AU2014200927B2

AU2014200927B2 - Carbon dioxide recovery method and carbon-dioxide-recovery-type steam power generation system

Info

Publication number: AU2014200927B2
Application number: AU2014200927A
Authority: AU
Inventors: Hideo Kitamura; Toshihisa Kiyokuni; Yuya Murakami; Nobuo Okita; Takeshi Sasanuma; Takeo Suga; Takeo Takahashi; Mikio Takayanagi
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2010-10-22
Filing date: 2014-02-21
Publication date: 2016-03-31
Anticipated expiration: 2031-10-21
Also published as: AU2014200927A1

Abstract

According to one embodiment, a carbon-dioxide-recovery-type steam power generation system 5 comprises a boiler that produces steam and generates an exhaust gas by combusting fuel, a first turbine that is connected to a generator and is rotationally driven by the steam supplied from the boiler, an absorption tower that is supplied with the exhaust gas from the boiler and allows carbon dioxide contained 10 in the exhaust gas to be absorbed into an absorption liquid, a regeneration tower that is supplied with the absorption liquid absorbing the carbon dioxide from the absorption tower, discharges a carbon dioxide gas from the absorption liquid, and discharges the carbon dioxide gas, a reboiler that heats the 15 absorption liquid from the regeneration tower and supplies the generated steam to the regeneration tower,. a condenser that removes moisture from the carbon dioxide gas, discharged from th-e regeneration tower, by condensing the carbon dioxide gas using cooling water, a compressor that compresses the carbon 20 dioxide gas from which the moisture is removed by the condenser, and a second turbine that drives the compressor. The steam produced by the cooling water recovering the heat from the carbon dioxide gas in the condenser is supplied to the first turbine or the second turbine.

Description

H:spuumenvovenuNmrormnusl.Lwamouzv1AJIz aac-I4iAmoU4 1 This is a divisional of Australian Patent Application No. 2011239263 the entire contents of which are incorporated herein by reference. FIELD 5 Embodiments described herein relate generally to a carbon-dioxide-recovery-type steam power generation system and a carbon dioxide recovery method. BACKGROUND In a power generation system such as a thermal power plant using a large amount 10 of fossil fuel, an amine absorption method is employed as a method of removing and recovering carbon dioxide that is one of causes of global warming. However, in the amine absorption method, thermal energy obtained from a great amount of steam having low pressure (for example, approximately 0.3 MPa) is required to regenerate an absorption liquid having absorbed carbon dioxide. 15 In order to compensate this thermal energy, there is proposed a method of joining condensate, which is branched from a turbine condensate system, to a deaerator after performing heat exchanging between the amount of heat of absorbed carbon dioxide and the amount of heat generated by compressing carbon dioxide to high pressure (for example, approximately 8 MPa) that is suitable for injecting carbon dioxide into the 20 ground. However, there has been a problem in that the amount of condensate is not enough to recover the total amount of heat of carbon dioxide. As a result, the amount of condensate flowing in a low-pressure heater is reduced, the amount of gas extracted from a turbine is reduced, and the heat dumped to a steam condenser is increased, so that the 25 effect of a regeneration cycle in the related art is decreased. For this reason, thee has been a problem in that the output of the turbine is not particularly increased by the amount of recovered heat.

2 Further, in the injection of the recovered carbon dioxide into the ground, carbon dioxide needs to be compressed to be a high pressure. However, in order to ensure the power source of such a compression, the output of the power plant is excessively 5 and inevitably decreased. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 Is a diagram Illustrating the schematic structure of a carbon-dioxide-recovery-type steam power generation system 10 according to a first embodiment; Fig. 2 is a diagram illustrating the schematic structure of a carbon-dioxide-recovery-type steam power generation system according to a second embodiment; Fig. 3 is a diagram illustrating the schematic structure of 15 a carbon-dioxide-recovery-type steam power generation system according to a third embodiment; Fig. 4 is a diagram Illustrating the schematic structure of a carbon-dioxide-recovery-type steam power generation system according to a fourth embodiment; 20 Fig. 5 is a diagram illustrating the schematic structure of a carbon-dioxide-recovery-type steam power generation system according to a modified example; Fig. 6 is a diagram Illustrating the schematic structure of a carbon-dioxide- recovery-type steam power generation system 25 according to a fifth embodiment; and Fig. 7 is a diagram illustrating the schematic structure of a carbon-dioxide-recovery-type steam power generation system according to a sixth embodiment. 30 DETAILED DESCRIPTION According to one embodiment, a carbon-dioxide-recovery-type steam power generation system comprises a boiler that produces steam and generates an exhaust gas by combusting fuel, a first turbine that is connected 35 to a generator and is rotationally driven by the steam supplied from the boiler, an absorption tower that is supplied with the 3 exhaust gas from the boiler and allows carbon dioxide contained in the exhaust gas to be absorbed into an absorption liquid, a regeneration tower that is supplied with the absorption liquid absorbing the carbon dioxide from the absorption tower, 5 discharges a carbon dioxide gas from the absorption liquid, and discharges the carbon dioxide gas, a reboiler that heats the absorption liquid from the regeneration tower and supplies the generated steam to the regeneration tower, a condenser that removes moisture from the carbon dioxide gas, discharged from 10 the regeneration tower, by condensing the carbon dioxide gas using cooling water, a compressor that compresses the carbon dioxide gas from which the moisture is removed by the condenser, and a second turbine that drives the compressor. The steam produced by the cooling water recovering the heat 15 from the carbon dioxide gas in the condenser is supplied to the first turbine or the second turbine, Embodiments will now be explained with reference to the accompanying drawings. (First Embodiment) 20 Fig. 1 illustrates an overall structure of a carbon-dioxide-recovery-type steam power generation system according to a first embodiment. A carbon -dioxide-recovery-type steam power generation system 1 includes a steam power generation plant la that produces 25 turbine steam 4 through the combustion of fuel and generates power by rotationally driving a turbine and a carbon dioxide recovery plant lb that recovers carbon dioxide from an exhaust gas 5 produced in a boiler 6 by using an absorption liquid which absorbs carbon dioxide contained in the exhaust gas 5. 30 The boiler 6 is supplied with fuel and air for combustion and fuel is combusted in a furnace, so that the turbine steam 4 is produced and the exhaust gas 5 Is generated. The boiler 6 includes a superheater 9 that generates main steam by heating the turbine steam 4 through the combustion in the furnace and 35 a reheater 10 that is provided adjacent to the superheater 9 and generates reheat steam by reheating the turbine steam 4 4 which is supplied from the superheater 9 through a high-pressure steam turbine 21 to be described below. The steam power generation plant la includes a high-pressure steam turbine (high-pressure turbine) 21 that is 5 rotationally driven by the turbine steam 4 (main steam) supplied from the superheater 9 of the boiler 6 and an intermediate-pressure steam turbine (Intermediate-pressure turbine) 22 that is connected to the high-pressure turbine 21 by a turbine shaft 20 and is rotationally driven by the turbine 10 steam 4 (reheat steam) supplied from the high-pressure turbine 21 through the reheater 10 of the boiler 6. Further, a low-pressure steam turbine (low-pressure turbine) 23 is connected to the intermediate-pressure turbine 22 by the turbine shaft 20, and the low-pressure turbine 23 is configured 15 to be rotationally driven by the turbine steam 4 (exhaust steam (Intermediate-pressure exhaust steam) from the intermediate-pressure turbine 22) supplied from the intermediate-pressure turbine 22. Furthermore, a generator 24, which generates power by the rotation of the turbine shaft 20, 20 is connected to the turbine shaft 20. Furthermore, in the embodiment, the rotating shafts of the high-pressure turbine 21, the intermediate-pressure turbine 22, the low-pressure turbine 23, and the generator 24 are connected to each other so as to form one turbine shaft 20. 25 However, the embodiment is not limited to this structure. The steam power generation plant la may include two or more turbine shafts each including at least one steam turbine and a plurality of generators connected to the respective turbine shafts. 30 A steam condenser 26, which generates condensate 27 by cooling and condensing the turbine steam (exhaust steam (low-pressure exhaust steam) from the low-pressure turbine 23) discharged from the low-pressure turbine 23, is provided below the low-pressure turbine 23. The condensate 27 discharged 35 from the steam condenser 26 is sent to the downstream side of a line 28 by a condensate pump 31, and is sent to the boiler 6 5 by a water supply pump 34 through a line 33. As shown in Fig. 1, the carbon dioxide recovery plant lb is provided with a known carbon dioxide separation and recovery plant 40 to which the exhaust gas 5 is supplied from 5 the boiler 6 and which separates and recovers carbon dioxide contained In the exhaust gas 5. The carbon dioxide separation and recovery plant 40 includes an absorption tower (not shown) that absorbs carbon dioxide contained in the exhaust gas 5 into a carbon dioxide absorption liquid and a regeneration tower (not 10 shown) to which the absorption liquid (rich liquid) absorbing the carbon dioxide is supplied from the absorption tower and which discharges a carbon dioxide gas 42 containing water vapor by emitting the carbon dioxide gas from the rich liquid and regenerates the absorption liquid. The absorption liquid 15 regenerated In the regeneration tower is supplied to the absorption tower. An amine compound aqueous solution, which is obtained by dissolving an amine compound in water, may be used as the absorption liquid that is used to absorb carbon dioxide. 20 The regeneration tower is provided with a reboiler 41. The reboiler 41 allows the temperature of the lean liquid (regenerated absorption liquid having a small content of carbon dioxide) to rise and produces steam by heating a part of the lean liquid stored In the regeneration tower and supplies the 25 steam to the regeneration tower. When the lean liquid is heated in the reboller 41, a carbon dioxide gas is discharged from the lean liquid, and is supplied to the regeneration tower together with the absorption liquid steam. The absorption liquid steam ascends in the regeneration tower, and heats the 30 rich liquid. Therefore, the carbon dioxide gas is discharged from the rich liquid. Steam 18, which Is extracted or exhausted from the high-pressure turbine 21, the intermediate-pressure turbine 22, or the low-pressure turbine 23 and decreases in temperature to 35 a temperature appropriate for heating a carbon dioxide absorption liquid by a temperature decreasing unit 44, is 6 supplied to the reboller 41. Any one of the steams of the high-pressure turbine 21, the intermediate-pressure turbine 22, or the low-pressure turbine 23 may be selected by valves 37 to 39. 5 The steam discharged from the reboller 41 is joined as drainage to the appropriate position in the line 28 between the condensate pump 31 and the water supply pump 34. As shown In Fig. 1, the carbon dioxide gas 42 containing water vapor discharged from the top portion of the regeneration 10 tower of the carbon dioxide separation and recovery plant 40 Is supplied to a CO 2 condenser (condenser) 51. The water vapor (moisture) condensed by the CO 2 condenser 51 is returned to the regeneration tower of the carbon dioxide separation and recovery plant 40 (not shown). 15 A carbon dioxide 52 from which the water vapor (moisture) is removed to increase purity by the CO 2 condenser 51 is compressed by compressors 53 and 54 into a high pressure state (for example, approximately 8 MPa) which is appropriate to be injected into the ground. The carbon dioxide 20 52 compressed by the compressor 53 is cooled by an intermediate cooler 55 and Is compressed by the compressor 54. Further, the carbon dioxide 52 compressed by the compressor 54 is cooled by an exit cooler 56. When the intermediate cooler 55 and the exit cooler 56 are provided in this way, it is 25 possible to improve the compressing efficiency and recover heat from the carbon dioxide 52 increasing in temperature with the compressing. The compressors 53 and 54 are coaxially connected to a turbine (driving turbine) 57 and a motor 58 driving the 30 compressors 53 and 54. The motor 58 is supplied with, for example, electric power generated by the generator 24. A turbine 57 Is supplied with steam 62, which is generated by the heat-exchanging between cooling water 61 and the carbon dioxide gas 42 containing water vapor In the CO 2 condenser 51, 35 and the steam is used to drive the turbine 57. Accordingly, the heat recovered by the CO 2 condenser 51 may be used as the 7 power of the turbine 57, and may supplement a part of the power of the compressors 53 and 54. The steam discharged from the turbine 57 is changed into condensate by a steam condenser 63, and is sent as the 5 cooling water 61 to the CO 2 condenser 51 by a pump 64. In this way, in the embodiment, the thermal energy of the carbon dioxide 42 emitted from the regeneration tower of the carbon dioxide separation and recovery plant 40 may be recovered, and the generated steam may be supplied to the 10 compressor-driven turbine 57 so as to supplement a part of power of the compressors 53 and 54. For this reason, the carbon-dioxide- recovery-type steam power generation system 1 may efficiently recover the thermal energy and realize the high thermal efficiency. Further, the carbon-dioxide-recovery-type 15 steam power generation system 1 may suppress degradation of the output of the steam power generation plant la in accordance with the ensured power source for compressing the carbon dioxide. (Second Embodiment) 20 Fig. 2 illustrates a schematic structure of a carbon-dioxide-recovery-type steam power generation system according to a second embodiment. This embodiment is different from the first embodiment shown in Fig. 1 in that the cooling water 61 performs the heat exchanging between the 25 carbon dioxide gas 42 containing water vapor and the steam 18 for heating the reboiler. In Fig. 2, the same portions as the portions of the first embodiment shown In Fig. 1 are denoted by the same reference numerals. The description thereof will not be repeated. 30 As shown in Fig. 2, the cooling water 61 exchanges heat with the carbon dioxide gas 42 containing water vapor in the

CO

2 condenser 51, and then exchanges heat with the steam 18 which Is a heat source of the reboller 41 in the temperature decreasing unit 44. The steam 62 generated by the heat 35 exchanging between the carbon dioxide gas 42 containing water vapor and the steam 18 is supplied to the turbine 57, and 8 supplements a part of the power of the compressors 53 and 54. That is, in the embodiment, the steam 18 extracted or exhausted from the high-pressure turbine 21, the intermediate-pressure turbine 22, or the low-pressure turbine 5 23 is guided to the reboller 41 so as to be used as a heat source of the absorption liquid used to absorb the carbon dioxide, and is also used as a heat source of the steam 62 which drives the turbine 57. In this way, the carbon-dioxide-recovery-type steam 10 power generation system 1 according to the embodiment may more efficiently recover the thermal energy and realize the higher thermal efficiency by recovering heat from the steam 18 for heating the reboiler. (Third Embodiment) 15 Fig. 3 illustrates a schematic structure of a carbon-dioxide-recovery-type steam power generation system according to a third embodiment. This embodiment is different from the second embodiment shown In Fig. 2 in that the system includes a valve 71 adjusting the flow rate of the cooling water 20 61 and a control unit 72 measuring the temperature of the steam 18 decreased in temperature by the temperature decreasing unit 44 and controlling the opening degree of the valve 71. In Fig. 3, the same portions as the portions of the second embodiment shown In Fig. 2 are denoted by the same 25 reference numerals. The description thereof will not be repeated. The valve 71 is provided between the pump 64 and the

CO

2 condenser 51, and may change the flow rate of the cooling water 61 supplied to the CO2 condenser 51 and the temperature 30 decreasing unit 44, that is, the flow rate of the cooling water 61 exchanging heat with the carbon dioxide gas 42 containing water vapor and the steam 18 in accordance with the opening degree of the valve 71. The control unit 72 measures the temperature of the 35 steam 18 passing through the temperature decreasing unit 44, and controls the opening degree of the valve 71 so that the 9 temperature of the steam 18 supplied to the reboiler 41 becomes a temperature necessary for emitting the carbon dioxide from the absorption liquid in the regeneration tower of the carbon dioxide separation and recovery plant 40. 5 Specifically, in the case where the measurement temperature of the steam 18 is higher than the necessary temperature, the opening degree of the valve 71 Is made to be large so as to increase the flow rate of the cooling water 61. Accordingly, the amount of the cooling water 61 exchanging 10 heat with the steam 18 in the temperature decreasing unit 44 increases, and hence the temperature of the steam 18 supplied to the reboiler 41 decreases. On the other hand, in the case where the measurement temperature of the steam 18 is lower than the necessary 15 temperature, the opening degree of the valve 71 is made to be small so as to decrease the flow rate of the cooling water 61. Accordingly, the amount of the cooling water 61 exchanging heat with the steam 18 in the temperature decreasing unit 44 decreases, and hence the temperature of the steam 18 supplied 20 to the reboller 41 increases, In this way, the carbon-dioxide-recovery-type steam power generation system may recover the heat from the carbon dioxide gas 42 containing water vapor and the steam 18 for heating the reboller and set the temperature of the steam 18 25 supplied to the reboiler 41 at a desired temperature by adjusting the flow rate of the cooling water 61 exchanging heat with the carbon dioxide gas 42 containing water vapor and the steam 18. (Fourth Embodiment) 30 Fig. 4 illustrates a schematic structure of a carbon-dioxide-recovery-type steam power generation system according to a fourth embodiment. This embodiment is different from the second embodiment shown in Fig. 2 in that steam 82 generated by branching a part of the cooling water 61 35 and causing heat-exchanging with the carbon dioxide 52 In the intermediate cooler 55 is supplied to the turbine 57. In Fig. 4, 10 the same portions as the portions of the second embodiment shown in Fig. 2 are denoted by the same reference numerals. The description thereof will not be repeated. The cooling water 61 supplied from the pump 64 is 5 branched, so that one part of the cooling water is supplied to the CO2 condenser 51 and the other part of the cooling water is supplied to the intermediate cooler 55. The flow rate of the cooling water 61 supplied to the intermediate cooler 55 may be adjusted by a valve 81. 10 The cooling water 61 supplied to the intermediate cooler 55 exchanges heat with the carbon dioxide 52 with high temperature (for example, heated up to approximately 200 to 250*C) compressed by the compressor 53, so that the steam 82 Is generated. The steam 82 is supplied to the turbine 57, and 15 is used to drive the turbine 57. Accordingly, the heat recovered by the intermediate cooler 55 may be used as the power of the turbine 57, and may supplement a part of the power of the compressors 53 and 54. In this way, It Is possible to efficiently recover the 20 thermal energy and realize the high thermal efficiency by recovering heat from the compressed carbon dioxide 52. In the structure shown in Fig. 4, the branched cooling water 61 exchanges heat with the carbon dioxide 52 compressed by the compressor 53 In the Intermediate cooler 55, 25 but may exchange heat with the carbon dioxide 52 compressed by the compressor 54 in the exit cooler 56. Further, the heat exchanging may be performed In the Intermediate cooler 55 after the heat exchanging in the exit cooler 56. Furthermore, the carbon-dioxide-recovery-type steam 30 power generation system according to the embodiment may further includes the valve 71 and the control unit 72 described in the third embodiment. Such a structure is shown in Fig. 5. Furthermore, the control unit 72 may be configured to control the opening degree of the valve 81. 35 In the first to fourth embodiments, the cooling water 61 Is used so as to recover heat from the carbon dioxide gas 42 11 containing water vapor or the steam 18 for heating the reboiler, but a medium with a low boiling point such as ammonia may be used. (Fifth Embodiment) 5 Fig. 6 Illustrates a schematic structure of a carbon-dioxide-recovery-type steam power generation system according to a fifth embodiment. This embodiment is different from the first embodiment shown in Fig. I in that a part of the condensate 27 is used to exchange heat with the carbon dioxide 10 gas 42 containing water vapor and generated steam 91 is supplied to the low-pressure turbine 23. In Fig, 6, the same portions as the portions of the first embodiment shown in Fig. 1 are denoted by the same reference numerals. The description thereof will not be repeated. Further, in Fig. 6, the turbine 57 15 driving the compressors 53 and 54 are not shown. As shown in Fig. 6, the steam 91 is obtained in such a manner that the cooling water (condensate 27) branched from the line 28 at the downstream side of the condensate pump 31 recovers the heat of the carbon dioxide gas 42 containing water 20 vapor In the CO 2 condenser 51, and the steam 91 is supplied to the low-pressure turbine 23. The steam 91 supplied to the low-pressure turbine 23 is used as steam for driving the low-pressure turbine 23. It is possible to increase the output of the steam power generation plant la by using the thermal 25 energy included in the carbon dioxide gas 42 containing water vapor emitted from the regeneration tower of the carbon dioxide separation and recovery plant 40 as the driving energy of the low-pressure turbine 23. In this way, according to the embodiment, the 30 carbon-dioxide-recovery-type steam power generation system may exchange heat with the carbon dioxide gas 42 containing water vapor using a part of the condensate 27 and use the generated steam 91 as a part of the steam for driving the low-pressure turbine 23. Accordingly, it is possible to 35 efficiently recover the thermal energy and realize the high thermal efficiency.

12 (Sixth Embodiment) Fig. 7 illustrates a schematic structure of a carbon-dioxide-recovery-type steam power generation system according to a sixth embodiment. This embodiment is different 5 from the fifth embodiment shown in Fig. 6 in that the steam 91 is supplied to the turbine 57 driving the compressors 53 and 54. In Fig. 7, the same portions as the portions of the fifth embodiment shown In Fig. 6 are denoted by the same reference numerals. The description thereof will not be repeated, 10 As shown in Fig. 7, the steam 91, which is generated by the heat exchanging between a part of the condensate 27 in the

CO

2 condenser 51 and the carbon dioxide gas 42 containing water vapor is supplied to the turbine 57. The steam 91 is used to drive the turbine 57. Accordingly, the heat recovered 15 by the CO2 condenser 51 may be used as the power of the turbine 57, and may supplement a part of the power of the compressors 53 and 54. The steam discharged from the turbine 57 is joined as drainage to an appropriate position of the line 28 between the 20 condensate pump 31 and the water supply pump 34. In this way, in the embodiment, the thermal energy of the carbon dioxide 42 emitted from the regeneration tower of the carbon dioxide separation and recovery plant 40 is recovered, and the generated steam is supplied to the 25 compressor-driven turbine 57, so that a part of the power of the compressors 53 and 54 may be supplemented. For this reason, the carbon-dioxide-recovery-type steam power generation system 1 may efficiently recover the thermal energy and realize the high thermal efficiency. Further, the 30 carbon-dioxide-recovery-type steam power generation system 1 may suppress degradation of the output of the steam power generation plant la in accordance with the ensured power source for compressing carbon dioxide. In the first to sixth embodiments, a structure Is shown in 35 which two compressors compressing the carbon dioxide and two coolers cooling the compressed carbon dioxide are provided, but 13 the number thereof may be one or three or more. While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, 5 the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the Inventions. The accompanying 10 claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates,

Claims

1. A carbon-dioxide-recovery-type steam power generation system comprising: a boiler for producing steam and for generating an exhaust gas by combusting fuel; a first turbine that is connected to a generator and adapted for being rotationally driven by the steam supplied from the boiler; an absorption tower for being supplied with the exhaust gas from the boiler and for allowing carbon dioxide contained in the exhaust gas to be absorbed into an absorption liquid; a regeneration tower for being supplied with the absorption liquid that has absorbed the carbon dioxide from the absorption tower, for discharging a carbon dioxide gas from the absorption liquid, and for discharging the carbon dioxide gas; a reboiler for heating the absorption liquid from the regeneration tower and for supplying the generated steam to the regeneration tower; a condenser for removing moisture from the carbon dioxide gas, discharged from the regeneration tower, by condensing the carbon dioxide gas using cooling medium; a compressor for compressing the carbon dioxide gas from which the moisture is removed by the condenser; and a second turbine for driving the compressor, wherein said system is adapted for supplying steam produced by the cooling medium recovering heat from the carbon dioxide gas in the condenser to the first turbine or the second turbine.

2. The carbon-dioxide-recovery-type steam power generation system according to claim 1, further comprising: a steam condenser for producing the cooling medium by cooling and condensing exhaust steam from the second turbine.

3. The carbon-dioxide-recovery-type steam power generation system according to claim 1, further comprising: n %parvnIenvovc IhNvrw~uwaKxbanvouI.UL~uLvUflU 14 15 a temperature decreasing unit for decreasing the temperature of the steam from the first turbine and for supplying the steam to the reboiler, wherein said system is adapted for using the cooling medium to recover the heat from the carbon dioxide gas in the condenser, and thereafter, to recover heat from the steam from the first turbine in the temperature decreasing unit.

4. The carbon-dioxide-recovery-type steam power generation system according to claim 3, further comprising: a control unit for measuring the temperature of the steam decreased in temperature by the temperature decreasing unit and for controlling the flow rate of the cooling medium supplied to the condenser based on the measurement result.

5. The carbon-dioxide-recovery-type steam power generation system according to claim 1, further comprising: a cooler adapted for being supplied with a part of the cooling medium and for cooling the carbon dioxide gas compressed by the compressor, wherein said system is adapted for supplying the steam produced by cooling the carbon dioxide gas in the cooler to the second turbine.

6. The carbon-dioxide-recovery-type steam power generation system according to claim 1, wherein: the boiler includes a superheater for generating main steam and a reheater for generating reheat steam, the first turbine includes a high-pressure turbine for being rotationally driven by the main steam supplied thereto, an intermediate-pressure turbine for being rotationally driven by the reheat steam supplied thereto, and a low-pressure turbine for being rotationally driven by the exhaust steam supplied thereto from the intermediate-pressure turbine, the cooling medium is a part of condensate produced by cooling and condensing the exhaust steam from the low-pressure turbine, and the low-pressure turbine is for being supplied with the steam produced in the condenser. H:parumerwvnw ronmDutwncuAm nu t.1VLUzw2Iumu 16

7. The carbon-dioxide-recovery-type steam power generation system according to claim 1, wherein the cooling medium is a part of condensate produced by cooling and condensing the exhaust steam from the first turbine, and the second turbine is for being supplied with the steam produced in the condenser.

8. A carbon dioxide recovery method comprising: producing steam, which drives a turbine, and generating an exhaust gas by combusting fuel; allowing carbon dioxide, which is contained in the exhaust gas, to be absorbed into an absorption liquid; emitting a carbon dioxide gas by heating the absorption liquid that has absorbed the carbon dioxide and discharging the carbon dioxide gas; cooling the discharged carbon dioxide gas using cooling medium and removing moisture from the carbon dioxide gas by condensing the moisture; compressing the carbon dioxide gas, from which moisture is removed, using a compressor; and supplying steam generated by the cooling medium recovering heat at the time of condensing the moisture from the carbon dioxide gas to a driving turbine driving the compressor or the turbine.

9. The carbon dioxide recovery method according to claim 8, wherein the cooling medium is produced by cooling and condensing an exhaust steam from the driving turbine.

10. The carbon dioxide recovery method according to claim 8, wherein the steam from the turbine is used as a heat source of the absorption liquid and a heat source of the steam generated by the cooling medium recovering heat at the time of condensing the moisture.

11. The carbon dioxide recovery method according to claim 10, wherein the temperature of the steam decreased in temperature by the HXpurntenoven\NRPortbIUDCCWARWD38961.DOC-2002/214 17 temperature decreasing unit is measured, and the flow rate of the cooling medium is controlled based on the temperature measurement result.

12. The carbon dioxide recovery method according to claim 8, wherein a part of the cooling medium is used to cool the carbon dioxide gas compressed by the compressor.

13. The carbon dioxide recovery method according to claim 8, wherein the cooling medium is a part of condensate generated by cooling and condensing the exhaust steam from the turbine, and the steam generated by the cooling medium recovering heat at the time of condensing the moisture is supplied to the turbine.

14. The carbon dioxide recovery method according to claim 8, wherein the cooling medium is a part of condensate generated by cooling and condensing the exhaust steam from the turbine, and the steam generated by the cooling medium recovering heat at the time of condensing the moisture is supplied to the driving turbine.