Floating body and carbon dioxide capture method

Abstract

To provide a carbon dioxide recovery method capable of suppressing required energy for separating carbon dioxide from exhaust gas and of efficiently recovering carbon dioxide.SOLUTION: A floating body comprises a combustion apparatus to operate on a liquified combustible gas as a fuel and to discharge an exhaust gas, a liquified combustible gas storage part to store a liquified combustible gas, a fuel supply line to supply the liquified combustible gas from the liquified combustible gas storage part to the combustion apparatus, an absorption tower that the carbon dioxide included in the exhaust gas is absorbed into absorbent, a carbon dioxide recovery apparatus with a regeneration tower to separate a gaseous carbon dioxide from the absorbent into which the carbon dioxide is absorbed in the absorption tower, a carbon dioxide liquified apparatus to liquefy the carbon dioxide discharged from the carbon dioxide recovery apparatus which uses the liquified combustible gas supplied from the liquified combustible gas storage part to the combustion apparatus through the fuel supply line as a cold heat source, and a liquified carbon dioxide storage part to store a carbon dioxide liquified by the carbon dioxide liquified apparatus.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to floating bodies and carbon dioxide capture methods. [Background technology]

[0002] In floating bodies such as ships, there is a demand for reducing nitrogen oxides and the like in exhaust gases discharged from engines, etc. For example, Patent Document 1 proposes a technology that uses boil-off gas of liquefied flammable gases such as liquefied natural gas stored in a cargo tank as part of the fuel for combustion devices such as main engines and generators. Furthermore, Patent Document 1 proposes a technology that separates carbon dioxide contained in exhaust gases and refrigerates it as liquid carbon dioxide or solid carbon dioxide using the cold energy of liquefied natural gas in order to reduce carbon dioxide emissions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-245995 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a ship such as that described in Patent Document 1, energy is required to separate and liquefy carbon dioxide from exhaust gas, but generating such energy on a floating body requires driving an engine or the like, which results in the emission of carbon dioxide. Therefore, it is desirable to reduce the energy required to separate and liquefy carbon dioxide from exhaust gas. The present disclosure has been made in consideration of the above circumstances, and provides a float and a carbon dioxide capture method that can efficiently capture carbon dioxide by reducing the energy required to separate and liquefy carbon dioxide from exhaust gas. [Means for solving the problem]

[0005] In order to solve the above problems, the following configuration is adopted. According to a first aspect of the present disclosure, the floating body comprises: Possible A combustion device that operates using a combustible gas as fuel and discharges exhaust gas; The flammable gas in liquid form A carbon dioxide recovery device having a liquefied flammable gas storage section for storing liquefied flammable gas, a fuel supply line for supplying the liquefied flammable gas from the liquefied flammable gas storage section to the combustion device, an absorption tower for absorbing carbon dioxide contained in the exhaust gas into an absorption liquid, and a regeneration tower for separating gaseous carbon dioxide from the absorption liquid that has absorbed the carbon dioxide in the absorption tower, and a fuel supply line for supplying the liquefied flammable gas from the liquefied flammable gas storage section to the combustion device by the fuel supply line. Liquid A carbon dioxide liquefaction device that liquefies the carbon dioxide discharged from the carbon dioxide capture device using the liquefied flammable gas as a cold heat source, and a liquefied carbon dioxide storage unit that stores the carbon dioxide liquefied by the carbon dioxide liquefaction device; a vaporizer that is provided in the fuel supply line on a side closer to the combustion device than the carbon dioxide liquefaction device, and vaporizes the liquefied flammable gas used as a cold source in the carbon dioxide liquefaction device to convert it into a flammable gas; Equipped with The fuel supply line introduces the flammable gas vaporized by the vaporizer into the combustion device as fuel. do.

[0006] According to a second aspect of the present disclosure, a method for capturing carbon dioxide includes: Possible A carbon dioxide recovery method for recovering carbon dioxide from exhaust gas discharged by burning a combustible gas, comprising: a step of absorbing carbon dioxide contained in the exhaust gas into an absorption liquid; and a step of separating gaseous carbon dioxide from the absorption liquid having absorbed the carbon dioxide. The flammable gas in liquid form A step of liquefying the gaseous carbon dioxide separated from the absorption liquid using a liquefied flammable gas as a cold heat source; and a step of storing the liquefied carbon dioxide. A step of vaporizing the liquefied flammable gas used as a cold source for liquefying the carbon dioxide into a flammable gas and then combusting the flammable gas; Includes. Effect of the Invention

[0007] The float and carbon dioxide capture method disclosed herein can reduce the energy required to separate and liquefy carbon dioxide from exhaust gas, thereby enabling efficient capture of carbon dioxide. [Brief description of the drawings]

[0008] [Figure 1]FIG. 1 is a diagram showing a schematic configuration of a float according to an embodiment of the present disclosure. [Diagram 2] 1 is a flowchart of a carbon dioxide capture method in a first embodiment of the present disclosure. [Diagram 3] FIG. 1 is a diagram showing a schematic configuration of a carbon dioxide capture system provided on a floating body according to a first embodiment of the present disclosure. [Figure 4] FIG. 11 is a diagram showing a schematic configuration of a carbon dioxide capture system provided on a floating body in a second embodiment of the present disclosure. [Diagram 5] FIG. 13 is a diagram showing a schematic configuration of a carbon dioxide capture system provided on a floating body in a third embodiment of the present disclosure. [Figure 6] FIG. 13 is a diagram showing a schematic configuration of a carbon dioxide capture system provided on a floating body in a fourth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] First Embodiment Next, a float and a carbon dioxide capture method according to the first embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a floating body according to this embodiment. (Vessel configuration) As shown in FIG. 1, in this embodiment, the floating body 1A at least includes a floating body main body 2, a combustion device 9, a carbon dioxide capture system 10A (see FIG. 3), a liquefied carbon dioxide storage section 11, a liquefied flammable gas storage section 21, a fuel supply line 22, and a vaporization device 23. The floating body 1A in this embodiment is described as an example of a ship that can navigate by a main engine or the like, but is not limited to a ship as long as it is a float that is equipped with at least a combustion device 9 that uses liquefied flammable gas F as fuel. When the floating body 1A is a ship, the type of ship is not limited to a specific type of ship, and examples of the ship include a liquefied gas carrier, a ferry, a RORO ship, a car carrier, and a passenger ship. Examples of the floating body 1A that is not a ship include a FSU (Floating Storage Unit), an FSRU (Floating Storage and Regasification Unit), and the like.

[0010] (Floating structure) The floating body 2 has a pair of side panels 3A, 3B, a bottom panel (not shown), and an upper deck 5, which form the outer hull of the floating body 2. The side panels 3A, 3B have a pair of side panel shells that form the left and right sides, respectively. The bottom panel has a bottom panel shell that connects the side panels 3A, 3B. The pair of side panels 3A, 3B and the bottom panel form the outer hull of the floating body 2 in a U-shape in a cross section perpendicular to the bow-stern direction Da. The upper deck 5 illustrated in this embodiment is a full deck exposed to the outside. The floating body 2 has a superstructure 7 having a living area formed on the upper deck 5 on the stern 2b side. Furthermore, the floating body 2 illustrated in this embodiment has a cargo carrying section 8 (in other words, a cargo hold) formed on the bow 2a side of the superstructure 7. The positions of the superstructure 7 and the cargo carrying section 8 are merely examples, and for example, the superstructure 7 may be disposed on the bow 2a side of the floating body 2 and the cargo carrying section 8 on the stern 2b side.

[0011] The combustion device 9 is disposed within the floating body 2. The combustion device 9 performs the required functions by burning the liquefied flammable gas F. Examples of the combustion device 9 include a main engine, a generator, and a boiler. The main engine is an engine (internal combustion engine) fueled by the liquefied flammable gas F, and generates the propulsive force for propelling the floating body 2. The generator includes an engine (internal combustion engine) fueled by the liquefied flammable gas F, and generates electricity used within the floating body 2 by the driving force of the engine. The boiler burns the liquefied flammable gas F to generate steam used within the floating body 2.

[0012] FIG. 3 is a diagram showing a schematic configuration of a carbon dioxide capture system provided on a floating body according to the first embodiment of the present disclosure. 1 and 3, the liquefied carbon dioxide storage unit 11 is a tank that stores the liquefied carbon dioxide recovered by the carbon dioxide recovery system 10A. In other words, the liquefied carbon dioxide storage unit 11 is configured to be able to store carbon dioxide in a liquid state.

[0013] The liquefied flammable gas storage section 21 stores the liquefied flammable gas F. The liquefied flammable gas F in this embodiment is a fuel used in the floating body 1A and is burned by the combustion device 9. In other words, the liquefied flammable gas storage section 21 is a fuel tank for storing fuel. The liquid phase of the liquefied flammable gas F stored in the liquefied flammable gas storage section 21 has a lower temperature than the liquid phase of the carbon dioxide C stored in the liquefied carbon dioxide storage section 11. Examples of the liquefied flammable gas F include liquefied natural gas (LNG), methane, and ethane. In this embodiment, a case where liquefied natural gas is used as the liquefied flammable gas F will be described as an example.

[0014] The fuel supply line 22 supplies the liquefied flammable gas F from the liquefied flammable gas storage section 21 to the combustion device 9. The vaporizer 23 is provided in the fuel supply line 22 and vaporizes the liquefied flammable gas F. The flammable gas G obtained by vaporizing the liquefied flammable gas F is introduced into the combustion device 9 and combusted.

[0015] The carbon dioxide capture system 10A captures and liquefies carbon dioxide contained in the exhaust gas E from the combustion device 9. The carbon dioxide capture system 10A includes a carbon dioxide capture device 31, a carbon dioxide liquefaction device 32, and a liquefied carbon dioxide storage unit 11. The carbon dioxide capture unit 31 captures carbon dioxide from the flue gas E discharged from the combustion unit 9. The carbon dioxide capture unit 31 includes an exhaust gas cooling tower , an absorption tower 35, and a regeneration tower .

[0016] The exhaust gas cooling tower 34 cools the exhaust gas E discharged from the combustion device 9. In this embodiment, the exhaust gas cooling tower 34 cools the exhaust gas E discharged from the combustion device 9 (for example, to about 40°C) using as a cold source the seawater surrounding the floating body 2 or fresh water stored in a fresh water tank (not shown) provided within the floating body 2. The exhaust gas cooling tower 34 may be provided as necessary, and may be omitted, for example, when the temperature of the exhaust gas introduced into the absorption tower 35 has been sufficiently reduced.

[0017] The absorption tower 35 absorbs the carbon dioxide contained in the flue gas E into an absorbing liquid (not shown). The absorption tower 35, for example, drops the absorbing liquid from the upper part of the absorption tower 35 and brings it into contact with the flue gas E introduced into the absorption tower 35, thereby absorbing the carbon dioxide contained in the flue gas E into the absorbing liquid. The flue gas E after the carbon dioxide is absorbed into the absorbing liquid is discharged from the top of the absorption tower 35 and introduced into the flue gas scrubbing tower 38. The flue gas scrubbing tower 38 drops fresh water from the upper part of the flue gas scrubbing tower 38 to wash away the absorbing liquid contained in the flue gas E that has left the absorption tower 35. The flue gas E that has left the flue gas scrubbing tower 38 is led, for example, to an exhaust funnel (not shown) or the like provided on the floating body 1 and released into the atmosphere. An example of a liquid that absorbs carbon dioxide by chemical absorption is MEA (monoethanolamine).

[0018] The regenerator 36 separates gaseous carbon dioxide from the absorbing liquid that has absorbed carbon dioxide in the absorption tower 35. More specifically, the regenerator 36 heats the absorbing liquid sent into the regenerator 36 from the lower part of the absorption tower 35 with steam or the like generated by a boiler (not shown) provided in the floating body main body 2. As a result, gaseous carbon dioxide is separated from the absorbing liquid in the regenerator 36, and this separated gaseous carbon dioxide is introduced into the carbon dioxide liquefaction device 32 via the gaseous carbon dioxide introduction line 37. Meanwhile, the absorbing liquid from which gaseous carbon dioxide has been separated and regenerated is returned to the absorption tower 35 and reused.

[0019] The carbon dioxide liquefaction device 32 liquefies gaseous carbon dioxide discharged from the carbon dioxide capture device 31. The carbon dioxide liquefaction device 32 includes a compressor 41 that compresses gaseous carbon dioxide, and a liquefier 42 that liquefies the gaseous carbon dioxide compressed by the compressor 41. The carbon dioxide liquefaction device 32 of this embodiment uses the liquefied flammable gas F supplied from the liquefied flammable gas storage section 21 to the combustion device 9 via the fuel supply line 22 as a cold heat source used in the liquefier 42. That is, the liquefier 42 is provided midway along the fuel supply line 22. The carbon dioxide liquefied by the liquefier 42 is introduced into the liquefied carbon dioxide storage section 11 via the liquefied carbon dioxide discharge line 43 and stored therein.

[0020] Here, the liquefied flammable gas F after being used as a cold heat source in the liquefier 42 has a temperature higher than the liquid phase of the liquefied flammable gas F stored in the liquefied flammable gas storage section 21, but still contains liquid. The vaporizer 23 described above is provided in the fuel supply line 22 on the combustion device 9 side of the liquefier 42, and heats and vaporizes the liquefied flammable gas F after being used as a cold heat source. The vaporizer 23 of this embodiment heats the liquefied flammable gas F with a heat medium such as steam from the boiler described above, for example.

[0021] (Carbon dioxide capture method) Next, a carbon dioxide capture method according to an embodiment of the present disclosure will be described with reference to the drawings. Fig. 2 is a flowchart of the carbon dioxide capture method according to the first embodiment of the present disclosure. 2, carbon dioxide contained in the exhaust gas E is absorbed in an absorbing liquid (step S01). In this embodiment, the exhaust gas E discharged from a combustion device operating using a liquefied flammable gas F as fuel is introduced into an absorption tower 35. Then, the gaseous carbon dioxide contained in the exhaust gas E is absorbed in the absorbing liquid using the absorption tower 35.

[0022] Next, the gaseous carbon dioxide is separated from the absorbing liquid in which the carbon dioxide has been absorbed (step S02). In this embodiment, the absorbing liquid in a state in which the carbon dioxide has been absorbed is introduced into the regenerator 36, and the gaseous carbon dioxide is separated from the absorbing liquid. Furthermore, the gaseous carbon dioxide separated from the absorbing liquid is liquefied using the liquefied flammable gas as a cold heat source (step S03). In this embodiment, the gaseous carbon dioxide is compressed by the compressor 41, and the compressed gaseous carbon dioxide is introduced into the liquefier 42. Then, the gaseous carbon dioxide is liquefied by exchanging heat with the liquefied flammable gas F supplied as fuel from the liquefied flammable gas storage section 21 to the combustion device 9 via the fuel supply line 22 by the liquefier 42. Thereafter, the liquefied carbon dioxide is stored (step S04). In this embodiment, the carbon dioxide liquefied by the liquefier 42 is stored in the liquefied carbon dioxide storage section 11 via the liquefied carbon dioxide discharge line 43.

[0023] (Action and effect) According to the first embodiment, the gaseous carbon dioxide contained in the exhaust gas E discharged from the floating body 2 can be efficiently separated by the absorption tower 35 and the regeneration tower 36 of the carbon dioxide capture device 31. Therefore, the energy required for separating and liquefying the carbon dioxide from the exhaust gas E can be reduced, and the carbon dioxide can be efficiently captured. Furthermore, the volume of carbon dioxide can be reduced by liquefying the carbon dioxide separated by the carbon dioxide capture device 31 using the carbon dioxide liquefaction device 32, thereby preventing the container for storing the captured carbon dioxide from becoming too large.

[0024] According to the first embodiment, the liquefied flammable gas F used as a cold source for the carbon dioxide liquefaction device 32 is further introduced into the vaporization device 23. This allows the liquefied flammable gas F, which is the fuel for the combustion device 9, to be heated before being introduced into the vaporization device 23. Therefore, the energy required to vaporize the liquefied flammable gas F in the vaporization device 23 can be reduced, making it possible to recover carbon dioxide more efficiently.

[0025] Second Embodiment Next, a second embodiment of the float according to the present disclosure will be described. In the second embodiment described below, the configuration of the fuel supply system using the fuel supply line 22 is different from that of the first embodiment. Therefore, FIG. 1 will be used, and the same parts as those in the first embodiment will be denoted by the same reference numerals, and duplicated explanations will be omitted.

[0026] FIG. 4 is a diagram showing a schematic configuration of a carbon dioxide capture system provided on a floating body in the second embodiment of the present disclosure. The float 1B in the second embodiment, like the float 1A in the first embodiment, at least comprises a float main body 2, a combustion device 9, a carbon dioxide capture system 10B (see Figure 4), a liquefied carbon dioxide storage section 11, a liquefied flammable gas storage section 21, a fuel supply line 22, and a vaporization device 23.

[0027] The carbon dioxide capture system 10B of the second embodiment captures and liquefies carbon dioxide contained in the exhaust gas E of the combustion device 9. As shown in Fig. 4, the carbon dioxide capture system 10B includes a carbon dioxide capture device 31, a carbon dioxide liquefaction device 32, and a liquefied carbon dioxide storage unit 11. The carbon dioxide capture unit 31 captures carbon dioxide from the flue gas E discharged from the combustion unit 9. The carbon dioxide capture unit 31 includes an exhaust gas cooling tower , an absorption tower 35, and a regeneration tower .

[0028] The exhaust gas cooling tower 134 cools the exhaust gas E discharged from the combustion device 9, similarly to the exhaust gas cooling tower 34 in the first embodiment. The exhaust gas cooling tower 134 in this second embodiment cools the exhaust gas E discharged from the combustion device 9 (for example, to about 40° C.) using the liquefied combustible gas F used as a cold source by the carbon dioxide liquefaction device 32 as a cold source. The exhaust gas E cooled by this exhaust gas cooling tower 134 is introduced into the absorption tower 35. Then, the carbon dioxide absorbed by the absorbing liquid in the absorption tower 35 is heated in the regeneration tower 36 and separated from the absorbing liquid, and is introduced into the carbon dioxide liquefaction device 32.

[0029] The carbon dioxide liquefaction device 32 is equipped with a compressor 41 and a liquefier 42, as in the first embodiment, and utilizes liquefied flammable gas F supplied from the liquefied flammable gas storage section 21 to the combustion device 9 via a fuel supply line 22 as a cold heat source for the liquefier 42.

[0030] The fuel supply line 22 supplies the liquefied flammable gas F from the liquefied flammable gas storage section 21 toward the combustion device 9. On the other hand, the fuel supply line 22 of the second embodiment guides the liquefied flammable gas F used as a cold heat source in the liquefier 42 of the carbon dioxide liquefaction device 32 to the exhaust gas cooling tower 134 to be further used as a cold heat source. The fuel supply line 22 guides the liquefied flammable gas F used as a cold heat source in the exhaust gas cooling tower 134 to the vaporizer 23. In other words, the vaporizer 23 of the second embodiment is provided on the fuel supply line 22 closer to the combustion device 9 than the exhaust gas cooling tower 134. The vaporizer 23 of the second embodiment is also provided in the middle of the fuel supply line 22 as in the first embodiment, and vaporizes the liquefied flammable gas F. The flammable gas G obtained by vaporizing the liquefied flammable gas F is introduced into the combustion device 9 and burned as fuel.

[0031] (Action and effect) According to the second embodiment, similarly to the first embodiment, gaseous carbon dioxide contained in the exhaust gas E discharged from the floating body 2 can be efficiently separated by the absorption tower 35 and the regeneration tower 36 of the carbon dioxide capture device 31. Therefore, it is possible to efficiently capture carbon dioxide while suppressing the energy required for separating and liquefying carbon dioxide from the exhaust gas E. Furthermore, since the volume of carbon dioxide can be reduced by liquefying the carbon dioxide separated by the carbon dioxide capture device 31 by the carbon dioxide liquefaction device 32, it is possible to suppress an increase in size of a container for storing the captured carbon dioxide.

[0032] Moreover, in the second embodiment, the liquefied flammable gas F used as a cold source for the carbon dioxide liquefaction device 32 is further used as a cold source for the exhaust gas cooling tower 34, and then introduced into the vaporization device 23. This allows the liquefied flammable gas F, which is the fuel for the combustion device 9, to be heated before being introduced into the vaporization device 23, so that the energy required to vaporize the liquefied flammable gas F in the vaporization device 23 can be further reduced.

[0033] Third Embodiment Next, a third embodiment of the floating body according to the present disclosure will be described. The third embodiment described below differs from the second embodiment in that the evaporated gas from the liquefied carbon dioxide can be re-liquefied. Therefore, FIG. 1 will be used to explain the same parts as those in the second embodiment, and the same reference numerals will be used to denote the same parts as those in the second embodiment, and duplicate explanations will be omitted.

[0034] FIG. 5 is a diagram showing a schematic configuration of a carbon dioxide capture system provided on a floating body in the third embodiment of the present disclosure. 1 and 5, like the floating body 1B of the second embodiment, the floating body 1C of the third embodiment at least includes a floating body main body 2, a combustion device 9, a carbon dioxide capture system 10C (see FIG. 5), a liquefied carbon dioxide storage section 11, a liquefied flammable gas storage section 21, a fuel supply line 22, and a vaporization device 23. The floating body 1C of the third embodiment also includes a cargo tank 51 provided in the cargo carrying section 8, an evaporated gas introduction line 52, a re-liquefied carbon dioxide discharge line 53, and valve devices 54, 55, 59, and 57.

[0035] The cargo tank 51 stores liquefied carbon dioxide as a cargo. A gas phase exists in the upper part and a liquid phase exists in the lower part in the cargo tank 51. The gas phase mainly consists of evaporative gas (natural BOG) B that evaporates due to natural heat input to the cargo tank 51.

[0036] The evaporative gas introduction line 52 introduces the gas phase gas (evaporative gas B) in the cargo tank 51 to the compressor 41 of the carbon dioxide capture system 10C. The evaporative gas introduction line 52 in this embodiment is joined and connected to a gaseous carbon dioxide introduction line 37 that introduces gaseous carbon dioxide discharged from the carbon dioxide capture device 31 to the carbon dioxide liquefaction device 32. That is, the evaporative gas B in the cargo tank 51 can be introduced into the carbon dioxide liquefaction device 32 via the evaporative gas introduction line 52 and the gaseous carbon dioxide introduction line 37. The evaporative gas B in the cargo tank 51 is compressed by the compressor 41 of the carbon dioxide liquefaction device 32, and then cooled and re-liquefied by the liquefier 42 using the liquefied flammable gas F as a cold source.

[0037] The re-liquefied carbon dioxide discharge line 53 introduces the liquefied carbon dioxide re-liquefied by the carbon dioxide liquefaction device 32 into the cargo tank 51. The re-liquefied carbon dioxide discharge line 53 in this embodiment is branched off and connected to the liquefied carbon dioxide discharge line 43.

[0038] The valve devices 54 and 55 are capable of switching the gaseous carbon dioxide introduced into the carbon dioxide liquefaction device 32 between the carbon dioxide from the carbon dioxide capture device 31 and the carbon dioxide from the cargo tank 51. In addition, the valve devices 56 and 57 are capable of switching the location for storing the liquefied carbon dioxide liquefied by the carbon dioxide liquefaction device 32. In other words, the liquefied carbon dioxide liquefied by the carbon dioxide liquefaction device 32 is stored in either the cargo tank 51 or the liquefied carbon dioxide storage section 11.

[0039] (Action and effect) According to the third embodiment, in addition to the effects of the first and second embodiments, the evaporated gas B generated in the cargo tank 51 can be reliquefied by the carbon dioxide liquefaction device 32 of the carbon dioxide capture system 10C. Therefore, it is not necessary to provide a dedicated reliquefaction device for reliquefying the evaporated gas B, and therefore it is possible to suppress an increase in size of the floating body 1. Also, when reliquefying the evaporated gas B, the liquefied flammable gas F can be used as a cold heat source, thereby achieving further energy savings.

[0040] In addition, the liquefied carbon dioxide obtained by reliquefying the evaporated gas B can be returned to the cargo tank 51. Furthermore, the liquefied carbon dioxide recovered and liquefied by the carbon dioxide capture device 31 can be stored in the liquefied carbon dioxide storage section 11. Therefore, when the liquefied carbon dioxide obtained by reliquefying the evaporated gas B and the liquefied carbon dioxide recovered and liquefied by the carbon dioxide capture device 31 have different compositions, it is possible to prevent the liquefied carbon dioxide recovered and liquefied from the exhaust gas E from being mixed into the liquefied carbon dioxide as the cargo.

[0041] (Modification of the third embodiment) In the above-described third embodiment, a case has been described as an example in which the carbon dioxide liquefaction device 32 for liquefying the carbon dioxide recovered from the exhaust gas E is also used as a device for re-liquefying the evaporated gas B in the cargo tank 51. However, the present invention is not limited to this configuration. For example, only one of the compressor 41 and the liquefier 42 of the carbon dioxide liquefaction device 32 may be used for re-liquefying the evaporated gas B. In this case as well, it is possible to reduce the compressor 41 or the liquefier 42 for re-liquefaction.

[0042] In addition, in the above-mentioned third embodiment, a case has been described in which the liquefied carbon dioxide discharged from the carbon dioxide liquefaction device 32 is stored separately in the cargo tank 51 and the liquefied carbon dioxide storage section 11, but it is also possible to provide only one of the liquefied carbon dioxide storage section 11 or the cargo tank 51, and store, for example, all of the liquefied carbon dioxide discharged from the carbon dioxide liquefaction device 32 in only one of the liquefied carbon dioxide storage section 11 or the cargo tank 51.

[0043] Furthermore, in the above-described third embodiment, the case where the evaporated gas B generated in the cargo tank 51 is reliquefied by the carbon dioxide liquefaction device 32 of the carbon dioxide capture system 10C has been described. However, the evaporated gas B is not limited to that generated in the cargo tank 51. For example, as shown by a dashed line in FIG. 4, in addition to the evaporated gas B generated in the cargo tank 51, the evaporated gas B generated in the liquefied carbon dioxide storage section 11 may be introduced into the carbon dioxide liquefaction device 32 via the evaporated gas introduction line 152 (similar to the fourth embodiment described later). In this case, the evaporated gas B to be introduced into the carbon dioxide liquefaction device 32 may be selected from the evaporated gas B in the cargo tank 51 and the evaporated gas B in the liquefied carbon dioxide storage section 11. Also, for example, the above-described cargo tank 51 and the evaporated gas introduction line 52 may be omitted, and the evaporated gas B generated in the liquefied carbon dioxide storage section 11 and the gaseous carbon dioxide discharged from the carbon dioxide capture device 31 may be configured to be introduced into the carbon dioxide liquefaction device 32.

[0044] Fourth Embodiment Next, a fourth embodiment of the float according to the present disclosure will be described. The fourth embodiment described below differs from the third embodiment in that the evaporated gas B in the cargo tank 51 and the carbon dioxide discharged from the carbon dioxide capture device 31 are mixed and then introduced into the carbon dioxide liquefaction device 32. Therefore, FIG. 1 will be used to describe the same parts as those in the second embodiment, with the same reference numerals given to them, and duplicated descriptions will be omitted.

[0045] FIG. 6 is a diagram showing a schematic configuration of a carbon dioxide capture system provided on a floating body in the fourth embodiment of the present disclosure. 1 and 6, like the floating body 1C of the third embodiment, the floating body 1D of the fourth embodiment at least includes a floating body main body 2, a combustion device 9, a carbon dioxide capture system 10D (see FIG. 6), a liquefied carbon dioxide storage section 11, a liquefied flammable gas storage section 21, a fuel supply line 22, and a vaporization device 23. The floating body 1D of the fourth embodiment also includes a cargo tank 51 provided in the cargo carrying section 8, an evaporated gas introduction line 52, a re-liquefied carbon dioxide discharge line 53, valve devices 56, 57, and an introduction adjustment section 61.

[0046] The introduction adjustment unit 61 adjusts the amount of carbon dioxide introduced from the carbon dioxide capture unit 31 to the carbon dioxide liquefaction unit 32 and the amount of carbon dioxide introduced to the carbon dioxide liquefaction unit 32 through the evaporative gas introduction line 52. The introduction adjustment unit 61 includes an inlet detection unit 62, an outlet detection unit 63, and a control valve 64. The inlet detection unit 62 detects at least the temperature at the inlet of the compressor 41, and outputs the detection result to the control valve 64. The outlet detection unit 63 detects at least the temperature at the outlet of the compressor 41, and outputs the detection result to the control valve 64. The inlet detection unit 62 and the outlet detection unit 63 in this fourth embodiment detect pressure in addition to temperature.

[0047] The control valve 64 adjusts the opening of the flow path in the evaporative gas introduction line 52 based on the detection results of the inlet detection unit 62 and the outlet detection unit 63. Furthermore, the control valve 64 adjusts the opening of the flow path in the gaseous carbon dioxide introduction line 37 based on the detection results of the inlet detection unit 62 and the outlet detection unit 63. The control valve 64 is capable of adjusting the mixing ratio of the carbon dioxide introduced from the carbon dioxide capture device 31 to the carbon dioxide liquefaction device 32 and the carbon dioxide introduced from the evaporative gas introduction line 52 to the carbon dioxide liquefaction device 32 so that the liquefaction of carbon dioxide performed in the carbon dioxide liquefaction device 32 is optimally efficient. Note that in this fourth embodiment, a three-way flow rate adjustment valve is exemplified as the control valve 64, but the control valve 64 is not limited to a three-way valve.

[0048] Furthermore, the introduction adjustment unit 61 suppresses a situation in which the temperature of the carbon dioxide at the inlet of the compressor 41 is high, causing the discharge temperature at the outlet of the compressor 41 to rise more than necessary, and also suppresses a situation in which the carbon dioxide temperature at the inlet of the compressor 41 rises too much, causing a decrease in the charging efficiency of the compressor 41. Furthermore, by detecting the inlet pressure and outlet pressure of the compressor 41, the introduction adjustment unit 61 adjusts the carbon dioxide pressure on the inlet side so that the pressure at the outlet of the compressor 41 is the desired pressure and the compression ratio by the compressor 41 is not excessive.

[0049] Here, the carbon dioxide discharged from the regenerator 36 and flowing through the gaseous carbon dioxide introduction line 37 is, for example, at room temperature or slightly warmer than room temperature. On the other hand, the carbon dioxide discharged from the cargo tank 51 and flowing through the evaporative gas introduction line 52 is, for example, at about −20° C. to −30° C. In the introduction adjustment unit 61 of the fourth embodiment, the gaseous carbon dioxide discharged from the cargo tank 51 is mixed with the carbon dioxide flowing through the gaseous carbon dioxide introduction line 37, thereby increasing the temperature difference between the carbon dioxide heat exchanged in the liquefier 42 and the liquefied flammable gas F, thereby improving the heat exchange efficiency. The above-mentioned mixture ratio at which the liquefaction in the liquefier 42 is optimally efficient can be obtained in advance based on experiments, simulations, etc. The opening adjustment of the control valve 64 described above may be performed based on a map, table, formula, etc. of the flow rates of the evaporative gas introduction line 52 and the gaseous carbon dioxide introduction line 37 relative to the detection results of the inlet detection unit 62 and the outlet detection unit 63 obtained by experiments, simulations, etc.

[0050] In this fourth embodiment, the liquefied carbon dioxide storage section 11 and the cargo tank 51 are provided, and the carbon dioxide liquefied by the liquefier 42 can be allocated and stored in each of them. An example of a method of allocating carbon dioxide to the liquefied carbon dioxide storage section 11 and the cargo tank 51 is to store the liquefied carbon dioxide in the tank having a larger free capacity. As in the modified example of the third embodiment, only one of the liquefied carbon dioxide storage section 11 and the cargo tank 51 may be provided, and all of the liquefied carbon dioxide discharged from the carbon dioxide liquefaction device 32 may be stored in only one of the liquefied carbon dioxide storage section 11 and the cargo tank 51. As in the modified example of the third embodiment, the evaporated gas B of the liquefied carbon dioxide storage section 11 may be introduced into the carbon dioxide liquefaction device 32.

[0051] (Action and effect) According to the fourth embodiment, in addition to the effects of the first and second embodiments, the evaporated gas B generated in the cargo tank 51 can be reliquefied by the carbon dioxide liquefaction device 32 of the carbon dioxide capture system 10D. Therefore, it is not necessary to provide a dedicated reliquefaction device for reliquefying the evaporated gas B, and it is possible to suppress an increase in size of the floating body 1. Also, when reliquefying the evaporated gas B, the liquefied flammable gas F can be used as a cold heat source, so that further energy saving can be achieved.

[0052] Furthermore, since the evaporated gas B in the cargo tank 51 and the gaseous carbon dioxide discharged from the carbon dioxide capture device 31 can be mixed and then introduced into the carbon dioxide liquefaction device 32, the discharge temperature at the outlet of the compressor 41 can be adjusted to improve the heat exchange efficiency in the liquefier 42, and the charging efficiency of the compressor 41 can be improved by adjusting the inlet temperature of the compressor 41. Therefore, the liquefaction efficiency of carbon dioxide can be increased.

[0053] Other Embodiments The present disclosure is not limited to the configurations of the above-described embodiments, and design changes are possible without departing from the spirit of the present disclosure. For example, in each of the above-described embodiments, a ship has been described as an example of the floating bodies 1A, 1B, 1C, and 1D, but the floating bodies may also be, for example, floating storage units (FSUs) and floating storage and regasification units (FSRUs).

[0054] In addition, in the above-mentioned fourth embodiment, the case where the inlet detection unit 62 and the outlet detection unit 63 each detect pressure has been described, but the inlet detection unit 62 and the outlet detection unit 63 may be configured to detect only temperature.

[0055] <Additional Notes> The float described in the embodiment can be understood, for example, as follows.

[0056] (1) According to the first aspect, the floating bodies 1A, 1B, 1C, and 1D include a combustion device 9 that operates using liquefied flammable gas F as fuel and discharges exhaust gas E, a liquefied flammable gas storage section 21 that stores the liquefied flammable gas F, a fuel supply line 22 that supplies the liquefied flammable gas F from the liquefied flammable gas storage section 21 to the combustion device 9, a carbon dioxide capture device 31 having an absorption tower 35 that absorbs carbon dioxide contained in the exhaust gas E into an absorption liquid and a regeneration tower 36 that separates gaseous carbon dioxide from the absorption liquid having absorbed the carbon dioxide in the absorption tower 35, a carbon dioxide liquefaction device 32 that liquefies the carbon dioxide discharged from the carbon dioxide capture device 31 using the liquefied flammable gas F supplied from the liquefied flammable gas storage section 21 to the combustion device 9 via the fuel supply line 22 as a cold heat source, and a liquefied carbon dioxide storage section 11 that stores the carbon dioxide liquefied in the carbon dioxide liquefaction device 32. Examples of floating bodies include ships such as liquefied gas carriers, ferries, RORO ships, car carriers, and passenger ships, FSUs (Floating Storage Units), and FSRUs (Floating Storage and Regasification Units). Examples of combustion devices 9 include engines (internal combustion engines) for main engines and generators, and boilers. Examples of liquefied flammable gases F include liquefied natural gas, methane, ethane, and hydrogen.

[0057] This reduces the energy required to separate and liquefy carbon dioxide from exhaust gas E, making it possible to capture carbon dioxide efficiently.

[0058] (2) According to a second aspect, the float is a float as in (1), and is provided with a vaporization device 23 that is provided in the fuel supply line 22 on the combustion device 9 side relative to the carbon dioxide liquefaction device 32 and vaporizes the liquefied combustible gas F used as a cold source in the carbon dioxide liquefaction device 32. This makes it possible to reduce the energy required for vaporizing the liquefied flammable gas F in the vaporizer 23, thereby making it possible to recover carbon dioxide more efficiently.

[0059] (3) According to a third aspect, the float is the float of (2), and the carbon dioxide recovery device 31 further includes an exhaust gas cooling tower 34 that cools the exhaust gas E discharged from the combustion device 9, and the exhaust gas cooling tower 34 cools the exhaust gas E using the liquefied combustible gas F used as a cold source by the carbon dioxide liquefaction device 32 as a cold source, and the vaporization device 23 vaporizes the liquefied combustible gas F used as a cold source by the exhaust gas cooling tower 34. This allows the liquefied flammable gas F, which is the fuel for the combustion device 9, to be heated before being introduced into the vaporization device 23, thereby further reducing the energy required to vaporize the liquefied flammable gas F in the vaporization device 23.

[0060] (4) According to a fourth aspect, the float is any one of the floats (1) to (3) and includes a cargo tank 51 for storing liquefied carbon dioxide as cargo, an evaporative gas introduction line 52 for introducing evaporative gas B generated in the cargo tank 51 into the carbon dioxide liquefaction device 32, and a valve device for switching between the carbon dioxide introduced from the carbon dioxide capture device 31 to the carbon dioxide liquefaction device 32 and the carbon dioxide introduced by the evaporative gas introduction line 52 into the carbon dioxide liquefaction device 32. This eliminates the need to provide a dedicated re-liquefaction device for re-liquefying the evaporated gas B, thereby preventing the floating bodies 1C and 1D from becoming larger.

[0061] (5) According to a fifth aspect, the float is a float as in (4), and is provided with a re-liquefied carbon dioxide discharge line 53 that returns the carbon dioxide introduced into the carbon dioxide liquefaction device 32 via the evaporated gas introduction line 52 and liquefied in the carbon dioxide liquefaction device 32 to the cargo tank 51. This allows, for example, the liquefied carbon dioxide obtained by re-liquefying the evaporated gas B to be returned to the cargo tank 51.

[0062] (6) According to a sixth aspect, the float is any one of the floats (1) to (3) and includes a cargo tank 51 for storing liquefied carbon dioxide as cargo, an evaporative gas introduction line 52 for introducing evaporative gas B generated in the cargo tank 51 into the carbon dioxide liquefaction device 32, and an introduction adjustment unit 61 for adjusting the mixing ratio of the carbon dioxide introduced from the carbon dioxide capture device 31 to the carbon dioxide liquefaction device 32 and the carbon dioxide introduced into the carbon dioxide liquefaction device 32 by the evaporative gas introduction line 52, based on at least the temperature of the carbon dioxide at the inlet of the carbon dioxide liquefaction device 32. This makes it possible to improve the heat exchange efficiency in the carbon dioxide liquefaction device 32.

[0063] (7) According to a seventh aspect, the float is the float of (6) and is provided with a re-liquefied carbon dioxide discharge line 53 that returns the carbon dioxide liquefied in the carbon dioxide liquefaction device 32 to the cargo tank 51. This eliminates the need to provide a dedicated re-liquefaction device for re-liquefying the evaporated gas B, thereby preventing the floating bodies 1C and 1D from becoming larger.

[0064] (8) According to an eighth aspect, a carbon dioxide recovery method is a carbon dioxide recovery method for recovering carbon dioxide from exhaust gas E discharged by burning liquefied flammable gas F, and includes a step S01 of absorbing carbon dioxide contained in the exhaust gas E into an absorption liquid, a step S02 of separating gaseous carbon dioxide from the absorption liquid having absorbed the carbon dioxide, a step S03 of liquefying the gaseous carbon dioxide separated from the absorption liquid using the liquefied flammable gas F as a cold heat source, and a step S04 of storing the liquefied carbon dioxide. [Explanation of symbols]

[0065] 1A, 1B, 1C, 1D... Floating body 2... Floating body main body 2a... Bow 2b... Stern 3A, 3B... Ship side 7... Superstructure 8... Cargo carrying area 9... Combustion device 10A, 10B, 10C, 10D... Carbon dioxide capture system 11... Liquefied carbon dioxide storage section 21... Liquefied flammable gas storage section 22... Fuel supply line 23... Vaporization device 31... Carbon dioxide capture device 32... Carbon dioxide liquefaction device 34, 134... Exhaust gas cooling tower 35... Absorption tower 36... Regeneration tower 37... Gaseous carbon dioxide introduction line 38... Exhaust gas scrubbing tower 41... Compressor 42... Liquefier 43... Liquefied carbon dioxide discharge line 51... Cargo tank 52... Evaporation gas introduction line 53... Re-liquefied carbon dioxide discharge line 54, 55, 56, 57... Valve gear 61... Introduction adjustment section 62...Inlet detector 63...Outlet detector 64...Control valve 152...Evaporative gas introduction line B...Evaporative gas E...Exhaust gas F...Liquefied flammable gas G...Flammable gas

Claims

1. A combustion device that uses flammable gas as fuel and emits exhaust gas; A liquefied flammable gas storage section that stores a liquefied flammable gas, which is the flammable gas in a liquid state; a fuel supply line that supplies the liquefied flammable gas from the liquefied flammable gas storage portion toward the combustion device; a carbon dioxide recovery apparatus including an absorption tower for absorbing carbon dioxide contained in the exhaust gas into an absorption liquid, and a regeneration tower for separating gaseous carbon dioxide from the absorption liquid that has absorbed the carbon dioxide in the absorption tower; a carbon dioxide liquefaction device that liquefies carbon dioxide discharged from the carbon dioxide capture device by using the liquefied flammable gas in a liquid form that is supplied from the liquefied flammable gas storage unit to the combustion device through the fuel supply line as a cold heat source; A liquefied carbon dioxide storage section that stores the carbon dioxide liquefied by the carbon dioxide liquefaction device; a vaporizer that is provided in the fuel supply line on a side closer to the combustion device than the carbon dioxide liquefaction device, and vaporizes the liquefied flammable gas used as a cold source in the carbon dioxide liquefaction device to convert it into a flammable gas; Equipped with The fuel supply line is a float that introduces the flammable gas vaporized by the vaporizer into the combustion device as fuel.

2. The carbon dioxide capture device further includes an exhaust gas cooling tower that cools the exhaust gas discharged from the combustion device, The exhaust gas cooling tower cools the exhaust gas using the liquefied flammable gas used as a cold source by the carbon dioxide liquefaction device as a cold source, The vaporizer vaporizes the liquefied flammable gas used as a cold source by the exhaust gas cooling tower. The floating body according to claim 1.

3. a cargo tank for storing liquefied carbon dioxide as cargo; an evaporation gas introduction line for introducing the evaporation gas generated in the cargo tank into the carbon dioxide liquefaction device; and a valve device for switching between the carbon dioxide introduced from the carbon dioxide capture device to the carbon dioxide liquefaction device and the carbon dioxide introduced into the carbon dioxide liquefaction device through the evaporation gas introduction line.

3. A floating body according to claim 1 or 2.

4. a re-liquefied carbon dioxide discharge line for returning the carbon dioxide introduced into the carbon dioxide liquefaction device through the evaporated gas introduction line and liquefied in the carbon dioxide liquefaction device to the cargo tank; The floating body according to claim 3.

5. a cargo tank for storing liquefied carbon dioxide as cargo; an evaporation gas introduction line for introducing the evaporation gas generated in the cargo tank into the carbon dioxide liquefaction device; an introduction adjustment unit that adjusts a mixing ratio of the carbon dioxide introduced from the carbon dioxide capture device to the carbon dioxide liquefaction device and the carbon dioxide introduced into the carbon dioxide liquefaction device through the evaporation gas introduction line, based on at least the temperature of the carbon dioxide at an inlet of the carbon dioxide liquefaction device; Equipped 3. A floating body according to claim 1 or 2.

6. A re-liquefied carbon dioxide discharge line is provided for returning the carbon dioxide liquefied by the carbon dioxide liquefaction device to the cargo tank. The floating body according to claim 5.

7. A carbon dioxide recovery method for recovering carbon dioxide from exhaust gas discharged by burning a combustible gas, comprising: A step of absorbing carbon dioxide contained in the exhaust gas into an absorption liquid; A step of separating gaseous carbon dioxide from the absorption liquid having absorbed the carbon dioxide; A step of liquefying the gaseous carbon dioxide separated from the absorption liquid by using a liquefied flammable gas, which is the flammable gas in a liquid state, as a cold heat source; storing the liquefied carbon dioxide; A step of vaporizing the liquefied flammable gas used as a cold source for liquefying the carbon dioxide into a flammable gas and then combusting the flammable gas; A method for capturing carbon dioxide, comprising:

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