Method for immobilizing carbon dioxide

Abstract

To provide a method for fixing carbon dioxide by which bubbles of carbon dioxide introduced into a solution can be made fine without increasing energy consumption.SOLUTION: A carbon dioxide fixation method comprising a precipitation step of introducing a gas containing carbon dioxide into a carbon dioxide fixation solution in which calcium ions are eluted to generate bubbles of the gas containing carbon dioxide in the carbon dioxide fixation solution, thereby reacting the calcium ions eluted in the carbon dioxide fixation solution with carbon dioxide to precipitate calcium carbonate, wherein the carbon dioxide fixation solution is an aqueous solution in which calcium ions are eluted in an aqueous solution of methylparaben.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for fixation of carbon dioxide. [Background technology]

[0002] Toward the realization of carbon neutrality, various technologies for capturing carbon dioxide have been proposed. For example, Patent Documents 1 and 2 disclose a technology for fixing (capturing) carbon dioxide as calcium carbonate by bringing a gas containing carbon dioxide into contact with an aqueous solution into which calcium ions have been dissolved, thereby precipitating calcium carbonate in the solution.

[0003] In conventional carbon dioxide fixation methods using solutions containing dissolved calcium ions, the larger the bubbles of carbon dioxide-containing gas introduced into the solution, the smaller the specific surface area of ​​gas-liquid contact between the solution and the gas, making it more difficult for the calcium ions to react with carbon dioxide. Therefore, the larger the size of the gas bubbles, the longer it takes to fix carbon dioxide. Furthermore, the amount of carbon dioxide that escapes from the aqueous amino acid solution without reacting with calcium ions increases, resulting in a larger amount of carbon dioxide being released into the atmosphere without being fixed as calcium carbonate.

[0004] As a configuration for generating fine bubbles in a liquid, Patent Document 3 discloses a configuration in which a bubble generator with fine pores is used to generate fine carbon dioxide bubbles, thereby bringing an aqueous solution into gas-liquid contact with the carbon dioxide. Patent Document 4 discloses a configuration in which ultrafine bubbles are generated by heating a liquid. Patent Document 5 discloses a configuration in which ionized water containing nanobubbles is generated by electrolysis. Patent Document 6 discloses a configuration in which a cooling process is used during bubble generation to produce ultrafine bubble water with a high density of ultrafine bubbles.

[0005] However, in a configuration using a porous material with fine pores (for example, a bubbling stone) as described in Patent Document 3, the precipitated calcium carbonate adheres to the porous material, causing problems such as clogging over time and preventing the generation of fine bubbles. Also, in a configuration in which the solution is heated or cooled to generate bubbles as described in Patent Documents 4 to 6, energy is consumed to generate the bubbles, reducing or canceling out the effect of reducing carbon dioxide emissions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-83681 [Patent Document 2] Japanese Patent Application Publication No. 2019-52065 [Patent Document 3] Japanese Patent Application Publication No. 2023-28788 [Patent Document 4] Japanese Patent Application Publication No. 2023-86897 [Patent Document 5] Japanese Patent Application Publication No. 2023-15964 [Patent Document 6] Japanese Patent Publication No. 2023-2197 Summary of the Invention

[0007] (Problem to be solved by the invention) In view of the above circumstances, one of the objects of the present invention is to provide a method for immobilizing carbon dioxide, which can reduce the size of carbon dioxide-containing gas bubbles introduced into a carbon dioxide immobilization solution without increasing (or suppressing) the amount of energy consumed.

[0008] (Means for solving the problem) The carbon dioxide fixation method according to the present disclosure includes: A method for immobilizing carbon dioxide, comprising a precipitation step of introducing a gas containing carbon dioxide into a carbon dioxide immobilization solution into which calcium ions have been dissolved, and generating bubbles of the gas containing carbon dioxide in the carbon dioxide immobilization solution, thereby causing a reaction between the calcium ions dissolved in the carbon dioxide immobilization solution and carbon dioxide, thereby precipitating calcium carbonate, The carbon dioxide fixation solution is a preparation step of preparing an aqueous solution of methylparaben by dissolving methylparaben in water; an elution step of immersing a calcium-containing solid material in the aqueous solution of methylparaben prepared in the preparation step, thereby eluting calcium ions from the solid material into the aqueous solution of methylparaben; The aqueous solution is produced by a method comprising:

[0009] According to the carbon dioxide fixation method of the present disclosure, it is possible to reduce the size of carbon dioxide-containing gas bubbles introduced into a carbon dioxide fixation solution without using any mechanical or electrical components. Therefore, it is possible to provide a carbon dioxide fixation method that reduces the size of carbon dioxide-containing gas bubbles introduced into a solution without increasing (or suppressing) the amount of energy consumed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flowchart showing the carbon dioxide fixation method according to this embodiment. [Figure 2] FIG. 2 is a graph showing the relationship between the concentration of methylparaben in the carbon dioxide fixation solution and the availability of calcium. [Figure 3] FIG. 3 is a graph showing the relationship between the concentration of amino acids in the carbon dioxide fixation solution and the calcium availability. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings.

[0012] Fig. 1 is a flowchart showing the method for immobilizing carbon dioxide according to this embodiment. As shown in Fig. 1, the method for immobilizing carbon dioxide according to this embodiment includes a solution preparation step, an elution step, and a precipitation step.

[0013] In the solution preparation step, an aqueous solution of methylparaben is prepared by dissolving methylparaben in water (e.g., ion-exchanged water). The concentration of methylparaben in this aqueous solution is greater than 0% by mass. That is, when this aqueous solution contains methylparaben as a solute, it has the effect of miniaturizing carbon dioxide-containing gas bubbles. The concentration of methylparaben in this aqueous solution is preferably 0.001% or greater, more preferably 0.1% or greater. While almost all of methylparaben dissolves in water at a concentration of 0.2% by mass or less, a portion remains undissolved as a solid at a concentration exceeding 0.2% by mass. The remaining solid methylparaben does not contribute to miniaturizing carbon dioxide-containing gas bubbles. Therefore, the concentration of methylparaben in this aqueous solution is greater than 0% by mass but less than 0.2% by mass, preferably between 0.01% and 0.2% by mass, and more preferably between 0.1% and 0.2% by mass.

[0014] This aqueous solution may contain an amino acid as a solute. If this aqueous solution contains an amino acid as a solute, the amino acid and calcium ions will form a chelate complex in the elution step described below, thereby increasing the amount of calcium available for carbon dioxide fixation. Amino acids are organic compounds having both amino and carboxyl functional groups. Amino acids with an isoelectric point in the pH range of 5 to 7 are particularly preferred. In this case, examples of amino acids include alanine, cysteine, phenylalanine, threonine, glutamine, serine, hydroxyproline, methionine, citrulline, isoleucine, valine, glycine, proline, 4-aminobutyric acid, histidine, ornithine hydrochloride, arginine hydrochloride, lysine hydrochloride, leucine, asparagine monohydrate, tryptophan, tyrosine, and glucosamine. The concentration of the amino acid in this aqueous solution can be appropriately set depending on the amount of calcium ions to be eluted.

[0015] In this case, in the solution preparation step, for example, predetermined amounts of water, methylparaben, and an amino acid (e.g., alanine) are weighed and placed in a container. Then, the methylparaben and amino acid placed in the container are stirred until they are completely dissolved in water. Thus, an aqueous solution of methylparaben containing an amino acid is prepared.

[0016] (Elution process) In the elution process, a solid material containing calcium silicate (hereinafter referred to as a calcium silicate-containing solid material) is immersed in an aqueous solution of methylparaben. Calcium silicate is a general term for a composition in which calcium oxide, silicon dioxide, etc. are bonded together, and is generally referred to as Ca n SiO n+2 Examples of calcium silicate include dicalcium silicate (Ca2SiO4) and tricalcium silicate (Ca3SiO5). As a calcium silicate-containing solid, for example, research cement specified by the Cement Association of Japan can be used.

[0017] The calcium silicate-containing solid material is preferably in the form of granules (or powder). When the calcium silicate-containing solid material is in the form of granules, the surface area of ​​the calcium silicate-containing solid material that comes into contact with the aqueous solution of methylparaben in the elution step is increased, allowing calcium ions to be eluted efficiently.

[0018] By carrying out the elution step, calcium contained in the calcium silicate-containing solid material is eluted as calcium ions into the aqueous solution of methylparaben. Furthermore, when the aqueous solution of methylparaben contains an amino acid, the elution step is expected to cause, for example, the following reaction: (1) Ca n SiO n+2 +2HL →nCaL2(aq)+H2SiO3(s)+(n-2)H2O Here, L represents the amino acid ligand.

[0019] As can be seen from equation (1), calcium ions (Ca 2+ ) undergoes a chelate reaction with the carboxyl and amino groups of the amino acid, producing a chelate complex (CaL2). Furthermore, calcium hydroxide (Ca(OH)2) produced in the reaction process of equation (1) separates into calcium ions and hydroxide ions. Thus, calcium dissolves into the aqueous solution of methylparaben as calcium ions. This shifts the pH of the carbon dioxide fixation solution to the alkaline side.

[0020] In this way, by going through the solution preparation step and the elution step, an aqueous solution of methylparaben into which calcium ions have been eluted, i.e., a carbon dioxide fixation solution, is produced.

[0021] (Precipitation process) In the precipitation step, a carbon dioxide-containing gas is introduced into the carbon dioxide fixation solution to bring the carbon dioxide-containing gas into contact with the carbon dioxide fixation solution. Examples of the carbon dioxide-containing gas include, but are not limited to, exhaust gas emitted from a vehicle or exhaust gas emitted from a blast furnace. In other words, the carbon dioxide-containing gas may be any gas as long as it contains carbon dioxide.

[0022] The method for introducing a gas containing carbon dioxide into the carbon dioxide fixation solution is to introduce the gas containing carbon dioxide into the carbon dioxide fixation solution from near the bottom of a container in which the carbon dioxide fixation solution is stored or filled, using a pipe or tube.

[0023] When a gas containing carbon dioxide is introduced into a carbon dioxide fixation solution containing methylparaben by carrying out the precipitation process, the bubbles of the introduced gas become finer. The mechanism by which the bubbles of the introduced gas become finer is not clear, but it is presumed that by mixing methylparaben into a carbon dioxide fixation solution into which calcium ions have been dissolved, the membrane elasticity of the CO2 bubbles in the solution increases, preventing the bubbles from becoming thinner, thereby resulting in the finer bubbles.

[0024] Furthermore, by stirring the carbon dioxide fixation solution while the carbon dioxide-containing gas is being introduced, the bubbles of the introduced gas become finer. Therefore, it is preferable to introduce the carbon dioxide-containing gas into the carbon dioxide fixation solution while stirring the carbon dioxide fixation solution with a stirrer or the like.

[0025] With this configuration, it is not necessary to provide a "structure for generating fine bubbles" such as a bubbling stone at the tip of the pipe or tube. In other words, with the carbon dioxide fixation solution according to this embodiment, it is possible to reduce the size of bubbles in the carbon dioxide-containing gas without using a "structure for generating fine bubbles." The configuration of the agitator is not particularly limited, and various known agitators can be used.

[0026] Alternatively, a carbon dioxide-containing gas may be introduced into the carbon dioxide fixation solution through a throw-in filter. Specifically, a throw-in filter is installed at the bottom of a container in which the carbon dioxide fixation solution is stored or filled, and a carbon dioxide-containing gas is fed to the throw-in filter by an external air pump. With this configuration, the carbon dioxide-containing gas turns into bubbles as it passes through the throw-in filter, and the resulting bubbles are introduced into the carbon dioxide fixation solution. The carbon dioxide fixation solution according to this embodiment can reduce the size of the introduced gas bubbles. The configuration of the throw-in filter is not particularly limited, and various known agitators can be used.

[0027] Furthermore, a configuration may be adopted in which a gas containing carbon dioxide is introduced into the carbon dioxide fixation solution via an injector. Specifically, the injector is equipped with a needle valve through which a gas (working fluid) passes, and is configured to suck in a liquid by the negative pressure generated by the gas passing through the needle valve and to mix and inject the gas and liquid. In this case, a gas containing carbon dioxide is used as the gas (working fluid), and the carbon dioxide fixation solution is used as the liquid (the carbon dioxide fixation solution is circulated). The carbon dioxide fixation solution is then mixed with the gas containing carbon dioxide by the injector and injected into the carbon dioxide fixation solution. With this configuration, the gas containing carbon dioxide becomes bubbles when injected from the injector, and the bubbles are introduced into the carbon dioxide fixation solution. The carbon dioxide fixation solution according to this embodiment can reduce the size of the introduced gas bubbles. The configuration of the injector is not particularly limited, and various known agitators can be used.

[0028] It is assumed that the following reaction occurs in the carbon dioxide fixation solution by carrying out the precipitation step. (2) Ca 2+ +2OH - +CO2→H2O+CaCO3↓ Furthermore, when the carbon dioxide fixation solution contains an amino acid, the following reaction is expected to occur in the carbon dioxide fixation solution by carrying out the precipitation step. (3) CO2 + H2O → H2CO3 (4) H2CO3 → HCO3 - +H + or HCO3- → CO3 2- +H + (5) CaL2 + H2CO3 → CaCO3 + 2HL

[0029] As shown in formula (2), calcium ions in the carbon dioxide fixation solution react with hydroxide ions and carbon dioxide to precipitate calcium carbonate. Furthermore, if the carbon dioxide fixation solution contains an amino acid, calcium ions separate from the chelate complex in the precipitation step, precipitating calcium carbonate, while the amino acid separates from the chelate complex, as shown in formula (5). This removes calcium ions from the carbon dioxide fixation solution (unreacted calcium ions remain in the carbon dioxide fixation solution as chelate complexes). The carbon dioxide fixation solution from which calcium ions have been removed still contains calcium carbonate and other solid by-products. Therefore, after the precipitation step is completed, the carbon dioxide fixation solution is filtered to separate the filtrate from the solids. The separated filtrate can be used in the subsequent elution step as an aqueous solution of methylparaben containing eluted calcium ions (i.e., the carbon dioxide fixation solution). In other words, the filtrate after the precipitation step is reusable.

[0030] Meanwhile, calcium carbonate precipitated in the precipitation step is recovered. Here, the calcium carbonate precipitated in the precipitation step is produced using calcium ions and carbon dioxide as raw materials. In other words, it can be said that carbon dioxide is fixed in calcium carbonate. That is, the method according to this embodiment is a method for fixing carbon dioxide in calcium carbonate.

[0031] As described above, the method according to this embodiment can reduce the size of carbon dioxide-containing gas bubbles in the precipitation step. This increases the contact area between the carbon dioxide and the carbon dioxide fixation solution, promoting gas-liquid contact. As a result, the amount of carbon dioxide that reacts with calcium ions can be increased, thereby increasing the amount of carbon dioxide that can be fixed and recovered. Furthermore, the method according to this embodiment can reduce the size of carbon dioxide bubbles introduced into the solution without using any mechanical or electrical configuration. Therefore, it is possible to reduce the size of carbon dioxide-containing gas bubbles introduced into the carbon dioxide fixation solution without increasing (or suppressing) the amount of energy consumed.

[0032] (Example) <Solution preparation process> In one container, an aqueous solution of methylparaben was prepared by dissolving methylparaben in 2750 g of ion-exchanged water to a concentration of 0.01% by mass, in another container, an aqueous solution of methylparaben was prepared by dissolving methylparaben in 2750 g of ion-exchanged water to a concentration of 0.1% by mass, and in three containers, an aqueous solution of methylparaben was prepared by dissolving methylparaben in 2750 g of ion-exchanged water to a concentration of 0.2% by mass. As raw materials for Examples (Examples 2, 4, and 5) to verify the influence of the methylparaben concentration, an aqueous solution of methylparaben with a concentration of 0.01% by mass (Example 4), an aqueous solution of 0.1% by mass (Example 5), and one of the 0.2% by mass aqueous solutions of the three containers (Example 2) was dissolved with an amino acid to a concentration of 2.82% by mass. As raw materials for Examples (Examples 1, 2, and 3) for verifying the effect of amino acids, one of the three containers had a 0.2% by mass aqueous solution. One (Example 1) contained no amino acid, while the other (Example 2) contained an amino acid dissolved therein to a concentration of 2.82% by mass. The other (Example 3) contained an amino acid dissolved therein to a concentration of 10.40% by mass. Alanine was used as the amino acid. In this way, in the solution preparation step, aqueous solutions of methylparaben with different methylparaben concentrations and aqueous solutions of methylparaben with the same methylparaben concentration but different amino acid concentrations were prepared.

[0033] Furthermore, carbon dioxide fixation solutions not containing methylparaben as a solute were prepared for Comparative Examples 1 to 3. Specifically, 2750 g of ion-exchanged water was prepared as a raw material for the carbon dioxide fixation solution according to Comparative Example 1, a solution (amino acid aqueous solution) in which an amino acid was dissolved in 2750 g of ion-exchanged water to a concentration of 2.82 mass% was prepared as a raw material for the carbon dioxide fixation solution according to Comparative Example 2, and a solution (amino acid aqueous solution) in which an amino acid was dissolved in 2750 g of ion-exchanged water to a concentration of 10.40 mass% was prepared as a raw material for the carbon dioxide fixation solution according to Comparative Example 3.

[0034] <Elution process> 680.6 g of laboratory cement was mixed with each of the aqueous solutions of methylparaben according to Examples 1 to 5 and the aqueous solutions of ion-exchanged water and amino acids according to Comparative Examples 1 to 3, which had been prepared in the solution preparation step. The amount of calcium contained in the 680.6 g of laboratory cement was 7.80 mol. Through the above steps, the carbon dioxide fixation solutions of Examples 1 to 5 and Comparative Examples 1 to 3 were obtained.

[0035] Comparative Example 1 is a comparative example corresponding to Example 1, Comparative Example 2 is a comparative example corresponding to Example 2, and Comparative Example 3 is a comparative example corresponding to Example 3. The carbon dioxide fixation solutions according to the respective comparative examples have the same components as the carbon dioxide fixation solutions according to the corresponding examples, except that methylparaben is not dissolved therein.

[0036] <Precipitation process> The carbon dioxide fixation solution according to each Example and Comparative Example was stored (sealed) in a sealed container, and the remaining air was removed by evacuation. Then, carbon dioxide was introduced into the carbon dioxide fixation solution while stirring it with a magnetic stirrer. The carbon dioxide was introduced into the carbon dioxide fixation solution while measuring the flow rate to maintain a flow rate of 6 L / min until the pH of the carbon dioxide fixation solution stabilized at 7 or less. An exhaust pipe was connected to the sealed container so that it opened into a part of the container where the carbon dioxide fixation solution was not stored. The flow rate of the gas flowing through the exhaust pipe was measured as the flow rate of carbon dioxide discharged from the sealed container.

[0037] When the carbon dioxide fixation solutions of each Example and Comparative Example were observed during the precipitation step, the carbon dioxide fixation solutions of each Example became cloudy, whereas the carbon dioxide fixation solutions of each Comparative Example did not become cloudy. From this, it is inferred that fine bubbles were generated in the carbon dioxide fixation solutions of each Example, but fine bubbles were not generated in the carbon dioxide fixation solutions of each Comparative Example.

[0038] <Calculation of calcium utilization rate> After the precipitation step, the utilization rate of calcium dissolved in the carbon dioxide fixation solution was calculated. The "calcium utilization rate" is the ratio of the mass of calcium used for carbon dioxide fixation (i.e., reacted with carbon dioxide to produce calcium carbonate) to the mass of calcium contained in the carbon dioxide fixation solution; the larger this value, the greater the amount of carbon dioxide fixed. The "calcium utilization rate" was calculated (measured) as follows: First, the total number of moles of carbon dioxide introduced into the carbon dioxide fixation solution in each Example and Comparative Example was calculated (measured) from the flow rate (6 L / min) of carbon dioxide introduced into the sealed container storing (sealing) the carbon dioxide fixation solution in each Example and Comparative Example. Furthermore, in each Example and Comparative Example, the total number of moles of carbon dioxide discharged from the sealed container was calculated from the measurement results of the flow rate of carbon dioxide discharged from the sealed container.

[0039] Then, in each example and comparative example, the difference Δ between the total number of moles of carbon dioxide introduced into the sealed container and the total number of moles of carbon dioxide discharged from the sealed container was calculated. Here, the number of moles of calcium that reacted with carbon dioxide to produce calcium carbonate was equal to the number of moles of carbon dioxide that reacted with calcium ions. Therefore, the number of moles of calcium that reacted with carbon dioxide to produce calcium carbonate was equal to the difference Δ. In other words, the number of moles of calcium used for the fixation of carbon dioxide was equal to the difference Δ.

[0040] After calculating the number of moles of calcium used for carbon dioxide fixation as described above, the mass of calcium corresponding to the calculated number of moles was calculated as the mass of calcium used for carbon dioxide fixation. The ratio of the mass of calcium used for carbon dioxide fixation to the mass of calcium used was then calculated as the calcium utilization rate. The mass of calcium used can be calculated from the mass (g) of the research cement used in each example and the mass concentration of calcium contained in that research cement.

[0041] Table 1 shows the components of the carbon dioxide fixation solutions for each Example (Examples 1 to 5) and each Comparative Example (Comparative Examples 1 to 3), the mass of the research cement used, the amount of calcium (number of moles) contained in the research cement, and the measurement results of the calcium utilization rate.

[0042] [Table 1]

[0043] As shown in Table 1, the calcium utilization rate of the carbon dioxide fixation solution of Example 1 was 41%, which was higher than the 32% of the carbon dioxide fixation solution of Comparative Example 1. The calcium utilization rate of the carbon dioxide fixation solution of Example 2 was 43%, which was higher than the 38% of the carbon dioxide fixation solution of Comparative Example 2. The calcium utilization rate of the carbon dioxide fixation solution of Example 3 was 60%, which was higher than the 55% of the carbon dioxide fixation solution of Comparative Example 3. As described above, when the carbon dioxide fixation solution was an aqueous solution containing methylparaben as a solute, the calcium utilization rate was higher than when the aqueous solution did not contain methylparaben. This is presumably because fine bubbles were generated in the carbon dioxide fixation solution, increasing the gas-liquid contact area between the carbon dioxide and the carbon dioxide fixation solution, which in turn increased the amount of carbon dioxide fixation and the calcium utilization rate.

[0044] FIG. 2 is a graph showing the relationship between the concentration of methylparaben in the carbon dioxide immobilization solution and the measurement results of calcium utilization. As shown in FIG. 2, it was confirmed that when the concentration of methylparaben in the carbon dioxide immobilization solution is 0.01% by mass or higher, the bubbles of carbon dioxide-containing gas can be made finer, and as a result, the amount of carbon dioxide immobilized can be increased. Furthermore, when the carbon dioxide immobilization solution contains methylparaben (Examples 2, 4, and 5), the calcium utilization is linear with respect to the methylparaben concentration. On the other hand, when the carbon dioxide immobilization solution does not contain methylparaben (Comparative Example 2), the calcium utilization is lower than the intercept of the approximation line in the case where the carbon dioxide immobilization solution contains methylparaben. From these results, it is inferred that when the concentration of methylparaben in the carbon dioxide immobilization solution is greater than 0% by mass, there is an effect of making the bubbles of carbon dioxide-containing gas finer.

[0045] Figure 3 is a graph showing the relationship between the concentration of amino acids in the carbon dioxide fixation solution and the measurement results of calcium utilization. As shown in Figure 3, when the carbon dioxide fixation solution was an aqueous solution containing methylparaben, the calcium utilization was high regardless of the amino acid concentration. Furthermore, as shown in Example 1 and Comparative Example 1, even if the carbon dioxide fixation solution did not contain an amino acid, the calcium utilization was high when the carbon dioxide fixation solution contained methylparaben. Thus, it was confirmed that when the carbon dioxide fixation solution was an aqueous solution containing methylparaben, it was possible to reduce the size of carbon dioxide-containing gas bubbles, regardless of whether an amino acid was contained, and as a result, it was possible to increase the amount of carbon dioxide fixed.

[0046] As shown in Table 1, it was confirmed that when the methylparaben concentration in the carbon dioxide fixation solution is 0.1% by mass or higher (Examples 1, 2, 3, and 5), the calcium utilization rate is 40% or higher, regardless of the amino acid concentration. Therefore, it can be said that when the methylparaben concentration in the carbon dioxide fixation solution is 0.1% by mass or higher, the effect of miniaturizing carbon dioxide-containing gas bubbles can be enhanced. Therefore, it is more preferable that the methylparaben concentration in the carbon dioxide fixation solution is 0.1% by mass or higher.

[0047] <Summary of the embodiment> (1) The carbon dioxide fixation method according to this embodiment includes the steps of: A method for immobilizing carbon dioxide, comprising a precipitation step of introducing a gas containing carbon dioxide into a carbon dioxide immobilization solution into which calcium ions have been dissolved, and generating bubbles of the gas containing carbon dioxide in the carbon dioxide immobilization solution, thereby causing a reaction between the calcium ions dissolved in the carbon dioxide immobilization solution and carbon dioxide, thereby precipitating calcium carbonate, The carbon dioxide fixation solution is a preparation step of preparing an aqueous solution of methylparaben by dissolving methylparaben in water; an elution step of immersing a calcium-containing solid material in the aqueous solution of methylparaben prepared in the preparation step, thereby eluting calcium ions from the solid material into the aqueous solution of methylparaben; The aqueous solution is produced by a method comprising:

[0048] According to the carbon dioxide fixation method of this embodiment, it is possible to reduce the size of carbon dioxide bubbles introduced into a solution without using any mechanical or electrical components. Therefore, it is possible to provide a carbon dioxide fixation method that can reduce the size of carbon dioxide bubbles introduced into a solution without increasing (or suppressing) the amount of energy consumed.

[0049] (2) The concentration of methylparaben in the carbon dioxide fixation solution is greater than 0% by mass and 0.2% by mass or less.

[0050] When the concentration of methylparaben in the carbon dioxide fixation solution is greater than 0%, the effect of miniaturizing carbon dioxide bubbles can be obtained. On the other hand, methylparaben is saturated at approximately 0.2% by mass. Therefore, the concentration of methylparaben in the carbon dioxide fixation solution is preferably greater than 0% by mass and equal to or less than 0.2% by mass.

[0051] (3) The concentration of methylparaben in the carbon dioxide fixation solution is 0.1% by mass or more and 0.2% by mass or less.

[0052] When the concentration of methylparaben in the carbon dioxide fixation solution is 0.1% by mass or more, the calcium utilization rate is high, and the carbon dioxide bubbles are effectively reduced in size. Therefore, the concentration of methylparaben in the carbon dioxide fixation solution is preferably 0.1% by mass or more and 0.2% by mass or less.

[0053] (4) The carbon dioxide fixation solution contains an amino acid as a solute.

[0054] When the carbon dioxide fixation solution contains an amino acid as a solute, the amino acid dissolved in the carbon dioxide fixation solution and calcium ions form a chelate complex. Therefore, when the carbon dioxide fixation solution contains an amino acid as a solute, the amount (number of moles) of calcium ions dissolved in the carbon dioxide fixation solution can be made larger than when the solution does not contain an amino acid. Therefore, the amount of calcium carbonate produced when a carbon dioxide-containing gas is introduced (i.e., the amount of carbon dioxide that can be fixed) can be made larger.

[0055] (5) In the precipitation step, the carbon dioxide fixation solution is stirred with a stirrer.

[0056] According to this configuration, it is possible to enhance the effect of reducing the size of bubbles of the gas containing carbon dioxide.

[0057] (6) In the precipitation step, the carbon dioxide-containing gas is introduced into the carbon dioxide fixation solution through a throw-in filter.

[0058] According to this configuration, it is possible to enhance the effect of reducing the size of bubbles of the gas containing carbon dioxide.

[0059] (7) In the deposition step, the carbon dioxide and the carbon dioxide fixation solution are mixed by an injector that uses the gas containing carbon dioxide as a working fluid.

[0060] According to this configuration, it is possible to enhance the effect of reducing the size of bubbles of the gas containing carbon dioxide.

[0061] Although the embodiments and examples of the present invention have been described above, the technical scope of the present invention is not limited to the above-described embodiments and examples. The present invention can be modified in various ways without departing from the spirit of the invention, and such modifications are also included in the technical scope of the present invention.

Claims

1. A method for immobilizing carbon dioxide, comprising a precipitation step of introducing a gas containing carbon dioxide into a carbon dioxide immobilization solution into which calcium ions have been dissolved, and generating bubbles of the gas containing carbon dioxide in the carbon dioxide immobilization solution, thereby causing a reaction between the calcium ions dissolved in the carbon dioxide immobilization solution and carbon dioxide, thereby precipitating calcium carbonate, The carbon dioxide fixation solution is a preparation step of preparing an aqueous solution of methylparaben by dissolving methylparaben in water; an elution step of immersing a calcium-containing solid material in the aqueous solution of methylparaben prepared in the preparation step, thereby eluting calcium ions from the solid material into the aqueous solution of methylparaben; an aqueous solution produced by a method comprising: Methods for fixing carbon dioxide.

2. The method for fixation of carbon dioxide according to claim 1, The concentration of methylparaben in the carbon dioxide fixation solution is more than 0% by mass and 0.2% by mass or less. Methods for fixing carbon dioxide.

3. The method for fixation of carbon dioxide according to claim 2, The concentration of methylparaben in the carbon dioxide fixation solution is more than 0.1% by mass and not more than 0.2% by mass. Methods for fixing carbon dioxide.

4. The method for fixation of carbon dioxide according to claim 1, The carbon dioxide fixation solution contains an amino acid as a solute. Methods for fixing carbon dioxide.

5. The method for fixation of carbon dioxide according to claim 1, In the precipitation step, the carbon dioxide fixation solution is stirred with a stirrer. Methods for fixing carbon dioxide.

6. The method for fixation of carbon dioxide according to claim 1, In the precipitation step, the carbon dioxide-containing gas is introduced into the carbon dioxide fixation solution through a throw-in filter. Methods for fixing carbon dioxide.

7. The method for fixation of carbon dioxide according to claim 1, In the precipitating step, the carbon dioxide and the carbon dioxide fixation solution are mixed by an injector using the gas containing carbon dioxide as a working fluid. Methods for fixing carbon dioxide.

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