Process and a plant for recycling carbon dioxide emissions from power plants into useful carbonated species

• US 20060048517A1
• Filed: 09/29/2003
• Published: 03/09/2006
• Est. Priority Date: 09/27/2002
• Status: Active Grant

• Current Assignee: Saipem SPA (Saipem)
• Original Assignee: CO2 Solutions Inc.
• Inventors: Ruel, Jean, Fradette, Sylvie
• Granted Patent: US 7,596,952 B2
• Time in Patent Office: Days
• US Class Current: 60/772
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 53/84 Biological processes
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02E 20/32 Direct CO2 mitigation

Abstract

A process is disclosed for recycling carbon dioxide emissions from a fossil-fuel power plant into useful carbonated species The process primarily comprises the steps of: a) burning the fossil fuel, thereby generating heat and a hot exhaust gas containing CO₂; and b) converting the heat into energy. The process is characterized in that it further comprises the steps of: c) cooling the exhaust gas; and d) biologically transforming the CO₂ contained in the cooled exhaust gas into carbonated species, thereby obtaining a low CO₂ exhaust gas and producing useful carbonated species. The low CO₂ exhaust gas obtained in step d) can be released in the atmosphere without increasing the problem of greenhouse effect.

Claims

1. A process for recycling carbon dioxide emissions from a fossil-fuel power plant into carbonated species, comprising the steps of:

a) combustion of a fossil fuel, thereby generating heat and a hot exhaust gas containing CO₂;

b) converting said heat into energy;

the process being characterized in that it comprises the steps of;

c) cooling said exhaust gas; and

d) reducing the amount of CO₂ contained in the cooled exhaust gas by biologically transforming said CO₂ into carbonated species;

thereby obtaining a low CO₂ exhaust gas.

2. A process as defined in claim 1, characterized in that step d) comprises the steps of:

catalyzing the hydration of at least a portion of the CO₂ contained in the exhaust gas and producing a solution containing hydrogen ions and carbonate ions; and

adding to said solution metal ions, and adjusting the pH of the solution to precipitate a carbonate of said metal;

wherein said hydration is catalyzed by a biocatalyst capable of catalyzing the hydration of dissolved CO₂ into hydrogen ions and bicarbonate ions.

3. A process as defined in claim 2, characterized in that said biocatalyst is selected from the group consisting of enzyme, cellular organelle, mammal cells and vegetal cells.

4. A process as defined in claim 3, characterized in that the biocatalyst is the enzyme carbonic anhydrase or an analogue thereof.

5. A process as defined in claim 2, wherein step d) comprises the step of:

feeding liquid H₂O and at least a portion of the exhaust gas into a bioreactor containing therein a reaction chamber filled with said biocatalyst.

6. A process as defined in claim 5, characterized in that the biocatalyst is immobilized on solid supports packing the bioreactor.

7. A process as defined in claim 2, wherein step d) comprises the step of:

feeding at least a portion of the exhaust gas into a bioreactor containing therein a reaction chamber filled with said biocatalyst in suspension in a liquid phase.

8. A process as defined in claim 7, characterized in that the biocatalyst is free in said aqueous liquid phase, or immobilized on solid supports or entrapped inside a solid matrix.

9. A process as defined in claim 2, characterized in that, in step c), the exhaust gas is cooled to a temperature sufficiently low so as to maintain a catalytic effect of the biocatalyst.

10. A process as defined in claim 1, characterized in that it comprises, prior to step d) of reducing, the step of:

removing from the exhaust gas additional contaminants contained in the exhaust gas.

11. A process as defined in claim 10, characterized in that said additional contaminants are selected from the group consisting of ash, NO_x and SO₂.

12. A process as claimed in claim 2, characterized in that the metal ions are selected from the group consisting of calcium, barium, magnesium and sodium ions.

13. A process as defined in claim 12, characterized in that said metal ions are Ca++ and the carbonate is CaCO₃.

14. A process as defined in claim 1, characterized in that step c) of cooling is performed by means of a heat exchanger that removes heat from said cooled exhaust gas, the heat removed being recycled in step b) of the process.

15. A power plant for producing energy from fossil fuel, and recycling carbon dioxide emissions into carbonated species, the plant comprising:

a combustion unit for burning fossil fuel, thereby producing heat and an exhaust gas containing CO₂;

means for converting said heat into energy;

the plant being characterized in that it comprises;

means for cooling the exhaust gas;

biological means for biologically transforming at least a portion of the CO₂ from the cooled exhaust gas into hydrogen ions and carbonate ions; and

precipitation means for precipitating carbonated species from the carbonate ions.

16. A power plant as defined in claim 15, characterized in that said means for cooling the exhaust gas comprises a heat exchanger.

17. A power plant as defined in claim 15, characterized in that said biological means comprises a bioreactor including a reaction chamber filled with a biocatalyst capable of catalyzing the hydration of dissolved CO₂ into hydrogen ions and bicarbonate ions.

18. A power plant as defined in claim 17, characterized in that the reaction chamber comprises:

a liquid inlet for receiving an aqueous liquid;

a gas inlet for receiving the cooled exhaust gas to be treated;

a gas outlet for releasing a low CO₂ gas; and

a liquid outlet for releasing a solution containing carbonate ions.

19. A power plant as defined in claim 18, characterized in that the precipitating means comprises:

a precipitation vessel to react said bicarbonate ions with metal ions and precipitate a carbonate of said metal.

20. A power plant as defined in claim 18, characterized in that the biocatalyst is immobilized on solid supports packing the reaction chamber.

21. A power plant as defined in claim 18, characterized in that the biocatalyst is in suspension in an aqueous phase filling the reaction chamber.

22. A power plant as defined in claim 21, characterized in that the biocatalyst is free in said liquid phase, immobilized on solid supports or entrapped inside a solid matrix.