Wet-type carbon dioxide capturing equipment

Abstract

Wet-type carbon dioxide capturing equipment includes a CO.sub.2 absorption tower where CO.sub.2 of an exhaust gas reacts with an absorbent, a CO.sub.2 stripping tower where CO.sub.2 is separated from a rich solution absorbed the CO.sub.2 in the CO.sub.2 absorption tower, a reboiler for supplying thermal energy to the CO.sub.2 stripping tower to separate the CO.sub.2 from the rich solution in the CO.sub.2 stripping tower, a first heat exchanger for heating the rich solution by exchanging heat between a lean solution having the CO.sub.2 separated therefrom in the CO.sub.2 stripping tower and the rich solution, a mechanical vapor recompressor (MVR) for compressing a CO.sub.2 gas separated in the CO.sub.2 stripping tower, and a second heat exchanger for separating a portion of CO.sub.2 from the rich solution by heating the rich solution by exchanging heat between the CO.sub.2 gas compressed in the MVR and the rich solution passing through the first heat exchanger, in which the rich solution having CO.sub.2 that is not separated in the second heat exchanger is input to the CO.sub.2 stripping tower where the CO.sub.2 is separated.

Claims

1. Wet-type carbon dioxide capturing equipment, comprising: a CO.sub.2 absorption tower configured to have CO.sub.2 of an exhaust gas react with an absorbent; a CO.sub.2 stripping tower configured to separate CO.sub.2 from a rich solution that absorbs the CO.sub.2 in the CO.sub.2 absorption tower; a reboiler configured to supply thermal energy to the CO.sub.2 stripping tower to separate the CO.sub.2 from the rich solution in the CO.sub.2 stripping tower; a first heat exchanger configured to heat the rich solution by exchanging heat between a lean solution having the CO.sub.2 separated therefrom in the CO.sub.2 stripping tower and the rich solution that absorbs the CO.sub.2 in the CO.sub.2 absorption tower; a mechanical vapor recompressor (MVR) configured to compress a CO.sub.2 gas that is separated in the CO.sub.2 stripping tower; and a second heat exchanger configured to separate a portion of CO.sub.2 from the rich solution by heating the rich solution by exchanging heat between the CO.sub.2 gas compressed in the MVR and the rich solution passing through the first heat exchanger, wherein the rich solution having CO.sub.2 that is not separated in the second heat exchanger is input to the CO.sub.2 stripping tower where the CO.sub.2 is separated.

2. The wet-type carbon dioxide capturing equipment of claim 1, wherein the first heat exchanger is a plate-type heat exchanger, the second heat exchanger is a shell & tube heat exchanger, the CO.sub.2 gas compressed in the mechanical vapor recompressor is input to a tube side of the second heat exchanger, and the rich solution passing through the first heat exchanger is input to a shell side of the second heat exchanger.

3. The wet-type carbon dioxide capturing equipment of claim 1, wherein steam is input to the reboiler as a heat source, the steam is condensed by transferring latent heat to the CO.sub.2 stripping tower via the reboiler, and condensed water generated as the steam is condensed is input to a first condensed water tank.

4. The wet-type carbon dioxide capturing equipment of claim 3, wherein the condensed water is generated as the CO.sub.2 gas input to the second heat exchanger loses heat, a mixed fluid of the CO.sub.2 gas, vapor, and the condensed water is input to a second condensed water tank, and the condensed water separated from the mixed fluid in the second condensed water tank is input to the CO.sub.2 stripping tower.

5. The wet-type carbon dioxide capturing equipment of claim 4, further comprising a third heat exchanger that is configured to exchange heat between the exhaust gas removed of the CO.sub.2 in the CO.sub.2 absorption tower and the CO.sub.2 gas removed of the condensed water in the second condensed water tank.

6. The wet-type carbon dioxide capturing equipment of claim 4, further comprising: a second mechanical vapor recompressor (MVR) configured to compress the CO.sub.2 gas removed of the condensed water in the second condensed water tank; a fourth heat exchanger configured to separate a portion of the CO.sub.2 from the rich solution by heating the rich solution by exchanging heat between the compressed CO.sub.2 gas compressed in the second MVR and a portion of the rich solution passing through the first heat exchanger, wherein the rich solution having CO.sub.2 that is not separated in the fourth heat exchanger is input to the CO.sub.2 stripping tower together with the rich solution having CO.sub.2 that is not separated in the second heat exchanger.

7. The wet-type carbon dioxide capturing equipment of claim 6, wherein the fourth heat exchanger is a shell & tube heat exchanger, the CO.sub.2 gas compressed in the second mechanical vapor recompressor is input to a tube side of the fourth heat exchanger, and a portion of the rich solution passing through the first heat exchanger is input to a shell side of the fourth heat exchanger.

8. The wet-type carbon dioxide capturing equipment of claim 6, wherein the condensed water is generated as the CO.sub.2 gas input to the fourth heat exchanger loses heat, a mixed fluid of the CO.sub.2 gas, vapor, and the condensed water is input to a third condensed water tank, and the condensed water separated from the mixed fluid in the third condensed water tank is input to the CO.sub.2 stripping tower.

9. The wet-type carbon dioxide capturing equipment of claim 8, further comprising a third heat exchanger that is configured to exchange heat between the exhaust gas removed of the CO.sub.2 in the CO.sub.2 absorption tower and the CO.sub.2 gas removed of the condensed water in the third condensed water tank.

10. The wet-type carbon dioxide capturing equipment of claim 4, further comprising a thermal vapor recompressor (TVR) that is configured to compress revaporized vapor generated in the first condensed water tank and supply the revaporized vapor to the reboiler.

11. The wet-type carbon dioxide capturing equipment of claim 10, wherein a heat exchanger is mounted in the first condensed water tank, and the heat exchanger exchanges heat between the CO.sub.2 gas removed of the condensed water in the second condensed water tank and the condensed water in the first condensed water tank.

12. The wet-type carbon dioxide capturing equipment of claim 11, further comprising a third heat exchanger that is configured to exchange heat between the exhaust gas removed of the CO.sub.2 in the CO.sub.2 absorption tower and the CO.sub.2 gas passing through the heat exchanger mounted in the first condensed water tank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which:

(2) FIG. 1 illustrates a wet-type carbon dioxide capturing equipment employing a general wet type amine process, according to the related art;

(3) FIG. 2 illustrates a wet-type carbon dioxide capturing equipment according to an embodiment;

(4) FIG. 3 illustrates a wet-type carbon dioxide capturing equipment according to another embodiment; and

(5) FIG. 4 illustrates a wet-type carbon dioxide capturing equipment according to another embodiment.

DETAILED DESCRIPTION

(6) Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, the term and/or includes any and all combinations of one or more of the associated listed items.

(7) FIG. 2 illustrates a wet-type carbon dioxide capturing equipment according to an embodiment.

(8) Referring to FIG. 2, the wet-type carbon dioxide capturing equipment according to the present embodiment is used to separate carbon dioxide (CO.sub.2) from an exhaust gas discharged from a thermal power plant in a chemical absorption process. For example, a wet-type amine carbon capture & storage (CCS) process may be employed. However, the present disclosure is not limited to the wet-type amine CCS process.

(9) The wet-type carbon dioxide capturing equipment according to the present embodiment may include a CO.sub.2 absorption tower 120, a CO.sub.2 stripping tower 130, a reboiler 140, a first heat exchanger 150, a mechanical vapor recompressor (MVR) 180, and a second heat exchanger 152.

(10) For example, the exhaust gas discharged from the thermal power plant passes through exhaust gas pretreatment equipment, for example, flue-gas desulfurization (FGD) equipment, selective catalytic reduction (SCR) equipment, and/or dust collection equipment. The content of carbon dioxide among the exhaust gas varies according to a combusted fuel and operating conditions, but is generally about 15 Vol. %. The exhaust gas passing through the FGD equipment passes through a gas-gas heat exchanger (GGH), and an exhaust gas 301 is input to a SOx absorption tower 110 where sulfur oxides are further removed. As such, although SOx is removed while the exhaust gas 301 passes through the exhaust gas pretreatment equipment, an exhaust gas 302 including CO.sub.2 is input to a lower portion of the CO.sub.2 absorption tower 120.

(11) The CO.sub.2 absorption tower 120 is where the CO.sub.2 of the exhaust gas reacts with a liquid absorbent, for example, an amine absorbent. In detail, a liquid absorbent 311 is input to an upper portion of the CO.sub.2 absorption tower 120. As the absorbent 311 and the exhaust gas 302 flow counter to each other in the CO.sub.2 absorption tower 120, gas-liquid contact is performed, and thus, CO.sub.2 of the exhaust gas 302 is absorbed by the absorbent 311. In this state, a removal rate of the CO.sub.2 of the exhaust gas is about 90%.

(12) A CO.sub.2-rich absorbent 312 absorbing CO.sub.2 as above (hereinafter, referred to as the rich solution 312) is discharged through a lower portion of the CO.sub.2 absorption tower 120. The rich solution 312 contains CO.sub.2 and has a temperature of about 40-50 C.

(13) An exhaust gas 303 removed of CO.sub.2 is discharged from the upper portion of the CO.sub.2 absorption tower 120. In the process, the temperature of the exhaust gas 303 may be lowered to about 40 C. due to water spray in the upper portion of the CO.sub.2 absorption tower 120.

(14) The rich solution 312 discharged through the CO.sub.2 absorption tower 120 is input to the first heat exchanger 150 by a rich solution pump 161. A plate-type heat exchanger may be used as the first heat exchanger 150. The temperature of the rich solution 312 may be increased as the rich solution 312 collects sensible heat through heat exchange with an absorbent 315 to be described later while passing though the first heat exchanger 150. In this state, the rich solution 312 is heated to a temperature of, for example, about 90-100 C., at which a two-phase phenomenon may be prevented and a liquid phase may be maintained.

(15) As such, a rich solution 313 heated by collecting the sensible heat is input to the second heat exchanger 152. A shell & tube heat exchanger may be used as the second heat exchanger 152. While passing through the second heat exchanger 152, the rich solution 313 is heated through heat exchange with a CO.sub.2 gas 322 compressed by the MVR 180 to be described later.

(16) As the rich solution 313 is heated in the second heat exchanger 152, CO.sub.2 is partially separated from the rich solution 313, and a rich solution 314 having CO.sub.2 that is not yet separated is input to an upper portion of the CO.sub.2 stripping tower 130.

(17) The CO.sub.2 stripping tower 130 is where CO.sub.2 is separated from the rich solution 314 through heating. In detail, the rich solution 314 is separated into the absorbent and CO.sub.2 by being heated by thermal energy while flowing from the upper portion of the CO.sub.2 stripping tower 130 to a lower portion thereof.

(18) The reboiler 140 supplies thermal energy to the CO.sub.2 stripping tower 130 to separate CO.sub.2.

(19) In detail, steam 351 of about 3 bar.Math.g or more, as a heat source, is input to the reboiler 140. Furthermore, a portion of an absorbent 341 in the CO.sub.2 separation process in the CO.sub.2 stripping tower 130 is input to the reboiler 140 and heated in the reboiler 140 by the steam 351. Accordingly, CO.sub.2 and vapor are generated from the absorbent 341 in the reboiler 140, and a mixed gas 342 of CO.sub.2 and vapor is input to the CO.sub.2 stripping tower 130 and provides thermal energy to separate CO.sub.2 from the rich solution 314. An absorbent 343 removed of CO.sub.2 in the reboiler 140 is input again to the CO.sub.2 stripping tower 130. The steam 351 input to the reboiler 140 transfers latent heat and is condensed, and condensed water 352 generated accordingly is input to a first condensed water tank 170 where water is collected and then transferred to a steam production process.

(20) The CO.sub.2 separated in the CO.sub.2 stripping tower 130 is discharged from the upper portion of the CO.sub.2 stripping tower 130, and the absorbent 315 removed of CO.sub.2 (hereinafter, referred to as the lean solution) is discharged from the lower portion of the CO.sub.2 stripping tower 130.

(21) The temperature of the lean solution 315 is about 105-120 C., and as described above, is input to the first heat exchanger 150 and transfers the sensible heat to the rich solution 312 through heat exchange. The lean solution 315 removed of CO.sub.2 and having lost the sensible heat, that is, the recycled absorbent 311, is input to the upper portion of the CO.sub.2 absorption tower 120 by a lean solution pump 162, so as to contact the exhaust gas 302 removed of sulfur oxide.

(22) A CO.sub.2 gas 321 discharged from the upper portion of the CO.sub.2 stripping tower 130 has a temperature of about 105-120 C., a pressure of about 0.3-0.8 bar.Math.g, and moisture of about 40%. The CO.sub.2 gas 321 is input to the MVR 180 to be compressed. In this state, the moisture included in the CO.sub.2 gas 321 has latent heat energy that increases as the pressure increases. Compared to a compression ratio of a typical compressor of about 4, the MVR 180 that compresses vapor has a compression ratio of about 2. The CO.sub.2 gas 321 may be compressed by using a one-step or multi-step compressor. A CO.sub.2 gas 322 compressed in the MVR 180 is input to the second heat exchanger 152 at a high temperature. A shell & tube heat exchanger may be used as the second heat exchanger 152. The CO.sub.2 gas 322 that is compressed may be input to a tube side of the second heat exchanger 152.

(23) Furthermore, as described above, the rich solution 313 that is heated by collecting the sensible heat from the first heat exchanger 150 is input to a shell side of the second heat exchanger 152. The rich solution 313 is heated through the heat exchange with the compressed CO.sub.2 gas 322 in the second heat exchanger 152. Since the CO.sub.2 gas 322 compressed in the MVR 180 has a higher temperature than the rich solution 313, heat exchange is possible. Accordingly, CO.sub.2 is partially separated from the rich solution 313 and vapor is partially generated therefrom. A mixed gas 323 of the CO.sub.2 gas and the vapor separated in the second heat exchanger 152 is input to the upper portion of the CO.sub.2 stripping tower 130. The rich solution 314 having CO.sub.2 that is not yet separated in the second heat exchanger 152 is input to the upper portion of the CO.sub.2 stripping tower 130 as described above.

(24) The compressed CO.sub.2 gas 322 input to the second heat exchanger 152 loses heat, and the moisture thereof is condensed so that condensed water is generated. However, since the temperature of the CO.sub.2 gas 322 is still high, a portion of the moisture remains as vapor. A mixed fluid 324 in which the compressed CO.sub.2 gas, the vapor, and the condensed water are mixed is input to a second condensed water tank 172. Condensed water 325 separated from the mixed fluid 324 in the second condensed water tank 172 is input to the upper portion of the CO.sub.2 stripping tower 130.

(25) A compressed CO.sub.2 gas 326 removed of the condensed water 325 in the second condensed water tank 172 is input to a third heat exchanger 153. A shell & tube heat exchanger may be used as the third heat exchanger 153. The compressed CO.sub.2 gas 326 may be input to a shell side of the third heat exchanger 153. The exhaust gas 303 removed of CO.sub.2 in the CO.sub.2 absorption tower 120 is input to a tube side of the third heat exchanger 153. The temperature of the exhaust gas 303 is lowered to about 40 C. due to water spray in the upper portion of the CO.sub.2 absorption tower 120. However, since the exhaust gas 303 is discharged through the GGH of the FGD equipment or a separate funnel, a temperature of about 95-100 C. is needed.

(26) Accordingly, in the third heat exchanger 153, the exhaust gas 303 is heated through heat exchange, and as the temperature of the compressed CO.sub.2 gas 326 is lowered, the compressed CO.sub.2 gas 326 loses latent heat, and thus moisture of the compressed CO.sub.2 gas 326 is condensed and condensed water 327 is generated. The condensed water 327 is input to the CO.sub.2 stripping tower 130. A CO.sub.2 gas 328 that has partially lost moisture and is compressed is transferred to a compression and liquefaction process in a low-temperature state. The temperature of the exhaust gas 303 removed of CO.sub.2 is increased by heat exchange, and an exhaust gas 304 having an increased temperature is discharged through the GGH of the FGD equipment or a separate funnel.

(27) As described above, in the wet-type carbon dioxide capturing equipment according to an embodiment, since a portion of CO.sub.2 is separated from the rich solution 313 by the MVR 180 and the second heat exchanger 152, the amount of the rich solution 314 input to the upper portion of the CO.sub.2 stripping tower 130, where CO.sub.2 is not separated, is reduced compared to the related art. Accordingly, as the amount of thermal energy supplied to the CO.sub.2 stripping tower 130 via the reboiler 140 may be reduced, heat duty of the reboiler 140 may be further reduced.

(28) Furthermore, according to the related art, when CO.sub.2, from which only the moisture is removed in the CO.sub.2 stripping tower 130, is input to a compression/liquefaction process, the pressure of the CO.sub.2 is within about 0.3-0.8 barg. In contrast, when the CO.sub.2 gas 328 removed of condensed water, according to the present embodiment, is input to the compression/liquefaction process, the pressure of the CO.sub.2 gas 328 increases, and thus load of the compression process is lowered.

(29) FIG. 3 illustrates wet-type carbon dioxide capturing equipment according to another embodiment.

(30) Referring to FIG. 3, the wet-type carbon dioxide capturing equipment according to the present embodiment may further include a second MVR 182 and a fourth heat exchanger 154, in addition to the CO.sub.2 absorption tower 120, the CO.sub.2 stripping tower 130, the reboiler 140, the first heat exchanger 150, the MVR 180, and the second heat exchanger 152.

(31) Since some of the constituent elements of the embodiment of FIG. 3 are the same as those of the embodiment of FIG. 2, descriptions of the same constituent elements are omitted or briefly discussed, and additional constituent elements are mainly discussed below.

(32) In the embodiment of FIG. 3, for example, since the pretreatment equipment with respect to the exhaust gas discharged from a thermal power plant is the same as that according to the embodiment of FIG. 2, a description thereof is omitted.

(33) Furthermore, since the CO.sub.2 absorption tower 120, the CO.sub.2 stripping tower 130, the reboiler 140, the first heat exchanger 150, the MVR 180, and the second heat exchanger 152 are the same as those described in the embodiment of FIG. 2, a description thereof is omitted.

(34) In the embodiment of FIG. 3, since the compressed CO.sub.2 gas 326 removed of the condensed water 325 in the second condensed water tank 172 still includes moisture, the compressed CO.sub.2 gas 326 is input to the second MVR 182. As such, when the compressed CO.sub.2 gas 326 passes through the second MVR 182, the pressure of the compressed CO.sub.2 gas 326 is further increased, and thus the load of the compression equipment in the compression and liquefaction process may be reduced.

(35) A compressed CO.sub.2 gas 329 that is compressed in the second MVR 182 is input to the fourth heat exchanger 154. The fourth heat exchanger 154 may be a shell & tube heat exchanger, and the compressed CO.sub.2 gas 329 may be input to a tube side of the fourth heat exchanger 154.

(36) In the embodiment of FIG. 3, a portion of the rich solution 313 which has obtained sensible heat while passing through the first heat exchanger 150 is input to a shell side of the fourth heat exchanger 154 and exchanges heat with the compressed CO.sub.2 gas 329. A mixed gas 330 of CO.sub.2 gas and vapor separated from the rich solution 313 through the heat exchange in the fourth heat exchanger 154 is input to the CO.sub.2 stripping tower 130 together with the mixed gas 323 of the CO.sub.2 gas and the vapor separated in the second heat exchanger 152.

(37) A rich solution 316 having CO.sub.2 that is not yet separated in the fourth heat exchanger 154 is input to the upper portion of the CO.sub.2 stripping tower 130 together with the rich solution 314 having CO.sub.2 that is not yet separated in the second heat exchanger 152, and thus CO.sub.2 is separated in the CO.sub.2 stripping tower 130.

(38) The compressed CO.sub.2 gas 329 input to the fourth heat exchanger 154 loses heat and moisture thereof is condensed so that condensed water is generated. However, since the temperature of the CO.sub.2 gas 329 is still high, a portion of the moisture remains as vapor. A mixed fluid 331 in which the compressed CO.sub.2 gas, the vapor, and the condensed water are mixed is input to a third condensed water tank 173. Condensed water 332 separated from the mixed fluid 331 in the third condensed water tank 173 is input to the upper portion of the CO.sub.2 stripping tower 130.

(39) A compressed CO.sub.2 gas 333 removed of the condensed water 332 in the third condensed water tank 173 is input to the shell side of the third heat exchanger 153. The operation of the third heat exchanger 153 and the subsequent operations are the same as those described in the embodiment of FIG. 2.

(40) The above-described wet-type carbon dioxide capturing equipment of FIG. 3 according to the present embodiment has the same advantages as those of the embodiment of FIG. 2. In particular, in the embodiment of FIG. 3, since the second MVR 182 and the fourth heat exchanger 154 are further included in addition to the MVR 180 and the second heat exchanger 152, a portion of CO.sub.2 is separated from the rich solution 313 in two steps. Accordingly, the amounts of the rich solutions 314 and 316, each having CO.sub.2 that is not separated, input to the upper portion of the CO.sub.2 stripping tower 130, may be further reduced. Thus, the amount of thermal energy supplied to the CO.sub.2 stripping tower 130 via the reboiler 140 may be further reduced.

(41) FIG. 4 illustrates wet-type carbon dioxide capturing equipment according to another embodiment.

(42) Referring to FIG. 4, the wet-type carbon dioxide capturing equipment according to the present embodiment may further include a thermal vapor recompressor (TVR) 190, in addition to the CO.sub.2 absorption tower 120, the CO.sub.2 stripping tower 130, the reboiler 140, the first heat exchanger 150, the MVR 180, and the second heat exchanger 152.

(43) Since some of the constituent elements of the embodiment of FIG. 4 are the same as those of the embodiment of FIG. 2, descriptions of the same constituent elements are omitted or briefly discussed, and additional constituent elements are mainly discussed below.

(44) In the embodiment of FIG. 4, for example, since the pretreatment equipment with respect to the exhaust gas discharged from a thermal power plant is the same as that according to the embodiment of FIG. 2, a description thereof is omitted.

(45) Furthermore, since the CO.sub.2 absorption tower 120, the CO.sub.2 stripping tower 130, the reboiler 140, the first heat exchanger 150, the MVR 180, and the second heat exchanger 152 are the same as those described in the embodiment of FIG. 2, descriptions thereof are omitted.

(46) In the embodiment of FIG. 4, the thermal vapor recompressor 190 compresses revaporized vapor 353 generated in the first condensed water tank 170 and supplies the compressed revaporized vapor 353 to the reboiler 140.

(47) As described above, the steam 351 input to the reboiler 140 loses latent heat to be condensed, and thus condensed water 352 generated accordingly is input to the first condensed water tank 170. In this state, since the temperature of the condensed water 352 in the first condensed water tank 170 that has lost latent heat is equal to or greater than about 140 C., when the thermal vapor recompressor 190 is connected to the first condensed water tank 170, the first condensed water tank 170 is depressurized and thus the revaporized vapor 353 is generated from the condensed water 352. As such, when the revaporized vapor 353 is generated, the temperature of the condensed water 352 is about 100 C. Since the revaporized vapor 353 may be compressed by the thermal vapor recompressor 190 and supplied to the reboiler 140, the amount of the steam 351 supplied to the reboiler 140 may be reduced.

(48) Furthermore, in the embodiment of FIG. 4, the compressed CO.sub.2 gas 326 removed of the condensed water 325 in the second condensed water tank 172 may be input to a separate heat exchanger 175 mounted in the first condensed water tank 170, before being input to the third heat exchanger 153.

(49) Since the compressed CO.sub.2 gas 326 is in a high-temperature state, the compressed CO.sub.2 gas 326 may supply heat to the condensed water 352 through heat exchange while passing through the heat exchanger 175 mounted in the first condensed water tank 170. Accordingly, as the amount of the revaporized vapor 353 generated from the condensed water 352 is further increased, the amount of the steam 351 supplied to the reboiler 140 may be further reduced.

(50) The compressed CO.sub.2 gas 326 is input to the shell side of the third heat exchanger 153 after passing through the heat exchanger 175 mounted in the first condensed water tank 170. The operation of the third heat exchanger 153 and the subsequent operations are the same as those of the embodiment of FIG. 2.

(51) The above-described wet-type carbon dioxide capturing equipment of FIG. 4 according to the present embodiment has the same advantages as those of the embodiment of FIG. 2. In particular, in the embodiment of FIG. 4, since the thermal vapor recompressor 190 is further included, and the revaporized vapor 353 is generated as the compressed CO.sub.2 gas 326 of a high temperature exchanges heat with the condensed water 352 through the heat exchanger 175 mounted in the first condensed water tank 170, the amount of the steam supplied to the reboiler 140 may be reduced. Thus, the amount of thermal energy supplied to the CO.sub.2 stripping tower 130 via the reboiler 140 may be further reduced.

(52) It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.

(53) While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.