Method for obtaining magnetite
The invention relates to a method for obtaining magnetite using red mud, which is produced by the method used by Bayer for the manufacture of aluminum. The method according to the invention comprises at least the reduction of hematite and/or goethite to form magnetite using at least one reductant, said reductant containing at least one vegetable oil and/or a fat and/or carbon.
1. Method for obtaining magnetite by means of red mud, which is produced by the Bayer method used for aluminum production,
wherein the method includes at least the reduction of goethite in said red mud to magnetite with at least one reductant, comprising the steps of:
a) mixing the red mud with the reductant, wherein the reductant includes at least a vegetable oil and/or a fat;
b) combusting the reaction mixture with controlled air supply during a predetermined time interval in a predetermined temperature range;
c) separating the solid components from the reaction mixture;
d) crushing the solid components; and
e) separating at least a first component including at least magnetite and at least a second solid component, wherein
in step b), the air supply is controlled such that the reaction first proceeds under over-stoichiometric conditions and subsequently proceeds under sub-stoichiometric conditions.
2. Method according to claim 1 ,
characterized in that
a palm oil and/or a soya oil and/or a rape oil is used as the vegetable oil.
3. Method according to claim 1 ,
characterized in that
the predetermined temperature range in step b) is at least 650° C. and/or at most 1000° C.
4. Method according to claim 1 ,
characterized in that
combustion gases developing in step b) are returned into the reaction mixture.
5. Method according to claim 4 ,
characterized in that
the returned combustion gases include at least carbon monoxide and/or hydrogen.
6. Method according to claim 1 ,
characterized in that
step e) includes use of a magnetic separator.
7. Method according to claim 1 ,
characterized in that
in step a), at least one further component including at least calcium carbonate is additionally admixed to the red mud and the reductant.
8. Method according to claim 7 ,
characterized in that
the second component separated in step e) includes at least one cement addition material.
9. Method according to claim 8 ,
characterized in that
the cement addition material includes silica and/or silicates and/or aluminosilicates.
10. Method according to claim 1 , further comprising the step of:
reducing hematite in said red mud to magnetite.