Magnesite, brucite and magnesium hydroxide extracted from seawater or brine are calcined at 800 ~ 1000 C to decompose and discharge CO2 or H2O. Caustic calcined magnesia, also known as lightly burned magnesia, caustic magnesia or lightly burned magnesia, is commonly called bitter earth powder. Light burned magnesia powder has loose texture and high chemical activity. It can be used to make magnesia cement, MAGNESITE Building materials, heat insulation materials and so on. It is also the intermediate product of two-step calcination method to produce high quality magnesia sand [1-2].

When magnesite is heated, equiaxed periclase occurs at about 600 C, equiaxed periclase disappears at 650 C and non-equiaxed periclase occurs at 650 C, and equiaxed periclase disappears completely at 850 C. The lattice of these calcite appears to have higher surface energy due to punctate defects and dislocations. The lattice size of MgO is less than that of MgCO_3, so the lattice porosity increases, the porosity is high, the specific surface area is large and the activity is high.

Light burnt magnesium powder is yellowish and light brown powder with particle size mostly below - 100 mesh, periclase crystals very small (< 3 micron), true specific gravity 3.07 ~ 3.22, accumulative density 0.8 ~ 1.2 g/cm 3, refractive index 1.68 ~ 1.70, lattice constant large (a = 0.4212) lattice defects, brittle texture, high reaction activity, easy to carry out solid phase inversion. Should be or sintered, water and Mg (OH) 2 will be hardened and bonded. Light-burned magnesia powder calcined from magnesite has a volume shrinkage of about 5%; usually 3%-5% CO2 remains due to incomplete decomposition.

The light burning temperature and light burning time of magnesite have certain effect on the activity of light burned magnesia powder. The magnesite was calcined at 600, 650, 700, 750, 800, 850 and 900 C, respectively, and the calcination temperatures of 700, 750 and 800 C had no obvious effect on the activity of lightly calcined magnesia powder in 15-90 minutes. The activity of calcined at 850 and 900 degrees decreased significantly with the prolongation of hydrocarbon burning time.