Fireclays

Refractory fireclays embrace all types of clays commercially available. Because of the abundant supply of fireclay and its comparative cheapness, refractory bricks made out of it are the most common and extensively used in all places of heat generation. In fact, several technical designations are used in the ceramic industry for classifying refractory clays these are fire clay, China clay, ball clay, flint clay, and chamotte. 

Industrial applications and uses. As a general rule fireclays are used in both shaped refractories (i.e., bricks) and monolithic refractories (i.e., castables), while super-duty plastic fireclay is used in the preparation of castable recipes. Therefore, the major applications of 

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Acid refractory materials include fireclays, flint clays, china clays (kaolins), silica, flint, chalcedony, ganister and titanium dioxide. 

Fireclay. Fireclays consist mainly of the mineral kaolinite [1318-74-7] 2 3 small amounts of other clay minerals, quart2ite,... 

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. 

A few fireclay refractories are produced by the stiff-mud process using an auger machine that pugs, de-aks, and continuously extmdes a clay column. A wke cutter cuts the clay into blanks which are then sized, shaped, and branded by a repress machine. 

Sihca brick and large fireclay shapes are fired in circular downdraft kilns. These kilns vary in diameter and can accommodate up to 150,000 23-cm bricks or their equivalent in other si2es. The complete burning cycle for a typical periodic kiln ranges from 21 to 27 days as compared with four to seven days for a tunnel kiln. 

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

Fireclay Refractories. These products are made from clay minerals containing ca 17—45% AI2O2. Pure kaolin has the highest alumina content. 

Fireclay refractories are used in kilns, ladles, and heat regenerators, acid—slag-resistant apphcations, boilers, blast furnaces, and rotary kilns. They are generally inexpensive. 

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. 

Fireclays can be dividea into plastic clays and hard flint clays they may also be classified as to alumina content. Firebricks are usually made of a blended mixture of flint clays and plastic clays which is formed, after mixing with water, to the requirea shape. Some or all of the flint clay may be replaced by highly burned or calcined clay, called... 

Tne insulating firebrick is a class of brick that consists of a highly porous fire clay or kaolin. Such bricks are light in weight (about one-half to one-sixth of the weight of fireclay), low in thermal conductivity, and yet sufficiently resistant to temperature to be used successbilly on... 

Red and blue acid-resistant bricks are resistant to all inorganic and organic chemicals, except for hydrofluoric acid and hot concentrated caustic alkalis. Acid-resistant fireclay bricks are used for conditions involving elevating temperatures and corrosive condensates. Highly vitrified materials such as chemical stoneware, porcelain and basalts are used for extremely severe duties or where contamination of the process liquors is undesirable. 

Kaschu, n. catechu, cutch. kaschutieren, v.t. dye with catechu or cutch. Kase. m. cheese cheese-shaped object, as a disk of fireclay iised as a crucible stand, kfiseartig, a. cheesy, caseous. 

Traditionally ceramic raw materials have been dug out of the ground and used with little or no treatment or purification. Sand, fireclay, talc, and gypsum are examples. The energy expenditure for producing these materials is therefore small. Some of these materials can be found naturally in high purity. Silica sands (SiO,) with less than 100 ppm (parts per mil-... 

Procedure. The method to be described is especially suitable for ceramic materials such as fireclay, firebrick, or silica brick. The finely ground sample should be dried at 110 °C. The weight of sample to be employed depends largely upon the silica content of the material, since not more than 35 40 mg of silica should be present in the aliquot employed for the determination. For samples... 

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