Brief analysis of properties and raw materials of sintered magnesia

Sintered magnesia is usually a product obtained by calcining magnesite, brucite and magnesium hydroxide extracted from seawater or brine using a rotary kiln and a shaft kiln.

 

Light-burned magnesite is magnesium oxide obtained after magnesite is calcined at about 700 ~ 1100 ° C. It is also called light-burned magnesite. Light-burned magnesium powder is light and soft, has a porous structure, a density of 3.07-3.22 g / cm3, and the periclase grains are very small (<3 μm), have a large reactivity, and are prone to solid-phase reactions and sintering.

Products with high bulk density and low porosity, obtained from magnesite or lightly burned magnesia fully sintered at 1450-1900 ° C, are called dead burned magnesite, also called sintered magnesite and reburned magnesite. Dead burned magnesia is very dense. According to the impurity content, phase composition and structure, the density fluctuates between 2.95 and 3.65 g / cm3. The magnesia produced from the magnesia obtained from seawater is called seawater magnesia. It is made from Mg (OH) 2 or hydrobromite obtained by precipitation of Mg2 + in seawater, and is prepared by calcination and decomposition and high temperature sintering. . The advantage of seawater magnesia is that the seawater is inexhaustible. The obtained product has high purity, MgO content above 95%, chemical composition is easy to adjust, and the density is 3.30-3.49g / cm3.

The judgment of the magnesia sintering degree is usually measured by body density, hydration performance, and reheating linear shrinkage. According to the purity of magnesia, magnesia can be divided into high-grade (high-purity) magnesia with MgO content greater than 97%, mid-range magnesia with 95% ~ 96%, and ordinary magnesia (brick magnesia) with less than 95% MgO content. Mid-range magnesia is an indispensable magnesia type in magnesium products. It is used in mid-range magnesia bricks, magnesium composite spinel bricks, direct bonded magnesia bricks and some magnesia-shaped refractory materials. The MgO content in high-purity magnesia is not less than 97%, which can be used as the main raw material for directly combining magnesia bricks and magnesia composite spinel bricks.