The light fired magnesium powder produced by the company is composed of 41%, 44%, 45%, 46%, 47% content of magnesite, magnesite and magnesium hydroxide extracted from seawater or brine by calcination at about 800~1000℃, so that it can decompose and discharge CO2 or H2O, that is, light fired magnesium powder, also known as light fired magnesium oxide, caustic magnesium oxide or light fired magnesium, commonly known as bitter earth powder. Light fired magnesium powder has loose texture and high chemical activity, which can be used in the manufacture of magnesium cement, magnesite building materials, heat insulation materials, etc. It is also the intermediate product of the two-step calcination process to produce high-quality magnesia.
The light firing temperature and time of magnesite have certain influence on the activity of light firing magnesite powder. The magnesite was calcined at 600, 650, 700, 750, 800, 850 and 900℃, respectively. The calcination temperature of 700, 750 and 800℃ had no obvious effect on the activity of light fired magnesite powder within 15~90 minutes. The effect of 600, 650, 850 and 900℃ on the activity is particularly significant. At 600 and 650℃, the activity increases obviously with the extension of time. The activity of calcination at 850 ℃ and 900℃ decreased with the extension of burning time.
When magnesite is heated, equiaxed system of cubic magnesite appears at about 600℃. At 650℃, the isaemic system of magnesite disappeared and non-isaemic magnesite appeared. At 850℃, the isaemic system of galaite completely disappeared. These cubic magnesite lattices have high surface energies due to the presence of spot defects and dislocations. The lattice of MgO has less water than that of MgCO3 lattice group, so the interlattice pores increase, the porosity is high, the specific surface area is large, and the activity is high.
Light burnt magnesium powder is light yellow and light brown powder with particle size below -100 mesh, small crystal size (< 3μm), true specific gravity 3.07~3.22, accumulation density 0.8~1.2g/cm3, refractive index 1.68~1.70, large lattice constant (α=0.4212), many lattice defects, brittle texture, pore structure, etc. High reactivity, easy to solid reaction or sintering, with water to produce Mg(HO)2 and hardening, have bonding ability. Light fired magnesia powder from magnesite calcination, volume shrinkage of about 5%; Usually 3% to 5% of CO2 remains due to incomplete decomposition.