Gypsum calcinating

Calcia [1305-78-8] Calci-Bind Calcimar Calcimycin [52665-69-7] Calcination Calcined gypsum Calcined limestone... 

Gypsum, calcined, V4 in and under 55-60 C27 Talcum powder 40-60 A27Y... 

In considering other factors that may influence water demand, many intrinsic stucco properties must be taken into account such as purity, particle size and morphology of the gypsum, calcination methods, and stucco surface properties. In addition, the water demand of stucco is dependent on its history such as aging time and conditions, aridization, and presence of surface active agents. 

Parlon, Chlorinated Rubber Plaster of Paris (Gypsum, Calcined) Phosphorus, Red-Yellow Phosphorus, Stabilized Photoflash Powder... 

Calcium sulfate hemihydrate n. CaS04-V2H2O. See gypsum (calcined) and plaster of Paris. 

Gypsum, calcined n. CaS04-ViG20. Gypsum partially dehydrated by heat. 

Calcium Sulfate Hemihydrate n CaS04-y2H20. See Gypsum (Calcined) and Plaster of Paris. 

Gelatin Powder Guar Beans Gypsum, Calcined Hydrated Lime Inert Chemicals Iron Ore Isophthalic Acid Kaolin Clay Malt Mill Feed... 

In 1843 he told British prime minister Robert Peel that the most indispensable nourishment taken up from the soil is the phosphate of lime, and two years later he began marketing in England his line of low-solubility mineral fertilizers. These mixes were prepared from plant ashes, gypsum, calcined bones, potassium silicate, and magnesium sulfate. Even those mixtures that contained some ammonium sulfate had too little nitrogen to become commercially successful, and the enterprise, launched jointly with Sheridan Muspratt (1793-1886), an alkali manufacturer in Liverpool, failed after only about three years. ... 

P-Hemihydrate. The dehydration of gypsum, commonly referred to as calcination in the gypsum industry, is used to prepare hemihydrate, or anhydrite. Hemihydrate is generally called stucco in North America and plaster in many other continents. In North America, plaster is differentiated from hemihydrate or stucco by the inclusion of additives to control intended use properties, eg, rehydration time, density, coverage, strength, and viscosity. 

In another process water is introduced into the hot calcined gypsum mass in a kettie to reduce the temperature of a portion of the mass to below the boiling point of water. The mass is then reheated (2). Stabilized setting and water demand properties are claimed as are water demand levels below those attainable through aridizing. 

OC-Hemihydrate. Three processing methods are used for the production of a-hemihydrate. One, developed in the 1930s, involves charging lump gypsum rock 1.3—5 cm in size into a vertical retort, sealing it, and applying steam at a pressure of 117 kPa (17 psi) and a temperature of about 123°C (6). After calcination under these conditions for 5—7 h the hot moist rock is quickly dried and pulverized. 

Anhydrite. In addition to ketde calcination (Fig. 1), soluble anhydrite is commercially manufactured in a variety of forms, from fine powders to granules 4.76 mm (4 mesh) in size, by low temperature dehydration of gypsum. 

Calcined Anhydrite. Soluble anhydrite, or second-settle stucco, has physical properties similar to those of gypsum plaster. It hydrates to the dihydrate rapidly in water. Its outstanding property is its extreme affinity for any moisture, which makes it a very efficient drying agent (see Desiccants). In ambient moisture-laden air, it readily hydrates to hemihydrate. Soluble anhydrite, under the trade name Drierite, is widely used as a desiccant in the laboratory and in iadustry. A small amount is also used as an insecticide carrier. Small amounts of soluble anhydrite are unintentionally produced in most commercial calciners during hemihydrate production. 

In 1989, 4,689,000 metric tons of uncalcined gypsum was sold or used 3,229,000 metric tons for use in Pordand cement and the remainder for agriculture and miscellaneous uses. About 17,778,000 metric tons of calcined material was used to produce 1.9 million square meters of board products. Over one million square meters of this material was regular board and about 560,000 m was Type X board. 

Gypsum is widely distributed naturally as calcium sulfate dihydrate [101012-1-4], CaS04-2H2 0. When partially calcined, the hemihydrate, CaS04 H2 0, is formed (see Calciumcompounds-calciumsulfates). Gypsum has been used in one form since 1756 for making dental casts, and in another form since 1844 for dental impressions (101). 

Plaster is the rehydrated calcined gypsum. The American Dental Association classifies five types of dental plaster according to the physical properties type 1, impression plaster type 11, model plaster type 111, dental stone type IV, high-strength dental stone and type V, high-strength. 

Each 100 g of calcined gypsum theoretically requires only 18.6 mL of water to complete the chemical reaction from the hermhydrate to the dihydrate. Any amount of water greater than 18.6 mL/100 g of powder is excess and reduces the strength of the hardened plaster. When a mixture of the hermhydrate and water hardens, linear expansion takes place. This expansion may amount to as much as 0.5% for plaster. Dental stones also expand on setting, but the amount is significantly less than that permitted in plaster, ie, 0.2% for type III, 0.1% for type IV, and 0.3% for type V. 

Gypsum, raw 25 total 5 Imp-mill type grind and calcine to stucco... 

Typical applications in the chemical field (Beaver, op. cit.) include detarring of manufactured gas, removal of acid mist and impurities in contact sulfuric acid plants, recovery of phosphoric acid mists, removal of dusts in gases from roasters, sintering machines, calciners, cement and lime Idlns, blast furnaces, carbon-black furnaces, regenerators on fluid-catalyst units, chemical-recoveiy furnaces in soda and sulfate pulp mills, and gypsum kettles. Figure 17-74 shows a vertical-flow steel-plate-type precipitator similar to a type used for catalyst-dust collection in certain fluid-catalyst plants. 

Gypsum When gypsum is calcined in rotaiy Idlns, it is first crushed and screened. After calcining it is pulverized. Tube mills are usually used. These impart plasticity and workability. Occasionally such calcined gypsum is passed through ring-roller mills ahead of the tube mills. 

Gips-brei, m. paste of plaster (Paris), -bren-nen, n. gypsum burning, -brennerei, /. calcination of gypsum plaster kiln, -brenn-ofen, m. plaster kiln, gipaen, v.t. plaster. — a. gypseous. 

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