Dolomite (CaMg(CO3)2), dead-burned refractory Chemical Properties

EPA Substance Registry System

Dolomite (CaMg(CO3)2), dead-burned refractory (69227-00-5)

Dolomite (CaMg(CO3)2), dead-burned refractory Usage And Synthesis

Description

Calcined dolomite or simply dolomite or dolomite (i.e., CaO + MgO) is a product produced by calcination at relatively low temperatures and is highly porous and reactive. Like other carbonates, upon heating above 900°C dolomite decomposes completely into a mixture of calcium and magnesium oxides, and carbon dioxide:
CaMg(CO₃)₂(s) —> CaO(s) + MgO(s) + 2CO₂(g)

Uses

Dead burned dolomite exhibits high refractoriness and can withstand temperatures up to 2300°C. It is widely used as a refractory material wherever steel is refined using basic slag. It is used for original hearth installations in open hearth furnaces as well as for hearth maintenance. These hearths are installed using tar-dolomite ramming mixes and rammed dolomite. Dolomite refractories are also used in electrical furnaces and in the cement industry during clinker manufacture.

Preparation

Dead burned refractory dolomite is produced in vertical shaft or rotary kilns. Generally high-purity dolomite, with total impurities of less than 3 wt.%, is selected. As it is difficult to densify high-purity dolomite in a rotary kiln, it is customary to use some mineralizers to facilitate sintering. Iron sesquioxide is a common additive. The manufacturing process varies with the grade of dead burned dolomite needed. Most plants use rotary kilns lined in the hot zone with basic bricks and fired with powdered coal. The temperature reached in the hot zone is ca. 1760°C or above when iron oxide is added. After dead burning, dead burned dolomite is cooled in either rotary or reciprocating recuperative coolers. The air used for cooling gets heated and is again used as secondary air for combustion in the kilns.

Dolomite (CaMg(CO3)2), dead-burned refractory(69227-00-5)Related Product Information

• DOLOMITE