Bubble Alumina bricks have exceptional hot strength and low thermal conductivity, which is an effective high-temperature thermal insulator in structural applications where insulating capabilities cannot be sacrificed, and appropriate for use at temperatures as high as 1850°C.
The brick are available in standard brick shapes and special shapes for bespoke applications.
-Refractories sinter furnace such as shuttle kiln, tunnel kiln, pusher slab kiln, electric furnace;
– Ceramics kilns & furnaces to sinter high alumina ceramics, polycrystalline alumina, fine ceramics, technical ceramics, etc;
– Metallurgical industry stainless steel or non-ferrous alloy metal bright annealing furnace, galvanizing furnace, brazing furnace, powder metallurgy (PM) sinter kiln, metal injection molded (MIM) sinter furnace;
– Electronic Industry secondary battery materials sinter furnace & semiconductor material firing furnace;
– Chemical & petrochemical industry gasifiers, hazardous waste and fluorine processing incinerators, secondary ammonia reformer, carbon black reactor, methanol production reactors, hydrogen generators, etc.
– Experimental electric furnaces, dental electric furnaces, molybdenum wire furnaces, tungsten rod furnaces, induction furnaces, nitriding furnaces, etc.
-Nuclear fuels sintering furnaces, gas turbines combustion chambers, glass furnace, etc.
3 reasons to explain why bubble alumina brick is an excellent insulation refractory used for high temperatures furnace
1. Bubble alumina is made by fused alumina. Alumina does not exhibit high thermal conductivity, and when in the form of hollow spheres, its thermal conductivity is additionally reduced.
2. When the outside of the outermost bubble heats up, the heat is transferred through the solid portion of the bubble by conduction. When the heat energy reaches the air inside the bubble, it changes transport mechanisms and the result is a loss in energy. The heat then proceeds across the airspace and reaches the wall of the sphere, changes its transport mechanism again (losing additional energy), and continues through the bubble wall.
3. When the heat transfers either into another bubble, through the matrix, or through the airspace between bubbles, it loses additional energy. This process repeats itself all the way through the thickness of the insulating lining. This continual energy loss makes bubble alumina an excellent insulating material that can withstand exceptionally high temperatures.
Alumina bubbles can be produced by various methods depending on the chemistry of the bubble and the final desired properties.
Alumina bubbles can be produced by various methods depending on the chemistry of the bubble and the final desired properties. For fused alumina bubbles, the fusion process involves melting the raw materials in an electric arc furnace at temperatures in excess of 2000ºC and pouring the material out of the furnace through a high-pressure air stream. The molten stream is transformed into a barrage of particles that rapidly cools as the particles fly across the contained area in front of the furnace. Surface tension causes these molten particles to form perfect spheres as they are blown across the room. As the bubbles get farther from the furnace, the exterior of the spheres cools more rapidly than the interior. This results in the walls shrinking away from the center of each particle, leaving an open core inside. The open core provides the lightweight insulating properties of the bubbles, which exhibit extremely fine crystals resulting from the rapid cooling. By the time the particles have moved 10-20 ft from the pouring spout, they have solidified and are firm hollow spheres. The size distributions of the bubbles are controlled by the velocity of the air stream and typically range from 5 mm to 100 microns. The bubbles are then moved from the furnace floor to the screening operation for sizing/grading. The screening system allows for the sizing and separation of the bubbles from magnetics with minimal handling and rework. The bubbles can be placed in several types of packaging, ranging from small bags and drums to large totes and boxes.
| Items | Grade | BA-85 | BA90-1.2 | BA-90 | BA-99 | BA-99+ |
| Max Service Temperature | ℃ | 1750 | 1750 | 1800 | 1850 | 1850 |
| AI2O3 | % | 85 | 91.2 | 90 | 99 | 99.3 |
| SiO2 | % | 14 | 8 | 8 | 0.2 | 0.15 |
| Fe2O3 | % | 0.2 | 0.1 | 0.2 | 0.1 | 0.1 |
| Bulk Density | g/cm3 | 1.4-1.9 | 1.2 | 1.4-1.9 | 1.4-1.8 | 1.4-1.8 |
| Cold Crushing Strength | MPa | 18 | 11.9 | 15 | 15 | 12 |
| Refractoriness under load (0.1 MPa, 0.6%) | °C | ≥ 1700 | ≥ 1700 | ≥ 1700 | ≥ 1700 | ≥ 1700 |
| Permanent Linear Change (1650°C x 12h) | % | ±0.3 | ±0.2 | ±0.2 | -0.25 | -0.25 |
| Thermal expansion coefficient Room temp. to 1300°C | x10-6 | 7.8 | 8 | 8 | 8.6 | 8.6 |
| Thermal Conductivity (Average 800°C) | W/m·K | 0.55 | 0.21 | 0. 6 | 0.75 | 0.75 |
