Method for carbon dioxide fixation, method for carbon dioxide capture, and device for carbon dioxide fixation and environmentally friendly industrial equipment including same

Abstract

This method for carbon dioxide fixation comprises: a step in which a metal complex of a metallic element with a chelating agent is formed in an aqueous alkali solution containing hydrogen carbonate ions or the like, the chelating agent, and a raw material including both the metallic element, which is capable of forming a carbonate with the hydrogen carbonate ions or the like and capable of reacting with the chelating agent to form a complex, and ions unnecessary for the formation of the metal carbonate or for the formation of the metal complex of the metallic element with the chelating agent; a step in which the aqueous alkali solution is heated to react the hydrogen carbonate ions or the like with the metal complex, thereby forming a metal carbonate; and a step in which carbon dioxide is injected into the aqueous alkali solution containing the formed metal carbonate to thereby form hydrogen carbonate ions or the like. The raw material is supplied and the metal complex formation step, the metal carbonate formation step, and the step for forming hydrogen carbonate ions or the like are performed. The method for carbon dioxide fixation further includes a step in which the unnecessary ions are removed.

Description

Carbon dioxide fixation method, carbon dioxide recovery method, carbon dioxide fixation device, and environmentally friendly industrial facility equipped with the same

[0001] The present invention relates to a carbon dioxide fixation method, a carbon dioxide recovery method, a carbon dioxide fixation device, and an environmentally friendly industrial facility equipped with the same.

[0002] In recent years, the mass consumption of fossil fuels and other fuels has led to an increase in carbon dioxide emissions into the atmosphere, which is the main cause of global warming. Furthermore, there are concerns that the increased amount of carbon dioxide dissolved in seawater will cause the seawater to become more acidic, adversely affecting ecosystems. Therefore, countries around the world are considering ways to reduce carbon dioxide emissions, and carbon dioxide fixation is also attracting attention.

[0003] Patent Document 1 describes a carbon dioxide fixation method including the steps of: forming an alkaline aqueous solution containing a raw material containing a metal element capable of combining with carbonate ions to form a carbonate salt, and a chelating agent; reacting the metal element with the chelating agent in the aqueous solution to separate the metal element from the raw material as metal ions; adding a compound capable of generating carbonate ions in the aqueous solution after the separation step to form a carbonate salt by reacting the carbonate ions generated from the compound with the metal ions; injecting carbon dioxide gas into the aqueous solution after the carbonate salt formation step to lower the pH to the same value as or close to the pH value of the aqueous solution formed in the aqueous solution formation step; and repeating the steps from the separation step to the pH lowering step by adding a new raw material of the same type as the raw material to the aqueous solution after the pH lowering step.

[0004] Japanese Patent Application Laid-Open No. 2022-102786

[0005] Incidentally, it is known that the bottom ash, incineration fly ash, slag, etc. obtained by incinerating waste (automobile shredder dust, waste plastics, discarded office equipment, electronic devices, etc.) contain trace elements such as silver, arsenic, gold, boron, bismuth, cadmium, cobalt, chromium, cesium, and copper, in addition to calcium, silicon, aluminum, iron, chlorine, sodium, magnesium, potassium, titanium, and phosphorus (see the 2019 Tokyo Metropolitan Research Institute for Environmental Protection Public Research Presentation (Recycling of Municipal Waste Incineration Ash - Significance and Challenges - Hiroshi Sakakura, Center for Resource Circulation and Waste Management Research, National Institute for Environmental Studies, December 20, 2019)). It is also known that refuse incineration fly ash contains zinc, lead, copper, cadmium, etc. (see Proceedings of the Japan Society of Civil Engineers (Estimation of Chemical Forms of Zinc, Lead, Copper, and Cadmium in Fly Ash by Sequential Extraction Method, Takaoka, Masateru, Kuramoto, Yasuhiro, Takeda, Nobuo, Fujiwara, Takeshi, No. 685 / V11-20: 79-90, August 2001)). Furthermore, gypsum and the like contain sulfate ions, etc.

[0006] The above-mentioned Patent Document 1 describes, as a conventional technique, that when a raw material contains unnecessary ions in addition to a metal element that can combine with carbonate ions to form a metal carbonate salt, fixation of carbon dioxide becomes insufficient.

[0007] The present invention aims to solve the various problems in the prior art and to achieve the following object: That is, the present invention aims to provide a carbon dioxide fixation method and a carbon dioxide fixation apparatus that can efficiently fix carbon dioxide even when the raw material contains unnecessary ions in addition to metal elements that can combine with bicarbonate ions or carbonate ions to form metal carbonate salts.

[0008] The means for solving the above problems are as follows: Namely, <1> a metal complex forming step of forming a metal complex of a metal element and a chelating agent in an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material containing a metal element capable of combining with the bicarbonate ions or carbonate ions to form a metal carbonate salt and capable of reacting with the chelating agent to form a complex, and ions unnecessary for forming the metal carbonate salt or the metal complex of the metal element and the chelating agent, a metal carbonate salt forming step of heating the alkaline aqueous solution to react the bicarbonate ions or carbonate ions with the metal complex to form the metal carbonate, and a bicarbonate ion or carbonate ion forming step of injecting carbon dioxide into the alkaline aqueous solution in which the metal carbonate salt has been formed to form bicarbonate ions or carbonate ions, thereby obtaining a liquid containing the bicarbonate ions or carbonate ions and the chelating agent, The carbon dioxide fixation method includes: supplying the raw material to a liquid containing the bicarbonate ions or carbonate ions obtained in the bicarbonate ion or carbonate ion formation step and a chelating agent, thereby performing the metal complex formation step, the metal carbonate salt formation step, and the bicarbonate ion or carbonate ion formation step; and further including an unnecessary ion removal step of removing the unnecessary ions using an unnecessary ion removal substance (excluding ion-bonding binary compounds) after the metal complex formation step and before the metal carbonate salt formation step, after the metal carbonate salt formation step and before the bicarbonate ion or carbonate ion formation step, or after the bicarbonate ion or carbonate ion formation step and before the metal complex formation step. <2> The carbon dioxide fixation method according to <1>, wherein the unnecessary ion removal substance is an ion exchange resin. <3> The carbon dioxide fixation method according to <2>, wherein the unnecessary ions are copper (Cu) ions, magnesium (Mg) ions, zinc (Zn) ions, or sulfate ions. <4> The carbon dioxide fixation method according to <1>, wherein the metal element is calcium (Ca). <5> The carbon dioxide fixation method according to <1>, wherein the heating temperature in the metal carbonate formation step is 80°C or higher and lower than 100°C.<6> The method for fixing carbon dioxide according to <1>, wherein the chelating agent is biodegradable. <7> The method for fixing carbon dioxide according to <1>, wherein the chelating agent is tetrasodium L-glutamate diacetate. <8> The method for fixing carbon dioxide according to <1>, wherein the raw material is bottom ash or gypsum. <9> The method for fixing carbon dioxide according to <1>, wherein the alkaline aqueous solution is prepared using sodium hydrogen carbonate. <10> A method for producing a metal complex of a metal element with a chelating agent in an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material containing a metal element capable of combining with the bicarbonate ions or carbonate ions to form a metal carbonate salt and capable of reacting with the chelating agent to form a complex, and ions unnecessary for forming the metal carbonate salt or the metal complex of the metal element and the chelating agent; a metal carbonate salt forming step of heating the alkaline aqueous solution to react the bicarbonate ions or carbonate ions with the metal complex to form the metal carbonate; and a bicarbonate ion or carbonate ion forming step of injecting carbon dioxide into the alkaline aqueous solution in which the metal carbonate salt has been formed to form bicarbonate ions or carbonate ions, thereby obtaining a liquid containing the bicarbonate ions or carbonate ions and the chelating agent, the metal complex formation step, the metal carbonate formation step, and the bicarbonate ion or carbonate ion formation step are carried out by supplying the raw material to a liquid containing the bicarbonate ions or carbonate ions obtained in the bicarbonate ion or carbonate ion formation step and a chelating agent, and further comprising an unnecessary ion removal step of removing the unnecessary ions using an unnecessary ion removal substance (excluding ion-bonding binary compounds) that removes the unnecessary ions after the metal complex formation step and before the metal carbonate formation step, after the metal carbonate formation step and before the bicarbonate ion or carbonate ion formation step, or after the bicarbonate ion or carbonate ion formation step and before the metal complex formation step.<11> A metal complex forming means for forming a metal complex of the metal element and the chelating agent in an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material containing a metal element capable of combining with the bicarbonate ions or carbonate ions to form a metal carbonate salt and capable of reacting with the chelating agent to form a complex, and ions unnecessary for forming the metal carbonate salt or the metal complex of the metal element and the chelating agent; a metal carbonate salt forming means for heating the alkaline aqueous solution to react the bicarbonate ions or carbonate ions with the metal complex to form the metal carbonate; and a bicarbonate ion or carbonate ion forming means for injecting carbon dioxide into the alkaline aqueous solution in which the metal carbonate salt has been formed to form bicarbonate ions or carbonate ions, thereby obtaining a liquid containing the bicarbonate ions or carbonate ions and the chelating agent. a control means for supplying the raw materials to a liquid containing the bicarbonate ions or carbonate ions obtained by the bicarbonate ion or carbonate ion forming means and a chelating agent, and for controlling the operation of the metal complex forming means, the metal carbonate forming means, and the bicarbonate ion or carbonate ion forming means; and an unnecessary ion removing means for removing the unnecessary ions using an unnecessary ion removing substance (excluding ion-bonding binary compounds) after the operation of the metal complex forming means and before the operation of the metal carbonate forming means, after the operation of the metal carbonate forming means and before the operation of the bicarbonate ion or carbonate ion forming means, or after the operation of the bicarbonate ion or carbonate ion forming means and before the operation of the metal complex forming means. <12> An environmentally friendly industrial facility comprising the carbon dioxide fixation apparatus according to <11>.

[0009] The present invention can solve the various problems encountered in the past and provide a carbon dioxide fixation method and a carbon dioxide fixation apparatus that can efficiently fix carbon dioxide even when the raw material contains unnecessary ions in addition to metal elements that can combine with bicarbonate ions or carbonate ions to form metal carbonate salts.

[0010] FIG. 1 is a diagram showing an example of the process flow of a carbon dioxide fixation method according to a first embodiment. FIG. 2 is a diagram showing an example of the process flow of a carbon dioxide fixation method according to a second embodiment. FIG. 3 is a diagram showing an example of the process flow of a carbon dioxide fixation method according to a third embodiment. FIG. 4 is a diagram showing the concentrations (accumulation amounts) of copper (Cu), magnesium (Mg), and zinc (Zn) in each cycle of Experimental Example 1. FIG. 5 is a diagram showing the element concentrations in a liquid sample collected in Test Example 1. FIG. 6 is a diagram showing the sulfate ion concentrations in liquid samples collected before and after treatment with a strong basic anion exchange resin in Test Example 2. FIG. 7 is a diagram showing the GLDA concentrations in liquid samples collected before and after treatment with a strong basic anion exchange resin in Test Example 2.

[0011] (Method and Apparatus for Fixing Carbon Dioxide) The method for fixating carbon dioxide of the present invention comprises a metal complex forming step, a metal carbonate forming step, a bicarbonate ion or carbonate ion forming step, and an unnecessary ion removing step, and may further comprise other steps as necessary. The apparatus for fixating carbon dioxide of the present invention comprises a metal complex forming means, a metal carbonate forming means, a bicarbonate ion or carbonate ion forming means, an unnecessary ion removing means, and a control means, and may further comprise other means as necessary.

[0012] The carbon dioxide fixation method can be suitably carried out by the carbon dioxide fixation apparatus, the metal complex formation step can be suitably carried out by the metal complex formation means, the metal carbonate formation step can be suitably carried out by the metal carbonate formation means, the bicarbonate ion or carbonate ion formation step can be suitably carried out by the bicarbonate ion or carbonate ion formation means, the unnecessary ion removal step can be suitably carried out by the unnecessary ion removal means, and the other steps can be suitably carried out by the other means. According to the carbon dioxide fixation method and carbon dioxide fixation apparatus of the present invention, carbon dioxide can be efficiently fixed even when the raw material contains, in addition to a metal element that can combine with bicarbonate ion or carbonate ion to form a metal carbonate, unnecessary ions that will not be used in forming the metal carbonate or in forming a metal complex between the metal element and the chelating agent.

[0013] In the carbon dioxide fixation method, after the metal complex formation step, the metal carbonate formation step, and the bicarbonate ion or carbonate ion formation step (first cycle) are performed, raw materials are supplied again, and the metal complex formation step, the metal carbonate formation step, and the bicarbonate ion or carbonate ion formation step (second cycle) are performed. An unnecessary ion removal step is performed between any of these steps. In the carbon dioxide fixation device, after the first cycle is operated by the control means, raw materials are supplied again, and the second cycle is operated. That is, the control means controls the supply of raw materials and the operation of the metal complex formation means, the metal carbonate formation means, and the bicarbonate ion or carbonate ion formation means.

[0014] The unnecessary ion removal step only needs to be performed at least once and is not an essential step in all cycles. For example, the unnecessary ion removal step may be performed after each of the metal complex formation step, the metal carbonate formation step, and the bicarbonate ion or carbonate ion formation step in one cycle, or after any of the metal complex formation step, the metal carbonate formation step, and the bicarbonate ion or carbonate ion formation step. Furthermore, the unnecessary ion removal step may be performed once per cycle or once per multiple cycles.

[0015] The chelating agent initially introduced in the metal complex formation step is not consumed in subsequent steps, and can therefore be reused in the metal complex formation step in the second or subsequent cycles. In this way, the metal complex formation step in the second or subsequent cycles can be performed under substantially the same conditions as the metal complex formation step in the first cycle, and the metal carbonate formation step, bicarbonate ion or carbonate ion formation step, and unnecessary ion removal step in the second or subsequent cycles can also be performed in the same manner as in the first cycle. This allows carbon dioxide to be immobilized in the metal carbonate formation step in the second or subsequent cycles. The bicarbonate ions or carbonate ions formed in the previous bicarbonate ion or carbonate ion formation step can be used in the metal complex formation step in the second or subsequent cycles. Therefore, by supplying bicarbonate ions or carbonate ions, or carbon dioxide, and a raw material, the metal complex formation step, the metal carbonate formation step, the bicarbonate ion or carbonate ion formation step, and the unnecessary ion removal step can be repeatedly performed to immobilize carbon dioxide.

[0016] Hereinafter, each step in the carbon dioxide fixation method of the present invention and each means in the carbon dioxide fixation apparatus of the present invention will be described in detail.

[0017] <Metal Complex Forming Step and Metal Complex Forming Means> The metal complex forming step is a step of forming a metal complex in an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material, and is carried out by the metal complex forming means.

[0018] The bicarbonate ion or carbonate ion is not particularly limited and can be appropriately selected depending on the purpose, and may be a bicarbonate ion or carbonate ion derived from sodium bicarbonate, or a bicarbonate ion or carbonate ion derived from carbon dioxide formed in the bicarbonate ion or carbonate ion forming step described below. Note that the term "bicarbonate ion or carbonate ion" herein includes the case where both bicarbonate ion and carbonate ion are present.

[0019] —Chelating Agent— The chelating agent is not particularly limited and can be appropriately selected depending on the purpose. Examples of the chelating agent include ethylenediamine-N,N′-disuccinic acid (EDDS), L-glutamic acid diacetate (GLDA), L-glutamic acid diacetate tetrasodium salt (GLDA-4Na), nitrilotriacetic acid (NTA), 1,3-diamino-2-hydroxypropane-N,N,N′,N′-tetraacetic acid (DPTA-OH), diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid (EDTPO), nitrilotri(methylphosphonic acid) (NTPO), and amino acids. Among these, in terms of efficiently fixing carbon dioxide, biodegradable chelating agents such as ethylenediamine-N,N'-disuccinic acid (EDDS), L-glutamic acid diacetate (GLDA), and tetrasodium L-glutamic acid diacetate (GLDA-4Na) are preferred, L-glutamic acid diacetate (GLDA) and tetrasodium L-glutamic acid diacetate (GLDA-4Na) are more preferred, and tetrasodium L-glutamic acid diacetate (GLDA-4Na) is even more preferred.

[0020] The concentration of the chelating agent in the alkaline aqueous solution is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the concentration is preferably from 0.01 mol / L to 1 mol / L, more preferably from 0.01 mol / L to 0.5 mol / L, even more preferably from 0.01 mol / L to 0.3 mol / L, still more preferably from 0.05 mol / L to 0.15 mol / L, and particularly preferably from 0.07 mol / L to 0.13 mol / L.

[0021] -Raw Material- The raw material contains at least a metal element and unnecessary ions, and may contain other metal elements or ions. The raw material can be appropriately selected depending on the purpose, and examples include silicates, steel slag, waste, ash, gypsum, etc. Among these, ash or gypsum is preferred in terms of efficiently fixing carbon dioxide.

[0022] The ash can be obtained by burning input materials in a boiler, incinerator, or the like (incinerator ash). The input materials are not particularly limited and can be selected appropriately depending on the purpose, and examples thereof include burnable waste, non-burnable waste, and industrial waste such as plastics. The ash is not particularly limited and can be selected appropriately depending on the purpose, and examples thereof include bottom ash (incinerator bottom ash), which is ash that falls to the bottom of an incinerator, and fly ash (incinerator fly ash), which is ash blown by the wind and collected by a dust collector or the like. Among these, bottom ash is preferred in terms of efficient carbon dioxide fixation.

[0023] --Metal Element-- The metal element is an element that can combine with the bicarbonate ion or carbonate ion to form a metal carbonate salt and can react with the chelating agent to form a complex. The metal element can be appropriately selected depending on the purpose, but from the viewpoint of efficiently fixing carbon dioxide, metal elements that form carbonates with low solubility, such as calcium (Ca), magnesium (Mg), and strontium (Sr), are preferred. Note that the form of the metal element includes not only metal elements but also ionic forms.

[0024] The metal carbonate is not particularly limited and can be appropriately selected depending on the purpose. However, calcium carbonate (CaCO ３ ), magnesium carbonate (MgCO ３ ) and the like are preferred.

[0025] The concentration of the metal element in the alkaline aqueous solution is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the concentration is preferably from 0.01 mol / L to 1 mol / L, more preferably from 0.01 mol / L to 0.5 mol / L, even more preferably from 0.01 mol / L to 0.1 mol / L, and particularly preferably from 0.02 mol / L to 0.08 mol / L.

[0026] --Unwanted ions-- The unwanted ions are ions that are unnecessary in the formation of the metal carbonate salt or the formation of a metal complex between the metal element and the chelating agent. The unwanted ions may be impurities that inhibit the extraction of the metal element. While it is desirable that the unwanted ions are not contained in the raw materials, they can be considered unavoidable impurities that are contained when incineration bottom ash, incineration fly ash, gypsum, or the like is used as the raw material. Examples of the unwanted ions include copper (Cu) ions, magnesium (Mg) ions, zinc (Zn) ions, and sulfate ions.

[0027] The concentration of the unnecessary ions in the alkaline aqueous solution is not particularly limited and can be appropriately selected depending on the purpose. The unnecessary ions can be removed in the unnecessary ion removal step described below. By repeatedly performing the metal complex formation step, the metal carbonate salt formation step, and the bicarbonate ion or carbonate ion formation step, the concentration of the unnecessary ions in the alkaline aqueous solution increases. When the concentration of the unnecessary ions in the alkaline aqueous solution increases, it is preferable to remove the unnecessary ions in the unnecessary ion removal step described below.

[0028] -Alkaline aqueous solution- In the metal complex formation step, the alkaline aqueous solution often exhibits alkaline properties unless pH adjustment is performed, and is therefore referred to as an alkaline aqueous solution. The pH of this alkaline aqueous solution is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of efficiently fixing carbon dioxide, a pH of 6 to 10 is preferred, a pH of 7 to 9 is more preferred, a pH of 7.5 to 8.5 is even more preferred, and a pH of 7.7 to 8.3 is particularly preferred. The pH of the alkaline aqueous solution can be adjusted to a preferred range using nitric acid.

[0029] The alkaline aqueous solution is not particularly limited and can be appropriately selected depending on the purpose, but is preferably prepared using sodium hydrogen carbonate in terms of efficiently fixing carbon dioxide.

[0030] The concentration of sodium hydrogencarbonate in the alkaline aqueous solution is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the concentration is preferably 0.1 mol / L or more and 1 mol / L or less, more preferably 0.5 mol / L or more and 1 mol / L or less, even more preferably 0.6 mol / L or more and 1 mol / L or less, and particularly preferably 0.7 mol / L or more and 1 mol / L or less.

[0031] -Metal Complex- The metal complex is a product of the metal element and a chelating agent. For example, when the metal element is calcium (Ca) and the chelating agent is GLDA, the metal complex is Ca-GLDA2. － Examples include:

[0032] The temperature at which the metal complex-forming step is carried out is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the temperature is preferably 0°C or higher and 50°C or lower, more preferably 0°C or higher and 40°C or lower, even more preferably 0°C or higher and 30°C or lower, and particularly preferably 0°C or higher and 20°C or lower.

[0033] The time for the metal complex formation step is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the time is preferably from 1 minute to 60 minutes, more preferably from 10 minutes to 50 minutes, even more preferably from 20 minutes to 40 minutes, and particularly preferably from 25 minutes to 35 minutes.

[0034] <Metal Carbonate Forming Step and Metal Carbonate Forming Means> The metal carbonate forming step is a step of heating the alkaline aqueous solution to react the bicarbonate ions or carbonate ions with the metal complex to form a metal carbonate, and is carried out by the metal carbonate forming means. Carbon dioxide can be fixed by the metal carbonate forming step.

[0035] -Metal Carbonate- The metal carbonate is a carbonate of the metal element. For example, when the metal element is calcium (Ca), calcium carbonate is used.

[0036] The temperature at which the metal carbonate-forming step is carried out is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of efficiently fixing carbon dioxide, the lower limit is, for example, 20°C or more, 40°C or more, 60°C or more, 70°C or more, 80°C or more, and 90°C or more, in this order. The upper limit is, for example, 170°C or less, 160°C or less, 120°C or less, 100°C or less, and less than 100°C, in this order, in terms of preventing deterioration of the equipment used and energy efficiency. Suitable numerical ranges for the temperature include numerical ranges that are equal to or greater than any of the lower limit values ​​and equal to or less than any of the upper limit values. Among these, 20°C or more and 170°C or less are preferred, 40°C or more and 160°C or less are more preferred, 60°C or more and 120°C or less are even more preferred, 70°C or more and 100°C or less are even more preferred, 80°C or more and less than 100°C are particularly preferred, and 90°C or more and less than 100°C are most preferred.

[0037] The time for the metal carbonate formation step is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the time is preferably from 1 minute to 60 minutes, more preferably from 10 minutes to 50 minutes, even more preferably from 20 minutes to 40 minutes, and particularly preferably from 25 minutes to 35 minutes.

[0038] In the metal carbonate forming step, the pH of the alkaline aqueous solution before heating is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of efficiently fixing carbon dioxide, the pH is preferably from 6 to 13, more preferably from 8 to 10, and even more preferably from 8.5 to 9.5. The pH of the alkaline aqueous solution can be adjusted to a preferred range using nitric acid.

[0039] <Bicarbonate ion or carbonate ion forming step and bicarbonate ion or carbonate ion forming means> The bicarbonate ion or carbonate ion forming step is a step of injecting carbon dioxide into the alkaline aqueous solution in which the metal carbonate salt has been formed to form bicarbonate ions or carbonate ions, and is carried out by the bicarbonate ion or carbonate ion forming means.

[0040] The amount of carbon dioxide injected is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoint of efficiently fixing carbon dioxide, it is preferable to inject the carbon dioxide until the pH of the alkaline aqueous solution reaches a desired value. The method of injecting carbon dioxide is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoint of efficiently fixing carbon dioxide, a method of blowing (bubbling) the carbon dioxide into the alkaline aqueous solution is preferable.

[0041] The alkaline aqueous solution after the bicarbonate ion or carbonate ion formation step (after carbon dioxide injection) often exhibits alkaline properties unless pH adjustment is performed, and is therefore referred to as an alkaline aqueous solution. The pH of this alkaline aqueous solution is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of efficiently fixing carbon dioxide, the pH is preferably from 6 to 10, more preferably from 7 to 9, even more preferably from 7.5 to 8.5, and particularly preferably from 7.7 to 8.3.

[0042] The temperature at which the bicarbonate ion or carbonate ion forming step is carried out is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the temperature is preferably 0°C or higher and 50°C or lower, more preferably 10°C or higher and 40°C or lower, even more preferably 20°C or higher and 30°C or lower, and particularly preferably 22°C or higher and 28°C or lower.

[0043] The time for the bicarbonate ion or carbonate ion forming step is not particularly limited and can be appropriately selected depending on the purpose.

[0044] <Unwanted Ion Removal Step and Unwanted Ion Removal Means> The unwanted ion removal step is a step of removing the unwanted ions using an unwanted ion removal substance (excluding ion-bonded binary compounds) that removes the unwanted ions, and is performed by the unnecessary ion removal means. Here, the ion-bonded binary compound refers to an ion-bonded binary compound (e.g., iron (Fe)) that can combine with the bicarbonate ion or carbonate ion to form a metal carbonate salt and is less likely to form a complex with the chelating agent than a metal element that can react with the chelating agent to form a complex) and another element (e.g., sulfur (S)) that can combine with the metal element A but is different from the metal element A (e.g., iron sulfide (FeS)).

[0045] The unnecessary ion removal step is carried out after the metal complex formation step and before the metal carbonate formation step, after the metal carbonate formation step and before the bicarbonate ion or carbonate ion formation step, or after the bicarbonate ion or carbonate ion formation step and before the metal complex formation step.

[0046] The substance for removing unnecessary ions is not particularly limited and can be appropriately selected depending on the purpose, but an ion exchange resin is preferred in terms of efficiently fixing carbon dioxide.

[0047] The ion exchange resin is not particularly limited and can be appropriately selected depending on the purpose, but a chelate resin or an anion exchange resin is preferred in terms of efficiently fixing carbon dioxide. When the unnecessary ions are copper (Cu) ions, magnesium (Mg) ions, zinc (Zn) ions, or the like, the ion exchange resin is preferably a chelate resin. When the unnecessary ions are sulfate ions, or the like, the ion exchange resin is preferably an anion exchange resin.

[0048] The chelating resin is not particularly limited and can be appropriately selected depending on the purpose, but an iminodiacetic acid type chelating resin is preferred in terms of efficiently fixing carbon dioxide. Commercially available iminodiacetic acid type chelating resins can be used. Examples of commercially available iminodiacetic acid type chelating resins include Murimac Murochelate B-1 (manufactured by Muromachi Chemical Co., Ltd.).

[0049] The anion exchange resin is not particularly limited and can be appropriately selected depending on the purpose, but a strongly basic anion exchange resin is preferred in terms of efficiently fixing carbon dioxide. Commercially available strongly basic anion exchange resins can be used. Examples of commercially available strongly basic anion exchange resins include Muromac XSB-2613 (manufactured by Muromachi Chemical Co., Ltd.).

[0050] The pH of the alkaline aqueous solution in the unnecessary ion removal step is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of efficiently fixing carbon dioxide, the pH is preferably from 7.5 to 13, more preferably from 8 to 11, and even more preferably from 8 to 9. The pH of the alkaline aqueous solution can be adjusted to a preferred range using nitric acid.

[0051] The temperature at which the unnecessary ion removal step is carried out is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the temperature is preferably 0°C or higher and 50°C or lower, more preferably 10°C or higher and 40°C or lower, even more preferably 20°C or higher and 30°C or lower, and particularly preferably 22°C or higher and 28°C or lower.

[0052] The time for the unnecessary ion removal step is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the time is preferably from 10 minutes to 60 minutes, more preferably from 10 minutes to 50 minutes, even more preferably from 10 minutes to 40 minutes, and particularly preferably from 10 minutes to 30 minutes.

[0053] The order in which the unnecessary ion removal step is performed is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of efficiently fixing carbon dioxide, the unnecessary ion removal step is preferably performed before the metal carbonate formation step, and more preferably before the metal complex formation step and the metal carbonate formation step.

[0054] The carbon dioxide fixation method can include, for example, first performing the metal complex formation step, then performing the metal carbonate formation step, then performing the bicarbonate ion or carbonate ion formation step, then performing the unnecessary ion removal step, supplying a raw material and performing the metal complex formation step, subsequently performing the metal carbonate formation step, and then performing the bicarbonate ion or carbonate ion formation step.

[0055] In the carbon dioxide fixation method, an unnecessary ion removal step can be carried out when the unnecessary ions reach a predetermined concentration. The predetermined concentration is not particularly limited and can be appropriately selected depending on the purpose, but examples of the predetermined concentration include 10 mmol / L or more, 20 mmol / L or more, and 30 mmol / L or more in terms of efficiently fixing carbon dioxide.

[0056] <Other Steps and Other Means> The other steps are not particularly limited and can be appropriately selected depending on the purpose. The other steps are carried out by the other means.

[0057] (Carbon dioxide capture method and carbon dioxide capture apparatus) The carbon dioxide capture method of the present invention includes a metal complex formation step, a metal carbonate salt formation step, a bicarbonate ion or carbonate ion formation step, and an unnecessary ion removal step, and may further include other steps as necessary. The carbon dioxide capture apparatus of the present invention includes a metal complex formation means, a metal carbonate salt formation means, a bicarbonate ion or carbonate ion formation means, an unnecessary ion removal means, and a control means, and may further include other means as necessary.

[0058] The carbon dioxide capture method can be suitably carried out by the carbon dioxide capture apparatus, the metal complex formation step can be suitably carried out by the metal complex formation means, the metal carbonate formation step can be suitably carried out by the metal carbonate formation means, the bicarbonate ion or carbonate ion formation step can be suitably carried out by the bicarbonate ion or carbonate ion formation means, the unnecessary ion removal step can be suitably carried out by the unnecessary ion removal means, and the other steps can be suitably carried out by the other means. According to the carbon dioxide capture method and carbon dioxide capture apparatus of the present invention, carbon dioxide can be efficiently captured even when the raw material contains, in addition to a metal element that can combine with bicarbonate ions or carbonate ions to form a metal carbonate, unnecessary ions that will be used in the formation of the metal carbonate or the formation of a metal complex between the metal element and the chelating agent.

[0059] The metal complex formation step, the metal carbonate formation step, the bicarbonate ion or carbonate ion formation step, the unnecessary ion removal step, and the other steps are as described above in (Carbon dioxide fixation method and carbon dioxide fixation device). The term "carbon dioxide fixation" in (Carbon dioxide fixation method and carbon dioxide fixation device) is replaced with "carbon dioxide recovery" as necessary. The metal complex formation means, the metal carbonate formation means, the bicarbonate ion or carbonate ion formation means, the unnecessary ion removal means, the control means, and the other means are as described above in (Carbon dioxide fixation method and carbon dioxide fixation device). The term "carbon dioxide fixation" in (Carbon dioxide fixation method and carbon dioxide fixation device) is replaced with "carbon dioxide recovery" as necessary.

[0060] (Environmentally Conscious Industrial Facility) The environmentally conscious industrial facility is a facility equipped with a carbon dioxide fixation device. The carbon dioxide fixation device is as described above in (Carbon Dioxide Fixation Method and Carbon Dioxide Fixation Device).

[0061] <First embodiment> Here, an example of an embodiment of the carbon dioxide fixation method of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing an example of a process flow in the first embodiment of the carbon dioxide fixation method of the present invention.

[0062] First, an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material is prepared. The raw material includes a metal element capable of combining with the bicarbonate ions or carbonate ions to form a metal carbonate salt and reacting with the chelating agent to form a complex, and unnecessary ions that are required for forming the metal carbonate salt or the metal complex between the metal element and the chelating agent. In the metal complex formation step, a metal complex between the metal element and the chelating agent is formed in the alkaline aqueous solution. A metal complex between the unnecessary ions and the chelating agent is also formed.

[0063] Next, in the metal carbonate formation step, the alkaline aqueous solution is heated to react the bicarbonate ions or carbonate ions with the metal complex (metal complex of the metal element and the chelating agent) to form a metal carbonate.

[0064] Next, in the bicarbonate ion or carbonate ion forming step, carbon dioxide is injected into the alkaline aqueous solution in which the metal carbonate has been formed, to form bicarbonate ions or carbonate ions.

[0065] Next, the unnecessary ions are removed in the unnecessary ion removal step. Subsequently, new raw materials are supplied, and the metal complex formation step, the metal carbonate formation step, and the bicarbonate ion or carbonate ion formation step in a second cycle are performed. Note that in the metal complex formation step in the second cycle, the chelating agent used in the metal complex formation step in the first cycle and the bicarbonate ion or carbonate ion formed in the bicarbonate ion or carbonate ion formation step in the first cycle are reused.

[0066] In the first embodiment, the unnecessary ions are removed in the unnecessary ion removal step. Therefore, in the subsequent metal complex formation step, a larger number of metal complexes between the metal element and the chelating agent are formed in the alkaline aqueous solution, thereby enabling efficient fixation of carbon dioxide.

[0067] Second Embodiment FIG. 2 is a diagram showing an example of a process flow in a second embodiment of the carbon dioxide fixation method of the present invention.

[0068] First, an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material is prepared. The raw material includes a metal element capable of combining with the bicarbonate ions or carbonate ions to form a metal carbonate salt and reacting with the chelating agent to form a complex, and unnecessary ions that are required for forming the metal carbonate salt or the metal complex between the metal element and the chelating agent. In the metal complex formation step, a metal complex between the metal element and the chelating agent is formed in the alkaline aqueous solution. A metal complex between the unnecessary ions and the chelating agent is also formed.

[0069] Next, in the unnecessary ion removal step, the unnecessary ions are removed.

[0070] Next, in the metal carbonate formation step, the alkaline aqueous solution is heated to react the bicarbonate ions or carbonate ions with the metal complex (metal complex of the metal element and the chelating agent) to form a metal carbonate.

[0071] Next, in the bicarbonate ion or carbonate ion forming step, carbon dioxide is injected into the alkaline aqueous solution in which the metal carbonate salt has been formed, thereby forming bicarbonate ions or carbonate ions. Subsequently, new raw materials are supplied, and the metal complex forming step, the metal carbonate salt forming step, and the bicarbonate ion or carbonate ion forming step of a second cycle are performed. Note that in the metal complex forming step of the second cycle, the chelating agent used in the metal complex forming step of the first cycle and the bicarbonate ion or carbonate ion formed in the bicarbonate ion or carbonate ion forming step of the first cycle are reused.

[0072] In the second embodiment, the unnecessary ions are removed in the unnecessary ion removal step. Therefore, in the subsequent metal complex formation step, a larger number of metal complexes between the metal element and the chelating agent are formed in the alkaline aqueous solution, thereby enabling efficient fixation of carbon dioxide.

[0073] Third Embodiment FIG. 3 is a diagram showing an example of a process flow in a third embodiment of the carbon dioxide fixation method of the present invention.

[0074] First, an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material is prepared. The raw material includes a metal element capable of combining with the bicarbonate ions or carbonate ions to form a metal carbonate salt and reacting with the chelating agent to form a complex, and unnecessary ions that are required for forming the metal carbonate salt or the metal complex between the metal element and the chelating agent. In the metal complex formation step, a metal complex between the metal element and the chelating agent is formed in the alkaline aqueous solution. A metal complex between the unnecessary ions and the chelating agent is also formed.

[0075] Next, in the metal carbonate formation step, the alkaline aqueous solution is heated to react the bicarbonate ions or carbonate ions with the metal complex (metal complex of the metal element and the chelating agent) to form a metal carbonate.

[0076] Next, in the unnecessary ion removal step, the unnecessary ions are removed.

[0077] Next, in the bicarbonate ion or carbonate ion forming step, carbon dioxide is injected into the alkaline aqueous solution in which the metal carbonate salt has been formed, thereby forming bicarbonate ions or carbonate ions. Subsequently, new raw materials are supplied, and the metal complex forming step, the metal carbonate salt forming step, and the bicarbonate ion or carbonate ion forming step of a second cycle are performed. Note that in the metal complex forming step of the second cycle, the chelating agent used in the metal complex forming step of the first cycle and the bicarbonate ion or carbonate ion formed in the bicarbonate ion or carbonate ion forming step of the first cycle are reused.

[0078] In the third embodiment, the unnecessary ions are removed in the unnecessary ion removal step. Therefore, in the subsequent metal complex formation step, a larger number of metal complexes between the metal element and the chelating agent are formed in the alkaline aqueous solution, thereby enabling efficient fixation of carbon dioxide.

[0079] Examples of the present invention will be described below, but the present invention is not limited to these examples in any way.

[0080] (Experimental Example 1: Investigation of accumulation of elements other than calcium) Using bottom ash (main ash: ash that falls to the bottom of an incinerator) obtained by incinerating automobile shredder dust as a raw material and tetrasodium L-glutamate diacetate as a chelating agent, carbon dioxide fixation was carried out as follows. The component composition of the bottom ash used was analyzed by X-ray fluorescence analysis. The results are shown in Table 1.

[0081]

[0082] As mentioned above, incineration ash and the like are generally known to contain elements such as calcium, silicon, aluminum, iron, chlorine, sodium, magnesium, potassium, titanium, phosphorus, silver, arsenic, gold, boron, bismuth, cadmium, cobalt, chromium, cesium, zinc, lead, and copper (see, for example, the Tokyo Metropolitan Research Institute for Environmental Protection's 2019 public research presentation (Recycling of Municipal Waste Incineration Ash: Significance and Challenges, National Institute for Environmental Studies, Center for Resource Circulation and Waste Management Research, National Research and Development Agency, Sakakura Hiroshi, December 20, 2019), and the Proceedings of the Japan Society of Civil Engineers (Estimation of the Chemical Forms of Zinc, Lead, Copper, and Cadmium in Fly Ash by Sequential Extraction Method, Takaoka Masateru, Kuramoto Yasuhiro, Takeda Nobuo, and Fujiwara Takeshi, No. 685 / Vll-20:79-90, August 2001)). The results in Table 1 also show that the bottom ash obtained by incinerating automobile shredder dust also contains elements such as calcium, silicon, aluminum, sulfur, and copper.

[0083] (Experimental Example 1-1: Formation of Metal Complex) Tetrasodium L-glutamate diacetate (GLDA-4Na: N,N-Dicarboxymethyl glutamic acid, tetrasodium salt, manufactured by Tokyo Chemical Industry Co., Ltd.) (chelating agent) was added to water to prepare 0.15 L of an aqueous solution of tetrasodium L-glutamate diacetate with a concentration of 1% by weight. Sodium bicarbonate (NaHCO 3 ) was added to the solution to make the concentration 0.8 mol / L. ３), and then nitric acid was added to adjust the pH to 8. Finally, bottom ash (ash that fell to the bottom of the incinerator) was added (20 g / L) to adjust the alkaline aqueous solution. The alkaline aqueous solution was reacted at room temperature for 30 minutes to form a metal complex of calcium and the chelating agent.

[0084] (Experimental Example 1-2: Formation of Metal Carbonate) The solid was removed from the alkaline aqueous solution, and the alkaline aqueous solution from which the solid had been removed was heated at 95°C for 20 minutes to react the hydrogen carbonate ions with the metal complex to form a metal carbonate (CaCO ３ ) was formed.

[0085] (Experimental Example 1-3: Formation of bicarbonate ions or carbonate ions) ３ The solid was removed from the alkaline aqueous solution in which HCl had been formed, and carbon dioxide was injected into the alkaline aqueous solution from which the solid had been removed to form bicarbonate ions or carbonate ions.

[0086] The bottom ash (20 g / L) was then supplied to the liquid into which carbon dioxide had been newly injected to form bicarbonate ions or carbonate ions, and the second cycle of the metal complex formation process was carried out. Subsequently, the second cycle of the metal carbonate ore formation process was carried out in the same manner as in Experimental Example 1-2, and the second cycle of the bicarbonate ion formation or carbonate ion formation process was carried out in the same manner as in Experimental Example 1-3. This cycle was repeated up to the fifth cycle, and the concentrations (accumulation amounts) of elements other than calcium (Ca) in the liquid were measured. As a result, significant accumulation of copper (Cu), magnesium (Mg), and zinc (Zn) was found. The concentrations (accumulation amounts) of copper (Cu), magnesium (Mg), and zinc (Zn) in each cycle were analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES; Agilent 5100). The results are shown in Figure 4. In FIG. 4, S1, S2, and S3 respectively indicate a "metal complex forming step," a "metal carbonate forming step," and a "bicarbonate ion or carbonate ion forming step," and C1 to C5 indicate the first to fifth cycles.

[0087] (Test Example 1) 100 mL of the solution containing 1 wt % GLDA (chelating agent) obtained in Experimental Example 1, which had been repeatedly used up to the fifth cycle for the carbonation of boiler ash, was placed in an I-Boy bottle (I-Boy wide-mouth bottle (capacity: 250 mL), manufactured by AS ONE Corporation). Iminodiacetic acid (IDA)-type chelating resin Murochelate B-1 (manufactured by Muromachi Chemical Co., Ltd.) was weighed out and dispersed in the solution at 400 g / L, 600 g / L, or 700 g / L. The reaction was carried out at room temperature for 10 minutes while stirring at 100 rpm using a vibrator. After the reaction, each solution was filtered through a 0.45 μm filter, and the solution and the chelating resin (iminodiacetic acid (IDA)-type chelating resin Murochelate B-1) were separately recovered. The element concentrations in the collected liquid samples were quantified using an ICP optical emission spectrometer (ICP-OES, Agilent 5110). The pH was measured using a pH meter before and after the test. The results are shown in Figure 5 and Table 2.

[0088]

[0089] The results of FIG. 5 and Table 2 show that unnecessary ions, such as copper (Cu) ions, magnesium (Mg) ions, and zinc (Zn) ions, which are not required for the formation of the metal carbonate salt or the formation of a metal complex between the metal element and the chelating agent, are efficiently removed, while calcium (Ca) ions and the like, which are necessary for the formation of the metal carbonate salt or the formation of a metal complex between the metal element and the chelating agent, are not removed.

[0090] Test Example 2 Tetrasodium L-glutamic acid diacetate (GLDA-4Na: N,N-Dicarboxymethyl glutamic acid, tetrasodium salt, manufactured by Tokyo Chemical Industry Co., Ltd.) (chelating agent) was added to water to prepare 0.15 L of an aqueous solution of tetrasodium L-glutamic acid diacetate with a concentration of 4% by weight. Sodium bicarbonate (NaHCO3) was added to the solution to make the concentration 0.8 mol / L, and nitric acid was further added to adjust the pH to 8. Finally, gypsum (CaSO4) was added to the solution. ４ ・2H ２O, provided by DOWA Holdings Co., Ltd.) was added (10 g / L) to prepare an alkaline aqueous solution. The alkaline aqueous solution was reacted at room temperature for 30 minutes to form a metal complex of calcium and the chelating agent.

[0091] The solids were removed from the alkaline aqueous solution, and 100 mL of the alkaline aqueous solution (gypsum extract) from which the solids had been removed was placed in an i-boy bottle (i-boy wide-mouth bottle (capacity 250 mL), manufactured by AS ONE Corporation). A strongly basic anion exchange resin (manufactured by Muromachi Chemical Co., Ltd.) was weighed out to a concentration of 500 g / L and dispersed in the extract. The reaction was carried out at room temperature for 10 minutes while stirring at 100 rpm using a vibrator. After the reaction was completed, each solution was filtered through a 0.45 μm filter, and the solution and the chelating resin (strongly basic anion exchange resin) were separately recovered. The anion concentration in the collected liquid samples was quantified using an ion chromatograph (IC, Metrohm 881 Compact IC Pro), and the GLDA concentration was quantified using ultra-high performance liquid chromatography (UPLC, Waters). The pH before and after the experiment was measured using a pH meter. The results are shown in Figure 6 (sulfate ions (SO ４ ２－ ) and FIG. 7 (changes in GLDA concentration).

[0092] From the results of Fig. 6 and Fig. 7, sulfate ions (SO ４ ２－ It has been found that unnecessary ions, such as ions of the metal carbonate or the metal complex between the metal element and the chelating agent, are efficiently removed, but the chelating agent is not removed.

Claims

1. A method for producing a metal complex comprising: forming a metal complex of a metal element and a chelating agent in an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material containing a metal element capable of combining with the bicarbonate ions or carbonate ions to form a metal carbonate salt and capable of reacting with the chelating agent to form a complex, and ions unnecessary for forming the metal carbonate salt or the metal complex of the metal element and the chelating agent; a metal carbonate salt forming step of heating the alkaline aqueous solution to react the bicarbonate ions or carbonate ions with the metal complex to form a metal carbonate; and a bicarbonate ion or carbonate ion forming step of injecting carbon dioxide into the alkaline aqueous solution in which the metal carbonate salt has been formed to form bicarbonate ions or carbonate ions, thereby obtaining a liquid containing the bicarbonate ions or carbonate ions and the chelating agent, a method for fixation of carbon dioxide, comprising: supplying the raw material to a liquid containing the bicarbonate ions or carbonate ions obtained in the bicarbonate ion or carbonate ion formation step and a chelating agent, thereby carrying out the metal complex formation step, the metal carbonate salt formation step, and the bicarbonate ion or carbonate ion formation step; and further comprising an unnecessary ion removal step of removing the unnecessary ions using an unnecessary ion removal substance (excluding ion-bonding binary compounds) that removes the unnecessary ions after the metal complex formation step and before the metal carbonate salt formation step, after the metal carbonate salt formation step and before the bicarbonate ion or carbonate ion formation step, or after the bicarbonate ion or carbonate ion formation step and before the metal complex formation step.

2. The method for fixing carbon dioxide according to claim 1, wherein the unnecessary ion removing material is an ion exchange resin.

3. The carbon dioxide fixation method according to claim 2, wherein the unwanted ions are copper (Cu) ions, magnesium (Mg) ions, zinc (Zn) ions, or sulfate ions.

4. The carbon dioxide fixation method according to claim 1, wherein the metal element is calcium (Ca).

5. The method for fixing carbon dioxide according to claim 1, wherein the heating temperature in the metal carbonate forming step is 80°C or higher and lower than 100°C.

6. The method for fixing carbon dioxide according to claim 1, wherein the chelating agent is biodegradable.

7. The method for fixing carbon dioxide according to claim 1, wherein the chelating agent is tetrasodium L-glutamate diacetate.

8. The carbon dioxide fixation method according to claim 1, wherein the raw material is bottom ash or gypsum.

9. The method for fixing carbon dioxide according to claim 1, wherein the alkaline aqueous solution is prepared using sodium bicarbonate.

10. A method for producing a metal complex comprising: forming a metal complex of a metal element and a chelating agent in an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material containing a metal element capable of combining with the bicarbonate ions or carbonate ions to form a metal carbonate salt and capable of reacting with the chelating agent to form a complex, and ions unnecessary for forming the metal carbonate salt or the metal complex of the metal element and the chelating agent; a metal carbonate salt forming step of heating the alkaline aqueous solution to react the bicarbonate ions or carbonate ions with the metal complex to form a metal carbonate; and a bicarbonate ion or carbonate ion forming step of injecting carbon dioxide into the alkaline aqueous solution in which the metal carbonate salt has been formed to form bicarbonate ions or carbonate ions, thereby obtaining a liquid containing the bicarbonate ions or carbonate ions and a chelating agent, the metal complex formation step, the metal carbonate formation step, and the bicarbonate ion or carbonate ion formation step are carried out by supplying the raw material to a liquid containing the bicarbonate ions or carbonate ions obtained in the bicarbonate ion or carbonate ion formation step and a chelating agent, and further comprising an unnecessary ion removal step of removing the unnecessary ions using an unnecessary ion removal substance (excluding ion-bonding binary compounds) that removes the unnecessary ions after the metal complex formation step and before the metal carbonate formation step, after the metal carbonate formation step and before the bicarbonate ion or carbonate ion formation step, or after the bicarbonate ion or carbonate ion formation step and before the metal complex formation step.

11. A metal complex forming means for forming a metal complex of the metal element and the chelating agent in an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material containing a metal element capable of combining with the bicarbonate ions or carbonate ions to form a metal carbonate salt and capable of reacting with the chelating agent to form a complex, and ions unnecessary for forming the metal carbonate salt or the metal complex of the metal element and the chelating agent; a metal carbonate salt forming means for heating the alkaline aqueous solution to react the bicarbonate ions or carbonate ions with the metal complex to form the metal carbonate; and a bicarbonate ion or carbonate ion forming means for injecting carbon dioxide into the alkaline aqueous solution in which the metal carbonate salt has been formed to form bicarbonate ions or carbonate ions, thereby obtaining a liquid containing the bicarbonate ions or carbonate ions and the chelating agent. a control means for supplying the raw materials to a liquid containing the bicarbonate ions or carbonate ions obtained by the bicarbonate ion or carbonate ion forming means and a chelating agent, and for controlling the operation of the metal complex forming means, the metal carbonate forming means, and the bicarbonate ion or carbonate ion forming means; and an unwanted ion removing means for removing the unwanted ions using an unwanted ion removing substance (excluding ion-bonding binary compounds) after the operation of the metal complex forming means and before the operation of the metal carbonate forming means, after the operation of the metal carbonate forming means and before the operation of the bicarbonate ion or carbonate ion forming means, or after the operation of the bicarbonate ion or carbonate ion forming means and before the operation of the metal complex forming means.

12. An environmentally friendly industrial facility comprising the carbon dioxide fixation device according to claim 11.

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