Doloma high purity

II. HIGH-PURITY DOLOMITE FOR THE PRODUCTION OF DOLOMA REFRACTORIES... 

Currently, high-purity doloma is produced in several European countries, Canada, and the United States, based on natural dolomite synffietic dolomite is only produced in Japan and China. There are approximately 10 producers worldwide of all types of doloma. 

Silica, iron oxide, and alumina are the most common impurities in high-purity doloma. Since the impurity levels are low and the melting points of the liquid phases are so high, the dolomite can be difficult to calcine. Temperatures in excess of 1850°C are usually required in order to achieve satisfactory density and hydration resistance. The microstructure of a typical high-purity doloma as shown in Fig. 1 consists of magnesia crystallites (3-5 microns in size) embedded in a matrix of lime. 

The chemistry of Dolomite 2 corresponds to the upper limit of impurities that would be suitable for the production of doloma for refractory brick purposes. This dolomite would have to be dead-birmed in such a way that there would be no significant pickup of impruities during the process (i.e., requires high-purity fuels). 

Tabie 2 Chemical and Physical Properties of a Typical High-Purity Doloma... 

IV. CHARACTERISTICS OF REFRACTORIES BASED ON HIGH-PURITY DOLOMA... 

Further improvements to the slag resistance of both direct-bonded and carbon-bonded doloma bricks have been made through the addition of high-purity magnesia. Doloma bricks that have been enriched with MgO are typically used in areas of ladles and AOD vessels where higher slag resistance is required. The chemical and physical properties of the direct-bonded bricks used in steel making are shown in Table 6. 

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