CO2 immobilization ceramics and manufacturing method of CO2 immobilized material

Abstract

A CO2 fixation ceramic according to the present invention includes: a γ crystalline phase configured from γ-2CaO · SiO2 (γ-C2S); and 2CaO · Al2O3 · SiO2 (C2AS).

Description

Technical Field

[0001] The present invention relates to CO2-fixing ceramics and a method for producing CO2-fixed products.

Background Art

[0002] As an effort to reduce greenhouse gas emissions, concrete products (hereinafter referred to as CO2-absorbing concrete) that forcibly absorb or carbonize CO2 during production have been partially put into practical use. CO2-absorbing concrete, which is a type of CCUS technology (abbreviation for Carbon dioxide Capture, Utilization and Storage, carbon dioxide recovery and storage technology), is also mentioned in the "Carbon Recycling Technology Roadmap" announced by the Ministry of Economy, Trade and Industry in 2019, and technology development for its widespread use is underway.

[0003] Patent Document 1 discloses a method for forcibly absorbing or carbonizing CO2 during the production of concrete. Specifically, a method for immobilizing carbon dioxide is disclosed, which includes a contact step of bringing a carbon dioxide-containing gas into contact with a cementitious hardened body to immobilize the carbon dioxide contained in the carbon dioxide-containing gas in the cementitious hardened body. The cementitious hardened body of Patent Document 1 is obtained by filling a mold with a cement paste formed by mixing early-strength Portland cement and water and subjecting it to water curing (paragraph 0019 of Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention aims to provide a CO2 fixation ceramic that can fix CO2 by carbonation, and a method for producing a CO2 fixation product using the same. [Means for solving the problem]

[0006] The inventors discovered that by using ceramics containing γ-2CaO·SiO2 and 2CaO·Al2O3·SiO2, it is possible to realize CO2 fixation ceramics that can fix CO2 through carbonation, and have completed the present invention.

[0007] According to one aspect of the present invention, there are provided the following CO2 fixation ceramics and methods for producing a CO2 fixation product. 1. The γ crystalline phase consists of γ-2CaO·SiO2 (γ-C2S) and CO2 fixation ceramics including 2CaO·Al2O3·SiO2 (C2AS). 2. The CO2 fixation ceramic according to 1., CO2 fixation ceramics containing glass phase and / or CaO·2Al2O3 (CA2). 3. The CO2 fixation ceramic according to 1. or 2., A CO2 fixation ceramic, wherein the content of the γ-C2S is 30% by mass or more and 98% by mass or less, based on 100% by mass of the CO2 fixation ceramic. 4. The CO2 fixation ceramic according to any one of 1. to 3., A CO2 fixation ceramic, wherein the content of the C2AS is 0.5% by mass or more and 50% by mass or less relative to 100% by mass of the γ-C2S. 5. The CO2 fixation ceramic according to any one of 1. to 4., A CO2 fixation ceramic comprising a heterogeneous phase present in the γ crystalline phase, wherein the C2AS is contained in the heterogeneous phase. 6. The CO2 fixation ceramic according to 5., A CO2 fixation ceramic in which Al2O3 is not contained in the γ crystalline phase. 7. The CO2 fixation ceramic according to any one of 1. to 6., CO2 fixation ceramics containing a β crystalline phase composed of β-2CaO·SiO2 (β-C2S). 8. The CO2 fixation ceramic according to 7., A CO2 fixation ceramic, wherein Al2O3 is contained in the β crystalline phase. 9. The CO2 fixation ceramic according to 7. or 8., A CO2 fixation ceramic, wherein the content of the β-C2S is 1.0 mass% or more and 50 mass% or less relative to 100 mass% of the γ-C2S. 10. The CO2 fixation ceramic according to any one of 1. to 9., CO2 fixation ceramics containing disaccharides. 11. The CO2 fixation ceramic according to 10., A CO2 fixation ceramic, wherein the content of the disaccharide is 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the CO2 fixation ceramic. 12. The CO2 fixation ceramic according to 10. or 11., A CO2 fixation ceramic, wherein the disaccharide comprises trehalose. 13. The CO2 fixation ceramic according to any one of 1. to 12., CO2 fixation ceramics in powder form.

[0008] 14. A method for producing a CO2 immobilized material, comprising a step of carbonation treatment of the CO2 immobilization ceramic described in any one of 1. to 13. under conditions of less than 75°C and / or 50% RH or more. [Effects of the Invention]

[0009] According to the present invention, there are provided a CO2 fixation ceramic having excellent CO2 fixation ability, and a method for producing a CO2 fixated product using the same. [Brief explanation of the drawings]

[0010] [Figure 1] This is an SEM image of fixed ceramic A. [Figure 2] This is an SEM image of fixed ceramic B. DETAILED DESCRIPTION OF THE INVENTION

[0011] The CO2 fixation ceramic of this embodiment will be outlined below.

[0012] The CO2 fixation ceramic of this embodiment contains a γ crystalline phase composed of γ-2CaO·SiO2 (hereinafter sometimes abbreviated as γ-C2S) and 2CaO·Al2O3·SiO2 (hereinafter sometimes abbreviated as C2AS).

[0013] According to the findings of the present inventors, it has been confirmed that CO2 can be fixed in a relatively short period of time by using CO2 fixation ceramics containing γ-C2S and C2AS. Although the detailed mechanism is unclear, when powders that are highly reactive with CO2, such as γ-C2S, are subjected to carbonation curing, they become lumpy, preventing the penetration of CO2 and causing the reaction to stagnate.On the other hand, it is thought that the presence of an appropriate amount of C2AS, which is a stable phase, prevents the powder from forming overly dense lumps, allowing CO2 to penetrate deep into the powder and allowing the reaction to proceed.

[0014] According to this embodiment, it is possible to provide a CO2 fixation ceramic that can fix CO2 through carbonation. According to the CO2 fixation ceramic of this embodiment, CO2 fixation can be promoted by carbonation treatment under relatively low temperature and / or relatively high humidity conditions, such as below 75°C and / or 50% RH or higher.

[0015] The CO2 fixation ceramics of this embodiment can be used for a variety of purposes, such as a trapping material that adsorbs CO2 gas emitted from industrial facilities, power generation facilities, or transportation vehicles including automobiles, a chemical heat storage material that stores waste heat in factories or renewable energy whose power generation amount fluctuates depending on the weather, and a CO2 absorbent that absorbs CO2 in exhaled breath to enable safe anesthesia and accurate examinations using medical equipment.The CO2 fixation ceramics can also be used as a cement additive (admixture).

[0016] [Method of manufacturing CO2 immobilization] An example of the method for producing a CO2 immobilized material of this embodiment includes a step of subjecting a CO2 immobilized ceramic to a carbonation treatment at 75°C or lower and / or 50% RH or higher. The carbonation treatment method is not particularly limited, but examples include a method in which the material is treated in a CO2-containing gas atmosphere by appropriately heating and / or humidifying (adding water) to achieve specified temperature and humidity conditions.

[0017] The temperature of the carbonation treatment is, for example, preferably 5°C or higher and lower than 75°C, and more preferably 5°C or higher and 50°C or lower. The relative humidity during the carbonation treatment is preferably 50% RH or more and 100% RH or less, and more preferably 80% RH or more and 100% RH or less.

[0018] The CO2-containing gas may be exhaust gas generated from a cement factory or a coal-fired power plant, exhaust gas generated during exhaust treatment in a paint factory, etc. The proportion of CO2 in the CO2-containing gas is preferably 5% by volume or more, more preferably 10% by volume or more, and even more preferably 15% by volume or more. Furthermore, the CO2-containing gas may contain moisture (water vapor).

[0019] The CO2 fixation ceramics of this embodiment can not only effectively fix CO2 in the atmosphere, but can also be effectively used as a concrete material. That is, the CO2 fixation material can be used, for example, as a cement additive (admixture), or as an aggregate for mortar or concrete, a roadbed material, an embankment material, a backfill material, etc. Furthermore, the CO2 fixation material can be used as a filler extender for paints, inks, and rubber.

[0020] The CO2 fixation ceramic of this embodiment will be described in detail below.

[0021] The CO2 fixation ceramics include inorganic fired products containing γ-C2S and C2AS. The inorganic fired products are formed or powdered products having a predetermined shape obtained by heating and firing inorganic raw materials.

[0022] The CO2 fixation ceramic may also be in the form of a powder. For example, by appropriately controlling the CaO / SiO2 molar ratio according to the Al2O3 content in the inorganic raw materials, it is possible to realize a completely powdered CO2 fixation ceramic.

[0023] The CO2 fixation ceramics may contain not only inorganic substances such as inorganic fired products but also organic substances such as disaccharides, which will be described later. For example, the CO2 fixation ceramics containing organic substances can be obtained by mixing a powdered inorganic fired product with a disaccharide.

[0024] γ-C2S is known to have α-, β-, and γ-type crystal forms. These differ in crystal structure and density. Among these, γ-C2S, which is γ-type, exhibits a carbonation inhibitory effect. Forced carbonation can increase the densification of hardened cement by using γ-C2S.

[0025] γ-C2S constitutes the γ crystalline phase of the CO2 fixation ceramic. The γ crystalline phase may be contained as an inorganic matrix in the CO2 fixation ceramic.

[0026] The lower limit of the content of γ-C2S is, for example, 30 parts by mass or more, preferably 35 parts by mass or more, and more preferably 40 parts by mass or more, per 100 parts by mass of the CO2 fixation ceramic. On the other hand, the upper limit of the content of γ-C2S is, for example, 98 parts by mass or less, preferably 95 parts by mass or less, and more preferably 93 parts by mass or less, per 100 parts by mass of the CO2 fixation ceramic. By setting the temperature within this range, the carbonation rate can be improved.

[0027] The CO2 fixation ceramic may contain a different phase present in the γ crystalline phase.

[0028] The heterogeneous phase is present inside the grains of the crystalline body composed of the γ crystalline phase consisting of γ-C2S or along the grain interfaces in at least one SEM image of the fracture surface of the CO2 fixation ceramic. In the SEM image, one or more heterogeneous phases may be contained in the crystal grains.

[0029] It is preferable that the CO2 fixation ceramic contains C2AS as a component constituting the heterogeneous phase, which can further improve the carbonation rate. In addition, components other than C2AS may inevitably be present in the heterogeneous phase.

[0030] The lower limit of the C2AS content is, for example, 0.5 mass% or more, preferably 1.0 mass% or more, and more preferably 2.0 mass% or more, relative to 100 mass% of γ-C2S. This allows CO2 to be fixed in a short period of time. On the other hand, the upper limit of the C2AS content is, for example, 50% by mass or less, preferably 40% by mass or less, and more preferably 30% by mass or less, relative to 100% by mass of γ-C2S, thereby preventing an excessive decrease in the carbonation rate.

[0031] In this embodiment, it is possible to control the presence of the heterogeneous phases and the contents of the components that make up the heterogeneous phases by, for example, appropriately selecting the type and amount of each component contained in the CO2 fixation ceramic, the method for preparing the CO2 fixation ceramic, etc. Among these, factors that can be cited for achieving the desired presence of the heterogeneous phases and the desired contents of the components that make up the heterogeneous phases include, for example, using a raw material mixture containing a CaO raw material, a SiO2 raw material, and an Al2O3 raw material, using a rotary kiln lined with high-purity aluminum bricks, and / or applying a predetermined concentration of alumina mortar to the brick surfaces inside the kiln, and appropriately adjusting the firing temperature, dry crushing, and granulation size conditions.

[0032] The content of each mineral component in CO2 fixation ceramics can be confirmed using common analytical methods. For example, the mineral composition of a crushed sample can be confirmed using powder X-ray diffraction, and the data can be analyzed using the Rietveld method to quantify the mineral composition. Furthermore, the mineral composition can be calculated based on the identification results of the chemical components and powder X-ray diffraction.

[0033] The CO2 fixation ceramic may be configured so that Al2O3 is not contained in the γ crystalline phase, which can improve the carbonation rate.

[0034] The CO2 fixation ceramic may be configured to include a β crystalline phase composed of β-2CaO·SiO2 (hereinafter sometimes abbreviated as β-C2S).

[0035] The lower limit of the β-C2S content is, for example, 1.0 mass% or more, preferably 2.0 mass% or more, and more preferably 3.0 mass% or more, relative to 100 mass% of γ-C2S. This allows CO2 to be fixed in a short period of time. On the other hand, the upper limit of the β-C2S content is, for example, 50% by mass or less, preferably 30% by mass or less, and more preferably 20% by mass or less, relative to 100% by mass of γ-C2S, which can prevent a decrease in the carbonation rate due to the formation of dense lumps as the hydration reaction progresses.

[0036] The CO2 fixation ceramic containing β-C2S may be configured so that Al2O3 is contained in the β crystalline phase.

[0037] The CO2 fixation ceramic may contain a glass phase and / or CaO·2Al2O3 (hereinafter sometimes abbreviated as CA2).

[0038] The lower limit of the glass phase content is, for example, 20 mass % or more, preferably 30 mass % or more, and more preferably 40 mass % or more, relative to 100 mass % of γ-C2S, which makes it possible to realize a CO2 fixation ceramic that is entirely powdered. On the other hand, the upper limit of the glass phase content is, for example, 120% by mass or less, preferably 100% by mass or less, and more preferably 90% by mass or less, relative to 100% by mass of γ-C2S. This makes it possible to realize a CO2 fixation ceramic that is entirely powdered.

[0039] The lower limit of the CA2 content is, for example, 0.01 mass% or more, preferably 0.05 mass% or more, and more preferably 0.1 mass% or more, relative to 100 mass% of γ-C2S. This makes it possible to realize a CO2 fixation ceramic that is entirely powdered. On the other hand, the upper limit of the CA2 content is, for example, 20 mass% or less, preferably 18 mass% or less, and more preferably 15 mass% or less, relative to 100 mass% of γ-C2S, thereby realizing a CO2 fixation ceramic that is entirely powdered.

[0040] The water content of the CO2 fixation ceramic is preferably 10 mass% or less, and more preferably 0.01 to 10 mass%, for example, which makes it possible to maintain an appropriate level of contact between the surface of the CO2 fixation ceramic and the CO2-containing gas.

[0041] The moisture content can be calculated from the difference between the mass of the sample before drying and the mass after heating and drying at 105°C. The moisture content of the CO2 fixation ceramics can also be adjusted by adding an appropriate amount of water and stirring after heating and drying at 105°C.

[0042] The average particle size of the CO2 fixation ceramic is, for example, preferably 1 to 100 μm, and more preferably 1 to 70 μm. By setting the average particle size to 1 to 70 μm, it is possible to promote the elution of Ca into the water on the particle surface and accelerate the carbonation reaction. The average particle size can be determined by measurement using a laser diffraction / scattering particle size distribution analyzer.

[0043] The Blaine specific surface area of ​​the CO2 fixation ceramics is, for example, 1,000 to 10,000 cm 2 / g, and 2,500 to 10,000 cm 2 / g. It is more preferable that the specific surface area is 2,500 to 10,000 cm 2 / g, the contact area between the particles and the water on the particle surface increases, promoting the elution of Ca and thereby accelerating the carbonation reaction. The Blaine specific surface area can be determined by measurement using a Blaine air permeation device as described in JIS R 5201.

[0044] As used herein, fixation of CO2 refers to carbonation of a material, with CO2 forming a carbonate compound with the material. In this embodiment, when the CO2 fixation ceramic comes into contact with CO2, a carbonate compound is formed by carbonation, and this carbonate compound can be formed (fixed) inside and / or on the surface of the CO2 fixation ceramic. The CO2 fixation ceramic in which CO2 is fixed as a carbonate compound is called a CO2 fixated product.

[0045] Furthermore, the carbonation of such CO2 fixation ceramics can be promoted by a specific carbonation treatment. For this carbonation treatment, conditions of relatively low temperature and / or relatively high humidity can be used, for example, conditions of less than 75°C and / or 50% RH or higher can also be used. It is possible to fix CO2 in the CO2 fixation ceramics of this embodiment not only by carbonation treatment at high temperature but also by carbonation treatment at relatively low temperature.

[0046] In this specification, the carbonation rate is the ratio of the CaO component in the CO2 fixation ceramic to the CO2 theoretically fixed. The carbonation rate can be calculated using the following formula:

[0047] Equation (1): Carbonation rate = (ΔM × 56.08) / (M × wCaO × 44.01) In the above formula (1), ΔM is the increase in mass due to carbonation [g], M is the mass [g] of the CO2 fixation ceramic before carbonation, and wCaO is the CaO [wt%] in the CO2 fixation ceramic before carbonation. In the above formula (1), the mass increase due to carbonation refers to the mass obtained by subtracting the sample weight before carbonation from the sample weight after carbonation. CaO in the CO2 fixation ceramics before carbonation can be measured by X-ray fluorescence analysis.

[0048] The manufacturing method for CO2 fixation ceramics will be explained.

[0049] An example of a method for producing a CO2 fixation ceramic includes a step of firing a raw material mixture containing a CaO raw material, an SiO2 raw material, and an Al2O3 raw material, for example, in a kiln.

[0050] The CaO raw material may be commercially available as an industrial raw material, or may contain, for example, one or more selected from the group consisting of limestone, coal ash, quicklime, slaked lime, and acetylene-generated waste. Among these, slaked lime and by-product slaked lime may be used.

[0051] The SiO2 raw material may be commercially available as an industrial raw material, such as silica stone, silica sand, quartz, or diatomaceous earth. These may be used alone or in combination of two or more. However, these may not be used if the CaO raw material or Al2O3 raw material contains the necessary amount of SiO2. For example, when coal ash containing SiO2 is used as the CaO raw material, the above SiO2 raw material does not need to be added.

[0052] Here, coal ash (fly ash, etc.) is a general term for combustion ash obtained by burning coal, such as coal combustion ash discharged from the boiler of a thermal power plant. Examples of coal ash that can be used include ash generated in a coal-fired power plant by pulverized coal combustion and coal ash that falls and is collected from the combustion gas of the combustion boiler as it passes through an air preheater or a coal economizer, coal ash collected by an electrostatic precipitator, and coal ash that falls to the bottom of the combustion boiler furnace.

[0053] The Al2O3 raw material may be commercially available as an industrial raw material, or may contain, for example, one or more selected from the group consisting of bauxite, aluminum hydroxide, and aluminum ash. The aluminum ash may be mainly composed of aluminum hydroxide. Among these, bauxite may be used.

[0054] These raw materials are mixed and crushed to obtain a raw material mixture so as to have a predetermined mineral composition ratio after firing.

[0055] The method of mixing and grinding is not particularly limited, and either a dry grinding method or a wet grinding method can be applied. In the case of the wet grinding method, a dehydration treatment is required for subsequent granulation. In addition, when quicklime is used as the raw material, a dry grinding method is preferable. In addition, the γ-C2S / C2AS ratio in the CO2 fixation ceramics can be controlled by adjusting the ratio of raw materials used.

[0056] The raw material mixture may be granulated before firing. The granules are adjusted to an appropriate size, for example, 0.5 to 3.0 cm.

[0057] The firing temperature may be, for example, 1,200°C to 1,600°C, preferably 1,300°C to 1,550°C, and more preferably 1,400°C to 1,450°C.

[0058] For firing, a kiln such as a rotary kiln can be used. For example, a rotary kiln may be used in which the bricks in the firing zone are made of high-purity alumina bricks with an Al2O3 content of 99% or more by mass, and / or alumina mortar adjusted to an appropriate concentration may be applied to the inner surface of the bricks in the firing zone of the rotary kiln before firing.

[0059] The CO2 fixation ceramics may be obtained as an inorganic fired product (clinker) obtained by firing inorganic raw materials, or may be obtained as a powdered inorganic fired product by pulverizing the clinker.

[0060] In addition to the inorganic fired material containing the above-mentioned inorganic components such as γ-CS and C2AS, the CO2 fixation ceramics may also contain disaccharides as other organic components. The disaccharides can form a chelate with Ca eluted into the water on the surface of the inorganic fired material, promoting further elution.

[0061] The CO2 fixation ceramic preferably contains one or more disaccharides selected from the group consisting of trehalose, maltose, and sucrose. Among these, trehalose is more preferred because it has a high effect of promoting the carbonation reaction.

[0062] From the perspective of the promoting effect on the carbonation reaction, it is preferable that the CO2-fixing ceramics contain 0.5 to 10 parts by mass of disaccharides with respect to 100 parts by mass of the CO2-fixing ceramics, and more preferably 5 to 10 parts by mass. Further, in order to obtain a sufficient carbonation promoting effect, the content of trehalose in the disaccharides is preferably 90% by mass or more, and more preferably 95% by mass or more in 100% by mass of the disaccharides.

[0063] As described above, the embodiments of the present invention have been described, but these are examples of the present invention, and various configurations other than the above can be adopted. Further, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the range capable of achieving the object of the present invention are included in the present invention.

Examples

[0064] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the descriptions of these examples at all.

[0065] <Production of CO2-fixing ceramics> (Raw materials used) · By-product slaked lime: Slaked lime produced as a by-product after reacting calcium carbide with water to generate acetylene. SiO2 is 0.8% by mass, Al2O3 is 0.6% by mass, Fe2O3 is 0.3% by mass, CaO is 68.5% by mass, MgO is 0.02% by mass, Na2O is 0.01% by mass, K2O is 0.01% by mass, and SO3 is 0.5% by mass. The loss on ignition (L.O.I.) is 24.1% by mass.

[0066] · Silica: Silica fine powder, SiO2 is 99.3% by mass, Al2O3 is 0.01% by mass, Fe2O3 is 0.0% by mass, CaO is 0.0% by mass, MgO is 0.04% by mass, Na2O is 0.02% by mass, K2O is 0.3% by mass, SO3 is 0.04% by mass, and the loss on ignition (L.O.I.) is 0.6% by mass.

[0067] Alumina: 99.03% by weight Al2O3, 0.14% by weight SiO2, <0.01% by weight Fe2O3, <0.01% by weight CaO, 0.06% by weight TiO2, loss on ignition (LOI) 0.82% by weight.

[0068] [Experimental Example 1] (Fixed ceramics A) As a raw material containing CaO and SiO2, the above-mentioned by-product slaked lime and silica stone were blended to obtain the CaO / SiO2 molar ratio shown in Table 1, and then dry mixed and pulverized to obtain a mixed raw material. The obtained mixed raw material was granulated to produce granules with a diameter of approximately 1 cm to 2.5 cm. The resulting granulated material was placed in a rotary kiln whose firing zone consisted of high-purity alumina bricks (with an Al2O3 content of 99% or more by mass), where it was fired at a firing point of 1,400°C and powdered into clinker during the cooling process to room temperature. The resulting powdered clinker was used as CO2 fixation ceramics A. In addition, CO2 fixation ceramics may be abbreviated simply as "fixation ceramics."

[0069] (Immobilized ceramics B, C) Clinker powder with the mineral proportions shown in Table 1 was synthesized in the same manner as immobilization ceramics A, except that the above-mentioned alumina was used instead of silica stone and the CaO / SiO2 molar ratio and Al2O3 content shown in Table 1 were adopted. These were used as CO2 immobilization ceramics B and C.

[0070] (Immobilized ceramics D) Calcium carbonate powder with a purity of 99.0% by mass or higher and silicon oxide powder with a purity of 99.0% by mass or higher were mixed so that the molar ratio of CaO / SiO2 was 2.0, and the mixture was heat-treated at 1,400°C for 2 hours and slowly cooled in an electric furnace to synthesize γ-CS powder. The resulting γ-CS powder was used as CO2 fixation ceramics D. The γ-C2S powder obtained here contains C2AS and C 12 A7 was not included as it was not dissolved.

[0071] The obtained SEM images and elemental surface analysis using an energy dispersive X-ray analyzer (EDS) confirmed that C2AS exists in the γ crystalline phase composed of γ-C2S in immobilized ceramics A to C, and that Al2O3 is not contained in the γ crystalline phase. Furthermore, β-C2S was confirmed in the CO2 immobilized ceramics A to C, and that Al2O3 is contained in the β crystalline phase composed of β-C2S. Furthermore, the fracture surfaces of the clinker powders of the obtained fixed ceramics A to C were observed using an SEM, and it was confirmed that C2AS was present in the γ crystalline phase composed of γ-C2S. Figure 1 shows an SEM image of the fracture surface of the clinker of fixed ceramic A, and Figure 2 shows an SEM image of the fracture surface of the clinker of fixed ceramic B. In Figures 1 and 2, arrow A (white area) represents C2AS, and arrow B (gray area) represents γ-C2S.

[0072] [Calculation of carbonation rate] 25 g of each of the obtained immobilized ceramics A to D was placed in a plastic cup, and a carbonation treatment was carried out in a temperature and humidity chamber under conditions of 20°C, 80% RH, and a CO2 concentration of 20% by volume. After carbonation for each of the specified periods (1 day, 3 days, 7 days) shown in Table 1, the samples were dried at 105°C for 24 hours, and the mass of each sample was measured. The carbonation rate was calculated from the change in mass before and after the carbonation treatment using the following formula (1). The results are shown in Table 1. Equation (1): Carbonation rate = (ΔM × 56.08) / (M × wCaO × 44.01) In the above formula (1), ΔM is the mass increase due to carbonation [g], M is the mass of the immobilized ceramic before carbonation [g], and wCaO is the CaO content [wt%] in the immobilized ceramic before carbonation. The mass increase due to carbonation was calculated by subtracting the sample weight before carbonation from the sample weight after carbonation. The CaO content in the CO2 immobilized ceramic before carbonation was measured by X-ray fluorescence analysis.

[0073] [Table 1]

[0074] In Table 1, γ-C2S:γ-2CaO·SiO2, β-C2S:β-2CaO·SiO2, and C2AS:2CaO·Al2O3·SiO2 are represented. In Table 1, the proportions of mineral composition were calculated based on the results of chemical composition quantified using fluorescent X-rays and the results of identification by powder X-ray diffraction.

[0075] [Experimental Example 2] Various auxiliary agents were added to 100 parts by mass of CO2 fixation ceramics A in the prescribed ratios shown in Table 2 and mixed to obtain CO2 fixation ceramics E. The obtained CO2 fixation ceramic E was subjected to a carbonation treatment in the same manner as in Experimental Example 1, and the carbonation rate was calculated. The results are shown in Table 2.

[0076] [Table 2]

[0077] [Experimental Example 3] The carbonation rate was calculated in the same manner as in Experimental Example 1, except that CO2 fixation ceramics A was used and the conditions for the carbonation treatment in the temperature and humidity chamber were changed to those shown in Table 3. The results are shown in Table 3.

[0078] [Table 3]

[0079] The results in Table 1 show that the CO2 fixation ceramics of Examples 1 to 3 have a higher carbonation rate than Comparative Example 1. The results in Table 2 show that the carbonation effect was greater when disaccharides were added, and the carbonation effect was particularly greater when trehalose was added. From the results in Table 3, a good carbonation rate was obtained by setting the carbonation temperature at 75°C or lower and / or 50% RH or higher.

[0080] By using the CO2 fixation ceramics of Examples 1 to 3 and carrying out a carbonation treatment under conditions of relatively low temperature and / or relatively high humidity, a CO2 fixation product in which CO2 is fixed can be obtained. Such CO2 immobilized materials can be used in the civil engineering and construction fields, for example, as cement additives, and can also be effectively used as aggregate for mortar and concrete, roadbed materials, embankment materials, backfill materials, and as filler extenders for paints, inks, and rubber.

[0081] This application claims priority based on Japanese Patent Application No. 2022-019300, filed February 10, 2022, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. γ-2CaO.SiO ２ (γ-C ２ S), and a γ crystalline phase composed of 2CaO.Al ２ O ３ SiO ２ (C ２ AS), the content of the γ-C 2 S is 30% by mass or more and 98% by mass or less in 100% by mass of the CO 2 fixation ceramic; The content of the C 2 AS is 0.5 mass % or more and 50 mass % or less with respect to 100 mass % of the γ-C 2 S. ２ Immobilization ceramics.

2. The CO according to claim 1 ２ An immobilized ceramic, Glass phase and / or CaO.2Al ２ O ３ (CA ２ ), including CO ２ Immobilization ceramics.

3. CO according to claim 1 or 2 ２ An immobilized ceramic, The heterogeneous phase is present in the γ crystalline phase, and the heterogeneous phase contains the C ２ Contains AS, CO ２ Immobilization ceramics.

4. The CO according to claim 3 ２ An immobilized ceramic, In the γ crystalline phase, Al ２ O ３ does not contain CO ２ Immobilization ceramics.

5. CO according to claim 1 or 2 ２ An immobilized ceramic, β-2CaO.SiO ２ (β-C ２ S), including a β crystalline phase composed of CO ２ Immobilization ceramics.

6. The CO according to claim 5 ２ An immobilized ceramic, In the β crystal phase, Al ２ O ３ Contains CO ２ Immobilization ceramics.

7. The CO according to claim 5 ２ An immobilized ceramic, Said β-C ２ The content of S is ２ CO is 1.0 mass% or more and 50 mass% or less relative to 100 mass% of S. ２ Immobilization ceramics.

8. CO according to claim 1 or 2 ２ An immobilized ceramic, Disaccharide-containing CO ２ Immobilization ceramics.

9. The CO according to claim 8 ２ An immobilized ceramic, The content of the disaccharide is ２ CO is 0.5 parts by mass or more and 10 parts by mass or less in 100 parts by mass of the immobilized ceramic. ２ Immobilization ceramics.

10. The CO according to claim 8 ２ An immobilized ceramic, The disaccharide comprises trehalose. ２ Immobilization ceramics.

11. CO according to claim 1 or 2 ２ An immobilized ceramic, CO in powder form ２ Immobilization ceramics.

12. 3. The CO 2 according to claim 1 or 2, ２ A CO2 fixation method comprising the step of carbonating the immobilized ceramics. ２ Method for producing immobilized material.

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