Co2 recovery system

Abstract

To provide a CO2 recovery system that is able to increase an amount of treatment of a CO2 containing gas and is excellent in facility cost, maintainability, and workability.SOLUTION: A CO2 recovery system 1 includes: a connection manifold 40 that connects a plurality of reaction vessels 10 to each other to cause the plurality of reaction vessels 10 to internally communicate with each other; a pipe body 45 that communicates with the plurality of reaction vessels 10 via the connection manifold 40 and has a height equal to or higher than liquid surfaces of a reaction liquid L in the reaction vessels 10 when the upper limit amount of reaction liquid is supplied to the reaction vessels 10; and a liquid-surface height detection unit 46 that detects a height of a liquid surface, in a pipe body 45, of the reaction liquid L flowing into the pipe body 45 from the plurality of reaction vessels 10 via the connection manifold 40 when the reaction liquid L is supplied from a reaction-liquid supply unit 20 to the plurality of reaction vessels 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a CO2 capture system. [Background technology]

[0002] In recent years, there has been a demand to reduce emissions of CO2 gas as a greenhouse gas, and various methods for capturing CO2 gas have been investigated. One method for capturing CO2 involves reacting CO2 with an alkaline solution such as NaOH in a reaction tank. For example, Patent Document 1 discloses a configuration including multiple reaction tanks in which a CO2-containing gas containing CO2 is brought into contact with a reaction liquid to absorb the CO2 in the CO2-containing gas into the reaction liquid. Patent Document 2 also discloses a configuration in which CO2 is absorbed and the reaction liquid is collected in multiple reaction tanks, and the amount of CO2 stored in the reaction tanks is monitored by a level controller installed in the reaction tanks. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-171451 [Patent Document 2] Japanese Patent Publication No. 2023-52063 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configurations disclosed in Patent Documents 1 and 2, increasing the capacity of the reaction vessel is considered to process large amounts of CO2-containing gas. However, treating large amounts of CO2-containing gas in a large-capacity reaction vessel is undesirable because excessive reaction heat is generated in the reaction vessel. Therefore, using multiple low-capacity reaction vessels to increase the amount of CO2-containing gas that can be processed is considered. However, in the configurations disclosed in Patent Documents 1 and 2, increasing the number of reaction vessels would correspondingly increase the number of liquid level detection devices installed in each reaction vessel, which is expected to significantly increase equipment costs. In addition, the wiring and piping connecting each device tend to become complicated, reducing maintainability. Furthermore, when a reaction liquid is injected into a reaction vessel, the liquid level of the reaction liquid in the reaction vessel ripples, which may result in false detection. Furthermore, accurately detecting the liquid level requires waiting for the liquid level to subside, which reduces workability.

[0005] The present invention has been made in view of the above problems, and aims to provide a CO2 recovery system that increases the amount of CO2-containing gas that can be treated, and that is excellent in terms of equipment cost, maintainability, and operability. [Means for solving the problem]

[0006] One aspect of the present invention is A CO2 recovery system that recovers CO2 by bringing a CO2-containing gas into contact with a reaction liquid capable of reacting with CO2 to generate a reaction product, A plurality of reaction vessels configured to store the reaction liquid; a reaction solution supply unit that supplies the reaction solution into the plurality of reaction vessels; a connecting manifold connected to the plurality of reaction vessels and configured to collectively discharge the reaction liquid containing the reaction product discharged from the plurality of reaction vessels; a pipe that communicates with the plurality of reaction vessels via the connecting manifold and has a height equal to or higher than the liquid level of the reaction liquid in the reaction vessel when an upper limit amount of the reaction liquid is supplied to the reaction vessel; and a liquid level detection unit that detects the liquid level in the pipe body of the reaction liquid that has flowed into the pipe body from the multiple reaction tanks via the connecting manifold when the reaction liquid is supplied from the reaction liquid supply unit to the multiple reaction tanks. [Effects of the Invention]

[0007] In one embodiment of the CO2 capture system, the use of multiple reaction vessels increases the amount of CO2-containing gas that can be treated, allowing for larger-scale operation. The system also includes a connecting manifold connected to the multiple reaction vessels to communicate with each other, and the piping provided in the connecting manifold is connected to the multiple reaction vessels via the connecting manifold. This allows the liquid levels of the multiple reaction vessels to be estimated by detecting the liquid levels of the reaction liquid flowing into the piping from the multiple reaction vessels. This eliminates the need for a liquid level detector for detecting the liquid level in each of the multiple reaction vessels, thereby reducing equipment costs. Furthermore, the number of parts can be reduced compared to when a liquid level detector is provided for each of the multiple reaction vessels, improving maintainability. Furthermore, even when the reaction liquid is injected into the reaction vessels, the ripples that occur on the liquid surface of the reaction liquid flowing into the piping from the reaction vessels via the connecting manifold are extremely small, allowing the liquid level to be accurately detected without waiting for the ripples to subside, improving operability.

[0008] As described above, according to the above-described embodiment, it is possible to provide a CO2 recovery system that increases the amount of CO2-containing gas that can be treated, and that is excellent in terms of facility cost, maintainability, and operability. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic side view showing the configuration of a CO2 capture system according to a first embodiment, in which a part of a reaction vessel is shown in cross section. [Figure 2] 1 is a conceptual top view illustrating the configuration of a CO2 capture system according to a first embodiment. [Figure 3]FIG. 2 is a conceptual side view of the bubbling unit according to the first embodiment. [Figure 4] FIG. 2 is a conceptual side view of the bubbling unit according to the first embodiment. [Figure 5] FIG. 2 is a diagram showing the relationship between the pH and weight of the reaction solution and the amount of each component remaining in the reaction vessel in the first embodiment. [Figure 6] FIG. 2 is a flow diagram of an automatic operation process for CO2 capture in the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) 1. Overview of CO2 Capture System 1 The CO2 recovery system 1 of the present embodiment 1 recovers CO2 by bringing a CO2-containing gas into contact with a reaction liquid L capable of reacting with CO2 to generate a reaction product. Each component of the CO2 recovery system 1 will be described in detail below.

[0011] 2. Reactor 10 As shown in FIGS. 1 and 2, the CO2 capture system 1 is equipped with multiple reaction vessels 10. In this embodiment, as shown in FIG. 2, four reaction vessels 10a, 10b, 10c, and 10d are provided. The reaction vessels 10a to 10d have a hollow cylindrical shape. The reaction vessels 10a to 10d have the same shape. An NaOH aqueous solution is introduced into the reaction vessel 10 as a reaction liquid L via a reaction liquid supply unit 20 (described below). The material of the reaction vessel 10 is not particularly limited as long as it is alkali-resistant, and may be made of resin such as polyethylene resin or polyvinyl chloride resin. The reaction vessel 10 may also be made of stainless steel or metal with a surface treatment such as a resin lining. In this embodiment, a 50 L reaction vessel 10 made of polyethylene resin is used. A reaction vessel discharge unit 12 (described below) is provided at the bottom of the reaction vessel 10 to discharge the reaction product.

[0012] 1 and 2, a lid 11 is removably attached to an opening provided on the top surface of the reaction vessel 10. A CO2-containing gas supply unit 60 and a CO2-removed gas discharge unit 80, which will be described later, are inserted into the lid 11, with the tips of both being located inside the reaction vessel 10. In addition, a thermocouple 48 constituting a temperature detection unit, which will be described later, and a reaction liquid supply unit 20, which supplies reaction liquid L into the reaction vessel 10, are also inserted into the lid 11.

[0013] In FIG. 1, Lmax denotes the liquid level of the reaction liquid L in the reaction tank 10 when an upper limit amount of the reaction liquid is supplied to the reaction tank 10, and Lmin denotes the liquid level of the reaction liquid L remaining in the reaction tank when the reaction liquid L has been completely discharged from the reaction tank 10 (i.e., the liquid level of the lower limit amount of the reaction liquid). Lmin coincides with the opening position of the reaction tank discharge section 12 provided in the reaction tank 10. Lmax is set in consideration of the volume of the reaction liquid that is pushed back into the reaction tank 10 by supplying a CO2-containing gas from the bypass flow path 64 into the pipe 45, which will be described later. Lof denotes the liquid level when an excess amount of reaction liquid L is supplied to the reaction tank 10, causing leakage from the CO2-removed gas discharge section 80, which will be described later.

[0014] 3. Reaction liquid supply unit 20 and injection valve abnormality detection unit 30 The reaction liquid supply unit 20 supplies the reaction liquid L stored in the reaction liquid supply source 21 to the reaction tank 10. As shown in Fig. 1, the reaction liquid supply unit 20 is provided with an injection valve 25 that controls the injection of the reaction liquid L into the reaction tank 10. The reaction liquid supply unit 20 is provided with branch points downstream of the injection valve 25 that branch off to each of the reaction tanks 10a to 10d, and is configured so that the reaction liquid L is injected into each of the reaction tanks 10a to 10d.

[0015] The reaction liquid L can be an aqueous solution of an alkali metal hydroxide or an aqueous solution of an alkaline earth metal hydroxide. In this embodiment, an aqueous solution of NaOH was used as the reaction liquid L. The concentration of the aqueous NaOH solution is not limited and can be set appropriately as needed.

[0016] Furthermore, the reaction liquid supply unit 20 is provided with a reaction liquid flow sensor 22 that detects the pressure or flow rate of the reaction liquid L flowing through the reaction liquid supply unit 20. In this embodiment, the injection valve abnormality detection unit 30 detects an abnormality in the injection valve 25 based on the pressure or flow rate of the reaction liquid L flowing through the reaction liquid supply unit 20 detected by the reaction liquid flow sensor 22.

[0017] For example, if a malfunction occurs in which the injection valve 25 is stuck in the open position, the reaction liquid L will continue to be supplied to the reaction tank 10 by the reaction liquid supply unit 20. When the reaction liquid L is supplied to the reaction tank 10 above the upper limit height position Lmax shown in FIG. 1 and reaches the overflow height position Lof, the reaction liquid L will leak from the CO2 removal gas discharge unit 80, causing the pressure of the reaction liquid L in the reaction liquid supply unit 20 to increase rapidly and the flow rate to decrease rapidly. Based on this, the injection valve abnormality detection unit 30 can detect a malfunction in which the injection valve 25 is stuck in the open position when the amount of change in the pressure or flow rate of the reaction liquid L detected by the reaction liquid flow sensor 22 is equal to or greater than a reference value.

[0018] 4. CO2-containing gas supply unit 60 The CO2-containing gas supply unit 60 supplies a CO2-containing gas to the reaction vessel 10. In this specification, the term "CO2-containing gas" refers to a gas containing CO2 as a constituent component. The CO2-containing gas may be a gas containing only CO2 as a constituent component, or may further contain unavoidable impurities. The CO2-containing gas may also be a mixed gas containing CO2 and other substances as constituent components. The proportion of CO2 in the mixed gas is not limited, and the main component with the largest proportion in the mixed gas may be CO2 or a substance other than CO2.

[0019] The CO2-containing gas is supplied via a pump 62 from a CO2-containing gas supply source 61 connected to a CO2-containing gas supply unit 60, and is blown into the reaction liquid L from a bubbling unit 63 connected to the tip of the CO2-containing gas supply unit 60. The type of CO2-containing gas supply source 61 is not limited, and may be, for example, a CO2-containing gas discharge facility that discharges the CO2-containing gas as an exhaust gas. Examples of the CO2-containing gas discharge facility include a facility with a boiler, a fuel cell, an incinerator, and a heat treatment facility.

[0020] 5. Bubbling Unit 63 As shown in FIGS. 3 and 4, the bubbling unit 63 of this embodiment is connected to the tip of the CO2-containing gas supply unit 60. The bubbling unit 63 includes a first unit 63a and a second unit 63b. The first unit 63a has a first extension portion 631 extending vertically and multiple (six in this embodiment) second extension portions 632 branching off and extending from the first extension portion 631. The number of second extension portions 632 is not particularly limited and may be two to five, or seven or more. The second extension portions 632 are arranged in a fan-shaped manner so that they are spaced apart from each other toward the tip. Multiple (two in this embodiment) outlets 633 are arranged at the tips of the multiple second extension portions 632, respectively. The second unit 63b is provided vertically below the first unit 63a and has a configuration similar to that of the first unit 63a.

[0021] 4, the first unit 63a is provided with six second extension portions 632, and the outlets 633 located at the tips of the respective second extension portions 632 are inclined slightly inward with respect to the tangent direction of an imaginary circle R centered on the central axis O when viewed from the direction of the central axis O of the first unit 63a and the second unit 63b. The CO2-containing gas is blown out from each outlet 633 in the direction indicated by arrow A, thereby generating a flow B in the reaction liquid L in the reaction tank 10 that rotates in the circumferential direction around the central axis O. Similarly, in the second unit 63b, a flow B in the reaction liquid L in the reaction tank 10 that rotates in the circumferential direction around the central axis O is generated.

[0022] 6. CO2 fixation reaction Next, a description will be given of the CO fixation reaction in the reaction tank 10. As described above, the CO fixation reaction progresses when the CO-containing gas F1 is blown into the reaction liquid L in the reaction tank 10. In the present embodiment 1, a case where an aqueous NaOH solution is used as the reaction liquid L will be described.

[0023] As a CO2 fixation reaction in the reaction tank 10, the reaction of the following formula 1 takes place, and then the reaction of the following formula 2 takes place. 2NaOH+CO2→ Na2CO3+H2O (Formula 1) Na2CO3+CO2+H2O→ 2NaHCO3 (formula 2)

[0024] Before the reaction begins, there is no NaHCO3 or Na2CO3 in the reaction vessel 10. However, depending on the progress of the reaction, one of the following states occurs: Na2CO3 is produced and no NaHCO3 is present; some Na2CO3 further reacts with CO2 to produce NaHCO3, resulting in both NaHCO3 and NaHCO3; or all Na2CO3 is converted to NaHCO3, resulting in the absence of NaHCO3 and the presence of NaHCO3. Both NaHCO3 and Na2CO3 produced by the reaction dissolve in the water in the reaction vessel 10 and form aqueous solutions. In this specification, the aqueous solutions of NaHCO3, Na2CO3, and their mixture are collectively referred to as the "reaction product." The reaction product recovered from the reaction vessel 10 can be recovered in a solid state by dehydrating and drying it. The recovered reaction product can be used as a resource.

[0025] 7. CO2 removal gas discharge section 80 The CO2-removed gas from which CO2 has been removed by the above-described CO2 fixation reaction is discharged to the outside of the reaction vessel 10 from a CO2-removed gas discharge part 80 shown in Figures 1 and 2. In this embodiment, in consideration of the possibility that the CO2-removed gas may contain harmful components, a filter 81 for collecting the harmful components is provided in the CO2-removed gas discharge part 80.

[0026] 8. Connecting manifold 40 As shown in FIGS. 1 and 2, the CO2 capture system 1 is provided with a connection manifold 40 connected to each of the reaction vessel discharge sections 12 of the multiple reaction vessels 10. The connection manifold 40 connects the multiple reaction vessels 10 to each other, thereby communicating the insides of the multiple reaction vessels 10. In this embodiment, the connection manifold 40 has a reaction product discharge section 41 that collectively discharges reaction products discharged from the reaction vessel discharge sections 12 of the multiple reaction vessels 10. The reaction product discharge section 41 is provided with a discharge valve 42 that controls the discharge of the reaction products. The reaction products discharged from the reaction product discharge section 41 are recovered in the product recovery section 70. Note that, although not usually performed, the reaction liquid L can also be discharged from the reaction product discharge section 41. In this embodiment, the reaction product discharge section 41 in the connection manifold 40 is located vertically below the position Lmin, which is the lower limit position of the reaction liquid L in the reaction vessel 10.

[0027] 9. Tube 45 The connection manifold 40 is provided with a pipe 45. In this embodiment, the pipe 45 is cylindrical and communicates with the plurality of reaction vessels 10 via the connection manifold 40. The pipe 45 is installed vertically and has a height equal to or greater than the liquid level Lmax of the reaction liquid L in the reaction vessel 10 when an upper limit amount of the reaction liquid is supplied to the reaction vessel 10. As a result, when the reaction liquid L is supplied from the reaction liquid supply unit 20 to the plurality of reaction vessels 10, the reaction liquid L flows into the pipe 45 from the plurality of reaction vessels 10 via the connection manifold 40. As a result, the liquid level of the reaction liquid L supplied into the reaction vessel 10 and the liquid level of the reaction liquid L flowing into the pipe 45 in the pipe 45 are the same.

[0028] The shape of the tubular body 45 is not limited to a cylindrical shape, and may be a rectangular tube shape. The opening diameter of the hollow part of the tubular body 45 is not limited, but is preferably relatively small, and may be, for example, in the range of 10 to 30 mm, and is set to 16 mm in this embodiment. This makes it easy to detect the liquid level of the reaction liquid that has flowed into the tubular body 45 from the multiple reaction vessels 10 via the connecting manifold 40, while keeping the volume of the hollow part of the tubular body 45 relatively small.

[0029] 10. Liquid level detection unit 46, lower limit liquid level detection unit 13, and liquid level determination unit 31 The pipe 45 is provided with a liquid level detection unit 46. The liquid level detection unit 46 detects the liquid level of the reaction liquid that has flowed into the pipe 45 from the multiple reaction vessels 10. There are no limitations on the configuration of the liquid level detection unit 46, but it is preferable that the liquid level detection unit 46 be a non-contact detection device that is provided outside the pipe 45 and configured to detect the presence or absence of the reaction liquid inside the pipe 45. This is because by not coming into contact with the reaction liquid L, which is a strong alkali, the required alkali resistance performance can be lowered, and equipment costs can be reduced.

[0030] The non-contact detection device constituting the liquid level detection unit 46 can be, for example, a capacitance sensor, a laser sensor, an acoustic sensor, or a radio wave sensor. In this embodiment, a capacitance proximity switch, which is a type of capacitance sensor, is used. In addition, in this embodiment, the capacitance proximity switch constituting the liquid level detection unit 46 is of a normally closed type, in which an output signal is ON when no reaction liquid is detected in the tubular body 45 and an output signal is OFF when a reaction liquid is detected. In this embodiment, the liquid level detection unit 46 is provided in the tubular body 45 at a height that coincides with the liquid level of the reaction liquid L in the reaction tank 10 when an upper limit amount of the reaction liquid L is supplied to the reaction tank 10.

[0031] In this embodiment, a lower limit liquid level detector 13 is provided below each reaction vessel 10 to detect the position Lmin, which is the lower limit of the reaction liquid L in the reaction vessel 10. The configuration of the lower limit liquid level detector 13 is not limited, but it is preferable to use a non-contact detection device, similar to the liquid level height detector 46 provided in the pipe body 45. In this embodiment, a capacitance-type proximity switch is used as the lower limit liquid level detector 13. In addition, in this embodiment, the capacitance-type proximity switch constituting the lower limit liquid level detector 13 is of a normally open type, in which the output signal is OFF when no reaction liquid is detected in the reaction vessel 10 and the output signal is ON when reaction liquid is detected.

[0032] As a result, when the lower limit liquid level detector 13 switches from a state in which it detects the reaction product when the reaction product is discharged after the reaction in each reaction tank 10 is completed to a state in which it does not detect the reaction product, it can detect that the amount of reaction product remaining in the reaction tank 10 is at the lower limit, i.e., that the discharge of the reaction product from each reaction tank 10 has been completed. The lower limit liquid level detector 13 may be provided at a position corresponding to the position Lmin, which is the lower limit position of the reaction product in the reaction tank 10, on the pipe body 45. In this case, the number of parts can be reduced compared to when the lower limit liquid level detector 13 is provided in each reaction tank 10.

[0033] The liquid level determination unit 31 determines the liquid level of the reaction tank 10 based on the detection results of the liquid level detection unit 46 and the lower limit liquid level detection unit 13. In this embodiment, when the reaction liquid L is supplied, the liquid level in the pipe 45 detected by the liquid level detection unit 46 is compared with Lmax, and when the liquid level in the pipe 45 reaches Lmax, it is determined that the upper limit amount of the reaction liquid L has been injected into the reaction tank 10. Furthermore, when the reaction product is discharged, it is determined that the discharge of the reaction product has been completed when the liquid level in the reaction tank 10 detected by the lower limit liquid level detection unit 13 reaches Lmin.

[0034] 11. Liquid level detection abnormality determination unit 32 In this embodiment, the liquid level detection abnormality judgment unit 32 detects that the reaction liquid L in the reaction tank 10 has reached an upper limit amount using a normally closed type liquid level detection unit 46, and detects that the reaction liquid L in the reaction tank 10 has reached a lower limit amount using a normally open type lower limit liquid level detection unit 13, thereby making it possible to judge abnormalities in the liquid level detection unit 46 and the lower limit liquid level detection unit 13.

[0035] That is, when the liquid level detection unit 46 and the lower limit liquid level detection unit 13 are operating normally, the output signals of both units cannot be turned OFF during the supply of the reaction liquid L and the discharge of the reaction products. Based on this, if a failure occurs in which the liquid level detection unit 46 does not operate due to a break in the power line, the output signals of the liquid level detection unit 46 and the lower limit liquid level detection unit 13 will be turned OFF within the set time for reaching the target liquid level after the command to start supplying the reaction liquid L and the command to discharge the reaction products, so that a failure of the liquid level detection unit 46 can be detected. Furthermore, when a failure occurs in which the lower limit liquid level detection unit 13 does not operate due to a break in the power line, the output signals of the liquid level detection unit 46 and the lower limit liquid level detection unit 13 will be turned OFF within the set time for reaching the target liquid level after the command to start supplying the reaction liquid L and the command to discharge the reaction products, so that a failure of the lower limit liquid level detection unit 13 can be detected.

[0036] 12. Bypass flow path 64 As shown in FIG. 1, a bypass flow path 64 is provided, bypassing the CO2-containing gas supply unit 60 and connected to the tubular body 45. The bypass flow path 64 can supply a CO2-containing gas into the tubular body 45. The bypass flow path 64 is provided with a bypass valve 65 that controls the flow of the CO2-containing gas in the bypass flow path. When the reaction liquid L is present in the tubular body 45, the CO2-containing gas is supplied into the tubular body 45 via the bypass flow path 64, and the reaction liquid L present in the tubular body 45 and the connecting manifold 40 is pushed back into each reaction vessel 10 via the connecting manifold 40. This allows the reaction liquid L present in the tubular body 45 and the connecting manifold 40 to be subjected to a CO2 fixation reaction.

[0037] 13. Physical quantity detection unit 47 and reaction state determination unit 33 1, the connection manifold 40 is provided with a physical quantity detection unit 47. The physical quantity detection unit 47 detects a physical quantity of the reaction liquid L flowing through the connection manifold 40. Examples of the physical quantity of the reaction liquid L to be detected include pH, temperature, conductivity, and weight, and the physical quantity detection unit 47 can be a detection device corresponding to the physical quantity to be detected. In this embodiment, a pH meter that detects the pH of the reaction liquid L is used as the physical quantity detection unit 47.

[0038] 1 determines the progress of the CO2 fixation reaction in the multiple reaction vessels 10 based on the detection results of the physical quantity detection unit 47. In this embodiment, the reaction state determination unit 33 can estimate the progress of the CO2 fixation reaction based on the pH of the reaction solution L measured by the physical quantity detection unit 47.

[0039] Here, the relationship between the pH and weight gain of the reaction solution L in the reaction tank 10 and the progress of the CO2 fixation reaction will be described in detail using Figures 5(a) to 5(d). First, before the start of the reaction, the reaction tank 10 is charged with an aqueous NaOH solution, so the pH of the reaction solution L in the reaction tank 10 is a high value of about 14, as shown in Figure 5(a). Therefore, after the CO2 gas supply start time T0, only the reaction of the above formula 1 progresses.

[0040] After time T0, as the reaction of Equation 1 progresses, the NaOH in the aqueous solution is consumed as shown in Figure 5(c), and the pH gradually decreases as shown in Figure 5(a). As a result, CO2 is fixed in the aqueous solution as Na2CO3, and the amount of Na2CO3 produced gradually increases as shown in Figure 5(d). As a result, the weight of the aqueous solution also gradually increases as shown in Figure 5(b).

[0041] Then, as shown in Figure 5(c), at time T1, all of the NaOH in reaction solution L reacts with CO2, disappearing from reaction solution L, and the pH drops to approximately 12 as shown in Figure 5(a). Then, as shown in Figure 5(b), the weight gain of the aqueous solution reaches R1, and the amount of Na2CO3 produced reaches a maximum as shown in Figure 5(d).

[0042] After time T1, the supply of CO2 gas continues, causing the reaction of formula 2 to proceed. As a result, Na2CO3 in the reaction solution L is gradually consumed as shown in Figure 5(d), and the pH further decreases as shown in Figure 5(a). As a result, in the reaction tank 10, CO2 reacted with Na2CO3 is taken into the reaction solution L as Na2CO3, and the amount of NaHCO3 produced begins to increase as shown in Figure 5(e). As a result, the weight of the reaction solution L further increases as shown in Figure 5(b).

[0043] Then, at time T2, as shown in Figure 5(d), all of the Na2CO3 in the aqueous solution reacts with CO2, resulting in the disappearance of Na2CO3 from the reaction solution L, and the pH drops to approximately 8.5 as shown in Figure 5(a). Then, as shown in Figure 5(b), the weight gain of the reaction solution L reaches R2, and the amount of NaHCO3 produced reaches a maximum as shown in Figure 5(d). If the supply of CO2 gas continues after time T2, the CO2 gas dissolves into the reaction solution L as H2CO3, causing the pH to further decrease as shown in Figure 5(a) and the weight of the reaction solution L to further increase as shown in Figure 5(b), but the amount of NaHCO3 produced remains at its maximum as shown in Figure 5(e).

[0044] From the above, the following correspondence relationship is established between the pH and weight increase of the reaction liquid L in the reaction tank 10 and the progress of the CO2 fixation reaction. (1) At time T0 before the start of the reaction shown in Figure 5(a), that is, when the pH is approximately 14 and the weight increase of the reaction liquid L is 0, the initial state is one in which NaOH is present but Na2CO3 and NaHCO3 are not present. (2) In the first section I from time T0 to just before T1, that is, when the pH drops from about 14 to about 12 and the weight increase of the reaction liquid L is greater than 0 and less than R1, the first state is reached in which NaOH and Na2CO3 coexist and NaHCO3 is not present. (3) At time T1, i.e., when the pH is about 12 and the weight gain of the aqueous solution is R1, a second state is reached in which there is no NaOH, there is Na2CO3, and there is no NaHCO3. (4) After time T1, in the second section II until the pH drops from about 12 to about 8.5 and before T2, that is, when the weight increase of the reaction liquid L is greater than R1 and less than R2, NaOH is not present and a third state is reached in which Na2CO3 and NaHCO3 coexist. (5) At time T2 and in the third section III after T2, that is, when the pH is below approximately 8.5 and the weight gain of the reaction liquid L is equal to or greater than R2, a fourth state is reached in which NaOH and Na2CO3 are absent but NaHCO3 is present.

[0045] Based on these, the reaction state determination unit 33 determines that the reaction of the above formula (1) is completed when the pH of the reaction liquid L in the connecting manifold 40 reaches approximately 12 based on the detection results of the physical quantity detection unit 47, and determines that the reaction of the above formula (2) is completed when the pH reaches approximately 8.5.

[0046] The physical quantity detection unit 47 can also be configured with a thermocouple, which is a temperature sensor. Both Equations 1 and 2 above are exothermic reactions, but the exothermic energy of the Na2CO3 production reaction shown in Equation 1 is approximately eight times that of the NaHCO3 production reaction shown in Equation 2, and the exothermic energies of the two reactions are significantly different. As described above, the CO2 fixation reaction is carried out by the reaction of Equation 1 followed by the reaction of Equation 2. Therefore, the temperature (liquid temperature) of the reaction liquid L in the reaction tank 10 is affected by the exothermic energy of Equations 1 and 2 above and changes depending on the progress of the reaction. Therefore, the reaction status determination unit 33 can determine the progress of the CO2 fixation reaction based on the temperature of the reaction liquid L in the connection manifold 40 detected by the thermocouple, which is a temperature sensor, serving as the physical quantity detection unit 47.

[0047] In this embodiment, as shown in FIG. 1, a temperature acquisition unit 48 is inserted into the lid 11 of each of the reaction vessels 10a to 10d. The temperature acquisition unit 48 acquires the temperature (liquid temperature) of the reaction liquid in each of the reaction vessels 10a to 10d. In this embodiment 1, the temperature acquisition unit 43 is configured with a thermocouple. As described above, the progress of the CO2 fixation reaction can be determined based on the temperature of the reaction liquid L in the reaction vessels 10a to 10d. Therefore, the reaction status determination unit 33 can determine the progress of the CO2 fixation reaction for each of the reaction vessels 10a to 10d based on the detection results by the temperature acquisition unit 48. Note that, since the progress of the CO2 fixation reaction is generally more accurately determined based on the pH of the reaction liquid L than based on the temperature of the reaction liquid L, the progress of the CO2 fixation reaction can be preliminarily determined based on the liquid temperature detected by the temperature acquisition unit 43.

[0048] 14. Exhaust valve abnormality detection unit 34 1 acquires the detection result of the physical quantity detection unit 47, and when the amount of change in the physical quantity detected by the detection result is equal to or greater than a reference value, detects an abnormality in the discharge valve 42. In this embodiment, a pH meter is used as the physical quantity detection unit 47, and when the amount of change in pH acquired by the physical quantity detection unit 47 is equal to or greater than a reference value, an abnormality in the discharge valve 42 is detected.

[0049] For example, if a fault occurs in which the discharge valve 42 is stuck in the open position, the reaction products in the reaction vessel 10 are discharged from the reaction product discharge section 41 via the connection manifold 40. Even after the lower limit amount Lmin in the reaction vessel 10 is reached, the discharge valve 42 remains open, so the reaction products in the connection manifold 40 are discharged from the reaction product discharge section 41. As a result, the electrodes of the pH meter serving as the physical quantity detection section 47 are exposed to the atmosphere, causing a sudden drop in the pH value. The discharge valve abnormality detection section 34 detects that the amount of change in pH detected by the physical quantity detection section 47 is equal to or greater than the reference value, thereby identifying the sudden drop in the pH value and detecting a fault in the discharge valve 42.

[0050] Furthermore, even when a temperature sensor (thermocouple) is used as the physical quantity detection unit 47, if the discharge valve 42 remains open and the reaction products in the connecting manifold 40 continue to be discharged from the reaction product discharge unit 41, the detected temperature will drop sharply when the thermocouple serving as the physical quantity detection unit 47 is exposed to the atmosphere. The discharge valve abnormality detection unit 34 detects that the amount of change in the temperature detected by the physical quantity detection unit 47 is equal to or greater than a reference value, thereby grasping the sharp drop in the temperature value and detecting a failure of the discharge valve 42 based on this.

[0051] 15. Control Unit 2 1 controls the flow of CO2-containing gas in the CO2-containing gas supply unit 60 and the open / close states of the injection valve 25 and the exhaust valve 42. In this embodiment, the flow of CO2-containing gas in the CO2-containing gas supply unit 60 is controlled by controlling the operation of a pump 62 provided in the CO2-containing gas supply unit 60. In this embodiment, the control unit 2 also controls the open / close state of a bypass valve 65 that controls the flow of CO2-containing gas in a bypass flow path 64.

[0052] 16. Automatic operation of CO2 capture by CO2 capture system 1 Next, the flow of the automatic operation process for CO2 capture in the CO2 capture system 1 of the first embodiment will be described with reference to the flow diagram in Fig. 6. First, in step S1, the control unit 2 receives a command to inject a reaction liquid. Then, in step S2, the control unit 2 closes the discharge valve 42 and opens the injection valve 25. As a result, in step S3, the reaction liquid L is supplied to each of the reaction vessels 10a to 10b. At this time, a portion of the reaction liquid L supplied to each of the reaction vessels 10a to 10b is also supplied to the pipe 45 via the connecting manifold 40.

[0053] Thereafter, in step S4, the liquid level determination unit 31 determines whether the liquid level of the reaction liquid L in each reaction vessel 10 has reached the upper limit liquid level Lmax based on the detection result of the liquid level detection unit 46 provided in the tubular body 45. If it is determined that the liquid level has not reached the upper limit liquid level Lmax, proceed to No in step S4 and perform step S4 again.

[0054] On the other hand, if it is determined in step S4 that the liquid level of the reaction liquid L in each reaction vessel 10 has reached the upper limit liquid level Lmax, the process proceeds to step S4 (Yes). Then, in step S5, the control unit 2 closes the injection valve 25. Furthermore, in step S6, the control unit 2 opens the bypass valve 65. Thereafter, in step S7, the control unit 2 drives the pump 62 to supply CO2-containing gas from the CO2-containing gas supply source 61 to the bubbling unit 63 via the CO2-containing gas supply unit 60, and blows the gas from the bubbling unit 63 into the reaction liquid L. At the same time, CO2-containing gas is supplied into the pipe 45 via the bypass flow path 64, and the reaction liquid L in the pipe 45 and the connecting manifold 40 is pushed back into each reaction vessel 10. The volume of CO2-containing gas required to push back the reaction liquid L in the pipe 45 and the connecting manifold 40 is preset, and the supply of CO2-containing gas continues until the set volume of CO2-containing gas is supplied to the pipe 45.

[0055] Then, in step S8, after the set volume of CO2-containing gas is supplied to the pipe 45, the control unit 2 closes the bypass valve 65. Note that the supply of CO2-containing gas to each reaction vessel 10 continues.

[0056] Then, in step S9, the reaction status determination unit 33 determines whether the reaction to produce the target product has been completed based on the pH measurement result by the physical quantity detection unit 47. If the target product is Na2CO3, the reaction is determined to be completed when the pH measurement result by the physical quantity detection unit 47 reaches approximately 12. If the target product is NaHCO3, the reaction is determined to be completed when the pH measurement result by the physical quantity detection unit 47 reaches approximately 8.5. If it is determined in step S9 that the reaction to produce the target product has not been completed, proceed to No in step S9 and perform step S9 again.

[0057] On the other hand, if it is determined in step S9 that the reaction for producing the target product has been completed, the process proceeds to Yes in step S9, and in step S10, the control unit 2 stops the pump 62 to stop the supply of the CO2-containing gas. Next, in step S11, the control unit 2 opens the discharge valve 42, and the reaction products in each reaction tank 10 are collectively discharged from the reaction product discharge unit 41.

[0058] Thereafter, in step S12, the liquid level determination unit 31 determines whether the liquid level is at the lower limit level Lmin based on the detection result by the lower limit liquid level detection unit 13. If it is determined in step S12 that the liquid level is not at the lower limit level Lmin, proceed to No in step S12 and perform step S12 again. On the other hand, if it is determined in step S12 that the liquid level is at the lower limit level Lmin, it is determined that the discharge is complete and proceed to Yes in step S12.

[0059] Then, in step S13, the control unit 2 closes the discharge valve 42. Thereafter, in step S14, the control unit 2 determines whether or not an end command for the flow has been received. If it is determined in step S14 that an end command has been received, the process proceeds to Yes in step S14, where the flow ends. On the other hand, if it is determined in step S14 that an end command has not been received, the process proceeds to No in step S14, where step S1 and subsequent steps are performed again. According to this flow, the CO2 capture system 1 of this embodiment 1 can absorb CO2 and obtain the target product by automatic processing.

[0060] 17. Action and Effects Next, the effects of the CO2 capture system 1 of this embodiment will be described in detail. In the CO2 capture system 1 of this embodiment, by using multiple reaction vessels 10, the amount of CO2-containing gas that can be processed can be increased, allowing for larger-scale operation. The CO2 capture system 1 is provided with a connection manifold 40 that is connected to the multiple reaction vessels 10 to communicate between the reaction vessels 10, and a pipe 45 provided in the connection manifold 40 communicates with the multiple reaction vessels 10 via the connection manifold 40. This allows the liquid level of the multiple reaction vessels 10 to be estimated by detecting the liquid level in the pipe 45 of the reaction liquid L that has flowed into the pipe 45 from the multiple reaction vessels 10. Therefore, since there is no need to provide a liquid level detection device for detecting the liquid level in each of the multiple reaction vessels 10, equipment costs can be reduced. Furthermore, the number of parts can be reduced compared to when a liquid level detection device is provided in each of the multiple reaction vessels 10, improving maintainability.

[0061] Furthermore, even when the reaction liquid L is injected into the reaction vessels 10, the reaction vessels 10 are connected by the connecting manifold 40, so that the reaction liquid L flows so as to equalize the liquid levels in each of the reaction vessels 10 (including the tubular body 45). The opening diameter of the hollow part of the tubular body 45 is smaller than the inner diameter of the reaction vessels 10, and resistance is generated on the inner surface of the tubular body 45 against the liquid flowing through the tubular body 45. Therefore, even if waves are generated on the liquid surface of the reaction vessel 10, the waves are unlikely to propagate to the liquid level in the tubular body 45 above the connecting manifold 40, and therefore, rippling generated on the liquid surface of the reaction liquid L that flows into the tubular body 45 from multiple reaction vessels 10 via the connecting manifold 40 is extremely small. Therefore, the liquid level can be accurately detected without waiting for the rippling of the liquid surface to subside, resulting in excellent operability.

[0062] In this embodiment, the liquid level detection unit 46 is configured as a non-contact detection device that is provided outside the pipe 45 and configured to detect the presence or absence of the reaction liquid L inside the pipe 45. As a result, the liquid level detection unit 46 does not come into contact with the reaction liquid L, which is a strong alkali, and therefore the required alkali resistance performance can be lowered, and installation costs can be reduced.

[0063] Furthermore, in this embodiment, the connection manifold 40 includes a reaction liquid discharge section 41 that collectively discharges the reaction liquid L containing the reaction products discharged from the multiple reaction vessels 10. This achieves both the function of collectively estimating the liquid level heights of the multiple reaction vessels 10 using the pipe body 45 and the function of consolidating the discharge sections of the multiple reaction vessels 10 in one place, thereby reducing the number of parts and making the device more compact as a whole.

[0064] In addition, this embodiment is equipped with an injection valve 25 provided in the reaction liquid supply unit 20 and controlling the injection of the reaction liquid L into the reaction tank 10, an exhaust valve 42 provided in the reaction liquid discharge unit 41 and controlling the discharge of the reaction product from the connecting manifold 40, a liquid level determination unit 31 that determines whether the height of the reaction liquid L in the pipe body 45 detected by the liquid level detection unit 46 has reached a reference value, a reaction state determination unit 33 that determines the progress state of the reaction that produces the reaction product in the reaction tank 10, a CO2-containing gas supply unit 60 that supplies a CO2-containing gas to the multiple reaction tanks 10, and a control unit 2 that controls the flow of the CO2-containing gas in the CO2-containing gas supply unit 60 and the open / close states of the injection valve 25 and the exhaust valve 42.

[0065] Then, based on a command to start supplying the reaction liquid L, the control unit 2 closes the exhaust valve 42 and opens the injection valve 25. When the liquid level determination unit 31 determines that the height of the reaction liquid L in the pipe 45 has reached a reference value, the control unit 2 closes the injection valve 25 and controls the flow of CO2-containing gas in the CO2-containing gas supply unit 60 so that CO2-containing gas is supplied into the reaction vessel 10. When the reaction state determination unit 33 determines that the reaction is complete, the control unit 2 controls the flow of CO2-containing gas in the CO2-containing gas supply unit 60 so that the supply of CO2-containing gas is stopped, and opens the exhaust valve 42. This allows the reaction liquid L to be appropriately supplied into the reaction vessel 10, the CO2-containing gas to be appropriately supplied into the reaction vessel 10, the completion of the reaction to be appropriately determined, the supply of CO2-containing gas to be stopped, the exhaust valve 42 to be opened, and the reaction products to be appropriately discharged. Therefore, the supply of the reaction liquid L and the discharge of the reaction products can be performed automatically.

[0066] Furthermore, this embodiment includes a bypass flow path 64 that bypasses the CO2-containing gas supply unit 60 and is connected to the pipe 45 to supply the CO2-containing gas into the pipe 45, and a bypass valve 65 that is provided in the bypass flow path 64 and controls the flow of the CO2-containing gas in the bypass flow path 64. Thus, by supplying the CO2-containing gas into the pipe 45 via the bypass flow path 64 and the bypass valve 65, the reaction liquid L remaining in the pipe 45 and the connecting manifold 40 can be returned to the reaction tank 10, thereby preventing unreacted reaction liquid from remaining.

[0067] Furthermore, in this embodiment, when a command to start supplying the reaction liquid L is sent, the control unit 2 closes the exhaust valve 42 and the bypass valve 65 and opens the injection valve 25. When the liquid level determination unit 31 determines that the height of the reaction liquid L in the tubular body 45 has reached a reference value, the control unit 2 closes the injection valve 25 and opens the bypass valve 65. After controlling the flow of CO2-containing gas in the CO2-containing gas supply unit 60 so that the CO2-containing gas is supplied into the reaction tank 10 and the tubular body 45, the control unit 2 closes the bypass valve 65 when the reaction liquid L present in the tubular body 45 and the connecting manifold 40 has completely moved into the reaction tank 10. This allows the bypass flow path 64 and the bypass valve 65 to appropriately start and stop the supply of the reaction liquid L to the reaction tank 10, and also allows the CO2-containing gas to be appropriately supplied into the tubular body 45 while the CO2-containing gas is being supplied into the reaction tank 10. As a result, it is possible to automatically prevent unreacted reaction liquid L from remaining.

[0068] Furthermore, this embodiment includes a CO2 removal gas discharge unit 80 that is provided at a position higher than the liquid level of the upper limit amount of reaction liquid L in the reaction tank 10 and is configured to be able to discharge gas within the reaction tank 10 from the reaction tank 10, an injection valve 25 that is provided in the reaction liquid supply unit 20 and controls the flow of reaction liquid L in the reaction liquid supply unit 20, a reaction liquid flow sensor 22 that detects the pressure or flow rate of the reaction liquid flowing through the reaction liquid supply unit 20, and an injection valve abnormality detection unit 30 that detects an abnormality in the injection valve 25 based on the pressure or flow rate of the reaction liquid L detected by the reaction liquid flow sensor 22. This makes it possible to appropriately start and stop the supply of reaction liquid L to the reaction tank 10, supply a CO2-containing gas into the reaction tank 10, and appropriately discharge the CO2-removed gas from which CO2 has been removed outside the reaction tank 10 from the CO2 removal gas discharge unit 80, while automatically detecting an abnormality in the injection valve 25.

[0069] Furthermore, the control unit 2, reaction state determination unit 33, liquid level height determination unit 31, liquid level detection abnormality determination unit 32, injection valve abnormality detection unit 30, and discharge valve abnormality detection unit 34 may be implemented by a control device such as a personal computer (PC), a server, or a mobile terminal such as a smartphone, and may be equipped with a CPU (Central Processing Unit) and a storage device to perform control, determination, detection, etc. The control unit 2, reaction state determination unit 33, liquid level height determination unit 31, liquid level detection abnormality determination unit 32, injection valve abnormality detection unit 30, and discharge valve abnormality detection unit 34 may be provided in a single control device, or at least one of each may be provided in a separate control device. Furthermore, the control device may be an embedded control device such as a PLC or CNC (Computerized Numerical Control) device. In addition, the control device may be equipped with a display unit such as a display (liquid crystal, organic electroluminescence, etc.) (some devices are equipped with a display unit), and the display unit may display conditions such as the reaction status (including abnormalities), liquid level (including abnormalities), opening and closing of the injection valve (including abnormalities), and opening and closing of the discharge valve (including abnormalities).

[0070] As described above, according to the above-described embodiment, it is possible to provide a CO2 recovery system 1 that increases the amount of CO2-containing gas that can be treated, and that is excellent in terms of facility cost, maintainability, and operability.

[0071] The present invention is not limited to the above-described embodiment and modified forms, and can be applied to various embodiments without departing from the spirit of the present invention. [Explanation of symbols]

[0072] 1...CO2 capture system 10, 10a to 10d...Reaction tank 11…Lid 12...Reactor discharge section 13...Lower limit liquid level detector 20...Reaction liquid supply section 22...Reaction liquid flow sensor 25...Injection valve 30...Injection valve abnormality detection unit 31…Judgment section 32...Liquid level detection abnormality judgment unit 33...Reaction state determination unit 34...Discharge valve abnormality detection unit 40...Connecting manifold 41...Reaction product discharge section 42...Exhaust valve 43…Temperature acquisition section 45...Body 46...Liquid level detector 47...Physical quantity detection unit 48...Thermocouple 48…Temperature acquisition section 50L…Capacity 60...CO2-containing gas supply unit 64...Bypass flow path 65...Bypass valve 70...Product recovery section 80...Removed gas exhaust section 81...Filter

Claims

1. CO ２ CO in the reaction solution that can react with ２ CO by contacting the containing gas to produce reaction products ２ CO2 recovery ２ 1. A recovery system comprising: A plurality of reaction vessels configured to store the reaction liquid; a reaction solution supply unit that supplies the reaction solution into the plurality of reaction vessels; a connecting manifold that connects the plurality of reaction vessels to each other to allow communication between the interiors of the plurality of reaction vessels; a pipe that communicates with the plurality of reaction vessels via the connecting manifold and has a height equal to or higher than the liquid level of the reaction liquid in the reaction vessel when an upper limit amount of the reaction liquid is supplied to the reaction vessel; a liquid level detection unit that detects the liquid level in the tubular body of the reaction liquid that has flowed into the tubular body from the plurality of reaction vessels via the connecting manifold when the reaction liquid is supplied from the reaction liquid supply unit to the plurality of reaction vessels. ２ Collection system.

2. 2. The CO 2 solution according to claim 1, wherein the liquid level detector is a non-contact detector that is provided outside the pipe and configured to detect the presence or absence of the reaction liquid inside the pipe. ２ Collection system.

3. 3. The CO 2 system according to claim 1, wherein the connecting manifold includes a reaction product discharge section that collectively discharges the reaction products discharged from the plurality of reaction vessels. ２ Collection system.

4. an injection valve provided in the reaction solution supply unit and configured to control the injection of the reaction solution into the reaction tank; a discharge valve provided in the reaction product discharge section and configured to control discharge of the reaction product from the connecting manifold; a liquid level determination unit that determines whether the height of the reaction liquid in the pipe detected by the liquid level detection unit has reached a reference value; a reaction state determination unit that determines a progress state of the reaction that produces the reaction product in the reaction tank; The CO ２ supplying a CO containing gas to the plurality of reaction vessels; ２ a containing gas supply unit; The CO ２ The CO-containing gas supply unit ２ a control unit that controls the flow of the contained gas and the open / close states of the injection valve and the exhaust valve; Equipped with The control unit based on a command to start supplying the reaction solution, the discharge valve is closed and the injection valve is opened; When the liquid level determination unit determines that the height of the reaction liquid in the pipe has reached a reference value, the injection valve is closed and the CO ２ The CO containing gas is supplied into the reaction vessel. ２ The CO-containing gas supply unit ２ Controlling the flow of contained gas, When the reaction state determination unit determines that the reaction is complete, ２ The supply of the CO containing gas is stopped. ２ The CO-containing gas supply unit ２ 4. The CO 2 gas according to claim 3, wherein the flow of the contained gas is controlled to open the exhaust valve. ２ Collection system.

5. The CO ２ The CO 2 gas is bypassed from the containing gas supply unit and connected to the pipe body, and the CO 2 gas is introduced into the pipe body. ２ a bypass flow path for supplying the contained gas; The bypass flow path is provided with the CO ２ and a bypass valve for controlling the flow of the contained gas. ２ Collection system.

6. The control unit based on a command to start supplying the reaction solution, the discharge valve and the bypass valve are closed and the injection valve is opened; When the liquid level determination unit determines that the height of the reaction liquid in the pipe has reached a reference value, the injection valve is closed and the bypass valve is opened, ２ The CO containing gas is supplied into the reaction vessel and the tubular body. ２ The CO-containing gas supply unit ２ 6. The CO 2 gas control method according to claim 5, wherein, after controlling the flow of the reactant gas, the bypass valve is closed when the reactant liquid present in the tubular body and the connecting manifold is completely moved into the reaction tank. ２ Collection system.

7. a CO 2 gas supply system that is provided at a position higher than the liquid level of the reaction liquid in the reaction tank and is configured to be able to discharge gas from the reaction tank. ２ a removal gas exhaust section; an injection valve provided in the reaction solution supply unit and controlling the flow of the reaction solution in the reaction solution supply unit; a reaction liquid flow sensor for detecting a pressure or a flow rate of the reaction liquid flowing through the reaction liquid supply section; and an injection valve abnormality detection unit that detects an abnormality in the injection valve based on the pressure or flow rate of the reaction liquid detected by the reaction liquid flow sensor. ２ Collection system.

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