Method for industrial manufacture of pure MgCO3 from an olivine containing species of rock

• US 7,682,589 B2
• Filed: 11/23/2006
• Issued: 03/23/2010
• Est. Priority Date: 11/24/2005
• Status: Expired due to Fees

• Current Assignee: Institutt For Energiteknikk
• Original Assignee: Institutt For Energiteknikk
• Inventors: Raaheim, Arne, Gorset, Oddvar, Munz, Ingrid Anne, Johansen, Harald, Kihle, Jan
• Primary Examiner(s): Kastler; Scott
• Assistant Examiner(s): Walck; Brian
• Application Number:
  US12/094,171
• Publication Number:
  US 20080299024A1
• Time in Patent Office: 1,216 Days
• Field of Search: 423/155, 423158-161, 423/165, 423/430, 423/432
• US Class Current: 423/430
• 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 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 purified MgCO₃ comprising the steps of:

providing an olivine containing species of rock,

comminuting the olivine containing species of rock to increase surface area thereof,

contacting the comminuted olivine containing species of rock with water and CO₂, said contacting comprising at least first and second separate steps;

a first step under pressure and at a first pH in which a reaction dissolving the comminuted olivine containing rock in water containing CO₂ takes place generally according to a reaction equation;

Mg₂SiO_4(s)+4H⁺=2Mg²⁺+SiO_2(aq)+2H₂O,

 

producing thereby a solution and non-reacted solid components and precipitated materials which are separated from the solution, and

a second step in which purified MgCO₃ is precipitated from the solution from the first step, conducted at a second pH which is higher than the first pH, with silicate remaining in the solution from which purified MgCO₃ has been precipitated, the second step being represented generally by reaction equations;

Mg²⁺+HCO₃⁻

=MgCO_3(s)+H⁺, and

Mg²⁺+CO₃²⁻

=MgCO_3(s),

the presence of HCO₃⁻

and H⁺ ions in the contacting steps being due mainly to a reaction between the CO₂ and the water with which the comminuted olivine containing rock is contacted.

2. Method as claimed in claim 1, wherein the olivine containing species of rock is comminuted to a general grain size less than 3 mm.

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

4. Method as claimed in claim 1, wherein the olivine containing species of rock contains iron that is precipitated as iron hydroxide in first step.

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

6. Method as claimed in claim 5, wherein the pressure is reduced from the first reactor chamber to the second reactor chamber so that some CO₂ thereby is released from solution, causing a corresponding increase in pH.

7. Method as claimed in claim 5, wherein a higher temperature is used in the second reactor chamber than in the first reactor chamber, to thereby favor precipitation of MgCO₃.

8. Method as claimed in claim 1, wherein said contacting comprises a three step process and the third step is a step of precipitating amorphous silica (SiO₂).

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

10. Method as claimed in claim 5, wherein the pressure in the first reactor is in the range 1-200 bar.

11. Method as claimed in claim 5, wherein the temperature in the first reactor is in the range 50-220°

C.

12. Method as claimed in claim 5, wherein the pressure in second reactor is in the range 1-150 bar.

13. Method as claimed in claim 5, wherein the temperature in the second reactor is in the range 100-300°

C.

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

15. Method as claimed in claim 1, wherein the process is conducted as a continuous process with respect to liquid flows, solids being retained in each step.

16. Method as claimed in claim 1, wherein the process is conducted as a wholly continuous process.

17. Method as claimed in claim 1, wherein the dissolving reaction takes place without addition of mineral acids and organic acids.

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

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

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

19. Method as claimed in claim 1, wherein the MgCO₃ produced is used as a raw material for production of Mg or as a filler paper or plastic products.

20. Method as claimed in claim 8, wherein the SiO₂ produced is used as a raw material for the manufacture of amorphous SiO₂ qualities, as a raw material for the manufacture of silicon or as a filler in car tires.

21. Method as claimed in claim 1, wherein the olivine containing species of rock contains iron which is discharged as iron oxides/iron hydroxides together with insoluble platinum group containing chromite from the dissolving step for further treatment in a production plant for the manufacture of iron, chrome and platinum group metals.

22. Method as claimed in claim 1, wherein the CO₂ is obtained from an industrial source and immobilized by the method.