Dolomite calcination

Cement, dry process Cement, wet process, 44% water Limestone calcination Dolomite calcination Alumina preparation Barium sulfide preparation Ignition of inorganic pigments Iron pyrite roasting... 

The MgO component of magnesian/dolomitic limes and dolime (or calcined dolomite) calcines more rapidly and is understood to sinter more readily than the CaO component (at least in terms of reactivity to water). Little appears to have been published on this topic. 

Iron ore fines, limestone, dolomite, calcined lime, BF return fines and coke breeze were used and pot grate sintering experiments were carried out. Table I gives the chemical composition of the raw materials in the pot grate sintering test. The size distribution of raw material is shown in Table II. The raw material consists of iron ore fines, limestone, dolomite, calcined lime, BF return fines, coke breeze and sinter return fines. Table III shows the proportion of raw material. 

Material Iron ore fines Limestone Dolomite Calcined lime BF return fines Coke breeze Return fines... 

Ib/ft ). Again, dolomitic limes average about 4% denser than their high calcium counterparts. The severity of the calcination process largely determines the porosity of a quicklime the higher the temperature of calcination and the longer its duration, the more the porosity declines. 

Stability. AH calcitic and dolomitic limestones are extremely stable compounds, decomposing only in fairly concentrated strong acids or at calcining temperatures of 898°C for high calcium and about 725°C for dolomitic stones at 101.3 kPa (1 atm). A very mild destabilizing effect is caused by C02-saturated water, as described in the preceding section on solubihty. Aragonite, however, is not as stable as calcite. In sustained contact with moisture,... 

Two types of magnesia, caustic-calcined and periclase (a refractory material), are derived from dolomitic lime. Lime is required in refining food-grade salt, citric acid, propjiene and ethylene oxides, and ethylene glycol, precipitated calcium carbonate, and organic salts, such as calcium stearate, lactate, caseinate. 

In seawater—dolime and hrine—dolime processes, calcined dolomite or dolime, CaO MgO, is used as a raw material (Table 9). Dolime typically contains 58% CaO, 41% MgO, and less than 1% combined Si02, P O, and CO2 where R is a trivalent metal ion, eg, Al " or Fe " ( 4). Roughly one-half of the magnesia is provided by the magnesium salts in the seawater or brine and the other half is from dolime (75). Plant size is thus reduced using dolime and production cost is probably lower. 

Better recoveries can be made by replacing calcium hydroxide [1305-62-0] with dolomite [39445-23-3] that has been calcined. Sometimes NaOH is used when low calcium in the product is requited. 

Thermally efficient calcination of lime dolomite and clay can be carried out in a multicompartmeut fluidized bed (Fig. 17-27). Fuels are burned in a fluidized bed of the product to produce the required heat. Bunker C oil, natural gas, and coal are used in commercial units. Temperature control is accurate enough to permit production of hme of very high availability with close control of slaking characteristics. Also, half calcination or dolomite is an accepted practice. The requirement of large crystal size for the hmestoue limits apphcatiou. SmaU-sized crystals in the hmestoue result in low yields due to high dust losses. 

High 50,000 0,000 8-16 Aluminum, copper, zinc, vanadium, calcined dolomite, hme, magnesia, magnesium carhonates, sodium chloride, sodium and potassium compounds Flue dust, natural and reduced iron ores Flue dust, iron oxide, natural and reduced iron ores, scrap metals... 

There have been several kinetic studies of the calcination of dolomite [29], a reaction of considerable technological importance. As in many reversible reactions, the rate of carbon dioxide release is sensitive to the prevailing pressure of this product (.Pco2) in the vicinity of the reaction interfaces. At low pressures (PCo2 < 12 Torr), reaction proceeds to completion in a single stage between 900 and 950 K... 

Thermal analysis has been widely and usefully applied in the solution of technical problems concerned with the commercial exploitation of natural dolomite including, for example, the composition of material in different deposits, the influence of impurities on calcination temperatures, etc. This approach is not, however, suitable for the reliable determination of kinetic parameters for a reversible reaction (Chap. 3, Sect. 6). 

The most widely employed thermal reduction process for preparing Mg metal uses PeSi as reducing agent. Mixtures of the substrate, usually calcined dolomite (i.e., MgO, CaO) and PeSi are fabricated into briquettes with a hydrocarbon binder and loaded into Ni-Cr steel (15/28) retorts. After evacuation the retort is subjected to a temperature gradient Mg distills from the hot mixture (at 1150°C) and high-purity Mg crystals collect at the water-cooled end of the retort ... 

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