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Quick Lime in Refractory Products Industry

Quick Lime in Refractory Products Industry



High-purity refractory “dolomite” (frequently called Doloma) and lower purity fettling grade “dead-burned dolomite” (usually referred to as DBD) are both manufactured by calcining dolomite limestone. The production method is similar to the manufacture of ordinary lime, except that the burning time is longer and temperatures considerably higher (in the range of 1600 – 1850º C). High purity doloma is fired in rotary kilns to the upper end of the temperature range and without the addition of impurities. High purity doloma is used to manufacture refractory bricks employed in cement and lime rotary kiln linings, and in steel ladles and refining vessels. The lower-purity DBD is fired in rotary kilns to the lower end of the temperature range, and iron oxides are added during calcinations to stabilize the resulting hard-burned quicklime against decomposition from moisture. DBD is used for the manufacture of monolithic patching and repair materials for steel furnaces.

Large quantities of light-burned dolomitic lime are used in the production of synthetic refractory grade magnesia (MgO). The quicklime is slaked in magnesium chloride brine, precipitating magnesium hydroxide. The mag-hydroxide is calcined and fired into dense, high-purity magnesium oxide. Refractory magnesia is used in the production of linings for cement and lime kilns, in addition to steel ladles and furnaces.

Stabilized zirconium oxide (ZrO2) is produced by adding about 3% lime during the fusion or sintering process. ZrO2 is widely used for analysis crucibles and thermocouple tubes in addition to crucibles and furnaces used for the production of high-temperature aero-space alloys.

One form of silica brick, a specialized refractory used for lining coke ovens and glass furnaces, is made by thoroughly mixing ground silica (usually quartzite) with the addition of ½ to 3 percent milk-of-lime as a sintering (firing) aid. This mixture is formed into various shapes and then fired in kilns.

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