In Martin Marietta Magnesia Specialties’ synthetic magnesia process, naturally occurring brine is reacted with both dolomitic lime and water to produce an aqueous suspension containing magnesium hydroxide solids and calcium chloride.
Gravity is used to separate the solids from the liquid in the aqueous suspension since magnesium hydroxide is heavier than water. In the photo at right, the freshly made magnesium hydroxide slurry (white) is pumped to a thickener to promote settling. The blue color represents the watery layer containing dissolved calcium chloride that has formed above the settled magnesium hydroxide particles. The bottom solids are then filtered through a drum filter to remove any remaining water.
The washed filter cake is ultimately directed to the production of high purity, ultra-stable magnesium hydroxide slurry, or to a heat source, such as a rotary kiln, where it is treated thermally to produce various grades of magnesium hydroxide powders and magnesium oxides.