Carbon dioxide recovery apparatus and recovery method

Abstract

To provide a carbon dioxide recovery apparatus and a recovery method which exhibit excellent versatility and enable effective utilization of calcium to reduce carbon dioxide contained in exhaust gas.SOLUTION: Provided are a carbon dioxide recovery apparatus and a carbon dioxide recovery method. The apparatus comprises a carbon dioxide recovery tower having an alkaline metal-containing aqueous solution supply port, a screen, and a carbon dioxide-containing exhaust gas supply port. The aqueous solution supply port is provided at an upper portion of the carbon dioxide recovery tower, while the exhaust gas supply port is provided at a lower portion of the carbon dioxide recovery tower. The screen is disposed between the aqueous solution supply port and the exhaust gas supply port, and a calcium-containing material is placed on the screen.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a carbon dioxide capture device and capture method. [Background technology]

[0002] In recent years, interest in global warming has grown, and there is a demand for reducing the amount of carbon dioxide emitted into the atmosphere. At various facilities, such as power plants, incinerators, cement plants, ready-mix concrete plants, precast concrete plants, steel mills, and other industrial facilities, efforts are being made to reduce and capture the amount of exhaust gases, including carbon dioxide, emitted into the atmosphere during their operations. Reducing carbon dioxide emissions from cement plants, in particular, is seen as an urgent issue.

[0003] For example, Patent Document 1 discloses a method for producing calcium carbonate, which includes a carbon dioxide absorption step of absorbing carbon dioxide gas in exhaust gas from a combustion furnace or the like with a caustic soda solution by a gas-liquid contact method to produce a sodium carbonate solution, a step of hydrating quicklime to produce milk of lime, and a carbonation step of reacting the milk of lime with the sodium carbonate solution produced in the carbon dioxide absorption step. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-293537 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a carbon dioxide recovery device and recovery method that has excellent versatility and can reduce the carbon dioxide contained in exhaust gas while effectively utilizing calcium. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides the following carbon dioxide recovery device. 1. A carbon dioxide recovery tower having a supply port for an alkali metal-containing aqueous solution, a screen, and a supply port for a carbon dioxide-containing exhaust gas, a supply port for the aqueous solution is provided at an upper portion of the carbon dioxide recovery tower, the exhaust gas supply port is provided in a lower part of the carbon dioxide absorption tower, the screen is provided between the aqueous solution supply port and the exhaust gas supply port; A calcium-containing material is placed on the screen. Carbon dioxide capture equipment.

[0007] The present invention provides the following carbon dioxide recovery device as a preferred embodiment. 2. The carbon dioxide recovery apparatus according to 1 above, having two or more supply ports for the aqueous solution and two or more screens, and the screens and the supply ports for the aqueous solution are alternately provided from the bottom to the top of the carbon dioxide absorption tower. 3. The carbon dioxide recovery device according to claim 1 or 2, further comprising a storage tank for the aqueous solution below the exhaust gas supply port of the carbon dioxide absorption tower, and a circulation means for supplying the aqueous solution stored in the storage tank from the aqueous solution supply port.

[0008] The present invention also provides the following method for recovering carbon dioxide. 4. Contacting an aqueous solution of an alkali metal hydroxide with exhaust gas containing carbon dioxide to obtain an aqueous solution of an alkali metal carbonate; and contacting the aqueous solution of the alkali metal carbonate with a calcium-containing substance to obtain calcium carbonate; A method for capturing carbon dioxide, comprising: 5. The method for recovering carbon dioxide according to 4 above, wherein obtaining the aqueous solution of alkali carbonate and obtaining the calcium carbonate are carried out in a single carbon dioxide absorption tower. 6. A method for recovering carbon dioxide according to the above 4 or 5, wherein an aqueous solution of alkali metal hydroxide obtained by obtaining calcium carbonate is used in obtaining an aqueous solution of alkali metal carbonate. 7. The method for recovering carbon dioxide according to any one of the above items 4 to 6, wherein the calcium-containing material is selected from calcium-containing waste and calcium-containing minerals. 8. A method for recovering carbon dioxide according to any one of the above items 4 to 7, wherein the supply rate of the aqueous solution of alkali metal hydroxide per 1 part by mass of the calcium-containing material is 0.01 part by mass / minute or more and 1.0 part by mass / minute or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a carbon dioxide recovery device and recovery method that have excellent versatility and can reduce the carbon dioxide contained in exhaust gas while effectively utilizing calcium. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a preferred embodiment of a carbon dioxide recovery device according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. The present invention is not limited to the following embodiment, and can be implemented with any modifications within the scope that does not impair the effects of the invention. In this specification, the notation of a numerical range as "AA to BB" means "at least AA and at most BB." In addition, in this specification, the numbers associated with "at least," "at most," and "to" in describing a numerical range are numbers that can be arbitrarily combined. For example, when a certain numerical range is described as "CC to DD" and "EE to FF," the numerical ranges "CC to FF" and "EE to DD" are also included.

[0012] [Carbon dioxide capture device] The carbon dioxide recovery device of this embodiment includes: a carbon dioxide recovery tower provided with a supply port for an alkali metal-containing aqueous solution, a screen, and a supply port for a carbon dioxide-containing flue gas; a supply port for the aqueous solution is provided at an upper portion of the carbon dioxide recovery tower, the exhaust gas supply port is provided in a lower part of the carbon dioxide absorption tower, the screen is provided between the aqueous solution supply port and the exhaust gas supply port; A calcium-containing material is placed on the screen. That is it.

[0013] The production method described in Patent Document 1 aims to produce calcium carbonate by utilizing carbon dioxide contained in exhaust gases from combustion furnaces such as lime kilns, boilers, refuse incinerators, and cement incinerators (Patent Document 1, Problems to be Solved by the Invention section). This method requires equipment for performing at least three steps: a carbon dioxide gas absorption step, a milk of lime production step, and a carbonation step. This naturally results in a large and complicated apparatus. Among the various facilities that emit exhaust gases containing carbon dioxide, such as the power plants, incinerators, cement plants, steel mills, and factory facilities, some large-scale plants can independently implement the method described in Patent Document 1, while others are small- and medium-sized plants that cannot independently implement the method due to site limitations, economic constraints, and other reasons. Therefore, there is a demand for a method and apparatus for producing calcium carbonate by utilizing carbon dioxide emitted from these various facilities that is versatile enough to easily accommodate increases or decreases in scale and be miniaturized, allowing installation anywhere.

[0014] Incidentally, among the various facilities, such as power plants, incinerators, cement plants, steel mills, and factory facilities, which emit exhaust gases containing carbon dioxide, some facilities generate substances containing at least one calcium compound (hereinafter also referred to as "calcium-containing materials"). Examples of calcium-containing materials include materials that have primarily been disposed of, such as ready-mixed concrete sludge, waste concrete, garbage incineration ash, biomass ash, and slaked lime. By producing calcium carbonate by reacting the calcium compounds contained in such calcium-containing materials with carbon dioxide emitted from the various facilities, it is possible to reduce the amount of carbon dioxide released into the atmosphere while effectively utilizing the calcium contained in the calcium-containing materials. In this regard, the method described in Patent Document 1 employs quicklime as the calcium compound, but does not consider other calcium compounds, i.e., does not consider the effective utilization of calcium-containing materials emitted from various facilities, such as factory facilities.

[0015] Furthermore, calcium-containing waste such as ready-mixed concrete sludge is mainly generated at ready-mixed concrete plants and precast concrete plants, but may also be generated at various other sites, such as construction sites and building sites. Because these various sites are temporary, it is not practical to treat calcium-containing waste generated as work progresses on-site. Furthermore, the method described in Patent Document 1 lacks versatility as mentioned above, and therefore cannot be applied to various sites.

[0016] Under these circumstances, the inventors of the present invention have been studying carbon dioxide capture devices and methods, focusing on the versatility of devices, such as their ability to easily accommodate increases or decreases in scale and their ability to be miniaturized, so that they can be installed anywhere. As a result, they have found that a device configuration that can be used in combination with an alkali metal-containing aqueous solution, a carbon dioxide-containing exhaust gas, and a calcium-containing substance is extremely effective in terms of device versatility. They have also found that this is extremely effective in terms of reducing the carbon dioxide contained in the exhaust gas while effectively utilizing calcium. Thus, the carbon dioxide recovery device of this embodiment has excellent versatility, such as being able to easily accommodate increases or decreases in scale and being able to be made smaller, and is equipment that can reduce the carbon dioxide contained in exhaust gas while effectively utilizing calcium.

[0017] (Reactions occurring in the carbon dioxide capture tower) The carbon dioxide recovery device and recovery method of this embodiment will be described below with reference to Fig. 1. Fig. 1 is a schematic diagram showing a preferred embodiment of the carbon dioxide recovery device of this embodiment. The carbon dioxide recovery device shown in FIG. 1 has a carbon dioxide absorption tower, which has a supply port for an alkali metal-containing aqueous solution at its upper part, a supply port for flue gas at its lower part, and a screen provided between the supply port for the alkali metal-containing aqueous solution and the supply port for flue gas. In other words, the carbon dioxide absorption tower has a supply port for the alkali metal-containing aqueous solution, a screen, and a supply port for flue gas containing carbon dioxide provided in this order from the top.

[0018] By providing the supply port and the screen in the carbon dioxide absorption tower with such a configuration, reactions between the alkali metal-containing aqueous solution, the carbon dioxide-containing exhaust gas, and the calcium-containing substance occur simultaneously in the carbon dioxide absorption tower. Preferred examples of the reactions that occur in the carbon dioxide absorption tower include the following reactions 1 and 2.

[0019] Reaction 1:2M A OH+CO2→M A2 CO3+H2O Reaction 2: M A2 CO3 + CaO + H2O → CaCO3 + 2M A OH In the above reactions 1 and 2, M A indicates an alkali metal ion.

[0020] The above reaction 1 is a reaction formula showing that an aqueous solution of alkali metal carbonate is obtained by contacting an alkali metal salt (preferably an alkali metal hydroxide) contained in an alkali metal-containing aqueous solution with exhaust gas containing carbon dioxide. The above reaction 2 is a reaction formula showing that calcium carbonate is obtained by contacting the aqueous solution of alkali metal carbonate obtained in the above reaction 1 with a calcium-containing material (preferably a material containing calcium oxide).

[0021] The carbon dioxide absorption tower can also be called a gas-liquid contact tower where gas-liquid contact occurs. In gas-liquid contact towers, metal, plastic, or porcelain packings having various shapes, such as Raschig rings, Lessing rings, Pall rings, Berl saddles, interlocking saddles, and terrarettes, are generally installed on a screen, and the packings improve the dispersion and contact of the liquid and gas. The carbon dioxide capture tower of this embodiment is packed with a calcium-containing material instead of commonly used packings. The calcium-containing material improves the dispersion and contact of the alkali metal-containing aqueous solution and the exhaust gas containing carbon dioxide in place of the packings, and the calcium contained in the calcium-containing material functions as a calcium supply source in the above reaction 2.

[0022] In this way, the calcium-containing material functions as a filler and as a calcium supply source, allowing the above reactions 1 and 2 to proceed simultaneously inside the carbon dioxide absorption tower. The above reactions 1 and 2, i.e., obtaining an aqueous solution of alkali carbonate and obtaining the calcium carbonate, can be performed in a single carbon dioxide absorption tower. Therefore, the carbon dioxide absorption tower can be made smaller, and a recovery device can be provided that can be installed anywhere. Because the carbon dioxide absorption tower can be made smaller, it can be transported by transportation means such as a truck to various facilities that require carbon dioxide capture, and then transported to other necessary locations for use, thereby enabling a method of circulating use among a plurality of various facilities. Furthermore, because the capture device of this embodiment can be made smaller and has a relatively simple structure, it can also be assembled and used at the location where carbon dioxide capture is required. In this respect, too, the carbon dioxide capture device of this embodiment can be a capture device that can be installed anywhere.

[0023] Furthermore, since the carbon dioxide absorption tower basically has a configuration similar to that of a gas-liquid contact tower, it can easily be adapted to increases or decreases in scale. As a result, the carbon dioxide recovery system of this embodiment has excellent versatility and can also reduce the carbon dioxide contained in the flue gas while effectively utilizing calcium.

[0024] (Configuration of carbon dioxide capture tower) The carbon dioxide capture tower has a supply port for an alkali metal-containing aqueous solution at its top and a supply port for a carbon dioxide-containing flue gas at its bottom. The positional relationship between the supply port for the alkali metal-containing aqueous solution and the supply port for the carbon dioxide-containing flue gas may be such that the supply port for the alkali metal-containing aqueous solution is above the supply port for the carbon dioxide-containing flue gas, and a screen is provided between the supply port for the alkali metal-containing aqueous solution and the supply port for the carbon dioxide-containing flue gas.

[0025] 1 shows that the carbon dioxide absorption tower has two supply ports for the alkali metal-containing aqueous solution, the carbon dioxide absorption tower preferably has two or more supply ports for the alkali metal-containing aqueous solution. Since the progress of the preferred reactions 1 and 2 can be promoted, the versatility of the device can be improved, such as by achieving more efficient miniaturization, and carbon dioxide can be reduced. The number of supply ports for the alkali metal-containing aqueous solution can be determined taking into consideration the size of the carbon dioxide absorption tower, the amount of the alkali metal-containing aqueous solution supplied to the absorption tower, and the like, and cannot be generally specified, but is preferably 2 or more, with the upper limit being preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0026] 1 shows that the carbon dioxide absorption tower has two screens, it is preferable that the carbon dioxide absorption tower has two or more screens. Since the reactions 1 and 2 can be promoted more efficiently, the versatility of the device can be improved, such as by achieving miniaturization, and carbon dioxide can be reduced. As with the number of supply ports for the alkali metal-containing aqueous solution, the number of screens can be determined taking into consideration the size of the carbon dioxide absorption tower, the amount of alkali metal-containing aqueous solution supplied to the absorption tower, and the like, and cannot be generally specified, but is preferably 2 or more, with the upper limit being preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0027] When two or more screens are used, it is sufficient that the calcium-containing material is placed on one of the screens, and it is preferable that the calcium-containing material is placed on all of the screens as shown in FIG.

[0028] From the viewpoint of more efficiently improving the versatility of the carbon dioxide recovery device and reducing carbon dioxide, it is preferable to have two or more supply ports for the alkali metal-containing aqueous solution and two or more screens. In this case, it is more preferable that two or more supply ports for the alkali metal-containing aqueous solution and two or more screens are provided, and that the screens and the supply ports for the alkali metal-containing aqueous solution are provided alternately from the bottom to the top of the carbon dioxide absorption tower, and it is even more preferable that a calcium-containing material is provided on all of the screens.

[0029] The supply port for the alkali metal-containing aqueous solution and the supply port for the carbon dioxide-containing exhaust gas are preferably configured by connectable jigs such as flanges, taking into consideration ensuring a variety of destinations for the alkali metal-containing aqueous solution and the exhaust gas containing carbon dioxide, the maintainability of the carbon dioxide recovery device, and the retention of the interior by a closing flange of the carbon dioxide recovery tower during transportation.

[0030] The carbon dioxide capture tower may be provided with an internal pipe for supplying the alkali metal-containing aqueous solution from a supply port for the alkali metal-containing aqueous solution to the interior. Furthermore, the internal pipe may be a pipe provided with a spraying tool such as a shower nozzle. 1, by having an internal pipe provided with a spraying jig, the alkali metal-containing aqueous solution supplied from the alkali metal-containing aqueous solution supply port can be sprayed and supplied into the carbon dioxide capture tower. By supplying the alkali metal-containing aqueous solution by spraying, the alkali metal-containing aqueous solution is dispersed and supplied inside the carbon dioxide capture tower, which makes it easier to proceed with the above reactions 1 and 2, thereby improving the versatility of the device, such as allowing for more efficient and more compact size, and also enabling a reduction in carbon dioxide emissions.

[0031] The carbon dioxide capture tower may be provided with an internal pipe for supplying the carbon dioxide-containing exhaust gas to the interior from a carbon dioxide-containing exhaust gas supply port. As the internal pipe, a pipe having a curved shape at the bottom of the carbon dioxide capture tower is preferred, as shown in Fig. 1. Having an internal pipe with such a shape makes it easier to uniformly disperse the carbon dioxide-containing exhaust gas inside the carbon dioxide capture tower, making it easier to promote the above reactions 1 and 2, and improving the versatility of the device, such as enabling more efficient and more compact size, and enabling carbon dioxide reduction.

[0032] The carbon dioxide capture tower is preferably provided with an exhaust gas outlet at its top. In consideration of ensuring a variety of destinations for exhaust gas containing carbon dioxide, ease of maintenance of the carbon dioxide capture device, and holding the inside of the carbon dioxide capture tower by a closing flange during transportation, the exhaust gas outlet is preferably configured as a connectable jig such as a flange.

[0033] The carbon dioxide capture tower may be provided with a demister to remove mist, impurities, and the like from the exhaust gas discharged to the outside, as shown in Fig. 1. As the demister, a wire mesh demister made of metal or synthetic resin, or the like, can be used.

[0034] (Carbon dioxide capture tower shape) Preferred shapes of the carbon dioxide capture tower include a cylinder and a rectangular pillar. This allows for the carbon dioxide capture device to be made smaller, making it easier to install the device anywhere. In addition, a cylinder is preferred from the viewpoint of further promoting the reaction in the carbon dioxide capture tower.

[0035] The dimensions of the carbon dioxide capture tower are not particularly limited, and may be determined taking into consideration the amounts of the alkali metal-containing aqueous solution and the carbon dioxide-containing exhaust gas to be supplied, the amount of the calcium-containing material to be installed, and, if the calcium-containing material is to be transported, the size of the transport means, and so cannot be generalized. For example, when the carbon dioxide capture tower is assumed to be permanently installed and is cylindrical, the cross-sectional diameter is 30 cm or more, 50 cm or more, or 1 m or more, with an upper limit of 3 m or less. When it is assumed to be transported, the cross-sectional diameter is 10 cm or more, 30 cm or more, or 50 cm or more, with an upper limit of 2 m or less, or 1 m or less. When the shape is other than cylindrical, the diameter of the inscribed circle of the cross section should be within the above range.

[0036] The height of the carbon dioxide capture tower is not particularly limited, and can be determined taking into consideration the amounts of the alkali metal-containing aqueous solution and the carbon dioxide-containing exhaust gas to be supplied, the amount of the calcium-containing material to be installed, and the size of the transport means when the calcium-containing material is transported, and therefore cannot be generalized. For example, if it is intended to be permanently installed, the length should be at least 50 cm, at least 1 m, at least 5 m, with an upper limit of 10 m or less, and at most 7 m. If it is intended to be transported, the length should be at least 20 cm, at least 50 cm, at least 1 m, with an upper limit of 8 m or less, and at most 5 m or less, and at most 1 m.

[0037] The internal volume of the carbon dioxide capture tower (excluding the storage tank) is preferably 3×Vc (volume parts) or more, more preferably 20×Vc (volume parts) or more, and even more preferably 100×Vc (volume parts) or more, relative to the supply rate Vc (volume parts / minute) of exhaust gas containing carbon dioxide, and the upper limit is preferably 200×Vc (volume parts) or less, more preferably 80×Vc (volume parts) or less, and even more preferably 50×Vc (volume parts) or less. The internal volume of the carbon dioxide capture tower (excluding the storage tank) can also be considered as the "supply amount of flue gas containing carbon dioxide relative to the internal volume of the carbon dioxide capture tower (excluding the storage tank)," and can therefore be considered as the recommended supply amount of flue gas containing carbon dioxide to the capture device of this embodiment. Therefore, the supply amount of flue gas containing carbon dioxide to the capture device of this embodiment can be determined within the above-mentioned numerical range.

[0038] Furthermore, for easy transportation and installation, it is preferable that the carbon dioxide absorption tower has a disassembly structure, for example, a structure that allows the carbon dioxide absorption tower to be divided into two or more parts in the horizontal direction, or a structure that allows the spraying jig for the alkali metal-containing aqueous solution and the screen to be detachable.

[0039] (alkali metal-containing aqueous solution) The alkali metal-containing aqueous solution can be any aqueous solution containing an alkali metal, and is preferably an aqueous solution of an alkali metal salt. As mentioned above, preferred examples of alkali metal salts include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. Furthermore, waste materials such as waste alkalis, such as waste soda solution, waste photographic developer solution, waste degreasing solution, and waste metal soap solution, also contain alkali metals, and these can be used as the alkali metal-containing aqueous solution. Furthermore, an aqueous solution of concentrated alkali metals obtained by separating a liquid containing an alkali metal salt, such as seawater, by electrolysis, membrane separation, or the like, can also be used.

[0040] The content of the alkali metal contained in the alkali metal-containing aqueous solution is preferably 1% by mass or more, more preferably 3% by mass or more, as the content of the alkali metal salt, with the upper limit being preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and even more preferably 12% by mass or less. When the alkali metal content is within the above range, the reactions 1 and 2 described above are more likely to proceed, and the versatility of the device can be improved, such as more efficient miniaturization, and carbon dioxide emissions can be reduced.

[0041] (circulation means) The carbon dioxide capture device of this embodiment preferably includes a storage tank for storing the alkali metal-containing aqueous solution below the supply port for the carbon dioxide-containing exhaust gas. By providing the storage tank at the bottom of the carbon dioxide capture tower, the carbon dioxide capture device of this embodiment can be made smaller, making it easier to install the device anywhere.

[0042] Furthermore, the carbon dioxide capture apparatus of this embodiment may be operated while constantly supplying and discarding new alkali metal-containing aqueous solution, or may be operated while supplying the alkali metal-containing aqueous solution stored in the storage tank through an alkali metal-containing aqueous solution supply port of the carbon dioxide capture tower, i.e., while circulating the alkali metal-containing aqueous solution. From the viewpoint of improving the versatility of the apparatus, such as achieving more efficient miniaturization, and reducing carbon dioxide, it is preferable to operate while circulating the alkali metal-containing aqueous solution. Since the carbon dioxide capture apparatus of this embodiment operates while circulating the alkali metal-containing aqueous solution, it is preferable to include a circulation means for supplying the alkali metal-containing aqueous solution stored in the storage tank through the alkali metal-containing aqueous solution supply port of the carbon dioxide capture tower.

[0043] In the above reactions 1 and 2, which are preferred reactions that occur in the carbon dioxide capture tower, focusing on the alkali metal-containing aqueous solution, when the alkali metal-containing aqueous solution (preferably an aqueous solution of an alkali metal hydroxide) is supplied into the carbon dioxide capture tower from a supply port, it reacts with the exhaust gas containing carbon dioxide to produce an aqueous solution of alkali metal carbonate, and the alkali metal carbonate reacts with a calcium-containing substance (preferably a substance containing calcium oxide) to produce an alkali metal-containing aqueous solution (preferably an aqueous solution of alkali metal hydroxide). In other words, when the alkali metal-containing aqueous solution discharged from the storage tank is supplied to the carbon dioxide capture tower, it undergoes the above reactions 1 and 2 and is recovered in the storage tank as an alkali metal-containing aqueous solution. Therefore, by providing a circulation means together with the storage tank, if an alkali metal-containing aqueous solution is initially stored in the storage tank, it becomes possible to capture carbon dioxide as calcium carbonate in the carbon dioxide capture tower without newly supplying an alkali metal-containing aqueous solution. In addition, there is no need to consider the supply of an alkali metal-containing aqueous solution from the outside, and since the system can be made compact, there is no need to select an installation location, thereby improving versatility.

[0044] As described above, the circulation means preferably has a storage tank, and also preferably has an alkali metal-containing aqueous solution supply pump for sending the alkali metal-containing aqueous solution from the storage tank through a supply port for the alkali metal-containing aqueous solution into the carbon dioxide capture tower. The presence of the storage tank and pump is shown in Figure 1.

[0045] The alkali metal-containing aqueous solution supply pump can be a submersible pump as shown in Figure 1, or a land-based pump installed on land. Considering that the carbon dioxide absorption tower can be made smaller and that the capture device can be installed anywhere, it is preferable to use a submersible pump.

[0046] Furthermore, when the recovery device of this embodiment uses a submersible pump as the alkali metal-containing aqueous solution supply pump, it may be provided with a pump tank for installing the submersible pump, connected to the storage tank, as shown in Figure 1 in which the submersible pump is installed.

[0047] (Calcium-containing substances) The calcium-containing material can be any material containing a substance containing calcium atoms, and is preferably a material containing a substance that can promote the above reactions 1 and 2, i.e., a material containing calcium oxide. The calcium-containing material is preferably a material containing calcium oxide, from the viewpoint of facilitating the above-mentioned preferred reactions 1 and 2. Preferred examples of materials capable of promoting the reactions 1 and 2, preferably materials containing calcium oxide, include calcium-containing waste materials such as garbage incineration ash, slag, waste concrete, ready-mixed concrete sludge, and biomass ash, as well as calcium-containing minerals such as slaked lime.

[0048] Ready-mixed concrete sludge, which is an example of the calcium-containing waste, is a waste generated mainly in ready-mixed concrete plants and precast concrete plants, as described above. The ready-mixed concrete sludge generated in these plants can be used as is, or can be formed into ready-mixed concrete sludge cake and then used.

[0049] Taking ready-mixed concrete sludge as an example of a calcium-containing material, ready-mixed concrete sludge contains calcium oxide as a main component, which is a substance containing calcium atoms. The calcium oxide content cannot be generally defined, but is usually 10% by mass or more, preferably 20% by mass or more, and more preferably 30% by mass or more, with the upper limit usually being 60% by mass or less. Various metal oxides, such as silicon oxide, alumina, iron oxide, and manganese oxide, are also included.

[0050] The shape of the calcium-containing material is not particularly limited and may be any of an approximately spherical shape, an approximately rectangular parallelepiped shape, an approximately cubic shape, etc. The size of the calcium-containing material can be appropriately selected depending on the size of the carbon dioxide absorption tower, etc., and cannot be generally specified. However, for example, the diameter of the circumscribing sphere is preferably 0.5 mm or more, more preferably 1.0 mm or more, and even more preferably 1.5 mm or more, with the upper limit being preferably 10.0 cm or less, more preferably 5.0 cm or less, and even more preferably 2.5 cm or less. When the size of the calcium-containing material is within the above range, the reactions 1 and 2 described above are easily promoted, and the versatility of the device can be improved, such as more efficient miniaturization, and carbon dioxide emissions can be reduced.

[0051] The amount of calcium-containing material to be installed can be determined appropriately depending on the supply rate of the alkali metal-containing aqueous solution and the progress of the above reactions 1 and 2. Therefore, the amount of calcium content to be installed cannot be generally defined. However, for example, the supply rate of the alkali metal-containing aqueous solution (preferably an alkali metal hydroxide aqueous solution) per 1 part by mass of the calcium-containing material is preferably 0.01 parts by mass / min or more, more preferably 0.05 parts by mass / min or more, and even more preferably 0.1 parts by mass / min or more, with the upper limit being preferably 1.0 parts by mass / min or less, more preferably 0.75 parts by mass / min or less, and even more preferably 0.5 parts by mass / min or more. When the amount of calcium-containing material installed is within the above range, the above reactions 1 and 2 are more likely to proceed, and the versatility of the device can be improved, such as by being more efficient and being more compact, while also reducing carbon dioxide emissions. The amount of the calcium-containing substance to be installed can also be considered as the "amount of the alkali metal-containing aqueous solution to be supplied relative to the amount of the calcium-containing substance installed," and can therefore be regarded as the recommended amount of the alkali metal-containing aqueous solution to be supplied to the recovery device of this embodiment. Therefore, the amount of the alkali metal-containing aqueous solution to be supplied to the recovery device of this embodiment can be determined within the above-mentioned numerical range.

[0052] The amount of calcium content to be installed may be determined by the height of the calcium content when installed on the screen. In this case, the height of the calcium content may be determined taking into consideration the size of the carbon dioxide capture tower, etc., and is preferably 2 cm or more, more preferably 10 cm or more, with an upper limit of 60 cm or less. By setting the height in this manner, the reactions 1 and 2 described above can be easily promoted, and the versatility of the device can be improved, such as more efficient and more compact, and carbon dioxide emissions can be reduced.

[0053] (exhaust gas containing carbon dioxide) The carbon dioxide-containing exhaust gas can be any gas containing carbon dioxide without any particular limitation, and preferred examples include exhaust gas containing carbon dioxide generated during the operation of various facilities such as power plants, incinerators, cement plants, steel mills, factory facilities, etc. This is because the use of exhaust gas generated in these various facilities can reduce the amount of carbon dioxide emitted into the atmosphere.

[0054] The exhaust gas containing carbon dioxide can be directly received from the various facilities described above. The temperature at which the exhaust gas is supplied to the carbon dioxide recovery tower is not particularly limited and cannot be generalized as it may vary depending on the various facilities described above, but is usually 20°C or higher and 250°C or lower, or even 50°C or higher or 80°C or higher, with the upper limit being 200°C or lower or 150°C or lower.

[0055] The carbon dioxide content contained in the carbon dioxide-containing exhaust gas is not particularly limited, and cannot be generalized as it may vary depending on the various types of equipment described above, but is usually 0.5% by volume or more and 25% by volume or less, further 1% by volume or more, or 3% by volume or more, with the upper limit being 25% by volume or less, 15% by volume or less, or 10% by volume or less.

[0056] The carbon dioxide capture device of this embodiment can be easily adapted to changes in scale and is versatile enough to be installed anywhere, so that the carbon dioxide-containing exhaust gas used in the carbon dioxide absorption tower can be easily installed in the various facilities described above. By installing the device in the various facilities described above, the carbon dioxide-containing exhaust gas can be procured at the various facilities. Furthermore, as described above, calcium-containing materials are waste materials discarded in factory facilities such as ready-mix concrete plants and precast concrete plants.

[0057] On the other hand, the carbon dioxide capture apparatus of this embodiment preferably can perform the above reactions 1 and 2 in a single carbon dioxide capture tower, and therefore has the advantage of being easy to miniaturize. Therefore, carbon dioxide capture can be performed by transporting the carbon dioxide capture apparatus of this embodiment to multiple various facilities using a transportation means such as a truck, and traveling around while repeatedly capturing carbon dioxide. Furthermore, when traveling around, carbon dioxide capture can be performed while replenishing calcium-containing material at the above-mentioned factory facilities. Furthermore, since the capture apparatus of this embodiment can be miniaturized and has a relatively simple structure, it can also be assembled and used at locations where carbon dioxide capture is required. As described above, the carbon dioxide recovery device of this embodiment has excellent versatility, can be easily miniaturized, and as a result, can be said to be a device with excellent distribution capabilities.

[0058] (Other aspects) The above has described the case where an alkali metal-containing aqueous solution is used, but in the carbon dioxide recovery equipment of this embodiment, an ammonium ion-containing aqueous solution can be used together with the alkali metal-containing aqueous solution or as an aqueous solution separate from the alkali metal-containing aqueous solution. That is, an alkali metal-containing aqueous solution and an ammonium ion-containing aqueous solution can be used together (it can also be said that the alkali metal-containing aqueous solution is an aqueous solution that further contains ammonium ions). Furthermore, as an embodiment separate from the recovery device of this embodiment and as an embodiment separate from the alkali metal-containing aqueous solution, an ammonium ion-containing aqueous solution can be used alone instead of the alkali metal-containing aqueous solution.

[0059] In another embodiment of the recovery facility, an ammonium ion-containing aqueous solution is used alone instead of the alkali metal-containing aqueous solution. a carbon dioxide recovery tower provided with a supply port for an ammonium ion-containing aqueous solution, a screen, and a supply port for a carbon dioxide-containing flue gas; a supply port for the aqueous solution is provided at an upper portion of the carbon dioxide recovery tower, the exhaust gas supply port is provided in a lower part of the carbon dioxide absorption tower, the screen is provided between the aqueous solution supply port and the exhaust gas supply port; A calcium-containing material is placed on the screen. The configuration of this recovery apparatus is the same as that described above in connection with the recovery apparatus in which the aqueous solution used is an aqueous solution containing an alkali metal.

[0060] When an aqueous solution containing ammonium ions is used, the following reactions 3 and 4 are preferably exemplified as reactions that occur in the carbon dioxide absorption tower.

[0061] Reaction 3:2(NH4) n M + nCO2 + nH2O → n(NH4)2(CO3) + 2H n M Reaction 4: n(NH4)2(CO3) + nCaO + 2H n M → nCa(CO3) + 2(NH4) n M+nH2O In the above reactions 3 and 4, M represents an anion selected from a halide ion, a hydroxide ion, an inorganic acid ion, and an organic acid ion, and n represents an integer of 1 to 3.

[0062] The ammonium ion-containing aqueous solution can be any aqueous solution containing ammonium ions without any particular limitation, and preferred examples include aqueous solutions of ammonium salts such as ammonium halides such as ammonium chloride; ammonium hydroxide; inorganic ammonium salts such as ammonium nitrate, ammonium sulfate, and ammonium phosphate; and organic ammonium salts such as ammonium oxalate and ammonium acetate, as shown in the reaction formulas of Reactions 3 and 4 above.

[0063] [Method of capturing carbon dioxide] The carbon dioxide recovery method of the present embodiment includes: contacting an aqueous solution of an alkali metal hydroxide with exhaust gas containing carbon dioxide to obtain an aqueous solution of an alkali metal carbonate; contacting the aqueous solution of the alkali metal carbonate with a calcium-containing substance to obtain calcium carbonate; This is a method for capturing carbon dioxide, including:

[0064] The carbon dioxide recovery method of this embodiment is not limited in its mode as long as it can obtain the aqueous solution of the alkali metal carbonate and calcium carbonate, and can be preferably carried out using the carbon dioxide recovery apparatus of this embodiment. This is because the carbon dioxide recovery method of this embodiment can be easily carried out by using the carbon dioxide recovery apparatus of this embodiment. Therefore, according to the carbon dioxide recovery method of this embodiment, it is possible to reduce the carbon dioxide contained in the exhaust gas while effectively utilizing calcium, and also to improve the versatility of the recovery device used.

[0065] More specifically, the recovery method of this embodiment can be carried out by supplying an aqueous solution of alkali metal hydroxide to a carbon dioxide capture tower through an alkali metal-containing aqueous solution supply port, placing a calcium-containing material on a screen of the carbon dioxide capture tower, and supplying a carbon dioxide-containing flue gas to a carbon dioxide absorption tower through a carbon dioxide-containing flue gas supply port. That is, obtaining the aqueous solution of alkali metal carbonate and obtaining calcium carbonate can be carried out in a single carbon dioxide absorption tower. In this way, the recovery method of this embodiment can more efficiently obtain the aqueous solution of alkali metal carbonate and calcium carbonate based on the above reactions 1 and 2, respectively.

[0066] The aqueous solution of alkali metal hydroxide, the exhaust gas containing carbon dioxide, and the calcium-containing substance in the recovery method of this embodiment are the same as those described in the recovery apparatus of this embodiment. The amounts of the aqueous solution of alkali metal hydroxide, the exhaust gas containing carbon dioxide, and the calcium-containing substance used, and the reactions caused by these are also the same as those described in the recovery apparatus of this embodiment.

[0067] It is preferable to use the aqueous solution of alkali metal hydroxide obtained by obtaining calcium carbonate in obtaining an aqueous solution of alkali metal carbonate, i.e., to circulate the aqueous solution of alkali metal hydroxide. The circulation of the aqueous solution of alkali metal hydroxide can be carried out by using a circulation means preferably provided in the recovery apparatus of the present embodiment.

[0068] (Other forms) As explained above with respect to the recovery apparatus of this embodiment, in the recovery method of this embodiment, an ammonium ion-containing aqueous solution can be used as an aqueous solution used together with the alkali metal-containing aqueous solution or as an aqueous solution separate from the alkali metal-containing aqueous solution. That is, an alkali metal-containing aqueous solution and an ammonium ion-containing aqueous solution can be used in combination (it can also be said that the alkali metal-containing aqueous solution is an aqueous solution further containing ammonium ions). Furthermore, as an embodiment different from the recovery method of this embodiment, an ammonium ion-containing aqueous solution can be used alone instead of the alkali metal-containing aqueous solution.

[0069] In another embodiment of the recovery method, an ammonium ion-containing aqueous solution is used alone instead of the alkali metal-containing aqueous solution, contacting an aqueous solution containing ammonium ions with exhaust gas containing carbon dioxide to obtain an aqueous solution of ammonium carbonate; and contacting the aqueous solution of ammonium carbonate with a calcium-containing substance to obtain calcium carbonate; This is a carbon dioxide capture method that includes:

[0070] In a recovery method according to another embodiment in which an ammonium ion-containing aqueous solution alone is used, the recovery method can be preferably carried out using the recovery apparatus according to the present embodiment, as in the recovery method according to the present embodiment. In this case, the preferred reactions occurring in the carbon dioxide recovery tower are the above-mentioned reactions 3 and 4, and other aspects are the same as in the recovery method according to the present embodiment. [Example]

[0071] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0072] (Measured using a thermogravimetric differential thermal analyzer) Thermogravimetric differential thermal analysis (TG-DTA) was performed using a thermogravimetric differential thermal analyzer (TG-DTA) ("STA 2500Regulus (model number)" manufactured by NETZSCH). More specifically, samples (approximately 10 mg to 20 mg) were packed into a Pt pan and heated from 30°C at a rate of 10°C / min in an N2 atmosphere. The weight change of each sample was analyzed to measure the calcium carbonate content.

[0073] Example 1 A carbon dioxide absorption tower with the configuration shown in Figure 1 was used (stainless steel, internal capacity: 1700 L, diameter: 700 mm (internal diameter: 600 mm), height: 6000 mm). A sodium hydroxide aqueous solution (sodium hydroxide content: 5% by mass) was used as the alkali metal-containing aqueous solution, and ready-mixed concrete sludge (300 kg, particle size: 2-10 mm) with the composition shown in Table 1 was used as the calcium-containing material. 150 kg of each was placed on the upper and lower screens (height of ready-mixed concrete sludge: 300 mm). Furthermore, combustion exhaust gas from an aggregate drying boiler was used as the carbon dioxide-containing exhaust gas (carbon dioxide content: 5% by volume, temperature: 100°C).

[0074] [Table 1] The composition of the above-mentioned fresh concrete sludge was measured by measuring a fresh concrete sludge sample (3 g) using an X-ray fluorescence spectrometer (energy dispersive type) (Epsilon 3XLE (model number), manufactured by Marvern Panalytical).

[0075] Using the recovery device equipped with the carbon dioxide absorption tower, the alkali metal-containing aqueous solution supply pump was started, and the alkali metal-containing aqueous solution was supplied at a rate of 100 L / min from the supply ports so that the same amount was supplied (50 L / min from each of the upper and lower supply ports). 3 The supply of exhaust gas containing carbon dioxide to the carbon dioxide absorption tower was started at a supply rate of 1 / min, and operation was carried out for one hour. The calcium carbonate content in the fresh concrete sludge before and after the operation was measured using a thermogravimetric differential thermal analyzer (TG-DTA device), and it was found to have increased significantly from 15.9 mass% before operation to 27.3 mass% after operation.

[0076] Examples 2 to 4 The carbon dioxide recovery apparatus was operated in the same manner as in Example 1, except that the supply amount and concentration of the alkali metal-containing aqueous solution and the amount of fresh concrete sludge used were changed to the values ​​shown in Table 1. The measurement results of the calcium carbonate content in the fresh concrete sludge before and after operation are shown in Table 1.

[0077] [Table 2]

[0078] The results of Examples 1 to 4 confirmed that the recovery device of this embodiment is a compact and highly versatile device, and that the recovery device and recovery method of this embodiment can effectively utilize calcium while reducing the carbon dioxide contained in exhaust gas.

[0079] Example 5 A carbon dioxide absorption tower with the configuration shown in Figure 1 was used (stainless steel, internal volume: 120 L, diameter: 500 mm (internal diameter: 490 mm), height: 800 mm). A sodium hydroxide aqueous solution (sodium hydroxide content: 7% by mass) was used as the alkali metal-containing aqueous solution, and ready-mixed concrete sludge (100 g, particle size: 2-10 mm) discarded from a ready-mixed concrete plant with the composition shown in Table 1 above was used as the calcium-containing material. 50 g of each was placed on the upper and lower screens (height of ready-mixed concrete sludge: 20 mm). Furthermore, a mixed gas (a mixture of carbon dioxide gas at 1 L / min and air at 28 L / min) was used as the carbon dioxide-containing exhaust gas (carbon dioxide content: 3% by volume, temperature: 25°C).

[0080] Using the recovery device equipped with the carbon dioxide absorption tower, the alkali metal-containing aqueous solution supply pump was started, and the alkali metal-containing aqueous solution was supplied at a rate of 30 mL / min from the supply ports so that the same amount was supplied (50 L / min from each of the two upper and lower supply ports). Next, the supply of the mixed gas to the carbon dioxide absorption tower was started at a rate of 29 L / min, and operation was carried out for 1 hour. The carbon dioxide concentration in the mixed gas discharged from the carbon dioxide absorption tower was measured, and the amount of carbon dioxide reduction (moles) calculated from the difference between the carbon dioxide concentration in the mixed gas supplied to the carbon dioxide recovery tower and the carbon dioxide concentration in the discharged mixed gas was divided by the amount (moles) of alkali metal salt contained in the alkali metal-containing aqueous solution supplied to obtain the reaction rate, which was found to be 82.2%.

[0081] (Examples 6 to 8 and Comparative Example 1) The carbon dioxide recovery apparatus was operated in the same manner as in Example 5, except that the contents of the alkali metal salt and the alkali metal salt contained in the alkali metal-containing aqueous solution were set to the values ​​shown in Table 3. The reaction rate results are shown in Table 3.

[0082] [Table 3]

[0083] The results of Examples 5 to 8 confirmed that an extremely high reaction rate can be obtained by using an alkali metal-containing aqueous solution.The results of these Examples confirmed that the use of an alkali metal-containing aqueous solution can reduce the carbon dioxide contained in the exhaust gas while effectively utilizing calcium.

Claims

1. a carbon dioxide recovery tower provided with a supply port for an alkali metal-containing aqueous solution, a screen, and a supply port for a carbon dioxide-containing flue gas; a supply port for the aqueous solution is provided at an upper portion of the carbon dioxide recovery tower, the exhaust gas supply port is provided in a lower part of the carbon dioxide absorption tower, the screen is provided between the aqueous solution supply port and the exhaust gas supply port; A calcium-containing material is placed on the screen. Carbon dioxide capture equipment.

2. 2. The carbon dioxide recovery apparatus according to claim 1, comprising two or more of the aqueous solution supply ports and the screen, and the screens and the aqueous solution supply ports are provided alternately from the bottom to the top of the carbon dioxide absorption tower.

3. 3. The carbon dioxide recovery device according to claim 1, further comprising: a storage tank for the aqueous solution located below the exhaust gas supply port of the carbon dioxide absorption tower; and a circulation unit that supplies the aqueous solution stored in the storage tank from the aqueous solution supply port.

4. contacting an aqueous solution of an alkali metal hydroxide with exhaust gas containing carbon dioxide to obtain an aqueous solution of an alkali metal carbonate; contacting the aqueous solution of the alkali metal carbonate with a calcium-containing substance to obtain calcium carbonate; A method for capturing carbon dioxide, comprising:

5. 5. The method for recovering carbon dioxide according to claim 4, wherein obtaining the aqueous solution of alkali metal carbonate and obtaining the calcium carbonate are carried out in a single carbon dioxide absorption tower.

6. 6. The method for recovering carbon dioxide according to claim 4 or 5, wherein the aqueous solution of alkali metal hydroxide obtained by obtaining calcium carbonate is used in obtaining the aqueous solution of alkali metal carbonate.

7. 6. The method for recovering carbon dioxide according to claim 4, wherein the calcium-containing material is selected from calcium-containing waste and calcium-containing minerals.

8. 6. The method for recovering carbon dioxide according to claim 4, wherein the supply rate of the aqueous solution of alkali metal hydroxide per part by mass of the calcium-containing material is 0.01 parts by mass / minute or more and 1.0 parts by mass / minute or less.

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