JP2015165100A - Mist separator, exhaust gas treatment device, and ship - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mist separator, an exhaust gas treatment device, and a ship in which mist can be properly collected even if a gas flow rate fluctuates.SOLUTION: A mist separator is provided with: a first gas passage 62 having a first passage area; a second gas passage 63 having a second passage area larger than the first passage area and arranged on the downstream side in a gas flow direction in the first gas passage 62; a first mist collection part 65 arranged in the first gas passage 62; and a second mist collection part 66 arranged in the second gas passage 63.

Description

  The present invention relates to, for example, a mist separator, an exhaust gas treatment device, and a ship that are applied to an exhaust gas treatment device that treats exhaust gas discharged from a marine diesel engine.

  Exhaust gas discharged from a diesel engine contains harmful substances such as NOx, SOx, and dust. In particular, marine diesel engines using low-quality fuel also increase the amount of harmful substances contained in the exhaust gas. Therefore, the marine diesel engine requires an exhaust gas treatment device for treating this harmful substance.

  Conventional exhaust gas treatment devices are generally exhaust gas recirculation (EGR) devices. This EGR device mixes a part of exhaust gas discharged from a combustion chamber of a diesel engine into combustion air and returns it to the combustion chamber. Therefore, in the combustion air, the oxygen concentration is lowered, the combustion temperature is lowered by delaying the combustion speed, which is a reaction between the fuel and oxygen, and the amount of NOx generated can be reduced.

  By the way, exhaust gas discharged from a diesel engine in an exhaust gas treatment device is mixed with combustion air sucked from the atmosphere after removing harmful substances such as NOx and soot through an EGR valve by a scrubber. Returned to diesel engine. At this time, the scrubber removes harmful substances by performing water injection on the exhaust gas, and the mist separator separates moisture contained in the exhaust gas.

  In addition, as an exhaust gas recirculation system, there exists a thing described in the following patent document 1, for example. Moreover, as a mist separator, there exists a thing described in patent document 2, for example. In the multistage steam-water separator described in Patent Document 2, the steam-water separator is made multistage, the angle of the swirl blade at the lowermost stage is decreased, and the angle of the swirl blade is gradually increased along the upper side. The angle of the upper swirl blade is maximized.

JP 2012-127205 A Japanese Patent Laid-Open No. 06-075082

  By the way, in the exhaust gas treatment apparatus described above, the gas flow rate to be treated in the exhaust gas recirculation line varies depending on the operation state of the diesel engine. Since the mist collection rate of the mist separator changes according to the gas flow velocity that passes through it, for example, when it is adjusted to a large flow rate (high-speed flow), the mist removal amount decreases at a small flow rate (low-speed flow), and a small flow rate ( Mist re-scatters at a large flow rate (high-speed flow) when adjusted to low-speed flow. When the gas flow rate changes, it is conceivable to change the passage area using a shutter or the like, but the equipment becomes larger and the cost is increased. Note that the multistage steam-water separator described above has a multi-stage steam-water separator and reduces the pressure loss by changing the angle of each swirl blade. Absent.

  The present invention solves the above-described problems, and an object thereof is to provide a mist separator, an exhaust gas treatment device, and a ship that can properly collect mist even if the gas flow rate fluctuates.

  In order to achieve the above object, a mist separator according to the present invention includes a first gas passage having a first passage area and a gas in the first gas passage having a second passage area larger than the first passage area. A second gas passage disposed on the downstream side in the flow direction, a first mist collecting portion disposed in the first gas passage, and a second mist collecting portion disposed in the second gas passage. It is characterized by having.

  Therefore, the mist collection part changes in the mist collection part according to the gas flow rate (gas flow velocity) to pass. Therefore, when a gas having a small flow rate (low-speed flow) flows into the first gas passage having a small passage area, the first mist collecting unit can appropriately separate and collect the mist from the gas. On the other hand, if a gas with a large flow rate (high-speed flow) flows into the first gas passage having a small passage area, the first mist collecting part cannot properly collect the mist from the gas, and the mist re-scatters. However, since the gas flows into the second gas passage with a large passage area after that, the gas flow rate (gas flow velocity) decreases, and the mist is properly separated from the gas including the mist re-scattered by the second mist collecting part. And can be collected. As a result, even if the gas flow rate (gas flow rate) fluctuates, the mist can be properly collected by the mist collecting unit arranged in the gas passages having two kinds of passage areas.

  In the mist separator according to the present invention, a third gas passage having a passage area that gradually increases is provided between the first gas passage and the second gas passage, and the first mist collecting section includes the third gas passage. The second mist collecting portion is disposed upstream of the gas passage in the gas flow direction, and the second mist collecting portion is disposed downstream of the third gas passage in the gas flow direction.

  Accordingly, the gas flow rate can be gradually reduced from the third gas passage, and even if the gas is in a large flow rate (high-speed flow), the gas flow rate is appropriately reduced in the second gas passage to reduce the flow rate (low-speed flow). The second mist collecting section can efficiently collect mist.

  In the mist separator according to the present invention, the first mist collecting section and the second mist collecting section are set to have the same aperture ratio.

  Therefore, it is possible to reduce the cost by sharing the configuration of the first mist collecting unit and the second mist collecting unit.

  In the mist separator according to the present invention, the first mist collecting unit and the second mist collecting unit are configured such that a plurality of folded plates are arranged at predetermined intervals in the radial direction of the gas passage. Yes.

  Therefore, by arranging a plurality of folded plates at predetermined intervals to constitute each mist collecting section, it is possible to efficiently separate and collect mist from the gas with a simple configuration.

  Moreover, the exhaust gas treatment apparatus of the present invention injects water into the exhaust gas recirculation line that recirculates a part of the exhaust gas discharged from the marine diesel engine as combustion air, and the exhaust gas flowing through the exhaust gas recirculation line. It has a scrubber and the mist separator that separates mist from the exhaust gas that has passed through the scrubber.

Therefore, after the exhaust gas discharged from the marine diesel engine partly flows into the exhaust gas recirculation line, water is injected by the scrubber, harmful substances are removed, and the mist is separated and removed by the mist separator. Compressed by the supercharger and recirculated to the marine diesel engine as combustion air. Even if the amount of gas flowing in the gas recirculation line fluctuates, the mist separator is provided with a mist collecting part in each of two gas passages having different passage areas.
The 1st, 2nd mist collection part can isolate | separate and collect mist from gas appropriately. As a result, even if the gas flow rate (gas flow rate) fluctuates, the mist can be properly collected by the two types of mist collecting portions, and the appropriate exhaust gas can be recirculated to the marine diesel engine.

  Moreover, the ship of this invention has an exhaust gas processing apparatus, It is characterized by the above-mentioned.

  Accordingly, appropriate exhaust gas can be recirculated to the marine diesel engine.

  According to the mist separator, the exhaust gas treatment apparatus, and the ship of the present invention, the first gas passage and the second gas passage having different passage areas are provided, and the mist collecting part is disposed in each gas passage. Even if the flow rate) fluctuates, the mist can be properly collected by the two kinds of mist collecting portions.

FIG. 1 is a schematic configuration diagram illustrating a mist separator according to the present embodiment. FIG. 2 is a schematic diagram showing a processing state of a small flow rate of exhaust gas by the mist separator of the present embodiment. FIG. 3 is a schematic diagram showing a treatment state of a large flow rate of exhaust gas by the mist separator of the present embodiment. FIG. 4 is a schematic configuration diagram illustrating the exhaust gas treatment apparatus of the present embodiment.

  Exemplary embodiments of a mist separator, an exhaust gas treatment device, and a ship according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment, and when there are two or more embodiments, what comprises combining each embodiment is also included.

  FIG. 4 is a schematic configuration diagram illustrating the exhaust gas treatment apparatus of the present embodiment.

  When the mist separator of this embodiment compresses a part of the exhaust gas discharged from the marine diesel engine by the supercharger and recirculates it as combustion air to the marine diesel engine, harmful substances are removed from the recirculated exhaust gas. To be removed.

  In the exhaust gas treatment apparatus of the present embodiment, as shown in FIG. 4, the marine diesel engine 11 is a propulsion engine (main engine) that drives and rotates the propeller for propulsion via a propeller shaft, although not shown. This marine diesel engine 11 is a uniflow scavenging exhaust type diesel engine, which is a two-stroke diesel engine, in which the flow of intake and exhaust in the cylinder is unidirectional from the bottom to the top so as to eliminate residual exhaust. Is. The diesel engine 11 includes a cylinder (combustion chamber) 12 in which a piston moves up and down, a scavenging chamber 13 communicating with the cylinder 12, and an exhaust port 14 communicating with the cylinder 12 and provided with an exhaust valve. In the diesel engine 11, the air supply line G <b> 1 is connected to the scavenging chamber 13, and the exhaust line G <b> 2 is connected to the exhaust port 14.

  The supercharger 21 is configured by connecting a compressor 22 and a turbine 23 so as to rotate integrally with a rotary shaft 24. In the supercharger 21, the turbine 23 is rotated by the exhaust gas discharged from the exhaust line G2 of the diesel engine 11, the rotation of the turbine 23 is transmitted by the rotating shaft 24, the compressor 22 is rotated, and the compressor 22 is recirculated. The gas is compressed and supplied to the diesel engine 11 from the supply line G1.

  The supercharger 21 is connected to an exhaust line G3 that discharges exhaust gas that has rotated the turbine 23. The exhaust line G3 is connected to a chimney (funnel) (not shown). Further, the exhaust gas recirculation line G4 branches off from the exhaust line G3. The exhaust gas recirculation line G4 is provided with an EGR valve (flow rate control valve) 41 and is connected to a scrubber (NOx removal scrubber) 42. The EGR valve 41 adjusts the flow rate of the exhaust gas that passes through the exhaust gas recirculation line G4. The scrubber 42 removes harmful substances such as NOx and dust contained therein by injecting water into the exhaust gas. In this embodiment, a Venturi type scrubber is adopted, but it is not limited to this configuration.

  The scrubber 42 has a hollow main body 43, a venturi section 44 into which exhaust gas is introduced, and a water storage section 45 that stores drainage. The scrubber 42 has a water injection unit 46 that injects water to the exhaust gas introduced into the venturi unit 44, and a drain circulation line W <b> 1 for circulating the drainage of the water storage unit 45 to the water injection unit 46 is provided. A pump 47 is provided in the drainage circulation line W1. The scrubber 42 is provided with a gas discharge part 48 for discharging exhaust gas from which harmful substances have been removed, and is connected to a gas discharge line G5. The gas discharge line G <b> 5 is provided with a mist separator (mist eliminator) 49 and a blower (blower) 50, and is connected to a mixer (mixer) 51.

  The blower 50 discharges the exhaust gas in the scrubber 42 from the gas discharge part 48 to the gas discharge line G5. The mist separator 49 separates moisture (water vapor) contained in the exhaust gas from which harmful substances have been removed by water injection, and the separated separated water is returned to the water storage unit 45 of the scrubber 42 by the separated water line W2. . The mixer (mixer) 51 generates combustion air by mixing the air sucked from the outside air and the exhaust gas (recirculation gas) from the gas discharge line G <b> 5, and this combustion air is supplied to the supercharger 21. A combustion air supply line G6 for supplying to the compressor 22 is provided. In the supercharger 21, the compressor 22 can supply the compressed combustion air from the supply line G1 to the diesel engine 11, and the supply line G1 is provided with an air cooler (cooler) 52. The air cooler 52 cools the recirculated gas that has been compressed by the compressor 22 to a high temperature by exchanging heat with cooling water.

  In the air cooler 52, the temperature and pressure are reduced by cooling the high-temperature recirculation gas, so that the water vapor contained is condensed and condensed water (drain water) is generated. The air cooler 52 is provided with a drain water discharge line W <b> 3 for discharging the generated drain water, and the drain water discharge line W <b> 3 is connected to the processing device 53. The treatment device 53 removes oil such as lubricating oil and system oil of the diesel engine 11 from the drain water, the treated water is drained as it is, and the separated waste is stored in a waste container (not shown).

  Here, the effect | action of the exhaust gas processing apparatus of this embodiment is demonstrated.

  In the exhaust gas treatment apparatus of the present embodiment, when the marine diesel engine 11 is supplied with combustion air from the scavenging chamber 13 into the cylinder 12, the combustion air is compressed by the piston, and the high-temperature air is fueled. Ignites spontaneously and burns when injected. The generated combustion gas is discharged from the exhaust port 14 to the exhaust line G2 as exhaust gas. The exhaust gas discharged from the marine diesel engine 11 is discharged to the exhaust line G3 after rotating the turbine 23 in the supercharger 21, and when the EGR valve 41 is closed, the entire amount is discharged to the outside from the exhaust line G3. Is done.

  On the other hand, when the EGR valve 41 is open, a part of the exhaust gas flows from the exhaust line G3 to the exhaust gas recirculation line G4. The scrubber 42 removes harmful substances such as NOx and soot contained in the exhaust gas flowing into the exhaust gas recirculation line G4. That is, when the exhaust gas passes through the venturi section 44 at a high speed in the scrubber 42, water is injected from the water injection section 46 to be cooled by the water and fine particles (PM) such as NOx and dust. Falls with water and is removed. The water containing NOx, dust, and the like is stored in the water storage unit 45 and returned to the water injection unit 46 again by the pump 47 through the drainage circulation line W1.

  The exhaust gas from which harmful substances have been removed by the scrubber 42 is discharged from the gas discharge section 48 to the gas discharge line G5, and after water (water vapor) is separated by the mist separator 49, it is mixed with the air sucked by the mixer 51. It becomes combustion air. The combustion air passes through the combustion air supply line G6, is compressed by the compressor 22 of the supercharger 21, is cooled by the air cooler 52, and is supplied to the diesel engine 11 from the air supply line G1.

  Further, the air cooler 52 cools the high-temperature recirculation gas, so that the water vapor is condensed and drain water is generated, and this drain water is discharged to the drain water discharge line W3. Since this drain water contains oil, the processing device 63 purifies the drain water.

  Here, the mist separator 49 of the present embodiment will be described in detail.

  In the mist separator 49 of the present embodiment, as shown in FIG. 1, the gas passage 61 has a first gas passage 62, a second gas passage 63, and a third gas passage 64. The first gas passage 62 has a cylindrical shape and has a predetermined first passage area. The second gas passage 63 has a cylindrical shape and has a predetermined second passage area larger than the first passage area. In the first gas passage 62, a second gas passage 63 is disposed on the downstream side in the gas flow direction.

  The third gas passage 64 has a truncated cone shape and is disposed between the first gas passage 62 and the second gas passage 63, and the passage area gradually increases from the first passage area to the second passage area. doing. The third gas passage 64 continuously connects the downstream end portion of the first gas passage 62 in the gas flow direction and the upstream end portion of the second gas passage 63 in the gas flow direction. In addition, although the passage area of the third gas passage 64 is linearly expanded, the third gas passage 64 may be expanded in a curved line or may be expanded in a staircase shape. Moreover, even if it is not a truncated cone shape, it may be a truncated pyramid shape according to the piping shape as long as the piping is a square-shaped surface.

  The first gas passage 62 is provided with a first mist collecting portion 65, and the second gas passage 63 is provided with a second mist collecting portion 66. In other words, the first mist collecting unit 65 is disposed upstream of the third gas passage 64 in the gas flow direction, and the second mist collecting unit 66 is disposed downstream of the third gas passage 64 in the gas flow direction. Has been. Specifically, the first mist collecting unit 65 is disposed at a connecting portion between the first gas passage 62 and the third gas passage 64, and the second mist collecting unit 66 is provided with the second gas passage 63 and the third gas passage. It arrange | positions at 64 connection parts.

  The first mist collecting unit 65 and the second mist collecting unit 66 have substantially the same configuration and are set to have substantially the same aperture ratio. Here, the same aperture ratio does not necessarily have to be the same, and there may be a slight difference. The first mist collecting section 65 and the second mist collecting section 66 are configured by arranging a plurality of folding plates 65a, 66a with gaps of predetermined intervals S1, S2 in the radial direction of the gas passages 62, 63. The folding plates 65a and 66a have at least one bent portion (two in this embodiment), and mist particles contained in the exhaust gas collide with and adhere to the folding plates 65a and 66a. The fine particles are separated from the exhaust gas. Here, the predetermined gap S2 is preferably larger than the predetermined gap S1.

  In this case, the flow rate of the exhaust gas flowing through the exhaust gas recirculation line G4 where the mist separator 49 is arranged varies according to the amount of exhaust gas discharged from the marine diesel engine 11 and the opening of the EGR valve 41. Therefore, the first passage area of the first gas passage 62 and the opening ratio of the first mist collecting portion 65 are set according to the minimum flow rate of the exhaust gas flowing through the exhaust gas recirculation line G4. The passage area and the opening ratio of the second mist collecting unit 66 are set according to the maximum flow rate of the exhaust gas flowing through the exhaust gas recirculation line G4.

  In the mist collecting sections 65 and 66, the mist collecting rate changes according to the gas flow rate (gas flow velocity) of the exhaust gas passing through. Therefore, as shown in FIG. 2, when the exhaust gas G has a small flow rate (low-speed flow), the exhaust gas G flows into the first gas passage 62 having a small passage area. Then, the first mist collecting unit 65 separates and collects the mist m1 from the exhaust gas G for the small flow rate (low speed flow) exhaust gas G. In this case, since the first gas passage 62 is for a small flow rate (low speed flow) gas, the first mist collecting unit 65 appropriately separates the mist m1 contained in the exhaust gas G having a small flow rate (low speed flow). And can be collected.

  On the other hand, as shown in FIG. 3, when the exhaust gas G has a large flow rate (high-speed flow), the exhaust gas G first flows into the first gas passage 62 having a small passage area. Then, the first mist collecting unit 65 separates the mist m1 from the exhaust gas G and collects the large amount (high speed flow) of the exhaust gas G. However, since the first gas passage 62 is for a small flow rate (low-speed flow gas), the first mist collecting unit 65 separates and captures the mist m1 contained in the exhaust gas G having a large flow rate (high-speed flow). Although it can be collected, the fine particles of mist m2 are scattered again on the downstream side. The re-scattered fine particles of the mist m2 have a larger particle size than the fine particles of the mist m1 contained in the exhaust gas G.

  Therefore, the exhaust gas G having a large flow rate (high-speed flow) that has passed through the first mist collecting section 65 flows into the second gas passage 63 having a large passage area. Then, the second mist collecting unit 66 separates the mist m1 from the exhaust gas G and collects the exhaust gas G having a large flow rate (high-speed flow). In this case, since the second gas passage 63 is for a large flow rate (high-speed flow) gas, the second mist collecting unit 66 appropriately separates the mist m2 contained in the exhaust gas G having a large flow rate (high-speed flow). And can be collected. That is, the exhaust gas G flowing from the first gas passage 62 through the third gas passage 64 to the second gas passage 63 is reduced in flow rate due to the passage area being expanded, and becomes a small amount of exhaust gas G. Therefore, the 2nd mist collection part 66 can isolate | separate and collect mist m1, m2 from waste gas G including the re-scattered mist m1.

  As described above, in the mist separator of the present embodiment, the first gas passage 62 having the first passage area and the gas flow in the first gas passage 62 having the second passage area larger than the first passage area. A second gas passage 63 disposed on the downstream side in the direction, a first mist collecting portion 65 disposed in the first gas passage 62, and a second mist collecting portion 66 disposed in the second gas passage 63. Is provided.

  Accordingly, when the first gas passage 62 having a small passage area flows into the first gas passage 62 having a small flow rate (low-speed flow), the first mist collecting unit 65 can appropriately separate and collect the mist from the exhaust gas. On the other hand, when the first gas passage 62 having a small passage area flows into the exhaust gas having a large flow rate (high-speed flow), the first mist collecting unit 65 cannot properly collect the mist from the gas, and the mist is re-scattered. Resulting in. However, after that, since the exhaust gas flows into the second gas passage 63 having a large passage area, the gas flow rate (gas flow velocity) decreases, and the mist including the mist re-scattered by the second mist collecting unit 66 is appropriately removed from the exhaust gas. It can be collected separately. As a result, even if the gas flow rate (gas flow velocity) fluctuates, the mist can be properly collected by the mist collecting portions 65 and 66 disposed in the gas passages 62 and 63 having two kinds of passage areas.

  In the mist separator of the present embodiment, a third gas passage 64 whose passage area gradually increases is provided between the first gas passage 62 and the second gas passage 63, and the first mist collecting portion 65 is connected to the third gas. The second mist collecting portion 66 is disposed on the upstream side in the gas flow direction from the passage 64, and the second mist collecting portion 66 is disposed on the downstream side in the gas flow direction from the third gas passage 64. Therefore, the gas flow rate can be gradually reduced from the third gas passage 64, and even if the exhaust gas has a large flow rate (high-speed flow), the gas flow rate is appropriately reduced in the second gas passage 63 to reduce the flow rate (low-speed). The second mist collecting unit 66 can efficiently collect mist.

  In the mist separator of the present embodiment, the first mist collecting unit 65 and the second mist collecting unit 55 are set to substantially the same aperture ratio. Therefore, by making the configurations of the first mist collecting unit 65 and the second mist collecting unit 66 common, the cost can be reduced.

  In the mist separator according to the present embodiment, the first mist collecting unit 65 and the second mist collecting unit 66 include a plurality of folded plates 65a, 66a having gaps S1, S2 with a predetermined interval in the radial direction of the gas passages 62, 63. Are arranged and configured. Therefore, the mist can be separated and collected from the gas efficiently with a simple configuration.

  In the exhaust gas treatment apparatus of the present embodiment, part of the exhaust gas discharged from the marine diesel engine 11 is compressed by the supercharger 21 and recirculated to the marine diesel engine 11 as combustion air. Line G4, a scrubber 42 that removes harmful substances by injecting water into the exhaust gas flowing through the exhaust gas recirculation line G4, and a mist separator 49 that separates mist from the exhaust gas after the harmful substances are removed by the scrubber 42 And have.

  Accordingly, a part of the exhaust gas discharged from the marine diesel engine 11 flows into the exhaust gas recirculation line G4, water is injected by the scrubber 42, harmful substances are removed, and the mist is separated by the mist separator 49. After being removed, it is compressed by the supercharger 21 and recirculated to the marine diesel engine 11 as combustion air. The mist separator 49 is provided with mist collecting portions 65 and 66 in two gas passages 62 and 63 having different passage areas, respectively, so that the amount of exhaust gas (exhaust gas flow velocity) flowing in the gas recirculation line G4 varies. The first and second mist collecting portions 65 and 66 arranged in the gas passages 62 and 63 having two kinds of passage areas can appropriately separate and collect the mist from the exhaust gas. As a result, appropriate exhaust gas can be recirculated to the marine diesel engine 11.

  In the above-described embodiment, the first mist collection unit 65 and the second mist collection unit 66 have substantially the same aperture ratio, but may have different aperture ratios. Moreover, although the 1st mist collection part 65 and the 2nd mist collection part 66 were comprised by arrange | positioning the several folding plates 65a and 66a at predetermined intervals, it is not limited to this structure, For example, A mesh structure or a perforated plate structure may be used.

  In the above-described embodiment, two types of gas passages 62 and 63 set to different passage areas are connected and the mist collecting portions 65 and 66 are provided in the gas passages 62 and 63. Three or more set gas passages may be connected, and a mist collecting part may be provided in each gas passage. In this case, it is desirable to arrange a gas passage having a larger passage area toward the downstream side in the flow direction of the exhaust gas.

  Moreover, in embodiment mentioned above, although demonstrated using the main engine as a marine diesel engine, it is applicable also to the diesel engine used as a generator.

  In the above-described embodiment, the scrubber 42 and the mist separator 49 are provided in the exhaust gas recirculation line G4. However, the present invention is not limited to this configuration. The mist separator of the present invention can appropriately separate mist from gas flowing through a gas flow path with a varying gas flow rate (gas flow velocity), and can be applied to each gas processing facility such as a boiler. .

DESCRIPTION OF SYMBOLS 11 Marine diesel engine 21 Supercharger 42 Scrubber 49 Mist separator 61 Gas passage 62 First gas passage 63 Second gas passage 64 Third gas passage 65 First mist collection part 65a Folding plate 66 Second mist collection part 66a Folding plate G exhaust gas m1, m2 mist (fine particles)
S1, S2 gap

Claims (6)

A first gas passage having a first passage area;
A second gas passage having a second passage area larger than the first passage area and disposed downstream in the gas flow direction in the first gas passage;
A first mist collecting part disposed in the first gas passage;
A second mist collecting portion disposed in the second gas passage;
The mist separator characterized by having.   A third gas passage having a passage area gradually expanding is provided between the first gas passage and the second gas passage, and the first mist collecting portion is upstream of the third gas passage in the gas flow direction. 2. The mist separator according to claim 1, wherein the second mist collecting unit is disposed on a downstream side of the third gas passage in a gas flow direction.   The mist separator according to claim 1 or 2, wherein the first mist collecting unit and the second mist collecting unit are set to have the same aperture ratio.   The said 1st mist collection part and the said 2nd mist collection part are comprised by the some folding plate being arrange | positioned with the clearance gap of the predetermined space | interval in the radial direction of the said gas passage. Item 4. The mist separator according to any one of items 3. An exhaust gas recirculation line that recirculates part of the exhaust gas discharged from the marine diesel engine as combustion air;
A scrubber for injecting water to the exhaust gas flowing through the exhaust gas recirculation line;
The mist separator according to any one of claims 1 to 4, wherein the mist is separated from the exhaust gas that has passed through the scrubber.
An exhaust gas treatment apparatus comprising:   A ship having the exhaust gas treatment apparatus according to claim 5.

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