Calcium carbonate manufacturing system, calcium carbonate manufacturing method, sodium carbonate manufacturing method, silicon oxide-containing gel manufacturing method, concrete material treatment method, and carbon dioxide fixation method

Abstract

To provide a novel method for recovering calcium carbonate from concrete materials.SOLUTION: A calcium carbonate manufacturing system according to an embodiment comprises a base treatment device that precipitates calcium hydroxide by treating concrete materials with a base, and a calcium hydroxide carbonation device that generates calcium carbonate by carbonating calcium hydroxide.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present invention relate to a calcium carbonate production system, a method for producing calcium carbonate, a method for producing sodium carbonate, a method for producing a silicon oxide-containing gel, a method for treating concrete materials, and a method for immobilizing carbon dioxide.

Background Art

[0002] Every year, more than 3 billion tons of construction and demolition waste are generated, and about 40% of it is concrete. For this reason, recycling technologies for concrete waste materials have been developed (such as Patent Document 1).

[0003] In addition, carbon dioxide, which is considered to be a cause of global warming and climate change, is not only emitted as exhaust gas from automobiles and factories, but also emitted in large quantities during the production of cement, which is a raw material for concrete. Technologies for immobilizing such carbon dioxide gas as a solid such as calcium carbonate have also been developed (such as Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the currently used methods have various problems such as complicated processes, the need for expensive treatment agents, and insufficient purity of the recovered materials, and new methods are continuously being explored.

[0006] The problem to be solved by the present invention is to provide a novel method for recovering calcium carbonate from concrete materials.

[0007] The problem to be solved by the present invention is to provide a novel method for recovering silicon dioxide-containing gel and / or sodium carbonate from concrete materials.

[0008] Another problem to be solved by the present invention is to facilitate the extraction of calcium components from concrete materials.

[0009] Another problem to be solved by the present invention is to provide a novel method for immobilizing carbon dioxide.

[0010] The present invention aims to solve, for example, one or more of the above problems. However, the problems of the present invention are not limited to the above, and the present invention may solve other problems.

Means for Solving the Problems

[0011] The present invention may include the following aspects. [1] A calcium carbonate production system, A base treatment device for precipitating calcium hydroxide by treating concrete materials with a base, A calcium hydroxide carbonation device for generating calcium carbonate by carbonating calcium hydroxide, A system comprising: [2] The system according to [1], further comprising a water washing device for washing the precipitated calcium hydroxide with water. [3] The system according to [2], wherein the water washing device separates the precipitated calcium hydroxide from other precipitates in the form of an aqueous calcium hydroxide solution. [4] The system according to [3], wherein the carbonation device performs carbonation treatment on the aqueous calcium hydroxide solution. [5] Further comprising a concrete carbonation device for carbonating the concrete materials, The base treatment device is the system according to any one of [1] to [4], which performs base treatment on the carbonated concrete material. [6] The system according to any one of [1] to [5], further comprising a separation device that separates the filtrate from the precipitated calcium hydroxide. [7] The system according to [6], further comprising a circulation device that supplies the separated filtrate to the base treatment device. [8] The system according to [6], further comprising a filtrate carbonation device that carbonates the separated filtrate. [9] The base is sodium hydroxide, The system according to [8], further comprising a filtrate separation device that separates sodium carbonate from the carbonated filtrate.

[10] The system according to [9], wherein the separation device comprises a centrifuge.

[11] A method for producing sodium carbonate, which uses the system according to [9] or

[10] to produce sodium carbonate.

[12] The system according to [9], further comprising a filtrate separation device that precipitates silicon oxide-containing gel from the carbonated filtrate.

[13] A method for producing silicon oxide-containing gel, which uses the system according to

[12] to produce silicon oxide-containing gel.

[14] A method for producing calcium carbonate, comprising: a step of precipitating calcium hydroxide by treating the concrete material with a base; a step of producing calcium carbonate by carbonating the precipitated calcium hydroxide; and.

[15] The step of producing calcium carbonate comprises: a step of separating the precipitated calcium hydroxide from the water-insoluble precipitate by dissolving the precipitated calcium hydroxide in water; a step of producing calcium carbonate by carbonating the separated calcium hydroxide; and is the method according to

[14] .

[16] The step of producing the calcium carbonate includes the step of washing the precipitate containing calcium hydroxide with a base before the step of dissolving the precipitated calcium hydroxide in water, according to the method described in

[15] .

[17] The method according to any one of

[14] to

[16] , further comprising the step of carbonating the concrete material before treating the concrete material with a base.

[18] The method according to any one of

[14] to

[17] , further comprising the step of supplying the filtrate filtered from the precipitated calcium hydroxide to a reaction vessel for the treatment with the base after the step of precipitating the calcium hydroxide.

[19] The method according to any one of

[14] to

[17] , further comprising the step of carbonating the filtrate filtered from the precipitated calcium hydroxide after the step of precipitating the calcium hydroxide.

[20] The method according to

[19] , further comprising the step of separating sodium carbonate from the carbonated filtrate after the step of carbonating the filtrate.

[21] The method according to

[19] , further comprising the step of separating a silicon oxide-containing gel from the carbonated filtrate after the step of carbonating the filtrate.

[22] The base is one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide, according to the method described in any one of

[14] to

[21] .

[23] The concentration of the base is 1 mol / L or more and 20 mol / L or less, according to the method described in any one of

[14] to

[22] .

[24] The base treatment is performed at a temperature of 10°C or more and less than 100°C, according to the method described in any one of

[14] to

[23] .

[25] The concrete material is a powder of concrete, according to the method described in any one of

[14] to

[24] .

[26] The concrete material is carbonated concrete, according to the method described in any one of

[14] to

[25] .

[27] A method for treating a concrete material, A method comprising the step of converting calcium carbonate contained in a concrete material into calcium hydroxide by treating the concrete material with a base.

[28] A method for immobilizing carbon dioxide, a step of carbonating a concrete material with carbon dioxide, a step of precipitating calcium hydroxide by treating the carbonated concrete material with a base, a step of carbonating the precipitated calcium hydroxide with carbon dioxide, and a method comprising the above steps.

Effect of the Invention

[0012] According to the present invention, a novel method for recovering calcium carbonate from a concrete material can be provided.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0014] Hereinafter, a calcium carbonate production system, a calcium carbonate production method, a sodium carbonate production method, a silicon oxide-containing gel production method, a concrete material treatment method, and a carbon dioxide fixation method according to embodiments will be described. Note that the following embodiments show one aspect of the present invention, do not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. In addition, each configuration and each feature of the embodiment can be arbitrarily combined. A numerical range represented by the description "lower limit value to upper limit value" includes the values at both ends and means "lower limit value or more and upper limit value or less" unless otherwise specified.

[0015] <1. Calcium Carbonate Production System and Production Method> A calcium carbonate production system according to an embodiment includes a base treatment device that precipitates calcium hydroxide by treating a concrete material with a base, and a calcium hydroxide carbonation device that produces calcium carbonate by carbonating calcium hydroxide.

[0016] A calcium carbonate production method according to an embodiment includes a step of precipitating calcium hydroxide by treating a concrete material with a base, and a step of producing calcium carbonate by carbonating the precipitated calcium hydroxide.

[0017] FIG. 1 is a schematic diagram of a calcium carbonate production system 1 according to an embodiment. The raw concrete material M is supplied to the base treatment device 10 for base treatment, then carbonated in the calcium hydroxide carbonation device 20, and finally converted into calcium carbonate.

[0018] General concrete is a mixture of cement, gravel, sand, and water and contains a large amount of calcium hydroxide. The calcium hydroxide in the concrete reacts with carbon dioxide in the air and gradually changes to calcium carbonate (neutralization). For this reason, generally, concrete contains the following components. · Calcium hydroxide Ca(OH)2 ·Calcium carbonate CaCO3 · Calcium silicate hydrate C-S-H (such as 3CaO·2SiO2·3H2O) · Calcium aluminate hydrate · Calcium sulfoaluminate hydrate · Other various cement hydrates

[0019] (Base treatment) By subjecting the concrete material M to base treatment in the base treatment apparatus 10, the calcium carbonate contained in the concrete material M reacts with the base. For example, when using high-concentration sodium hydroxide, as shown in the following reaction formula (1), precipitation of calcium hydroxide Ca(OH)2 occurs. CaCO3 + 2NaOH → Ca(OH)2 + Na2CO3…(1)

[0020] (Carbonation of calcium hydroxide) After converting calcium carbonate to calcium hydroxide in this way, it is separated from other components as necessary and supplied to the calcium hydroxide carbonation apparatus 20. In the calcium hydroxide carbonation apparatus 20, calcium hydroxide is carbonated, and as shown in the following reaction formula (2), precipitation of calcium carbonate Ca(OH)2 occurs. Ca(OH)2 + CO2 → CaCO3 + H2O …(2)

[0021] Thus, according to the calcium carbonate production apparatus 1, calcium carbonate can be recovered from the concrete material M using a strong base and carbon dioxide.

[0022] (Concrete carbonation) The concrete material M may be carbonated by the concrete carbonation device 30 before being supplied to the base treatment device 10. Alternatively, the concrete material M may be supplied in the form of the concrete material M that has been sufficiently carbonated from the beginning. By the carbonation treatment of the concrete carbonation device 30, calcium hydroxide and calcium silicate hydrate C-S-H contained in the concrete material M are converted into calcium carbonate. The former chemical reaction is the same as the above reaction formula (2). The latter chemical reaction is represented by, for example, the following reaction formula (3). 3CaO·2SiO2·3H2O+3CO2 → 3CaCO3+2SiO2(gel)+3H2O …(3)

[0023] Thereafter, through the above reactions (1) and (2) in the base treatment device 10 and the calcium hydroxide carbonation device 20, the calcium component derived from C-S-H can also be finally recovered as calcium carbonate. Therefore, when carbonating the concrete material M before the base treatment, the recovery rate of calcium carbonate from the concrete material M can be greatly improved.

[0024] (Water washing) After converting calcium carbonate to calcium hydroxide in the base treatment device 10, the concrete material M may be washed with water by the water washing device 40. Since calcium hydroxide dissolves in water to a certain extent, by washing the concrete material M with water, calcium hydroxide in the concrete material M can be efficiently separated from other solid components in the form of an aqueous calcium hydroxide solution. If the separated aqueous calcium hydroxide solution is subjected to a carbonation treatment in the calcium hydroxide carbonation device 20, high-purity calcium carbonate can be obtained.

[0025] Hereinafter, the configuration and processing method of a more specific manufacturing system will be described. As typical embodiments, the first embodiment shown in FIG. 2 and the second embodiment shown in FIG. 3 will be described, but the present invention is not limited to these embodiments. For example, in the following, it is described that each component is connected by piping and the product in a certain component is mechanically sent to the next component, but it is not always necessary for each component to be connected to each other. For example, even when the product in a certain component (for example, a reaction vessel) is put into the next component (for example, a reaction vessel) by hand, it can be said that each component constitutes a manufacturing system as a whole.

[0026] <1-1. First Embodiment> Hereinafter, the calcium carbonate manufacturing system 100 according to the first embodiment will be described. FIG. 2 is a configuration diagram of the calcium carbonate manufacturing system 100 according to the first embodiment.

[0027] <1-1-1. Configuration of the Calcium Carbonate Manufacturing System 100> As shown in FIG. 2, the calcium carbonate manufacturing system 100 according to the first embodiment includes a concrete supply source 50, a concrete carbonation device 30, a base treatment device 10, a first separation device 60, a circulation device 70, a water washing device 40, and a calcium hydroxide carbonation device 20. Hereinafter, each component will be described.

[0028] (Concrete Supply Source 50) The concrete supply source 50 supplies the raw concrete material M to the concrete carbonation device 30 through the concrete supply pipe 51. The concrete supply source 50 can supply, for example, a concrete material M that has been made into a form suitable for processing in the calcium carbonate manufacturing system 100 by a pretreatment device such as a pulverizing device, a particle size adjusting device, and a separating device (not shown).

[0029] (Concrete Carbonation Device 30) The concrete carbonation device 30 performs carbonation treatment on the concrete material M supplied from the concrete supply source 50. The concrete carbonation device 30 includes a reaction vessel 31, a carbon dioxide supply source 33, and a water supply source 36. The reaction vessel 31 is a vessel that functions as a reaction field for carbonating the concrete material M. The carbon dioxide supply source 33 supplies carbon dioxide to the reaction vessel 31. The water supply source 36 supplies water to the reaction vessel 31. The concrete supply pipe 51 supplies the concrete material M to the reaction vessel 31.

[0030] The carbon dioxide supply source 33 includes a carbon dioxide storage tank 34 and a carbon dioxide supply pipe 35. The carbon dioxide storage tank 34 stores carbon dioxide. The carbon dioxide is stored in any form such as gas, liquid, or solid. The carbon dioxide supply pipe 35 connects the carbon dioxide storage tank 34 and the reaction vessel 31. The carbon dioxide supply source 33 can adjust the supply amount and supply rate of carbon dioxide to the reaction vessel 31 by a flow regulator and a valve (not shown).

[0031] The water supply source 36 includes a water storage tank 37 and a water supply pipe 38. The water storage tank 37 stores water. The stored water may be pure water or an aqueous solution of a specific substance. The water supply pipe 38 connects the water storage tank 37 and the reaction vessel 31. The water supply source 36 sends water from the water storage tank 37 through the water supply pipe 38 to the reaction vessel 31 by a water supply pump (not shown). Note that the configurations of the carbon dioxide supply source 33 and the water supply source 36 are not limited to the above examples. For example, the carbon dioxide supply source 33 and the water supply source 36 may be provided as a single configuration. For example, the integrated carbon dioxide supply source 33 and water supply source 36 may supply water in which carbon dioxide is dissolved to the reaction vessel 31. Also, the carbon dioxide supply source 33 and the water supply source 36 may be supplied to the reaction vessel 31 after being once mixed upstream of the reaction vessel 31. The same applies to the concrete material M, and the timing of mixing these three components is not particularly limited.

[0032] The reaction vessel 31 causes the concrete material M and carbon dioxide to react in water. The reaction vessel 31 is provided with a stirring mechanism 32 for stirring the reaction solution. The stirring mechanism 32 may have any known configuration, such as a magnetic stir bar, a stirring blade connected to a motor, etc. In the reaction vessel 31, carbonation treatment of the concrete material M is performed, and calcium hydroxide and C-S-H contained in the concrete material M are converted into calcium carbonate.

[0033] The reaction vessel 31 is connected to the reaction vessel 11 of the base treatment device 10 via a pipe 39. The reaction product in the reaction vessel 31 is supplied from the reaction vessel 31 to the reaction vessel 11 through the pipe 39.

[0034] (Base treatment device 10) The base treatment device 10 performs base treatment on the carbonated concrete material M supplied from the concrete carbonation device 30. The base treatment device 10 includes a reaction vessel 11 and a base supply source 13. The reaction vessel 11 is a vessel that functions as a reaction field for the concrete material M and the base. The base supply source 13 supplies the base to the reaction vessel 11.

[0035] The base supply source 13 includes a base storage tank 14 and a base supply pipe 15. The base storage tank 14 stores the base. For example, the base storage tank 14 stores an aqueous base solution. The base is not particularly limited as long as it reacts with calcium carbonate to produce calcium hydroxide. The base may be an inorganic base or an organic base. For example, the base is one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide. The base supply pipe 15 connects the base storage tank 14 and the reaction vessel 11. The base supply source 13 sends the base from the base storage tank 14 through the base supply pipe 15 to the reaction vessel 11 by a pump (not shown). The base supply source 13 may mix and dilute the base in transit with a separate solvent. Note that the base supply source 13 may be provided with a base generation device (not shown) that generates the base. The base generation device is, for example, a device that generates a base from a salt by electrolysis. As an example, a device that generates a base by bipolar membrane electrodialysis can be mentioned.

[0036] The reaction vessel 11 reacts the concrete material M with a base. The reaction vessel 11 is provided with an arbitrary stirring mechanism 12, similar to the reaction vessel 31. In the reaction vessel 11, calcium carbonate in the concrete material M reacts with hydroxide ions and is converted into calcium hydroxide.

[0037] The reaction vessel 11 is connected to the first separation device 60 via a pipe 16. The reaction product in the reaction vessel 11 is supplied from the reaction vessel 11 to the first separation device 60 through the pipe 16.

[0038] (The first separation device 60) The first separation device 60 separates the reaction product obtained in the reaction vessel 11. For example, the first separation device 60 is a filtering device that filters the reaction product to separate the solid component and the filtrate. Specifically, the first separation device 60 separates the filtrate from the precipitate containing calcium hydroxide. Note that the first separation device 60 may be provided integrally with the reaction vessel 11.

[0039] The first separation device 60 includes a filter 61. The first separation device 60 is connected to the base supply source 13 or another base supply source (not shown) by a base supply pipe 62, and the filtered solid component can be washed with a base. Thereby, components soluble in the base can be removed. Specifically, when sodium hydroxide is used as the base, sodium carbonate Na2CO3, sodium silicate Na2SiO3, calcium silicate CaSiO3, etc. can be separated from the solid component as a filtrate in a state dissolved in the aqueous sodium hydroxide solution.

[0040] The filtered solid component is supplied from the first separation device 60 to the second separation device 41 of the water washing device 40 through a pipe 63. On the other hand, the filtrate is supplied from the first separation device 60 to the filtrate storage unit 71 through the first circulation supply pipe 72 of the circulation device 70.

[0041] (Circulation device 70) The circulation device 70 circulates the filtrate filtered by the first separation device 60 in the system and supplies it to the base treatment device 10 again. As a result, the base treatment of the unreacted calcium component in the filtrate can be performed, so that the recovery rate of the calcium component can be improved. In addition, the base component in the filtrate can also be reused for the base treatment of the base treatment device 10.

[0042] The circulation device 70 includes a filtrate storage unit 71, a first circulation supply pipe 72, and a second circulation supply pipe 73. The filtrate storage unit 71 is connected to the first separation device 60 via the filtrate storage unit 71 and is connected to the reaction vessel 11 via the second circulation supply pipe 73. The filtrate storage unit 71 temporarily stores the filtrate to be circulated. The circulation device 70 can supply the filtrate stored in the filtrate storage unit 71 to the reaction vessel 11 through the second circulation supply pipe 73 by a pump (not shown). The filtrate storage unit 71 may be omitted, and the filtrate from the first separation device 60 may be directly sent to the reaction vessel 11.

[0043] (Water washing device 40) The water washing device 40 washes the solid component filtered by the first separation device 60 with water. Specifically, the water washing device 40 can wash the precipitated calcium hydroxide with water. As a result, calcium hydroxide in the solid component can be eluted in water and efficiently separated from other solid components. That is, the water washing device 40 can separate the precipitated calcium hydroxide from other precipitates in the form of an aqueous calcium hydroxide solution. The water washing device 40 includes a second separation device 41 and a water supply source 43.

[0044] The second separation device 41 separates calcium hydroxide dissolved in water from other solid components. For example, the second separation device 41 is a filtering device that filters the reaction product to separate the solid component and the filtrate, similar to the first separation device 60. The second separation device 41 includes a filter 42.

[0045] The water supply source 43 includes a water storage tank 44 and a water supply pipe 45, similar to the water supply source 36 of the concrete carbonation device 30, and supplies water to the second separation device 41.

[0046] For example, in a state where the solid component filtered by the first separation device 60 is located on the filter 42, the water washing device 40 washes the solid component with water. Calcium hydroxide eluted in water passes through the filter 42, but other solid components insoluble in water cannot pass through the filter 42. As a result, the water washing device 40 can efficiently separate calcium hydroxide and other solid components. The remaining solid components can be a mixture of various silicates having base insolubility. The aqueous calcium hydroxide solution that has passed through the filter 42 is supplied to the calcium hydroxide carbonation device 20 through the pipe 46. Note that a base washing device (not shown) for washing the aqueous calcium hydroxide solution with a base may be provided between the filter 42 and the calcium hydroxide carbonation device 20. The base washing device can precipitate calcium hydroxide again by adding a base to the aqueous calcium hydroxide solution.

[0047] (Calcium Hydroxide Carbonation Device 20) The calcium hydroxide carbonation device 20 carbonates calcium hydroxide. Specifically, the calcium hydroxide carbonation device 20 performs a carbonation treatment on the aqueous calcium hydroxide solution supplied from the water washing device 40. The calcium hydroxide carbonation device 20 includes a reaction vessel 21 and a carbon dioxide supply source 23. The reaction vessel 21 is a vessel that functions as a reaction field for carbonating calcium hydroxide. The carbon dioxide supply source 23 supplies carbon dioxide to the reaction vessel 21. The calcium hydroxide carbonation device 20 may further include a water supply source as in the case of the concrete carbonation device 30, if necessary.

[0048] The carbon dioxide supply source 23 includes a carbon dioxide storage tank 24 and a carbon dioxide supply pipe 25. Since the configuration of the carbon dioxide supply source 23 is the same as that of the carbon dioxide supply source 33, it is omitted.

[0049] The reaction vessel 21 reacts an aqueous calcium hydroxide solution with carbon dioxide. The reaction vessel 21 is provided with an optional stirring mechanism 22, similar to the reaction vessel 31. In the reaction vessel 21, calcium hydroxide is carbonated and converted into calcium carbonate. By drying the calcium carbonate with a drying device (not shown), calcium carbonate powder is obtained.

[0050] <1-1-2. Method of Using the Calcium Carbonate Production System 100> Next, a method for producing calcium carbonate using the calcium carbonate production system 100 will be described. Note that points already described regarding the configuration of the system 100 will be omitted as appropriate.

[0051] The method for producing calcium carbonate using the calcium carbonate production system 100 may include the following steps. (S10) Concrete Material Supply Step (S11) Concrete Carbonation Step (S12) Base Treatment Step (S13) Separation Step (S14) Water Washing Step (S15) Calcium Hydroxide Carbonation Step

[0052] (Concrete Material Supply Step) In the concrete material supply step, the concrete supply source 50 supplies the concrete material M to the production system 100. The concrete material M is preferably concrete powder in terms of high reactivity and ease of uniform treatment throughout. The concrete material supply step can include a step of pulverizing the concrete material, a step of adjusting the particle size of the pulverized concrete material, a step of separating the concrete powder, and the like.

[0053] (Concrete Carbonation Step) In the concrete carbonation step, the concrete carbonation device 30 carbonates the concrete material M. The concrete carbonation step can include a step of carbonating the concrete material M by supplying carbon dioxide gas to the concrete material M. The mixing ratio of the concrete material M and water is, on a mass basis, for example, 1:2 to 1:50, preferably 1:5 to 1:20. Within the above range, the concrete material M can be well dispersed in water and become a reaction solution with a viscosity suitable for carbonation. The flow rate of the carbon dioxide gas is not particularly limited, but is, for example, 0.1 L / min to 10 L / min, preferably 1 L / min to 5 L / min. Within the above range, carbonation can be carried out efficiently.

[0054] (Base treatment step) In the base treatment step, the base treatment device 10 precipitates calcium hydroxide by treating the concrete material M with a base. The type of the base is as described above. The concentration of the base is, for example, 1 mol / L to 20 mol / L, preferably 2 mol / L to 15 mol / L, more preferably 5 mol / L to 12 mol / L, and still more preferably 8 mol / L to 10 mol / L. Within the above range, the reaction of converting calcium carbonate to calcium hydroxide can proceed sufficiently, and calcium hydroxide can be precipitated.

[0055] The mixing ratio of the concrete material M and the base is, on a mass basis, for example, 1:1 to 1:20, preferably 1:2 to 1:10. Within the above range, the reaction of converting calcium carbonate to calcium hydroxide can proceed sufficiently, and calcium hydroxide can be precipitated.

[0056] The base treatment can be carried out at a temperature of, for example, 10°C or higher and less than 100°C, 20°C or higher and 90°C or lower, or 40°C or higher and 80°C or lower. Within the above range, the reaction of converting calcium carbonate to calcium hydroxide can proceed sufficiently.

[0057] (Separation step) In the separation step, the first separator 60 separates the solid component containing calcium hydroxide and the liquid component. The separation step can include a step of filtering off the precipitate containing calcium hydroxide from the liquid component and a step of washing the precipitate containing calcium hydroxide with a base. The concentration of the base is, for example, 1 mol / L to 20 mol / L, preferably 2 mol / L to 15 mol / L, more preferably 5 mol / L to 12 mol / L, and even more preferably 8 mol / L to 10 mol / L. The mixing ratio of the precipitate to be washed and the base is, on a mass basis, for example, 1:1 to 1:20, preferably 1:2 to 1:10. Within the above range, the precipitate can be washed efficiently and sufficiently.

[0058] Regarding the filtrate filtered off from the precipitate containing calcium hydroxide, the circulation device 70 can supply it to the reaction vessel 11 of the base treatment device 10.

[0059] (Water washing step) In the water washing step, the water washing device 40 dissolves the precipitated calcium hydroxide in water. Specifically, the water washing device 40 can elute calcium hydroxide from the precipitate by washing the precipitate with water and separate it from the precipitate insoluble in water. The mixing ratio of the precipitate to be washed and water is, on a mass basis, for example, 1:100 to 1:5000, preferably 1:200 to 1:2000, more preferably 1:300 to 1:1000. Within the above range, calcium hydroxide can be efficiently separated from the precipitate.

[0060] (Calcium hydroxide carbonation step) In the calcium hydroxide carbonation step, the calcium hydroxide carbonation device 20 generates calcium carbonate by carbonating the calcium hydroxide separated in the water washing step. The calcium hydroxide carbonation step can include a step of carbonating calcium hydroxide by supplying carbon dioxide gas to the calcium hydroxide obtained in the water washing step, a step of filtering off the precipitated calcium carbonate, and a step of drying the filtered calcium carbonate. The flow rate of the carbon dioxide gas is not particularly limited and may be the same as in the concrete carbonation step.

[0061] Note that the above calcium hydroxide carbonation step may further include a step of precipitating calcium hydroxide by adding a base to the aqueous calcium hydroxide solution obtained in the water washing step before the step of carbonating calcium hydroxide. Thereby, the amount of calcium ions dissolved in the aqueous solution even after carbonation can be reduced, and the recovery rate of calcium carbonate can be improved.

[0062] According to the calcium carbonate production system 100 as described above, a novel method for producing calcium carbonate from the concrete material M by base treatment and carbonation treatment is realized. Since this method can use inexpensive sodium hydroxide and carbon dioxide as treatment agents (although not limited thereto), it is inexpensive and simple. Also, when converting calcium hydroxide to calcium carbonate with carbon dioxide, the carbon dioxide is immobilized in the form of calcium carbonate, so it is excellent from the perspective of global warming. The obtained calcium carbonate can be used for various applications such as raw materials for cement, fillers, paper, additives for rubber, and pigments.

[0063] When carbonating the concrete material M, not only the calcium hydroxide component contained in the concrete material M but also the C-S-H component can be converted to calcium carbonate. Therefore, most of the calcium component of the concrete material M can be recovered as calcium carbonate. Also, when using carbon dioxide for carbonation, the carbon dioxide can be immobilized in the form of calcium carbonate.

[0064] When separating calcium hydroxide from other residues by washing the precipitate after base treatment with water, only calcium hydroxide, which is a raw material for calcium carbonate, can be simply and efficiently separated from a mixture of calcium hydroxide and various silicates. Therefore, calcium carbonate of very high purity can be recovered as compared with the conventional method.

[0065] <1-2. Second Embodiment> Hereinafter, the calcium carbonate production system 200 according to the second embodiment will be described. Hereinafter, the differences from the first embodiment will be mainly described, and the description of the features common to the first embodiment will not be repeated. FIG. 3 is a configuration diagram of the calcium carbonate production system 200 according to the second embodiment.

[0066] <1-2-1. Configuration of Calcium Carbonate Production System 200> As shown in FIG. 3, the calcium carbonate production system 200 according to the second embodiment includes a concrete supply source 50, a concrete carbonation device 30, a base treatment device 10, a first separation device 60, a water washing device 40, a calcium hydroxide carbonation device 20, a filtrate carbonation device 80, and a filtrate separation device 90. Instead of the circulation device 70 of the first embodiment, a filtrate carbonation device 80 and a filtrate separation device 90 are added, and the functions and configurations of the other components are basically common to those of the first embodiment. Therefore, hereinafter, the filtrate carbonation device 80 and the filtrate separation device 90 will be mainly described.

[0067] (Filtrate Carbonation Device 80) The filtrate carbonation device 80 carbonates the filtrate separated from the solid components in the first separation device 60. Specifically, the filtrate carbonation device 80 causes the silicon-based component contained in the filtrate to react with carbon dioxide to precipitate a gel containing silicon dioxide.

[0068] For example, when using sodium hydroxide as the base, this filtrate is an aqueous sodium hydroxide solution in which sodium carbonate (Na2CO3), sodium silicate (Na2SiO3), calcium silicate (CaSiO3), etc. are dissolved. By performing carbonation treatment on this filtrate in water, it is considered that silicates such as sodium silicate and calcium silicate are converted into a gel rich in silicon oxide (for example, amorphous silicon oxide with a SiO2 composition) (hereinafter referred to as "silicon oxide-containing gel"). On the other hand, sodium carbonate remains dissolved in the supernatant liquid.

[0069] The filtrate carbonation device 80 includes a reaction vessel 81 and a carbon dioxide supply source 83. The reaction vessel 81 is a vessel that functions as a reaction site for carbonating the filtrate. The carbon dioxide supply source 83 supplies carbon dioxide to the reaction vessel 81. The filtrate carbonation device 80 may further include a water supply source as needed, similar to the concrete carbonation device 30.

[0070] The carbon dioxide supply source 83 includes a carbon dioxide storage tank 84 and a carbon dioxide supply pipe 85. Since the configuration of the carbon dioxide supply source 83 is the same as that of the carbon dioxide supply source 33, it will be omitted. The reaction vessel 81 reacts the filtrate with carbon dioxide. The reaction vessel 81 is provided with an arbitrary stirring mechanism 82, similar to the reaction vessel 31. The reaction vessel 81 is connected to the filtrate separation device 90 via a pipe 86. The reaction product in the reaction vessel 81 is supplied from the reaction vessel 81 to the filtrate separation device 90 through the pipe 86.

[0071] (Filtrate separation device 90) The filtrate separation device 90 separates the components of the reaction solution (i.e., the carbonated filtrate) supplied from the filtrate carbonation device 80. For example, the filtrate separation device 90 separates the reaction solution into a liquid component containing sodium carbonate and a solid component containing silicon oxide-containing gel. The filtrate separation device 90 includes a centrifuge 91 and a drying device 93. The centrifuge 91 is connected to the drying device 93 via a pipe 92. The centrifuge 91 separates the carbonated filtrate into a liquid component containing sodium carbonate and a solid component containing silicon oxide-containing gel by centrifuging. The liquid component is supplied to the drying device 93 and dried to be recovered as sodium carbonate powder. On the other hand, the centrifuged solid component is dried to be recovered as silicon oxide-containing gel. In this way, sodium carbonate and silicon oxide-containing gel are obtained. Note that the separation method of the filtrate separation device 90 is not limited to centrifugation, and any method capable of separating the liquid component and the solid component can be used.

[0072] <1-2-2. Method of Using the Calcium Carbonate Production System 200> Next, a method of producing calcium carbonate using the calcium carbonate production system 200 will be described. Note that the points already described regarding the configuration of the system 200 will be omitted as appropriate.

[0073] The method of producing calcium carbonate using the calcium carbonate production system 100 may include the following steps. Among these, (S20) to (S25) are the same as (S10) to (S15) of the first embodiment, so the filtrate carbonation step and the filtrate separation step will be described below. (S20) Concrete Material Supply Step (S21) Concrete Carbonation Step (S22) Base Treatment Step (S23) Separation Step (S24) Water Washing Step (S25) Calcium Hydroxide Carbonation Step (S26) Filtrate Carbonation Step (S27) Filtrate Separation Step

[0074] (Filtrate carbonation step) The filtrate carbonation step can be carried out independently of the water washing step and the calcium hydroxide carbonation step after the separation step. In the filtrate carbonation step, the filtrate carbonation device 80 carbonates the filtrate supplied from the first separation device 60. The filtrate carbonation step can include a step of generating silicon oxide-containing gel by supplying carbon dioxide gas to the filtrate obtained in the separation step.

[0075] The supply of carbon dioxide can be stopped when the pH of the reaction solution in the reaction vessel 81 decreases to a predetermined value. The predetermined value is, for example, pH 8 to pH 10, preferably pH 8.2 to pH 9, more preferably pH 8.3 to pH 8.7. The flow rate of the carbon dioxide gas is not particularly limited and may be the same as that in the concrete carbonation step or the calcium hydroxide carbonation step.

[0076] (Filtrate separation step) In the filtrate separation step, the filtrate separation device 90 separates the liquid component and the solid component of the carbonated filtrate. For example, when sodium hydroxide is used as the base, the filtrate separation device 90 separates the carbonated filtrate into a liquid component containing sodium carbonate and a solid component containing silicon oxide-containing gel. Thereby, the filtrate separation device 90 can separate sodium carbonate from the carbonated filtrate. Also, the filtrate separation device 90 can separate silicon oxide-containing gel from the carbonated filtrate. For example, the filtrate separation step can include a step of centrifuging the carbonated filtrate.

[0077] For example, the filtrate separation step can further include a step of drying each separated component. By drying the liquid component with the drying device 93, sodium carbonate powder is obtained. By drying the solid component, silicon oxide-containing gel is obtained. Note that instead of recovering sodium carbonate as a powder, the liquid component may be supplied again to the concrete carbonation device 30 or the base treatment device 10 and circulated.

[0078] According to the calcium carbonate production system 200 as described above, not only calcium carbonate but also sodium carbonate and silicon oxide-containing gel can be recovered. However, depending on the base used, sodium carbonate can be another carbonate. Thereby, carbon dioxide can be fixed as a carbonate.

[0079] <2. Method for Producing Sodium Carbonate> In the above-described second embodiment, sodium carbonate can be recovered from the filtrate. Therefore, it is possible to produce sodium carbonate by the production system 200. That is, a method for producing sodium carbonate according to one embodiment is a method for producing sodium carbonate using the above production system.

[0080] Specifically, the method can include a step of carbonating a filtrate after treating the concrete material M with sodium hydroxide, a step of separating a liquid component containing sodium carbonate from the carbonated filtrate, and a step of obtaining sodium carbonate powder by drying the liquid component.

[0081] According to the method for producing sodium carbonate as described above, carbon dioxide can be solidified in the form of sodium carbonate.

[0082] <3. Method for Producing Silicon Oxide-Containing Gel> In the above-described second embodiment, a silicon oxide-containing gel can be recovered from the filtrate. Therefore, it is possible to produce a silicon oxide-containing gel by the production system 200. That is, a method for producing a silicon oxide-containing gel according to one embodiment is a method for producing a silicon oxide-containing gel using the above production system.

[0083] Specifically, the method can include a step of carbonating a filtrate after treating the concrete material M with a base, and a step of obtaining a silicon oxide-containing gel by separating a solid component containing the silicon oxide-containing gel from the carbonated filtrate.

[0084] According to the method for producing a silicon oxide-containing gel as described above, a silicon oxide-containing gel can be obtained from the concrete material M. The silicon oxide-containing gel thus obtained can be a nanosized amorphous gel. This silicon oxide-containing gel can be used in various applications such as accelerating the hydration of cement, increasing the initial compressive strength of concrete, repairing cementitious materials, and removing heavy metal ions from wastewater.

[0085] <4. Method for treating concrete material> The method for treating a concrete material according to one embodiment includes a step of generating calcium hydroxide by treating calcium carbonate contained in the concrete material with a base.

[0086] The above treatment method corresponds to the base treatment step of the calcium carbonate production method described above. The advantage of this treatment method is that calcium carbonate, which is hardly soluble in water, can be converted into calcium hydroxide having some water solubility, making it easier to extract the subsequent calcium component. For example, when the above treatment method is performed on a mixture of calcium carbonate and other solid components that are hardly soluble in water (such as concrete), the calcium carbonate in the mixture is converted into calcium hydroxide, so that only calcium hydroxide can be eluted by washing with water and separated from other solid components. In this way, the calcium component can be easily extracted from the solid mixture containing calcium carbonate.

[0087] <5. Method for immobilizing carbon dioxide> The method for immobilizing carbon dioxide according to one embodiment includes a step of carbonating the concrete material with carbon dioxide, a step of precipitating calcium hydroxide by treating the carbonated concrete material with a base, and a step of carbonating the precipitated calcium hydroxide with carbon dioxide.

[0088] The above immobilization method regards the above-described calcium carbonate production method as an invention from the perspective of carbon dioxide immobilization. That is, in the above-described calcium carbonate production method, in the carbonation of the concrete material M by the concrete carbonation device 30 and the carbonation of calcium hydroxide by the calcium hydroxide carbonation device 20, carbon dioxide is consumed and can ultimately be immobilized in the form of calcium carbonate.

[0089] As described above, some embodiments of the present invention have been explained. However, these embodiments are presented as examples and do not limit the scope of the invention. These embodiments may be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention.

Examples

[0090] Hereinafter, the present invention will be described by experimental examples, but the present invention is not limited to the following experimental examples.

[0091] <Preparation of Concrete Powder> The raw material concrete used was prepared from ordinary Portland cement (density 434.5 kg / m 3 ), gravel (density 748.8 kg / m 3 ), and sand (density 1082.6 kg / m 3 ). The mass ratio of water to cement was 0.4. This concrete was pulverized, subjected to ball mill treatment, sieved through a 300 μm sieve, and then dispersed in distilled water. Next, in order to improve the reactivity in the carbonation treatment, fine concrete powder was separated from the cement paste by centrifugation at 4000 rpm for 10 minutes.

[0092] <Carbonation of Concrete Powder> 100 g of the concrete powder obtained by the above centrifugation was dispersed in 1 L of distilled water and stirred to obtain a uniform dispersion. Carbon dioxide gas (purity 99.9%) was introduced into this dispersion at a flow rate of 2 L / min for 3 hours to perform carbonation treatment on the concrete powder. The slurry after the carbonation treatment was recovered and dried at 105 °C for 24 hours.

[0093] <Base treatment of carbonated concrete powder> The carbonated concrete powder was dispersed in a high-concentration sodium hydroxide NaOH aqueous solution (9 mol / L). At this time, the mass ratio of the NaOH aqueous solution to the carbonated concrete powder was 5:1. Stirring was carried out at a reaction temperature of 50 °C for 2 hours to perform base treatment on the carbonated concrete powder. The precipitate after the reaction was recovered by vacuum filtration. In order to avoid carbonation of the obtained precipitate during drying, freeze-drying was carried out at -80 °C for 48 hours under a vacuum atmosphere using a freeze dryer (EYELA / FDU-2100, manufactured by Tokyo Rikakikai Co., Ltd.). In order to remove residual Na2SiO3, the obtained precipitate was washed with a 5 mol / L NaOH aqueous solution. Further, filtrate A separated from the precipitate by vacuum filtration and filtrate B after washing the precipitate with the NaOH aqueous solution were mixed to obtain filtrate C.

[0094] <Preparation of calcium hydroxide aqueous solution> Next, 0.155 g of the obtained precipitate was washed with 100 mL of distilled water to dissolve calcium hydroxide Ca(OH)2 in the precipitate and separate the Ca(OH)2 aqueous solution from other precipitates.

[0095] <Carbonation of calcium hydroxide> Sodium hydroxide was added to the obtained Ca(OH)2 aqueous solution until the pH reached 12.5, and calcium hydroxide was precipitated again. Carbon dioxide gas was introduced into the slurry containing this calcium hydroxide at a flow rate of 0.5 L / min to perform carbonation of calcium hydroxide. As a result, calcium carbonate precipitated. In order to prevent dissolution of calcium carbonate, the carbonation treatment was stopped when the pH decreased to 8.3. Thereafter, the obtained calcium carbonate precipitate was dried at 105 °C for 24 hours to obtain high-purity calcium carbonate powder.

[0096] <Carbonation of filtrate C> On the other hand, carbon dioxide gas was introduced into the filtrate C after the above-mentioned vacuum filtration and NaOH washing, and carbonation treatment was carried out. The carbonation treatment was stopped when the pH decreased to 9.8. As a result, SiO2-rich gel was precipitated, and a slurry containing SiO2-rich gel was obtained.

[0097] <Centrifugation of SiO2-rich gel> The obtained slurry was centrifuged at 4000 rpm for 5 minutes to separate the precipitate of SiO2-rich gel and the aqueous sodium carbonate solution. The precipitate of SiO2-rich gel was washed with distilled water and dried at 105 °C for 24 hours to obtain amorphous SiO2-rich gel. On the other hand, the aqueous sodium carbonate solution was dried to obtain sodium carbonate powder.

[0098] <Evaluation of calcium carbonate> Using a thermogravimetric-differential thermal analysis (TG-DTA) apparatus (STA 2500 Regulus, NETZSCH), the amount of calcium carbonate in the obtained calcium carbonate powder was evaluated. The purity of the obtained calcium carbonate powder was 98.54%. Also, the recovery rate of calcium carbonate calculated by dividing the mass of the obtained calcium carbonate by the mass of calcium carbonate in the raw concrete powder was 81.5%. In this experiment, 0.24 g of carbon dioxide was incorporated and immobilized per 1 g of the raw concrete powder. In addition, as described above, even if sodium hydroxide was added before the carbonation of calcium hydroxide and calcium hydroxide was not precipitated again, the aqueous calcium hydroxide solution could be carbonated, but in that case, the recovery rate of calcium carbonate was about 60%, which was lower than that in the above example where calcium hydroxide was reprecipitated.

[0099] The obtained calcium carbonate powder was observed with a scanning electron microscope (SEM, TM4000PlusII, Hitachi High-Tech Corporation). Figure 4 is an SEM image of the obtained calcium carbonate powder. The calcium carbonate particles had a rhombohedral shape and a narrow particle size distribution. The average particle size of the calcium carbonate particles was about 208 μm.

[0100] <Examination of Sodium Hydroxide Concentration and Reaction Temperature> Experiments were conducted under various conditions with the sodium hydroxide concentration set at 3 mol / L, 5 mol / L, 7 mol / L, or 9 mol / L and the reaction temperature set at 30 °C, 50 °C, 70 °C, or 90 °C. In all conditions, it was confirmed by X-ray diffraction (XRD) patterns that at least a part of the calcium carbonate was converted to calcium hydroxide and precipitated. In particular, when treated with 9 mol / L of sodium hydroxide, it was confirmed that almost all of the calcium carbonate was converted to calcium hydroxide. The amount of calcium hydroxide in the precipitate after the base treatment is summarized in Table 1 below.

[0101]

Table 1

Description of Symbols

[0102] 1, 100, 200... Calcium carbonate production system, 10... Base treatment device, 20... Calcium hydroxide carbonation device, 30... Concrete carbonation device, 40... Water washing device, 50... Concrete source, 60... First separation device, 70... Circulation device, 80... Filtrate carbonation device, 90... Filtrate separation device, M... Concrete material

Claims

1. A calcium carbonate production system, comprising: A base treatment device that precipitates calcium hydroxide by treating concrete materials with a base; A calcium hydroxide carbonation device that produces calcium carbonate by carbonating calcium hydroxide; A system comprising the above.

2. The system according to claim 1, further comprising a water washing device for washing the precipitated calcium hydroxide. The system according to claim 1.

3. The water washing device according to claim 2 separates the precipitated calcium hydroxide from other precipitates in the form of an aqueous calcium hydroxide solution. The system according to claim 2.

4. The system according to any one of claims 1 to 3, further comprising a concrete carbonation device for carbonating the concrete materials, wherein the base treatment device performs base treatment on the carbonated concrete materials. The system according to any one of claims 1 to 3.

5. The system according to any one of claims 1 to 3, further comprising a filtrate carbonation device for carbonating the filtrate separated from the precipitated calcium hydroxide. The system according to any one of claims 1 to 3.

6. The base is sodium hydroxide, and the system according to claim 5 further comprises a filtrate separation device for separating sodium carbonate from the carbonated filtrate. The system according to claim 5.

7. A method for producing sodium carbonate using the system according to claim 6.

8. The system according to claim 5, further comprising a filtrate separation device for precipitating a silicon oxide-containing gel from the carbonated filtrate. The system according to claim 5.

9. A method for producing a silicon oxide-containing gel using the system according to claim 8.

10. A method for producing calcium carbonate, comprising: Precipitating calcium hydroxide by treating concrete materials with a base; Producing calcium carbonate by carbonating the precipitated calcium hydroxide. A method comprising the above.

11. The step of producing calcium carbonate includes: Separating the precipitated calcium hydroxide from precipitates insoluble in water by dissolving it in water; Producing calcium carbonate by carbonating the separated calcium hydroxide. Including the above, The method according to claim 10.

12. The method according to any one of claims 10 or 11, further comprising a step of carbonating the concrete materials before treating the concrete materials with a base. The method according to any one of claims 10 or 11.

13. The concentration of the base is 1 mol / L or more and 20 mol / L or less. ​ ​ The method according to claim 10 or 11.

14. A method for treating a concrete material, comprising the step of converting calcium carbonate contained in the concrete material into calcium hydroxide by treating the concrete material with a base.

15. A method for immobilizing carbon dioxide, comprising the steps of carbonating a concrete material with carbon dioxide, precipitating calcium hydroxide by treating the carbonated concrete material with a base, and carbonating the precipitated calcium hydroxide with carbon dioxide. ​

Images