Basic Introduction to Light Burned Magnesium Oxide Powder

Light burned magnesium refers to the calcination of magnesite, brucite, and magnesium hydroxide extracted from seawater or brine at around 800-1000 ℃ to decompose and discharge CO2 or H2O, resulting in the production of light burned magnesium powder, also known as light burned magnesium oxide, caustic magnesium oxide, or light burned magnesium, commonly known as bitter earth powder. Light burned magnesium powder has a loose texture and high chemical activity, which can be used for manufacturing magnesium cement, magnesite building materials, thermal insulation materials, etc. It is also an intermediate product of the two-step calcination method for producing high-quality magnesium sand.

When magnesite is heated, equiaxed periclase appears at around 600 ℃; At 650 ℃, equiaxed periclase disappears and non equiaxed periclase occurs; At 850 ℃, equiaxed periclase completely disappears. These periclase lattices exhibit high surface energy due to the appearance of point like defects and dislocations. The lattice size of MgO is not much smaller than that of MgCO3, resulting in an increase in inter lattice pores, high porosity, large specific surface area, and high activity.

Light burned magnesium powder appears as a light yellow and light brown powder, with particle size mostly below 100 mesh, and periclase crystals are very small (<3 μ m) , with a true specific gravity of 3.07~3.22, a bulk density of 0.8~1.2g/cm3, a refractive index of 1.68~1.70, and a large lattice constant（ α= 0.4212) has many lattice defects, brittle texture, pore structure, high reactivity, and is easy to undergo solid-state reaction or sintering. It hardens by reacting with water to form Mg (OH) 2, and has bonding ability. Light burned magnesium oxide powder made by calcining magnesite, with a volume shrinkage of about 5%; Usually, due to incomplete decomposition, there is residual CO2 of 3% to 5%.

The light burning temperature and time of magnesite have a certain impact on the activity of light burned magnesium powder. Calcined magnesite at 600, 650, 700, 750, 800, 850, and 900 ℃ respectively, and the calcination temperatures of 700, 750, and 800 ℃ within 15-90 minutes had no significant effect on the activity of lightly burned magnesium powder; The influence of 600, 650, 850, and 900 ℃ on the activity is particularly significant. When calcined at 600 and 650 ℃, the activity increases significantly with time; When calcined at 850 and 900 ℃, the activity significantly decreases with the prolongation of hydrocarbon calcination time.