Magnesium Extraction by Magnola Process

Magnola Process use Serpentine as Raw Material as fig 1:

Fig. 1. Sepentine

 

A magnesium chloride-rich solution (27%) is poured into the spray dryer. In this installation,with the aid of hot gases, by burning of natural gas, the magnesium chloride is dried to MgCl2*2H2O, Eqs. (1) and (2), as in the hydro magnesium drying process.

 

MgCl2*6H2O = MgCl2*4H2O + 2H2O(g)             T = 117oC    (1)

MgCl2*4H2O = MgCl2*2H2O + 2H2O(g)             T = 185oC    (2)

 

The main difference lies in the fact that in the magnola process drying is carried out in one stage (see Fig. 2). The “price” is the relatively high percentage of hydrolysis,which causes a concentration of magnesium oxide of up to about 2%. During the second stage the material is transferred to a unique chlorinator called “super chlorinator”. The melting process is carried out as follows: an electrolyte low in magnesium chloride is pumped from the electrolysis cell to the chlorinator where it assists in the melting of  magnesium chloride hydrate; this electrolyte returns to the electrolysis cell richer in magnesium chloride in the overflow. The reason for the melting in the electrolyte is the relatively high melting temperature of pure magnesium chloride; melting in the electrolyte enables the melting temperature to be decreased 200–300°C. The electrolyte temperature is about 650°C, and this is also the temperature at which the material is returned to the electrolysis cell,with the assistance of heating by the graphite electrodes.

 

The chlorinator is fed with dry, gaseous HCl, which is produced from all the chlorine manufactured in the electrolysis cells.Feeding is carried out with the assistance of a number of graphite mixers, which are introduced from the chlorinator ceiling. These mixers assist in dispersing the HCl and improve the efficiency of the following reaction:

 

MgO + 2HCl(g)  = MgCl2(l) + H2O(g) (2.21)

The high concentration of HCl in the melt and above the melt prevents the back hydrolysis reaction between the water vapors to the magnesium chloride. The concentration of magnesium oxide in the electrolyte returning to the electrolysis cell is about 0.05%.

 

The HCl discharged from the two drying stages is received in watery solutions and transferred back to the extraction process, according to Fig. 2, thus closing the process circle for the production of magnesium from raw material that does not contain chlorine.

 

Fig. 2. Magnola Process

 

Extraction of Lateritic Nickel Ore

(Hydrometallurgical Route)

Genesis And Types Of Nickel Laterites

Usually, nickel ore type in the world are sulphide and oxide minerals. In East Indonesia, we often see nickel oxide mineral that is called nickel laterite. Lateritic nickel ores formed by intensive tropical weathering of ultramafic rocks above all serpentinites which consist largely of the magnesium silicate serpentine and contains approx. 0,3% nickel. This initial nickel content is strongly enriched in the course of lateritization. Two kinds of lateritic nickel ore have to be distinguished: limonite types and silicate type.
1. Saprolite : Low iron (Fe), contains generally 1.5-2.5% nickel and consists largely of Mg- depleted serpentine in which nickel is incorporated. In pockets and fissures of the serpentinite rock green garnierite can be present in minor quantities, but with high nickel contents – Mostly 20-40%

Picture 1. Garnierite Picture

Picture 2. Serpentine

2. Limonite : High iron (Fe), consist largely of goethite and contain 1-2% nickel incorporated
in goethite.

Picture 3. Goethite

Route of Lateritic Nickel Ore Processing

There are 3 routes of lateritic nickel ore processing:
Pyrometallurgical route
1. Electric Smelting Furnace Technology
2. Krupp Renn Technology
3. Blast Furnace Technology

Hydro-Pyrometallurgical route
1. Caron Process
2. Modified Caron Process

Hydrometallurgical route
1. Atmosferic Leach
2. High Pressure Acid Leach (HPAL)
3. Acid Heap Leach
4. Chloride Leach

Comparation of these processes can be seen in table1.

Table 1. Comparation of Nickel Processing Technology

Experiments still be done by researcher to get the best process for limonitic ores. Until now, Caron Process & modified and HPAL is used by industry to extract nickel from limonitic ores. Flow diagram for Caron Process and HPAL can be seen in Figure 1-3.

Figure 1. Caron Process Flow Diagram

Figure 2. Modified Caron Process Flow Diagram

Figure 3. HPAL Process Flow Diagram