Due to the low purity and density of calcined magnesia, it is difficult to meet production needs. In order to further improve the density and purity of magnesia, a series of new processes and processes suitable for China's national conditions have been studied and developed. The two-step calcination method is the process with the best application effect and the widest range of promotion. The middle grade magnesium obtained by this process has a MgO content of more than 95 (w)% and a bulk density of more than 3.15g/cm3. At the same time, this process has been promoted for the production of synthetic sand products such as synthetic magnesium calcium sand.

Currently, the production process of medium grade magnesia is to first put the ore into a light calcined kiln to obtain light calcined magnesium oxide at 1100 ℃, then mix the light calcined magnesium oxide with water, press the ball twice, and naturally dry it. Finally, calcine it in a high temperature solid kiln at 1600-1650 ℃, resulting in a product with good sintering degree and dense crystallization.

Among them, primary compaction is an important process to ensure the body density of the product. After secondary pressure ball molding, natural drying is usually used, but in winter, it is necessary to make a fire for drying.

Classification of medium grade magnesia:

According to the size of the ball, it is divided into 40mm ball and 60mm ball.

Identification of medium grade magnesia:

Medium grade magnesia with good quality should not have loose and under burnt blocks visible, and its surface should emit light. If the ball is smashed open, its internal condition should be well crystallized, dense, and uniform.

Selection of medium grade magnesia:

(1) The main component of black lump is CaO, which is caused by the pollution of coal gangue dissolved at 400-500 ℃;

(2) Underburned white lumps, mainly falling from the wind tunnel.

Medium grade magnesia also belongs to sintered magnesia and currently has two brands, 94 and 95. It is an important variety of magnesia and a high-quality raw material for preparing magnesia refractory materials, mainly used to produce medium grade magnesia bricks and amorphous refractory materials.