Bricks silica

Use for sprinkling the moulds of silica bricks, namely bricks or other articles composed of refractory material and containing not less than 80% of silica... 

Dinas-stein, m. Dinas brick, silica brick, -ton, m. Dinas clay. ziegeli m. DitMsiegel. Dinaton, m. Dinas clay. 

Silika-gel, n. silica gel. -stein, m. silica brick. Silikat, n. silicate. -emaUle, /. sUicate enamel. 

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... 

Notes. (1) Silica brick, No. 267 (a British Chemical Standard) may be used. 

A rectangular iron ingot 15 cm by 15 cm by 30 cm is supported at the centre of a reheating furnace. The furnace has walls of silica-brick at 1400 K, and the initial temperature of the ingot is 290 K How long will il take to heat the ingot to 600 K ... 

Silica bricks are manufactured from crushed ganister rock containing about 97 to 98 percent silica. A bond consisting of 2 percent lime is used, and the bricks are fired in periodic kilns at temperatures of 1,500 to 1,540°C (2,700 to 2,800°F) for several days until a stable volume is obtained. They are especially valuable when good strength is required at high temperatures. Superduty silica bricks are finding some use in the steel industry. They have a lowered alumina content and often a lowered porosity. 

Silica bricks are used extensively in coke ovens, the roofs and walls of open-hearth furnaces, and the roofs and sidewalls of glass tanks and... 

Brick. See also Refractory brick entries Silica brick... 

Silica analysis of water, 26 39 Silica-based glass fibers fabrication of, 77 136-137 transparency of, 77 132 Silica brick, ASTM classifications and specifications for, 27 509 Silica components, production of, 23 56 Silica fibers... 

Temp, °C Fireclay Silica Brick Magnesite Chrome Forsterite Mullite Cristobalite Periclase Corundum... 

Silica 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 sizes. 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. 

Silica Brick. Under ASTM C416, types A and B silica bricks are classified according to chemical composition and strength. Silica brick must have an average modulus of rupture of 3.5 MPa (500 psi), <1.5% A O no more than 0.2% Ti02, <2.50% Fe203, and <4.00% CaO. Type A brick must have a flux factor <0.5. The flux factor is equal to the percent alumina plus twice the percent of alkalies. Type B are all other silica brick covered by the standard chemical and strength specifications. 

The existence of tridymite as a distinct phase of pure crystalline silica has been questioned (42,58—63). According to this view, the only true crystalline phases of pure silica at atmospheric pressure are quartz and a highly ordered three-layer cristobalite having a transition temperature variously estimated from 806 250°C to about 1050°C (50,60). Tridymites are considered to be defect structures in which two-layer sequences predominate. The stability of tridymite as found in natural samples and in fired silica bricks has been attributed to the presence of foreign ions. This view is, however, disputed by those who cite evidence of the formation of tridymite from very pure silicon and water and of the conversion of tridymite M, but not tridymite S, to cristobalite below 1470°C (47). It has been suggested that the phase relations of silica are determined by the purity of the system (42), and that tridymite is not a true form of pure silica but rather a solid solution of mineralizer and silica (63). However, the assumption of the existence of tridymite phases is well established in the technical literature pertinent to practical work. 

Crystalline Silica. Quartz sand is of course the principal raw material for the production of glass (qv). Cristobalite and 3-quartz are used in glass ceramics (qv), ie, ceramics produced by the controlled crystallization of glass. Silica is a main constituent of ceramics (qv). For example, refractory silica brick containing small amounts of A O is used as roof brick for open-hearth furnaces at temperatures >1600° C (see Refractories). Silica sand or flour (ground quartz) is the raw material for soluble silicates, such as sodium silicate, which is consistently ranked as one of the top 50 U.S. industrial chemicals (98) (see Silicon compounds, synthetic inorganic silicates). 

In this assay, the tar vapors are cracked over crushed silica brick and the increased yield of gas is accommodated in a larger receiver of some 10 L capacity. Owing to the possibility of tar fog remaining uncondensed, the condenser in this case is followed by a U-tube packed with absorbent cotton wool, and both are immersed... 

The apparatus for the chlorination of titanium raw stock in a fluidised layer is a cylindrical shaft lined with thick silica brick. There are several shelves with gas distribution grates located one above another for better chlorine consumption and titanium extraction. The parent mixture is loaded onto the top shelf where it is partially chlorinated with unreacted chlorine coming from below and is sent onto the next shelf through a pipe. The most intensive chlorination occurs on the lower shelf. 

Reverberatory furnaces3 are particularly suitable for fines and flue-dust from the blast-furnaces. Their walls and roof are lined with silica bricks, and the hearth with silica sand. A typical charge consists of2 ... 

Silica bricks are used extensively in coke ovens, the roofs and walls of open-hearth furnaces, and the roofs and sidewalls of glass tanks and as linings of acid electric steel furnaces. Although silica brick is readily spalled (cracked by a temperature change) below red heat, it is very stable if the temperature is kept above this range and for this reason... 

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