Carbon dioxide immobilization method

Abstract

A method for immobilizing carbon dioxide according to one embodiment of the present invention comprises: a contact step in which a mixed solution containing a polyol compound and water is brought into contact with a calcium-containing material; an aeration step in which carbon dioxide is aerated into the liquid mixture after the contact step; a separation step for separating, from the mixed liquid after the aeration step, the precipitate to which the carbon dioxide has been immobilized; and a recovery step for recovering the mixed solution from which the precipitate has been separated in the separation step, and using the mixed solution recovered in the recovery step as at least a part of the mixed solution to be brought into contact with the material.

Description

Technical Field

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

[0002] In recent years, climate change caused by global warming has become a problem. Carbon dioxide in the atmosphere is one of the greenhouse gases and is considered to be the main cause of global warming. Therefore, it is required to reduce carbon dioxide emissions and lower the concentration of carbon dioxide in the atmosphere. As one of the means, a method for carbon dioxide fixation is known.

[0003] For example, a method for carbon dioxide fixation has been proposed, in which calcium oxide and magnesium oxide contained in industrial waste are brought into contact with water to dissolve calcium ions and magnesium ions in water, and the solution is brought into contact with carbon dioxide gas to form calcium carbonate and magnesium carbonate (Japanese Patent Laid-Open No. 7-265688).

[0004] In addition, a method has been proposed in which carbon dioxide is supplied to an aqueous solution in which blast furnace slag and an alkali are mixed, and the carbon dioxide is fixed in calcium dissolved from the blast furnace slag (Japanese Patent No. 6653108).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Laid-Open No. 7-265688

[0008] Patent Document 2: Japanese Patent No. 6653108 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] Considering the solubility of calcium in water, sufficient calcium cannot be extracted into the above-mentioned water. Therefore, in the method of Patent Document 1, the fixation of carbon dioxide to calcium may also be insufficient.

[0011] In the method of Patent Document 2, an alkaline aqueous solution is used to extract calcium from blast furnace slag. However, generally, in an alkaline solution environment, the solubility of calcium saturates at around pH 12.5. Therefore, sufficient calcium may not be able to be extracted by this method. In addition, in the method of Patent Document 2, treatment devices including a boiler, a hydrolysis reactor, a condenser, etc. are used, so equipment investment is required, and carbon dioxide fixation may not be able to be carried out at low cost.

[0012] In view of such a situation, an object of the present invention is to provide a method for carbon dioxide fixation that can fix carbon dioxide at low cost and efficiently.

[0013] Means for Solving the Problems

[0014] One method for carbon dioxide fixation according to an aspect of the present invention for solving the above problems includes the following steps: a contacting step of bringing a mixed solution containing a polyol compound and water into contact with a calcium-containing material; an aeration step of aerating carbon dioxide into the mixed solution after the contacting step; a separation step of separating a precipitate having the carbon dioxide fixed therein from the mixed solution after the aeration step; and a recovery step of recovering the mixed solution from which the precipitate has been separated by the separation step, and using at least a part of the mixed solution recovered by the recovery step as the mixed solution to be brought into contact with the above material.

[0015] Effect of the Invention

[0016] The carbon dioxide fixation method of the present invention can fix carbon dioxide at low cost and efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a conceptual diagram showing a carbon dioxide fixation method according to an embodiment of the present invention.

[0018] Figure 2 It is a conceptual diagram showing a carbon dioxide fixation method according to another embodiment of the present invention.

[0019] Figure 3 It is a conceptual diagram showing a carbon dioxide fixation method according to still another embodiment of the present invention.

[0020] Figure 4 It is a diagram showing the extraction state of the polyol compound in the extraction step when a water contacting step and an extraction step are performed after the contacting step. DETAILED DESCRIPTION OF THE INVENTION

[0021] One method for carbon dioxide fixation according to an aspect of the present invention includes the following steps: a contacting step of bringing a mixed solution containing a polyol compound and water into contact with a calcium-containing material; an aeration step of aerating carbon dioxide into the mixed solution after the contacting step; a separation step of separating a precipitate having the carbon dioxide fixed therein from the mixed solution after the aeration step; and a recovery step of recovering the mixed solution from which the precipitate has been separated by the separation step, and using at least a part of the mixed solution recovered by the recovery step as the mixed solution to be brought into contact with the above material.

[0022] In this carbon dioxide fixation method, a mixed solution of a polyol compound and water is brought into contact with the above-mentioned material in order to extract calcium from a calcium (Ca)-containing material. Therefore, the above-mentioned calcium can be efficiently extracted as calcium ions into the above-mentioned mixed solution. By aerating carbon dioxide into the above-mentioned mixed solution containing a large amount of calcium ions due to contact with the above-mentioned material, the above-mentioned calcium ions react with carbonate ions, and calcium carbonate precipitates as a precipitate. In other words, since the above-mentioned mixed solution contains many calcium ions, a large amount of carbon dioxide can be fixed. In addition, this carbon dioxide fixation method does not require large-scale equipment for extracting calcium from the above-mentioned material, so carbon dioxide can be fixed at low cost. Furthermore, the above-mentioned precipitate is separated from the mixed solution in which the above-mentioned precipitate has precipitated, and this mixed solution is reused as the mixed solution for extracting calcium from the above-mentioned material, so carbon dioxide can be fixed at even lower cost.

[0023] Preferably, it further includes the following steps: a water contact step of further bringing water into contact with the material after the above-mentioned contact step; a contact water recovery step of recovering the water after the above-mentioned water contact step, and further using the water recovered in the above-mentioned contact water recovery step as at least a part of the mixed solution in contact with the above-mentioned material. By bringing water into contact with the material that has been in contact with the above-mentioned mixed solution, the polyol compound remaining in the voids of the above-mentioned material can be removed. By further using the water containing the remaining polyol compound as at least a part of the above-mentioned mixed solution in the above-mentioned contact step, carbon dioxide can be fixed at lower cost.

[0024] It may also include the following steps: replacing the above-mentioned contact water recovery step, separating the water after the above-mentioned water contact step into a polyol compound and water in a contact water separation step; a polyol compound recovery step of recovering the polyol compound separated in the above-mentioned contact water separation step, and further using the polyol compound recovered in the above-mentioned polyol compound recovery step as at least a part of the mixed solution in contact with the above-mentioned material. Separating the polyol compound from the water containing the polyol compound remaining in the voids of the above-mentioned material in the above-mentioned water contact step, and further using the separated polyol compound as at least a part of the above-mentioned mixed solution in the above-mentioned contact step can also fix carbon dioxide at lower cost.

[0025] Preferably, the concentration of the above-mentioned polyol compound in the above-mentioned mixed solution in the above-mentioned contact step is 60% by mass or less. By doing so, carbon dioxide can be fixed more efficiently.

[0026] Preferably, the above-mentioned polyol compound is a diol compound or a triol compound. By doing so, the calcium in the above-mentioned material can be extracted as calcium ions more efficiently.

[0027] Preferably, the above-mentioned diol compound is one or more selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol. By doing so, calcium in the above-mentioned material can be extracted as calcium ions more efficiently.

[0028] Preferably, the above-mentioned triol compound is glycerol. By doing so, calcium in the above-mentioned material can be extracted as calcium ions more efficiently.

[0029] Herein, the so-called "polyol compound" refers to an organic compound having multiple alcoholic hydroxyl groups (a group in which a hydrogen atom of an aliphatic hydrocarbon is replaced by a hydroxyl group (-OH)). Similarly, the so-called "diol compound" refers to an organic compound having two of the above-mentioned alcoholic hydroxyl groups, and the so-called "triol compound" refers to an organic compound having three of the above-mentioned alcoholic hydroxyl groups.

[0030] [Details of the mode for carrying out the invention]

[0031] Hereinafter, a detailed description will be given with reference to the drawings as appropriate. In addition, the drawings are explanatory diagrams, which schematically depict each structure (each component). The shape, proportion, etc. may be different from the actual situation, and various components such as a pump for transporting a substance (the mixed liquid M or water, etc. described later) or a valve for transporting the substance at an appropriate time are also partially omitted. In addition, in this specification, a plurality of upper limit values and a plurality of lower limit values are described as the numerical ranges of the constitution of the present invention. Any one of these described plurality of upper limit values and plurality of lower limits can be arbitrarily selected and combined.

[0032] [First Embodiment]

[0033] A carbon dioxide fixation method according to an embodiment of the present invention mainly includes the following steps: a contact step of bringing a mixed liquid containing a polyol compound and water into contact with a calcium-containing material; an aeration step of aerating carbon dioxide into the mixed liquid after the contact step; a separation step of separating a precipitate in which the carbon dioxide is fixed from the mixed liquid after the aeration step; and a recovery step of recovering the mixed liquid from which the precipitate has been separated by the separation step. The mixed liquid recovered by the recovery step is used as at least a part of the mixed liquid in contact with the above-mentioned material.

[0034] 〔Contact Step〕

[0035] In the contact step, a mixed liquid containing a polyol compound and water is brought into contact with a calcium-containing material. Specifically, as Figure 1 shown, the mixed liquid M is supplied to the reaction vessel 1 containing the material S, and the material S is brought into contact with the mixed liquid M. In other words, this carbon dioxide fixation method includes a step of supplying the material S and the mixed liquid M to the reaction vessel 1 before the contact step.

[0036] In the supply process, a calcium-containing material S and a mixed solution M are supplied into a reaction vessel 1. The reaction vessel 1 is not particularly limited as long as it can accommodate the material S in a specified amount and can supply and discharge the mixed solution M.

[0037] When supplying the material S and the mixed solution M into the reaction vessel 1, it can be that after filling the reaction vessel 1 with an amount of the mixed solution M capable of submerging the material S, the material S is supplied, or the material S can be supplied into the reaction vessel 1 first and then the mixed solution M is supplied, or the material S and the mixed solution M can be supplied simultaneously. Additionally, after supplying a certain amount of the material S, the material S can be appropriately added.

[0038] In the contact process, the mixed solution M is continuously supplied from a storage tank 2 in a certain amount and continuously discharged in a certain amount. That is, the mixed solution M is not continuously stored in the reaction vessel 1 in a certain amount, but is continuously supplied in a manner of passing through while contacting the material S in the reaction vessel 1. The supply amount of the mixed solution M and the discharge amount of the mixed solution M can be the same amount or different amounts as long as the state where all the material S in the reaction vessel 1 is submerged can be maintained. The time for the mixed solution M to contact the material S is appropriately set according to the type (material) of the material S, the total amount of the material S, etc.

[0039] After the contact process, for the material S, for example, when the material S is steelmaking slag, after contacting with the mixed solution M in the above contact process, it is taken out from the reaction vessel 1 and dried, and thus can be utilized as a resource such as a subgrade material (road material) or fertilizer.

[0040] (Material)

[0041] As the calcium-containing material S, for example, blast furnace slag, steelmaking slag and other slags, cement, concrete waste, glass waste, coal ash, sludge incineration ash can be cited. In these materials, calcium exists, for example, in the form of calcium oxide (CaO). The above blast furnace slag is blast furnace slag generated in the iron-making process and contains calcium. The above steelmaking slag is slag generated in the steel-making process such as converter slag or electric furnace slag and contains calcium.

[0042] (Polyol compound)

[0043] The above polyol compound is a medium for extracting calcium from the material S. The above polyol compound is an organic compound having multiple alcoholic hydroxyl groups. The alcoholic hydroxyl group is a hydroxyl group that replaces the hydrogen atom of an aliphatic hydrocarbon and does not include the hydroxyl group that replaces the hydrogen atom of a hydrocarbon constituting an aromatic ring (for example, the hydroxyl group of phenol).

[0044] As the above polyol compound, there is no particular limitation as long as it is an organic compound having a plurality of alcoholic hydroxyl groups. For example, a diol compound or a triol compound is preferred. These diol compounds and triol compounds are usually liquid at normal temperature and pressure, and thus can be easily mixed with the above water to contact the material S.

[0045] As the above diol compound, there is no particular limitation as long as it is an organic compound having two alcoholic hydroxyl groups. As the above diol compound, for example, ethylene glycol, propylene glycol, diethylene glycol, butanediol or diethanolamine can be cited. Among them, as the above diol compound, for example, one or more selected from the group consisting of ethylene glycol, propylene glycol and diethylene glycol are preferred.

[0046] For example, it is generally known that the solubility of calcium in ethylene glycol is about 10 times that in water. In other words, the solubility of calcium in the diol compound is much greater than that in water. Therefore, by using one or more selected from the above group as the diol compound, calcium can be extracted from the material S more efficiently.

[0047] As the above triol compound, there is no particular limitation as long as it is an organic compound having three alcoholic hydroxyl groups. For example, glycerol is preferred. By using glycerol, calcium can be extracted from the material S more efficiently.

[0048] As the upper limit value of the concentration of the above polyol compound in the mixed liquid M in the above contact step, 60% by mass is preferred, 50% by mass is more preferred, and 40% by mass is further preferred. If the concentration of the above polyol compound is higher than the above upper limit value, the precipitation of calcium carbonate in the subsequent aeration step may decrease. That is, the efficiency of carbon dioxide fixation may be reduced. As the lower limit value of the concentration of the above polyol compound in the mixed liquid M in the above contact step, 20% by mass is preferred, and 30% by mass is more preferred. If the concentration of the above polyol compound is lower than the above lower limit value, a sufficient amount of calcium may not be dissolved from the material S into the mixed liquid M.

[0049] (Water)

[0050] The above water is a supply source of protons (H ＋ ) for ionizing carbon dioxide (carbonic acid ionization). In addition, in the mixed liquid M in the above contact step, the calcium ions extracted by the above polyol compound move (diffuse) in water, and carbon dioxide is dissolved in this water as carbonate ions (CO3 2－ ). As a result, calcium ions and carbonate ions react in this water as a reaction field and precipitate as calcium carbonate. As such water, as long as it functions in a catalytic manner as described above, there is no particular limitation. For example, pure water can be cited.

[0051] 〔Aeration Process〕

[0052] In the aeration process, carbon dioxide C is aerated into the mixed liquid M after the above-mentioned contact process. Specifically, the mixed liquid M discharged from the reaction vessel 1 is stored in the aeration tank 3, and carbon dioxide C is aerated into the stored mixed liquid M. As the aeration method, there is no particular limitation. For example, a known gas injection device 4 or the like can be used to discharge carbon dioxide C into the mixed liquid M. It is preferable to aerate carbon dioxide C while stirring the mixed liquid M in the aeration tank 3.

[0053] As the carbon dioxide C, carbon dioxide contained in the waste gas of the factory can be used, etc. In addition, a mixed gas in which carbon dioxide C is mixed with other gases can also be aerated. In this case, the concentration of carbon dioxide C in the above-mentioned mixed gas is not particularly limited. For example, as the concentration of carbon dioxide C in the above-mentioned mixed gas, it is not particularly limited, and it can be the same concentration as the carbon dioxide in the atmosphere, or the same concentration as the carbon dioxide concentration in the above-mentioned waste gas, or a concentration after dilution or concentration thereof.

[0054] In the water in the mixed liquid M after the above-mentioned contact process, calcium ions dissolved from the material S are dissolved. If carbon dioxide C is aerated into the mixed liquid M that has contacted the material S, the water carbon dioxide in the mixed liquid M is dissolved as carbonate ions, and in this water, the above-mentioned calcium ions react with the above-mentioned carbonate ions and precipitate as calcium carbonate (precipitate).

[0055] 〔Separation Process〕

[0056] In the separation process, the precipitate fixed with the above-mentioned carbon dioxide is separated from the mixed liquid M after the above-mentioned aeration process. That is, the precipitate precipitated in the above-mentioned aeration process and the mixed liquid M are separated. As the separation method, there is no particular limitation. For example, a method of performing solid-liquid separation using a known centrifuge 5 or the like can be cited.

[0057] The separated mixed liquid M is used as a part of the mixed liquid M in the above-mentioned contact process. By reusing the mixed liquid M in this way, carbon dioxide can be fixed at low cost. The separated precipitate can be used, for example, as a part of the material for concrete or cement.

[0058] 〔Recovery Process〕

[0059] In the recovery process, the mixed liquid M from which the precipitate D is separated in the above-mentioned separation process is recovered. The mixed liquid M is recovered into the storage tank 1 and used as a part of the mixed liquid in contact with the material S. That is, the mixed liquid M after the above-mentioned separation process is reused. Since the recovered mixed liquid M has removed the precipitate D through the above-mentioned separation process, it has the same quality as before contacting the material S.

[0060] 〔Advantages〕

[0061] In this carbon dioxide fixation method, since the mixed liquid M of a polyol compound and water is brought into contact with the calcium-containing material S, calcium in the material S can be efficiently extracted. Therefore, the mixed liquid M that has been in contact with the material S contains a large amount of calcium. By aerating carbon dioxide C into the mixed liquid M, carbon dioxide can be efficiently fixed. By separating and removing the precipitate from the aerated mixed liquid M, the separated mixed liquid M can be reused as the mixed liquid M for contacting the material S. Therefore, this carbon dioxide fixation method can fix carbon dioxide at low cost.

[0062] [Second Embodiment]

[0063] The carbon dioxide fixation method of another embodiment of the present invention includes the above-described contact step, the above-described aeration step, the above-described separation step, and the above-described recovery step, and uses the mixed liquid recovered by the above-described recovery step as part of the mixed liquid for contacting the above-described material. This carbon dioxide fixation method further includes the following steps: a water contact step of further bringing water into contact with the material after the above-described contact step; a contact water recovery step of recovering the water after the above-described water contact step, and further using the water recovered in the above-described contact water recovery step as at least part of the mixed liquid for contacting the above-described material. For the same components as those in the above-described embodiment, the same reference numerals are used and the description is omitted.

[0064] 〔Water Contact Step〕

[0065] In the carbon dioxide fixation method of this embodiment, after the material S is brought into contact with the sufficient mixed liquid M, it is further brought into contact with water. Specifically, as Figure 2 shown, the supply of the mixed liquid M to the reaction vessel 1 is stopped by closing the valve V1, and the other valve V2 is opened to supply water W to the material S in the reaction vessel 1 for contact. The water W is continuously supplied in a certain amount and continuously discharged in a certain amount. The supply amount of the water W and the discharge amount of the water W may be the same amount or different amounts as long as the state of completely submerging all the material S in the reaction vessel 1 can be maintained. The water W used in the water contact step may be the same as the water used for the mixed liquid M in the contact step.

[0066] By further bringing the water W into contact with the material S that has been in contact with the mixed liquid M, the polyol compound remaining in the voids of the material S can be extracted. Therefore, the drying of the material S taken out from the reaction vessel 1 after the water contact step can be effectively performed.

[0067] 〔Contact Water Recovery Step〕

[0068] In the contact water recovery process, the water W after the above water contact process is recovered. The water W after the water contact process is recovered into the storage tank 1. When diluting the polyol compound in the mixed liquid M in the storage tank 1 with the recovered water W, the polyol compound may be added in a manner to achieve an appropriate concentration. In the water W that has contacted the material S in the water contact process, the polyol compound remaining in the voids of the material S is dissolved. The water W containing the polyol compound is used as a part of the mixed liquid M in the above contact process. By reusing the water W in this way, carbon dioxide fixation can be carried out at a lower cost.

[0069] 〔Advantages〕

[0070] In this carbon dioxide fixation method, since the water W is brought into contact with the material S after contacting the mixed liquid M, the material S taken out from the reaction vessel 1 can be effectively dried. In this carbon dioxide fixation method, since the mixed liquid M that has contacted the material S and the water W that has contacted the material S are reused, carbon dioxide fixation can be carried out at a lower cost.

[0071] [Third Embodiment]

[0072] The carbon dioxide fixation method according to another embodiment of the present invention includes the above contact process, the above aeration process, the above separation process, and the above recovery process, and uses the mixed liquid recovered in the above recovery process as a part of the mixed liquid in contact with the above material. This carbon dioxide fixation method further includes the following processes: a water contact process in which water further contacts the material after the above contact process; a contact water separation process in which the water after the above water contact process is separated into a polyol compound and water; a polyol compound recovery process for recovering the polyol compound separated in the above contact water separation process, and further using the polyol compound recovered in the above polyol compound recovery process as at least a part of the mixed liquid in contact with the above material.

[0073] 〔Water Contact Process〕

[0074] In the water contact process, after the material S contacts the sufficient mixed liquid M, it further contacts the water W. Specifically, as Figure 3 shown, the valve V1 is closed to stop supplying the mixed liquid M to the reaction vessel 1, and another valve V2 is opened to supply the water W to the material S in the reaction vessel 1 for contact.

[0075] 〔Contact Water Separation Process〕

[0076] In the water contact separation process, the polyol compound P is separated from the water W after the above water contact process. Specifically, the water W after the above water contact process is separated into water W and the polyol compound P by a separator 6. There is no particular limitation on the separator 6. For example, a boiler, a multi-functional tank, etc. can be used. The supply of the water W discharged from the reaction vessel 1 to the separator 6 is carried out, for example, by switching the flow path using a three-way valve V3.

[0077] The water W separated by the water contact separation process can be discharged from the separator 6 as water vapor H. The discharged water vapor H can also be reduced to water W and used as part of the water in contact with the material S in the reaction vessel 1.

[0078] 〔Polyol compound recovery process〕

[0079] In the polyol compound recovery process, the separated polyol compound P is recovered. The separated polyol compound P is recovered into the storage tank 1. When concentrating the polyol compound in the mixed liquid M in the storage tank 1 by the recovered polyol compound P, water can be added in a manner to achieve an appropriate concentration. The recovered polyol compound P is used as part of the mixed liquid M in the above contact process. In this way, by reusing the polyol compound P, carbon dioxide fixation can be carried out at a lower cost.

[0080] 〔Advantages〕

[0081] In this carbon dioxide fixation method, since the mixed liquid M that has contacted the material S and the polyol compound P separated from the water W that has contacted the material S are reused, carbon dioxide fixation can be carried out at a lower cost.

[0082] Furthermore, the present invention is not limited to the above embodiments. For example, in the addition process of the above embodiments, the mixed liquid may also contain other solvents other than water and polyol compounds. As other solvents, for example, hydrophilic solvents. As hydrophilic solvents, ethanol or methanol, etc. can be cited. In addition, in the contact process, a mixed liquid of a polyol compound and an aqueous solution in which additives other than the solvent are dissolved in water can also be used.

[0083] Examples

[0084] Hereinafter, the present invention will be further described by examples, but the present invention is not limited by these examples.

[0085] [Example 1]

[0086] As Test Example 1, a mixed liquid of 50% by mass of glycerol and water (pure water) was prepared. As the calcium-containing material, 50 g of converter slag with an average particle size of 10 mm was prepared. The above materials were added to the beaker in a mass ratio of 1:10 and shaken at 200 spm under room temperature conditions.

[0087] Use filter paper to perform solid-liquid separation on the material and the mixture in Test Example 1, and recover the separated mixture as the mixture in Test Example 2. Take 50 ml from the mixture in Test Example 2 to measure the calcium concentration, and calculate the calcium extraction amount in Test Example 1. Thereafter, bubble carbon dioxide into the mixture in Test Example 2 at 0.5 L / min for 30 minutes to precipitate calcium carbonate.

[0088] Filter and separate calcium carbonate from the mixture in Test Example 2 using filter paper to obtain the mixture in Test Example 3. Prepare the same material as in Test Example 1 again, add this material and the mixture in Test Example 3 to a beaker, and shake under the same conditions as in Test Example 1.

[0089] Use filter paper to perform solid-liquid separation on the mixture and the material in Test Example 3, and recover the separated mixture as the mixture in Test Example 4. Take 50 ml from the mixture in Test Example 4 to measure the calcium concentration, and calculate the calcium extraction amount in Test Example 3. Thereafter, bubble air into the mixture in Test Example 4 under the same conditions as in Test Example 2.

[0090] Filter and separate calcium carbonate from the mixture in Test Example 4 using filter paper to obtain the mixture in Test Example 5. Prepare the same material as in Test Example 1 again, add this material and the mixture in Test Example 5 to a beaker, and shake under the same conditions as in Test Example 1.

[0091] Use filter paper to perform solid-liquid separation on the mixture and the material in Test Example 5, and recover the separated mixture as the mixture in Test Example 6. Take 50 ml from the mixture in Test Example 6 to measure the calcium concentration, and calculate the calcium extraction amount in Test Example 5. Thereafter, bubble air into the mixture in Test Example 6 under the same conditions as in Test Example 2.

[0092] Filter and separate calcium carbonate from the mixture in Test Example 6 using filter paper to obtain the mixture in Test Example 7. Prepare the same material as in Test Example 1 again, add this material and the mixture in Test Example 7 to a beaker, and shake under the same conditions as in Test Example 1.

[0093] Use filter paper to perform solid-liquid separation on the mixture and the material in Test Example 7, take 50 ml from the separated mixture to measure the calcium concentration, and calculate the calcium extraction amount in Test Example 7.

[0094] Test Examples 1 to 7 are shown in Table 1. In Table 1, "-" means that the matter does not exist. In Table 1, the so-called water temperature "RT" means measurement at room temperature. The reason why the amount of the mixture gradually decreases in each test example is that a part of the mixture is collected as a sample. In Test Examples 2 and 5, 20 ml of water is added. In Test Example 6, 10 ml of water is added.

[0095]

Table 1

[0096]

[0097] The results of the calcium extraction amounts, pH values, and water ratios of each mixed solution in Test Examples 1, 3, 5, and 7 are shown in Table 2.

[0098]

Table 2

[0099]

[0100] According to Table 2, for each of the reused mixed solutions in Test Examples 3, 5, and 7, calcium extraction amounts equivalent to those of the non-reused mixed solution in Test Example 1 can also be obtained. In addition, almost no changes were observed in the pH value and the water ratio in the mixed solution. From this, it can be understood that even if the mixed solution is reused, the efficiency of fixing carbon dioxide can be maintained.

[0101] [Example 2]

[0102] As a reaction vessel, a packed column with an inner diameter of 42 mm and a total length of 230 mm (inner volume: 330 cm 3 ) was prepared. 450 g-dry of converter slag was filled in this packed column, and a mixed solution was supplied to contact with the above material. The mixed solution used was 40 mass% glycerol and water. This mixed solution was supplied into the above packed column at a rate of 0.08 mm / s. The above packed column was arranged in a vertical direction along the longitudinal axis, and the above mixed solution was supplied from below and discharged from above.

[0103] After the supply of the mixed solution was stopped to extract calcium from the above material, water was supplied to the above packed column in the same manner as the above mixed solution. The water discharged was recovered at regular intervals and dried at 70°C for 8 hours or more, and the glycerol concentration in the discharged water was calculated based on the weight change. The results are shown in Figure 4 .

[0104] From Figure 4 , it can be seen that by supplying approximately three times the inner volume of the packed column with water, the total amount of glycerol remaining in the material in the above packed column can be recovered. In addition, the water reaching approximately three times the inner volume of the packed column can become a reusable mixed solution.

[0105] Industrial Applicability

[0106] The present invention can efficiently fix carbon dioxide to calcium at low cost, and while achieving effective utilization of calcium-containing materials, it can also contribute to suppressing the emission of carbon dioxide into the atmosphere.

[0107] Explanation of Reference Numerals

[0108] 1 Reaction vessel

[0109] 2 Storage tank

[0110] 3 Aeration tank

[0111] 4 Gas injection device

[0112] 5 Centrifugal separator

[0113] 6 Separator

[0114] C Carbon dioxide

[0115] D Precipitate

[0116] H Water (water vapor)

[0117] M Mixed liquid

[0118] P Polyol compound

[0119] S Material

[0120] V1, V2 Valve

[0121] V3 Three-way valve

[0122] W Water

Claims

1. A method for carbon dioxide fixation, wherein, It has the following processes: Contact process: bringing a mixed solution containing a polyol compound and water into contact with a calcium-containing material; Aeration process: aerating carbon dioxide into the mixed solution after the contact process; Separation process: separating the precipitate fixed with the carbon dioxide from the mixed solution after the aeration process; Recovery process: recovering the mixed solution from which the precipitate has been separated by the separation process, using the mixed solution recovered by the recovery process as at least a part of the mixed solution in contact with the material.

2. The carbon dioxide fixation method according to claim 1, wherein, It also has the following processes: Water contact process: further bringing water into contact with the material after the contact process; Contact water recovery process: recovering the water after the water contact process, further using the water recovered by the contact water recovery process as at least a part of the mixed solution in contact with the material.

3. The carbon dioxide fixation method according to claim 1, wherein It also has the following processes: Water contact process: further bringing water into contact with the material after the contact process; Contact water separation process: separating the water after the water contact process into a polyol compound and water; Polyol compound recovery process: recovering the polyol compound separated by the contact water separation process, further using the polyol compound recovered by the polyol compound recovery process as at least a part of the mixed solution in contact with the material.

4. The carbon dioxide fixation method according to claim 1, claim 2 or claim 3, wherein The concentration of the polyol compound in the mixed solution in the contact process is 60% by mass or less.

5. The carbon dioxide fixation method according to claim 1, claim 2 or claim 3, wherein The polyol compound is a diol compound or a triol compound.

6. The carbon dioxide fixation method according to claim 5, wherein, The diol compound is one or more selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol.

7. The carbon dioxide fixation method according to claim 5, wherein, The triol compound is glycerol.

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