APPARATUS AND METHOD FOR RECOVERING CO2

Description

TECHNICAL FIELD

[0001] The present invention relates to a CO₂ recovery system and method for achieving energy saving.

BACKGROUND ART

[0002] in recent years the greenhouse effect due to CO₂ has been pointed out as one of causes of the global warming, and a countermeasure against it is urgently required internationally to protect global environment. CO₂ sources range various fields of human activities, including burning of fossil fuels, and demands to suppress their CO₂ emission from these sources are on constant increase. In association with this, people have energetically studied means and methods for suppressing emission of CO₂ from power generation facilities such as power plants which use an enormous amount of fossil fuels. One of the methods includes bringing combustion exhaust gas of boilers into contact with an amine-based CO₂-absorbing solution. This method allows removal and recovery of CO₂ from the combustion exhaust gas. Another method includes storing recovered CO₂, i.e., not returning the recovered CO₂ to the atmosphere.

[0003] Various methods are known to remove and recover CO₂ from combustion exhaust gas using the CO₂-absorbing solution. One of the methods includes contacting the combustion exhaust gas with the CO₂-absorbing solution in an absorption tower, heating an absorbing solution having absorbed CO₂ in a regeneration tower, and releasing CO₂, regenerating the absorbing solution, and circulating the regenerated absorbing solution to the absorption tower again to be reused (Patent document 1).

[0004] Patent document 1: Japanese Patent Application JP 7051537 A
Further methods for removing CO₂ by means of absorption are disclosed in WO 2004/005818 A2 and in US 3,563,696. A related method, but for the removal of H₂S, is described in US 4,973,340.

DISCLOSURE OF INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION

[0005] In the conventional method, however, the steps of removing, and recovering CO₂ from CO₂-containing gas are provided additionally in combustion facilities, and hence, the operation costs should be reduced as much as possible. Particularly, among the processes, a regenerating process consumes a large amount of heat energy, and therefore, the regenerating process needs to be provided as an energy saving process as much as possible.

[0006] The present invention has been achieved to solve the problems, and it is an object of the present invention to provide a CO₂ recovery system and method in which an energy efficiency is further improved.

MEANS FOR SOLVING PROBLEM

[0007] To solve the above problems, a first aspect of the present invention relates to a CO₂ recovery system including an absorption tower (13) that contacts CO2-containing gas with a CO2-absorbing solution to remove CO2 and a regeneration tower (15) that regenerates a rich solution having absorbed CO2, and reusing a lean solution, obtained by removing CO2 from the rich solution in the regeneration tower, in the absorption tower, comprising: a regeneration heater (18) that extracts the lean solution recovered near a bottom portion of the regeneration tower (15) to the outside, and heat-exchanges the lean solution with saturated steam; and a steam-condensate heat exchanger (21) that heats the rich solution to be supplied to the regeneration tower (15) with residual heat of steam condensate fed from the regeneration heater, the CO₂ recovery system further comprising: a rich-solution supply line (20) that conveys the rich solution from the absorption tower (13) to the regeneration tower (15); a lean solution supply line (22) that extracts the lean solution from the regeneration tower (15) and conveys extracted lean solution to the absorption tower (13); and a lean-solution heat exchanger (23) that is interposed in the rich-solution supply line (20) and the lean-solution supply line (22), and heats the rich solution in the rich-solution supply line (20) with residual heat of the lean solution in the lean-solution supply line (22), wherein the steam-condensate heat exchanger (21) heats the rich solution to be supplied to the regeneration tower (15) at a position downstream of the lean-solution heat exchanger (23).
According to a second aspect of the present invention, a CO2 recovery system including an absorption tower (13) that contacts CO2-containing gas with a CO2-absorbing solution to remove CO2 and a regeneration tower (15) that regenerates a rich solution having absorbed CO2, and reusing a lean solution, obtained by removing CO2 from the rich solution in the regeneration tower, in the absorption tower, comprising: a regeneration heater (18) that extracts the lean solution recovered near a bottom portion of the regeneration tower (15) to the outside, and heat-exchanges the lean solution with saturated steam; and a steam-condensate heat exchanger (21) that heats the rich solution to be supplied to the regeneration tower (15) with residual heat of steam condensate fed from the regeneration heater, the regeneration tower (15) including an upper-portion regeneration tower (15-U) and a lower-portion regeneration tower (15-L), and the CO2 recovery system further comprising: a rich-solution supply line (20) that conveys the rich solution from the absorption tower (13) to the regeneration tower (15); a branching node (24) provided in the rich-solution supply line (20) and that branches the rich-solution supply line (20) into a first rich-solution supply line (20-1) and a second rich-solution supply line (20-2), wherein the steam-condensate heat exchanger (21) is provided in the first rich-solution supply line (20-1) and heats the rich solution in the first rich-solution supply line (20-1) with residual heat of the steam condensate; a semi-lean-solution supply line (30) that extracts semi-lean solution from the upper-portion regeneration tower (15-U) and conveys extracted semi-lean solution to a middle stage portion of the absorption tower (13); a semi-lean-solution heat exchanger (29) that is provided in the second rich-solution supply line (20-2) and the semi-lean-solution supply line (30), and heats the rich solution in the second rich-solution supply line (20-2) with residual heat of the semi-lean solution (28) in the semi-lean solution supply line (30), and a lean-solution supply line (22) that extracts the lean solution from the regeneration tower (15) and conveys extracted lean solution to the absorption tower (13); and a lean-solution heat exchanger (23) that is interposed in the first rich-solution supply line (20-1) and the lean-solution supply line (22), and heats the rich solution in the first rich-solution supply line (20-1) with residual heat of the lean solution in the lean-solution supply line (22), wherein the steam-condensate heat exchanger (21) heats the rich solution to be supplied to the regeneration tower (15) at a position downstream of the lean-solution heat exchanger (23), wherein one end of the first rich-solution supply line (20-1) being connected to the lower-portion regeneration tower (15-L), and one end of the second rich-solution supply line (20-2) being connected to the upper-portion regeneration tower (15-U).

EFFECT OF THE INVENTION

[0008] According to the present invention, it is possible to provide a CO₂ recovery system and method in which energy saving is achieved by using residual heat of steam condensate.
Furthermore, it is possible to provide a CO₂ recovery system and method with improved energy efficiency by heating a semi-lean solution with residual heat of a lean solution, the semi-lean solution obtained by removing part of CO₂ from a rich solution and extracted from the middle of the regeneration tower when the rich solution having absorbed CO₂ is regenerated in the regeneration tower.

BRIEF DESCRIPTION OF DRAWINGS

[0009] 

Fig. 1 is a schematic of a CO₂ recovery system according to a first embodiment;

Fig. 2 is a schematic of a CO₂ recovery system according to a first comparative embodiment;

Fig. 3 is a schematic of a CO₂ recover system according to a second comparative embodiment;

Fig. 4 is a schematic of a CO₂ recovery system according to a second embodiment;

Fig. 5 is a schematic of a CO₂ recovery system according to a third comparative embodiment;

Fig. 6 is a schematic of a CO₂ recovery system according to a fourth comparative embodiment;

Fig. 7 is a schematic of a CO₂ recovery system according to a firth comparative embodiment;

Fig. 8 is a schematic of a CO₂ recovery system according to a sixth and seventh comparative embodiment;

Fig. 9 is a schematic of a CO₂ recovery system according to a eighth comparative embodiment;

Fig. 10 is a schematic of a CO₂ recovery system according to example 1;

Fig. 11 is a schematic of a CO₂ recovery system according to example 2;

Fig. 12 is a schematic of a CO₂ recovery system according to example 3;

Fig. 13 is a schematic of a CO₂ recovery system according to comparative example 4;

Fig. 14 is a schematic of a CO₂ recovery system according to comparative example 5;

Fig. 15 is a schematic of a CO₂ recovery system according to comparative example 6;

Fig. 16 is a schematic of a CO₂ recovery system according to example 7;

Fig. 17 is a schematic of a CO₂ recovery system according to comparative example 8;

Fig. 18 is a schematic of a CO₂ recovery system according to comparative example 9;

Fig. 19 is a schematic of a CO₂ recovery system according to comparative example 10;

Fig. 20 is a schematic of a CO₂ recovery system according to comparative example 11;

Fig. 21 is a schematic of a CO₂ recovery system according to comparative example 12, and

Fig. 22 is a schematic of a CO₂ recovery system according to a conventional example.

EXPLANATIONS OF LETTERS OR NUMERALS

[0010] 

11	CO2-containing gas
12	CO2-absorbing solution
13	Absorption tower
14	Rich solution
15	Regeneration tower
16	Lean solution
17	Steam
18	Regeneration heater
19	Steam condensate
21	Steam-condensate heat exchanger
22	Lean-solution supply line
23	Lean-solution heat exchanger
8	Nozzle
9	Chimney tray
10	CO2-removed exhaust gas

BEST MODE(S) FOR CARRYING OUT THE INVENTION

[0011] The present invention is explained in detail below with reference to the attached drawings. It is noted that the present invention is not limited by its exemplary embodiments and examples. It is also noted that components in the following embodiments and examples contain those persons skilled in the art can easily think of or those substantially equivalent thereto.
The embodiments of the present invention are explained first, and the exemplary examples are explained in detail next.

[First Embodiment]

[0012] Fig. 1 is a schematic of a CO₂ recovery system according to a first embodiment.
As shown in Fig. 1, the CO₂ recovery system according to the first embodiment of the present invention includes an absorption tower 13 that makes CO₂-containing gas 11 containing CO₂ to contact with a CO₂-absorbing solution 12 to produce a CO₂-rich solution 14; and a regeneration tower 15 that regenerates a rich solution 14 to produce a lean solution (regenerated solution) 15. The regenerated solution 16 is reused in the absorption tower 13. The CO₂ recovery system includes a regeneration heater 18 that implements heat exchange between the lean solution 16, which accumulates near the bottom of the regeneration tower 15, and high temperature steam 17; a rich-solution supply line 20 which supplies the rich solution 14 from the absorption tower 13 to the regeneration tower 15; a steam-condensate heat exchanger 21 that is provided in rich-solution supply line 20 and heats the rich solution 14 with the residual heat of steam condensate 19 fed from the regeneration heater 18.

[0013] In the first embodiment, the lean solution 16 being the regenerated solution is supplied from the regeneration tower 15 to the absorption tower 13 through a lean-solution supply line 22. A lean-solution heat exchanger 23, which heats the rich solution 14 with residual heat of the lean solution 16, is provided in the rich-solution supply line 20.
In Fig. 1, reference numeral 8 represents a nozzle, 9 a chimney tray, 10 CO₂-removed exhaust gas, 25a and 25b filling layers provided in the absorption tower 13, and 26a and 26b filling layers provided in the regeneration tower 15.

[0014] The heat exchanger used in the first embodiment is not particularly limited. In other words, a known heat exchanger such as a plate heat exchanger and a shell and tube heat exchanger can be used.

[0015] The CO₂-absorbing solution used in the present invention is not particularly limited. For example, an alkanolamine and a hindered amine group having alkanolamine and alcoholic hydroxyl can be exemplified. The alkanolamine can be exemplified by monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, diisopropanolamine, diglycolamine, and the like, but generally, monoethanolamine (MEA) is preferably used. The hindered amine having alcoholic hydroxyl can be exemplified by 2-amino-2-methyl-1-propanol(AMP), 2-(ethylamino)-ethanol(EAE), 2-(methylamino)-ethanol(MAE), and 2-(diethylamino)-ethanol(DEAE).

[0016] Thus, there is provided the steam-condensate heat exchanger 21 that heats the rich solution 14 with the residual heat of the steam condensate 19 fed from the regeneration heater 18. Thus, the residual heat of the steam condensate 19 can be effectively used to raise the supply temperature of the rich solution 14 to be supplied to the regeneration tower 15, so that reduction in the supply amount of steam used in the regeneration tower 15 can be achieved.

[0017] The CO₂-containing gas 11 to be supplied to the CO₂ recovery device is first cooled by a cooling device (not shown) to about 40°C to 50°C and supplied to the CO₂ recovery device. On the other hand, the lean solution 16 which is the absorbing solution 12 regenerated is cooled to about 40°C by a cooling device (not shown).
The rich solution 14 output from the absorption tower 13 of the CO₂ removal device is sent toward the regeneration tower 15 at about 50°C due to heat reaction. The rich solution 14 is then heated up to about 110°C in the lean-solution heat exchanger 23 and supplied to the regeneration tower 15. However, by providing the steam-condensate heat exchanger 21 in which the rich solution 14 is heat-exchanged with the heat (e.g., 137°C) of the steam condensate 19, the temperature of the rich solution 14 can be increased by several degrees.

[0018] In the configuration of Fig. 1, a flash drum for causing the rich solution to flash can be provided in either one of an upstream side and a downstream side of the steam-condensate heat exchanger 21, and the flash drum can be made to discharge CO₂ contained in the rich solution in the outside of the regeneration tower. According to such configuration, part of CO₂ in the rich solution 14 to be regenerated in the regeneration tower 15 is previously removed by the flash drum, and it becomes possible to reduce the supply amount of steam to be used for CO₂ removal in the regeneration tower 15.

[First comparative Embodiment]

[0019] Fig. 2 is a schematic of a CO₂ recovery system according to a first comparative embodiment.
Components the same as those of the CO₂ recovery system according to the first embodiment are assigned with the same reference numerals, and explanation thereof is omitted.
As show in Fig. 2, the CO₂ recovery system according to the first comparative embodiment further includes, in addition to the configuration of the first embodiment, a branching node 24 provided in the rich-solution supply line 20 that branches the rich solution 14 into the first rich-solution supply line 20-1 and the second rich-solution supply line 20-2; the steam-condensate heat exchanger 21 that is provided in the first rich-solution supply line 20-1 and heats the rich solution 14; a flash drum 27 provided in the downstream side of the steam-condensate heat exchanger 21; and a semi-lean-solution heat exchanger 29 that is provided in the second rich-solution supply line 20-2 and heats the rich solution 14 with the residual heat of a semi-lean solution 28 obtained by removing part of CO₂ from the rich solution in the flash drum 27. An end of a semi-lean-solution supply line 30 for supplying the semi-lean solution 28 is connected to a middle stage portion of the absorption tower 13. The second rich-solution supply line 20-2 is connected near the upper stage of the regeneration tower 15, and CO₂ is removed and recovered in the regeneration tower 15.

[0020] Thus, the steam-condensate heat exchanger 21 heats the rich solution 14 with the residual heat of the steam condensate 19 fed from the regeneration heater 18, in which the rich solution is heated with the residual heat of the steam condensate, therefore, the residual heat of the steam condensate 19 having been used in the regeneration heater 18 is effectively used. The rich solution 14 heated with the residual heat is introduced into the flash drum 27. Then, the rich solution 14 is caused to flash in the flash drum 27 to enable improvement of CO₂ removal efficiency. Moreover, the rich solution 14 is heat-exchanged with the residual heat of the semi-lean solution 28 obtained by removing part of CO₂ from the rich solution and fed from the flash drum 27, in the semi-lean-solution heat exchanger 29 interposed in the second rich-solution supply line 20-2 branched. Therefore, it is possible to increase the temperature of the rich solution 14 to be introduced into the regeneration tower 15, and as a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced. Most of CO₂ is removed from the semi-lean solution 28, obtained by removing part of CO₂ from the rich solution, in the flash drum 27. Therefore, by supplying this semi-lean solution 28 to the middle stage portion of the absorption tower 13, CO₂ is absorbed without being regenerated in the regeneration tower 15.
Furthermore, CO₂ removed in the flash drum 27 joins CO₂ fed from the regeneration tower 15, to be recovered separately.

[0021] The ratio of division of the rich solution 14 into the first rich-solution supply line 20-1 and the second rich-solution supply line 20-2 at the branching node 24 is simply set to a range from 30:70 to 70:30, preferably 50:50.

[0022] The first comparative embodiment is configured to further divide the inner side of the absorption tower 13 into two stages: an upper-stage filling layer 13-U and a lower-stage filling layer 13-L; to extract the absorbing solution 12 having absorbed CO₂, from the upper-stage filling layer 13-U to the outside; and to mix the absorbing solution 12 with the semi-lean solution 28 to be cooled. This is because it is preferable to decrease the temperature of a solution to be supplied because the absorption reaction is an exothermic reaction. In this embodiment, the temperature is decreased to about 40°C to 50°C.

[Second comparative Embodiment]

[0023] Fig. 3 is a schematic of a CO₂ recovery system according to a second comparative embodiment.
Components the same as those in each of the CO₂ recovery systems according to the first and the first comparative embodiments are assigned with the same reference numerals, and explanation thereof is omitted.
As shown in Fig. 3, the CO₂ recovery system according to the second comparative embodiment further includes, in addition to the configuration of the first embodiment, the branching node 24 provided in the rich-solution supply line 20 and divides the rich solution 14 into the first rich-solution supply line 20-1 and the second rich-solution supply line 20-2; a steam-condensate heat exchanger 31 that is provided in an end of the first rich-solution supply line 20-1 and causes the rich solution 14 to flash; and the semi-lean-solution heat exchanger 29 that is provided in the second rich-solution supply line 20-2 and heats the rich solution 14 with the residual heat of the semi-lean solution 28 obtained by removing part of CO₂ from the rich solution in the steam-condensate heat exchanger 31. And the end of the semi-lean-solution supply line 30 for supplying the semi-lean solution 28 is connected to the middle stage portion of the absorption tower 13.

[0024] In the second comparative embodiment, the steam-condensate heat exchanger 31 is not an exchanger such as the plate heat exchanger, but includes, as shown in Fig. 3, a first flash drum 33 in which a flash portion 32, for causing the rich solution 14 to flash, is provided in its upper side; a filling layer 34 provided in the first flash drum 33; and a steam supply portion 36 that is provided in the lower-portion of the flash drum and supplies steam 35 from the steam condensate 19.
If the steam condensate 19 is pressurized saturated steam, a second flash drum 37 is provided to make it as atmospheric pressure steam 35, and the steam 35 is supplied to the first flash drum 33, where CO₂ is removed from the rich solution 14 using the heat of the steam 35.
The semi-lean-solution heat exchanger 29 heats the rich solution 14 using the residual heat of the semi-lean solution 28 obtained by removing part of CO₂ from the rich solution in the first flash drum 33, and then, the rich solution is supplied to the middle stage portion of the absorption tower 13.

[0025] Thus, the steam-condensate heat exchanger 31 heats the rich solution 14 in the first rich-solution supply line 20-1, with the residual heat of the steam condensate 19 fec from the regeneration heater 18, in which the rich solution is heated with the steam 35. Therefore, the residual heat of the steam condensate 19 having been used in the regeneration heater 18 is effectively used. The rich solution 14 is heat-exchanged using the residual heat of the semi-lean solution 28 obtained by removing CO₂ by flash in the steam-condensate heat exchanger 31, in the semi-lean-solution heat exchanger 29 interposed in the second rich-solution supply line 20-2 branched. Therefore, it is possible to increase the temperature of the rich solution 14 to be introduced into the regeneration tower 15, and as a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.
Furthermore, CO₂ removed in the first flash drum 33 joins CO₂ fed from the regeneration tower 15, to be recovered separately.
The first flash drum 33 functions as an auxiliary regeneration tower for the regeneration tower 15.

[Second Embodiment]

[0026] Fig. 4 is a schematic of a CO₂ recovery system according to a second embodiment.
Components the same as those in each of the CO₂ recovery systems according to the preceding embodiments are assigned with the same reference numerals, and explanation thereof is omitted.
As shown in Fig. 4, the CO₂ recovery system according to the second embodiment of the present invention further includes, in addition to the configuration of the first embodiment, an upper-portion regeneration tower 15-U and a lower-portion regeneration tower 15-L into which the inner side of the regeneration tower 15 is vertically divided; the branching node 24 provided in the rich-solution supply line 20 and dividing the rich solution 14; the steam-condensate heat exchanger 21 interposed in the first rich-solution supply line 20-1 branched; and the semi-lean-solution heat exchanger 29 that is provided in the second rich-solution supply line 20-2, and heats the rich solution 14 with the residual heat of the semi-lean solution 28 obtained by removing part of CO₂ from the rich solution in the upper-portion regeneration tower 15-U. And, the end of the first rich-solution supply line 20-1 is connected to the lower-portion regeneration tower 15-L, the end of the second rich-solution supply line 20-2 is connected to the upper-portion regeneration tower 15-U, and the end of the semi-lean-solution supply line 30 for supplying the semi-lean solution 28 is connected to the middle stage portion of the absorption tower 13.

[0027] The second embodiment is configured to provide the steam-condensate heat exchanger 21 that heats the rich solution 14 with the residual heat of the steam condensate 19 fed from the regeneration heater 18, in which the rich solution is heated with the residual heat of the steam condensate. Therefore, the residual heat of the steam condensate 19 having been used in the regeneration heater 18 is effectively used. Furthermore, the rich solution 14 heated with the residual heat is introduced into the lower-portion regeneration tower 15-L, where it is regenerated.
The semi-lean solution 28, obtained by removing part of CO₂ from the rich solution 14 in the upper-portion regeneration tower 15-U, is extracted to the outside through the semi-lean-solution supply line 30, and the rich solution 14 is heat-exchanged with the residual heat of the semi-lean solution in the semi-lean-solution heat exchanger 29 interposed in the second rich-solution supply line 20-2 branched. Therefore, it is possible to increase the temperature of the rich solution 14 to be introduced into the regeneration tower 15, and as a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.

[0028] The ratio of division of the rich solution 14 into the first rich-solution supply line 20-1 and the second rich-solution supply line 20-2 at the branching node 24 is simply set to a range from 25:75 to 75:25.

[Third Comparative Embodiment]

[0029] Fig. 5 is a schematic of a CO₂ recovery system according to a third comparative embodiment.
Components the same as those in each of the CO₂ recovery systems according to the preceding embodiments are assigned with the same reference numerals, and explanation thereof is omitted.
As shown in Fig. 5, the CO₂ recovery system according to the third comparative embodiment. Includes the upper-portion regeneration tower 15-U, a middle-portion regeneration tower 15-M, and the lower-portion regeneration tower 15-L, which are obtained by dividing the regeneration tower 15 into three: upper, middle, and lower portions; the branching node 24 provided in the rich-solution supply line 20 and dividing the rich solution 14; the lean-solution heat exchanger 23 interposed in the first rich-solution supply line 20-1 branched; the semi-lean-solution heat exchanger 29 that is provided in the second rich-solution supply line 20-2, and heats the rich solution with the residual heat of the semi-lean solution 28 obtained by removing part of CO₂ from the rich solution in the upper-portion regeneration tower 15-U; and the steam-condensate heat exchanger 21 that extracts the semi-lean solution 28 obtained by removing part of CO₂ from the rich solution in the middle-portion degeneration tower 15-M, to the outside of the regeneration tower through an extraction line 41, and that heats the semi-lean solution 28 with the residual heat of the steam condensate 19. And, the end of the first rich-solution supply line 20-1 is connected to the middle-portion regeneration tower 15-M, the end of the second rich-solution supply line 20-2 is connected to the upper-portion regeneration tower 15-U, the extraction line 41 is connected to the lower-portion regeneration tower 15-L, and the end of the supply line 30 for supplying the semi-lean solution 28 is connected to the middle stage portion of the absorption tower 13.

[0030] The third comparative embodiment is configured to provide the steam-condensate heat exchanger 21 that heats the semi-lean solution 28 extracted through the extraction line 41, in which the semi-lean solution 28 is heated with the residual heat of the steam condensate 19. Therefore, the residual heat of the steam condensate 19 having been used in the regeneration heater 18 is effectively used, and as a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.
Furthermore, the rich solution 14 is heat-exchanged, using the lean solution 16 regenerated in the regeneration tower 15, in the lean-solution heat exchanger 23 interposed in the first rich-solution supply line 20-1, and the rich solution 14 heated with the residual heat is introduced into the middle-portion regeneration tower 15-M, which allows reduction in the supply amount of steam to be used in the regeneration tower.
The semi-lean solution 28, obtained by removing part of CO₂ from the rich solution in the upper-portion regeneration tower 15-U, is extracted to the outside through the semi-lean-solution supply line 30, and the rich solution 14 is heat-exchanged with the residual heat of the semi-lean solution 28 in the semi-lean-solution heat exchanger 29 interposed in the second rich-solution supply line 20-2 branched. Therefore, it is possible to increase the temperature of the rich solution 14 to be introduced into the upper-portion regeneration tower 15-U, and as a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.

[0031] The ratio of division of the rich solution 14 into the first rich-solution supply line 20-1 and the second rich-solution supply line 20-2 at the branching node 24 is simply set to a range from 25:75 to 75:25.

[Fourth comparative embodiment]

[0032] Fig. 6 is a schematic of a CO₂ recovery system according to a fourth comparative embodiment.
Components the same as those in each of the CO₂ recovery systems according to the preceding embodiments are assigned with the same reference numerals, and explanation thereof is omitted.
As shown in Fig. 6, the CO₂ recovery system according to the fourth comp. embodiment includes the upper-portion regeneration tower 15-U and the lower-portion regeneration tower 15-L, which are obtained by dividing the regeneration tower at least into two portions; and the steam-condensate heat exchanger 21 that heats the semi-lean solution 28, obtained by removing part of CO₂ from the rich solution, with the residual heat of the steam condensate, the semi-lean solution 28 having been extracted from the upper-portion regeneration tower 15-U through the extraction pipe 41. And the semi-lean solution 28 heated is supplied to the lower-portion regeneration tower 15-L.

[0033] The fourth comp. embodiment is configured to provide the steam-condensate heat exchanger 21 that heats the semi-lean solution 28 extracted through the extraction line 41, with the residual heat of the steam condensate 19 fed from the regeneration heater 18, in which the semi-lean solution 28 is heated with the residual heat of the steam condensate. Therefore, the residual heat of the steam condensate 19 having been used in the regeneration heater 18 is effectively used, and as a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.

[Fifth comparative embodiment]

[0034] Fig. 7 is a schematic of a CO₂ recovery system according to a fifth comparative embodiment.
Components the same as those in each of the CO₂ recovery systems according to the preceding embodiments are assigned with the same reference numerals, and explanation thereof is omitted.
As shown in Fig. 7, the CO₂ recovery system according to the fifth comparative embodiment includes, in addition to the system of the fourth comp. embodiment, a first branching node 24-1 provided in the rich-solution supply line 20 and dividing the rich solution 14; a first lean-solution heat exchanger 23-1 interposed in the first rich-solution supply line 20-1 branched at the first branching node 24-1; the semi-lean-solution heat exchanger 29 that is provided in the second rich-solution supply line 20-2 branched at the first branching node 24-1, and heats the rich solution 14 with the residual heat of the semi-lean solution 28 obtained by removing part of CO₂ from the rich solution in the upper-portion regeneration tower 15-U; a second lean-solution heat exchanger 23-2 in which the rich solution 14 joined at a joint 42 between the first rich-solution supply line 20-1 and the second rich-solution supply line 20-2, is heat-exchanged after the heat exchange in the semi-lean-solution heat exchanger 29; a second branching node 24-2 provided in the downstream side of the semi-lean-solution heat exchanger 29 provided in the supply pipe 30 for supplying the semi-lean solution 28; and the steam-condensate heat exchanger 21 interposed in a first semi-lean-solution supply line 30-1 branched at the second branching node 24-2. And the end of the first semi-lean-solution supply line 30-1 is connected to the lower-portion regeneration tower 15-L, and the end of a second semi-lean-solution supply line 30-2 branched at the second branching node 24-2 is connected to the middle stage portion of the absorption tower 13.

[0035] In the fifth comparative embodiment, the semi-lean solution heat exchanger 29 uses the residual heat of the semi-lean solution 28 extracted from the upper-portion regeneration tower 15-U to heat the rich solution 14, and the residual heat of the semi-lean solution 28 is thereby effectively used. Moreover, because the steam-condensate heat exchanger 21 is provided in the way in which part of the semi-lean solution 28 is returned again to the lower-portion regeneration tower 15-L through the first semi-lean-solution supply line 30-1, the semi-lean solution 28 can be heated with the residual heat of the steam condensate 19. The residual heat of the steam condensate 19 having been used in the regeneration heater 18 is thereby effectively used, and as a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.

[0036] One part of the rich solution 14 once divided is heat-exchanged in the semi-lean-solution heat exchanger 29, and the other part of the rich solution 14 divided is also heat-exchanged in the first lean-solution heat exchanger 23-1, and these parts of the rich solution 14 are jointed at the joint 42, and are further heat-exchanged in the second lean-solution heat exchanger 23-2, to be supplied to the upper-portion regeneration tower 15-U. The temperature of the rich solution 14 to be introduced into the regeneration tower thereby increases, and as a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.

[Sixth and seventh comparative embodiment]

[0037] Fig. 8 is a schematic of a CO₂ recovery system according to a sixth and seventh comparative embodiment.
Components the same as those in each of the CO₂ recovery systems according to the preceding embodiments are assigned with the same reference numerals, and explanation thereof is omitted.
As shown in Fig. 8, the CO₂ recovery system according to the sixth and seventh comparative embodiment of the invention includes the upper-portion regeneration tower 15-U and the lower-portion regeneration tower 15-L, which are obtained by dividing the regeneration tower at least into two portions; the first lean-solution heat exchanger 23-1 that is interposed in the extraction line 41 for extracting the semi-lean solution 28, obtained by removing part of CO₂ from the rich solution, from the upper-portion regeneration tower 15-U divided, and heats the semi-lean solution 28 with the residual heat of the lean solution 16 that flows through the lean-solution supply line 22; and the steam-condensate heat exchanger 21 that is provided in the downstream side of and adjacent to the first lean-solution heat exchanger 23-1 in the extraction line 41, and reheats the semi-lean solution 28 having been heated once, with the steam condensate 19. And the second lean-solution heat exchanger 23-2, which heats the rich solution 14 with the residual heat of the lean solution after the semi-lean solution 28 is heated, is provided in the rich-solution supply line 20.

[0038] In the sixth and seventh comparative embodiment, the semi-lean solution 28 extracted from the upper-portion regeneration tower 15-U is heated in the first lean-solution heat exchanger 23-1, and further heated in the steam-condensate heat exchanger 21, and the residual heat of the steam condensate 19 having been used in the regeneration heater 18 is thereby effectively used. As a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.

[0039] Furthermore, when the inside of the regeneration tower is divided into a plurality of stages and the semi-lean solution 28, extracted from each stage of the regeneration tower divided, is returned to the regeneration tower on the lower stage side, the semi-lean solution 28 is heat-exchanged in the lean-solution heat exchanger and the steam-condensate heat exchanger respectively. This causes the temperature of the semi-lean solution 28, which is regenerated in the regeneration tower 15, to be increased, and consequently, the supply amount of steam to be used in the regeneration tower 15 can be reduced.

[Eighth comparative embodiment]

[0040] Fig. 9 is a schematic of a CO₂ recovery system according to an eighth comparative embodiment. Components the same as those in each of the CO₂ recovery systems according to the preceding embodiments are assigned with the same reference numerals, and explanation thereof is omitted.
As shown in Fig. 9, the CO₂ recovery system according to the eighth comparative embodiment of the invention includes the upper-portion regeneration tower 15-U, the middle-portion regeneration tower 15-M, and the lower-portion regeneration tower 15-L, which are obtained by dividing the regeneration tower 15 into three: upper, middle, and lower portions; the first lean-solution heat exchanger 23-1 that heats the semi-lean solution 28, obtained by removing part of CO₂ from the rich solution and extracted from the upper-portion regeneration tower 15-U through a first extraction pipe 41-1, with the lean solution fed from the regeneration tower; the steam-condensate heat exchanger 21 that heats the semi-lean solution 28, obtained by removing part of CO₂ from the rich solution and extracted from the middle-portion regeneration tower 15-M through a second extraction pipe 41-2, with the steam condensate; the semi-lean-solution heat exchanger 29 that is provided in the rich-solution supply line 20, and heats the rich solution 14 with the part of the semi-lean solution 28 extracted from the middle-portion regeneration tower 15-M; and the second lean-solution heat exchanger 23-2 that is provided in the downstream side of the semi-lean-solution heat exchanger 29 in the rich-solution supply line 20, and heats the rich solution 14 with the residual heat of the lean solution 16 after the semi-lean solution 28 is heated. And the semi-lean solution heated is supplied to the lower stage side of the regeneration tower, and the semi-lean solution 28 after heat exchange is performed in the semi-lean-solution heat exchanger 29 is supplied to the middle stage portion of the absorption tower 13 through the semi-lean-solution supply pipe 30.

[0041] In the eighth comparative embodiment, the semi-lean solution 28 respectively extracted from the upper-portion regeneration tower 15-U and the middle-portion regeneration tower 15-M is heated in the first lean-solution heat exchanger 23-1 or in the steam-condensate heat exchanger 21, and the residual heat of the lean solution 16 and of the steam condensate 19 is thereby effectively used. As a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.
The residual heat of the semi-lean solution 28 after heat exchange is performed in the steam-condensate heat exchanger 21 is used for heating the rich solution, and the residual heat of the lean solution heat-exchanged in the first lean-solution heat exchanger 23-1 is used for heating the rich solution in the second lean-solution heat exchanger 23-2. It is thereby possible to increase the temperature of the rich solution 14 to be supplied to the regeneration tower 15, and as a result, the supply amount of steam to be used in the regeneration tower 15 can be reduced.

[0042] The exemplary examples indicating the effect of the present invention are explained below, but the present invention is not limited by the examples.

Example 1

[0043] A CO₂ recovery system according to example 1 of the present invention is explained below with reference to the following drawing.
Fig. 10 is a schematic of the CO₂ recovery system according to example 1.
As shown in Fig. 10, the CO₂-containing exhaust gas 11 supplied to the CO₂ absorption tower 13 is brought into countercurrent contact with the absorbing solution 12 in a filling portion, the absorbing solution 12 having predetermined concentration and being supplied from the nozzle 8. CO₂ in the combustion exhaust gas is absorbed and removed by the CO₂-absorbing solution 12, and the remaining CO₂-removed exhaust gas 10, from which CO₂ has been absorbed and removed, is fed to the outside. The absorbing solution 12 supplied to the CO₂ absorption tower 13 absorbs CO₂, and reaction heat due to the absorption causes the temperature of the absorbing solution 12 to become higher than normal temperature in a tower head. The absorbing solution having absorbed CO₂ is sent by a discharge pump 51 for the absorbing solution, as the rich solution 14, to the lean-solution heat exchanger 23 and the steam-condensate heat exchanger 21, where it is heated, to be introduced into the regeneration tower 15.

[0044] In the regeneration tower 15, the absorbing solution is regenerated by being heated with the steam 17 by the regeneration heater 18, cooled as the lean solution 16 by the lean-solution heat exchanger 23 and a cooler 52 provided as necessary, and is returned to the CO₂ absorption tower 13. In the upper portion of the regeneration tower 15, CO₂ separated from the absorbing solution is cooled by a regeneration-tower reflux condenser 53, the steam associated with CO₂ is separated from condensed reflux water in a CO₂ separator 54, and output to the outside of the system through a recovered-CO₂ discharge line 55. Reflux water 56 is flowed back to the regeneration tower 15 by a reflux pump 57.

[0045] In the example 1, the steam used in the regeneration heater 18 is introduced into a separator to be flashed, and the residual heat of the steam flashed as the steam condensate 19 is used for heating the rich solution 14 in the steam-condensate heat exchanger 21.

[0046] As a comparison, the case where the steam-condensate heat.exchanger 21 is not provided is shown in Fig. 22.

[0047] If the temperature of the rich solution 14 to be discharged from the absorption tower 13 was 50.5°C, the temperature was 114.2°C when only the lean-solution heat exchanger 23 was provided, while in the example 1, the steam-condensate heat exchanger 21 was provided, and the temperature thereby increased to 116.7°C, consequently, the amount of steam consumed in the regeneration tower 15 became 97.96 MMkcal/h.
In Fig. 10, temperature (°C) is surrounded by a rectangle, flow rate (t/h) is surrounded by a parallelogram, and the amount of heat (MMkcal/h) is represented with angled brackets. The same goes for Fig. 11 to Fig. 21.

[0048] The amount of steam consumed in the comparative example of Fig. 22 was 98.77 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 99.2%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 0.8%.

Example 2

[0049] A CO₂ recovery system according to example 2 of the present invention is explained below with reference to the following drawing.
Fig. 11 is a schematic of the CO₂ recovery system according to example 2. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 2, a flash drum 61 is provided in the downstream side of the steam-condensate heat exchanger 21 that heats the rich solution 14. In the upstream side of the flash drum 61, the rich solution 14 is heated in the steam-condensate heat exchanger 21, and therefore, CO₂ in the rich solution 14 can be removed in the flash drum 61.
The temperature of the rich solution fed from the flash drum 61 is 103.9°C, but because part of CO₂ has been removed, decreasing inlet temperature of the regeneration tower 15 causes the steam discharged from the tower head to be reduced, which is preferable.
In example 2, as the result, the amount of steam consumed in the regeneration tower 15 became 97.64 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 98.9%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 1.1%.

Example 3

[0050] A CO₂ recovery system according to example 3 of the present invention is explained below with reference to the following drawing.
Fig. 12 is a schematic of the CO₂ recovery system according to example 3. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 3, the flash drum 61 is provided in the upstream side of the steam-condensate heat exchanger 21 that heats the rich solution 14. In the downstream side of the flash drum 61, the rich solution 14 was heated in the steam-condensate heat exchanger 21, to thereby increase the temperature of the rich solution 14 to be supplied to the regeneration tower 15.
In example 3, as the result, the amount of steam consumed in the regeneration tower 15 became 97.27 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 98.5%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 1.5%.

Example 4 (Comparative)

[0051] A CO₂ recovery system according to example 4 is explained below with reference to the following drawing.
Fig. 13 is a schematic of the CO₂ recovery system according to example 4. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 4, the rich solution 14 was divided, part of the rich solution 14 divided was sent to the heat exchanger 31 of flash drum type, where the rich solution 14 was heat-exchanged with the steam from the steam condensate and CO₂ was removed from the rich solution 14. Using the residual heat of the semi-lean solution 28 after the heat exchange, the other part of the rich solution 14 divided was hear-exchanged in the semi-lean-solution heat exchanger 29, to increase the temperature of the rich solution 14 to be supplied to the regeneration tower 15.
In example 4, as the result, the amount of steam consumed in the regeneration tower 15 became 97.56 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 98.8%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 1.2%.

Example 5 (Comparative)

[0052] A CO₂ recovery system according to example 5 is explained below with reference to the following drawing.
Fig. 14 is a schematic of the CO₂ recovery system according to example 5. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 5, the rich solution 14 was divided, and part of the rich solution 14 divided was sent to the heat exchanger 31 of flash drum type, but on the way to the heat exchanger 31, the rich solution 14 was heat-exchanged with the residual heat of the steam condensate in the steam-condensate heat exchanger 21, to improve the removal rate of CO₂ from the rich solution 14 in the flash drum 31. Using the residual heat of the semi-lean solution 28 after the heat exchange, the other part of the rich solution 14 divided was heat-exchanged in the semi-lean-solution heat exchanger 29, to thereby increase the temperature of the rich solution 14 to be supplied to the regeneration tower 15.
In example 5, as the result, the amount of steam consumed in the regeneration tower 15 became 95.52 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 96.7%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 3.3%.

Example 6 (Comparative)

[0053] A CO₂ recovery system according to example 6 of the present invention is explained below with reference to the following drawing.
Fig. 15 is a schematic of the CO₂ recovery system according to example 6. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 6, the regeneration tower 15 was divided into two portions, the semi-lean solution 28 extracted from the upper-portion regeneration tower 15-U was heat-exchanged with the residual heat of the steam condensate 19 in the steam-condensate heat exchanger 21, and the semi-lean solution 28 heat-exchanged was returned to the lower-portion regeneration tower 15-L. This caused an increase in the temperature of the semi-lean solution to be supplied to the lower portion side of the regeneration tower 15.
In example 6, as the result, the amount of steam consumed in the regeneration tower 15 became 93.65 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 94.8%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 5.2%.

Example 7

[0054] A CO₂ recovery system according to example 7 of the present invention is explained below with reference to the following drawing.
Fig. 16 is a schematic of the CO₂ recovery system according to example 7. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 7, the regeneration tower 15 was divided into two portions, and the rich solution 14 was divided. The lean-solution heat exchanger 23 was provided in the first rich-solution supply line 20-1, and in the downstream side thereof, the steam-condensate heat exchanger 21 was provided, to thereby increase the temperature of the rich solution 14 to be supplied to the lower-portion regeneration tower 15-L. Furthermore, the semi-lean-solution heat exchanger 29, which uses the residual heat of the semi-lean solution 28 fed from the upper-portion regeneration tower 15-U, was provided in the second rich-solution supply line 20-2, to thereby increase the temperature of the rich solution to be supplied to the upper-portion regeneration tower 15-U.

[0055] The ratio of division of the rich solution 14 is such that the first rich solution was set to 70% and the second rich solution was set to 30%.
In example 7, as the result, the amount of steam consumed in the regeneration tower 15 became 93.58 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 94.8%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 5.2%.

Example 8 (Comparative)

[0056] A CO₂ recovery system according to example 8 is explained below with reference to the following drawing.
Fig. 17 is a schematic of the CO₂ recovery system according to example 8. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 8, the regeneration tower 15 was divided into two portions, and the semi-lean solution 28 extracted from the upper-portion regeneration tower 15-U was first heat-exchanged in the first lean-solution heat exchanger 23-1, and then, was heat-exchanged with the residual heat of the steam condensate 19 in the steam-condensate heat exchanger 21, and the semi-lean solution 28 heat-exchanged was returned to the lower-portion regeneration tower 15-L. This caused an increase in the temperature of the semi-lean solution to be supplied to the lower portion side of the regeneration tower 15.
In example 8, as the result, the amount of steam consumed in the regeneration tower 15 became 91.1 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 92.3%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 7.7%.

Example 9 (Comparative)

[0057] A CO₂ recovery system according to example 9 is explained below with reference to the following drawing.
Fig. 18 is a schematic of the CO₂ recovery system according to example 9. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 9, the regeneration tower 15 was divided into four portions such as a first regeneration tower 15-1, a second regeneration tower 15-2, a third regeneration tower 15-3, and a fourth regeneration tower 15-4. The semi-lean solution 28 respectively extracted from the first regeneration tower 15-1 and the third regeneration tower 15-3 was heat-exchanged with the respective residual heat of the steam condensate in a first steam-condensate heat exchanger 21-1 and a second steam-condensate heat exchanger 21-2, respectively. Because the temperature in the lower portion side of the regeneration tower was high, the residual heat of the steam condensate 19 was effectively used.

[0058] Furthermore, the semi-lean solution extracted from the second regeneration tower 15-2 was heat-exchanged with the residual heat of the lean solution 16 in the first lean-solution heat exchanger 23-1. The semi-lean solution 28 extracted from the first regeneration tower 15-1, before being returned to the second regeneration tower 15-2 in the lower stage side, was heat-exchanged in the second lean-solution heat exchanger 23-2 in which the semi-lean solution 28 was heat-exchanged with the residual heat of the lean solution 16 that had been heat-exchanged in the first lean-solution heat exchanger 23-1. In example 9, after the heat exchange, the rich solution 14 fed from the absorption tower 13 was heat-exchanged in a third lean-solution heat exchanger 23-3.
In example 9, as the result, the amount of steam consumed in the regeneration tower 15 became 85.49 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 86.6%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 13.4%.

Example 10 (Comparative)

[0059] A CO₂ recovery system according to example 10 is explained below with reference to the following drawing.
Fig. 19 is a schematic of the CO₂ recovery system according to example 10. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 10, the regeneration tower 15 was divided into three portions such as the upper-portion regeneration tower 15-U, the middle-portion regeneration tower 15-M, and the lower-portion regeneration tower 15-L. The semi-lean solution 28 extracted from the middle-portion regeneration tower 15-M was heat-exchanged with the residual heat of the steam condensate in the steam-condensate heat exchanger 21. Part of the semi-lean solution 28 extracted was supplied to the semi-lean-solution heat exchanger 29 that heats the rich solution 14, where the residual heat of the semi-lean solution was effectively used.
Furthermore, the semi-lean solution 28 extracted from the upper-portion regeneration tower 15-U was heat-exchanged with the residual heat of the lean solution 16 in the first lean-solution heat exchanger 23-1.
The rich solution 14 heat-exchanged in the semi-lean-solution heat exchanger 29 was heat-exchanged in the second lean-solution heat exchanger 23-2 in which the rich solution 14 was heat-exchanged with the residual heat of the lean solution 16 that had been heat-exchanged in the first lean-solution heat exchanger 23-1.
In example 10, as the result, the amount of steam consumed in the regeneration tower 15 became 91.9 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 93.0%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 7%.

Example 11 (Comparative)

[0060] A CO₂ recovery system according to example 11 is explained below with reference to the following drawing.
Fig. 20 is a schematic of the CO₂ recovery system according to example 11. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 11, the regeneration tower 15 was divided into two portions such as the upper-portion regeneration tower 15-U and the lower-portion regeneration tower 15-L. The semi-lean solution 28, extracted from the upper-portion regeneration tower 15-U, was used to heat the rich solution in the second rich-solution supply line 20-2, in the semi-lean-solution heat exchanger 29. Thereafter, the semi-lean solution 28 was divided, to be heat-exchanged with the residual heat of the steam condensate in the steam-condensate heatexchanger21 before being supplied to the lower-portion regeneration tower 15-L. The rich solution in the first rich-solution supply line 20-1 was heat-exchanged in the first lean-solution heat exchanger 23-1, was jointed with the other one to be heat-exchanged with the residual heat of the lean solution 16 in the second lean-solution heat exchanger 23-2, and was supplied to the regeneration tower 15.
In example 11, as the result, the amount of steam consumed in the regeneration tower 15 became 93.96 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 95.1%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 4.9%.

Example 12 (Comparative)

[0061] A CO₂ recovery system according to example 12 is explained below with reference to the following drawing.
Fig. 21 is a schematic of the CO₂ recovery system according to example 12. Components the same as those of example 1 are assigned with the same reference numerals and explanation thereof is omitted.
In example 12, the regeneration tower 15 was divided into three portions such as the upper-portion regeneration tower 15-U, the middle-portion regeneration tower 15-M, and the lower-portion regeneration tower 15-L. The semi-lean solution 28 extracted from the middle-portion regeneration tower 15-M was heat-exchanged with the residual heat of the steam condensate in the steam-condensate heat exchanger 21.
Furthermore, the rich solution 14 was divided, and the lean-solution heat exchanger 23 was provided in the first rich-solution supply line 20-1. The semi-lean-solution heat exchanger 29 was provided in the second rich-solution supply line 20-2 where heat exchange was performed using the semi-lean solution 28 extracted from the upper-portion regeneration tower 15-U, so that the residual heat of the semi-lean solution was effectively used.
In example 12, as the result, the amount of steam consumed in the regeneration tower 15 became 91.14 MMkcal/h. Assuming the comparative example is 100, the amount of steam consumed in this example becomes 92.3%. Therefore, the reduction rate of specific steam consumption (improvement effect) was 7.7%.

INDUSTRIAL APPLICABILITY

[0062] The CO₂ recovery system according to the present invention is suitable for reduction in the supply amount of heated steam used in the regeneration tower by effectively using the residual heat of the steam condensate and the residual heat of the semi-lean solution.

Claims

1. A CO₂ recovery system including an absorption tower (13) that contacts CO₂-containing gas with a CO₂-absorbing solution to remove CO₂ and a regeneration tower (15) that regenerates a rich solution having absorbed CO₂, and reusing a lean solution, obtained by removing CO₂ from the rich solution in the regeneration tower, in the absorption tower, comprising:

a regeneration heater (18) that extracts the lean solution recovered near a bottom portion of the regeneration tower (15) to the outside, and heat-exchanges the lean solution with saturated steam; and

a steam-condensate heat exchanger (21) that

heats the rich solution to be supplied to the regeneration tower (15) with residual heat of steam condensate fed from the regeneration heater,

the CO₂ recovery system further comprising:

a rich-solution supply line (20) that conveys the rich solution from the absorption tower (13) to the regeneration tower (15);

a lean solution supply line (22) that extracts the lean solution from the regeneration tower (15) and conveys extracted lean solution to the absorption tower (13); and

a lean-solution heat exchanger (23) that is interposed in the rich-solution supply line (20) and the lean-solution supply line (22), and heats the rich solution in the rich-solution supply line (20) with residual heat of the lean solution in the lean-solution supply line (22),

wherein the steam-condensate heat exchanger (21) heats the rich solution to be supplied to the regeneration tower (15) at a position downstream of the lean-solution heat exchanger (23).

2. A CO₂ recovery system including an absorption tower (13) that contacts CO₂-containing gas with a CO₂-absorbing solution to remove CO₂ and a regeneration tower (15) that regenerates a rich solution having absorbed CO₂, and reusing a lean solution, obtained by removing CO₂ from the rich solution in the regeneration tower, in the absorption tower, comprising:

a regeneration heater (18) that extracts the lean solution recovered near a bottom portion of the regeneration tower (15) to the outside, and heat-exchanges the lean solution with saturated steam; and

a steam-condensate heat exchanger (21) that

heats the rich solution to be supplied to the regeneration tower (15) with residual heat of steam condensate fed from the regeneration heater,
the regeneration tower (15) including an upper-portion regeneration tower (15-U) and a lower-portion regeneration tower (15-L), and the CO₂ recovery system further comprising:

a rich-solution supply line (20) that conveys the rich solution from the absorption tower (13) to the regeneration tower (15);

a branching node (24) provided in the rich-solution supply line (20) and that branches the rich-solution supply line (20) into a first rich-solution supply line (20-1) and a second rich-solution supply line (20-2), wherein the steam-condensate heat exchanger (21) is provided in the first rich-solution supply line (20-1) and heats the rich solution in the first rich-solution supply line (20-1) with residual heat of the steam condensate;

a semi-lean-solution supply line (30) that extracts semi-lean solution from the upper-portion regeneration tower (15-U) and conveys extracted semi-lean solution to a middle stage portion of the absorption tower (13);

a semi-lean-solution heat exchanger (29) that is provided in the second rich-solution supply line (20-2) and the semi-lean-solution supply line (30), and heats the rich solution in the second rich-solution supply line (20-2) with residual heat of the semi-lean solution (28) in the semi-lean solution supply line (30), and

a lean-solution supply line (22) that extracts the lean solution from the regeneration tower (15) and conveys extracted lean solution to the absorption tower (13); and a lean-solution heat exchanger (23) that is interposed in the first rich-solution supply line (20-1) and the lean-solution supply line (22), and heats the rich solution in the first rich-solution supply line (20-1) with residual heat of the lean solution in the lean-solution supply line (22),

wherein the steam-condensate heat exchanger (21) heats the rich solution to be supplied to the regeneration tower (15) at a position downstream of the lean-solution heat exchanger (23),

wherein
one end of the first rich-solution supply line (20-1) being connected to the lower-portion regeneration tower (15-L), and
one end of the second rich-solution supply line (20-2) being connected to the upper-portion regeneration tower (15-U).

Ansprüche

1. CO₂-Rückgewinnungssystem, welches einen Absorptionsturm (13), der CO₂-haltiges Gas mit einer CO₂-absorbierenden Lösung in Kontakt bringt, um CO₂ zu entfernen, und einen Regenerationsturm (15), der eine reiche Lösung, die CO₂ absorbiert hat, regeneriert, enthält und welches eine magere Lösung, die durch Entfernen von CO₂ aus der reichen Lösung in dem Regenerationsturm erhalten wird, in dem Absorptionsturm wiederverwendet und umfasst:

eine Regenerationsheizvorrichtung (18), welche die in der Nähe eines unteren Bereichs des Regenerationsturms (15) wiedergewonnene magere Lösung nach außen entnimmt und einen Wärmeaustausch der mageren Lösung mit gesättigtem Dampf durchführt; und

einen Dampf-Kondensat-Wärmetauscher (21), der die reiche Lösung, die dem Regenerationsturm (15) zuzuführen ist, mit der Restwärme des Dampfkondensats, das aus der Regenerationsheizvorrichtung eingespeist wird, erwärmt, das CO₂-Rückgewinnungssystem weiterhin umfasst:

eine Versorgungsleitung für die reiche Lösung (20), welche die reiche Lösung von dem Absorptionsturm (13) zu dem Regenerationsturm (15) befördert;

eine Versorgungsleitung für die magere Lösung (22), welche die magere Lösung dem Regenerationsturm (15) entnimmt und die entnommene magere Lösung zu dem Absorptionsturm (13) befördert; und

einen Wärmetauscher für die magere Lösung (23), der zwischen der Versorgungsleitung für die reiche Lösung (20) und der Versorgungsleitung für die magere Lösung (22) angeordnet ist und die reiche Lösung in der Versorgungsleitung für die reiche Lösung (20) mit Restwärme der mageren Lösung in der Versorgungsleitung für die magere Lösung (22) erwärmt,

wobei der Dampf-Kondensat-Wärmetauscher (21) die dem Regenerationsturm (15) zuzuführende reiche Lösung an einer Stelle, die dem Wärmetauscher für die magere Lösung (23) nachgeschaltet ist, erwärmt.

2. CO₂-Rückgewinnungssystem, welches einen Absorptionsturm (13), der CO₂-haltiges Gas mit einer CO₂-absorbierenden Lösung in Kontakt bringt, um CO₂ zu entfernen, und einen Regenerationsturm (15), der eine reiche Lösung, die CO₂ absorbiert hat, regeneriert, enthält und welches eine magere Lösung, die durch Entfernen von CO₂ aus der reichen Lösung in dem Regenerationsturm erhalten wird, in dem Absorptionsturm wiederverwendet und umfasst:

eine Regenerationsheizvorrichtung (18), welche die in der Nähe eines unteren Bereichs des Regenerationsturms (15) wiedergewonnene magere Lösung nach außen entnimmt und einen Wärmeaustausch der mageren Lösung mit gesättigtem Dampf durchführt; und

einen Dampf-Kondensat-Wärmetauscher (21), der die reiche Lösung, die dem Regenerationsturm (15) zuzuführen ist, mit der Restwärme des Dampfkondensats, das aus der Regenerationsheizvorrichtung eingespeist wird, erwärmt, wobei der Regenerationsturm (15) einen oberen Regenerationsturmbereich (15-U) und einen unteren Regenerationsturmbereich (15-L) enthält und das CO₂-Rückgewinnungssystem weiterhin umfasst:

eine Versorgungsleitung für die reiche Lösung (20), welche die reiche Lösung von dem Absorptionsturm (13) zu dem Regenerationsturm (15) befördert;

einen Verzweigungsknoten (24), der sich in der Versorgungsleitung für die reiche Lösung (20) befindet und der die Versorgungsleitung für die reiche Lösung (20) in eine erste Versorgungsleitung für die reiche Lösung (20-1) und eine zweite Versorgungsleitung für die reiche Lösung (20-2) verzweigt, wobei der Dampf-Kondensat-Wärmetauscher (21) sich in der ersten Versorgungsleitung für die reiche Lösung (20-1) befindet und die reiche Lösung in der ersten Versorgungsleitung für die reiche Lösung (20-1) mit Restwärme des Dampfkondensats erwärmt;

eine Versorgungsleitung für die halbmagere Lösung (30), die die halbmagere Lösung aus dem oberen Regenerationsturmbereich (15-U) entnimmt und die entnommene halbmagere Lösung zu einem mittleren Abschnittsbereich des Absorptionsturms (13) befördert;

einen Wärmetauscher für die halbmagere Lösung (29), der sich in der zweiten Versorgungsleitung für die reiche Lösung (20-2) und der Versorgungsleitung für die halbmagere Lösung (30) befindet und die reiche Lösung in der zweiten Versorgungsleitung für die reiche Lösung (20-2) mit Restwärme der halbmageren Lösung (28) in der Versorgungsleitung für die halbmagere Lösung (30) erwärmt, und

eine Versorgungsleitung für die magere Lösung (22), die die magere Lösung aus dem Regenerationsturm (15) extrahiert und die extrahierte magere Lösung zu dem Absorptionsturm (13) befördert; und einen Wärmetauscher für die magere Lösung (23), der zwischen der ersten Versorgungsleitung für die reiche Lösung (20-1) und der Versorgungsleitung für die magere Lösung (22) angeordnet ist und die reiche Lösung in der ersten

Versorgungsleitung für die reiche Lösung (20-1) mit Restwärme der mageren Lösung in der Versorgungsleitung für die magere Lösung (22) erwärmt,

wobei der Dampf-Kondensat-Wärmetauscher (21) die dem Regenerationsturm (15) zuzuführende reiche Lösung an einer Stelle, die dem Wärmetauscher für die magere Lösung (23) nachgeschaltet ist, erwärmt,

wobei

ein Ende der ersten Versorgungsleitung für die reiche Lösung (20-1) mit dem unteren Regenerationsturmbereich (15-L) verbunden ist und

ein Ende der zweiten Versorgungsleitung für die reiche Lösung (20-2) mit dem oberen Regenerationsturmbereich (15-U) verbunden ist.

Revendications

1. Système de récupération de CO₂ incluant une tour d'absorption (13) qui met en contact un gaz contenant du CO₂ avec une solution d'absorption de CO₂ pour retirer le CO₂ et une tour de régénération (15) qui régénère une solution riche ayant absorbé du CO₂, et réutilisant une solution pauvre, obtenue en retirant le CO₂ de la solution riche dans la tour de régénération, dans la tour d'absorption, comprenant :

un réchauffeur de régénération (18) qui extrait la solution pauvre récupérée à proximité d'une partie inférieure de la tour de régénération (15) vers l'extérieur, et échange la chaleur entre la solution pauvre et une vapeur saturée ; et

un échangeur de chaleur à condensat de vapeur (21) qui chauffe la solution riche à fournir à la tour de régénération (15) avec la chaleur résiduelle d'un condensat de vapeur fourni par le réchauffeur de régénération,

le système de récupération de CO₂ comprenant en outre :

une ligne d'alimentation en solution riche (20) qui transporte la solution riche de la tour d'absorption (13) à la tour de régénération (15) ;

une ligne d'alimentation en solution pauvre (22) qui extrait la solution pauvre de la tour de régénération (15) et transporte la solution pauvre extraite à la tour d'absorption (13) ; et

un échangeur de chaleur à solution pauvre (23) qui est interposé dans la ligne d'alimentation en solution riche (20) et la ligne d'alimentation en solution pauvre (22), et chauffe la solution riche dans la ligne d'alimentation en solution riche (20) avec la chaleur résiduelle de la solution pauvre dans la ligne d'alimentation en solution pauvre (22),

dans lequel l'échangeur de chaleur à condensat de vapeur (21) chauffe la solution riche à fournir à la tour de régénération (15) à une position en aval de l'échangeur de chaleur à solution pauvre (23).

2. Système de récupération de CO₂ incluant une tour d'absorption (13) qui met en contact un gaz contenant du CO₂ avec une solution d'absorption de CO₂ pour retirer le CO₂ et une tour de régénération (15) qui régénère une solution riche ayant absorbé du CO₂, et réutilisant une solution pauvre, obtenue en retirant le CO₂ de la solution riche dans la tour de régénération, dans la tour d'absorption, comprenant :

un réchauffeur de régénération (18) qui extrait la solution pauvre récupérée à proximité d'une partie inférieure de la tour de régénération (15) vers l'extérieur, et échange la chaleur entre la solution pauvre et une vapeur saturée ; et

un échangeur de chaleur à condensat de vapeur (21) qui chauffe la solution riche à fournir à la tour de régénération (15) avec la chaleur résiduelle d'un condensat de vapeur fourni par le réchauffeur de régénération,

la tour de régénération (15) incluant une tour de régénération de partie supérieure (15-U) et une tour de régénération de partie inférieure (15-L), et le système de récupération de CO₂ comprenant en outre :

une ligne d'alimentation en solution riche (20) qui transporte la solution riche de la tour d'absorption (13) à la tour de régénération (15) ;

un nœud de ramification (24) prévu dans la ligne d'alimentation en solution riche (20) et qui ramifie la ligne d'alimentation en solution riche (20) en une première ligne d'alimentation en solution riche (20-1) et une seconde ligne d'alimentation en solution riche (20-2), dans lequel l'échangeur de chaleur à condensat de vapeur (21) est prévu dans la première ligne d'alimentation en solution riche (20-1) et chauffe la solution riche dans la première ligne d'alimentation en solution riche (20-1) avec la chaleur résiduelle du condensat de vapeur ;

une ligne d'alimentation en solution semi-pauvre (30) qui extrait une solution semi-pauvre de la tour de régénération de partie supérieure (15-U) et transporte la solution semi-pauvre extraite à une partie d'étage intermédiaire de la tour d'absorption (13) ;

un échangeur de chaleur à solution semi-pauvre (29) qui est prévu dans la seconde ligne d'alimentation en solution riche (20-2) et la ligne d'alimentation en solution semi-pauvre (30), et chauffe la solution riche dans la seconde ligne d'alimentation en solution riche (20-2) avec la chaleur résiduelle de la solution semi-pauvre (28) dans la ligne d'alimentation en solution semi-pauvre (30), et

une ligne d'alimentation en solution pauvre (22) qui extrait la solution pauvre de la tour de régénération (15) et transporte la solution pauvre extraite à la tour d'absorption (13) ; et un échangeur de chaleur à solution pauvre (23) qui est interposé dans la première ligne d'alimentation en solution riche (20-1) et la ligne d'alimentation en solution pauvre (22), et chauffe la solution riche dans la première ligne d'alimentation en solution riche (20-1) avec la chaleur résiduelle de la solution pauvre dans la ligne d'alimentation en solution pauvre (22),

dans lequel l'échangeur de chaleur à condensat de vapeur (21) chauffe la solution riche à fournir à la tour de régénération (15) à une position en aval de l'échangeur de chaleur à solution pauvre (23),

dans lequel

une extrémité de la première ligne d'alimentation en solution riche (20-1) est reliée à la tour de régénération de partie inférieure (15-L), et

une extrémité de la seconde ligne d'alimentation en solution riche (20-2) est reliée à la tour de régénération de partie supérieure (15-U).

Drawing