Lightweight Alumina Hollow Ball Brick

Lightweight alumina hollow ball brick is a new type of high-temperature thermal insulation material, mainly made of alumina hollow balls and alumina powder as the main raw materials, with a maximum operating temperature of 1800℃. The product has high mechanical strength, which is several times that of general lightweight products, and good thermal stability. Small reburning line change rate: small thermal conductivity: good thermal shock resistance: high high temperature structural strength: high mechanical strength, volume density is only half of that of corundum products, and is an ideal ultra-high temperature material and energy-saving thermal insulation material. Alumina hollow ball bricks not only have a small body density, which can optimize the structure and reduce the weight of the furnace body, but also have a low thermal conductivity, which has a good thermal insulation effect. It is widely used in petrochemical and chemical industries, gasification furnaces, carbon black industrial reactors, metallurgical induction furnaces, gasification furnaces, thermal insulation linings, hard and super-hard alloy vacuum medium frequency ultra-high temperature furnaces and ceramics, refractory materials and other high temperature and ultra-high temperature kilns.

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Description

Lightweight alumina hollow ball bricks are heat-insulating refractory products made of alumina hollow balls as the main raw material.

Performance Lightweight alumina hollow ball bricks have an AlO content of not less than 98%, a SiO content of not more than 0.5%, a FezO content of not more than 0.2%, a bulk density of 1.3~1.4g/cm', an apparent porosity of 60%~70%, a compressive strength of not less than 9.8MPa, a softening temperature under load (0.2MPa) of not less than 1700℃, and a thermal conductivity of 0.7~0.8W/(m·K). The preparation of alumina hollow balls uses industrial alumina as raw material, which is melted by electric melting and then sprayed.

The electric melting equipment is an arc furnace. The molten pool is made of graphite products or other fire-resistant materials, and the electrodes are graphite products. After adding industrial alumina powder into the molten pool, it can be powered for melting. When the temperature of the molten liquid reaches or exceeds 2200℃, the molten liquid rolls, that is, the furnace body is tilted to make the molten liquid flow out; at the same time, the molten liquid stream is sprayed with compressed air. Due to the viscosity and surface tension of the molten liquid, the molten liquid forms hollow balls wrapped in air during the spraying and condensation process. After being collected and screened, they are stored separately according to different particles for standby use. The number ratio of hollow alumina balls of different particle sizes varies with the different compressed air spraying pressures. The greater the pressure, the more small balls there are. The wall thickness of the hollow ball varies with the particle size. When the particle size fluctuates in the range of 5~0.5mm, the wall thickness fluctuates in the range of 0.3~0.1mm accordingly.

Products Description

The larger the particle size of the hollow ball, the smaller its natural bulk density; the smaller the particle size, the greater its natural bulk density. For example: when the particle size is 5.13~3.22mm, the natural bulk density is 470g/L; when it is 3.22~2.0mm, it is 670g/L; when it is 2.0~1.0mm, it is 810g/L; when it is 1.0~0.5mm, it is 915 g/L.

The manufacture of lightweight alumina hollow ball bricks is to mix alumina hollow balls, sintered alumina fine powder and binder in a certain proportion, shape, dry and sinter them to obtain lightweight alumina hollow ball bricks.

Alumina fine powder is made from industrial alumina as raw material, calcined at 1500℃, ground, pickled and dried.

The binder used for lightweight alumina hollow ball bricks is usually an aqueous solution of aluminum sulfate or an aqueous solution of aluminum dihydrogen phosphate.

The particle size of hollow alumina balls is generally 5-0.5mm, and the dosage is 65%-70%, and the dosage of fine alumina powder is 30%-35%; the dosage of binder.

Mix the above materials evenly, and form them by vibration molding. After drying, the bricks are fired at 1500-1800℃ to obtain fired bricks; they can also be made into unfired products without firing, or directly build furnace linings with amorphous materials. Lightweight hollow alumina ball bricks are mainly used as linings for high-temperature industrial kilns below 1800℃, such as lining bricks for high-temperature kilns in refractory materials, electronics, and ceramic industries; thermal insulation layers for high-temperature thermal equipment, such as gasification furnaces, gasification furnaces, carbon black industrial reactors, and thermal insulation bricks for induction furnaces in the petrochemical industry. Application in the above fields can save energy by 20%-30%. Lightweight alumina hollow ball bricks are used as linings for high-temperature kilns. The heating rate during baking cannot be too fast, otherwise cracks will occur, reducing strength and service life. Due to their high apparent porosity, they cannot be used in areas that come into contact with slag, otherwise they will be damaged by the penetration of slag.

Alumina hollow ball products, corundum mullite lightweight bricks

Brand/project	Alumina hollow ball products				Corundum mullite, mullite
	HX-GK-99	HX-GK-90	HX-GK-85	HX-GK-80	HX-GM -1.5-2.0	HX-GM -1.3	HX-M -1.0	HX-M -0.9	HX-M -0.8
Al₂O₃ %	≥98	≥90	≥85	≥80	≥80	≥63	≥60	≥60	≥55
Bulk density g/cm³	1.4～2.0	1.4～2.0	1.4～2.0	1.4～2.0	1.5～2.0	1.2～1.5	1.0L	0.9L	0.8L
Normal temperature compressive strength MPa	≥8	≥10	≥10	≥10	≥12	≥7	≥4	≥4	≥3
0.1MPa Load softening Starting temperature T2℃	≥1700	≥1700	≥1680	≥1650	≥1700
Reburning line change rate %						1500℃ × 8h -1.0	1450℃ × 8h -1.0	1450℃ × 8h -1.0	1350℃ × 8h -1.0
Maximum operating temperature ℃	1780	1750	1720	1700	1680	1550	1500	1450	1400
Application	Suitable for high temperature insulation belts and working linings of high temperature kilns and thermal equipment

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