Carbon dioxide capture system and carbon dioxide capture method

Abstract

To improve carbon dioxide recovery efficiency in a system which adsorbs / desorbs carbon dioxide with an adsorbent to recover carbon dioxide.SOLUTION: A carbon dioxide recovery system includes: multiple adsorption parts 20 in which an adsorbent 22 for adsorbing and desorbing carbon dioxide are stored; a cleaning off gas storage part 14 where an off gas from the adsorption parts 20 is stored as a cleaning off gas; a cleaning off gas storage execution part which causes a carbon dioxide rich gas desorbed from one of the adsorption parts 20 to be stored in the cleaning off gas storage part; and a cleaning off gas supply passage 38 which is connected to the adsorption parts 20 and supplies the cleaning off gas stored in the cleaning off gas storage part 14 to the adsorption parts 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon dioxide capture system and a carbon dioxide capture method. [Background technology]

[0002] Conventionally, systems have been proposed that use an adsorbent to adsorb / desorb carbon dioxide and recover carbon dioxide. Patent Document 1 discloses a technology that uses three adsorption towers and recovers carbon dioxide through the processes of pressure equalization, pressurization, adsorption, washing, and desorption. In Patent Document 1, high-concentration carbon dioxide recovered as a product is used as a washing gas in the washing process. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. H6-170144 Summary of the Invention [Problem to be solved by the invention]

[0004] If only the high-concentration carbon dioxide recovered as a product is used as cleaning gas, a large amount of product carbon dioxide will be used for cleaning to increase the carbon dioxide recovery concentration, which will reduce recovery efficiency. There is a need to improve carbon dioxide recovery efficiency.

[0005] The present invention has been made in view of the above circumstances, and aims to improve the carbon dioxide recovery efficiency in a system that recovers carbon dioxide by adsorbing and desorbing carbon dioxide using an adsorbent. [Means for solving the problem]

[0006] of the first aspectThe carbon dioxide capture system includes a plurality of adsorption units that contain an adsorbent that adsorbs and desorbs carbon dioxide and separates a raw material gas containing carbon dioxide into a carbon dioxide-rich gas and an off-gas that contains impurities other than carbon dioxide, and that are connected to one side of the adsorbent by an off-gas delivery path that delivers the off-gas and the other side by a carbon dioxide gas delivery path that delivers the carbon dioxide-rich gas; a cleaning off-gas storage unit that is connected to the off-gas delivery path and that stores the off-gas from the adsorption units as cleaning off-gas; a cleaning off-gas storage execution unit that stores the off-gas from one of the adsorption units in the cleaning off-gas storage unit during cleaning, in which the carbon dioxide-rich gas desorbed from one of the adsorption units is supplied to another adsorption unit for cleaning, and a cleaning off-gas supply path that is connected to the adsorption units and that supplies the cleaning off-gas stored in the cleaning off-gas storage unit to the adsorption unit.

[0007] of the first aspect The carbon dioxide capture system includes a plurality of adsorption units. The plurality of adsorption units contain an adsorbent that adsorbs and desorbs carbon dioxide, and separates a raw material gas containing carbon dioxide into a carbon dioxide-rich gas and an off-gas that contains impurities other than carbon dioxide. An off-gas delivery path for delivering the off-gas is connected to one side of the adsorption units across the adsorbent, and a carbon dioxide gas delivery path for delivering the carbon dioxide-rich gas is connected to the other side.

[0008] A cleaning off-gas storage unit that stores the off-gas from the adsorption unit as cleaned off-gas is connected to the off-gas delivery path. During cleaning, in which carbon dioxide-rich gas desorbed from one adsorption unit is supplied to another adsorption unit for cleaning, the cleaning off-gas storage execution unit stores the off-gas from the other adsorption unit in the cleaning off-gas storage unit. The cleaning off-gas stored in the cleaning off-gas storage unit is supplied to the adsorption unit via the cleaning off-gas supply path.

[0009] First AspectAccording to this carbon dioxide capture system, the off-gas discharged from the adsorption unit during cleaning can be stored in a cleaning off-gas storage unit and supplied to the adsorption unit for use. Since the cleaning off-gas has a higher carbon dioxide concentration than the off-gas discharged when the raw material gas is supplied to the adsorption unit, it can be supplied to the adsorption unit before cleaning to discharge impurities (substances other than carbon dioxide) from within the adsorption unit. This reduces the amount of carbon dioxide-rich gas used during cleaning, thereby improving the carbon dioxide capture efficiency.

[0010] of the second aspect In the carbon dioxide recovery system, the scrubbed off-gas supply passage is connected to the other side of the adsorption section to supply the scrubbed off-gas to the adsorption section.

[0011] Second Aspect According to the carbon dioxide recovery system of the above, the impurities in the adsorption section can be discharged from the off-gas discharge path by supplying the cleaning off-gas from the side opposite to the side from which the off-gas is discharged.

[0012] of the third aspect The carbon dioxide capture system includes a water vapor supply unit that supplies water vapor from the one side of the adsorption unit.

[0013] Third Aspect According to the carbon dioxide recovery system, when carbon dioxide adsorbed by the adsorbent in the adsorption section is desorbed, the desorption can be promoted by supplying water vapor.

[0014] The fourth aspectThe carbon dioxide capture method is a carbon dioxide capture method using a carbon dioxide capture system equipped with a plurality of adsorption units each containing an adsorbent that adsorbs and desorbs carbon dioxide, and includes the following steps: an adsorption step in which a raw material gas containing carbon dioxide is supplied to the adsorption unit to cause the adsorbent to adsorb the carbon dioxide; a cleaning step in which, with the carbon dioxide adsorbed by the adsorbent, carbon dioxide gas is supplied to the adsorption unit to clean it; a cleaning off-gas storage step in which, during the cleaning step, off-gas delivered from the adsorption unit is stored as cleaning off-gas; a desorption step in which, after the cleaning step, carbon dioxide is desorbed from the adsorbent; and a rough cleaning step in which, after the adsorption step and before the cleaning step, the cleaning off-gas is supplied to the adsorption unit to perform rough cleaning.

[0015] Fourth Aspect In the carbon dioxide capture method, the off-gas delivered from the adsorption unit during the cleaning step is stored as cleaned off-gas, and the cleaned off-gas is supplied to the adsorption unit after the adsorption step and before the cleaning step to roughly clean the adsorption unit. The cleaned off-gas has a higher carbon dioxide concentration than the off-gas delivered when the raw gas is supplied to the adsorption unit. Therefore, by roughly cleaning the adsorption unit using the cleaned off-gas, impurities (substances other than carbon dioxide) in the adsorption unit can be discharged before cleaning. This makes it possible to reduce the amount of carbon dioxide-rich gas used during cleaning, thereby improving the carbon dioxide capture efficiency.

[0016] The fifth aspect In the carbon dioxide recovery method, water vapor is supplied to the adsorption section in the desorption step.

[0017] Fifth Aspect According to the carbon dioxide recovery method, the desorption of carbon dioxide can be promoted by water vapor in the desorption step. [Effects of the Invention]

[0018] According to the present invention, in a system that uses an adsorbent to adsorb / desorb carbon dioxide and recover carbon dioxide, it is possible to improve the efficiency of recovering carbon dioxide. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic configuration diagram of a carbon dioxide capture system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram of a control unit of the carbon dioxide capture system according to the present embodiment and its connecting members. [Figure 3] 3 is a flowchart showing the flow of a carbon dioxide recovery process according to the present embodiment. [Figure 4] 3 is a flowchart showing the flow of a first process treatment according to the present embodiment. [Figure 5] 1A, 1B, and 1C are explanatory steps showing the gas flow in the first process. [Figure 6] 4 is a flowchart showing the flow of a second process treatment according to the present embodiment. [Figure 7] 1A, 1B, and 1C are explanatory steps showing the gas flow in the second process. [Figure 8] 10 is a flowchart showing the flow of a third process treatment according to the present embodiment. [Figure 9] 1A, 1B, and 1C are explanatory steps showing the gas flow in the third process. [Figure 10] FIG. 10 is a diagram showing the timing of the first step, the second step, and the third step in each adsorption section. DETAILED DESCRIPTION OF THE INVENTION

[0020] An example of a carbon dioxide capture system according to an embodiment of the present invention will be described with reference to the drawings.

[0021] The carbon dioxide capture system 10 uses exhaust gas containing carbon dioxide emitted from equipment such as a gas engine or a gas boiler, or from a factory, as a raw material gas, and captures a high-concentration carbon dioxide-rich gas from the raw material gas. Note that Fig. 1 shows a schematic configuration of the carbon dioxide capture system 10, and the carbon dioxide capture system 10 may include other components.

[0022] As shown in FIG. 1, the carbon dioxide capture system 10 according to this embodiment includes three adsorption units 20A, 20B, and 20C, a CO2 capture pump 12, a cleaning off-gas storage unit 14, an off-gas blower 16, and a water vapor supply unit 18.

[0023] The adsorption units 20A, 20B, and 20C have the same configuration, and when describing them without distinction, they will be collectively referred to as "adsorption unit 20." The adsorption unit 20 adsorbs carbon dioxide therein and is filled with an adsorbent 22 that can desorb the adsorbed carbon dioxide by changing the conditions inside the adsorption unit 20. For example, an amine-supported porous material or an aminosilane-modified porous material can be used as the adsorbent 22. In this embodiment, an amine-supported porous material is used, in which desorption of the adsorbed carbon dioxide is promoted by supplying water vapor.

[0024] A one-side connection part 24 is formed on one side of the adsorbent 22 of the adsorption part 20, and a other-side connection part 26 is formed on the other side. A first gas passage 40 serving as a carbon dioxide gas delivery passage is connected to the one-side connection part 24, and a second gas passage 30 serving as an off-gas delivery passage is connected to the other-side connection part 26.

[0025] A raw material gas supply line 42, a CO2 supply line 44, and a CO2 recovery line 46 are connected to the first gas line 40. A raw material supply valve V1 is provided in the raw material gas supply line 42, a CO2 supply valve V2 is provided in the CO2 supply line 44, and a CO2 recovery valve V3 is provided in the CO2 recovery line 46. The first gas line 40, raw material gas supply line 42, CO2 supply line 44, CO2 recovery line 46, raw material supply valve V1, CO2 supply valve V2, and CO2 recovery valve V3 are provided corresponding to the adsorption units 20A, 20B, and 20C, respectively. In the following illustrations, the reference numerals corresponding to adsorption unit 20A are suffixed with "A," the reference numerals corresponding to adsorption unit 20B are suffixed with "B," and the reference numerals corresponding to adsorption unit 20C are suffixed with "C." When distinctions are made in the description, the reference numerals corresponding to the adsorption units will be suffixed with the corresponding reference numerals.

[0026] The upstream side of the raw material gas supply path 42 is connected to a raw material gas supply source (such as a gas engine or a factory exhaust gas path) (not shown), and is branched into raw material gas supply paths 42A, 42B, and 42C upstream of the raw material supply valve V1. The downstream ends of the raw material gas supply paths 42A, 42B, and 42C are connected to the first gas paths 40A, 40B, and 40B, respectively. The raw material supply valve V1 is provided on each of the raw material gas supply paths 42A, 42B, and 42C.

[0027] The CO2 capture path 46 is provided with a CO2 capture pump 12. The CO2 capture pump 12 may be, for example, a vacuum pump. The CO2 capture path 46 branches into CO2 capture paths 46A, 46B, and 46C on the adsorption unit 20 side of the CO2 capture pump 12. One end of the CO2 capture paths 46A, 46B, and 46C is connected to the first gas paths 40A, 40B, and 40B, respectively. One end of the CO2 supply path 44 is connected to the CO2 capture path 46 via a three-way valve V9 on the opposite side of the CO2 capture pump 12 from the branching portion of the CO2 capture paths 46A, 46B, and 46C. A CO2 capture valve V3 is provided on each of the CO2 capture paths 46A, 46B, and 46C.

[0028] The CO2 supply channel 44 branches into CO2 supply channels 44A, 44B, and 44C on the side opposite the adsorption unit 20, with the CO2 supply valve V2 in between. The CO2 supply channels 44A, 44B, and 44C are connected to the first gas channels 40A, 40B, and 40B, respectively. The CO2 supply valve V2 is provided on each of the CO2 supply channels 44A, 44B, and 44C.

[0029] An off-gas delivery path 32, a cleaning off-gas delivery path 34, and a steam supply path 36 are connected to the second gas path 30. An off-gas exhaust valve V4 is provided in the off-gas delivery path 32, a cleaning off-gas valve V5 is provided in the cleaning off-gas delivery path 34, and a steam supply valve V6 is provided in the steam supply path 36. The second gas path 30, the off-gas delivery path 32, the cleaning off-gas delivery path 34, the steam supply path 36, the off-gas exhaust valve V4, the cleaning off-gas valve V5, and the steam supply valve V6 are provided corresponding to each of the adsorption units 20A, 20B, and 20C. In the following drawings, the reference numerals of the parts corresponding to the adsorption unit 20A are suffixed with "A," the reference numerals of the parts corresponding to the adsorption unit 20B are suffixed with "B," and the reference numerals of the parts corresponding to the adsorption unit 20C are suffixed with "C," and when distinctions are made in the description, the respective reference numerals are used.

[0030] The off-gas delivery path 32 branches into off-gas delivery paths 32A, 32B, and 32C, which are connected to the second gas paths 30A, 30B, and 30C, respectively. Off-gas exhaust valves V4A, V4B, and V4C are provided on the off-gas delivery paths 32A, 32B, and 32C, respectively.

[0031] The cleaning off-gas storage section 14 is connected to the cleaning off-gas delivery path 34. The cleaning off-gas storage section 14 is a tank that stores cleaning off-gas, and the cleaning off-gas delivery path 34 is connected to an inlet 14IN of the cleaning off-gas storage section 14. The off-gas blower 16 is provided closer to the second gas path 30 than the cleaning off-gas storage section 14.

[0032] One end of a cleaning off-gas supply path 38 is connected to the outlet 14OUT of the cleaning off-gas reservoir 14. The other end of the cleaning off-gas supply path 38 is connected via a three-way valve V8 to a location upstream of the branched portion of the raw material gas supply path 42. A cleaning off-gas supply valve V7 is provided in the cleaning off-gas supply path 38.

[0033] The cleaning off-gas delivery path 34 is connected to the discharge path 35 via a three-way valve V10. The three-way valve V10 is provided closer to the second gas path 30 than the off-gas blower 16. The cleaning off-gas delivery path 34 branches into cleaning off-gas delivery paths 34A, 34B, and 34C on the second gas path 30 side of the three-way valve V10. One ends of the cleaning off-gas delivery paths 34A, 34B, and 34C are connected to the second gas paths 30A, 30B, and 30B, respectively. A cleaning off-gas valve V5 is provided in each of the cleaning off-gas delivery paths 34A, 34B, and 34C.

[0034] One end of the water vapor supply channel 36 is connected to the water vapor supply unit 18. As an example, a vaporizer or the like can be used as the water vapor supply unit 18. The water vapor supply channel 36 branches into water vapor supply channels 36A, 36B, and 36C on the side opposite the adsorption unit 20, with a water vapor supply valve V6 in between. The water vapor supply channels 36A, 36B, and 36C are connected to the second gas channels 30A, 30B, and 30B, respectively. The water vapor supply valve V6 is provided on each of the water vapor supply channels 36A, 36B, and 36C.

[0035] 2, the carbon dioxide capture system 10 includes a control unit 50. The control unit 50 has a CPU (Central Processing Unit: processor) 50A, a ROM (Read Only Memory) 50B, a RAM (Random Access Memory) 50C, a storage 50D, and an input / output interface (I / F) 50E. Each component is connected to each other via a bus 52 so as to be able to communicate with each other.

[0036] The CPU 50A is a central processing unit that executes various programs and controls each component. That is, the CPU 50A reads programs from the ROM 50B or storage 50D and executes the programs using the RAM 50C as a work area. The CPU 50A controls the above components and performs various arithmetic operations according to the programs recorded in the ROM 50B or storage 50D.

[0037] The ROM 50B stores various programs and various data. The RAM 50C temporarily stores programs or data as a working area. The storage 50D is configured with an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs including an operating system and various data. In this embodiment, the ROM 50B or the storage 50D stores programs (carbon dioxide capture processing) for executing the adsorption process, rough cleaning process, cleaning process, cleaning off-gas storage process, etc. of the carbon dioxide capture system 10, which will be described later, as well as various data.

[0038] The input / output I / F 50E is connected via signal lines to the raw material supply valve V1, CO2 supply valve V2, CO2 recovery valve V3, off-gas exhaust valve V4, cleaning off-gas valve V5, steam supply valve V6, cleaning off-gas supply valve V7, and three-way valves V8, V9, and V10. The control unit 50 controls the opening and closing of these valves and the switching of the flow paths of the three-way valves. The input / output I / F 50E is also connected to the CO2 recovery pump 12 and the off-gas blower 16. The control unit 50 controls the operation of the CO2 recovery pump 12 and the off-gas blower 16.

[0039] Next, the operation of the carbon dioxide capture system 10 of this embodiment will be described.

[0040] In the adsorption step, the raw material supply valve V1 and the off-gas exhaust valve V4 are opened, and the raw material gas is supplied from the raw material gas supply path 42 to the adsorption unit 20 via the first gas path 40. Carbon dioxide contained in the raw material gas is adsorbed by the adsorbent 22. The raw material gas flows through the adsorption unit 20 from the one-side connection part 24 side to the other-side connection part 26 side, and the gas not adsorbed by the adsorbent 22 is sent as off-gas to the second gas path 30 and released to the atmosphere via the off-gas delivery path 32. At this time, the pressure inside the adsorption unit 20 is set to a predetermined adsorption pressure.

[0041] In the desorption step, the CO2 capture valve V3 and the steam supply valve V6 are opened, the pressure inside the adsorption unit 20 is set to a predetermined desorption pressure, and steam is supplied from the steam supply unit 18 to the adsorption unit 20 via the steam supply path 36. In addition, the CO2 capture pump 12 is driven. As a result, the carbon dioxide adsorbed to the adsorbent 22 is desorbed from the adsorbent 22 and sent together with the steam from the one-side connection part 24 through the first gas path 40 to the CO2 capture path 46. Water is separated from the carbon dioxide sent to the CO2 capture path 46 in a condenser (not shown) and recovered as product carbon dioxide. The carbon dioxide after water separation is also used in the cleaning step described below.

[0042] In the cleaning step, the CO2 supply valve V2 and the cleaning off-gas valve V5 are opened, and carbon dioxide is supplied from the CO2 supply line 44 to the adsorption unit 20, in which carbon dioxide is adsorbed by the adsorbent 22. The carbon dioxide used is the carbon dioxide sent to the CO2 recovery line 46 in the desorption step described above. A portion of the carbon dioxide sent to the CO2 recovery line 46 is sent to the CO2 supply line 44 by opening the portion of the three-way valve V9 that communicates with the CO2 supply line 44. The carbon dioxide sent to the CO2 supply line 44 is supplied via the first gas line 40 from the one-side connector 24 to the adsorption unit 20, in which carbon dioxide is adsorbed. The supplied carbon dioxide flows from the one-side connector 24 to the other-side connector 26 together with impurities in the adsorption unit 20 and is stored as cleaning off-gas in the cleaning off-gas storage unit 14 via the second gas line 30 and the cleaning off-gas delivery line 34. At this time, the pressure in the adsorption unit 20 is set to a predetermined adsorption pressure.

[0043] During the cleaning process, cleaning off-gas recovery processing is performed at the same time, but the cleaning off-gas contains a relatively large amount of impurities in the early stage of the cleaning process. Therefore, in the early stage of the cleaning process, the three-way valve V10 may be switched to discharge the cleaning off-gas to the discharge path 35, and the cleaning off-gas may be stored in the cleaning off-gas storage section 14 from the middle of the cleaning process.

[0044] In the rough cleaning step, the cleaning off-gas is supplied from the cleaning off-gas reservoir 14 to the adsorption unit 20 in which carbon dioxide has been adsorbed by the adsorbent 22 after the cleaning step. The cleaning off-gas passes through the cleaning off-gas supply path 38, the raw gas supply path 42, and the first gas path 40, and is supplied from the one-side connecting part 24 to the adsorption unit 20 in which carbon dioxide has been adsorbed. The supplied cleaning off-gas flows together with impurities in the adsorption unit 20 from the one-side connecting part 24 to the other-side connecting part 26, and is released as rough cleaning off-gas through the second gas path 30 and the off-gas delivery path 32 to the atmosphere. At this time, the pressure inside the adsorption unit 20 is set to a predetermined adsorption pressure.

[0045] These adsorption process, desorption process, rough cleaning process, and cleaning process are performed by executing a carbon dioxide capture process program by the control unit 50. In the carbon dioxide capture process, a first step S1, a second step S2, and a third step S3 are repeatedly executed, as shown in Fig. 3. Note that before the program is executed, valves V1 to V7 are closed.

[0046] 4, in the first process S1, the adsorption process is performed by opening the raw material supply valve V1A and the off-gas exhaust valve V4A for the adsorption unit 20A in step S10, thereby causing carbon dioxide to be adsorbed by the adsorbent 22A of the adsorption unit 20A.

[0047] In step S12, a desorption process is performed for the adsorption unit 20C by opening the CO2 capture valve V3C and the steam supply valve V6C and driving the CO2 capture pump 12. This causes carbon dioxide to be desorbed from the adsorbent 22C of the adsorption unit 20C, and the carbon dioxide sent to the CO2 capture path 46 can be captured as product carbon dioxide.

[0048] In step S14, the CO supply valve V2B, the cleaning off-gas valve V5B, and the three-way valve V9 on the adsorption unit 20 side are opened to perform a cleaning process for the adsorption unit 20B. This allows impurities remaining in the adsorption unit 20B to be replaced with carbon dioxide.

[0049] In step S16, the three-way valve V10 is switched to the side toward the cleaning off-gas reservoir 14, and the cleaning off-gas is stored in the cleaning off-gas reservoir 14 (cleaning off-gas storage process).

[0050] FIG. 5(A) shows the open / closed states of the valves and the gas flow after steps S10 to S16 have been executed.

[0051] In step S18, it is determined whether a predetermined time T1 has elapsed since the execution of the cleaning process (step S14). The predetermined time T1 is set to the time required to clean the adsorption unit 20B. If the determination is affirmative, in step S20, the CO2 supply valve V2B, the cleaning off-gas valve V5B, and the three-way valve V9 on the adsorption unit 20 side are closed (closing process) (see FIG. 5(B)).

[0052] Next, in step S22, it is determined whether a predetermined time T2 has elapsed since the execution of the adsorption step (step S10). The predetermined time T2 is set to the time required for carbon dioxide to be sufficiently adsorbed by the adsorbent 22A of the adsorption section 20A. If the determination is affirmative, in step S24, a rough cleaning step is executed. The rough cleaning step is executed by opening the cleaning off-gas supply valve V7 while keeping the raw material supply valve V1A and the off-gas exhaust valve V4A open, switching the three-way valve V8 so that the cleaning off-gas supply path 38 communicates with the downstream side of the raw material gas supply path 42, and driving the off-gas blower 16 (see FIG. 5(C)). This allows impurities remaining in the adsorption section 20A to be replaced with the cleaning off-gas. The cleaning off-gas has a relatively high carbon dioxide concentration, so it can remove impurities from the adsorption section 20A to a certain extent.

[0053] Next, in step S26, it is determined whether a predetermined time T3 has elapsed since the execution of the desorption process (step S12). The predetermined time T3 is set to the time required for the carbon dioxide adsorbed by the adsorbent 22C of the adsorption section 20C to be sufficiently desorbed. If the determination is affirmative, in step S28, the cleaning off-gas supply valve V7 is closed and the three-way valve V8 is switched so that the cleaning off-gas supply path 38 and the downstream side of the raw material gas supply path 42 are in communication with each other, thereby completing the first step.

[0054] 6, in the second step, in step S30, the raw material supply valve V1C and the off-gas exhaust valve V4C of the adsorption unit 20C are opened to perform an adsorption process, thereby causing carbon dioxide to be adsorbed by the adsorbent 22C of the adsorption unit 20C.

[0055] In step S32, a desorption process is performed for the adsorption unit 20B by opening the CO2 capture valve V3B and the steam supply valve V6B and driving the CO2 capture pump 12. This causes carbon dioxide to be desorbed from the adsorbent 22B of the adsorption unit 20B, and the carbon dioxide sent to the CO2 capture path 46 can be captured as product carbon dioxide.

[0056] In step S34, the cleaning process is performed for the adsorption unit 20A by opening the CO supply valve V2A, the cleaning off-gas valve V5A, and the three-way valve V9 on the adsorption unit 20 side. This allows impurities remaining in the adsorption unit 20A to be replaced with carbon dioxide.

[0057] In step S36, the three-way valve V10 is switched to the side toward the cleaning off-gas reservoir 14, and the cleaning off-gas is stored in the cleaning off-gas reservoir 14 (cleaning off-gas storage process).

[0058] FIG. 7(A) shows the open / closed states of the valves and the gas flow after steps S30 to S36 have been executed.

[0059] In step S38, it is determined whether a predetermined time T1 has elapsed since the execution of the cleaning process (step S34). The predetermined time T1 is set to the time required to clean the adsorption unit 20A. If the determination is affirmative, in step S20, the CO2 supply valve V2A, the cleaning off-gas valve V5A, and the three-way valve V9 on the adsorption unit 20 side are closed (closing process) (see FIG. 7(B)).

[0060] Next, in step S42, it is determined whether a predetermined time T2 has elapsed since the execution of the adsorption step (step S30). The predetermined time T2 is set to the time required for carbon dioxide to be sufficiently adsorbed by the adsorbent 22C of the adsorption section 20C. If the determination is affirmative, in step S44, a rough cleaning step is executed. The rough cleaning step is executed by opening the cleaning off-gas supply valve V7 while keeping the raw material supply valve V1C and the off-gas exhaust valve V4C open, switching the three-way valve V8 so that the cleaning off-gas supply path 38 communicates with the downstream side of the raw material gas supply path 42, and driving the off-gas blower 16 (see FIG. 7(C)). This allows impurities remaining in the adsorption section 20C to be replaced with the cleaning off-gas. The cleaning off-gas has a relatively high carbon dioxide concentration, so it can remove impurities from the adsorption section 20C to a certain extent.

[0061] Next, in step S46, it is determined whether a predetermined time T3 has elapsed since the execution of the desorption process (step S32). The predetermined time T3 is set to the time required for the carbon dioxide adsorbed by the adsorbent 22B of the adsorption section 20B to be sufficiently desorbed. If the determination is affirmative, in step S48, the cleaning off-gas supply valve V7 is closed and the three-way valve V8 is switched so that the cleaning off-gas supply path 38 and the downstream side of the raw material gas supply path 42 are in communication with each other, thereby completing the second process.

[0062] 8, in step S50, the adsorption step is performed by opening the raw material supply valve V1B and the off-gas exhaust valve V4B for the adsorption unit 20B, thereby causing carbon dioxide to be adsorbed by the adsorbent 22B of the adsorption unit 20B.

[0063] In step S52, the desorption process is performed for the adsorption unit 20A by opening the CO2 recovery valve V3A and the steam supply valve V6A and driving the CO2 recovery pump 12. This causes carbon dioxide to be desorbed from the adsorbent 22A of the adsorption unit 20A, and the carbon dioxide sent to the CO2 recovery path 46 can be recovered as product carbon dioxide.

[0064] In step S54, a cleaning process is performed for the adsorption unit 20C by opening the CO supply valve V2C, the cleaning off-gas valve V5C, and the three-way valve V9 on the adsorption unit 20 side. This allows impurities remaining in the adsorption unit 20C to be replaced with carbon dioxide.

[0065] In step S56, the three-way valve V10 is switched to the side toward the cleaning off-gas reservoir 14, and the cleaning off-gas is stored in the cleaning off-gas reservoir 14 (cleaning off-gas storage process).

[0066] FIG. 9(A) shows the open / closed states of the valves and the gas flow after steps S50 to S56 have been executed.

[0067] In step S58, it is determined whether a predetermined time T1 has elapsed since the execution of the cleaning process (step S54). The predetermined time T1 is set to the time required to clean the adsorption unit 20C. If the determination is affirmative, in step S60, the CO2 supply valve V2C, the cleaning off-gas valve V5C, and the three-way valve V9 on the adsorption unit 20 side are closed (closing process) (see FIG. 9(B)).

[0068] Next, in step S62, it is determined whether a predetermined time T2 has elapsed since the execution of the adsorption step (step S50). The predetermined time T2 is set to the time required for carbon dioxide to be sufficiently adsorbed by the adsorbent 22B of the adsorption section 20B. If the determination is affirmative, in step S64, a rough cleaning step is executed. The rough cleaning step is executed by opening the cleaning off-gas supply valve V7 while keeping the raw material supply valve V1B and the off-gas exhaust valve V4B open, switching the three-way valve V8 so that the cleaning off-gas supply path 38 communicates with the downstream side of the raw material gas supply path 42, and driving the off-gas blower 16 (see FIG. 9(C)). This allows impurities remaining in the adsorption section 20B to be replaced with the cleaning off-gas. The cleaning off-gas has a relatively high carbon dioxide concentration, so it can remove impurities from the adsorption section 20B to a certain extent.

[0069] Next, in step S66, it is determined whether a predetermined time T3 has elapsed since the execution of the desorption process (step S52). The predetermined time T3 is set to the time required for the carbon dioxide adsorbed by the adsorbent 22A of the adsorption section 20A to be sufficiently desorbed. If the determination is affirmative, in step S68, the cleaning off-gas supply valve V7 is closed and the three-way valve V8 is switched so that the cleaning off-gas supply path 38 and the downstream side of the raw material gas supply path 42 are in communication with each other, thereby completing the third process.

[0070] FIG. 10 shows the timings of the first step, the second step, and the third step in each of the adsorption units 20A, 20B, and 20C.

[0071] In the carbon dioxide capture system 10 of this embodiment, the adsorption unit 20 is roughly cleaned using the cleaning off-gas delivered from the adsorption unit 20 in the cleaning step. The cleaning off-gas has a higher carbon dioxide concentration than the off-gas delivered when the raw material gas is supplied to the adsorption unit 20. Therefore, by supplying the cleaning off-gas to the adsorption unit 20 before the cleaning treatment, impurities (substances other than carbon dioxide) in the adsorption unit 20 can be discharged. This makes it possible to reduce the amount of carbon dioxide-rich gas used in the cleaning step, thereby improving the carbon dioxide capture efficiency.

[0072] Furthermore, during rough cleaning, the cleaning off-gas is supplied from the one-side connecting portion 24 side, so that impurities during rough cleaning can be sent out from the off-gas sending path 32.

[0073] In addition, in this embodiment, water vapor is used to desorb carbon dioxide, and the water vapor can be easily separated after desorption. [Explanation of symbols]

[0074] 10 Carbon dioxide capture system 20 Adsorption part 22 Adsorbents 24 One-side connection part (one side) 26 Other side connection part (other side) 32 Off-gas outlet 46 CO2 recovery line (carbon dioxide gas transmission line) 50 control unit (cleaning off-gas storage execution unit) 18 Steam supply section

Claims

1. A carbon dioxide capture method using a carbon dioxide capture system including a plurality of adsorption units each containing an adsorbent that adsorbs and desorbs carbon dioxide, an adsorption step of supplying a raw material gas containing carbon dioxide to the adsorption section and adsorbing carbon dioxide onto the adsorbent; a cleaning step of supplying carbon dioxide gas to the adsorption section and cleaning the adsorption section while the adsorbent has adsorbed carbon dioxide; a cleaning off-gas storage step of storing the off-gas delivered from the adsorption section as cleaning off-gas during the cleaning step; a desorption step of desorbing carbon dioxide from the adsorbent after the cleaning step; a rough cleaning step of supplying the cleaning off-gas to the adsorption section after the adsorption step and before the cleaning step to perform rough cleaning; A carbon dioxide capture method.

2. In the desorption step, water vapor is supplied to the adsorption section. The carbon dioxide recovery method according to claim 1.

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