Exhaust gas treatment system, acid gas recovery system, and ship

Abstract

To remove impurities from exhaust gas while suppressing the use amount of washing water.SOLUTION: An air pollution control system includes a scrubber unit that performs a primary cleaning treatment on exhaust gas by bringing primary cleaning water into contact with the exhaust gas, a primary storage unit that stores primary drainage, a primary supply unit that supplies the primary drainage to the scrubber unit as the primary cleaning water, and an air pollution control device into which the exhaust gas subjected to the primary cleaning treatment is introduced. The wastewater treatment apparatus includes an electric dust collecting unit that performs secondary cleaning treatment by performing electric dust collection with a dust collecting electrode and cleans the dust collecting electrode with secondary cleaning water, a secondary storage unit that stores secondary wastewater, a secondary supply unit that supplies the secondary wastewater to the scrubber unit as the secondary cleaning water, a return unit that supplies the secondary wastewater stored in the secondary storage unit to the primary storage unit, a makeup water supply unit that supplies makeup water to the secondary storage unit, and a wastewater treatment unit that removes the impurities from the primary wastewater and supplies the primary wastewater to the secondary storage unit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an exhaust gas treatment system, an acid gas recovery system, and a ship. [Background technology]

[0002] In recent years, attention has been focused on the concentration of carbon dioxide (CO2) in the atmosphere from the perspective of carbon neutrality. From the perspective of reducing the concentration of carbon dioxide in the atmosphere, carbon dioxide capture systems that capture acidic gases such as carbon dioxide from flue gas are known. For example, in carbon dioxide capture systems using the chemical absorption method, an absorption liquid is circulated between a regenerator and an absorber to capture carbon dioxide from flue gas.

[0003] For example, Patent Document 1 describes an exhaust gas treatment system that recovers acidic gases such as carbon dioxide from exhaust gas. In this exhaust gas treatment system, impurities are removed from the exhaust gas before it is sent to an absorption tower that recovers carbon dioxide. Specifically, in this exhaust gas treatment system, impurities such as soot and dust are removed from the exhaust gas by passing the exhaust gas through a denitration device, a dry electrostatic precipitator, a desulfurization device, and a wet electrostatic precipitator in that order. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6045652 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, as in Patent Document 1, in denitration devices and wet electrostatic precipitators that remove impurities from flue gas before it is sent to an absorption tower, water is used as wash water to remove impurities. However, depending on the installation location of the acid gas recovery system, there may be restrictions on the amount of wash water used and the amount of wastewater discharged. Therefore, it is desirable to remove impurities from flue gas while reducing the amount of wash water used.

[0006] The present disclosure has been made to address the above-mentioned needs, and aims to provide an exhaust gas treatment system, an acid gas recovery system, and a ship that are capable of removing impurities from exhaust gas while reducing the amount of wash water used. [Means for solving the problem]

[0007] In order to solve the above problems, an exhaust gas treatment system according to the present disclosure includes a scrubber section into which exhaust gas is introduced and which performs a primary cleaning treatment on the exhaust gas by bringing primary cleaning water into contact with the exhaust gas; a primary storage section that stores primary wastewater, which is the primary cleaning water that has come into contact with the exhaust gas in the scrubber section; a primary supply section that supplies the primary wastewater stored in the primary storage section to the scrubber section as the primary cleaning water; and a primary supply section that receives exhaust gas that has been subjected to the primary cleaning treatment, performs secondary cleaning treatment by subjecting the exhaust gas to electric dust collection using dust collecting electrodes, and cleans the dust collecting electrodes with secondary cleaning water. a secondary storage section that stores secondary wastewater, which is the secondary cleaning water used in the electric dust collector; a secondary supply section that supplies the secondary wastewater stored in the secondary storage section to the electric dust collector as the secondary cleaning water; a return section that supplies a portion of the secondary wastewater stored in the secondary storage section to the primary storage section; a makeup water supply section that supplies makeup water containing fewer impurities than the secondary cleaning water to the secondary storage section; and a wastewater treatment section that removes the impurities from the primary wastewater stored in the primary storage section and supplies the primary wastewater from which the impurities have been removed to the secondary storage section.

[0008] In addition, the acid gas recovery system according to the present disclosure includes the exhaust gas treatment system, and an absorption tower that contacts the exhaust gas treated in the exhaust gas treatment system with an absorption liquid and discharges the absorption liquid that has absorbed the acid gas in the exhaust gas and an absorption tower exhaust gas that includes the exhaust gas from which the acid gas has been removed.

[0009] A ship according to the present disclosure includes the exhaust gas treatment system and a hull in which the exhaust gas treatment system is disposed. [Effects of the Invention]

[0010] According to the exhaust gas treatment system, acid gas recovery system, and ship of the present disclosure, impurities can be removed from exhaust gas while reducing the amount of wash water used. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing a ship equipped with an acid gas recovery system and an exhaust gas treatment system according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing an exhaust gas treatment system according to a first embodiment. [Figure 3] FIG. 4 is a schematic diagram showing an exhaust gas treatment system according to a second embodiment. [Figure 4] FIG. 10 is a schematic diagram showing an exhaust gas treatment system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments for carrying out an exhaust gas treatment system, an acid gas recovery system, and a ship according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to only these embodiments.

[0013] First Embodiment (ship) As shown in FIG. 1, a ship 1 of this embodiment includes at least a hull 2, a combustion device 6, and a carbon dioxide capture system (acid gas capture system) 8.

[0014] (Hull) The hull 2 ​​has a pair of side walls 3A, 3B that form its outer shell, a bottom wall 4, and an upper deck 5. The side walls 3A, 3B are made up of a pair of side walls 3A, 3B outer plates that form the port and starboard sides, respectively. The bottom wall 4 is made up of a bottom outer plate that connects the side walls 3A, 3B. The upper deck 5 is a full-length deck that is exposed to the outside. The hull 2 ​​has a superstructure (not shown) with accommodation areas formed on the upper deck 5, for example, near the stern 2b.

[0015] The hull 2 ​​exemplified in this embodiment has a cargo carrying section 7 located near the bow 2a. The cargo carrying section 7 has, for example, a plurality of cargo tanks (not shown). Note that the cargo carrying section 7 may be configured to carry various types of cargo, such as containers.

[0016] (Combustion equipment) The combustion device 6 is an exhaust gas generation device that generates thermal energy by burning fuel. The combustion device 6 is disposed inside the hull 2. Examples of the combustion device 6 include an internal combustion engine used as the main engine for propelling the ship 1, an internal combustion engine used in a power generation facility that supplies electricity to the ship, and a boiler that generates steam as a working fluid. The combustion device 6 burns the supplied fuel to generate exhaust gas and discharges the generated exhaust gas.

[0017] (Carbon dioxide capture system) The carbon dioxide capture system 8 is a facility for capturing acidic gases from the exhaust gas from the combustion device 6. The carbon dioxide capture system 8 of this embodiment separates and captures the carbon dioxide contained in the exhaust gas using an absorption liquid, and is capable of supplying the captured carbon dioxide to another device. The exhaust gas from this combustion device 6 contains gases to be captured, ash, heavy metals, etc. The gases to be captured include carbon dioxide (CO2), as well as nitrogen oxides (NO) such as nitric oxide (NO). x The absorbent contains acidic gases such as ethanol (ethanolamine), hydrogen sulfide (HS), etc. A highly viscous liquid is preferred as the absorbent to improve the gas absorption rate and reduce the regeneration energy required. For example, when absorbing carbon dioxide, an amine aqueous solution or a non-aqueous amine liquid using a physical absorption solvent instead of water is preferred. Specific examples of alkanolamines that can be used as the amine absorbent include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), diisopropanolamine (DIPA), and diglycolamine (DGA). Hindered amines can also be used. Aqueous solutions of these compounds alone or a mixture of two or more of these compounds can also be used.

[0018] The carbon dioxide capture system 8 is disposed in the hull 2. The carbon dioxide capture system 8 is disposed on the upper deck 5 or in the hull 2 ​​so as to penetrate the upper deck 5 in the vertical direction Dv. The carbon dioxide capture system 8 of this embodiment includes an exhaust gas treatment system 9 and an absorption tower 81.

[0019] (Exhaust gas treatment system) The exhaust gas treatment system 9 removes impurities from the exhaust gas from the combustion device 6. In this embodiment, the impurities contained in the exhaust gas include suspended solids (SS) such as particulate matter (PM) and sulfur oxides (SO) such as sulfur dioxide (SO) and sulfur trioxide (SO). x The flue gas treatment system 9 uses seawater or fresh water (fresh water) as wash water to remove impurities from the flue gas. The flue gas treatment system 9 supplies the flue gas from which the impurities have been removed to an absorption tower 81.

[0020] As shown in Figure 2, the exhaust gas treatment system 9 of this embodiment includes a supply line L1, a first cleaning device 10, a primary storage section 20, a primary supply section 30, a first discharge line L2, a second cleaning device 40, an intermediate storage section 50, an intermediate supply section 60, a second discharge line L3, an electrostatic precipitator 70, a secondary storage section 80, a secondary supply section 90, a final discharge line L4, a return section L5, a return branch section L501, an intermediate return section L6, a makeup water supply section 101, a wastewater treatment section 110, and a storage casing 150.

[0021] The supply line L1 sends the exhaust gas containing carbon dioxide generated in the combustion device 6 to the first scrubbing device 10. The supply line L1 is a pipe that connects the combustion device 6 and the first scrubbing device 10.

[0022] The first scrubbing device 10 is a wet scrubber that uses primary wash water. The first scrubbing device 10 scrubs the exhaust gas first in the exhaust gas treatment system 9. The first scrubbing device 10 of this embodiment has a first scrubber casing 11, a first scrubber section (scrubber section) 12, a first demister 13, and a primary drainage line L14.

[0023] The first scrubber casing 11 is a cylindrical container extending in the vertical direction Dv. Inside the first scrubber casing 11, exhaust gas can flow from a lower position Dvd in the vertical direction Dv to an upper position Dvu. A primary drainage line L14 is connected near the bottom of the first scrubber casing 11. A first discharge line L2 is connected near the top of the first scrubber casing 11. A supply line L1 is connected to the first scrubber casing 11 at a position Dvu above the connection position with the primary drainage line L14 in the vertical direction Dv and at a position Dvd below the connection position with the first discharge lines L2, L21 in the vertical direction Dv.

[0024] The first scrubber section 12 receives exhaust gas and brings primary wash water into contact with the exhaust gas, thereby subjecting the exhaust gas to primary wash treatment. The first scrubber section 12 is disposed inside the first scrubber casing 11. The first scrubber section 12 is disposed above Dvu in the vertical direction Dv with respect to the connection position between the first scrubber casing 11 and the supply line L1. The first scrubber section 12 is disposed below Dvd in the vertical direction Dv with respect to the connection position between the first scrubber casing 11 and the first discharge line L2. The exhaust gas supplied from the supply line L1 to the inside of the first scrubber casing 11 flows through the first scrubber section 12 from the lower Dvd to the upper Dvu in the vertical direction Dv. The first scrubber section 12 also sprays primary wash water onto the flowing exhaust gas from the upper Dvu to the lower Dvd in the vertical direction Dv. In the first scrubber section 12, primary cleaning water comes into contact with the exhaust gas, thereby carrying out a primary cleaning process in which most of the sulfur dioxide contained in the exhaust gas and about half of the amount of suspended solids are removed.

[0025] The first demister 13 removes mist (small droplets) contained in the exhaust gas as the exhaust gas flows through it. The first demister 13 is formed, for example, by stacking multiple layers of mesh woven from thin wires. The first demister 13 is disposed inside the first scrubber casing 11. The first demister 13 is disposed above Dvu in the vertical direction Dv with respect to the first scrubber section 12. The first demister 13 is disposed below Dvd in the vertical direction Dv with respect to the connection position between the first scrubber casing 11 and the first discharge line L2. Exhaust gas flows through the first demister 13 from below Dvd in the vertical direction Dv to above Dvu.

[0026] The primary drainage line L14 supplies primary drainage, which is primary cleaning water after coming into contact with exhaust gas in the first scrubber section 12, to the primary storage section 20. The primary drainage is primary cleaning water that has come into contact with exhaust gas in the first scrubber section 12 and thus contains impurities from the exhaust gas. In other words, the primary drainage is water with more impurities than the primary cleaning water. The primary drainage line L14 is a pipe that connects the first scrubber casing 11 and the primary storage section 20.

[0027] The primary storage section 20 stores the primary wastewater. The primary storage section 20 is a tank capable of storing the primary wastewater. In this embodiment, the primary storage section 20 is disposed at a position away from the first cleaning device 10. The primary storage section 20 is formed in a storage casing 150, which will be described later. In addition, secondary wastewater and intermediate wastewater are supplied to the primary storage section 20 to dilute the primary wastewater. As a result, the concentration of impurities in the primary wastewater stored in the primary storage section 20 is lower than that in the primary wastewater passing through the primary wastewater line L14.

[0028] The primary supply unit 30 supplies the primary wastewater stored in the primary storage unit 20 as primary cleaning water to the first scrubber unit 12. The primary supply unit 30 of this embodiment has a primary cleaning water supply line L31, a primary supply pump 32, a primary supply cooler 33, and a primary neutralizing agent supply unit 34.

[0029] The primary cleaning water supply line L31 sends the primary wastewater stored in the primary storage section 20 to the first scrubber section 12. The primary cleaning water supply line L31 is a pipe that connects the primary storage section 20 and the first scrubber section 12.

[0030] The primary supply pump 32 pumps up the primary wastewater stored in the primary storage section 20, pressurizes it, and sends it to the first scrubber section 12. The primary supply pump 32 is arranged midway along the primary cleaning water supply line L31.

[0031] The primary supply cooler 33 adjusts the temperature of the primary wash water passing through the primary wash water supply line L31 by heat exchange with a coolant. The primary supply cooler 33 cools the primary wash water to a temperature equal to or lower than the temperature of the exhaust gas flowing through the supply line L1. In this embodiment, seawater is supplied as a coolant to the primary supply cooler 33. Therefore, the primary supply cooler 33 adjusts the temperature of the primary wash water to maintain it within a predetermined temperature range so that it reaches an appropriate temperature required in the first scrubber section 12. Therefore, if the temperature of the supplied seawater is too low, the primary supply cooler 33 may allow some or all of the primary wash water to pass through the primary wash water supply line L31 via a bypass valve (not shown) without cooling it. Note that the waste heat recovered from the primary wash water by the primary supply cooler 33 may be used in other equipment.

[0032] The primary neutralizing agent supply unit 34 supplies a neutralizing agent that neutralizes the primary cleaning water passing through the primary cleaning water supply line L31. The primary neutralizing agent supply unit 34 neutralizes the primary cleaning water before it is cooled by the primary supply cooler 33. For example, since the primary cleaning water passing through the primary cleaning water supply line L31 becomes acidic, an alkaline neutralizing agent is supplied. The primary neutralizing agent supply unit 34 of this embodiment supplies caustic soda as the neutralizing agent.

[0033] The first discharge line L2 supplies the exhaust gas that has been subjected to primary cleaning treatment in the first cleaning device 10 to the second cleaning device 40. The first discharge line L2 sends the exhaust gas that has passed through the first scrubber section 12 and the first demister 13 to the second cleaning device 40. The first discharge line L2 is a pipe that connects the first cleaning device 10 and the second cleaning device 40.

[0034] The second scrubbing device 40 is a wet scrubber that uses intermediate scrubbing water. The intermediate scrubbing water contains fewer impurities than the primary scrubbing water. In other words, the intermediate scrubbing water is cleaner water with a higher degree of purity than the primary scrubbing water. The second scrubbing device 40 scrubs the exhaust gas after the first scrubbing device 10 in the exhaust gas treatment system 9. The second scrubbing device 40 has substantially the same structure as the first scrubbing device 10. The second scrubbing device 40 of this embodiment has a second scrubber casing 41, a second scrubber section (successive scrubber section) 42, a second demister 43, and an intermediate drainage line L44.

[0035] The second scrubber casing 41 is a cylindrical container extending in the vertical direction Dv. Inside the second scrubber casing 41, exhaust gas can flow from a lower position Dvd in the vertical direction Dv to an upper position Dvu. The second scrubber casing 41 has a structure similar to that of the first scrubber casing 11. An intermediate drainage line L44 is connected near the bottom of the second scrubber casing 41. A second discharge line L3 is connected near the top of the second scrubber casing 41. A first discharge line L2 is connected to the second scrubber casing 41 at a position Dvu above the connection position with the intermediate drainage line L44 in the vertical direction Dv and at a position Dvd below the connection position with the second discharge line L3 in the vertical direction Dv.

[0036] The second scrubber section 42 receives exhaust gas and brings intermediate cleaning water into contact with the exhaust gas, thereby subjecting the exhaust gas to primary cleaning again. The exhaust gas that has been subjected to primary cleaning is introduced into the second scrubber section 42 from the first discharge line L2. The second scrubber section 42 is disposed inside the second scrubber casing 41. The second scrubber section 42 is disposed above Dvu in the vertical direction Dv with respect to the connection position between the second scrubber casing 41 and the first discharge line L2. The second scrubber section 42 is disposed below Dvd in the vertical direction Dv with respect to the connection position between the second scrubber casing 41 and the second discharge line L3. The exhaust gas supplied from the first discharge line L2 to the inside of the second scrubber casing 41 flows from below Dvd to above Dvu in the vertical direction Dv through the second scrubber section 42. The second scrubber section 42 sprays intermediate wash water from above Dvu to below Dvd in the vertical direction Dv against the flowing exhaust gas. In the second scrubber section 42, the intermediate wash water comes into contact with the exhaust gas, thereby carrying out a primary wash treatment in which most of the sulfur dioxide contained in the exhaust gas and about half of the amount of suspended solids are removed. The second scrubber section 42 performs a similar wash treatment to the first scrubber section 12, except that the wash water used is different.

[0037] The second demister 43 removes mist contained in the exhaust gas as the exhaust gas flows through it. The second demister 43 is formed, for example, like the first demister 13, by stacking multiple layers of mesh woven with thin wires. The second demister 43 is disposed inside the second scrubber casing 41. The second demister 43 is disposed above Dvu in the vertical direction Dv with respect to the second scrubber section 42. The second demister 43 is disposed below Dvd in the vertical direction Dv with respect to the connection position between the second scrubber casing 41 and the second discharge line L3. Exhaust gas flows through the second demister 43 from below Dvd in the vertical direction Dv toward above Dvu.

[0038] The intermediate drainage line L44 supplies intermediate drainage, which is intermediate cleaning water after coming into contact with exhaust gas in the second scrubber section 42, to the intermediate storage section 50. The intermediate drainage is intermediate cleaning water that contains impurities in the exhaust gas due to contact with the exhaust gas in the second scrubber section 42. The exhaust gas supplied to the second scrubber section 42 has had impurities reduced in the first scrubber section 12, so the impurity concentration is lower than that of the exhaust gas supplied to the first scrubber section 12. Therefore, the impurity concentration of the intermediate drainage is lower than that of the primary drainage. The intermediate drainage line L44 is a pipe that connects the second scrubber casing 41 and the intermediate storage section 50.

[0039] The intermediate storage section 50 stores intermediate wastewater. The intermediate storage section 50 is a tank that can store intermediate wastewater. The intermediate storage section 50 of this embodiment is disposed at a position away from the second cleaning device 40. The intermediate storage section 50 is formed in a storage casing 150, which will be described later. Therefore, the intermediate storage section 50 is disposed adjacent to the primary storage section 20.

[0040] The intermediate supply section 60 supplies the intermediate wastewater stored in the intermediate storage section 50 as intermediate cleaning water to the second scrubber section 42. The intermediate supply section 60 of this embodiment has an intermediate cleaning water supply line L61, an intermediate supply pump 62, an intermediate supply cooler 63, and an intermediate neutralizing agent supply section 64.

[0041] The intermediate cleaning water supply line L61 sends the intermediate wastewater stored in the intermediate storage section 50 to the second scrubber section 42. The intermediate cleaning water supply line L61 is a pipe that connects the intermediate storage section 50 and the second scrubber section 42.

[0042] The intermediate supply pump 62 pumps up the intermediate wastewater stored in the intermediate storage section 50, increases the pressure, and sends it to the second scrubber section 42. The intermediate supply pump 62 is disposed midway along the intermediate cleaning water supply line L61.

[0043] The intermediate supply cooler 63 adjusts the temperature of the intermediate wash water passing through the intermediate wash water supply line L61 by heat exchange with a coolant. The intermediate supply cooler 63 cools the intermediate wash water to a temperature equal to or lower than the temperature of the exhaust gas flowing through the supply line L1. The intermediate supply cooler 63 preferably cools the intermediate wash water to a temperature equal to or lower than the temperature of the exhaust gas flowing through the first discharge line L2. Seawater is supplied to the intermediate supply cooler 63 in this embodiment as a coolant. Therefore, the intermediate supply cooler 63 adjusts the temperature of the intermediate wash water to maintain it within a predetermined temperature range so that it becomes an appropriate temperature required in the second scrubber section 42. Therefore, if the temperature of the supplied seawater is too low, the intermediate supply cooler 63 may allow some or all of the intermediate wash water to pass through the intermediate wash water supply line L61 via a bypass valve (not shown). Note that the waste heat recovered from the intermediate wash water by the intermediate supply cooler 63 may be used in other equipment.

[0044] The intermediate neutralizing agent supply unit 64 supplies a neutralizing agent that neutralizes the intermediate cleaning water passing through the intermediate cleaning water supply line L61. The intermediate neutralizing agent supply unit 64 neutralizes the intermediate cleaning water before it is cooled in the intermediate supply cooler 63. For example, since the intermediate cleaning water passing through the intermediate cleaning water supply line L61 becomes acidic, an alkaline neutralizing agent is supplied. As with the primary neutralizing agent supply unit 34, the intermediate neutralizing agent supply unit 64 of this embodiment supplies caustic soda as the neutralizing agent.

[0045] The second discharge line L3 supplies the exhaust gas that has been subjected to primary cleaning treatment in the second cleaning device 40 to the electrostatic precipitator 70. The second discharge line L3 sends the exhaust gas that has passed through the second scrubber section 42 and the second demister 43 to the electrostatic precipitator 70. The second discharge line L3 is a pipe that connects the second cleaning device 40 and the electrostatic precipitator 70.

[0046] The electrostatic precipitator 70 is a cleaning device that applies an electric charge to attract impurities to a dust collecting electrode 721, which is an electrode, and uses secondary cleaning water to wash away the impurities adhering to the dust collecting electrode 721. The secondary cleaning water contains fewer impurities than the primary cleaning water and intermediate cleaning water. In other words, the secondary cleaning water is cleaner water with a higher degree of purity than the primary cleaning water and intermediate cleaning water. The electrostatic precipitator 70 cleans the flue gas after the second cleaning device 40 in the flue gas treatment system 9. The electrostatic precipitator 70 of this embodiment has a dust collection casing 71, an electrostatic precipitator 72, a dust collecting demister 73, and a secondary drainage line L74.

[0047] The dust collecting casing 71 is a cylindrical container extending in the vertical direction Dv. Exhaust gas can flow inside the dust collecting casing 71 from a lower position Dvd in the vertical direction Dv to an upper position Dvu. A secondary drainage line L74 is connected near the bottom of the dust collecting casing 71. A final discharge line L4 is connected near the top of the dust collecting casing 71. A second discharge line L3 is connected to the dust collecting casing 71 at a position Dvu above the connection position with the secondary drainage line L74 in the vertical direction Dv and at a position Dvd below the connection position with the final discharge line L4 in the vertical direction Dv.

[0048] The electrostatic precipitator 72 receives exhaust gas that has undergone primary cleaning treatment in the second scrubber section 42, and performs secondary cleaning treatment on the introduced exhaust gas by electrostatically collecting dust using dust collecting electrodes 721. The dust collecting electrodes 721 are cleaned with secondary cleaning water. The electrostatic precipitator 72 receives exhaust gas that has undergone primary treatment in the first scrubber section 12 and the second scrubber section 42. The electrostatic precipitator 72 has a plurality of dust collecting electrodes 721. The plurality of dust collecting electrodes 721 are arranged inside the dust collecting casing 71. The plurality of dust collecting electrodes 721 impart an electric charge to sulfur trioxide and suspended solids, which are impurities contained in the exhaust gas, and cause most of them to adhere to the dust collecting electrodes 721, thereby removing dust from the exhaust gas. The electrostatic precipitator 72 is arranged at a position Dvu above the vertical direction Dv of the connection between the dust collecting casing 71 and the second discharge line L3. The electrostatic precipitator 72 is disposed below Dvd in the vertical direction Dv with respect to the connection position between the dust collecting casing 71 and the final discharge line L4. Through the electrostatic precipitator 72, exhaust gas supplied into the dust collecting casing 71 from the second discharge line L3 flows from the lower Dvd to the upper Dvu in the vertical direction Dv. The electrostatic precipitator 72 also sprays secondary cleaning water onto the dust collecting electrodes 721 from the upper Dvu to the lower Dvd in the vertical direction Dv. In the electrostatic precipitator 72, the secondary cleaning water is sprayed onto the dust collecting electrodes 721, thereby washing away most of the sulfur trioxide and suspended solids adhering to the dust collecting electrodes 721, thereby performing a secondary cleaning process. Specifically, in the secondary cleaning process, impurities in the exhaust gas are attached to the dust collecting electrodes 721 by applying an electric charge, and then secondary cleaning water is intermittently sprayed onto the dust collecting electrodes 721 to wash away the impurities adhering to the dust collecting electrodes 721, thereby removing the impurities from the exhaust gas. In other words, the secondary cleaning process is different from the primary cleaning process, which allows the electrostatic precipitator 72 to remove fine dust with a higher degree of cleanliness than the first scrubber 12.

[0049] The dust collecting demister 73 removes mist contained in the exhaust gas as the exhaust gas flows through it. The dust collecting demister 73 is formed, for example, like the first demister 13, by stacking multiple layers of mesh woven with thin wires. The dust collecting demister 73 is disposed inside the dust collecting casing 71. The dust collecting demister 73 is disposed above Dvu in the vertical direction Dv with respect to the electrostatic precipitator 72. The dust collecting demister 73 is disposed below Dvd in the vertical direction Dv with respect to the connection position between the dust collecting casing 71 and the final discharge line L4. Exhaust gas flows through the dust collecting demister 73 from below Dvd in the vertical direction Dv to above Dvu.

[0050] The secondary drainage line L74 supplies secondary drainage, which is secondary cleaning water after being sprayed onto the dust collecting electrodes 721 in the electrostatic precipitator 72, to the secondary storage section 80. The secondary drainage is secondary cleaning water that contains impurities that have adhered to the dust collecting electrodes 721 by being sprayed onto the dust collecting electrodes 721 in the electrostatic precipitator 72. The flue gas supplied to the electrostatic precipitator 72 has had impurities reduced in the second scrubber section 42, so the impurity concentration is lower than that of the flue gas supplied to the second scrubber section 42. Therefore, the impurity concentration of the secondary drainage is lower than that of the intermediate drainage. The secondary drainage line L74 is a pipe that connects the dust collecting casing 71 and the secondary storage section 80.

[0051] The secondary storage section 80 stores the secondary wastewater. The secondary storage section 80 is a tank capable of storing the secondary wastewater. In this embodiment, the secondary storage section 80 is disposed at a position away from the electrostatic precipitator 70. The secondary storage section 80 is formed in a storage casing 150, which will be described later. Furthermore, makeup water is supplied to the secondary storage section 80 to replenish the amount of secondary wastewater in order to maintain a constant amount of water in the system circulating between the electrostatic precipitator 70 and the secondary storage section 80. Furthermore, by adding makeup water, the concentration of impurities in the secondary wastewater stored in the secondary storage section 80 is lower than that in the secondary wastewater passing through the secondary wastewater line L74.

[0052] The secondary supply unit 90 supplies the secondary wastewater stored in the secondary storage unit 80 as secondary cleaning water to the electrostatic precipitator 72. The secondary supply unit 90 of this embodiment has a secondary cleaning water supply line L91, a secondary supply pump 92, a secondary supply cooler 93, and a secondary neutralizing agent supply unit 94.

[0053] The secondary cleaning water supply line L91 sends the secondary wastewater stored in the secondary storage unit 80 to the electrostatic precipitator 72. The secondary cleaning water supply line L91 is a pipe that connects the secondary storage unit 80 and the electrostatic precipitator 72.

[0054] The secondary supply pump 92 pumps up the secondary wastewater stored in the secondary storage section 80, increases the pressure, and sends it to the electrostatic precipitator section 72. The secondary supply pump 92 is disposed midway along the secondary cleaning water supply line L91.

[0055] The secondary supply cooler 93 adjusts the temperature of the secondary wash water passing through the secondary wash water supply line L91 by heat exchange with a coolant. The secondary supply cooler 93 cools the secondary wash water to a temperature equal to or lower than the temperature of the exhaust gas flowing through the supply line L1. The secondary supply cooler 93 preferably cools the secondary wash water to a temperature equal to or lower than the temperature of the exhaust gas flowing through the second discharge line L3. In this embodiment, seawater is supplied as a coolant to the secondary supply cooler 93. Therefore, the secondary supply cooler 93 adjusts the temperature of the secondary wash water to maintain it within a predetermined temperature range so as to achieve an appropriate temperature required by the electrostatic precipitator 72. Therefore, if the temperature of the supplied seawater is too low, the secondary supply cooler 93 may allow some or all of the secondary wash water to pass through the secondary wash water supply line L91 without cooling it via a bypass valve (not shown). Note that the waste heat recovered from the secondary wash water by the secondary supply cooler 93 may be used in other equipment.

[0056] The secondary neutralizing agent supply unit 94 supplies a neutralizing agent that neutralizes the secondary cleaning water passing through the secondary cleaning water supply line L91. The secondary neutralizing agent supply unit 94 neutralizes the secondary cleaning water before it is cooled in the secondary supply cooler 93. For example, since the secondary cleaning water passing through the secondary cleaning water supply line L91 becomes acidic, an alkaline neutralizing agent is supplied. Similar to the primary neutralizing agent supply unit 34, the secondary neutralizing agent supply unit 94 of this embodiment supplies caustic soda as the neutralizing agent.

[0057] The final discharge line L4 supplies the flue gas from which dust has been removed by secondary cleaning treatment in the electrostatic precipitator 70 to the outside of the flue gas treatment system 9. The final discharge line L4 sends the flue gas that has passed through the electrostatic precipitator 72 to the absorption tower 81. The final discharge line L4 is a pipe that connects the electrostatic precipitator 70 and the absorption tower 81.

[0058] The return section L5 supplies a portion of the secondary wastewater stored in the secondary storage section 80 to the primary storage section 20. The return section L5 in this embodiment is a pipe that connects the secondary cleaning water supply line L91 and the primary drainage line L14. In other words, the return section L5 sends a portion of the secondary wastewater sent to the electrostatic precipitator 72 by the secondary cleaning water supply line L91 to the primary drainage line L14, thereby sending a portion of the secondary wastewater stored in the secondary storage section 80 to the primary storage section 20. In addition, the return section L5 is connected to the secondary cleaning water supply line L91 between the secondary supply pump 92 and the secondary neutralizing agent supply section 94.

[0059] The return branch section L501 sends a portion of the secondary drainage water flowing through the return section L5 to the intermediate drainage line L44. In this embodiment, the return branch section L501 is a pipe that connects the return section L5 and the intermediate drainage line L44. In other words, the return branch section L501 sends a portion of the secondary drainage water sent to the primary drainage line L14 by the return section L5 to the intermediate drainage line L44, thereby sending a portion of the secondary drainage water stored in the secondary storage section 80 to the intermediate storage section 50 and maintaining a constant amount of water in the intermediate storage section.

[0060] The intermediate return section L6 supplies a portion of the intermediate wastewater stored in the intermediate storage section 50 to the primary storage section 20. The intermediate return section L6 in this embodiment is a pipe that connects the intermediate cleaning water supply line L61 and the primary drainage line L14. In other words, the intermediate return section L6 sends a portion of the intermediate wastewater sent to the second scrubber section 42 by the secondary cleaning water supply line L91 to the primary drainage line L14, thereby sending a portion of the intermediate wastewater stored in the intermediate storage section 50 to the primary storage section 20. In addition, the intermediate return section L6 is connected to the intermediate cleaning water supply line L61 between the intermediate supply pump 62 and the intermediate neutralizing agent supply section 64.

[0061] The makeup water supply unit 101 supplies makeup water to the secondary reservoir 80. Makeup water is water with fewer impurities than the secondary flush water. In this embodiment, clean water (fresh water) or seawater is supplied as makeup water. The makeup water supply unit 101 takes in, for example, seawater to generate fresh water to be used as makeup water. The makeup water supply unit 101 directly sends makeup water in an amount equivalent to the amount of secondary drainage water that is insufficient to the secondary reservoir 80.

[0062] The wastewater treatment device 110 removes impurities from the primary wastewater stored in the primary storage unit 20. The wastewater treatment device 110 supplies treated water, which is the primary wastewater from which impurities have been removed, to the secondary storage unit 80. The wastewater treatment device 110 stores only the impurities removed from the primary wastewater, and discards it after it is unloaded. The wastewater treatment device 110 of this embodiment has a primary wastewater transfer line L111, a wastewater treatment device 112, a wastewater return line L113, a treated water storage unit 102, a treated water supply line L104, and a treated water pump 103.

[0063] The primary wastewater transfer line L111 sends a portion of the primary wastewater stored in the primary storage unit 20 to the wastewater treatment device 112. The primary wastewater transfer line L111 is a pipe connecting the primary storage unit 20 and the wastewater treatment device 112. The wastewater treatment device 112 removes impurities from the supplied primary wastewater. The wastewater treatment device 112 filters or centrifuges the supplied primary wastewater to separate it into impurities and treated water. The separated impurities are temporarily stored in the hull 2, and after the ship arrives at a port or the like, they are unloaded and sent for disposal treatment. The wastewater treatment device 112 discharges treated water, which is the primary wastewater from which impurities have been removed, into the wastewater return line L113. The wastewater return line L113 sends the treated water from which impurities have been removed in the wastewater treatment device 112 to the treated water storage unit 102. The wastewater return line L113 is a pipe connecting the wastewater treatment device 112 and the treated water storage unit 102.

[0064] The treated water storage unit 102 stores the treated water generated in the wastewater treatment device 112. The treated water storage unit 102 is capable of discharging a portion of the stored treated water to the outside (mainly to the sea). The treated water storage unit 102 is disposed at a position away from the storage casing 150. The treated water supply line L104 sends the treated water stored in the treated water storage unit 102 to the secondary storage unit 80. The treated water supply line L104 is a pipe connecting the treated water storage unit 102 and the secondary storage unit 80. The treated water pump 103 pumps up the treated water stored in the treated water storage unit 102, increases the pressure, and sends it to the secondary storage unit 80. The treated water pump 103 is disposed midway along the treated water supply line L104.

[0065] The storage casing 150 is disposed at a position separate from the first scrubber section 12, the second scrubber section 42, and the electrostatic precipitator section 72. The storage casing 150 has a primary storage section 20, an intermediate storage section 50, and a secondary storage section 80. The storage casing 150 is formed as a single independent tank. The storage casing 150 has a partition section that separates the primary storage section 20 from the secondary storage section 80. The storage casing 150 of this embodiment has two partition sections: a first partition section 151 that separates the primary storage section 20 from the intermediate storage section 50, and a second partition section 152 that separates the intermediate storage section 50 from the secondary storage section 80. In other words, the first partition section 151 and the second partition section 152 form three spaces within the storage casing 150 that can store liquid: the primary storage section 20, the intermediate storage section 50, and the secondary storage section 80.

[0066] The exhaust gas treated in the exhaust gas treatment system 9 is introduced into the absorption tower 81 via the final discharge line L4. The absorption tower 81 brings the exhaust gas into contact with an absorbing liquid to remove carbon dioxide from the exhaust gas. The absorption tower 81 sends the exhaust gas from which the carbon dioxide has been removed to an external supply destination (not shown). The absorption tower 81 also sends the absorbing liquid from which carbon dioxide has been recovered to a regeneration tower (not shown).

[0067] (Flow of exhaust gas and washing water in carbon dioxide capture system) In the carbon dioxide capture system 8 having the above configuration, as shown in FIG. 1, the exhaust gas emitted from the combustion device 6 is supplied to the exhaust gas treatment system. Specifically, as shown in FIG. 2, the exhaust gas is supplied to the first scrubbing device 10 via a supply line L1. Furthermore, primary wash water is supplied to the first scrubbing device 10 from the primary storage section 20 via the primary supply section 30. Specifically, the primary wastewater stored in the primary storage section 20 is pressurized by the primary supply pump 32, neutralized in the primary neutralizing agent supply section 34, and cooled in the primary supply cooler 33. The cooled primary wastewater is then supplied to the first scrubber section 12 as primary wash water. The supplied exhaust gas flows inside the first scrubber casing 11 from the lower Dvd to the upper Dvu in the vertical direction Dv. The primary wash water sprayed from the first scrubber section 12 from the upper Dvu to the lower Dvd in the vertical direction Dv comes into contact with the exhaust gas. This completes the primary cleaning process, removing most of the sulfur dioxide contained in the exhaust gas and approximately half of the suspended solids. The exhaust gas is also cooled by coming into contact with the primary cleaning water. The exhaust gas then passes through the first demister 13, where the mist is removed. The cleaned and cooled exhaust gas is then discharged into the first discharge line L2. The primary cleaning water that has come into contact with the exhaust gas becomes primary wastewater containing impurities, and is sent to the primary storage section 20 through the primary drainage line L14. The primary wastewater sent to the primary storage sections 20, 20B is temporarily stored, and then supplied again to the first scrubber section 12 as primary cleaning water by the primary supply section 30.

[0068] The exhaust gas discharged into the first discharge line L2 is supplied to the second scrubbing device 40. Intermediate wash water is supplied to the second scrubbing device 40 from the intermediate storage unit 50 via the intermediate supply unit 60. Specifically, the intermediate wastewater stored in the intermediate storage unit 50 is pressurized by the intermediate supply pump 62, neutralized by the intermediate neutralizing agent supply unit 64, and cooled by the intermediate supply cooler 63. The cooled intermediate wastewater is then supplied to the second scrubber unit 42 as intermediate wash water. The supplied exhaust gas flows through the second scrubber casing 41 from the downward direction Dvd to the upward direction Dvu in the vertical direction Dv. The intermediate wash water sprayed from the second scrubber unit 42 from the upward direction Dvu to the downward direction Dvd in the vertical direction Dv comes into contact with the exhaust gas. This again performs a primary scrubbing process, removing most of the sulfur dioxide contained in the exhaust gas and approximately half of the suspended solids. The exhaust gas is also cooled by contact with the intermediate wash water. Thereafter, the exhaust gas that has come into contact with the intermediate wash water passes through a second demister 43, where the mist is removed. The exhaust gas that has been cleaned and cooled in this manner is discharged to a second discharge line L3. The intermediate wash water that has come into contact with the exhaust gas becomes intermediate wastewater containing impurities, and is sent to an intermediate storage section 50 through an intermediate wastewater line L44. The intermediate wastewater sent to the intermediate storage section 50 is temporarily stored, and then supplied again to the second scrubber section 42 by an intermediate supply section 60 as intermediate wash water.

[0069] The exhaust gas discharged to the second discharge line L3 is supplied to the electrostatic precipitator 70. Secondary cleaning water is supplied to the electrostatic precipitator 70 from the secondary storage unit 80 via the secondary supply unit 90. Specifically, the secondary wastewater stored in the secondary storage unit 80 is pressurized by the secondary supply pump 92, neutralized in the secondary neutralizing agent supply unit 94, and cooled in the secondary supply cooler 93. The cooled secondary wastewater is then supplied to the electrostatic precipitator 72 as secondary cleaning water. The supplied exhaust gas flows inside the dust collection casing 71 from the downward direction Dvd to the upward direction Dvu in the vertical direction Dv. The exhaust gas then comes into contact with the dust collecting electrode 721. As a result, the dust collecting electrode 721 is used to remove most of the sulfur trioxide and suspended solids contained in the exhaust gas. The secondary cleaning water, which is sprayed from the electrostatic precipitator 72 in the vertical direction Dv from above Dvu to below Dvd, comes into contact with the dust collecting electrode 721, washing away most of the sulfur trioxide and suspended solids adhering to the dust collecting electrode 721. In this way, the electrostatic precipitator 70 performs a secondary cleaning process. The flue gas is also cooled by coming into contact with the secondary cleaning water. The flue gas that has come into contact with the second cleaning water then passes through the dust collecting demister 73, where the mist is removed. The cleaned and cooled flue gas is discharged into the final discharge line L4. The secondary cleaning water that has come into contact with the flue gas becomes secondary wastewater containing impurities and is sent to the secondary storage unit 80 through the secondary drainage line L74. The secondary wastewater sent to the secondary storage unit 80 is temporarily stored and then supplied again to the electrostatic precipitator 72 as secondary cleaning water by the secondary supply unit 90.

[0070] The flue gas discharged to the final discharge line L4 is sent to the absorption tower 81. In the absorption tower 81, the flue gas is brought into contact with an absorbing liquid, thereby removing carbon dioxide from the flue gas.

[0071] Furthermore, a portion of the secondary wastewater stored in the secondary storage section 80 is supplied to the primary storage section 20 via the return section L5. Specifically, a portion of the secondary wastewater sent to the electrostatic precipitator section 72 via the secondary cleaning water supply line L91 is sent to the primary drainage line L14 via the return section L5. As a result, a portion of the secondary wastewater stored in the secondary storage section 80 is sent to the primary storage section 20. Furthermore, a portion of the intermediate wastewater stored in the intermediate storage section 50 is supplied to the primary storage section 20 via the intermediate return section L6. Specifically, a portion of the intermediate wastewater sent to the second scrubber section 42 via the intermediate cleaning water supply line L61 is sent to the primary drainage line L14 via the intermediate return section L6. As a result, a portion of the intermediate wastewater stored in the intermediate storage section 50 is sent to the primary storage section 20. As a result, the amount of water that decreases while circulating between the first cleaning device 10 and the primary storage section 20 is replenished with the secondary wastewater and intermediate wastewater.

[0072] Furthermore, a portion of the secondary wastewater stored in the secondary storage section 80 is supplied to the intermediate storage section 50 via the return branch section L501. Specifically, a portion of the secondary wastewater sent to the electrostatic precipitator 72 by the secondary cleaning water supply line L91 is sent to the intermediate drainage line L44 via the return branch section L501. As a result, a portion of the secondary wastewater stored in the secondary storage section 80 is sent to the intermediate storage section 50. This allows the secondary wastewater to replenish the amount of water that has decreased while circulating between the second cleaning device 40 and the intermediate storage section 50.

[0073] Furthermore, a portion of the primary wastewater stored in the primary storage unit 20 is sent to the wastewater treatment unit 110. In the wastewater treatment unit 110, the primary wastewater is supplied to the wastewater treatment device 112 via a primary wastewater transfer line L111, where impurities are removed from the primary wastewater. The treated water, which is the primary wastewater from which impurities have been removed in the wastewater treatment device 112, is sent to the secondary storage unit 80 via a wastewater return line L113. Specifically, the treated water sent to the wastewater return line L113 is stored in the treated water storage unit 102, then pressurized by the treated water pump 103, and sent to the secondary storage unit 80 via the treated water supply line L104. Furthermore, make-up water is supplied to the secondary storage unit 80 from a make-up water supply unit 101. The amount of water that decreases while circulating between the electrostatic precipitator 70 and the secondary storage unit 80 is replenished with the treated water and make-up water.

[0074] As described above, the primary wastewater stored in the primary storage unit 20 is discharged to the wastewater treatment unit 110, and the return unit L5 and the intermediate return unit L6 replenish the secondary wastewater and intermediate wastewater, thereby maintaining a constant liquid level of the primary wastewater in the primary storage unit 20. As a result, the primary wastewater stored in the primary storage unit 20 is diluted, and the concentration of impurities in the primary wastewater decreases. Furthermore, the intermediate storage unit 50 is replenished with secondary wastewater by the return branch unit L501, thereby maintaining a constant liquid level of the intermediate wastewater in the intermediate storage unit 50. As a result, the intermediate wastewater stored in the intermediate storage unit 50 is diluted, and the concentration of impurities in the intermediate wastewater decreases. Furthermore, the secondary storage unit 80 is replenished with treated water from the treated water supply line L104 and makeup water from the makeup water supply unit 101, thereby maintaining a constant liquid level of the secondary wastewater in the secondary storage unit 80. As a result, the secondary wastewater stored in the secondary storage section 80 is diluted, and the concentration of impurities in the secondary wastewater decreases.

[0075] (Action and effect) In the exhaust gas treatment system 9 of this embodiment as described above, primary wash water and secondary wash water are circulated. Specifically, the primary wash water is sent to the first wash device 10, used in the first scrubber section 12, becomes primary wastewater, and is stored in the primary storage section 20. The primary wastewater stored in the primary storage section 20 is then sent again to the first scrubber section 12 as primary wash water. Similarly, the intermediate wash water is sent to the second wash device 40, used in the second scrubber section 42, becomes intermediate wastewater, and is stored in the intermediate storage section 50. The intermediate wastewater stored in the intermediate storage section 50 is then sent again to the second scrubber section 42 as intermediate wash water. The secondary wash water is sent to the electrostatic precipitator 70, used in the electrostatic precipitator 72, becomes secondary wastewater, and is stored in the secondary storage section 80. The secondary wastewater stored in the secondary storage section 80 is then sent again to the electrostatic precipitator 72 as secondary wash water.

[0076] Furthermore, a portion of the secondary wastewater stored in the secondary storage section 80 is returned to the primary storage section 20 by the return section L5 and to the intermediate storage section 50 by the return branch section L501. The secondary wastewater contains fewer impurities than the primary wastewater stored in the primary storage section 20 and the intermediate wastewater stored in the intermediate storage section 50.

[0077] Furthermore, a portion of the intermediate wastewater stored in the intermediate storage section 50 is returned to the primary storage section 20 by the intermediate return section L6. The intermediate wastewater contains fewer impurities than the primary wastewater stored in the primary storage section 20.

[0078] Furthermore, a portion of the primary wastewater stored in the primary reservoir 20 has most of the impurities removed in the wastewater treatment unit 110, and then is returned to the secondary reservoir 80 via the wastewater return line L113, the treated water reservoir 102, and the treated water supply line L104. The treated water contains fewer impurities than the secondary wastewater stored in the secondary reservoir 80.

[0079] Furthermore, makeup water is sent to the secondary reservoir 80 by makeup water supply unit 101. The makeup water contains fewer impurities than the secondary flush water.

[0080] In this way, by circulating cleaning water within each device and replenishing cleaning water, treated water, or makeup water with fewer impurities, it is possible to balance the liquid levels of the liquids circulating in each circulation system and transfer the concentrations of the primary wastewater, intermediate wastewater, and secondary wastewater. As a result, it is possible to remove impurities from the exhaust gas while reducing the amount of new cleaning water supplied by the makeup water supply unit 101, which needs to be replenished throughout the entire exhaust gas treatment system 9. Furthermore, by reducing the amount of makeup water supplied from the makeup water supply unit 101, it is possible to make the makeup water supply unit 101 more compact.

[0081] As a result, when the carbon dioxide capture system 8 is disposed in the hull 2 ​​as in this embodiment, impurities can be stably removed from the exhaust gas even when it is difficult to supply new fresh water.

[0082] In addition, the exhaust gas is supplied to the first cleaning device 10 before being supplied to the electrostatic precipitator 70. The electrostatic precipitator 72 has a higher impurity removal efficiency than the first scrubber section 12, but is limited in the flow velocity and temperature of the exhaust gas that it can handle. For example, it is preferable that the flow velocity and temperature of the exhaust gas do not increase too much in the electrostatic precipitator 72. In contrast, when the exhaust gas passes through the first scrubber section 12 and comes into contact with the primary cleaning water, the flow velocity and temperature of the exhaust gas are reduced and maintained at a constant, stable state. Therefore, compared to when the exhaust gas is directly supplied to the electrostatic precipitator 72 from the combustion device 6, the decrease in the impurity removal efficiency in the electrostatic precipitator 72 can be suppressed. Therefore, impurities can be efficiently removed from the exhaust gas.

[0083] Furthermore, the wastewater treatment unit 110 treats only the primary wastewater, which is the dirtiest. By not treating secondary wastewater or intermediate wastewater, which have low concentrations of impurities, the amount of wastewater to be treated by the wastewater treatment unit 110 can be reduced. Therefore, by reducing the amount of wastewater to be treated by the wastewater treatment unit 110, the wastewater treatment unit 110 can be made more compact. Furthermore, the energy required for wastewater treatment can be reduced.

[0084] Furthermore, the exhaust gas that has undergone primary cleaning treatment in the first cleaning device 10 is sent to the second cleaning device 40. In the second cleaning device 40, the exhaust gas is subjected to primary cleaning treatment again in the second scrubber section 42 using intermediate cleaning water. Therefore, the exhaust gas is sent to the electrostatic precipitator 72 in a state in which impurities have been further removed by the second scrubber section 42. As a result, the amount of impurities in the exhaust gas treated in the electrostatic precipitator 72 is reduced, which makes it possible to further suppress a decrease in the efficiency of impurity removal in the electrostatic precipitator 72. Therefore, impurities can be removed from the exhaust gas more efficiently.

[0085] Furthermore, the intermediate wash water used in the second scrubber section 42 is circulated, similar to the primary wash water and secondary wash water. Specifically, the intermediate wash water is sent to the second cleaning device 40, used in the second scrubber section 42, becomes intermediate wastewater, and is stored in the intermediate storage section 50. The intermediate wastewater stored in the intermediate storage section 50 is then sent back to the second scrubber section 42 as intermediate wash water. Therefore, by circulating the intermediate wash water, the amount of primary wastewater stored in the primary storage section 20 is reduced. As a result, the amount of primary wastewater treated is reduced, further reducing the amount of new wash water required for the entire exhaust gas treatment system 9. Therefore, by separating the primary storage section 20 and the intermediate storage section 50, intermediate wastewater with fewer impurities than the primary wastewater can be supplied to the second scrubber section 42. This prevents the primary wastewater, which is dirtier than the intermediate wastewater, from being used again as wash water for the second scrubber section 42, thereby reducing the cleaning efficiency. As a result, the cleaning efficiency of the second cleaning device is improved, and impurities can be removed from the exhaust gas more efficiently.

[0086] In addition, a portion of the intermediate wastewater stored in the intermediate storage section 50 is returned to the primary storage section 20 by the intermediate return section L6. Although the intermediate wastewater contains more impurities than the secondary wastewater, it is a medium-concentration wastewater with fewer impurities than the primary wastewater stored in the primary storage section 20. Therefore, by using the intermediate wastewater to replenish the liquid water stored in the primary storage section 20, impurities move in the order of secondary wastewater, intermediate wastewater, and primary wastewater. Therefore, a transfer of impurity concentration occurs between the secondary wastewater, intermediate wastewater, and primary wastewater. This allows impurities to be collected in the primary wastewater, enabling efficient wastewater treatment.

[0087] The primary supply unit 30 also has a primary supply cooler 33 and a bypass valve (not shown) that cool the primary wash water passing through the primary wash water supply line L31. Similarly, the intermediate supply unit 60 also has an intermediate supply cooler 63 and a bypass valve (not shown) that cool the intermediate wash water passing through the intermediate wash water supply line L61. Furthermore, the secondary supply unit 90 also has a secondary supply cooler 93 and a bypass valve (not shown) that cool the secondary wash water passing through the secondary wash water supply line L91. The temperatures of the primary wash water, intermediate wash water, and secondary wash water may gradually increase during circulation. However, by cooling the various wash waters circulating in the primary supply cooler 33, intermediate supply cooler 63, and secondary supply cooler 93, the temperatures of the wash waters can be adjusted and maintained within a predetermined temperature range. As a result, contact between the heated wash water and the flue gas can be suppressed, thereby preventing the temperature of the flue gas from increasing. When an aqueous solution containing an amine is used as the absorption liquid in the absorption tower 81, it is preferable to maintain the temperature of the flue gas at a certain temperature or higher in order to ensure the fluidity of the amine. On the other hand, it is undesirable for the temperature of the flue gas to rise too high in the electrostatic precipitator 72. However, by cooling the various types of circulating cleaning water, the temperature of the flue gas can be maintained within an appropriate temperature range in the absorption tower 81 and the electrostatic precipitator 72. This allows impurities to be stably removed from the flue gas, and carbon dioxide to be stably recovered in the absorption tower 81.

[0088] Furthermore, the primary storage section 20, the intermediate storage section 50, and the secondary storage section 80 are formed in the storage casing 150 by being partitioned by a first partition 151 and a second partition 152. Furthermore, the storage casing 150 is arranged away from the first scrubber section 12, the second scrubber section 42, and the electrostatic precipitator 72. Therefore, the equipment for storing wastewater, which is used cleaning water from the primary storage section 20, the intermediate storage section 50, the secondary storage section 80, etc., and the equipment for cleaning the exhaust gas, such as the first scrubber section 12, the second scrubber section 42, and the electrostatic precipitator 72, can be arranged independently. Therefore, even in a case where the space available for arranging the equipment of the exhaust gas treatment system 9 is limited, such as in a narrow hull 2, flexibility in arrangement can be ensured.

[0089] Furthermore, by supplying the flue gas treated in the flue gas treatment system 9 as described above to the absorption tower 81, the flue gas with few impurities can be brought into contact with the absorption liquid. Therefore, the purity and recovery efficiency of carbon dioxide can be improved.

[0090] Furthermore, the exhaust gas treatment system 9B as described above is disposed in the hull 2. Even in a location where a stable supply of fresh water is difficult, such as the ship 1, impurities can be removed from the exhaust gas while reducing the amount of new fresh water used.

[0091] Second Embodiment Next, an exhaust gas treatment system 9A according to a second embodiment of the present disclosure will be described. In the second embodiment described below, components common to those of the first embodiment will be denoted by the same reference numerals in the drawings, and descriptions thereof will be omitted. Unlike the first embodiment, the exhaust gas treatment system 9A of the second embodiment does not include the second scrubbing device 40 and the components associated with the second scrubbing device 40, and instead includes a seawater cleaning device 170 that cleans exhaust gas with seawater before the first scrubbing device 10.

[0092] As shown in FIG. 3, the air pollution control system 9A of the second embodiment further includes a seawater supply unit 160, a seawater cleaning device 170, and a seawater cleaning discharge line L7.

[0093] The seawater supply unit 160 supplies seawater to be used when washing the exhaust gas in the seawater washing device 170. Seawater is a liquid different from the primary wash water, intermediate wash water, and second wash water. The seawater supply unit 160 has a seawater supply line L161 and a seawater pump 162.

[0094] The seawater supply line L161 sends seawater to the seawater cleaning device 170. The seawater supply line L161 takes in seawater from the sea and supplies it. The seawater supply line L161 is a pipe that connects the sea to the seawater cleaning device 170. The seawater pump 162 sucks up seawater from the sea, increases the pressure of the water, and sends it to the seawater supply line L161.

[0095] The seawater cleaning device 170 is capable of cleaning the exhaust gas supplied to the first cleaning device 10 by using more seawater than the primary cleaning water. The seawater cleaning device 170 cleans the exhaust gas with seawater before supplying it to the first cleaning device 10. Moreover, unlike the first cleaning device 10, the seawater cleaning device 170 cleans the exhaust gas with only seawater. The seawater cleaning device 170 of this embodiment has a seawater cleaning casing 171, a seawater cleaning section 172, a seawater cleaning demister 173, a seawater disposal line L174, and a dilution section 175.

[0096] The seawater cleaning casing 171 is a cylindrical container extending in the vertical direction Dv. Exhaust gas can flow inside the seawater cleaning casing 171 from a lower position Dvd in the vertical direction Dv to an upper position Dvu. A seawater disposal line L174 is connected near the bottom of the seawater cleaning casing 171. A seawater cleaning discharge line L7 is connected near the top of the seawater cleaning casing 171. A supply line L1 is connected to the seawater cleaning casing 171 at a position Dvu above the connection position with the seawater disposal line L174 in the vertical direction Dv and at a position Dvd below the connection position with the seawater cleaning discharge line L7 in the vertical direction Dv.

[0097] The seawater cleaning unit 172 performs seawater cleaning treatment on the exhaust gas by introducing more seawater than the primary cleaning water into the exhaust gas. The seawater cleaning unit 172 is disposed inside the seawater cleaning casing 171. The seawater cleaning unit 172 is disposed above Dvu in the vertical direction Dv with respect to the connection position between the seawater cleaning casing 171 and the supply line L1. The seawater cleaning unit 172 is disposed below Dvd in the vertical direction Dv with respect to the connection position between the seawater cleaning casing 171 and the seawater cleaning discharge line L7. Exhaust gas supplied from the supply line L1 into the seawater cleaning casing 171 flows from below Dvd in the vertical direction Dv to above Dvu in the seawater cleaning unit 172. The seawater cleaning unit 172 also sprays seawater onto the flowing exhaust gas from above Dvu in the vertical direction Dv to below Dvd. In the seawater washing section 172, a large amount of seawater comes into contact with the exhaust gas, thereby performing a seawater washing process in which most of the sulfur dioxide contained in the exhaust gas and about half of the amount of suspended solids are removed. In addition, in the seawater washing section 172, more seawater than the primary washing water comes into contact with the exhaust gas, thereby humidifying the exhaust gas until it becomes saturated.

[0098] The seawater cleaning demister 173 removes mist contained in the exhaust gas as the exhaust gas flows through it. Like the first demister 13, the seawater cleaning demister 173 is formed, for example, by stacking multiple layers of mesh woven with thin wires. The seawater cleaning demister 173 is disposed inside the seawater cleaning casing 171. The seawater cleaning demister 173 is disposed above Dvu in the vertical direction Dv with respect to the seawater cleaning section 172. The seawater cleaning demister 173 is disposed below Dvd in the vertical direction Dv with respect to the connection position between the seawater cleaning casing 171 and the seawater cleaning discharge line L7. Exhaust gas flows through the seawater cleaning demister 173 from below Dvd in the vertical direction Dv to above Dvu.

[0099] The seawater disposal line L174 discharges used seawater, which is seawater that has come into contact with the exhaust gas in the seawater cleaning section 172, to the outside (to the sea in this embodiment). The seawater disposal line L174 is a pipe that connects the seawater cleaning casing 171 to the sea.

[0100] The dilution unit 175 supplies seawater to the used seawater flowing through the seawater disposal line L174. The dilution unit 175 dilutes the concentration of impurities in the used seawater with new seawater.

[0101] The seawater cleaning discharge line L7 supplies the flue gas that has been subjected to seawater cleaning treatment in the seawater cleaning device 170 to the first scrubbing device 10. The seawater cleaning discharge line L7 sends the flue gas that has passed through the seawater cleaning section 172 and the seawater cleaning demister 173 to the first scrubbing device 10. The seawater cleaning discharge line L7 is a pipe that connects the seawater cleaning device 170 and the first scrubbing device 10. Therefore, the first scrubber section 12 of the first scrubbing device 10 is supplied with flue gas that has been subjected to seawater cleaning treatment in the seawater cleaning section 172 and has an increased water concentration. In the first scrubber section 12, the primary cleaning water comes into contact with the flue gas, thereby performing the primary cleaning treatment, as in the first embodiment. At the same time, in the first scrubber section 12, the primary cleaning water comes into contact with the flue gas, thereby removing salt contained in the flue gas by the seawater cleaning treatment.

[0102] Furthermore, the exhaust gas treatment system 9A of the second embodiment does not have the second cleaning device 40, the intermediate storage section 50, the intermediate supply section 60, or the second discharge line L3. Therefore, the exhaust gas discharged from the first cleaning device 10 is sent directly to the electrostatic precipitator 70 from the first discharge line L21. Furthermore, the intermediate storage section 50 is not formed in the storage casing 150A, and only the primary storage section 20 and the secondary storage section 80, which are partitioned by a partition section, are formed.

[0103] (Action and effect) In the flue gas treatment system 9A of the second embodiment, the flue gas is supplied to the seawater washing device 170 before being supplied to the first scrubbing device 10. When the flue gas is dry and has low humidity, even if primary washing water is supplied to the first scrubbing device 10 to perform primary washing, the primary washing water is used to increase the humidity of the flue gas, requiring a large amount of water to be replenished in the primary storage section 20. Therefore, the flue gas before being supplied to the first scrubber section 12 is supplied to the seawater washing section 172, where a large amount of seawater is used to wash the flue gas and increase the moisture concentration of the flue gas to a saturated state. As a result, the flue gas supplied to the first scrubber section 12 is sufficiently humidified in addition to having many impurities removed. Therefore, the primary washing water supplied from the first scrubber section 12 is hardly used to increase the moisture concentration of the flue gas. Therefore, the additional supply of primary washing water is suppressed, and the liquid level of the primary wastewater stored in the primary storage section 20 can be maintained. As a result, the amount of new washing water other than seawater that needs to be added can be reduced throughout the entire exhaust gas treatment system 9A.

[0104] Furthermore, seawater is supplied to the seawater washing section 172. In other words, seawater can be used to humidify the exhaust gas, without using primary washing water or secondary washing water. This makes it possible to prevent the primary washing water or secondary washing water from being consumed for humidifying the exhaust gas. This also makes it possible to reduce the amount of makeup water supplied to replenish the circulating primary washing water and secondary washing water.

[0105] Third Embodiment Next, an exhaust gas treatment system 9B according to a third embodiment of the present disclosure will be described. In the third embodiment described below, components common to the first and second embodiments will be denoted by the same reference numerals in the drawings, and descriptions thereof will be omitted. The exhaust gas treatment system 9B according to the third embodiment differs from the other embodiments in that it does not have a storage casing 150, 150A.

[0106] As shown in FIG. 4, in an exhaust gas treatment system 9B of the second embodiment, a primary storage section 20B, an intermediate storage section 50B, and a secondary storage section 80B are not formed in storage casings 150, 150A.

[0107] Specifically, the primary storage section 20B is housed in the first scrubber casing 11B together with the first scrubber section 12. That is, the primary storage section 20B is formed as a part of the first cleaning device 10B. The primary storage section 20B is disposed inside the first scrubber casing 11B, below the first scrubber section 12 in the vertical direction Dv, at a position Dvd. Furthermore, the first cleaning device 10B does not have a primary drainage line L14. That is, the primary cleaning water used in the first scrubber section 12 is directly stored in the primary storage section 20B as primary drainage.

[0108] The intermediate storage section 50B is housed in the second scrubber casing 41B together with the second scrubber section 42. That is, the intermediate storage section 50B is formed as part of the second cleaning device 40B. The intermediate storage section 50B is disposed inside the second scrubber casing 41B, below the second scrubber section 42 in the vertical direction Dv, Dvd. The second cleaning device 40B does not have an intermediate drainage line L44. That is, the intermediate cleaning water used in the second scrubber section 42 is directly stored in the intermediate storage section 50B as intermediate drainage.

[0109] Furthermore, secondary storage section 80B is housed in dust collection casing 71B together with electrostatic precipitator 72. That is, secondary storage section 80B is formed as part of electrostatic precipitator 70B. Secondary storage section 80B is disposed inside dust collection casing 71B, below electrostatic precipitator 72 in the vertical direction Dv, at a position Dvd. Furthermore, electrostatic precipitator 70B does not have a secondary drainage line L74. That is, the secondary cleaning water used in electrostatic precipitator 72 is directly stored in secondary storage section 80B as secondary drainage.

[0110] The return section L51 of the third embodiment is a pipe that connects the secondary cleaning water supply line L91 and the primary storage section 20B. In other words, the return section L51 directly sends a portion of the secondary wastewater sent to the electrostatic precipitator 72 by the secondary cleaning water supply line L91 to the primary storage section 20B.

[0111] The intermediate return section L601 of the third embodiment is a pipe that connects the intermediate cleaning water supply line L61 and the primary storage section 20B. That is, the intermediate return section L601 sends a portion of the intermediate wastewater sent to the second scrubber section 42 by the intermediate cleaning water supply line L61 to the return section L51. Therefore, the intermediate return section L601 sends a portion of the intermediate wastewater flowing through the intermediate cleaning water supply line L61 to the primary storage section 20B via the return section L51. In addition, the intermediate return section L601 is connected to the intermediate cleaning water supply line L61 between the intermediate supply pump 62 and the intermediate supply cooler 63.

[0112] The wastewater treatment device 110B of the third embodiment is capable of supplying treated water to the primary reservoir 20B and the secondary reservoir 80B. Specifically, the treated water supply line L1041 of the third embodiment sends the treated water stored in the treated water storage unit 102 to the primary reservoir 20B, the intermediate reservoir 50B, and the secondary reservoir 80B. The treated water supply line L1041 has a pipe connecting the treated water storage unit 102 and the primary reservoir 20B, a pipe connecting the treated water storage unit 102 and the intermediate reservoir 50B, and a pipe connecting the treated water storage unit 102 and the secondary reservoir 80B.

[0113] Furthermore, the wastewater treatment unit 110B removes impurities from the primary wastewater on the way from the primary storage unit 20B to the first scrubber unit 12. Specifically, the primary wastewater transfer line L1111 is a pipe that connects the primary cleaning water supply line L31 and the wastewater treatment unit 112. The primary wastewater transfer line L1111 is connected to the primary cleaning water supply line L31 between the primary supply pump 32 and the primary supply cooler 33.

[0114] (Action and effect) In an exhaust gas treatment system 9B of the third embodiment, a primary storage section 20B is accommodated in a first scrubber casing 11B together with a first scrubber section 12 as part of a first cleaning device 10B. Similarly, an intermediate storage section 50B is accommodated in a second scrubber casing 41B together with a second scrubber section 42 as part of a second cleaning device 40B. Furthermore, a secondary storage section 80B is accommodated in a dust collection casing 71B together with an electrostatic precipitator 72 as part of an electrostatic precipitator 70B. In this way, a storage section for storing cleaning water is not separately arranged like the storage casings 150, 150A, but is arranged below the first scrubber section 12, the second scrubber section 42, and the electrostatic precipitator 72 in the vertical direction Dvd. This eliminates the need for equipment to send wastewater from the first scrubber section 12, the second scrubber section 42, and the electrostatic precipitator section 72 to the primary storage section 20B, the intermediate storage section 50B, and the secondary storage section 80B. This allows for more compact equipment around the primary storage section 20B, the intermediate storage section 50B, and the secondary storage section 80B.

[0115] (Other embodiments) The above describes in detail the embodiments of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure.

[0116] The carbon dioxide capture system (acid gas capture system) 8 and the flue gas treatment systems 9, 9A, and 9B described above are not limited to being installed mainly on the ship hull 2 ​​located at sea. The carbon dioxide capture system 8 and the flue gas treatment systems 9, 9A, and 9B may also be installed on land. In this case, the carbon dioxide capture system 8 and the flue gas treatment systems 9, 9A, and 9B may be installed in an area where there are restrictions on the amount of wash water used or the amount of wastewater discharged. Therefore, for example, the source of the flue gas is not limited to the combustion device 6. Examples of sources of flue gas include waste incinerators, coal- or natural gas-fired power plants, gas turbines, gas engines, cement plants, steel plants, glass melting plants, and ethanol production plants.

[0117] Furthermore, the exhaust gas treatment systems 9, 9A, 9B are not limited to the configurations described above. For example, the exhaust gas treatment systems 9, 9B of the first embodiment and the third embodiment may not have the second scrubber section 42. Conversely, the exhaust gas treatment systems 9, 9B of the first embodiment and the third embodiment may have multiple second scrubber sections 42. Furthermore, the exhaust gas treatment system 9A of the second embodiment may have multiple second scrubber sections 42 or one second scrubber section 42. Furthermore, the exhaust gas treatment systems 9, 9B of the first embodiment and the third embodiment may have a seawater cleaning section 172.

[0118] Furthermore, in the exhaust gas treatment systems 9, 9A, and 9B, the flow rates of the cleaning water and the exhaust gas may be adjustable. Specifically, in the exhaust gas treatment systems 9, 9A, and 9B, valves may be provided in the lines that are the piping through which the cleaning water and the exhaust gas flow. In this case, the opening degree of the valves may be controlled in accordance with the load on the combustion device 6, the concentration of impurities in the exhaust gas, and the flow rate of the exhaust gas. Furthermore, the load of each pump in the exhaust gas treatment systems 9, 9A, and 9B, such as the degree of pressure increase, may be controlled in accordance with the load on the combustion device 6, the concentration of impurities in the exhaust gas, and the flow rate of the exhaust gas.

[0119] Furthermore, the gas to be recovered is not limited to carbon dioxide as in this embodiment. The gas to be recovered may be any acidic gas, such as hydrogen sulfide (H2S) or sulfur dioxide (SO2), or may be a combination of multiple acidic gases.

[0120] Furthermore, the primary neutralizing agent supply unit 34 may perform neutralization at any location as long as it can neutralize the primary cleaning water used in the first scrubber unit 12. In other words, the primary neutralizing agent supply unit 34 is not limited to a structure in which the neutralizing agent is supplied to the primary cleaning water supply line L31. For example, the primary neutralizing agent supply unit 34 may be connected to the primary drainage line L14 or directly to the primary storage unit 20.

[0121] Furthermore, the intermediate neutralizing agent supply unit 64 may perform neutralization at any position as long as it can neutralize the intermediate wash water used in the second scrubber unit 42. In other words, the intermediate neutralizing agent supply unit 64 is not limited to a structure that supplies neutralizing agent to the intermediate wash water supply line L61. For example, the intermediate neutralizing agent supply unit 64 may be connected to the intermediate drainage line L44 or may be directly connected to the intermediate storage unit 50.

[0122] Furthermore, the secondary neutralizing agent supply unit 94 may perform neutralization at any location as long as it can neutralize the secondary cleaning water used in the electrostatic precipitator 72. In other words, the secondary neutralizing agent supply unit 94 is not limited to a structure that supplies a neutralizing agent to the secondary cleaning water supply line L91. For example, the secondary neutralizing agent supply unit 94 may be connected to the secondary drainage line L74 or may be directly connected to the secondary storage unit 80.

[0123] Furthermore, the secondary supply unit 90 only needs to include the secondary cleaning water supply line L9 and the secondary supply pump 92. Therefore, the secondary supply unit 90 does not necessarily have to include the secondary supply cooler 93 and the secondary neutralizing agent supply unit 94.

[0124] Furthermore, the electrostatic precipitator 70 is not limited to a structure in which the exhaust gas flows from the lower Dvd to the upper Dvu in the vertical direction Dv. The electrostatic precipitator 70 may also be a structure in which the exhaust gas flows from the upper Dvu to the lower Dvd in the vertical direction Dv. That is, the electrostatic precipitator 72 may be disposed below the Dvd in the vertical direction Dv with respect to the connection position between the dust collecting casing 71 and the second discharge line L3. In this case, the electrostatic precipitator 72 is disposed above the Dvu in the vertical direction Dv with respect to the connection position between the dust collecting casing 71 and the final discharge line L4. Therefore, the exhaust gas supplied from the second discharge line L3 to the inside of the dust collecting casing 71 flows from the upper Dvu to the lower Dvd in the vertical direction Dv through the electrostatic precipitator 72. Furthermore, the electrostatic precipitator 72 may inject secondary cleaning water from the lower Dvd to the upper Dvu in the vertical direction Dv toward the dust collecting electrode 721.

[0125] Furthermore, the dust collecting demister 73 may be disposed anywhere as long as it can remove mist from the exhaust gas after passing through the electrostatic precipitator 72. Therefore, the dust collecting demister 73 is not limited to being disposed inside the dust collecting casing 71. The dust collecting demister 73 may also be disposed inside the final discharge line L4. Furthermore, when the flow direction of the exhaust gas in the electrostatic precipitator 70 is from upward Dvu to downward Dvd in the vertical direction Dv, even if the dust collecting demister 73 is disposed inside the dust collecting casing 71, the dust collecting demister 73 is disposed inside the final discharge line L4.

[0126] Furthermore, the return section L5 is not limited to being a pipe connecting the secondary flush water supply line L91 and the primary drainage line L14. The return section L5 only needs to be able to supply a portion of the secondary drainage water stored in the secondary storage section 80 to the primary storage section 20. Therefore, the return section L5 may be directly connected to the primary storage section 20.

[0127] Furthermore, the return branch section L501 is not limited to being a pipe connecting the return section L5 and the intermediate drainage line L44. The return branch section L501 only needs to be able to supply a portion of the secondary drainage stored in the secondary storage section 80 to the intermediate storage section 50. Therefore, the return branch section L501 may be directly connected to the intermediate storage section 50.

[0128] Furthermore, the intermediate return section L6 is not limited to being a pipe connecting the intermediate flush water supply line L61 and the primary drain line L14. The intermediate return section L6 only needs to be able to supply a portion of the intermediate drainage water stored in the intermediate storage section 50 to the primary storage section 20. Therefore, the intermediate return section L6 may be directly connected to the primary storage section 20.

[0129] Furthermore, when the primary storage section 20, the intermediate storage section 50, and the secondary storage section 80 are formed at positions separate from the first scrubber section 12, the second scrubber section 42, and the electrostatic precipitator section 72, they are not limited to a structure in which they are formed inside one storage casing 150. The primary storage section 20, the intermediate storage section 50, and the secondary storage section 80 may each be formed inside an independent storage casing arranged separate from one another.

[0130] <Additional Notes> The exhaust gas treatment systems 9, 9A, and 9B, the acid gas recovery system, and the ship 1 described in each embodiment can be understood, for example, as follows.

[0131] (1) An exhaust gas treatment system 9, 9A, 9B according to a first aspect includes a scrubber section into which exhaust gas is introduced and which performs a primary cleaning treatment on the exhaust gas by bringing primary cleaning water into contact with the exhaust gas; a primary storage section 20, 20B which stores primary wastewater that is the primary cleaning water that has come into contact with the exhaust gas in the scrubber section; a primary supply section 30 which supplies the primary wastewater stored in the primary storage section 20, 20B to the scrubber section as the primary cleaning water; an electric dust collector 72 which receives the exhaust gas that has been subjected to the primary cleaning treatment and performs a secondary cleaning treatment by performing electric dust collection on the exhaust gas using a dust collecting electrode 721 and cleaning the dust collecting electrode with secondary cleaning water; and a secondary cleaning water used in the electric dust collector 72. a secondary supply unit 90 that supplies the secondary wastewater stored in the secondary storage units 80, 80B to the electrostatic precipitator 72 as the secondary cleaning water; a return unit L5, L51 that supplies a portion of the secondary wastewater stored in the secondary storage units 80, 80B to the primary storage units 20, 20B; a makeup water supply unit 101 that supplies makeup water having fewer impurities than the secondary cleaning water to the secondary storage units 80, 80B; and a wastewater treatment unit 110 that removes the impurities from the primary wastewater stored in the primary storage units 20, 20B and removes the impurities from the primary wastewater and supplies the primary wastewater from which the impurities have been removed to the secondary storage units 80, 80B.

[0132] According to this configuration, primary wash water and secondary wash water are circulated. Specifically, the primary wash water is used in the scrubber section and becomes primary wastewater, which is then stored in the primary storage sections 20 and 20B. The primary wastewater stored in the primary storage sections 20 and 20B is then sent back to the scrubber section as primary wash water. Similarly, the secondary wash water is used in the electrostatic precipitator 72 and becomes secondary wastewater, which is then stored in the secondary storage sections 80 and 80B. The secondary wastewater stored in the secondary storage sections 80 and 80B is then sent back to the electrostatic precipitator 72 as secondary wash water. By circulating wash water through each device in this manner, the concentration of the primary wastewater and the secondary wastewater can be transferred while balancing the liquid levels of the liquids circulating in each circulation system. As a result, the amount of new wash water required to be added to the entire exhaust gas treatment system 9, 9A, and 9B can be reduced. Furthermore, makeup water is sent to the secondary storage sections 80 and 80B by the makeup water supply section 101. The makeup water is cleaner water with fewer impurities than the secondary flush water. Therefore, by adding makeup water to replenish the liquid water stored in the secondary storage unit 80, the secondary wastewater stored in the secondary storage unit 80 is diluted, and the concentration of impurities in the secondary wastewater can be reduced. Furthermore, a portion of the secondary wastewater stored in the secondary storage units 80, 80B is returned to the primary storage units 20, 20B via the return units L5, L51. The secondary wastewater is a low-concentration wastewater with fewer impurities than the primary wastewater stored in the primary storage units 20, 20B. In addition, the concentration of impurities in the secondary wastewater is further reduced by the makeup water. Therefore, by adding the secondary wastewater whose impurity concentration has been reduced by the makeup water, the amount of liquid water stored in the primary storage unit 20 is replenished. As a result, the primary wastewater stored in the primary storage unit 20 is diluted. As a result, the concentration of impurities in the primary wastewater can be reduced. Therefore, it is possible to suppress a decrease in the efficiency of removing impurities from the exhaust gas even when the primary cleaning water and secondary cleaning water are circulated and used in the scrubber section and the electrostatic precipitator section 72. As a result, it is possible to remove impurities from the exhaust gas while reducing the amount of cleaning water used.

[0133] (2) An exhaust gas treatment system 9, 9B according to a second aspect is the exhaust gas treatment system 9, 9A, 9B of (1), further comprising: a downstream scrubber section into which exhaust gas that has been subjected to the primary cleaning treatment is introduced and which performs the primary cleaning treatment again on the exhaust gas by bringing intermediate cleaning water into contact with the exhaust gas; an intermediate storage section 50, 50B which stores intermediate wastewater that is the intermediate cleaning water that has come into contact with the exhaust gas in the downstream scrubber section; and an intermediate supply section 60 which supplies the intermediate wastewater stored in the intermediate storage section 50, 50B to the downstream scrubber section as the intermediate cleaning water, and the exhaust gas that has been subjected to the primary cleaning treatment in the downstream scrubber section is introduced into the electric dust collector 72.

[0134] According to this configuration, the exhaust gas is subjected to primary scrubbing treatment again by the downstream scrubber section using intermediate wash water. Therefore, the exhaust gas is sent to the electrostatic precipitator 72 in a state in which impurities have been further removed by the downstream scrubber section. As a result, the amount of impurities in the exhaust gas treated by the electrostatic precipitator 72 is reduced, which further prevents a decrease in the efficiency of impurity removal by the electrostatic precipitator 72. Therefore, impurities can be removed from the exhaust gas more efficiently.

[0135] (3) The exhaust gas treatment system 9, 9B according to the third aspect is the exhaust gas treatment system 9, 9B of (2), further comprising an intermediate return section L6, L601 that supplies a portion of the intermediate wastewater stored in the intermediate storage section 50, 50B to the primary storage section 20, 20B.

[0136] With this configuration, the intermediate wastewater contains more impurities than the secondary wastewater, but is a medium-concentration wastewater with fewer impurities than the primary wastewater stored in the primary storage units 20 and 20B. Therefore, by using the intermediate wastewater to replenish the liquid stored in the primary storage unit 20, impurities move in the order of the secondary wastewater, intermediate wastewater, and primary wastewater. Therefore, a transfer of impurity concentration occurs between the secondary wastewater, intermediate wastewater, and primary wastewater. This allows wastewater with a high impurity content that requires treatment to be collected in the primary wastewater, allowing for efficient wastewater treatment.

[0137] (4) The exhaust gas treatment system 9, 9A according to the fourth aspect is any one of the exhaust gas treatment systems 9, 9A of (1) to (3), and further comprises a storage casing 150, 150A arranged at a position away from the scrubber section and the electrostatic precipitator section 72, and having the primary storage section 20, 20B and the secondary storage section 80, 80B, and the storage casing 150, 150A has a partition section that separates the primary storage section 20, 20B and the secondary storage section 80, 80B.

[0138] With this configuration, it is possible to independently arrange the equipment for storing wastewater, such as the primary storage sections 20, 20B and secondary storage sections 80, 80B, and the equipment for cleaning exhaust gas, such as the scrubber section and electrostatic precipitator section 72. Therefore, even in cases where the space available for arranging the equipment for the exhaust gas treatment systems 9, 9A, 9B is limited, such as in a narrow hull 2, it is possible to ensure flexibility in arrangement.

[0139] (5) The exhaust gas treatment system 9A according to the fifth aspect is any one of the exhaust gas treatment systems 9, 9A, 9B according to (1) to (4), and further includes a seawater cleaning section 172 before the primary cleaning process, into which exhaust gas is introduced and which performs seawater cleaning on the exhaust gas by bringing more seawater than the primary cleaning water into contact with the exhaust gas, and the exhaust gas that has come into contact with the seawater in the seawater cleaning section 172 is supplied to the scrubber section.

[0140] According to this configuration, the exhaust gas is supplied to the seawater washing section 172 before being supplied to the scrubber section. When the exhaust gas is dry and has low humidity, supplying primary wash water to the scrubber section for primary scrubbing would result in the primary wash water being used to increase the humidity of the exhaust gas, requiring a large amount of primary wash water. Therefore, the exhaust gas before being supplied to the scrubber section is supplied to the seawater washing section 172, where a large amount of seawater is used to wash the exhaust gas and increase the moisture concentration of the exhaust gas. As a result, the exhaust gas supplied to the scrubber section is sufficiently humidified, with many impurities removed. Therefore, the primary wash water supplied from the scrubber section is hardly used to increase the moisture concentration of the exhaust gas. Therefore, the additional supply of primary wash water can be suppressed, and the liquid level of the primary wastewater stored in the primary storage section 20 can be maintained. As a result, the amount of additional wash water (other than seawater) that needs to be added throughout the exhaust gas treatment system 9A can be reduced.

[0141] (6) The exhaust gas treatment system 9B according to the sixth aspect is any one of the exhaust gas treatment systems 9, 9A, 9B of (1) to (5), and further comprises a scrubber casing that accommodates the primary storage section 20, 20B and the scrubber section, and a dust collection casing 71, 71B that accommodates the secondary storage section 80, 80B and the electrostatic precipitator 72, wherein the primary storage section 20, 20B is arranged inside the scrubber casing, below Dvd in the vertical direction Dv relative to the scrubber section, and the secondary storage section 80, 80B is arranged inside the dust collection casing 71, 71B, below Dvd in the vertical direction Dv relative to the electrostatic precipitator 72.

[0142] According to this configuration, a storage section for storing cleaning water is not provided separately, but is arranged at Dvd below the scrubber section and the electrostatic precipitator 72 in the vertical direction Dv. This eliminates the need for equipment to send wastewater from the scrubber section and the electrostatic precipitator 72 to the primary storage sections 20, 20B and the secondary storage sections 80, 80B. This makes it possible to make the equipment around the primary storage sections 20, 20B and the secondary storage sections 80, 80B more compact.

[0143] (7) The acidic gas recovery system according to the seventh aspect comprises the exhaust gas treatment system 9, 9A, 9B of (1) to (6), and an absorption tower 81 that contacts the exhaust gas treated in the exhaust gas treatment system 9, 9A, 9B with an absorption liquid and discharges the absorption liquid that has absorbed the acidic gas in the exhaust gas and the exhaust gas from which the acidic gas has been removed.

[0144] According to this configuration, by supplying the flue gas treated in the flue gas treatment systems 9, 9A, and 9B to the absorption tower 81, the flue gas with few impurities can be brought into contact with the absorption liquid. Therefore, the purity and recovery efficiency of the acid gas can be improved.

[0145] (8) A ship 1 according to an eighth aspect includes any one of the exhaust gas treatment systems 9, 9A, 9B according to any one of (1) to (7) and a hull 2 ​​in which the exhaust gas treatment system 9, 9A, 9B is arranged.

[0146] With this configuration, even in a location where a stable supply of fresh water is difficult, such as the ship 1, it is possible to remove impurities from exhaust gas while reducing the amount of new fresh water used. [Explanation of symbols]

[0147] 1 ship 2. Hull 3A,3B side 4. Ship's Bottom 5 Upper Deck 2a bow 2b stern 6 Combustion equipment 7 Cargo compartment 8 Carbon dioxide capture system 9,9A,9B Exhaust Gas Treatment System L1 supply line 10,10B First cleaning device 11,11B First scrubber casing 12 First scrubber section 13 First Demister L14 Primary drainage line 20,20B Primary storage section 30 Primary supply section L31 Primary cleaning water supply line 32 Primary supply pump 33 Primary supply cooler 34 Primary neutralizer supply section L2, L21 First discharge line 40,40B Second cleaning device 41,41B Second scrubber casing 42 Second scrubber section 43 Second Demister L44 Intermediate drainage line 50,50B Intermediate storage section 60 Intermediate supply section L61 Intermediate cleaning water supply line 62 Intermediate supply pump 63 Intermediate supply cooler 64 Intermediate neutralizer supply section L3 Second discharge line 70,70B Electrostatic Precipitator 71,71B Dust collection casing 72 Electrostatic precipitator 721 Dust collecting pole 73 Dust collection demister L74 Secondary drain line 80,80B Secondary storage section 90 Secondary supply section L91 Secondary cleaning water supply line 92 Secondary supply pump 93 Secondary supply cooler 94 Secondary neutralizer supply section L4 Final discharge line L5, L51 return part L501 Return branch L6, L601 Intermediate return section 101 Makeup water supply section 102 Treated water storage section 103 Treated water pump L104, L1041 Treated water supply line 110 Wastewater treatment facility L111, L1111 Primary wastewater transfer line 112 Wastewater treatment equipment L113 Drain return line 150,150A storage casing 151 First Section 152 Second Compartment 81 Absorption Tower 160 Seawater Supply Department L161 Seawater supply line 162 Seawater pump 170 Seawater cleaning device 171 Seawater washed casing 172 Seawater cleaning section 173 Seawater cleaning demister L174 Seawater Disposal Line 175 Dilution section L7 Seawater cleaning discharge line Dv vertical direction Dvu upper dvd below

Claims

1. a scrubber section into which exhaust gas is introduced and which performs primary cleaning treatment on the exhaust gas by bringing primary cleaning water into contact with the exhaust gas; a primary storage section that stores primary wastewater, which is the primary cleaning water that has come into contact with the exhaust gas in the scrubber section; a primary supply unit that supplies the primary wastewater stored in the primary storage unit to the scrubber unit as the primary cleaning water; an electric dust collector unit into which the exhaust gas that has been subjected to the primary cleaning treatment is introduced, which performs secondary cleaning treatment by electrostatically collecting dust from the exhaust gas using a dust collecting electrode, and cleaning the dust collecting electrode with secondary cleaning water; a secondary storage section that stores secondary wastewater, which is the secondary cleaning water used in the electric dust collector; a secondary supply unit that supplies the secondary wastewater stored in the secondary storage unit to the electric dust collector unit as the secondary cleaning water; A return section that supplies a portion of the secondary drainage water stored in the secondary storage section to the primary storage section; a makeup water supply unit that supplies makeup water containing fewer impurities than the secondary cleaning water to the secondary reservoir; a wastewater treatment unit that removes the impurities from the primary wastewater stored in the primary storage unit and supplies the primary wastewater from which the impurities have been removed to the secondary storage unit.

2. a downstream scrubber section into which the exhaust gas that has been subjected to the primary cleaning treatment is introduced and into which intermediate cleaning water is brought into contact with the exhaust gas, thereby subjecting the exhaust gas to the primary cleaning treatment again; an intermediate storage section that stores intermediate wastewater, which is the intermediate wash water that has come into contact with the exhaust gas in the downstream scrubber section; an intermediate supply unit that supplies the intermediate wastewater stored in the intermediate storage unit to the wake scrubber unit as the intermediate wash water, The exhaust gas treatment system according to claim 1 , wherein the exhaust gas that has been subjected to the primary cleaning treatment in the downstream scrubber section is introduced into the electric dust collector section.

3. The exhaust gas treatment system according to claim 2 , further comprising an intermediate return section that supplies a portion of the intermediate wastewater stored in the intermediate storage section to the primary storage section.

4. The apparatus further includes a storage casing that is disposed at a position separated from the scrubber unit and the electrostatic precipitator unit and has the primary storage unit and the secondary storage unit, The exhaust gas treatment system according to claim 1 or 2, wherein the storage casing has a partition that separates the primary storage section and the secondary storage section.

5. a seawater washing unit, which is provided before the primary washing process, into which the exhaust gas is introduced and which performs a seawater washing process on the exhaust gas by bringing a larger amount of seawater into contact with the exhaust gas than the primary washing water; The exhaust gas treatment system according to claim 1 or 2, wherein the exhaust gas that has come into contact with the seawater in the seawater cleaning section is supplied to the scrubber section.

6. a scrubber casing that accommodates the primary storage section and the scrubber section; a dust collection casing that houses the secondary storage unit and the electric dust collector, The primary storage section is disposed inside the scrubber casing and vertically below the scrubber section, The exhaust gas treatment system according to claim 1 or 2, wherein the secondary storage section is disposed inside the dust collection casing and below the electric precipitator section in the vertical direction.

7. The exhaust gas treatment system according to claim 1 or 2; an absorption tower that contacts the exhaust gas treated in the exhaust gas treatment system with an absorption liquid and discharges the absorption liquid that has absorbed the acid gas in the exhaust gas and the exhaust gas from which the acid gas has been removed.

8. The exhaust gas treatment system according to claim 1 or 2; and a hull in which the exhaust gas treatment system is disposed.

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