Process and a plant for recycling carbon dioxide emissions from power plants into useful 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 said 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 the steps of:
catalyzing the hydration of at least a portion of the CO 2 contained in the exhaust gas and producing a solution containing hydrogen ions and carbonate ions; and wherein said hydration is catalyzed by the enzyme carbonic anhydrase or an analog thereof.
2. A process as defined in claim 1 , wherein step d) comprises:
adding to said solution metal ions, and adjusting the pH of the solution to precipitate a carbonate of said metal.
3. 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.
4. A process as defined in claim 3 , characterized in that the enzyme carbonic anhydrase or said analog thereof is immobilized on solid supports packing the bioreactor.
5. 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.
6. A process as defined in claim 5 , characterized in that the enzyme carbonic anhydrase or said analog thereof is free in said aqueous liquid phase, or immobilized on solid supports or entrapped inside a solid matrix.
7. 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 catalytic effect of the enzyme carbonic anhydrase or said analog thereof.
8. 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.
9. A process as defined in claim 8 , characterized in that said additional contaminants are selected from the group consisting of ash, NO x and SO 2 .
10. 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.
11. A process as defined in claim 10 , characterized in that said metal ions are Ca++ and the carbonate is CaCO 3 .
12. 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.
13. A power plant comprising:
a combustion unit for burning fossil fuel, thereby producing heat and an exhaust gas containing CO 2 ;
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 CO 2 from the cooled exhaust gas into hydrogen ions and carbonate ions; and
precipitation means for precipitating carbonated species from the carbonate ions,
wherein said biological means comprises a bioreactor including a reaction chamber filled with the enzyme carbonic anhydrase or an analog thereof to catalyze the hydration of dissolved CO 2 into hydrogen ions and bicarbonate ions.
14. A power plant as defined in claim 13 , characterized in that said means for cooling the exhaust gas comprises a heat exchanger.
15. A power plant as defined in claim 13 , 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 CO 2 gas; and
a liquid outlet for releasing a solution containing carbonate ions.
16. A power plant as defined in claim 15 , 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.
17. A power plant as defined in claim 15 , characterized in that the enzyme carbonic anhydrase or the analog thereof is immobilized on solid supports packing the reaction chamber.
18. A power plant as defined in claim 15 , characterized in that the enzyme carbonic anhydrase or the analog thereof is in suspension in an aqueous phase filling the reaction chamber.
19. A power plant as defined in claim 18 , characterized in that the enzyme carbonic anhydrase or the analog thereof is free in said liquid phase, immobilized on solid supports or entrapped inside a solid matrix.