Al2o3 Bubble Bricks are hollow spheres made of industrial alumina as raw materials, melted at high temperature in an electric arc furnace, and blown with compressed air. It is molded by molding. The high-purity alumina hollow sphere brick made of alumina hollow spheres and alumina fine powder has excellent thermal insulation performance and high temperature resistance, and the operating temperature can be as high as 1800 ℃. The working lining of the high-temperature kiln that is in direct contact with the high-temperature melt can also be used as the insulation layer material of the high-temperature kiln. However, because the aggregate and matrix mineral phases in the alumina bubble brick are corundum phase, the thermal expansion rate is large, resulting in extremely poor thermal shock stability of the product, which greatly affects the service life of the alumina hollow ball. Bricks are prone to cracking and peeling, especially when used in environments with large temperature fluctuations, and have a short service life. It is difficult to meet the use requirements of high temperature or ultra-high temperature batch kilns. Therefore, we have developed mullite-bonded Al2o3 Bubble Bricks below 1700°C and alumina bubble bricks with high thermal stability at 1800°C to meet the needs of high-temperature kilns under different conditions of use, and to meet the national energy conservation and emission reduction policies. The development direction of low carbon economy.
Trial production of low temperature type (1700 degrees Celsius) high thermal shock stability thermal insulation product alumina hollow spherical brick
Ordinary high-purity Al2o3 Bubble Bricks are spherical, because the alumina hollow spherical aggregate particles are point-bonded, and cannot form a staggered network structure, a high structure inlaid with each other, and the bonding force between the particles is poor. The matrix phase of alumina ball bricks is corundum, resulting in extremely poor thermal shock stability of the product, which greatly affects the service life of alumina ball bricks. Through the research and analysis of imported alumina hollow spherical bricks, it is believed that the introduction of the second phase mullite phase with a small expansion coefficient into the alumina hollow spherical bricks can effectively improve the thermal shock stability of the products. , three stone, clay and other micropowders replace part of the sintered alumina micropowder to make the matrix mullite. The introduction of the mullite binding phase can greatly improve the thermal shock stability, but the introduction of impurities also reduces its more high operating temperature.
Raw materials have a great influence on the high temperature performance. Therefore, high-purity raw materials are used in the selection of raw materials, and the content of iron oxide and titanium dioxide is minimized. The mullite chemical test is to use silicon-containing mineral fine powder, alumina fine powder and an appropriate amount of mineralizer to blend, and add pulp as a binder. Al2o3 Bubble Bricks are trial-produced with alumina hollow balls as aggregate and mixed powder of silicon-containing minerals and alumina fine powder as matrix. After cutting, shape 230mmx114mmx65mm standard alumina hollow ball bricks on a pressurized vibration molding machine. The formed bricks are dried and fired in a high temperature shuttle kiln.
Trial production of high temperature type (1800 degrees Celsius) high thermal shock stability thermal insulation product alumina hollow spherical brick
The 3-0.2mm alumina hollow spheres and magnesium-aluminum hollow spheres are used as aggregates, and the sintered alumina fine powder and magnesium-containing additives are used as the matrix. After the aggregates are evenly mixed, the binder is added in advance for mixing. The fine powder is mixed and kneaded. After the mud is collected, it is formed into a standard alumina hollow spherical brick with a size of 230mm*114mm*65mm on a wood mold pressure vibration forming machine. The formed alumina hollow ball bricks are naturally placed for 12 hours and then enter the drying tunnel for drying. The dried bricks are fired in a high temperature shuttle kiln. The matrix part of the ordinary high-purity alumina hollow ball brick insulation material is mainly composed of corundum, and the thermal expansion coefficient of corundum is relatively large, which is one of the main reasons for the poor thermal shock stability of the alumina hollow ball brick. The composite material is formed by introducing a second phase with a smaller thermal expansion coefficient, and the thermal shock resistance of the composite material is improved by using the micro-cracks generated by the mismatch of the two expansion coefficients.
