JP5586358B2 - Carbon dioxide separation and recovery system and operation method thereof - Google Patents

Description

  The present invention relates to a carbon dioxide separation and recovery system and an operation method thereof.

  In recent years, for thermal power plants that use large amounts of fossil fuels, a method for separating and recovering carbon dioxide in combustion exhaust gas by bringing the combustion exhaust gas into contact with an amine-based absorbent and releasing the recovered carbon dioxide to the atmosphere Research has been done on how to store without doing.

  Specifically, an absorption tower that absorbs carbon dioxide contained in combustion exhaust gas in an amine-based absorption liquid and an absorption liquid (rich liquid) that has absorbed carbon dioxide are supplied from the absorption tower, the rich liquid is heated, and the rich liquid A carbon dioxide recovery system is known that includes a regeneration tower that regenerates the absorbing liquid by releasing carbon dioxide gas from the atmosphere, and supplies the regenerated absorbing liquid (lean liquid) to the absorbing tower for reuse (for example, Patent Documents). 1).

  Since the carbon dioxide recovery system as described above is installed in addition to existing power generation facilities and the like, it is required to reduce its operating cost as much as possible. In particular, in the regeneration step of the absorbing liquid in the regeneration tower, a large amount of heat energy is required to release carbon dioxide gas from the rich liquid. Therefore, in order to reduce the operating cost of the carbon dioxide recovery system, it is important to reduce the thermal energy required in the absorption liquid regeneration process.

  The conventional carbon dioxide recovery system is a regenerative heat exchange system that heats the rich liquid supplied from the absorption tower to the regeneration tower between the absorption tower and the regeneration tower, using the lean liquid supplied from the regeneration tower to the absorption tower as a heat source. A vessel is provided to recover the heat of the lean liquid.

  However, the flow rate of the absorption liquid circulating in the carbon dioxide recovery system is not constant and varies depending on the operating conditions. Therefore, if the flow rate of the absorbing liquid is lower than the rated value of the regenerative heat exchanger, the heat exchanging performance of the regenerative heat exchanger is reduced, the temperature of the rich liquid cannot be raised sufficiently, and is necessary in the regenerating process of the absorbing liquid There has been a problem of increasing thermal energy.

JP 2004-323339 A

  It is an object of the present invention to provide a carbon dioxide separation and recovery system that suppresses an increase in thermal energy required in the regeneration process of the absorbing liquid and a method for operating the same, in response to fluctuations in the flow rate of the absorbing liquid.

A carbon dioxide separation and recovery system according to an aspect of the present invention is provided with an absorption tower that absorbs carbon dioxide contained in combustion exhaust gas into an absorption liquid, an absorption liquid that absorbs carbon dioxide from the absorption tower, and vapor from the absorption liquid. A regeneration tower for releasing the carbon dioxide gas containing the carbon dioxide gas and regenerating the absorption liquid, and discharging the exhaust gas containing the released carbon dioxide gas and steam; and the regeneration tower is provided between the absorption tower and the regeneration tower. A plurality of regenerative heat exchangers for heating the absorption liquid that has absorbed carbon dioxide supplied from the absorption tower to the regeneration tower, using the regenerated absorption liquid supplied from the tower to the absorption tower as a heat source, wherein the plurality of regenerative heat exchangers are connected in parallel, Ri each capacity Do different, the flow rate of the absorption solution supplied is intended to be adjusted respectively.

An operation method of a carbon dioxide separation and recovery system according to an aspect of the present invention includes an absorption tower that absorbs carbon dioxide contained in combustion exhaust gas in an absorption liquid, and an absorption liquid that absorbs carbon dioxide from the absorption tower. A regeneration tower for releasing carbon dioxide gas containing steam from the liquid and regenerating the absorbing liquid and discharging exhaust gas containing the released carbon dioxide gas and steam, and provided between the absorption tower and the regeneration tower A plurality of refrigerating absorption liquids supplied from the regeneration tower to the absorption tower are used as heat sources to heat the absorption liquid that has absorbed carbon dioxide supplied from the absorption tower to the regeneration tower, and have different capacities. of the regenerative heat exchanger, wherein the plurality of method of operating a regenerative heat exchanger connected to the carbon dioxide separation and recovery system in parallel, the absorption liquid to the plurality of regenerative heat exchanger Amounts, and adjusts so that less than 100% or 0% over 75% of the capacity.

  ADVANTAGE OF THE INVENTION According to this invention, the increase in the heat energy required by the reproduction | regeneration process of an absorption liquid can be suppressed with respect to the fluctuation | variation of the flow volume of an absorption liquid.

1 is a schematic configuration diagram of a carbon dioxide separation and recovery system according to an embodiment of the present invention. It is a graph which shows an example of the relationship between the absorption liquid flow volume of a regeneration heat exchanger, and the difference of the absorption liquid supplied to a regeneration tower, and regeneration tower operating temperature. It is a graph which shows an example of the relationship between the difference of the absorption liquid supplied to a regeneration tower, and the regeneration tower operating temperature, and the input energy to a reboiler.

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

  FIG. 1 shows a schematic configuration of a carbon dioxide separation and recovery system according to an embodiment of the present invention. Here, the carbon dioxide separation and recovery system recovers carbon dioxide contained in the combustion exhaust gas generated by the combustion of fossil fuel using an absorbing solution capable of absorbing carbon dioxide.

  As shown in FIG. 1, the carbon dioxide separation and recovery system 1 includes an absorption tower 3 that absorbs carbon dioxide contained in the combustion exhaust gas 2a into an absorption liquid, and an absorption liquid that absorbs carbon dioxide from the absorption tower 3 (hereinafter, rich liquid 4a). The rich liquid 4a is heated, the carbon dioxide gas containing water vapor is released from the absorbing liquid, the exhaust gas 2d containing carbon dioxide gas and water vapor is discharged, and the absorbing liquid is regenerated. And a tower 5.

  For example, combustion exhaust gas 2a generated in a power generation facility such as a thermal power plant is supplied to the lower part of the absorption tower 3 via the exhaust gas introduction line 8, and the combustion exhaust gas 2b from which carbon dioxide has been removed from the top of the absorption tower 3 is obtained. It is supposed to be discharged.

  The absorption tower 3 has an absorption tower still (tank) 3a for storing the rich liquid 4a generated by the absorption liquid absorbing carbon dioxide. Similarly, the regeneration tower 5 has a regeneration tower still (tank) 5a for storing an absorbing liquid regenerated by releasing the carbon dioxide gas from the rich liquid 4a (hereinafter referred to as a lean liquid 4b).

  Here, as the absorbing solution capable of absorbing carbon dioxide, for example, an amine compound aqueous solution in which an amine compound is dissolved in water is used.

  As shown in FIG. 1, a reboiler 6 is provided in the regeneration tower 5. The reboiler 6 generates a steam by heating a part of the lean liquid 4b stored in the regeneration tower still 5a by using the plant steam supplied from the power generation equipment as a heat source to increase the temperature thereof, thereby generating the steam. To supply. In addition, when heating the lean solution 4b in the reboiler 6, carbon dioxide gas is released from the lean solution 4b and supplied to the regeneration tower 5 together with the absorbing solution vapor. The absorption liquid vapor rises in the regeneration tower 5 through the packed bed 5b and heats the rich liquid 4a. Thereby, carbon dioxide gas is released from the rich liquid 4a. The packed bed 5b may be formed of a material having a porous structure, a honeycomb structure, or the like, for example, as long as it has an action of disturbing the absorption liquid passing through the packed bed 5b.

  The exhaust gas 2d containing the carbon dioxide gas and the absorption liquid vapor discharged from the regeneration tower 5 passes through the gas line 35 and is condensed by the gas cooler 31, and then the carbon dioxide gas and the absorption liquid by the gas-liquid separator 32. Gas-liquid separation into refluxing water containing components. The carbon dioxide gas 2e from the gas-liquid separator 32 is discharged through the recovered carbon dioxide derivation line 33 and stored in a storage facility (not shown). The reflux water from the gas-liquid separator 32 is returned to the regeneration tower 5 through the reflux line 34.

  Between the absorption tower 3 and the regeneration tower 5, three liquids 4a supplied from the absorption tower 3 to the regeneration tower 5 are heated by using the lean liquid 4b supplied from the regeneration tower 5 to the absorption tower 3 as a heat source. Regenerative heat exchangers 41, 51, and 61 are provided and configured to recover the heat of the lean liquid 4b. Here, as described above, when the carbon dioxide gas is released from the rich liquid 4 a in the regeneration tower 5, the rich liquid 4 a is heated using high-temperature steam from the reboiler 6 as a heat source. Therefore, the temperature of the lean solution 4b supplied to the regenerative heat exchangers 41, 51, 61 is relatively high, and this lean solution 4b is used as a heat source.

  The three regenerative heat exchangers 41, 51, 61 have different rated values (capacities) of the flow rate of the absorbing liquid. Each rated value will be described later.

  A rich liquid line 11 for supplying the rich liquid 4a to the regenerative heat exchangers 41, 51, 61 from the bottom of the absorption tower tank 3a is connected between the absorption tower 3 and the regenerative heat exchangers 41, 51, 61. . The rich liquid line 11 is provided with a rich liquid pump 12 that feeds the rich liquid 4 a from the absorption tower 3 to the regenerative heat exchangers 41, 51, 61. The rich liquid line 11 is branched into three rich liquid lines 11a, 11b, and 11c and connected to the regenerative heat exchangers 41, 51, and 61.

  The rich liquid line 11 a is provided with a flow meter 42 that measures the flow rate of the rich liquid 4 a and an adjustment valve 43 that adjusts the flow rate of the rich liquid 4 a supplied to the regenerative heat exchanger 41. Similarly, the rich liquid line 11 b is provided with a flow meter 52 that measures the flow rate of the rich liquid 4 a and an adjustment valve 53 that adjusts the flow rate of the rich liquid 4 a supplied to the regenerative heat exchanger 51. Similarly, the rich liquid line 11c is provided with a flow meter 62 for measuring the flow rate of the rich liquid 4a and an adjustment valve 63 for adjusting the flow rate of the rich liquid 4a supplied to the regenerative heat exchanger 61.

  Between the regeneration heat exchangers 41, 51, 61 and the regeneration tower 5, the rich liquid line 13 for supplying the rich liquid 4 a from the regeneration heat exchangers 41, 51, 61 to the upper part of the regeneration tower 5 is connected. The rich liquid line 13 branches into three rich liquid lines 13a, 13b, and 13c and is connected to the regenerative heat exchangers 41, 51, and 61.

  The rich liquid line 13 a is provided with a closing valve 44 for closing the regenerative heat exchanger 41 when the rich liquid 4 a is not passed through the regenerative heat exchanger 41. Similarly, the rich liquid line 13b is provided with a closing valve 54 for closing the regenerative heat exchanger 51 when the rich liquid 4a does not flow through the regenerative heat exchanger 51. Similarly, the rich liquid line 13c is provided with a closing valve 64 for closing the regenerative heat exchanger 61 when the rich liquid 4a does not flow through the regenerative heat exchanger 61.

  Between the regeneration tower 5 and the regeneration heat exchangers 41, 51, 61, a lean liquid line 14 for supplying the lean liquid 4b to the regeneration heat exchangers 41, 51, 61 from the bottom of the regeneration tower tank 5a is connected. . The lean liquid line 14 is provided with a lean liquid pump 15 that sends the lean liquid 4b from the regeneration tower 5 to the regenerative heat exchangers 41, 51, and 61. The lean liquid pump 15 can adjust the flow rate of the lean liquid 4b drawn from the bottom of the regeneration tower tank 5a. The lean liquid line 14 branches into three lean liquid lines 14a, 14b, and 14c, and is connected to the regenerative heat exchangers 41, 51, and 61.

  The lean liquid line 14a is provided with a flow meter 45 for measuring the flow rate of the lean liquid 4b and an adjustment valve 46 for adjusting the flow rate of the lean liquid 4b supplied to the regenerative heat exchanger 41. Similarly, a flow meter 55 that measures the flow rate of the lean solution 4b and an adjustment valve 56 that adjusts the flow rate of the lean solution 4b supplied to the regenerative heat exchanger 51 are provided in the lean solution line 14b. Similarly, a flow meter 65 for measuring the flow rate of the lean liquid 4b and an adjustment valve 66 for adjusting the flow rate of the lean liquid 4b supplied to the regenerative heat exchanger 61 are provided in the lean liquid line 14c.

  The lean liquid 4 b from the regenerative heat exchangers 41, 51, 61 is stored in the buffer tank 10. In order to close the regenerative heat exchangers 41, 51, 61 between the regenerative heat exchangers 41, 51, 61 and the buffer tank 10 when the lean liquid 4 b does not flow through the regenerative heat exchangers 41, 51, 61. Close valves 47, 57 and 67 are provided.

  The pump 16 feeds the lean solution 4 b stored in the buffer tank 10 to the upper part of the absorption tower 3. An absorbing liquid cooler 17 is provided between the pump 16 and the absorption tower 3. The absorption liquid cooler 17 cools the absorption liquid supplied to the absorption tower 3 using cooling water (cooling medium) as a cooling source.

  The absorption liquid supplied to the upper part of the absorption tower 3 descends from the upper part toward the absorption tower tank 3a in the absorption tower 3. On the other hand, the combustion exhaust gas 2 a supplied to the absorption tower 3 rises from the lower part toward the top in the absorption tower 3. Therefore, the combustion exhaust gas 2a containing carbon dioxide and the absorption liquid are in countercurrent contact (direct contact) in the packed bed 3b, the absorption liquid absorbs the carbon dioxide in the combustion exhaust gas 2a, and the rich liquid 4a is generated. The combustion exhaust gas 2b from which carbon dioxide has been removed is discharged from the top of the absorption tower 3, and the rich liquid 4a is stored in the absorption tower tank 3a of the absorption tower 3. The packed bed 3b may be formed of a material having a porous structure, a honeycomb structure, or the like, for example, as long as it has a function of disturbing the absorption liquid passing through the packed bed 3b.

  The combustion exhaust gas 2b discharged from the top of the absorption tower 3 is cooled by the gas cooler 21 and condensed with water, and then separated into gas and liquid by the gas / liquid separator 22 into the exhaust gas and the reflux water containing the absorption liquid component. The exhaust gas 2 c from the gas-liquid separator 22 is discharged out of the system through the exhaust gas outlet line 23, and the reflux water is returned to the absorption tower 3 through the reflux line 24.

  Furthermore, a control unit 70 is provided in the carbon dioxide separation and recovery system. The control unit 70 receives the measurement results from the flow meters 42, 52, 62, controls the opening degree of the adjustment valves 43, 53, 63, and adjusts the supply amount of the rich liquid 4a to the regenerative heat exchangers 41, 51, 61. can do. In addition, the control unit 70 receives the measurement results from the flow meters 45, 55, 65, controls the opening degree of the regulating valves 46, 56, 66, and supplies the lean liquid 4 b to the regenerative heat exchangers 41, 51, 61. Can be adjusted. The control unit 70 acquires information about the flow rate of the exhaust gas 2a supplied to the absorption tower 3 through the exhaust gas introduction line 8 and the carbon dioxide concentration in the exhaust gas 2a, and based on these information, separates and recovers carbon dioxide. The flow rate of the absorbing liquid circulating in the system can be obtained, and the supply amount of the rich liquid 4a and the supply amount of the lean liquid 4b to the regenerative heat exchangers 41, 51, 61 can be calculated.

  Next, the relationship between the absorption liquid flow rate and the heat exchange performance in the regenerative heat exchanger will be described.

In general, the overall heat transfer coefficient K [W / m ² · K] indicating the heat exchange performance of the regenerative heat exchanger is proportional to about 0.8 power of the liquid flow rate. FIG. 2 shows an example of the relationship between the absorption liquid flow rate L of the regeneration heat exchanger and the difference ΔT [K] between the absorption liquid supplied to the regeneration tower and the regeneration tower operating temperature. The absorption liquid flow rate L of the regenerative heat exchanger is ΔT = 10 [K] at 100% of the rated value. That is, when the flow rate of the regenerative heat exchanger is the rated value, it indicates that the temperature of the absorption liquid supplied from the regenerative heat exchanger to the regeneration tower is 10 [K] lower than the regeneration tower operating temperature.

  As can be seen from FIG. 2, when the absorption liquid flow rate L of the regenerative heat exchanger decreases, ΔT increases. That is, the heat exchange performance of the regenerative heat exchanger decreases as the flow rate L decreases.

  FIG. 3 shows an example of the relationship between the difference ΔT [K] between the absorption liquid supplied to the regeneration tower and the regeneration tower operating temperature and the input energy in the reboiler. Here, the input energy is based on the case of ΔT = 10 [K] (100%). FIG. 3 shows that the input energy increases as ΔT increases. This is because the energy required to raise the temperature of the absorbent to the regeneration tower operating temperature increases.

  In general, a carbon dioxide separation and recovery system is required to suppress an increase in reboiler input energy during operation to 5% or less. Therefore, FIG. 3 shows that ΔT needs to be 12.3 [K] or less. Further, FIG. 2 shows that the flow rate L of the regenerative heat exchanger needs to be 75% or more of the rated value in order to set ΔT to 12.3 [K] or less.

  From the above, in this embodiment, the flow rate of each of the regenerative heat exchangers 41, 51, 61 is adjusted so as to be 100% to 75% of the rated value.

  Subsequently, in describing the rated value of the flow rate of the absorbing liquid in the regenerative heat exchangers 41, 51, 61, first, a case where two regenerative heat exchangers having the same flow rate rating value (capacity) are provided will be described. . The flow rate of the absorption liquid circulating through the carbon dioxide separation and recovery system is 100, and the flow rate rating values of the two regenerative heat exchangers are 50. Since the flow rate of the regenerative heat exchanger is in the range of 100% to 75% of the rated value, the flow rate range of one regenerative heat exchanger is 50 to 37.5.

  Therefore, if the flow rate of the absorbent circulating through the carbon dioxide separation and recovery system is in the range of 100 to 75, the flow rate of the two regenerative heat exchangers can be set to 100% to 75% of the rated value. Moreover, if the flow rate of the absorption liquid circulating through the carbon dioxide separation and recovery system is in the range of 50 to 37.5, one of the two regenerative heat exchangers is closed and the other flow rate is set to 100% to the rated value. 75% can be handled. However, when the flow rate of the absorption liquid circulating through the carbon dioxide separation and recovery system is in the range of 75 to 50 or less than 37.5, the flow rates of these two regenerative heat exchangers are set to 100% to 75% of the rated value. % Can not cope.

  Of the two regenerative heat exchangers, by setting the rated value of one flow rate to 75% of the rated value of the other flow rate, the range in which the flow rate of the absorbent that circulates in the carbon dioxide separation and recovery system can be accommodated. spread. When the flow rate rating value of one regenerative heat exchanger is a and the other is 0.75 × a, the relationship of a + 0.75 × a = 100 is established. Therefore, one flow rate rating value of the regenerative heat exchanger is 57.1, and the other is 42.9. A practical ratio is 57:43.

  However, even if these two regenerative heat exchangers are used, if the flow rate of the absorption liquid circulating through the carbon dioxide separation and recovery system is less than 32.2, the flow rates of the two regenerative heat exchangers are rated. It cannot respond by making it 100%-75% of a value.

  In a normal plant, the flow rate fluctuation range of the absorption liquid circulating in the carbon dioxide separation and recovery system is often from 100 to 25 with a ¼ load. Therefore, it is desired that the regenerative heat exchanger can continuously cope with the flow rate of the absorbing liquid circulating through the carbon dioxide separation and recovery system from 100 to 25.

  Therefore, by adding one regenerative heat exchanger and providing three regenerative heat exchangers as in the present embodiment, the range in which the flow rate of the absorption liquid circulating in the carbon dioxide separation and recovery system can be further expanded. . For example, 42.9 of the flow rate rating values 57.1 and 42.9 of the two regenerative heat exchangers described above are divided into two. The flow rate rating value of the second regenerative heat exchanger is set to 32.2 which is the minimum value of the flow rate that can be handled in the case of the above two units, and the flow rate rating value of the third regenerative heat exchanger is The remaining 10.7 (= 42.9-32.2).

  By setting the three regenerative heat exchangers to such a capacity ratio, it is possible to continuously cope with the flow rate fluctuation range 100 to 24.2 of the absorbent circulating in the carbon dioxide separation and recovery system.

  Therefore, the capacity ratio of the regenerative heat exchangers 41, 51, 61 is preferably 57.1: 32.2: 10.7. As a practical ratio, (56 to 57): (32 to 33): It is preferable to be about (10-11).

Of the three regenerative heat exchangers, the maximum capacity is b, the second largest capacity is 0.75 × b, the minimum capacity is 0.75 ² × b, and b + 0.75 × b + 0.75 ² × b By satisfying the relationship = 100, the range in which the flow rate of the absorption liquid circulating in the carbon dioxide separation and recovery system can be handled is further expanded. At this time, the capacity of the three regenerative heat exchangers is 43.2, 32.4, and 24.3. By setting such a ratio, it is possible to continuously cope with the flow rate fluctuation range from 100 to 18.2.

  Therefore, it is more preferable that the capacity ratio of the regenerative heat exchangers 41, 51, 61 is 43.2: 32.4: 24.3, and the practical ratio is (43 to 44) :( 32-33): about (23-25).

  As described above, the regenerative heat exchangers 41, 51, 61 having the capacity ratio are provided, and the control unit 70 causes the flow rate of each regenerative heat exchanger to be 100% to 75% or 0% (closed) of the rated value. The control valves 43, 53, 63, 45, 55, and 65 are controlled. Thereby, even if the flow rate of the absorption liquid circulating in the carbon dioxide separation and recovery system fluctuates, the increase in the input energy of the reboiler 6 can be suppressed to less than 5%.

  As described above, according to the present embodiment, by providing three regenerative heat exchangers having different capacities, an increase in heat energy required in the regenerating step of the absorbing liquid is suppressed with respect to fluctuations in the flow rate of the absorbing liquid. can do.

  In the above embodiment, an example in which three regenerative heat exchangers are provided has been described, but four or more may be provided.

  In addition, when it is sufficient to correspond to the fluctuation range 100 to 32.2 of the flow rate of the absorption liquid circulating in the carbon dioxide separation and recovery system, as described above, the capacity of the two units having the capacities of 57.1 and 42.9 A regenerative heat exchanger may be provided. Since the number of regenerative heat exchangers can be reduced, costs can be reduced.

  In the above-described embodiment, an example in which the amount of absorbent supplied to the regenerative heat exchanger is 100% to 75% of the capacity (rated value) has been described, but this range varies depending on the allowable increase range of the input energy of the reboiler 6. Accordingly, the suitable capacity ratio of the plurality of regenerative heat exchangers also changes.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 Carbon dioxide separation and recovery system 3 Absorption tower 5 Regeneration tower 6 Reboiler 41, 51, 61 Regenerative heat exchange

Claims (6)

An absorption tower for absorbing carbon dioxide contained in the combustion exhaust gas into the absorption liquid;
An absorption liquid that absorbs carbon dioxide is supplied from the absorption tower, and carbon dioxide gas containing vapor is released from the absorption liquid and the absorption liquid is regenerated, and the discharged carbon dioxide gas and exhaust gas containing vapor are discharged. A regenerating tower,
The carbon dioxide supplied from the absorption tower to the regeneration tower is absorbed by the regenerated absorption liquid provided between the absorption tower and the regeneration tower and supplied from the regeneration tower to the absorption tower as a heat source. A plurality of regenerative heat exchangers for heating the absorbent,
With
Wherein the plurality of regenerative heat exchangers are connected in parallel, Ri each capacity Do different, the carbon dioxide separation and recovery system, wherein the flow rate of the absorption liquid can be adjusted respectively supplied.   2. The carbon dioxide separation and recovery system according to claim 1, wherein two regeneration heat exchangers are provided and a capacity ratio is 57:43.   The carbon dioxide separation and recovery system according to claim 1, wherein three regeneration heat exchangers are provided, and a capacity ratio is 57:33:10.   The carbon dioxide separation and recovery system according to claim 1, wherein three regenerative heat exchangers are provided, and a capacity ratio is 43:33:24. A flow meter for measuring the flow rate of the absorbent supplied to each of the plurality of regenerative heat exchangers;
A regulating valve that regulates the flow rate of the absorbent supplied to each of the plurality of regenerative heat exchangers;
A controller that calculates the amount of absorbent supplied to each regenerative heat exchanger using the measurement result of the flow meter, and controls the opening of the regulating valve based on the calculation result;
The carbon dioxide separation and recovery system according to any one of claims 1 to 4, further comprising: An absorption tower for absorbing carbon dioxide contained in the combustion exhaust gas into the absorption liquid;
An absorption liquid that absorbs carbon dioxide is supplied from the absorption tower, and carbon dioxide gas containing vapor is released from the absorption liquid and the absorption liquid is regenerated, and the discharged carbon dioxide gas and exhaust gas containing vapor are discharged. A regenerating tower,
The carbon dioxide supplied from the absorption tower to the regeneration tower is absorbed by the regenerated absorption liquid provided between the absorption tower and the regeneration tower and supplied from the regeneration tower to the absorption tower as a heat source. A plurality of regenerative heat exchangers that heat the absorbent and have different capacities,
A method of operating a carbon dioxide separation and recovery system in which the plurality of regenerative heat exchangers are connected in parallel ,
A method for operating a carbon dioxide separation and recovery system, wherein the flow rate of absorbing liquid to the plurality of regenerative heat exchangers is adjusted to 75% to 100% or 0% of the capacity.

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