Carbon dioxide recovery device

Abstract

A carbon dioxide recovery device comprising: a tank that stores an alkaline reaction solution; a pump that feeds a gas containing carbon dioxide to the inside of the tank; and a bubbler that turns the gas into a plurality of bubbles and supplies the gas into the reaction solution, wherein the bubbler is formed such that the average diameter of the plurality of bubbles in the reaction solution is 0.01-1.5 mm.

Description

Carbon dioxide capture equipment

[0001] The present disclosure relates to a carbon dioxide capture device. This application claims priority to Japanese Patent Application No. 2024-070681, filed on April 24, 2024. The entire contents of the Japanese patent application are incorporated herein by reference.

[0002] It is desirable to reduce the amount of carbon dioxide emitted into the environment. Carbon dioxide is contained in exhaust gas from factories, for example. Patent Document 1 discloses a CO ２ A recovery device is disclosed. An aqueous solution is stored in a reaction tank. The aqueous solution is an alkali metal hydroxide aqueous solution or an alkaline earth metal hydroxide aqueous solution. A gas discharge unit is provided in the reaction tank. The gas discharge unit turns gas containing carbon dioxide into bubbles and discharges them into the aqueous solution. In the reaction tank, the bubbles come into contact with the aqueous solution, causing a reaction between the alkali metal hydroxide or alkaline earth metal hydroxide and carbon dioxide. This reaction reduces the amount of carbon dioxide emitted into the environment. Hereinafter, the aqueous solution that reacts with the bubbles of gas containing carbon dioxide is referred to as the reaction solution.

[0003] JP 2023-65903 A

[0004] The carbon dioxide capture device of the present disclosure includes a tank for storing an alkaline reaction solution, a pump for feeding a gas containing carbon dioxide into the tank, and a bubbler for generating a plurality of bubbles from the gas and supplying the bubbles to the reaction solution, the bubbler being formed so that the average diameter of the plurality of bubbles in the reaction solution is 0.01 mm or more and 1.5 mm or less.

[0005] Fig. 1 is a schematic diagram of a carbon dioxide capture apparatus according to a first embodiment. Fig. 2 is a schematic diagram showing an example of the arrangement of a bubbler provided in the carbon dioxide capture apparatus according to the first embodiment. Fig. 3 is a schematic diagram showing an example of a bubbler provided in the carbon dioxide capture apparatus according to the first embodiment. Fig. 4 is a schematic diagram of a carbon dioxide capture apparatus according to a second embodiment. Fig. 5 is a schematic diagram of a carbon dioxide capture apparatus according to a third embodiment. Fig. 6 is a schematic diagram of a carbon dioxide capture apparatus according to a fourth embodiment.

[0006] [Problem to be Solved by the Present Disclosure] Gas bubbles containing carbon dioxide are typically formed by a bubbler placed in the reaction solution. The bubbler has multiple holes. The gas sent to the bubbler by a pump passes through each hole and forms bubbles of the gas in the reaction solution. Electricity is required to drive the pump. When power is generated to drive the pump using fossil fuels, if the amount of carbon dioxide emitted as a result of that power generation is greater than the amount of carbon dioxide captured by the carbon dioxide capture device, the amount of carbon dioxide released into the environment cannot be reduced.

[0007] One of the objects of the present disclosure is to provide a carbon dioxide capture device that can capture more carbon dioxide than the amount of carbon dioxide emitted converted from the power consumption required to operate the carbon dioxide capture device. [Effects of the Present Disclosure] The carbon dioxide capture device of the present disclosure can capture more carbon dioxide than the amount of carbon dioxide emitted converted from the power consumption required to operate the carbon dioxide capture device.

[0008] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0009] (1) A carbon dioxide capture device according to an embodiment of the present disclosure includes a tank for storing an alkaline reaction solution, a pump for feeding a gas containing carbon dioxide into the tank, and a bubbler for generating a plurality of bubbles from the gas and supplying the bubbles to the reaction solution, the bubbler being formed so that the average diameter of the plurality of bubbles in the reaction solution is 0.01 mm or more and 1.5 mm or less.

[0010] The bubbles in the reaction solution are formed when a gas containing carbon dioxide passes through multiple holes in the bubbler. The size of the holes in the bubbler is one of the factors that determine the average diameter of the bubbles in the reaction solution. The smaller the size of the holes in the bubbler, the smaller the average diameter of the bubbles in the reaction solution. However, the smaller the size of the holes in the bubbler, the greater the driving power of the pump. If the bubbler is formed so that the average diameter of the bubbles in the reaction solution is 0.01 mm or more, the driving power of the pump will not be too high. Therefore, even if the driving power of the pump is generated using fossil fuels, the amount of carbon dioxide emitted during the power generation is unlikely to exceed the amount of carbon dioxide captured by the carbon dioxide capture device. If the average diameter of the bubbles in the reaction solution is 1.5 mm or less, the reaction between the reaction solution and carbon dioxide will easily occur.

[0011] (2) The carbon dioxide capture device of (1) above may capture more carbon dioxide than the carbon dioxide emission amount calculated from the amount of power consumption required to operate the carbon dioxide capture device.

[0012] Carbon dioxide capture devices are operated using electricity. When fossil fuels are used to generate electricity for the carbon dioxide capture device, carbon dioxide is emitted from the power generation equipment. The electricity generated using fossil fuels is called "electric power F," the amount of carbon dioxide emitted from the power generation equipment per unit time in conjunction with the generation of electricity consumed by the carbon dioxide capture device is called "emissions amount d," and the amount of carbon dioxide that can be captured per unit time by the carbon dioxide capture device is called "captured amount c." Even if the carbon dioxide capture device is operated using electric power F, if the captured amount c is greater than the emissions amount d, the amount of carbon dioxide emitted into the environment can be reduced.

[0013] (3) In the carbon dioxide recovery device of (1) or (2) above, the bubbler may be disposed in the reaction solution so as to be spaced apart from the bottom surface of the tank.

[0014] Carbon dioxide reacts with the reaction solution and is recovered as a solid. This solid settles on the bottom of the tank. If the bubbler is placed in the reaction solution so as to have a gap between it and the bottom of the tank, the settled solid is less likely to clog the holes in the bubbler, making it difficult to reduce the amount of bubbles generated by the bubbler over the long term.

[0015] (4) In any of the carbon dioxide recovery devices described in (1) to (3) above, the bubbler may include an inlet for the gas and a plurality of outlet holes for forming the plurality of bubbles, and the plurality of outlet holes may be positioned so that the distance from the liquid surface of the reaction solution is 50 mm or more.

[0016] If the discharge hole is positioned at a distance of 50 mm or more from the liquid surface of the reaction solution, the residence time of the bubbles in the reaction solution will be long. If the residence time of the bubbles is long, the contact time between the reaction solution and the bubbles will be long, and the reaction between the reaction solution and carbon dioxide will be more likely to occur.

[0017] (5) In the carbon dioxide recovery device of (4) above, the plurality of discharge holes may be formed from a porous material.

[0018] When the plurality of discharge holes are formed from a porous material, the average diameter of the plurality of bubbles in the reaction solution tends to be 0.01 mm or more and 1.5 mm or less.

[0019] (6) In the carbon dioxide recovery device of (5) above, the porous material may have an opening of 0.5 mm or less.

[0020] If the opening of the porous material is 0.5 mm or less, the average diameter of the bubbles in the reaction solution is likely to be 0.01 mm or more and 1.5 mm or less.

[0021] (7) In any of the carbon dioxide recovery devices described in (4) to (6) above, the plurality of discharge holes may comprise, when the bubbler is viewed from above, a plurality of first discharge holes located in a first region that is visible from above, and a plurality of second discharge holes located in a second region that is not visible from above, and the number density of the plurality of first discharge holes may be smaller than the number density of the plurality of second discharge holes.

[0022] Solid matter formed by the reaction of the reaction solution with carbon dioxide may accumulate on the bubbler. The solid matter accumulated on the bubbler may clog the first discharge hole. If the second discharge hole is provided, it is difficult to reduce the amount of bubbles generated by the bubbler over a long period of time, even if the first discharge hole is clogged.

[0023] (8) In the carbon dioxide recovery device according to any one of (4) to (7) above, the pressure of the gas in the inlet may be 105 kPa or more and 200 kPa or less.

[0024] If the gas pressure at the inlet is 105 kPa or more, it is easy to form a plurality of bubbles with an average diameter of 0.01 mm to 1.5 mm. If the gas pressure at the inlet is 200 kPa or less, the power required to drive the pump is not too large.

[0025] (9) In the carbon dioxide recovery device according to any one of (1) to (8) above, the bubbler may be made of a material selected from titanium, a titanium alloy, or stainless steel.

[0026] A bubbler made of the above material has excellent corrosion resistance, and the holes formed in the bubbler are less likely to become clogged.

[0027] (10) The carbon dioxide recovery device according to any one of (1) to (9) above may further include a temperature adjustment unit that adjusts the temperature of the reaction solution.

[0028] By adjusting the temperature of the reaction solution, it is possible to increase the reaction efficiency between the reaction solution and carbon dioxide, and to increase the recovery efficiency of the solid matter formed by the reaction between the reaction solution and carbon dioxide.

[0029] (11) In the carbon dioxide recovery device of (10) above, the temperature adjustment unit may include a heating unit that sets the temperature of at least a part of the reaction solution that contacts the bubbler to 30° C. or higher.

[0030] By setting the temperature of the reaction solution in contact with the bubbler to 30° C. or higher, the reaction efficiency between the reaction solution and carbon dioxide tends to increase.

[0031] (12) In the carbon dioxide recovery device of (10) or (11) above, a cooling unit may be provided that sets the temperature of the reaction solution in contact with the bubbler and at least a part of the reaction solution below the bubbler to 25°C or less.

[0032] By setting the temperature of the reaction solution to 25°C or less, the solid matter formed by the reaction of the reaction solution with carbon dioxide is less likely to dissolve, and the recovery efficiency of the solid matter is likely to be increased.

[0033] (13) In the carbon dioxide recovery device according to any one of (1) to (12) above, the reaction solution may contain a hydroxide, carbonate, or bicarbonate containing one selected from the group consisting of sodium, potassium, magnesium, and calcium.

[0034] The hydroxides, carbonates, and hydrogencarbonates listed above are likely to react with carbon dioxide. (14) In the carbon dioxide recovery device according to any one of (1) to (13), the viscosity of the reaction solution may be 0.3 mPa·s or more and 3.0 mPa·s or less.

[0035] In a reaction solution having a viscosity of 0.3 mPa·s or more and 3.0 mPa·s or less, the average diameter of the bubbles tends to be 0.01 mm or more and 1.5 mm or less.

[0036] (15) The carbon dioxide recovery apparatus of (13) above may further include a measurement unit that measures at least one of the pH and viscosity of the reaction solution, and a supply unit that replenishes the hydroxide, the carbonate, or the bicarbonate in accordance with the measurement result of the measurement unit.

[0037] When a solid is formed by the reaction of the reaction solution with carbon dioxide, the concentration of the alkaline component in the reaction solution decreases, resulting in a decrease in reaction efficiency. The alkaline component is, for example, a hydroxide, carbonate, or bicarbonate containing one selected from the group consisting of sodium, potassium, magnesium, and calcium. If the decrease in the concentration of the alkaline component in the reaction solution can be measured by a measurement unit and the alkaline component can be replenished in accordance with the measurement result, the concentration of the alkaline component in the reaction solution is less likely to decrease, and the reaction efficiency is less likely to decrease.

[0038] [Details of the embodiment of the present disclosure] Specific examples of the carbon dioxide capture device of the present disclosure will be described with reference to the drawings. The same reference numerals in the drawings indicate the same or equivalent parts. In each drawing, for the convenience of explanation, some of the configuration may be exaggerated or simplified. The dimensional ratios of each part in the drawings may also differ from the actual ratios. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0039] <Embodiment 1> A carbon dioxide capture device 1 of Embodiment 1 will be described with reference to Figures 1 to 3. As shown in Figure 1, the carbon dioxide capture device 1 includes a tank 2, a pump 3, and a bubbler 4. An alkaline reaction solution 10 is stored in the tank 2. The pump 3 sends a gas containing carbon dioxide into the tank 2. The bubbler 4 turns the gas into a plurality of bubbles 40 and supplies the bubbles 40 into the reaction solution 10 in the tank 2. In Embodiment 1, the bubbler 4 is disposed on the bottom surface 21 of the tank 2. One of the features of the carbon dioxide capture device 1 of Embodiment 1 is that the bubbler 4 is formed so that the average diameter of the plurality of bubbles 40 in the reaction solution 10 is 0.01 mm or more and 1.5 mm or less. The carbon dioxide-containing gas is, for example, exhaust gas from a heat engine such as a boiler.

[0040] <<Tank>> The tank 2 is a container having an internal space in which the reaction solution 10 is stored. The size of the internal space can be selected appropriately depending on the required amount of the reaction solution 10. The tank 2 in which the reaction solution 10 is stored has a gas phase section 25 above the tank 2.

[0041] The shape of the tank 2 is not particularly limited and can be selected appropriately. The shape of the tank 2 is, for example, a rectangular parallelepiped or cylindrical shape. In Fig. 1, the external appearance of the tank 2 is shown in a simplified form for ease of understanding.

[0042] In the tank 2 of this example, the height of the internal space of the tank 2 is greater than the width. As will be described later, bubbles 40 are formed in the reaction solution 10 stored in the tank 2. If the height of the internal space of the tank 2 is greater, it is easier to increase the depth of the reaction solution 10, and it is easier to increase the distance L1 from the liquid surface of the reaction solution 10 to the bubbler 4. If the distance L1 is longer, the residence time of the bubbles 40 is likely to be longer, and the reaction between the reaction solution 10 and carbon dioxide is likely to occur. If the depth of the reaction solution 10 is greater, there is a greater degree of freedom in the location of the bubbler 4. However, if the depth of the reaction solution 10 is too deep, the water pressure on the bubbler 4 is greater, and the driving power of the pump 3 for ejecting multiple bubbles 40 from the bubbler 4 becomes greater.

[0043] A plurality of through-holes are provided in the upper part of the tank 2. The plurality of through-holes include through-holes through which the inlet pipe 5 and the outlet pipe 6 are respectively inserted. The inlet pipe 5 is a flow path for gas containing carbon dioxide. In this example, one inlet pipe 5 is arranged to extend vertically. The open end of the inlet pipe 5 is connected to an inlet hole 41 (FIG. 3) of the bubbler 4, which will be described later. The outlet pipe 6 is a flow path for gas from which carbon dioxide has been removed. In this example, one outlet pipe 6 is arranged. The open end of the outlet pipe 6 is arranged in the gas phase section 25.

[0044] The tank 2 is made of, for example, stainless steel. <<Reaction Solution>> The reaction solution 10 stored in the tank 2 is alkaline. An alkaline reaction solution 10 easily absorbs carbon dioxide. The reaction solution 10 contains, for example, a hydroxide, carbonate, or bicarbonate containing one selected from the group consisting of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca). The alkaline component contained in the reaction solution 10 is, for example, sodium hydroxide (NaOH), sodium carbonate (NaCO ３ ), or sodium bicarbonate (NaHCO ３ The alkaline component contained in the reaction solution 10 may be sodium sesquicarbonate. The hydroxides, carbonates, or hydrogen carbonates listed above are likely to react with carbon dioxide.

[0045] For example, the reaction solution 10 may contain sodium carbonate (NaCO ３), when the reaction solution 10 comes into contact with carbon dioxide, the following reaction takes place:

[0046] NaCO ３ +CO ２ +H ２ O → 2NaHCO ３ 2NaHCO formed by the reaction of reaction solution 10 with carbon dioxide ３ , or so-called baking soda, is a solid 100 (FIG. 2). That is, carbon dioxide reacts with the reaction solution 10 and is recovered as a solid 100. This solid 100 precipitates on the bottom surface 21 of the tank 2. The gas from which carbon dioxide has been removed passes through the gas phase section 25 and is discharged to the outside of the tank 2 from the discharge pipe 6. Even when the alkaline component contained in the reaction solution 10 is other than sodium carbonate, a similar reaction occurs, and carbon dioxide is recovered as a solid 100.

[0047] The viscosity of the reaction solution 10 is, for example, 0.3 mPa·s or more and 3.0 mPa·s or less. In a reaction solution 10 having a viscosity of 0.3 mPa·s or more and 3.0 mPa·s or less, the average diameter of the plurality of bubbles 40 formed by the bubbler 4 described below tends to be 0.01 mm or more and 1.5 mm or less. The viscosity of the reaction solution 10 may be 0.4 mPa·s or more and 2.0 mPa·s or less, or 0.6 mPa·s or more and 1.6 mPa·s or less.

[0048] <Pump> The pump 3 is a device that sends a gas containing carbon dioxide into the tank 2 at a predetermined pressure, and is disposed in the inlet pipe 5. The pump 3 in this example is an electric pump.

[0049] <Bubbler> The bubbler 4 is placed in the reaction solution 10 stored in the tank 2. The bubbler 4 converts the gas sent into the tank 2 through the inlet pipe 5 into a plurality of bubbles 40 and supplies the gas into the reaction solution 10.

[0050] In this example, as shown in FIG. 2 , three bubblers 4 are arranged. Each of the three bubblers 4 has a similar configuration. Three branched introduction pipes 51 are connected to the tip of the introduction pipe 5. In this example, one bubbler 4 is connected to each branch introduction pipe 51. The three bubblers 4 are arranged to extend radially from the axis of the introduction pipe 5. In this example, the three bubblers 4 are arranged at equal intervals of 120°. If multiple bubblers 4 are arranged at equal intervals, multiple bubbles 40 are likely to be supplied to the reaction solution 10 evenly throughout. As a result, the reaction solution 10 is likely to react with carbon dioxide uniformly throughout, rather than in a concentrated area. A space is provided between adjacent bubblers 4. The solid matter 100 formed by the reaction of the reaction solution 10 with carbon dioxide is mainly deposited in the space between adjacent bubblers 4. The number and placement of the bubblers 4 can be selected as appropriate. For example, the plurality of bubblers 4 may be arranged in a regular line with intervals between them, or may be arranged in a random line with intervals between them.

[0051] As shown in FIG. 3 , each bubbler 4 has one or more inlet holes 41 and multiple outlet holes 42. For clarity, FIG. 3 only shows a portion of the multiple outlet holes 42. In this example, the bubbler 4 is cylindrical, with one inlet hole 41 located at the center of the end face of the bubbler 4. The inlet hole 41 is connected to an inlet pipe 5, which in this example is a branched inlet pipe 51. The multiple outlet holes 42 are distributed around the circumferential surface of the bubbler 4. Distributed outlet holes 42 mean that the multiple outlet holes 42 are not unevenly distributed around the circumferential surface of the bubbler 4, but are uniformly distributed over the entire circumferential surface. For example, adjacent outlet holes 42 are spaced apart from each other by a certain distance. The inlet hole 41 and each outlet hole 42 communicate with the internal space 45 of the bubbler 4. For clarity, FIG. 3 only shows a simplified representation of some of the multiple outlet holes 42, and the internal space 45 of the bubbler 4 is indicated by a dashed line. The gas introduced from the inlet 41 flows through the bubbler 4 along the axis of the bubbler 4 and is discharged from each outlet 42 in the form of bubbles into the reaction solution 10 .

[0052] Each bubbler 4 is arranged so that the distance L1 ( FIG. 1 ) from the liquid level of the reaction solution 10 to each outlet hole 42 is, for example, 50 mm or more. In other words, the distance L1 between the liquid level of the reaction solution 10 and the outlet hole 42 closest to the liquid level of the reaction solution 10 is 50 mm or more. If each outlet hole 42 is arranged at a position where the distance L1 is 50 mm or more, the residence time of the bubbles 40 in the reaction solution 10 is increased. If the residence time of the bubbles 40 is long, the contact time between the reaction solution 10 and the bubbles 40 is increased, making it easier for the reaction solution 10 to react with carbon dioxide. The distance L1 may be 100 mm or more, or 200 mm or more.

[0053] Distance L1 is, for example, 1000 mm or less. If each outlet hole 42 is located at a position where distance L1 is 1000 mm or less, the water pressure on the bubbler 4 will not be too high, and the driving power of the pump 3 for discharging bubbles 40 from each outlet hole 42 will not be too high. Distance L1 is, for example, 50 mm to 1000 mm, 100 mm to 600 mm, or 200 mm to 400 mm.

[0054] The bubbler 4 is formed so that the average diameter of the bubbles 40 in the reaction solution 10 is 0.01 mm or more and 1.5 mm or less. The size of each outlet hole 42 is one of the factors that determine the average diameter of the bubbles 40 in the reaction solution 10. The smaller the size of each outlet hole 42, the smaller the average diameter of the bubbles 40 in the reaction solution 10. However, the smaller the size of each outlet hole 42, the greater the driving power of the pump 3. If the bubbler 4 is formed so that the average diameter of the bubbles 40 in the reaction solution 10 is 0.01 mm or more, the driving power of the pump 3 will not be too high. If the average diameter of the bubbles 40 in the reaction solution 10 is 1.5 mm or less, the reaction between the reaction solution 10 and carbon dioxide will be facilitated. The average diameter of the bubbles 40 in the reaction solution 10 may be formed so that it is 0.05 mm or more and 1.0 mm or less, or 0.1 mm or more and 0.7 mm or less. The average diameter of the bubbles 40 in the reaction solution 10 is determined by the measurement method described in the test example below.

[0055] The multiple discharge holes 42 are formed, for example, from a porous material. The porous material may be, for example, a sintered material formed by sintering powder, or a laminated material formed by stacking multiple plates with multiple holes formed therein. When the multiple discharge holes 42 are formed from a porous material, the average diameter of the multiple bubbles 40 in the reaction solution 10 is likely to be 0.01 mm or more and 1.5 mm or less. The opening of the porous material is, for example, 0.5 mm or less. If the opening of the porous material is 0.5 mm or less, the average diameter of the multiple bubbles 40 in the reaction solution 10 is likely to be 0.01 mm or more and 1.5 mm or less. The opening of the porous material is, for example, 0.05 mm or more. The opening of the porous material can be appropriately selected within a range such that the average diameter of the multiple bubbles 40 in the reaction solution 10 is 0.01 mm or more and 1.5 mm or less. The opening of the porous material may be 0.05 mm or more and 0.5 mm or less, or 0.075 mm or more and 0.25 mm or less.

[0056] In this example, when the bubbler 4 is viewed from above, the multiple discharge holes 42 include multiple first discharge holes 421 located in a first region visible from above and multiple second discharge holes 422 located in a second region invisible from above. Solids 100 ( FIG. 2 ) formed by the reaction of the reaction solution 10 with carbon dioxide may accumulate on the bubbler 4. The solids 100 accumulated on the bubbler 4 may clog the first discharge holes 421. The provision of multiple second discharge holes 422 allows the bubbler 4 to supply multiple bubbles 40 even if the first discharge holes 421 are clogged. The number of the multiple second discharge holes 422 is, for example, greater than the number of the multiple first discharge holes 421. If the number of the multiple second discharge holes 422 is greater than the number of the multiple first discharge holes 421, fewer discharge holes 42 are clogged with solids 100, making it difficult to reduce the amount of bubbles 40 generated by the bubbler 4 over the long term.

[0057] The number density of the multiple first discharge holes 421 is, for example, smaller than the number density of the multiple second discharge holes 422. The number density of the first discharge holes 421 is the number of first discharge holes 421 provided per unit area of ​​the first region of the bubbler 4. The number density of the second discharge holes 422 is the number of second discharge holes 422 provided per unit area of ​​the second region of the bubbler 4. If the number density of the multiple first discharge holes 421 is smaller than the number density of the multiple second discharge holes 422, it is difficult to reduce the amount of bubbles 40 generated by the bubbler 4 over a long period of time even if the first discharge holes 421 are blocked.

[0058] The cross-sectional shape of the bubbler 4 may be circular, rectangular, or polygonal, including a triangle. Circles include, for example, perfect circles and ellipses. Quadrilaterals include, for example, squares, rectangles, and trapezoids. For example, when the cross-sectional shape of the bubbler 4 is square or rectangular, the first region is formed as a horizontal plane. If the first region is formed as a horizontal plane, the solids 100 tend to accumulate in the first region, but the bubbles 40 supplied from each first outlet hole 421 tend to float independently without combining. For example, when the cross-sectional shape of the bubbler 4 is square or rectangular, the second region is formed as a vertical plane. If the second region is formed as a vertical plane, the bubbles 40 supplied from each second outlet hole 422 may combine to form larger bubbles 40, but the solids 100 are less likely to accumulate in the second region. For example, when the cross-sectional shape of the bubbler 4 is trapezoidal or triangular, the first region may have an inclined surface whose width increases from top to bottom. When the first region has an inclined surface, solid matter 100 is less likely to accumulate than when the first region has only horizontal and vertical surfaces, and the bubbles 40 supplied from each first discharge hole 421 are more likely to float independently of each other without combining with each other.

[0059] The bubbler 4 is made of a material selected from titanium, a titanium alloy, or stainless steel, for example. A bubbler 4 made of the above material has excellent corrosion resistance. A bubbler 4 made of the above material is less likely to clog the multiple discharge holes 42.

[0060] The gas pressure at the inlet 41 is, for example, 105 kPa or more and 200 kPa or less. If the gas pressure at the inlet 41 is 105 kPa or more, it is easy to form a plurality of bubbles 40 having an average diameter of 0.01 mm or more and 1.5 mm or less. If the gas pressure at the inlet 41 is 200 kPa or less, the power required to drive the pump 3 does not become too large. The gas pressure at the inlet 41 may be 110 kPa or more and 150 kPa or less, or 110 kPa or more and 130 kPa or less.

[0061] Electric power is required to operate the carbon dioxide capture device 1. One example of the power consumption required to operate the carbon dioxide capture device 1 is the power to drive the pump 3, which sends gas to the bubbler 4. As described above, the bubbler 4 is formed so that the average diameter of the bubbles 40 in the reaction solution 10 is 0.01 mm or more. Therefore, the driving power of the pump 3 is not too large. Therefore, even when the driving power of the pump 3 is generated using fossil fuel, the amount of carbon dioxide emitted as a result of the power generation is unlikely to be greater than the amount of carbon dioxide captured by the carbon dioxide capture device 1. The carbon dioxide capture device 1 of this example captures more carbon dioxide than the amount of carbon dioxide emitted calculated from the amount of power consumption required to operate the carbon dioxide capture device 1. Even when the carbon dioxide capture device 1 is operated using electricity generated using fossil fuel, if more carbon dioxide can be captured than the amount of carbon dioxide emitted as a result of the power generation, the amount of carbon dioxide emitted into the environment can be reduced.

[0062] <Embodiment 2> The carbon dioxide capture device 1 of Embodiment 2 will be described with reference to Fig. 4. In the carbon dioxide capture device 1 of Embodiment 2, the bubbler 4 is disposed in the reaction solution 10 so as to be spaced from the bottom surface 21 of the tank 2. The carbon dioxide capture device 1 of Embodiment 2 has the same configuration as that of Embodiment 1 except for the location of the bubbler 4.

[0063] Solid matter 100 formed by the reaction of reaction solution 10 with carbon dioxide settles on bottom surface 21 of tank 2. If bubbler 4 is disposed in reaction solution 10 so as to be spaced from bottom surface 21 of tank 2, the settled solid matter 100 is less likely to clog each of discharge holes 42 (FIG. 3) provided in bubbler 4, and the amount of bubbles 40 generated by bubbler 4 is less likely to be reduced over the long term.

[0064] The bubbler 4 is disposed, for example, such that the distance L2 from the bottom surface 21 of the tank 2 is 50 mm or more. In other words, the distance L2 between the bottom surface of the bubbler 4 and the bottom surface 21 of the tank 2 is 50 mm or more. If the distance L2 is 50 mm or more, the settled solids 100 are unlikely to accumulate on the bubbler 4. Even if the solids 100 accumulate on the bubbler 4, if the bubbler 4 has discharge holes 42 on its side and bottom surfaces, the discharge holes 42 are unlikely to be blocked by the solids 100, and the bubbler 4 can adequately supply a plurality of bubbles 40. The distance L2 may be 100 mm or more, or 200 mm or more.

[0065] The bubbler 4 may be disposed so that the distance L1 from the liquid surface of the reaction solution 10 is 50 mm or more and the distance L2 from the bottom surface 21 of the tank 2 is 50 mm or more. If the distance L1 is 50 mm or more, the residence time of the bubbles 40 in the reaction solution 10 increases, facilitating the reaction of the reaction solution 10 with carbon dioxide. In other words, if the distance L1 is 50 mm or more, a large amount of solid matter 100 will settle. If the distance L2 is 50 mm or more, even if a large amount of solid matter 100 settles, the discharge hole 42 of the bubbler 4 is unlikely to be clogged by the solid matter 100.

[0066] The bubbler 4 may be fixed to, for example, the side surface 22 of the tank 2 or may be fixed to a support member (not shown) fixed to the bottom surface 21 of the tank 2 .

[0067] <Embodiment 3> The carbon dioxide capture device 1 of Embodiment 3 will be described with reference to Fig. 5. The carbon dioxide capture device 1 of Embodiment 3 further includes a temperature adjustment unit 7 that adjusts the temperature of the reaction solution 10. In the carbon dioxide capture device 1 of Embodiment 3, the bubbler 4 is disposed in the reaction solution 10 so as to be spaced apart from the bottom surface 21 of the tank 2. The carbon dioxide capture device 1 of Embodiment 3 has the same configuration as that of Embodiment 2, except that it includes the temperature adjustment unit 7.

[0068] The temperature adjusting unit 7 includes at least one of a heating unit 71 and a cooling unit 72. The temperature adjusting unit 7 of this example includes the heating unit 71 and the cooling unit 72.

[0069] The heating unit 71 maintains the temperature of the reaction solution 10 in contact with the bubbler 4 at 30°C or higher. The heating unit 71 is, for example, a heater. In this example, the heating unit 71 is disposed in the internal space 45 (FIG. 3) of the bubbler 4. In this example, the heating unit 71 is a linear heating element corresponding to the length of the bubbler 4. When the temperature of the bubbler 4 is increased by the heating unit 71, the temperature of the reaction solution 10 around the bubbler 4 and above the bubbler 4 also increases. If the temperature of the reaction solution 10 is 30°C or higher, the reaction efficiency between the reaction solution 10 and carbon dioxide is likely to be high. The heating unit 71 may be configured to maintain the temperature of the reaction solution 10 at 35°C or higher or 38°C or higher. The heating unit 71 may be configured to maintain the temperature of the reaction solution 10 at 80°C or lower. If the temperature of the reaction solution 10 is 80°C or lower, the reaction solution 10 is less likely to evaporate.

[0070] The heating unit 71 may be arranged around the bubbler 4. The heating unit 71 may be arranged above, below, or on the side of the bubbler 4. The heating unit 71 may be a planar heating element on which a plurality of bubblers 4 are placed. If the planar heating element has openings partially formed in a lattice pattern, the openings serve as passages for the solid material 100.

[0071] The heating unit 71 may utilize the gas before it is introduced into the pump 3. For example, a region of the inlet pipe 5 upstream of the pump 3 may be disposed in the reaction solution 10. If the gas before it is introduced into the pump 3 is at a high temperature, when the gas flows through the inlet pipe 5 disposed in the reaction solution 10, heat is exchanged between the gas and the reaction solution 10, causing the temperature of the reaction solution 10 to rise. In this case, electricity consumed for heating is not required, and the carbon dioxide capture device 1 can be operated efficiently.

[0072] The cooling unit 72 keeps the temperature of the reaction solution 10 in contact with the bubbler 4 and at least a portion of the reaction solution 10 below the bubbler 4 at 25° C. or less. In this example, the cooling unit 72 is disposed in a lower region of the tank 2 located below the bubbler 4, and keeps the temperature of the reaction solution 10 in contact with at least a portion of the lower region at 25° C. or less. The lower region of the tank 2 is the bottom surface 21 of the tank 2 and the region of the side surface 22 of the tank 2 located below the bubbler 4. The cooling unit 72 is disposed in at least a portion of the bottom surface 21 and side surface 22 of the tank 2. In this example, a high temperature region is formed in the upper layer of the reaction solution 10, and a low temperature region is formed in the lower layer.

[0073] The cooling section 72 in this example is a planar cooling section arranged to contact the outer surface of the wall forming the bottom surface 21 of the tank 2. The cooling section 72 in this example is flat and has no openings. When the temperature of at least a portion of the bottom surface 21 and side surface 22 of the tank 2 located below the bubbler 4 is lowered by the cooling section 72, the temperature of the reaction solution 10 below the bubbler 4 is lowered. The solid matter 100 formed by the reaction of the reaction solution 10 with carbon dioxide accumulates below the bubbler 4. If the temperature of the reaction solution 10 below the bubbler 4 is 25°C or lower, the solid matter 100 that comes into contact with the reaction solution 10 is less likely to dissolve, and the recovery efficiency of the solid matter 100 is likely to be improved. The cooling section 72 may be configured to maintain the temperature of the reaction solution 10 at 20°C or lower or 15°C or lower. The cooling section 72 may be configured to maintain the temperature of the reaction solution 10 at 5°C or higher. If the temperature of the reaction solution 10 is 5°C or higher, precipitation of the alkaline components in the reaction solution 10, which can occur when the temperature of the entire reaction solution 10 drops, is less likely to occur, and the absorption capacity of the reaction solution 10 is not lost.

[0074] The cooling unit 72 is, for example, a heat pipe or a heat dissipation fin. For example, a cool plate with built-in water-cooling piping or a Peltier-type cool plate can be used as the cooling unit 72. The cool plate is, for example, a copper plate. The cooling unit 72 may be formed by joining or building in water-cooling piping to at least a portion of the bottom surface 21 and side surface 22 of the tank 2, or by disposing the water-cooling piping in the reaction solution 10. The cooling unit 72 may be formed by forcibly cooling the portion of the water-cooling piping exposed from the reaction solution 10 or the portion exposed from the tank 2 with a fan. The cooling unit 72 may be formed by disposing the portion of the tank 2 below the bubbler 4 in the cooling water stored in the tank.

[0075] The cooling unit 72 may be arranged around the bubbler 4. For example, when a plurality of bubblers 4 are arranged as in this example, a heating unit 71 may be arranged in each bubbler 4, and the cooling unit 72 may be arranged to surround the plurality of bubblers 4. In this case, a high-temperature region is formed in the center of the reaction solution 10, and a low-temperature region is formed in the outer periphery.

[0076] The temperature adjustment unit 7 is not essential. The temperature adjustment unit 7 may include the heating unit 71 but not the cooling unit 72. If the cooling unit 72 is not included, the bubbler 4 may be disposed on the bottom surface 21 of the tank 2. The temperature adjustment unit 7 may include the cooling unit 72 but not the heating unit 71.

[0077] One of the power consumptions required to operate the carbon dioxide capture device 1 is the power to operate the temperature adjustment unit 7. If the reaction efficiency between the reaction solution 10 and carbon dioxide can be increased by the heating unit 71, it is possible to capture more carbon dioxide than the amount of carbon dioxide emitted calculated from the amount of power consumption required to operate the carbon dioxide capture device 1. The temperature adjustment unit 7 may utilize exhaust heat from a factory that uses a heat engine such as a boiler. Using the exhaust heat from the heat engine can reduce the power required to operate the temperature adjustment unit 7. In particular, if the exhaust gas from the heat engine is used as the gas supplied to the carbon dioxide capture device 1 and the exhaust heat from the heat engine is used as the temperature adjustment unit 7, the carbon dioxide capture device 1 can be operated efficiently.

[0078] <Fourth Embodiment> A carbon dioxide capture apparatus 1 of Embodiment 4 will be described with reference to Fig. 6. The carbon dioxide capture apparatus 1 of Embodiment 4 includes a measurement unit 8 that measures the state of the reaction solution 10, and a supply unit 9 that replenishes the reaction solution 10 with an alkaline component in accordance with the measurement results of the measurement unit 8. The alkaline component is, for example, a hydroxide, carbonate, or bicarbonate containing one selected from the group consisting of sodium, potassium, magnesium, and calcium. In the carbon dioxide capture apparatus 1 of Embodiment 4, the bubbler 4 is disposed in the reaction solution 10 so as to be spaced from the bottom surface 21 of the tank 2. The carbon dioxide capture apparatus 1 of Embodiment 4 has the same configuration as that of Embodiment 2, except for including the measurement unit 8 and the supply unit 9.

[0079] The measurement unit 8 measures at least one of the pH and viscosity in the reaction solution 10. When the reaction solution 10 reacts with carbon dioxide to form a solid 100, the concentration of the alkaline component in the reaction solution 10 decreases, and the reaction efficiency decreases. When the concentration of the alkaline component in the reaction solution 10 decreases, the pH decreases. Furthermore, when the concentration of the alkaline component in the reaction solution 10 decreases, the viscosity decreases. Therefore, by measuring at least one of the pH and viscosity in the reaction solution 10, the concentration of the alkaline component in the reaction solution 10 can be determined from the measurement results.

[0080] The supply unit 9 includes a storage 91 and an introduction pipe 92. The storage 91 stores the alkaline component contained in the reaction solution 10. The storage 91 in this example is provided with an openable and closable lid (not shown). The supply unit 9 in this example includes an actuator that operates to open and close the lid. The actuator is, for example, a motor. The introduction pipe 92 connects the storage 91 and the tank 2. The supply unit 9 replenishes the alkaline component in accordance with the measurement results of the measurement unit 8. The alkaline component may be replenished manually. In the case of manual replenishment, the alkaline component can be replenished as appropriate by checking the measurement results of the measurement unit 8.

[0081] The alkaline component may be replenished automatically. In the automatic mode, the alkaline component is replenished by a controller (not shown) based on the measurement results of the measurement unit 8. The processing performed by the controller is realized by a processing circuit (circuitry) including one or more processors. The processing circuit may be formed by an integrated circuit that combines one or more memories, various analog circuits, and various digital circuits in addition to the one or more processors. The one or more memories store programs (instructions) that cause the one or more processors to execute the processing. The one or more processors may execute the processing according to the program read from the one or more memories, or may execute the processing according to a logic circuit designed in advance to execute the processing. The processor may be any of various processors suitable for computer control, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit). Note that the physically separated processors may cooperate with each other to execute the above processing. For example, the processors installed in the physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), or the Internet to execute the above processing. The program may be installed into the memory from an external server device or the like via the network, or may be distributed in a state stored on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a semiconductor memory, and then installed into the memory from the recording medium.

[0082] The one or more memories store threshold values ​​for at least one of pH and viscosity. When the pH or viscosity exceeds the threshold value, the controller drives the actuator to open the lid of the storage 91 and replenish the tank 2 with the alkaline component. When the pH or viscosity exceeds the threshold value as the alkaline component is replenished, the controller drives the actuator to close the lid. The controller may automatically replenish a predetermined amount of alkaline component after a predetermined time has elapsed. In this case, the measurement unit 8 is not required because the replenishment of the alkaline component is controlled based only on time.

[0083] If the decrease in the concentration of the alkaline component in the reaction solution 10 can be measured by the measurement unit 8 and the alkaline component can be replenished according to the measurement results, the concentration of the alkaline component in the reaction solution 10 is less likely to decrease and the reaction efficiency is less likely to decrease.

[0084] The carbon dioxide capture device 1 may, at the beginning of operation, include a reaction solution 10 saturated with the alkaline component, and a solid alkaline component disposed in the reaction solution 10. The solid alkaline component is, for example, a compact obtained by pressure-molding a dried alkaline component. The solid alkaline component is disposed, for example, near the bubbler 4. When the bubbler 4 is disposed in the reaction solution 10 so as to be spaced from the bottom surface 21 of the tank 2, the solid alkaline component is disposed, for example, so as to overlap the bubbler 4 when viewed from above. The solid alkaline component may be suspended from the side of the tank while being placed in a net or the like. When the carbon dioxide capture device 1 includes a heating unit 71 ( FIG. 5 ), the solid alkaline component is disposed, for example, near the heating unit 71. When the reaction solution 10 reacts with carbon dioxide during operation of the carbon dioxide capture device 1 and the concentration of the alkaline component in the reaction solution 10 decreases, a margin is created relative to the saturated solubility of the alkaline component in the reaction solution 10. When a solid alkaline component is placed in the reaction solution 10, the solid alkaline component dissolves to the extent that there is a margin relative to the saturated solubility, and the alkaline component is more likely to be saturated in the reaction solution 10. In other words, when a solid alkaline component is placed in the reaction solution 10 in advance, this solid alkaline component serves as a supply source, and the alkaline component is replenished into the reaction solution 10 so that the alkaline component is saturated. When a solid alkaline component is placed in the reaction solution 10, the measurement unit 8 and supply unit 9 shown in FIG. 6 are not essential.

[0085] [Test Example 1] In Test Example 1, a plurality of test specimens simulating the carbon dioxide capture device 1 of Embodiment 1 or Embodiment 2 were prepared, and the carbon dioxide capture rate of each test specimen was measured. The plurality of test specimens differ in the configuration of the bubbler 4. The plurality of test specimens have the same configuration other than the bubbler 4, for example, the configurations of the tank 2, the reaction solution 10 stored in the tank 2, and the pump 3. The reaction solution 10 was sodium carbonate (NaCO ３ ) aqueous solution.

[0086] <Test specimen> The configuration of the test specimen is shown in Table 1. Table 1 shows the configuration of the bubbler 4, such as the location, material, opening, and average diameter of the plurality of bubbles formed by the bubbler 4.

[0087] Test specimens 1 to 4 imitate the carbon dioxide capture device 1 of embodiment 1 shown in FIG. 1, and the bubbler 4 is disposed on the bottom surface 21 of the tank 2. When the bubbler 4 is disposed on the bottom surface 21 of the tank 2, this is indicated as "bottom surface" in Table 1. The distance L1 between the top surface of the bubbler 4 and the liquid surface of the reaction solution 10 is 200 mm. Test specimens 1 and 2 use the same bubbler 4. Test specimens 3 and 4 use the same bubbler. The differences between test specimens 1 and 2, and between test specimens 3 and 4, are as shown in Table 2. ２ ) is the concentration.

[0088] The bubblers 4 of specimens 1 to 4 are formed from a porous material made of a sintered material obtained by baking silica sand. The opening size of the porous material of the bubblers 4 of specimens 1 and 2 is 0.5 mm. The bubblers 4 of specimens 1 and 2 are formed so that the average diameter of the bubbles 40 in the reaction solution 10 is 1.5 mm. The opening size of the porous material of the bubblers 4 of specimens 3 and 4 is 0.2 mm. The bubblers 4 of specimens 3 and 4 are formed so that the average diameter of the bubbles 40 in the reaction solution 10 is 0.5 mm. The average diameter of the bubbles 40 in the reaction solution 10 was measured as follows: The bubbler 4 is placed on the bottom of a glass container containing the reaction solution 10. Gas is fed into the bubbler 4, and the gas is turned into bubbles 40, which are then supplied into the reaction solution 10. The bubbles 40 in the reaction solution 10 are photographed with a high-speed camera, and the captured image is analyzed to determine the average diameter of the bubbles 40. The number of bubbles 40 used to determine the average diameter was set to 500 or more. The average diameters of the bubbles 40 in the reaction solution 10 of the other test specimens were determined in the same manner.

[0089] Specimens 5 to 8 mimic the carbon dioxide capture device 1 of embodiment 2 shown in FIG. 4 , with the bubbler 4 positioned at a distance from the bottom surface 21 of the tank 2. Specifically, the bubbler 4 is suspended from a frame (not shown) separately provided within the tank 2. When the bubbler 4 is positioned at a distance from the bottom surface 21 of the tank 2, this is indicated as "suspended" in Table 1. The distance L1 between the top surface of the bubbler 4 and the liquid surface of the reaction solution 10 is 100 mm. The distance L2 between the bottom surface of the bubbler 4 and the bottom surface 21 of the tank 2 is 100 mm. The bubbler 4 of specimen 5 is made of the same material and has the same mesh size as the bubblers 4 of specimens 3 and 4, and is formed so that the average diameter of the bubbles 40 in the reaction solution 10 is 0.5 mm. The bubblers 4 of specimens 6 and 7 are formed from a laminate of multiple plates made of SUS304 stainless steel. The bubbler 4 of specimen 8 is formed from a laminate of multiple plates made of pure titanium. Each of the multiple plates has multiple holes formed therein. A porous material is formed by laminating multiple plates having multiple holes. The opening size of the porous material of the bubbler 4 of test specimen 6 is 0.2 mm. The bubbler 4 of test specimen 6 is formed so that the average diameter of the multiple bubbles 40 in the reaction solution 10 is 0.5 mm. The opening size of the porous material of the bubbler 4 of test specimen 7 and test specimen 8 is 0.1 mm. The bubblers 4 of test specimens 7 and 8 are formed so that the average diameter of the multiple bubbles 40 in the reaction solution 10 is 0.3 mm.

[0090]

[0091] <Carbon dioxide (CO ２ ) Recovery Rate> Gas containing carbon dioxide was supplied to each test specimen by a pump. Gas with a carbon dioxide concentration of 2.5±0.25% by volume was supplied to test specimens 1 and 3. Gas with a carbon dioxide concentration of 8.5±0.5% by volume was supplied to test specimens 2 and 4 to 8.

[0092] Sensors for measuring carbon dioxide concentration were installed in each of the inlet pipe 5 and outlet pipe 6 connected to the tank 2, and the carbon dioxide concentration A in the gas supplied to each test specimen and the carbon dioxide concentration B in the gas discharged from the tank 2 were measured. The measured carbon dioxide concentrations A and B were used to calculate the carbon dioxide recovery rate. The carbon dioxide recovery rate is calculated as (A - B) / A. The carbon dioxide recovery rate was calculated at the beginning of operation of the carbon dioxide recovery device and after 60 hours had passed. The results are shown in Table 2.

[0093] <Carbon dioxide (CO ２ ) Balance> For each test specimen, the difference between the amount of carbon dioxide emitted converted from the amount of power consumption required to operate the carbon dioxide capture device 1 and the amount of carbon dioxide captured by the carbon dioxide capture device 1 was calculated. In Test Example 1, the amount of power consumption required to operate the carbon dioxide capture device 1 is the amount of power required to drive the pump 3. The unit of this difference is [g-CO ２ / Wh] and represents the mass of carbon dioxide emitted when 1 Wh of energy is generated. This difference is called the carbon dioxide balance. The carbon dioxide balance was determined at the beginning of operation of the carbon dioxide capture device and after 60 hours had passed. The results are shown in Table 2. In the carbon dioxide balance, a - (minus) sign means that the amount of carbon dioxide emitted, calculated from the amount of power consumption required to operate the carbon dioxide capture device 1, was greater than the amount of carbon dioxide captured by the carbon dioxide capture device 1.

[0094]

[0095] Comparing test specimens 1 and 3, test specimens 2 and 4, and test specimens 6 and 7, it is clear that both at the beginning of operation of the carbon dioxide capture device 1 and after 60 hours, the smaller the average diameter of the bubbles 40, the higher the carbon dioxide capture rate and carbon dioxide balance. For all test specimens, the carbon dioxide capture rate and carbon dioxide balance decreased after 60 hours compared to the beginning of operation. The longer the operation time, the more solid matter 100 formed by the reaction between the reaction solution 10 and carbon dioxide increases. It is believed that the solid matter 100 also accumulated on the bubbler 4, clogging the outlet hole 42 of the bubbler 4, and reducing the amount of bubbles 40 formed. It is believed that the reduction in the amount of bubbles 40 formed reduced the carbon dioxide capture rate and carbon dioxide balance. It is believed that the smaller the average diameter of the bubbles 40, the more likely it is that the outlet hole 42 of the bubbler 4 will become clogged. Therefore, it is thought that by adjusting the aperture of the bubbler 4, that is, the average diameter of the bubbles 40, clogging can be prevented and the carbon dioxide balance can be prevented from decreasing.

[0096] Comparing test specimen 4 and test specimen 5, the carbon dioxide recovery rate and carbon dioxide balance are higher when the bubbler 4 is arranged with a gap between it and the bottom surface 21 of the tank 2. In test specimen 5, the gap between the bubbler 4 and the bottom surface 21 of the tank 2 makes it difficult for the solids 100 to accumulate on the bubbler 4 and the solids 100 to clog the outlet hole 42 of the bubbler 4, which is thought to be why a sufficient amount of bubbles 40 was formed.

[0097] Comparing test specimen 5 and test specimen 6, the bubbler 4 made of stainless steel has a higher carbon dioxide recovery rate and carbon dioxide balance. Even if the bubbler 4 is arranged with a gap between it and the bottom surface 21 of the tank 2, the solids 100 may settle on the bubbler 4. Even if the solids 100 settle on the bubbler 4, it is thought that clogging is less likely to occur if the bubbler 4 is made of stainless steel.

[0098] Comparing test specimen 7 and test specimen 8, the titanium bubbler 4 had a higher carbon dioxide recovery rate and a higher carbon dioxide balance after 60 hours. It is believed that a titanium bubbler 4 is less likely to become clogged over time, even if solid matter 100 settles on the bubbler 4.

[0099] Test Example 2 In Test Example 2, a test specimen simulating the carbon dioxide capture device 1 of Embodiment 3 was prepared, and the carbon dioxide absorption rate of the test specimen was measured. The distance L1 between the upper surface of the bubbler 4 and the liquid level of the reaction solution 10 was 100 mm. The distance L2 between the lower surface of the bubbler 4 and the bottom surface 21 of the tank 2 was 100 mm.

[0100] The test specimen in test example 2 is equipped with a temperature adjustment unit 7. The temperature adjustment unit 7 is equipped with a heating unit 71 and a cooling unit 72. A throw-in heater was used for the heating unit 71. A Peltier-type cool plate was used for the cooling unit 72. In this example, the carbon dioxide absorption rate was measured when the temperature of the heating unit 71 was set to 25°C or 40°C. All conditions were the same except for the temperature of the heating unit 71. The set temperature of the cooling unit 72 was set to 20°C. In test example 2, the amount of power consumption required to operate the carbon dioxide capture device 1 is the sum of the amount of power consumed to drive the pump 3 and the amount of power consumed to operate the temperature adjustment unit 7.

[0101] When gas with a carbon dioxide concentration of 2.5±0.25% by volume was supplied, the carbon dioxide absorption rate was 0.01% / min when the temperature of the heating unit 71 was 25° C. and 0.04% / min when it was 40° C. When gas with a carbon dioxide concentration of 8.5±0.5% by volume was supplied, the carbon dioxide absorption rate was 0.04% / min when the temperature of the heating unit 71 was 25° C. and 0.09% / min when it was 40° C.

[0102] Regardless of the carbon dioxide concentration, the carbon dioxide absorption rate increased when the temperature of the heating part 71 was set to 40° C. It is believed that increasing the temperature of the heating part 71 increased the temperature of the reaction solution 10 in contact with the bubbler 4, and this increased the reaction efficiency between the reaction solution 10 and carbon dioxide, thereby increasing the carbon dioxide absorption rate.

[0103] 1 Carbon dioxide recovery device, 2 Tank, 21 Bottom, 22 Side, 25 Gas phase section, 3 Pump, 4 Bubbler, 40 Bubbles, 41 Inlet hole, 42 Outlet hole, 421 First outlet hole, 422 Second outlet hole, 45 Internal space, 5 Inlet pipe, 51 Branch inlet pipe, 6 Outlet pipe, 7 Temperature adjustment section, 71 Heating section, 72 Cooling section, 8 Measurement section, 9 Supply section, 91 Storage, 92 Inlet pipe, 10 Reaction solution, 100 Solid, L1, L2 Distance.

Claims

1. A carbon dioxide recovery device comprising: a tank for storing an alkaline reaction solution; a pump for feeding a gas containing carbon dioxide into said tank; and a bubbler for generating a plurality of bubbles from said gas and supplying them into said reaction solution, said bubbler being formed so that the average diameter of said plurality of bubbles in said reaction solution is 0.01 mm or more and 1.5 mm or less.

2. The carbon dioxide capture device according to claim 1, which captures more carbon dioxide than the carbon dioxide emission amount calculated from the amount of power consumption required to operate the carbon dioxide capture device.

3. A carbon dioxide recovery device according to claim 1 or 2, wherein the bubbler is disposed in the reaction solution so as to be spaced apart from the bottom surface of the tank.

4. A carbon dioxide recovery device as described in any one of claims 1 to 3, wherein the bubbler has an inlet for the gas and a plurality of outlet holes for forming the plurality of bubbles, and the plurality of outlet holes are arranged so as to be at a distance of 50 mm or more from the liquid surface of the reaction solution.

5. The carbon dioxide recovery device according to claim 4, wherein the plurality of discharge holes are formed from a porous material.

6. A carbon dioxide recovery device according to claim 5, wherein the opening of the porous material is 0.5 mm or less.

7. A carbon dioxide recovery device as described in any one of claims 4 to 6, wherein the plurality of discharge holes comprises, when the bubbler is viewed from above, a plurality of first discharge holes located in a first region that is visible from above, and a plurality of second discharge holes located in a second region that is not visible from above, and the number density of the plurality of first discharge holes is smaller than the number density of the plurality of second discharge holes.

8. A carbon dioxide recovery device according to any one of claims 4 to 7, wherein the pressure of the gas at the inlet is 105 kPa or more and 200 kPa or less.

9. A carbon dioxide capture device according to any one of claims 1 to 8, wherein the bubbler is formed from a material selected from titanium, a titanium alloy, or stainless steel.

10. A carbon dioxide recovery device described in any one of claims 1 to 9, further comprising a temperature adjustment unit that adjusts the temperature of the reaction solution.

11. The carbon dioxide recovery device according to claim 10, wherein the temperature adjustment unit includes a heating unit that sets the temperature of at least a portion of the reaction solution in contact with the bubbler to 30°C or higher.

12. A carbon dioxide recovery device as described in claim 10 or claim 11, wherein the temperature adjustment unit is equipped with a cooling unit that sets the temperature of the reaction solution in contact with the bubbler and at least a portion of the reaction solution below the bubbler to 25°C or below.

13. A carbon dioxide recovery device according to any one of claims 1 to 12, wherein the reaction solution contains a hydroxide, carbonate, or bicarbonate containing one selected from the group consisting of sodium, potassium, magnesium, and calcium.

14. A carbon dioxide recovery device according to any one of claims 1 to 13, wherein the viscosity of the reaction solution is 0.3 mPa·s or more and 3.0 mPa·s or less.

15. The carbon dioxide recovery device according to claim 13, further comprising: a measuring unit that measures at least one of the pH and viscosity of the reaction solution; and a supply unit that replenishes the hydroxide, carbonate, or bicarbonate in accordance with the measurement result of the measuring unit.

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