Carbon dioxide capture and mitigation of carbon dioxide emissions
View Patent ↗The present invention describes methods and systems for extracting, capturing, reducing, storing, sequestering, or disposing of carbon dioxide (CO 2 ), particularly from the air. The CO 2 extraction methods and systems involve the use of chemical processes, mineral sequestration, and solid and liquid sorbents. Methods are also described for extracting and/or capturing CO 2 via condensation on solid surfaces at low temperature.
1. A method of extracting or sequestering carbon dioxide, comprising:
(a) dissolving a magnesium bearing silicate in an aqueous acid to form an acidic solution;
(b) increasing the pH of the solution of step (a) to precipitate one or more magnesium components;
(c) carbonating the precipitated magnesium components from step (b) to bind carbon dioxide; and
(d) recovering ammonia gas and acid by thermal decomposition or by electrodialysis.
2. The method according to claim 1 , wherein the acid of step (a) is present in an amount at least 10% in excess of a stoichiometric amount for neutralizing magnesium in the magnesium bearing silicate.
3. The method according to claim 1 , wherein the magnesium bearing silicate of step (a) comprises peridotite rock.
4. The method according to claim 1 , wherein the magnesium bearing silicate of step (a) is selected from serpentine or olivine.
5. The method according to claim 1 , wherein the aqueous acid of step (a) is selected from citric acid, acetic acid, chromic acid, sulfuric acid, orthophosphoric acid, oxalic acid, ammonium bisulfate, or a combination of two or more thereof.
6. The method according to claim 1 , wherein the pH of the acidic solution is less than or equal to about pH 4.5.
7. The method according to claim 1 , further comprising the step of neutralizing the acidic solution of step (a) with a neutralizing agent to precipitate iron and silicate prior to the precipitation of the one or more magnesium components.
8. The method according to claim 7 , wherein the neutralizing step comprises a neutralizing agent selected from ammonia or magnesium hydroxide.
9. The method according to claim 7 , wherein the pH of the neutralized solution is less than or equal to about pH 8.
10. The method according to claim 1 , wherein increasing the pH in step (b) comprises an ammonia-containing reagent.
11. The method according to claim 1 , wherein increasing the pH in step (b) comprises a reagent selected from NaOH, KOH, NH 3 , NH 4 OH, NH 4 HCO 3 , (NH 4 ) 2 CO 3 , Na 2 CO 3 , or a combination thereof.
12. The method according to claim 1 , further comprising following step (c):
(i) washing the precipitated magnesium component to remove residual salt; and
(ii) exposing the precipitated and washed magnesium component to carbon dioxide at elevated temperature and pressure.
13. The method according to claim 12 , wherein the elevated temperature comprises about 300° C. to 500° C. or above.
14. The method according to claim 12 , wherein the elevated pressure comprises about 1 to about 50 atmospheres.
15. The method according to claim 12 , wherein the precipitated magnesium component is magnesium hydroxide or magnesium oxide.
16. The method according to claim 1 , wherein the one or more magnesium components of step (b) is Mg(OH) 2 .
17. The method according to claim 1 , wherein carbon dioxide is extracted or sequestered from air.
18. The method according to claim 1 , wherein the one or more precipitated magnesium components is carbonated in step (c) in a gas solid reaction between magnesium components and carbon dioxide at elevated temperature.
19. The method according to claim 18 , wherein the temperature is about 300° C. to less than about 900° C.
20. The method according to claim 18 , wherein the temperature elevation is performed in an autoclave under pressure.
21. The method according to claim 20 , wherein the pressure is about 1 to about 50 atmospheres or greater.
22. The method according to claim 1 , comprising recovering ammonia gas and acid following step (c) by electrodialysis.