Process for recycling carbon dioxide emissions from power plants into carbonated species
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 CO 2 ; 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 CO 2 contained in the cooled exhaust gas into carbonated species, thereby obtaining a low CO 2 exhaust gas and producing useful carbonated species. The low CO 2 exhaust gas obtained in step d) can be released in the atmosphere without increasing the problem of greenhouse effect.
1. A process comprising:
a) combustion of a fossil fuel, thereby generating heat and a hot exhaust gas containing CO 2 ;
b) converting said heat into energy;
the process being characterized in that it comprises the steps of:
c) cooling at least a portion of said exhaust gas to produce a cooled exhaust gas; and
d) reducing the amount of CO 2 contained in the cooled exhaust gas by biologically transforming said CO 2 into carbonated species; thereby obtaining a low CO 2 exhaust gas, wherein step d) comprises:
contacting an aqueous liquid phase with the cooled exhaust gas to cause at least a portion of the CO 2 to dissolve into the aqueous liquid phase and catalyzing the hydration of at least a portion of the dissolved CO 2 and producing a solution containing hydrogen ions and carbonate ions; and wherein said hydration is catalyzed by the enzyme carbonic anhydrase or an analogue thereof.
2. A process as defined in claim 1 , wherein step d) comprises:
adding to said solution cations, and adjusting the pH of the solution to precipitate a carbonated species of said cation.
3. A process as claimed in claim 2 , characterized in that the cations are selected from the group consisting of calcium, barium, magnesium and sodium ions.
4. A process as defined in claim 3 , characterized in that said cations are Ca++ and the carbonated species is CaCO 3 .
5. A process as defined in claim 1 , characterized in that the carbonated species comprise precipitates.
6. A process as defined in claim 1 , characterized in that the carbonated species comprise solid precipitates.
7. A process as defined in claim 1 , characterized in that the carbonated species consist of solid precipitates.
8. A process as defined in claim 1 , wherein step d) comprises the step of:
feeding liquid H 2 O and at least a portion of the exhaust gas into a bioreactor containing therein a reaction chamber filled with said enzyme carbonic anhydrase or said analog thereof.
9. A process as defined in claim 1 , characterized in that the enzyme carbonic anhydrase or said analog thereof is immobilized on solid supports packing the bioreactor.
10. A process as defined in claim 1 , 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 enzyme carbonic anhydrase or said analog thereof in suspension in a liquid phase.
11. A process as defined in claim 10 , wherein the enzyme is free in the liquid phase.
12. A process as defined in claim 10 , wherein the enzyme is immobilised on a solid support which is in suspension in the aqueous liquid.
13. A process as defined in claim 10 , wherein the enzyme is entrapped inside a matrix which is in suspension in the aqueous liquid.
14. A process as defined in claim 1 , wherein the enzyme is entrapped inside a matrix in the reactor.
15. A process as defined in claim 1 , wherein the cooling of the exhaust gas comprises passing the exhaust gas through a heat exchanger.
16. A process as defined in claim 15 , wherein heat removed by the heat exchanger is recovered to convert into energy.
17. A process as defined in claim 1 , wherein the cooling of the exhaust gas is performed while removing additional contaminants contained in the exhaust gas.
18. A process as defined in claim 17 , wherein the additional contaminants are removed from the exhaust gas by scrubbing.
19. A process as defined in claim 18 , wherein the additional contaminants removed by scrubbing are selected from the group consisting of ash, NO x and SO 2 .
20. A process as defined in claim 1 , characterized in that, in step c), the exhaust gas is cooled to a temperature sufficiently low so as to maintain a desired catalytic effect of the enzyme carbonic anhydrase or said analog thereof.
21. 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.
22. A process as defined in claim 21 , characterized in that said additional contaminants are selected from the group consisting of ash, NO x and SO 2 .
23. 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.
24. The process as defined in claim 20 , characterized in that in step c) the temperature to which the exhaust gas is cooled avoids a given denaturing of free carbonic anhydrase.
25. The process as defined in claim 20 , characterized in that in step c) the temperature to which the exhaust gas is cooled avoids a given denaturing of immobilized carbonic anhydrase.
26. The process as defined in claim 1 , characterized in that the exhaust gas has a CO 2 concentration between 0.5% and 12%.