System for evaluating amount of carbon dioxide fixation and method for evaluating amount of carbon dioxide fixation

Abstract

The present invention aims to provide a system and method for evaluating carbon dioxide fixation, which, when carbon dioxide is fixed via a carbonate precipitation reaction, eliminates the need for crystal growth-related operations, enabling simple quantification of the amount of fixed carbon dioxide and accurate evaluation of the carbon dioxide fixation. To address the above-mentioned problems, a system and method for evaluating carbon dioxide fixation are provided. The system comprises: a reaction unit that performs a carbonate precipitation reaction related to carbon dioxide fixation under conditions of preferential calcium carbonate precipitation; a first measuring unit and a second measuring unit that measure the calcium ion concentration before and after the reaction; and a calculation unit that quantifies the amount of fixed carbon dioxide based on the measurement results of the first and second measuring units. According to the present invention, the amount of carbon dioxide fixation can be easily quantified and accurately evaluated without the need for crystal growth-related operations.

Description

Technical Field

[0001] This invention relates to a system and method for evaluating carbon dioxide fixation. More specifically, this invention relates to a system and method for quantitatively evaluating the amount of carbon dioxide fixed in the form of carbonate. Background Technology

[0002] In recent years, curbing carbon dioxide emissions, which are considered to have a significant impact on environmental problems such as the greenhouse effect, has become an urgent issue. Research is underway on technologies related to reducing carbon dioxide emissions, as well as technologies for recovering and immobilizing emitted carbon dioxide.

[0003] In particular, various methods are being researched as technologies related to the recovery / immobilization of carbon dioxide. For example, in addition to chemical absorption methods that dissolve carbon dioxide in absorbents such as monoethanolamine or physical adsorption methods that adsorb carbon dioxide onto adsorbents with gas adsorption capabilities, membrane separation methods using membranes are also known as methods for recovering carbon dioxide from carbon dioxide-containing gases.

[0004] In addition to these methods, carbonate fixation, which converts carbon dioxide into carbonates through chemical reactions, is also known. Here, divalent metal ions are known as components that react with carbon dioxide to form carbonates.

[0005] For example, Patent Document 1 describes a method for immobilizing carbon dioxide, in which carbon dioxide is supplied to an aqueous solution of a specific mixture of blast furnace slag and alkali, causing calcium dissolved from the blast furnace slag to react with the carbon dioxide to generate carbonates.

[0006] Previous technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2017-214262 Summary of the Invention

[0007] The technical problem to be solved by the invention Carbonate fixation has the following advantages: since the reaction associated with carbonate precipitation is a spontaneous reaction, no external energy supply is required in carbon dioxide fixation, and the generated carbonate can be stably stored for a long time.

[0008] On the other hand, among initiatives related to curbing carbon dioxide emissions into the environment, also known as decarbonization, in addition to chemical carbon dioxide emission reduction methods such as carbon dioxide recycling / immobilization, methods that promote carbon dioxide emission reduction (carbon pricing) by assigning a price to emitted carbon dioxide (taxation) or by securitizing and trading the value of carbon dioxide emission reductions are gaining attention. When applying carbon pricing, information on the extent to which carbon dioxide emissions can be curbed is needed. In other words, it is necessary to quantify and evaluate how much carbon dioxide can be immobilized.

[0009] Here, as described in Patent Document 1, in the case of a carbonate fixation method that reacts divalent metal ions with carbon dioxide to generate carbonates, the conventional method for evaluating the amount of carbon dioxide fixed involves recovering all the generated carbonates as solid components and measuring the amount recovered. That is, if the carbonates cannot be recovered as solid components and their weight cannot be measured, the amount of carbon dioxide fixed cannot be evaluated. Therefore, it is necessary to grow carbonate crystals so that the generated carbonates can be recovered as solid components. However, as carbon dioxide fixation progresses, the cost of pharmaceuticals and the time spent on crystal growth increase in order to promote carbonate crystal growth until it can be recovered, resulting in a heavier workload related to evaluating the amount of carbon dioxide fixed.

[0010] Therefore, the objective of this invention is to provide a system and method for evaluating carbon dioxide fixation, which, when carbon dioxide is fixed through a carbonate precipitation reaction, does not require operations related to crystal growth, can easily quantify the amount of fixed carbon dioxide, and can appropriately evaluate the amount of carbon dioxide fixation.

[0011] means for solving technical problems The inventors of this application have conducted in-depth research on the above-mentioned issues and found that by carrying out a carbonate precipitation reaction related to carbon dioxide immobilization under specific conditions and determining the amount of immobilized carbon dioxide based on the calcium ion concentration before and after the reaction, the amount of immobilized carbon dioxide can be easily quantified and appropriately evaluated without the need for crystal growth-related operations.

[0012] That is, the present invention provides an evaluation system and a method for evaluating carbon dioxide fixation.

[0013] The carbon dioxide fixation evaluation system of the present invention for solving the above-mentioned problems is characterized by comprising: a reaction unit that performs a carbonate precipitation reaction related to carbon dioxide fixation under conditions of preferential precipitation of calcium carbonate; a first measuring unit that measures the calcium ion concentration before the reaction; a second measuring unit that measures the calcium ion concentration after the reaction; and a calculation unit that quantifies the amount of fixed carbon dioxide based on the measurement results of the first measuring unit and the second measuring unit.

[0014] According to the carbon dioxide fixation evaluation system of the present invention, a specific carbonate (calcium carbonate) is preferentially precipitated as carbonate generated through a carbonate precipitation reaction. The change in the concentration of metal ions (calcium ions) before and after the reaction is correlated with the amount of carbonate generated, thereby enabling the conversion of the amount of carbonate generated into the amount of carbon dioxide fixed. Therefore, simple quantification and appropriate evaluation of the amount of carbon dioxide fixed can be performed without the need for crystal growth-related operations. Furthermore, the cost and time required for carbonate crystal growth can be reduced, thereby alleviating the workload associated with evaluating carbon dioxide fixation.

[0015] Furthermore, as one embodiment of the carbon dioxide fixation evaluation system of the present invention, it is characterized in that the reaction section carries out a carbonate precipitation reaction at a pH of 10.5 or below.

[0016] Solubility, an indicator of the ease with which carbonates formed by the reaction of divalent metal ions with carbon dioxide precipitate, depends on pH. Furthermore, by comparing the pH dependence of the solubility of various carbonates or hydroxides, the inventors of this application discovered a pH range in which calcium carbonate preferentially precipitates.

[0017] According to this carbon dioxide fixation evaluation system, calcium carbonate can preferentially precipitate even in the presence of multiple divalent metal ions. Therefore, the preparation / procurement costs of solutions that can be used as divalent metal ion sources for carbonate precipitation can be reduced.

[0018] Furthermore, as one embodiment of the carbon dioxide fixation evaluation system of the present invention, the reaction section is characterized by having a concentration section that generates a concentrate by using the permeation of a semi-permeable membrane, and a second measuring section that measures at least the calcium ion concentration on the concentrate side.

[0019] Typically, in carbonate precipitation, the following steps are taken: divalent metal ions are reacted with carbon dioxide in solution, and the solution is concentrated to promote carbonate precipitation.

[0020] According to this carbon dioxide fixation evaluation system, since concentration is achieved through osmosis using a semi-permeable membrane, the carbonate precipitation reaction can be carried out with less energy compared to concentration by heating and evaporating the solution, thus obtaining carbonates. Furthermore, since the concentrate generated using the semi-permeable membrane is a product of the carbonate precipitation reaction, the calcium ion concentration after the reaction can be accurately and easily determined by measuring the calcium ion concentration in the concentrate. Therefore, the accuracy of the quantitative correlation with the amount of carbon dioxide fixed is improved, enabling a more appropriate evaluation.

[0021] The method for evaluating the amount of carbon dioxide fixation of the present invention for solving the above-mentioned problems is characterized by comprising: a reaction step in which a carbonate precipitation reaction related to carbon dioxide fixation is carried out under conditions of preferential precipitation of calcium carbonate; a first determination step in which the calcium ion concentration before the reaction is determined; a second determination step in which the calcium ion concentration after the reaction is determined; and a calculation step in which the amount of fixed carbon dioxide is quantified based on the determination results of the first determination step and the second determination step.

[0022] According to the method for evaluating carbon dioxide fixation of the present invention, a specific carbonate (calcium carbonate) is preferentially precipitated as a carbonate generated through a carbonate precipitation reaction, and the change in the concentration of metal ions (calcium ions) before and after the reaction is observed, thereby determining the amount of carbon dioxide fixed. Therefore, the amount of fixed carbon dioxide can be easily quantified and appropriately evaluated without the need for crystal growth-related operations. Furthermore, the cost and time required for carbonate crystal growth can be reduced, thereby alleviating the workload associated with evaluating carbon dioxide fixation.

[0023] Invention Effects According to the present invention, a system and method for evaluating carbon dioxide fixation can be provided. When carbon dioxide is fixed by carbonate precipitation reaction, no crystal growth-related operations are required, the amount of fixed carbon dioxide can be easily quantified, and the appropriate evaluation of carbon dioxide fixation can be performed. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating one example of an evaluation system for carbon dioxide fixation according to the first embodiment of the present invention.

[0025] Figure 2 It is a graph showing the pH dependence of the presence ratios of various forms of carbon dioxide (carbonic acid, bicarbonate ions, and carbonate ions) in aqueous solution.

[0026] Figure 3It is a graph showing the relationship between the pH of an aqueous solution and the solubility (logarithm) of carbonates and hydroxides formed by divalent metal ions (calcium ions, magnesium ions).

[0027] Figure 4 This is a schematic diagram illustrating an example of another mode of the evaluation system for carbon dioxide fixation according to the first embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram illustrating one example of an evaluation system for carbon dioxide fixation according to the second embodiment of the present invention. Detailed Implementation

[0029] The carbon dioxide fixation evaluation system and method of the present invention evaluate the amount of carbon dioxide fixation by acquiring information related to the amount of carbon dioxide that can be fixed, i.e., by quantifying the amount of carbon dioxide fixation, when carbon dioxide is fixed through a carbonate precipitation reaction.

[0030] Furthermore, the carbon dioxide fixation evaluation system and method of the present invention can evaluate carbon dioxide fixation without recovering the carbonate generated by the carbonate precipitation reaction, and without performing crystal growth operations to recover the carbonate.

[0031] In addition, the "carbon dioxide" in this invention includes not only gaseous carbon dioxide (CO2), but also carbonic acid (H2CO3) and bicarbonate ions (HCO3-) in aqueous solution. - ), carbonate ions (CO3) 2- Hereinafter, when referring specifically to gaseous carbon dioxide, it will be referred to as "carbon dioxide".

[0032] The following is a detailed description of the implementation of the carbon dioxide fixation evaluation system according to the present invention. Furthermore, the description of the carbon dioxide fixation evaluation method according to the present invention will be replaced with a description related to the operation of the carbon dioxide fixation evaluation system according to the present invention.

[0033] Furthermore, the evaluation system and method for carbon dioxide fixation described in the embodiments are merely examples to illustrate the evaluation system and method for carbon dioxide fixation involved in this invention, and are not intended to limit the invention to these aspects.

[0034] [First Embodiment] Figure 1 This is a schematic diagram illustrating the evaluation system for carbon dioxide fixation in the first embodiment of the present invention.

[0035] like Figure 1 As shown, the carbon dioxide fixation evaluation system 100A (hereinafter also simply referred to as "evaluation system 100A") according to this embodiment includes a reaction unit 10, a first measuring unit 20, a second measuring unit 30, and a calculation unit 40. Furthermore, Figure 1 The dashed arrows in the diagram indicate connections that allow for input and output.

[0036] The following describes the structure of the evaluation system 100A.

[0037] The reaction section 10 is used to carry out carbonate precipitation reactions related to carbon dioxide immobilization, and also to carry out carbonate precipitation reactions under conditions where calcium carbonate preferentially precipitates.

[0038] As for the reaction section 10, as long as it can react carbon dioxide with divalent metal ions that react with carbon dioxide to form carbonate, and carbonate is precipitated under the condition that calcium carbonate is preferentially precipitated, there are no particular limitations on the specific method or apparatus structure related to the reaction section 10.

[0039] In the reaction section 10 of this embodiment, as Figure 1 As shown, carbon dioxide and divalent metal ions (including calcium ions) are introduced through pipeline L1. Carbonate ions, a form of carbon dioxide in the aqueous solution, react with calcium ions to form calcium carbonate, which precipitates as calcium carbonate crystals. Then, the remaining calcium ions that are not used for carbonate formation (carbonate precipitation) are discharged through pipeline L2.

[0040] At this point, the carbon dioxide and divalent metal ions (calcium ions) introduced via pipeline L1 can be in the form of an aqueous solution containing carbonate ions and divalent metal ions (calcium ions) within the reaction section 10, and their source is not particularly limited. For example, the carbon dioxide introduced via pipeline L1 can be introduced directly as carbon dioxide gas, or an aqueous solution artificially dissolved with carbon dioxide gas, or a solution containing carbon dioxide dissolved from the beginning. Furthermore, the divalent metal ions introduced via pipeline L1 can be an aqueous solution of a substance artificially dissolved to form divalent metal ions (calcium ions), or a solution containing divalent metal ions (calcium ions) dissolved from the beginning. Additionally, solutions containing carbon dioxide and divalent metal ions dissolved from the beginning can include, for example, seawater, river water, tap water, pure water, wastewater / wastewater from factories, and leachate from landfills.

[0041] As the reaction unit 10 in this embodiment, for example, an apparatus is provided that has a tank (reaction tank) capable of storing an aqueous solution, and performs a carbonate precipitation reaction by introducing carbon dioxide and an aqueous solution of divalent metal ions into the reaction tank or by introducing an aqueous solution of carbon dioxide and divalent metal ions pre-dissolved in the reaction tank.

[0042] Here, as a method to promote the carbonate precipitation reaction in the reaction section 10, one can exemplify is to concentrate or adjust the pH of the aqueous solution in the reaction tank.

[0043] Furthermore, carbon dioxide or other gases can be introduced into the aqueous solution contained in the reaction vessel in the form of microbubbles (micro-nanobubbles, microbubbles, etc.) to form an extremely small gas-liquid interface reaction field, thereby enabling the carbonate precipitation reaction without the accompaniment of aqueous solution concentration. More specifically, for example, for a reaction vessel containing an aqueous solution pre-dissolved with carbon dioxide and divalent metal ions, the type of gas introduced in the form of microbubbles is not particularly limited, as long as it can form an extremely small gas-liquid interface reaction field between carbonate ions and calcium ions. Furthermore, for a reaction vessel containing an aqueous solution of divalent metal ions, carbon dioxide can be introduced in the form of microbubbles. In this case, the carbon dioxide introduced in the form of microbubbles not only forms an extremely small gas-liquid interface reaction field but also functions as a carbon dioxide source in the carbonate precipitation reaction.

[0044] Furthermore, one specific example of the reaction section 10, as another embodiment, will be described later.

[0045] In reaction section 10, regarding the conditions for preferential precipitation of calcium carbonate, for example, one could exemplify this by setting the aqueous solution of divalent metal ions used in reaction section 10 to be an aqueous solution containing only calcium ions. Therefore, the carbonate precipitated in reaction section 10 would naturally be only calcium carbonate.

[0046] Furthermore, as another reaction condition in the reaction section 10, setting the pH to 10.5 or below can be cited as an example.

[0047] In situations where multiple carbonates may be formed, the solubility of a particular carbonate can be used as an indicator of whether it precipitates preferentially. Specifically, among carbonates formed under the same conditions, those with lower solubility are more likely to precipitate in crystalline form, i.e., they precipitate preferentially.

[0048] Furthermore, by comparing the pH dependence of the solubility of various carbonates or hydroxides, the inventors of this application discovered a pH range in which the solubility of calcium carbonate is lower compared to other carbonates or hydroxides, i.e., a pH range that becomes the condition for preferential precipitation of calcium carbonate.

[0049] The following describes the derivation process related to the pH range that predisposes calcium carbonate to precipitate.

[0050] First, regarding carbon dioxide dissolved in aqueous solution, a chemical equilibrium is established as shown in Equation 1.

[0051] [Formula 1]

[0052] As shown in Equation 1, carbonic acid (H2CO3) is generated by dissolving carbon dioxide (CO2) in water (H2O), and a portion of the carbonic acid ionizes into hydrogen ions (H+). + ) and bicarbonate ions (HCO3) - Furthermore, hydrogen ions further ionize from bicarbonate ions to produce carbonate ions (CO3). 2- ).

[0053] Moreover, the direction of the reaction in this chemical equilibrium (equilibrium shift) depends on the pH of the aqueous solution.

[0054] Figure 2 It is a graph showing the pH dependence of the presence ratios of various forms of carbon dioxide (carbonic acid, bicarbonate ions, and carbonate ions) in aqueous solution.

[0055] from Figure 2 It can be seen that by raising the pH above the neutral region, carbonate ions (CO3-) can be increased. 2- The existence of ) is increasing.

[0056] On the other hand, regarding the solubility of a compound, it can be calculated based on the solubility product K, which is an intrinsic value in each substance. s Let p be the value.

[0057] For example, by divalent metal ions (M 2+ ) and carbonate ions (CO3) 2- The solubility product K of carbonates composed of ) sp The relationship between solubility Cs and α can be expressed by equations 2 to 4. Additionally, α represents the fraction of carbonate ions relative to the total carbon dioxide concentration in the aqueous solution.

[0058] [Equation 2]

[0059] [Formula 3]

[0060] [Formula 4]

[0061] Equation 4 shows that the solubility of carbonates is related to α, which is the fraction (presence ratio) of carbonate ions relative to the total carbon dioxide concentration in the aqueous solution. Furthermore, as... Figure 2 As shown, the value of α exhibits pH dependence, and therefore the solubility of carbonates also exhibits pH dependence.

[0062] Furthermore, by adjusting the pH of the aqueous solution, hydroxides can be generated simultaneously with carbonates, so the solubility of hydroxides generated from divalent metal ions is also considered.

[0063] Composed of divalent metal ions (M 2+ ) and hydroxide ions (OH) - The solubility product K of the hydroxides formed by ) sp It can be represented by Equation 5.

[0064] [Formula 5]

[0065] Here, if we take the logarithm of Equation 5, it becomes as shown in Equation 6.

[0066] [Formula 6]

[0067] Moreover, as shown in Equation 7, the logarithm of the hydroxide ion concentration in Equation 6 is expressed using pH.

[0068] [Formula 7]

[0069] Here, the solubility product K sp Since is an inherent value (constant), the concentration of divalent metal ions in Equation 5 corresponds to the solubility of hydroxides. Therefore, substituting Equation 7 into Equation 6 and transforming it to move the logarithm of the divalent metal ion concentration to the left side of the equation, it can be seen that the logarithm of the solubility of hydroxides shows a correlation with pH.

[0070] Figure 3 It is a graph showing the relationship between the pH of an aqueous solution and the solubility (logarithm) of carbonates and hydroxides formed by divalent metal ions (calcium ions, magnesium ions).

[0071] More specifically, Figure 3 In this study, calcium and magnesium ions were used as divalent metal ions to demonstrate the pH dependence of the solubility (logarithm) of calcium carbonate, magnesium carbonate, calcium hydroxide, and magnesium hydroxide.

[0072] like Figure 3 As shown, the solubility of magnesium hydroxide becomes the lowest when the pH is above 10.5, but the solubility of calcium carbonate becomes the lowest when the pH is below 10.5.

[0073] That is, by conducting the carbonate precipitation reaction in the reaction section 10 at a pH below 10.5, calcium carbonate can be preferentially precipitated even in the presence of multiple divalent metal ions. This easily reduces the costs associated with the preparation / procurement of solutions that can be used as aqueous solutions of divalent metal ions. In particular, for solutions that initially contain dissolved carbon dioxide and divalent metal ions, such as seawater, river water, tap water, pure water, wastewater from factories, and leachate from landfills, and which can be procured at low cost, calcium carbonate can be preferentially precipitated through the simple method of pH adjustment.

[0074] In addition, although Figure 3 Not shown, but in the presence of both calcium and magnesium ions, dolomite (CaMg(CO3)2) can be formed as a carbonate. Here, even if the solubility of dolomite is set to be lower than that of calcium carbonate over the entire pH range, the reaction section 10 can proceed with the carbonate precipitation reaction as long as calcium carbonate is preferentially precipitated (pH 10.5 or below).

[0075] As described below, the evaluation system 100A in this embodiment evaluates the amount of carbon dioxide fixed based on the calcium ion concentration before and after the reaction in the reaction section 10. The evaluation of carbon dioxide fixed is based on the difference between the total amount of calcium ions before and after the reaction. Therefore, the amount of calcium ions utilized in the dolomite precipitation reaction and the amount of calcium ions utilized in the calcium carbonate precipitation reaction are both included in the total amount of calcium ions utilized in the carbonate precipitation reaction, and thus do not affect the evaluation of carbon dioxide fixed.

[0076] The first measuring unit 20 is used to measure the calcium ion concentration before the reaction. More specifically, the first measuring unit 20 measures the concentration of free calcium ions in the solution before it is introduced into the reaction unit 10, rather than the concentration of calcium ions in their ionic form. That is, the first measuring unit 20 determines the total amount of calcium ions present in ionic form before the carbonate precipitation reaction.

[0077] As the first measuring unit 20 in this embodiment, an example is a measuring device capable of measuring calcium ion concentration installed on the pipeline L1 provided at the front end of the reaction unit 10. As such a measuring device, an example is a device that uses Ca... 2+ The measuring equipment for colorimetric / spectral analysis of the test reagents or the measuring equipment using ion-selective electrodes.

[0078] The second measuring unit 30 is used to measure the calcium ion concentration after the reaction. More specifically, the second measuring unit 30 measures the concentration of free calcium ions in the solution discharged from the reaction unit 10, rather than the concentration of calcium ions in any ionic form. That is, the second measuring unit 30 determines the total amount of calcium ions present in ionic form after the carbonate precipitation reaction.

[0079] As the second measuring unit 30 in this embodiment, an example is a measuring device capable of measuring calcium ion concentration that is installed on the pipeline L2 located at the rear end of the reaction unit 10.

[0080] The measurement results from the first measuring unit 20 and the second measuring unit 30 are input into the calculation unit 40.

[0081] Furthermore, the first measuring unit 20 and the second measuring unit 30 only need to be able to measure the calcium ion concentration before and after the reaction, such as Figure 1 As shown, measuring devices can be permanently installed on pipelines L1 and L2, but are not limited to this. For example, the first measuring unit 20 and the second measuring unit 30 can be configured to be detachably installed on pipelines L1 and L2, allowing measurements to be performed only when needed. Furthermore, the first measuring unit 20 and the second measuring unit 30 can be used without installing measuring devices on pipelines L1 and L2, instead measuring the calcium ion concentration of samples collected from pipelines L1 and L2.

[0082] Here, in the evaluation system 100A of this embodiment, such as Figure 1 As shown, the first measuring unit 20 and the second measuring unit 30 are not limited to being set independently.

[0083] Figure 4 This is a schematic diagram illustrating another aspect of the evaluation system 100A of this embodiment.

[0084] like Figure 4 As shown, another embodiment of the evaluation system 100A can be described by installing a measuring device M capable of measuring calcium ion concentration on the reaction section 10, and having this measuring device M perform the functions of both the first measuring section 20 and the second measuring section 30. Simultaneously, as one method for performing / promoting the carbonate precipitation reaction in the reaction section 10, a method can be described by installing a pipeline L3 to introduce a reaction promoter into the reaction section 10, and measuring the calcium ion concentration in the reaction section 10 before and after adding the reaction promoter using the measuring device M. Thus, the calcium ion concentration measured by the measuring device M before adding the reaction promoter is equivalent to the calcium ion concentration measured by the first measuring section 20 before the reaction, and the calcium ion concentration measured by the measuring device M after adding the reaction promoter is equivalent to the calcium ion concentration measured by the second measuring section 30 after the reaction.

[0085] Here, regarding the reaction promoter introduced into the reaction section 10 via pipeline L3 for carrying out / promoting the carbonate precipitation reaction, examples include pH adjusters and microbubbles for forming extremely small gas-liquid interface reaction fields.

[0086] Furthermore, the timing for measuring calcium ion concentration using measuring device M is simply before or after the carbonate precipitation reaction, except... Figure 4 In addition to the addition of a reaction promoter via pipeline L3, calcium ion concentration can also be measured via measuring device M before and after the application of methods to promote carbonate precipitation reactions (such as concentration of aqueous solutions).

[0087] The calculation unit 40 is used to quantify the amount of immobilized carbon dioxide based on the measurement results of the first measuring unit 20 and the second measuring unit 30.

[0088] More specifically, the calculation unit 40 calculates the total amount of calcium ions utilized in the carbonate precipitation reaction in the reaction unit 10 based on the difference in calcium ion concentration obtained by the first measuring unit 20 and the second measuring unit 30.

[0089] Since the concentration of free calcium ions is measured by the first measuring unit 20 and the second measuring unit 30, the difference in calcium ion concentration (the total amount of calcium ions before the reaction minus the total amount of calcium ions after the reaction) is equivalent to the total amount of calcium ions used in the carbonate precipitation reaction.

[0090] Furthermore, since the total amount of calcium ions is related to the amount of calcium carbonate generated, and calcium carbonate is preferentially precipitated in the reaction section 10, the calculation section 40 calculates the amount of calcium carbonate generated based on the total amount of calcium ions utilized through the carbonate precipitation reaction, and then converts it into the amount of carbon dioxide fixed, thereby enabling the quantitative determination of the amount of carbon dioxide fixed.

[0091] The calculation unit 40 may include calculations or operations performed by operators, but it is preferable to use a computing device that has data input / output functions for acquiring information and executes a program for performing calculations related to carbon dioxide fixation via a processor such as a CPU. This allows for rapid and accurate evaluation of carbon dioxide fixation.

[0092] Previously, in carbon dioxide immobilization via carbonate precipitation reactions, to quantitatively evaluate the amount of carbon dioxide immobilized, it was necessary to completely separate and recover the precipitated carbonate as a solid component and measure its weight. However, in this case, separating and recovering the carbonate as a solid component requires operations related to carbonate crystal growth, thus increasing the costs associated with drug use or the time required for crystal growth. In particular, when tiny carbonate crystals precipitate during the carbonate precipitation reaction, although carbon dioxide immobilization has been achieved simply by precipitating as carbonate, it cannot be evaluated as the amount of carbon dioxide immobilized due to the difficulty in recovering it as a solid component.

[0093] On the other hand, in the evaluation system 100A of this embodiment, a specific carbonate (calcium carbonate) is preferentially precipitated as the carbonate generated by the carbonate precipitation reaction. Therefore, the change (difference) in calcium ion concentration before and after the reaction is correlated with the amount of carbonate generated, and the amount of carbonate generated can be converted into carbon dioxide fixation. That is, without separating and recovering the carbonate as a solid component, the amount of carbonate generated can be easily calculated, and thus it can be appropriately evaluated as carbon dioxide fixation.

[0094] Therefore, in the evaluation system 100A of this embodiment, the amount of immobilized carbon dioxide can be easily quantified and the appropriate evaluation of the amount of carbon dioxide immobilized can be performed without performing operations related to crystal growth. Furthermore, it can reduce the costs and time associated with the use of reagents required for carbonate crystal growth, thereby alleviating the workload related to evaluating the amount of carbon dioxide immobilized.

[0095] Furthermore, in the evaluation system 100A of this embodiment, even when carbonate is precipitated as microcrystals through a carbonate precipitation reaction, it is not necessary to directly measure the weight of the carbonate to evaluate the carbon dioxide immobilization, thus enabling high-precision evaluation of the amount of carbon dioxide immobilized. Additionally, when carbonate is precipitated as microcrystals in a carbonate precipitation reaction, examples include states where the supersaturation related to the ions required for the carbonate precipitation reaction is high, making it easy to generate microcrystal nuclei. More specifically, examples include carbonate precipitation reactions in extremely small gas-liquid interface reaction fields using microbubbles of carbon dioxide, or carbonate precipitation reactions using a semi-permeable membrane for concentration, as described later.

[0096] [Second Implementation] Figure 5 This is a schematic diagram illustrating the evaluation system for carbon dioxide fixation in the second embodiment of the present invention.

[0097] The carbon dioxide fixation evaluation system 100B (hereinafter also simply referred to as "evaluation system 100B") according to this embodiment is an improvement upon the evaluation system 100A in the first embodiment described above. The reaction unit 10 includes a concentration unit 11, which generates a concentrate Wc by permeation through a semi-permeable membrane 12. The second measurement unit 30 includes a concentrate measurement unit 31 for measuring the calcium ion concentration on the concentrate Wc side and a permeable water measurement unit 32 for measuring the calcium ion concentration on the permeable water Wp side that permeates through the semi-permeable membrane 12. Then, in the calculation unit 40 of the evaluation system 100B, the result combining the measurement results of the concentrate measurement unit 31 and the permeable water measurement unit 32 is input as the measurement result of the second measurement unit 30.

[0098] Furthermore, the structures of the evaluation system 100B in this embodiment that are the same as those of the evaluation system 100A in the first embodiment will be omitted from the description.

[0099] In the evaluation system 100B of this embodiment, the reaction unit 10 includes a concentration unit 11 that concentrates the solution by using the permeation of a semi-permeable membrane 12. The carbonate precipitation reaction is carried out by concentrating the aqueous solution containing carbon dioxide and divalent metal ions introduced into the reaction unit 10 in the concentration unit 11.

[0100] In this embodiment, the carbon dioxide and divalent metal ions introduced via pipeline L1 will be described as being in the form of pre-dissolved aqueous solutions (hereinafter referred to as "introduced solution W0").

[0101] As the concentration section 11 in this embodiment, an example is a concentration section that includes a semi-permeable membrane 12 and a processing tank 13 that is separated from the interior by the semi-permeable membrane 12.

[0102] The treatment tank 13 is only required to store the introductory solution W0 introduced via pipeline L1; its material, shape, and size are not limited. Furthermore, the treatment tank 13 is divided into a first chamber 13a and a second chamber 13b by a semi-permeable membrane 12 (described later). Assume that the introductory solution W0 is introduced into the first chamber 13a side, where a concentrated solution Wc is generated. On the other hand, an aqueous solution (not shown) that does not contain at least carbon dioxide and calcium ions is introduced into the second chamber 13b side, causing the permeate water Wp that has passed through the semi-permeable membrane 12 to flow into the second chamber 13b side. Then, the concentrated solution Wc is discharged outside the system via pipeline L3 located on the first chamber 13a side, and the permeate water Wp (including the aqueous solution originally introduced into the second chamber 13b side) is discharged outside the system via pipeline L4 located on the second chamber 13b side.

[0103] The semipermeable membrane 12 is a membrane that allows water molecules in the aqueous solution (introducing solution W0 in this embodiment) to pass through, and prevents or makes it difficult for ions required for the carbonate precipitation reaction, such as carbonate ions or divalent metal ions contained in the aqueous solution (introducing solution W0 in this embodiment), to pass through.

[0104] Using a semi-permeable membrane 12, the introductory solution W0, containing dissolved carbon dioxide and divalent metal ions, is concentrated by allowing water molecules to pass through and thus reducing their concentration, while simultaneously preventing or hindering the passage of carbonate ions present in the introductory solution W0, thereby increasing the carbonate ion concentration. Consequently, on the side of chamber 13a (the side of the concentrated solution Wc), carbonate ions react effectively with divalent metal ions, thereby effectively generating and precipitating carbonates.

[0105] Furthermore, when concentrating the introductory solution W0 with a pH exceeding 7 using the semipermeable membrane 12, the concentration of water molecules and hydroxide ions increases in the concentrated solution Wc obtained using the semipermeable membrane 12. That is, the pH of the concentrated solution Wc will increase, therefore, as mentioned above... Figure 2 As shown, carbonate ions are easily generated, thereby achieving a more efficient effect in the formation and precipitation of carbonates. Furthermore, in the reaction section 10 of this embodiment, it is preferable to carry out the carbonate precipitation reaction at a pH of 10.5 or below, setting the condition for preferential precipitation of calcium carbonate.

[0106] Furthermore, the semipermeable membrane 12 preferably allows carbon dioxide dissolved in the aqueous solution (the introductory solution WO in this embodiment) to pass through.

[0107] When carbon dioxide dissolved in the introductory solution W0 permeates through the semipermeable membrane 12, the concentration of carbon dioxide does not increase on the side of the concentrated solution Wc (side of chamber 13a) obtained by concentrating the introductory solution W0. Therefore, it is possible to suppress the unintentional decrease in pH of the concentrated solution Wc caused by the ionization of carbon dioxide contained in the introductory solution W0 to generate hydrogen ions, and to easily maintain a pH range in which carbonate ions are easily generated and calcium carbonate preferentially precipitates.

[0108] In particular, when using an aqueous solution with a pH greater than 7 as the introductory solution W0, the effect of increasing pH due to the increase in hydroxide ion concentration and suppressing the increase in carbon dioxide concentration can facilitate the formation of carbonate ions.

[0109] The reaction section 10 in this embodiment includes a concentration section 11, which concentrates the introduced solution WO using a semi-permeable membrane 12. As a result, compared with conventional methods of concentrating carbonates by heating and evaporating aqueous solutions (such as the simple distillation method), the aqueous solution can be concentrated with less energy, and the carbonate precipitation reaction can proceed.

[0110] Furthermore, in the reaction section 10 of this embodiment, the concentration of the introduced solution WO by the concentration section 11 increases the ion concentration required for the carbonate precipitation reaction near the semipermeable membrane 12, thereby maintaining a high supersaturation state. In this case, although a large number of tiny crystals that become carbonate nuclei are generated, the crystal growth rate decreases. Therefore, in order to recover the carbonate crystals as solid components through separation operations such as filtration, time is required for the use of reagents and for crystal growth. However, in the evaluation system 100B of this embodiment, it is not necessary to recover the carbonate crystals as solid components. Even if tiny carbonate crystals are generated in the reaction section 10 of this embodiment, the amount of carbon dioxide fixed can be easily quantified and appropriately evaluated.

[0111] In the concentration section 11 of this embodiment, it is preferable to introduce solutions with salt concentrations into both the concentration side (first chamber 13a side) and the dilution side (second chamber 13b side) of the processing tank 13. Furthermore, the salt concentration of the solution introduced into the dilution side is more preferably the same as the salt concentration of the solution introduced into the concentration side. Moreover, the salt concentration of the solution introduced into the dilution side is even more preferably higher than the salt concentration of the solution introduced into the concentration side.

[0112] By introducing a solution with a salt concentration to the dilution side, the concentration difference between the salt concentration of the introduced solution W0 introduced to the concentration side and the salt concentration of the solution introduced to the dilution side becomes smaller, enabling the introduced solution W0 to be concentrated with less energy and allowing the carbonate precipitation reaction related to carbon dioxide immobilization to proceed. Furthermore, by generating osmotic pressure by making the salt concentration of the solution introduced to the dilution side higher than that of the introduced solution W0 introduced to the concentration side, the introduced solution W0 can be concentrated with even less energy.

[0113] Furthermore, in this embodiment, the reaction unit 10 can be equipped with a pressurizing mechanism as the concentration unit 11. The pressurizing mechanism is not particularly limited to any mechanism that applies pressure to the introduced solution WO in the first chamber 13a and the semi-permeable membrane 12. Therefore, concentration can be performed without adjusting the salt concentration of each solution introduced into the processing tank 13.

[0114] Alternatively, a pressurization mechanism can be used while adjusting the salt concentration of each solution introduced into the treatment tank 13. This reduces costs associated with the use of chemicals required for salt concentration adjustment, while also reducing energy consumption in the pressurization mechanism.

[0115] Furthermore, when the introduced solution W0 contains other salts that do not participate in the carbonate precipitation reaction, has a pH of 7 or higher, and contains carbonate ions, a membrane that allows water molecules, carbon dioxide, and hydrogen ions to pass through, but prevents or makes it difficult for other ions (except hydrogen ions) required for the carbonate precipitation reaction to pass through, can be used as the semipermeable membrane 12. In this case, since the concentration of hydrogen ions remaining on the side of chamber 13a (the concentrate Wc side) can be suppressed from increasing, the pH decrease can be suppressed. As a result, the concentration of carbonate ions in the concentrate Wc increases, facilitating the formation and precipitation of carbonate.

[0116] In the evaluation system 100B of this embodiment, the calcium ion concentration before and after the reaction is also measured by the first measuring unit 20 and the second measuring unit 30, and the total amount of calcium ions existing in ionic form before and after the carbonate precipitation reaction is determined.

[0117] The first measuring unit 20 in this embodiment is the same as that shown in the evaluation system 100A described above, so its description is omitted.

[0118] The second measuring unit 30 in this embodiment includes: a concentrate measuring unit 31, which measures the calcium ion concentration on the Wc side of the concentrate; and a permeate measuring unit 32, which measures the calcium ion concentration on the Wp side of the permeate that permeates through the semipermeable membrane 12. More specifically, as Figure 5As shown, the following examples can be cited: as the concentrate measuring unit 31, a measuring device capable of measuring calcium ion concentration is installed on the pipeline L3 located at the downstream end of the reaction unit 10; and as the permeate measuring unit 32, a measuring device capable of measuring calcium ion concentration is installed on the pipeline L4 located at the downstream end of the reaction unit 10.

[0119] Since the concentrate Wc, generated by using the semi-permeable membrane 12 and discharged from the system via pipeline L3, is a product obtained after the carbonate precipitation reaction, the concentration of calcium ions contained in the concentrate Wc can be measured with high precision and ease by setting up the concentrate measuring unit 31. This also improves the accuracy of the quantitative correlation with the amount of immobilized carbon dioxide, enabling more appropriate evaluation.

[0120] As the second measuring unit 30, at least the concentrated liquid measuring unit 31 is used for measurement, while the permeate measuring unit 32 may be omitted.

[0121] Whether the permeable water measuring unit 32 can be omitted depends on the ion permeability of the semipermeable membrane 12. When a membrane that is completely impermeable to calcium ions is used as the semipermeable membrane 12, the total amount of calcium ions after the reaction can be determined by measuring the calcium ion concentration in the concentrate Wc, thus the permeable water measuring unit 32 can be omitted. On the other hand, when a membrane that is not easily permeable to calcium ions is used as the semipermeable membrane 12, some of the calcium ions remaining in the carbonate precipitation reaction in the reaction section 10 will move to the dilution side (second chamber 13b side). In this case, in order to determine the total amount of calcium ions after the reaction, in addition to measuring the calcium ion concentration in the concentrate Wc as the second measuring unit 30, it is also necessary to measure the calcium ion concentration in the permeable water Wp. Therefore, the permeable water measuring unit 32 is not omitted, and it functions as the second measuring unit 30.

[0122] The measurement results of the first measuring unit 20 and the second measuring unit 30 (concentrate measuring unit 31 and permeate measuring unit 32) are input into the calculation unit 40.

[0123] In the calculation unit 40, the amount of immobilized carbon dioxide is quantified based on the measurement results of the first measuring unit 20 and the second measuring unit 30. Here, the content related to the quantification of the amount of carbon dioxide immobilized is the same as that shown in the evaluation system 100A described above, and therefore its explanation is omitted.

[0124] In the evaluation system 100B of this embodiment, similar to the evaluation system 100A described above, the amount of carbonate generated can be easily determined without separating and recovering carbonate as a solid component, and thus can be appropriately evaluated as the amount of carbon dioxide fixed.

[0125] Furthermore, in evaluation system 100B, since a semi-permeable membrane is used and concentration is achieved through osmosis, the carbonate precipitation reaction can be carried out with less energy compared to the case of concentration by heating and evaporating the solution, thereby obtaining carbonate. Sometimes, small crystals precipitate as carbonate, but as mentioned above, when evaluating carbon dioxide fixation using evaluation system 100B, it is not necessary to recover the carbonate as a solid component; therefore, a simple and appropriate quantitative evaluation of carbon dioxide fixation can be performed.

[0126] Furthermore, the above embodiments illustrate one example of a carbon dioxide fixation evaluation system and method. The carbon dioxide fixation evaluation system and method of the present invention are not limited to the above embodiments; modifications can be made to the carbon dioxide fixation evaluation system and method described in the above embodiments without altering the spirit of the technical solution.

[0127] Furthermore, the carbon dioxide sequestration evaluation system and method of the present invention are applicable to various equipment / facilities (systems) that require quantitative evaluation of carbon dioxide sequestration. Specifically, examples include facilities suitable for directly recovering / separating carbon dioxide from the atmosphere and storing it underground (DACCS system), carbon dioxide recovery / storage equipment attached to thermal power generation (CCS system), and carbonation equipment installed on ships or at sea for the sequestration of carbon dioxide from seawater.

[0128] Industrial availability The carbon dioxide fixation evaluation system and method of the present invention can quantify the amount of carbon dioxide fixed (carbon dioxide fixation) related to the carbon dioxide fixation based on the carbonate precipitation reaction, and are therefore preferably used for evaluating carbon dioxide fixation.

[0129] Furthermore, the carbon dioxide fixation evaluation system and method of the present invention do not require carbonate crystal growth or direct weight measurement of carbonates, and are therefore particularly preferred when carbonates precipitate in the form of tiny crystals during carbonate precipitation reactions.

[0130] Symbol Explanation 100A, 100B - Evaluation system for carbon dioxide fixation, 10 - Reaction section, 11 - Concentration section, 12 - Semi-permeable membrane, 13 - Treatment tank, 13a - Chamber 1, 13b - Chamber 2, 20 - First measuring section, 30 - Second measuring section, 31 - Concentrate measuring section, 32 - Permeate measuring section, 40 - Calculation section, L1~L4 - Piping, M - Measuring equipment, W0 - Introduced solution, Wc - Concentrate, Wp - Permeate.

Claims

1. A system for evaluating carbon dioxide fixation, characterized in that, have: The reaction section carries out carbonate precipitation reactions related to carbon dioxide immobilization under conditions of preferential precipitation of calcium carbonate. The first measuring section measures the calcium ion concentration before the reaction. The second measuring unit measures the calcium ion concentration after the reaction; and The calculation unit quantifies the amount of immobilized carbon dioxide based on the measurement results of the first measurement unit and the second measurement unit.

2. The carbon dioxide fixation evaluation system according to claim 1, characterized in that, The reaction section carries out a carbonate precipitation reaction at a pH below 10.

5.

3. The carbon dioxide fixation evaluation system according to claim 1 or 2, characterized in that, The reaction section includes a concentration section, which generates a concentrated solution by using the permeation of a semi-permeable membrane. The second measuring unit measures at least the calcium ion concentration on the concentrate side.

4. A method for evaluating carbon dioxide fixation, characterized in that, include: The reaction steps involve a carbonate precipitation reaction related to carbon dioxide immobilization under conditions of preferential precipitation of calcium carbonate. The first determination step involves measuring the calcium ion concentration before the reaction. The second determination step involves measuring the calcium ion concentration after the reaction; and The calculation step quantifies the amount of immobilized carbon dioxide based on the measurement results of the first and second measurement steps.

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