Method For Industrial Manufacture Of Pure MgCo3 From An Olivine Containing Species Of Rock

• US 20080299024A1
• Filed: 11/23/2006
• Published: 12/04/2008
• Est. Priority Date: 11/24/2005
• Status: Active Grant

• Current Assignee: Institutt For Energiteknikk
• Original Assignee: Institutt For Energiteknikk
• Inventors: Raaheim, Arne, Gorset, Oddvar, Munz, Ingrid Anne, Johansen, Harald, Kihle, Jan
• Granted Patent: US 7,682,589 B2
• Time in Patent Office: Days
• US Class Current: 423/22
• CPC Class Codes: C01F 5/24 Magnesium carbonates
• CPC Class Codes: C22B 26/22 Obtaining magnesium
• CPC Class Codes: C22B 3/04 by leaching C22B3/18 takes precedence
• CPC Class Codes: C22B 3/22 by physical processes, e.g. by filtration, by magnetic means , or by thermal decomposition treatment or purification of solutions by liquid-liquid extraction C22B3/26
• CPC Class Codes: C22B 3/44 by chemical processes treatment or purification of solutions by liquid-liquid extraction C22B3/26, by ion-exchange extraction C22B3/42
• CPC Class Codes: Y02P 10/20 Recycling

Abstract

Method for industrial manufacture of pure MgCO₃ comprising providing an olivine containing species of rock, to comminute the olivine containing species of rock to increase its surface, to contact the comminuted olivine containing species of rock with water and CO₂. The process is conducted in at least two steps, namely a first step (R1) at a first pH where a dissolving reacting as represented by the equation: Mg₂SiO_4(S)+4H⁺=2Mg²⁺+SiO_2(aq)+2H₂O, takes place. Then a precipitation takes place in the second step (R2) at a higher pH as represented by the equations: Mg²⁺+HCO₃⁻=MgCO_3(S)+H⁺, and Mg²⁺+CO₃²⁻=MgCO_3(S), the presence of HCO₃⁻ and H⁺ ions mainly provided by the reaction between CO₂ and water.

Claims

1. Method for industrial manufacture of pure MgCO3 comprising providing an olivine containing species of rock, to comminute the olivine containing species of rock to increase its surface, to contact the comminuted species of rock with water and CO₂, characterized in that the process is conducted in at least two separate steps, namely a first pressurized step at a first pH in which a dissolving reaction generally takes place according to the reaction equation:

Mg₂SiO_4(s)+4H⁺═

2Mg²⁺+SiO_2(aq)+2H₂O,

after which a precipitation is conducted in a second step at a higher pH, the reaction in said second step generally being represented by the reaction equations;

Mg²⁺+HCO₃⁻

═

MgCO_3(s)+H⁺, and

Mg²⁺+CO₃²⁻

═

MgCO_3(s),

the presence of HCO₃⁻

and H⁺ ions mainly being due to the reaction between CO₂ and water.

2. Method as claimed in claim 1, characterized in that the olivine containing species of rock is comminuted to a general grain size less than 3 mm, more preferred less than about 0.5 mm and most preferred less than 0.1 mm.

3. Method as claimed in claim 1, characterized in that pH in said first step is in the range 3-5 while pH in said second step for precipitation of magnesium carbonate is in the range 5-13.

4. Method as claimed in claim 1, characterized in that iron that accompanies the raw material is precipitated as iron hydroxide in first step.

5. Method as claimed in claim 1, characterized in that the first step is conducted in a first reactor chamber and precipitation of magnesium carbonate is conducted in another reactor chamber which solely receives liquid material from the first reactor chamber while non-reacted reactant and precipitated bi-products in first reactor chamber are separated out.

6. Method as claimed in claim 1, characterized in that the pressure is reduced from the first reactor chamber to the second reactor chamber so that some CO₂ thereby is released from the solution and the pH correspondingly increased.

7. Method as claimed in claim 1, characterized in that a higher temperature is used in the second reactor chamber than in the first reactor chamber to thereby favour precipitation of MgCO₃.

8. Method as claimed in claim 1, characterized in that a three step process is used and that the third step is one of precipitating amorphous silica (SiO₂).

9. Method as claimed in claim 8, characterized in that SiO₂ is precipitated from the reaction mixture after that MgCO₃ has been precipitated and at a lower temperature.

10. Method as claimed in claim 1, characterized in that the pressure in the first reactor is in the range 1-200 bar, more preferred 20-170 bar and most preferred from 50-150 bar.

11. Method as claimed in claim 1, characterized in that the temperature in the first reactor is in the range 50-220°

C., more preferred in the range 100-170°

C.

12. Method as claimed in claim 1, characterized in that the pressure in second reactor is in the range 1-150 bar, more preferred 20-130 bar and most preferred from 50 to 80 bar.

13. Method as claimed in claim 1, characterized in that the temperature in the second reactor is in the range 100-300°

C., more preferred in the range 140-250°

C.

14. Method as claimed in claim 1, characterized in that the olivine containing species of rock is Dunite.

15. Method as claimed in claim 1, characterized in that the process is conducted as a continuous process with respect to the liquid flows of the process.

16. Method as claimed in claim 15, characterized in that the process is conducted as a wholly continuous process.

17. Method as claimed in claim 1, characterized in that the dissolving reaction takes place in absence of strong mineral acids and strong organic acids.

18. Method as claimed in claim 1, characterized in that the comminuted species of rock has a particle size less than 0.1 mm, that the pressure in the first reactor is in the range 50-150 bar, that the pressure in the second reactor is in the range 50-80 bar, that pH in the first reactor is in the range 3-5, that pH in the second reactor is in the range 5-13, that the temperature in the first reactor is in the range 100-170°

C., that the temperature in the second reactor is in the range 140-250°

C., that the process is run free from acid other than CO₂ dissolved in water and that the process is run as a continuous process.

19. Method as claimed in claim 1, characterized in that MgCO₃ is used as a raw material for production of Mg or as a filler in other products such as paper and plastic products.

20. Method as claimed in claim 1, characterized in that SiO₂ is used as a raw material for the manufacture of various amorphous SiO₂ qualities, as a raw material for the manufacture of silicon or as a filler in other products such as car tyres.

21. Method as claimed in claim 1, characterized in that iron oxides/iron hydroxides together with insoluble PGE containing chromite is discharged from the dissolving reactor for further treatment in a production plant for the manufacture of iron, chrome and platinum group metals.

22. Method as claimed in claim 1, characterized in that the method is also used to immobilize industrial quantities of CO₂ as carbonate in valuable end and intermediate products.