Method and apparatus for immobilizing carbon dioxide

Abstract

To improve a fixing rate of carbon dioxide in a fixing technique of carbon dioxide using crushed waste concrete.SOLUTION: The crushed matter of waste concrete is housed in a treatment container 1 and the pressure in the treatment container 1 is reduced by a pressure reducing means 2 and, thereafter, carbon dioxide-containing gas is injected into the treatment container 1 under pressure by a gas injection means 3 to fix carbon dioxide in the carbon dioxide-containing gas to the crushed matter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for immobilizing carbon dioxide using crushed waste concrete. [Background technology]

[0002] To achieve carbon neutrality, it is strongly required to reduce carbon dioxide emissions from economic activities and daily life, and to fix the carbon dioxide that cannot be reduced so that it is not released into the atmosphere. One known carbon dioxide fixation technology is one that uses crushed waste concrete (for example, Patent Documents 1-3 and Non-Patent Document 1). That is, carbon dioxide fixation technology that uses crushed waste concrete is a technology that fixes carbon dioxide through the carbonation reaction (Ca(OH)2 + CO2 = CaCO3 + HO) of cement hydration products (Ca(OH)2) contained in the waste concrete.

[0003] However, concrete is a relatively dense material, and so internal diffusion of carbon dioxide is not easy. Therefore, conventional carbon dioxide fixation technologies cannot be said to achieve a sufficiently high carbon dioxide fixation rate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-28581 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-90198 [Patent Document 3] Japanese Patent Publication No. 2023-118125 [Non-patent literature]

[0005] [Non-Patent Document 1] Mai Nanao, Takato Nozaki, Tsutomu Wang, Takafumi Noguchi: CO2 fixation in waste concrete by thermal carbonation treatment using separated and recovered CO2 from cement kiln exhaust gas, Journal of Cement and Concrete, Vol. 76, pp. 512-520, 2022 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to improve the carbon dioxide fixation rate in a carbon dioxide fixation technology using crushed waste concrete. [Means for solving the problem]

[0007] As described above, the carbon dioxide fixation technology using crushed waste concrete utilizes the carbonation reaction of cement hydration products contained in the crushed waste concrete, i.e., the reaction of producing calcium carbonate. Based on the technical idea that increasing the contact between the interior of the crushed waste concrete and carbon dioxide will promote the reaction of producing calcium carbonate and improve the carbon dioxide fixation rate, the inventors of the present invention have intensively studied specific techniques for this purpose and discovered that the reduced pressure / pressure injection method, i.e., reducing the pressure in a treatment vessel containing crushed waste concrete and then injecting a carbon dioxide-containing gas into the treatment vessel under pressure, is effective, which led to the completion of the present invention.

[0008] That is, according to one aspect of the present invention, there is provided the following method for immobilizing carbon dioxide. A first step of placing crushed waste concrete in a treatment container; a second step of depressurizing the processing vessel; a third step of injecting a carbon dioxide-containing gas under pressure into the treatment vessel; a fourth step of immobilizing carbon dioxide in the carbon dioxide-containing gas on the crushed material; A method for fixing carbon dioxide, comprising the steps of:

[0009] According to another aspect of the present invention, there is provided the following carbon dioxide fixation device. A carbon dioxide fixation device for fixating carbon dioxide in crushed waste concrete, a processing vessel for accommodating crushed waste concrete; a pressure reducing means for reducing the pressure in the processing vessel; a gas injection means for injecting a carbon dioxide-containing gas under pressure into the treatment vessel; A carbon dioxide fixation device comprising: [Effects of the Invention]

[0010] According to the present invention, the use of the vacuum / pressure injection method as a carbon dioxide fixation technology increases the contact between the interior of the crushed waste concrete and carbon dioxide, accelerating the reaction to produce calcium carbonate. As a result, the carbon dioxide fixation rate (hereinafter referred to as "CO2 fixation rate") is improved. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram conceptually illustrating the configuration of a carbon dioxide fixation device according to one embodiment of the present invention. [Figure 2] Graph showing the effect of initial water content on CO2 fixation rate. [Figure 3] Graph showing the effect of vacuum level on CO2 fixation rate. [Figure 4] Graph showing the effect of atmospheric pressure of carbon dioxide-containing gas on CO2 fixation rate. [Figure 5] Graph showing the effect of treatment time on CO2 fixation rate. [Figure 6] Graph showing the effect of environmental temperature on CO2 fixation rate. [Figure 7] A graph showing the difference in CO2 fixation rate depending on the treatment method. [Figure 8] Graph showing the change in density before and after treatment. [Figure 9] Graph showing the difference in particle size distribution depending on the processing method. [Figure 10] Photographs showing the appearance of samples treated with different methods. [Figure 11] X-ray diffraction analysis results of samples treated with different methods. [Figure 12] FIG. 1 is a diagram conceptually showing the configuration of a carbon dioxide fixation device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described based on the results of experiments carried out by the present inventors. 1. Overview of carbon dioxide fixation method and fixation device 1.1 Configuration of the carbon dioxide fixation device Fig. 1 conceptually shows the configuration of a carbon dioxide fixation apparatus (hereinafter simply referred to as "fixation apparatus") according to one embodiment of the present invention. The fixation apparatus basically comprises a treatment vessel 1 that accommodates crushed waste concrete material (hereinafter simply referred to as "crushed material") A, a vacuum pump 2 that is a pressure reducing means for reducing the pressure in the treatment vessel 1, and a gas injection means 3 that pressurizes and injects a carbon dioxide-containing gas into the treatment vessel 1. Additional components include a temperature-controlled constant-temperature water circulator 4, a thermo-hygrometer 5, a vacuum gauge 6, a pressure gauge 7, etc.

[0013] The treatment vessel 1 is a steel pressure-resistant vessel with an inner diameter of 208 mm and a depth of 300 mm. It can withstand a maximum pressure of 1 MPa, but pressures above 0.7 MPa are exhausted through a safety valve 13. The lid 12 of the vessel body 11 is fastened with 12 bolts, and a rubber gasket (not shown) is sandwiched between the vessel body 11 and the lid 12 to seal the vessel. A thermo-hygrometer 5, a vacuum gauge 6, and a pressure gauge 7 are fixed to the lid 12 and inserted into the treatment vessel 1. The treatment vessel 1 is connected to a vacuum pump 2 and a carbon dioxide gas cylinder 8 or a dual-use gas pump 10. In this experiment, the carbon dioxide gas cylinder 8 was used as a carbon dioxide-containing gas supply source for convenience. To control the internal temperature of the treatment vessel 1, a circular water tank 41 with a diameter of 300 mm and a depth of 300 mm is installed outside the vessel body 11 and connected to a temperature-controlled constant-temperature water circulator 4.

[0014] Appropriate humidity is required for the carbonation reaction of the cement hydration product (Ca(OH)2) contained in crushed material A. Therefore, in order to humidify the carbon dioxide-containing gas and adjust its humidity, the carbon dioxide-containing gas is passed through a humidification container 31 (inner diameter 55 mm x depth 200 mm, pressure resistance 1.0 MPa) that holds water so that the carbon dioxide-containing gas can be injected into the treatment container 1. Specifically, to humidify the carbon dioxide-containing gas, a sheet heater 311 is wrapped around the outside of the humidification container 31, and the heating temperature can be set up to 80°C. To ensure pressure resistance and prevent gas leakage, the lid 32 of the humidification container 31 is also fastened with bolts (not shown). On the other hand, dry crushing is generally used at manufacturing sites for crushed waste concrete with a particle size of 40 mm or less. When shipping the crushed material, the moisture content of the crushed material is adjusted to approximately 8 to 13% in consideration of workability on site. Therefore, in this experiment, the humidification container 31 was not used, and the moisture content of the crushed material was adjusted in advance to ensure an appropriate humidity.

[0015] As described above, in this experiment, a carbon dioxide gas cylinder 8 was used as the supply source of the carbon dioxide-containing gas. Specifically, a carbon dioxide gas cylinder 8 with a maximum discharge pressure of 0.7 MPa was used, and the discharge pressure of the carbon dioxide gas was adjusted using the cylinder's pressure regulator 81. Note that combustion exhaust gas is typically used as the actual carbon dioxide-containing gas. In this case, the combustion exhaust gas is pressurized and injected into the treatment vessel via a dual-purpose gas pump (suction / pressurized discharge) 10. In addition to combustion exhaust gas, atmospheric air can also be used as the carbon dioxide-containing gas, and carbon dioxide-containing gas filled in a separately supplied cylinder or the like can also be used. When humidifying these carbon dioxide-containing gases, valve 33A shown in FIG. 1 is closed and valve 33B is opened. The lid 12 of the treatment vessel 1, which is equipped with hoses and instruments, is heavy, so the current system uses a hand-operated pulley 9 to open and close it, but other automatic lid opening and closing devices can also be used. An outlet for the treated crushed material can also be provided at the bottom of the treatment vessel 1.

[0016] 1.2 Carbon dioxide fixation process (1) First step (1-1) The moisture content of the crushed material A is measured, and the moisture content is adjusted by drying or humidifying (adding water) to a predetermined value. (1-2) The crushed material A whose moisture content has been adjusted is placed in the treatment vessel 1. Thereafter, the lid 12 is closed, and the valves 33A and 33B, the valve of the exhaust port 14 (not shown), and the valve of the pressure gauge 7 (not shown) are closed.

[0017] (2) Second step The vacuum pump 2 is turned on to begin depressurizing the processing vessel 1. The pressure is continued to be reduced to a predetermined vacuum level while checking the vacuum gauge 6. After that, the vacuum pump 2 is turned off and the valve 21 attached to the hose of the vacuum pump 2 is closed.

[0018] (3) The third step The valve of the pressure gauge 7 and the valve 33A of the hose connecting the carbon dioxide gas cylinder 8 to the treatment vessel 1 are opened (if passing through the humidification vessel 31, valve 33B is opened and valve 33A is closed as described above), the carbon dioxide gas discharge pressure is set using the pressure regulator 81 of the carbon dioxide gas cylinder 8, and the carbon dioxide gas (carbon dioxide-containing gas) is pressurized and injected into the treatment vessel 1. At this time, the actual pressure inside the treatment vessel 1 is confirmed using the pressure gauge 7.

[0019] (4) The fourth step When the pressure inside the processing vessel 1 reaches a predetermined value (the set value of the pressure regulator 81), the valve 33A or 33B and the main valve (not shown) of the carbon dioxide gas cylinder 8 are left open to maintain the pressure until the scheduled processing time, allowing the carbon dioxide in the carbon dioxide-containing gas to continue reacting with the crushed material A.

[0020] After the above steps (hereinafter simply referred to as "treatment") are completed, the main valve of the carbon dioxide gas cylinder 8 is closed, the exhaust port 14 is opened, the pressure in the treatment vessel 1 is released, and the lid 12 is opened to remove the crushed material A. The CO2 fixation rate of the removed crushed material A is measured, and other characteristics are evaluated.

[0021] 2. Experimental Overview 2.1 Crushed material used in the experiment In this experiment, crushed waste concrete with a particle size of 5 mm or less (hereinafter referred to as "recycled fine aggregate") was used as crushed material A. The changes in density, particle size distribution, and chemical composition of the recycled fine aggregate before and after treatment will be described later, along with the measurement results of the CO2 fixation rate after treatment. 2.2 Processing conditions In this experiment, the CO2 fixation rate and its influencing factors were examined under the treatment conditions shown in Table 1. The assumed influencing factors were the initial moisture content, degree of vacuum, air pressure, treatment time, and environmental temperature. Specifically, the levels of each factor were set as shown in Table 1.

[0022] [Table 1]

[0023] 2.3 Test items and methods (1) Measurement of CO2 fixation rate In this experiment, the CO2 fixation rate was measured using the electric furnace analysis method. The procedure involves taking a sample of 30g or more from the treated recycled fine aggregate, drying it, and then measuring its initial mass (m0) and placing it in a heat-resistant container. The sample is then transferred to an electric furnace, heated to 550°C over one hour, and maintained at 550°C for another hour. The heating is then stopped, and the sample is allowed to cool to room temperature while still in the furnace, and its mass (m1) is measured after cooling. The sample heated to 550°C is then transferred back to the electric furnace, heated to 800°C over one hour, maintained at 800°C for one hour, and its mass (m2) is measured after cooling. The CO2 fixation rate is calculated using equation (1). CO2 fixation rate (%)=(m2-m1) / m0×100 (1) The temperature at which CaCO3 begins to decompose varies depending on the sample, but recent research results (Ishiseki Yoshikazu, Sakurai Kuniaki: The effect of differential thermal analysis methods on the calculated amount of CO2 fixed in cement paste, Concrete Engineering Annual Proceedings, Vol. 45, No. 1, pp. 1072-1077, 2023) show that if the starting temperature is set at 550°C, the accuracy of the CO2 fixation rate measurement results will be relatively high.

[0024] (2) Measurement of density and water absorption The density of the recycled fine aggregate before and after treatment was measured according to the standard test method for density of fine aggregate (JIS A1109).

[0025] (3) Particle size The particle size of the recycled fine aggregate was measured before and after processing. The samples were sieved through sieves and trays of 5mm, 2.5mm, 1.2mm, 0.6mm, 0.3mm, 0.15mm, and 0.075mm from top to bottom, and the mass retained on each sieve and tray was measured. A particle size curve was created from the measurement results.

[0026] (4)Chemical composition The chemical composition of the recycled fine aggregate before and after treatment was investigated using X-ray fluorescence analysis (XRF) and X-ray diffraction analysis (XRD). The XRD measurement conditions were: scan angle 5° to 60°, tube voltage current 40kV / 30mA, sampling width 0.02°, and scan speed 2° / s.

[0027] 3. Experimental results and discussion 3.1 Effects of processing conditions (1) Effect of initial water content on CO2 fixation rate Figure 2 shows the effect of initial moisture content on the CO2 fixation rate. The CO2 fixation rate increases with increasing initial moisture content, but a tendency for it to decrease once the moisture content exceeds 14% is observed. This is thought to be because if the moisture content of the sample is insufficient, the carbonation reaction is unlikely to occur, but if the moisture content within the sample becomes excessive, the moisture in the gaps inhibits the internal diffusion of carbon dioxide. Based on these results, we have determined that the optimal moisture content is 14%.

[0028] (2) Effect of vacuum level on CO2 fixation rate Figure 3 shows the effect of vacuum level on CO2 fixation rate. At a vacuum level of 500 Pa, CO2 fixation rate was at its highest. Below 500 Pa, the higher the vacuum level (lower air pressure), the lower the CO2 fixation rate. Furthermore, above 500 Pa, the CO2 fixation rate decreased as the vacuum level decreased (increased air pressure). As the vacuum level increased, more air was removed from the sample, making it easier for carbon dioxide to enter, and the CO2 fixation rate increased. However, it is thought that the water content decreased too much as the vacuum level increased, which reduced the carbonation reaction.

[0029] (3) Effect of atmospheric pressure of carbon dioxide-containing gas on CO2 fixation rate Figure 4 shows the effect of the atmospheric pressure of the carbon dioxide-containing gas on the CO2 fixation rate. Figure 4 shows that the higher the atmospheric pressure, the higher the CO2 fixation rate. The two are roughly proportional. However, since energy is required to pressurize the carbon dioxide-containing gas, it is best to treat it at an appropriate pressure. The atmospheric pressure should be determined by comprehensively evaluating the CO2 emissions due to the power consumption for pressurization and the amount of CO2 fixation.

[0030] (4) Effect of treatment time on CO2 fixation rate The effect of treatment time on the CO2 fixation rate is shown in Figure 5. The CO2 fixation rate increases rapidly up to 3 hours of treatment, but the increase in CO2 fixation rate tends to slow down after 3 hours. Considering treatment efficiency, the optimal treatment time was set at 2 to 3 hours.

[0031] (5) Effect of ambient temperature on CO2 fixation rate The effect of environmental temperature on the CO2 fixation rate is shown in Figure 6. The CO2 fixation rate was almost the same within the range of environmental temperatures from 5 to 40°C, and no effect of environmental temperature was observed.

[0032] (6) Differences in CO2 fixation rate depending on treatment method Based on the results of the above-mentioned investigation of processing conditions, as an example of the present invention, crushed material A (recycled fine aggregate) was processed under the following conditions: initial moisture content: 14%, vacuum: 500 Pa, atmospheric pressure: 0.5 MPa, ambient temperature: 20°C, and processing time: 3 hours. The CO2 fixation rate was measured (denoted as "vacuum and pressure" in the drawings). Additionally, as comparative examples, the CO2 fixation rates of an untreated (before treatment) sample (denoted as "untreated" in the drawings) and a sample processed at atmospheric pressure for 24 hours (denoted as "no vacuum and pressure" in the drawings) were also measured. The results are shown in Figure 7. The CO2 fixation rate for the "vacuum and pressure" method was 5.06%, demonstrating a higher rate than the other processing methods. Specifically, the CO2 fixation rate for concrete using the "vacuum and pressure" method was 50.6 kg / t-concrete. This CO2 fixation rate, converted to the CO2 fixation rate for cement, is approximately 120 kg / t-cement. This significantly exceeds the CO2 fixation rate (75 kg / t-cement) reported in the aforementioned Non-Patent Document 1. Furthermore, the fixation of CO2 without treatment is attributed to natural neutralization reactions (carbonation reactions) during the service life of the concrete.

[0033] 3.2 Changes in physical properties and chemical composition of treated recycled fine aggregate (1) Density Figure 8 shows the bone dry density of recycled fine aggregate before and after treatment. The three results are the measurements of the "untreated", "unvacuumed and unpressurized", and "vacuumed and pressurized" samples, respectively. Figure 8 shows that the "vacuumed and pressurized" sample had the highest density. This is thought to be because the "vacuumed and pressurized" sample had a high CO2 fixation rate, resulting in the production of a large amount of CaCO3.

[0034] (2) Particle size distribution The particle size distribution of the recycled fine aggregate before and after processing is shown in Figure 9, and the state is shown in Figure 10. It was found that the particle size became coarser after processing. This is thought to be because the CaCO3 generated in the sample connects the fine particles.

[0035] (3)Chemical composition The results of the XRD and XRF analyses of the three samples are shown in Figure 11 and Table 2, respectively. In Figure 11, the bottom row is the "untreated" sample, the middle row is the "non-vacuum, non-pressurized" sample, and the top row is the "vacuum and pressurized" sample. Figure 11 shows that Ca(OH)2 decreased and CaCO3 increased after treatment. Table 2 also shows that the CO2 analysis value increased by 7.2% in the "vacuum and pressurized" sample compared to the "non-treated" sample. Furthermore, the CO2 component of the "vacuum and pressurized" sample increased compared to the "non-vacuum, non-pressurized" sample.

[0036] [Table 2]

[0037] From the above, it can be said that the carbon dioxide fixation method and fixation device of the present invention can promote the fixation of carbon dioxide in crushed waste concrete.

[0038] 4. Summary of this study In this study, we investigated carbon dioxide fixation technology using crushed waste concrete, developed a treatment device, and examined fixation conditions, i.e., treatment conditions and changes in physical properties and chemical composition after treatment. The following findings were obtained. (1) The treatment method and treatment device of the present invention can promote the fixation of carbon dioxide in crushed waste concrete. Under the treatment conditions of this experiment (initial moisture content 14%, vacuum degree 500 Pa, atmospheric pressure 0.5 MPa, ambient temperature 20°C, treatment time 3 hours), the CO2 fixation rate was approximately 5%. (2) The CO2 fixation rate is highest when the initial moisture content of crushed material A is 14%. Also, under the conditions of the apparatus of the present invention, the CO2 fixation rate is highest when the degree of vacuum is 500 Pa. (3) The higher the atmospheric pressure of the carbon dioxide-containing gas or the longer the treatment time, the higher the CO2 fixation rate. The relationship between atmospheric pressure and CO2 fixation rate is almost proportional, but when the treatment time exceeds 2 to 3 hours, the increase in CO2 fixation rate becomes gradual. (4) After processing, the density of the recycled fine aggregate increases and the particle size becomes coarser. (5) The chemical composition of the crushed material after treatment showed a decrease in Ca(OH)2 and an increase in CaCO3, confirming the CO2 fixation effect.

[0039] In this experiment, particles with a particle size of 5 mm or less were used as crushed waste concrete, but the particle size of the crushed material is not limited to 5 mm or less; for example, crushed waste concrete with a particle size of 40 mm or less can also be used.

[0040] In this experiment, manual valves 21, 33A, and 33B were installed as switching means for switching between the depressurization operation of the processing vessel 1 by the vacuum pump 2 and the pressurized injection operation of the carbon dioxide-containing gas into the processing vessel 1 by the gas injection means 3. However, these valves can also be replaced with automatic valves and a controller that controls the operation of the valves can be installed to provide switching means that automatically switches between the depressurization operation of the processing vessel 1 by the vacuum pump 2 and the pressurized injection operation of the carbon dioxide-containing gas into the processing vessel 1 by the gas injection means 3.

[0041] In this experiment, the carbon dioxide-containing gas was humidified by passing it through the humidification container 31, but the method of humidification is not limited to this, and for example, the carbon dioxide-containing gas can also be humidified by mixing water vapor into it. Also, the treatment container 1 can be humidified by introducing water vapor directly into the treatment container 1. Furthermore, as described above, the crushed waste concrete can also be humidified by adding water as appropriate before the crushed waste concrete is placed in the treatment container, for example, at the stage of crushing the waste concrete.

[0042] In this experiment, the residual gas remaining in the treatment vessel 1 after treatment was simply discharged from the exhaust port 14, but since this residual gas contains unreacted carbon dioxide, the carbon dioxide in this residual gas can also be fixed in other crushed waste concrete. For example, as conceptually shown in Figure 12, the residual gas can be discharged from the treatment vessel 1 using a dual-purpose gas pump 10 or the like, and then injected under pressure into a treatment vessel 1' that has been depressurized with a vacuum pump, and the carbon dioxide in the residual gas can be fixed in untreated crushed material A' charged into the treatment vessel 1'. The residual gas can also be used in other carbon dioxide recycling processes. [Explanation of symbols]

[0043] A, A' crushed material 1, 1' Processing container 11 Container body 12 Lid 13 Safety valve 14 Exhaust port 2. Vacuum pump (pressure reducing means) 21 Valve 3 Gas injection means 31 Humidification container 311 Seat heater 32 Lid 33A, 33B valves 4 Constant temperature water circulation device 41 Circular Aquarium 5 Thermohygrometer 6 Vacuum gauge 7. Pressure gauge 8 Carbon Dioxide Gas Cylinders 9 Pulley 10. Dual-use gas pump

Claims

1. A first step of placing crushed waste concrete in a treatment container; a second step of depressurizing the processing vessel; a third step of injecting a carbon dioxide-containing gas under pressure into the treatment vessel; a fourth step of immobilizing carbon dioxide in the carbon dioxide-containing gas on the crushed material; A method for fixing carbon dioxide, comprising the steps of:

2. 2. The method for fixation of carbon dioxide according to claim 1, wherein crushed waste concrete having a particle size of 40 mm or less is accommodated in the first step.

3. 2. The method for fixation of carbon dioxide according to claim 1, wherein the second step reduces the pressure in the treatment vessel to a degree of vacuum of 500 Pa or less.

4. 2. The method for fixation of carbon dioxide according to claim 1, wherein in the first step, the crushed material is humidified before being placed in a treatment vessel, or in the third step, the carbon dioxide-containing gas or the treatment vessel is humidified when the carbon dioxide-containing gas is pressurized and injected into the treatment vessel.

5. 2. The method for fixation of carbon dioxide according to claim 1, further comprising the step of discharging the residual gas remaining in the treatment vessel from the treatment vessel after completion of the fourth step, and fixating the carbon dioxide in the residual gas in other crushed waste concrete or another carbon dioxide recycling step.

6. A carbon dioxide fixation device for fixating carbon dioxide in crushed waste concrete, a processing vessel for accommodating crushed waste concrete; a pressure reducing means for reducing the pressure in the processing vessel; a gas injection means for injecting a carbon dioxide-containing gas under pressure into the treatment vessel; A carbon dioxide fixation device comprising:

7. 7. The carbon dioxide fixation device according to claim 6, further comprising a switching means for switching between a depressurization operation of the treatment vessel by the depressurization means and an operation of pressurizing and injecting a carbon dioxide-containing gas into the treatment vessel by the gas injection means.

8. 8. The carbon dioxide fixation apparatus according to claim 6, wherein the gas injection means has a function of humidifying the carbon dioxide-containing gas or the treatment vessel.

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