Method and device for separating carbon dioxide gas from combustion exhaust gas

Abstract

The present invention is capable of efficiently separating a carbon dioxide gas by mixing alkaline fine particles into a combustion exhaust gas, and reduces running cost by separating an alkali substance that generates alkaline fine particles from a material discharged from a combustion furnace of the combustion exhaust gas and effectively utilizing the alkali substance. In a method for separating a carbon dioxide gas from a combustion exhaust gas, alkali fine particles that contain either or both of mist and vapor of an alkali substance are mixed into the combustion exhaust gas, and the carbon dioxide gas is absorbed into the alkali fine particles so as to be separated from the combustion exhaust gas. An alkali substance, which is contained in a material discharged from a combustion furnace that discharges the combustion exhaust gas, is used as the alkali substance of the alkali fine particles.

Description

Method and apparatus for separating carbon dioxide from combustion exhaust gas

[0001] The present disclosure relates to a method and apparatus for separating carbon dioxide gas from combustion exhaust gas, and more particularly to a method and apparatus for separating carbon dioxide gas contained in combustion exhaust gas by absorbing it into an alkaline substance.

[0002] Apparatuses for separating carbon dioxide gas from combustion exhaust gas have been developed (see Patent Documents 1 to 3). These patent documents disclose a technique for absorbing carbon dioxide gas by bringing an alkaline substance containing a carbon dioxide gas absorbent into contact with the combustion exhaust gas.

[0003] JP 2005-211878 A JP 2005-211878 A International Publication No. 2020 / 241654

[0004] Patent Documents 1 to 3 disclose conventional methods and apparatuses for separating carbon dioxide gas from combustion exhaust gas. These publications involve bringing an alkaline substance into contact with the combustion exhaust gas, dissolving carbon dioxide gas and other gases in the combustion exhaust gas in the alkaline substance, and separating them from the combustion exhaust gas. These methods can efficiently separate carbon dioxide gas by using calcium hydroxide (Patent Document 1), potassium carbonate or amines (Patent Document 2), an amine aqueous solution (Patent Document 3), or the like as the alkaline substance, but there is a problem in that the consumption of the alkaline substance increases in proportion to the amount of carbon dioxide gas to be separated, resulting in high running costs.

[0005] In recent years, there has been an urgent need to separate carbon dioxide from the vast amount of combustion exhaust gas emitted into the atmosphere in order to reduce the concentration of carbon dioxide, which has been increasing significantly. However, since the economic benefits of separating carbon dioxide from combustion exhaust gas are insufficient, it is an important issue to find a way to reduce the cost required for carbon dioxide separation. Since being able to efficiently absorb carbon dioxide is effective in reducing costs, conventional methods use alkaline substances to efficiently absorb carbon dioxide, so it is an important issue to find a way to reduce the consumption of alkaline substances.

[0006] The present disclosure has been developed with the aim of resolving the above-mentioned problems, and one of the objects of the present disclosure is to provide a method and apparatus that can separate carbon dioxide gas while reducing running costs by mixing alkaline fine particles into combustion exhaust gas to efficiently separate carbon dioxide gas, while separating and effectively utilizing the alkaline substance that generates the alkaline fine particles from the exhaust of a combustion furnace that emits the combustion exhaust gas.

[0007] A method for separating carbon dioxide gas from combustion exhaust gas according to one embodiment of the present disclosure involves mixing alkaline fine particles containing either or both of a mist and vapor of an alkaline substance with the combustion exhaust gas, causing the alkaline fine particles to absorb carbon dioxide gas and separate it from the combustion exhaust gas, and generating alkaline fine particles using an alkaline substance contained in the effluent of a combustion furnace that emits combustion exhaust gas.

[0008] Another aspect of the present disclosure provides an apparatus for separating carbon dioxide from combustion exhaust gas, which comprises a mixing and separation section that mixes alkaline fine particles containing either or both of a mist and vapor of an alkaline substance with the combustion exhaust gas, causing the carbon dioxide in the combustion exhaust gas to be absorbed by the alkaline fine particles and separated, and an alkali supply section that supplies the alkaline substance to the mixing and separation section, wherein the alkali supply section recovers alkaline substances contained in the exhaust of a combustion furnace that emits combustion exhaust gas from which carbon dioxide is to be separated, and generates alkaline fine particles from the recovered alkaline substances.

[0009] The above-described method and apparatus for separating carbon dioxide gas from combustion exhaust gas has the advantage that it can efficiently separate carbon dioxide gas by mixing alkaline microparticles into the combustion exhaust gas, and also that the alkaline substances that produce the alkaline microparticles can be separated from the exhaust gas from the combustion furnace and effectively utilized, thereby reducing running costs.

[0010] 1 is a schematic block diagram of a carbon dioxide gas separation method and apparatus according to an embodiment of the present disclosure; FIG. 2 is a schematic block diagram of an example of a carbon dioxide gas absorption tower; and FIG. 3 is a schematic block diagram of another example of a carbon dioxide gas absorption tower.

[0011] The present invention 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 shown below are illustrative 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 to those specific embodiments or examples. 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. Ammonium hydrogen phosphate (NH ４ ) ２ H １ P.O. ４ ((NH ４ ) ２ HPO ４ ) and ammonium dihydrogen phosphate (NH ４ ) １ H ２ P.O. ４ ((NH ４ ) H ２ P.O. ４ (synonymous with)

[0012] A method for separating carbon dioxide from combustion exhaust gas according to one embodiment of the present disclosure involves mixing alkaline fine particles containing either or both of a mist and vapor of an alkaline substance with the combustion exhaust gas, causing the alkaline fine particles to absorb carbon dioxide and separate it from the combustion exhaust gas, in which the alkaline substance in the alkaline fine particles is an alkaline substance contained in the effluent of a combustion furnace that emits combustion exhaust gas.

[0013] The above-described method for separating carbon dioxide from combustion exhaust gas effectively utilizes alkaline substances contained in the exhaust from a combustion furnace that emits combustion exhaust gas to generate alkaline microparticles to separate carbon dioxide, and therefore has the advantage of being able to efficiently separate carbon dioxide from combustion exhaust gas while reducing the amount of alkaline substance used to absorb carbon dioxide and lowering running costs.

[0014] In the method of separating carbon dioxide gas by absorbing it into alkaline microparticles, the amount of alkaline material used increases in proportion to the amount of carbon dioxide gas to be separated. Therefore, methods of separating carbon dioxide gas from large amounts of continuously emitted combustion exhaust gas have the problem of consuming extremely large amounts of alkaline material, resulting in high running costs. In methods of separating carbon dioxide gas from combustion exhaust gas, reducing running costs is an important factor that determines their practical application. Separating carbon dioxide gas from combustion exhaust gas is extremely significant in reducing the carbon dioxide concentration in the atmosphere, but this imposes an economic burden on users. An economically advantageous method of separating carbon dioxide gas would reduce the economic burden on users, overcome one barrier to practical application, and be adopted by many users, further achieving a reduction in the carbon dioxide concentration in the atmosphere.

[0015] The above method has the advantage of reducing running costs by producing alkaline microparticles using alkaline substances contained in the exhaust of a combustion furnace that emits combustion exhaust gas. Some combustion furnaces emit and by-produce exhaust containing alkaline substances. For example, a coke oven, which carbonizes coal to produce coke, produces 75% of the coal by weight as coke, and also produces tar, diesel, and water as by-products. Approximately 15% of the coal is discharged as coke oven gas. This COG contains approximately 10,000 ppm (1% by weight) of ammonia. Therefore, the ammonia can be recovered and used as an alkaline substance to produce alkaline microparticles for use in separating carbon dioxide from the combustion exhaust gas.

[0016] In addition to the above, a method for separating carbon dioxide gas from combustion exhaust gas according to another embodiment of the present disclosure includes the addition of vapor of an alkaline substance, and the vapor of the alkaline substance can absorb carbon dioxide gas and condense to separate the carbon dioxide gas. The alkaline substance may be in any state of matter, including liquid, gas, solid, or a mixture thereof, and may also include an elemental substance or a compound.

[0017] The above method has the advantage of being able to efficiently absorb and separate carbon dioxide gas contained in combustion exhaust gas. This is because the above method mixes the vapor of an alkaline substance with the combustion exhaust gas to form a mixed gas, and then cools, liquefies, and separates the mixed gas containing the vapor of the alkaline substance. When the alkaline solution vaporizes to form vaporized alkaline molecules, 1 mole (18 g of water when the solvent is water) of alkaline solution will be converted into a huge number of vaporized molecules (Avogadro's constant: 6 x 10 ２３ ) Disperse in the exhaust gas. The vaporized alkali molecules dispersed in the combustion exhaust gas become a huge number of tiny molecules that are incomparable to non-vaporized mist. When the alkali molecules are cooled and condensed in this state, they efficiently absorb and liquefy the carbon dioxide contained in the combustion exhaust gas during the condensation process.

[0018] A method for separating carbon dioxide from combustion exhaust gas allows for efficient absorption of carbon dioxide by alkali particles by increasing the contact area between the combustion exhaust gas and alkali particles. The contact area between the combustion exhaust gas and alkali particles can be achieved by reducing the particle size of the alkali particles. Alkaline particles can be atomized into a mist using methods such as ultrasonic vibration or electrostatic atomization, but they can be further reduced to extremely small alkali particles by heating and vaporizing them into a vapor state. These methods heat and vaporize the alkali substance to produce vapor alkali particles, resulting in extremely fine alkali particles on the order of angstroms. When cooled, the vapor alkali substance liquefies, absorbing carbon dioxide extremely efficiently, and becomes a carbon dioxide recovery liquid. Therefore, this method has the advantage of being able to recover the carbon dioxide recovery liquid and separate carbon dioxide from combustion exhaust gas extremely efficiently.

[0019] In addition to the above, another embodiment of the carbon dioxide separation method for combustion exhaust gas according to the present disclosure can use the thermal energy of the combustion exhaust gas from which carbon dioxide is separated to generate alkali microparticles containing vaporized steam. The above method effectively utilizes the thermal energy of the combustion exhaust gas to generate alkali microparticles in vapor form. This method is characterized by the fact that, compared to ultrasonic vibration or electrostatic atomization, which generate fine alkali microparticles in the form of a mist, it uses a significantly simpler structure to generate fine alkali microparticles in vapor form with particle sizes on the order of angstroms, thereby achieving highly efficient absorption of carbon dioxide. Furthermore, the thermal energy required to generate the alkali microparticles can be reduced, thereby reducing the energy consumed to generate the alkali microparticles in vapor form, further reducing running costs.

[0020] In addition to the above, a method for separating carbon dioxide gas from combustion exhaust gas according to another embodiment of the present disclosure can spray an alkaline substance in the form of a mist from a nozzle into the combustion exhaust gas, and heat it with the thermal energy of the combustion exhaust gas to generate vaporized alkaline microparticles. The above method for separating carbon dioxide gas from combustion exhaust gas can generate alkaline microparticles by heating and vaporizing it with the thermal energy of the combustion exhaust gas, and has the advantage that the alkaline substance injected into the combustion exhaust gas can be quickly converted into vapor and efficiently absorb carbon dioxide. This is because the alkaline substance sprayed from the nozzle is dispersed in the combustion exhaust gas in the form of a fine mist, and is heated with the thermal energy of the combustion exhaust gas to generate vaporized alkaline microparticles.

[0021] In addition to the above, in a method for separating carbon dioxide gas from combustion exhaust gas according to another embodiment of the present disclosure, the alkaline fine particles can contain a mist of an alkaline substance. The above method for separating carbon dioxide gas from combustion exhaust gas has a feature that the alkaline fine particles containing a mist formed by atomizing an alkaline solution are mixed with the combustion exhaust gas, thereby enabling efficient absorption of carbon dioxide gas.

[0022] In addition to the above, a method for separating carbon dioxide gas from combustion exhaust gas according to another embodiment of the present disclosure may include the alkaline substance of the alkaline fine particles containing any of ammonia, amines, alkali carbonate, and calcium hydroxide. The above method for separating carbon dioxide gas from combustion exhaust gas has the advantage that the alkaline substance of the alkaline fine particles is mixed with the combustion exhaust gas, thereby efficiently absorbing carbon dioxide gas. In this disclosure, ammonia, amines, alkali carbonate, and calcium hydroxide are considered to include these compounds.

[0023] In another embodiment of the present disclosure, a carbon dioxide separation method for combustion exhaust gas further includes the steps of: (1) providing an alkaline substance containing ammonia; (2) utilizing ammonia separated from COG (coke oven gas) discharged from a coke oven; (3) utilizing ammonia separated from COG (coke oven gas) discharged from a coke oven; (4) utilizing ammonia separated from COG (coke oven gas) discharged from a coke oven; (5) utilizing ammonia separated from ammonia; (6) utilizing ammonia separated from ammonia; (7) utilizing ammonia separated from ammonia; (8) utilizing ammonia separated from ammonia; (9) utilizing ammonia separated from ammonia; (10) utilizing ammonia; (11) utilizing ammonia; (12) utilizing ammonia; (13) utilizing ammonia; (14) utilizing ammonia; (15) utilizing ammonia; (15) utilizing ammonia; (16) utilizing ammonia; (17) utilizing ammonia; (18) utilizing ammonia; (19) utilizing ammonia; (20) utilizing ammonia; (21) utilizing ammonia; (22) utilizing ammonia; (23) utilizing ammonia; (24) utilizing ammonia; (25) utilizing ammonia; (26) utilizing ammonia; (27) utilizing ammonia; (28) utilizing ammonia; (29) utilizing ammonia; (30) utilizing ammonia; (31) utilizing ammonia; (32) utilizing ammonia; (33) utilizing ammonia; (34) utilizing ammonia; (35) utilizing ammonia; (36) utilizing ammonia; (37) utilizing ammonia; (38) utilizing ammonia; (39) utilizing ammonia; (40) utilizing ammonia; (41) utilizing ammonia; (42) utilizing ammonia; (43) utilizing ammonia; (44) utilizing ammonia; (45) utilizing ammonia; (46

[0024] In addition to the above, a method for separating carbon dioxide gas from combustion exhaust gas according to another embodiment of the present disclosure includes mixing alkaline fine particles containing ammonia as the alkaline substance with the combustion exhaust gas, generating ammonium bicarbonate liquid, and reacting the generated ammonium bicarbonate liquid with ammonium dihydrogen phosphate to separate carbon dioxide gas from the ammonium bicarbonate liquid. The above method has the advantage of being able to efficiently separate carbon dioxide gas from combustion exhaust gas. This is because mixing alkaline fine particles containing ammonia as the alkaline substance with combustion exhaust gas containing carbon dioxide gas to generate ammonium bicarbonate liquid and reacting the generated ammonium bicarbonate liquid with ammonium dihydrogen phosphate allows efficient separation of carbon dioxide gas from a large amount of combustion exhaust gas containing carbon dioxide gas from a coke oven.

[0025] In addition to the above, another embodiment of the present disclosure provides a method for separating carbon dioxide from combustion exhaust gas. The method further includes adding ammonium dihydrogen phosphate to COG discharged from a coke oven to produce ammonium hydrogen phosphate, separating the alkaline substance ammonia from the ammonium hydrogen phosphate, and generating alkaline fine particles from the separated ammonia, which are then mixed with the combustion exhaust gas. The above method effectively utilizes the ammonia contained in the COG discharged from the coke oven to efficiently separate carbon dioxide from the combustion exhaust gas, reducing the amount of alkaline substance consumed and lowering running costs. This is because the ammonia contained in the COG is effectively utilized, and alkaline fine particles are mixed with the combustion exhaust gas containing carbon dioxide to produce ammonium hydrogen carbonate liquid, which is then reacted with ammonium dihydrogen phosphate to efficiently separate carbon dioxide.

[0026] In addition to the above, a method for separating carbon dioxide gas in combustion exhaust gas according to another embodiment of the present disclosure can include mixing alkaline fine particles, in which the alkaline substance is ammonia, with the combustion exhaust gas from a coke oven that dry distills coal to produce an ammonium bicarbonate liquid, reacting ammonium dihydrogen phosphate with the produced ammonium bicarbonate liquid to separate carbon dioxide gas from the ammonium bicarbonate liquid and produce ammonium bicarbonate, adding ammonium dihydrogen phosphate to COG discharged from the coke oven to produce ammonium bicarbonate, separating the alkaline substance ammonia from the produced ammonium bicarbonate and produce ammonium bicarbonate, and producing alkaline fine particles from the separated ammonia to mix with the combustion exhaust gas.

[0027] The above method effectively utilizes ammonia contained in COG discharged from coke ovens, reducing the consumption of alkaline substances and running costs, and efficiently separates carbon dioxide from combustion exhaust gas. The above method also has the advantage of allowing the generated ammonium dihydrogen phosphate and ammonium hydrogen phosphate to be recycled and reused. This is because the above method involves mixing combustion exhaust gas with alkaline fine particles containing ammonia as the alkaline substance to produce ammonium bicarbonate liquid (carbon dioxide absorption process), reacting ammonium dihydrogen phosphate with the ammonium bicarbonate liquid to separate carbon dioxide from the ammonium bicarbonate liquid and produce ammonium hydrogen phosphate (carbon dioxide purification process), and adding ammonium dihydrogen phosphate to ammonia-containing COG discharged from coke ovens to produce ammonium hydrogen phosphate (ammonia absorption process), separating the alkaline ammonia from the produced ammonium hydrogen phosphate and producing ammonium dihydrogen phosphate (ammonia purification process). The ammonium hydrogen phosphate produced in the carbon dioxide purification process and / or ammonia absorption process can be used in the ammonia purification process to separate the alkaline ammonia from the ammonium hydrogen phosphate and produce ammonium dihydrogen phosphate. Furthermore, ammonium dihydrogen phosphate produced in the ammonia purification step can be recycled to the ammonia absorption step and / or the carbon dioxide purification step. As a result, in the ammonia absorption step, ammonium dihydrogen phosphate can be produced by adding ammonium dihydrogen phosphate to COG discharged from a coke oven, and in the carbon dioxide purification step, ammonium dihydrogen phosphate can be reacted with ammonium hydrogen carbonate liquid to separate carbon dioxide from the ammonium hydrogen carbonate liquid and produce ammonium hydrogen phosphate.

[0028] Another embodiment of the present disclosure provides an apparatus for separating carbon dioxide gas from combustion exhaust gas, which comprises a mixing and separation section that mixes alkaline fine particles containing either or both of a mist and vapor of an alkaline substance with the combustion exhaust gas, causing the carbon dioxide gas in the combustion exhaust gas to be absorbed by the alkaline fine particles and separated, and an alkali supply section that supplies the alkaline substance to the mixing and separation section, wherein the alkali supply section recovers the alkaline substance contained in the exhaust from a combustion furnace that emits combustion exhaust gas, and supplies the alkaline fine particles generated from the recovered alkaline substance to the mixing and separation section.

[0029] The carbon dioxide separation device described above effectively utilizes alkaline substances contained in the exhaust gas discharged from a combustion furnace to generate alkaline microparticles to separate carbon dioxide. This allows for efficient separation of carbon dioxide from the combustion exhaust gas while reducing the amount of alkaline substance used to generate the alkaline microparticles that absorb carbon dioxide and thereby reducing running costs. Devices that separate carbon dioxide by absorbing it into alkaline microparticles of alkaline substances require an increased amount of alkaline substance in proportion to the amount of carbon dioxide to be separated. Devices that generate alkaline microparticles by supplying alkaline substances externally consume a large amount of alkaline substance in proportion to the amount of combustion exhaust gas emitted, resulting in high running costs. Reducing running costs for devices that separate carbon dioxide from combustion exhaust gas is a crucial issue that determines their practical application. Separating carbon dioxide from combustion exhaust gas is crucial for reducing the carbon dioxide concentration in the atmosphere, but the economic burden required to achieve this goal has hindered practical application and is one of the factors hindering the reduction of carbon dioxide concentrations. An apparatus that can separate carbon dioxide gas in an economically advantageous manner will reduce the economic burden on users, be adopted by many users, and be able to greatly reduce the carbon dioxide gas concentration in the atmosphere.

[0030] The separation device described above effectively utilizes alkaline substances contained in the exhaust of a combustion furnace that emits combustion exhaust gas to generate alkaline microparticles, thereby reducing running costs. Some combustion furnaces emit exhaust containing alkaline substances. For example, a coke oven, which carbonizes coal to produce coke, produces 75% of the coal by weight as coke, along with tar, light oil, and water. Approximately 15% of the coal is separated and discharged as coke oven gas (COG), which contains approximately 10,000 ppm (1% by weight) of ammonia. By purifying the ammonia contained in the COG and effectively utilizing it as an alkaline substance to separate carbon dioxide, the coke oven achieves the advantage of significantly reducing running costs.

[0031] In another embodiment of the present disclosure, a carbon dioxide separation device for combustion exhaust gas further includes the above-described configuration. The combustion furnace is a coke oven, the alkaline substance contains ammonia, and the alkali supply unit recovers ammonia contained in COG (coke oven gas) discharged from the coke oven and supplies it to the mixing and separation unit. This separation device is characterized by its ability to efficiently separate carbon dioxide from the combustion exhaust gas by effectively utilizing the ammonia contained in COG discharged from the coke oven. In a coke oven, 75% of the coal weight is converted into coke, and the remaining coal is tar, light oil, and water. Approximately 15% of the coal weight is discharged as COG (coke oven gas) through an exhaust path separate from the combustion exhaust gas. Since this COG contains approximately 10,000 ppm of ammonia, the ammonia contained in this COG can be purified and effectively utilized as an alkaline substance to reduce the consumption of alkaline substances. Furthermore, this separation device is characterized by its ability to separate ammonia from ammonia compounds with less energy because ammonia has a weaker bonding strength than amines, thereby reducing running costs.

[0032] In addition to the above configuration, the carbon dioxide separation device for combustion exhaust gas according to another embodiment of the present disclosure is configured such that the mixing and separating section can mix alkaline fine particles containing vapor of an alkaline substance into the combustion exhaust gas.

[0033] The above separation device has the advantage of being able to efficiently absorb and separate carbon dioxide gas contained in combustion exhaust gas. This is because the separation device heats an alkaline substance (solution) to make it vapor, mixes the vapor of the alkaline substance with the combustion exhaust gas, cools the vapor of the alkaline substance in the combustion exhaust gas, liquefies it, and separates it. When the alkaline solution vaporizes and becomes vaporized alkaline fine particles, 1 mole (18 g of water when the solvent is water) of alkaline aqueous solution will be in the form of a huge number of vaporized molecules (Avogadro's constant: 6 x 10 ２３ ) Disperse in the exhaust gas. The vaporized alkali particles dispersed in the combustion exhaust gas are so fine that they disperse in a huge number of molecules, incomparable to the unvaporized mist. When the alkali particles are cooled and condensed in this state, they efficiently absorb and liquefy the carbon dioxide contained in the combustion exhaust gas during the condensation process.

[0034] The device for separating carbon dioxide from combustion exhaust gas can efficiently absorb carbon dioxide into alkali particles by increasing the contact area between the alkali particles and the combustion exhaust gas. The contact area between the combustion exhaust gas and the alkali particles can be achieved by reducing the particle size of the alkali particles. Alkali particles can be atomized into a mist using methods such as ultrasonic vibration or electrostatic atomization, but they can also be heated and vaporized to form even smaller alkali particles. The above separation device heats and vaporizes the alkaline substance to produce vapor alkali particles, resulting in extremely fine alkali particles with a particle size on the order of angstroms. When the vapor alkali particles are cooled, they efficiently absorb and liquefy carbon dioxide, becoming a carbon dioxide recovery liquid. Therefore, this device has the advantage of being able to recover the carbon dioxide recovery liquid and efficiently separate carbon dioxide from the combustion exhaust gas.

[0035] In another embodiment of the carbon dioxide separation device for combustion exhaust gas according to the present disclosure, in addition to the above configuration, the mixing / separation section can vaporize alkaline substances using the thermal energy of the combustion exhaust gas to produce vaporized alkaline microparticles. The above separation device effectively utilizes the thermal energy of the combustion exhaust gas to generate vaporized alkaline microparticles. Compared to ultrasonic vibration or electrostatic atomization, which generate fine mist of alkaline microparticles, the device has a significantly simpler structure and can generate fine vaporized alkaline microparticles with particle sizes on the order of angstroms, achieving the advantage of highly efficient absorption of carbon dioxide. Furthermore, the device reduces the thermal energy required to generate the alkaline microparticles, thereby reducing the energy consumed to generate the vaporized alkaline microparticles, further reducing running costs.

[0036] In addition to the above configuration, the carbon dioxide separation device for combustion exhaust gas according to another embodiment of the present disclosure can include a carbon dioxide absorption tower in which the mixing / separation section cools a mixed gas in which alkali fine particles are mixed with the combustion exhaust gas and recovers a carbon dioxide recovery liquid in which carbon dioxide is dissolved, and a carbon dioxide purification tower in which carbon dioxide is separated from the carbon dioxide recovery liquid discharged from the carbon dioxide absorption tower.

[0037] In addition to the above configuration, the carbon dioxide separation apparatus for combustion exhaust gas according to another embodiment of the present disclosure can include an ammonia absorption tower in which the alkali supply unit produces ammonium hydrogen phosphate by reacting ammonium dihydrogen phosphate with ammonia contained in COG discharged from the coke oven, and an ammonia purification tower that separates ammonia to be supplied to the mixing separation unit from the ammonium hydrogen phosphate supplied from the ammonia absorption tower.

[0038] In another embodiment of the present disclosure, in addition to the above configuration, a carbon dioxide separation apparatus for combustion exhaust gas includes a mixing / separation unit that cools a mixed gas obtained by mixing the combustion exhaust gas with alkali fine particles and recovers a carbon dioxide recovery liquid containing dissolved carbon dioxide, and a carbon dioxide purification unit that separates carbon dioxide from the carbon dioxide recovery liquid discharged from the carbon dioxide absorption unit, and an ammonia absorption unit that reacts ammonium dihydrogen phosphate with ammonia contained in COG discharged from a coke oven to produce ammonium hydrogen phosphate, and an ammonia purification unit that separates ammonia from the ammonium hydrogen phosphate supplied from the ammonia absorption tower, wherein the ammonium hydrogen carbonate produced by mixing the alkali fine particles with the combustion exhaust gas in the carbon dioxide absorption tower is supplied to the carbon dioxide purification tower, and the ammonium hydrogen phosphate reacts with the ammonium hydrogen phosphate in the carbon dioxide purification tower to separate carbon dioxide and produce ammonium hydrogen phosphate, and the produced ammonium hydrogen phosphate can be recycled to the ammonia purification tower. The above apparatus has the advantage of being able to recycle and reuse the produced ammonium hydrogen phosphate. Ammonium hydrogen phosphate produced in the carbon dioxide purification tower is supplied to and circulated in the ammonia purification tower, whereby the alkaline substance ammonia is separated from the ammonium hydrogen phosphate and ammonium dihydrogen phosphate is produced.Similarly, ammonium hydrogen phosphate produced in the ammonia absorption tower is supplied to and circulated in the ammonia purification tower, whereby the alkaline substance ammonia is separated from the ammonium hydrogen phosphate and ammonium dihydrogen phosphate is produced.

[0039] In another embodiment of the present disclosure, in addition to the above configuration, a carbon dioxide separation apparatus for separating carbon dioxide from combustion exhaust gas includes: a mixing / separation unit that cools a mixed gas obtained by mixing alkali fine particles with the combustion exhaust gas and recovers a carbon dioxide recovery liquid obtained by dissolving carbon dioxide; and a carbon dioxide purification unit that separates carbon dioxide from the carbon dioxide recovery liquid discharged from the carbon dioxide absorption unit; the alkali supply unit that includes an ammonia absorption tower that produces ammonium hydrogen phosphate by reacting ammonium dihydrogen phosphate with ammonia contained in COG discharged separately from the combustion exhaust gas from the coke oven; and an ammonia purification tower that separates ammonia from the ammonium hydrogen phosphate supplied from the ammonia absorption tower; and the ammonium hydrogen phosphate produced by the reaction of the COG from the coke oven with the ammonium dihydrogen phosphate in the ammonia absorption tower is supplied to the ammonia purification tower. In the ammonia purification tower, ammonia is separated from the ammonium hydrogen phosphate and ammonium dihydrogen phosphate is produced. The separated ammonia is supplied to the carbon dioxide absorption tower as alkali fine particles, and the produced ammonium dihydrogen phosphate can be circulated to the carbon dioxide purification tower.

[0040] The above-described apparatus effectively utilizes ammonia contained in COG discharged from coke ovens, reducing the consumption of alkaline substances and running costs, and has the advantage of being able to efficiently separate carbon dioxide from combustion exhaust gas. The above-described apparatus also has the advantage of being able to recycle and use the ammonium dihydrogen phosphate and ammonium hydrogen phosphate produced. Ammonium dihydrogen phosphate produced in the ammonia purification tower can be supplied and circulated to the carbon dioxide purification tower, where it reacts with ammonium dihydrogen phosphate to separate carbon dioxide from the ammonium bicarbonate solution and produce ammonium hydrogen phosphate. Furthermore, the ammonium dihydrogen phosphate produced in the ammonia purification tower can be supplied and circulated to the ammonia absorption tower, where it can add ammonium dihydrogen phosphate to COG to produce ammonium hydrogen phosphate. (Embodiment 1)

[0041] The carbon dioxide separation apparatus 100 shown in the block diagram of Fig. 1 includes a mixing / separation section 1 that mixes alkaline fine particles of an alkaline substance into combustion exhaust gas and separates the carbon dioxide gas by absorbing it into the alkaline fine particles, and an alkali supply section 2 that generates alkaline fine particles to be supplied to the mixing / separation section 1. The alkali supply section 2 preferably recovers alkaline substances contained in the effluent from a combustion furnace 3 to generate alkaline fine particles.

[0042] The combustion furnace 3 that discharges the alkaline substance can be, for example, a coke oven 3a that carbonizes coal to produce coke. The coke oven 3a discharges COG containing ammonia from a separate exhaust path separated from the combustion exhaust gas. The coke oven 3a heats a closed chamber filled with coal with combustion gas from the outside to convert the coal in the closed chamber into coke. During this process, COG containing ammonia is discharged from the closed chamber. Since the combustion gas that heated the closed chamber is discharged to the outside without entering the closed chamber, the COG is a flue gas separated from the combustion exhaust gas containing carbon dioxide and is discharged separately from combustion exhaust gases such as heavy oil. Coke plants separate ammonia from the COG, which is the exhaust product of the coke oven 3a, and sell it commercially. The ammonia in the COG can be used as an alkaline substance to generate alkaline microparticles. Since the coke oven 3a discharges COG containing ammonia, the ammonia in the COG discharged can be effectively utilized to produce alkaline microparticles. However, the present disclosure does not limit the alkaline substance used to produce alkaline microparticles to COG from the coke oven 3a. Discharges from all combustion furnaces other than coke ovens that discharge discharges containing alkaline substances can also be used. The carbon dioxide separation device 100 shown in FIG. 1 mixes alkaline microparticles with the combustion exhaust gas from the coke oven 3a, which carbonizes coal, and absorbs the carbon dioxide into the alkaline microparticles for separation. The combustion exhaust gas is supplied to the carbon dioxide absorption tower 10 of the mixing and separation section 1 via the exhaust duct 4 of the coke oven 3a. (Mixing and Separation Section 1)

[0043] The mixing and separation section 1 in Fig. 1 includes a carbon dioxide absorption tower 10 that mixes alkali fine particles with combustion exhaust gas to form a mixed gas and cools the mixed gas to recover carbon dioxide recovery liquid 10a in which carbon dioxide is dissolved, and a carbon dioxide purification tower 20 that separates carbon dioxide from the carbon dioxide recovery liquid 10a recovered in the carbon dioxide absorption tower 10. The mixing and separation section 1 in Fig. 1 mixes the combustion exhaust gas from a coke oven 3a via an exhaust duct 4 with alkali fine particles in the carbon dioxide absorption tower 10 and recovers it as carbon dioxide recovery liquid 10a. (Carbon dioxide absorption tower 10)

[0044] The carbon dioxide absorption tower 10 mixes alkaline fine particles with the combustion flue gas, cools the mixture, and absorbs the carbon dioxide contained in the combustion flue gas as a carbon dioxide recovery liquid 10a. The carbon dioxide absorption tower 10 reacts with the carbon dioxide contained in the combustion flue gas to generate a compound (carbon dioxide recovery liquid 10a), which absorbs the carbon dioxide. The carbon dioxide absorption tower 10 illustrated in FIG. 2 includes a mixing section 12 that mixes alkaline fine particles with the combustion flue gas to produce a mixed gas, and a gas-liquid separation section 14 that cools the mixed gas discharged from the mixing section 12 in a cooling section 13 and recovers the carbon dioxide recovery liquid 10a. The mixing section 12 can convert the entire alkaline fine particles into alkaline substance vapor, or convert the alkaline fine particles into a steam mist containing both alkaline substance vapor and mist, or convert the entire alkaline fine particles into an alkaline substance mist, and further heat the vaporized alkaline fine particles to 100°C or higher to produce heated alkaline substance vapor and mix it with the combustion flue gas.

[0045] The mixing section 12 sprays an alkaline solution (alkaline water) into the high-temperature combustion exhaust gas in the steam generating section 11, and vaporizes it using the thermal energy of the combustion exhaust gas to generate vaporous alkaline microparticles. The alkaline water, which is an alkaline substance, can be sprayed into the combustion exhaust gas from the nozzle 12a and mixed with the combustion exhaust gas. The method and apparatus for spraying a fine mist of alkaline microparticles from the nozzle 12a into the combustion exhaust gas can efficiently heat the fine mist at low cost by utilizing the thermal energy of the combustion exhaust gas, and can quickly generate vaporous alkaline microparticles. The mist of alkaline microparticles can be heated and vaporized using the thermal energy of the combustion exhaust gas, but the vaporization of the alkaline microparticles does not necessarily depend on the thermal energy of the combustion exhaust gas; they can also be vaporized into steam by heating with other heat sources, such as solar heat or a dedicated heater.

[0046] The vaporized alkaline fine particles are mixed with the combustion exhaust gas and efficiently absorb and condense carbon dioxide. However, the alkaline fine particles do not necessarily have to be vaporized; they can be mixed with the combustion exhaust gas in the form of a mist to absorb carbon dioxide. The non-vaporizable alkaline fine particles can be produced by a simple mechanism in which alkaline water is sprayed into the combustion exhaust gas from the nozzle 12a. The method and apparatus for mixing the alkaline fine particles in the mist with the combustion exhaust gas to separate carbon dioxide does not require the thermal energy of the combustion exhaust gas to vaporize the mist and vaporize it, and the combustion exhaust gas does not require thermal energy to vaporize the mist. Carbon dioxide can be absorbed by mixing the alkaline fine particles with the low-temperature combustion exhaust gas.

[0047] The method and apparatus for spraying mist from a nozzle 12a into combustion exhaust gas vaporizes a portion of the mist sprayed from the nozzle 12a and mixes alkaline fine particles of the steam mist, which contains both steam and mist, into the combustion exhaust gas. The alkaline fine particles in the steam condense and absorb carbon dioxide, and the alkaline fine particles in the mist absorb the carbon dioxide and coagulate, so that both the steam and the mist absorb carbon dioxide to produce a carbon dioxide recovery liquid 10a. The alkaline fine particles in the steam absorb and condense carbon dioxide more efficiently than the mist, but the unvaporized mist also absorbs carbon dioxide and coagulates, so that both the steam and the mist absorb carbon dioxide and form the carbon dioxide recovery liquid 10a.

[0048] The gas-liquid separation section 14 of the carbon dioxide gas absorption tower 10 cools the mixed gas of the combustion exhaust gas and the alkaline fine particles to produce a carbon dioxide gas recovery liquid 10a that has absorbed the carbon dioxide gas. The carbon dioxide gas recovery liquid 10a is discharged to the carbon dioxide gas purification tower 20. The mixed gas of the alkaline fine particles, which has the alkaline substance as ammonia, is converted into carbon dioxide gas (CO ２ ) and alkaline aqueous solution of alkaline fine particles (NH ４ OH) reacts with ammonium bicarbonate (NH ４ HCO ３ ) to form a carbon dioxide gas recovery liquid 10a. ２ +NH ４ OH→NH ４ HCO ３ ... (1) The ammonium bicarbonate liquid of the carbon dioxide recovery liquid 10a is supplied to the carbon dioxide purification tower 20 via a liquid pump P. The carbon dioxide absorption tower 10 can recover carbon dioxide from the combustion exhaust gas or reduce the carbon dioxide concentration in the combustion exhaust gas and discharge it from the exhaust duct 17.

[0049] The gas-liquid separation section 14 cools the mixed gas to a temperature lower than the dew point temperature, condenses the vapor of the alkali particulates that has become supersaturated, and liquefies the vapor to recover ammonium bicarbonate in the carbon dioxide recovery liquid 10a. The relative humidity of the mixed gas varies depending on the amount of vapor (g) of the alkali substance contained and the temperature (°C). The temperature of the mixed gas is preferably set to 70°C (saturated water vapor amount 197 g / m) in order to increase the amount of vapor of the alkali particulates that becomes supersaturated when cooled. ３ ) or less, more preferably 60°C (saturated water vapor amount 130g / m ３ ) or less, and optimally 50°C (saturated water vapor amount 83g / m ３ The mixed gas is cooled and supersaturated by lowering the temperature, and the carbon dioxide gas recovery liquid 10a that absorbs and liquefies carbon dioxide gas can be increased.

[0050] Whether vaporized vapor alkali microparticles can be produced using the thermal energy of the combustion exhaust gas depends on the temperature and flow rate of the combustion exhaust gas. Because the heat of vaporization of water is large, approximately 540 calories / g, high-temperature combustion exhaust gas is required to vaporize liquid alkali substances. The thermal energy required to vaporize liquid alkali substances can be obtained not only from the thermal energy of the combustion exhaust gas, but also from the exhaust heat of the plant that is equipped with the combustion furnace 3. Since the exhaust heat of a plant increases in proportion to the amount of combustion exhaust gas emitted, even if the combustion exhaust gas increases and the thermal energy required to vaporize the alkali substances increases, the alkali substances can be heated and vaporized using the exhaust heat of the plant. Therefore, in plants where vaporized alkali microparticles cannot be produced using only the thermal energy of the combustion exhaust gas, the alkali substances can be heated and vaporized using the waste heat.

[0051] The combustion furnaces of plants waste a considerable amount of heat energy as unused heat without making effective use of it. The amount of unused heat varies from plant to plant, and the temperature distribution of the unused heat also differs depending on the industry, such as electricity, steel, or ceramics. The temperature of the waste heat from electricity is 100-150°C, and that from steel and ceramics is 100-200°C, both of which are in the temperature range suitable for vaporizing liquid alkaline substances. Therefore, the unused waste heat from these plants can be used to heat and vaporize liquid alkaline substances to produce alkaline microparticles.

[0052] As shown in FIG. 2 , the mixing section 12 of the carbon dioxide absorption tower 10 supplies an alkaline solution, which is a liquid alkaline substance, to the combustion exhaust gas flow path 18 and heats it with the thermal energy of the combustion exhaust gas to produce vaporized alkaline microparticles. This structure allows the liquid alkaline substance to directly contact the combustion exhaust gas, thereby efficiently producing vaporized alkaline microparticles. This structure allows the liquid alkaline substance to be converted into vaporized alkaline microparticles using a simple structure, such as pressurizing the liquid alkaline substance with a liquid pump 19 and spraying it from a nozzle 12 a into the combustion exhaust gas, or by sprinkling water, thereby simplifying the structure. Furthermore, by effectively utilizing the thermal energy of the combustion exhaust gas, energy consumption required for external supply can be reduced. In other words, the above-described structure for supplying a liquid alkaline substance to combustion exhaust gas reduces the energy consumption required to vaporize the liquid alkaline substance, thereby reducing running costs. It also simplifies and downsizes the mechanism for vaporizing the liquid alkaline substance, thereby reducing equipment costs.

[0053] As shown in Figure 3, the carbon dioxide gas absorption tower can also supply water and an alkaline substance separately to generate alkaline microparticles and mix them with the combustion exhaust gas. The mixing section 12 in Figure 3 is provided with a nozzle 12b for injecting water and a nozzle 12c for spraying ammonia in the combustion exhaust gas flow path 18. Nozzle 12b injects pressurized water, and nozzle 12c injects ammonia stored under pressure in an ammonia tank 44. The injected ammonia is absorbed into the water mist and becomes alkaline microparticles of the ammonia solution, which absorb carbon dioxide gas in the combustion exhaust gas flow path 18. The mixing section 12 in Figure 3 supplies water and the alkaline substance ammonia to the mixing section 12 through nozzles 12b and 12c, so that ammonia can be supplied from the ammonia tank 44 to nozzle 12c and injected into the mixing section 12. (Carbon dioxide gas purification tower 20)

[0054] The carbon dioxide purifying tower 20 separates carbon dioxide from the carbon dioxide recovery liquid 10a. The carbon dioxide purifying tower 20 separates carbon dioxide from compounds (carbon dioxide recovery liquid 10a) that have absorbed carbon dioxide in the carbon dioxide absorption tower 10. The carbon dioxide purifying tower 20 is a closed chamber that connects a carbon dioxide exhaust duct 21, a first circulation path 51, a second circulation path 52, and a third circulation path 53. The exhaust duct 21 discharges carbon dioxide separated from the carbon dioxide recovery liquid 10a, such as ammonium bicarbonate, to a cylinder or the like. The first circulation path 51 connects the carbon dioxide absorption tower 10 and the carbon dioxide purifying tower 20, and supplies ammonium bicarbonate from the carbon dioxide recovery liquid 10a from the carbon dioxide absorption tower 10 to the carbon dioxide purifying tower 20. The second circulation path 52 connects the ammonia purifying tower 40 and the carbon dioxide purifying tower 20, and ammonium dihydrogen phosphate is supplied from the ammonia purifying tower 40. The third circulation line 53 connects the carbon dioxide gas purification column 20 and the ammonia purification column 40 , and supplies the ammonium hydrogen phosphate produced in the carbon dioxide gas purification column 20 to the ammonia purification column 40 .

[0055] The carbon dioxide gas purifying tower 20 is supplied with the ammonium bicarbonate solution (NH ) of the carbon dioxide gas recovery solution 10a from the carbon dioxide gas absorption tower 10 via the first circulation path 51. ４ HCO ３ ), and ammonium dihydrogen phosphate ((NH ４ ) １ H ２ P.O. ４ ) are mixed together to form ammonium bicarbonate (NH ４ HCO ３ ) to carbon dioxide (CO ２ ) was separated to obtain ammonium hydrogen phosphate ((NH ４ ) ２ H １ P.O. ４ In this reaction, the carbonate ions of the weak acid are replaced by the phosphate ions of the strong acid, the ammonium ions of ammonium bicarbonate are incorporated into ammonium hydrogen phosphate, and carbon dioxide gas is separated from the ammonium bicarbonate. ４ HCO ３ + (NH ４ )１ H ２ P.O. ４ →CO ２ + (NH ４ ) ２ H １ P.O. ４ …(2)

[0056] The carbon dioxide gas purification tower 20 separates and discharges high-purity carbon dioxide gas from the ammonium hydrogen carbonate through the above reaction. The separated carbon dioxide gas is recovered from the purification tower in a gas cylinder (not shown) and can be used for various purposes. The ammonium hydrogen phosphate discharged from the carbon dioxide gas purification tower 20 is supplied to the ammonia purification tower 40 described below and can be recycled.

[0057] The carbon dioxide purifying tower 20 reacts 1 mole of ammonium bicarbonate liquid supplied from the carbon dioxide absorption tower 10 with 1 mole of ammonium dihydrogen phosphate to produce 1 mole of ammonium bicarbonate and separate carbon dioxide. Therefore, the carbon dioxide purifying tower 20 supplies 1 mole of ammonium dihydrogen phosphate for every 1 mole of ammonium bicarbonate liquid supplied from the carbon dioxide absorption tower 10, and can separate carbon dioxide from the supplied ammonium bicarbonate liquid. Therefore, the carbon dioxide purifying tower 20 detects the supply amount of ammonium bicarbonate liquid and controls the supply amount of ammonium dihydrogen phosphate, thereby efficiently separating carbon dioxide from the supplied ammonium bicarbonate liquid. (Alkali supply unit 2)

[0058] The alkali supply unit 2 includes an ammonia absorption tower 30 to which COG is supplied from the coke oven 3 a, and an ammonia purification tower 40 connected to the discharge side of the ammonia absorption tower 30. (Ammonia absorption tower 30)

[0059] The ammonia absorption tower 30 receives COG separated from the combustion exhaust gas from the coke oven 3a and absorbs the ammonia contained in the COG. The ammonia absorption tower 30 reacts with the ammonia contained in the COG to generate a compound (ammonia recovery product), which absorbs the ammonia. The ammonia absorption tower 30 is a closed chamber that connects a supply duct 31 through which COG is supplied from the coke oven 3a, a fourth circulation path 54 through which ammonium dihydrogen phosphate is supplied from the ammonia refining tower 40, a fifth circulation path 55 through which ammonium hydrogen phosphate is supplied to the ammonia refining tower 40, and an exhaust duct 32 through which the COG from which ammonia has been separated is supplied to the coke oven 3a as fuel. The ammonia absorption tower 30 reacts with the ammonia (NH ３ ) and ammonium dihydrogen phosphate ((NH ４ ) １ H ２ P.O. ４ ) to give ammonium hydrogen phosphate ((NH ４ ) ２ H １ P.O. ４ The COG supplied to the ammonia absorption tower 30 reacts according to the following reaction formula (3) to produce ammonia (NH ３ The purified COG is supplied to the coke oven 3a as fuel via the exhaust duct 32. ３ ) + (NH ４ ) １ H ２ P.O. ４ →COG+(NH ４ ) ２ H １ P.O. ４ …(3)

[0060] In the ammonia absorption tower 30, 1 mole of ammonia contained in the COG reacts with 1 mole of ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 to produce 1 mole of ammonium hydrogen phosphate. The ammonia absorption tower 30 sprinkles or sprays the liquid ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 onto COG, which is supplied and produced from the coke oven 3a via a route separate from the combustion exhaust gas. The liquid ammonium dihydrogen phosphate sprinkled or sprayed onto the COG absorbs the ammonia contained in the COG. The refined COG, from which the ammonia has been absorbed and removed and from which other impurities have been removed, is supplied to the coke oven 3a as fuel COG and used as fuel for heating coal. The refined COG is supplied to the combustion chamber of the coke oven 3a as fuel COG, thereby improving the combustion efficiency of the coke oven 3a. The ammonia absorption tower 30 reacts with the COG (before purification) (+NH ３ ) + (NH ４ ) １ H ２ P.O. ４ → (purified) COG + (NH ４ ) ２ H １ P.O. ４As shown in the figure, one mole of ammonia reacts with one mole of ammonium dihydrogen phosphate to produce one mole of ammonium hydrogen phosphate. Therefore, the amount of ammonium dihydrogen phosphate supplied is controlled in accordance with the amount of ammonia supplied, i.e., the flow rate of the COG before purification. The ammonia absorption tower 30 detects the amount of ammonia contained in the COG before purification and controls the amount of ammonium dihydrogen phosphate supplied, thereby enabling efficient recovery of ammonia from the COG. Since the amount of ammonia contained in the COG before purification is as low as approximately 1 wt%, the ammonia purification tower 40 supplies most of the ammonium dihydrogen phosphate produced to the carbon dioxide purification tower 20 while supplying the ammonia absorption tower 30 with an amount of ammonium dihydrogen phosphate necessary to absorb the ammonia contained in the COG before purification, thereby enabling the ammonia absorption in the ammonia absorption tower 30. The liquid ammonium dihydrogen phosphate that has absorbed the ammonia is stored in the bottom of the ammonia absorption tower 30 and supplied to the ammonia purification tower 40 via the fifth circulation path 55. (Ammonia purification tower 40)

[0061] The ammonia purifying tower 40 separates ammonia from ammonia compounds (ammonium hydrogen phosphate) that have absorbed ammonia contained in COG in the ammonia absorption tower 30. The ammonia purifying tower 40 is a closed chamber to which an ammonia pipe 41, a second circulation path 52, a third circulation path 53, a fourth circulation path 54, and a fifth circulation path 55 are connected. The ammonia pipe 41 connects the ammonia purifying tower 40 and the carbon dioxide gas absorption tower 10. A generator 42 that dissolves ammonia in water to produce ammonia water is provided between the ammonia purifying tower 40 and the carbon dioxide gas absorption tower 10. The generator 42 produces alkaline water from gaseous and / or liquid ammonia. The ammonia pipe 41 supplies the ammonia produced in the ammonia purifying tower 40 to the generator 42. The generator 42 converts the ammonia supplied from the ammonia purifying tower 40 into ammonia water (NH ４OH) and supplied to the carbon dioxide absorption tower 10 (mixing section 12). The ammonia water generator 42 can produce ammonia water by contacting ammonia with water. The carbon dioxide separation apparatus 100 of FIG. 1 circulates and repeatedly uses ammonia while continuously recovering and separating ammonia from COG in the ammonia absorption tower 30 and the ammonia purification tower 40. Therefore, a portion of the recovered ammonia can be discharged to the outside and used for other purposes. In principle, the recycled ammonia is not consumed and can be used to recover carbon dioxide from combustion exhaust gas. However, in an actual operating environment, it is impossible to completely eliminate emissions and leakage of ammonia in the circulation path. Therefore, in an actual operating environment, the ammonia absorption tower 30 must be operated while continuously recovering ammonia from COG and adding the recovered ammonia to the circulation path. The carbon dioxide separation apparatus 100, which continuously recovers ammonia from COG, recovers more ammonia than leaks and discharges it to the outside. Therefore, the excess ammonia can be discharged to the outside and effectively used for other purposes.

[0062] The second circulation path 52 connects the ammonia purification column 40 and the carbon dioxide purification column 20, and supplies ammonium dihydrogen phosphate produced in the ammonia purification column 40 to the carbon dioxide purification column 20. The fourth circulation path 54 connects the ammonia purification column 40 and the ammonia absorption column 30, and supplies the produced ammonium dihydrogen phosphate to the ammonia absorption column 30. The ammonia purification column 40 supplies ammonium dihydrogen phosphate to the carbon dioxide purification column 20 and the ammonia absorption column 30 via the second circulation path 52 and the fourth circulation path 54, and as described above, most of the ammonium dihydrogen phosphate is supplied to the carbon dioxide purification column 20. This is because the supply amount of ammonium dihydrogen phosphate supplied from the ammonia purification column 40 to the ammonia absorption column 30 is controlled using the amount of ammonia supplied from the coke oven 3a to the ammonia absorption column 30 as a parameter. The amount of ammonia supplied to the ammonia absorption tower 30 is determined by the flow rate of the COG supplied and the ammonia concentration contained in the COG, but the ammonia concentration of the COG supplied from the coke oven 3a is low, on the order of ppm, so the flow rate of ammonium dihydrogen phosphate sufficient to absorb a small amount of ammonia is controlled to be low. However, the flow rate of ammonium dihydrogen phosphate supplied to the ammonia absorption tower 30 is controlled to a value that can absorb all of the ammonia contained in the COG supplied, thereby increasing the recovery rate of ammonia contained in the COG. As described above, the flow rate of ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 to the ammonia absorption tower 30 is determined by the amount of ammonia supplied to the ammonia absorption tower 30, and the remaining ammonium dihydrogen phosphate produced is supplied to the carbon dioxide purification tower 20.

[0063] The second circulation path 52 and the fourth circulation path 54 are connected to a liquid pump P that can control the flow rate of ammonium dihydrogen phosphate discharged. The flow rate of ammonium dihydrogen phosphate supplied from the ammonia purification column 40 to the carbon dioxide purification column 20 via the second circulation path 52 and the flow rate of ammonium dihydrogen phosphate supplied to the ammonia absorption column 30 via the fourth circulation path 54 can be controlled to optimal values ​​by the liquid pumps P connected to the second and fourth circulation paths 52, 54, respectively. The third circulation path connects the carbon dioxide purification column 20 and the ammonia purification column 40, and ammonium hydrogen phosphate produced in the carbon dioxide purification column 20 is circulated and supplied to the ammonia purification column 40. The fifth circulation path 55 connects the ammonia absorption column 30 and the ammonia purification column 40, and ammonium hydrogen phosphate is supplied from the ammonia absorption column 30 to the ammonia purification column 40.

[0064] The ammonia purification column 40 can separate ammonia by heating and pressurizing ammonium hydrogen phosphate to a temperature and pressure at which the ammonia vaporizes but the ammonium hydrogen phosphate does not. The ammonia purification column 40 can separate ammonia, for example, by distilling ammonium hydrogen phosphate. The apparatus for distilling ammonium hydrogen phosphate can be set to a temperature and pressure at which ammonia gas can be separated and ammonium dihydrogen phosphate can be produced, and ammonia gas can be separated from ammonium dihydrogen phosphate by heating and pressurizing, for example, at a pressure of 1 to 2 MPa and a temperature of 120 to 200°C, preferably 120 to 180°C.

[0065] The ammonia purifying tower 40 receives ammonium hydrogen phosphate ((NH ４ ) ２ H １ P.O. ４ ) to ammonia (NH ３ ) was separated to obtain ammonium dihydrogen phosphate ((NH ４ ) １ H ２ P.O. ４The ammonia is supplied to the carbon dioxide gas absorption tower 10 via the ammonia pipe 41 and used to generate alkaline fine particles, and the ammonium dihydrogen phosphate is supplied to the carbon dioxide gas purification tower 20 and the ammonia absorption tower 30 via the second and fourth circulation paths 52 and 54. (NH ４ ) ２ H １ P.O. ４ →NH ３ + (NH ４ ) １ H ２ P.O. ４ …(4)

[0066] The ammonia purification tower 40 decomposes 1 mole of ammonium hydrogen phosphate supplied from the ammonia absorption tower 30 and the carbon dioxide purification tower 20 to produce 1 mole of ammonia and 1 mole of ammonium dihydrogen phosphate. The ammonium dihydrogen phosphate produced in the ammonia purification tower 40 is supplied to the ammonia absorption tower 30 and the carbon dioxide purification tower 20. Ammonium hydrogen phosphate and ammonium dihydrogen phosphate are circulated between the ammonia purification tower 40 and the ammonia absorption tower 30, ammonia is absorbed from COG in the ammonia absorption tower 30, and ammonia is separated in the ammonia purification tower 40. The ammonium dihydrogen phosphate produced in the ammonia purification tower 40 is circulated between the ammonia absorption tower 30 and the carbon dioxide purification tower 20, ammonia is absorbed from COG in the ammonia absorption tower 30, and carbon dioxide is separated from ammonium hydrogen carbonate in the carbon dioxide purification tower 20. The flow rate of ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 to the ammonia absorption tower 30 and the flow rate of ammonium dihydrogen phosphate supplied to the carbon dioxide purification tower 20 can be set to optimal values ​​taking into consideration the amount of ammonia recovered from COG and the flow rate at which carbon dioxide is separated from the ammonium hydrogen carbonate liquid.

[0067] The flow rate of ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 to the ammonia absorption tower 30 can be determined taking into consideration the amount of ammonia contained in the COG supplied to the ammonia absorption tower 30. The ammonium dihydrogen phosphate supplied to the ammonia absorption tower 30 is reacted with COG (+NH ３ ) + (NH ４ ) １ H２ P.O. ４ →Refined fuel COG+(NH ４ ) ２ H １ P.O. ４ ), one mole of ammonium dihydrogen phosphate absorbs one mole of ammonia to produce one mole of ammonium hydrogen phosphate, so the amount of ammonia absorbed from the COG of the coke oven 3a can be controlled by the flow rate of ammonium dihydrogen phosphate supplied to the ammonia absorption tower 30. Furthermore, the ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 to the carbon dioxide purification tower 20 reacts with the ammonium dihydrogen phosphate in the reaction (NH ４ HCO ３ + (NH ４ ) １ H ２ P.O. ４ →CO ２ + (NH ４ ) ２ H １ P.O. ４ As shown in this reaction formula, 1 mole of ammonium dihydrogen phosphate supplied to the carbon dioxide gas purification tower 20 reacts with 1 mole of ammonium hydrogen carbonate to separate 1 mole of carbon dioxide gas, so the amount of carbon dioxide gas separated from ammonium hydrogen carbonate can be controlled by the flow rate of ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 to the carbon dioxide gas purification tower 20.

[0068] The alkali supply unit 2 may include a phosphoric acid tank 43 that stores and supplies phosphoric acid (including phosphoric acid compounds). For example, in the initial stage of operation start-up, the phosphoric acid tank 43 can supply phosphoric acid (including phosphoric acid compounds) to absorb ammonia contained in COG until ammonium dihydrogen phosphate is sufficiently circulated and supplied to the ammonia absorption tower 30. The phosphoric acid tank 43 supplies phosphoric acid to produce a substance that easily absorbs and incorporates ammonia in the COG (easily reacts with ammonia), such as ammonium dihydrogen phosphate, and can supply it to the ammonia absorption tower 30. The ammonia purification tower 40 in FIG. 1 is connected to the phosphoric acid tank 43 via a liquid pump P. The liquid pump P is operated initially when the operation of the apparatus is started to supply phosphoric acid to the ammonia purification tower 40. The phosphoric acid supplied to the ammonia purification tower 40 is then supplied to the ammonia absorption tower 30, where it absorbs ammonia from the COG to form ammonium hydrogen phosphate, which is then circulated to the ammonia purification tower 40. Although not shown, the phosphoric acid tank 43 may be connected to the ammonia absorber 30 via a liquid pump P to supply phosphoric acid to the ammonia absorber 30 at the beginning of operation.

[0069] The alkali supply unit 2 is provided with an alkali tank for storing and supplying an alkali substance separated and recovered from the effluent, and can supply the alkali substance in the alkali tank to the carbon dioxide absorption tower 10. The alkali supply unit 2, which discharges ammonia, uses the ammonia tank 44 as an alkali tank and can store and supply ammonia (including ammonia compounds) separated and recovered from COG in the ammonia purification tower 40. The ammonia tank 44 supplies a portion of the ammonia supplied from the ammonia purification tower 40 to the carbon dioxide absorption tower 10, and discharges the excess ammonia to the outside and stores it in a cylinder, where it can be sold as an ammonia product or used for another purpose. The carbon dioxide separation device 100 in FIG. 1 continuously recovers ammonia from COG, so the amount of ammonia recovered gradually increases. On the other hand, ammonia is circulated to the carbon dioxide absorption tower 10, the carbon dioxide purification tower 20, and the ammonia purification tower 40 without being discharged to the outside, eliminating ammonia leakage in the circulation path and eliminating the need to add ammonia to the circulation path. However, since it is not possible to completely eliminate ammonia leaking from the circulation path to the outside, the ammonia tank 44 operates while replenishing some of the stored ammonia into the circulation path to separate carbon dioxide from the combustion exhaust gas. The ammonia in the ammonia tank 44 can also be reacted with phosphoric acid in the phosphoric acid tank 43 to produce ammonium dihydrogen phosphate, which can be supplied to the ammonia absorption tower 30.

[0070] The carbon dioxide separation method and apparatus ideally separate all of the carbon dioxide contained in the combustion exhaust gas, but it is possible to separate a portion of the carbon dioxide without necessarily separating all of the carbon dioxide, thereby reducing the amount and concentration of the carbon dioxide emitted. Therefore, the method and apparatus of the present invention ideally recover 100% of the carbon dioxide, but as the carbon dioxide recovery rate increases, the recovery efficiency decreases and the recovery cost rises, so the carbon dioxide recovery rate is actually specified taking into account the economic effect and the carbon dioxide recovery rate. The apparatus that separates a portion of the carbon dioxide contained in the combustion exhaust gas has the advantage that the alkaline fine particles mixed with the combustion exhaust gas can efficiently absorb and separate the carbon dioxide.

[0071] In the method and device for separating a portion of carbon dioxide gas without separating 100% of the carbon dioxide gas in the combustion exhaust gas, most of the alkaline fine particles mixed with the combustion exhaust gas absorb carbon dioxide gas and become ammonium hydrogen carbonate. This method is based on the reaction formula (1) (CO ２ +NH ４ OH→NH ４ HCO ３ ), 1 mole of alkali fine particles mixed with the combustion exhaust gas in the carbon dioxide absorption tower 10 absorbs approximately 1 mole of carbon dioxide and produces 1 mole of ammonium hydrogen carbonate. Therefore, 1 mole of alkali fine particles of ammonia water is supplied from the ammonia purification tower 40 to the carbon dioxide absorption tower 10, and the carbon dioxide absorption tower 10 absorbs approximately 1 mole of carbon dioxide and supplies approximately 1 mole of ammonium hydrogen carbonate to the carbon dioxide purification tower 20. The carbon dioxide purification tower 20, to which 1 mole of ammonium hydrogen carbonate is supplied, reacts with 1 mole of ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 and discharges 1 mole of carbon dioxide. Therefore, the ammonia absorption tower 30 supplies 1 mole of ammonium dihydrogen phosphate to the carbon dioxide purification tower 20 and supplies alkali fine particles consisting of 1 mole of ammonia water to the carbon dioxide absorption tower 10, so that 1 mole of carbon dioxide is absorbed in the carbon dioxide absorption tower 10, and the absorbed 1 mole of carbon dioxide can be separated and discharged from the carbon dioxide purification tower 20. For this reason, in the ammonia purification tower 40, the number of moles of ammonia water discharged to the carbon dioxide absorption tower 10 and the number of moles of ammonium dihydrogen phosphate supplied to the carbon dioxide purification tower 20 are set to be the same, and the carbon dioxide supplied as the carbon dioxide recovery liquid 10a can be separated in the carbon dioxide purification tower 20.

[0072] The carbon dioxide separation apparatus 100 shown in FIG. 1 detects parameters such as the temperature of the combustion exhaust gas from which carbon dioxide is separated, the discharge amount, carbon dioxide concentration, COG discharge amount, and ammonia concentration in the COG in real time, and controls these parameters to optimal values, thereby efficiently separating carbon dioxide from the combustion exhaust gas and efficiently recovering ammonia contained in the COG. Since the combustion furnace 3 used for various purposes varies over time in the discharge amount of the combustion exhaust gas, the amount of carbon dioxide contained in the combustion exhaust gas, the COG discharge amount, and the ammonia contained in the COG, various parameters are detected in real time and controlled to efficiently utilize the ammonia in the COG and optimize the amount of combustion exhaust gas separated. (Method for Separating Carbon Dioxide from Combustion Exhaust Gas)

[0073] The carbon dioxide separation apparatus 100 in Figure 1 separates carbon dioxide contained in the combustion exhaust gas of a combustion furnace 3 by the following method. Carbon dioxide is separated from the combustion exhaust gas discharged from a coke oven 3a. The carbon dioxide contained in the combustion exhaust gas is separated from the combustion exhaust gas via alkali fine particles mixed therein. In this method, alkali fine particles are mixed with the combustion exhaust gas to form a mixed gas of the combustion exhaust gas and the alkali fine particles, the mixed gas is cooled, and a carbon dioxide recovery liquid 10a that has absorbed the carbon dioxide is recovered (carbon dioxide absorption step), and the carbon dioxide is separated from the carbon dioxide recovery liquid 10a to separate the carbon dioxide from the combustion exhaust gas (carbon dioxide purification step). The method for separating carbon dioxide gas from combustion exhaust gas can include a carbon dioxide gas absorption process in which an alkaline substance is mixed with the combustion exhaust gas to absorb carbon dioxide gas, a carbon dioxide gas purification process in which the carbon dioxide gas absorbed in the carbon dioxide gas absorption process is separated, an ammonia absorption process (alkali absorption process) in which an alkaline substance contained in the COG discharged from the coke oven 3a is absorbed, and an ammonia purification process in which the alkaline substance (ammonia) absorbed in the alkali absorption process is separated.

[0074] Alkali fine particles can dissolve and absorb carbon dioxide gas as fine particles of various alkaline substances. However, the carbon dioxide separation apparatus 100 in FIG. 1 uses the alkali fine particles as fine particles of ammonia water and ammonia contained in COG discharged from a coke oven 3a as the ammonia to generate the alkali fine particles. Since the COG discharged from the coke oven 3a contains 10,000 ppm (1 wt%) of ammonia, ammonia is recovered from the COG and sold as a product. The carbon dioxide separation apparatus 100 in FIG. 1 recovers ammonia from the COG and uses it as the alkaline substance to generate the alkali fine particles. The ammonia from the COG is absorbed in the ammonia absorption tower 30. The ammonia is absorbed into ammonium dihydrogen phosphate, which reacts with the ammonia to produce ammonium hydrogen phosphate (first ammonia). The COG from which the ammonia has been separated in the ammonia absorption tower 30 is purified so that it can be used as fuel, and then supplied to the coke oven 3a as fuel COG. The ammonium hydrogen phosphate (first ammonia) that has absorbed the ammonia is supplied from the ammonia absorption tower 30 to the ammonia purification tower 40. The ammonia purification tower 40 separates ammonia gas from the supplied ammonium hydrogen phosphate and circulates the first ammonia as ammonium dihydrogen phosphate (second ammonia) to the ammonia absorption tower 30. The ammonia recovered in the ammonia purification tower 40 is sent to the carbon dioxide gas absorption tower 10 and used to produce alkali fine particles. The ammonium dihydrogen phosphate produced in the ammonia purification tower 40 is circulated to the ammonia absorption tower 30 and absorbs ammonia from the COG.

[0075] The carbon dioxide absorption tower 10 uses ammonia supplied from the ammonia purification tower 40 as an alkaline substance to generate alkaline microparticles. In the carbon dioxide absorption tower 10, alkaline microparticles using ammonia as the alkaline substance absorb carbon dioxide in the combustion exhaust gas to generate ammonium hydrogen carbonate. The ammonium hydrogen carbonate generated in the carbon dioxide absorption tower 10 is supplied to the carbon dioxide purification tower 20. The carbon dioxide purification tower 20 reacts the ammonium hydrogen carbonate supplied from the carbon dioxide absorption tower 10 with ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 to separate carbon dioxide from the ammonium hydrogen carbonate, and supplies the ammonium dihydrogen phosphate as ammonium hydrogen phosphate to the ammonia purification tower 40. The carbon dioxide separated in the carbon dioxide purification tower 20 is high-concentration carbon dioxide with few impurities, and can be stored in an external gas cylinder for further use or for other purposes. The ammonium hydrogen phosphate generated in the carbon dioxide purification tower 20 is circulated to the ammonia purification tower 40 and used to generate ammonia.

[0076] 1 circulates ammonium hydrogen phosphate and ammonium dihydrogen phosphate between the ammonia absorption tower 30 and the ammonia purification tower 40, and further circulates ammonium hydrogen phosphate and ammonium dihydrogen phosphate between the ammonia purification tower 40 and the carbon dioxide purification tower 20. The ammonia absorption tower 30 and the ammonia purification tower 40 are connected by a fourth circulation path 54 and a fifth circulation path 55, and the fourth circulation path 54 supplies ammonium dihydrogen phosphate from the ammonia purification tower 40 to the ammonia absorption tower 30, and the fifth circulation path 55 supplies ammonium hydrogen phosphate from the ammonia absorption tower 30 to the ammonia purification tower 40, thereby circulating the ammonium hydrogen phosphate and ammonium dihydrogen phosphate. Furthermore, the ammonia purification column 40 and the carbon dioxide purification column 20 are connected via a second circulation path 52 and a third circulation path 53. The second circulation path 52 supplies ammonium dihydrogen phosphate from the ammonia purification column 40 to the carbon dioxide purification column 20, and the third circulation path 54 supplies ammonium hydrogen phosphate from the carbon dioxide purification column 20 to the ammonia purification column 40, thereby circulating ammonium hydrogen phosphate and ammonium dihydrogen phosphate.

[0077] The fourth circulation path 54 supplies ammonium dihydrogen phosphate from the ammonia purification tower 40 to the ammonia absorption tower 30. The ammonia absorption tower 30 absorbs ammonia contained in the COG using the supplied ammonium dihydrogen phosphate to produce ammonium hydrogen phosphate. The ammonium dihydrogen phosphate produced in the ammonia purification tower 40 is circulated to the ammonia purification tower 40 via the second circulation path 52. The ammonia purification tower 40 separates ammonia from the ammonium hydrogen phosphate supplied from the carbon dioxide purification tower 20 and the ammonia absorption tower 30 via the third circulation path 53 and the fifth circulation path 55, to produce ammonium dihydrogen phosphate. The ammonium dihydrogen phosphate produced in the ammonia purification tower 40 is supplied to the ammonia absorption tower 30 via the fourth circulation path 54 and to the carbon dioxide purification tower 20 via the second circulation path 52. The alkali supply unit 2 circulates ammonium hydrogen phosphate and ammonium dihydrogen phosphate to the ammonia absorption tower 30 and the ammonia purification tower 40 to continuously recover ammonia from the COG, so that the amount of ammonia recovered increases over time. The alkali supply unit 2 recovers ammonia from COG containing 1 wt % ammonia, and the amount of recovered ammonia increases over time, so that it can produce the amount of alkali fine particles necessary to separate carbon dioxide gas contained in the combustion exhaust gas. After the alkali supply unit 2 has produced an amount of alkali fine particles sufficient to separate carbon dioxide gas from the combustion exhaust gas, the recovered ammonia can be disposed and stored outside and used for other purposes.

[0078] The second circulation path 52 supplies ammonium dihydrogen phosphate from the ammonia purification column 40 to the carbon dioxide purification column 20. The carbon dioxide purification column 20 reacts the supplied ammonium dihydrogen phosphate with ammonium hydrogen carbonate supplied from the carbon dioxide absorption column 10 to separate carbon dioxide and produce ammonium hydrogen phosphate. The ammonium hydrogen phosphate produced in the carbon dioxide purification column 20 is supplied to the ammonia purification column 40 via a third circulation path 53. The second circulation path 52 and the third circulation path 53 supply ammonium dihydrogen phosphate and ammonium hydrogen phosphate to the carbon dioxide purification column 20 and the ammonia purification column 40, respectively, and circulate the ammonium dihydrogen phosphate and ammonium hydrogen phosphate between the ammonia purification column 40 and the carbon dioxide purification column 20.

[0079] The fourth circulation path 54 and the fifth circulation path 55 circulate ammonium dihydrogen phosphate and ammonium hydrogen phosphate composed of ammonium dihydrogen phosphate to the ammonia absorption tower 30 and the ammonia purification tower 40, so that the ammonia absorption tower 30 absorbs ammonia from the COG, and the ammonia purification tower 40 separates the ammonia and supplies the ammonia to the carbon dioxide absorption tower 10. Furthermore, the second circulation path 52 and the third circulation path 53 circulate ammonium dihydrogen phosphate and ammonium hydrogen phosphate composed of ammonium dihydrogen phosphate between the ammonia purification tower 40 and the carbon dioxide purification tower 20, so that ammonia is separated in the ammonia purification tower 40 and carbon dioxide is separated in the carbon dioxide purification tower 20.

[0080] In the carbon dioxide separation apparatus 100 of Fig. 1 , the alkali supply unit 2 recovers ammonia from COG and supplies the recovered ammonia to the carbon dioxide absorption tower 10 to generate alkali fine particles that absorb carbon dioxide from the combustion exhaust gas. The ammonium bicarbonate liquid discharged from the carbon dioxide absorption tower 10 after absorbing carbon dioxide is supplied to the carbon dioxide purification tower 20. The carbon dioxide purification tower 20 reacts the supplied ammonium bicarbonate liquid with ammonium dihydrogen phosphate supplied from the ammonia purification tower 40 to separate carbon dioxide, and further converts the supplied ammonium dihydrogen phosphate into ammonium hydrogen phosphate, which is circulated to the ammonia purification tower 40. The ammonium dihydrogen phosphate produced in the ammonia purification tower 40 is circulated to the carbon dioxide purification tower 20.

[0081] As described above, the carbon dioxide separation apparatus 100 in FIG. 1 circulates ammonium dihydrogen phosphate and ammonium hydrogen phosphate between the ammonia absorption tower 30 and the ammonia purification tower 40 to recover ammonia from COG, and further circulates ammonium dihydrogen phosphate and ammonium hydrogen phosphate between the ammonia purification tower 40 and the carbon dioxide purification tower 20 to supply ammonia from the ammonia purification tower 40 to the carbon dioxide absorption tower 10 to produce alkali fine particles that absorb carbon dioxide, and separates carbon dioxide from the ammonium hydrogen carbonate liquid that is discharged after the alkali fine particles absorb carbon dioxide, and circulates the ammonium dihydrogen phosphate as ammonium hydrogen phosphate from the carbon dioxide purification tower 20 to the ammonia purification tower 40. The flow rate of ammonium dihydrogen phosphate circulated from the ammonia purification tower 40 to the ammonia absorption tower 30 is set and controlled to an optimum value taking into consideration the COG and the supply amount and content of ammonia, and the flow rate of ammonium hydrogen phosphate circulated from the carbon dioxide purification tower 20 to the ammonia purification tower 40 is set and controlled to an optimum value taking into consideration the supply amount of ammonium hydrogen phosphate from the ammonia absorption tower 30 and the recovery of ammonia from the ammonium hydrogen phosphate, thereby achieving efficient recovery of ammonia from COG and efficient separation of carbon dioxide from the combustion exhaust gas.

[0082] The separation method and separation device 100 for combustion exhaust gas disclosed herein aims to separate carbon dioxide from combustion exhaust gas to reduce the carbon dioxide concentration in the combustion exhaust gas, but the present disclosure is not limited to a method and device that separates 100% of carbon dioxide from combustion exhaust gas. For example, the carbon dioxide concentration in the combustion exhaust gas can be reduced by separating 10% of carbon dioxide from the combustion exhaust gas. Therefore, the carbon dioxide separation method and separation device 100 disclosed herein detects various parameters and controls the flow rates of ammonium hydrogen phosphate and ammonium dihydrogen phosphate, etc., so that carbon dioxide can be separated from the combustion exhaust gas at a preset set value.

[0083] The carbon dioxide separation method and separation device disclosed herein can efficiently separate carbon dioxide by mixing alkaline microparticles into the combustion exhaust gas, and can also effectively separate and utilize the alkaline substances that generate the alkaline microparticles from the exhaust gas from the combustion furnace, thereby reducing running costs. Thus, the method and device can be effectively used to separate carbon dioxide from the combustion exhaust gas.

[0084] 100... Carbon dioxide separation apparatus 1... Mixing and separation section 2... Alkali supply section 3... Combustion furnace 3a... Coke oven 4... Exhaust duct 10... Carbon dioxide absorption tower 10a... Carbon dioxide recovery liquid 11... Steam generation section 12... Mixing section 12a... Nozzle (for supplying alkaline solution) 12b... Nozzle (for supplying water) 12c... Nozzle (for supplying alkaline substance) 13... Cooling section 14... Gas-liquid separation section 17... Exhaust duct 18... Flow path 19... Liquid pump 20... Carbon dioxide purification tower 21... Exhaust duct 30... Ammonia absorption tower 31... Supply duct 32... Exhaust duct 40... Ammonia purification tower 41... Ammonia pipe 42... Generator 43... Phosphoric acid tank 44... Ammonia tank 51... First circulation path 52... Second circulation path 53... Third circulation path 54... Fourth circulation path 55... Fifth circulation path P...liquid pump

Claims

1. A method for separating carbon dioxide gas from combustion exhaust gas by mixing alkaline fine particles containing either or both of an alkaline substance mist and vapor with combustion exhaust gas, and absorbing carbon dioxide gas into the alkaline fine particles and separating it from the combustion exhaust gas, wherein the alkaline substance in the alkaline fine particles is an alkaline substance contained in the exhaust from a combustion furnace that emits combustion exhaust gas.

2. A method for separating carbon dioxide gas from combustion exhaust gas as described in claim 1, wherein the alkaline fine particles contain vapor of the alkaline substance, and the vapor of the alkaline substance absorbs and condenses the carbon dioxide gas, thereby separating the carbon dioxide gas.

3. A method for separating carbon dioxide gas from combustion exhaust gas as described in claim 2, wherein the thermal energy of the combustion exhaust gas from which carbon dioxide gas is separated is used to generate the alkali fine particles containing vaporized steam.

4. A method for separating carbon dioxide gas from combustion exhaust gas as described in claim 3, comprising spraying the alkaline substance in the form of mist from a nozzle into the combustion exhaust gas, and heating the alkaline substance with the thermal energy of the combustion exhaust gas to generate vapor of the alkaline fine particles.

5. A method for separating carbon dioxide gas from combustion exhaust gas according to claim 1, wherein the alkaline fine particles contain a mist of the alkaline substance.

6. A method for separating carbon dioxide gas from combustion exhaust gas as described in claim 1, wherein the alkaline substance of the alkaline fine particles contains any of ammonia, amines, alkali carbonate, and calcium hydroxide.

7. A method for separating carbon dioxide gas from combustion exhaust gas according to any one of claims 1 to 6, wherein the alkaline substance contains ammonia, and ammonia separated from COG (Coke Oven Gas), which is a discharge from a coke oven, is used.

8. A method for separating carbon dioxide gas from combustion exhaust gas as set forth in claim 7, wherein the combustion exhaust gas is combustion exhaust gas from a coke oven used for carbonizing coal, the method comprising: mixing the combustion exhaust gas with the alkaline fine particles that convert the alkaline substance into ammonia to produce an ammonium bicarbonate liquid; reacting the produced ammonium bicarbonate liquid with ammonium dihydrogen phosphate; and separating carbon dioxide gas from the ammonium bicarbonate liquid.

9. A method for separating carbon dioxide gas from combustion exhaust gas as set forth in claim 7, comprising: adding ammonium dihydrogen phosphate to the COG discharged from the coke oven to produce ammonium hydrogen phosphate; separating the alkaline substance ammonia from the ammonium hydrogen phosphate; and generating alkaline fine particles from the separated ammonia and mixing the alkaline fine particles with the combustion exhaust gas.

10. A method for separating carbon dioxide gas from combustion exhaust gas as set forth in claim 7, wherein the combustion exhaust gas is combustion exhaust gas from a coke oven used for carbonizing coal, and the method comprises mixing the combustion exhaust gas with the alkaline fine particles that convert the alkaline substance into ammonia to produce an ammonium hydrogen carbonate solution, reacting ammonium dihydrogen phosphate with the produced ammonium hydrogen carbonate solution to separate carbon dioxide gas from the ammonium hydrogen carbonate solution and produce ammonium hydrogen phosphate, adding ammonium dihydrogen phosphate to the COG discharged from the coke oven to produce ammonium hydrogen phosphate, separating the ammonia, which is the alkaline substance, from the produced ammonium hydrogen phosphate and producing ammonium dihydrogen phosphate, and producing the alkaline fine particles from the separated ammonia and mixing them into the combustion exhaust gas.

11. An apparatus for separating carbon dioxide gas from combustion exhaust gas, comprising: a mixing / separating section that mixes alkaline fine particles containing either or both of a mist and vapor of an alkaline substance with combustion exhaust gas, and separates carbon dioxide gas in the combustion exhaust gas by absorbing it into the alkaline fine particles; and an alkali supplying section that supplies the alkaline substance to the mixing / separating section, wherein the alkali supplying section recovers the alkaline substance contained in the exhaust of a combustion furnace that discharges combustion exhaust gas, and supplies the recovered alkaline substance to the mixing / separating section.

12. An apparatus for separating carbon dioxide gas from combustion exhaust gas as described in claim 11, wherein the combustion furnace is a coke oven, the alkaline substance contains ammonia, and the alkali supply section recovers ammonia contained in COG, which is an exhaust product of the coke oven, and supplies the ammonia to the mixing and separation section.

13. An apparatus for separating carbon dioxide gas from combustion exhaust gas as described in claim 11, wherein the mixing and separation section mixes the alkaline fine particles containing the vapor of the alkaline substance with the combustion exhaust gas.

14. An apparatus for separating carbon dioxide gas from combustion exhaust gas as described in claim 13, wherein the mixing and separating section vaporizes the alkaline substance using thermal energy of the combustion exhaust gas to form the alkaline fine particles in the form of vapor.

15. An apparatus for separating carbon dioxide gas from combustion exhaust gas as described in claim 11, wherein the mixing and separation section comprises: a carbon dioxide absorption tower that cools a mixed gas in which the alkali fine particles are mixed with the combustion exhaust gas, and recovers a carbon dioxide gas recovery liquid in which carbon dioxide gas is dissolved; and a carbon dioxide gas purification tower that separates carbon dioxide gas from the carbon dioxide gas recovery liquid discharged from the carbon dioxide gas absorption tower.

16. An apparatus for separating carbon dioxide gas contained in combustion exhaust gas according to claim 11, wherein the alkali supply unit comprises: an ammonia absorption tower that produces ammonium hydrogen phosphate by reacting ammonium dihydrogen phosphate with ammonia contained in COG discharged from a coke oven; and an ammonia purification tower that separates ammonia from the ammonium hydrogen phosphate supplied from the ammonia absorption tower.

17. An apparatus for separating carbon dioxide gas contained in combustion exhaust gas as set forth in claim 11, wherein the mixing and separation section comprises: a carbon dioxide gas absorption tower that cools a mixed gas obtained by mixing the combustion exhaust gas with the alkali fine particles and recovers a carbon dioxide gas recovery liquid formed by dissolving carbon dioxide gas; and a carbon dioxide gas purification tower that separates carbon dioxide gas from the carbon dioxide gas recovery liquid discharged from the carbon dioxide gas absorption tower; the alkali supply section comprises: an ammonia absorption tower that produces ammonium hydrogen phosphate by reacting ammonium dihydrogen phosphate with ammonia contained in COG discharged from a coke oven; and an ammonia purification tower that separates ammonia from the ammonium hydrogen phosphate supplied from the ammonia absorption tower; wherein the ammonium hydrogen carbonate produced by mixing the alkali fine particles with the combustion exhaust gas in the carbon dioxide gas absorption tower is supplied to the carbon dioxide gas purification tower; and wherein the ammonium hydrogen carbonate and ammonium dihydrogen phosphate react in the carbon dioxide gas purification tower to separate carbon dioxide gas and produce ammonium hydrogen phosphate, and the produced ammonium hydrogen phosphate is circulated to the ammonia purification tower.

18. An apparatus for separating carbon dioxide gas contained in combustion exhaust gas according to claim 11, wherein the mixing and separation section comprises: a carbon dioxide gas absorption tower that cools a mixed gas obtained by mixing the combustion exhaust gas with the alkali fine particles and recovers a carbon dioxide gas recovery liquid obtained by dissolving carbon dioxide gas; and a carbon dioxide gas purification tower that separates carbon dioxide gas from the carbon dioxide gas recovery liquid discharged from the carbon dioxide gas absorption tower; the alkali supply section comprises: an ammonia absorption tower that produces ammonium hydrogen phosphate by reacting ammonium dihydrogen phosphate with ammonia contained in COG discharged from a coke oven; and an ammonia purification tower that separates ammonia from the ammonium hydrogen phosphate supplied from the ammonia absorption tower; wherein the ammonium hydrogen phosphate produced by the reaction of COG from the coke oven with the ammonium dihydrogen phosphate in the ammonia absorption tower is supplied to the ammonia purification tower; and wherein ammonia is separated from the ammonium hydrogen phosphate and ammonium dihydrogen phosphate is produced in the ammonia purification tower; and The carbon dioxide gas separation apparatus for combustion exhaust gas, wherein the produced ammonium dihydrogen phosphate is circulated to the carbon dioxide gas purification tower.

Images