CO

1. A CO 2 recovery apparatus comprising:

an absorber that brings flue gas containing CO 2 into counter-current contact with CO 2 absorbent to reduce CO 2 ;

a regenerator that regenerates rich solution that has absorbed CO 2 through heat exchange, in which lean solution having CO 2 reduced in the regenerator is reused in the absorber, wherein

the absorber includes at least one CO 2 absorbing unit that recovers CO 2 in the flue gas containing CO 2 ; a washing unit arranged above the at least one CO 2 absorbing unit within the absorber; and a water supplying apparatus configured to supply the washing unit with water from a top thereof;

a lean-solution supplying apparatus that is connected to a position between the washing unit and the absorbing unit, and configured to supply the absorber with the lean solution regenerated from the rich solution in the regenerator; and

an absorbent circulating line connecting a lower side of the CO 2 absorbing unit to a position between the upper side of the CO 2 absorbing unit and the lower side of the CO 2 absorbing unit without passing through the regenerator, the absorbent circulating line being arranged separately from the lean-solution supplying apparatus, and having a pump that extracts the CO 2 absorbent and a heat exchanger that cools the CO 2 absorbent extracted from the absorber and circulating in the absorbent circulating line.

2. The CO 2 recovery apparatus according to claim 1 , wherein

the CO 2 absorbing unit includes an upper-stage CO 2 absorbing unit and a lower-stage CO 2 absorbing unit, and the CO 2 recovery apparatus further comprises:

an absorbent extracting line through which CO2 absorbent is extracted from a lower side of the upper-stage CO2 absorbing unit, wherein

the absorbent circulating line connects a lower side of the lower-stage CO 2 absorbing unit and an upper side of the lower-stage CO 2 absorbing unit to supply the lower-stage CO 2 absorbing unit with the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit merged with the CO 2 absorbent extracted from the lower side of the upper-stage CO 2 absorbing unit, and

the heat exchanger cools the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit before or after the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit is merged with the CO 2 absorbent extracted via the absorbent extracting line.

3. The CO 2 recovery apparatus according to claim 1 , wherein

the CO 2 absorbing unit includes an upper-stage CO 2 absorbing unit, a middle-stage CO 2 absorbing unit, and a lower-stage CO 2 absorbing unit, and the CO 2 recovery apparatus further comprises:

an absorbent extracting line through which CO 2 absorbent is extracted from a lower side of the upper-stage CO 2 absorbing unit, wherein

the absorbent circulating line connects a lower side of the middle-stage CO 2 absorbing unit and the upper side of the middle-stage CO 2 absorbing unit to supply the middle-stage CO 2 absorbing unit with the CO 2 absorbent extracted from the lower side of the middle-stage CO 2 absorbing unit merged with the CO 2 absorbent extracted from the lower side of the upper-stage CO 2 absorbing unit, and

the heat exchanger cools the CO 2 absorbent extracted from the lower side of the middle-stage CO 2 absorbing unit before or after the CO 2 absorbent extracted from the rich side of the upper-stage CO 2 absorbing unit is merged with the CO 2 absorbent extracted via the absorbent extracting line.

4. The CO 2 recovery apparatus according to claim 3 , further comprising a circulating absorbent extracting line through which a part of the CO 2 absorbent extracted from the lower side of the middle-stage CO 2 absorbing unit via the absorbent circulating line is supplied to an upper side of the lower-stage CO 2 absorbing unit.

5. The CO 2 recovery apparatus according to claim 1 , wherein

the CO 2 absorbing unit includes an upper-stage CO 2 absorbing unit, a middle-stage CO 2 absorbing unit, and a lower-stage CO 2 absorbing unit, and the CO 2 recovery apparatus further comprises:

an absorbent extracting line through which CO 2 absorbent extracted from a lower side of the upper-stage CO 2 absorbing unit, wherein

the absorbent circulating line connects the lower side of the lower-stage CO 2 absorbing unit and the upper side of the middle-stage CO 2 absorbing unit to supply the middle-stage CO 2 absorbing unit with the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit merged with the CO 2 absorbent extracted from the lower side of the upper-stage CO 2 absorbing unit, and

the heat exchanger cools the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit before the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit is merged with the CO 2 absorbent extracted via the absorbent extracting line.

6. The CO 2 recovery apparatus according to claim 5 , wherein CO 2 absorbent extracted from a lower side of the middle-stage CO 2 absorbing unit is supplied to an upper side of the lower-stage CO 2 absorbing unit.

7. The CO 2 recovery apparatus according to claim 6 , further comprising a heat exchanger that cools the CO 2 absorbent extracted from the lower side of the middle-stage CO 2 absorbing unit.

8. The CO 2 recovery apparatus according to claim 2 , wherein an end of the absorbent extracting line is connected to a rich solution supply line through which the rich solution is supplied to the regenerator, and the rich solution is extracted through the rich solution supply line.

9. The CO 2 recovery apparatus according to claim 2 , wherein the absorbent circulating line is configured to be supplied with a mass flow of the CO 2 absorbent having a mass flow ratio between 0.1 to 6.0 with respect to a mass flow of the rich solution supplied to the rich solution supply line through which the rich solution is supplied to the regenerator.

10. The CO 2 recovery apparatus according to claim 1 , wherein the heat exchanger is configured to cool the CO 2 absorbent extracted from the CO 2 absorbing unit to a temperature of 30 to 50 degrees Celsius.

11. A CO 2 recovery method comprising the steps of: bringing flue gas containing CO 2 into counter-current contact with CO 2 absorbent in a CO 2 absorbing unit included in an absorber to reduce CO 2 ;

supplying a regenerator with rich solution of the CO 2 absorbent that has absorbed CO 2 and regenerating the rich solution therein into lean solution having CO 2 reduced;

supplying the absorber with the lean solution and reusing therein the lean solution;

washing CO 2 -reduced flue gas by bringing the CO 2 -reduced flue gas into counter-current contact with water supplied from a top of a washing unit arranged above the CO 2 absorbing unit within the absorber;

supplying the absorber with the lean solution regenerated from the rich solution in the regenerator to a position between the washing unit and the absorbing unit;

extracting the CO 2 absorbent that has absorbed CO 2 as circulating absorbent from a lower side of the CO 2 absorbing unit to exterior;

cooling the circulating absorbent;

supplying the lean solution to a position between the washing unit and the absorbing unit;

supplying the circulating absorbent to a position between the upper side of the CO 2 absorbing unit and the lower side of the CO 2 absorbing unit without passing through the regenerator; and

circulating the circulating absorbent separately from the lean solution through an absorbent circulating line having a pump that extracts the CO 2 absorbent and a heat exchanger that cools the CO 2 absorbent extracted from the absorber.

12. The CO 2 recovery method according to claim 11 , further comprising:

extracting the CO 2 absorbent from a lower side of a lower-stage CO 2 absorbing unit in the absorber including two such CO 2 absorbing units that are an upper-stage CO 2 absorbing unit and the lower-stage CO 2 absorbing unit;

merging CO 2 absorbent extracted from a lower side of the upper-stage CO 2 absorbing unit with the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit;

cooling the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit before or after the CO 2 absorbent extracted from the lower side of the upper-stage CO 2 absorbing unit is merged with the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit; and

supplying the CO 2 absorbent thus merged to an upper side of the lower-stage CO 2 absorbing unit so as to recover CO 2 contained in the flue gas containing CO 2 .

13. The CO 2 recovery method according to claim 11 , further comprising:

extracting CO 2 absorbent from a lower side of a middle-stage CO 2 absorbing unit in the absorber wherein the CO 2 absorbing unit comprises an upper-stage CO 2 absorbing unit, the middle-stage CO 2 absorbing unit, and a lower-stage CO 2 absorbing unit;

merging CO 2 absorbent extracted from a lower side of the upper-stage CO 2 absorbing unit with the CO 2 absorbent extracted from the lower side of the middle-stage CO 2 absorbing unit;

cooling the CO 2 absorbent extracted from the lower side of the middle-stage CO 2 absorbing unit before or after the CO 2 absorbent extracted from the lower side of the middle-stage CO 2 absorbing unit is merged with the CO 2 absorbent extracted from the lower side of the upper-stage CO 2 absorbing unit; and

supplying the CO 2 absorbent thus merged to an upper side of the middle-stage CO 2 absorbing unit so as to recover CO 2 contained in the gas containing CO 2 .

14. The CO 2 recovery method according to claim 13 , further comprising supplying a part of the CO 2 absorbent extracted from the lower side of the middle-stage CO 2 absorbing unit to an upper side of the lower-stage CO 2 absorbing unit.

15. The CO 2 recovery method according to claim 11 , further comprising:

extracting the CO 2 absorbent from a lower side of a lower-stage CO 2 absorbing unit in the absorber wherein the CO 2 absorbing unit comprises an upper-stage CO 2 absorbing unit, a middle-stage CO 2 absorbing unit, and the lower-stage CO 2 absorbing unit;

merging CO 2 absorbent extracted from a lower side of the upper-stage CO 2 absorbing unit with the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit;

cooling the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit before or after the CO 2 absorbent extracted from the lower side of the upper-stage CO 2 absorbing unit is merged with the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit; and

supplying the CO 2 absorbent thus merged to an upper side of the middle-stage CO 2 absorbing unit so as to recover CO 2 contained in the gas containing CO 2 .

16. The CO 2 recovery method according to claim 15 , further comprising supplying CO 2 absorbent extracted from a lower side of the middle-stage CO 2 absorbing unit to an upper side of the lower-stage CO 2 absorbing unit.

17. The CO 2 recovery method according to claim 16 , further comprising cooling the CO 2 absorbent extracted from the lower side of the middle-stage CO 2 absorbing unit and thereafter supplying the CO 2 absorbent to the upper side of the lower-stage CO 2 absorbing unit.

18. The CO 2 recovery method according to claim 12 , further comprising:

extracting rich solution from a rich solution supply line through which the rich solution is supplied to the regenerator; and

circulating the rich solution extracted through the rich solution supply line to the lower side of any one of the upper-stage CO 2 absorbing unit, the middle-stage CO 2 absorbing unit, and the lower-stage CO 2 absorbing unit.

19. The CO 2 recovery method according to claim 12 , further comprising extracting the rich solution, wherein a dividing ratio between a circulation mass flow of the CO 2 absorbent extracted from the lower side of the lower-stage CO 2 absorbing unit to any one of the upper-stage CO 2 absorbing unit, the middle-stage CO 2 absorbing unit, and the lower-stage CO 2 absorbing unit and a mass flow of the rich solution supplied to the regenerator is between 0.1 to 1.0 and 6.0 to 1.0.

20. The CO 2 recovery method according to claim 12 , wherein a temperature of the CO 2 absorbent extracted from the CO 2 absorbing unit after being cooled is 30 to 50 degrees Celsius.

21. The CO 2 recovery method according to claim 11 , wherein a mass flow ratio between a mass flow of the rich solution supplied to the regenerator and an amount of absorbent circulation is optimally controlled depending on a gas temperature of flue gas introduced to the absorber so as to reduce operation costs.

22. The CO 2 recovery method according to claim 21 , wherein, when the CO 2 absorbent has a decreased concentration thereof as a result of extended operation, an amount of circulation in an entire system is increased to maintain a CO 2 absorption capability.