Carbon dioxide recovery system and carbon dioxide recovery method

Abstract

A carbon dioxide recovery system for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen includes: a first compressor configured to compress the target gas; a first membrane separation device including a separation membrane through which carbon dioxide gas preferentially permeates before nitrogen gas, configured to separate the target gas compressed by the first compressor into a nitrogen-rich gas and a carbon dioxide-rich gas using the separation membrane; a first expander configured to expand the nitrogen-rich gas discharged from the first membrane separation device; and a liquefaction unit configured to liquefy at least a portion of the carbon dioxide gas discharged from the first membrane separation device using the cold energy of the nitrogen-rich gas expanded by the first expander.

Description

Technical Field

[0001] This disclosure relates to carbon dioxide recovery systems and methods.

[0002] This application claims priority based on Japanese Patent Application No. 2023-196440 filed with the Japan Patent Office on November 20, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] Patent Document 1 describes a method for separating biomethane into carbon dioxide and methane using a two-stage membrane separation device. The carbon dioxide-rich gas that has passed through the second-stage membrane separation device is then recirculated upstream of the first-stage membrane separation device, thereby recovering a high concentration of methane. In this method, the carbon dioxide gas separated from the methane separated by the first-stage membrane separation device is compressed by a compressor, liquefied in a cooler, and recovered.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-95727 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The method described in Patent Document 1 requires equipment for supplying a cold or heat source to liquefy carbon dioxide gas, which easily leads to the large size and complexity of the equipment used to recover carbon dioxide contained in the target gas.

[0009] In view of the above, the object of at least one embodiment of this disclosure is to provide a carbon dioxide recovery system and method capable of suppressing the large-scale and complexization of the equipment used for recovering carbon dioxide contained in the target gas.

[0010] Methods for solving problems

[0011] To achieve the above objectives, at least one embodiment of the present disclosure provides a carbon dioxide recovery system for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen. The carbon dioxide recovery system comprises: a first compressor configured to compress the target gas; a first membrane separation device including a separation membrane that allows carbon dioxide gas to permeate preferentially over nitrogen gas, configured to separate the target gas compressed by the first compressor into a nitrogen-rich gas and a carbon dioxide-rich gas using 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 a portion of the carbon dioxide gas discharged from the first membrane separation device using the cold energy of the nitrogen-rich gas expanded by the first expander.

[0012] To achieve the above objectives, at least one embodiment of the present disclosure provides a carbon dioxide recovery method for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen. The carbon dioxide recovery method comprises: a compression step for compressing the target gas; a membrane separation step for separating the compressed target gas into a carbon dioxide-rich gas and a nitrogen-rich gas using a separation membrane; an expansion step for expanding the nitrogen-rich gas generated in the membrane separation step; and a liquefaction step for liquefying the carbon dioxide-rich gas generated in the membrane separation step using the cold energy of the expanded nitrogen-rich gas.

[0013] Invention Effects

[0014] According to at least one embodiment of the present disclosure, a carbon dioxide recovery system and method are provided that can suppress the large-scale and complex equipment used for recovering carbon dioxide contained in the target gas. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating a carbon dioxide recovery system 1A according to one embodiment of the present disclosure.

[0016] Figure 2 This is a schematic diagram illustrating a carbon dioxide recovery system 1B according to one embodiment of the present disclosure.

[0017] Figure 3 This is a schematic diagram illustrating a carbon dioxide recovery system 1C according to one embodiment of the present disclosure.

[0018] Figure 4 This is a schematic diagram illustrating a carbon dioxide recovery system 1D according to one embodiment of the present disclosure.

[0019] Figure 5 This is a schematic diagram illustrating a carbon dioxide recovery system 1E according to one embodiment of the present disclosure. Detailed Implementation

[0020] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the constituent components described as embodiments or shown in the drawings are not intended to limit the scope of the invention, but are merely illustrative examples.

[0021] For example, expressions such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" indicate a relative or absolute configuration, which not only strictly indicate such a configuration, but also indicate a state of relative displacement by angle or distance with tolerance or to the extent that the same function can be obtained.

[0022] For example, terms like "same," "equal," and "uniform" indicate that things are equal, not only that they are strictly equal, but also that there is a difference in degree or tolerance that allows them to achieve the same function.

[0023] For example, the representation of shapes such as quadrilaterals and cylinders not only represents shapes in the strict geometric sense, but also includes shapes with concave and convex parts, chamfers, etc., within the range where the same effect can be achieved.

[0024] On the other hand, expressions such as "including," "possessing," "having," "comprise," or "having" a constituent element are not exclusive expressions that exclude the existence of other constituent elements.

[0025] Figure 1 This is a schematic diagram illustrating a carbon dioxide recovery system 1A according to one embodiment of the present disclosure. The carbon dioxide recovery system 1A is a system for recovering carbon dioxide contained in exhaust gas discharged from carbon dioxide emission source 2. Hereinafter, when referred to only as "exhaust gas," it refers to exhaust gas discharged from carbon dioxide emission source 2.

[0026] exist Figure 1 In the exemplary embodiment shown, the carbon dioxide recovery system 1A includes a carbon dioxide discharge source 2, a compressor 4, a cooler 6, a membrane separator 8, a regenerative heat exchanger 10, an expander 12, a liquefier 14, a compressor 16, a cooler 18, a membrane separator 20, an expander 22, a compressor 24, a cooler 26, and a storage tank 28.

[0027] The carbon dioxide emission source 2 can be, for example, a combustion device such as an engine, which discharges exhaust gas containing carbon dioxide (the target gas for carbon dioxide recovery). The carbon dioxide emission source 2 is connected to the membrane separation device 8 by an exhaust pipe 30, which serves as the exhaust flow path.

[0028] The compressor 4 is located between the carbon dioxide discharge source 2 and the membrane separation device 8 in the exhaust pipeline 30 to compress the exhaust gas discharged from the carbon dioxide discharge source 2.

[0029] A cooler 6 is disposed between the compressor 4 and the membrane separator 8 in the exhaust line 30, and is configured to cool the exhaust gas compressed by the compressor 4. The cooler 6 may also be a water-cooled heat exchanger that performs heat exchange between the exhaust gas compressed by the compressor 4 and cooling water.

[0030] The membrane separation device 8 includes a separation membrane 13 that allows carbon dioxide gas to pass through preferentially than nitrogen gas. It is configured to separate exhaust gas (supply from exhaust line 30) compressed by the compressor 4 into nitrogen-rich gas and carbon dioxide-rich gas using the separation membrane 13. The membrane separation device 8 is configured to utilize the pressure difference across the separation membrane 13 to allow carbon dioxide gas to pass through it. High-pressure nitrogen-rich gas containing nitrogen is discharged from the non-permeable side (high-pressure side of the separation membrane 13) of the membrane separation device 8 as the non-permeable side gas, while low-pressure carbon dioxide-rich gas containing carbon dioxide gas as the main component is discharged from the permeable side (low-pressure side of the separation membrane 13) of the membrane separation device 8 as the permeable side gas. It should be noted that, in this specification, regarding a specific component contained in a gas, "rich gas" refers to a gas with a higher concentration of that specific component compared to the exhaust gas supplied from the exhaust line 30 to the membrane separation device 8. For example, nitrogen-rich gas refers to a gas with a higher concentration of nitrogen compared to the exhaust gas supplied from the exhaust line 30 to the membrane separation device 8 (including gas with a nitrogen concentration higher than that in the exhaust gas), and carbon dioxide-rich gas refers to a gas with a higher concentration of carbon dioxide compared to the exhaust gas supplied from the exhaust line 30 to the membrane separation device 8 (including gas with a carbon dioxide concentration higher than that in the exhaust gas). Furthermore, hereinafter, the non-permeable side of the separation membrane 13 in the membrane separation device 8 (the inlet side of the membrane separation device 8 that is closer to the exhaust gas than the separation membrane 13) will be abbreviated as "non-permeable side of the membrane separation device 8," and the permeable side of the separation membrane 13 in the membrane separation device 8 (the outlet side of the membrane separation device 8 that is closer to the carbon dioxide-rich gas than the separation membrane 13) will be abbreviated as "permeable side of the membrane separation device 8."

[0031] The non-permeable side of the membrane separation device 8 is connected to the inlet of the expander 12 by a nitrogen first pipeline 32 (first gas pipeline) with nitrogen-rich gas flow. The regeneration heat exchanger 10 is located in the nitrogen first pipeline 32 between the membrane separation device 8 and the expander 12.

[0032] The regenerative heat exchanger 10 is configured to perform heat exchange between nitrogen-rich gas flowing in the first nitrogen line 32 and nitrogen-rich gas flowing in the downstream line 34 of the liquefier (described later). The nitrogen-rich gas flowing in the first nitrogen line 32 is cooled by the heat exchange with the nitrogen-rich gas flowing in the downstream line 34 of the liquefier and then supplied to the expander 12.

[0033] Expander 12 is configured to expand nitrogen-rich gas supplied from nitrogen first line 32. In the illustrated structure, expander 12 is a turbine (power recovery expander), and expander 12 and compressor 4 are connected by rotating shaft 9. Compressor 4, rotating shaft 9, and expander 12 (turbine) constitute power recovery turbocharger 15 (first turbocharger). Additionally, carbon dioxide recovery system 1A includes an electric motor 11 that drives rotating shaft 9. Electric motor 11 is supplied with current from a power source (generator, etc.) not shown, and is driven by the current supplied from the power source to drive rotating shaft 9, compressor 4, and expander 12. In expander 12, a portion of the expansion energy generated during the expansion of nitrogen-rich gas is recovered, and this recovered expansion energy is used to assist in driving compressor 4.

[0034] The nitrogen-rich gas expanded by the expander 12 is supplied to the liquefier 14 through the expander downstream pipeline 36 (the first pipeline downstream of the expander) which connects the outlet of the expander 12 to the liquefier 14.

[0035] The permeate side of membrane separator 8 is connected to the inlet of membrane separator 20 via a first carbon dioxide pipeline 38 for supplying carbon dioxide-rich gas. In the first carbon dioxide pipeline 38, a compressor 16 and a cooler 18 are sequentially arranged 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 membrane separator 8 is compressed in the compressor 16, cooled in the cooler 18, and then supplied to membrane separator 20. Alternatively, the cooler 18 can be a water-cooled heat exchanger that performs heat exchange between the carbon dioxide-rich gas compressed by the compressor 16 and cooling water.

[0036] The membrane separation device 20 includes a separation membrane 40 that allows carbon dioxide gas to pass through preferentially than nitrogen gas. It is configured to separate carbon dioxide-rich gas, compressed by the compressor 16, into nitrogen-rich gas and carbon dioxide-rich gas using the separation membrane 40. Specifically, the membrane separation device 20 is configured to discharge carbon dioxide-rich gas with a purity higher than that supplied to the membrane separation device 20 from the permeate side of the separation membrane 40. The membrane separation device 20 is also configured to allow carbon dioxide gas to pass through the separation membrane 40 using the pressure difference across it. High-pressure nitrogen-rich gas containing nitrogen is discharged from the non-permeate side (high-pressure side of the separation membrane 40) as the non-permeate side gas, while low-pressure carbon dioxide-rich gas containing carbon dioxide gas as the main component is discharged from the permeate side (low-pressure side of the separation membrane 40) as the permeate side gas. It should be noted that, in the following, the non-permeable side of the separation membrane 40 in the membrane separation device 20 (the inlet side of the membrane separation device 20 that is closer to the exhaust gas than the separation membrane 40) will be referred to as the "non-permeable side of the membrane separation device 20", and the permeable side of the separation membrane 40 in the membrane separation device 20 (the outlet side of the membrane separation device 20 that is closer to the carbon dioxide-rich gas than the separation membrane 40) will be referred to as the "permeable side of the membrane separation device 20".

[0037] The non-permeable side of the membrane separation device 20 is connected to the inlet of the expander 22 by a nitrogen second pipeline 42 (second gas pipeline) with nitrogen-rich gas flow. The regeneration heat exchanger 10 is located in the nitrogen second pipeline 42 between the membrane separation device 20 and the expander 22.

[0038] The regenerative heat exchanger 10 is configured to exchange heat between nitrogen-rich gas flowing in the nitrogen second line 42 and nitrogen-rich gas flowing in the downstream line 34 of the liquefier. The nitrogen-rich gas flowing in the nitrogen second line 42 is cooled by heat exchange with the non-permeable side gas flowing in the downstream line 34 of the liquefier and then supplied to the expander 22.

[0039] Expander 22 is configured to expand nitrogen-rich gas supplied from nitrogen second line 42. In the illustrated structure, expander 22 is a turbine (power recovery expander), and expander 22 and compressor 16 are connected by rotating shaft 19. Additionally, carbon dioxide recovery system 1A includes an electric motor 21 that drives rotating shaft 19. Electric motor 21 is supplied with current from a power source (generator, etc., not shown), and is driven by the current supplied from the power source to drive rotating shaft 19, compressor 16, and expander 22. In expander 22, a portion of the expansion energy generated during the expansion of nitrogen-rich gas is recovered, and this recovered expansion energy is used to assist in driving compressor 16.

[0040] One end of the downstream pipeline 46 (the second downstream pipeline of the expander) is connected to the outlet of the expander 22, and the other end of the downstream pipeline 46 is connected to the position between the expander 12 and the liquefier 14 in the downstream pipeline 36. A valve 48 is installed upstream of the connection position between the downstream pipeline 46 and the downstream pipeline 36.

[0041] The nitrogen-rich gas expanded by the expander 22 flows into the downstream pipeline 36 of the expander through the downstream pipeline 46 of the expander, and is supplied to the liquefier 14 through the downstream pipeline 36 of the expander.

[0042] The permeate side of the membrane separator 20 is connected to the inlet (carbon dioxide gas inlet) of the liquefier 14 by a second carbon dioxide pipeline 50 for supplying carbon dioxide-rich gas. In the second carbon dioxide pipeline 50, a compressor 24 and a cooler 26 are sequentially arranged 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 separator 20 is compressed by the compressor 24 driven by the electric motor 25, cooled in the cooler 26, and then supplied to the liquefier 14. Alternatively, the cooler 26 can be a water-cooled heat exchanger that performs heat exchange between the carbon dioxide-rich gas compressed by the compressor 24 and cooling water.

[0043] The liquefier 14 is configured to liquefy at least a portion of the carbon dioxide gas discharged from the permeate side of the membrane separation unit 8 using the cold 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 in the second carbon dioxide line 50 by heat exchange between the nitrogen-rich gas flowing in the downstream line 36 of the expander and the carbon dioxide-rich gas flowing in the second carbon dioxide line 50. The carbon dioxide liquefied in the liquefier 14 is supplied to the storage tank 28 via the liquid line 59 and stored in the storage tank 28.

[0044] According to the carbon dioxide recovery system 1B described above, at least a portion of the carbon dioxide gas discharged from the membrane separation unit 8 can be liquefied in the liquefier 14 using the cold energy of the nitrogen-rich gas expanded by the expander 12. Therefore, it is not necessary to install additional equipment for supplying cold and heat sources for liquefying carbon dioxide gas, and it is possible to suppress the large-scale and complex nature of equipment for recovering carbon dioxide contained in the exhaust gas of the carbon dioxide discharge source 2.

[0045] Figure 2 This is a schematic diagram illustrating a carbon dioxide recovery system 1B according to one embodiment of the present disclosure. Figure 2 Unless otherwise specified, the reference numerals common to the components of the carbon dioxide recovery system 1B shown in the figure are used in conjunction with those of the components of the carbon dioxide recovery system 1A described above. Figure 1The components of the carbon dioxide recovery system 1A shown are identical, so descriptions are omitted.

[0046] like Figure 2 As shown, the difference between carbon dioxide recovery system 1B and carbon dioxide recovery system 1A is that carbon dioxide recovery system 1B has an adsorption tower 60 (adsorption device) instead of the membrane separation device 20. In addition, the difference between carbon dioxide recovery system 1B and carbon dioxide recovery system 1A is that carbon dioxide recovery system 1B does not have the compressor 16, motor 21 and expander 22, but has a dehumidification tower 62 (dehumidification device) and regeneration heat exchanger 92.

[0047] like Figure 2 As shown, in the carbon dioxide recovery system 1B, the permeate side of the membrane separation device 8 is connected to the liquefier 14 by a carbon dioxide pipeline 66 supplying carbon dioxide-rich gas. On the carbon dioxide pipeline 66, a dehumidification tower 62, an adsorption tower 60, a vacuum pump 68, a cooler 70, a compressor 72, and a cooler 84 are sequentially arranged from the upstream side in the direction of carbon dioxide-rich gas flow.

[0048] The dehumidification tower 62 contains a dehumidifying material 86 (e.g., alumina, silica gel, zeolite, or MOF) that adsorbs moisture. The dehumidification tower 62 is configured to remove moisture contained in the carbon dioxide-rich gas discharged from the permeate side of the membrane separation unit 8 by the adsorption material 86. The carbon dioxide-rich gas, from which moisture has been removed in the dehumidification tower 62, is then supplied to the adsorption tower 60.

[0049] The adsorption tower 60 contains adsorbent material 88 for adsorbing carbon dioxide gas. The adsorption tower 60 is configured such that the adsorbent material 88 adsorbs carbon dioxide contained in carbon dioxide-rich gas (carbon dioxide-rich gas from which moisture has been removed in the dehumidification tower 62) discharged from the permeate side of the membrane separation unit 8. The adsorbent material 88 adsorbs carbon dioxide contained in the carbon dioxide-rich gas flowing in 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 the separation means for separating carbon dioxide from the exhaust gas. That is, in pressure swing adsorption, the pressure of the atmosphere surrounding the adsorbent material 88 is reduced to a second predetermined pressure lower than a first predetermined pressure at which carbon dioxide is adsorbed onto the adsorbent material 88, thereby separating the carbon dioxide gas from the adsorbent material 88. In temperature swing adsorption (TSA), a temperature difference is used as the separation means for separating carbon dioxide from the exhaust gas. That is, in temperature-switched adsorption (TSA), carbon dioxide gas is separated from the adsorbent by heating the adsorbent material 88, which has adsorbed carbon dioxide, to a second predetermined temperature that is higher than the first predetermined temperature at which carbon dioxide is adsorbed on the adsorbent material 88.

[0050] Examples of adsorbent materials 88 include solid adsorbent materials such as zeolites. Furthermore, any solid material capable of adsorbing carbon dioxide is acceptable, and it is not limited to zeolites. Examples of adsorbent materials include metal-organic frameworks (MOFs).

[0051] Vacuum pump 68 is configured to reduce the pressure of the atmosphere in the adsorbent material 88 within adsorption tower 60, and to discharge carbon dioxide-rich gas containing carbon dioxide separated from the adsorbent material 88 from adsorption tower 60. The carbon dioxide-rich gas discharged from adsorption tower 60 is supplied to cooler 70 via vacuum pump 68, cooled in cooler 70, compressed in compressor 72, and then cooled in cooler 84 before being supplied to liquefier 14. Alternatively, cooler 70 and cooler 84 can be water-cooled heat exchangers, respectively, for heat exchange between the carbon dioxide-rich gas flowing in carbon dioxide line 66 and cooling water. In the illustrated embodiment, vacuum pump 68 is connected to motor 69, which drives vacuum pump 68. Additionally, motor 73 is connected to compressor 72, which drives compressor 72.

[0052] The liquefier 14 is configured to liquefy at least a portion of the carbon dioxide gas discharged from the permeate side of the membrane separator 8 by utilizing the cold energy of the nitrogen-rich gas expanded by the expander 12. In the illustrated embodiment, the liquefier 14 is configured as a heat exchanger that liquefies the carbon dioxide gas flowing in the carbon dioxide line 66 by heat exchange between the nitrogen-rich gas flowing in the downstream line 36 of the expander and the carbon dioxide-rich gas flowing downstream of the cooler 84 in the carbon dioxide line 66. The carbon dioxide liquefied in the liquefier 14 is supplied to the storage tank 28 via the liquid line 59 and stored in the storage tank 28.

[0053] Additionally, the carbon dioxide recovery system 1B includes a regenerative heat exchanger 92 and a heated pipeline 95. The regenerative heat exchanger 92 is located downstream of the regenerative heat exchanger 10 in the downstream pipeline 34 of the liquefier, and is configured to use the heat energy of the exhaust gas compressed by the compressor 4 to heat the nitrogen-rich gas flowing in the downstream pipeline 34 of the liquefier. 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 downstream pipeline 34 of the liquefier and the exhaust gas flowing between the compressor 4 and the cooler 6 in the exhaust pipeline 30.

[0054] After heating, pipeline 95 connects the outlet of the nitrogen-rich gas in the regenerating heat exchanger 92 to the dehumidification tower 62. The heating pipeline 95 is configured to supply the nitrogen-rich gas heated by the regenerating heat exchanger 92 to the dehumidification tower 62, thereby drying the dehumidifying material 86 in the dehumidification tower 62.

[0055] according to Figure 2 In the structure shown, the moisture contained in the nitrogen-rich gas expanded by the expander 12 is removed by the liquefaction unit 14, the regeneration heat exchanger 10, and the regeneration heat exchanger 92, thus allowing the dried nitrogen-rich gas to be supplied to the dehumidification tower 62 from the heated pipeline 95. Therefore, the dried nitrogen-rich gas supplied from the heated pipeline 95 can be used for the drying (regeneration) of the dehumidifying material 86, eliminating the need for separate preparation of drying gas and reducing the energy required for drying the dehumidifying material 86.

[0056] Figure 3 This is a schematic diagram illustrating a carbon dioxide recovery system 1C according to one embodiment of the present disclosure. Figure 3 In the various components of the carbon dioxide recovery system 1C shown, unless otherwise specified, the reference numerals that are common to the various components of the carbon dioxide recovery system 1B described above indicate the same components as those of the carbon dioxide recovery system 1B, and the description is omitted.

[0057] like Figure 3 As shown, the carbon dioxide recovery system 1C differs from the carbon dioxide recovery system 1B in that it includes a heater 90. The heater 90 is located in the adsorption tower 60 and functions as a separator that heats the adsorbent material 88 and separates carbon dioxide gas from it. The adsorbent material 88 adsorbs carbon dioxide contained in the carbon dioxide-rich gas flowing in the carbon dioxide pipeline 66 through the aforementioned temperature swing adsorption and pressure swing adsorption, and separates the adsorbed carbon dioxide.

[0058] The heater 90 can also be configured to heat the adsorbent material 88 using exhaust heat (e.g., a heat medium at approximately 50°C to 90°C) from the carbon dioxide exhaust source 2 or an auxiliary device of the carbon dioxide exhaust source 2, thereby separating the carbon dioxide adsorbed on the adsorbent material 88. Since the adsorbent material has the characteristic that carbon dioxide is easily separated as the temperature rises, compared to the case without the heater 90, the vacuum level of the suction pressure of the vacuum pump 68 required to separate a sufficient amount of carbon dioxide from the adsorbent material 88 can be reduced. Therefore, the power of the vacuum pump 68 is reduced, and the operating cost of the carbon dioxide recovery system can be lowered.

[0059] Figure 4 This is a schematic diagram illustrating a carbon dioxide recovery system 1D according to one embodiment of the present disclosure. Figure 4 In the various components of the carbon dioxide recovery system 1D shown, unless otherwise specified, the reference numerals that are common to the various components of the carbon dioxide recovery system 1C described above indicate the same components as those of the carbon dioxide recovery system 1C, and the description is omitted.

[0060] like Figure 4As shown, the carbon dioxide recovery system 1D includes an engine 91, an intake line 93, an air cooler 94, an exhaust line 30, an engine-attached turbocharger 96, a residual exhaust line 97, a waste heat recovery steam boiler 98, and a residual exhaust power recovery turbocharger 131.

[0061] exist Figure 4 In the illustrated embodiment, engine 91 constitutes carbon dioxide emission source 2. Intake line 93 is configured to supply air compressed by compressor 99 of engine-attached turbocharger 96 to engine 91. Air cooler 94 is provided on intake line 93 to cool the air supplied to engine 91. On exhaust line 30, starting from the upstream side in the exhaust flow direction, are sequentially arranged turbine 100 of engine-attached turbocharger 96, exhaust heat recovery steam boiler 98, compressor 4 of power recovery turbocharger 15, regenerative heat exchanger 92, cooler 6, and membrane separator 8. That is, exhaust line 30 is configured to supply exhaust from engine 91 to membrane separator 8 via turbine 100 of engine-attached turbocharger 96, exhaust heat recovery steam boiler 98, compressor 4, regenerative heat exchanger 92, and cooler 6.

[0062] The residual exhaust line 97 is configured to branch off upstream of the turbine 100 in the exhaust line 30, bypass the turbine 100, and connect to the downstream side of the turbine 100 in the exhaust line 30. That is, the residual exhaust line 97 supplies exhaust from the engine 91 to the downstream side of the turbine 100, bypassing the turbine 100 of the engine-attached turbocharger 96. A bypass valve 101 is provided in the residual exhaust line 97. Downstream of the bypass valve 101 in the residual exhaust line 97, the turbine 140 of the residual exhaust power recovery turbocharger 131 is provided, and the exhaust from the engine 91 passing through the residual exhaust line 97 is supplied to the exhaust heat recovery steam boiler 98 after driving the turbine 140. The exhaust from the engine 91 passing through the turbine 100 or the residual exhaust line 97 is supplied to the exhaust heat recovery steam boiler 98, where water is heated to generate steam.

[0063] Figure 4 The carbon dioxide recovery system 1 shown includes a bypass line 143. One end of the bypass line 143 is connected between the exhaust heat recovery steam boiler 98 and the compressor 4 in the exhaust line 30, and the other end of the bypass line 143 is connected between the compressor 4 and the regenerative heat exchanger 92 in the exhaust line 30. A compressor 141 of a residual exhaust power recovery turbocharger 131 is installed in the bypass line 143, and exhaust gas from the engine 91 discharged from the exhaust heat recovery steam boiler 98 is supplied to the regenerative heat exchanger 92 through the compressor 4 in the exhaust line 30 or the compressor 141 in the bypass line 143.

[0064] according to Figure 4 The structure shown allows the power recovered by the residual exhaust power recovery turbocharger 131 to supplement the power required to pressurize the exhaust gas to ensure the differential pressure across the separation membrane 13 in the membrane separation device 8, thereby reducing the operating cost of the carbon dioxide recovery system 1D. Furthermore, for example, when the residual exhaust power recovery turbocharger 131 is connected to the vacuum pump 68, the power recovered from the residual exhaust power recovery turbocharger 131 can supplement the power used to drive the vacuum pump 68, further reducing the operating cost of the carbon dioxide recovery system 1D. Additionally, for example, when the residual exhaust power recovery turbocharger 131 is connected to the compressor 72, the power recovered from the residual exhaust power recovery turbocharger 131 can supplement the power used to drive the compressor 72, further reducing the operating cost of the carbon dioxide recovery system 1D.

[0065] Figure 5 This is a schematic diagram illustrating a carbon dioxide recovery system 1E according to one embodiment of the present disclosure. Figure 4 In the various components of the carbon dioxide recovery system 1E shown, unless otherwise specified, the reference numerals that are common to the various components of the carbon dioxide recovery system 1D described above indicate the same components as those of the carbon dioxide recovery system 1D, and the description is omitted.

[0066] like Figure 5 As shown, the carbon dioxide recovery system 1E also includes a bypass line 110, which is configured to supply a portion of the carbon dioxide-rich gas discharged from the permeate side of the separation membrane 13 in the membrane separator 8 to the inlet 4a of the compressor 4 of the power recovery turbocharger 15. In the illustrated embodiment, one end of the bypass line 110 is connected between the exhaust heat recovery steam boiler 98 in the exhaust line 30 and the compressor 4, and the other end of the bypass line 110 is connected between the membrane separator 8 in the first carbon dioxide line 38 and the dehumidification tower 62. A valve 112 is provided in the bypass line 110 to regulate the flow rate of the carbon dioxide-rich gas flowing in the bypass line 110.

[0067] In the structure including engine 91 and engine-attached turbocharger 96, due to seasonal variations in air density (air density of the intake air of engine 91), especially in winter, a large amount of residual exhaust gas (exhaust gas flowing in residual exhaust line 97) tends to bypass the turbine 100 of engine-attached turbocharger 96. Therefore, the exhaust gas flow rate of compressor 4 downstream of heat recovery steam boiler 98 tends to be less in winter than in summer.

[0068] Because compressor 4 is designed to operate at maximum flow rate in summer, it may operate at partial load in winter, potentially causing the operating point to deviate from the design point and resulting in decreased efficiency.

[0069] Therefore, by providing the bypass line 110, during periods such as winter when the flow rate of the compressor 4 tends to decrease, a portion of the carbon dioxide-rich gas discharged from the permeate side of the membrane separator 8 can be supplied to the inlet 4a of the compressor 4 of the power recovery turbocharger 15, thereby stabilizing the flow rate of the compressor 4 and suppressing the reduction in the efficiency of the compressor 4.

[0070] In addition, by using the bypass line 110 to return the carbon dioxide-rich gas with a high carbon dioxide concentration to the upstream side of the membrane separation unit 8, the carbon dioxide concentration of the carbon dioxide-rich gas discharged from the permeate side of the membrane separation unit 8 can be further increased, thereby reducing the load on the adsorption tower 60 and reducing the operating cost of the carbon dioxide recovery system 1E.

[0071] In several implementations, for example in Figure 5 In the carbon dioxide recovery system 1E shown, coolers 6, 70, 84, and 94 can each be configured as water-cooled heat exchangers that cool the heat medium through heat exchange with cooling water. Here, the heat medium is the exhaust gas of engine 91 in the case of cooler 6, carbon dioxide-rich gas in the case of cooler 70, carbon dioxide-rich gas in the case of cooler 84, and intake air of engine 91 in the case of cooler 94. In addition, the carbon dioxide recovery system 1E may include a used cooling water line 114, which is configured to supply cooling water that has been used to cool the heat medium in any of the coolers 6, 70, 84, and 94, which are water-cooled heat exchangers, to heater 90. In this case, heater 90 may be configured to heat adsorbent material 88 using the used cooling water (cooling water used to heat the heat medium in any of the coolers 6, 70, 84, and 94) supplied from the used cooling water line 114. For example, when the adsorbent 88 is zeolite, the outlet temperature of the cooling water in the coolers 6, 70, 84, and 94, which are connected to the cooling water pipeline 114 after use, can also be around 80°C (e.g., 50°C to 90°C). Therefore, compared to the case where a separate heating source (e.g., a boiler) is set up to heat the adsorbent, the equipment of the carbon dioxide recovery system 1E can be simplified, and the increase in equipment costs can be suppressed.

[0072] This disclosure is not limited to the embodiments described above, but also includes modifications to the embodiments described above, and appropriate combinations of these embodiments. For example, in the embodiments described above, the expander 12 and expander 22 are both turbines, but one or both of expander 12 and expander 22 may also be an expansion valve, etc.

[0073] The contents described in the above embodiments are as follows.

[0074] 1) A carbon dioxide recovery system according to at least one embodiment of the present disclosure is used to recover carbon dioxide from a target gas containing carbon dioxide and nitrogen. The carbon dioxide recovery system (1A-1E) includes: a first compressor (4, 16) configured to compress the target gas; a first membrane separation device (8, 20) including a separation membrane (13, 40) through which carbon dioxide gas preferentially permeates before nitrogen gas, configured to separate the target gas compressed by the first compressor into a nitrogen-rich gas and a carbon dioxide-rich gas using the separation membrane; a first expander (12, 22) configured to expand the nitrogen-rich gas discharged from the first membrane separation device; and a liquefaction device (14) configured to liquefy at least a portion of the carbon dioxide gas discharged from the first membrane separation device using the cold energy of the nitrogen-rich gas expanded by the first expander.

[0075] According to the carbon dioxide recovery system described in 1) above, at least a portion of the carbon dioxide gas discharged from the first membrane separation device can be liquefied by utilizing the cold energy of the nitrogen-rich gas expanded by the first expander. Therefore, it is not necessary to set up additional equipment for supplying cold and heat sources for liquefying carbon dioxide gas, and it can suppress the large-scale and complex nature of equipment for recovering carbon dioxide contained in the target gas.

[0076] 2) In several embodiments, in the carbon dioxide recovery system described in 1) above, the first expander is a turbine (12, 22), and the carbon dioxide recovery system further includes: a rotating shaft (9, 19) connecting the first compressor to the turbine; and an electric motor (11, 21) configured to drive the rotating shaft.

[0077] According to the carbon dioxide recovery system described in 2) above, at least a portion of the carbon dioxide gas discharged from the first membrane separation unit can be liquefied using the cold energy of the nitrogen-rich gas after turbine expansion. Therefore, it eliminates the need for additional equipment to supply a heat source or cold source for liquefying the carbon dioxide gas, thus preventing the equipment for recovering carbon dioxide contained in the target gas from becoming too large and complex. Furthermore, the energy recovered by the turbine can be used to increase the ejection pressure of the target gas in the first compressor, ensuring the differential pressure across the separation membrane in the first membrane separation unit. This effectively prevents the equipment for recovering carbon dioxide contained in the target gas from becoming too large and complex. Moreover, the ejection pressure of the first compressor can be adjusted by adjusting the output of the electric motor, thus allowing the amount of carbon dioxide recovered to be adjusted according to the flow rate of the target gas.

[0078] 3) In several embodiments, the carbon dioxide recovery system described in 1) or 2) above further includes: 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 downstream pipeline (34) for the flow of the nitrogen-rich gas from the liquefier; and 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 in the downstream pipeline of the liquefier.

[0079] According to the carbon dioxide recovery system described in 3) above, by exchanging heat between the nitrogen-rich gas flowing between the first membrane separator and the first expander in the first gas pipeline and the nitrogen-rich gas flowing in the downstream pipeline of the liquefier, the cooling energy of the nitrogen-rich gas flowing in the downstream pipeline of the liquefier before expansion by the first expander can be used to cool the nitrogen-rich gas flowing in the first gas pipeline. Therefore, it is possible to effectively suppress the large-scale and complex nature of equipment used to recover carbon dioxide contained in the target gas.

[0080] 4) In several embodiments, the carbon dioxide recovery system described in any one of 1) to 3) above includes: 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 allows carbon dioxide gas to pass through preferentially than nitrogen gas, configured to separate the carbon dioxide-rich gas compressed by the second compressor into nitrogen-rich gas and carbon dioxide gas using the separation membrane; and a second expander (22) configured to expand the nitrogen-rich gas discharged from the second membrane separation device, and the liquefier configured to liquefy at least a portion of the carbon dioxide gas discharged from the second membrane separation device using the cold energy of the nitrogen-rich gas expanded by the first expander and the cold energy of the nitrogen-rich gas expanded by the second expander.

[0081] According to the carbon dioxide recovery system described in 4) above, carbon dioxide gas separated (extracted) from the target gas using the first membrane separation device is adsorbed onto the adsorption material of the adsorption device and then separated from the adsorption material, thereby obtaining high-purity carbon dioxide gas from the adsorption device. Furthermore, by utilizing the cold energy of the nitrogen-rich gas expanded by the first expander, the carbon dioxide gas separated from the adsorption material can be liquefied, thus preventing the equipment used to recover carbon dioxide contained in the target gas from becoming larger and more complex.

[0082] 5) In several embodiments, the carbon dioxide recovery system described in any one of 1) to 4) above includes an adsorption device (60) configured to adsorb carbon dioxide contained in the carbon dioxide-rich gas discharged from the first membrane separation device by an adsorption material (88), and the liquefaction device is configured to liquefy the carbon dioxide gas separated from the adsorption material by utilizing the cold energy of the nitrogen-rich gas expanded by the first expander.

[0083] According to the carbon dioxide recovery system described in 5) above, carbon dioxide gas extracted from the target gas using the first membrane separation device is adsorbed onto the adsorption material of the adsorption device and then separated from the adsorption material, thereby obtaining high-purity carbon dioxide gas from the adsorption device. Furthermore, by utilizing the cold energy of the nitrogen-rich gas expanded by the first expander, the carbon dioxide gas separated from the adsorption material can be liquefied, thus preventing the equipment used to recover carbon dioxide contained in the target gas from becoming larger and more complex.

[0084] 6) In several embodiments, the carbon dioxide recovery system described in 3) above further includes: a dehumidification device (62) configured to adsorb moisture contained in the carbon dioxide-rich gas discharged from the first membrane separation device by a dehumidification material (86); a heater (92) disposed downstream of the heat exchanger in the downstream pipeline of the liquefier, configured to heat the nitrogen-rich gas flowing in the downstream pipeline of the liquefier using the thermal energy of the target gas compressed by the first compressor; and a heated gas pipeline (95) configured to supply the nitrogen-rich gas heated by the heater to the dehumidification device to dry the dehumidification material of the dehumidification device.

[0085] According to the carbon dioxide recovery system described in 6) above, the moisture contained in the nitrogen-rich gas expanded by the first expander is removed by passing through the heat exchanger, thus allowing the dried nitrogen-rich gas to be supplied to the dehumidification unit from the heated pipeline. Therefore, the dried nitrogen-rich gas supplied from the heated pipeline can be used for drying (regenerating) the dehumidification material, eliminating the need for additional drying gas and reducing the energy required for drying the dehumidification material.

[0086] 7) In several embodiments, the carbon dioxide recovery system described in 5) above includes: a carbon dioxide gas pipeline (66) for supplying the carbon dioxide gas separated from the adsorbent material of the adsorption device to the liquefier; a vacuum pump (68) provided in the carbon dioxide gas pipeline; and a heater configured to heat the adsorbent material by utilizing exhaust heat from an exhaust source (2, 91) or an accessory device (96, 98, 131, 15) that discharges the target gas.

[0087] According to the carbon dioxide recovery system described in 7) above, the adsorbent material is heated by a heater using heat exhaust from the carbon dioxide emission source or an auxiliary device of the carbon dioxide emission source, thereby enabling the separation of carbon dioxide adsorbed on the adsorbent material. The adsorbent material has the characteristic that carbon dioxide is easily separated as the temperature rises; therefore, compared to the case without a heater, the vacuum level of the vacuum pump suction pressure required to separate a sufficient amount of carbon dioxide from the adsorbent material can be reduced, thus reducing the power of the vacuum pump and lowering the operating cost of the carbon dioxide recovery system.

[0088] 8) In several embodiments, the carbon dioxide recovery system in any one of 1) to 7) above includes: an engine (91); and an engine-attached turbocharger (96) configured to compress the intake air of the engine driven by the exhaust of the engine, the carbon dioxide recovery system comprising: a first turbocharger (15) for compressing the exhaust gas discharged from the turbine (100) of the engine-attached turbocharger; a residual exhaust line (97) for supplying the exhaust gas of the engine to a downstream side of the turbine bypassing the turbine of the engine-attached turbocharger; and a second turbocharger (131) including a turbine (140) disposed in the residual exhaust line and a compressor (4) for compressing the exhaust gas discharged from the turbine (100) of the engine-attached turbocharger, the first compressor being the compressor (4) of the first turbocharger and the first expander being the turbine (12) of the first turbocharger.

[0089] According to the carbon dioxide recovery system described in 8) above, the power recovered by the second turbocharger can be used to supplement the power required to pressurize the exhaust gas to ensure the differential pressure across the separation membrane in the first membrane separation unit, thereby reducing the operating cost of the carbon dioxide recovery system. Furthermore, for example, when the residual exhaust power recovery turbocharger is connected to the vacuum pump described in 7) above, the power recovered from the residual exhaust power recovery turbocharger can be used to supplement the power used to drive the vacuum pump, further reducing the operating cost of the carbon dioxide recovery system.

[0090] 9) In several embodiments, the carbon dioxide recovery system described in 8) above also includes a bypass line (110) configured to supply the carbon dioxide-rich gas discharged from the first membrane separation device to the inlet (4a) of the compressor of the first turbocharger.

[0091] In the carbon dioxide recovery system described in 8) above, which includes an engine and an engine-attached turbocharger, seasonal variations in air density, particularly in winter, tend to generate a large amount of residual exhaust gas (exhaust gas flowing in the residual exhaust line) that bypasses the turbine of the engine-attached turbocharger. Therefore, the exhaust flow rate of the compressor (first compressor) of the first turbocharger tends to be lower in winter than in summer. The first compressor is designed for maximum flow in summer, so without specific research, it may operate under partial load in winter, potentially causing its operating point to deviate from its design point and resulting in decreased efficiency. Therefore, by installing the bypass line described in 9) above, during periods when the flow rate of the first compressor tends to be lower, a portion of the carbon dioxide-rich gas discharged from the permeate side of the separation membrane in the first membrane separator can be supplied to the inlet of the first compressor, thereby stabilizing the flow rate of the first compressor and suppressing any decrease in its efficiency.

[0092] In addition, by using a bypass line to return the carbon dioxide-rich gas with a high carbon dioxide concentration to the upstream side of the first membrane separation unit, the carbon dioxide concentration of the carbon dioxide-rich gas discharged from the permeate side of the separation membrane in the first membrane separation unit can be further increased, thereby reducing the load on the adsorption unit and reducing the operating cost of the carbon dioxide recovery system.

[0093] 10) In several embodiments, the carbon dioxide recovery system described in any one of 1) to 9) above comprises: an adsorption device (60) configured to adsorb carbon dioxide contained in the carbon dioxide-rich gas discharged from the first membrane separation device by an adsorption material (88); a water-cooled heat exchanger (6, 70, 84, 94) configured to cool the heat medium by heat exchange with cooling water; a used cooling water line (114) configured to supply the cooling water used in the water-cooled heat exchanger to cool at least a portion of the target gas to the adsorption device; and a heater (90) configured to heat the adsorption material using the used cooling water supplied from the used cooling water line.

[0094] According to the carbon dioxide recovery system described in 10) above, the used cooling water supplied from the used cooling water pipeline can be used to heat the adsorbent material. Therefore, compared with the case where a separate heating source (such as a boiler) is set up to heat the adsorbent material, the equipment of the carbon dioxide recovery system can be simplified and the increase in equipment costs can be suppressed.

[0095] 11) A 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, comprising: a compression step for compressing the target gas; a membrane separation step for separating the target gas compressed in the compression step into a carbon dioxide-rich gas and a nitrogen-rich gas using separation membranes (13, 40); an expansion step for expanding the nitrogen-rich gas generated in the membrane separation step; and a liquefaction step for liquefying the carbon dioxide-rich gas generated in the membrane separation step using the cold energy of the nitrogen-rich gas expanded in the expansion step.

[0096] According to the carbon dioxide recovery method described in 11) above, at least a portion of the carbon dioxide gas separated in the membrane separation step can be liquefied by utilizing the cold energy of the nitrogen-rich gas after expansion in the expansion step. Therefore, there is no need to set up a separate device for supplying a cold or heat source for liquefying the carbon dioxide gas, and the large-scale and complex nature of the equipment for recovering carbon dioxide contained in the target gas can be suppressed.

[0097] Explanation of reference numerals in the attached figures

[0098] Carbon dioxide recovery systems 1A, 1B, 1C, 1D, and 1E

[0099] 2. Sources of carbon dioxide emissions

[0100] 4, 16, 24, 72, 99, 141 compressors

[0101] 4a entrance department

[0102] 6, 18, 26, 70, 84 coolers

[0103] 8.20 Membrane Separation Unit

[0104] 9, 19 Rotating Axis

[0105] 10, 92 Regenerative Heat Exchanger

[0106] 11, 21, 25, 69, 73 electric motors

[0107] 12, 22 expanders

[0108] 13, 40 separation membrane

[0109] 14 Liquefied Tank

[0110] 15 Energy Recovery Turbocharger

[0111] 28 storage tanks

[0112] 30 exhaust pipe

[0113] 32 Nitrogen Gas First Pipeline

[0114] 38 Carbon Dioxide First Pipeline

[0115] 34. Downstream pipeline of liquefier

[0116] 36, 46 downstream pipelines

[0117] 42 Nitrogen Second Pipeline

[0118] 50 CO2 Second Pipeline

[0119] 48, 112 valves

[0120] 59 Liquid Pipeline

[0121] 60 adsorption tower

[0122] 62 Dehumidification Tower

[0123] 64 heat exchanger

[0124] 66 Carbon Dioxide Pipeline

[0125] 68 vacuum pump

[0126] 86 Dehumidifying Materials

[0127] 88 Adsorption Materials

[0128] 90 heater

[0129] 91 engine

[0130] 93 intake pipe

[0131] 94 Air Cooler

[0132] 95 heating pipeline

[0133] 96 engine auxiliary turbocharger

[0134] 97 Remaining exhaust pipes

[0135] 98 Exhaust Heat Recovery Steam Boiler

[0136] 100, 140 turbo

[0137] 101 Bypass Valve

[0138] 110, 143 bypass pipelines

[0139] 131 Residual Exhaust Power Recovery Turbocharger

Claims

1. A carbon dioxide recovery system for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen, said carbon dioxide recovery system comprising: The first compressor is configured to compress the target gas; The first membrane separation device includes a separation membrane that allows carbon dioxide gas to pass through preferentially than nitrogen gas, and is configured to use the separation membrane to separate the target gas compressed by the first compressor into nitrogen-rich gas and carbon dioxide-rich gas. A first expander is configured to expand the nitrogen-rich gas discharged from the first membrane separation device; and The liquefier is configured to use the cold energy of the nitrogen-rich gas expanded by the first expander to liquefy at least a portion of the carbon dioxide gas discharged from the first membrane separation device.

2. The carbon dioxide recovery system according to claim 1, wherein, The first expander is a turbine. The carbon dioxide recovery system also includes: a rotating shaft connecting the first compressor and the turbine; and an electric motor configured to drive the rotating shaft.

3. The carbon dioxide recovery system according to claim 1, wherein, The carbon dioxide recovery system also features: The first gas pipeline is configured to supply the nitrogen-rich gas discharged from the first membrane separation device to the first expander; Downstream piping of the liquefier supplies the flow of the nitrogen-rich gas exiting the liquefier; and The heat exchanger is configured to exchange heat 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 in the downstream line of the liquefier.

4. The carbon dioxide recovery system according to claim 1, wherein, The carbon dioxide recovery system includes: The second compressor is configured to compress the carbon dioxide-rich gas discharged from the first membrane separation device; The second membrane separation device includes a separation membrane that allows carbon dioxide gas to pass through preferentially than nitrogen gas, and is configured to use the separation membrane to separate the carbon dioxide-rich gas compressed by the second compressor into nitrogen-rich gas and carbon dioxide gas. and The second expander is configured to expand the nitrogen-rich gas discharged from the second membrane separation device. The liquefier is configured to liquefy at least a portion of the carbon dioxide gas discharged from the second membrane separation device by utilizing the cold energy of the nitrogen-rich gas expanded by the first expander and the cold energy of the nitrogen-rich gas expanded by the second expander.

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

6. The carbon dioxide recovery system according to claim 3, wherein, The carbon dioxide recovery system also features: The dehumidification device is configured to allow a dehumidifying material to adsorb moisture contained in the carbon dioxide-rich gas discharged from the first membrane separation device; A heater, disposed downstream of the heat exchanger in the downstream pipeline of the liquefier, is configured to heat the nitrogen-rich gas flowing in the downstream pipeline of the liquefier using the thermal energy of the target gas compressed by the first compressor; and The heated gas pipeline is configured to supply the nitrogen-rich gas, heated by the heater, to the dehumidification device to dry the dehumidification material of the dehumidification device.

7. The carbon dioxide recovery system according to claim 5, wherein, The carbon dioxide recovery system includes: A carbon dioxide gas pipeline supplies carbon dioxide gas separated from the adsorbent material of the adsorption device to the liquefier; A vacuum pump is installed on the carbon dioxide gas pipeline; and The heater is configured to heat the adsorbent material by utilizing exhaust heat from an exhaust source that discharges the target gas or an accessory device of the exhaust source.

8. The carbon dioxide recovery system according to claim 1, wherein, The carbon dioxide recovery system includes: Engine; and An engine-attached turbocharger is configured to compress the engine's intake air, driven by the engine's exhaust. The carbon dioxide recovery system includes: A first turbocharger compresses the exhaust gas discharged from the turbine of the engine-attached turbocharger; The remaining exhaust lines supply the engine's exhaust gas downstream of the turbine of the engine's auxiliary turbocharger; and The second turbocharger includes a turbine disposed on the remaining exhaust line and a compressor for compressing the exhaust gas discharged from the turbine of the engine-attached turbocharger. 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, wherein, The carbon dioxide recovery system also includes a bypass line configured to supply the carbon dioxide-rich gas discharged from the first membrane separator to the inlet of the compressor of the first turbocharger.

10. The carbon dioxide recovery system according to claim 1, wherein, The carbon dioxide recovery system includes: An adsorption device is configured to adsorb carbon dioxide contained in the carbon dioxide-rich gas discharged from the first membrane separation device by an adsorption material. A water-cooled heat exchanger is configured to cool the heat medium flowing within the carbon dioxide recovery system by utilizing heat exchange with cooling water. The cooling water pipeline is configured to supply the cooling water, which has been used to cool at least a portion of the target gas in the water-cooled heat exchanger, to the adsorption device. and The heater is configured to heat the adsorbent material using the used cooling water supplied from the used cooling water line.

11. A carbon dioxide recovery method for recovering carbon dioxide from a target gas containing carbon dioxide and nitrogen, the carbon dioxide recovery method comprising: The compression step involves compressing the target gas; The membrane separation step uses a separation membrane to separate the target gas, which has been compressed in the compression step, into a carbon dioxide-rich gas and a nitrogen-rich gas. An expansion step, wherein the nitrogen-rich gas generated in the membrane separation step is expanded; and The liquefaction step utilizes the cold energy of the nitrogen-rich gas expanded in the expansion step to liquefy the carbon dioxide-rich gas generated in the membrane separation step.

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