Carbon dioxide immobilization unit and carbon dioxide immobilization method using the same

Abstract

To provide a carbon dioxide immobilization apparatus capable of highly efficiently immobilizing carbon dioxide to a granular material having a wide range of particle size. And the like.SOLUTION: The carbon dioxide immobilization unit 100 includes a first curing tank 10, a second curing tank 20, a classifying unit 30 that classifies a granular material P made of a cement cured material into coarse-grained P1 and fine-grained P2, supplies the coarse-grained P1 to the first curing tank 10, and supplies the fine-grained P2 to the second curing tank 20, a gas supplying unit 40 that supplies a carbon dioxide-containing gas G to each of the first and second curing tanks 1020 and, a first immobilization amount measuring unit 50 that measures an immobilization amount of carbon dioxide immobilized in the coarse-grained P1 discharged from the first curing tank 10, and a first resupplying unit 70 that resupplies the coarse-grained P1 discharged from the first curing tank 10 to the first curing tank 10 when a measured value measured by the first immobilization amount measuring unit 50 is less than a predetermined first value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] One known technology for reducing the atmospheric emissions of carbon dioxide (CO2), a greenhouse gas, is to fix the carbon dioxide contained in the exhaust gas from industrial furnaces in cementitious hardened materials such as waste concrete and cement.

[0003] One such technique that has been developed is one in which carbon dioxide is efficiently fixed by bringing a powdery or granular material made of a cementitious hardened body into contact with a carbon dioxide-containing gas at 75°C to 110°C to carbonate it. For example, Patent Document 1 discloses that carbon dioxide is efficiently fixed by adjusting the relative humidity in a reactor depending on the particle size of the powdery or granular material and the adjustment status of the moisture content of the powdery or granular material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-131076 Summary of the Invention

[0005] However, since the efficiency of carbon dioxide fixation varies depending on the particle size of the powder or granular material, when carbon dioxide fixation is performed on powder or granular materials having a wide range of particle sizes, a long treatment time is required to fix a sufficient amount of carbon dioxide even in powder or granular materials with large particle sizes. If the treatment time is short, a sufficient amount will not be fixed in powder or granular materials with large particle sizes, and the carbon dioxide reduction effect will be small. [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a carbon dioxide fixation device capable of highly efficiently fixating carbon dioxide in powdered or granular materials having a wide range of particle sizes, and a carbon dioxide fixation method using the same. [Means for solving the problem]

[0007] The carbon dioxide fixation device of the present invention is characterized by comprising: a first curing tank; a second curing tank; a classification means for classifying a powder or granular material made of a hardened cement body into coarse particles made of powder or granular material having a large average particle size and fine particles made of powder or granular material having a small average particle size, and supplying the coarse particles to the first curing tank and the fine particles to the second curing tank; a gas supply means for supplying a carbon dioxide-containing gas to each of the first curing tank and the second curing tank; a first fixation amount measurement means for measuring the amount of fixation of carbon dioxide fixed in the coarse particles discharged from the first curing tank; and a first re-supply means for re-supplying the coarse particles discharged from the first curing tank to the first curing tank if the amount of fixation of carbon dioxide measured by the first fixation amount measurement means is less than a predetermined first value.

[0008] According to the carbon dioxide fixation apparatus of the present invention, a powdery or granular material made of a hardened cement paste is classified into coarse particles and fine particles by a classification means. The coarse particles are contacted with a carbon dioxide-containing gas in a first curing tank, and the fine particles are contacted with a carbon dioxide-containing gas in a second curing tank, respectively, to fix the carbon dioxide. For coarse particles that take a long time to fix carbon dioxide, if the amount of fixed carbon dioxide is less than a first value when discharged from the first curing tank, the coarse particles are resupplied to the first curing tank for further carbon dioxide fixation. This ensures that coarse particles with a fixed amount of carbon dioxide equal to or greater than the first value are obtained. Furthermore, even when the particle size of the powdery or granular material ranges over a wide range, the coarse particles and fine particles are classified and the carbon dioxide fixation process is performed for each particle, making it possible to perform each fixation process in an environment and / or for a time suitable for highly efficient fixation.

[0009] It is preferable that the carbon dioxide fixation apparatus of the present invention further comprises a second fixation amount measurement means for measuring the amount of carbon dioxide fixed in the fine granules discharged from the second curing tank, and a second re-supply means for re-supplying the fine granules discharged from the second curing tank to the second curing tank when the amount of carbon dioxide fixation measured by the second fixation amount measurement means is less than a predetermined second value.

[0010] In this case, if the amount of carbon dioxide fixed in the fine granules discharged from the second curing tank is less than the second value, the fine granules are supplied to the second curing tank again for further carbon dioxide fixation treatment. This ensures that fine granules with an amount of carbon dioxide fixed that is equal to or greater than the second value are obtained. Note that the first value and the second value may be the same or different.

[0011] Furthermore, in the carbon dioxide fixation apparatus of the present invention, it is preferable that the classification means supplies the coarse particles from an upper portion of the first curing tank into the interior of the first curing tank and the fine particles from an upper portion of the second curing tank into the interior of the second curing tank, and that the gas supply means supplies the carbon dioxide-containing gas from a lower portion of the first curing tank and the second curing tank into the interior of the first curing tank and the second curing tank, respectively.

[0012] In this case, inside the first and second curing tanks, the coarse particles and fine particles descend from the top downward, while the carbon dioxide-containing gas rises from the bottom upward. This causes countercurrent contact between the coarse particles and fine particles and the carbon dioxide-containing gas, thereby increasing the contact efficiency and frequency between the coarse particles and fine particles and the carbon dioxide-containing gas, and making it possible to further promote the carbon dioxide fixation reaction.

[0013] In the carbon dioxide fixation apparatus of the present invention, it is preferable that the first re-supply means is a screw conveyor, and supplies the coarse particles discharged from the lower part of the first curing tank from the upper part of the first curing tank into the inside of the first curing tank.

[0014] In this case, the coarse particles can be transported well, and the inside of the screw conveyor can be sealed to allow the carbon dioxide-containing gas to flow in the opposite direction to the transport direction of the coarse particles, so that the coarse particles and the carbon dioxide-containing gas can come into countercurrent contact with each other, thereby promoting the carbon dioxide fixation reaction.

[0015] In the carbon dioxide fixation apparatus of the present invention, it is preferable that the second re-supply means is a bucket elevator, and supplies the fine granules discharged from the lower part of the second curing tank from the upper part of the second curing tank into the second curing tank.

[0016] In this case, the bucket elevator, unlike the screw conveyor, can transport the fine granules well. Also, since the interior of the bucket elevator can be sealed and the carbon dioxide-containing gas can be made to flow in the opposite direction to the direction of transport of the fine granules, the fine granules and the carbon dioxide-containing gas can be brought into countercurrent contact with each other, thereby allowing the carbon dioxide fixation reaction to proceed.

[0017] In addition, it is preferable that the carbon dioxide fixation apparatus of the present invention further comprises a water supply means for supplying water from an upper portion of the first re-supply means or the second re-supply means to the inside of the first re-supply means or the second re-supply means.

[0018] In this case, moisture can be supplied to the coarse particles resupplied to the first curing tank or the fine particles resupplied to the second curing tank, and therefore the moisture content of these coarse particles or fine particles and / or the humidity inside the first or second curing tank can be adjusted within an appropriate range that allows for highly efficient fixation of carbon dioxide.

[0019] In addition, in the carbon dioxide fixation apparatus of the present invention, it is preferable that the classification means has a sieve body with a predetermined mesh size of 3 mm or more and 10 mm or less, and classifies the powdery or granular material remaining on the sieve body as the coarse particles and the powdery or granular material that has passed through the sieve body as the fine particles.

[0020] In this case, it is possible to easily classify the powdery or granular material into coarse particles and fine particles.

[0021] Furthermore, in the carbon dioxide fixation apparatus of the present invention, it is preferable that the classification means has a first sieve body having a predetermined first mesh size and a second sieve body having a predetermined second mesh size smaller than the first mesh size, and classifies the powder / granular material remaining on the first sieve body as coarse particles and the powder / granular material that has passed through the second sieve body as fine particles, and also classifies the powder / granular material that has passed through the first sieve body but remained on the second sieve body as coarse particles and / or fine particles.

[0022] In this case, the powdery or granular material that passes through the first sieve body but remains on the second sieve body is classified as coarse particles and / or fine particles, making it possible to appropriately adjust the processing amounts of coarse particles and fine particles.

[0023] The carbon dioxide fixation method of the present invention uses a carbon dioxide fixation device comprising: a first curing tank; a second curing tank; classification means for classifying a powdery or granular material made of a cement hardened body into coarse particles made of powdery or granular material having a large average particle size and fine particles made of powdery or granular material having a small average particle size, and supplying the coarse particles to the first curing tank and the fine particles to the second curing tank; gas supply means for supplying a carbon dioxide-containing gas to each of the first curing tank and the second curing tank; and first re-supply means for re-supplying the coarse particles discharged from the first curing tank to the first curing tank, wherein the method is characterized in that when a measured value of the amount of carbon dioxide fixed in the coarse particles discharged from the first curing tank is less than a predetermined first value, the coarse particles discharged from the first curing tank are re-supplied to the first curing tank by the first re-supply means.

[0024] The carbon dioxide fixation method of the present invention has the same effects as the carbon dioxide fixation apparatus of the present invention described above. [Brief explanation of the drawings]

[0025] [Figure 1]1 is a schematic diagram of a carbon dioxide fixation device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] A carbon dioxide fixation apparatus 100 according to an embodiment of the present invention will be described with reference to Fig. 1. In the carbon dioxide fixation apparatus 100, a powdery or granular material P made of a cementitious hardened body is brought into contact with carbon dioxide (CO2) contained in a carbon dioxide-containing gas G at 60°C to 150°C and is carbonated, and the carbon dioxide is fixed as calcium carbonate (CaCO3).

[0027] The term "cementitious hardened product" refers to a product formed by hardening a composition containing cement and water, such as a hardened product made of concrete, a hardened product made of mortar, a hardened product made of cement paste, etc. In this specification, the term "cementitious hardened product" includes not only a completely hardened product but also a semi-hardened product (in other words, a product in the process of hardening).

[0028] From the viewpoint of promoting the utilization of waste, the hardened cement product to be recycled is preferably used as the hardened cement product. Examples of the hardened cement product to be recycled include recycled aggregate, waste building materials made of concrete (waste concrete) or mortar, waste hardened cement paste, and sludge (completely hardened or semi-hardened sludge after dehydration treatment) generated in ready-mixed concrete.

[0029] The powdery granular material P made of a cementitious hardened material has a particle size of 100 mm or less, preferably 80 mm or less, and more preferably 40 mm or less, in order to increase the contact area with the carbon dioxide-containing gas G and thereby increase the amount of immobilized carbon dioxide. Here, the particle size refers to the maximum dimension of the powdery granular material P (for example, the dimension of the major axis when the cross section is elliptical).

[0030] Furthermore, the carbon dioxide-containing gas G may be exhaust gas from a cement factory or a coal-fired power plant, or may be highly purified gas separated and recovered from factory exhaust gas.

[0031] The proportion of carbon dioxide gas in the carbon dioxide-containing gas G is preferably 5% or more, more preferably 10% or more, even more preferably 15% or more, and particularly preferably 20% or more, in terms of volume fraction. If the proportion is 5% or more, a large amount of carbon dioxide is fixed, which is preferable because it increases the effect of reducing carbon dioxide emissions into the atmosphere.

[0032] The carbon dioxide fixation apparatus 100 includes a first curing tank 10, a second curing tank 20, a classification means 30, a gas supply means 40, a first fixation amount measurement means 50, a second fixation amount measurement means 60, a first re-supply means 70, and a second re-supply means 80.

[0033] The first curing tank 10 comprises a curing tank body 11, an inlet 12 provided at the top of the curing tank body 11 and capable of charging a powdered or granular material P made of a cementitious hardened body into the interior and closable with a valve or the like, a gas supply port 13 provided at the bottom of the curing tank body 11 and capable of supplying a carbon dioxide-containing gas G into the interior of the curing tank body 11 and closable with a valve or the like, an outlet 14 provided at the bottom of the curing tank body 11 and capable of discharging the carbonated powdered or granular material P to the outside of the curing tank body 11, and a gas outlet 15 provided at the top of the curing tank body 11 and capable of discharging the carbon dioxide-containing gas G to the outside of the curing tank body 11.

[0034] The curing tank body 11 is a sealed or semi-sealed container made of stainless steel or the like. Although not shown, a heater may be disposed around the curing tank body 11 so that the internal region of the curing tank body 11 surrounded by the heater is heated. This makes it easier to control the internal temperature environment of the curing tank body 11.

[0035] As will be described later, powdery granular material P1 (hereinafter also referred to as coarse particles P1) having a large average particle size is supplied to the first curing tank 10. Therefore, although not shown, it is preferable to provide a baffle plate or the like inside the curing tank main body 11 so that the coarse particles P1 supplied inside the curing tank main body 11 descend over time.

[0036] In this example, the discharge outlet 14 is provided at the lower end of the curing tank body 11. The discharge outlet 14 is configured to ensure airtightness of the curing tank body 11. For example, it is preferable to provide the discharge outlet 14 with an opening / closing means such as a rotary valve, a double flap damper, or a non-sliding valve.

[0037] Furthermore, the first curing tank 10 is provided with a temperature sensor 16 capable of measuring the temperature inside the curing tank main body 11 and a humidity sensor 17 capable of measuring the humidity inside the curing tank main body 11.

[0038] Although not described in detail, the second curing tank 20 is configured similarly to the first curing tank 10 described above. It is also preferable to provide a circle feeder at the discharge port 24 of the second curing tank 20. As will be described later, the second curing tank 20 is supplied with powdered granular material P2 (hereinafter also referred to as fine particles P2) having a small average particle size. Therefore, there is a risk that the fine particles P2 may adhere to the inner surface of the curing tank main body 21. Therefore, although not shown, it is also preferable to provide a straightening plate with a large number of straightening holes on the inner surface of the curing tank main body 21, and supply the carbon dioxide-containing gas G from the gas supply means 40 into the inside of the curing tank main body 21 by dividing it into high-pressure and low-pressure gases.

[0039] The upper part of the curing tank body 11 of the first curing tank 10 and the upper part of the curing tank body 21 of the second curing tank 20 may be connected by a sealed passage. This makes it possible to easily unify the internal atmospheres of the two curing tank bodies 11, 21.

[0040] The classification means 30 classifies the powdered material P into coarse particles P1 and fine particles P2, and supplies the coarse particles P1 to the inside of the curing tank body 11 through the inlet 12 of the first curing tank 10, and supplies the fine particles P2 to the inside of the curing tank body 21 through the inlet 22 of the second curing tank 20.

[0041] The classifying means 30 is supplied with powdered or granular material P via a constant volume feeder 32, such as a circle feeder, table feeder, or screw feeder, which is capable of constant volume supply of the powdered or granular material P supplied from a hopper 31 that contains the powdered or granular material P. The classifying means 30 may also be provided with water supplying means 33 that supplies water to the powdered or granular material P contained in the hopper 31 or to the powdered or granular material P supplied by the constant volume feeder 32. It is preferable that the water supplying means 33 sprays hot water at about 60°C, for example.

[0042] Here, the classification means 30 has a first sieve body 34 having a predetermined first mesh size and a second sieve body 35 having a predetermined second mesh size smaller than the first mesh size. The first and second sieve bodies 34, 35 are preferably vibrable. The sizes of the first and second mesh sizes may be set appropriately within a range of, for example, 3 mm to 10 mm. For example, the first mesh size may be 5 mm and the second mesh size may be 3 mm. Alternatively, the first mesh size may be 10 mm and the second mesh size may be 5 mm.

[0043] Then, the powder and granular material (coarse particles) P1 remaining on the first sieve body 34 is supplied to the first curing tank 10, and the powder and granular material (fine particles) P2 that passed through the second sieve body 35 is supplied to the second curing tank 20. Furthermore, the powder and granular material P that passed through the first sieve body 34 but remained on the second sieve body 35 is supplied to the first curing tank 10 or the second curing tank 20 as the coarse particles P1 or the fine particles P2.

[0044] Whether the powder and granular material is to be supplied to the first curing tank 10 or the second curing tank 20 can be determined by an operator or the like by comparing the amount of coarse particles P1 remaining on the first sieve body 34 with the amount of fine particles P2 passing through the second sieve body 35, so that the carbon dioxide fixation process in the first and second curing tanks 10, 20 is performed at an appropriate ratio. Alternatively, the powder and granular material may be supplied to the first curing tank 10 and the second curing tank 20 at an appropriate ratio. Even in this case, the average particle size of the powder and granular material (coarse particles) P1 supplied to the first curing tank 10 will be larger than the average particle size of the powder and granular material (fine particles) P2 supplied to the second curing tank 20.

[0045] Although not shown, the classification means 30 may have only a single sieve body with a predetermined mesh size. In this case, the coarse particles P1 remaining on the sieve body are supplied to the first curing tank 10, and the fine particles P2 that have passed through the sieve body are supplied to the second curing tank 20. The predetermined mesh size may be set appropriately within the range of, for example, 3 mm to 10 mm.

[0046] Here, the gas supply means 40 has a gas storage tank 41 that stores a carbon dioxide-containing gas G, and a pump 42 and flow rate controllers 43 and 44 that are disposed downstream of the gas storage tank 41. The gas supply means 40 supplies the carbon dioxide-containing gas G, the flow rate of which is controlled by the flow rate controller 43, to the inside of the curing tank body 11 via the gas supply port 13 of the first curing tank 10, and also supplies the carbon dioxide-containing gas G, the flow rate of which is controlled by the flow rate controller 44, to the inside of the curing tank body 21 via the gas supply port 23 of the second curing tank 20.

[0047] The first fixed amount measuring means 50 extracts a sample from the coarse particles P1 that are discharged outside the curing tank body 11 through the outlet 14 of the first curing tank 10 and temporarily stored in the buffer tank 51, and measures the amount of carbon dioxide fixed in this sample.

[0048] The second immobilization amount measuring means 60 extracts a sample from the fine granules P2 that have been discharged to the outside of the curing tank body 21 through the outlet 24 of the second curing tank 20 and temporarily stored in the buffer tank 61, and measures the amount of carbon dioxide immobilized in the sample. Note that in the first and second immobilization amount measuring means 50, 60, the work of extracting the sample, measuring the amount of carbon dioxide immobilization, etc. may be performed by an operator.

[0049] The amount of carbon dioxide fixed may be measured, for example, by TG-DTA in the first and second fixation amount measuring means 50, 60. The TG-DTA method uses a TG-DTA (differential thermal-thermogravimetric simultaneous analysis) device to quantify the amount of carbon dioxide from the mass loss of a sample under conditions in a temperature range corresponding to the decarboxylation reaction of calcium carbonate (e.g., 500°C to 850°C).

[0050] Measurement is not limited to the TG-DTA method, and may also be performed by the TOC method, coulometer method, etc. The TOC method measures inorganic carbon (IC) using a TOC meter (total organic carbon analyzer) equipped with a solid sample combustion device and quantifies it as a carbon dioxide percentage. The coulometer method decomposes carbonates in the sample with hydrochloric acid, vaporizes the carbon dioxide, introduces it into the absorption solution, calculates the amount of carbon (C) from the amount of electricity required to maintain the pH of the absorption solution constant, and converts it into the amount of carbon dioxide.

[0051] If the amount of carbon dioxide fixed in the coarse particles P1 measured by the first fixation amount measuring means 50 is less than a predetermined first value, an operator or the like operates the bifurcated chute 52 provided at the bottom end of the buffer tank 51, and the coarse particles P1 stored in the buffer tank 51 are resupplied to the first curing tank 10 by the first resupply means 70. The first value is, for example, 50 kg-CO2 / t-cement, 100 kg-CO2 / t-cement, or the like, and is determined depending on the coarse particles P1 to be shipped as a product.

[0052] Here, the first re-supply means 70 is a screw-type conveyor. The screw-type conveyor 70 has a shaft 71 and a spiral blade 72 attached to the outer periphery of the shaft 71. As the shaft 71 rotates, the blade 72 transports the coarse particles P1 upward, and is suitable for transporting powdered or granular materials with large particle sizes. However, the type of the first re-supply means 70 is not limited as long as it can transport the coarse particles P1. The first re-supply means 70 supplies the coarse particles P1 discharged from the bottom of the first curing tank 10 and stored in the buffer tank 51 from the top of the first curing tank 10 into the curing tank main body 11.

[0053] The passage 73 that resupplies the coarse particles P1 from the top of the first resupply means 70 to the inside of the curing tank body 11 preferably has a sealed space. The passage 73 may be equipped with an air slider or the like. It is preferable that the internal space of the first resupply means 70 be sealable, and from this perspective, a screw-type conveyor is also preferable.

[0054] The carbon dioxide-containing gas G in the curing tank body 11 is discharged from the gas outlet 15 and supplied to the first re-supply means 70 from the upper part thereof via the passage 73. The carbon dioxide-containing gas G flows downward within the first re-supply means 70. At this time, the coarse particles P1 transported upward through the first re-supply means 70 come into countercurrent contact with the carbon dioxide-containing gas G, and carbonation of the coarse particles P1 progresses.

[0055] Furthermore, the first re-supply means 70 preferably has a water supply means 74 that supplies water from above toward the inside. In this case, the first immobilization amount measurement means 50 measures the moisture content of a sample of the coarse particles P1, and based on the results of comparing this measurement value with a moisture content range suitable for highly efficient fixation of carbon dioxide, water is sprayed appropriately from the water supply means 74. Note that the water supply means 74 preferably sprays hot water at about 60°C, for example.

[0056] The first re-supply means 70 also has, at its bottom, a gas outlet 75 that can discharge the carbon dioxide-containing gas G and that can be closed with a valve or the like. A pump 91 is provided downstream of the gas outlet 75, and a dust collector 92, such as a bag filter, is provided upstream of the pump 91 to capture fine powder contained in the carbon dioxide-containing gas G and the powdered or granular material P, and the clean gas is discharged outside the carbon dioxide fixation device 100. The captured fine powder can be used as a cement admixture (mineral admixture), etc.

[0057] In addition, when the passage 73 for resupplying the coarse particles P1 from the top of the first resupply means 70 into the first curing tank 10 is open to the outside, a pump 91 and a dust collector 92 can be connected to the gas exhaust port 15 provided at the top of the curing tank body 11, although this is not shown.

[0058] On the other hand, if the amount of carbon dioxide fixed in the coarse particles P1 measured by the first fixation amount measuring means 50 is equal to or greater than a predetermined first value, the worker or the like operates the bifurcated chute 52, and the coarse particles P1 stored in the buffer tank 51 are supplied to the product tank 53 for shipping as products such as roadbed material or liquefied treated soil.

[0059] Furthermore, if the amount of carbon dioxide fixed in the fine granules P2 measured by the second fixation amount measuring means 60 is less than a predetermined second value, an operator or the like operates the bifurcated chute 62 provided at the bottom end of the buffer tank 61, and the fine granules P2 stored in the buffer tank 61 are resupplied to the second curing tank 20 by the second resupply means 80. The second value is, for example, 150 kg-CO2 / t-cement, 100 kg-CO2 / t-cement, etc., and is determined depending on the fine granules P2 to be shipped as a product. The second value may be the same as or different from the first value.

[0060] Here, the second re-supply means 80 is a bucket elevator. The bucket elevator 80 circulates multiple buckets 81, each of which scoops up fine particles P2 and transports them upward, and is suitable for transporting powdery or granular materials with small particle sizes. However, the type of the second re-supply means 80 is not limited as long as it can transport fine particles P2. The second re-supply means 80 supplies the fine particles P2 discharged from the bottom of the second curing tank 20 into the second curing tank 20 from the top of the second curing tank 20.

[0061] Although not described in detail, the second re-supply means 80 also has a passage 83, a water supply means 84, and a gas discharge port 85, similar to the above-mentioned first re-supply means 70, and the gas discharge port 85 is connected to a pump 91 and a dust collector 92. It is preferable that the internal space of the second re-supply means 80 is sealable, and from this point of view, it is also preferable that the second re-supply means 80 is a bucket-type elevator.

[0062] On the other hand, if the amount of carbon dioxide fixed in the fine particles P2 measured by the second fixation amount measuring means 60 is equal to or greater than a predetermined second value, the worker or the like operates the bifurcated chute 62, and the fine particles P2 stored in the buffer tank 61 are supplied to the product tank 63 for shipping as products such as roadbed material or liquefied treated soil.

[0063] Hereinafter, a carbon dioxide fixation method according to an embodiment of the present invention using the above-described carbon dioxide fixation apparatus 100 will be described.

[0064] First, a powdery or granular material P made of hardened cement stored in a hopper 31 is supplied to the classification means 30 via a constant volume feeder 32. It is preferable to remove large powdery or granular materials P, such as those with a particle size of 40 mm or more, in advance.

[0065] The powdered and granular material P is classified by classification means 30, and coarse particles P1 having a large average particle size are supplied into the curing tank body 11 of the first curing tank 10, and fine particles P2 having a small average particle size are supplied into the curing tank body 21 of the second curing tank 20. At the same time, a carbon dioxide-containing gas G is supplied into each of the curing tank bodies 11 and 21 by gas supply means 40.

[0066] As a result, in the curing tank body 11 of the first curing tank 10, the coarse particles P1 supplied from above descend and the carbon dioxide-containing gas G supplied from below ascend, so that they come into countercurrent contact and carbonation of the coarse particles P1 progresses. Similarly, in the curing tank body 21 of the second curing tank 20, carbonation of the fine particles P2 progresses.

[0067] At this time, carbonation of the coarse particles P1 and the fine particles P2 is highly efficient when the internal temperature and humidity of the curing tank bodies 11, 21 are within appropriate ranges. For example, carbonation is highly efficient when the internal temperature of the curing tank bodies 11, 21 is within a range of 60°C to 150°C, so it is preferable that an operator or the like controls the heaters (not shown) provided in the curing tank bodies 11, 21 so that the temperatures measured by the temperature sensors 16, 26 are within this range.

[0068] Furthermore, when the internal humidity of the curing tank main body 11, 21 is in the range of 40%RH to 90%RH, for example, carbonation of the coarse particles P1 and the fine particles P2 is highly efficient, so it is preferable that an operator or the like controls the sprinkling of water using the water supply means 33, 74, 84 so that the relative humidity measured by the humidity sensors 17, 27 is within this range. Furthermore, although not shown, a means for supplying water or steam into the curing tank main body 11, 21 may be provided in the first and second curing tanks 10, 20. The temperature and / or relative humidity inside the curing tank main body 11, 21 may be set to different ranges.

[0069] The coarse particles P1 that have been carbonated in the first curing tank 10 and discharged are stored in a buffer tank 51. A sample is extracted from the coarse particles P1, and the amount of carbon dioxide fixed in the coarse particles P1 is measured by a first fixed amount measuring means 50.

[0070] If this measured value is equal to or greater than a predetermined first value, the coarse particles P1 stored in the buffer tank 51 are shipped as a product.

[0071] On the other hand, if the measured value is less than the predetermined first value, the coarse particles P1 stored in the buffer tank 51 are again supplied to the first curing tank 10 by the first re-supply means 70. At this time, the pump 91 is operated to suck the carbon dioxide-containing gas G from the curing tank main body 11 of the first curing tank 10. As a result, in the first re-supply means 70, the coarse particles P1 being transported upward come into countercurrent contact with the carbon dioxide-containing gas G flowing downward, and carbonation of the coarse particles P1 progresses. The coarse particles P1 again come into countercurrent contact with the carbon dioxide-containing gas G in the curing tank main body 11, which also progresses carbonation.

[0072] Then, the coarse particles P1 are discharged from the first curing tank 10, and the amount of carbon dioxide fixed in the coarse particles P1 is measured again. In this way, the amount of carbon dioxide fixed in the coarse particles P1 can be reliably made equal to or greater than the first value, and therefore, the coarse particles P1 suitable for products can be obtained.

[0073] Furthermore, a sample may be extracted from the coarse particles P1 stored in the buffer tank 51 to measure the moisture content of the coarse particles P1. When the coarse particles P1 stored in the buffer tank 51 are supplied again to the first curing tank 10, it is preferable that an operator or the like controls the water spraying by the water supply means 74 so that the moisture content of the coarse particles P1 falls within a range in which carbon dioxide fixation is highly efficient, for example, a moisture content range of 2% to 6%.

[0074] The fine particles P2 carbonated in the second curing tank 20 and discharged may be treated in the same manner as the coarse particles P1 carbonated in the first curing tank 10 and discharged.

[0075] Note that the time T1 required for all or nearly all of the coarse particles P1 to be discharged from the first curing tank 10 and stored in the buffer tank 51 is usually different from the time T2 required for all or nearly all of the fine particles P2 to be discharged from the second curing tank 20 and stored in the buffer tank 61. Since it takes longer for the coarse particles P1 to immobilize carbon dioxide to the same extent as the fine particles P2, it is preferable to configure the time T1 to be longer than the time T2 so that immobilization progresses to the same extent. For example, the first and second curing tanks 10, 20 are configured so that the time T1 is 2 hours and the time T2 is 1 hour.

[0076] Furthermore, the curing tank bodies 11 and 21 are heated, making it difficult to maintain the moisture content of the coarse particles P1 and fine particles P2 present therein within a suitable range for a long period of time. Therefore, even if the coarse particles P1 and fine particles P2 are retained in the curing tank bodies 11 and 21 for, for example, more than two hours, carbonation does not progress significantly. Therefore, it is preferable to limit the retention time in the curing tank bodies 11 and 21 to two hours or less, and to supply moisture to the coarse particles P1 and fine particles P2 using the water supply means 74 and 84 when resupplying the coarse particles P1 and fine particles P2 using the first and second resupply means 70 and 80. The curing tank bodies 11 and 21 may have the same or different capacities. Furthermore, at least one of the curing tanks 10 and 20 may be a plurality of curing tanks.

[0077] According to the carbon dioxide fixation device and carbon dioxide fixation method of the above-described embodiment of the present invention, the powdered granular material P consisting of a hardened cement body is classified into coarse particles P1 and fine particles P2 by classification means 30, and the coarse particles P1 are brought into contact with a carbon dioxide-containing gas G in the first curing tank 10, and the fine particles P2 are brought into contact with a carbon dioxide-containing gas G in the second curing tank 20, respectively, to fix the carbon dioxide.

[0078] If the amount of carbon dioxide fixed by the coarse granules P1, which take a long time to fix, is less than the first value when discharged from the first curing tank 10, the coarse granules P1 are supplied again to the first curing tank 10 for further carbon dioxide fixation. If the amount of carbon dioxide fixed by the fine granules P2, which are discharged from the second curing tank 20, is less than the second value, the coarse granules P1 are supplied again to the second curing tank 20 for further carbon dioxide fixation. This ensures that the coarse granules P1 and the fine granules P2 each have a predetermined amount of carbon dioxide fixation or more.

[0079] Furthermore, even if the particle size of the powdered or granular material P ranges over a wide range, the material is classified into coarse particles P1 and fine particles P2 and the carbon dioxide fixation process is carried out for each of them, so that each fixation process can be carried out in an environment and / or for a processing time suitable for carrying out the fixation process with high efficiency.

[0080] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the claims. For example, in the above-described embodiment, the powder / granular material P made of hardened cement is classified into two groups, coarse particles P1 and fine particles P2, by the classification means 30, and then supplied to two separate curing tanks 10 and 20 for carbonation. However, the present invention is not limited to this, and the powder / granular material P made of hardened cement may be classified into three or more groups by the classification means, and each of these may be supplied to a separate curing tank for carbonation.

[0081] Also, in the above description, when the amount of fixed carbon dioxide measured by the second fixation amount measuring means 60 is less than the second value, the fine granules P2 stored in the buffer tank 61 are resupplied to the second curing tank 20 by the second resupply means 80. However, since carbon dioxide fixation progresses more easily in the fine granules P2 than in the coarse granules P1, it is possible to reliably make the amount of fixed carbon dioxide equal to or greater than the second value by performing the carbon dioxide fixation process for a sufficient amount of time in an appropriate internal environment in the second curing tank 20. Therefore, the second resupply means 80 and the like may be omitted.

[0082] In addition, the case where the inlets 12, 22 are provided at the top of the curing tank bodies 11, 21 and the gas supply ports 13, 23 are provided at the bottom has been described. However, the locations where these are provided are not limited to this. For example, if the curing tank bodies 11, 21 extend horizontally, the inlets 12, 22 may be provided at one horizontal end and the gas supply ports 13, 23 at the other horizontal end.

[0083] Also, the case where the carbon dioxide-containing gas G discharged from the first and second curing tanks 10, 20 is supplied to the first and second re-supply means 70, 80 has been described. However, this is not limiting, and the carbon dioxide-containing gas G discharged from the first curing tank 10 and / or the second curing tank 20 may be discharged to the outside without being supplied to the first re-supply means 70 and / or the second re-supply means 80. In this case, a pump 91 and a dust collector 92 may be connected to the gas outlets 15, 25 of the first and second curing tanks 10, 20. Also, the passages 73, 83 do not need to be sealed. [Explanation of symbols]

[0084] DESCRIPTION OF SYMBOLS 10...First curing tank, 11,21...Curing tank body, 12,22...Inlet, 13,23...Gas supply port, 14,24...Outlet, 15,25...Gas outlet, 16,26...Temperature sensor, 17,27...Humidity sensor, 20...Second curing tank, 30...Classifying means, 31...Hopper, 32...Quantitative feeder, 33...Water supply means, 34...First sieve body, 35...Second sieve body, 40...Gas supply means, 41...Gas storage tank, 42...Pump, 43,44...Flow rate controller, 50...First fixed amount measuring means, 51,61...Buffer tank, 52,62...Two-branch chute, 53,63...Product tank, 60...Second fixed amount measuring means, 70...first re-supply means, screw conveyor, 71...shaft, 72...blade, 73, 83...passageway, 74, 84...water supply means, 75, 85...gas outlet, 80...second re-supply means, bucket elevator, 81...bucket, 91...pump, 92...dust collector, 100...carbon dioxide fixation device, G...carbon dioxide-containing gas, P...powder and granular material made of hardened cement, P1...powder and granular material with a large average particle size, coarse particles, P2...powder and granular material with a small average particle size, fine particles.

Claims

1. a first curing tank; a second curing tank; a classifying means for classifying a powder or granular material made of a hardened cement body into coarse particles having a large average particle size and fine particles having a small average particle size, and supplying the coarse particles to the first curing tank and the fine particles to the second curing tank; a gas supply means for supplying a carbon dioxide-containing gas to each of the first curing tank and the second curing tank; a first immobilization amount measuring means for measuring the amount of carbon dioxide immobilized in the coarse particles discharged from the first curing tank; and first re-supply means for re-supplying the coarse particles discharged from the first curing tank to the first curing tank when the amount of fixed carbon dioxide measured by the first fixation amount measurement means is less than a predetermined first value.

2. a second fixed amount measuring means for measuring the amount of carbon dioxide fixed in the fine granules discharged from the second curing tank; 2. The carbon dioxide fixation device according to claim 1, further comprising: second re-supply means for re-supplying the fine granules discharged from the second curing tank to the second curing tank when the amount of fixed carbon dioxide measured by the second fixation amount measurement means is less than a predetermined second value.

3. The classification means supplies the coarse particles from an upper portion of the first curing tank into the interior of the first curing tank and the fine particles from an upper portion of the second curing tank into the interior of the second curing tank, and 2. The carbon dioxide fixation device according to claim 1, wherein the gas supply means supplies the carbon dioxide-containing gas into the first curing tank and the second curing tank from a lower portion of each of the first curing tank and the second curing tank.

4. 2. The carbon dioxide fixation apparatus according to claim 1, wherein the first re-supply means is a screw conveyor that supplies the coarse particles discharged from a lower part of the first curing tank to the inside of the first curing tank from an upper part of the first curing tank.

5. 3. The carbon dioxide fixation apparatus according to claim 2, wherein the second re-supply means is a bucket elevator that supplies the fine granules discharged from a lower part of the second curing tank to the inside of the second curing tank from an upper part of the second curing tank.

6. 3. The carbon dioxide fixation device according to claim 2, further comprising a water supply means for supplying water from an upper portion of the first re-supply means or the second re-supply means to an inside of the first re-supply means or the second re-supply means.

7. the classification means has a sieve body with a predetermined mesh size, 2. The carbon dioxide fixation device according to claim 1, wherein the powder and granular material remaining on the sieve body is classified as the coarse particles, and the powder and granular material passing through the sieve body is classified as the fine particles.

8. the classification means has a first sieve body having a predetermined first mesh size of 3 mm or more and 10 mm or less, and a second sieve body having a predetermined second mesh size smaller than the first mesh size; The carbon dioxide fixation device according to claim 1, characterized in that the powder and granular material remaining on the first sieve body is classified as the coarse particles, and the powder and granular material passing through the second sieve body is classified as the fine particles, and the powder and granular material passing through the first sieve body but remaining on the second sieve body is classified as the coarse particles and / or the fine particles.

9. a first curing tank; a second curing tank; a classifying means for classifying a powder or granular material made of a hardened cement body into coarse particles having a large average particle size and fine particles having a small average particle size, and supplying the coarse particles to the first curing tank and the fine particles to the second curing tank; a gas supply means for supplying a carbon dioxide-containing gas to each of the first curing tank and the second curing tank; a first re-supply means for re-supplying the coarse particles discharged from the first curing tank to the first curing tank, a first re-supply means for re-supplying the coarse particles discharged from the first curing tank to the first curing tank when a measured value of the amount of carbon dioxide fixed in the coarse particles discharged from the first curing tank is less than a predetermined first value.

Images