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.
Hydro Magnesium Processes use MAGNESITE (MgCO3) as Raw Material (see fig 1).
Fig. 1. One of Magnesite Minerals
In nature, this material is composed mainly from carbonated magnesium and contains low concentrations of calcium,iron and manganese as impurities. Magnesite belongs to the calcite group, which is a group of carbonates that are similar in their physical characteristics.Magnesite is usually produced when rocks rich in magnesium come into contact with carbonate-rich solutions thereby producing a first degree metamorphosis. The Magnesite does not normally produce crystals with a defined form. It has a crystalline structure similar to calcite and it is white.
Magnesite is common in Brazil, Austria, Korea, China and the West Coast of the United States of America, and it is extracted by mining.The magnesium concentration by weight is 28.8%.
In the hydro magnesium process used in Canada the raw material for the process is magnesite, which is mined in mines (mainly in China). The magnesite is dissolved in a hot HCl solution, thus arriving at a magnesium chloride-rich solution:
MgCO3(s) + 2HCl(aq) = MgCl2(aq) + CO2(g)
The acid solution must be hot for an efficient melting process. The basic ore of the magnesite is rich in various metallic impurities, sulfates and boron,which can be a problem at the electrolysis stage. Therefore, already at this stage a number of processes are carried out,whose purpose is to separate the impurities from the
magnesium chloride.
During the preliminary drying process, the magnesium chloride solution is heated in the evaporator by the residual heat from the process until almost pure bischofite with a water content of 45–50% is obtained (MgCl2*6H2O). The bischofite, which is melted during this process is turned into prills in the prilling tower. One of the main reasons for the transfer to prills is the wish to reduce the quantities of dust during
the next drying stages.
The next drying stage is performed in a fluidized bed dryer. At this stage, the bischofite with six molecules of water is dried by hot air to MgCl2*2H2O, as described in Eqs. below:
MgCl2*6H2O = MgCl2*4H2O + 2H2O(g) T = 117°C
MgCl2*4H2O = MgCl2*2H2O + 2H2O(g) T = 185°C
The last stage of drying, to extract anhydrous magnesium chloride is carried out by gaseous HCl drying at temperatures of about 330°C. The reason for performing this stage with heated gaseous HCl is the difficulty in preventing hydrolysis, and the wish to obtain solid and dry magnesium chloride with magnesium oxide qualities of about 0.1%. From Eqs. below:
MgO + HCl(g) = MgOHCl
MgOHCl + HCl(g) = MgCl2(s) + H2O(g)
it appears that the use of gaseous HCl will fundamentally reduce the hydrolysis reactions, thus reducing the concentration of magnesium oxide in the product.A further point is that opposite reactions to hydrolysis take place with HCl,which also reduce the concentration of magnesium oxide.
The HCl from the drying process is transferred to the raw materials extraction and preparation process, according to Fig. 2.
In The Earth, Molybdenum is found as Molybdenite (MoS2), Jordisit (MoS2), Drisdallite (Mo(Se,S)2).
Figure 1. Molybdenite (MoS2)
Figure 2. Jordisite (MoS2)
Figure 3. Drysdallite (Mo(Se,S)2)
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Many products flow from the mining and processing of ores containing molybdenite (MoS2), including:
1. Chemical Mo products
Used in catalysts, polymer compounding, corrosion inhibitors, and high-performance lubricant formulations, these include pure molybdic oxide and molybdates, and lubricant grade MoS2.
2. Meltstock products
Used as alloy additions to iron, steel, nickel, and titanium alloys, these include technical Mo oxide, ferromolybdenum, and Mo metal pellets.
3. Mo metal products
These include powder, Mo metal and Mo-base alloy mill products, and products fabricated from them such as LCD Screen, Air Plane Avionics etc.
Most of molybdenum used in stainless steel industry. Molybdenum is a ferrite former, so corrosion resistivity is very high.
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Before used, concentrate from flotation should be freed of sulfide which is done by roasting:
MoS2 + 3 ½ O2= MoO3 + 2 SO2
MoS2 + 3 O2= MoO2 + 2 SO2
Reaction in roasting occurs with heat evolution, process is carried out at 590-620 oC in Multiple hearth furnace.
Figure 4.
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Figure 5. Roasting Plant
The next process for Chemical Mo dan Mo metal can be shown in Figure 6.
Figure 6. Production of Molydenum Chemical
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Ferromolybdenum (FeMo) producted by aluminothermic reaction:
MoO2 + FeO + 2 Al = FeMo + Al2O3
This is a spontaneous reaction until 2000 oC with KMnO4 as an ignition, phase diagram of Fe-Mo can be shown in figure 7.
Figure 7. Phase Diagram of Fe-Mo
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Ferromolybdenum (FeMo)
FeMo can be used in any melting or refining unit to produce Mo-containing steel or cast iron. It is frequently used as ladle addition to achieve accurate final adjustment of composition. In steels with low Mo content (usually no more than 0.2% Mo) like High Strength Low Alloy (HSLA) steel, all of the Mo is added as FeMo.
FeMo typically contains 65 – 75% Mo and a maximum of 0.5% Cu.
The product is produced in size ranges between:
0 and 10 mm, and 10 mm on the low side and several maximum size limits between 20 and 100 mm. It is available as powder for special applications like welding electrodes.
Figure 8. Ferromolybdenum
Figure 9. Ferromolybdenum Plant
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Packaging is normally in steel drums or big bags.
Product standards include:
ASTM A132-04 Standard Specification for Ferromolybdenum
