Concentration measurement method, carbon dioxide recovery method, and carbon dioxide recovery device

Abstract

Provided are a concentration measurement method, a carbon dioxide recovery method, and a carbon dioxide recovery device (10), whereby the carbon dioxide concentration of a desorbed gas can be accurately determined using a general-purpose sensor. A concentration measurement method for measuring the carbon dioxide concentration of a desorbed gas containing carbon dioxide desorbed from an adsorbent to which carbon dioxide contained in the gas is adsorbed, the concentration measurement method including: a first process for detecting the flow rate of the gas and the carbon dioxide concentration; a second treatment for detecting the flow rate of the remaining gas after the carbon dioxide is adsorbed from the gas by the adsorbent and the carbon dioxide concentration; and a calculation process in which the carbon dioxide concentration of the outgassing gas is obtained on the basis of the results of the first process and the results of the second process.

Description

Technical Field

[0001] The present invention relates to a method for measuring the concentration of carbon dioxide, a method for recovering carbon dioxide and a recovery device. Background Art

[0002] In a carbon dioxide recovery device using pressure swing adsorption that changes the affinity of carbon dioxide to an adsorbent by pressure, the prior art disclosed in Patent Document 1 is to detect the carbon dioxide concentration of a gas (desorbed gas) including carbon dioxide desorbed from an adsorbent and control the recovery device.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-40025 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] The conventional technology has the following problems: since the flow rate of the desorbed gas varies greatly, it is difficult to accurately detect the concentration of carbon dioxide in the desorbed gas. Also, since the carbon dioxide in the desorbed gas is concentrated, a dedicated sensor is required to detect high-concentration carbon dioxide.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a concentration measuring method, a carbon dioxide recovery method, and a carbon dioxide recovery device for accurately determining the carbon dioxide concentration of desorbed gas using a general-purpose sensor.

[0009] Solutions for solving problems

[0010] The first technical solution for achieving this purpose is a concentration measurement method, which measures the carbon dioxide concentration of a desorbed gas containing carbon dioxide that is desorbed from an adsorbent that adsorbs carbon dioxide contained in a gas, wherein the concentration measurement method includes: a first process, in which the flow rate and carbon dioxide concentration of the gas are detected; a second process, in which the flow rate and carbon dioxide concentration of the remaining gas after the adsorbent adsorbs carbon dioxide from the gas are detected; and an operation process, in which the carbon dioxide concentration of the desorbed gas is calculated based on the results of the first process and the results of the second process.

[0011] The second technical solution is a method for recovering carbon dioxide, which includes: an adsorption treatment, in which an adsorbent adsorbs carbon dioxide contained in a gas; and a desorption treatment, in which carbon dioxide is desorbed from the adsorbent to obtain a desorbed gas containing carbon dioxide, wherein, based on the carbon dioxide concentration of the desorbed gas obtained in the first technical solution, any one or more of the time of the adsorption treatment, the flow rate of the residual gas remaining after the adsorbent adsorbs the carbon dioxide contained in the gas in the adsorption treatment, the time of the desorption treatment, and the flow rate of the desorbed gas are adjusted.

[0012] According to the second technical solution, the third technical solution also includes a purge treatment, in which the carbon dioxide existing around the adsorbent from which the carbon dioxide is desorbed is removed using residual gas, and based on the carbon dioxide concentration of the desorbed gas, one or more of the time of the purge treatment and the flow rate of the residual gas in the purge treatment are adjusted.

[0013] The fourth technical solution is a method for recovering carbon dioxide, comprising: an adsorption process in which an adsorbent adsorbs carbon dioxide contained in a gas; and a desorption process in which carbon dioxide is desorbed from the adsorbent to obtain a desorbed gas containing carbon dioxide, wherein the method further comprises a mixing process in which the amount of the desorbed gas mixed in the gas is adjusted based on the carbon dioxide concentration of the desorbed gas obtained in the first technical solution. In the adsorption process, the mixed gas obtained by mixing the desorbed gas in the gas is brought into contact with the adsorbent.

[0014] The fifth technical solution is a recovery device, which is a carbon dioxide recovery device, which makes an adsorbent adsorb carbon dioxide contained in a gas, and makes carbon dioxide desorb from the adsorbent to obtain a desorbed gas containing carbon dioxide, wherein the recovery device includes: a first measuring unit, which detects the flow rate and carbon dioxide concentration of the gas; a second measuring unit, which detects the flow rate and carbon dioxide concentration of the remaining gas after the adsorbent adsorbs carbon dioxide from the gas; and a calculation unit, which calculates the carbon dioxide concentration of the desorbed gas based on the measurement results obtained by the first measuring unit and the measurement results obtained by the second measuring unit.

[0015] According to the fifth technical solution, in the sixth technical solution, the recovery device also includes an adjustment unit, which adjusts any one or more of the time of adsorption treatment of carbon dioxide contained in the adsorbent gas, the flow rate of residual gas remaining after the adsorbent adsorbs carbon dioxide contained in the gas during the adsorption treatment, the time of desorption treatment of desorbing carbon dioxide from the adsorbent to obtain desorption gas containing carbon dioxide, and the flow rate of the desorption gas based on the carbon dioxide concentration of the desorption gas.

[0016] According to the 5th or 6th technical scheme, in the 7th technical scheme, the recovery device also includes a purge section for performing a purge treatment, in which the carbon dioxide existing around the adsorbent from which the carbon dioxide is desorbed is removed by utilizing the residual gas, and the purge section adjusts one or more of the time of the purge treatment and the flow rate of the residual gas in the purge treatment based on the carbon dioxide concentration of the desorbed gas.

[0017] According to any one of the 5th to 7th technical solutions, in the 8th technical solution, the recovery device also includes a mixing section for performing a mixing treatment, in which the amount of the desorbed gas mixed in the gas is adjusted based on the carbon dioxide concentration of the desorbed gas, and the mixing section allows the mixed gas formed by mixing the desorbed gas in the gas to contact with the adsorbent.

[0018] Effects of the Invention

[0019] According to the concentration measurement method of the present invention, the carbon dioxide concentration of the gas and the carbon dioxide concentration of the remaining gas are lower than the carbon dioxide concentration of the desorbed gas, so the carbon dioxide concentration of the gas and the carbon dioxide concentration of the remaining gas can be detected using a general sensor. Compared with the change in the flow rate of the desorbed gas, the change in the flow rate of the gas and the flow rate of the remaining gas is smaller, so the carbon dioxide concentration and the flow rate can be accurately detected in the first process and the second process. Therefore, the carbon dioxide concentration of the desorbed gas can be accurately obtained through calculation processing.

[0020] According to the carbon dioxide recovery method of the present invention, based on the carbon dioxide concentration of the desorbed gas obtained by the concentration measurement method, at least one of the time of the adsorption treatment, the flow rate of the residual gas remaining after the adsorbent adsorbs the carbon dioxide contained in the gas during the adsorption treatment, the time of the desorbed treatment, and the flow rate of the desorbed gas is adjusted. Since the carbon dioxide concentration of the desorbed gas is accurately obtained, the recovery rate of carbon dioxide can be improved by adjusting the flow rate and the treatment time based on the accurate carbon dioxide concentration.

[0021] According to the carbon dioxide recovery method of the present invention, the amount of the desorbed gas mixed in the gas is adjusted in the mixing process based on the carbon dioxide concentration of the desorbed gas obtained by the concentration measurement method, and the mixed gas obtained by mixing the desorbed gas in the gas is brought into contact with the adsorbent in the adsorption process. Since the carbon dioxide concentration of the desorbed gas is accurately obtained, the amount of the desorbed gas contained in the mixed gas is adjusted based on the accurate carbon dioxide concentration, and the mixed gas is brought into contact with the adsorbent, thereby improving the recovery rate of carbon dioxide.

[0022] According to the recovery device of the present invention, the carbon dioxide concentration and flow rate can be accurately detected in the first measuring unit and the second measuring unit. Therefore, the carbon dioxide concentration of the desorbed gas can be accurately obtained by the calculation unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a piping system diagram of a recovery device according to one embodiment.

[0024] Figure 2 is a block diagram of the control device. DETAILED DESCRIPTION

[0025] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 1 is a piping system diagram of a recovery device 10 according to an embodiment. The recovery device 10 is a device that uses pressure swing adsorption to recover carbon dioxide contained in a gas. Examples of the gas include exhaust gas discharged from power plants, factories, waste treatment facilities, natural gas fields, oil fields, and the like.

[0026] The recovery device 10 includes a gas supply pipe 11 for supplying gas, gas supply pipes 14 and 18 branched from the gas supply pipe 11 and connected to two adsorption towers 16 and 20, exhaust pipes 17 and 21 connected to the adsorption towers 16 and 20, and an exhaust pipe 22 connected to the exhaust pipes 17 and 21 and merging the exhaust pipes 17 and 21. A second measuring unit 23 is arranged in the exhaust pipe 22.

[0027] The first measuring unit 12 and the pressurizing device 13 are arranged in order from the upstream of the gas supply pipe 11. The first measuring unit 12 includes a flow meter for detecting the flow rate of the gas flowing in the gas supply pipe 11, and a concentration meter for detecting the concentration of carbon dioxide contained in the gas flowing in the gas supply pipe 11. The concentration meter can be exemplified by a relatively inexpensive general-purpose sensor of a non-dispersive infrared (NDIR) spectroscopic method. In the first measuring unit 12, the flow meter and the concentration meter can also be integrated.

[0028] The pressurizing device 13 is a device for pressurizing the gas flowing in the gas supply pipe 11 and setting the adsorption towers 16 and 20 to an appropriate pressure, and examples thereof include a compressor and a blower. The adsorption towers 16 and 20 contain adsorbents, respectively. Examples of adsorbents include activated carbon, zeolite, mesoporous silica, metal-organic structure (MOF), and porous coordination polymer (PCP).

[0029] The gas supply pipe 11 branches into gas supply pipes 14 and 18 downstream of the pressurizing device 13. Three-way valves (three-port valves) 15 and 19 are respectively arranged on the gas supply pipes 14 and 18. Two ports of the three-way valve 15 are connected to the gas supply pipe 14, and the remaining port is connected to the recovery pipe 24. The three-way valve 15 is a solenoid valve, which switches to a flow path A (arrow A) for allowing gas to flow from the gas supply pipe 11 through the gas supply pipe 14 to the adsorption tower 16, and a flow path B (arrow B) for allowing gas to flow from the adsorption tower 16 to the recovery pipe 24 through the input of an electrical signal.

[0030] Two ports of the three-way valve 19 are connected to the gas supply pipe 18, and the remaining port is connected to the recovery pipe 24. The three-way valve 19 is a solenoid valve, which switches to a flow path A (arrow A) for allowing gas to flow from the gas supply pipe 11 through the gas supply pipe 18 to the adsorption tower 20, and a flow path B (arrow B) for allowing gas to flow from the adsorption tower 20 to the recovery pipe 24 through the input of an electrical signal.

[0031] A recovery pipe 25 is connected to the middle position of the recovery pipe 24 connecting the three-way valves 15 and 19. A first end of a mixing pipe 26 is connected to the end of the recovery pipe 25. A second end of the mixing pipe 26 is connected to the upstream of the first measuring part 12 in the air supply pipe 11. A recovery pipe 27 is branched from the recovery pipe 25 to which the first end of the mixing pipe 26 is connected.

[0032] A flow regulating valve 28 is disposed in the mixing pipe 26. When the flow regulating valve 28 is closed, all the gas flowing in the recovery pipe 25 flows to the recovery pipe 27. By adjusting the opening of the flow regulating valve 28, the amount of the gas flowing in the recovery pipe 25 that flows to the mixing pipe 26 can be adjusted.

[0033] The second measuring unit 23 includes a flow meter for detecting the flow rate of the gas flowing in the exhaust pipe 22, and a concentration meter for detecting the concentration of carbon dioxide contained in the gas flowing in the exhaust pipe 22. The concentration meter can be exemplified by a relatively inexpensive general-purpose sensor of a non-dispersive infrared (NDIR) spectroscopic method. In the second measuring unit 23, the flow meter and the concentration meter may be integrated.

[0034] A variable throttle valve 29 is connected between the exhaust pipe 17 and the exhaust pipe 21. The exhaust pipes 17, 21, 22 and the variable throttle valve 29 are set so that the ratio of the flow rate of the air supply pipe 14 or the air supply pipe 18 to the flow rate of the exhaust pipe 22 is, for example, in the range of 10:2 to 10:4. The variable throttle valve 29 is a needle valve type, and the flow rate between the exhaust pipe 17 and the exhaust pipe 21 can be adjusted steplessly by changing the opening. The variable throttle valve 29 usually sets the opening to a constant. The recovery device 10 includes a control device 30.

[0035] Figure 2 : is a block diagram of a control device 30. The control device 30 includes an input unit 31 for inputting the detection results of the first measurement unit 12 and the second measurement unit 23, a display unit 32 for displaying the input and output results on a liquid crystal panel or the like, a calculation unit 33 for calculating the carbon dioxide concentration of the desorbed gas based on the detection results of the first measurement unit 12 and the second measurement unit 23, an adjustment unit 34 and a purge unit 35 for switching the three-way valves 15 and 19 based on the output of the calculation unit 33, and a mixing unit 36 ​​for adjusting the opening of the flow control valve 28. The adjustment unit 34 and the purge unit 35 can also control the opening of the variable throttle valve 29.

[0036] The control device 30 includes a CPU, a ROM, and a RAM (none of which is shown in the figure). The ROM stores a program for calculating the concentration of carbon dioxide, switching the three-way valves 15 and 19, adjusting the opening of the flow control valve 28, etc. The CPU performs various processes in the calculation unit 33, the adjustment unit 34, and the purge unit 35 based on the program stored in the ROM.

[0037] An example of a method for recovering carbon dioxide using the recovery device 10 is described in the order of recovering carbon dioxide adsorbed by the adsorption tower 20 while the adsorption tower 16 is adsorbing carbon dioxide, and then recovering carbon dioxide adsorbed by the adsorption tower 16 while the adsorption tower 20 is adsorbing carbon dioxide. The adjustment unit 34 and the purge unit 35 first set the flow path A to the three-way valve 15 and set the flow path B to the three-way valve 19.

[0038] When a certain flow of gas (waste gas) is supplied to the gas supply pipe 11 and the pressurizing device 13 is operated, the gas enters the adsorption tower 16 through the gas supply pipe 14, and the pressure of the adsorption tower 16 rises. As a result, the carbon dioxide contained in the gas is adsorbed (adsorption treatment) by the adsorbent of the adsorption tower 16. The remaining gas (gas with a carbon dioxide partial pressure lower than that of the waste gas) after the adsorbent adsorbs carbon dioxide from the gas is discharged from the adsorption tower 16 to the outside of the recovery device 10 through the exhaust pipes 17 and 22. A portion of the remaining gas enters the adsorption tower 20 through the variable throttle valve 29.

[0039] On the other hand, the carbon dioxide adsorbed by the adsorbent of the adsorption tower 20 connected to the three-way valve 19 set in the flow path B is separated (separation treatment). The separated gas containing carbon dioxide separated from the adsorbent of the adsorption tower 20 passes through the recovery pipes 24 and 25 and is recovered from the recovery pipe 27. The remaining gas coming out of the adsorption tower 16 and entering the adsorption tower 20 through the variable throttle valve 29 relatively reduces the carbon dioxide partial pressure of the adsorption tower 20, promotes the separation of carbon dioxide from the adsorbent, squeezes the separated gas in the adsorption tower 20 toward the recovery pipe 24, and purifies the adsorption tower 20 (purge treatment). The separation treatment and purge treatment of the adsorption tower 20 are carried out in parallel with the adsorption treatment of the adsorption tower 16.

[0040] If the adsorbent of the adsorption tower 16 adsorbs carbon dioxide, the adsorption capacity decreases, so the carbon dioxide concentration of the residual gas discharged from the adsorption tower 16 increases over time. On the other hand, the carbon dioxide concentration of the desorbed gas discharged from the adsorption tower 20 gradually decreases over time. Therefore, after a certain period of time, the adjustment unit 34 and the purge unit 35 switch the three-way valves 15 and 19, and after setting the flow path B to the three-way valve 15, the flow path A is set to the three-way valve 19. By setting the flow path B to the three-way valve 15, the pressure of the adsorption tower 16 becomes atmospheric pressure.

[0041] When the three-way valve 19 is set to flow path A, the gas pressurized by the pressurizing device 13 enters the adsorption tower 20 through the gas supply pipe 18, and the pressure of the adsorption tower 20 rises. As a result, the carbon dioxide contained in the gas is adsorbed by the adsorbent of the adsorption tower 20 (adsorption treatment). The remaining gas after the adsorbent adsorbs carbon dioxide from the gas is discharged from the adsorption tower 20 to the outside of the recovery device 10 through the exhaust pipes 21 and 22. A part of the remaining gas enters the adsorption tower 16 through the variable throttle valve 29.

[0042] On the other hand, the carbon dioxide adsorbed by the adsorbent of the adsorption tower 16 connected to the three-way valve 15 set as the flow path B is separated (separation treatment). The separated gas containing carbon dioxide separated from the adsorbent of the adsorption tower 16 passes through the recovery pipes 24 and 25 and is recovered from the recovery pipe 27. The remaining gas coming out of the adsorption tower 20 and entering the adsorption tower 16 through the variable throttle valve 29 relatively reduces the carbon dioxide partial pressure of the adsorption tower 16, promotes the separation of carbon dioxide from the adsorbent, squeezes the separated gas in the adsorption tower 16 toward the recovery pipe 24, and purifies the adsorption tower 16 (purge treatment). The separation treatment and purge treatment of the adsorption tower 16 are carried out in parallel with the adsorption treatment of the adsorption tower 20.

[0043] The adjustment unit 34 and the purge unit 35 repeatedly switch the three-way valves 15 and 19 to alternately perform adsorption treatment in the adsorption towers 16 and 20, and recover the degassing gas containing concentrated carbon dioxide from the recovery pipe 27. The recovered carbon dioxide can react with hydrogen to produce methane, or carbon dioxide and hydrogen can be used as raw materials to produce synthesis gas, methanol, ethanol and other intermediates, and fuels such as light oil and gasoline, BTX (benzene, toluene, xylene), DME (dimethyl ether), butadiene, chemical products, etc. can be produced from the intermediates.

[0044] The first measuring unit 12 detects the flow rate F1 and the carbon dioxide concentration C1 of the gas flowing in the gas supply pipe 11 (first process). The second measuring unit 23 detects the flow rate F2 and the carbon dioxide concentration C2 of the remaining gas flowing in the exhaust pipe 22 (second process). The mass flow rate of carbon dioxide contained in the gas flowing in the gas supply pipe 11 is represented by F1×C1. The mass flow rate of carbon dioxide contained in the remaining gas flowing in the exhaust pipe 22 is represented by F2×C2.

[0045] The gas flowing in the gas supply pipe 11 is divided into the remaining gas flowing in the exhaust pipe 22 and the desorbed gas flowing in the recovery pipe 25. Therefore, the flow rate F3 of the desorbed gas flowing in the recovery pipe 25 is the flow rate F1-F2 obtained by subtracting the flow rate F2 of the remaining gas from the flow rate F1 of the gas. Carbon dioxide contained in the gas is divided into carbon dioxide contained in the remaining gas and carbon dioxide contained in the desorbed gas. Therefore, the mass flow rate of carbon dioxide contained in the desorbed gas is F1×C1-F2×C2 obtained by subtracting the mass flow rate F2×C2 of carbon dioxide in the remaining gas from the mass flow rate F1×C1 of carbon dioxide in the gas. Therefore, the carbon dioxide concentration C3 of the desorbed gas flowing in the recovery pipe 25 is obtained by dividing the mass flow rate F1×C1-F2×C2 of carbon dioxide contained in the desorbed gas by the flow rate F3 (=F1-F2) of the desorbed gas, and becomes C3=(F1×C1-F2×C2) / (F1-F2) (calculation processing). The calculation unit 33 outputs the carbon dioxide concentration C3 in this way.

[0046] When the carbon dioxide concentration C3 of the desorbed gas is less than the target value, the mixing unit 36 ​​can increase the opening of the flow regulating valve 28, thereby increasing the flow rate of the desorbed gas flowing from the recovery pipe 25 to the mixing pipe 26 (mixing process). The desorbed gas entering the gas supply pipe 11 from the mixing pipe 26 is mixed with the gas flowing in the gas supply pipe 11. In this way, it is possible to avoid the desorbed gas whose carbon dioxide concentration C3 is less than the target value from being recovered. The mixed gas mixed with the desorbed gas enters the adsorption tower 16 or the adsorption tower 20 via the pressurizing device 13, and the carbon dioxide contained in the mixed gas is adsorbed by the adsorbent.

[0047] On the other hand, when the carbon dioxide concentration C3 of the desorbed gas is above the target value, the mixing unit 36 ​​can reduce the opening of the flow regulating valve 28, reduce the flow of the desorbed gas flowing from the recovery pipe 25 to the mixing pipe 26, and increase the flow of the desorbed gas flowing in the recovery pipe 27 (mixing process). At this time, the flow regulating valve 28 can also be completely closed. Since only the desorbed gas containing a high concentration of carbon dioxide above the target value is discharged from the recovery pipe 27 to the outside of the recovery device 10, the recovery rate of carbon dioxide can be improved. In addition, of course, the opening of the flow regulating valve 28 can be continuously changed according to the carbon dioxide concentration C3 of the desorbed gas during the mixing process.

[0048] Since the gas (exhaust gas) supplied to the gas supply pipe 11 at a constant flow rate is much greater than the amount of desorbed gas supplied from the mixing pipe 26 to the gas supply pipe 11, the flow rate of the gas (including the mixed gas) passing through the first measuring section 12 is approximately constant. In addition, the flow rate of the remaining gas passing through the second measuring section 23 is also set to be approximately constant by the variable throttle valve 29. If the flow rate of the gas changes greatly, the detection of the carbon dioxide concentration using the gas sensor lacks accuracy, and if the flow rate of the gas changes slightly, the carbon dioxide concentration can be accurately detected. Therefore, the carbon dioxide concentration C1 of the gas (including the mixed gas) can be accurately detected using the first measuring section 12, and the carbon dioxide concentration C2 of the remaining gas can be accurately detected using the second measuring section 23.

[0049] Furthermore, the gas is the gas before carbon dioxide is concentrated by the adsorption towers 16 and 20, and the residual gas is the gas after carbon dioxide contained in the gas is adsorbed by the adsorbent. Therefore, the carbon dioxide concentrations C1 and C2 of the gas and the residual gas are lower than the carbon dioxide concentration C3 of the desorbed gas after carbon dioxide is concentrated. In addition, the desorbed gas having a carbon dioxide concentration C3 less than the target value is mixed with the gas flowing in the gas supply pipe 11 through the mixing pipe 26, so the carbon dioxide concentration of the mixed gas hardly increases.

[0050] Therefore, it is possible to detect the carbon dioxide concentration of the residual gas and the gas (including the mixed gas) using a common and relatively cheap sensor such as the NDIR method instead of using a dedicated and expensive sensor for detecting high-concentration carbon dioxide. According to the recovery device 10, it is possible to accurately measure the carbon dioxide concentration C3 of the desorbed gas through calculation processing based on the detection of the first measuring unit 12 and the second measuring unit 23 realized by the common sensor instead of directly detecting the carbon dioxide concentration of the desorbed gas. As a result, it is possible to obtain a desorbed gas with a high carbon dioxide concentration at a high recovery rate.

[0051] As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited at all to the said embodiment, It can be easily guessed that various improvements and modifications can be made within the range which does not deviate from the summary of this invention.

[0052] For example, the piping system of the recovery device 10 is an example and can be set appropriately. In the embodiment, the recovery device 10 is described as having two adsorption towers 16 and 20, but it is not necessarily limited to this. Of course, more than three adsorption towers can be set, and adsorption treatment and desorption treatment can be performed in sequence in more than three adsorption towers.

[0053] In the embodiment, the recovery device 10 using the PSA method is described, wherein the gas is supplied to the adsorption towers 16 and 20 at a pressure that becomes the adsorption pressure and is desorbed near the atmospheric pressure, but it is not necessarily limited to this. Of course, the first measuring unit 12, the second measuring unit 23, and the computing unit 33 can be provided in the recovery device using the VSA method or the PVSA method, wherein the gas is pressurized to form the adsorption pressure and desorbed under reduced pressure using a vacuum pump.

[0054] In the embodiment, the case where the exhaust pipe 17 and the exhaust pipe 21 are connected using the variable throttle valve 29 is described, but it is not necessarily limited to this. It is also possible that, instead of the variable throttle valve 29, the exhaust pipe 17 and the exhaust pipe 21 are connected in parallel using multiple throttle holes, and an on-off valve is provided for each throttle hole. In this case, the on-off valve can also be controlled to adjust the flow rate between the exhaust pipe 17 and the exhaust pipe 21. In the case where there is no need to adjust the flow rate between the exhaust pipe 17 and the exhaust pipe 21, of course, a throttle hole with a certain opening can be used to connect the exhaust pipe 17 and the exhaust pipe 21. In addition, it is of course possible to configure multiple valves for realizing the function of the three-way valve instead of the three-way valves 15 and 19.

[0055] In the embodiment, the adjustment unit 34 is described as switching the three-way valves 15 and 19 to alternate the adsorption towers 16 and 20 that perform the adsorption process after a certain period of time, but it is not necessarily limited to this. Instead of alternating the adsorption towers 16 and 20 that perform the adsorption process based on the elapsed time, it is of course possible to alternate the adsorption towers 16 and 20 that perform the adsorption process based on the carbon dioxide concentration C2 of the remaining gas detected by the second measuring unit 23. Since there is an upper limit to the amount of carbon dioxide that can be adsorbed by the adsorbent, if the adsorbent adsorbs carbon dioxide, the adsorption capacity decreases and the carbon dioxide concentration C2 of the remaining gas increases. Therefore, when the carbon dioxide concentration C2 exceeds a predetermined value, by alternating the adsorption towers 16 and 20 that perform the adsorption process, the adsorption performance of the adsorbent can be always ensured.

[0056] In the embodiment, it is described that after a certain period of time, the purge section 35 alternates the adsorption towers 16 and 20 that perform the desorption process and the purge process by switching the three-way valves 15 and 19, but it is not necessarily limited to this. Instead of alternating the adsorption towers 16 and 20 that perform the desorption process and the purge process based on the elapsed time, it is of course possible to alternate the adsorption towers 16 and 20 that perform the desorption process and the purge process based on the carbon dioxide concentration C3 of the desorbed gas. Since the adsorbent desorbs the adsorbed carbon dioxide, the carbon dioxide concentration C3 of the desorbed gas decreases as the desorption of carbon dioxide proceeds. Therefore, when the carbon dioxide concentration C3 is less than the target value, by alternating the adsorption towers 16 and 20 that perform the desorption process and the purge process, the desorbed gas having a carbon dioxide concentration C3 above the target value can be always recovered. Therefore, the recovery rate of carbon dioxide can be improved.

[0057] In the embodiment, the recovery device 10 is described as performing the desorption process and the purge process in a state where the opening of the variable throttle valve 29 is constant, but the present invention is not necessarily limited to this. The adjustment unit 34 and the purge unit 35 can of course adjust the opening of the variable throttle valve 29 based on the carbon dioxide concentration C3 of the desorption gas, and adjust the flow rate of the residual gas flowing in the exhaust pipe 22 and the flow rate of the desorption gas flowing in the recovery pipe 25.

[0058] For example, when the carbon dioxide concentration C3 of the desorbed gas is above the target value during the desorbed process and the purge process, the adjustment unit 34 and the purge unit 35 may also increase the opening of the variable throttle valve 29. If the opening of the variable throttle valve 29 is increased, the flow rate of the residual gas flowing in the exhaust pipe 22 is reduced, the flow rate of the residual gas entering the adsorption tower 20 from the adsorption tower 16, or the flow rate of the residual gas entering the adsorption tower 16 from the adsorption tower 20 increases, and the flow rate of the desorbed gas flowing in the recovery pipe 25 increases. If the flow rate of the residual gas entering the adsorption tower 20 from the adsorption tower 16, or the flow rate of the residual gas entering the adsorption tower 16 from the adsorption tower 20 increases, the carbon dioxide partial pressure of the adsorption towers 16 and 20 performing the desorbed process and the purge process decreases relatively quickly, and the desorbed speed of carbon dioxide becomes faster. Therefore, the recovery rate of carbon dioxide can be improved. In addition, the adjustment unit 34 and the purge unit 35 can of course continuously change the opening of the variable throttle valve 29 according to the carbon dioxide concentration C3 of the desorbed gas during the desorbed process and the purge process.

[0059] In the embodiment, a case where a constant flow of gas (exhaust gas) is supplied to the gas supply pipe 11 of the recovery device 10 is described, but the present invention is not necessarily limited thereto. The adjustment unit 34 can of course adjust the flow of gas supplied to the gas supply pipe 11 within a range where the detection accuracy of the first measuring unit 12 is not reduced based on the carbon dioxide concentration C3 of the desorbed gas.

[0060] For example, when the carbon dioxide concentration C3 of the desorbed gas is greater than the target value, the adjustment unit 34 may also increase the flow rate of the gas supplied to the gas supply pipe 11. When the flow rate of the gas supplied to the gas supply pipe 11 is increased, the flow rate of the residual gas flowing in the exhaust pipe 22 increases, the flow rate of the residual gas entering the adsorption tower 20 from the adsorption tower 16, or the flow rate of the residual gas entering the adsorption tower 16 from the adsorption tower 20 also increases, and the flow rate of the desorbed gas flowing in the recovery pipe 25 also increases. As a result, the recovery rate of carbon dioxide can be improved.

[0061] Description of Reference Numerals

[0062] 10. Recovery device; 12. First measuring section; 23. Second measuring section; 33. Calculation section; 34. Adjustment section; 35. Purge section; 36. Mixing section.

Claims

1. A method for measuring a concentration of carbon dioxide in a desorbed gas containing carbon dioxide desorbed from an adsorbent that adsorbs carbon dioxide contained in a gas, wherein: The concentration determination method comprises: a first process in which the flow rate and the carbon dioxide concentration of the gas are detected; a second process in which a flow rate and a carbon dioxide concentration of a remaining gas after the adsorbent adsorbs carbon dioxide from the gas are detected; and A calculation process is performed in which the carbon dioxide concentration of the desorbed gas is obtained based on the result of the first process and the result of the second process.

2. A method for recovering carbon dioxide, comprising: Adsorption treatment, in which the adsorbent is made to adsorb carbon dioxide contained in the gas; as well as a desorption process in which carbon dioxide is desorbed from the adsorbent to obtain a desorbed gas containing carbon dioxide, in, Based on the carbon dioxide concentration of the desorbed gas obtained by the concentration measurement method according to claim 1, adjust any one or more of the time of the adsorption treatment, the flow rate of the residual gas remaining after the adsorbent adsorbs the carbon dioxide contained in the gas during the adsorption treatment, the time of the desorbed treatment, and the flow rate of the desorbed gas.

3. The method for recovering carbon dioxide according to claim 2, wherein: The carbon dioxide recovery method further includes a purge process in which the carbon dioxide existing around the adsorbent from which the carbon dioxide has been desorbed is removed by using the residual gas. Based on the carbon dioxide concentration of the desorbed gas obtained by the concentration measurement method, one or more of the duration of the purge process and the flow rate of the remaining gas in the purge process are adjusted.

4. A method for recovering carbon dioxide, comprising: Adsorption treatment, in which the adsorbent is made to adsorb carbon dioxide contained in the gas; as well as A desorption process in which carbon dioxide is desorbed from the adsorbent to obtain a desorbed gas containing carbon dioxide, wherein: The carbon dioxide recovery method further includes a mixing process in which the amount of the desorbed gas mixed in the gas is adjusted based on the carbon dioxide concentration of the desorbed gas obtained by the concentration measurement method according to claim 1, In the adsorption treatment, a mixed gas obtained by mixing the desorbed gas with the gas is brought into contact with the adsorbent.

5. A recovery device, which is a carbon dioxide recovery device, wherein an adsorbent adsorbs carbon dioxide contained in a gas, and carbon dioxide is desorbed from the adsorbent to obtain a desorbed gas containing carbon dioxide, wherein: The recovery device comprises: a first measuring unit for detecting the flow rate and carbon dioxide concentration of the gas; a second measuring unit for detecting a flow rate and a carbon dioxide concentration of a remaining gas after the adsorbent adsorbs carbon dioxide from the gas; and A calculation unit that obtains the carbon dioxide concentration of the desorbed gas based on the measurement result obtained by the first measurement unit and the measurement result obtained by the second measurement unit.

6. The recovery device according to claim 5, wherein: The recovery device also includes an adjustment unit that adjusts any one or more of the time of adsorption treatment in which the adsorbent adsorbs the carbon dioxide contained in the gas, the flow rate of residual gas remaining after the adsorbent adsorbs the carbon dioxide contained in the gas during the adsorption treatment, the time of desorption treatment in which the carbon dioxide is desorbed from the adsorbent to obtain a desorption gas containing carbon dioxide, and the flow rate of the desorption gas, based on the carbon dioxide concentration of the desorption gas.

7. The recovery device according to claim 5 or 6, wherein: The recovery device further includes a purge unit that performs a purge process, in which the carbon dioxide existing around the adsorbent from which the carbon dioxide has been desorbed is removed by using the residual gas. The purge unit adjusts one or more of a duration of the purge process and a flow rate of the surplus gas in the purge process based on a carbon dioxide concentration of the desorbed gas.

8. The recovery device according to claim 5 or 6, wherein: The recovery device further includes a mixing unit that performs a mixing process in which the amount of the desorbed gas mixed with the gas is adjusted based on the carbon dioxide concentration of the desorbed gas. The mixing unit brings a mixed gas obtained by mixing the desorbed gas with the gas into contact with the adsorbent.

Images