Carbon dioxide recovery device and recovery method

Abstract

To provide a recovery device and a recovery method capable of improving carbon dioxide recovery efficiency.SOLUTION: A recovery device according to one embodiment includes: an adsorption tower for recovering a target gas containing carbon dioxide separated from a raw gas by making a first adsorbent and a second adsorbent adsorb carbon dioxide in the raw gas and desorbing carbon dioxide from the first and second adsorbents; a first line for introducing the raw gas into the adsorption tower; a second line for discharging an off-gas separated from the raw gas by adsorption of carbon dioxide to the first and second adsorbents from the adsorption tower; and a third line for recovering the target gas from the adsorption tower. The first adsorbent is a zeolite-based adsorbent, and the second adsorbent is a carbon-based adsorbent. The second adsorbent is disposed downstream of the first adsorbent in a flow direction of the raw gas in the adsorption tower. The first line and the third line are connected to an upstream end portion of the adsorption tower in the flow direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Carbon dioxide is seen as a major cause of global warming, and there has been a growing movement worldwide to curb emissions. Various research efforts are being actively pursued to enable the capture and storage of carbon dioxide from exhaust gases without releasing it into the atmosphere. For example, known carbon dioxide capture methods include pressure swing adsorption, membrane separation and concentration, and chemical absorption, which utilizes reactive absorption by basic compounds. However, the current cost of carbon dioxide capture is high, and these methods have not yet reached the stage of widespread adoption.

[0003] The pressure swing adsorption method involves repeatedly carrying out an adsorption process in which a mixed gas is introduced at a predetermined pressure into an adsorption tower filled with an adsorbent to adsorb specific gas components, and a desorption process in which the adsorption tower to which the specific gas components have been adsorbed is depressurized to a predetermined pressure and the gas components are recovered or discharged.

[0004] A specific method for recovering carbon dioxide by pressure swing adsorption is known in which carbon dioxide is physically adsorbed onto an adsorbent, and the pressure is reduced using a vacuum pump to desorb the carbon dioxide adsorbed onto the adsorbent, thereby concentrating and recovering the carbon dioxide (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. 1-172204 Summary of the Invention [Problem to be solved by the invention]

[0006] The carbon dioxide recovery method using pressure swing adsorption still has room for improvement in terms of recovery rate.

[0007] Therefore, an object of the present disclosure is to provide a capture device and a capture method that can improve the carbon dioxide capture rate. [Means for solving the problem]

[0008] One aspect of the present disclosure provides a recovery device as described in the following paragraphs.

[0009] [1] A recovery apparatus comprising: an adsorption tower for adsorbing carbon dioxide in a raw material gas onto a first adsorbent and a second adsorbent, and recovering a target gas containing the carbon dioxide separated from the raw material gas by desorbing the carbon dioxide from the first adsorbent and the second adsorbent; a first line for introducing the raw material gas into the adsorption tower; a second line for discharging, from the adsorption tower, an off-gas separated from the raw material gas by adsorption of the carbon dioxide onto the first adsorbent and the second adsorbent; and a third line for recovering the target gas from the adsorption tower, wherein the first adsorbent is a zeolite-based adsorbent, and the second adsorbent is a carbon-based adsorbent, and the second adsorbent is disposed downstream of the first adsorbent in the flow direction of the raw material gas within the adsorption tower; and the first line and the third line are connected to an upstream end of the adsorption tower in the flow direction of the raw material gas within the adsorption tower.

[0010] [2] The recovery device according to [1], wherein the proportion of the second adsorbent in the adsorption tower is greater than the proportion of the first adsorbent.

[0011] [3] The recovery device according to [1] or [2], wherein the proportion of the second adsorbent in the adsorption tower is at least twice the proportion of the first adsorbent.

[0012] Another aspect of the present disclosure provides a recovery method as described below.

[0013] [4] A recovery method comprising: an adsorption step of introducing a raw material gas into an adsorption tower, adsorbing carbon dioxide in the raw material gas onto a first adsorbent and a second adsorbent, and discharging an off-gas separated from the raw material gas as a result of the carbon dioxide being adsorbed onto the first adsorbent and the second adsorbent from the adsorption tower; and a desorption step of desorbing the carbon dioxide adsorbed onto the first adsorbent and the second adsorbent in the adsorption step from the first adsorbent and the second adsorbent, and recovering a target gas containing the carbon dioxide in the adsorption tower, wherein the first adsorbent is a zeolite-based adsorbent, and the second adsorbent is a carbon-based adsorbent, and the second adsorbent is disposed downstream of the first adsorbent in the flow direction of the raw material gas within the adsorption tower; and the desorption step recovers the target gas from the first adsorbent side of the adsorption tower. [Effects of the Invention]

[0014] According to the recovery method and recovery device of the present disclosure, it is possible to recover carbon dioxide with high purity and to achieve an improved recovery rate. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a recovery device according to an embodiment. [Figure 2] FIG. 2 is a chart showing the results of Examples 1 to 7. [Figure 3] FIG. 3 is a table showing the results of Examples 8 to 12 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The same elements are designated by the same reference numerals, and duplicate explanations will be omitted. The dimensional proportions in the drawings do not necessarily correspond to those in the description.

[0017] Fig. 1 is a schematic diagram showing the configuration of an example of a carbon dioxide recovery apparatus according to one embodiment. The pressure swing adsorption apparatus 1 shown in Fig. 1 is an apparatus used to separate and recover carbon dioxide (CO2) from a feed gas G1 containing carbon dioxide. Therefore, the pressure swing adsorption apparatus 1 is also a recovery apparatus that recovers carbon dioxide. Hereinafter, the pressure swing adsorption apparatus 1 will be referred to as "adsorption apparatus 1."

[0018] The raw material gas G1 is a mixed gas of carbon dioxide and impurity gases such as nitrogen and oxygen. Examples of the raw material gas G1 include combustion exhaust gas. The raw material gas G1 is supplied from a raw material gas supply source (not shown) such as a boiler in a chemical plant or the like. The carbon dioxide concentration contained in the raw material gas G1 supplied from the raw material gas supply source is, for example, 40 vol% or less, for example, 20 vol% or less or 15 vol% or less. The carbon dioxide concentration contained in the raw material gas G1 is preferably 5.0 vol% or more and 15.0 vol% or less, and more preferably 7 vol% or more and 12 vol% or less. The raw material gas G1 supplied from the raw material gas supply source may be a compressed gas at atmospheric pressure or higher. If the raw material gas G1 supplied from the raw material gas supply source is not a compressed gas, it may be compressed using a blower or the like.

[0019] [Adsorption device] The adsorption apparatus 1 has at least one adsorption tower 10. The adsorption tower 10 is a tower for concentrating the carbon dioxide in the raw material gas G1 by adsorbing the carbon dioxide contained in the raw material gas G1 onto an adsorbent by a pressure swing adsorption (PSA) method and then desorbing the carbon dioxide.

[0020] In this embodiment, the gas extracted from the adsorption tower and containing concentrated carbon dioxide is referred to as "recovered gas." In this embodiment, the recovered gas corresponds to the target gas. The gas discharged from the adsorption tower and containing gas components other than carbon dioxide adsorbed to the adsorbent in the raw material gas G1 is referred to as "off-gas" (exhaust gas).

[0021] The adsorption tower 10 has a gas passage port 11 and a gas passage port 12. In the flow direction (predetermined direction) of the raw material gas G1 introduced into the adsorption tower 10 within the adsorption tower 10, the gas passage port 11 is located at the upstream end of the adsorption tower 10, and the gas passage port 12 is located at the downstream end of the adsorption tower 10.

[0022] The adsorption tower 10 contains a first adsorbent and a second adsorbent. In this embodiment, the adsorption tower 10 has a lower adsorption layer (first adsorption layer) 13 formed from the first adsorbent and an upper adsorption layer (second adsorption layer) 14 formed from the second adsorbent. The terms "lower" and "upper" in the lower adsorption layer 13 and the upper adsorption layer 14 refer to the positional relationship shown in FIG. 1 . The lower adsorption layer 13 and the upper adsorption layer 14 are arranged in this order from the gas passage port 11 toward the gas passage port 12.

[0023] The first adsorbent is a zeolite-based adsorbent. The zeolite-based adsorbent is an adsorbent known as zeolite X. An example of the first adsorbent is zeolite.

[0024] The zeolite is, for example, a zeolite in which at least a portion of the cation species has been exchanged with Na ions, and from the viewpoint of the specific surface area of ​​the adsorbent, a zeolite having a three-dimensional skeleton is preferred. Examples of zeolites having a three-dimensional skeleton include FAU-type, LTA-type, MFI-type, AEI-type, CHA-type, EMT-type, ERI-type, GIS-type, MEL-type, MSE-type, and RHO-type zeolites, with FAU-type zeolites being more preferred.

[0025] From the viewpoint of pressure loss in the adsorption tower 10 in the pressure swing adsorption method, zeolite having a particle size of 1.0 mm or more and 2.0 mm or less is preferred, and the packing density of the zeolite in the adsorption tower 10 is preferably 0.5 kg / L or more and 1.0 kg / L or less.

[0026] The second adsorbent is a carbon-based adsorbent known as a CMS (carbon molecular sieve). An example of the second adsorbent is activated carbon.

[0027] Activated carbon is made from coconut shells, for example. The specific surface area of ​​activated carbon is, for example, 500 m 2 / g or more and 2500m 2 / g or less, and the pore size is, for example, 1 nm or more and 20 nm or less. From the viewpoint of pressure loss in the adsorption tower 10 in the pressure swing adsorption method, activated carbon having a particle size of 1.0 mm or more and 2.5 mm or less is preferred, and the packing density of the activated carbon in the adsorption tower 10 is preferably 0.5 kg / L or more and 1.0 kg / L or less.

[0028] The proportion of the second adsorbent in the adsorption tower 10 may be greater than the proportion of the first adsorbent (for example, it may be more than twice as large). The "proportion of the second adsorbent" refers to the proportion of the amount of the second adsorbent relative to the total amount of adsorbent in the adsorption tower 10, and the "proportion of the first adsorbent" refers to the proportion of the amount of the first adsorbent relative to the total amount of adsorbent in the adsorption tower 10. The "total amount of adsorbent in the adsorption tower 10" is the sum of the amount of the first adsorbent and the amount of the second adsorbent. The "amount" here refers to the volume of the adsorbent packed in the adsorption tower, and the adsorbent is packed while applying sufficient vibration to the adsorption tower to achieve the closest possible packing.

[0029] Unless otherwise specified, the following describes an embodiment in which the adsorption apparatus 1 includes three adsorption towers 10. When the three adsorption towers 10 are to be distinguished from one another, the three adsorption towers 10 are referred to as adsorption tower 10a, adsorption tower 10b, and adsorption tower 10c.

[0030] Each of the adsorption towers 10a, 10b, and 10c is connected to an introduction flow path (first line) 21, an off-gas flow path (second line) 22, and a recovered gas flow path (third line) 23. At least one of a pressure release gas flow path 24 and a cleaning gas flow path 25 may be connected to each of the adsorption towers 10a, 10b, and 10c. Each gas flow path is configured using gas piping. In this embodiment, a configuration in which the pressure release gas flow path 24 and the cleaning gas flow path 25 are connected to each of the adsorption towers 10a, 10b, and 10c will be described.

[0031] The inlet flow path 21 is a gas flow path for introducing the raw material gas G1 from a raw material gas supply source into the adsorption towers 10a, 10b, and 10c. The inlet flow path 21 may be provided with a buffer tank 31 for storing the raw material gas G1 from the raw material gas supply source. The downstream end of the inlet flow path 21 (the portion closer to the adsorption towers 10a, 10b, and 10c) branches off toward the adsorption towers 10a, 10b, and 10c and is connected to the gas passages 11 of the adsorption towers 10a, 10b, and 10c.

[0032] On-off valves 41a, 41b, and 41c corresponding to the adsorption towers 10a, 10b, and 10c are provided at the downstream end (the portion closer to the adsorption towers 10a, 10b, and 10c) of the introduction flow path 21. By individually opening and closing the on-off valves 41a, 41b, and 41c, the source gas G1 can be introduced into each of the adsorption towers 10a, 10b, and 10c.

[0033] A blower 32 may be provided in the inlet flow path 21. The blower 32 is disposed upstream of the on-off valves 41a, 41b, and 41c. As shown in FIG. 1, in a configuration in which the buffer tank 31 is provided in the inlet flow path 21, the blower 32 is disposed between the buffer tank 31 and the on-off valves 41a, 41b, and 41c. The blower 32 may be used to compress the source gas G1 when the source gas G1 is not a compressed gas.

[0034] The off-gas flow path 22 is a gas flow path for discharging gas (off-gas) to be discharged from the adsorption towers 10a, 10b, and 10c to the outside (normal pressure space) of the adsorption apparatus 1. The upstream side of the off-gas flow path 22 (the portion closer to the adsorption towers 10a, 10b, and 10c) branches off toward the adsorption towers 10a, 10b, and 10c and is connected to the gas passage ports 12 of the adsorption towers 10a, 10b, and 10c.

[0035] On-off valves 42a, 42b, and 42c corresponding to the adsorption towers 10a, 10b, and 10c are provided at the upstream end of the off-gas passage 22. The on-off valves 42a, 42b, and 42c individually open and close the communication between each of the adsorption towers 10a, 10b, and 10c and the off-gas passage 22, thereby allowing the off-gas G2 to be discharged from each of the adsorption towers 10a, 10b, and 10c.

[0036] The downstream end of the off-gas passage 22 (the end opposite the adsorption towers 10a, 10b, and 10c) is an outlet for the off-gas G2 and communicates with a normal pressure space under atmospheric pressure. The off-gas G2 discharged through the off-gas passage 22 is discharged to the outside of the adsorption apparatus 1. A pressure control valve 43 for adjusting the back pressure is provided on the downstream end side of the off-gas passage 22.

[0037] The pressure release gas flow path 24 is a gas flow path for discharging gas (hereinafter referred to as "pressure release gas G3") discharged from the adsorption towers 10a, 10b, and 10c to the outside of the adsorption apparatus 1 when the pressure in the adsorption towers 10a, 10b, and 10c is released in a pressure release step described below. The pressure release gas G3 is also an off-gas because it is a gas discharged from the adsorption towers 10a, 10b, and 10c. The upstream end of the pressure release gas flow path 24 (the portion closer to the adsorption towers 10a, 10b, and 10c) branches toward the adsorption towers 10a, 10b, and 10c and is connected to the gas passage ports 12 at the downstream ends of the adsorption towers 10a, 10b, and 10c. The downstream end of the pressure release gas flow path 24 is an outlet for the pressure release gas G3 and communicates with a normal-pressure space under atmospheric pressure.

[0038] The pressure release gas flow path 24 is provided with on-off valves 44a, 44b, and 44c corresponding to the adsorption towers 10a, 10b, and 10c. The on-off valves 44a, 44b, and 44c individually open and close the communication between each of the adsorption towers 10a, 10b, and 10c and the pressure release gas flow path 24, thereby allowing the pressure release gas G3 to be discharged from each of the adsorption towers 10a, 10b, and 10c. A pressure control valve 45 for adjusting back pressure is provided at the downstream end of the pressure release gas flow path 24.

[0039] The recovered gas flow path 23 is a gas flow path for flowing the recovered gas extracted from the adsorption towers 10a, 10b, and 10c into the buffer tank 34 via the vacuum pump 33. The upstream end of the recovered gas flow path 23 (the portion closer to the adsorption towers 10a, 10b, and 10c) branches off toward the adsorption towers 10a, 10b, and 10c and is connected to the gas passage ports 11 of the adsorption towers 10a, 10b, and 10c. The downstream end of the recovered gas flow path 23 is connected to the buffer tank 34 via the vacuum pump 33. The recovered gas that flows into and is stored in the buffer tank 34 is extracted from the buffer tank 34 through the gas transport flow path 26 and used as product gas G4.

[0040] For example, the product gas G4 is supplied to a downstream process such as a liquefaction device. The use of the product gas G4 is not limited. In the example shown in FIG. 1, the recovered gas is temporarily stored in the buffer tank 34, but, for example, the buffer tank 34 does not have to be provided. In this case, the recovered gas flowing through the recovered gas flow path 23 can be directly supplied to a downstream process as the product gas G4.

[0041] On-off valves 46a, 46b, and 46c corresponding to the adsorption towers 10a, 10b, and 10c are provided at the upstream end of the recovered gas flow path 23. The on-off valves 46a, 46b, and 46c individually open and close the connection between each of the adsorption towers 10a, 10b, and 10c and the recovered gas flow path 23, allowing the recovered gas to flow from each of the adsorption towers 10a, 10b, and 10c to the recovered gas flow path 23.

[0042] An on-off valve 47b is provided in the collected gas flow path 23 between the vacuum pump 33 and the buffer tank 34. The on-off valve 47b can control the inflow of the collected gas into the buffer tank 34.

[0043] The cleaning gas flow path 25 is a gas flow path for passing cleaning gas through the adsorption towers 10a, 10b, and 10c in the cleaning step described below. The downstream end of the cleaning gas flow path 25 (the portion closer to the adsorption towers 10a, 10b, and 10c) branches off toward the adsorption towers 10a, 10b, and 10c and is connected to the gas passage ports 11 of each of the adsorption towers 10a, 10b, and 10c. The upstream end of the cleaning gas flow path 25 is connected to the recovered gas flow path 23. Specifically, in the configuration illustrated in FIG. 1 , the connection point X between the upstream end of the cleaning gas flow path 25 and the recovered gas flow path 23 is located between the vacuum pump 33 and the on-off valve 47b in the recovered gas flow path 23.

[0044] An on-off valve 47a is provided in the cleaning gas flow path 25 near the connection part X. As shown in FIG. 1, the on-off valve 47a is provided between the connection part X of the cleaning gas flow path 25 and the recovered gas flow path 23 and on-off valves 48a, 48b, and 48c, which will be described later. The on-off valve 47a can control the flow of the recovered gas flowing in the recovered gas flow path 23 to the cleaning gas flow path 25. By opening the on-off valve 47a, the recovered gas flowing in the cleaning gas flow path 25 functions as a cleaning gas.

[0045] On-off valves 48a, 48b, and 48c corresponding to the adsorption towers 10a, 10b, and 10c are provided at the downstream end of the cleaning gas passage 25. The on-off valves 48a, 48b, and 48c individually open and close the communication between the cleaning gas passage 25 and each of the adsorption towers 10a, 10b, and 10c, respectively, so that cleaning gas can be supplied to each of the adsorption towers 10a, 10b, and 10c.

[0046] The cleaning gas flow path 25 may be provided with a blower 35 for causing the cleaning gas to flow toward the on-off valves 48a, 48b, and 48c.

[0047] An example of a method for recovering carbon dioxide using the adsorption apparatus 1 will be described. The carbon dioxide recovery method is a method for recovering carbon dioxide from a raw material gas G1 by pressure swing adsorption. In this example of the carbon dioxide recovery method, the carbon dioxide contained in the raw material gas G1 is concentrated, and the concentrated carbon dioxide (recovered gas) is recovered.

[0048] The carbon dioxide recovery method includes an adsorption step and a desorption step. In the carbon dioxide recovery method, the carbon dioxide contained in the raw material gas G1 is adsorbed by the first adsorbent and the second adsorbent in the adsorption step, and then the carbon dioxide is desorbed from the first adsorbent and the second adsorbent to obtain concentrated carbon dioxide. Therefore, the adsorption step and the desorption step correspond to a carbon dioxide concentration step.

[0049] In the carbon dioxide recovery method of this embodiment, at least one of a pressure release step and a washing step may be further carried out between the adsorption step and the desorption step. When recovering carbon dioxide, a first desorption step and a second desorption step may be carried out as desorption steps to obtain high-purity carbon dioxide.

[0050] In the following, a description will be given of a mode in which the pressure release step and the cleaning step are performed, and the first and second desorption steps are performed in the desorption step. Since the steps performed in the adsorption towers 10a, 10b, and 10c are the same, only the steps performed in the adsorption tower 10a will be described.

[0051] [Adsorption process] In the adsorption process, the on-off valves 41a and 42a are opened to allow the raw material gas G1 to flow into the adsorption tower 10a, and carbon dioxide contained in the raw material gas G1 is adsorbed by the first and second adsorbents stored in the adsorption tower 10a. During this process, the on-off valves 44a, 48a, and 46a are closed, and the pressure in the adsorption tower 10a is adjusted by the pressure control valve 43 to an adsorption pressure that appropriately exceeds atmospheric pressure and is suitable for adsorption of carbon dioxide into the first and second adsorbents. The adsorption pressure is, for example, 0 kPaG or higher and 100 kPaG or lower. In the adsorption process, the portion of the raw material gas G1 that is not adsorbed by the adsorbents is discharged as off-gas G2 from the off-gas flow path 22 to the outside of the adsorption device 1. The "G" in the pressure unit "kPaG" indicates that the pressure is a gauge pressure.

[0052] In the adsorption step, the raw material gas G1 is introduced through the gas passage port 11. Because the on-off valve 42a is open, the raw material gas G1 flows from the gas passage port 11 toward the gas passage port 12. That is, the flow direction of the raw material gas G1 in the adsorption tower 10a is from the gas passage port 11 toward the gas passage port 12. The lower adsorption layer 13 and the upper adsorption layer 14 are arranged in this order along the flow direction of the raw material gas G1. Therefore, in the adsorption step, the raw material gas G1 passes through the lower adsorption layer 13 and the upper adsorption layer 14 in this order.

[0053] The adsorption step may be performed for 150 seconds or less. The adsorption step is typically performed for 70 seconds or more. Therefore, an example of the adsorption step time is 70 seconds or more and 150 seconds or less. The adsorption rates of carbon dioxide and impurities other than carbon dioxide (oxygen, nitrogen, etc.) to the adsorbents are different, and typically, the adsorption rate of carbon dioxide to the first adsorbent and the second adsorbent is faster than that of impurities. In particular, the adsorption rate of carbon dioxide to the second adsorbent is faster than that of impurities. Therefore, if the adsorption step is performed for 150 seconds or less, the difference in adsorption rates can be utilized to more selectively adsorb carbon dioxide to the second adsorbent.

[0054] [Pressure release process] The pressure release step is performed after the adsorption step. In the pressure release step, the on-off valves 41a and 42a are closed, and the on-off valve 44a is opened to release the pressure in the adsorption tower 10a. At this time, the pressure in the adsorption tower 10a is adjusted by the pressure control valve 45 to a pressure release pressure that is lower than the pressure in the adsorption step and is suitable for pressure release. An example of the pressure release pressure is -9.9 kPaG or more and 30 kPaG or less. In the pressure release step, the portion of the raw material gas G1 that is not adsorbed by the adsorbent is discharged as pressure release gas G3 from the pressure release gas flow path 24 to the outside of the adsorption device 1.

[0055] [Cleaning process] The cleaning step is performed after the pressure release step. In the cleaning step, the on-off valve 48a is opened and the blower 35 is operated to cause the cleaning gas to flow into the adsorption tower 10a through the cleaning gas flow path 25. The cleaning gas that has flowed into the adsorption tower 10a is discharged to the outside of the adsorption apparatus 1 through the pressure release gas flow path 24.

[0056] In the cleaning step, the cleaning gas flows through the adsorption tower 10a, and gas components other than carbon dioxide that have adhered to the walls of the adsorption tower 10a are carried along with the cleaning gas and discharged to the outside of the adsorption apparatus 1. That is, the cleaning gas discharges the gas components other than carbon dioxide that remain in the adsorption tower 10a from the adsorption tower 10a.

[0057] The cleaning gas in this embodiment is the recovered gas obtained by performing the first desorption step in one of the adsorption towers 10a, 10b, and 10c other than the adsorption tower in which the cleaning step is being performed, and is also the recovered gas returned to the adsorption tower in which the cleaning step is being performed via the cleaning gas flow path 25. For example, when the cleaning step is being performed in the adsorption tower 10a, the recovered gas from the adsorption tower 10b or 10c is returned to the adsorption tower 10a and used as the cleaning gas for cleaning the adsorption tower 10a.

[0058] The cleaning gas is the recovered gas obtained by carrying out the first desorption step, and therefore is a gas containing concentrated carbon dioxide.

[0059] In the cleaning step, the on-off valve 47b is closed and the on-off valve 47a is open, so that the recovered gas obtained by carrying out the first desorption step flows from the recovered gas flow path 23 to the cleaning gas flow path 25.

[0060] Note that even after the adsorption tower performing the first desorption step has transitioned to the second desorption step, the adsorption tower that had been performing the cleaning step may continue the cleaning step. As will be described later, in the second desorption step, the on-off valve 47a is closed while the on-off valve 47b is opened, and in this case, the cleaning gas remaining in the cleaning gas passage 25 flows to the cleaning step.

[0061] As described above, when the recovered gas is used as a cleaning gas, the carbon dioxide contained in the recovered gas is re-adsorbed by the adsorbent.

[0062] [First desorption process] The first desorption step is performed after the cleaning step. The first desorption step is an initial step in the desorption step. In the first desorption step, the on-off valves 48a and 44a are closed, while the on-off valve 46a is opened. In this state, the vacuum pump 33 is operated to reduce the pressure in the adsorption tower 10a, and the gas in the adsorption tower 10a is caused to flow into the recovered gas flow path 23. In the first desorption step, the pressure in the adsorption tower 10a is reduced as described above, causing carbon dioxide to be desorbed from the first adsorbent and the second adsorbent. As a result, the gas (recovered gas) flowing into the recovered gas flow path 23 contains carbon dioxide.

[0063] In the first desorption step, the vacuum pump 33 is operated with the on-off valve 46a open, thereby reducing the pressure in the adsorption tower 10a and causing the gas in the adsorption tower 10a to flow into the recovered gas flow path 23. Therefore, in the first desorption step, the gas in the adsorption tower 10a flows in the direction from the gas passage port 12 toward the gas passage port 11.

[0064] In the first desorption step, the on-off valve 47b is closed, while the on-off valve 47a is open, so that the recovered gas (initial recovered gas) that has flowed into the recovered gas flow path 23 in the first desorption step flows into the cleaning gas flow path 25, as described in the cleaning step.

[0065] The time for performing the first desorption step may be any time that allows gas components other than carbon dioxide adhering to the wall surfaces of the adsorption tower 10a to be sufficiently discharged, and that the carbon dioxide adsorbed on the adsorbent is not desorbed more than necessary. The time for performing the first desorption step is, for example, 0% to 75% of the time for performing the desorption step (a step including the first desorption step and the second desorption step). The time for performing the first desorption step may be, for example, 0 seconds to 75 seconds, assuming that the desorption time is 100 seconds.

[0066] [Second desorption process] The second desorption step is a step in the desorption step that occurs a certain time after the start of the first desorption step. In the second desorption step, the on-off valve 47a is closed, while the on-off valve 47b is opened. As a result, the recovered gas flowing from the adsorption tower 10a to the recovered gas flow path 23 flows into the buffer tank 34 and is stored there. The recovered gas stored in the buffer tank 34 is appropriately extracted as product gas G4. In the second desorption step, the gas in the adsorption tower 10a flows from the gas passage 12 toward the gas passage 11, as in the first desorption step. The time for which the second desorption step is performed is, for example, 25% or more and 100% or less of the time for which the desorption step is performed. For example, if the desorption time is 100 seconds, the time for which the second desorption step is performed may be 25 seconds or more and 100 seconds or less.

[0067] The second desorption step is a step that occurs after the first desorption step has been performed for a certain period of time, and therefore the pressure inside the adsorption tower 10a is lower than when the first desorption step was started. Therefore, after the transition from the first desorption step to the second desorption step, more carbon dioxide is desorbed from the adsorbent. Therefore, in the second desorption step, the gas flowing from the adsorption tower 10a to the recovered gas flow path 23 is a recovered gas containing concentrated carbon dioxide. Furthermore, since impurities remaining in the adsorption tower 10a in the first desorption step are also discharged, a highly pure recovered gas can be obtained in the second desorption step.

[0068] In the adsorption tower 10a, the basic cycle is repeated, with the adsorption step, pressure release step, cleaning step, first desorption step, and second desorption step being the basic cycle.

[0069] In the adsorption tower 10b, the on-off valves 41b, 46b, 48b, 42b, and 44b are operated in the same manner as the corresponding on-off valves 41a, 46a, 48a, 42a, and 44a, to perform the adsorption, pressure release, cleaning, first desorption, and second desorption steps. In the adsorption tower 10b, the adsorption, pressure release, cleaning, first desorption, and second desorption steps form a basic cycle, which is repeated. The on-off states of the on-off valves 47a and 47b in the cleaning, first desorption, and second desorption steps are the same as in the adsorption tower 10a.

[0070] In the adsorption tower 10c, the on-off valves 41c, 46c, 48c, 42c, and 44c are operated in the same manner as the corresponding on-off valves 41a, 46a, 48a, 42a, and 44a, to perform the adsorption, pressure release, cleaning, first desorption, and second desorption steps. In the adsorption tower 10c, the adsorption, pressure release, cleaning, first desorption, and second desorption steps form a basic cycle, which is repeated. The on-off states of the on-off valves 47a and 47b in the cleaning, first desorption, and second desorption steps are the same as in the adsorption tower 10a.

[0071] In the adsorption apparatus 1, the basic cycles in the adsorption towers 10a, 10b, and 10c are performed with a time lag. For example, as shown in Table 1, while the adsorption step is performed in the adsorption tower 10a, the depressurization step and the cleaning step are performed in the adsorption tower 10b, and the first desorption step and the second desorption step are performed in that order in the adsorption tower 10c.

[0072] Specifically, the processes in adsorption towers 10b and 10c while the adsorption tower 10a is performing the adsorption process will be described. When the pressure release process is started in adsorption tower 10b, the first desorption process is performed in adsorption tower 10c. When the adsorption tower 10b transitions from the pressure release process to the cleaning process, the first desorption process is still being performed in adsorption tower 10c. When the adsorption tower 10c transitions from the first desorption process to the second desorption process, the cleaning process is still being performed in adsorption tower 10b. [Table 1]

[0073] The basic cycles in the adsorption towers 10a, 10b, and 10c are time-shifted, so that recovered gas (gas enriched with carbon dioxide) can be obtained intermittently at short intervals.

[0074] The adsorption tower 10 of the adsorption apparatus 1 contains a first adsorbent and a second adsorbent as adsorbents. The second adsorbent is disposed downstream of the first adsorbent in the flow direction of the raw material gas G1 within the adsorption tower 10. The first adsorbent is a zeolite-based adsorbent, and the second adsorbent is a carbon-based adsorbent. Therefore, in the adsorption step, the raw material gas G1 passes through the zeolite-based adsorbent (first adsorbent) and then through the carbon-based adsorbent (second adsorbent). Meanwhile, in the desorption step (first desorption step and second desorption step), the on-off valve 46a is opened to allow the recovered gas (concentrated gas) within the adsorption tower 10a to flow into the recovered gas flow path 23. In this case, in the desorption step (first desorption step and second desorption step), the recovered gas within the adsorption tower 10 flows from the gas passage 12 toward the gas passage 11. That is, the recovered gas flows from the first adsorbent side of the adsorption tower 10 to the recovered gas flow path 23.

[0075] Between zeolite-based adsorbents and carbon-based adsorbents, carbon-based adsorbents have a higher carbon dioxide desorption capacity, and carbon dioxide is more easily desorbed from carbon-based adsorbents. On the other hand, although zeolite-based adsorbents have a lower carbon dioxide adsorption capacity than carbon-based adsorbents, their adsorption capacity for impurities (oxygen, nitrogen, etc.) is lower than their carbon dioxide adsorption capacity, and therefore zeolite-based adsorbents have a better separation ratio between carbon dioxide and impurities than carbon-based adsorbents. Therefore, in a configuration of adsorption tower 10 in which the carbon-based adsorbent (second adsorbent) is located upstream in the gas flow direction (direction from gas passage port 12 toward gas passage port 11) within adsorption tower 10 during the desorption process, carbon dioxide is more easily recovered in a state where the carbon dioxide purity is high, thereby improving the recovery rate of high-purity carbon dioxide.

[0076] The recovery rate can be further improved when the ratio of the second adsorbent to the total amount of adsorbents in the adsorption tower 10 is greater (e.g., twice or more) than the ratio of the first adsorbent to the total amount of adsorbents. In particular, when the carbon dioxide concentration in the raw material gas G1 is 20 vol% or less, it is effective for the ratio of the second adsorbent to be greater than the ratio of the first adsorbent as described above.

[0077] Although the embodiments of the present invention have been described above, the present invention is not limited to the illustrated embodiments, and is intended to include all modifications within the scope of the claims, as well as the meaning and scope equivalent to the claims.

[0078] Although the configuration has been described in which a second adsorption layer formed from a second adsorbent is arranged on a first adsorption layer formed from a first adsorbent within an adsorption tower, for example, a first adsorption section filled with the first adsorbent and a second adsorption section filled with the second adsorbent may be connected by a gas flow path within a single adsorption tower.

[0079] Although the recovery device has been described as having three adsorption towers, the number of adsorption towers provided in the recovery device is not limited. For example, the number of adsorption towers provided in the recovery device may be one, or four or more. [Example]

[0080] Next, the present invention will be specifically described using examples, but the present invention is not limited to the following examples. In the description of Examples 1 to 12, the elements described in the embodiment are given the same reference numerals, and duplicated description will be omitted.

[0081] [Example 1] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 1 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0082] The carbon dioxide concentration in the raw material gas G1, the flow rate of the raw material gas G1 introduced into each of the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows. "NL" in the flow rate unit stands for normal liter. Carbon dioxide concentration: 10 vol% Raw material gas flow rate: 3.17 NL / min Raw material gas temperature: 25℃

[0083] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0084] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0085] The first and second adsorbents used were as follows: First adsorbent: Zeolite (Zeolite F-9HA manufactured by Tosoh Corporation) Second adsorbent: activated carbon (ZK420 manufactured by Osaka Gas Chemicals Co., Ltd.)

[0086] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 250 mL and 250 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c were 50% and 50%, respectively.

[0087] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0088] The implementation times of the adsorption step, depressurization step, washing step, first desorption step and second desorption step, the adsorption pressure in the adsorption step, the depressurization pressure in the depressurization step and the desorption pressure (pressure in the second desorption step) were as follows: Adsorption process: 100 seconds Pressure release process: 3 seconds Cleaning process: 97 seconds 1st desorption process: 13 seconds 2nd desorption process: 87 seconds Adsorption pressure (gauge pressure): 20 kPaG Discharge pressure (gauge pressure): 0 kPaG Desorption pressure (gauge pressure): -95kPaG

[0089] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 2. As shown in Figure 2, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 42.2 vol%, and the carbon dioxide recovery rate was 96.5%.

[0090] Fig. 2 is a chart showing the results of Examples 1 to 7. In Fig. 2, "feedstock CO2 concentration" is the carbon dioxide concentration in the feedstock gas G1, "feedstock gas flow rate" is the flow rate when the feedstock gas G1 is introduced into the adsorption towers 10a, 10b, and 10c, and "product CO2 concentration" is the carbon dioxide concentration in the recovered product gas G4.

[0091] [Example 2] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 2 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0092] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 10 vol% Raw material gas flow rate: 3.1 NL / min Raw material gas temperature: 25℃

[0093] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0094] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0095] The first and second adsorbents used were the same as those in Example 1.

[0096] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 150 mL and 350 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c were 30% and 70%, respectively.

[0097] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0098] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0099] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 2. As shown in Figure 2, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 40.7 vol%, and the carbon dioxide recovery rate was 97.4%.

[0100] [Example 3] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 3 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0101] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 10 vol% Raw material gas flow rate: 3.18 NL / min Raw material gas temperature: 25℃

[0102] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0103] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0104] The first and second adsorbents used were the same as those in Example 1.

[0105] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 350 mL and 150 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c, respectively, were 70% and 30%.

[0106] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0107] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0108] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 2. As shown in Figure 2, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 45.9 vol%, and the carbon dioxide recovery rate was 90.7%.

[0109] [Example 4] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 4 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0110] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 20 vol% Source gas flow rate: 3.2 NL / min Raw material gas temperature: 25℃

[0111] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0112] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0113] The first and second adsorbents used were the same as those in Example 1.

[0114] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 250 mL and 250 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c were 50% and 50%, respectively.

[0115] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0116] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0117] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 2. As shown in Figure 2, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 59.7 vol%, and the carbon dioxide recovery rate was 97.1%.

[0118] [Example 5] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 5 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0119] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 40 vol% Source gas flow rate: 3.2 NL / min Raw material gas temperature: 25℃

[0120] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0121] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0122] The first and second adsorbents used were the same as those in Example 1.

[0123] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 250 mL and 250 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c were 50% and 50%, respectively.

[0124] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0125] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0126] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 2. As shown in Figure 2, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 74.3 vol%, and the carbon dioxide recovery rate was 98.0%.

[0127] [Example 6] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 6 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0128] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 5 vol% Source gas flow rate: 3.4 NL / min Raw material gas temperature: 25℃

[0129] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0130] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0131] The first and second adsorbents used were the same as those in Example 1.

[0132] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 250 mL and 250 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c were 50% and 50%, respectively.

[0133] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0134] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0135] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 2. As shown in Figure 2, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 35.8 vol%, and the carbon dioxide recovery rate was 95.1%.

[0136] [Example 7] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 7 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0137] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 20 vol% Source gas flow rate: 3.2 NL / min Raw material gas temperature: 25℃

[0138] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0139] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0140] The first and second adsorbents used were the same as those in Example 1.

[0141] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 150 mL and 350 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c were 30% and 70%, respectively.

[0142] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0143] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0144] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 2. As shown in Figure 2, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 58.7 vol%, and the carbon dioxide recovery rate was 98.0%.

[0145] [Example 8] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 8 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0146] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 20 vol% Source gas flow rate: 3.2 NL / min Raw material gas temperature: 25℃

[0147] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0148] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0149] The first and second adsorbents used were the same as those in Example 1.

[0150] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 350 mL and 150 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c, respectively, were 70% and 30%.

[0151] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0152] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0153] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 3. As shown in Figure 3, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 63.8 vol%, and the carbon dioxide recovery rate was 95.1%.

[0154] 3 is a chart showing the results of Examples 8 to 12 and Comparative Examples 1 and 2. The meanings of "feedstock CO2 concentration," "feedstock gas flow rate," and "product CO2 concentration" in FIG. 3 are the same as those in FIG.

[0155] [Example 9] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 9 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0156] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 40 vol% Source gas flow rate: 3.3 NL / min Raw material gas temperature: 25℃

[0157] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0158] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0159] The first and second adsorbents used were the same as those in Example 1.

[0160] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 150 mL and 350 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c were 30% and 70%, respectively.

[0161] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0162] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0163] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 3. As shown in Figure 3, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 73.8 vol%, and the carbon dioxide recovery rate was 99.1%.

[0164] [Example 10] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 10 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0165] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 40 vol% Source gas flow rate: 3.3 NL / min Raw material gas temperature: 25℃

[0166] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0167] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0168] The first and second adsorbents used were the same as those in Example 1.

[0169] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 350 mL and 150 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c, respectively, were 70% and 30%.

[0170] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0171] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0172] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 3. As shown in Figure 3, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 78.2 vol%, and the carbon dioxide recovery rate was 96.7%.

[0173] [Example 11] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 11 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0174] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 5 vol% Source gas flow rate: 3.4 NL / min Raw material gas temperature: 25℃

[0175] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0176] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0177] The first and second adsorbents used were the same as those in Example 1.

[0178] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 150 mL and 350 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c were 30% and 70%, respectively.

[0179] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0180] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0181] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 3. As shown in Figure 3, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 35.3 vol%, and the carbon dioxide recovery rate was 95.2%.

[0182] [Example 12] Carbon dioxide was recovered from raw material gas G1 according to the recovery method described in the above embodiment using an adsorption apparatus (recovery apparatus) 1 equipped with three adsorption towers 10a, 10b, and 10c shown in Fig. 1. The adsorption apparatus 1 used in Example 12 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35, as shown in Fig. 1.

[0183] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 5 vol% Raw material gas flow rate: 3.7 NL / min Raw material gas temperature: 25℃

[0184] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0185] In each adsorption tower 10a, 10b, 10c, a lower adsorption layer 13 composed of a first adsorption material and an upper adsorption layer 14 composed of a second adsorption material were arranged in the order of lower adsorption layer 13 and upper adsorption layer 14 from gas passage port 11 toward gas passage port 12.

[0186] The first and second adsorbents used were the same as those in Example 1.

[0187] The amounts of the first adsorbent and the second adsorbent in the adsorption towers 10a, 10b, and 10c were 350 mL and 150 mL, respectively, and the proportions of the first adsorbent and the second adsorbent to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c, respectively, were 70% and 30%.

[0188] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0189] The durations of the adsorption process, depressurization process, washing process, first desorption process and second desorption process, the adsorption pressure in the adsorption process, the depressurization pressure in the depressurization process and the desorption pressure (pressure in the second desorption process) were the same as in Example 1.

[0190] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus 1 under the above conditions are shown in Figure 3. As shown in Figure 3, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus 1 was 36.2 vol%, and the carbon dioxide recovery rate was 81.3%.

[0191] Next, Comparative Examples 1 and 2 were carried out in relation to Examples 1 to 12. In the explanation of Comparative Examples 1 and 2, for the sake of convenience, the same reference numerals are used to designate elements corresponding to the elements in the above embodiment, and redundant explanations will be omitted.

[0192] [Comparative Example 1] In Comparative Example 1, an adsorption apparatus having the same configuration as the adsorption apparatus (recovery apparatus) equipped with the three adsorption towers 10a, 10b, and 10c shown in Figure 1 was used, except that each of the adsorption towers 10a, 10b, and 10c was equipped with one type of adsorbent. The adsorption apparatus used in Comparative Example 1 is referred to as adsorption apparatus A. Like the adsorption apparatus 1 shown in Figure 1, adsorption apparatus A was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35.

[0193] In Comparative Example 1, carbon dioxide was recovered from the raw material gas G1 using the adsorption apparatus A according to the recovery method described in the above embodiment.

[0194] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 10 vol% Raw material gas flow rate: 3.06 NL / min Raw material gas temperature: 25℃

[0195] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0196] The adsorbent stored in the adsorption towers 10a, 10b, and 10c was zeolite (Zeolite F-9HA manufactured by Tosoh Corporation).

[0197] The amount of adsorbent (zeolite) in each of the adsorption towers 10a, 10b, and 10c was 500 mL.

[0198] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0199] The implementation times of the adsorption step, depressurization step, washing step, first desorption step and second desorption step, the adsorption pressure in the adsorption step, the depressurization pressure in the depressurization step and the desorption pressure (pressure in the second desorption step) were as follows. Adsorption process: 100 seconds Pressure release process: 3 seconds Cleaning process: 97 seconds 1st desorption process: 13 seconds 2nd desorption process: 87 seconds Adsorption pressure (gauge pressure): 20 kPaG Discharge pressure (gauge pressure): 0 kPaG Desorption pressure (gauge pressure): -95kPaG

[0200] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus A under the above conditions are shown in Figure 3. As shown in Figure 3, the carbon dioxide concentration of product gas G4 recovered by adsorption apparatus A was 49.7 vol%, and the carbon dioxide recovery rate was 50.6%. For convenience, Figure 3 indicates in the column for second adsorbent that the adsorbent used in Comparative Example 1 was zeolite.

[0201] Comparative Example 2 In Comparative Example 2, an adsorption apparatus having the same configuration as the adsorption apparatus (recovery apparatus) equipped with three adsorption towers 10a, 10b, and 10c shown in FIG. 1 was used, except that activated carbon was used as the first adsorbent constituting the lower adsorption layer and zeolite was used as the second adsorbent constituting the upper adsorption layer. The adsorption apparatus used in Comparative Example 2 is referred to as adsorption apparatus B. Like the adsorption apparatus 1 shown in FIG. 1, adsorption apparatus B used in Comparative Example 2 was equipped with a pressure release gas flow path 24, a cleaning gas flow path 25, buffer tanks 31 and 34, and blowers 32 and 35.

[0202] In Comparative Example 2, carbon dioxide was recovered from the raw material gas G1 using the adsorption apparatus B according to the recovery method described in the above embodiment.

[0203] The carbon dioxide concentration in the raw material gas G1, the flow rates of the raw material gas G1 introduced into the adsorption towers 10a, 10b, and 10c in the adsorption step, and the temperature of the raw material gas G1 were as follows: Carbon dioxide concentration: 10 vol% Source gas flow rate: 3.2 NL / min Raw material gas temperature: 25℃

[0204] Each of the adsorption towers 10a, 10b, and 10c had a cylindrical shape with an inner diameter of 37.1 mm and an inner height of 500 mm.

[0205] Activated carbon (ZK420 manufactured by Osaka Gas Chemicals Co., Ltd.) was used as the first adsorbent housed in the adsorption towers 10a, 10b, and 10c, and zeolite (Zeolite F-9HA manufactured by Tosoh Corporation) was used as the second adsorbent.

[0206] The amounts of the first adsorbent (activated carbon) and the second adsorbent (zeolite) in the adsorption towers 10a, 10b, and 10c were 250 mL and 250 mL, respectively, and the proportions of the first adsorbent and the second adsorbent relative to the total amount of adsorbent in the adsorption towers 10a, 10b, and 10c were 50% and 50%, respectively.

[0207] In each of the adsorption towers 10a, 10b, and 10c, a basic cycle consisting of an adsorption process, a pressure release process, a cleaning process, a first desorption process, and a second desorption process was repeated. The basic cycle was performed by shifting the timing of the execution of the basic cycle in the adsorption towers 10a, 10b, and 10c.

[0208] The implementation times of the adsorption step, depressurization step, washing step, first desorption step and second desorption step, the adsorption pressure in the adsorption step, the depressurization pressure in the depressurization step and the desorption pressure (pressure in the second desorption step) were the same as in Example 1.

[0209] In Comparative Example 2, the first adsorbent was activated carbon and the second adsorbent was zeolite, so that in the adsorption step, the raw material gas G1 passed through the activated carbon and then through the zeolite.

[0210] The results of recovering carbon dioxide from raw material gas G1 using adsorption apparatus B under the above conditions are shown in Figure 3. As shown in Figure 3, the carbon dioxide concentration of product gas G4 recovered by the adsorption apparatus was 45.3 vol%, and the carbon dioxide recovery rate was 70.7%.

[0211] [evaluation] As mentioned above, FIG. 2 is a diagram showing the results of Examples 1 to 7, and FIG. 3 is a diagram showing the results of Examples 8 to 12 and Comparative Examples 1 and 2.

[0212] As shown in Figures 2 and 3, it can be seen that Examples 1 to 12, which use zeolite as the first adsorbent and activated carbon as the second adsorbent, can achieve a higher recovery rate than Comparative Example 1, which uses only activated carbon as the adsorbent, and Comparative Example 2, which uses activated carbon as the first adsorbent and zeolite as the second adsorbent.

[0213] For example, as can be seen from a comparison between Examples 1 to 3, in which the carbon dioxide concentration in the raw material gas G1 and the flow rate of the raw material gas G1 were substantially the same, a higher recovery rate was obtained when the proportion of the second adsorbent was higher than that of the first adsorbent (more than twice as high in the results shown in Figures 2 and 3). This was also the case in a comparison between Examples 4, 7, and 8, a comparison between Examples 5, 9, and 10, and a comparison between Examples 6, 11, and 12, in which the carbon dioxide concentration in the raw material gas G1 and the flow rate of the raw material gas G1 were substantially the same. Therefore, from the perspective of improving the recovery rate, it is more effective for the proportion of the second adsorbent to be higher than the proportion of the first adsorbent. In particular, when the raw material gas concentration was 10 vol% or more and 20 vol% or less, a higher proportion of the second adsorbent than the proportion of the first adsorbent was advantageous for improving the recovery rate.

[0214] As described above, when improving the recovery rate, it is better to use a larger amount of the second adsorbent than the first adsorbent. On the other hand, the results shown in Figures 2 and 3 indicate that when it is desired to increase the product purity while maintaining a certain level of recovery rate, it is better to use a larger amount of the first adsorbent than the second adsorbent. [Industrial Applicability]

[0215] The capture device and capture method of the present disclosure can capture carbon dioxide at a high capture rate, which can reduce greenhouse gas emissions and contribute to the preservation of the global environment. [Explanation of symbols]

[0216] 1...adsorption device (recovery device), 10, 10a, 10b, 10c...adsorption towers, 21...introduction flow path (first line), 22...off-gas flow path (second line), 23...recovered gas flow path (third line).

Claims

1. an adsorption tower for recovering a target gas containing carbon dioxide separated from the raw material gas by adsorbing carbon dioxide in the raw material gas onto a first adsorbent and a second adsorbent and desorbing the carbon dioxide from the first adsorbent and the second adsorbent; a first line for introducing the raw material gas into the adsorption tower; a second line for discharging, from the adsorption tower, an off-gas separated from the raw material gas by the carbon dioxide being adsorbed by the first adsorbent and the second adsorbent; a third line for recovering the target gas from the adsorption tower; Equipped with the first adsorbent is a zeolite adsorbent, the second adsorbent is a carbon-based adsorbent; the second adsorbent is disposed downstream of the first adsorbent in the flow direction of the source gas in the adsorption tower, the first line and the third line are connected to an upstream end of the adsorption tower in the flow direction of the raw material gas in the adsorption tower. Recovery device.

2. a proportion of the second adsorbent in the adsorption tower is greater than a proportion of the first adsorbent; The recovery device according to claim 1 .

3. the proportion of the second adsorbent in the adsorption tower is at least twice the proportion of the first adsorbent; The recovery device according to claim 1 or 2.

4. an adsorption step of introducing a raw material gas into an adsorption tower, causing carbon dioxide in the raw material gas to be adsorbed by a first adsorbent and a second adsorbent, and discharging an off-gas separated from the raw material gas as a result of the carbon dioxide being adsorbed by the first adsorbent and the second adsorbent from the adsorption tower; a desorption step of desorbing the carbon dioxide adsorbed by the first adsorbent and the second adsorbent in the adsorption step from the first adsorbent and the second adsorbent, and recovering the target gas containing the carbon dioxide in the adsorption tower; and the first adsorbent is a zeolite adsorbent, the second adsorbent is a carbon-based adsorbent; the second adsorbent is disposed downstream of the first adsorbent in the flow direction of the source gas in the adsorption tower, In the desorption step, the target gas is recovered from the first adsorbent side in the adsorption tower. Recovery method.

Images