Coke Oven Silica Brick

Coke oven silica bricks should be acid refractory materials composed of scale stone, cristobalite and a small amount of residual quartz and glass phase.

1. The silicon dioxide content is more than 93%. The true density is 2.38g/cm3. It has resistance to acid slag erosion. Higher high temperature strength. The starting temperature of load softening is 1620～1670℃. It will not deform after long-term use at high temperature. There is generally no crystal conversion above 600°C. Smaller temperature expansion coefficient. High thermal shock resistance. Below 600℃, the crystal form changes more, the volume changes greatly, and the thermal shock resistance becomes worse. Natural silica is used as the raw material, and an appropriate amount of mineralizer is added to promote the conversion of quartz in the green body into phosphorite. Slowly fired at 1350～1430℃ in reducing atmosphere.

2. Mainly used for the coking chamber and the partition wall of the combustion chamber of the coke oven, the regenerator and slag chamber of the steel-making open-hearth furnace, the soaking furnace, the glass melting furnace, the firing kiln of refractory materials and ceramics, etc. And other load-bearing parts. It is also used for high-temperature load-bearing parts of hot blast stoves and acid open-hearth furnace roofs.

3. The material of silica brick is quartzite as raw material, adding a small amount of mineralizer. When fired at high temperature, its mineral composition is composed of tridymite, cristobalite and glass formed at high temperature. Its AiO2 content is more than 93%. Among the well-fired silica bricks, the content of tridymite is the highest, accounting for 50% to 80%; cristobalite is second, accounting for only 10% to 30%; and the content of quartz and glass phase fluctuates between 5% and 15%.

4. The material of silica brick is made of quartzite, added with a small amount of mineralizer, and fired at high temperature. Its mineral composition is tridymite, cristobalite and glassy formed at high temperature. Its SiO2 content Above 93%.

5. Silica brick is an acidic refractory material, which has strong resistance to acidic slag erosion, but when it is strongly corroded by alkaline slag, it is easily damaged by oxides such as Al2O3, and has good resistance to oxides such as iCaO, FeO, and Fe2O3. sex.

6. The biggest disadvantage of load is low thermal shock stability and low refractoriness, generally between 1690-1730℃, which limits its application range.

Silica brick-physical properties

1. Acid-base resistance

Silica bricks are acidic refractory materials that have strong resistance to acid slag erosion, but when they are strongly corroded by alkaline slag, they are easily damaged by oxides such as AI2O3, and have good resistance to oxides such as CaO, FeO, and Fe2O3.

2. Expansibility

The thermal conductivity of silica bricks increases with the increase of working temperature without residual shrinkage. During the oven process, the volume of silica bricks increases with the increase of temperature. In the oven process, the maximum expansion of silica bricks occurs between 100 and 300 ℃, and the expansion before 300 ℃ is about 70% to 75% of the total expansion. The reason is that SiO2 has four crystal form transformation points of 117℃, 163℃, 180~270℃ and 573℃ in the oven process. Among them, the volume expansion caused by cristobalite is the largest between 180~270℃.

3. Deformation temperature under load

The higher deformation temperature under load is the advantage of silica bricks. It is close to the melting point of tridymite and cristobalite, which is between 1640 and 1680°C.

4. Thermal stability

The biggest shortcomings of silica bricks are low thermal shock stability and low refractoriness, generally between 1690 and 1730°C, which limits their application range. The key to determining the thermal stability of silica bricks is the density, which is one of the important indicators for determining its quartz conversion. The lower the density of the silica brick, the more complete the lime conversion, and the smaller the residual expansion during the oven process.

5. Silica brick-matters needing attention

1. When the working temperature is lower than 600~700℃, the volume of the silica brick changes greatly, the performance of resisting rapid cold and heat is poor, and the thermal stability is not good. If the coke oven is operated at this temperature for a long time, the masonry will be easily broken.

2. Performance Physical properties of coke oven silica bricks:

(1) The load softening temperature is high. Coke oven silica bricks can withstand the dynamic load of the coal loading car on the roof of the furnace under high temperature, and can be used for a long time without deformation;

(2) High thermal conductivity. Coke is made from coking coal in the coking chamber by conduction heating on the walls of the combustion chamber, so the silica bricks used to build the walls of the combustion chamber should have a higher thermal conductivity. In the temperature range of the coke oven combustion chamber, silica bricks have higher thermal conductivity than clay bricks and high alumina bricks. Compared with ordinary coke oven silica bricks, the thermal conductivity of dense coke oven silica bricks can be increased by 10% to 20%;

(3) Good thermal shock resistance at high temperature. Due to the periodic charging and coking of the coke oven, the temperature of the silica bricks on both sides of the combustion chamber wall changes drastically. The temperature fluctuation range of normal operation will not cause serious cracks and peeling of silica bricks, because above 600℃, coke oven silica bricks have good thermal shock resistance;

(4) Stable volume at high temperature. In the silicon bricks with good crystal form conversion, the remaining quartz is not more than 1%, and the expansion during heating is concentrated before 600C, and then the expansion slows down significantly. During the normal operation of the coke oven, the temperature does not drop below 600°C, and the masonry will not change much, and the stability and tightness of the masonry can be maintained for a long time.