Alumina Hollow Ball Brick

Alumina hollow ball refractory brick is a lightweight refractory brick which is made of alumina hollow sphere as the main raw refractory material and sintered at 1800 ℃. It is a high grade insulating refractory product. Use high temperature kiln with temperature above 1500℃. Lining, such as refractory materials, industrial ceramics and other industries, high temperature kiln lining refractory brick, thermal equipment thermal insulation layer, such as petrochemical gasification furnace, gas furnace.
 
Alumina Hollow Ball Brick Features
 
1. Lightweight and high temperature resistant.
 
2. The change in the reburning line is small.
 
3. Good thermal shock resistance.
 
4. low thermal conductivity, good insulation effect.
 
5. Strong resistance to slag and gas erosion.
 
6. Energy saving effect is good.
 
Alumina Hollow Ball Brick Application
 
Alumina hollow ball refractory brick adopts alumina hollow sphere as the main raw refractory material, the high performance micropowder is used as an additive, the organic material is used as a temporary binder, refractory brick is fired at a high temperature in a shuttle kiln. The refractory product contains a large number of closed pores, which has the characteristics of light weight, high temperature resistance, good heat preservation performance, small re-sintering shrinkage, excellent thermal shock resistance, and strong resistance to aggressive gases and slag. The refractory product can greatly improve the thermal efficiency of the kiln, shorten the production cycle, reduce the weight of the kiln, achieve energy saving. Alumina hollow ball brick products can directly contact flame, suitable for cracking furnace, hot blast stove, heating furnace, tunnel kiln, push plate kiln, crucible furnace and various electric furnace, electric kiln lining, widely used in metallurgy, refractory, Light industry, chemical, ceramics, glass, electronics and other industries
 
Alumina Hollow Ball Brick Manufacturing Process
 
The preparation of the alumina hollow spherical brick requires firstly manufacturing an alumina hollow sphere, the preparation method of the alumina hollow sphere has a ball burning loss method and a melt blowing method. The rolling ball method is to first make a core pellet with an organic resin or a low melting refractory material, put it in a rotating disc, and then sprinkle the moist alumina fine powder containing a certain amount of water on the disc, and adhere it to the core pellet to form A shell is like a icing on the outside of a pill. The pellets are then fired at a high temperature, in which the core pellets are burned out and the shell is sintered to form hollow spheres. The disadvantage of this method is that it is low in efficiency, the spherical surface is not smooth, and the wall thickness and size are not easy to control, so it is not used much in industrial production.
 
The process flow for preparing alumina hollow spheres by meltblowing is shown in Fig. 1. Industrial Al2O3 is used as a raw refractory material and directly melted in an electric arc furnace. The electric arc furnace can be used in single-phase or three-phase, and three-phase is preferred. The furnace body is provided with a tilting device, the discharge port is provided with a gas nozzle at an angle thereto. The furnace lining refractory material is graphite. Assuming that the furnace diameter is 550 mm, the furnace height is 300 mm, the graphite electrode diameter is 150 mm, and the electrode radius is 150 mm, the melting voltage is 100 V and the current is 1500 to 1700 A. During the melting process, the alumina fine powder is gradually and intermittently added until the melt reaches a sufficient amount to stop the feeding.
 
When the refractory material is completely melted, the viscosity of the melt is appropriate, and when the temperature of the melt is about 2200~2300 ℃, the furnace body can be tilted to make the melt flow out from the discharge tank, and the pneumatic valve is opened at the same time, and the exhaust gas volume is 10 m3/min. The compressed air with a pressure of 0.6~0.8MPa blows the liquid into droplets. The droplets solidify rapidly in the air due to the melt viscosity and surface tension, forming a shell-shaped sphere. Go to the collection room. After sorting, sieving or rinsing, the frit fragments, and the large balls and the small balls having a particle diameter of more than 5 mm or less than 0.2 mm are removed, and the qualified hollow balls of 5 mm to 0.2 mm are classified according to the particle size.
 
The natural bulk density of the alumina hollow sphere is 0.42~0.97g/cm3, the perfect rate of the blowing ball is 70%~90%. As the ball diameter decreases, the ball's integrity rate increases and the ball's natural bulk density increases. The hollow spheres have an alumina content greater than 99.5%. This hollow ball can be used directly as a bulk insulating material. When used, the size of the ball can be matched, and the appropriate amount of lightly burned α-Al2O3 fine powder can be used for better thermal insulation. Alumina hollow spheres brick can be used up to 1800 °C.
 
The mixed billet is poured into a wooden mold and placed on a vibrating table to be gently pressed and molded to obtain a blank body with a complete and evenly distributed sphere. After the green body is dried, it can be fired at different temperatures of 1500~1800℃ according to different application requirements. The refractory product has a porosity of 50% to 70%, a compressive strength of 4 to 6 MPa, and a thermal conductivity of 3.3 to 3.8 kJ/m·h·°C. The thermal shock cycle of 1100 ℃ ~ air-cooled is more than 15 times. It is a kind of fire-resistant and heat-insulating refractory material with both strength and good heat insulation. The performance of the refractory product varies greatly with the amount of alumina fine powder added and the firing temperature. The change of the size ratio of the ball has little effect on the performance of the refractory product.
 
Alumina Hollow Ball Brick Using Precautions
 
1. When using refractory alumina hollow ball bricks, the heating rate during baking should not be too fast, otherwise cracks will occur, reducing strength and service life.
 
2. Alumina hollow ball brick generally not used to contact the slag erosion site, to avoid damage due to slag erosion.
 
3. Alumina hollow ball refractory brick use the corresponding alumina hollow ball brick mud masonry.Alumina