Alumina brick

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 Refractories. The desired alumina content, from 100% to just above 45%, is obtained by adding bauxites, synthetic aluminosihcates, and synthetic aluminas to clay and other bonding agents. These refractories are used in kilns, ladles, and furnaces that operate at temperatures or under conditions for which fireclay refractories are not suited. Phosphate-bonded alumina bricks have exceptionally high strength at low to intermediate temperatures and are employed in aluminum furnaces. High alumina and mullite are used in furnace roofs and petrochemical apphcations. 

Tonerde-hydrat, n. hydrate of alumina (aluminum hydroxide). -kali, n. potassium aluminate. -lack, m. alumina lake. -metaU, n. aluminum, -natron, n. sodium aluminate. -prMparat, n. alumina preparation, tonerderelch, a, rich in alumina, aluminous. Tonerde-galz, n. aluminum salt, -stein, m, alumina brick, -sulfat, n, sulfate of alumina... 

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. 

Another form of alkali metal attack on the hot faces of refractory linings involves their high temperature reaction with various components of the brick to form expansive crystalline phases which cause brick to bloat on their hot faces and, subsequently, erode or spall. An example Is the case of alumina brick exposed to sodium at temperatures from about 1700°F to 3000°F. Although sodium does not form a low temperature melt with alumina, it reacts with the alpha phase of alumina, corundum, to form beta alumina, sodium aluminate. Beta alumina has a much greater volume than the very dense corundum and, therefore, disrupts the brick bonding matrix, causing eventual bond failure. 

Alkalies will react with fireclay and high alumina brick. 

Sixty percent alumina brick seems to perform best in the 2000°F to 2400°F service temperature range. These bricks should also be high fired, low porosity and low in the impurities mentioned above. 

The advantage afforded by the 60% alumina brick over the super duty fireclay bricks mentioned above is a higher service temperature limit. The majority of the alumina in a 60% alumina brick is combined with silica to form mullite, and is therefore protected from the alkali/alumina reaction. 

From 2400°F up, 88% plus alumina brick is suggested. Although the alkali/alumina reaction will occur, the higher refractoriness of the alumina brick is necessary to ensure that the lining does not soften and sag during service in the high temperature exposure. 

Another alternative to the 88% plus alumina brick at 2400°F and above is alumina-chrome brick which performs very well against alkali but is very susceptible to thermal shock. 

The specimen corresponding to an 80% alumina brick, ratio 20 80 silica to alumina, had the mineralogical composition of mullite and corundum. The resulting phases present in this sample when mixed with the specified quantity of Na2C03 were sodium aluminate and corundum. 

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. 

The reaction phases are similar for the 70% alumina brick exposed to K20 however, corundum and potassium aluminate are also produced by potassia reaction. 

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%. 

Refractory Lining - Type Water-cooled Copper Elements plus Chrome-Magnesite Bricks Silica - Alumina Bricks stool water jackets Chrome-MagnesHe Bricke... 

Surficial deterioration of alite, amoeboid ragged belite, dendritic and lake periclase, loss of alumina brick Overturning from delayed petroleum coke, producing longer burning zone (Jefferson and Kruse, 1987)... 

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

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