Separation device for carbon dioxide gas

Abstract

The present invention reduces the consumption of a solute used for generating alkaline water while using the alkaline water for efficiently separating carbon dioxide gas from exhaust gas, so as to reduce running costs. A separation device for carbon dioxide gas according to the present invention comprises: a steam generation part that heats alkaline water to a boiling point or higher and generates alkaline water steam; a mixing part that mixes the alkaline water steam with exhaust gas to form steam-mixed exhaust gas; a cooling part that cools the steam-mixed exhaust gas to form mist-containing exhaust gas containing mist in which the carbon dioxide gas is absorbed and which is formed by condensation of the alkaline water steam having absorbed carbon dioxide gas; a recovered water separation part that recovers, as recovered water from the mist-containing exhaust gas, the mist in which the carbon dioxide gas is absorbed; a vaporization part that heats and vaporizes the recovered water to form mixed gas which contains the carbon dioxide gas and the alkaline water steam; a gas separation part that filters the mixed gas with a gas separation membrane to separate the carbon dioxide gas and solute gas of the alkaline water; and a solute mixing part that dissolves, in water, the solute gas of the alkaline water to form alkaline water.

Description

Carbon dioxide separator

[0001] The present invention relates to an apparatus for separating carbon dioxide gas from exhaust gas, and more particularly to an apparatus for separating carbon dioxide gas from exhaust gas emitted from plants such as power plants, cement factories, and blast furnaces, or from exhaust gas from internal combustion engines. Since air includes exhaust gas emitted from plants and internal combustion engines, the carbon dioxide gas separation apparatus disclosed herein is used in a broad sense to include an apparatus for separating carbon dioxide gas from air containing exhaust gas.

[0002] Apparatuses for removing carbon dioxide from exhaust gas have been developed (see Patent Documents 1 and 2). These patent documents disclose a technique for absorbing carbon dioxide by bringing alkaline water containing a carbon dioxide absorbent into contact with the exhaust gas.

[0003] JP 2005-211878 A JP 2018-79409 A

[0004] Conventional devices contact flue gas with alkaline water, allowing the alkaline water to absorb and separate carbon dioxide and other gases contained in the flue gas. This method presents a challenge in efficiently absorbing carbon dioxide contained in flue gas. Carbon dioxide absorption efficiency can be improved by converting alkaline water into fine droplets, i.e., a mist, to increase the contact area with the carbon dioxide. To absorb carbon dioxide in this state, structures are used, such as spraying alkaline water from a nozzle to form a mist and mixing the mist with the flue gas to increase the contact area, or forming a mat of fine fibers with voids. While spraying alkaline water onto the mat, the flue gas passes through the voids in the fibers, increasing the contact area between the flue gas and the alkaline water. However, even these structures cannot efficiently absorb carbon dioxide and other gases contained in flue gas. Conventional separation devices that cannot efficiently separate carbon dioxide and other gases are large, resulting in problems such as high capital and running costs.

[0005] Furthermore, by utilizing the physical property that carbon dioxide gas dissolves easily in alkaline water, carbon dioxide gas can be efficiently absorbed by contacting the alkaline water mist with exhaust gas. Furthermore, since alkaline water absorbs carbon dioxide gas by combining 1 mole of solute with 1 mole of carbon dioxide gas, the amount of solute used increases in proportion to the amount of carbon dioxide gas separated. Therefore, although separation devices that use alkaline water can efficiently absorb carbon dioxide gas, the amount of solute used to generate alkaline water increases in proportion to the amount of carbon dioxide gas separated, resulting in a problem of high running costs.

[0006] The present disclosure has been developed with the aim of eliminating the above drawbacks, and one of the objects of the present disclosure is to provide an apparatus that can efficiently separate carbon dioxide gas from exhaust gas using alkaline water while reducing the consumption of solutes used to generate the alkaline water, thereby reducing running costs and efficiently separating carbon dioxide gas from exhaust gas.

[0007] A carbon dioxide separation device according to one embodiment of the present disclosure includes a steam generation section that heats alkaline water above its boiling point to generate alkaline water vapor, a mixing section that mixes the alkaline water vapor generated in the steam generation section with exhaust gas to generate a steam-mixed exhaust gas, a cooling section that cools the steam-mixed exhaust gas obtained in the mixing section to generate a mist-containing exhaust gas containing carbon dioxide-absorbed mist formed when alkaline water vapor absorbs carbon dioxide and condenses, a recovered water separation section that recovers the carbon dioxide-absorbed mist from the mist-containing exhaust gas obtained in the cooling section as recovered water, an evaporation section that heats and vaporizes the carbon dioxide-absorbed water obtained in the recovered water separation section to generate a mixed gas containing carbon dioxide and alkaline water vapor, a gas separation section that filters the mixed gas obtained in the evaporation section using a gas separation membrane to separate the carbon dioxide and solute gas of the alkaline water, and a solute mixing section that dissolves the solute gas of the alkaline water separated in the gas separation section in water to generate alkaline water. The alkaline water obtained in the solute mixing section is circulated to the steam generation section, and carbon dioxide is separated from the exhaust gas.

[0008] The carbon dioxide separation device described above has the advantage of being able to efficiently separate carbon dioxide from exhaust gas using alkaline water while reducing the consumption of solutes used to generate the alkaline water, thereby reducing running costs and efficiently separating carbon dioxide from exhaust gas.

[0009] FIG. 1 is a schematic configuration diagram of a carbon dioxide gas separation device according to an embodiment of the present disclosure. FIG. 1 is a schematic configuration diagram showing an example of a steam generating section, a mixing section, a cooling section, and a recovered water separating section. FIG. 2 is a schematic configuration diagram showing an example of a steam generating section and a mixing section. FIG. 3 is a schematic configuration diagram showing another example of a steam generating section and a mixing section. FIG. 4 is a schematic configuration diagram showing another example of a steam generating section, a mixing section, a cooling section, and a recovered water separating section. FIG. 5 is a schematic configuration diagram showing another example of a steam generating section, a mixing section, a cooling section, and a recovered water separating section. FIG. 6 is a schematic configuration diagram showing another example of a recovered water separating section and a cooling section.

[0010] The present disclosure will be described in detail below with reference to the drawings. In the following description, terms indicating specific directions or positions (e.g., "upper," "lower," and other terms including these terms) will be used as necessary. However, the use of these terms is intended to facilitate understanding of the invention with reference to the drawings, and the meaning of these terms does not limit the technical scope of the present invention. Furthermore, parts with the same reference numerals appearing in multiple drawings indicate the same or equivalent parts or components. Furthermore, the embodiments described below are illustrative examples of the technical concept of the present invention and do not limit the scope of the present invention to the following. Furthermore, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described below are intended for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, the content described in one embodiment or example can also be applied to other embodiments or examples. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity.

[0011] The embodiments of the present disclosure may be specified by the following configurations and features. a cooling section that cools the steam-mixed exhaust gas obtained in the mixing section to produce a mist-containing exhaust gas containing a carbon dioxide gas-absorbed mist formed when the alkaline steam absorbs and condenses with carbon dioxide gas; a recovered water separation section that recovers the carbon dioxide gas-absorbed mist from the mist-containing exhaust gas obtained in the cooling section as recovered water; an evaporation section that heats and vaporizes the carbon dioxide gas-absorbed water obtained in the recovered water separation section to produce a mixed gas containing carbon dioxide gas and alkaline water vapor; a gas separation section that filters the mixed gas obtained in the evaporation section using a gas separation membrane to separate the carbon dioxide gas and the solute gas of the alkaline water; and a solute mixing section that dissolves the solute gas of the alkaline water separated in the gas separation section in water to produce alkaline water. The alkaline water obtained in the solute mixing section is circulated to the steam generating section, and carbon dioxide gas is separated from the exhaust gas.

[0012] The carbon dioxide separation device described above has the advantage of being able to efficiently absorb and separate carbon dioxide from exhaust gases. This is because, in addition to using alkaline water to absorb carbon dioxide, the alkaline water vapor mixed with the exhaust gas absorbs more carbon dioxide as it cools and becomes supersaturated, turning into mist, and then condenses into mist.

[0013] The alkaline water vapor (alkaline water vapor) generated in the steam generation section has a mass of 6 x 10 ２３The alkaline water vapor is dispersed into a vast number of water vapors, numbering approximately 100 (Avogadro's constant), and mixed into the exhaust gas. The alkaline water vapor dispersed and mixed into the exhaust gas becomes fine particles on the order of angstroms, which is incomparable to the mist of unvaporized alkaline water, and disperses into the exhaust gas and mixes with the carbon dioxide in the exhaust gas. When the alkaline water vapor mixed with the exhaust gas is cooled, the supersaturated alkaline water vapor condenses into mist. However, as the countless vaporized vapors condense into a liquefied mist, the alkaline water efficiently absorbs the carbon dioxide in the exhaust gas and condenses into mist. Therefore, a system that heats alkaline water to produce alkaline water vapor, mixes the alkaline water vapor with the exhaust gas, and then cools the mixture to absorb and separate the carbon dioxide into the mist has the advantage of being able to separate carbon dioxide extremely efficiently, compared to a system that sprays alkaline water mist into the exhaust gas, mixes the mist with carbon dioxide, and separates the carbon dioxide by absorbing the carbon dioxide into the mist.

[0014] The above separation device is able to absorb carbon dioxide gas extremely efficiently because (1) in addition to using alkaline water to absorb carbon dioxide gas, (2) alkaline water is mixed with exhaust gas in the form of vaporized water vapor (alkaline water vapor), and (3) the alkaline water vapor is further cooled and condensed in a supersaturated state, which is then separated from the exhaust gas.

[0015] In systems that spray alkaline water into exhaust gases to bring the alkaline water into contact with carbon dioxide, the average particle size of the sprayed alkaline water is incomparably larger than that of alkaline water vapor (alkaline water vapor). Since the surface area of ​​particles per unit weight increases inversely proportional to the particle size, alkaline water mist with a large average particle size has a small surface area per unit weight and a small contact area with carbon dioxide, making it unable to efficiently absorb carbon dioxide. While the mist generated by atomizing alkaline water using ultrasonic vibration or electrostatic spraying can be made smaller than that sprayed from a nozzle, systems that use ultrasonic vibration or electrostatic spraying to create fine mist require complex structures, resulting in high equipment costs, and also consumes a lot of energy, resulting in high running costs. Even with complex systems, even if the particle size of the vaporized vapor is incomparably larger, it is not possible to generate significantly finer particles of alkaline water.

[0016] The separation device disclosed herein vaporizes alkaline water into vapor instead of a fine mist, making it possible to make particle sizes extremely small (on the order of angstroms) and dramatically increasing the surface area per unit weight. Furthermore, the alkaline water vapor, which has an extremely large surface area, absorbs carbon dioxide as it cools and liquefies, becoming a mist that absorbs carbon dioxide. Therefore, a device that mixes alkaline water vapor (alkaline water vapor) with exhaust gas to produce a steam-mixed exhaust gas, cools this steam-mixed exhaust gas, and separates carbon dioxide from the exhaust gas has the advantage of being able to very efficiently absorb and separate carbon dioxide from the exhaust gas.

[0017] Furthermore, the above separation device uses alkaline water to efficiently recover carbon dioxide, but its unique structure recovers and reuses solutes such as ammonia used to generate the alkaline water to separate carbon dioxide, thereby achieving the advantage of reducing the amount of solute consumed to generate alkaline water. The unique structure for recovering solutes such as ammonia recovers carbon dioxide-absorbed mist formed by absorbing carbon dioxide and condensing the mist, recovering the carbon dioxide-absorbed mist as recovered water, heating the recovered water so that it contains carbon dioxide and alkaline vapor and is vaporized again, separating the vaporized carbon dioxide and alkaline vapor with a gas separation membrane, and dissolving the separated alkaline vapor in water to produce alkaline water.

[0018] A carbon dioxide separation device according to another embodiment of the present disclosure can use ammonia water instead of alkaline water to convert alkaline water vapor into ammonia water vapor. This device efficiently absorbs carbon dioxide gas with ammonia water vapor (ammonia water vapor), heats the recovered water that has absorbed carbon dioxide gas to form a mixed gas containing ammonia and carbon dioxide gas, filters this mixed gas with a gas separation membrane to separate it into carbon dioxide gas and ammonia, and effectively reuses the separated ammonia to generate ammonia water to absorb carbon dioxide gas. Therefore, this device has the advantage of being able to efficiently separate carbon dioxide gas using ammonia water while reusing the ammonia to reduce ammonia consumption and running costs.

[0019] A carbon dioxide separation device according to another embodiment of the present disclosure can use a solution of a primary amine in alkaline water. This device uses a primary amine solution or a solution containing a primary amine in alkaline water to efficiently absorb carbon dioxide with the alkaline water, heats the recovered water that has absorbed the carbon dioxide to produce a mixed gas containing the primary amine and carbon dioxide, filters this mixed gas using a gas separation membrane to separate it into carbon dioxide and the primary amine, and effectively reuses the separated primary amine to produce alkaline water to absorb carbon dioxide. Therefore, this device has the advantage of being able to efficiently separate carbon dioxide with alkaline water while reusing the primary amine to reduce consumption and running costs.

[0020] Furthermore, the steam generating unit of the carbon dioxide gas separation device according to another embodiment of the present disclosure can generate steam mist containing both alkaline water vapor and unvaporized alkaline water mist. This separation device mixes the alkaline water steam mist with exhaust gas, and the carbon dioxide gas in the exhaust gas is absorbed by both the alkaline water vapor and the alkaline water mist, allowing it to be separated from the exhaust gas.

[0021] Furthermore, the steam generating section of the carbon dioxide separation device according to another embodiment of the present disclosure can generate alkaline steam containing superheated alkaline water vapor. This separation device can increase the temperature of the steam-mixed exhaust gas to increase the content of vaporized alkaline water, and is therefore characterized by being able to more efficiently absorb carbon dioxide gas with the large amount of alkaline steam contained in the steam-mixed exhaust gas. The steam-mixed exhaust gas has a saturated water vapor content of 83 g / m at 50°C. ３ , saturated water vapor amount 130 g / m at 60 ° C. ３ , saturated water vapor amount at 70°C is 197g / m ３ Therefore, by increasing the temperature of the steam-mixed exhaust gas, the amount of alkaline water that can be contained in the steam state can be significantly increased. Therefore, the steam-mixed exhaust gas, which can be heated by mixing high-temperature superheated steam with exhaust gas, has the advantage of containing a large amount of alkaline water in the steam state, absorbing a large amount of carbon dioxide, and being able to be efficiently separated from the exhaust gas.

[0022] In another aspect of the carbon dioxide separation device of the present disclosure, the steam generating unit can generate alkaline water vapor using exhaust heat from a plant that emits exhaust gas. The carbon dioxide separation device described above uses exhaust heat from a plant that emits exhaust gas to vaporize alkaline water to generate alkaline water vapor, which is advantageous in that it can effectively utilize the exhaust heat from the plant that emits exhaust gas to generate alkaline water vapor, reducing running costs and separating carbon dioxide from the exhaust gas. Because the exhaust heat from the plant that emits exhaust gas is utilized, the location where the exhaust gas is discharged and the location where the plant's exhaust heat is generated are close to each other, which allows for more efficient use of the plant's exhaust heat and also allows for efficient treatment of the exhaust gas emitted from the plant.

[0023] In another aspect of the carbon dioxide separation device according to the present disclosure, the plant can be a power plant, a blast furnace, a cement plant, or a chemical plant. The exhaust gas is exhaust gas emitted from a power plant, a blast furnace, a cement plant, or a chemical plant (such as a power plant), and the steam generating unit can heat alkaline water using waste heat from a power plant or other power plant. The carbon dioxide separation device described above effectively uses waste heat from a power plant or other power plant to vaporize alkaline water, thereby reducing the energy consumed to vaporize alkaline water and reducing running costs while efficiently treating exhaust gas from a power plant or other power plant. For example, alkaline water can be heated to alkaline steam using waste heat from a steam turbine that drives a generator in a power plant, thereby reducing the thermal energy required to cool the condenser with seawater. This allows carbon dioxide and other gases to be efficiently separated from the exhaust gas by effectively using the waste heat from the steam turbine while also suppressing the temperature rise of seawater caused by the power plant. In addition, by using waste heat from blast furnaces, cement kilns in cement factories, or chemical factories to heat and vaporize alkaline water, the energy consumed to vaporize alkaline water can be reduced, energy efficiency can be improved, and running costs can be reduced while efficiently treating exhaust gases from power plants, etc.

[0024] In another aspect of the carbon dioxide separation device of the present disclosure, the steam generating unit can generate alkaline steam by heating and vaporizing alkaline water using solar or geothermal energy. The carbon dioxide separation device described above has the advantage of being able to separate carbon dioxide from exhaust gas by effectively utilizing natural energy such as solar or geothermal energy to generate alkaline steam, reducing running costs.

[0025] In another aspect of the carbon dioxide separation device of the present disclosure, the vaporization section can heat the carbon dioxide recovery water with exhaust heat from a plant that discharges exhaust gas and vaporize it into a mixed gas. The above carbon dioxide separation device has the advantage that the vaporization section effectively utilizes exhaust heat from a plant that discharges exhaust gas to heat the carbon dioxide recovery water and vaporize it into a mixed gas, thereby reducing running costs and being able to separate carbon dioxide from the exhaust gas.

[0026] In another aspect of the carbon dioxide separation device of the present disclosure, the plant can be any one of a power plant, a blast furnace, a cement plant, and a chemical plant. The exhaust gas is exhaust gas emitted from any one of a power plant, a blast furnace, a cement plant, and a chemical plant (such as a power plant), and the vaporization unit can heat recovered carbon dioxide water using exhaust heat from a power plant or other power generation plant to vaporize it into a mixed gas. The above carbon dioxide separation device effectively uses exhaust heat from a power plant or other power generation plant to heat recovered carbon dioxide water and vaporize it into a mixed gas, thereby reducing the energy consumed to heat the recovered water and reducing running costs, and is therefore characterized by being able to efficiently treat exhaust gas from a power plant or the like.

[0027] In another aspect of the carbon dioxide separation device of the present disclosure, the vaporization section can heat the carbon dioxide recovery water with solar heat or geothermal heat and vaporize it into a mixed gas. The above carbon dioxide separation device has the advantage of being able to separate carbon dioxide from exhaust gas by effectively utilizing natural energy such as solar heat or geothermal heat to heat the carbon dioxide recovery water and vaporize it into a mixed gas, thereby reducing running costs.

[0028] In a carbon dioxide gas separation device according to another aspect of the present disclosure, the temperature of the steam-mixed exhaust gas supplied from the mixing section to the cooling section can be set to 50° C. or higher. The above carbon dioxide gas separation device has the advantage that the temperature of the steam-mixed exhaust gas before cooling to supply alkaline water vapor is increased to 50° C. or higher, the amount of alkaline water vapor supplied to the exhaust gas is increased, and a large amount of steam can be vaporized to efficiently separate carbon dioxide gas.

[0029] A carbon dioxide gas separation device according to another aspect of the present disclosure can set the temperature difference between the steam-mixed exhaust gas supplied to the cooling section and the mist-containing exhaust gas discharged from the cooling section to 30°C or more. The above carbon dioxide gas separation device can increase the amount of alkaline water liquefied by increasing the temperature difference between the steam-mixed exhaust gas supplied to the cooling section and the mist-containing exhaust gas discharged from the cooling section to 30°C or more. In other words, by increasing the temperature difference to 30°C or more, the alkaline water vapor is cooled and becomes supersaturated, causing it to condense, increasing the amount of mist that absorbs carbon dioxide gas and liquefies, and has the advantage of being able to efficiently separate carbon dioxide gas from the exhaust gas.

[0030] A carbon dioxide separation device according to another aspect of the present disclosure further includes a pretreatment section that cools the exhaust gas and separates the condensed water generated by liquefying the water vapor contained in the exhaust gas, and the mixing section can mix alkaline water vapor with the exhaust gas from which the condensed water has been separated in the pretreatment section.

[0031] In a carbon dioxide gas separation device according to another aspect of the present disclosure, the pretreatment section can separate condensed water generated by cooling the exhaust gas, and can separate NOx and SOx contained in the exhaust gas. (Embodiment 1)

[0032] The block diagram of FIG. 1 shows a separation apparatus 100 for separating carbon dioxide gas from exhaust gas. The separation device 100 shown in this figure comprises a steam generation section 1 that heats alkaline water 9 to produce alkaline water vapor 10, a mixing section 2 that mixes the alkaline water vapor 10 with exhaust gas to produce steam-mixed exhaust gas 20, a cooling section 3 that cools the steam-mixed exhaust gas 20 obtained in the mixing section 2 and condenses the alkaline water vapor 10 to produce carbon dioxide absorption mist 40, and produces mist-containing exhaust gas 30 containing this absorption mist 40, a recovered water separation section 4 that separates the carbon dioxide absorption mist 40 from the mist-containing exhaust gas 30, a vaporization section 6 that heats carbon dioxide recovery water 41 to produce a mixed gas 50 containing carbon dioxide and alkaline water vapor 10, a gas separation section 6 that filters the mixed gas 50 produced in the vaporization section 6 with a gas separation membrane 61 to separate solute gas 60 from the alkaline water 9, and a solute mixing section 7 that dissolves the solute gas 60 separated in the gas separation section 6 in water to produce alkaline water 9. The alkaline water 9 obtained in the solute mixing section 7 is circulated to the steam generating section 1 for reuse. [Pretreatment section 8]

[0033] The separation device 100 of FIG. 1 includes a pre-treatment device 8 that cools exhaust gas and separates condensed water 80. The pre-treatment device 8 separates the condensed water 80 produced by cooling the exhaust gas, thereby separating the NOx and SOx contained in the exhaust gas. Therefore, the separation device 100 including the pre-treatment device 8 can separate carbon dioxide from the exhaust gas from which NOx and SOx have been separated. However, the carbon dioxide separation device of the present disclosure does not necessarily need to be equipped with a pre-treatment device. This is because carbon dioxide can be separated from exhaust gas without separating NOx and SOx. Furthermore, NOx and SOx are not contained in all exhaust gases at a predetermined concentration. NOx is generated at high combustion temperatures, and SOx is formed by the oxidation of sulfur in the fuel, so the amount of NOx and SOx contained in the exhaust gas varies depending on the combustion temperature and the components of the fuel.

[0034] The separation device 100 in Fig. 1 includes a pretreatment unit 8 that cools and liquefies exhaust gas to separate condensed water 80. The separation device 100 mixes alkaline water vapor 10 with the exhaust gas from which the condensed water 80 has been separated in the pretreatment unit 8. The pretreatment unit 8 separates the condensed water 80 from the exhaust gas to separate NOx and SOx. The condensed water 80 becomes acidic water due to the dissolution of carbon dioxide gas contained in the exhaust gas, so NOx, SOx, and the like, which are highly soluble in the acidic water, are dissolved in the acidic water and separated from the exhaust gas.

[0035] The pretreatment unit 8 has a simple structure and can separate NOx and SOx from the exhaust gas. The exhaust gas contains combustion water in the form of vapor, and the temperature is high and the relative humidity is close to 100%. The combustion water in the exhaust gas is acidic water, which dissolves NOx and SOx. The pretreatment unit 8 separates the combustion water (condensed water 80) containing dissolved NOx and SOx from the exhaust gas. The pretreatment unit 8 in FIG. 1 includes an exhaust gas heat exchanger 81 that cools the exhaust gas and liquefies the combustion water, and a gas-liquid separator 82 such as a cyclone 83 that separates the condensed water 80 cooled and liquefied by the exhaust gas heat exchanger 81 from the exhaust gas. The pretreatment unit 8 described above liquefies the condensed water 80 and separates it from the exhaust gas to separate NOx and SOx. This allows for the separation of NOx and SOx using a simple device without adding alkaline water 9 vapor to the exhaust gas. As shown in Figure 1, the exhaust gas heat exchanger 81 has heat dissipation fins 84 on its outer surface so that it can be cooled by outside air, and further, cooling air such as outside air or a refrigerant can be circulated through the exhaust gas heat exchanger 81 to cool the exhaust gas.

[0036] The exhaust gas from which the condensed water 80 has been separated in the pretreatment section 8 has a reduced moisture content and a reduced absolute humidity. The exhaust gas with a reduced absolute humidity also has a reduced relative humidity, allowing it to be mixed with a large amount of alkaline water 9 in a vapor state (alkaline water vapor 10) in the mixing section 2. [Steam generating section 1]

[0037] The steam generating section 1 can use any mechanism that can heat alkaline water 9 above its boiling point to generate alkaline steam 10. The alkaline steam 10 is mixed with exhaust gas in the mixing section 2, and the exhaust gas and alkaline steam 10 are mixed to form a steam-mixed exhaust gas 20. The alkaline water 9 can be generated by dissolving a solute such as ammonia or a primary amine in water, and the amount of carbon dioxide gas absorbed can be increased by increasing the pH, i.e., by increasing the amount of solute dissolved. This is because one mole of dissolved solute in alkaline water reacts with one mole of carbon dioxide gas to absorb carbon dioxide gas. Therefore, by increasing the pH of alkaline water, the amount of carbon dioxide gas absorbed per unit weight can be increased. For example, 1 m3 of water at 15°C can absorb 10 ... ３ 1m ３ It absorbs carbon dioxide, so it can be removed from the exhaust gas by 1m. ３ To separate carbon dioxide, 1 m ３ It is necessary to add steam of 1000 kJ / L. In alkaline water, the amount of carbon dioxide gas absorbed can be increased by the amount of ammonia dissolved in the water. Therefore, ammonia water, which has a carbon dioxide gas solubility 10 times that of water, can absorb the same amount of carbon dioxide gas from the exhaust gas by reducing the amount of steam mixed with the exhaust gas to 1 / 10 that of water. Since the amount of carbon dioxide gas absorbed by alkaline water can be controlled by adjusting the amount of solute dissolved, i.e., the pH, the pH of the ammonia water is adjusted to, for example, 8 or higher, preferably 8.5 or higher, so that a large amount of carbon dioxide gas can be absorbed.

[0038] Alkaline water 9 is produced by dissolving a solute such as ammonia in water. The solute can be any solute that can be dissolved in water to produce alkaline water 9, or that can be vaporized by heating and separate carbon dioxide gas using a gas separation membrane 61. Ammonia has a high solubility in water, so ammonia water can be used in alkaline water 9 to absorb a large amount of carbon dioxide gas. Furthermore, ammonia water has a low boiling point of 39.7°C, so ammonia vaporized by heating can be separated from carbon dioxide gas using a gas separation membrane 61. Carbon dioxide gas and ammonia can be separated using the gas separation membrane 61, and alkaline water 9 (ammonia water) can be produced from the separated ammonia. While ammonia is a suitable solute for alkaline water 9, the present disclosure does not limit the solute to ammonia. For example, primary amines in which the hydrogen atoms of ammonia are replaced with hydrocarbons can also be used. In alkaline water 9, one mole of solute combines with one mole of carbon dioxide gas to absorb carbon dioxide gas. Therefore, a solute with a small molecular weight has a lighter weight per mole, and therefore can absorb a larger amount of carbon dioxide gas per weight.

[0039] The steam generating unit 1 can vaporize the entire alkaline water 9 to produce steam, or produce a steam mist containing both the vapor and mist of the alkaline water 9, or heat the vapor of the alkaline water 9 to 100°C or higher to produce superheated steam. The steam mist contains not only the vaporized alkaline water vapor 10 but also the mist of the unvaporized alkaline water 9, so the relative humidity exceeds 100%. The alkaline water vapor 10 absorbs carbon dioxide and becomes liquefied, and the mist of the alkaline water 9 also absorbs carbon dioxide. The steam absorbs and condenses carbon dioxide, and the mist comes into contact with and absorbs carbon dioxide. The vapor of the alkaline water 9 absorbs and condenses carbon dioxide more efficiently than the mist, but the mist also absorbs carbon dioxide and condenses. Therefore, the steam mist is mixed with the exhaust gas, and both the steam and the mist can absorb carbon dioxide.

[0040] The steam mixed exhaust gas 20 is cooled to a temperature lower than the dew point temperature in the cooling section 3. In the steam mixed exhaust gas 20 cooled to a temperature below the dew point temperature, the supersaturated alkaline water vapor 10 liquefies and condenses to form mist. The relative humidity of the steam mixed exhaust gas 20 varies and is determined by the amount of vapor (g) of alkaline water 9 contained therein and the temperature (°C). The amount of alkaline water vapor that becomes supersaturated and turns into mist can be increased by increasing the amount of alkaline water vapor contained in the steam mixed exhaust gas 20. The amount of vapor contained in the steam mixed exhaust gas 20 can be increased by increasing the temperature. The temperature of the steam mixed exhaust gas 20 is set high, preferably at 50°C (saturated water vapor amount 83 g / m), in order to increase the amount of alkaline water vapor that becomes supersaturated when cooled. ３ ) or higher, more preferably 60°C (saturated water vapor content 130g / m ３ ) or higher, and optimally 70°C (saturated water vapor content 197g / m ３ ) or more. The steam-mixed exhaust gas 20 containing a large amount of alkaline water vapor 10 is cooled and becomes supersaturated and condenses, increasing the amount of mist that absorbs carbon dioxide and is liquefied. Increasing the amount of mist that can be cooled and condensed means that the mist absorbs and condenses carbon dioxide, allowing the carbon dioxide to be effectively separated from the exhaust gas.

[0041] The temperature of the steam-mixed exhaust gas 20 can be determined by the temperature of the exhaust gas and the temperatures of the alkaline water vapor 10, steam mist, and superheated steam mixed with the exhaust gas. The steam-mixed exhaust gas 20 can have a high saturated water vapor content by mixing superheated steam of 100°C or higher with the exhaust gas to increase the temperature. The saturated water vapor content of the steam-mixed exhaust gas 20 is 823 g / m at 50°C. ３ However, at 80°C it is 292 g / m ３ , 594 g / m at 100°C ３ , 821 g / m at 110°C ３The temperature rises and increases rapidly. Therefore, by mixing the exhaust gas with the superheated alkaline water vapor 10, the temperature of the steam-mixed exhaust gas 20 can be increased, and the amount of alkaline water vapor contained in the steam-mixed exhaust gas 20 per cubic meter can be increased. The steam-mixed exhaust gas 20 containing a large amount of alkaline water vapor can be cooled and supersaturated to generate a large amount of mist, allowing a large amount of carbon dioxide to be efficiently separated from the exhaust gas. Therefore, the steam-mixed exhaust gas 20 generated by mixing the superheated alkaline water vapor 10 with the exhaust gas can efficiently absorb a large amount of carbon dioxide and turn it into mist.

[0042] The steam generating unit 1 heats and vaporizes liquid alkaline water 9 to produce alkaline water vapor 10, so the alkaline water 9 must be heated with thermal energy equal to or greater than the heat of vaporization. Because the heat of vaporization of alkaline water 9 is large, approximately 540 calories / g, a large amount of thermal energy is required to vaporize the alkaline water 9. The steam generating unit 1 of FIG. 1 reduces energy costs by utilizing the exhaust heat of a plant 90 that emits exhaust gas as the thermal energy required to vaporize the alkaline water 9. The amount of alkaline water added to the exhaust gas increases in proportion to the amount of exhaust gas emitted from the plant 90, so the thermal energy required to vaporize the alkaline water 9 also increases in proportion to the amount of exhaust gas emitted. However, the exhaust heat from the plant 90 also increases in proportion to the amount of exhaust gas emitted. Therefore, even if the amount of exhaust gas increases and the thermal energy required to vaporize the alkaline water 9 increases, the alkaline water can be heated and liquefied using the exhaust heat from the plant 90.

[0043] Various plants 90 that emit exhaust gases wastefully radiate a considerable amount of heat energy as unused heat without effectively utilizing it. The amount of unused heat in each plant 90 varies, and the temperature distribution of the unused heat also varies depending on the plant, such as electricity (power plant 91), steel (blast furnace), or ceramics (cement factory, glass factory). For example, the temperature of the exhaust heat from electricity (power plant 91) is 100 to 150°C, while the temperature of the exhaust heat from steel (blast furnace) and ceramics (cement factory, glass factory) is 100 to 200°C, both of which are in the temperature range suitable for vaporizing alkaline water 9. Therefore, a device that uses the unused exhaust heat from these plants 90 to heat and vaporize alkaline water 9 can effectively utilize the exhaust heat from the plants 90 to liquefy alkaline water 9.

[0044] The steam generating unit 1 in FIG. 2 injects alkaline water 9 into the exhaust gas flow path 18 and vaporizes the alkaline water 9 using the thermal energy of the exhaust gas. This steam generating unit 1 can efficiently vaporize the alkaline water 9 by directly contacting the alkaline water 9 with the exhaust gas. This steam generating unit 1 can simplify its structure because it can vaporize the alkaline water 9 using a simple mechanism, such as by spraying the alkaline water 9 from one or more nozzles 14 into the exhaust gas or by sprinkling it. Furthermore, it effectively utilizes the thermal energy of the exhaust gas and the waste heat of the plant 90, thereby reducing the energy consumed from external sources. In other words, the steam generating unit 1 that supplies alkaline water 9 to the exhaust gas described above can reduce running costs by reducing the energy consumption for vaporizing the alkaline water 9, and can also achieve the advantages of simplifying and downsizing the mechanism for vaporizing the alkaline water 9, thereby reducing equipment costs.

[0045] The steam generating unit 1 that vaporizes alkaline water 9 using the thermal energy of the exhaust gas can be provided with a downwardly sloping flow path 18 exposed to the exhaust gas, for example, as shown in Fig. 3, where alkaline water 9 is supplied to the flow path 18 and the alkaline water 9 flowing through the flow path 18 is heated and vaporized by the thermal energy of the exhaust gas. Furthermore, as shown in Fig. 4, a heater 19 that is heated by the thermal energy of the exhaust gas can be disposed in the exhaust gas flow path 18, alkaline water 9 is supplied to the heater 19, and the heater 19 is heated by the thermal energy of the exhaust gas to generate steam of the alkaline water 9. For example, the heater 19 in Fig. 4 is a downwardly sloping gutter that allows alkaline water 9 supplied to the upper end to naturally flow downward, and the alkaline water 9 flowing through the gutter can be vaporized and vaporized by the thermal energy of the exhaust gas.

[0046] The steam generating unit 1 in FIG. 1 heats and vaporizes alkaline water 9 using exhaust heat from a plant 90. For example, as shown in FIG. 1 , the steam generating unit 1 can vaporize alkaline water 9 using exhaust heat from a steam turbine 93 of a power plant 91. The steam generating unit 1 heats and vaporizes alkaline water 9 using thermal energy from a condenser 94, which cools and liquefies steam discharged from the steam turbine 93 that drives a generator 92 of the power plant 91. Because the steam generating unit 1 uses the exhaust heat from the condenser 94 (plant 90) to vaporize alkaline water 9, the energy cost for vaporizing alkaline water 9 can be reduced. The steam discharged from the steam turbine 93 must absorb a large amount of thermal energy to be liquefied. The condenser 94 liquefies the steam discharged from the steam turbine 93 for circulation to a boiler 95. The water liquefied in the condenser 94 is heated in the boiler 95 and circulated to the steam turbine 93. The temperature of the steam supplied from the steam turbine 93 to the condenser 94 is as high as 100°C or more, so that the alkaline water 9 can be efficiently heated and liquefied in the steam generating section 1. In addition, the heat of condensation generated by the liquefaction of the steam is large, so that the alkaline water 9 can be efficiently vaporized.

[0047] The condenser 94 in Fig. 1 includes a heat exchanger 96 for seawater and a heat exchanger 97 for alkaline water. The heat exchanger 94 for seawater circulates seawater to cool and liquefy the steam discharged from the steam turbine 93, and the heat exchanger 97 for alkaline water passes alkaline water 9 through it to vaporize it. The condenser 94 cools and liquefies the steam supplied from the steam turbine 93 in both the heat exchanger 96 for seawater and the heat exchanger 97 for alkaline water. Therefore, the condenser 94 adjusts the thermal energy used by the heat exchanger 97 for alkaline water 9 to heat and vaporize it and the thermal energy absorbed by the heat exchanger 96 for seawater to liquefy the alkaline water 9 while liquefying the steam supplied from the steam turbine 93 and circulating it to the boiler 95.

[0048] The power plant 91 uses seawater to cool the condenser 94, and therefore heat radiation from the condenser 94 causes the seawater temperature to rise. A device that uses the thermal energy absorbed by the condenser 94 to vaporize the alkaline water 9 can reduce the amount of heat radiation to the seawater by the condenser 94, thereby reducing the rise in seawater temperature and suppressing the impact on the natural environment.

[0049] Not only power plants 91, but also cement plants, blast furnaces, and other plants 90 that burn coal, oil, gas, and other fuels release and radiate waste heat below 200°C as unused heat without effectively utilizing it. In particular, waste heat in the 100-200°C temperature range is discharged into the atmosphere without being effectively utilized. Plants 90 that emit exhaust gas can effectively utilize the unused heat to heat and vaporize alkaline water 9. The steam generation unit 1 in FIG. 5 includes a heat exchanger 11 that uses the waste heat from the plant 30 to heat and vaporize alkaline water 9. The heat exchanger 11 heats and vaporizes alkaline water 9 pumped by a pump 12, and supplies the vaporized alkaline water 9 (alkaline water vapor 10) to the mixing unit 2. This steam generation unit 1 has the advantage of being able to effectively utilize the waste heat from the plant 90, thereby significantly reducing the thermal energy required to vaporize alkaline water 9 and generate steam, thereby reducing running costs.

[0050] As shown in FIG. 1 , the steam generating unit 1 can efficiently vaporize alkaline water 9 using the exhaust heat of a steam turbine 93 in a power plant 91. However, as shown in FIG. 5 , in a plant 90 such as a blast furnace, cement plant, or chemical plant, the alkaline water 9 can also be heated and vaporized using the exhaust heat of the plant 30. For example, the steam generating unit in a cement plant can heat alkaline water using the exhaust heat of a cement kiln. Furthermore, as shown in FIG. 6 , the steam generating unit 1 can heat and vaporize alkaline water 9 using solar or geothermal thermal energy. [Mixing Unit 2]

[0051] The mixing section 2 can be any mechanism that mixes the vapor of alkaline water 9 (alkaline water vapor 10) supplied from the steam generating section 1 with the exhaust gas to produce steam-mixed exhaust gas 20. The mixing section 2 can be a mechanism whose sole purpose is to mix the exhaust gas with the vapor of alkaline water 9, or it can be part of the steam generating section 1. The present disclosure does not specify the structure of the mixing section 2, but the mixing section 2 can be, for example, a static mixer or a mixer that agitates the exhaust gas with the sprayed steam of alkaline water 9.

[0052] As shown in FIGS. 2 and 5 , the mixing section 2 can also constitute a part of the steam generating section 1. The steam generating section 1 of FIG. 2 injects liquid alkaline water 9 from a nozzle 14 into exhaust gas at a temperature of 100° C. or higher, vaporizes the injected liquid alkaline water 9 using thermal energy from the exhaust gas, and supplies vapor of the alkaline water 9 to the exhaust gas. This steam generating section 1 injects the liquid alkaline water 9 into the exhaust gas and disperses the vapor of the alkaline water 9 into the exhaust gas, so the mixing section 2 is provided as an integrated structure. The steam generating section 1 of FIG. 2 can heat the liquid alkaline water 9 in a heat exchanger 11 and inject alkaline water vapor 10 into the exhaust gas. Heating the alkaline water 9 in the heat exchanger 11 can vaporize the alkaline water 9 into alkaline water vapor 10, and can also produce steam mist containing both the alkaline water vapor 10 and a mist of the alkaline water 9, which can then be injected into the exhaust gas from a nozzle 14. The heat exchanger 11 heats alkaline water 9 supplied from a pump 12 using thermal energy supplied from a heating section, such as exhaust heat from the plant 90, and sprays alkaline steam 10 into the exhaust gas from a nozzle 14. The heating section can utilize exhaust heat from the plant 90, or a heater can be used. The steam generating section 1 in this figure can also generate alkaline steam 10 by heating the mist of alkaline water 9 sprayed from the nozzle 14 with exhaust gas at 100°C or higher, so the steam generating section 1 and the mixing section 2 can be integrated into one structure. The steam generating sections 1 in Figures 2 and 5 have an integrated mixing section 2, but a dedicated mixing section 2 independent of the steam generating section 1, as shown in Figure 1, can be provided to uniformly mix the exhaust gas and alkaline steam 10. Furthermore, the steam generating sections 1 in Figures 3 and 4 supply alkaline water 9 into the exhaust gas and vaporize it, so the steam generating section 1 and the mixing section 2 can be integrated into one structure.

[0053] The steam generating unit 1 controls the thermal energy for heating the alkaline water and the supply amount of alkaline water 9 to generate alkaline steam 10, superheated alkaline steam 10, and steam mist containing alkaline steam 10 and mist. The thermal energy for heating the alkaline water 9, specifically the thermal energy supplied from the heating unit or exhaust gas per unit time, is set equal to the total heat of vaporization of the alkaline water 9 supplied per unit time, thereby converting all of the alkaline water 9 into alkaline steam 10. Furthermore, the thermal energy supplied from the heating unit or exhaust gas per unit time can be set greater than the total heat of vaporization of the alkaline water 9 supplied per unit time to generate superheated alkaline steam 10. Furthermore, the thermal energy supplied from the heating unit or exhaust gas per unit time can be set less than the total heat of vaporization of the alkaline water 9 supplied per unit time but greater than the heat of vaporization required to vaporize some of the alkaline water 9, thereby generating steam mist containing a mixture of alkaline steam 10 and mist. Therefore, the steam generating unit 1 controls the thermal energy for heating the alkaline water 9 and the supply amount of the alkaline water 9 to generate alkaline steam 10, or to generate superheated alkaline steam 10, or to generate steam mist containing both alkaline steam 10 and mist.

[0054] The cooling section 3 can have any structure that cools the steam-mixed exhaust gas 20, liquefies the supersaturated alkaline water vapor 10, and discharges the mist-containing exhaust gas 30 condensed into a mist of fine water droplets. The cooling section 3 can liquefy a larger amount of alkaline water vapor 10 by lowering the temperature of the discharged mist-containing exhaust gas 30. This is because the temperature difference between the steam-mixed exhaust gas 20 and the mist-containing exhaust gas 30 determines the amount of alkaline water vapor that becomes supersaturated and liquefied. Since the alkaline water vapor 10 absorbs carbon dioxide and becomes liquefied as mist in the steam-mixed exhaust gas 20, lowering the temperature of the mist-containing exhaust gas 30 discharged from the cooling section 3 increases the amount of mist generated, allowing for effective absorption of carbon dioxide.

[0055] The cooling section 3 in Figures 1 and 2 cools the steam-mixed exhaust gas 20 using a heat exchanger 31 and discharges a mist-containing exhaust gas 30 containing mist that has absorbed carbon dioxide. While the cooling section 3 in Figures 1 and 2 is structured independently of the mixing section 2, the cooling section 3 shown in Figure 5 is cylindrical and integral with the mixing section 2, and has heat dissipation fins 32 on its surface. The heat dissipation fins 32 are thermally coupled to the surface of the cooling section 3 and are cooled by outside air. The heat dissipation fins 32 can be used to more efficiently cool the cooling section and lower the temperature of the mist-containing exhaust gas 30 by forcing air through a fan, but the heat dissipation fins 32 can also be used to cool the cooling section 3 with outside air without necessarily forcing air through the cooling section 3. The cooling section 3 in Figure 6 uses a long metal cooling pipe 33 cooled on the discharge side of the mixing section 2 to cool the steam-mixed exhaust gas 20 and discharge it as a mist-containing exhaust gas 30.

[0056] The alkaline water vapor 10 in the steam-mixed exhaust gas 20 can efficiently absorb carbon dioxide gas when it is cooled and condensed in the cooling section 3. This is because the extremely fine vapor of the alkaline water 9 (alkaline water vapor 10) condenses and liquefies. One mole (18 g) of alkaline water 9 vaporizes, and 6 × 10 ２３ The alkaline water 9 vapor becomes individual fine particles, and the fine particles condense and liquefy, efficiently absorbing carbon dioxide gas in the process of condensing and liquefying a huge amount of vapor. The condensed and liquid alkaline water 9 disperses in the exhaust gas as a mist, or condenses and adheres to the cooling surface. The cooling unit 3 cools the steam-mixed exhaust gas 20 to a temperature below the dew point temperature, liquefying the supersaturated alkaline water 9 vapor. The amount of saturated water vapor in the steam-mixed exhaust gas 20 varies with temperature, and as the temperature of the steam-mixed exhaust gas 20 decreases, the amount of saturated water vapor decreases. Therefore, the lower the temperature of the steam-mixed exhaust gas 20 cooled by the cooling unit 3, the greater the amount of liquefaction of the alkaline water 9 vapor (alkaline water vapor 10).

[0057] The amount of moisture that the steam-mixed exhaust gas 20 can contain in a gaseous state, i.e., the amount of saturated water vapor, changes with temperature as a parameter. As the temperature of the steam-mixed exhaust gas 20 decreases, the amount of saturated water vapor decreases. When the steam-mixed exhaust gas 20 is cooled, the amount of saturated water vapor decreases, and the supersaturated moisture liquefies. The amount of saturated water vapor in the steam-mixed exhaust gas 20 is 292 g / m at 80°C. ３, 30 g / m at 30°C ３ , 17 g / m at 20°C ３ , 13 g / m at 15°C ３ Therefore, in the cooling section 3, 20 ml of steam-mixed exhaust gas (relative humidity 100%) at 80°C is ３ When cooled to 20°C, 175g (292-17g / m ３ The vapor of the alkaline water 9 (alkaline water vapor 10) is liquefied and carbon dioxide gas is separated from the exhaust gas, so the amount of liquefied alkaline water 9 can be increased and carbon dioxide gas can be separated efficiently.

[0058] Since the amount of liquefaction of alkaline water 9 can be increased by increasing the temperature difference between the steam mixed exhaust gas 20 and the mist-containing exhaust gas 30 before and after cooling, the temperature difference between the steam mixed exhaust gas 20 and the mist-containing exhaust gas 30 in the cooling section 3 is set to, for example, 30°C or more, preferably 35°C or more, and more preferably 40°C or more. Since the cooling section 3 can increase the temperature difference for cooling by setting the temperature of the mist-containing exhaust gas 30 low, the temperature of the mist-containing exhaust gas 30 is set to, for example, 30°C (amount of saturated water vapor 30 g / m ３ ) or less, preferably 20°C (saturated water vapor content 17g / m ３ ) or less, more preferably 15°C (saturated water vapor amount 13g / m ３ ) below.

[0059] The steam-mixed exhaust gas 20 with a relative humidity of less than 100% can be cooled to a temperature lower than the dew point temperature to liquefy the vapor of the supersaturated alkaline water 9. For example, the steam-mixed exhaust gas 20 with a relative humidity of 80% and a temperature of 80°C can be liquefied by cooling it to a temperature lower than the dew point temperature. ３Therefore, when the steam-mixed exhaust gas 20 is cooled to 30°C and the saturated water vapor amount is reduced to 30g, 234-30g of alkaline water 9 vapor is liquefied. Therefore, the cooling section 3 can liquefy alkaline water vapor by cooling the steam-mixed exhaust gas 20 with a relative humidity of less than 100% to a temperature lower than the dew point temperature. Even if the cooling section 3 cools the steam-mixed exhaust gas 20 with a relative humidity of 80% and 80°C to 75°C, the alkaline water 9 vapor will not be liquefied. This is because the saturated water vapor amount of the steam-mixed exhaust gas 20 at 75°C is 240g, which is greater than the saturated water vapor amount of the steam-mixed exhaust gas 20 with a relative humidity of 80°C and 80%, and the alkaline water 9 vapor cannot be supersaturated. Therefore, the cooling section 3 cools the steam-mixed exhaust gas 20 with a relative humidity of less than 100% to a temperature lower than the dew point temperature to liquefy the alkaline water 9 vapor. [Recovered Water Separation Section 4]

[0060] The recovered water separation section 4 can have any structure that recovers mist (absorption mist 40) that has absorbed carbon dioxide gas from the mist-containing exhaust gas 30 obtained in the cooling section 3. The mist-containing exhaust gas 30 contains fine water droplets that have absorbed and condensed carbon dioxide gas, i.e., mist, dispersed throughout the exhaust gas. The recovered water separation section 4 recovers the absorption mist 40 that has absorbed carbon dioxide gas and recovered water 41. The recovered water separation section 4 can separate and recover the mist from the mist-containing exhaust gas 30 using a gas-liquid separator such as a cyclone 42. The cyclone 42 gas-liquid separator has a simple structure and can recover the absorption mist 40 that has absorbed carbon dioxide gas from the mist-containing exhaust gas 30 and discharge it as recovered carbon dioxide gas-containing water 41. The recovered water separation section 4 can recover the absorption mist 40 with a high concentration of carbon dioxide gas and discharge it as recovered water 41.

[0061] The recovered water separation section 4 can be provided independently of the cooling section 3, or can be integrated with the cooling section 3. The recovered water separation section 4 can cool the mist-containing exhaust gas 30 or the steam-mixed exhaust gas 20 and recover the absorption mist 40 that has absorbed carbon dioxide by condensing it on the cooling surface. The recovered water separation section 4 shown in Figures 7 and 8 is integrated with the cooling section 3 and can cool the steam-mixed exhaust gas 20, which is obtained by mixing the alkaline water vapor 10 with the exhaust gas in the mixing section 2, liquefy it, and recover the carbon dioxide absorption mist 40, which can be discharged as recovered water 41. The recovered water separation section 4 is provided with a trap 44 in the exhaust gas duct 43 that discharges the absorption mist 40 liquefied in the cooling section 3 to the outside. The recovered water separation section 4 cools the duct 43, allowing the absorption mist 40 that condenses on the inner surface to flow down and be discharged through the trap 44 and recovered as recovered water 41. For example, the exhaust gas duct 43A in FIG. 7 has a downward slope (a slope toward the lower left in the figure) in the opposite direction to the exhaust gas blowing direction (upper right in FIG. 7), and the duct 43B in FIG. 8 is disposed in a vertical position, causing the condensed carbon dioxide absorption mist 40 to flow downward and be discharged from the trap 44. The ducts 43A and 43B in FIGS. 7 and 8 are provided with heat dissipation fins 45 on their outer surfaces, which increase the contact area with the outside air and cool the steam-mixed exhaust gas 20. The duct 43 cooled with the heat dissipation fins 45 has a simple structure and can be cooled with room-temperature outside air or by forced air. The duct 43 can also be provided with a cooling plate protruding from the inner surface into the duct 43, with the surface of this cooling plate serving as the cooling surface. This duct 43 has a cooling plate on its inner surface that increases the surface area in contact with the exhaust gas (steam-mixed exhaust gas 20 or mist-containing exhaust gas 30) passing through the duct 43, thereby more efficiently condensing the exhaust gas containing the carbon dioxide absorption mist 40. Furthermore, the duct 43 can be thermally coupled to a heat exchanger pipe that circulates a cooling fluid, and can be forcibly cooled by the cooling fluid circulating through the heat exchanger pipe. The recovered water separation section 4 is integrally structured with the cooling section 3, so that the steam-mixed exhaust gas 20 can be cooled and the cooled, liquefied carbon dioxide absorption mist 40 can be recovered with a simple structure. [Evaporation section 5]

[0062] The vaporizer 5 heats and gasifies the recovered water 41. The vaporizer 5 vaporizes the recovered water 41 to separate the solute gas from the alkaline water 9 by filtering it through a gas separation membrane 61. The vaporizer 5 can have any structure capable of heating and vaporizing the recovered water 41. The recovered water 41 is alkaline water 9 with dissolved carbon dioxide gas. When heated and vaporized, the recovered water 41 becomes a mixed gas 50 containing carbon dioxide gas, the solute gas of the alkaline water 9, and water vapor. When heated and vaporized, the recovered water 41, which has ammonia as the solute, becomes a mixed gas 50 containing carbon dioxide gas, ammonia, and water vapor. The vaporizer 5 can have any structure capable of heating and gasifying the recovered water 41. The vaporizer 5 of FIG. 1 heats the recovered water 41 using a heat exchanger 51. The heat exchanger 51 can heat the recovered water 41 using a heat source such as exhaust heat from the plant 90 or a heater. [Gas Separation Unit 6]

[0063] The gas separation unit 6 separates the solute gas 60 of the alkaline water 9 from the mixed gas 50 obtained by heating and vaporizing the recovered water 41. The gas separation unit 6 filters the mixed gas 60 with a gas separation membrane 61 to separate the solute gas 60. The gas separation unit 6 separates the solute gas 60, which has a small molecular diameter, from the mixed gas 50 by allowing the solute gas 60 to pass through the gas separation membrane 61. Ammonia, which is the solute gas 60, has a smaller molecular diameter than carbon dioxide and can be separated from carbon dioxide by passing through the gas separation membrane 61. The gas separation unit 6 uses a gas separation membrane 61 that allows the solute gas 60, which has a smaller molecular diameter than carbon dioxide, to pass through and separate the solute gas 60 from carbon dioxide. The molecular diameter of ammonia, which is suitable as a solute, is 0.26 nm, while the molecular diameter of carbon dioxide is 0.33 nm, which is larger than ammonia, so carbon dioxide and ammonia can be separated using the gas separation membrane 61. The mixed gas 50 obtained by heating and vaporizing the recovered water 41 contains water vapor in addition to the solute gas 60 and carbon dioxide gas. However, the solute ammonia separated from the mixed gas 60 is dissolved in water and reused as alkaline water 9, so the presence of water vapor in the separated ammonia is not a problem. However, since the molecular diameter of water vapor is large at 0.4 nm, the solute ammonia can be separated from both the carbon dioxide gas and the water vapor using the gas separation membrane 61, and the separated ammonia can be dissolved in water to produce alkaline water 9. The gas separation unit 6 pressurizes the mixed gas 50 to force it to pass through the gas separation membrane 61, thereby efficiently separating the solute gas. The gas separation unit 6, which separates the solute gas 60 using the gas separation membrane 61, can separate the solute gas 60 with significantly less energy consumption than conventional distillation methods, thereby reducing running costs.

[0064] The gas separation unit 6 of FIG. 1 has a cylindrical gas separation membrane 61 disposed inside a closed chamber 62. Both ends of the cylindrical gas separation membrane 61 are in close contact with the end plates of the closed chamber 62, forming an inlet chamber 63 on the inside and an outlet chamber 64 on the outside. In the gas separation unit 6 of FIG. 1, a mixed gas 50 pressurized by a pressure pump 65 is supplied to one end of the inlet chamber 63 (the open end on the right side in FIG. 1 ), and a pressure control valve 66 is connected to the outlet side of the other end (the open end on the left side in FIG. 1 ). The pressure control valve 66 maintains the internal pressure of the inlet chamber 63 at a predetermined pressure, allowing the solute gas 60 to permeate through the gas separation membrane 61, while carbon dioxide gas that does not permeate the gas separation membrane 61 passes through the pressure control valve 66 and is discharged to the outside. The solute gas 60 that permeates the gas separation membrane 61 and flows out of the outlet chamber 64 is discharged to the outside without passing through the pressure control valve 66. The gas separation unit 6, which maintains the internal pressure of the inlet chamber 63 at a predetermined pressure using the pressure control valve 66, allows the solute gas 60 of the mixed gas 50 to quickly permeate through the gas separation membrane 61. The gas separation unit 6 discharges ammonia of the solute gas 60 through the gas separation membrane 61 to the outside from the discharge chamber 64, and discharges carbon dioxide through the pressure control valve 66 to the outside without permeating the gas separation membrane 61. The solute gas 60 discharged from the discharge chamber 64 is transferred to the solute mixing unit 7. The gas separation unit 6 separates carbon dioxide from the mixed gas 50. [Solute Mixing Unit 7]

[0065] The solute mixer 7 can use any structure or method for dissolving the solute gas 60 in water to produce alkaline water 9. The solute mixer 7 generates alkaline water 9 by, for example, spraying or showering the solute gas 60 in the alkaline water 9 with a mist of water, passing the solute gas 60 through water, diffusing it, contacting it, and pressurizing it. Ammonia gas has a very high solubility in water. The solute mixer 7 dissolves the solute gas 60 in the alkaline water 9 separated in the gas separation unit 6 in water to produce alkaline water 9, which is then circulated to the steam generation unit 1, allowing the solute gas 60 in the alkaline water 9 to be effectively reused. This carbon dioxide separation device 100 efficiently absorbs carbon dioxide with the alkaline steam 10 while recovering and effectively reusing the solute gas 60 in the alkaline water 9 to produce alkaline water 9 and absorb carbon dioxide, thereby reducing the consumption of the solute gas 60 in the alkaline water 9 and lowering running costs.

[0066] The block diagram of Figure 1 illustrates a separation device 100 that separates carbon dioxide gas from exhaust gas of a power plant 91, but this disclosure does not specify the carbon dioxide gas separation device 100 as an apparatus used in the power plant 91.

[0067] The exhaust gases emitted from various plants 90 are mainly generated by burning fuels such as coal, oil, gas, and wood. The exhaust gases contain carbon dioxide, NOx, SOx, etc., and the separation device 100 shown in the block diagram of FIG. 1 can separate carbon dioxide, NOx, SOx, etc. The separation device 100 of the present disclosure can separate carbon dioxide not only from combustion gases generated by combustion, but also from all exhaust gases containing carbon dioxide in the carrier gas. For example, in the case of air-based exhaust gas containing ammonia gas, the ammonia gas can be separated from the air and recovered, allowing the ammonia to be reused.

[0068] The carbon dioxide separation device disclosed herein can be used as a device that efficiently separates carbon dioxide gases such as carbon dioxide from exhaust gases while reducing the consumption of solutes used to produce alkaline water, thereby reducing running costs.

[0069] 100...Separation device 1...Steam generation section 2...Mixing section 3...Cooling section 4...Recovered water separation section 5...Vaporization section 6...Gas separation section 7...Solute mixing section 8...Pretreatment section 9...Alkaline water 10...Alkaline water vapor 11...Heat exchanger 12...Pump 14...Nozzle 18...Flow path 19...Heater 20...Steam mixed exhaust gas 30...Mist-containing exhaust gas 31...Heat exchanger 32...Heat radiation fin 33...Cooling pipe 40...Absorbed mist 41...Recovered water 42...Cyclone 43, 43A, 43B...Duct 44...Trap 45...Heat radiation fin 50...Mixed gas 51...Heat exchanger 60...Solute gas 61...Gas separation membrane 62...Closed chamber 63...Inlet chamber 64...Discharge chamber 65...Pressurization pump 66...Pressure control valve 80...Condensed water 81... Exhaust gas heat exchanger 82... Gas-liquid separator 83... Cyclone 84... Radiation fin 90... Plant 91... Power plant 92... Generator 93... Steam turbine 94... Condenser 95... Boiler 96... Heat exchanger for seawater 97... Heat exchanger for alkaline water

Claims

a mixing section for mixing the alkaline water generated in the steam generating section with exhaust gas to produce a steam-mixed exhaust gas; a cooling section for cooling the steam-mixed exhaust gas obtained in the mixing section to produce a mist-containing exhaust gas containing a carbon dioxide gas-absorbed mist formed by the alkaline water vapor absorbing carbon dioxide gas and condensing; a recovered water separation section for recovering the carbon dioxide gas-absorbed mist from the mist-containing exhaust gas obtained in the cooling section as recovered water; a vaporization section for heating and vaporizing the carbon dioxide gas-absorbed water obtained in the recovered water separation section to produce a mixed gas containing carbon dioxide gas and alkaline water vapor; a gas separation section for filtering the mixed gas obtained in the vaporization section with a gas separation membrane to separate the carbon dioxide gas and a solute gas of alkaline water; and a solute mixing section for dissolving the solute gas of alkaline water separated in the gas separation section in water to produce alkaline water, A carbon dioxide separation device in which carbon dioxide is separated from exhaust gas.

2. A carbon dioxide gas separation apparatus according to claim 1, wherein the alkaline water is ammonia water.

3. The carbon dioxide gas separation apparatus according to claim 1, wherein the alkaline water is a solution of a primary amine.

4. A carbon dioxide gas separation device as claimed in claim 1, wherein the steam generating section generates steam mist containing both the alkaline water vapor and the alkaline water mist.

5. A carbon dioxide gas separation apparatus according to claim 1, wherein the steam generating section generates alkaline water vapor containing superheated steam of the alkaline water.

6. A carbon dioxide separation apparatus as described in claim 1, wherein the steam generating section heats the alkaline water with exhaust heat from a plant that discharges the exhaust gas to generate steam mist.

7. The carbon dioxide gas separation apparatus according to claim 6, wherein the plant is any one of a power plant, a blast furnace, a cement plant, and a chemical plant.

8. A carbon dioxide gas separation apparatus according to claim 6, wherein the steam generating section heats and vaporizes the alkaline water with solar heat or geothermal heat.

9. A carbon dioxide separation apparatus as described in claim 1, wherein the vaporization section heats the carbon dioxide recovery water with exhaust heat from a plant that discharges the exhaust gas, and vaporizes it into a mixed gas.

10. The carbon dioxide gas separation apparatus according to claim 9, wherein the plant is any one of a power plant, a blast furnace, a cement plant, and a chemical plant.

11. A carbon dioxide separation apparatus as described in claim 9, wherein the vaporization section heats the carbon dioxide recovery water with solar heat or geothermal heat and vaporizes it into a mixed gas.

12. A carbon dioxide separation apparatus as claimed in any one of claims 1 to 11, wherein the temperature of the steam mixed exhaust gas supplied from the mixing section to the cooling section is 50°C or higher.

13. A carbon dioxide separation apparatus as described in claim 12, wherein the temperature difference between the steam mixed exhaust gas supplied to the cooling section and the mist-containing exhaust gas discharged from the cooling section is 30°C or more.

14. A carbon dioxide separation apparatus as described in claim 1, comprising a pre-treatment section that cools the exhaust gas and separates the condensed water generated by liquefying the water vapor contained in the exhaust gas, and the mixing section mixes alkaline water vapor with the exhaust gas from which the condensed water has been separated in the pre-treatment section.

15. A carbon dioxide separation apparatus as described in claim 14, wherein the pre-treatment unit separates condensed water produced by cooling the exhaust gas, and separates NOx and SOx contained in the exhaust gas.

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