JP6845744B2 - How to operate the carbon dioxide capture system and the carbon dioxide capture system - Google Patents

Description

Embodiments of the present invention relate to a carbon dioxide capture system and a method of operating the carbon dioxide capture system.

In recent years, it has been pointed out that one of the causes of global warming is the greenhouse effect of carbon dioxide contained in the combustion exhaust gas generated when fossil fuels are burned. To address this issue, countries are working to reduce greenhouse gas emissions in response to the Kyoto Protocol of the United Nations Framework Convention on Climate Change.

Under such circumstances, in thermal power plants that use a large amount of fossil fuels, carbon dioxide is used to prevent carbon dioxide contained in the combustion exhaust gas generated by burning fossil fuels from being released into the atmosphere. Carbon capture systems are being studied. In the carbon dioxide recovery system, the combustion exhaust gas is brought into contact with the amine-based absorption liquid, and carbon dioxide is separated and recovered from the combustion exhaust gas.

More specifically, in the carbon dioxide recovery system, an absorption tower that absorbs carbon dioxide contained in the combustion exhaust gas into an amine-based absorption liquid and an absorption liquid (rich liquid) that absorbs carbon dioxide are supplied from the absorption tower. It is equipped with a regeneration tower that heats the supplied rich liquid to release carbon dioxide from the rich liquid and regenerates the absorbed liquid. A reboiler that supplies a heat source is connected to the regeneration tower, and the rich liquid is heated in the regeneration tower. The absorption liquid (lean liquid) regenerated in the regeneration tower is supplied to the absorption tower, and the absorption liquid is configured to circulate in this system.

However, in such a carbon dioxide recovery system, when the combustion exhaust gas (decarboxylated combustion exhaust gas) obtained by absorbing carbon dioxide in an amine-based absorption liquid in the absorption tower is released from the absorption tower to the atmosphere, it is said that amine is accompanied. There was a challenge. That is, since a large amount of combustion exhaust gas is released in a thermal power plant or the like, there is a possibility that a large amount of amino group-containing compound (amine) is released along with the decarboxylated combustion exhaust gas. Therefore, when using a carbon capture system in a thermal power plant, it is desired to effectively reduce amines released into the atmosphere along with decarboxylated combustion exhaust gas in the absorption tower.

In order to deal with this, it is considered to wash the combustion exhaust gas after absorbing carbon dioxide in the absorption liquid in the absorption tower with a plurality of cleaning liquids. For example, the combustion exhaust gas after absorbing carbon dioxide may be first washed with the first cleaning liquid, then with the second cleaning liquid, and then with the third cleaning liquid.

In general, the amine concentration of each cleaning solution increases with the operating time of the carbon capture and storage system. Therefore, in order to secure the amine recovery performance of the cleaning liquid, it is effective to suppress the amine concentration of the cleaning liquid to a predetermined value or less. Therefore, it is conceivable to replace the cleaning solution with a new cleaning solution before the amine concentration exceeds a predetermined value. However, there is a problem that the amount of waste of the cleaning liquid increases as the frequency of replacement with a new cleaning liquid increases.

Japanese Patent No. 4274846 Japanese Patent No. 6045652 Japanese Patent No. 60455654

The present invention has been made in consideration of such a point, and it is possible to wash the combustion exhaust gas with a cleaning liquid to reduce the amount of amine released into the atmosphere and to reduce the amount of waste of the cleaning liquid. It is an object of the present invention to provide a carbon dioxide capture system capable of and a method of operating the carbon dioxide capture system.

The carbon dioxide recovery system according to the embodiment has absorbed an absorption tower having a carbon dioxide recovery unit that absorbs carbon dioxide contained in the combustion exhaust gas into an absorption liquid containing amine, and carbon dioxide supplied from the absorption tower. It includes a regeneration tower that releases carbon dioxide from the absorption liquid, a first heating unit, and a first bypass line. The absorption tower has a first cleaning unit, a second cleaning unit, and a third cleaning unit. Of these, the first cleaning unit cleans the combustion exhaust gas discharged from the carbon dioxide recovery unit with the first cleaning liquid heated by the first heating unit, and recovers the amine accompanying the combustion exhaust gas. The second cleaning unit cleans the combustion exhaust gas discharged from the first cleaning unit with the second cleaning liquid to recover the amine accompanying the combustion exhaust gas. The third cleaning unit cleans the combustion exhaust gas discharged from the second cleaning unit with the third cleaning liquid, and recovers the amine accompanying the combustion exhaust gas. The first bypass line mixes at least a part of the second cleaning liquid discharged from the second cleaning unit into the third cleaning liquid.

The method of operating the carbon dioxide recovery system according to the embodiment is a step of absorbing carbon dioxide contained in the combustion exhaust gas into an absorption liquid containing amine in the carbon dioxide recovery section of the absorption tower, and an absorption tower in the regeneration tower. It is provided with a step of releasing carbon dioxide from an absorption liquid that has absorbed carbon dioxide supplied from. The combustion exhaust gas discharged from the carbon dioxide recovery unit is washed with the first cleaning liquid heated by the first heating unit in the first cleaning unit, and the amine accompanying the combustion exhaust gas is recovered. The combustion exhaust gas discharged from the first cleaning unit is cleaned with the second cleaning liquid in the second cleaning unit, and the amine accompanying the combustion exhaust gas is recovered. The combustion exhaust gas discharged from the second cleaning unit is cleaned with the third cleaning liquid in the third cleaning unit, and the amine accompanying the combustion exhaust gas is recovered. At least a part of the second cleaning liquid discharged from the second cleaning unit is mixed with the third cleaning liquid.

According to the present invention, the combustion exhaust gas can be washed with a cleaning liquid to reduce the amount of amine released into the atmosphere and the amount of waste of the cleaning liquid can be reduced.

FIG. 1 is a diagram showing an overall configuration of a carbon dioxide capture system according to the first embodiment of the present invention. FIG. 2 is a diagram showing a modified example of the carbon dioxide capture system of FIG. FIG. 3 is a diagram showing the overall configuration of the carbon dioxide capture system according to the second embodiment of the present invention. FIG. 4 is a diagram showing the overall configuration of the carbon dioxide capture system according to the third embodiment of the present invention.

Hereinafter, the carbon dioxide capture system and the operation method of the carbon dioxide capture system according to the embodiment of the present invention will be described with reference to the drawings.

(First Embodiment)
First, the carbon dioxide capture system and the operation method of the carbon dioxide capture system according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the carbon dioxide recovery system 1 absorbs the carbon dioxide contained in the combustion exhaust gas 2 into the absorption tower 20 and the carbon dioxide supplied from the absorption tower 20. It is provided with a regeneration tower 30 that regenerates the absorbed liquid by releasing carbon dioxide from the absorbed liquid. The combustion exhaust gas 2 in which carbon dioxide is absorbed by the absorption liquid in the absorption tower 20 is discharged from the absorption tower 20 as decarboxylation combustion exhaust gas 3 (described later). Further, carbon dioxide is discharged from the regeneration tower 30 together with steam as carbon dioxide-containing gas 8 (carbon dioxide-containing steam). The combustion exhaust gas 2 supplied to the absorption tower 20 is not particularly limited, but may be, for example, combustion exhaust gas of a boiler (not shown) of a thermal power plant, process exhaust gas, or the like, and is necessary. Depending on the situation, it may be supplied to the absorption tower 20 after the cooling treatment.

The absorption liquid circulates between the absorption tower 20 and the regeneration tower 30, absorbs carbon dioxide in the absorption tower 20 to become the rich liquid 4, and releases carbon dioxide in the regeneration tower 30 to become the lean liquid 5. The absorption liquid is not particularly limited, but for example, monoethanolamine, alcoholic hydroxyl group-containing primary amines such as 2-amino-2-methyl-1-propanol, diethanolamine, and 2-methylamino. Alcoholic hydroxyl group-containing secondary amines such as ethanol, triethanolamine, alcoholic hydroxyl group-containing tertiary amines such as N-methyldiethanolamine, polyethylene polyamines such as ethylenediamine, triethylenediamine, diethylenetriamine, piperazins, piperidine , Cyclic amines such as pyrrolidines, polyamines such as xylylene diamine, amino acids such as methylaminocarboxylic acid, and mixtures thereof. These amine compounds are usually used as an aqueous solution of 10 to 70% by weight. Further, a carbon dioxide absorption accelerator or a corrosion inhibitor can be added to the absorption liquid, and methanol, polyethylene glycol, sulfolane or the like can be added as other media.

The absorption tower 20 includes a carbon dioxide recovery unit 20a (filled layer), a liquid disperser 20b provided above the carbon dioxide recovery unit 20a, and an absorption tower container 20c that houses the carbon dioxide recovery unit 20a and the liquid disperser 20b. And have. Of these, the carbon dioxide recovery unit 20a is configured as a countercurrent gas-liquid contact device, and is adapted to absorb carbon dioxide contained in the combustion exhaust gas 2 into the lean liquid 5. The liquid disperser 20b disperses and drops the lean liquid 5 supplied from the regeneration tower 30 toward the carbon dioxide recovery unit 20a. The absorption tower container 20c contains a carbon dioxide recovery unit 20a and a liquid disperser 20b, as well as a first cleaning unit 21, a second cleaning unit 22, a third cleaning unit 23, and demisters 81, 82, 83, and 84, which will be described later. It is contained. The absorption tower container 20c receives the combustion exhaust gas 2 from the lower part of the absorption tower container 20c, and discharges the combustion exhaust gas 2 from the top of the absorption tower container 20c as the decarbonized combustion exhaust gas 3 described later.

A combustion exhaust gas 2 containing carbon dioxide discharged from the outside of the carbon dioxide capture system 1 such as the boiler described above is supplied to the lower part of the absorption tower 20 by a blower (not shown). The supplied combustion exhaust gas 2 rises in the absorption tower 20 toward the carbon dioxide recovery unit 20a. On the other hand, the lean liquid 5 from the regeneration tower 30 is supplied to the liquid disperser 20b, dispersed and dropped, and is supplied to the carbon dioxide recovery unit 20a. In the carbon dioxide recovery unit 20a, the combustion exhaust gas 2 and the lean liquid 5 are in gas-liquid contact, and the carbon dioxide contained in the combustion exhaust gas 2 is absorbed by the lean liquid 5 to generate the rich liquid 4.

The generated rich liquid 4 is temporarily stored in the lower part of the absorption tower 20 and discharged from the lower part. Carbon dioxide is removed from the combustion exhaust gas 2 that is in gas-liquid contact with the lean liquid 5, and the combustion exhaust gas 2 rises further in the absorption tower 20 from the carbon dioxide recovery unit 20a as the decarboxylation combustion exhaust gas 3.

A heat exchanger 31 is provided between the absorption tower 20 and the regeneration tower 30. A rich liquid pump 32 is provided between the absorption tower 20 and the heat exchanger 31, and the rich liquid 4 discharged from the absorption tower 20 is regenerated by the rich liquid pump 32 via the heat exchanger 31. It is supplied to the tower 30. The heat exchanger 31 causes the rich liquid 4 supplied from the absorption tower 20 to the regeneration tower 30 to exchange heat with the lean liquid 5 supplied from the regeneration tower 30 to the absorption tower 20. As a result, the lean liquid 5 serves as a heat source, and the rich liquid 4 is heated to a desired temperature. In other words, the rich liquid 4 serves as a cooling heat source, and the lean liquid 5 is cooled to a desired temperature.

The regeneration tower 30 includes an amine regeneration unit 30a (filled layer), a liquid disperser 30b provided above the amine regeneration unit 30a, and a regeneration tower container 30c containing the amine regeneration unit 30a and the liquid disperser 30b. Have. Of these, the amine regeneration unit 30a is configured as a countercurrent gas-liquid contact device so as to release carbon dioxide from the rich liquid 4. The liquid disperser 30b disperses and drops the rich liquid 4 supplied from the absorption tower 20 toward the amine regeneration unit 30a. The regeneration tower container 30c houses the amine regeneration unit 30a and the liquid disperser 30b, as well as the regeneration tower cleaning unit 37, which will be described later, and the demisters 86 and 87, respectively. The regeneration tower container 30c is adapted to discharge the carbon dioxide-containing gas 8 released from the rich liquid 4 from the top of the regeneration tower container 30c.

A reboiler 33 is connected to the regeneration tower 30. The reboiler 33 heats the lean liquid 5 supplied from the regeneration tower 30 by the heating medium 6 to generate steam 7, and supplies the generated steam 7 to the regeneration tower 30. More specifically, the reboiler 33 is supplied with a part of the lean liquid 5 discharged from the lower part of the regeneration tower 30, and has a high temperature as a heating medium 6 from the outside such as a turbine (not shown). Steam is supplied. The lean liquid 5 supplied to the reboiler 33 is heated by exchanging heat with the heating medium 6, and steam 7 is generated from the lean liquid 5. The generated steam 7 is supplied to the lower part of the regeneration tower 30 to heat the lean liquid 5 in the regeneration tower 30. The heating medium 6 is not limited to high-temperature steam from the turbine.

Steam 7 is supplied from the reboiler 33 to the lower part of the regeneration tower 30, and rises in the regeneration tower 30 toward the amine regeneration section 30a. On the other hand, the rich liquid 4 from the absorption tower 20 is supplied to the liquid disperser 30b, dispersed and dropped, and is supplied to the amine regeneration unit 30a. In the amine regeneration unit 30a, the rich liquid 4 and the vapor 7 come into gas-liquid contact, and carbon dioxide gas is released from the rich liquid 4 to generate a lean liquid 5. In this way, the absorbing liquid is regenerated in the regeneration tower 30.

The generated lean liquid 5 is discharged from the lower part of the regeneration tower 30, and the vapor 7 in gas-liquid contact with the rich liquid 4 contains carbon dioxide and is discharged from the top of the regeneration tower 30 as carbon dioxide-containing gas 8. To The carbon dioxide-containing gas 8 emitted also contains steam.

A lean liquid pump 34 is provided between the regeneration tower 30 and the heat exchanger 31. The lean liquid 5 discharged from the regeneration tower 30 is supplied to the absorption tower 20 by the lean liquid pump 34 via the heat exchanger 31 described above. As described above, the heat exchanger 31 cools the lean liquid 5 supplied from the regeneration tower 30 to the absorption tower 20 by heat exchange with the rich liquid 4 supplied from the absorption tower 20 to the regeneration tower 30. Further, a lean liquid cooler 35 is provided between the heat exchanger 31 and the absorption tower 20. The lean liquid cooler 35 is supplied with a cooling medium such as cooling water from the outside, and further cools the lean liquid 5 cooled in the heat exchanger 31 to a desired temperature.

The lean liquid 5 cooled in the lean liquid cooler 35 is supplied to the liquid disperser 20b of the absorption tower 20 to be dispersed and dropped, and is supplied to the carbon dioxide recovery unit 20a. In the carbon dioxide recovery unit 20a, the lean liquid 5 comes into gas-liquid contact with the combustion exhaust gas 2, and the carbon dioxide contained in the combustion exhaust gas 2 is absorbed by the lean liquid 5 to become the rich liquid 4. In this way, in the carbon dioxide capture system 1, the absorption liquid circulates while repeating the state of becoming the lean liquid 5 and the state of becoming the rich liquid 4.

The carbon dioxide recovery system 1 shown in FIG. 1 includes a gas cooler 40 that cools the carbon dioxide-containing gas 8 discharged from the top of the regeneration tower 30 and condenses steam to generate condensed water 9, and gas cooling. It further includes a gas-liquid separator 41 that separates the condensed water 9 generated by the vessel 40 from the carbon dioxide-containing gas 8. In this way, the water content in the carbon dioxide-containing gas 8 is reduced, and the carbon dioxide-containing gas 8 is discharged from the gas-liquid separator 41 as the carbon dioxide gas 10 and supplied to equipment (not shown) for storage. To. On the other hand, the condensed water 9 separated in the gas-liquid separator 41 is supplied to the regeneration tower 30 by the condensed water pump 42 and mixed with the absorbing liquid. The gas cooler 40 is supplied with a cooling medium for cooling the carbon dioxide-containing gas 8 (for example, cooling water for the cleaning tower or seawater) from the outside.

By the way, the absorption tower 20 has a first cleaning unit 21, a second cleaning unit 22, and a third cleaning unit 23, of which the first cleaning unit 21 discharges from the carbon dioxide recovery unit 20a. The decarboxylated combustion exhaust gas 3 is washed with the first cleaning liquid 11 (first cleaning water) to recover the amine accompanying the decarboxylated combustion exhaust gas 3. The second cleaning unit 22 cleans the decarboxylated combustion exhaust gas 3 discharged from the first cleaning unit 21 with the second cleaning liquid 12 (second cleaning water) to recover the amine accompanying the decarboxylated combustion exhaust gas 3. .. The third cleaning unit 23 cleans the decarboxylated combustion exhaust gas 3 discharged from the second cleaning unit 22 with the third cleaning liquid 13 (third cleaning water), and recovers the amine accompanying the decarboxylated combustion exhaust gas 3. .. Of these, the first cleaning unit 21 is provided above the liquid disperser 20b, the second cleaning unit 22 is provided above the first cleaning unit 21, and the third cleaning unit 23 is the second cleaning unit 22. It is provided above.

The first cleaning section 21 includes a first recovery section 21a (filled layer), a first liquid disperser 21b provided above the first recovery section 21a, and a first recovery section 21a provided below the first recovery section 21a. The first recovery unit 21a, which has a cleaning liquid storage unit 21c, is configured as a countercurrent type gas-liquid contact device, and brings the first cleaning liquid 11 and the decarboxylated combustion exhaust gas 3 into gas-liquid contact. The amine, which is an absorption liquid component accompanying the decarboxylated combustion exhaust gas 3, is recovered. The first liquid disperser 21b disperses and drops the first cleaning liquid 11 toward the first recovery unit 21a. The first cleaning liquid storage unit 21c is configured to store the first cleaning liquid 11 flowing down from the first recovery unit 21a and to allow the decarboxylated combustion exhaust gas 3 discharged from the carbon dioxide recovery unit 20a to pass through.

A first circulation line 50 for circulating the first cleaning liquid 11 is connected to the first cleaning unit 21. That is, the first circulation pump 51 is provided in the first circulation line 50, and the first cleaning liquid 11 stored in the first cleaning liquid storage unit 21c is extracted and supplied to the first liquid disperser 21b. 1 The cleaning liquid 11 is circulated. The first cleaning liquid 11 supplied to the first liquid disperser 21b is dispersed and dropped and supplied to the first recovery unit 21a.

The first circulation line 50 is provided with a first heater 52a (first heating unit) for heating the first cleaning liquid 11. The first heater 52a raises the temperature of the first cleaning liquid 11 higher than the temperature of the upper end portion of the carbon dioxide recovery unit 20a and higher than the temperature of the second cleaning liquid 12. In the present embodiment, the first cleaning liquid 11 heated by the first heater 52a is further heated by the second heater 52b (second heating unit). In the embodiment shown in FIG. 1, the first heater 52a and the second heater 52b are provided on the downstream side of the first circulation pump 51 (the side of the first liquid disperser 21b) in the first circulation line 50. However, it is not limited to this.

The heat source for heating the first cleaning liquid 11 in the first heater 52a is the lean liquid 5 discharged from the regeneration tower 30 and passing through the heat exchanger 31. That is, in the present embodiment, the lean liquid 5 that has passed through the heat exchanger 31 is supplied to the first heater 52a to heat the first cleaning liquid 11.

The heat source for heating the first cleaning liquid in the second heater 52b is different from the heat source of the first heater 52a, and is the heating medium 6 discharged from the reboiler 33. That is, in the present embodiment, the heating medium 6 discharged from the reboiler 33 is supplied to the second heater 52b to further heat the first cleaning liquid 11 heated in the first heater 52a. ing.

The second cleaning section 22 includes a second recovery section 22a (filled layer), a second liquid disperser 22b provided above the second recovery section 22a, and a second recovery section 22a provided below the second recovery section 22a. It has a cleaning liquid storage unit 22c. Of these, the second recovery unit 22a is configured as a countercurrent gas-liquid contact device, and is an absorption liquid component that brings the second cleaning liquid 12 and the decarboxylated combustion exhaust gas 3 into gas-liquid contact and accompanies the decarboxylated combustion exhaust gas 3. Recover the amine that is. The second liquid disperser 22b disperses and drops the second cleaning liquid 12 toward the second recovery unit 22a. The second cleaning liquid storage unit 22c is configured to store the second cleaning liquid 12 flowing down from the second recovery unit 22a and to allow the decarboxylated combustion exhaust gas 3 discharged from the first recovery unit 21a to pass through.

A second circulation line 54 for circulating the second cleaning liquid 12 is connected to the second cleaning unit 22. That is, the second circulation pump 55 is provided in the second circulation line 54, and the second cleaning liquid 12 stored in the second cleaning liquid storage unit 22c is extracted and supplied to the second liquid disperser 22b. 2 The cleaning liquid 12 is circulated. The second cleaning liquid 12 supplied to the second liquid disperser 22b is dispersed and dropped and supplied to the second recovery unit 22a.

In the present embodiment, the second circulation line 54 is provided with a second cleaning cooler 56 for cooling the second cleaning liquid 12. A cooling medium (for example, cooling water for the cleaning tower or seawater) is supplied to the second cleaning cooler 56 from the outside of the carbon dioxide recovery system 1 as a cooling medium for cooling the second cleaning liquid 12. In this way, the second cleaning cooler 56 cools the second cleaning liquid 12 flowing through the second circulation line 54. In the embodiment shown in FIG. 1, the second cleaning cooler 56 is provided on the downstream side of the second circulation pump 55, but if the cooling capacity of the second cleaning liquid 12 can be secured, the second circulation pump 55 can be used. It may be provided at a position on the upstream side.

The third cleaning section 23 includes a third recovery section 23a (filling layer), a third liquid disperser 23b provided above the third recovery section 23a, and a third recovery section 23a provided below the third recovery section 23a. It has a cleaning liquid storage unit 23c. Of these, the third recovery unit 23a is configured as a countercurrent gas-liquid contact device, and is an absorption liquid component that brings the third cleaning liquid 13 and the decarboxylated combustion exhaust gas 3 into gas-liquid contact and accompanies the decarboxylated combustion exhaust gas 3. It is designed to recover the amine that is. The third liquid disperser 23b disperses and drops the third cleaning liquid 13 toward the third recovery unit 23a. The third cleaning liquid storage unit 23c is configured to store the third cleaning liquid 13 flowing down from the third recovery unit 23a and to allow the decarboxylated combustion exhaust gas 3 discharged from the second recovery unit 22a to pass through.

A third circulation line 57 for circulating the third cleaning liquid 13 is connected to the third cleaning unit 23. That is, the third circulation pump 58 is provided in the third circulation line 57, and the third cleaning liquid 13 stored in the third cleaning liquid storage unit 23c is extracted and supplied to the third liquid disperser 23b. 3 The cleaning liquid 13 is circulated. The third cleaning liquid 13 supplied to the third liquid disperser 23b is dispersed and dropped and supplied to the third recovery unit 23a.

In the present embodiment, the third circulation line 57 is provided with a third cleaning cooler 59 for cooling the third cleaning liquid 13. A cooling medium (for example, cooling water for the cleaning tower or seawater) is supplied to the third cleaning cooler 59 from the outside of the carbon dioxide recovery system 1 as a cooling medium for cooling the third cleaning liquid 13. In this way, the third cleaning cooler 59 cools the third cleaning liquid 13 flowing through the third circulation line 57. In the embodiment shown in FIG. 1, the third cleaning cooler 59 is provided on the downstream side of the third circulation pump 58, but if the cooling capacity of the third cleaning liquid 13 can be secured, the third circulation pump 58 can be used. It may be provided at a position on the upstream side.

Further, in the present embodiment, the third circulation line 57 is connected to the replenisher supply source 60 that supplies the cleaning replenisher liquid 14 to the third cleaning liquid 13. The cleaning replenisher liquid 14 is for reducing the amine concentration of the third cleaning liquid 13 to make up the third cleaning liquid 13. As the cleaning replenisher liquid 14, a liquid having an amine concentration lower than that of the third cleaning liquid 13 (for example, pure water) is used. The third circulation line 57 and the replenisher supply source 60 are connected by a replenishment line 61. The replenishment line 61 is preferably connected to a portion of the third circulation line 57 on the upstream side of the third cleaning cooler 59. In this case, the cleaning replenishing liquid 14 is used for the third cleaning. It is configured to be mixed with the third cleaning liquid 13 before being cooled by the cooler 59. The replenishment liquid supply source 60 may include a pump for supplying the cleaning replenisher liquid 14 to the third circulation line 57, or such a pump may be provided in the replenishment line 61. ..

By the way, a first demister 81 is provided above the carbon dioxide capture unit 20a. More specifically, the first demister 81 is provided between the liquid disperser 20b and the first cleaning liquid storage unit 21c of the first cleaning unit 21. As a result, the decarboxylated combustion exhaust gas 3 discharged from the carbon dioxide recovery unit 20a passes through the first demister 81 and rises. At this time, the first demister 81 captures the mist of the absorbing liquid accompanying the decarboxylated combustion exhaust gas 3.

A second demister 82 is provided above the first cleaning unit 21. More specifically, the second demister 82 is provided between the first liquid disperser 21b of the first cleaning unit 21 and the second cleaning liquid storage unit 22c of the second cleaning unit 22. As a result, the decarboxylated combustion exhaust gas 3 discharged from the first cleaning unit 21 passes through the second demister 82 and rises. At this time, the second demister 82 captures the mist of the absorbing liquid and the mist of the first cleaning liquid 11 accompanying the decarboxylated combustion exhaust gas 3.

A third demister 83 is provided above the second cleaning unit 22. More specifically, the third demister 83 is provided between the second liquid disperser 22b of the second cleaning unit 22 and the third cleaning liquid storage unit 23c of the third cleaning unit 23. As a result, the decarboxylated combustion exhaust gas 3 discharged from the second cleaning unit 22 passes through the third demister 83 and rises. At this time, the third demister 83 captures the mist of the absorbing liquid accompanying the decarboxylated combustion exhaust gas 3, the mist of the first cleaning liquid 11, and the mist of the second cleaning liquid 12.

A fourth demister 84 is provided above the third cleaning unit 23. More specifically, the fourth demister 84 is provided above the third liquid disperser 23b of the third cleaning unit 23 (between the third liquid disperser 23b and the top of the absorption tower container 20c). As a result, the decarboxylated combustion exhaust gas 3 discharged from the third cleaning unit 23 passes through the fourth demister 84 and rises. At this time, the fourth demister 84 captures the mist of the absorbing liquid accompanying the decarboxylated combustion exhaust gas 3, the mist of the first cleaning liquid 11, the mist of the second cleaning liquid 12, and the mist of the third cleaning liquid 13.

As shown in FIG. 1, the second circulation line 54 and the third circulation line 57 are connected by a first bypass line 62. The first bypass line 62 mixes at least a part of the second cleaning liquid 12 discharged from the second cleaning unit 22 into the third cleaning liquid 13.

It is preferable that the upstream end of the first bypass line 62 (the end on the side of the second circulation line 54) is connected to the portion of the second circulation line 54 on the upstream side of the second circulation pump 55. .. As a result, a part of the second cleaning liquid 12 discharged from the second cleaning liquid storage unit 22c is extracted.

On the other hand, the downstream end of the first bypass line 62 (the end on the side of the third circulation line 57) is a portion of the third circulation line 57 on the upstream side of the third cleaning cooler 59, and is the third. It is preferable that it is connected to a portion on the downstream side of the circulation pump 58. As a result, the second cleaning liquid 12 merges with the third cleaning liquid 13 at the portion.

In the form shown in FIG. 1, a pump (not shown) for sending the second cleaning liquid 12 to the third circulation line 57 may be provided in the first bypass line 62. However, when the upstream end of the first bypass line 62 is connected to the downstream portion of the second circulation pump 55 of the second circulation line 54, such a pump is installed in the first bypass line 62. It does not have to be provided.

The first bypass line 62 is provided with a first flow rate adjusting valve 63. The first flow rate adjusting valve 63 is for adjusting the flow rate of the second cleaning liquid 12 flowing through the first bypass line 62, and the opening degree can be adjusted by various methods.

For example, the first flow rate adjusting valve 63 may be controlled based on the liquid level of the second cleaning liquid 12 stored in the second cleaning liquid storage unit 22c. In this case, a liquid level meter (not shown) is provided in the second cleaning liquid storage unit 22c, and the liquid level of the second cleaning liquid 12 stored in the second cleaning liquid storage unit 22c is higher than a predetermined reference level. In this case, the opening degree of the first flow rate adjusting valve 63 may be increased, and when the opening degree is lower than the predetermined reference level, the opening degree of the first flow rate adjusting valve 63 may be decreased.

Alternatively, the first flow rate regulating valve 63 may be controlled based on the liquid level of the third cleaning liquid 13 stored in the third cleaning liquid storage unit 23c. In this case, a liquid level meter (not shown) is provided in the third cleaning liquid storage unit 23c, and the liquid level of the third cleaning liquid 13 stored in the third cleaning liquid storage unit 23c is lower than a predetermined reference level. In this case, the opening degree of the first flow rate adjusting valve 63 may be increased, and when the opening degree of the first flow rate adjusting valve 63 is higher than a predetermined reference level, the opening degree of the first flow rate adjusting valve 63 may be decreased.

As yet another method, the first flow rate regulating valve 63 may be controlled based on the amine concentration of the third cleaning liquid 13. In this case, for example, when an amine concentration meter (not shown) is provided on the third circulation line 57 and the amine concentration of the third cleaning liquid 13 is higher than a predetermined reference concentration, the opening degree of the first flow rate adjusting valve 63 If the concentration is lower than the predetermined reference concentration, the opening degree of the first flow rate adjusting valve 63 may be reduced.

Further, in the present embodiment, the third circulation line 57 and the first circulation line 50 are connected by the second bypass line 64. The second bypass line 64 mixes a part of the third cleaning liquid 13 discharged from the third cleaning unit 23 with the first cleaning liquid 11.

It is preferable that the upstream end of the second bypass line 64 (the end on the side of the third circulation line 57) is connected to the portion of the third circulation line 57 on the upstream side of the third circulation pump 58. .. As a result, a part of the third cleaning liquid 13 discharged from the third cleaning liquid storage unit 23c is extracted.

On the other hand, the downstream end of the second bypass line 64 (the end on the side of the first circulation line 50) is a portion of the first circulation line 50 on the upstream side of the first heater 52a and is the first circulation. It is preferable that the pump 51 is connected to a portion on the downstream side. As a result, the third cleaning liquid 13 joins the first cleaning liquid 11 in the portion.

In the embodiment shown in FIG. 1, a pump (not shown) for sending the third cleaning liquid 13 to the first circulation line 50 may be provided in the second bypass line 64. However, when the upstream end of the second bypass line 64 is connected to the downstream portion of the third circulation pump 58 of the third circulation line 57, such a pump is provided in the second bypass line 64. It does not have to be provided.

The second bypass line 64 is provided with a second flow rate adjusting valve 65. The second flow rate adjusting valve 65 is for adjusting the flow rate of the third cleaning liquid 13 flowing through the second bypass line 64, and the opening degree can be adjusted by various methods.

For example, the second flow rate adjusting valve 65 may be controlled based on the liquid level of the third cleaning liquid 13 stored in the third cleaning liquid storage unit 23c. In this case, a liquid level meter (not shown) is provided in the second cleaning liquid storage unit 22c, and the liquid level of the third cleaning liquid 13 stored in the third cleaning liquid storage unit 23c is higher than a predetermined reference level. In this case, the opening degree of the second flow rate adjusting valve 65 may be increased, and when it is lower than the predetermined reference level, the opening degree of the second flow rate adjusting valve 65 may be decreased.

Alternatively, the second flow rate regulating valve 65 may be controlled based on the liquid level of the first cleaning liquid 11 stored in the first cleaning liquid storage unit 21c. In this case, a liquid level meter (not shown) is provided in the first cleaning liquid storage unit 21c, and the liquid level of the first cleaning liquid 11 stored in the first cleaning liquid storage unit 21c is lower than a predetermined reference level. In this case, the opening degree of the second flow rate adjusting valve 65 may be increased, and when it is higher than a predetermined reference level, the opening degree of the second flow rate adjusting valve 65 may be decreased.

As yet another method, the second flow rate regulating valve 65 may be controlled based on the amine concentration of the third cleaning liquid 13. In this case, for example, when an amine concentration meter (not shown) is provided on the first circulation line 50 and the amine concentration of the first cleaning liquid 11 is higher than a predetermined reference concentration, the opening degree of the second flow rate adjusting valve 65 If the concentration is lower than the predetermined reference concentration, the opening degree of the second flow rate adjusting valve 65 may be reduced.

The carbon dioxide capture system 1 shown in FIG. 1 further includes a cleaning tower 70 (fourth cleaning unit). The cleaning tower 70 cleans the decarboxylated combustion exhaust gas 3 discharged from the third cleaning unit 23 of the absorption tower 20 with the fourth cleaning liquid 15 (fourth cleaning water), and removes the amine accompanying the decarboxylated combustion exhaust gas 3. to recover. The scrubber 70 is configured separately from the absorption tower 20.

The scrubber 70 accommodates a fourth recovery unit 70a (filled layer), a fourth liquid disperser 70b provided above the fourth recovery unit 70a, a fourth recovery unit 70a, and a fourth liquid disperser 70b. It has a scrubber container 70c. Of these, the fourth recovery unit 70a is configured as a countercurrent gas-liquid contact device, and is an absorption liquid component that brings the fourth cleaning liquid 15 and the decarboxylated combustion exhaust gas 3 into gas-liquid contact and accompanies the decarboxylated combustion exhaust gas 3. It is designed to recover the amine that is. The fourth liquid disperser 70b disperses and drops the fourth cleaning liquid 15 toward the fourth recovery unit 70a. The scrubber container 70c stores the fourth cleaning liquid 15 flowing down from the fourth recovery unit 70a. Further, the scrubber container 70c is configured to receive the decarbonized combustion exhaust gas 3 discharged from the absorption tower 20 from the lower part of the scrubber container 70c and discharge the decarbonized combustion exhaust gas 3 from the top of the scrubber container 70c. ing.

A fourth circulation line 71 for circulating the fourth cleaning liquid 15 is connected to the cleaning tower 70. That is, the fourth circulation pump 72 is provided in the fourth circulation line 71, and the fourth cleaning liquid 15 stored in the scrubber container 70c is extracted and supplied to the fourth liquid disperser 70b to supply the fourth cleaning liquid. Circulate 15. The fourth cleaning liquid 15 supplied to the fourth liquid disperser 70b is dispersed and dropped and supplied to the fourth recovery unit 70a.

The fourth circulation line 71 is provided with a fourth cleaning cooler 73 for cooling the fourth cleaning liquid 15. A cooling medium (for example, cooling water for the cleaning tower or seawater) is supplied to the fourth cleaning cooler 75 from the outside of the carbon dioxide recovery system 1 as a cooling medium for cooling the fourth cleaning liquid 15. In this way, the fourth cleaning cooler 73 cools the fourth cleaning liquid 15 flowing through the fourth circulation line 71. In the embodiment shown in FIG. 1, the fourth cleaning cooler 73 is provided on the downstream side of the fourth circulation pump 72, but if the cooling capacity of the fourth cleaning liquid 15 can be secured, the fourth circulation pump 72 can be used. It may be provided at a position on the upstream side.

The fourth cleaning liquid 15 contains an acid and is preferably acidic. Examples of the acid added to the fourth cleaning liquid 15 include sulfuric acid, nitric acid, phosphoric acid, acetic acid, boric acid and the like. It is preferable that the acid is added to the fourth cleaning liquid 15 at a desired concentration. The fourth cleaning liquid 15 to which the acid has been added is preferably controlled by a pH measuring instrument, an ultrasonic measuring instrument, an infrared absorption measuring instrument, a density measuring instrument, or the like, and among these, the pH measuring instrument is preferable. That is, the pH value decreases by adding an acid to the fourth cleaning solution 15, but since the amine has alkalinity, the pH value tends to increase as the amine concentration of the fourth cleaning solution 15 increases. It is in. Therefore, by controlling the pH value, the amine concentration of the fourth cleaning liquid 15 can be easily controlled. For example, by controlling the amine concentration so that the pH value is 8 or less, more preferably 7 or less, the decrease in the amine absorption rate can be effectively suppressed.

By the way, a fifth demister 85 is provided above the fourth recovery unit 70a. More specifically, the fifth demister 85 is provided above the liquid disperser 70b (between the fourth liquid disperser 70b and the top of the scrubber container 70c). As a result, the decarboxylated combustion exhaust gas 3 discharged from the fourth recovery unit 70a passes through the fifth demister 85 and rises. At this time, the fifth demister 85 is a mist of the absorbing liquid accompanying the decarboxylated combustion exhaust gas 3, a mist of the first cleaning liquid 11, a mist of the second cleaning liquid 12, a mist of the third cleaning liquid 13, and a mist of the fourth cleaning liquid 15. To capture.

Further, as shown in FIG. 1, the regeneration tower 30 washes the carbon dioxide-containing gas 8 discharged from the amine regeneration unit 30a described above with condensed water 9 to recover the amine accompanying the carbon dioxide-containing gas 8. It has a regeneration tower cleaning unit 37 to be used. The regeneration tower cleaning unit 37 is provided above the amine regeneration unit 30a.

The regeneration tower cleaning unit 37 has a regeneration tower recovery unit 37a (filled layer) and a liquid disperser 37b provided above the regeneration tower recovery unit 37a. Of these, the regeneration tower recovery unit 37a is configured as a countercurrent gas-liquid contact device, so that the carbon dioxide-containing gas 8 and the condensed water 9 are in gas-liquid contact to recover amine from the carbon dioxide-containing gas 8. It has become. The liquid disperser 37b disperses and drops the condensed water 9 toward the regeneration tower recovery unit 37a.

By the way, a sixth demister 86 is provided above the amine regeneration section 30a of the regeneration tower 30. More specifically, the sixth demister 86 is provided between the liquid disperser 30b and the regeneration tower recovery unit 37a of the regeneration tower cleaning unit 37. As a result, the carbon dioxide-containing gas 8 discharged from the amine regeneration unit 30a passes through the sixth demister 86 and rises. At this time, the sixth demister 86 captures the mist of the absorbing liquid accompanying the carbon dioxide-containing gas 8.

A seventh demister 87 is provided above the regeneration tower cleaning unit 37. More specifically, the 7th demister 87 is provided above the liquid disperser 37b (between the liquid disperser 37b and the top of the regeneration tower container 30c). As a result, the carbon dioxide-containing gas 8 discharged from the recycling tower cleaning unit 37 passes through the 7th demister 87 and rises. At this time, the 7th demister 87 captures the mist of the absorbing liquid and the mist of the condensed water 9 accompanying the carbon dioxide-containing gas 8.

Next, the operation of the present embodiment having such a configuration, that is, the operation method of the carbon dioxide capture system will be described.

First, a general problem in the gas cleaning method using the first cleaning unit 21 and the second cleaning unit 22 will be described.

Generally, a first cleaning unit 21 and a second cleaning unit 22 are provided in order to clean the decarboxylated combustion exhaust gas 3 and recover the amine accompanying the decarboxylated combustion exhaust gas 3. At this time, in order to increase the contact area between the decarboxylated combustion exhaust gas 3 and the cleaning liquid, the first recovery unit 21a and the second recovery unit 22a are composed of a packing layer, although they may be composed of shelves. Often. In this case, the following three issues are mainly raised.

[1] The cleaning liquid flowing down the surface of the packed bed tends to flow unevenly. As a result, the entire surface of the packed bed does not get wet (short pass occurs), so that there is a problem that the decarboxylated combustion exhaust gas 3 slips through the packed bed without being washed without coming into contact with the washing liquid.

[2] The form of amine released into the atmosphere along with the decarboxylated combustion exhaust gas 3 includes a gaseous form and a mist form. Of these, amines in the form of mist are difficult to recover in the packed bed. Therefore, a demister is provided to capture the mist. However, even a demister has a problem that it is difficult to capture mist having a diameter of 10 μm or less.

[3] The cleaning liquid flowing down the surface of the packed bed absorbs the amine associated with the decarboxylated combustion exhaust gas 3, and the absorption rate is the amine concentration of the cleaning liquid at the gas-liquid contact interface and the amine of the decarboxylated combustion exhaust gas 3. Depends on the concentration. That is, if the amine concentration of the cleaning liquid at the gas-liquid contact interface can always be maintained at a low concentration, the rate at which the cleaning liquid absorbs amine can be maintained high. However, the amine concentration of the cleaning liquid at the gas-liquid contact interface immediately increases by absorbing the amine in the decarboxylated combustion exhaust gas 3. Since the diffusion rate of amines in the cleaning liquid is slow, it is difficult for amines absorbed in the cleaning liquid at the gas-liquid contact interface to diffuse into the cleaning liquid. Therefore, there is a problem that the amine concentration of the cleaning liquid at the gas-liquid contact interface is maintained at a high concentration, which causes a decrease in the amine absorption rate.

In order to solve these problems, the present embodiment employs a method of utilizing the condensation phenomenon. That is, in the present embodiment, the temperature of the second cleaning unit 22 is lower than the temperature of the first cleaning unit 21, and the decarbonized combustion exhaust gas 3 discharged from the first cleaning unit 21 uses the second cleaning unit 22. When it passes through, it is cooled to condense the water vapor contained in the decarbonized combustion exhaust gas 3. We are trying to solve the above problems by utilizing the condensed water.

There are two conceivable methods for lowering the temperature of the second cleaning unit 22 than the temperature of the first cleaning unit 21. The first is a method of heating the first cleaning unit 21, and the second is a method of cooling the second cleaning unit 22.

The cleaning solution may be cooled for the purpose of reducing the amine vapor pressure in the cleaning solution. However, while the operating temperature of a general cleaning liquid is about 30 ° C. to 40 ° C., the temperature of the cooled cleaning liquid remains at about 20 ° C. to 30 ° C., and the temperature difference obtained by cooling becomes small. For this reason, it is difficult to increase the temperature difference between the first cleaning unit 21 and the second cleaning unit 22 by cooling the second cleaning liquid 12. Further, when the second cleaning liquid 12 is cooled by using a chiller having a high cooling capacity in order to increase the temperature difference, the temperature of the cleaning liquid can be further lowered, but the energy required for cooling increases sharply. .. One of the major issues of the carbon dioxide capture system 1 is how to reduce the energy required to capture carbon dioxide. Therefore, it is not preferable that the energy for cooling the decarboxylated combustion exhaust gas 3 is increased.

Therefore, in the present embodiment, waste heat from the outside (peripheral equipment) of the carbon dioxide capture system 1 is utilized. That is, the temperature of the first cleaning unit 21 is raised by heating the first cleaning liquid 11 which is normally used at room temperature or after being cooled with waste heat. As a result, the temperature difference between the first cleaning unit 21 and the second cleaning unit 22 is expanded, and the amount of condensed water in the second cleaning unit 22 is increased. The temperature of the first cleaning unit 21 is preferably 5 ° C. to 50 ° C. higher than the temperature at the upper end of the carbon dioxide recovery unit 20a, and even more preferably 10 ° C. to 30 ° C.

The reasons why the above-mentioned three problems are solved by utilizing the condensation phenomenon will be described below.

[1] Condensation is generated from the decarboxylation combustion exhaust gas 3 flowing through the voids of the packed bed. The decarboxylated combustion exhaust gas 3 flows uniformly through the packed bed. Therefore, the surface of the packed bed can be uniformly wetted by the condensed water, and the decarboxylated combustion exhaust gas 3 can be prevented from slipping through the packed bed without being washed.

[2] Condensation occurs with a small particle size mist as the nucleus. Therefore, the effect of increasing the mist diameter can be expected by increasing the amount of condensed water. As the mist diameter increases, the mist is more likely to be trapped by the packed bed or demister.

[3] By increasing the amount of condensed water, the condensed water is incorporated into the cleaning liquid. This replaces the gas-liquid contact interface of the cleaning liquid with the condensed moisture while the condensation is occurring. Therefore, the amine concentration of the cleaning liquid at the gas-liquid contact interface can be maintained at a low concentration, and the decrease in the amine absorption rate can be suppressed.

In this way, the above-mentioned three problems can be solved, the absorption rate of amines from the decarboxylated combustion exhaust gas 3 can be increased to effectively capture amines, and it is possible to suppress a decrease in the amount of amines recovered. ..

During the operation of the carbon dioxide recovery system shown in FIG. 1, in the carbon dioxide recovery unit 20a of the absorption tower 20, the combustion exhaust gas 2 comes into gas-liquid contact with the lean liquid 5 supplied from the lean liquid cooler 35, and carbon dioxide is produced. Is absorbed by the lean liquid 5 and discharged from the carbon dioxide recovery unit 20a as the decarbonized combustion exhaust gas 3. The discharged decarboxylated combustion exhaust gas 3 rises in the absorption tower container 20c, passes through the first demister 81 and the first cleaning liquid storage unit 21c of the first cleaning unit 21, and reaches the first recovery unit 21a.

On the other hand, the first cleaning liquid 11 stored in the first cleaning liquid storage unit 21c is extracted from the first cleaning liquid storage unit 21c by the first circulation pump 51, and passes through the first circulation line 50 to the first liquid disperser 21b. Be supplied. During this time, the first cleaning liquid 11 is heated by the first heater 52a and the second heater 52b.

That is, the first cleaning liquid 11 is first heated by the first heater 52a. In the first heater 52a, the first cleaning liquid 11 is heated by using the lean liquid 5 discharged from the regeneration tower 30 and passing through the heat exchanger 31 as a heat source. Since the lean liquid 5 that has passed through the heat exchanger 31 has a temperature higher than the temperature of the upper end portion of the carbon capture and storage unit 20a, the temperature of the first cleaning liquid 11 heated by the lean liquid 5 is set to carbon dioxide. The temperature can be higher than the temperature of the upper end portion of the recovery unit 20a and higher than the temperature of the second cleaning liquid 12. Since the lean liquid 5 discharged from the first heater 52a is cooled instead of heating the first cleaning liquid 11, the energy required to cool the lean liquid 5 in the lean liquid cooler 35 is reduced. can do.

The first cleaning liquid 11 heated by the first heater 52a is subsequently further heated by the second heater 52b. In the second heater 52b, the first cleaning liquid 11 is heated by using the heating medium 6 discharged from the reboiler 33 as a heat source. Since the temperature of the heating medium 6 that has passed through the reboiler 33 is higher than the temperature of the lean liquid 5 discharged from the heat exchanger 31, the heating medium 6 causes the first cleaning liquid 11 heated by the first heater 52a to be heated. It can be further heated, and the temperature of the first cleaning liquid 11 can be further increased.

In this way, the temperature of the first cleaning liquid 11 can be made higher than the temperature of the upper end portion of the carbon dioxide recovery unit 20a.

In the first recovery unit 21a, the decarboxylated combustion exhaust gas 3 and the heated first cleaning liquid 11 are in gas-liquid contact, and the decarbonated combustion exhaust gas 3 is cleaned. As a result, although it accompanies the decarboxylation combustion exhaust gas 3, it is absorbed by the first cleaning liquid 11 and recovered. The first cleaning liquid 11 in which the decarboxylated combustion exhaust gas 3 is washed in the first recovery unit 21a flows down from the first recovery unit 21a and is stored in the first cleaning liquid storage unit 21c.

Further, since the heated first cleaning liquid 11 is supplied to the first recovery unit 21a, the temperature of the first recovery unit 21a becomes high. Therefore, the decarboxylated combustion exhaust gas 3 is heated by the first cleaning liquid 11, and the temperature of the decarbonated combustion exhaust gas 3 rises. The decarboxylated combustion exhaust gas 3 is discharged from the first recovery unit 21a, further rises in the absorption tower container 20c, passes through the second cleaning liquid storage unit 22c of the second demister 82 and the second cleaning unit 22, and then passes through the second cleaning liquid storage unit 22c. It reaches the second recovery unit 22a.

On the other hand, the second cleaning liquid 12 stored in the second cleaning liquid storage unit 22c is extracted from the second cleaning liquid storage unit 22c by the second circulation pump 55, and passes through the second circulation line 54 to the second liquid disperser 22b. Be supplied. During this time, the second cleaning liquid 12 is cooled by the second cleaning cooler 56.

In the second recovery unit 22a, the heated decarbonated combustion exhaust gas 3 and the cooled second cleaning liquid 12 are in gas-liquid contact, and the decarbonated combustion exhaust gas 3 is cleaned. As a result, the amine accompanying the decarboxylated combustion exhaust gas 3 is absorbed by the second cleaning liquid 12 and recovered. The second cleaning liquid 12 in which the decarboxylated combustion exhaust gas 3 is washed in the second recovery unit 22a flows down from the second recovery unit 22a and is stored in the second cleaning liquid storage unit 22c.

Further, since the cooled second cleaning liquid 12 is supplied to the second recovery unit 22a, the temperature of the second recovery unit 22a becomes low. Therefore, the decarboxylated combustion exhaust gas 3 is cooled by the second cleaning liquid 12, and the temperature of the decarbonated combustion exhaust gas 3 is lowered. Due to the temperature drop of the decarboxylation combustion exhaust gas 3, the water vapor accompanying the decarbonation combustion exhaust gas 3 is condensed, and the condensed water is taken into the second cleaning liquid 12. That is, since the temperature difference between the first cleaning unit 21 and the second cleaning unit 22 is widening, the temperature drop width of the decarboxylated combustion exhaust gas 3 cooled by the second cleaning liquid 12 becomes large. Therefore, the amount of condensed water taken into the second cleaning liquid 12 from the decarboxylated combustion exhaust gas 3 can be increased. In this case, the amine concentration of the second cleaning liquid 12 may decrease.

The decarboxylated combustion exhaust gas 3 washed by the second cleaning liquid 12 is discharged from the second recovery unit 22a, further rises in the absorption tower container 20c, and stores the third cleaning liquid in the third demister 83 and the third cleaning unit 23. It passes through the section 23c and reaches the third recovery section 23a.

On the other hand, the third cleaning liquid 13 stored in the third cleaning liquid storage unit 23c is extracted from the third cleaning liquid storage unit 23c by the third circulation pump 58, and passes through the third circulation line 57 to the third liquid disperser 23b. Be supplied. During this time, the third cleaning liquid 13 is cooled by the third cleaning cooler 59.

In the third recovery unit 23a, the decarboxylated combustion exhaust gas 3 and the cooled third cleaning liquid 13 are in gas-liquid contact, and the decarbonated combustion exhaust gas 3 is cleaned. As a result, the amine accompanying the decarboxylated combustion exhaust gas 3 is absorbed by the third cleaning liquid 13 and recovered. The third cleaning liquid 13 in which the decarboxylated combustion exhaust gas 3 is washed in the third recovery unit 23a flows down from the third recovery unit 23a and is stored in the third cleaning liquid storage unit 23c.

Further, since the cooled third cleaning liquid 13 is supplied to the third recovery unit 23a, the temperature of the third recovery unit 23a becomes low. Therefore, the decarboxylated combustion exhaust gas 3 is cooled by the third cleaning liquid 13, and the temperature of the decarbonated combustion exhaust gas 3 is lowered. Due to the temperature drop of the decarboxylation combustion exhaust gas 3, the water vapor accompanying the decarbonation combustion exhaust gas 3 is condensed, and the condensed water is taken into the third cleaning liquid 13.

The decarboxylated combustion exhaust gas 3 washed by the third cleaning liquid 13 is discharged from the third recovery unit 23a, further rises in the absorption tower container 20c, passes through the fourth demister 84, and passes through the fourth demister 84 to reach the top of the absorption tower container 20c. Is discharged from. The decarboxylated combustion exhaust gas 3 discharged from the absorption tower 20 reaches the fourth recovery unit 70a of the cleaning tower 70.

On the other hand, the fourth cleaning liquid 15 stored in the cleaning tower container 70c is extracted from the cleaning tower container 70c by the fourth circulation pump 72 and supplied to the fourth liquid disperser 70b through the fourth circulation line 71. During this time, the fourth cleaning liquid 15 is cooled by the fourth cleaning cooler 73.

In the fourth recovery unit 70a, the decarboxylated combustion exhaust gas 3 and the cooled fourth cleaning liquid 15 come into gas-liquid contact, and the decarboxylated combustion exhaust gas 3 is cleaned. As a result, the amine accompanying the decarboxylated combustion exhaust gas 3 is absorbed by the fourth cleaning liquid 15 and recovered. In particular, since the fourth cleaning liquid 15 contains an acid, the amine remaining in the decarboxylation combustion exhaust gas 3 can be further recovered. The fourth cleaning liquid 15 in which the decarboxylated combustion exhaust gas 3 is washed in the fourth recovery unit 70a flows down from the fourth recovery unit 70a and is stored in the scrubber container 70c.

When the temperature of the decarboxylated combustion exhaust gas 3 supplied to the fourth recovery unit 70a is higher than that of the fourth cleaning liquid 15, the decarboxylated combustion exhaust gas 3 is cooled by the fourth cleaning liquid 15, and the temperature of the decarboxylated combustion exhaust gas 3 is increased. Decreases. Due to the temperature drop of the decarboxylation combustion exhaust gas 3, the water vapor accompanying the decarboxylation combustion exhaust gas 3 is condensed, and the condensed water is taken into the fourth cleaning liquid 15.

The decarboxylated combustion exhaust gas 3 cleaned by the fourth cleaning liquid 15 is discharged from the top of the scrubber container 70c and released into the atmosphere.

By the way, during the operation of the carbon dioxide recovery system 1, a part of the second cleaning liquid 12 discharged from the second cleaning liquid storage unit 22c of the second cleaning unit 22 passes through the first bypass line 62 to the third circulation line 57. It is supplied and mixed with the third cleaning liquid 13. Here, the advantage of mixing a part of the second cleaning liquid 12 with the third cleaning liquid 13 will be described below.

In general, the lower the amine concentration of the decarboxylated combustion exhaust gas 3 to be cleaned, the lower the amine concentration of the cleaning liquid is preferable from the viewpoint of vapor-liquid equilibrium. Therefore, as in the form shown in FIG. 1, when the amine accompanying the decarboxylated combustion exhaust gas 3 is recovered by the first cleaning unit 21, the second cleaning unit 22, and the third cleaning unit 23, it is in the downstream stage. Since the amine concentration of the decarboxylated combustion exhaust gas 3 is lower in the cleaning portion, it is preferable that the amine concentration of the cleaning liquid in the downstream stage is lower.

On the other hand, in the first embodiment, as described above, the temperature difference between the temperature of the first cleaning unit 21 and the temperature of the second cleaning unit 22 is increased. As a result, in the second recovery unit 22a, the decarboxylated combustion exhaust gas 3 is taken into the second cleaning liquid 12 to increase the amount of condensed water. Incorporating the water obtained by such condensation into the second cleaning liquid 12 has the same effect as replenishing the cleaning supplement liquid 14 as a make-up, and lowers the amine concentration of the second cleaning liquid 12. Contribute to. That is, the amine concentration of the second cleaning liquid 12 can be made lower than the amine concentration of the third cleaning liquid 13 in the third cleaning unit 23, which is the downstream stage. Therefore, the amine concentration of the third cleaning liquid 13 can be lowered by mixing a part of the second cleaning liquid 12 having a low amine concentration into the third cleaning liquid 13 via the first bypass line 62. In this case, since the second cleaning liquid 12 is reused as the third cleaning liquid 13, it is not necessary to dispose of the second cleaning liquid 12, which can contribute to reducing the amount of the cleaning liquid to be discarded. Furthermore, the replenishment amount of the cleaning replenisher liquid 14 can be reduced, and the procurement cost of the cleaning replenisher liquid 14 can be reduced.

Further, during the operation of the carbon dioxide recovery system 1, the cleaning replenishing liquid 14 is replenished to the third cleaning liquid 13 from the replenishing liquid supply source 60 connected to the third circulation line 57. As a result, the third cleaning liquid 13 is made up to further reduce the amine concentration, and it is possible to further prevent the amine recovery performance of the third recovery unit 23a of the third cleaning unit 23 from deteriorating.

Further, a part of the third cleaning liquid 13 discharged from the third cleaning liquid storage unit 23c of the third cleaning unit 23 is supplied to the first circulation line 50 through the second bypass line 64 and mixed with the first cleaning liquid 11. Will be done. That is, since the amine concentration of the decarboxylated combustion exhaust gas 3 in the third cleaning unit 23 is relatively low, when the amine concentration of the third cleaning liquid 13 becomes high, the amine in the third recovery unit 23a of the third cleaning unit 23 Recovery performance can be reduced. In this case, it is preferable that the third cleaning liquid 13 is mixed with the first cleaning liquid 11 or the second cleaning liquid 12 for cleaning the decarboxylated combustion exhaust gas 3 having a relatively high amine concentration and reused.

However, the amine concentration of the second cleaning liquid 12 is low as described above. Therefore, it is more effective to mix the third cleaning liquid 13 with the first cleaning liquid 11 than with the second cleaning liquid 12.

Therefore, in the present embodiment, the third circulation line 57 and the first circulation line 50 are connected by the second bypass line 64. As a result, a part of the third cleaning liquid 13 is mixed with the first cleaning liquid 11. Since the amine concentration of the decarboxylated combustion exhaust gas 3 in the first recovery unit 21a is relatively high, the amine can be effectively recovered even if the first cleaning liquid 11 has a higher amine concentration than the third cleaning liquid 13. Therefore, since the third cleaning liquid 13 is reused as the first cleaning liquid 11, it is not necessary to dispose of the third cleaning liquid 13, which can contribute to reducing the amount of the cleaning liquid to be discarded.

Although not shown, it is preferable that the disposal line is connected to the first cleaning liquid storage unit 21c or the first circulation line 50 of the first cleaning unit 21. For example, when the amine concentration of the first cleaning liquid 11 becomes high, or when the liquid level of the first cleaning liquid 11 stored in the first cleaning liquid storage unit 21c becomes high, the first cleaning liquid 11 is passed through this disposal line. A part of the cleaning liquid 11 may be discarded. Even in this case, since the second cleaning liquid 12 is reused as the third cleaning liquid 13 and the third cleaning liquid 13 is reused as the first cleaning liquid 11 as described above, the amount of waste of the cleaning liquid is reduced as a whole. can do.

As described above, according to the present embodiment, the amount of condensed water taken into the second cleaning liquid 12 from the decarboxylated combustion exhaust gas 3 increases due to the expansion of the temperature difference between the first cleaning unit 21 and the second cleaning unit 22. , The amine concentration of the second cleaning liquid 12 can be reduced. Then, a part of the second cleaning liquid 12 having a low amine concentration is mixed into the third cleaning liquid 13 by the first bypass line 62. As a result, the amine concentration of the third cleaning liquid 13 can be reduced, and it is possible to prevent the third cleaning unit 23 from deteriorating the amine recovery performance of the decarboxylated combustion exhaust gas 3 having a relatively low amine concentration. Further, since the second cleaning liquid 12 is reused as the third cleaning liquid 13, it is not necessary to dispose of the second cleaning liquid 12, and the amount of the cleaning liquid to be discarded can be reduced. As a result, the decarboxylated combustion exhaust gas 3 can be washed with a cleaning liquid to reduce the amount of amine released into the atmosphere and the amount of waste of the cleaning liquid can be reduced.

Further, according to the present embodiment, the second cleaning liquid 12 is cooled by the second cleaning cooler 56. As a result, the temperature difference between the temperature of the first cleaning unit 21 and the temperature of the second cleaning unit 22 can be further increased. Therefore, the amount of condensed water taken into the second cleaning liquid 12 from the decarboxylated combustion exhaust gas 3 can be increased, and the amine concentration of the second cleaning liquid 12 can be further reduced.

Further, according to the present embodiment, the first bypass line 62 is connected to a portion of the third circulation line 57 on the upstream side of the third cleaning cooler 59. As a result, the second cleaning liquid 12 mixed in the third cleaning liquid 13 can be cooled by the third cleaning cooler 59 before being supplied to the third cleaning unit 23. Therefore, it is possible to prevent the amine recovery performance of the third cleaning unit 23 from deteriorating.

Further, according to the present embodiment, a part of the third cleaning liquid 13 is mixed into the first cleaning liquid 11 by the second bypass line 64. As a result, the amine concentration of the first cleaning liquid 11 can be reduced, and it is possible to prevent the first cleaning unit 21 from deteriorating the amine recovery performance of the first cleaning unit 21. Further, since the third cleaning liquid 13 is reused as the first cleaning liquid 11, it is not necessary to dispose of the third cleaning liquid 13, and the amount of the cleaning liquid to be discarded can be reduced.

Further, according to the present embodiment, the second bypass line 64 is connected to a portion of the first circulation line 50 on the upstream side of the first heater 52a. As a result, the third cleaning liquid 13 mixed in the first cleaning liquid 11 can be heated by the first heater 52a before being supplied to the first cleaning unit 21. Therefore, it is possible to prevent the temperature of the decarboxylated combustion exhaust gas 3 in the first cleaning unit 21 from dropping, and to secure the temperature difference between the first cleaning unit 21 and the second cleaning unit 22.

Further, according to the present embodiment, the cleaning replenishing liquid 14 is replenished to the third cleaning liquid 13 by the replenishing liquid supply source 60. As a result, the amine concentration of the third cleaning liquid 13 can be reduced, and it is possible to prevent the amine recovery performance of the third cleaning unit 23 from being lowered.

Further, according to the present embodiment, the fourth cleaning liquid 15 for cleaning the decarboxylated combustion exhaust gas 3 discharged from the third cleaning unit 23 in the cleaning tower 70 contains an acid. As a result, it is possible to suppress a decrease in the amine absorption rate even in the decarboxylated combustion exhaust gas 3 in which the amine concentration is lowered by passing through the third cleaning unit 23. Therefore, the amine can be effectively recovered, and the amine concentration of the decarboxylated combustion exhaust gas 3 discharged from the scrubber 70 can be further reduced.

Further, according to the present embodiment, the cleaning tower 70 is configured separately from the absorption tower 20. This makes it possible to prevent the fourth cleaning liquid 15 containing an acid from being mixed with the absorption liquids 4 and 5. Therefore, it is possible to prevent the deterioration of the alkaline absorption liquids 4 and 5 from being accelerated. Further, when the fourth cleaning liquid 15 is mixed with the first cleaning liquid 11, the second cleaning liquid 12, and the third cleaning liquid 13, it becomes difficult to reuse these cleaning liquids 11, 12, and 13 as absorption liquids. However, according to the present embodiment, by configuring the cleaning tower 70 separately from the absorption tower 20, the cleaning liquids 11, 12, and 13 can be reused as the absorption liquid. Further, if the fourth cleaning liquid 15 containing an acid is mixed in the cleaning liquids 11, 12, and 13, there is a problem that it becomes difficult to dispose of the cleaning liquids 11, 12, and 13, but such a problem is avoided in the present embodiment. can do.

Further, according to the present embodiment, the second heater 52b heats the first cleaning liquid 11 heated by the first heater 52a. As a result, the first cleaning liquid 11 heated by the first heater 52a can be further heated, and the temperature of the first cleaning liquid 11 can be further raised. In particular, in the present embodiment, the heat source of the first heater 52a is the lean liquid 5 discharged from the regeneration tower 30 and passed through the heat exchanger 31, so that the temperature of the first cleaning liquid 11 is set to carbon dioxide. The temperature can be higher than the temperature of the upper end portion of the recovery unit 20a and higher than the temperature of the second cleaning liquid 12. Further, the heat source of the second heater 52b is the heating medium 6 discharged from the reboiler 33, and since the heating medium 6 is higher than the temperature of the lean liquid 5, the temperature of the first cleaning liquid 11 is set. It can be even higher. In this case, the temperature difference between the first cleaning unit 21 and the second cleaning unit 22 can be further increased. Therefore, the amount of condensed water taken into the second cleaning liquid 12 from the decarboxylated combustion exhaust gas 3 can be increased, and the amine concentration of the second cleaning liquid 12 can be further reduced.

Further, according to the present embodiment, the second demister 82 is provided above the first cleaning unit 21. As a result, the time from when the decarboxylated combustion exhaust gas 3 is discharged from the first recovery unit 21a of the first cleaning unit 21 to the demister can be shortened, and by passing through the first recovery unit 21a. The grown mist can be efficiently captured. That is, in the first recovery unit 21a, the decarboxylation combustion exhaust gas 3 comes into gas-liquid contact with the first cleaning liquid 11, and the mist contained in the decarboxylation combustion exhaust gas 3 grows and enlarges. As a result, the decarboxylated combustion exhaust gas 3 discharged from the first recovery unit 21a is passed through the second demister 82 before the mist enlarged to the extent that it can be captured by the second demister 82 is reduced. , Mist can be captured effectively.

Further, according to the present embodiment, the third demister 83 is provided above the second cleaning unit 22. As a result, the time from when the decarboxylated combustion exhaust gas 3 is discharged from the second recovery unit 22a of the second cleaning unit 22 to the demister can be shortened, and by passing through the second recovery unit 22a. The grown mist can be efficiently captured. That is, in the second recovery unit 22a, the decarboxylation combustion exhaust gas 3 comes into gas-liquid contact with the second cleaning liquid 12 and is cooled by the second cleaning liquid 12, and the water vapor accompanying the decarboxylation combustion exhaust gas 3 is condensed to decarboxylate. The mist contained in the carbon dioxide combustion exhaust gas 3 grows and enlarges. As a result, the decarboxylated combustion exhaust gas 3 discharged from the second recovery unit 22a is passed through the third demister 83 before the mist enlarged to the extent that it can be captured by the third demister 83 is reduced. , Mist can be captured effectively.

In the above-described embodiment, an example in which the third circulation line 57 is provided with a replenisher supply source 60 for supplying the cleaning replenisher liquid 14 to the third cleaning liquid 13 has been described. However, the present invention is not limited to this, and the third circulation line 57 may not be provided with such a replenisher supply source 60. Even in this case, the third cleaning liquid 13 can be made up by the second cleaning liquid 12 supplied by the first bypass line 62. Further, the replenisher supply source 60 may be provided in the second circulation line 54. In this case, the cleaning replenisher liquid 14 can be supplied to the second cleaning liquid 12, and the amine concentration of the second cleaning liquid 12 can be reduced to prevent the amine recovery performance of the second cleaning unit 22 from deteriorating.

Further, in the above-described embodiment, an example in which the decarboxylated combustion exhaust gas 3 discharged from the third cleaning unit 23 of the absorption tower 20 is cleaned by the cleaning tower 70 has been described. However, the present invention is not limited to this, and the cleaning tower 70 can be omitted if it can be considered that the amine concentration of the decarboxylated combustion exhaust gas 3 discharged from the third cleaning unit 23 is sufficiently reduced. ..

Further, in the above-described embodiment, an example in which the second heater 52b heats the first cleaning liquid 11 heated by the first heater 52a has been described. However, the present invention is not limited to this, and the second heater 52b can be omitted if it can be considered that the temperature of the first cleaning liquid 11 discharged from the first heater 52a is sufficiently high.

Further, in the above-described embodiment, an example has been described in which the heat source of the first heater 52a is the lean liquid 5 discharged from the regeneration tower 30 and passed through the heat exchanger 31. However, the present invention is not limited to this, and as shown in FIG. 2, the heat source of the first heater 52a may be the combustion exhaust gas 2 before being supplied to the absorption tower 20.

In the modified example shown in FIG. 2, the combustion exhaust gas 2 before being supplied to the absorption tower 20 is supplied to the first heater 52a to heat the first cleaning liquid 11, and then is supplied to the absorption tower 20. Also in this case, the temperature of the first cleaning liquid 11 can be raised by the combustion exhaust gas 2, and waste heat can be effectively used for the energy required to heat the first cleaning liquid 11. Generally, the combustion exhaust gas 2 discharged from the boiler has a temperature higher than the temperature of the upper end portion of the carbon dioxide recovery unit 20a. As a result, the combustion exhaust gas 2 discharged from the boiler heats the first cleaning liquid 11, and the temperature of the first cleaning liquid 11 is higher than the temperature of the upper end portion of the carbon dioxide recovery unit 20a, and the temperature of the second cleaning liquid 12 is higher. It can be higher than the temperature.

More specifically, the combustion exhaust gas discharged from the boiler of a thermal power plant passes through a denitration device, a dust removal device, a desulfurization device, etc. and is supplied to the carbon capture system 1, but the carbon capture system 1 The temperature of the combustion exhaust gas 2 before being supplied is about 50 ° C. to 90 ° C. As a result, the combustion exhaust gas 2 is often cooled by an exhaust gas cooler (not shown) before being supplied to the carbon dioxide capture system 1. Therefore, according to the form shown in FIG. 2, the combustion exhaust gas 2 is cooled by heating the first cleaning liquid 11 by the first heater 52a, so that the combustion exhaust gas 2 is cooled in the exhaust gas cooler. The energy required can be reduced, and in some cases, the exhaust gas cooler can be omitted. In FIG. 2, the lean liquid 5 discharged from the heat exchanger 31 is supplied to the lean liquid cooler 35 without being supplied to the first heater 52a.

Further, the heat source of the first heater 52a may be the heating medium 6 discharged from the reboiler 33. As described above, since the heating medium 6 is higher than the temperature of the lean liquid 5, the temperature of the first cleaning liquid 11 is higher than the temperature of the upper end portion of the carbon dioxide recovery unit 20a, and the temperature of the second cleaning liquid 12 is higher. It can be higher than the temperature of. In this case, the second heater 52b may be omitted. Furthermore, the first heater 52a is optional as long as it can heat the first cleaning liquid 11 to a desired temperature, and may be configured by an electric heater.

Further, in the above-described embodiment, an example in which the second demister 82 is provided above the first cleaning unit 21 and the third demister 83 is provided above the second cleaning unit 22 has been described. However, the present invention is not limited to this, and at least one of the second demister 82 and the third demister 83 may not be provided.

(Second Embodiment)
Next, the carbon dioxide capture system and the operation method of the carbon dioxide capture system according to the second embodiment of the present invention will be described with reference to FIG.

In the second embodiment shown in FIG. 3, the second cleaning liquid is supplied from the cleaning liquid supply source to the second cleaning unit, and the second cleaning liquid discharged from the second cleaning unit is supplied to the second cleaning unit. The main difference is that the third cleaning liquid is mixed with the third cleaning liquid via the first bypass line, and the other configurations are substantially the same as those of the first embodiment shown in FIG. In FIG. 3, the same parts as those in the first embodiment shown in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the present embodiment, as shown in FIG. 3, a cleaning liquid supply source 90 is connected to the second cleaning unit 22. The cleaning liquid supply source 90 is configured to supply a liquid having a low amine concentration (for example, pure water) as a second cleaning liquid to the second cleaning unit 22. The second liquid disperser 22b of the second cleaning unit 22 and the cleaning liquid supply source 90 are connected by a cleaning liquid line 91. The cleaning liquid line 91 is provided with the above-mentioned second cleaning cooler 56. As a result, the second cleaning liquid 12 supplied from the cleaning liquid supply source 90 is cooled by the second cleaning cooler 56, and then supplied to the second recovery unit 22a via the second liquid disperser 22b. .. The cleaning liquid supply source 90 may include a pump for supplying the second cleaning liquid 12 to the cleaning liquid line 91, or such a pump may be provided in the cleaning liquid line 91.

As shown in FIG. 3, the upstream end of the first bypass line 62 is connected to the second cleaning liquid storage unit 22c. A bypass pump 92 is provided in the first bypass line 62, and the second cleaning liquid 12 stored in the second cleaning liquid storage unit 22c is extracted and supplied to the third circulation line 57. As a result, the second cleaning liquid 12 is mixed with the third cleaning liquid 13.

With such a configuration, the second cleaning liquid 12 is supplied from the cleaning liquid supply source 90 to the second recovery unit 22a of the second cleaning unit 22, the decarboxylated combustion exhaust gas 3 is cleaned, and the decarboxylated combustion exhaust gas 3 is stored in the second cleaning liquid storage unit 22c. .. The second cleaning liquid 12 stored in the second cleaning liquid storage unit 22c is extracted from the second cleaning liquid storage unit 22c by the bypass pump 92 and supplied to the third circulation line 57 via the first bypass line 62. That is, in the present embodiment, the second circulation line 54 shown in FIG. 1 and the like is not provided. As a result, the second cleaning liquid 12 discharged from the second cleaning liquid storage unit 22c is mixed into the third cleaning liquid 13 without being supplied to the second recovery unit 22a again. Therefore, the second cleaning liquid 12 is mixed with the third cleaning liquid 13 once it passes through the second recovery unit 22a without circulating. In this case, it is preferable that all the second cleaning liquid 12 discharged from the second cleaning liquid storage unit 22c is mixed with the third cleaning liquid 13.

As described above, according to the present embodiment, the second cleaning liquid 12 supplied from the cleaning liquid supply source 90 to the second cleaning unit 22 is not supplied to the second cleaning unit 22 again, but is supplied by the first bypass line 62. It is supplied to the third circulation line 57. Therefore, it is possible to prevent the amine concentration of the second cleaning liquid 12 supplied to the second cleaning unit 22 from increasing, and it is possible to improve the amine recovery performance of the second cleaning unit 22. Further, since the second cleaning liquid 12 is reused as the third cleaning liquid 13, it is not necessary to dispose of the second cleaning liquid 12, and the amount of the cleaning liquid to be discarded can be reduced.

(Third Embodiment)
Next, the carbon dioxide capture system and the operation method of the carbon dioxide capture system according to the third embodiment of the present invention will be described with reference to FIG.

In the third embodiment shown in FIG. 4, a gas-liquid contact space is formed in which the falling second cleaning liquid and the rising decarboxylation combustion exhaust gas come into gas-liquid contact from the second liquid disperser to the cleaning liquid storage portion. The other configurations are substantially the same as those of the first embodiment shown in FIG. In FIG. 4, the same parts as those in the first embodiment shown in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the present embodiment, as shown in FIG. 4, a gas-liquid contact space 100 is formed between the second liquid disperser 22b of the second cleaning unit 22 and the second cleaning liquid storage unit 22c. The gas-liquid contact space 100 is a space in which the second cleaning liquid 12 dispersed and dropped from the second liquid disperser 22b and the decarboxylated combustion exhaust gas 3 rising through the second cleaning liquid storage unit 22c come into gas-liquid contact. Is. The gas-liquid contact space 100 is formed from the second liquid disperser 22b to the second cleaning liquid storage portion 22c.

That is, in the present embodiment, the second cleaning liquid 12 is adhered between the second liquid disperser 22b and the second cleaning liquid storage unit 22c to provide a contact area between the second cleaning liquid 12 and the decarboxylated combustion exhaust gas 3. There are no filling layers or shelves to increase. More preferably, no member for adhering the second cleaning liquid 12 is provided between the second liquid disperser 22b and the second cleaning liquid storage unit 22c, and the second liquid disperser 22b is dispersed and dropped. The droplets of the second cleaning liquid 12 reach the second cleaning liquid storage portion 22c without touching anything other than the inner wall of the absorption tower container 20c. The second cleaning liquid storage unit 22c covers the storage unit main body for storing the second cleaning liquid, the opening provided between the storage unit main body and the opening through which the decarboxylated combustion exhaust gas 3 passes, and the opening from above. It is composed of a cover for preventing the second cleaning liquid 12 from falling into the opening.

Here, a case where the decarboxylated combustion exhaust gas 3 is washed by using the packed bed as the second recovery unit 22a as in the form shown in FIG. 1 and the like will be described. The second washing liquid 12 supplied to the packed bed is the packed bed. Adheres to the surface of the members that make up. In this case, the condensation from the water vapor accompanying the decarboxylated combustion exhaust gas 3 is mainly performed on the surface of the second cleaning liquid 12 adhering to the packed bed, and is not so much performed on the mist accompanying the decarbonated combustion exhaust gas 3. There is no tendency. Therefore, it is difficult to increase the mist diameter to the extent that it can be captured by the demister.

On the other hand, according to the present embodiment, since the gas-liquid contact space 100 is formed from the second liquid disperser 22b to the second cleaning liquid storage portion 22c, the gas-liquid contact space 100 is formed evenly with respect to the rising decarboxylation combustion exhaust gas 3. The second cleaning liquid 12 can be dispersed and dropped. Therefore, the cooling of the decarboxylated combustion exhaust gas 3 by the second cleaning liquid 12 can be equalized, the condensation on the mist accompanying the decarboxylated combustion exhaust gas 3 can be promoted, and the mist can be grown. Further, since the droplets of the second cleaning liquid 12 come into contact with the mist accompanying the decarboxylated combustion exhaust gas 3 and are taken in, the mist can be grown at this point as well. As a result, the grown mist can be captured by the third demister 83, and the amount of amine released into the atmosphere can be further reduced. In order to equalize the cooling of the decarboxylated combustion exhaust gas 3, the second cleaning liquid 12 is spray-injected from the second liquid disperser 22b, so that the second cleaning liquid 12 can be dispersed and dropped in the gas-liquid contact space 100. It is preferable to make the droplets of the second cleaning liquid 12 finer.

According to the above-described embodiment, the combustion exhaust gas can be washed with a cleaning liquid to reduce the amount of amine released into the atmosphere and the amount of waste of the cleaning liquid can be reduced.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof. Further, as a matter of course, it is also possible to partially and appropriately combine these embodiments within the scope of the gist of the present invention.

1: Carbon dioxide recovery system, 2: Combustion exhaust gas, 3: Decarbonization combustion exhaust gas, 4: Rich liquid, 5: Lean liquid, 6: Heating medium, 8: Carbon dioxide-containing gas, 10: Carbon dioxide gas, 11: No. 1 cleaning liquid, 12: 2nd cleaning liquid, 13: 3rd cleaning liquid, 14: cleaning supplement liquid, 15: 4th cleaning liquid, 20: absorption tower, 20a: carbon dioxide recovery unit, 21: 1st cleaning unit, 22: 2nd Cleaning unit, 22b: 2nd liquid disperser, 22c: 2nd cleaning liquid storage unit, 23: 3rd cleaning unit, 30: regeneration tower, 31: heat exchanger, 33: reboiler, 50: 1st circulation line, 52a: 1st heater, 52b: 2nd heater, 57: 3rd circulation line, 59: 3rd cleaning cooler, 60: Replenisher supply source, 62: 1st bypass line, 64: 2nd bypass line, 70 : Scrubber, 90: Cleaning liquid supply source, 100: Gas-liquid contact space

Claims (13)

An absorption tower having a carbon dioxide recovery unit that absorbs carbon dioxide contained in combustion exhaust gas into an absorption liquid containing amine,
A regeneration tower that releases the carbon dioxide from the absorption liquid that has absorbed the carbon dioxide supplied from the absorption tower.
1st heating part and
With a first bypass line
The absorption tower
A first cleaning unit that recovers the amine accompanying the combustion exhaust gas by cleaning the combustion exhaust gas discharged from the carbon dioxide recovery unit with a first cleaning liquid heated by the first heating unit.
A second cleaning unit that cleans the combustion exhaust gas discharged from the first cleaning unit with a second cleaning liquid and recovers the amine accompanying the combustion exhaust gas.
It has a third cleaning unit that cleans the combustion exhaust gas discharged from the second cleaning unit with a third cleaning liquid and recovers the amine accompanying the combustion exhaust gas.
The first bypass line is a carbon dioxide capture system in which at least a part of the second cleaning liquid discharged from the second cleaning unit is mixed with the third cleaning liquid. The carbon dioxide capture system according to claim 1, further comprising a second cleaning cooler for cooling the second cleaning liquid. A third circulation line that circulates the third cleaning liquid and
A third cleaning cooler provided in the third circulation line to cool the third cleaning liquid is further provided.
The carbon dioxide capture system according to claim 1 or 2, wherein the first bypass line is connected to a portion of the third circulation line on the upstream side of the third cleaning cooler. The carbon dioxide capture system according to any one of claims 1 to 3, further comprising a second bypass line for mixing a part of the third cleaning liquid discharged from the third cleaning unit into the first cleaning liquid. .. A first circulation line for circulating the first cleaning liquid is further provided.
The first heating unit is provided in the first circulation line.
The carbon dioxide capture system according to claim 4, wherein the second bypass line is connected to a portion of the first circulation line on the upstream side of the first heating portion. The carbon dioxide capture system according to any one of claims 1 to 5, further comprising a supply liquid supply source for supplying the cleaning supplement liquid to the second cleaning liquid or the third cleaning liquid. A fourth cleaning unit for cleaning the combustion exhaust gas discharged from the third cleaning unit with the fourth cleaning liquid and recovering the amine accompanying the combustion exhaust gas is further provided.
The carbon dioxide capture system according to any one of claims 1 to 6, wherein the fourth cleaning liquid contains an acid. The carbon dioxide recovery system according to claim 7, wherein the fourth cleaning unit is configured separately from the absorption tower. The carbon dioxide capture system according to any one of claims 1 to 8, further comprising a second heating unit that heats the first cleaning liquid heated by the first heating unit. A heat exchanger provided between the absorption tower and the regeneration tower to exchange heat between the absorption liquid supplied from the absorption tower and the absorption liquid supplied from the regeneration tower.
A reboiler that heats the absorption liquid in the regeneration tower with a supplied heating medium is further provided.
The heat source for heating the first cleaning liquid in the first heating unit is the absorption liquid discharged from the regeneration tower and passing through the heat exchanger, the heating medium discharged from the reboiler, and the absorption tower. The dioxide according to claim 9, which is one of the combustion exhaust gases supplied to the vehicle and the heat source for heating the first cleaning liquid in the second heating unit is the other one. Carbon recovery system. The second cleaning unit is further provided with a cleaning liquid supply source for supplying the second cleaning liquid.
The second cleaning liquid discharged from the second cleaning part is mixed into the third cleaning liquid through the first bypass line without being supplied to the second cleaning part, according to claims 1 to 10. The carbon dioxide capture system according to any one item. The second cleaning unit is provided below a second liquid disperser that disperses and drops the second cleaning liquid, and the second liquid disperser that is dispersed and dropped from the second liquid disperser. It has a second cleaning liquid storage unit that stores two cleaning liquids,
Any of claims 1 to 11, wherein a gas-liquid contact space is formed in which the falling second cleaning liquid and the rising combustion exhaust gas are in gas-liquid contact from the second liquid disperser to the second cleaning liquid storage portion. The carbon dioxide capture system described in item 1. In the carbon dioxide recovery section of the absorption tower, the process of absorbing carbon dioxide contained in the combustion exhaust gas into the absorption liquid containing amine, and
In the regeneration tower, a step of releasing the carbon dioxide from the absorption liquid that has absorbed the carbon dioxide supplied from the absorption tower, and
A step of cleaning the combustion exhaust gas discharged from the carbon dioxide recovery unit with a first cleaning liquid heated by the first heating unit in the first cleaning unit to recover the amine accompanying the combustion exhaust gas.
A step of cleaning the combustion exhaust gas discharged from the first cleaning unit with a second cleaning liquid in the second cleaning unit to recover the amine accompanying the combustion exhaust gas.
A step of cleaning the combustion exhaust gas discharged from the second cleaning unit with a third cleaning liquid in the third cleaning unit to recover the amine accompanying the combustion exhaust gas.
A method for operating a carbon dioxide capture system, comprising a step of mixing at least a part of the second cleaning liquid discharged from the second cleaning unit into the third cleaning liquid.

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