Carbon dioxide fixation method and carbon dioxide fixation device

Abstract

To provide a method and so on that can fix carbon dioxide with good efficiency even if a raw material contains a second metal element that easily forms a complex with a chelating agent in addition to a first metal element which can form a carbonate.SOLUTION: This method includes: a process in which a metal complex of a first metal element and a chelating agent in an alkali aqueous solution containing hydrogen carbonate ion or the like, the chelating agent, the first metal element which can form a carbonate with the hydrogen carbonate ion or the like, reacts with the chelating agent and can form a complex, and a second metal element which forms a complex with the chelating agent more easily than the first metal element; a process in which the alkali aqueous solution is heated to react the hydrogen carbonate ion or the like and the metal complex with each other, and to form a metal carbonate; and a process in which carbon dioxide is injected to the alkali aqueous solution in which the metal carbonate is formed, thereby forming the hydrogen carbonate ion or the like. The method performs the metal complex formation process, the metal carbonate formation process, and the formation process of the hydrogen carbonate ion or the like by supplying the raw material, and further, includes a process in which the second metal element is removed by using an ionic bonding binary compound.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, the mass consumption of fossil fuels has led to an increase in carbon dioxide emissions into the atmosphere, which is the main cause of global warming. In addition, there are concerns that the increase in dissolved carbon dioxide in seawater will cause seawater acidification, 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 method for fixing carbon dioxide, which includes 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, and reacting the carbonate ions generated from the compound with the metal ions to form a carbonate salt; 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-102786 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, bottom ash, incineration fly ash, slag, etc. obtained by incinerating waste (automobile shredder dust, waste plastics, discarded office equipment, electronic devices, etc.) are known to 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, Sakakura Hiroshi, Center for Resource Recycling 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 the 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 / Vll-20:79-90, August 2001)).

[0006] In the prior art of Patent Document 1, it was found that when the raw material contains, in addition to a metal element (first metal element) that can combine with carbonate ions to form a metal carbonate salt, a second metal element that is more likely to form a complex with a chelating agent than the first metal element, the second metal element forms a complex with the chelating agent, reducing the formation of a complex between the first metal element and the chelating agent and resulting in insufficient fixation of carbon dioxide.

[0007] The present invention aims to solve the various problems encountered in the past and achieve the following objectives: Namely, 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 a raw material contains, in addition to a metal element (first metal element) that can combine with bicarbonate ions or carbonate ions to form a metal carbonate salt, a second metal element that more easily forms a complex with a chelating agent than the first metal element. [Means for solving the problem]

[0008] The means for solving the above problems are as follows: <1> bicarbonate ions or carbonate ions, A chelating agent; a raw material containing a first metal element capable of forming a metal carbonate salt by combining with the bicarbonate ion or carbonate ion and capable of reacting with the chelating agent to form a complex, and a second metal element that more easily forms a complex with the chelating agent than the first metal element; a metal complex formation step of forming a metal complex between the first metal element and the chelating agent in an alkaline aqueous solution containing a metal carbonate 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; 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 bicarbonate ions or carbonate ions and a chelating agent, supplying the raw material to a liquid containing the bicarbonate ions or carbonate ions obtained in the bicarbonate ion or carbonate ion forming step and a chelating agent, thereby carrying out the metal complex forming step, the metal carbonate salt forming step, and the bicarbonate ion or carbonate ion forming step; Furthermore, 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, a third metal element that is less likely to form a complex with the chelating agent than the first metal element; This carbon dioxide fixation method is characterized by including a second metal element removal step of using an ionic binary compound consisting of the third metal element and another element that can combine with the third metal element but is different from the third metal element to remove the second metal element by reacting it with the other element that can combine with the third metal element but is different from the third metal element. <2> The second metal element is copper (Cu), the third metal element is iron (Fe), and the other element capable of combining with the third metal element and different from the third metal element is sulfur (S). <1> This is a method for fixing carbon dioxide as described above. <3> The first metal element is calcium (Ca). <1> This is a method for fixing carbon dioxide as described above. <4> The heating temperature in the metal carbonate forming step is 80°C or higher and lower than 100°C. <1> This is a method for fixing carbon dioxide as described above. <5> The chelating agent is biodegradable. <1> This is a method for fixing carbon dioxide as described above. <6> the chelating agent is L-glutamic acid diacetate tetrasodium <1> This is a method for fixing carbon dioxide as described above. <7> The raw material is bottom ash. <1> This is a method for fixing carbon dioxide as described above. <8> The alkaline aqueous solution is prepared using sodium bicarbonate. <1> This is a method for fixing carbon dioxide as described above. <9> bicarbonate ions or carbonate ions, A chelating agent; a raw material containing a first metal element capable of forming a metal carbonate salt by combining with the bicarbonate ion or carbonate ion and capable of reacting with the chelating agent to form a complex, and a second metal element that more easily forms a complex with the chelating agent than the first metal element; a metal complex forming means for forming a metal complex between the first metal element and the chelating agent in an alkaline aqueous solution containing the metal complex; a metal carbonate forming means for heating the alkaline aqueous solution to react the bicarbonate ions or carbonate ions with the metal complex to form a metal carbonate; 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 bicarbonate ions or carbonate ions and a 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; 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, a third metal element that is less likely to form a complex with the chelating agent than the first metal element; a second metal element removal means for removing the second metal element by reacting the second metal element with another element capable of combining with the third metal element and different from the third metal element using an ionic binary compound comprising the third metal element and another element capable of combining with the third metal element; The carbon dioxide fixation device is characterized by having: [Effects of the Invention]

[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, in addition to a metal element (first metal element) that can combine with bicarbonate ions or carbonate ions to form a metal carbonate salt, a second metal element that more easily forms a complex with a chelating agent than the first metal element. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of the process flow of the carbon dioxide fixation method according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of the process flow of the carbon dioxide fixation method according to the second embodiment. [Figure 3] FIG. 3 is a diagram showing an example of a process flow of the carbon dioxide fixation method according to the third embodiment. [Figure 4] FIG. 4 is a diagram showing the concentrations (accumulation amounts) of copper (Cu), magnesium (Mg), and zinc (Zn) in each cycle. [Figure 5] FIG. 5 is a graph showing the change in the amount of metal complex formed between calcium and a chelating agent (calcium extraction amount) when copper (Cu) is added. [Figure 6] FIG. 6 is a graph showing the change in the amount of metal complex formed between calcium and a chelating agent (calcium extraction amount) when zinc (Zn) is added. [Figure 7] FIG. 7 is a graph showing the change in the amount of metal complex formed between calcium and a chelating agent (calcium extraction amount) when no copper (Cu) was added, when copper (Cu) was added, and when copper (Cu) was added and then removed using iron sulfide. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Method and device for fixing carbon dioxide) The carbon dioxide fixation method of the present invention includes a metal complex formation step, a metal carbonate formation step, a bicarbonate ion or carbonate ion formation step, and a second metal element removal step, and may further include other steps as necessary. The carbon dioxide fixation device of the present invention includes a metal complex forming means, a metal carbonate forming means, a bicarbonate ion or carbonate ion forming means, a second metal element removing means, and a control means, and may further include 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 second metal element removal step can be suitably carried out by the second metal element 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 fixed efficiently even when the raw material contains, in addition to a metal element (first metal element) that can combine with bicarbonate ions or carbonate ions to form a metal carbonate salt, a second metal element that more easily forms a complex with a chelating agent than the first metal element.

[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. A second metal element removal step is performed between any of these steps. In the carbon dioxide fixation device, after the first cycle described above is operated by the control means, raw materials are again supplied and a second cycle is operated. That is, the control means supplies the raw materials and controls the operation of the metal complex formation means, the metal carbonate formation means, and the bicarbonate ion or carbonate ion formation means.

[0014] The second metal element removal step only needs to be carried out at least once, and is not an essential step in all cycles. For example, the second metal element 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 second metal element removal step may be performed once per cycle or once per multiple cycles.

[0015] The chelating agent initially added in the metal complex formation step is not consumed in subsequent steps, and can therefore be reused in the metal complex formation steps of the second and subsequent cycles. Thus, the metal complex formation steps of the second and subsequent cycles can be carried out under substantially the same conditions as the metal complex formation step of the first cycle, and the metal carbonate formation step, bicarbonate ion or carbonate ion formation step, and second metal element removal step of the second and subsequent cycles can also be carried out in the same manner as the first cycle. This allows carbon dioxide to be immobilized in the metal carbonate formation step of the second and subsequent cycles. In the metal complex formation step in the second cycle or later, the bicarbonate ion or carbonate ion formed in the previous bicarbonate ion or carbonate ion formation step can be used. Therefore, by supplying bicarbonate ions or carbonate ions, or carbon dioxide, and the raw material, the metal complex formation step, the metal carbonate salt formation step, the bicarbonate ion or carbonate ion formation step, and the second metal element removal step can be repeatedly carried out, thereby fixing carbon dioxide.

[0016] 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 below.

[0017] <Metal complex formation step and metal complex formation 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] -Bicarbonate ion or carbonate ion- The bicarbonate ions or carbonate ions are not particularly limited and can be appropriately selected depending on the purpose, and may be bicarbonate ions or carbonate ions derived from sodium bicarbonate, or bicarbonate ions or carbonate ions derived from carbon dioxide formed in the bicarbonate ion or carbonate ion forming step described below. Note that the term "bicarbonate ions or carbonate ions" used herein includes the case where both bicarbonate ions and carbonate ions are present.

[0019] -Chelating agent- The chelating agent is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof 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 materials- The raw material contains at least a first metal element and a second metal element, and may contain other metal elements. The raw material can be appropriately selected depending on the purpose, and examples thereof include silicates, steel slag, waste, and ash. Among these, ash is preferred in terms of efficiently fixing carbon dioxide.

[0022] The ash that can be used is the ash obtained after input materials are burned in a boiler, an incinerator, or the like (incinerated ash). The input material is not particularly limited and can be appropriately selected depending on the purpose. Examples include burnable waste, non-burnable waste, and industrial waste such as plastics. The ash is not particularly limited and can be appropriately selected depending on the purpose. Examples include bottom ash (incineration bottom ash), which is ash that falls to the bottom of an incinerator, and fly ash (incineration 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 efficiently fixing carbon dioxide.

[0023] --The first metallic element-- The first 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 first metal element can be appropriately selected depending on the purpose. However, 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. The first metal element may be in the form of not only a metal element but also an ion.

[0024] The metal carbonate is not particularly limited and can be appropriately selected depending on the purpose, but calcium carbonate (CaCO3), magnesium carbonate (MgCO3), and the like are preferred in terms of efficiently fixing carbon dioxide.

[0025] The concentration of the first 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 0.01 mol / L or more and 1 mol / L or less, more preferably 0.01 mol / L or more and 0.5 mol / L or less, even more preferably 0.01 mol / L or more and 0.1 mol / L or less, and particularly preferably 0.02 mol / L or more and 0.08 mol / L or less.

[0026] --Second metallic element-- The second metal element is an element that is more likely to form a complex with the chelating agent (has better bonding properties with the chelating agent) than the first metal element. That is, the second metal element is an impurity that inhibits the extraction of the first metal element, and although it is desirable that the second metal element is not contained in the raw material, it can be said to be an unavoidable impurity that is contained when incineration bottom ash, incineration fly ash, or the like is used as the raw material. Examples of the second metal element include copper (Cu), magnesium (Mg), and zinc (Zn). The second metal element may be in the form of not only a metal element but also an ion.

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

[0028] -Alkaline aqueous solution- The alkaline aqueous solution in the metal complex formation step is often alkaline 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. 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 5 mol / L or less, more preferably 0.5 mol / L or more and 1.5 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 0.9 mol / L or less.

[0031] -Metal complexes- The metal complex is a product of the first metal element and a chelating agent. For example, when the first 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 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.

[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 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. The metal carbonate formation process allows carbon dioxide to be fixed.

[0035] -Metal carbonate- The metal carbonate is a carbonate of the first metal element, and when the first metal element is calcium (Ca), for example, calcium carbonate is included.

[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, but the lower limit is preferably, in this order, 20°C or higher, 40°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, and 90°C or higher, from the viewpoint of efficiently fixing carbon dioxide, and the upper limit is preferably, in this order, 170°C or lower, 160°C or lower, 120°C or lower, 100°C or lower, and less than 100°C, from the viewpoint of preventing deterioration of the equipment used and energy efficiency, etc. Suitable numerical ranges for the temperature include those that are equal to or higher than any of the lower limits and equal to or lower than any of the upper limits. Among these, 20°C or higher and 170°C or lower is preferred, 40°C or higher and 160°C or lower is more preferred, 60°C or higher and 120°C or lower is even more preferred, 70°C or higher and lower than 100°C is even more preferred, 80°C or higher and lower than 100°C is particularly preferred, and 90°C or higher and lower than 100°C is 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. From the viewpoint of efficiently fixing carbon dioxide, the pH is preferably from pH 6 to pH 13, more preferably from pH 8 to pH 10, and even more preferably from pH 8.5 to pH 9.5. The alkaline aqueous solution can be adjusted to a preferred pH 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 to be injected is not particularly limited and can be appropriately selected depending on the purpose. However, in terms 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 for injecting the carbon dioxide is not particularly limited and can be appropriately selected depending on the purpose. However, in terms of efficiently fixing carbon dioxide, a method in which the carbon dioxide is bubbled into the alkaline aqueous solution is preferred.

[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] <Second Metal Element Removal Step and Second Metal Element Removal Means> The second metal element removal step is a step of removing the second metal element by reacting it with another element that can combine with the third metal element but is different from the third metal element using an ionic binary compound consisting of a third metal element that is less likely to form a complex with the chelating agent than the first metal element and another element that can combine with the third metal element but is different from the third metal element, and is carried out by the second metal element removal means.

[0045] The second metal element 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 third metal element that is less likely to form a complex with the chelating agent than the first metal element is not particularly limited as long as it is a carrier for introducing an element to be bound in order to remove the second metal element, but iron (Fe), which can be easily removed from the system, is preferred. The third metal element may be in the form of not only a metal element but also an ion. The other element that can be compounded with the third metal element and is different from the third metal element is not particularly limited as long as it bonds with the second metal element. However, for example, when the third metal element is Fe, sulfur (S) can be used in order to efficiently fix the second metal element. The form of the other element that can be combined with the third metal element but is different from the third metal element includes not only elements but also ions. The ionic binary compound consisting of a third metal element that is less likely to form a complex with the chelating agent than the first metal element, and another element that can combine with the third metal element but is different from the third metal element, is not particularly limited and can be appropriately selected depending on the purpose, but iron sulfide (FeS) is preferred in terms of efficiently fixing carbon dioxide.

[0047] For example, when the second metal element is copper (Cu), the third metal element is iron (Fe), and the other element that can be combined with the third metal element but is different from the third metal element is sulfur (S), in the second metal element removal step, a complex of copper (Cu) and a chelating agent is reacted with iron sulfide to obtain a complex of iron (Fe) and a chelating agent and copper(II) sulfide (CuS). Thereafter, when the first metal element is added to the complex of iron (Fe) and a chelating agent, a complex of the first metal element and a chelating agent is obtained due to the bonding property of the first metal element.

[0048] The pH of the alkaline aqueous solution in the second metal element removal step is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, the pH is preferably 7.5 or higher and 13 or lower, more preferably 8 or higher and 11 or lower, and even more preferably 8 or higher and 9 or lower. The alkaline aqueous solution can be adjusted to a preferred pH range using nitric acid.

[0049] The temperature at which the second metal element 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.

[0050] The time for the second metal element 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 1 hour to 72 hours, more preferably from 6 hours to 48 hours, even more preferably from 12 hours to 40 hours, and particularly preferably from 20 hours to 30 hours.

[0051] The order in which the second metal element 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 second metal element 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.

[0052] 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 second metal element 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.

[0053] In the carbon dioxide fixation method, when the second metal element reaches a predetermined concentration, a second metal element removal step can be carried out. The predetermined concentration is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficiently fixing carbon dioxide, for example, the predetermined concentration may be 10 mmol / L or more, 20 mmol / L or more, or 30 mmol / L or more.

[0054] <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.

[0055] 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 the process flow in the first embodiment of the carbon dioxide fixation method of the present invention.

[0056] First, an alkaline aqueous solution containing bicarbonate ions or carbonate ions, a chelating agent, and a raw material is prepared, the raw material including a first 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 a second metal element that is more likely to form a complex with the chelating agent than the first metal element. In the metal complex forming step, a metal complex between the first metal element and the chelating agent is formed in the alkaline aqueous solution, and a metal complex between the second metal element and the chelating agent is also formed.

[0057] Next, in the metal carbonate forming step, the alkaline aqueous solution is heated to react the bicarbonate ions or carbonate ions with the metal complex (the metal complex of the first metal element and the chelating agent) to form a metal carbonate.

[0058] 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.

[0059] Next, in the second metal element removal step, the second metal element is removed. Subsequently, new raw materials are supplied, and the metal complex forming step, the metal carbonate forming step, and the hydrogen carbonate ion or carbonate ion forming step are carried out in a second cycle. 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 ions or carbonate ions formed in the bicarbonate ion or carbonate ion-forming step of the first cycle are reused.

[0060] In the first embodiment, since the second metal element is removed in the second metal element removal step, a larger number of metal complexes of the first metal element and the chelating agent are formed in the alkaline aqueous solution in the subsequent metal complex formation step, and carbon dioxide can be fixed efficiently.

[0061] <Second embodiment> FIG. 2 is a diagram showing an example of the process flow in the second 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 including a first 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 a second metal element that is more likely to form a complex with the chelating agent than the first metal element. In the metal complex forming step, a metal complex between the first metal element and the chelating agent is formed in the alkaline aqueous solution, and a metal complex between the second metal element and the chelating agent is also formed.

[0063] Next, in the second metal element removal step, the second metal element is removed.

[0064] Next, in the metal carbonate forming step, the alkaline aqueous solution is heated to react the bicarbonate ions or carbonate ions with the metal complex (the metal complex of the first metal element and the chelating agent) to form a metal carbonate.

[0065] 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. Subsequently, new raw materials are supplied, and the metal complex forming step, the metal carbonate forming step, and the hydrogen carbonate ion or carbonate ion forming step are carried out in a second cycle. 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 ions or carbonate ions formed in the bicarbonate ion or carbonate ion-forming step of the first cycle are reused.

[0066] In the second embodiment, since the second metal element is removed in the second metal element removal step, a larger number of metal complexes of the first metal element and the chelating agent are formed in the alkaline aqueous solution in the subsequent metal complex formation step, and carbon dioxide can be fixed efficiently.

[0067] <Third embodiment> FIG. 3 is a diagram showing an example of the process flow in the third 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 including a first 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 a second metal element that is more likely to form a complex with the chelating agent than the first metal element. In the metal complex forming step, a metal complex between the first metal element and the chelating agent is formed in the alkaline aqueous solution, and a metal complex between the second metal element and the chelating agent is also formed.

[0069] Next, in the metal carbonate forming step, the alkaline aqueous solution is heated to react the bicarbonate ions or carbonate ions with the metal complex (the metal complex of the first metal element and the chelating agent) to form a metal carbonate.

[0070] Next, in the second metal element removal step, the second metal element is removed.

[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 has been formed, to form bicarbonate ions or carbonate ions. Subsequently, new raw materials are supplied, and the metal complex forming step, the metal carbonate forming step, and the hydrogen carbonate ion or carbonate ion forming step are carried out in a second cycle. 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 ions or carbonate ions formed in the bicarbonate ion or carbonate ion-forming step of the first cycle are reused.

[0072] In the third embodiment, since the second metal element is removed in the second metal element removal step, a larger number of metal complexes of the first metal element and the chelating agent are formed in the alkaline aqueous solution in the subsequent metal complex formation step, and carbon dioxide can be fixed efficiently. [Example]

[0073] Examples of the present invention will be described below, but the present invention is not limited to these examples in any way.

[0074] (Experimental Example 1: Examination of accumulation of elements other than calcium) Carbon dioxide fixation was carried out using bottom ash (main ash: ash that falls to the bottom of the incinerator) obtained by incinerating automobile shredder dust as the raw material and tetrasodium L-glutamate diacetate as the chelating agent as described below. The component composition of the bottom ash used was analyzed by fluorescent X-ray analysis, and the results are shown in Table 1.

[0075] [Table 1]

[0076] As mentioned above, incineration ash is 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, Sakakura Hiroshi, National Institute for Environmental Studies, Center for Resource Circulation and Waste Management Research, 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, 2001.8)). 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.

[0077] (Experimental Example 1-1: Metal complex formation) 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 a 1 wt% aqueous solution of tetrasodium L-glutamate diacetate. Sodium bicarbonate (NaHCO3) was then added to the solution to make the concentration 0.8 mol / L, and nitric acid was added to adjust the pH to 8. Finally, bottom ash (ash that falls to the bottom of the incinerator) was added (20 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 between calcium and the chelating agent.

[0078] (Experimental Example 1-2: Metal Carbonate Formation) 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 metal carbonate (CaCO3).

[0079] (Experimental Example 1-3: Bicarbonate or Carbonate Ion Formation) The solid was removed from the alkaline aqueous solution in which the metal carbonate (CaCO3) 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.

[0080] Carbon dioxide was newly injected into the liquid into which bicarbonate ions or carbonate ions had been formed, and the bottom ash (20 g / L) was supplied to carry out the second cycle of the metal complex formation step. Subsequently, the second cycle of the metal carbonate ore formation step 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 step was carried out in the same manner as in Experimental Example 1-3. The above cycle was repeated up to the fifth cycle, and the concentrations (accumulation amounts) of elements other than calcium (Ca) in the solution were measured. As a result, it was found that copper (Cu), magnesium (Mg), and zinc (Zn) accumulated significantly. 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 Figure 4, S1, S2, and S3 represent the "metal complex formation step," "metal carbonate formation step," and "bicarbonate ion or carbonate ion formation step," respectively, and C1 to C5 represent the first to fifth cycles.

[0081] (Experimental Example 2: The effect of accumulation of elements other than calcium on the formation of metal complexes between calcium and chelating agents (calcium extraction))

[0082] 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 a 1 wt% aqueous solution of tetrasodium L-glutamate diacetate. Sodium bicarbonate (NaHCO3) was then added to the solution to make the concentration 0.8 mol / L, and nitric acid was added to adjust the pH to 8. Finally, bottom ash (ash that falls to the bottom of the incinerator) was added (20 g / L) to prepare an alkaline aqueous solution. To the alkaline aqueous solution, 0 mmol / L, 10 mmol / L, 20 mmol / L, or 30 mmol / L of Cu(NO3)2·3H2O or 0 mmol / L, 2 mmol / L, 5 mmol / L, 10 mmol / L, or 20 mmol / L of ZnCl2 was added, and the mixture was allowed to react at room temperature for 30 minutes to form a metal complex between calcium and the chelating agent.

[0083] When copper (Cu) was added (when copper (Cu) accumulated), the amount of metal complex formed between calcium and the chelating agent (calcium extraction amount) was analyzed by measuring the metal ion concentration of the extract using a Thermo Scientific ICP atomic emission spectrometer iCAP6300 Dou View. The results are shown in Figure 5. The results when 0 mmol / L and 30 mmol / L of Cu(NO3)2·3H2O were added are also shown in Figure 7. When zinc (Zn) was added (when zinc (Zn) accumulated), the change in the amount of metal complex formed between calcium and the chelating agent (calcium extraction amount) was analyzed in the same way as when copper (Cu) was added. The results are shown in Figure 6.

[0084] The results in Figures 5 and 6 show that zinc (Zn) does not affect the amount of metal complex formed between calcium and the chelating agent (calcium extraction amount), but copper (Cu) does affect the amount of metal complex formed between calcium and the chelating agent (calcium extraction amount). It was also confirmed that magnesium (Mg) does not affect the amount of metal complex formed between calcium and the chelating agent (calcium extraction amount). Furthermore, if the concentration of zinc (Zn) increases, it can be removed by precipitating as sulfide, and if the concentration of magnesium (Mg) increases, it can be removed by precipitating as carbonate.

[0085] (Reference example 1) 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 a 1 wt% aqueous solution of tetrasodium L-glutamate diacetate. Sodium bicarbonate (NaHCO3) was added to the solution to make the concentration 0.8 mol / L, nitric acid was added to adjust the pH to 8, and bottom ash (ash that falls to the bottom of the incinerator) was added (20 g / L) to prepare an alkaline aqueous solution. The alkaline aqueous solution was shaken at room temperature for 30 minutes, and then the calcium (Ca), copper (Cu), and iron (Fe) concentrations in the alkaline aqueous solution were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES; Agilent 5100). The calcium (Ca) concentration was confirmed to be 28 mmol / L.

[0086] (Test Example 1) (Test Example 1-1) 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 wt %, to which sodium bicarbonate (NaHCO3) was added to adjust the concentration to 0.8 mol / L, nitric acid was added to adjust the pH to 8, and copper nitrate trihydrate was added to adjust the copper (Cu) ion concentration to 30 mmol / L.

[0087] (Test Example 1-2: Removal of second metal element) 5 g of iron sulfide was added to the aqueous solution obtained in Test Example 1-1 and left to stand for one day. After that, a precipitate formed in the aqueous solution, which was removed by filtration.

[0088] (Test Example 1-3) Bottom ash (ash that fell to the bottom of the incinerator) was added (20 g / L) to the aqueous solution obtained in Test Example 1-2 and the solution was shaken at room temperature for 30 minutes. The calcium (Ca), copper (Cu), and iron (Fe) concentrations in the aqueous solution were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES; Agilent 5100). The calcium (Ca) concentration was 25 mmol / L, the copper (Cu) concentration was 3 mmol / L, and the iron (Fe) concentration was 28 mmol / L. The carbon dioxide in the solution was then fixed as calcium carbonate by heating to 95°C, and it was confirmed that the carbon dioxide could be fixed as calcium carbonate even after repeated cycles. The amount of metal complex formed between calcium and the chelating agent (calcium extraction amount) was analyzed by measuring the metal ion concentration of the extracted solution using a Thermo Scientific iCAP6300 Dou View ICP atomic emission spectrometer. The results are shown in Figure 7 (after FeS treatment).

[0089] (Comparative Test Example 1) In Test Example 1, except that (Test Example 1-2: Removal of the second metal element) was not performed, the calcium (Ca) concentration, copper (Cu) concentration, and iron (Fe) concentration were measured using inductively coupled plasma optical emission spectrometry (ICP-OES; Agilent 5100) in the same manner as in Test Example 1. The calcium (Ca) concentration was confirmed to be 22 mmol / L and the copper (Cu) concentration was confirmed to be 30 mmol / L.

[0090] The results of Reference Example 1, Test Example 1, Comparative Test Example 1, and FIG. 7 reveal that, by removing the second metal element, carbon dioxide can be fixed efficiently even when the raw material contains, in addition to a metal element (first metal element) that can combine with bicarbonate ions or carbonate ions to form a metal carbonate salt, a second metal element that more easily forms a complex with a chelating agent than the first metal element.

Claims

1. bicarbonate ions or carbonate ions, A chelating agent; a raw material containing a first metal element capable of forming a metal carbonate salt by combining with the bicarbonate ion or carbonate ion and capable of reacting with the chelating agent to form a complex, and a second metal element that more easily forms a complex with the chelating agent than the first metal element; a metal complex formation step of forming a metal complex between the first metal element and the chelating agent in an alkaline aqueous solution containing a metal carbonate 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; 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 bicarbonate ions or carbonate ions and a chelating agent, supplying the raw material to a liquid containing the bicarbonate ions or carbonate ions obtained in the bicarbonate ion or carbonate ion forming step and a chelating agent, thereby carrying out the metal complex forming step, the metal carbonate salt forming step, and the bicarbonate ion or carbonate ion forming step; Furthermore, 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, a third metal element that is less likely to form a complex with the chelating agent than the first metal element; A carbon dioxide fixation method comprising a second metal element removal step of using an ionic binary compound consisting of the third metal element and another element that can combine with the third metal element but is different from the third metal element to remove the second metal element by reacting it with the other element that can combine with the third metal element but is different from the third metal element.

2. 2. The carbon dioxide fixation method according to claim 1, wherein the second metal element is copper (Cu), the third metal element is iron (Fe), and the other element capable of combining with the third metal element but different from the third metal element is sulfur (S).

3. 2. The method for fixing carbon dioxide according to claim 1, wherein the first metal element is calcium (Ca).

4. 2. 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.

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

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

7. The method for fixing carbon dioxide according to claim 1 , wherein the raw material is bottom ash.

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

9. bicarbonate ions or carbonate ions, A chelating agent; a raw material containing a first metal element capable of forming a metal carbonate salt by combining with the bicarbonate ion or carbonate ion and capable of reacting with the chelating agent to form a complex, and a second metal element that more easily forms a complex with the chelating agent than the first metal element; a metal complex forming means for forming a metal complex between the first metal element and the chelating agent in an alkaline aqueous solution containing the metal complex; a metal carbonate forming means for heating the alkaline aqueous solution to react the bicarbonate ions or carbonate ions with the metal complex to form a metal carbonate; 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 bicarbonate ions or carbonate ions and a 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; 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, a third metal element that is less likely to form a complex with the chelating agent than the first metal element; a second metal element removal means for removing the second metal element by reacting the second metal element with another element capable of combining with the third metal element and different from the third metal element using an ionic binary compound comprising the third metal element and another element capable of combining with the third metal element; A carbon dioxide fixation device comprising:

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