JP2006342032A - Carbon dioxide recovery system and carbon dioxide recovery method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon dioxide recovery system and a carbon dioxide recovery method capable of achieving energy saving because it is possible to regenerate an absorbent solution and to separate carbon dioxide from the absorbent solution by heating the absorbent solution by using a low-temperature waste gas instead of steam. <P>SOLUTION: The carbon dioxide recovery apparatus is provided with an absorbent solution recirculation line that recirculates an absorbent solution into an absorption tower 100 for the absorption of carbon dioxide, another absorbent solution recirculation line that recirculates the absorbent solution into a regeneration tower 110 for the regeneration of the absorbent solution by releasing the carbon dioxide therefrom, these recirculation lines being provided independently of each other, a plurality of partition tanks 130a, 130b, and 130c capable of intervening in any one of the absorbent solution recirculation lines, and a heating medium recirculation line 182 that recirculates a heating medium 181 heated by a waste gas 103 through a heat recovery apparatus 180 into the partition tanks 130a, 130b, and 130c to heat the inside absorbent solution. This apparatus can efficiently utilize waste heat to regenerate the absorbent solution and to improve a heat efficiency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a carbon dioxide recovery system and a carbon dioxide recovery method for recovering carbon dioxide and the like contained in exhaust gas from a boiler, a waste incinerator, and the like of a thermal power plant.

  In recent years, the problem of global warming due to the greenhouse effect of carbon dioxide, which is a combustion product of fossil fuel, has been increasing. In the Kyoto Protocol of the United Nations Framework Convention on Climate Change, Japan's goal of reducing greenhouse gas emissions is to achieve the 1990 ratio of minus 6% between 2008 and 2012.

  Against this background, a system for recovering carbon dioxide by using, for example, an aqueous solution of an amine compound, which is an alkaline substance, as an absorbing solution is proposed. (For example, refer to Patent Document 1).

  Here, FIG. 2 shows an outline of a conventional carbon dioxide recovery system 200 that recovers carbon dioxide using an aqueous amine solution as an absorbing solution.

  In the conventional carbon dioxide recovery system 200 shown in FIG. 2, exhaust gas 201 discharged by burning fossil fuel is guided to an absorption tower 203 by a gas blower 202. An absorption liquid 204 having a temperature of about 50 ° C. is supplied to the upper portion of the absorption tower 203, and the supplied absorption liquid 204 comes into contact with the introduced exhaust gas 201 and absorbs carbon dioxide in the exhaust gas 201. On the other hand, the remaining exhaust gas 201 having absorbed the carbon dioxide in the absorbing liquid 204 is released from the upper part of the absorption tower 203 to the atmosphere.

  The absorption liquid 204 that has absorbed carbon dioxide is extracted from the lower part of the absorption tower 203 and guided to the heat exchanger 206 by the pump 205 and further to the regeneration tower 207.

  The absorbing liquid 204 guided to the regeneration tower 207 is heated to a temperature of about 120 ° C. by the steam 209 of the heater 208 and disturbed. Then, carbon dioxide is dissipated from the absorbing liquid 204 and regenerated into the absorbing liquid 204 that can absorb carbon dioxide again. The regenerated absorption liquid 204 is returned to the upper part of the absorption tower 203 by the circulation pump 210 through the heat exchanger 206 and the cooler 211. On the other hand, the carbon dioxide released from the absorbing liquid 204 is guided to the separator 213 through the cooler 212, and is recovered after moisture is removed by the separator 213.

In the conventional carbon dioxide recovery system 200 configured as described above, a circulation line of the absorbing liquid 204 is provided between the absorption tower 203 and the regeneration tower 207, and the regeneration tower 207 uses the steam 209 of the power generation boiler to circulate. The absorbed liquid 204 was heated and regenerated instantly to a temperature of about 120 ° C., and the regenerated absorbent 204 was instantaneously cooled to a temperature of about 50 ° C. and returned to the absorption tower 203.
JP 2002-126439 A

  In the conventional carbon dioxide recovery system 200 described above, a large amount of high-temperature steam 209 is used in the regeneration tower 207 in order to instantaneously heat the enormous absorption liquid 204 circulating to a predetermined temperature. Further, when the above-described absorbing liquid 204 is heated instantaneously to a predetermined temperature using the exhaust gas 201, there is a problem that desired heating cannot be performed when the temperature of the exhaust gas 201 is low.

  Therefore, the present invention has been made to solve the above-described problems. By heating the absorption liquid using low-temperature exhaust gas instead of steam, the regeneration of the absorption liquid and the carbon dioxide from the absorption liquid are performed. An object of the present invention is to provide a carbon dioxide recovery system and a carbon dioxide recovery method that can be separated and can save energy.

  In order to achieve the above object, a carbon dioxide recovery system of the present invention comprises an exhaust gas inlet, an absorption liquid inlet for absorption, a remaining exhaust gas outlet and an absorbent outlet, and the exhaust gas introduced from the exhaust gas inlet and An absorption device that causes gas-liquid contact with the absorption liquid introduced from the absorption liquid inlet for absorption and causes the absorption liquid to absorb carbon dioxide in the exhaust gas; an absorption liquid introduction port for regeneration; a regeneration absorption liquid discharge port; A regenerator having a carbon dioxide outlet and regenerating the absorbing liquid by releasing carbon dioxide from the absorbing liquid that has absorbed the carbon dioxide; and the absorbing liquid discharged from the absorbing liquid outlet of the absorbing apparatus for the absorption A first absorption liquid reflux line for refluxing to the absorbent inlet, and a second absorption liquid reflux line for refluxing the absorbent discharged from the regeneration absorbent outlet of the regeneration apparatus to the regeneration absorbent inlet for regeneration. A storage tank composed of a plurality of divided tanks that can be interposed by switching the reflux line of the absorbent liquid to either the first absorbent liquid reflux line or the second absorbent liquid reflux line; and A heat recovery device for transferring heat to the heat medium is interposed, and a heat medium reflux line capable of heating the absorption liquid in each of the divided layers by circulating the heat medium is provided.

  According to this carbon dioxide recovery system, the heat recovery device transfers the heat from the exhaust gas to the heat medium, circulates the heat medium, and provides the heat medium reflux line for heating the absorption liquid in the dividing tank, The absorbing liquid can be heated to the regeneration temperature with low temperature exhaust gas. In addition, a first absorption liquid reflux line that recirculates the absorption liquid to the absorption tower and absorbs carbon dioxide in the exhaust gas, and a second that recirculates the absorption liquid to the regeneration tower to release carbon dioxide and regenerate the absorption liquid. These absorption liquid reflux lines can be provided separately and independently, and the flow rates of the absorption liquid flowing through the respective absorption liquid reflux lines can be individually set.

  In the carbon dioxide recovery method of the present invention, the first absorbing liquid discharged from the absorbing liquid discharge port of the absorbing device is passed through the first dividing tank among the plurality of dividing tanks constituting the storage tank. The first absorption liquid is brought into gas-liquid contact with the exhaust gas introduced from the exhaust gas introduction port, and carbon dioxide in the exhaust gas is repeatedly absorbed by the first absorption liquid. The first absorption step and the first absorption liquid stored in the first division tank that has closed the reflux line of the first absorption liquid and absorbed carbon dioxide in the first absorption step, A first heating step for heating to a predetermined temperature and a reflux line for the first absorbing liquid are switched via a heat medium circulating in the heat medium reflux line heated by the exhaust gas. A first absorbent heated to a temperature, The first absorption liquid led to the regeneration absorption liquid inlet of the raw apparatus is returned to the regeneration absorption liquid inlet through the first division tank. And a first regeneration step in which carbon dioxide is released into the regeneration device to regenerate the carbon dioxide absorption capacity of the first absorbent.

  According to this carbon dioxide recovery method, in the first heating step, the first absorption liquid that has absorbed carbon dioxide in the first absorption step can be heated to the regeneration temperature with a relatively low temperature exhaust gas. This can improve the thermal efficiency of the system.

  According to the carbon dioxide recovery system and the carbon dioxide recovery method of the present invention, the absorption liquid is regenerated and the carbon dioxide from the absorption liquid is heated by using low-temperature exhaust gas for a predetermined time instead of steam. Carbon can be separated and energy saving can be achieved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows an outline of a carbon dioxide recovery system 10 according to a first embodiment of the present invention.

  The carbon dioxide recovery system 10 includes an absorption tower 100 that brings the introduced exhaust gas 103 into contact with an absorption liquid, a regeneration tower 110 that regenerates the absorption liquid by releasing carbon dioxide from the absorption liquid that has absorbed carbon dioxide, Absorption liquid reflux lines 120a and 120b for refluxing the absorption liquid discharged from the absorption liquid discharge port 101 of the absorption tower 100 to the absorption liquid introduction port 102 for absorption, and absorption discharged from the regenerative absorption liquid discharge port 111 of the regeneration tower 110 An absorbent liquid reflux line 121a, 121b for refluxing the liquid to the regeneration absorbent inlet 112, and a plurality of divided tanks 130a, 130b, 130c interposed in the absorbent liquid reflux lines 120a, 120b or the absorbent liquid reflux lines 121a, 121b. The storage tank 130 and the heat of the exhaust gas are recovered in the heat medium 181 via the heat recovery device 180, and the heat medium 18 Is mainly composed of a heat medium reflux line 182 capable of heating the absorption liquid stored in each of the divided tanks 130a, 130b, and 130c, and a control unit 140 that controls a pump, a valve, each device, and the like. .

  In FIG. 1, the control unit 140 is electrically connected to each pump, each valve, measurement device, each component device, and the like, which will be described later, but the connection lines are not shown for clarity of the drawing.

  First, an absorption liquid reflux path for returning the absorption liquid AL1 discharged from the absorption liquid discharge port 101 of the absorption tower 100 to the absorption liquid introduction port 102 for absorption will be described.

  An exhaust gas inlet 104 for guiding the exhaust gas 103 containing carbon dioxide discharged from a thermal power plant, a municipal waste incinerator, or the like into the absorption tower 100 is provided below the absorption tower 100. The exhaust gas inlet 104 is connected to a gas blower 105 for sending the exhaust gas 103 recovered through the heat recovery device 180 into the absorption tower 100. Further, an absorption liquid inlet 102 for absorption for introducing the absorption liquid AL1 supplied from the storage tank 130 by the liquid feed pump 150 is provided in the upper part of the absorption tower 100. The absorption liquid introduction port 102 for absorption is provided with an absorption liquid ejection part 106 that ejects the absorption liquid AL1. Further, inside the absorption tower 100, a filler 107 is mainly installed that makes gas-liquid contact between the absorption liquid AL1 ejected from the absorption liquid ejection section 106 and the exhaust gas 103 introduced into the absorption tower 100. The upper end of the absorption tower 100 functions as a remaining exhaust gas discharge port, and is provided with an exhaust port 108 for exhausting the exhaust gas 103 that has absorbed carbon dioxide into the atmosphere by passing through the filler 107. ing.

  Further, an absorption liquid discharge port 101 for discharging the absorption liquid AL1 that has absorbed carbon dioxide is provided at the bottom of the absorption tower 100. The absorption liquid discharge port 101 is connected to one end of an absorption liquid recirculation line 120 a provided with a derivation pump 151. The other end of the absorption liquid reflux line 120a branches corresponding to each of the divided tanks 130a, 130b, and 130c, and valves 170a, 170b, and 170c are respectively provided at the other ends of the branched absorption liquid circulation lines 120a. Is provided. Here, each division tank 130a, 130b, 130c is comprised by the tank etc. which can be sealed, for example.

  Each of the dividing tanks 130a, 130b, and 130c is provided with a valve 171a, 171b, and 171c, respectively, and an absorption liquid reflux line 120b that is branched at one end corresponding to each of the dividing tanks 130a, 130b, and 130c is installed. Yes. One end of the branched absorption liquid reflux line 120b is immersed in a relatively lower position in the absorption liquid stored in each of the divided tanks 130a, 130b, and 130c. The other end of the absorption liquid reflux line 120b is connected to the absorption liquid inlet for absorption 102 of the absorption tower 100 via a cooling device 190. Further, the absorption liquid reflux line 120b is provided with a liquid feed pump 150 that pumps the absorption liquid AL1 to the absorption tower 100.

  The cooling device 190 includes a heat exchanger that cools the absorbing liquid AL1 that flows back through the absorbing liquid reflux line 120b. For example, seawater may be used as a cooling medium for recovering heat from the absorbing liquid AL1.

  Here, for example, by opening the valves 170a and 171a corresponding to the division tank 130a and closing the valves 170b and 170c and valves 171b and 171c corresponding to the division tanks 130b and 130c, the absorption tower 100 and the absorption liquid reflux line 120a. Then, an absorption liquid reflux path for circulating the absorption liquid AL1 is formed in the order of the dividing tank 130a, the absorption liquid reflux line 120b, and the absorption tower 100.

  The liquid feed pump 150, the derivation pump 151, and the valves 170a, 170b, 170c, 171a, 171b, and 171c are operated based on signals from the control unit 140, and the flow rate of the absorbent AL1 flowing through the absorbent recirculation path, etc. Is adjusted.

  Moreover, it is preferable that the absorbing liquid AL1 ejected from the absorbing liquid ejecting section 106 is ejected uniformly. For example, a spray nozzle that can obtain a predetermined spray particle size and spray pattern is used for the absorbing liquid ejecting section 106. May be. If the absorption liquid AL1 can be dispersed substantially uniformly in the absorption tower 100 by the configuration of the absorption liquid introduction port 102 for absorption, the absorption liquid ejection part 106 may not be provided.

  The filler 107 is composed of, for example, a material having a porous structure, a honeycomb structure, or the like, and any material that disturbs the absorbing liquid AL1 passing through the filler 107 may be used. Moreover, the filler 107 may be installed in multiple stages in the absorption tower 100. In the case where the fillers 107 are installed in multiple stages, for example, an absorbing liquid ejection unit 106 that ejects the absorbing liquid AL1 may be provided corresponding to each stage. In addition, in the absorption tower 100, if the gas-liquid contact with the exhaust gas 103 and the absorption liquid AL1 can be performed efficiently, the absorption tower 100 can be configured without installing the filler 107.

  Next, an absorbent recirculation path for recirculating the regenerated absorbent discharged from the regenerated absorbent discharge port 111 of the regeneration tower 110 to the regenerating absorbent inlet 112 will be described.

  Each of the divided tanks 130a, 130b, 130c of the storage tank 130 is provided with valves 172a, 172b, 172c, respectively, and an absorption liquid reflux line 121a branched at one end corresponding to each of the divided tanks 130a, 130b, 130c. Is installed. On the other hand, the other end of the absorption liquid reflux line 121 a is connected to the regeneration absorption liquid discharge port 111 of the regeneration tower 110. The absorption liquid reflux line 121a is provided with a lead-out pump 152.

  Further, each of the dividing tanks 130a, 130b, and 130c is provided with a valve 173a, 173b, and 173c, respectively, and an absorption liquid reflux line 121b that is branched at one end corresponding to each of the dividing tanks 130a, 130b, and 130c is installed. Yes. One end of the branched absorption liquid reflux line 121b may be installed so as to be positioned relatively lower in the absorption liquid stored in each of the divided tanks 130a, 130b, and 130c. For example, as shown in FIG. Thus, you may provide in the bottom part of each division tank 130a, 130b, 130c. On the other hand, the other end of the absorbent reflux line 121 b is connected to the regeneration absorbent inlet 112 for regeneration of the regeneration tower 110. The absorbing liquid reflux line 121b is provided with a high-pressure liquid feeding pump 153 that pumps the absorbing liquid AL2 to the regeneration tower 110.

  Here, for example, by opening the valves 172b and 173b corresponding to the dividing tank 130b and closing the valves 172a and 172c and valves 173a and 173c corresponding to the dividing tanks 130a and 130c, the regeneration tower 110 and the absorption liquid reflux line 121a. Then, an absorption liquid reflux path for circulating the absorption liquid AL2 is formed in the order of the dividing tank 130b, the absorption liquid reflux line 121b, and the regeneration tower 110.

  The derivation pump 152, the high-pressure liquid feed pump 153, and the valves 172a, 172b, 172c, 173a, 173b, and 173c are operated based on a signal from the control unit 140, and the flow rate of the absorbent AL2 flowing through the absorbent recirculation path Etc. are adjusted.

  In addition, a carbon dioxide outlet 113 is provided at the upper part of the regeneration tower 110 for taking out carbon dioxide diffused by circulating the absorbing liquid AL2 that has absorbed carbon dioxide. The carbon dioxide outlet 113 is connected to a carbon dioxide recovery line 115 provided with a suction pump 114. The carbon dioxide diffused in the regeneration tower 110 is recovered by a carbon dioxide recovery means (not shown) installed outside through the carbon dioxide recovery line 115.

  The regeneration tower 110 uses a flushing tank when operating in a state where the internal pressure is reduced, and in the same way as the absorption tower 100 when operating in a state where the internal pressure is increased. A tank with a filler is used.

  Next, the heat of the exhaust gas is recovered in the heat medium 181 via the heat recovery device 180, and the heat medium reflux path for circulating the heat medium 181 and heating the absorption liquid stored in each of the divided tanks 130a, 130b, 130c. Will be described.

  A heat medium reflux line 182 branched in correspondence with each divided tank 130a, 130b, 130c is led into each divided tank 130a, 130b, 130c of the storage tank 130 described above. The heat medium reflux line 182 led to the inside of each division tank 130a, 130b, 130c has a structure such as a fin so that heat can be exchanged with the absorbing liquid stored in each division tank 130a, 130b, 130c. The heat exchanging portions 182a, 182b, and 182c are formed.

  Each of the branched heat medium reflux lines 182 is provided with valves 174a, 174b, and 174c, respectively. Further, the heat medium reflux line 182 is provided with a liquid feed pump 183 that circulates the heat medium 181 flowing in the heat medium reflux line 182 with a heat recovery device 180 interposed therebetween. The exhaust gas 103 is supplied to the heat recovery device 180, and the heat medium 181 recovers the heat of the exhaust gas by making gas-liquid contact with the exhaust gas 103 by, for example, a scrubber type. The heat medium 181 transmits the heat recovered through the heat recovery device 180 to the absorbing liquid stored in each of the dividing tanks 130a, 130b, and 130c. The temperature of the heat medium 181 is 100 as the heat medium 181. When it does not exceed ° C., industrial water or the like is used, and when it exceeds 100 ° C., oil with high heat resistance or the like is used.

  For example, by opening the valve 174b corresponding to the division tank 130b and closing the valves 174a and 174c corresponding to the division tanks 130a and 130c, the heat recovery device 180, the heat medium reflux line 182, the heat exchange unit 182b, and the heat medium reflux line. A reflux path for circulating the heat medium 181 is formed in the order of 182 and the heat recovery apparatus 180. In this way, by switching the valves 174a, 174b, and 174c, it is possible to heat the absorption liquid in each of the dividing tanks 130a, 130b, and 130c. For example, the optimum temperature and absorption liquid for absorbing carbon dioxide are regenerated. The absorption liquid can be heated to an optimum temperature for releasing carbon dioxide.

  Here, the number of division tanks constituting the storage tank 130 is not limited, but if there are at least two, for example, the absorption tower 100, the absorption liquid reflux line 120a, the division tank 130a, the absorption liquid reflux line 120b, Absorption liquid reflux path for circulating the absorption liquid AL1 in the order of the absorption tower 100, and an absorption liquid for circulating the absorption liquid AL2 in the order of the regeneration tower 110, the absorption liquid reflux line 121a, the dividing tank 130b, the absorption liquid reflux line 121b, and the regeneration tower 110. The carbon dioxide absorption line and the carbon dioxide recovery line can be operated continuously by forming a reflux path.

  Further, before the absorption liquid AL2 having absorbed carbon dioxide is refluxed to the regeneration tower 110 by the heat medium reflux line 182, the absorption liquid AL2 is heated to a predetermined temperature, but the heat of the relatively low temperature exhaust gas 103 is utilized. Therefore, a predetermined time (for example, 10 to 100 minutes) is required to reach the predetermined temperature. Therefore, for example, an absorption step of circulating the absorption liquid AL1 in the order of the absorption tower 100, the absorption liquid reflux line 120a, the dividing tank 130a, the absorption liquid reflux line 120b, and the absorption tower 100 is performed, and at the same time, the regeneration tower 110, the absorption liquid A regeneration step of circulating the absorbing liquid AL2 in the order of the reflux line 121a, the dividing tank 130b, the absorbing liquid reflux line 121b, and the regeneration tower 110 is performed, and at the same time, the absorbing liquid AL3 that has already absorbed carbon dioxide is divided into the dividing tank 130c. If the heating (heating process) is performed, the regeneration process may be performed on the absorbent AL3 stored in the dividing tank 130c immediately after the regeneration process of the absorbing liquid AL2 stored in the dividing tank 130b. it can. Therefore, as in the example described above, it is preferable that there are at least three divided tanks constituting the storage tank 130 so that the regeneration process, the absorption process, and the heating process can be performed simultaneously. In addition, it is preferable that each division tank 130a, 130b, 130c is thermally insulated.

  Although not shown in the figure, in each of the dividing tanks 130a, 130b, and 130c, the absorbents AL1, AL2, and AL3 are guided to a pH meter that measures the hydrogen ion exponent pH of the absorbents AL1, AL2, and AL3. One end of the measurement line is installed. This pH meter is electrically connected to the control unit 140 and outputs a signal based on the measurement result to the control unit 140.

  The absorption liquid used in the first embodiment is prepared by dissolving 10 to 28 g of sodium carbonate per 100 g of water and adjusting the weight concentration to 9 to 22%. The weight of the absorbent stored in each of the divided tanks 130a, 130b, and 130c is 1 to 5000 tons. Further, in the above-described regeneration process, absorption process and heating process, the regeneration process and the absorption process are terminated when, for example, the value of the hydrogen ion exponent pH of the absorption liquid falls within a predetermined range, and the heating process is performed on the absorption liquid. The process is terminated when the temperature reaches a predetermined temperature. The time from the start to the end of each of these steps is about 10 to 100 minutes.

  Further, when a reflux path for circulating the absorption liquid AL1 is formed in the order of the absorption tower 100, the absorption liquid reflux line 120a, the dividing tank 130a, the absorption liquid reflux line 120b, and the absorption tower 100 (absorption process), the absorption tower 100 and The temperature of the absorbing liquid AL1 in the dividing tank 130a is set to 40 to 75 ° C. In addition, when a reflux path for circulating the absorption liquid AL2 is formed in the order of the regeneration tower 110, the absorption liquid reflux line 121a, the dividing tank 130b, the absorption liquid reflux line 121b, and the regeneration tower 110 (regeneration step), the regeneration tower 110 and The temperature of the absorbing liquid AL2 in the dividing tank 130b is set to 60 to 90 ° C. In addition, absorption liquid AL2 is set to this temperature through a heating process. In the heating process in the division tank 130b, the temperature of the heat medium 181 in the heat exchange unit 182b of the heat medium reflux line 182 is set to 70 to 90 ° C., and the temperature of the absorption liquid AL2 stationary in the division tank 130b is 60 to Set to 90 ° C.

  Here, the temperature of the absorption liquid AL1 in the absorption tower 100 and the dividing tank 130a is set in the range of 40 to 75 ° C. The absorption liquid AL1 mainly containing sodium carbonate is less than 40 ° C. This is because the absorption into the absorption liquid AL1 is slow, and when it exceeds 75 ° C., carbon dioxide absorbed in the absorption liquid AL1 starts to be released. In addition, the temperature of the absorbing liquid AL2 in the regeneration tower 110 and the dividing tank 130c is set in the range of 60 to 90 ° C. The reason for the absorbing liquid AL2 containing sodium carbonate as the main solute is less than 60 ° C. even under reduced pressure. This is because a large amount of water disappears from the absorbing liquid AL2 even under pressure when the release of the water is over 90 ° C.

  Here, the internal pressure of the regeneration tower 110 when the absorption liquid is sodium carbonate as a main solute is set to a reduced pressure state of −0.08 to 0 MPa as a gauge pressure. Used.

  Next, the operation of the carbon dioxide recovery system 10 will be described.

  Here, when the carbon dioxide recovery system 10 is in operation, 10 to 28 g of sodium carbonate per 100 g of water was dissolved in the dividing tank 130a, the dividing tank 130b, and the dividing tank 130c to adjust the weight concentration to 9 to 22%. The operation of the carbon dioxide recovery system 10 will be described on the assumption that an absorbing liquid having a temperature of 40 to 75 ° C. is stored. In addition, here, the absorbing liquids stored in the dividing tank 130a, the dividing tank 130b, and the dividing tank 130c are referred to as an absorbing liquid ALa, an absorbing liquid ALb, and an absorbing liquid ALc, respectively.

  During the operation of the carbon dioxide recovery system 10, the valves 170a and 171a corresponding to the division tank 130a are opened, the valves 170b and 170c and valves 171b and 171c corresponding to the division tank 130b and the division tank 130c are closed, and the absorption tower. The absorbing liquid reflux path for circulating the absorbing liquid ALa is formed in the order of 100, the absorbing liquid reflux line 120a, the dividing tank 130a, the absorbing liquid reflux line 120b, and the absorption tower 100.

  Exhaust gas 103 discharged from a boiler of a thermal power plant, a municipal waste incineration plant or the like passes through a heat recovery device 180 and is supplied from the exhaust gas inlet 104 into the absorption tower 100 by a gas blower 105. Note that the temperature of the exhaust gas 103 is 110 to 120 ° C. before entering the heat recovery device 180, and 60 to 90 ° C. after leaving the heat recovery device 180.

  When the exhaust gas 103 is supplied into the absorption tower 100, the absorption liquid ALa accommodated in the dividing tank 130a is supplied to the absorption liquid inlet for absorption 102 through the absorption liquid recirculation line 120b and ejected from the absorption liquid ejection part 106. Is done. The flow rate of the absorbing liquid ALa ejected from the absorbing liquid ejecting unit 106 is adjusted by the liquid feeding pump 150 that is controlled based on a signal from the control unit 140.

  The absorbing liquid ALa ejected from the absorbing liquid ejecting portion 106 flows down through the filler 107 and comes into gas-liquid contact with the exhaust gas 103 flowing upward from below in the filler 107 to absorb carbon dioxide contained in the exhaust gas 103. To do. Then, the absorption liquid ALa that has absorbed carbon dioxide flows down to the bottom of the absorption tower 100. On the other hand, the remaining exhaust gas 103 such as nitrogen and carbon dioxide that has not been absorbed is discharged to the atmosphere from the exhaust port 108.

  The absorption liquid ALa that has flowed down through the filler 107 is guided to the absorption liquid reflux line 120a by the derivation pump 151, and is supplied to the dividing tank 130a. Further, the absorption liquid ALa guided to the dividing tank 130 a is guided to the absorption liquid reflux line 120 b by the liquid feed pump 150 and supplied to the absorption liquid inlet for absorption 102.

  Here, the reaction in which carbon dioxide is absorbed by the sodium carbonate water that is the absorption liquid ALa to generate sodium hydrogen carbonate is an exothermic reaction, and therefore the temperature of the absorption liquid ALa rises while the absorption liquid ALa is refluxed. . Therefore, the absorption liquid ALa is cooled by the cooling device 190 interposed in the absorption liquid reflux line 120b, and the temperature of the absorption liquid ALa is adjusted to be in the above-described range of 40 to 75 ° C. The temperature adjustment of the absorbing liquid ALa in the cooling device 190 is performed by adjusting the flow rate of the cooling medium supplied to the cooling device 190, for example, by a control signal from the control unit 140.

  As described above, the absorption liquid ALa is circulated in the order of the absorption tower 100, the absorption liquid reflux line 120a, the dividing tank 130a, the absorption liquid reflux line 120b, and the absorption tower 100, whereby the absorption liquid ALa contains the dioxide dioxide contained in the exhaust gas 103. Absorb carbon efficiently.

  Here, in the dividing tank 130a, a part of the refluxed absorption liquid ALa is guided to a pH meter via a measurement line (not shown). Then, the pH meter detects the hydrogen ion exponent pH of the guided absorption liquid ALa, and outputs a signal corresponding to the detected value to the control unit 140.

  The controller 140 determines whether or not the pH value of the absorption liquid ALa in the dividing tank 130a is in the range of 8.5 to 9.5 based on the signal from the pH meter. In addition, by absorbing the carbon dioxide contained in the exhaust gas 103, the absorbing liquid ALa becomes an aqueous solution containing sodium hydrogen carbonate, and the one whose pH value is 11 or more is lowered.

  When the control unit 140 determines that the pH value of the absorption liquid ALa is larger than 9.5, the absorption liquid ALa guided to the dividing tank 130a is continuously supplied by the liquid feeding pump 150 to the absorption liquid reflux line 120b. Is supplied to the absorption liquid inlet 102 for absorption, and the above-described reflux operation is repeated.

  On the other hand, if the control unit 140 determines that the pH value of the absorbent ALa is in the range of 8.5 to 9.5, the controller 170 corresponding to the dividing tank 130a provided in the absorbent reflux line 120a and The valve 171a corresponding to the dividing tank 130a provided in the absorbing liquid reflux line 120b is controlled to be closed, and at the same time, the valve 170b corresponding to the dividing tank 130b provided in the absorbing liquid reflux line 120a and the absorbing liquid reflux line 120b are provided. Control is performed to open the valve 171b corresponding to the divided tank 130b.

  Thus, by switching the opening and closing of the valves 170a and 170b and the valves 171a and 171b, the absorption liquid ALb is circulated in the order of the absorption tower 100, the absorption liquid reflux line 120a, the dividing tank 130b, the absorption liquid reflux line 120b, and the absorption tower 100. An absorption liquid reflux path is formed. And the absorption liquid ALb accommodated in the division tank 130b recirculates through the absorption liquid recirculation path, and the above-described recirculation operation of absorbing carbon dioxide is repeated.

  Subsequently, based on a control signal from the control unit 140, the valve 174a of the heat medium reflux line 182 corresponding to the division tank 130a is opened, and a reflux path for circulating the heat medium 181 to the heat exchange unit 182a in the division tank 130a is established. Form.

  Heat is transferred from the exhaust gas 103 having a temperature of about 110 to 120 ° C. to the heat medium 181 having a temperature of about 40 to 75 ° C. via the heat recovery device 180, and the temperature of the heat medium 181 gradually increases to 60 to 90 ° C. To rise. As the temperature of the heat medium 181 rises, the temperature of the absorption liquid ALa in the dividing tank 130a also rises to 60 to 90 ° C. in 10 to 100 minutes and reaches a temperature at which the absorption liquid can be regenerated.

  Subsequently, the control unit 140 opens the valve 173a and the valve 172a corresponding to the dividing tank 130a, and the absorbing liquid ALa in the order of the regeneration tower 110, the absorbing liquid reflux line 121a, the dividing tank 130a, the absorbing liquid reflux line 121b, and the regeneration tower 110. A reflux path is circulated. The absorption liquid ALa has a pH value in the range of 8.5 to 9.5 and a temperature of 60 to 90 ° C., and is in a state suitable for regeneration of the absorption liquid ALa.

  The absorbing liquid ALa accommodated in the dividing tank 130a is guided to the regenerating absorbing liquid inlet 112 of the regenerating tower 110 through the absorbing liquid reflux line 121b by the high-pressure liquid feeding pump 153. The absorption liquid ALa guided to the regeneration absorption liquid inlet 112 is ejected into the decompression regeneration tower 110 using the discharge pressure of the high-pressure liquid feed pump 153 to release carbon dioxide. The flow rate of the absorbing liquid ALa ejected from the regeneration absorbing liquid inlet 112 is adjusted by a high-pressure liquid feeding pump 153 that is controlled based on a signal from the control unit 140.

  The absorption liquid ALa ejected into the regeneration tower 110 is guided by the lead-out pump 152 from the regeneration absorption liquid discharge port 111 provided at the bottom of the regeneration tower 110 to the dividing tank 130a through the absorption liquid reflux line 121a.

  Here, the carbon dioxide released into the regeneration tower 110 is sucked by the suction pump 114, and a carbon dioxide recovery means (illustrated) from the carbon dioxide outlet 113 provided at the upper part of the regeneration tower 110 through the carbon dioxide recovery line 115. Not) and collected.

  Further, the absorption liquid ALa guided to the dividing tank 130a is guided to the regeneration absorbent inlet 112 of the regeneration tower 110 via the absorbent reflux line 121b by the high-pressure liquid feed pump 153, and the above-described reflux operation is repeated. As described above, the absorption liquid ALa is circulated in the order of the regeneration tower 110, the absorption liquid reflux line 121a, the dividing tank 130a, the absorption liquid reflux line 121b, and the regeneration tower 110, thereby efficiently releasing carbon dioxide from the absorption liquid ALa. Can do.

  Since the absorption liquid ALa in the dividing tank 130a has reached a temperature of 60 to 90 ° C., carbon dioxide may be released and moisture may be lost in the dividing tank 130a. A pipe that guides the carbon dioxide generated inside to the carbon dioxide recovery line 115 may be provided. At this time, it is preferable to interpose a cooler, for example, in a pipe leading to the carbon dioxide recovery line 115 to collect water vapor flowing through this pipe together with carbon dioxide as a drain and separate it from carbon dioxide.

  Here, the reaction for releasing the carbon dioxide absorbed by the absorbing liquid ALa, that is, the reaction for releasing carbon dioxide from the sodium hydrogen carbonate water and regenerating the sodium carbonate is an endothermic reaction, and the temperature of the absorbing liquid ALa is refluxed. Decreases each time the operation is repeated. Here, when the amount of heat supplied from the heat exchange unit 182a of the heat medium reflux line 182 cannot compensate for this reduced amount of heat, for example, a heat exchanger that can supply steam to the bottom of the regeneration tower 110, for example. The absorption liquid ALa accumulated at the bottom of the regeneration tower 110 may be heated. The heat source to be heated is not limited to steam. For example, the absorption liquid ALa accumulated at the bottom of the regeneration tower 110 may be heated with a heater or the like.

  In the dividing tank 130a, a part of the refluxed absorption liquid ALa is guided to a pH meter via a measurement line (not shown). Then, the pH meter detects the hydrogen ion exponent pH of the guided absorption liquid ALa, and outputs a signal corresponding to the detected value to the control unit 140.

  The controller 140 determines whether or not the pH value of the absorbing liquid ALa in the dividing tank 130a is in the range of 11 to 12 based on the signal from the pH meter. In addition, by releasing carbon dioxide from the absorbing liquid ALa, the pH value of the absorbing liquid ALa approaches the initial pH value of the absorbing liquid ALa before absorbing carbon dioxide.

  When the control unit 140 determines that the pH value of the absorption liquid ALa is smaller than 11, the absorption liquid ALa guided to the dividing tank 130a is continuously passed through the absorption liquid reflux line 121b by the high-pressure liquid feed pump 153. Then, it is guided to the regeneration absorbent inlet 112 of the regeneration tower 110, and the above reflux operation is repeated.

  On the other hand, when it is determined that the pH value of the absorbent ALA is in the range of 11 to 12, the control unit 140 is provided in the derivation pump 152 and the absorbent return line 121b provided in the absorbent return line 121a. Control to stop the high-pressure liquid feed pump 153 is performed. Further, control is performed to close the valve 172a corresponding to the dividing tank 130a provided in the absorbing liquid reflux line 121a and the valve 173a corresponding to the dividing tank 130a provided in the absorbing liquid reflux line 121b.

  Moreover, in the absorption process in the absorption liquid ALb started almost simultaneously with the heating process for the absorption liquid ALa in the division tank 130a, the control unit 140 performs the above-described absorption tower 100, absorption liquid reflux line 120a, division tank 130b, absorption liquid reflux. It is determined whether or not the hydrogen ion exponent pH in the absorption liquid ALb circulating through the absorption liquid ALb in the order of the line 120b and the absorption tower 100 is in the range of 8.5 to 9.5.

  When the controller 140 determines that the pH value of the absorbent ALb is greater than 9.5, the absorbent ALb guided to the dividing tank 130b is continuously fed by the liquid feed pump 150 to the absorbent reflux line 120b. Is supplied to the absorption liquid inlet 102 for absorption, and the above-described reflux operation is repeated.

  On the other hand, when the control unit 140 determines that the pH value of the absorption liquid ALb is in the range of 8.5 to 9.5, the valve 170b corresponding to the divided tank 130b provided in the absorption liquid reflux line 120a and At the same time as performing control to close the valve 171b corresponding to the dividing tank 130b provided in the absorption liquid reflux line 120b, control to open the valve 174b corresponding to the dividing tank 130b provided in the heat medium reflux line 182 is performed. Then, the absorbing liquid ALb in the dividing tank 130b is heated to a recyclable temperature. The heating process of the absorbing liquid ALb is performed when the regeneration process of the absorbing liquid ALa is being performed.

  Subsequently, the regenerated absorption liquid ALa stored in the division tank 130a is absorbed by circulating the absorption liquid ALa in the order of the absorption tower 100, the absorption liquid reflux line 120a, the division tank 130a, the absorption liquid reflux line 120b, and the absorption tower 100. It is guided to the liquid reflux path and again performs the operation of absorbing carbon dioxide. On the other hand, the absorption liquid ALb heated to a reproducible temperature in the heating step is absorbed by circulating the absorption liquid ALb in the order of the regeneration tower 110, the absorption liquid reflux line 121a, the dividing tank 130b, the absorption liquid reflux line 121b, and the regeneration tower 110. It is guided to the liquid reflux path, releases carbon dioxide, and is regenerated to the original absorbing liquid ALb.

  Here, in the description of the operation of the carbon dioxide recovery system 10 described above, an example is shown in which the absorption liquids of the two divided tanks of the divided tank 130a and the divided tank 130b are alternately used in the absorption process, the heating process, and the regeneration process. . That is, in the above-described example, first, the absorption process is performed using the absorption liquid ALa in the division tank 130a, and then the absorption process is performed using the absorption liquid ALb in the division tank 130b when the heating process is performed. Furthermore, it was shown that the heating step of the absorbing liquid ALb in the dividing tank 130b is performed during the regeneration process of the absorbing liquid ALa in the dividing tank 130a.

  Note that the operation of the carbon dioxide recovery system 10 is not limited to this, and the following cases are also included in the example of the operation of the carbon dioxide recovery system 10, which uses three divided tanks at the same time. This is an example of a case where

  First, an absorption process is performed using the absorption liquid ALa in the dividing tank 130a. Subsequently, the absorption process is performed using the absorption liquid ALb in the division tank 130b at the same time as the heating process is performed on the absorption liquid ALa in the division tank 130a having a predetermined hydrogen ion index pH value. Subsequently, with respect to the absorbing liquid ALb of the dividing tank 130b having a predetermined hydrogen ion index pH value at the same time as performing the regeneration process on the absorbing liquid ALa of the dividing tank 130a having reached a recyclable temperature, A heating step is performed, and at the same time, an absorption step is performed using the absorption liquid ALc in the dividing tank 130c.

  Here, in the absorption step described above, the absorption liquid absorbs not only carbon dioxide but also sulfur oxide contained in the exhaust gas 103, and sulfite ions accumulate in the absorption liquid when the absorption liquid is used for a long time. . This accumulation of sulfite ions is not preferable because it reduces the carbon dioxide recovery rate. Therefore, for example, when the concentration of sulfite ions contained in the absorption liquid ALa of the dividing tank 130a reaches 0.5% by weight, calcium chloride is added to the dividing tank 130a to precipitate the sulfite ions as calcium sulfite. It is preferable to remove from the dividing tank 130a.

  The concentration of sulfite ion contained in the absorption liquid ALa when adding calcium chloride is not limited to 0.5% by weight concentration, and even in the range of 0.01 to 1.0%. Good. Here, the concentration range of sulfite ions contained in the absorption liquid ALa when adding calcium chloride is set to 0.01 to 1.0% because the concentration of sulfite ions is smaller than 0.01% by weight. In this case, it is difficult to recover as calcium sulfate (gypsum), and when it is larger than 1.0%, the carbon dioxide recovery rate decreases.

  The concentration of sulfite ions is measured by, for example, an ion concentration measurement device such as ion chromatography connected via a line branched from a measurement line (not shown) installed in each of the dividing tanks 130a, 130b, and 130c. The This ion concentration measurement apparatus is electrically connected to the control unit 140, and the measurement information of the concentration of sulfite ions is output to the control unit 140. Moreover, new absorption liquid ALa is supplied to the division tank 130a from which sulfite ions have been removed as calcium sulfite.

  As described above, in the carbon dioxide recovery system 10 of the first embodiment, the heat of a relatively low temperature exhaust gas of 110 to 120 ° C. is recovered to the heat medium 181 via the heat recovery device 180, and the heat medium 181. Can be circulated to heat the absorption liquid accommodated in each of the dividing tanks 130a, 130b, and 130c. Thereby, for example, the absorbent after absorbing carbon dioxide can be heated to a reproducible temperature. In this way, the carbon dioxide recovery system 10 does not require a large heating device or a large amount of heat, and can effectively regenerate the absorbing liquid by effectively using exhaust heat, thereby improving the thermal efficiency of the system. This can save energy.

  Also, the absorption liquid discharged from the absorption liquid discharge port 101 of the absorption tower 100 is refluxed to the absorption liquid introduction port 102 for absorption, and an absorption liquid reflux path for absorbing carbon dioxide, and a regenerative absorption liquid discharge port 111 of the regeneration tower 110. The absorption liquid discharged from the refrigerant can be refluxed to the regeneration-use absorption liquid inlet 112, and an absorption liquid reflux path for regenerating the absorption liquid by releasing carbon dioxide can be provided independently. As a result, the flow rate of the absorption liquid flowing through each absorption liquid reflux path can be individually set, and the reflux flow rate of the absorption liquid suitable for each of the carbon dioxide absorption process and the absorption liquid regeneration process is set. be able to.

  Furthermore, since the carbon dioxide recovery system 10 includes at least three division tanks, each of the absorption process, the heating process, and the regeneration process can be performed at the same time, so that the operating efficiency of the system can be improved. System can be constructed.

  The carbon dioxide recovery system 10 can also recover sulfur oxides that are air pollutants. Furthermore, since the carbon dioxide recovery system 10 can recover a large amount of carbon dioxide emitted from thermal power plants and municipal waste incineration plants without using excessive energy, it contributes to the prevention of global warming. Can do.

(Second Embodiment)
The carbon dioxide recovery system according to the second embodiment of the present invention uses an aqueous potassium carbonate solution as an absorbent in the carbon dioxide recovery system 10 according to the first embodiment described above. Accordingly, the basic configuration and operation of the carbon dioxide recovery system of the second embodiment are the same as those of the carbon dioxide recovery system 10 of the first embodiment, and therefore the second embodiment will be described with reference to FIG. The carbon dioxide recovery system will be described, and the description overlapping with the description in the carbon dioxide recovery system 10 of the first embodiment will be omitted.

  The absorption liquid used in the carbon dioxide recovery system of the second embodiment is prepared by dissolving 10 to 43 g of potassium carbonate per 100 g of water and adjusting the weight concentration to 9 to 30%. Further, when the absorption liquid reflux path for circulating the absorption liquid ALa is formed in the order of the absorption tower 100, the absorption liquid reflux line 120a, the dividing tank 130a, the absorption liquid reflux line 120b, and the absorption tower 100, the absorption tower 100 and the division tank The temperature of the absorbing liquid ALa in 130a is set to about 40 to 75 ° C.

  Further, when the absorption liquid reflux path for circulating the absorption liquid ALb is formed in the order of the regeneration tower 110, the absorption liquid reflux line 121a, the division tank 130b, the absorption liquid reflux line 121b, and the regeneration tower 110, the regeneration tower 110 and the division tank. The temperature of the absorbing liquid ALb at 130b is set to about 90 to 110 ° C.

  Here, the temperature of the absorption liquid ALa in the absorption tower 100 and the dividing tank 130a is set to 40 to 75 ° C. In the absorption liquid ALa containing potassium carbonate as a main solute, the absorption of carbon dioxide is below 40 ° C. This is because the absorption into the liquid ALa is slow, and when it exceeds 75 ° C., a large amount of water disappears from the absorption liquid ALa.

  In addition, the temperature of the absorption liquid ALb in the regeneration tower 110 and the dividing tank 130b is set to 90 to 110 ° C. The absorption liquid ALb containing potassium carbonate as a main solute has a slow release of carbon dioxide below 90 ° C. This is because if the temperature exceeds 110 ° C., a large amount of water vapor is generated from the absorbing liquid ALb even in a pressurized state.

  Here, the internal pressure of the regeneration tower 110 when the absorbing solution contains potassium carbonate as a main solute can be set in the range of -0.08 to 0.15 MPa as a gauge pressure. When the internal pressure of the regeneration tower 110 is set to be reduced, a flushing tank is used as the regeneration tower 110. When the internal pressure of the regeneration tower 110 is set under pressure, a tank equipped with a filler is used as the regeneration tower 110 as in the absorption tower 100.

  In the carbon dioxide recovery system of the second embodiment using potassium carbonate as the main solute of the absorption liquid described above, the same effects as those of the carbon dioxide recovery system of the first embodiment described above are obtained. The heat of the exhaust gas at a relatively low temperature of 110 to 120 ° C. is recovered in the heat medium 181 through the heat recovery device 180, and the heat medium 181 is circulated to be stored in each of the divided tanks 130a, 130b, and 130c. The absorbent can be heated. Thereby, for example, the absorbent after absorbing carbon dioxide can be heated to a reproducible temperature. As described above, this carbon dioxide recovery system does not require a large heating device or a large amount of heat, and can effectively regenerate the absorbing liquid by effectively using exhaust heat, thereby improving the thermal efficiency of the system. This can save energy.

  Also, the absorption liquid discharged from the absorption liquid discharge port 101 of the absorption tower 100 is refluxed to the absorption liquid introduction port 102 for absorption, and an absorption liquid reflux path for absorbing carbon dioxide, and a regenerative absorption liquid discharge port 111 of the regeneration tower 110. The absorption liquid discharged from the refrigerant can be refluxed to the regeneration-use absorption liquid inlet 112, and an absorption liquid reflux path for regenerating the absorption liquid by releasing carbon dioxide can be provided independently. As a result, the flow rate of the absorption liquid flowing through each absorption liquid reflux path can be individually set, and the reflux flow rate of the absorption liquid suitable for each of the carbon dioxide absorption process and the absorption liquid regeneration process is set. be able to.

  Furthermore, in the carbon dioxide recovery system of the second embodiment, since at least three divided tanks are provided, each of the absorption process, the heating process, and the regeneration process can be performed at the same time, thereby improving the system operating efficiency. And an effective system can be constructed.

  In addition, this carbon dioxide recovery system can also recover sulfur oxides that are air pollutants. In addition, this carbon dioxide recovery system can recover a large amount of carbon dioxide emitted from thermal power plants and municipal waste incineration plants without using excessive energy, contributing to the prevention of global warming. Can do.

(Third embodiment)
The carbon dioxide recovery system according to the third embodiment of the present invention uses an aqueous amine solution as an absorbent in the carbon dioxide recovery system 10 according to the first embodiment described above. Accordingly, the basic configuration and operation of the carbon dioxide recovery system according to the third embodiment are the same as those of the carbon dioxide recovery system 10 according to the first embodiment. Therefore, the third embodiment will be described with reference to FIG. The carbon dioxide recovery system will be described, and the description overlapping with the description in the carbon dioxide recovery system 10 of the first embodiment will be omitted.

  The absorption liquid used in the carbon dioxide recovery system of the third embodiment is prepared by dissolving 10 to 43 g of amine compound per 100 g of water and adjusting the weight concentration to 9 to 30%. Examples of amine compounds used here include 2-amino-2-methyl-1-propanol (AMP) and methyldiethanolamine (MDEA).

Further, when the absorption liquid reflux path for circulating the absorption liquid ALa is formed in the order of the absorption tower 100, the absorption liquid reflux line 120a, the dividing tank 130a, the absorption liquid reflux line 120b, and the absorption tower 100, the absorption tower 100 and the division tank The temperature of the absorbing liquid ALa in 130a is set to about 40 to 60 ° C. Further, when the absorption liquid reflux path for circulating the absorption liquid ALb is formed in the order of the regeneration tower 110, the absorption liquid reflux line 121a, the division tank 130b, the absorption liquid reflux line 121b, and the regeneration tower 110, the regeneration tower 110 and the division tank. The temperature of the absorbing liquid ALb at 130b is set to about 115 to 125 ° C.
Furthermore, when using an absorbing solution containing an amine compound as a main solute, as described above, the regeneration temperature of the absorbing solution is set higher than when using an absorbing solution containing sodium carbonate or potassium carbonate as a main solute. There is a need. Therefore, the temperature of the exhaust gas 103 is about 140 to 160 ° C. before entering the heat recovery device 180 and about 120 to 140 ° C. after leaving the heat recovery device 180. In addition, oil with high heat resistance is used for the heat medium 181 circulating through the heat medium reflux line 182.

  Here, the temperature of the absorption liquid ALa in the absorption tower 100 and the dividing tank 130a is set to about 40 to 60 ° C. The absorption liquid ALa whose main solute is an amine compound is less than 40 ° C. This is because the absorption into the absorption liquid ALa is slow, and when it exceeds 60 ° C., a large amount of water disappears from the absorption liquid ALa.

  Further, the temperature of the absorption liquid ALb in the regeneration tower 110 and the dividing tank 130b is set to about 120 to 140 ° C. The absorption liquid ALb mainly composed of an amine compound releases carbon dioxide when the temperature falls below 120 ° C. This is because if the temperature is higher than 140 ° C., water vapor generated from the absorbing liquid ALb increases even in a pressurized state.

  Here, the internal pressure of the regeneration tower 110 in the case where the absorption liquid contains an amine compound as a main solute can be set in the range of 0.15 to 0.4 MPa as a gauge pressure. As with 100, a tank with a filler is used.

  In the carbon dioxide recovery system of the third embodiment using an amine compound as the main solute of the absorption liquid described above, the same action and effect as in the carbon dioxide recovery system of the first and second embodiments described above. An effect can be obtained.

  In the carbon dioxide recovery system of the third embodiment, the heat of a relatively low temperature exhaust gas of 140 to 160 ° C. is recovered to the heat medium 181 via the heat recovery device 180, and the heat medium 181 is circulated to each division. The absorption liquid stored in the tanks 130a, 130b, and 130c can be heated. Thereby, for example, the absorbent after absorbing carbon dioxide can be heated to a reproducible temperature. As described above, this carbon dioxide recovery system does not require a large heating device or a large amount of heat, and can effectively regenerate the absorbing liquid by effectively using exhaust heat, thereby improving the thermal efficiency of the system. This can save energy.

  Also, the absorption liquid discharged from the absorption liquid discharge port 101 of the absorption tower 100 is refluxed to the absorption liquid introduction port 102 for absorption, and an absorption liquid reflux path for absorbing carbon dioxide, and a regenerative absorption liquid discharge port 111 of the regeneration tower 110. The absorption liquid discharged from the refrigerant can be refluxed to the regeneration-use absorption liquid inlet 112, and an absorption liquid reflux path for regenerating the absorption liquid by releasing carbon dioxide can be provided independently. As a result, the flow rate of the absorption liquid flowing through each absorption liquid reflux path can be individually set, and the reflux flow rate of the absorption liquid suitable for each of the carbon dioxide absorption process and the absorption liquid regeneration process is set. be able to.

  Furthermore, in the carbon dioxide recovery system of the third embodiment, since at least three divided tanks are provided, each of the absorption process, the heating process, and the regeneration process can be performed at the same time, thereby improving the operation efficiency of the system. And an effective system can be constructed.

  In addition, this carbon dioxide recovery system can also recover sulfur oxides that are air pollutants. In addition, this carbon dioxide recovery system can recover a large amount of carbon dioxide emitted from thermal power plants and municipal waste incineration plants without using excessive energy, contributing to the prevention of global warming. Can do.

(Other embodiments)
In the first to third embodiments described above, an example in which the absorption liquid absorbs and releases carbon dioxide using a chemical reaction has been described. However, pressure conditions in the absorption process and the regeneration process are not accompanied by a chemical reaction. By adjusting, carbon dioxide can be absorbed and released through the absorbing solution. That is, the inside of the absorption tower 100 is pressurized, carbon dioxide is dissolved in the absorption liquid (absorption step), and the carbon dioxide is released from the absorption liquid by reducing the pressure in the regeneration tower 110 to be lower than the pressure in the absorption tower 100. (Regeneration process).

  In the carbon dioxide recovery system that does not involve this chemical reaction, for example, polyethylene glycol dimethyl ether or methanol is used as the absorbing solution. Using these absorbing liquids, carbon dioxide can be recovered using a system similar to the carbon dioxide recovery system of the first to third embodiments described above.

  In the case of this carbon dioxide recovery system, since no chemical reaction is involved, it is not necessary to heat the absorption liquid and it is not necessary to provide the heat medium reflux line 182. Moreover, the pressure in the absorption tower 100 which implements an absorption process is pressurized to about 2-3 MPa with a gauge pressure, and the pressure in the regeneration tower 110 which implements a regeneration process is 0.1-0.2 MPa with a gauge pressure. Pressurized to the extent. As the regeneration tower 110, a tank provided with a filler is used as in the absorption tower 100.

  In the carbon dioxide recovery system described above, the pressure in the absorption tower 100 for performing the absorption process and the pressure in the regeneration tower 110 for performing the regeneration process are adjusted via the absorption liquid without receiving heat from the outside. In addition, carbon dioxide can be absorbed and released (regeneration of the absorption liquid), and energy saving of the system can be achieved.

  Furthermore, in this carbon dioxide recovery system, since at least two divided tanks are provided, each of the absorption process and the regeneration process can be performed at the same time, so that the operating efficiency of the system can be improved, and an effective system Can be built. In addition, this carbon dioxide recovery system can recover a large amount of carbon dioxide emitted from thermal power plants and municipal waste incinerators without using excessive energy, contributing to the prevention of global warming. Can do.

The schematic diagram which shows the carbon dioxide collection system of embodiment of this invention. Schematic diagram showing a conventional carbon dioxide recovery system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Carbon dioxide collection system, 100 ... Absorption tower, 103 ... Exhaust gas, 105 ... Gas blower, 110 ... Regeneration tower, 114 ... Suction pump, 115 ... Carbon dioxide collection line, 120a, 120b, 121a, 121b ... Absorption liquid recirculation line, DESCRIPTION OF SYMBOLS 130 ... Storage tank, 130a, 130b, 130c ... Divided tank, 140 ... Control part, AL1, AL2, ALa, ALb, ALc ... Absorption liquid, 150 ... Liquid feed pump, 151, 152 ... Derivative pump, 153 ... High pressure liquid feed Pump, 170a, 170b, 170c, 171a, 171b, 171c, 172a, 172b, 172c, 173a, 173b, 173c ... Valve, 180 ... Heat recovery device, 181 ... Heat medium, 182 ... Heat medium reflux line, 182a, 182b, 182c ... Heat exchange part, 183 ... Liquid feed pump.

Claims (6)

An exhaust gas introduction port, an absorption liquid inlet for absorption, a remaining exhaust gas discharge port, and an absorption liquid discharge port are provided, and the exhaust gas introduced from the exhaust gas introduction port and the absorption liquid introduced from the absorption liquid introduction port for absorption are gas-liquid An absorbing device for contacting the absorbing liquid to absorb carbon dioxide in the exhaust gas;
A regeneration device comprising a regeneration absorbent inlet, a regeneration absorbent outlet, and a carbon dioxide outlet, and regenerating the absorbent by releasing carbon dioxide from the absorbent that has absorbed the carbon dioxide;
A first absorption liquid reflux line for refluxing the absorption liquid discharged from the absorption liquid discharge port of the absorption device to the absorption liquid introduction port for absorption;
A second absorption liquid reflux line for refluxing the absorption liquid discharged from the regeneration absorption liquid discharge port of the regeneration apparatus to the regeneration absorption liquid introduction port;
A storage tank composed of a plurality of divided tanks that can be interposed by switching the reflux line of the absorbing liquid to either the first absorbing liquid reflux line or the second absorbing liquid reflux line;
A heat recovery device for transferring heat from the exhaust gas to a heat medium, and a heat medium reflux line capable of heating the absorption liquid in each of the divided layers by circulating the heat medium. Carbon dioxide recovery system.   The carbon dioxide recovery system according to claim 1, wherein a main solute of the absorption liquid is sodium carbonate, potassium carbonate, or an amine compound. The first absorption liquid discharged from the absorption liquid discharge port of the absorption device is returned to the absorption liquid inlet for absorption of the absorption device through the first division tank among the plurality of division tanks constituting the storage tank. A first absorption step in which the exhaust gas introduced from the exhaust gas inlet and the first absorption liquid are brought into gas-liquid contact, and the first absorption liquid repeatedly absorbs carbon dioxide in the exhaust gas;
The reflux line of the first absorption liquid is closed, and the first absorption liquid stored in the first division tank that has absorbed carbon dioxide in the first absorption step is refluxed by the heat medium heated by the exhaust gas. A first heating step of heating to a predetermined temperature via a heat medium circulating in the line;
The reflux line of the first absorption liquid is switched, and the first absorption liquid heated to a predetermined temperature in the first heating step is guided to the regeneration absorption liquid inlet of the regeneration apparatus, and the regeneration absorption of the regeneration apparatus is performed. The first absorption liquid discharged from the liquid discharge port is refluxed to the regeneration absorption liquid introduction port through the first division tank, and carbon dioxide is released into the regeneration device, so that the first And a first regeneration step for regenerating the carbon dioxide absorption capacity of the absorbing liquid.   When performing the first heating step, the second absorption liquid capable of absorbing carbon dioxide stored in the second division tank of the storage tank is guided to the absorption liquid inlet for absorption of the absorption device, The second absorption liquid discharged from the absorption liquid discharge port of the absorption device is recirculated to the absorption liquid introduction port for absorption through the second division tank, and the exhaust gas and the second absorption liquid are recirculated. The carbon dioxide recovery method according to claim 3, further comprising a second absorption step in which gas-liquid contact is performed and the second absorption liquid repeatedly absorbs carbon dioxide in the exhaust gas. When the first regeneration step is performed, the second absorption liquid stored in the second division tank that closes the reflux line of the second absorption liquid and absorbs carbon dioxide in the second absorption step. A second heating step of heating to a predetermined temperature via a heat medium circulating in the heat medium reflux line heated by the exhaust gas,
When performing the first regeneration step, the third absorption liquid that has absorbed carbon dioxide stored in the third division tank of the storage tank is guided to the absorption liquid inlet for absorption of the absorption device, and The third absorption liquid discharged from the absorption liquid discharge port of the absorption device is recirculated to the absorption liquid introduction port for absorption through the third division tank, and the exhaust gas and the third absorption liquid are removed. The carbon dioxide recovery method according to claim 4, further comprising a third absorption step of bringing the third absorption liquid into contact with liquid and repeatedly absorbing carbon dioxide in the exhaust gas.   The carbon dioxide recovery method according to any one of claims 3 to 5, wherein a main solute of the absorption liquid is sodium carbonate, potassium carbonate, or an amine compound.

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