There are several kinds of mid-grade magnesia

The standard name of intermediate magnesia is sintered magnesia. GB/T 2273-1998 combines the two national standards of "magnesia" and "high quality magnesia" into one standard "sintered magnesia". Sintered magnesia is made by calcining magnesite, magnesite or magnesium hydroxide extracted from seawater at high temperature. Strong hydration resistance. The magnesite calcines at 700-950 (?) C and then escapes CO2. The magnesite obtained is a soft porous and porous material and can not be used as refractory. The magnesite calcined at 1550-1600 (?) C is called sintered magnesite. Sintered magnesia is made from natural magnesite by one-step or two-step calcination process with high temperature equipment such as shaft kiln and rotary kiln. Sintered magnesia is classified into 18 grades according to its physical and chemical indexes, as detailed in GB/T 2273-1998. Magnesium oxide is extracted from seawater and is called seawater magnesia. Magnesia is one of the most important raw materials for refractories. It is used to manufacture various magnesia bricks, magnesia-alumina bricks, ramming materials, furnace feeding materials, etc. Containing more impurities, it is used to pave the bottom of the steelmaking furnace, etc.

Medium grade magnesia is produced from light burned magnesia with 97% MgO content by pressing ball and calcining in high temperature shaft kiln. With good sintering degree and dense crystallization, it is a high quality raw material for producing medium-grade magnesia refractory products.