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Fused Quartz Bricks with Low Thermal Expansion and High Thermal Stability for Coke Oven Repair
Zero expansion silica brick is also called fused quartz brick or thermal shock resistant silica brick. It has the characteristics of extremely low thermal expansion coefficient, excellent resistance to rapid cooling and heating, good high temperature structural strength, high SiO2 content, etc. This product can be widely used in various coke oven rapid thermal repair projects. This product does not crack or peel during use, and its low thermal expansion performance close to zero makes the coke oven safe and reliable for long-term use after repair.
Low Thermal Expansion and High Thermal Stability of Fused Quartz Bricks
The following mainly analyzes the low thermal expansion and high thermal stability of zero expansion silica bricks from the perspective of silica crystal structure:
(1) The main mineral phase of zero-expansion silica bricks is amorphous silica, accounting for more than 90%
Zero expansion silica bricks are made of high-grade quartz ore, which is melted, cooled, crushed, screened, pickled and other processes in an electric arc furnace to prepare molten silica materials. The particles are mixed with a small amount of mineralizer and sintering agent to form semi-dry mud, which is then pressed, dried and fired. The main mineral component is amorphous molten silica. The thermal expansion coefficient of zero-expansion silica bricks mainly composed of amorphous molten silica is close to zero, so they are called zero-expansion silica bricks.
(2) Atomic structure of amorphous molten silicon oxide
Although both are silicon dioxide, the structure of amorphous SiO2 is different from that of crystalline SiO2. Each silicon atom and oxygen atom of crystalline silicon oxide form a silicon-oxygen tetrahedron [SiO4], and each tetrahedron is connected through corner vertices to form a three-dimensional network structure. It can be seen from the structure of amorphous silicon oxide that the disordered amorphous SiO2 has vacancies in its silicon-oxygen combination, its atomic structure is long-range disordered, and the bond angles between silicon-oxygen tetrahedrons are irregularly distorted, forming a three-dimensional structure cross-link.
The thermodynamic properties of materials are determined by the atomic crystal structure. SiO2 has a variety of isomorphous structures. The crystal phases formed under different conditions have different structures, so their thermodynamic properties are different.
Once the bond angle of crystalline SiO2 changes due to heat, it begins to transform into isomorphous at 180°C, accompanied by huge volume expansion. Therefore, the thermal stability is extremely poor, and it will crack after being water-cooled at 1100°C. Amorphous SiO2 has the characteristics of a small thermal expansion coefficient, excellent thermal stability, high viscosity at high temperature, and low thermal conductivity. However, amorphous SiO2 is unstable at high temperatures and will not change volume when heated within 1100℃. However, as the temperature rises, amorphous SiO2 begins to crystallize. Because the crystallization process is slow, it can still meet the construction requirements well during the thermal repair process.
Zero expansion silica bricks take effective measures to control the crystallization speed and crystallization ratio of amorphous amorphous molten silica at high temperature during the production process, so that they can better meet the thermal requirements.
(3) Thermal stability test of zero expansion silica bricks
After the zero expansion silica bricks were heated to 1100℃, they were immediately placed in normal temperature water. After 30 water cooling cycle tests, there was no change. After the zero expansion silica bricks were placed directly from room temperature to 1500℃ for 12 hours, there was no change after they were taken out. The actual test results also proved that the thermal stability of zero expansion silica bricks is excellent.
The application of fused quartz bricks in glass kilns is mainly reflected in its excellent properties such as high temperature resistance and corrosion resistance. Fused quartz bricks have high purity and uniform particle size, and can maintain stable physical and chemical properties in high temperature environments. Therefore, they are widely used in many parts of glass kilns.
Specific application parts of glass furnace
Pool wall bricks: Fused quartz bricks perform well in the pool wall of glass melting furnaces. It can withstand the erosion of high-temperature molten quartz and maintain the stability and durability of the pool wall. Especially when melting alkali-free or low-alkali glass fiber, due to severe acid erosion, the pool wall brick material should be AZS bricks or dense zircon bricks, and fused quartz bricks can also be used.
Advantages of fused quartz bricks in glass furnaces
High temperature resistance: Fused quartz bricks have extremely high temperature resistance and can remain stable in high temperature environments without deformation or damage due to temperature changes. This makes it perform well in the high temperature environment of the glass kiln and ensure the stable operation of the kiln.
Corrosion resistance: Fused quartz bricks have good corrosion resistance, can resist the erosion of acidic substances, and extend the service life of the kiln. When melting alkali-free or low-alkali glass fibers, fused quartz bricks can effectively resist acid erosion and maintain the integrity of the kiln.
Manufacturing process of fused quartz bricks and specific application cases in glass kilns
The manufacturing process of fused quartz bricks is special, and the production process needs to solve problems such as high melting temperature and high viscosity. Due to its high purity and uniform particle size, fused quartz bricks are used in many parts of glass kilns. For example, the use of fused quartz bricks in the pool wall can effectively resist high temperature and corrosion, ensuring the stable operation and long-term use of the kiln.
