Carbon dioxide recovery system

Abstract

This carbon dioxide recovery system comprises: a regeneration tower that dissipates carbon dioxide from an absorption liquid that has absorbed carbon dioxide; a flash drum that flashes the absorption liquid supplied from the regeneration tower; a pressure reduction device that reduces the pressure of the absorption liquid supplied from the regeneration tower to the flash drum; a reboiler that heats the absorption liquid by exchanging heat between the absorption liquid in the flash drum and a heated fluid; and a pressure increase device that supplies vapor generated in the flash drum to the regeneration tower.

Description

[0064] <Modified example of carbon dioxide recovery system according to first, second, and fourth embodiments of present disclosure> The reboiler 5 in the first and fourth embodiments and the second regenerator 73 in the second embodiment are each a once-through reboiler as illustrative examples, but FIG. 7 shows the configuration where the reboiler 5 is a thermosiphon reboiler. In the thermosiphon reboiler 5, a tray is not provided (see FIG. 1), and the line 5a is connected to the bottom of the flash drum 3. The configuration is otherwise the same as that of the once-through reboiler.

[0065] The operation of the thermosiphon reboiler 5 is the same as that of the once-through reboiler, except that the lean solvent with the reduced pressure entering the flash drum 3 via the line 7 and the lean solvent heated in the reboiler 5 and returned to the flash drum 3 are mixed at the bottom of the flash drum 3.

[0066] The contents described in the above embodiments would be understood as follows, for instance.

[0067] [1] A carbon dioxide recovery system according to one aspect is provided with: a regenerator (2) for stripping carbon dioxide from a solvent that has absorbed carbon dioxide; a flash drum (3) for flashing the solvent supplied from the regenerator (2); a pressure reducing device (4) for reducing a pressure of the solvent supplied from the regenerator (2) to the flash drum (3); a reboiler (5) for heating the solvent by heat exchange between the solvent in the flash drum (3) and a heating fluid; and a pressure boosting device (6) for supplying vapor generated in the flash drum (3) to the regenerator (2).

[0068] With the carbon dioxide recovery system of the present disclosure, the temperature of the solvent is lowered by flashing the solvent in the flash drum, and the solvent with the lowered temperature is supplied to the reboiler, thus lowering the temperature required for the heating fluid supplied to the reboiler. As a result, it is possible to strip carbon dioxide from the solvent in the regenerator by using a heat source with a lower temperature than steam.

[0069] [2] A carbon dioxide recovery system according to another aspect is the carbon dioxide recovery system of [1], in which the regenerator (2) includes at least two regenerator sections (71, 72). The pressure reducing device (4) is configured to reduce a pressure of the solvent supplied from a most downstream regenerator section (72) of the at least two regenerator sections (71, 72) to the flash drum (second regenerator 73).

[0070] With this configuration, compared to the case including a single regenerator, the pressure and temperature in the most downstream regenerator section are lowered, and the temperature of the solvent is further lowered by flashing the solvent in the flash drum, further lowering the temperature required for the heating fluid supplied to the reboiler. As a result, it is possible to strip carbon dioxide from the solvent in the regenerator by using a heat source with a lower temperature than in [1].

[0071] [3] A carbon dioxide recovery system according to sill another aspect is the carbon dioxide recovery system of [2], including: a second pressure reducing device (pressure reducing valve 76) for reducing a pressure of the solvent supplied from an upstream regenerator section (71) to a downstream regenerator section (72) of two regenerator sections (71, 72) that are directly connected to each other of the at least two regenerator sections (71, 72); and a second pressure boosting device (compressor 80) for supplying vapor in the downstream regenerator section (72) to the upstream regenerator section (71).

[0072] With this configuration, it is possible to flash the solvent in the downstream regenerator. As a result, the temperature of the solvent flashed in the flash drum is further lowered, further lowering the temperature required for the heating fluid supplied to the reboiler. As a result, it is possible to strip carbon dioxide from the solvent in the regenerator by using a heat source with a lower temperature than in [2].

[0073] [4] A carbon dioxide recovery system according to sill another aspect is the carbon dioxide recovery system of any one of [1] to [3], in which the reboiler (5) is a kettle reboiler.

[0074] In the kettle reboiler, not only the solvent is heated, but also the solvent is separated into gas and liquid phases. This facilitates stripping of carbon dioxide from the solvent in the reboiler, which in turn facilitates stripping of carbon dioxide in the regenerator.

[0075] [5] A carbon dioxide recovery system according to sill another aspect is the carbon dioxide recovery system of any one of [1] to [4], including at least one heat exchanger for heating at least part of the heating fluid by heat exchange between the at least part of the heating fluid and any of a fluid to be supplied to the carbon dioxide recovery system (1), a fluid in the carbon dioxide recovery system (1), or a fluid discharged from the carbon dioxide recovery system (1). The carbon dioxide recovery system is configured such that the heating fluid heated in the at least one heat exchanger is supplied to the reboiler (5).

[0076] With this configuration, the heat recovered in the carbon dioxide recovery system can be used to heat the heating fluid, so the thermal efficiency of the carbon dioxide recovery system can be improved as a whole.

[0077] [6] A carbon dioxide recovery system according to sill another aspect is the carbon dioxide recovery system of any one of [1] to [5], in which the pressure boosting device (6) is a steam ejector (6b) for increasing a pressure of the vapor generated in the flash drum (3) by driving steam.

[0078] With this configuration, unlike the case where the compressor is used as the pressure boosting device, the use of the steam ejector eliminates mechanical losses and is more energyefficient than the use of the compressor.

[0079] [7] A carbon dioxide recovery system according to sill another aspect is the carbon dioxide recovery system of [6], including: a condensing device (10) for condensing water from effluent vapor discharged from the regenerator (2); and at least one driving steam generation device (92) for generating at least part of the driving steam by heating the water condensed in the condensing device (10).

[0080] With this configuration, the heat recovered in the carbon dioxide recovery system can be used to generate driving steam supplied to the steam ejector, so the thermal efficiency of the carbon dioxide recovery system can be improved as a whole.

[0081] [8] A carbon dioxide recovery system according to sill another aspect is the carbon dioxide recovery system of any one of [1] to [7], including: an absorber (40) for causing the solvent to absorb carbon dioxide by bringing a treated gas containing at least carbon dioxide into gas-liquid contact with the solvent, the absorber (40) being configured to supply the solvent that has absorbed carbon dioxide to the regenerator (2); and a reclaimer (60) for generating vapor of the solvent by heat exchange between vapor discharged from a compressor (6a) which is the pressure boosting device (6) and part of the solvent discharged from the flash drum (3). The carbon dioxide recovery system is configured such that the vapor of the solvent is supplied to the absorber (40) or at least one of the regenerator (2) or the flash drum (3).

[0082] With this configuration, even if the heating fluid cannot be used as a heat source for the reclaimer to reduce the concentration of non-volatile accumulations in the solvent due to the low temperature of the heating fluid used as a heat source in the reboiler, the vapor from the compressor can be used as the heat source for the reclaimer.

[0083] [9] A carbon dioxide recovery system according to sill another aspect is the carbon dioxide recovery system of [8], including a condensing device (10) for condensing water from effluent vapor discharged from the regenerator (2). The reclaimer (60) is configured to generate vapor of the solvent by heat exchange of vapor discharged from a compressor (6a) which is the pressure boosting device (6) with part of the solvent discharged from the flash drum (3) and part of the water condensed in the condensing device (10).

[0084] With this configuration, even if water condensed in the condensing device contains non-volatile accumulations, the non-volatile accumulations are removed in the reclaimer, so that the concentration of non-volatile accumulations in the solvent can be further reduced. Reference Signs List

[0085] 1         Carbon dioxide recovery system 2         Regenerator 3         Flash drum 4         Pressure reducing device 5         Reboiler 6         Pressure boosting device 6a       Compressor 6b        Steam ejector 10       Condensing device 13        Condenser (Heat exchanger) 17        Effluent gas compressor 18       Heat exchanger 30       Quencher 32       Heat exchanger 35       Heat exchanger 40       Absorber 43       Heat exchanger 45       Heat exchanger 50       Heat exchanger 51        Heat exchanger 60       Reclaimer 71        Regenerator section 72        Regenerator section 73        Second regenerator (Flash drum) 76        Pressure reducing valve (Second pressure reducing device) 77        Pressure reducing valve (Pressure reducing device) 80        Compressor (Second pressure boosting device) 81        Compressor (Pressure boosting device) 92        Driving steam generation device

Claims

1. A carbon dioxide recovery system, comprising:a regenerator for stripping carbon dioxide from a solvent that has absorbed carbon dioxide;a flash drum for flashing the solvent supplied from the regenerator;a pressure reducing device for reducing a pressure of the solvent supplied from the regenerator to the flash drum;a reboiler for heating the solvent by heat exchange between the solvent in the flash drum and a heating fluid; anda pressure boosting device for supplying vapor generated in the flash drum to the regenerator.

2. The carbon dioxide recovery system according to claim 1,wherein the regenerator includes at least two regenerator sections, andwherein the pressure reducing device is configured to reduce a pressure of the solvent supplied from a most downstream regenerator section of the at least two regenerator sections to the flash drum.

3. The carbon dioxide recovery system according to claim 2, comprising:a second pressure reducing device for reducing a pressure of the solvent supplied from an upstream regenerator section to a downstream regenerator section of two regenerator sections that are directly connected to each other of the at least two regenerator sections; anda second pressure boosting device for supplying vapor in the downstream regenerator section to the upstream regenerator section.

4. The carbon dioxide recovery system according to any one of claims 1 to 3,wherein the reboiler is a kettle reboiler.

5. The carbon dioxide recovery system according to any one of claims 1 to 3, comprising at least one heat exchanger for heating at least part of the heating fluid by heat exchange between the at least part of the heating fluid and any of a fluid to be supplied to the carbon dioxide recovery system, a fluid in the carbon dioxide recovery system, or a fluid discharged from the carbon dioxide recovery system,wherein the carbon dioxide recovery system is configured such that the heating fluid heated in the at least one heat exchanger is supplied to the reboiler.

6. The carbon dioxide recovery system according to any one of claims 1 to 3, wherein the pressure boosting device is a steam ejector for increasing a pressure of the vapor generated in the flash drum by driving steam.

7. The carbon dioxide recovery system according to claim 6, comprising:a condensing device for condensing water from effluent vapor discharged from the regenerator; andat least one driving steam generation device for generating at least part of the driving steam by heating the water condensed in the condensing device.

8. The carbon dioxide recovery system according to any one of claims 1 to 3, comprising:an absorber for causing the solvent to absorb carbon dioxide by bringing a treated gas containing at least carbon dioxide into gas-liquid contact with the solvent, the absorber being configured to supply the solvent that has absorbed carbon dioxide to the regenerator; anda reclaimer for generating vapor of the solvent by heat exchange between vapor discharged from a compressor which is the pressure boosting device and part of the solvent discharged from the flash drum,wherein the carbon dioxide recovery system is configured such that the vapor of the solvent is supplied to the absorber or at least one of the regenerator or the flash drum.

9. The carbon dioxide recovery system according to claim 8, comprising a condensing device for condensing water from effluent vapor discharged from the regenerator,wherein the reclaimer is configured to generate vapor of the solvent by heat exchange of5 vapor discharged from a compressor which is the pressure boosting device with part of the solvent discharged from the flash drum and part of the water condensed in the condensing device.

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