Carbon dioxide recovery system and carbon dioxide recovery method

Abstract

To provide a carbon dioxide recovery system capable of suppressing an increase in the size of and complication of a facility for recovering carbon dioxide included in object gas.SOLUTION: A carbon dioxide recovery system for recovering carbon dioxide from object gas containing carbon dioxide and nitrogen includes: a first compressor configured to compress the object gas; a first membrane separation device including a separation membrane through which carbon dioxide gas permeates preferentially over nitrogen gas and configured to separate the object gas compressed by the first compressor into nitrogen rich gas and carbon dioxide rich gas through the separation membrane; a first expander configured to expand the nitrogen rich gas discharged from the first membrane separation device; and a liquefier configured to liquefy at least part of the carbon dioxide gas discharged from the first membrane separation device by using cold energy of the nitrogen rich gas expanded by the first expander.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a carbon dioxide recovery system and a carbon dioxide recovery method.

Background Art

[0002] Patent Document 1 describes a method for recovering high-concentration methane by separating biomethane into carbon dioxide and methane using a two-stage membrane separation device and recycling the carbon dioxide-rich gas that has passed through the second-stage membrane separation device to the upstream side of the first-stage membrane separation device. In this method, the carbon dioxide gas separated from the methane separated by the first-stage membrane separation device is compressed by a compressor and liquefied by a cooler for recovery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method described in Patent Document 1, equipment for supplying a cold heat source for liquefying carbon dioxide gas is required, which tends to cause enlargement and complication of the equipment for recovering carbon dioxide contained in the target gas.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a carbon dioxide recovery system and a carbon dioxide recovery method that can suppress enlargement and complication of the equipment for recovering carbon dioxide contained in the target gas.

Means for Solving the Problems

[0006] To achieve the above object, a carbon dioxide recovery system according to at least one embodiment of the present disclosure is A carbon dioxide recovery system for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen, a first compressor configured to compress the target gas, a first membrane separation device including a separation membrane that preferentially permeates carbon dioxide gas over nitrogen gas, and configured to separate the target gas compressed by the first compressor into a nitrogen-rich gas and a carbon dioxide-rich gas by the separation membrane, a first expander configured to expand the nitrogen-rich gas discharged from the first membrane separation device, a liquefier configured to liquefy at least a part of the carbon dioxide gas discharged from the first membrane separation device by the cold thermal energy of the nitrogen-rich gas expanded by the first expander, and comprising.

[0007] To achieve the above object, a carbon dioxide recovery method according to at least one embodiment of the present disclosure is a carbon dioxide recovery method for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen, a compression step of compressing the target gas, a membrane separation step of separating the target gas compressed in the compression step into a carbon dioxide-rich gas and a nitrogen-rich gas by a separation membrane, an expansion step of expanding the nitrogen-rich gas generated in the membrane separation step, a liquefaction step of liquefying the carbon dioxide-rich gas generated in the membrane separation step by the cold thermal energy of the nitrogen-rich gas expanded in the expansion step, and comprising.

Effect of the Invention

[0008] According to at least one embodiment of the present disclosure, there are provided a carbon dioxide recovery system and a carbon dioxide recovery method capable of suppressing the enlargement and complexity of equipment for recovering carbon dioxide contained in a target gas.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

FORM FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, several embodiments of this indication are described with reference to the attached drawings. However, dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the invention thereto, but are merely illustrative examples. For example, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent a state of being relatively displaced with tolerances or at an angle or distance that provides the same function. For example, expressions representing that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent a state in which there are tolerances or differences that provide the same function. For example, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent shapes such as a rectangular shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including uneven portions, chamfered portions, etc. within a range where the same effect can be obtained. On the other hand, the expressions "comprising", "having", "including", "containing", or "possessing" one component are not exclusive expressions that exclude the existence of other components.

[0011] FIG. 1 is a diagram schematically showing a carbon dioxide recovery system 1A according to an embodiment of the present disclosure. The carbon dioxide recovery system 1A is a system that recovers carbon dioxide contained in the exhaust gas discharged from a carbon dioxide emission source 2. Hereinafter, when simply described as "exhaust gas", it means the exhaust gas discharged from the carbon dioxide emission source 2.

[0012] In the exemplary form shown in FIG. 1, the carbon dioxide recovery system 1A includes a carbon dioxide emission source 2, a compressor 4, a cooler 6, a membrane separation device 8, a regenerative heat exchanger 10, an expander 12, a liquefier 14, a compressor 16, a cooler 18, a membrane separation device 20, an expander 22, a compressor 24, a cooler 26, and a storage tank 28.

[0013] The carbon dioxide emission source 2 may be a combustion device such as an engine, for example, and discharges exhaust gas containing carbon dioxide (target gas to be recovered of carbon dioxide). The carbon dioxide emission source 2 and the membrane separation device 8 are connected by an exhaust gas line 30 which is a flow path of the exhaust gas.

[0014] The compressor 4 is provided between the carbon dioxide emission source 2 and the membrane separation device 8 in the exhaust gas line 30, and compresses the exhaust gas discharged from the carbon dioxide emission source 2.

[0015] The cooler 6 is provided between the compressor 4 and the membrane separation device 8 in the exhaust gas line 30, and is configured to cool the exhaust gas compressed by the compressor 4. The cooler 6 may be, for example, a water-cooled heat exchanger that performs heat exchange between the exhaust gas compressed by the compressor 4 and cooling water.

[0016] The membrane separation device 8 includes a separation membrane 13 that preferentially permeates carbon dioxide gas over nitrogen gas, and is configured to separate the exhaust gas compressed by the compressor 4 (the exhaust gas supplied from the exhaust gas line 30) into a nitrogen-rich gas and a carbon dioxide-rich gas by the separation membrane 13. The membrane separation device 8 includes a separation membrane 13 that preferentially permeates carbon dioxide gas over nitrogen gas. The membrane separation device 8 is configured to allow carbon dioxide gas to permeate through the separation membrane 13 by utilizing the differential pressure across the separation membrane 13. A high-pressure nitrogen-rich gas containing nitrogen gas is discharged as the non-permeated gas from the non-permeated side (the high-pressure side of the separation membrane 13) of the separation membrane 13 in the membrane separation device 8, and a low-pressure carbon dioxide-rich gas containing carbon dioxide gas as the main component is discharged as the permeated gas from the permeated side (the low-pressure side of the separation membrane 13) of the separation membrane 13 in the membrane separation device 8. In this specification, for a specific component contained in the gas, the "rich gas" means a gas having a higher concentration of the specific component compared to the exhaust gas supplied from the exhaust gas line 30 to the membrane separation device 8. For example, the nitrogen-rich gas means a gas having a higher concentration of nitrogen gas compared to the exhaust gas supplied from the exhaust gas line 30 to the membrane separation device 8 (a gas containing nitrogen gas at a concentration higher than the concentration of nitrogen gas in the exhaust gas), and the carbon dioxide-rich gas means a gas having a higher concentration of carbon dioxide gas compared to the exhaust gas supplied from the exhaust gas line 30 to the membrane separation device 8 (a gas containing carbon dioxide gas at a concentration higher than the concentration of carbon dioxide gas in the exhaust gas). Further, hereinafter, the non-permeated side of the separation membrane 13 in the membrane separation device 8 (the side of the exhaust gas inlet closer to the separation membrane 13 in the membrane separation device 8) is simply referred to as the "non-permeated side of the membrane separation device 8", and the permeated side of the separation membrane 13 in the membrane separation device 8 (the side of the outlet of the carbon dioxide-rich gas closer to the separation membrane 13 in the membrane separation device 8) is simply referred to as the "permeated side of the membrane separation device 8".

[0017] The non-permeated side of the membrane separation device 8 and the inlet of the expander 12 are connected by a nitrogen first line 32 (first gas line) through which the nitrogen-rich gas flows, and the regenerative heat exchanger 10 is provided at a position between the membrane separation device 8 and the expander 12 in the nitrogen first line 32.

[0018] The regenerative heat exchanger 10 is configured to perform heat exchange between the nitrogen-rich gas flowing through the nitrogen first line 32 and the nitrogen-rich gas flowing through the liquefier downstream line 34 described later. The nitrogen-rich gas flowing through the nitrogen first line 32 is cooled by heat exchange with the nitrogen-rich gas flowing through the liquefier downstream line 34 and then supplied to the expander 12.

[0019] The expander 12 is configured to expand the nitrogen-rich gas supplied from the nitrogen first line 32. In the illustrated configuration, the expander 12 is a turbine (power recovery expander), and the expander 12 and the compressor 4 are connected by a rotating shaft 9. The compressor 4, the rotating shaft 9, and the expander 12 (turbine) constitute a power recovery turbocharger 15 (first turbocharger). The carbon dioxide recovery system 1A also includes an electric motor 11 that drives the rotating shaft 9. The electric motor 11 is adapted to be supplied with current from a power source (such as a generator) not shown, and is driven by the current supplied from the power source to drive the rotating shaft 9, the compressor 4, and the expander 12. In the expander 12, a part of the expansion energy generated when the nitrogen-rich gas expands is recovered, and the compressor 4 is assisted in its driving by the recovered expansion energy.

[0020] The nitrogen-rich gas expanded by the expander 12 is supplied to the liquefier 14 through an expander downstream line 36 (expander downstream first line) connecting the outlet of the expander 12 and the liquefier 14.

[0021] The permeate side of the membrane separation device 8 and the inlet of the membrane separation device 20 are connected by a carbon dioxide first line 38 through which the carbon dioxide-rich gas flows. The carbon dioxide first line 38 is provided with a compressor 16 and a cooler 18 in order from the upstream side in the flow direction of the carbon dioxide-rich gas. The carbon dioxide-rich gas discharged from the permeate side of the membrane separation device 8 is compressed by the compressor 16, cooled by the cooler 18, and then supplied to the membrane separation device 20. Note that the cooler 18 may be a water-cooled heat exchanger that performs heat exchange between the carbon dioxide-rich gas compressed by the compressor 16 and cooling water.

[0022] The membrane separation device 20 includes a separation membrane 40 that preferentially permeates carbon dioxide gas over nitrogen gas, and is configured to separate the carbon dioxide-rich gas compressed by the compressor 16 into a nitrogen-rich gas and a carbon dioxide-rich gas by the separation membrane 40. That is, the membrane separation device 20 is configured to discharge a carbon dioxide-rich gas with a higher purity than the carbon dioxide-rich gas supplied to the membrane separation device 20 from the permeation side of the separation membrane 40. The membrane separation device 20 is configured to permeate carbon dioxide gas through the separation membrane 40 by utilizing the differential pressure across the separation membrane 40. A high-pressure nitrogen-rich gas containing nitrogen gas is discharged as a non-permeating side gas from the non-permeating side (high-pressure side of the separation membrane 40) of the separation membrane 40 in the membrane separation device 20, and a low-pressure carbon dioxide-rich gas containing carbon dioxide gas as a main component is discharged as a permeating side gas from the permeation side (low-pressure side of the separation membrane 40) of the separation membrane 40 in the membrane separation device 20. Hereinafter, the non-permeating side of the separation membrane 40 in the membrane separation device 20 (the inlet side of the exhaust gas relative to the separation membrane 40 in the membrane separation device 20) will be simply referred to as the "non-permeating side of the membrane separation device 20", and the permeation side of the separation membrane 40 in the membrane separation device 20 (the outlet side of the carbon dioxide-rich gas relative to the separation membrane 40 in the membrane separation device 20) will be simply referred to as the "permeation side of the membrane separation device 20".

[0023] The non-permeating side of the membrane separation device 20 and the inlet of the expander 22 are connected by a nitrogen second line 42 (second gas line) through which the nitrogen-rich gas flows, and the regenerative heat exchanger 10 is provided at a position between the membrane separation device 20 and the expander 22 in the nitrogen second line 42.

[0024] The regenerative heat exchanger 10 is configured to perform heat exchange between the nitrogen-rich gas flowing through the nitrogen second line 42 and the nitrogen-rich gas flowing through the downstream line 34 of the liquefier. The nitrogen-rich gas flowing through the nitrogen second line 42 is cooled by heat exchange with the non-permeating side gas flowing through the downstream line 34 of the liquefier and then supplied to the expander 22.

[0025] The expander 22 is configured to expand the nitrogen-rich gas supplied from the nitrogen second line 42. In the illustrated configuration, the expander 22 is a turbine (power recovery expander), and the expander 22 and the compressor 16 are connected by a rotating shaft 19. Further, the carbon dioxide recovery system 1A includes an electric motor 21 that drives the rotating shaft 19. The electric motor 21 is adapted to be supplied with current from a power source (such as a generator) (not shown), and is driven by the current supplied from the power source to drive the rotating shaft 19, the compressor 16, and the expander 22. In the expander 22, a part of the expansion energy generated when the nitrogen-rich gas expands is recovered, and the recovered expansion energy assists in driving the compressor 16.

[0026] One end of a downstream line 46 of the expander (downstream second line of the expander) is connected to the outlet of the expander 22, and the other end of the downstream line 46 of the expander is connected to a position between the expander 12 and the liquefier 14 in the downstream line 36 of the expander. A valve 48 is provided upstream of the connection position of the downstream line 46 of the expander with the downstream line 36 of the expander.

[0027] The nitrogen-rich gas expanded by the expander 22 flows into the downstream line 36 of the expander through the downstream line 46 of the expander, and is supplied to the liquefier 14 through the downstream line 36 of the expander.

[0028] The permeate side of the membrane separation device 20 and the inlet of the liquefier 14 (carbon dioxide gas inlet) are connected by a carbon dioxide second line 50 through which the carbon dioxide-rich gas flows. A compressor 24 and a cooler 26 are provided in the carbon dioxide second line 50 in order from the upstream side in the flow direction of the carbon dioxide-rich gas. The carbon dioxide-rich gas discharged from the permeate side of the membrane separation device 20 is compressed by the compressor 24 driven by the electric motor 25, cooled by the cooler 26, and then supplied to the liquefier 14. Note that the cooler 26 may be a water-cooled heat exchanger that performs heat exchange between the carbon dioxide-rich gas compressed by the compressor 24 and cooling water.

[0029] The liquefier 14 is configured to liquefy at least a part of the carbon dioxide gas discharged from the permeate side of the membrane separation device 8 by the cold thermal energy of the nitrogen-rich gas expanded by the expander 12. In the illustrated exemplary embodiment, the liquefier 14 is configured as a heat exchanger that liquefies the carbon dioxide gas flowing through the carbon dioxide second line 50 by heat exchange between the nitrogen-rich gas flowing through the expander downstream line 36 and the carbon dioxide-rich gas flowing through the carbon dioxide second line 50. The carbon dioxide liquefied by the liquefier 14 is supplied to the storage tank 28 through the liquid line 59 and stored in the storage tank 28.

[0030] According to the carbon dioxide recovery system 1B, at least a part of the carbon dioxide gas discharged from the membrane separation device 8 can be liquefied by the liquefier 14 using the cold thermal energy of the nitrogen-rich gas expanded by the expander 12. Therefore, there is no need to separately provide equipment for supplying a cold heat source for liquefying the carbon dioxide gas, and it is possible to suppress the enlargement and complexity of the equipment for recovering the carbon dioxide contained in the exhaust gas of the carbon dioxide emission source 2.

[0031] FIG. 2 is a diagram schematically showing a carbon dioxide recovery system 1B according to an embodiment of the present disclosure. In each configuration of the carbon dioxide recovery system 1B shown in FIG. 2, the same reference numerals as those of each configuration of the above-described carbon dioxide recovery system 1A indicate the same configurations as those of each configuration of the carbon dioxide recovery system 1A shown in FIG. 1 unless otherwise specified, and the description thereof is omitted.

[0032] As shown in FIG. 2, the carbon dioxide recovery system 1B is different from the carbon dioxide recovery system 1A in that it includes an adsorption tower 60 (adsorption device) instead of the membrane separation device 20. Further, the carbon dioxide recovery system 1B is different from the carbon dioxide recovery system 1A in that it does not include the compressor 16, the electric motor 21, and the expander 22, and includes a dehumidification tower 62 (dehumidification device) and a regeneration heat exchanger 92.

[0033] As shown in FIG. 2, in the carbon dioxide recovery system 1B, the permeate side of the membrane separation device 8 and the liquefier 14 are connected by a carbon dioxide line 66 through which a carbon dioxide-rich gas flows. The carbon dioxide line 66 is provided with a dehumidifying tower 62, an adsorption tower 60, a vacuum pump 68, a cooler 70, a compressor 72, and a cooler 84 in order from the upstream side in the flow direction of the carbon dioxide-rich gas.

[0034] The dehumidifying tower 62 contains a dehumidifying material 86 (such as alumina, silica gel, zeolite, or MOF) that adsorbs moisture inside the dehumidifying tower 62. The dehumidifying tower 62 is configured to adsorb and remove the moisture contained in the carbon dioxide-rich gas discharged from the permeate side of the membrane separation device 8 by the dehumidifying material 86. The carbon dioxide-rich gas from which moisture has been removed in the dehumidifying tower 62 is supplied to the adsorption tower 60.

[0035] The adsorption tower 60 contains an adsorbent 88 for adsorbing carbon dioxide gas inside the adsorption tower 60. The adsorption tower 60 is configured to adsorb the carbon dioxide contained in the carbon dioxide-rich gas (the carbon dioxide-rich gas from which moisture has been removed in the dehumidifying tower 62) discharged from the permeate side of the membrane separation device 8 by the adsorbent 88. The adsorbent 88 adsorbs the carbon dioxide contained in the carbon dioxide-rich gas flowing through the carbon dioxide line 66 by at least one of pressure swing adsorption (PSA) and temperature swing adsorption (TSA), and separates the adsorbed carbon dioxide. In pressure swing adsorption, a pressure difference is used as a means for separating carbon dioxide from the exhaust gas. That is, in pressure swing adsorption, the pressure of the atmosphere of the adsorbent 88 is reduced to a second predetermined pressure that is lower than the first predetermined pressure at which carbon dioxide is adsorbed by the adsorbent 88, so as to separate the carbon dioxide gas from the adsorbent 88. In temperature swing adsorption (TSA), a temperature difference is used as a means for separating carbon dioxide from the exhaust gas. That is, in temperature swing adsorption (TSA), the adsorbent 88 that has adsorbed carbon dioxide is heated to a second predetermined temperature that is higher than the first predetermined temperature at which carbon dioxide is adsorbed by the adsorbent 88, so as to separate the carbon dioxide gas from the adsorbent.

[0036] Examples of the adsorbent 88 include solid adsorbents such as zeolite. Note that the adsorbent only needs to be a solid capable of adsorbing carbon dioxide and is not limited to zeolite. The adsorbent may be, for example, a metal-organic framework (MOF) or the like.

[0037] The vacuum pump 68 is configured to reduce the pressure of the atmosphere of the adsorbent 88 in the adsorption tower 60 and discharge the carbon dioxide-rich gas containing carbon dioxide separated from the adsorbent 88 from the adsorption tower 60. The carbon dioxide-rich gas discharged from the adsorption tower 60 is supplied to the cooler 70 through the vacuum pump 68, cooled by the cooler 70, compressed by the compressor 72, and further cooled by the cooler 84 before being supplied to the liquefier 14. Note that each of the cooler 70 and the cooler 84 may be a water-cooled heat exchanger that performs heat exchange between the carbon dioxide-rich gas flowing through the carbon dioxide line 66 and the cooling water. In the illustrated exemplary embodiment, an electric motor 69 is connected to the vacuum pump 68, and the vacuum pump 68 is driven by the electric motor 69. Also, an electric motor 73 is connected to the compressor 72, and the compressor 72 is driven by the electric motor 73.

[0038] The liquefier 14 is configured to liquefy at least a part of the carbon dioxide gas discharged from the permeate side of the membrane separation device 8 by the cold heat energy of the nitrogen-rich gas expanded by the expander 12. In the illustrated exemplary embodiment, the liquefier 14 is configured as a heat exchanger that liquefies the carbon dioxide gas flowing through the carbon dioxide line 66 by heat exchange between the nitrogen-rich gas flowing through the line 36 on the downstream side of the expander and the carbon dioxide-rich gas flowing through the downstream side of the cooler 84 in the carbon dioxide line 66. The carbon dioxide liquefied by the liquefier 14 is supplied to the storage tank 28 through the liquid line 59 and stored in the storage tank 28.

[0039] The carbon dioxide recovery system 1B further includes a regenerative heat exchanger 92 and a post-heating line 95. The regenerative heat exchanger 92 is provided downstream of the regenerative heat exchanger 10 in the liquefier downstream line 34, and is configured to heat the nitrogen-rich gas flowing through the liquefier downstream line 34 with the thermal energy of the exhaust gas compressed by the compressor 4. The regenerative heat exchanger 92 is configured to perform heat exchange between the nitrogen-rich gas flowing downstream of the regenerative heat exchanger 10 in the liquefier downstream line 34 and the exhaust gas flowing between the compressor 4 and the cooler 6 in the exhaust gas line 30.

[0040] The post-heating line 95 connects the outlet of the nitrogen-rich gas in the regenerative heat exchanger 92 and the dehumidifying tower 62. The post-heating line 95 is configured to dry the dehumidifying material 86 of the dehumidifying tower 62 with the nitrogen-rich gas by supplying the nitrogen-rich gas heated by the regenerative heat exchanger 92 to the dehumidifying tower 62.

[0041] According to the configuration shown in FIG. 2, the moisture contained in the nitrogen-rich gas expanded by the expander 12 is removed by passing through the liquefier 14, the regenerative heat exchanger 10, and the regenerative heat exchanger 92. Therefore, a dry nitrogen-rich gas can be supplied from the post-heating line 95 to the dehumidifying tower 62. As a result, the dry nitrogen-rich gas supplied from the post-heating line 95 can be used for drying (regenerating) the dehumidifying material 86. Thus, there is no need to separately prepare a drying gas for drying the dehumidifying material, and the energy required for drying the dehumidifying material 86 can be reduced.

[0042] FIG. 3 is a diagram schematically showing a carbon dioxide recovery system 1C according to an embodiment of the present disclosure. In each configuration of the carbon dioxide recovery system 1C shown in FIG. 3, components having the same reference numerals as those in the above-described carbon dioxide recovery system 1B represent the same configurations as those in the carbon dioxide recovery system 1B unless otherwise specified, and the description thereof will be omitted.

[0043] As shown in FIG. 3, the carbon dioxide recovery system 1C is different from the carbon dioxide recovery system 1B in that it includes a heater 90. The heater 90 is provided in the adsorption tower 60 and functions as a separator that heats the adsorbent 88 to separate carbon dioxide gas from the adsorbent 88. The adsorbent 88 is adapted to adsorb carbon dioxide contained in the carbon dioxide-rich gas flowing through the carbon dioxide line 66 by the above-described temperature swing adsorption and pressure swing adsorption, and to separate the adsorbed carbon dioxide.

[0044] The heater 90 may be configured to separate the carbon dioxide adsorbed on the adsorbent 88 by heating the adsorbent 88 using waste heat (for example, a heat medium at about 50°C to 90°C) from the carbon dioxide emission source 2 or equipment associated with the carbon dioxide emission source 2. Since the adsorbent has the property that carbon dioxide is more easily separated as the temperature rises, compared with the case where the heater 90 is not used, the degree of vacuum of the suction pressure of the vacuum pump 68 required to separate a sufficient amount of carbon dioxide from the adsorbent 88 can be lowered, so that the power of the vacuum pump 68 is reduced, and the running cost of the carbon dioxide recovery system can be reduced.

[0045] FIG. 4 is a diagram schematically showing a carbon dioxide recovery system 1D according to an embodiment of the present disclosure. In each configuration of the carbon dioxide recovery system 1D shown in FIG. 4, components having the same reference numerals as those of the carbon dioxide recovery system 1C described above represent the same configurations as those of the carbon dioxide recovery system 1C unless otherwise specified, and the description thereof is omitted.

[0046] As shown in FIG. 4, the carbon dioxide recovery system 1D includes an engine 91, an intake line 93, an air cooler 94, an exhaust gas line 30, an engine-attached turbocharger 96, a surplus exhaust gas line 97, an exhaust heat recovery steam boiler 98, and a surplus exhaust gas power recovery turbocharger 131.

[0047] In the embodiment shown in FIG. 4, the engine 91 constitutes the carbon dioxide emission source 2. The intake line 93 is configured to supply air compressed by the compressor 99 of the turbocharger 96 attached to the engine to the engine 91. The air cooler 94 is provided in the intake line 93 and is configured to cool the air supplied to the engine 91. In the exhaust gas line 30, in order from the upstream side in the flow direction of the exhaust gas, a turbine 100 of the turbocharger 96 attached to the engine, a waste heat recovery steam boiler 98, a compressor 4 of the power recovery turbocharger 15, a regenerative heat exchanger 92, a cooler 6, and a membrane separation device 8 are provided. That is, the exhaust gas line 30 is configured to supply the exhaust gas of the engine 91 to the membrane separation device 8 via the turbine 100 of the turbocharger 96 attached to the engine, the waste heat recovery steam boiler 98, the compressor 4, the regenerative heat exchanger 92, and the cooler 6.

[0048] The surplus exhaust gas line 97 branches from upstream of the turbine 100 in the exhaust gas line 30 to bypass the turbine 100 and is connected to the downstream side of the turbine 100 in the exhaust gas line 30. That is, the surplus exhaust gas line 97 supplies the exhaust gas of the engine 91 to the downstream side of the turbine 100 by bypassing the turbine 100 of the turbocharger 96 attached to the engine. A bypass valve 101 is provided in the surplus exhaust gas line 97. A turbine 140 of the surplus exhaust gas power recovery turbocharger 131 is provided on the downstream side of the bypass valve 101 in the surplus exhaust gas line 97, and the exhaust gas of the engine 91 passing through the surplus exhaust gas line 97 is supplied to the waste heat recovery steam boiler 98 after driving the turbine 140. The exhaust gas of the engine 91 passing through the turbine 100 or the surplus exhaust gas line 97 is supplied to the waste heat recovery steam boiler 98, and the waste heat recovery steam boiler 98 heats water to generate steam.

[0049] The carbon dioxide recovery system 1 shown in FIG. 4 is provided with a bypass line 143. One end of the bypass line 143 is connected to a position between the exhaust heat recovery steam boiler 98 and the compressor 4 in the exhaust gas line 30, and the other end of the bypass line 143 is connected to a position between the compressor 4 and the regenerative heat exchanger 92 in the exhaust gas line 30. A compressor 141 of the surplus exhaust gas power recovery turbocharger 131 is provided in the bypass line 143, and the exhaust gas of the engine 91 that has exited the exhaust heat recovery steam boiler 98 is supplied to the regenerative heat exchanger 92 through the compressor 4 of the exhaust gas line 30 or the compressor 141 of the bypass line 143.

[0050] According to the configuration shown in FIG. 4, the power required for pressurizing the exhaust gas to ensure the differential pressure before and after the separation membrane 13 in the membrane separation device 8 can be supplemented with the power recovered by the surplus exhaust gas power recovery turbocharger 131, and the running cost of the carbon dioxide recovery system 1D can be reduced. Also, for example, when the surplus exhaust gas power recovery turbocharger 131 is connected to the vacuum pump 68, the power for driving the vacuum pump 68 can be supplemented with the power recovered from the surplus exhaust gas power recovery turbocharger 131, and the running cost of the carbon dioxide recovery system 1D can be reduced. Further, for example, when the surplus exhaust gas power recovery turbocharger 131 is connected to the compressor 72, the power for driving the compressor 72 can be supplemented with the power recovered from the surplus exhaust gas power recovery turbocharger 131, and the running cost of the carbon dioxide recovery system 1D can be reduced.

[0051] FIG. 5 is a diagram schematically showing a carbon dioxide recovery system 1E according to an embodiment of the present disclosure. In each configuration of the carbon dioxide recovery system 1E shown in FIG. 4, components having the same reference numerals as those of the carbon dioxide recovery system 1D described above represent the same configurations as those of the carbon dioxide recovery system 1D unless otherwise specified, and the description thereof is omitted.

[0052] As shown in FIG. 5, the carbon dioxide recovery system 1E further includes a bypass line 110 configured to supply a part of the carbon dioxide-rich gas discharged from the permeate side of the separation membrane 13 in the membrane separation device 8 to the inlet portion 4a of the compressor 4 of the power recovery turbocharger 15. In the illustrated exemplary embodiment, one end of the bypass line 110 is connected to a position between the exhaust heat recovery steam boiler 98 and the compressor 4 in the exhaust gas line 30, and the other end of the bypass line 110 is connected to a position between the membrane separation device 8 and the dehumidifying tower 62 in the carbon dioxide first line 38. The bypass line 110 is provided with a valve 112 capable of adjusting the flow rate of the carbon dioxide-rich gas flowing through the bypass line 110.

[0053] In a configuration including the engine 91 and the engine-attached turbocharger 96, due to the change in air density (the air density of the intake air of the engine 91) caused by seasonal variations, surplus exhaust gas (exhaust gas flowing through the surplus exhaust gas line 97) that bypasses the turbine 100 of the engine-attached turbocharger 96 is likely to be generated, especially in winter. For this reason, the flow rate of the exhaust gas passing through the compressor 4 downstream of the exhaust heat recovery steam boiler 98 is likely to be less in winter than in summer.

[0054] Since the compressor 4 is designed to conform to the maximum flow rate in summer, the compressor 4 operates at a partial load in winter, and there is a risk that the operating point deviates from the design point and the efficiency decreases.

[0055] Therefore, by providing the bypass line 110, it becomes possible to supply a part of the carbon dioxide-rich gas discharged from the permeate side of the membrane separation device 8 to the inlet portion 4a of the compressor 4 of the power recovery turbocharger 15 during periods such as winter when the flow rate of the compressor 4 is likely to decrease. Thus, the flow rate of the compressor 4 can be stabilized and a decrease in the efficiency of the compressor 4 can be suppressed.

[0056] Further, by refluxing the carbon dioxide-rich gas with a high carbon dioxide concentration to the upstream side of the membrane separation device 8 through the bypass line 110, the carbon dioxide concentration of the carbon dioxide-rich gas discharged from the permeate side of the membrane separation device 8 can be further increased, the load on the adsorption tower 60 can be reduced, and the running cost of the carbon dioxide recovery system 1E can be reduced.

[0057] In some embodiments, for example, in the carbon dioxide recovery system 1E shown in FIG. 5, each of the coolers 6, 70, 84, 94 may be a water-cooled heat exchanger configured to cool the heat medium by heat exchange with cooling water. Here, the heat medium is the exhaust gas of the engine 91 in the case of the cooler 6, the carbon dioxide-rich gas in the case of the cooler 70, the carbon dioxide-rich gas in the case of the cooler 84, and the intake air of the engine 91 in the case of the cooler 94. Further, the carbon dioxide recovery system 1E may include a used cooling water line 114 configured to supply the cooling water after being used for cooling the heat medium by any of the coolers 6, 70, 84, 94 as the water-cooled heat exchanger to the heater 90. In this case, the heater 90 may be configured to heat the adsorbent 88 using the used cooling water (the cooling water after being used for heating the heat medium by any of the coolers 6, 70, 84, 94) supplied from the used cooling water line 114. For example, when the adsorbent 88 is zeolite, the outlet temperature of the cooling water of the cooler connected to the used cooling water line 114 among the coolers 6, 70, 84, 94 may be about 80°C (for example, 50°C to 90°C). Thereby, compared with the case of separately providing a heating source (such as a boiler) for heating the adsorbent, the equipment of the carbon dioxide recovery system 1E can be simplified, and an increase in equipment cost can be suppressed.

[0058] The present disclosure is not limited to the above-described embodiments, and also includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms. For example, in the above-described embodiments, the case where each of the expanders 12 and 22 is a turbine is exemplified, but one or both of the expanders 12 and 22 may be an expansion valve or the like.

[0059] The content described in each of the above embodiments is understood as follows, for example.

[0060] 1) A carbon dioxide recovery system according to at least one embodiment of the present disclosure is a carbon dioxide recovery system (1A to 1E) for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen, a first compressor (4, 16) configured to compress the target gas, including a separation membrane (13, 40) that preferentially permeates carbon dioxide gas over nitrogen gas, and configured to separate the target gas compressed by the first compressor into a nitrogen-rich gas and a carbon dioxide-rich gas by the separation membrane; a first membrane separation device (8, 20), a first expander (12, 22) configured to expand the nitrogen-rich gas discharged from the first membrane separation device, a liquefier (14) configured to liquefy at least a part of the carbon dioxide gas discharged from the first membrane separation device by the cold and heat energy of the nitrogen-rich gas expanded by the first expander, and is provided with.

[0061] According to the carbon dioxide recovery system described in 1) above, at least a part of the carbon dioxide gas discharged from the first membrane separation device can be liquefied using the cold and heat energy of the nitrogen-rich gas expanded by the first expander. Therefore, it is not necessary to separately provide equipment for supplying a cold heat source for liquefying the carbon dioxide gas, and it is possible to suppress the enlargement and complexity of the equipment for recovering carbon dioxide contained in the target gas.

[0062] 2) In some embodiments, in the carbon dioxide recovery system described in 1) above, the first expander is a turbine (12, 22), the carbon dioxide recovery system further includes a rotating shaft (9, 19) connecting the first compressor and the turbine, and a motor (11, 21) configured to drive the rotating shaft.

[0063] According to the carbon dioxide recovery system described in 2) above, at least a part of the carbon dioxide gas discharged from the first membrane separation device can be liquefied using the cold and heat energy of the nitrogen-rich gas expanded by the turbine. Therefore, it is not necessary to separately provide equipment for supplying a cold heat source for liquefying the carbon dioxide gas, and it is possible to suppress the enlargement and complication of the equipment for recovering carbon dioxide contained in the target gas. In addition, the energy recovered by the turbine can be used to increase the discharge pressure of the target gas in the first compressor, and the differential pressure before and after the separation membrane in the first membrane separation device can be ensured. Therefore, the enlargement and complication of the equipment for recovering carbon dioxide contained in the target gas can be effectively suppressed. Further, since the discharge pressure of the first compressor can be adjusted by adjusting the output of the motor, the recovery amount of carbon dioxide can be adjusted according to the flow rate of the target gas.

[0064] 3) In some embodiments, in the carbon dioxide recovery system described in 1) or 2) above, a first gas line (32, 42) configured to supply the nitrogen-rich gas discharged from the first membrane separation device to the first expander; a liquefier downstream line (34) through which the nitrogen-rich gas flowing out of the liquefier flows; a heat exchanger (10) configured to perform heat exchange between the nitrogen-rich gas flowing between the first membrane separation device and the first expander in the first gas line and the nitrogen-rich gas flowing through the liquefier downstream line; is further provided.

[0065] According to the carbon dioxide recovery system described in 3) above, by performing heat exchange between the nitrogen-rich gas flowing between the first membrane separation device and the first expander in the first gas line and the nitrogen-rich gas flowing through the liquefier downstream line, the nitrogen-rich gas flowing through the first gas line can be cooled by the cold and heat energy of the nitrogen-rich gas flowing through the liquefier downstream line before expansion by the first expander. Therefore, the enlargement and complication of the equipment for recovering carbon dioxide contained in the target gas can be effectively suppressed.

[0066] 4) In some embodiments, in the carbon dioxide recovery system according to any one of 1) to 3) above, a second compressor (16) configured to compress the carbon dioxide-rich gas discharged from the first membrane separation device (8); a second membrane separation device (20) including a separation membrane (40) that preferentially permeates carbon dioxide gas over nitrogen gas, and configured to separate the carbon dioxide-rich gas compressed by the second compressor into a nitrogen-rich gas and a carbon dioxide gas by the separation membrane; a second expander (22) configured to expand the nitrogen-rich gas discharged from the second membrane separation device; and the liquefier is configured to liquefy at least a part of the carbon dioxide gas discharged from the second membrane separation device by the cold thermal energy of the nitrogen-rich gas expanded by the first expander and the cold thermal energy of the nitrogen-rich gas expanded by the second expander.

[0067] According to the carbon dioxide recovery system described in 4) above, high-purity carbon dioxide gas can be obtained from the adsorption device by adsorbing the carbon dioxide gas separated (extracted) from the target gas by the first membrane separation device onto the adsorbent of the adsorption device and separating it from the adsorbent. Further, the cold thermal energy of the nitrogen-rich gas expanded by the first expander can be used to liquefy the carbon dioxide gas separated from the adsorbent, and it is possible to suppress the enlargement and complexity of the equipment for recovering carbon dioxide contained in the target gas.

[0068] 5) In some embodiments, in the carbon dioxide recovery system according to any one of 1) to 4) above, an adsorption device (60) configured to adsorb carbon dioxide contained in the carbon dioxide-rich gas discharged from the first membrane separation device onto an adsorbent (88); the liquefier is configured to liquefy the carbon dioxide gas separated from the adsorbent by the cold thermal energy of the nitrogen-rich gas expanded by the first expander.

[0069] According to the carbon dioxide recovery system described in 5) above, by adsorbing the carbon dioxide gas separated and extracted from the target gas by the first membrane separation device onto the adsorbent of the adsorption device and separating it from the adsorbent, high-purity carbon dioxide gas can be obtained from the adsorption device. In addition, the carbon dioxide gas separated from the adsorbent can be liquefied by the cold heat energy of the nitrogen-rich gas expanded by the first expander, and it is possible to suppress the enlargement and complication of the equipment for recovering carbon dioxide contained in the target gas.

[0070] 6) In some embodiments, in the carbon dioxide recovery system described in any of 3) above, a dehumidifying device (62) configured to adsorb moisture contained in the carbon dioxide-rich gas discharged from the first membrane separation device onto a dehumidifying material (86); a heater (92) provided downstream of the heat exchanger in the downstream line of the liquefier and configured to heat the nitrogen-rich gas flowing through the downstream line of the liquefier with the heat energy of the target gas compressed by the first compressor; a post-heating gas line (95) configured to supply the nitrogen-rich gas heated by the heater to the dehumidifying device to dry the dehumidifying material of the dehumidifying device; and further comprising.

[0071] According to the carbon dioxide recovery system described in 6) above, since the moisture contained in the nitrogen-rich gas expanded by the first expander is removed by passing through the heat exchanger, a dry nitrogen-rich gas can be supplied from the post-heating line to the dehumidifying device. As a result, the dry nitrogen-rich gas supplied from the post-heating line can be used for drying (regenerating) the dehumidifying material, so there is no need to separately prepare a drying gas for drying the dehumidifying material, and the energy required for drying the dehumidifying material can be reduced.

[0072] 7) In some embodiments, in the carbon dioxide recovery system described in 5) above, a carbon dioxide gas line (66) for supplying the carbon dioxide gas separated from the adsorbent of the adsorption device to the liquefier; a vacuum pump (68) provided in the carbon dioxide gas line; a heater configured to heat the adsorbent using waste heat from an exhaust source (2, 91) that discharges the target gas or equipment (96, 98, 131, 15) associated with the exhaust source.

[0073] According to the carbon dioxide recovery system described in 7) above, by heating the adsorbent with a heater using waste heat from a carbon dioxide emission source or equipment associated with the carbon dioxide emission source, carbon dioxide adsorbed on the adsorbent can be separated from the adsorbent. Since the adsorbent has the property that carbon dioxide is more easily separated as the temperature rises, compared to the case where a heater is not used, the degree of vacuum of the suction pressure of the vacuum pump required to separate a sufficient amount of carbon dioxide from the adsorbent can be lowered, so the power of the vacuum pump is reduced, and the running cost of the carbon dioxide recovery system can be reduced.

[0074] 8) In some embodiments, in the carbon dioxide recovery system according to any one of 1) to 7) above, an engine (91); an engine - attached turbocharger (96) configured to be driven by the exhaust gas of the engine to compress the intake air of the engine, the carbon dioxide recovery system includes a first turbocharger (15) that compresses the exhaust gas discharged from a turbine (100) of the engine - attached turbocharger; an excess exhaust gas line (97) that bypasses the turbine of the engine - attached turbocharger and supplies the exhaust gas of the engine to the downstream side of the turbine; a second turbocharger (131) including a turbine (140) provided in the excess exhaust gas line and a compressor (4) that compresses the exhaust gas discharged from the turbine (100) of the engine - attached turbocharger; and is provided with The first compressor is the compressor (4) of the first turbocharger, and the first expander is the turbine (12) of the first turbocharger.

[0075] According to the carbon dioxide recovery system described in the above (8), in order to ensure the differential pressure across the separation membrane in the first membrane separation device, the power required for pressurizing the exhaust gas can be supplemented with the power recovered by the second turbocharger, and the running cost of the carbon dioxide recovery system can be reduced. Further, for example, when connecting the surplus exhaust gas power recovery turbocharger to the vacuum pump described in the above (7), the power for driving the vacuum pump can be supplemented with the power recovered from the surplus exhaust gas power recovery turbocharger, and the running cost of the carbon dioxide recovery system can be reduced.

[0076] 9) In some embodiments, in the carbon dioxide recovery system described in the above (8), It further includes a bypass line (110) configured to supply the carbon dioxide-rich gas discharged from the first membrane separation device to the inlet portion (4a) of the compressor of the first turbocharger.

[0077] In the carbon dioxide recovery system including the engine and the engine-attached turbocharger described in the above (8), due to the change in air density caused by seasonal variations, particularly in winter, a large amount of surplus exhaust gas (exhaust gas flowing through the surplus exhaust gas line) that bypasses the turbine of the engine-attached turbocharger is likely to be generated. For this reason, the flow rate of the exhaust gas passing through the compressor (the first compressor) of the first turbocharger is likely to be less in winter than in summer. Since the first compressor is designed to match the maximum flow rate in summer, without particular measures, the first compressor is likely to operate at a partial load in winter, and there is a risk that the operating point deviates from the design point and the efficiency decreases. Therefore, by providing the bypass line described in the above (9), during periods such as winter when the flow rate of the first compressor is likely to decrease, a part of the carbon dioxide-rich gas discharged from the permeate side of the separation membrane in the first membrane separation device can be supplied to the inlet portion of the first compressor, so that the flow rate of the first compressor can be stabilized and a decrease in the efficiency of the first compressor can be suppressed.

[0078] Further, by refluxing the carbon dioxide-rich gas with a high carbon dioxide concentration to the upstream side of the first membrane separation device through a bypass line, the carbon dioxide concentration of the carbon dioxide-rich gas discharged from the permeate side of the separation membrane in the first membrane separation device can be further increased, the load on the adsorption device can be reduced, and the running cost of the carbon dioxide recovery system can be reduced.

[0079] 10) In some embodiments, in the carbon dioxide recovery system according to any one of the above 1) to 9), an adsorption device (60) configured to adsorb carbon dioxide contained in the carbon dioxide-rich gas discharged from the first membrane separation device to an adsorbent (88); a water-cooled heat exchanger (6, 70, 84, 94) configured to cool a heat medium by heat exchange with cooling water; a used cooling water line (114) configured to supply the cooling water after being used for cooling at least a part of the target gas in the water-cooled heat exchanger to the adsorption device; a heater (90) configured to heat the adsorbent using the used cooling water supplied from the used cooling water line; and is provided with.

[0080] According to the carbon dioxide recovery system described in the above 10), since the adsorbent can be heated using the used cooling water supplied from the used cooling water line, compared with the case of separately providing a heating source (such as a boiler, etc.) for heating the adsorbent, the equipment of the carbon dioxide recovery system can be simplified, and an increase in equipment costs can be suppressed.

[0081] 11) The carbon dioxide recovery system method according to at least one embodiment of the present disclosure is a carbon dioxide recovery method for recovering carbon dioxide contained in a target gas, a compression step of compressing the target gas; A membrane separation step of separating the target gas compressed in the compression step into a carbon dioxide-rich gas and a nitrogen-rich gas by a separation membrane (13, 40); An expansion step of expanding the nitrogen-rich gas generated in the membrane separation step; A liquefaction step of liquefying the carbon dioxide-rich gas generated in the membrane separation step by the cold thermal energy of the nitrogen-rich gas expanded in the expansion step; and is provided with.

[0082] According to the carbon dioxide recovery method described in the above 11), at least a part of the carbon dioxide gas separated in the membrane separation step can be liquefied using the cold thermal energy of the nitrogen-rich gas expanded in the expansion step. Therefore, it is not necessary to separately provide equipment for supplying a cold heat source for liquefying the carbon dioxide gas, and it is possible to suppress the enlargement and complexity of the equipment for recovering carbon dioxide contained in the target gas.

Explanation of symbols

[0083] 1A, 1B, 1C, 1D, 1E Carbon dioxide recovery system 2 Carbon dioxide emission source 4, 16, 24, 72, 99, 141 Compressor 4a Inlet part 6, 18, 26, 70, 84 Cooler 8, 20 Membrane separation device 9, 19 Rotating shaft 10, 92 Regenerative heat exchanger 11, 21, 25, 69, 73 Electric motor 12, 22 Expander 13, 40 Separation membrane 14 Liquefier 15 Power recovery turbocharger 28 Storage tank 30 Exhaust gas line 32 Nitrogen first line 38 Carbon dioxide first line 34 Liquefier downstream line 36, 46 Expander downstream line 42 Nitrogen second line 50 Carbon dioxide second line 48,112 Valve 59 Liquid line 60 Adsorption tower 62 Dehumidification tower 64 Heat exchanger 66 Carbon dioxide line 68 Vacuum pump 86 Dehumidifying material 88 Adsorbent 90 Heater 91 Engine 93 Intake line 94 Air cooler 95 Post - heating line 96 Engine - attached turbocharger 97 Excess exhaust gas line 98 Exhaust heat recovery steam boiler 100,140 Turbine 101 Bypass valve 110,143 Bypass line 131 Excess exhaust gas power recovery turbocharger

Claims

1. A carbon dioxide recovery system for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen, a first compressor configured to compress the target gas, a first membrane separation device including a separation membrane that preferentially permeates carbon dioxide gas over nitrogen gas, and configured to separate the target gas compressed by the first compressor into a nitrogen-rich gas and a carbon dioxide-rich gas by the separation membrane, a first expander configured to expand the nitrogen-rich gas discharged from the first membrane separation device, a liquefier configured to liquefy at least a part of the carbon dioxide gas discharged from the first membrane separation device by the cold and heat energy of the nitrogen-rich gas expanded by the first expander, A carbon dioxide recovery system comprising.

2. The first expander is a turbine, The carbon dioxide recovery system further includes a rotating shaft connecting the first compressor and the turbine, and a motor configured to drive the rotating shaft. The carbon dioxide recovery system according to claim 1.

3. A first gas line configured to supply the nitrogen-rich gas discharged from the first membrane separation device to the first expander, A liquefier downstream line through which the nitrogen-rich gas exiting the liquefier flows, A heat exchanger configured to perform heat exchange between the nitrogen-rich gas flowing between the first membrane separation device and the first expander in the first gas line and the nitrogen-rich gas flowing through the liquefier downstream line, The carbon dioxide recovery system according to claim 1, further comprising.

4. A second compressor configured to compress the carbon dioxide-rich gas discharged from the first membrane separation device, A second membrane separation device including a separation membrane that preferentially permeates carbon dioxide gas over nitrogen gas, and configured to separate the carbon dioxide-rich gas compressed by the second compressor into a nitrogen-rich gas and a carbon dioxide gas by the separation membrane, A second expander configured to expand the nitrogen-rich gas discharged from the second membrane separation device, Comprising, The liquefier is configured to liquefy at least a part of the carbon dioxide gas discharged from the second membrane separation device by the cold and heat energy of the nitrogen-rich gas expanded by the first expander and the cold and heat energy of the nitrogen-rich gas expanded by the second expander. The carbon dioxide recovery system according to claim 1.

5. An adsorption device configured to adsorb carbon dioxide contained in the carbon dioxide-rich gas discharged from the first membrane separation device to an adsorbent is provided. The liquefier is configured to liquefy the carbon dioxide gas separated from the adsorbent by the cold heat energy of the nitrogen-rich gas expanded by the first expander. The carbon dioxide recovery system according to claim 1.

6. A dehumidification device configured to adsorb moisture contained in the carbon dioxide-rich gas discharged from the first membrane separation device to a dehumidifying material; A heater provided downstream of the heat exchanger in the downstream line of the liquefier and configured to heat the nitrogen-rich gas flowing through the downstream line of the liquefier with the heat energy of the target gas compressed by the first compressor; A post-heating gas line configured to supply the nitrogen-rich gas heated by the heater to the dehumidification device to dry the dehumidifying material of the dehumidification device; The carbon dioxide recovery system according to claim 3, further comprising:

7. A carbon dioxide gas line configured to supply the carbon dioxide gas separated from the adsorbent of the adsorption device to the liquefier; A vacuum pump provided in the carbon dioxide gas line; A heater configured to heat the adsorbent using waste heat from an exhaust source that discharges the target gas or equipment associated with the exhaust source. The carbon dioxide recovery system according to claim 5.

8. An engine; An engine-attached turbocharger configured to be driven by the exhaust gas of the engine to compress the intake air of the engine. The carbon dioxide recovery system includes: A first turbocharger configured to compress the exhaust gas discharged from the turbine of the engine-attached turbocharger; An excess exhaust gas line configured to supply the exhaust gas of the engine around the turbine of the engine-attached turbocharger and to the downstream side of the turbine; A second turbocharger including a turbine provided in the excess exhaust gas line and a compressor configured to compress the exhaust gas discharged from the turbine of the engine-attached turbocharger; The carbon dioxide recovery system according to claim 1, wherein the first compressor is the compressor of the first turbocharger and the first expander is the turbine of the first turbocharger.

9. ​ The carbon dioxide recovery system according to claim 8, further comprising a bypass line configured to supply the carbon dioxide-rich gas discharged from the first membrane separation device to an inlet portion of the compressor of the first turbocharger.

10. An adsorption device configured to adsorb carbon dioxide contained in the carbon dioxide-rich gas discharged from the first membrane separation device to an adsorbent; A water-cooled heat exchanger configured to cool a heat medium flowing in the carbon dioxide recovery system by heat exchange with cooling water; A used cooling water line configured to supply the cooling water after being used for cooling at least a part of the target gas in the water-cooled heat exchanger to the adsorption device; A heater configured to heat the adsorbent using the used cooling water supplied from the used cooling water line; The carbon dioxide recovery system according to claim 1, comprising:

11. A carbon dioxide recovery method for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen, comprising: A compression step of compressing the target gas; A membrane separation step of separating the target gas compressed in the compression step into a carbon dioxide-rich gas and a nitrogen-rich gas by a separation membrane; An expansion step of expanding the nitrogen-rich gas generated in the membrane separation step; A liquefaction step of liquefying the carbon dioxide-rich gas generated in the membrane separation step by the cold heat energy of the nitrogen-rich gas expanded in the expansion step; The carbon dioxide recovery method, comprising:

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