WO2016132570A1 - Demister, exhaust gas recirculating system, and marine engine provided with same - Google Patents

Abstract

A demister (19A) is coupled to a downstream side of a scrubber (18) which uses droplets (L) to wash and collect particulate matter contained in recirculated exhaust gas (G) recirculating through an engine, and separates out the droplets (L) remaining in the recirculated exhaust gas (G) in the form of mist. The demister (19A) has a cyclone structure equipped with: a cylindrical casing (23) the axial direction of which lies in the vertical direction; a recirculated exhaust gas introduction port (233) which is provided in an upper portion outer peripheral surface of the casing (23) and which introduces the recirculated exhaust gas (G) from a tangential direction into the interior of the casing (23); a recirculated exhaust gas discharge port (234) which is provided in an upper portion of the casing (23), in a position coinciding with the axial center thereof, and which discharges the recirculated exhaust gas (G); and a droplet discharging portion (232) which is provided in a lower portion of the casing (23) and which discharges the droplets (L) that have been separated from the recirculated exhaust gas (G).

Description

Demista, exhaust gas recirculation system, and marine engine equipped with the same

The present invention relates to a demister, an exhaust gas recirculation system, and a marine engine provided with the same.

As disclosed in Patent Documents 1 and 2, etc., many diesel engines are included in the exhaust gas by mixing a part of the exhaust gas with the intake air to reduce the amount of oxygen and lowering the combustion temperature. An exhaust gas recirculation system (EGR: Exhaust Gas Recirculation) is provided to reduce NOx (nitrogen oxide) emissions.

In a marine diesel engine fueled with heavy oil, exhaust gas contains particulate matter, and if the particulate matter is recirculated to the intake side as it is, the engine is adversely affected. For this reason, a scrubber (washing and dust collecting device) is installed for washing and collecting (separating) particulate matter by droplet spray of water to the exhaust gas to be recirculated, and a demister (gas and liquid separation for separating water downstream thereof Device) is provided.

As shown in FIG. 2 and the like of Patent Document 1, the demister has a structure in which an exhaust gas containing water is passed through an element in which a plurality of walls bent in a waveform are arranged in proximity to one another. The water contained in the water is made to collide with the corrugated wall to separate it into gas and liquid. The exhaust gas from which water has been removed by the demister is supplied to the intake side of the engine by a dedicated blower, mixed with the intake air, and supplied to the combustion chamber.

JP 2002-332919 A JP, 2012-237242, A

However, as described above, the conventional demister has a structure in which the droplets contained in the exhaust gas are made to collide with the corrugated wall through the exhaust gas through an element composed of a plurality of walls bent in a corrugated manner so as to separate gas and liquid. The Therefore, there is a problem that pressure loss resistance is large and engine efficiency is reduced. If the distance between the corrugated walls is increased to reduce the pressure drop resistance, the water removal performance is reduced, and the water-containing exhaust gas flows to the intake side of the engine. In particular, in an engine equipped with a supercharger, there has been a concern that this moisture may collide with a high-speed rotating compressor wheel to cause erosion.

The present invention has been made to solve the above-mentioned problems, and a demister and exhaust gas capable of removing droplets such as water contained in recirculated exhaust gas recirculated to the engine side without increasing pressure drop resistance. An object of the present invention is to provide a recirculation system and a marine engine provided with the same.

In order to solve the above-mentioned subject, the present invention adopts the following means.

That is, the demister according to the first aspect of the present invention includes a cylindrical casing having an axial direction along the vertical direction, and an outer peripheral surface provided on the upper outer peripheral surface of the casing to recirculate the droplets from the tangential direction inside the casing. A recirculation exhaust gas inlet for introducing exhaust gas, a recirculation exhaust gas outlet provided at an upper portion of the casing and at a position coinciding with an axial center of the casing for discharging the recirculation exhaust gas, and provided at a lower portion of the casing And a droplet discharge unit for discharging the droplets separated from the recirculated exhaust gas.

According to the above-described demister, the particulate matter is washed and collected by droplets such as water in a scrubber or the like, and the recirculated exhaust gas containing a large amount of droplets is tangentially drawn from the recirculated exhaust gas inlet into the casing of the demister. Flow into the casing to form a swirling flow inside the casing, and the centrifugal separation action separates the droplets.

That is, when the recirculated exhaust gas swirls inside the casing, droplets contained in the recirculated exhaust gas adhere to the inner circumferential wall surface of the casing by centrifugal force, and the downward flow and gravity generated along the inner circumferential surface of the casing Flows downward from the casing and is discharged from the droplet discharge unit.

On the other hand, since the upward flow occurs in the central portion inside the casing, only the recirculated exhaust gas from which the droplets are removed rises and is discharged from the recirculated exhaust gas outlet formed in the upper portion of the casing. Therefore, the exhaust gas containing droplets such as moisture is prevented from flowing to the intake side of the engine, and the generation of erosion on the compressor wheel of the turbocharger can be prevented.

This demister does not lower the engine efficiency because it does not have an element member or the like that increases the pressure loss resistance in the flow path of the recirculated exhaust gas, unlike the demister that separates the recirculated exhaust gas by colliding with the wall etc. .

In the above-described demister, the casing includes a cylindrical portion forming an upper side in the vertical direction, and a conical portion connected to the lower portion of the cylindrical portion and having a cross-sectional diameter perpendicular to the axial direction decreasing from the upper portion to the lower portion. Is preferred.

Inside the casing, the number of revolutions of the swirling flow formed by the recirculating exhaust gas containing the droplets is accelerated as the diameter of the casing becomes smaller, and the centrifugal force acting on the droplets increases. Since the casing has a conical shape in which the diameter of the cross section orthogonal to the axial direction decreases downward, the centrifugal force acting on the recirculating exhaust gas which descends by gravity while rotating is increased, and the recirculated exhaust gas and droplets The gas-liquid separation action is increased. Therefore, the droplets L can be efficiently separated from the recirculated exhaust gas G.

In the demister of the above-described configuration, an electric particle collecting apparatus may be installed at the recirculated exhaust gas outlet to attract the droplets to an electrode by charging the droplets to separate them from the recirculated exhaust gas.

According to the above configuration, the droplets that could not be separated by the centrifugal force inside the demister are charged when passing through the electric particle collector installed at the recirculation exhaust gas outlet, and the electrode of the electric particle collector is charged. Attracted and separated from the recycle exhaust gas. That is, droplets that can not be collected in the casing of the demister are collected by the electric particle collector. Therefore, it is possible to reliably separate the droplets remaining in the recirculated exhaust gas.

In the demister of the above configuration, the recirculated exhaust gas outlet may be provided with a porous droplet separating member.

According to the above configuration, the droplets that can not be collected in the casing of the demister are collected by the droplet separating member. That is, since the droplets contained in the recirculating exhaust gas are separated in two stages of the casing of the demister and the droplet separating member, the droplet separating action of the recirculating exhaust gas can be further enhanced.

In the demister of the above configuration, a plurality of the casings may be connected in series, and the diameter of the cylindrical portion of the downstream casing may be smaller than the diameter of the cylindrical portion of the upstream casing.

According to the above configuration, since the diameter of the downstream side casing is smaller than the diameter of the upstream side casing, the swirling rotational speed of the swirling flow of the recirculation exhaust gas which has flowed out of the upstream side casing and flowed into the downstream side casing is Be accelerated.

Therefore, the rotational speed of the swirling flow in the downstream side casing can be kept high, and the centrifugal force can be maintained to enhance the droplet separating action.

An exhaust gas recirculation system according to a second aspect of the present invention comprises an exhaust gas recirculation passage for extracting a part of exhaust gas discharged from an engine and feeding the exhaust gas as recirculation exhaust gas to the intake side of the engine; A scrubber connected to a passage for washing and collecting particulate matter contained in the recirculated exhaust gas by droplets; and a demister according to any of the foregoing, connected downstream of the scrubber. There is.

According to the exhaust gas recirculation system configured as described above, the recirculation exhaust gas flowing through the exhaust gas recirculation passage is first cleaned and collected by the droplets of water and the like in the scrubber. The recycled and collected exhaust gas contains a large amount of droplets, and the recycled exhaust gas containing the droplets then flows tangentially into the interior of the demister to form a swirling flow, and its centrifugal separation action The droplets are separated by

That is, the recirculated exhaust gas swirls inside the casing of the demister, and the centrifugal force at that time causes droplets contained in the recirculated exhaust gas to adhere to the inner peripheral wall surface of the casing and flow downward, and only the recirculated exhaust gas flows over the demister It is discharged from the recirculated exhaust gas outlet formed in the Therefore, the exhaust gas containing droplets such as moisture is prevented from flowing to the intake side of the engine, and the generation of erosion on the compressor wheel of the turbocharger can be prevented.

This demister does not lower the engine efficiency because an element member or the like that increases the pressure loss resistance is not installed in the flow path of the recirculated exhaust gas, unlike the one in which the recirculated exhaust gas collides with the wall or the like.

In the exhaust gas recirculation system configured as described above, a centrifugal blower that feeds the recirculated exhaust gas to the demister is connected between the scrubber and the demister, and the centrifugal blower is discharged tangentially from the centrifugal blower. The recirculated exhaust gas may be connected tangentially to the demister.

According to the exhaust gas recirculation system configured as described above, particulate matter is washed and collected by droplets such as water in the scrubber, and the recirculated exhaust gas containing a large number of droplets is then sent to the demister by the centrifugal blower and is The remaining droplets are separated.

Inside the centrifugal blower, due to the centrifugal force accompanying the rotation of the blower fan, the droplets contained in the recirculated exhaust gas adhere to the inner peripheral wall surface of the blower casing and flow to the outlet side while forming a liquid film (liquid vein) layer . The flow of the liquid film layer is discharged tangentially from the centrifugal blower together with the recirculated exhaust gas, and flows into the interior of the demister from the tangential direction.

For this reason, inside the demister, there is a tendency for droplets to flow along the inner peripheral wall surface of the demister from the beginning when the recirculated exhaust gas flows in, and the air separation is excellent due to the centrifugal separation action of the swirling flow inside the demister. The liquid separation action is exhibited. Therefore, the exhaust gas containing droplets such as moisture is prevented from flowing to the intake side of the engine, and the generation of erosion on the compressor wheel of the turbocharger can be prevented.

In the exhaust gas recirculation system configured as described above, a gas-liquid separator may be provided between the scrubber and the centrifugal blower.

According to the exhaust gas recirculation system configured as described above, particulate matter is washed and collected by droplets such as water in the scrubber, and the recirculation exhaust gas containing a large number of droplets is roughly separated into droplets in the gas-liquid separator. Then, it is sent to the demister by a centrifugal blower, and the remaining droplets are further separated in the demister. Therefore, the droplets contained in the recirculated exhaust gas can be reliably separated.

In the exhaust gas recirculation system configured as described above, a drain pipe of the droplet separated from the recirculated exhaust gas by the demister may be connected to the droplet storage tank of the gas-liquid separator.

According to the above configuration, in the demister in which the pressure of the centrifugal blower acts, the droplets separated from the recirculated exhaust gas flow to the droplet storage tank of the gas-liquid separator in which the pressure of the centrifugal blower does not act. Therefore, due to the pressure difference, the droplets collected in the demister can be favorably flowed to the droplet storage tank of the gas-liquid separator, the droplet removal performance is improved, and the surplus related to the discharge of droplets is obtained. Power can be reduced.

Furthermore, a marine engine according to the present invention includes the exhaust gas recirculation system according to any one of the above aspects.

According to this marine engine, droplets such as water contained in the recirculated exhaust gas to be recirculated to the engine side can be removed without increasing the pressure loss resistance, that is, without reducing the engine efficiency. It is possible to prevent the generation of erosion on the compressor impeller of the turbocharger due to the droplets contained in the exhaust gas.

As described above, according to the demister, the exhaust gas recirculation system, and the marine engine provided with the same according to the present invention, the pressure drop resistance is increased by droplets such as water contained in the recirculated exhaust gas recirculated to the engine side. It can be removed without

It is a schematic block diagram of the exhaust gas recirculation system concerning a 1st embodiment of the present invention. It is a perspective view of a demister concerning a 1st embodiment of the present invention. It is a longitudinal cross-sectional view of a demister concerning a 1st embodiment of the present invention. It is a perspective view of a demister concerning a 2nd embodiment of the present invention. It is a longitudinal cross-sectional view of the demister which concerns on 2nd Embodiment of this invention. It is a longitudinal cross-sectional view of the demister which concerns on 3rd Embodiment of this invention. It is a schematic block diagram of the exhaust gas recirculation system concerning a 4th embodiment of the present invention. It is a perspective view of a demister concerning a 4th embodiment of the present invention. It is a schematic block diagram of the exhaust gas recirculation system concerning a 5th embodiment of the present invention. It is a cross-sectional view of the blower and the demister seen from the X arrow direction of FIG. It is a schematic block diagram of the exhaust gas recirculation system concerning a 6th embodiment of the present invention.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.

First Embodiment
FIG. 1 is a schematic configuration view showing a first embodiment of the present invention.
The marine engine 1 according to the first embodiment includes an engine body 2, a turbocharger 3, and an exhaust gas recirculation system 4A. The engine body 2 is, for example, a two-stroke diesel engine, and includes a plurality of cylinders 2a, and a scavenging chamber 5 is provided on one side thereof and an exhaust static pressure chamber 6 is provided on the other side.

In the turbocharger 3, a turbine 7 and a compressor 8 are provided coaxially, an exhaust gas supply pipe 9 extending from an exhaust static pressure chamber 6 is connected to an inlet side of the turbine 7, and an exhaust gas discharge pipe extending from an outlet side of the turbine 7 The other end of 10 is open to the outside. A fluid suction pipe 11 is connected to the inlet side of the compressor 8, and a compressed fluid supply pipe 12 extending from the outlet side of the compressor 8 is connected to the scavenging chamber 5.

When the marine engine 1 operates, the exhaust gas discharged from the cylinder 2 a of the engine body 2 flows into the static exhaust pressure chamber 6. The exhaust gas having flowed into the static exhaust pressure chamber 6 is supplied to the turbine 7 through the exhaust gas supply pipe 9 to drive the turbine 7. When the turbine 7 is driven, a compressor 8 provided coaxially with the turbine 7 is rotated, and a fluid is sucked from the fluid suction pipe 11 and compressed by a compressor wheel (not shown), and this compressed fluid is compressed fluid The gas is supplied from the supply pipe 12 to the scavenging chamber 5. As a result, the cylinder 2a is filled with a high density fluid, the combustion efficiency is improved, and the engine efficiency is improved.

An exhaust gas recirculation system 4A according to the first embodiment includes an EGR valve 16, an exhaust gas recirculation passage 17, a scrubber 18, a demister 19A, and a blower 20. The exhaust gas recirculation system 4A is a pollution reduction device that completely drives the turbine 7 and extracts a part of the exhaust gas passing through the exhaust gas discharge pipe 10 and mixes it with the compressed fluid to the engine body 2 as the recirculation exhaust gas G. As a result, the amount of oxygen in the compressed fluid is reduced, the combustion temperature is reduced, and the amount of NOx (nitrogen oxide) contained in the exhaust gas is reduced.

The exhaust gas recirculation passage 17 is branched from the middle of the exhaust gas discharge pipe 10, an EGR valve 16 is provided in the vicinity of the branch portion, and the other end of the exhaust gas recirculation passage 17 is connected to the air intake pipe 11. A scrubber 18, a demister 19A, and a blower 20 are sequentially connected in the middle of the exhaust gas recirculation passage 17. By adjusting the opening degree of the EGR valve 16 or the rotational speed of the blower 20, the amount of the recirculated exhaust gas G extracted from the exhaust gas discharge pipe 10 is adjusted according to the operating condition of the marine engine 1.

The scrubber 18 is a washing and collecting device for washing and collecting (separating) particulate matter contained in the recirculated waste gas G by spraying droplets such as water on the recirculated waste gas G passing therethrough. .
The demister 19A separates the droplets L (see FIG. 3) remaining in the form of mist in the recirculated exhaust gas G after the particulate matter is washed and collected by the droplets in the scrubber 18.
The blower 20 feeds the recirculated exhaust gas G from which the droplets L have been removed in the demister 19A to the air intake pipe 11 side.

As shown in FIGS. 2 and 3, the demister 19A according to the first embodiment includes a cylindrical casing 23 whose axial direction extends in the vertical direction, an outlet pipe 24, and a droplet storage tank 27.

The casing 23 includes a cylindrical portion 23a, a conical portion 23b, and a top plate 23c. The cylindrical portion 23a has a cylindrical shape with a constant diameter. The conical portion 23b is connected to the lower side of the cylindrical portion 23a and is orthogonal to the axial direction from the large end portion 231 forming one end in the axial direction to the small end portion 232 (droplet discharging portion) forming the other end in the axial direction It has a conical tubular shape whose cross-sectional diameter decreases, and its large end 231 is connected to the cylindrical portion 23a. The top plate 23c is provided at an end (upper part) of the cylindrical portion 23a opposite to the conical portion 23b.

A recirculation exhaust gas inlet port 233 for introducing the recirculation exhaust gas G in the tangential direction is formed inside the casing 23 on the upper outer peripheral surface of the casing 23, that is, the outer peripheral surface of the cylindrical portion 23a here. An exhaust gas recirculation passage 17 is tangentially connected to the recirculation exhaust gas inlet port 233. The recirculated exhaust gas G flowing from the exhaust gas recirculation passage 17 flows into the casing 23 along the tangential direction of the cylindrical portion 23 a from the recirculated exhaust gas inlet port 233.

A recirculated exhaust gas outlet 234 is bored in the upper part of the casing 23 and at a position coinciding with the axial center, that is, in the central part of the top plate 23c here, and the outlet pipe 24 is inserted therein. It is fixed along. The upper end side of the outlet pipe 24 is connected to the blower 20 side, and the lower end of the outlet pipe 24 is located inside the casing 23.

As shown in FIG. 3, the demister 19A causes the recirculation exhaust gas G to flow tangentially into the casing 23 from the exhaust gas recirculation passage 17 (recirculation exhaust gas inlet 233) to form a swirling flow R, and the centrifugal force thereof. It has a cyclone structure that separates the droplets L remaining in the recirculated exhaust gas G. The recirculated exhaust gas G from which the droplets L have been separated is discharged from the recirculated exhaust gas outlet 234 (outlet pipe 24) of the casing 23 and flows to the blower 20. In addition, the droplets L separated from the recirculated exhaust gas G are discharged from the small end 232.

The droplet storage tank 27 is, for example, a cylindrical tank having a diameter larger than the small end 232 of the conical portion 23b, and is connected to the bottom (small end 232) of the casing 23 (conical portion 23b) via the connecting pipe 236. Are connected. The droplet L separated from the recirculated exhaust gas G inside the casing 23 is collected in the droplet storage tank 27. The connection pipe 236 may be omitted, and the droplet storage tank 27 may be directly connected to the lower portion (recirculation exhaust gas outlet 234) of the conical portion 23b.

The cylindrical portion 23a, the conical portion 23b and the top plate 23c may be integrated, and it is not essential to provide both the cylindrical portion 23a and the conical portion 23b. For example, the cylindrical portion 23a is omitted, the top plate 23c is provided at the large end 231 of the conical portion 23b, and the recirculation exhaust gas inlet port 233 is bored in the upper outer peripheral surface of the conical portion 23b to connect the exhaust gas recirculation passage 17 It is good also as composition.

As described above, the demister 19A according to the first embodiment includes the casing 23 including the cylindrical portion 23a and the conical portion 23b. In the casing 23, the recirculation exhaust gas inlet port 233 is formed on the outer peripheral surface of the cylindrical portion 23a forming the upper part, and the exhaust gas recirculation passage 17 is provided in the recirculation exhaust gas inlet port 233. It is connected to flow along the tangential direction.

An exhaust gas recirculation passage 17 is connected to the recirculation exhaust gas inlet port 233 along the tangential direction of the cylindrical portion 23a. For this reason, as shown in FIG. 3, the recirculated exhaust gas G flows tangentially from the exhaust gas recirculation passage 17 into the casing 23 to form a swirling flow R. A large amount of droplets L mixed in the recirculating exhaust gas G and remaining in the form of mist are separated from the recirculating exhaust gas G by the centrifugal force acting on the swirling flow R.

That is, when the recirculating exhaust gas G swirls inside the casing 23, the droplets L contained in the recirculating exhaust gas G adhere to the inner peripheral wall surface of the casing 23 by the centrifugal force. The droplets L flow downward of the casing 23 by the downward flow and gravity generated along the inner circumferential surface of the casing 23, and are discharged from the droplet discharge portion 232 and collected in the droplet storage tank 27. On the other hand, since the upward flow is generated in the central portion inside the casing 23, only the recirculated exhaust gas G from which the droplet L is removed rises and is discharged from the recirculated exhaust gas outlet 234 at the top of the casing 23.

Inside the casing 23, the swirling rotational speed of the swirling flow R formed by the recirculating exhaust gas G including the droplet L is accelerated as the diameter of the casing 23 becomes smaller, and the centrifugal force acting on the droplet L increases ( Because of the swirling speed x radius = constant in free vortices). The conical portion 23 b forming the lower portion of the casing 23 is formed to decrease in diameter toward the side (small end portion 232 side) axially opposite to the cylindrical portion 23 a. For this reason, the centrifugal force acting on the droplet L which descends by gravity while swirling with the recirculating exhaust gas G inside the casing 23 increases from the large end 231 side to the small end 232 side of the conical portion 23b. The gas-liquid separation action of the recirculated exhaust gas G and the droplets L is increased. Therefore, the droplets L can be efficiently separated from the recirculated exhaust gas G.

Therefore, it is possible to suppress the recirculation exhaust gas G from flowing to the supercharged engine side while containing the droplets L. As a result, the occurrence of erosion due to the collision of the droplet L with the impeller of the compressor 8 can be prevented.

The demister 19A is different from the one in which the recirculation exhaust gas G collides with the wall etc., and no element member or the like that increases the pressure loss resistance is installed in the flow path of the recirculation exhaust gas G, so the flow of the recirculation exhaust gas G is blocked. Can be suppressed. For this reason, the efficiency reduction of the engine body 2 can be suppressed.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to FIGS. 4 and 5.
The demister 19B according to the second embodiment has a point at which the electric aggregater 30 is provided at the recirculation exhaust gas outlet 234 of the casing 23 through the outlet pipe 24, and the outlet pipe 24 has a lower outlet pipe 24a and an upper outlet pipe 24b. And is different from the demister 19A of the first embodiment in that it is divided into two. The configuration of the other parts is the same as that of the demister 19A of the first embodiment, and therefore the same reference numerals are given to the respective parts and redundant description will be omitted.

As shown in FIGS. 4 and 5, the electric granulating apparatus 30 is housed in a box-like housing 31, a cylindrical electrode tube 32 housed inside the housing 31, and inside the housing 31, and A negative electrode 33 provided at the axial center of the electrode tube 32 and a drain tube 38 are provided. The electric particle collector 30 separates the droplet L from the recirculated exhaust gas G by charging the droplet L contained in the recirculated exhaust gas G and causing the electrode tube 32 to adsorb the droplet L.

A recirculated exhaust gas inlet hole 31a is formed on the lower surface of the housing 31 of the electric granulator 30, and a recirculated exhaust gas outlet hole 31b is formed on the upper surface.
The lower outlet pipe 24 a is inserted into the recirculation exhaust gas outlet 234 drilled in the top plate 23 c of the casing 23 and fixed along the axial center of the casing 23. The lower end portion of the lower outlet pipe 24a extends to near the axially middle portion inside the casing 23, and the upper end portion is inserted into and fixed to the recirculation exhaust gas inlet hole 31a of the housing 31. The upper end portion of the lower outlet pipe 24 a protrudes above the lower surface of the housing 31.
The lower end portion of the upper outlet pipe 24b is inserted into and fixed to the recirculation exhaust gas outlet hole 31b of the housing 31. The lower end portion of the upper outlet pipe 24b protrudes below the upper surface of the housing 31, and the upper end portion of the upper outlet pipe 24b is connected to the blower 20 side.

As shown in FIG. 4, for example, in the electrode tube 32, two semi-cylindrical plates 32a and 32b (electrodes) formed by curving a porous plate are fixed to face each other, and an insulating member 32c is interposed therebetween. Are formed in a cylindrical shape. These half- cylindrical plates 32a and 32b function as plus electrodes.

The electrode tube 32 radially spaces the intermittent portion of the outlet tube 24 inside the housing 31, that is, the space between the lower outlet tube 24a and the upper outlet tube 24b, to both the tubes 24a and 24b. I am surrounded. As shown in FIGS. 4 and 5, the lower end of the electrode tube 32 is lower than the upper end of the lower outlet pipe 24a, and the upper end of the electrode tube 32 is higher than the lower end of the upper outlet pipe 24b. That is, the electrode pipe 32 axially overlaps the upper end portion of the lower outlet pipe 24 a and the lower end portion of the upper outlet pipe 24 b in the housing 31. The upper and lower end portions of the electrode tube 32 are separated from the upper and lower surfaces of the housing 31.

As shown in FIG. 5, the negative electrode 33 is disposed in the inner central region of the electrode tube 32, and between the two semi-cylindrical plates 32 a and 32 b and the negative electrode 33, the power supply line 34 and the power supply 35. And a high voltage current of direct current is applied.

The drain pipe 38 extends from the bottom of the housing 31 and is connected to the droplet storage tank 27. The drain pipe 38 is a pipe for discharging the droplets L separated from the recirculated exhaust gas G by the electric particle collector 30 into the droplet storage tank 27.

As described above, in the demister 19B according to the second embodiment, as shown in FIG. 5, the recirculated exhaust gas G that has flowed from the exhaust gas recirculation passage 17 through the recirculated exhaust gas inlet 233 of the demister 19B into the casing 23 Similar to the demister 19A in the first embodiment, a swirling flow R is formed in the casing 23, and the remaining droplets L are separated by the centrifugal separation action. The droplets L separated here flow downward and are collected in the droplet storage tank 27.

The droplets L which can not be separated from the recirculated exhaust gas G by the centrifugal force inside the casing 23 try to flow toward the blower 20 through the outlet pipe 24 (lower outlet pipe 24a, upper outlet pipe 24b). It separates in the electric particle collector 30 provided in the outlet pipe 24.
That is, the liquid contained in the recirculated exhaust gas G passing through the outlet pipe 24 by the direct current high voltage current applied between the electrode tube 32 ( semi-cylindrical plates 32a and 32b) which is the positive electrode and the negative electrode 33 The drop L is charged with a negative charge. The droplet L is attracted to and attached to the electrode tube 32 which is a positive electrode, and thus it is forcibly separated from the recirculated exhaust gas G and attached to the inner peripheral surfaces of the semi-cylindrical plates 32a and 32b.

Since a space is provided between the inner circumferential surface of the semi-cylindrical plates 32a and 32b and the outer periphery of the outlet tube 24 (24a and 24b), the droplets attached to the inner circumferential surface of the semi-cylindrical plates 32a and 32b Even if L flows downward, it does not enter the lower outlet pipe 24 a (the casing 23), and the droplet L flows from the bottom of the housing 31 through the drain pipe 38 to the droplet reservoir 27.

By providing the electric granulating device 30, the droplets L remaining in the recirculated exhaust gas G can be separated reliably, and the generation of erosion on the compressor wheel of the turbocharger 3 can be prevented. In the present embodiment, the semi-cylindrical plates 31a and 31b are described as being porous plates, but the plates may be non-perforated plates, wire nets or the like. By making the semi-cylindrical plates 31a and 31b into a porous plate or a wire net, the attracted droplet L also passes through the holes of the semi-cylindrical plates 31a and 31b and falls to the bottom of the housing 31. Recovery of L can be facilitated.

Third Embodiment
Next, a third embodiment of the present invention will be described with reference to FIG.
The demister 19C according to the third embodiment has a point that the droplet separating member 40 is provided at the recirculation exhaust gas outlet 234 of the casing 23 via the outlet pipe 24, and the outlet pipe 24 has the enlarged diameter portion 24c and the lower outlet. It differs from the demister 19A of the first embodiment in that it is divided into a pipe 24a and an upper outlet pipe 24b. The configuration of the other parts is the same as that of the demister 19A of the first embodiment, and therefore the same reference numerals are given to the respective parts and redundant description will be omitted.

The outlet pipe 24 includes a lower outlet pipe 24a fixed to the casing 23, an enlarged diameter portion 24c connected to the upper end of the lower outlet pipe 24a, and an upper outlet pipe 24b connected on the enlarged diameter portion 24c. And is configured. The upper outlet pipe 24b is connected to the blower 20 side. The diameter of the enlarged diameter portion 24c is increased in a tapered shape from the lower outlet pipe 24a side and becomes a maximum diameter and continues for a predetermined length, and then is reduced in diameter toward the upper outlet pipe 24b side . The maximum diameter of the enlarged diameter portion 24c is, for example, about twice the diameter of the lower outlet pipe 24a and the upper outlet pipe 24b, but this ratio may be changed as appropriate.

The droplet separating member 40 is accommodated in the portion of the largest diameter of the enlarged diameter portion 24c. The droplet separating member 40 is formed of a porous material, and as the material thereof, one obtained by compressing metal fibers, one obtained by arranging metal wires in a matrix, etc. have good air permeability. Although other porous materials may be used. As described above, by providing the enlarged diameter portion 24 c in the middle portion of the outlet pipe 24 and installing the droplet separating member 40 in the portion of the largest diameter, the surface area of the droplet separating member 40 can be increased.

According to the above configuration, the droplets L which can not be separated from the recirculated exhaust gas G in the casing 23 of the demister 19C can be collected by being attached to the droplet separating member 40. The collected droplets L flow down the outlet pipe 24 (lower outlet pipe 24 a) by gravity and pass through the casing 23 and are collected in the droplet storage tank 27. Therefore, the droplet L contained in the recirculated exhaust gas G can be separated in two steps of the casing 23 of the demister 19C and the droplet separating member 40, and the droplet separating function of the recirculated exhaust gas G can be further enhanced. Can.

The droplet separating member 40 provided in the enlarged diameter portion 24 c of the outlet pipe 24 has good air permeability because of its large surface area, and the air flow resistance of the recirculated exhaust gas G passing through the droplet separating member 40 It is hard to generate pressure loss in the flow of recirculation exhaust gas G.

Fourth Embodiment
Next, a fourth embodiment of the present invention will be described with reference to FIGS. 7 and 8.
An exhaust gas recirculation system 4B shown in FIG. 7 differs from the exhaust gas recirculation system 4A of the first embodiment in that a demister 19D in which a plurality of casings 23A and 23B are connected in series is provided. The configuration of the other parts is the same as that of the exhaust gas recirculation system 4A of the first embodiment, so the same reference numerals will be given to the respective parts and redundant explanations will be omitted.

As shown in FIG. 8, the demister 19D has a configuration in which the upstream side casing 23A and the downstream side casing 23B are connected in series, and the downstream side of the diameter (Da) of the cylindrical portion 23Aa of the upstream side casing 23A. The diameter (Db) of the cylindrical portion 23Ab of the casing 23B is set small. The shapes and structures of the upstream side casing 23A and the downstream side casing 23B are the same as those of the demister 19A in the first embodiment, and droplet reservoirs 27a and 27b are provided in the lower part of each.

As shown in FIG. 7, an exhaust gas recirculation passage 17 branched from the exhaust gas discharge pipe 10 is connected to the upstream side casing 23A. As shown in FIG. 8, the exhaust gas recirculation passage 17 is connected along a tangential direction to a recirculation exhaust gas inlet port 233a formed on the upper outer peripheral surface of the upstream side casing 23A. Therefore, the recirculated exhaust gas G flowing from the scrubber 18 through the exhaust gas recirculation passage 17 is introduced into the upstream side casing 23A from the tangential direction.

An outlet pipe 24a extending upward from the recirculation exhaust gas outlet 234a formed at the center of the upper surface of the upstream casing 23A is horizontally curved and formed on the upper outer peripheral surface of the downstream casing 23B. It is connected along a tangential direction to the circulating exhaust gas inlet 233b. Therefore, the recirculated exhaust gas G flowing from the upstream side casing 23A through the outlet pipe 24a is introduced into the downstream side casing 23B in the tangential direction. Further, an outlet pipe 24b extending upward from a recirculated exhaust gas outlet 234b formed at the center of the upper surface of the downstream side casing 23B is connected to the blower 20 side.

In the exhaust gas recirculation system 4B and the demister 19D configured as described above, the recirculation exhaust gas G containing the droplets L in the form of mist after the particulate matter is washed and collected (separated) by the scrubber 18 17 from the tangential direction into the first casing 23A of the demister 19D. Thereby, a swirling flow R as shown in FIG. 3 is formed inside the first casing 23A. A large amount of droplets L mixed in the recirculating exhaust gas G and remaining in the form of mist are separated from the recirculating exhaust gas G by the centrifugal force acting on the swirling flow R. The separated droplets L adhere to the inner wall surface of the first casing 23A, flow downward, and are collected in the droplet storage tank 27a.

The droplets L not separated from the recirculated exhaust gas G in the first casing 23A exit from the outlet pipe 24a together with the recirculated exhaust gas G and enter the second casing 23B in a tangential direction, even in the second casing 23B. Similarly, a swirling flow R is formed. Here too, the droplets L are separated from the recirculated exhaust gas G by centrifugal force and flow downward and are collected in the droplet storage tank 27b.

Thus, the upstream casing 23A and the downstream casing 23B of the demister 19D both cause the recirculated exhaust gas G to flow in the tangential direction to form the swirling flow R, and the liquid remaining in the recirculated exhaust gas G due to the centrifugal force. It has a cyclone structure that separates the droplets L. Moreover, the outlet pipe 24a of the upstream side casing 23A has a two-stage cyclone structure in which it flows into the downstream side casing 23B in a tangential direction.

According to this configuration, since the diameter Db of the cylindrical portion 23Ab of the downstream side casing 23B is smaller than the diameter Da of the cylindrical portion 23Aa of the upstream side casing 23A, the downstream side casing exits from the upstream side casing 23A. The swirling rotational speed of the swirling flow R of the recirculated exhaust gas G that has flowed into 23B is accelerated.

Therefore, the rotational speed of the swirling flow R in the downstream side casing 23B is kept high, the centrifugal force is maintained to enhance the separation action of the droplets L, and the generation of erosion on the compressor wheel of the turbocharger 3 is effective. Can be prevented. The electric particle collector 30 shown in FIGS. 4 and 5 or the droplet separating member 40 shown in FIG. 6 may be installed on at least one of the casings 23A and 23B. Also, three or more casings may be connected in series.

Fifth Embodiment
Next, a fifth embodiment of the present invention will be described with reference to FIG. 9 and FIG.
In an exhaust gas recirculation system 4C shown in FIG. 9, a gas / liquid separator 45, a centrifugal blower 50, and a demister 19E are sequentially connected downstream of the scrubber 18 in the exhaust gas recirculation passage 17 branched from the exhaust gas discharge pipe 10. And the exhaust gas recirculation system 4A of the first embodiment. The configuration of the other parts is the same as that of the exhaust gas recirculation system 4A of the first embodiment, so the same reference numerals will be given to the respective parts and redundant explanations will be omitted.

The gas-liquid separator 45 connected to the downstream side of the scrubber 18 has, for example, a structure in which the recirculation exhaust gas G passes through an internal element in which a plurality of wire mesh-like or porous droplet separation plates 45 a are arranged in parallel. As a result, droplets of water or the like remaining in the form of mist in the recirculated exhaust gas G collide with the droplet separating plate 45 a and are separated into gas and liquid. At the bottom of the gas-liquid separator 45, a droplet storage tank 45b is provided.

The centrifugal blower 50 feeds the recirculated exhaust gas G whose droplets are separated by the gas-liquid separator 45 to the intake side of the marine engine 1, that is, the demister 19E side. The demister 19E has a cyclone structure including a cylindrical (conical) casing 23 connected to the downstream side of the centrifugal blower 50 and further separating the droplets L remaining in the recirculated exhaust gas G discharged from the centrifugal blower 50. is there. The structure of the demister 19E is the same as that of the demister 19A of the first embodiment shown in FIGS. 2 and 3, and thus the description of its configuration and operation is omitted.

As shown in FIG. 10, the demister 19E is disposed such that the recirculated exhaust gas G discharged from the centrifugal blower 50 in the tangential direction flows into the demister 19E from the tangential direction. The centrifugal blower 50 has a structure in which a blower fan 50b is axially supported within the blower casing 50a, and the blower casing 50a and the demister 19E are connected by, for example, a connection passage 51 disposed horizontally. The connection passage 51 is tangentially connected to the blower casing and the casing of the demister 19E in plan view (see FIG. 10).

In the exhaust gas recirculation system 4C configured as described above, the recirculation exhaust gas G flowing through the exhaust gas recirculation passage 17 is first stripped of particulate matter by spraying droplets such as water in the scrubber 18. Thus, the recirculated exhaust gas G washed and collected by the scrubber 18 contains a large amount of droplets. The recirculated exhaust gas G containing the droplets first flows to the gas-liquid separator 45 where the droplets are roughly separated. The separated droplets are collected in a droplet storage tank 45 b provided at the bottom of the gas-liquid separator 45.

Next, the recirculated exhaust gas G is sent to the demister 19E by the centrifugal blower 50, and flows tangentially into the demister 19E of the cyclone structure to form a swirling flow R, as shown in FIG. The remaining droplet L is further separated by. The droplets L separated here are collected in the droplet storage tank 27 (see FIG. 9).

As shown in FIG. 10, inside the centrifugal blower 50, the droplets L included in the recirculated exhaust gas G adhere to the inner peripheral wall surface of the blower casing 50a by the centrifugal force accompanying the rotation of the blower fan 50b, The liquid film flows to the outlet side (demista 19E side) while forming the layer LF. The flow of the liquid (liquid film) layer LF is discharged from the centrifugal blower 50 in the tangential direction together with the recirculated exhaust gas G, and flows into the inside of the demister 19E having a cyclone structure from the tangential direction.

For this reason, in the interior of the demister 19E, the droplets L tend to flow along the inner circumferential wall surface of the demister 19E from the beginning of the inflow of the recirculated exhaust gas G. And, together with the centrifugal separation action of the swirling flow R generated by the cyclone structure, an excellent gas-liquid separation action is exhibited. Therefore, it is suppressed that the recirculation | reflux waste gas G flows into the supercharger 3 side, containing the droplet L, such as a water | moisture content, and it can prevent that an erosion generate | occur | produces in a compressor wheel.

According to the exhaust gas recirculation system 4D, the recirculated exhaust gas G containing the droplets L is first roughly separated from the droplets L in the gas-liquid separator 45 and then sent to the demister 19E by the centrifugal blower 50 to be left Droplets L are further separated. For this reason, it is possible to reliably separate the droplets L included in the recirculated exhaust gas G.

Sixth Embodiment
Next, a sixth embodiment of the present invention will be described with reference to FIG.
The exhaust gas recirculation system 4D shown in FIG. 11 is a fifth embodiment in that the drain pipe 53 extending from the bottom of the casing 23 of the demister 19E is connected to the droplet storage tank 45b provided in the gas-liquid separator 45. It differs from the exhaust gas recirculation system 4C. The configuration of the other parts is the same as that of the exhaust gas recirculation system 4C of the fifth embodiment, so the same reference numerals will be given to the respective parts and overlapping descriptions will be omitted.

As described above, by connecting the drain pipe 53 extending from the bottom of the demister 19E to the droplet storage tank 45b of the gas-liquid separator 45, it is collected in the demister 19E on which the pressure of the centrifugal blower 50 acts. The droplet L flows to the droplet storage tank 45b of the gas-liquid separator 45 where the pressure of the centrifugal blower 50 is not applied. Therefore, the pressure difference allows the droplets L collected in the demister 19E to be favorably flowed to the droplet storage tank 45b of the gas-liquid separator 45, and the droplet removal performance is improved. Surplus power related to the emission of

As described above, according to the demisters 19A to 19E, the exhaust gas recirculation systems 4A to 4D, and the marine engine 1 including the same according to the above embodiments, the water etc. contained in the exhaust gas to be recirculated to the engine side Can be reliably removed without increasing the pressure drop resistance, that is, without reducing the engine efficiency. And, it is possible to prevent the occurrence of erosion on the compressor wheel of the turbocharger 3 due to the droplets L contained in the recirculated exhaust gas.

The present invention is not limited to only the configurations of the first to sixth embodiments, and various changes and improvements can be made as appropriate without departing from the scope of the present invention. Embodiments are also included in the scope of the present invention.

For example, although the marine engine 1 has been described as being a two-stroke diesel engine, the present invention is not limited thereto, and the invention may be applied to other types of engines or an engine without the supercharger 3. can do.

1 Marine engine (engine)
3 Turbochargers 4A, 4B, 4C, 4D Exhaust gas recirculation system 7 Turbine 8 Compressor 16 EGR valve 17 Exhaust gas recirculation passage 18 Scrubbers 19A, 19B, 19C, 19D, 19E Demister 20 Blowers 23, 23A, 23B Casing 23Aa upstream side The cylindrical portion 23Ab of the casing of the casing The cylindrical portion 23a of the downstream side of the casing The cylindrical portion 23a The cylindrical portion 23b The conical portion 24 The outlet pipe 30 Electric collecting device 32a, 32b Half cylindrical plate (electrode)
40 Droplet separation member 45 Gas-liquid separator 45b Droplet storage tank 50 Centrifugal blower 53 Drain pipe 232 Small end (droplet discharge part)
233 Recirculation exhaust gas inlet 234 Recirculation exhaust gas outlet Da Diameter Db of the cylindrical portion of the casing on the upstream side Diameter D of the cylindrical portion of the casing on the downstream side Recirculation exhaust gas L Droplet R Swirling flow

Claims (10)

1. A cylindrical casing whose axial direction is along the vertical direction,
   A recirculation exhaust gas inlet provided on an upper outer peripheral surface of the casing for introducing recirculation exhaust gas containing droplets from the tangential direction into the interior of the casing;
   A recirculated exhaust gas outlet provided at an upper portion of the casing and at a position coinciding with an axial center of the casing for discharging the recirculated exhaust gas;
   A droplet discharge unit provided at a lower portion of the casing and discharging the droplets separated from the recirculated exhaust gas;
   Demista equipped with.
2. The casing is
   A cylindrical portion forming an upper side in the vertical direction;
   A conical portion connected to the lower portion of the cylindrical portion, the diameter of the cross section orthogonal to the axial direction decreasing from the upper portion to the lower portion;
   The demister according to claim 1, comprising
3. The demister according to claim 1 or 2, further comprising: an electric collecting device at the recirculation exhaust gas outlet for attracting the droplets to an electrode to separate it from the recirculation exhaust gas by charging the droplets.
4. The demister according to claim 1 or 2, wherein the recirculated exhaust gas outlet is provided with a porous droplet separating member.
5. The demister according to any one of claims 1 to 3, wherein the plurality of casings are connected in series and the diameter of the cylindrical portion of the downstream casing is smaller than the diameter of the cylindrical portion of the upstream casing.
6. An exhaust gas recirculation passage which extracts a part of exhaust gas discharged from the engine and feeds it to the intake side of the engine as recirculation exhaust gas;
   A scrubber connected to the exhaust gas recirculation passage for cleaning and collecting particulate matter contained in the recirculated exhaust gas by droplets;
   The demister according to any one of claims 1 to 5, which is connected to the downstream side of the scrubber;
   Exhaust gas recirculation system equipped with.
7. Connecting between the scrubber and the demister, a centrifugal blower for feeding the recirculated exhaust gas to the demister;
   The exhaust gas recirculation system according to claim 6, wherein the centrifugal blower is connected such that the recirculated exhaust gas discharged tangentially from the centrifugal blower flows tangentially into the demister.
8. The exhaust gas recirculation system according to claim 7, wherein a gas-liquid separator is provided between the scrubber and the centrifugal blower.
9. The exhaust gas recirculation system according to claim 8, wherein a drain pipe of the droplet separated from the recirculated exhaust gas by the demister is connected to a droplet storage tank of the gas-liquid separator.
10. A marine engine provided with the exhaust gas recirculation system according to any one of claims 6 to 9.

Images