High Alumina Bricks

High alumina bricks contain more than 46% alumina. The raw materials used for making such bricks are sillimanite, kyanite, and andalusite. These minerals exist as rocks and are used in as mined condition to get more alumina content. For a lower percentage of alumina, the as-mined minerals are mixed with clays. On firing, all these bricks contain mullite, glass, and cristobalite or tridymite as the phases. The same phases are also found in firebricks. 

The difference here is in the amount of mullite and fluxes. Mullite will be higher and fluxes will be lower in high alumina bricks. 

---

The resistance against thermal spalling of fireclay and high alumina brick is indicated in Table 5. No standard test has been adopted for basic brick. Refractories composed of 100% magnesia exhibit poor thermal shock resistance, which is improved by addition of chrome ore. So-called direct bonded basic brick, composed of magnesia and chrome additions, exhibits good thermal shock resistance. 

Includes regular fireclay, semisilica superduty fireclay, ladle brick, and insulating firebrick (IFB) below 23. Includes high alumina, mulhte, and extra high alumina brick. 

High alumina brick, ASTM classifications and specifications for, 21 508 High alumina catalysts, 11 724 High alumina refractories, 21 515, 518 High analysis fertilizers, 11 123, 124 High aspect ratio micromachining... 

Fireclay and High Alumina Brick. ASTM designation C27 covers fireclay and high alumina brick (Table 12). High alumina brick is classified according to alumina content, starting at 50% and continuing up to 99% Al Oy Manufacturers are allowed 2.5% of the nominal alumina content, except for 85 and 90% (2.0%) and 99% (min 97%). An additional requirement for alumina bricks with Al C content of 50, 60, 70, and 80%, are pyrometer cone equivalents (PCEs) of 34, 35, 36, and 37, respectively. 

Alkalies will react with fireclay and high alumina brick. 

On the other hand, Thompson and Rexford [40] reported that for high-alumina brick at temperatures around 2200°F, the liquid flow diminishes to the point that sufficient time is available for the liquid on the surface to become rich in alkalies. Nephelite thereby forms in the surface layer causing slabbing of the brick surface. If reactions are completed, only about 4% to 5% soda need be added to high-alumina compositions to consume mullite and produce corundum, nephelite, and albite. With an addition of 12% soda, the phases present are corundum and nephelite. 

Cerox. (Thermal Ceramics] High alumina brick. 

Tabular alumina is the ideal base material for high alumina brick and monoUth liners in the metal, ceramic, and petrochemical industries. 

Raw bauxite is frequently added to fireclay to increase its alumina content the high-alumina bricks made from such mixtures have a high resistance to fusion. 

High-alumina brick has an alumina content in the range 45-100 wt%. 

Fire bricks IS 8-1983 Type-II or higher grade High alumina bricks... 

Phosphate-bonded high-alumina bricks (>90% AI2O3) are used with phosphate mortars for aluminium smelting furnaces. 

Refractory Type Fireclay Silicon bricks carbide bricks High alumina bricks Silica bricks Chrome bricks Direct bonded bricks Magnesite bricks... 

Recuperators with high alumina bricks Alter the temperature of the exit air starts falling below a certain predetermined value, the unit is taken up for passing hot gases again. The hot gas and cold air streams are thus passed alternately by operating butterfly valves in the ducts which are switched over manually or automatically (can be by timers) as per temperature patterns desired. 

For very high temperature operations refractory brick must be used. These brick are made from alumina clays, of which there are two general classifications mullite or high alumina. High alumina bricks may vary in alumina content Ifom 90 to 99% AI2O3. 

Mullite brick contains very little free AI2O3 therefore its chemical resistance is superior to that of the high alumina brick. Typical physical properties are as... 

Furnace sizes vary widely, with hearth areas from 2 to 70 m. Construction commonly uses chrome magnesite brick to the slag level and high alumina brick above. Suspended arch roofs are used in the larger furnaces. A schematic of the reverberatory furnace is shown in Figure 11.2. 

High Alumina Brick High Alumina Brick Burnt Magnesite (Basic Brick)... 

---