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Calcination of magnesite, brucite and magnesium hydroxide extracted from seawater or brine at about 800-1000 C to decompose and discharge CO2 or hydrogen peroxide yields Caustic calcined magnesia, also known as light-burned magnesia, caustic magnesia or light-burned magnesia, commonly known as bitter soil powder. Light-burned magnesia powder has loose texture and high chemical activity. It can be used not only to produce magnesia cement, MAGNESITE Building materials, thermal insulation materials, etc., but also to produce high-quality magnesia by two-step calcination method [1-2].
When magnesite is heated, equiaxed periclase occurs at about 600 ~C, equiaxed periclase disappears at 650 ~C and non-equiaxed periclase occurs, and equiaxed periclase disappears completely at 850 ~C. These brucite lattices have high surface energy due to the occurrence of point defects and dislocations. The lattice water of MgO is less than that of MgCO 3 lattice group, so the interlattice pore increases, the porosity is higher, the specific surface area is larger and the activity is higher.
Light-burned magnesia powder is yellowish and light brown powder. Its particle size is mostly below - 100 mesh. The crystallization of periclase is very small (< 3 micron), its true specific gravity is 3.07-3.22, its bulk density is 0.8-1.2g/cm3, its refractive index is 1.68-1.70, its lattice constant is large (a=0.4212). It has many lattice defects, brittle texture, porous structure, high reaction activity, easy solid state reaction or sintering, and hardening with hydrated Mg(OH)2. Bonding ability. Light-burned magnesia powder calcined from magnesite has a volume shrinkage of about 5%. Usually, there is 3%~5% CO2 left due to incomplete decomposition.
The light-burning temperature and time of magnesite have certain influence on the activity of light-burned magnesia powder. Magnesite was calcined at 600, 650, 700, 750, 800, 850 and 900 (?) respectively. The calcination temperatures at 700, 750 and 800 (?) had no significant effect on the activity of light-burned magnesia powder within 15-90 minutes. The effects of 600, 650, 850 and 900 (?) on the activity were particularly significant, and the activity increased with the extension of calcination time at 600, 650 (?) and 650 (?) respectively. Long and marked decline.