amount is 2.0~3.0%; to produce electric furnace top silica bricks, the CaO addition amount is 1.4~1.75%.

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