Magnesium Extraction By The AMC Process

This process also use Magnesite as raw material. This company developed an innovative unique process, which apparently bypasses the problem of the hydrolysis reaction. At the completion of the drying process, a powdery anhydrous magnesium chloride is obtained, with a concentration of magnesium oxide lower than 0.1%.

In the preliminary stage, an organic solvent ethylene glycol and/or methanol are added to the concentrated magnesium chloride solution.Gaseous ammonia is then bubbled into the solution and the settling reaction (1) takes place:

MgCl2(aq) + 6NH3(g) = MgCl2*6NH3(s)       (1)

This reaction creates MgCl2*6NH3(s), which is the ammonia based analog of bischofite, with water exchanged for ammonia molecules. The settling process will only take place in a solution that contains a major organic component. The MgCl2*6NH3(s) that settles is separated and filtered from the solution. The remaining solution undergoes refining in which the organic solvent is separated and sent for reuse in the process.

The MgCl2*6NH3(s) is transferred to a drying furnace, in which it is heated to a temperature of about 550°C. The reason for this high temperature is that the ammonia molecules are linked tighter to the magnesium chloride than water molecules.During the heating process the material decomposes to ammonia and magnesium chloride (see Eq. (2)). In this case, unlike the bischofite drying process, there is no hydrolysis problem at all since there are no water molecules.

MgCl2*6NH3 (s) = MgCl2(s) + 6NH3(g)      (2)

The ammonia is cooled, cleaned and returned the process. The anhydrous solid magnesium chloride is sent to the electrolysis cells.

It is possible to track the drying process in Fig. 1.

Fig. 1. AMC Process