Hydrated dolomitic

Mutoclaved lime is a special form of highly hydrated dolomitic lime, used largely for stmctural purposes, that has been hydrated under pressure in an autoclave. 

The Bechtel confined zone dispersion (BCZ) process involves the injection of a fine slurry mist of pressure hydrated dolomitic lime or calcitic lime, using two-fluid atomizing nozzles. A demonstration at the 70 MWe Seward Station of the Pennsylvania Electric Co., performed in 15.2 m of ductwork with a 2.4-m by 3.4-m cross section, achieved a 50% removal of SO2 at a Ca S ratio around 1.1. 

CZD [Combined zone dispersion] Also called Bechtel CZD. A flue-gas desulfurization process in which a slurry of a chemically reactive form of lime (pressure-hydrated dolomitic lime) is injected into the duct. The water in the slurry evaporates quickly and the solid product is collected downstream in an electrostatic precipitator. Developed by Bechtel International in the late 1980s, intended for retrofitting to an existing plant. 

The starting material for refractory dolomite bricks is calcined dolomite, which is produced from dolomite by deacidification at temperatures of ca. 1000°C and then firing at 1500 to 1800°C. They are very much cheaper than magnesite products, but are also less slag-resistant. To prevent hydration, dolomite bricks have to be impregnated with tar. 

Specific gravity. High-calcium hydrated lime has a specific gravity of 2.24 g/cm [19.1]. The values for partially and fully hydrated dolomitic limes are about 2.7 and 2.5 g/cm, respectively [19.2]. 

Highly hydrated dolomitic lime is generally produced by reacting the quicklime with water under hydrothermal conditions (i.e. under steam pressure at temperatures in excess of 100 °C in an autoclave) for the requisite time. The heat of hydration is 211 kcal/kg CaO. 

High-calcium and partially hydrated dolomitic limes are hydrated at temperatures approaching 100 °C. This is achieved by adding a sufficient excess of water to moderate the temperature by boiling. In practice, with high-calcium quicklime, approximately double the stoichiometric quantity of water is added, with most of the excess being vented to atmosphere as steam, after absorbing much of the heat of reaction. 

Highly hydrated dolomitic lime is produced at steam pressures in the range 1.7 to 7 atmospheres, corresponding to temperatures of 115 to 165 °C. The optimum pressure and hydration time depends on the degree of burning of the quicklime. 

The requirements for highly hydrated dolomitic lime, (also called di-hydrated or double hydrated lime) are specified in [20.15, 20.16]. It is required to contain less than 8 % of free lime, to ensure that it is sound. 

Completely hydrated dolomitic limes see Type S hydrated lime. 

Dolomitic limes are limes mainly consisting of calcium oxide and magnesium oxide (see calcined dolomite), calcium hydroxide and magnesium oxide (see semi-hydrated dolomitic lime), or calcium hydroxide and magnesium hydroxide (see Type S hydrated Ume). 

Hydrated dolomitic limes are powdered slaked limes consisting of calcium hydroxide, magnesium hydroxide and magnesium oxide (see semi-hydrated lime and Type S hydrated lime). 

Lime, hydrated, dolomitic Finishing lime CaO MgO 2H2O CaO 0.423 2.363 Source of CaO... 

Hydration. Dolomite and other lime-containing refractories are attacked by atmospheric moisture. To protect them before use, they may be metal-cased tar-impregnated, wrapped in polythene sheeting etc. 

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