JP2014134154A - Marine vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a marine vessel having an internal combustion engine carrying out EGR with appropriately cleaned exhaust gas.SOLUTION: A marine vessel includes an engine body 3 for propelling the marine vessel, a supercharger 5 having a turbine 5a and a compressor 5b both driven by exhaust gas from the engine body 3, a second exhaust passage L2 into which exhaust gas from the turbine 5a is guided, an EGR route L3 bifurcated from a bifurcation point 17 of the second exhaust passage L2 upstream of the economizer 21 and guiding a part of exhaust gas into an upstream side of the compressor 5b, and a venturi scrubber 25 provided in the EGR route L3.

Description

  The present invention relates to a ship including an exhaust gas cleaning device that cleans exhaust gas and an internal combustion engine that performs EGR.

In recent years, regulations for exhaust gas discharged from an engine (internal combustion engine) mounted for ship propulsion are being strengthened for environmental consideration.
In order to reduce nitrogen oxide (NOx) contained in the exhaust gas, EGR (Exhaust Gas Recirculation) is performed to return a part of the exhaust gas to the supply side of the engine body (the following patent) Reference 1). The EGR disclosed in this document is a type of recirculating exhaust gas that has been made high pressure before flowing into the turbocharger turbine, and is called high pressure EGR.

On the other hand, EGR disclosed in Patent Document 2 is a system that recirculates exhaust gas after passing through a turbocharger turbine and being decompressed, and is called low-pressure EGR. In this document, an exhaust gas cleaning device is provided for removing SOx (nitrogen oxide) and PM (particulate matter) in the exhaust gas. Regulations on SOx in exhaust gas are expected to be further strengthened in the future, and as described in the same document, it is considered to install an exhaust gas cleaning device such as a scrubber.
Further, as described in Patent Document 3, a wet two-stage flue gas desulfurization apparatus including a venturi scrubber and a desulfurization absorption tower is known as an exhaust gas cleaning apparatus that removes not only SOx but also PM.
Further, as described in Non-Patent Document 1, various types of wet collecting devices for cleaning exhaust gas are known.

JP 2012-172647 A JP 2012-047056 A JP 2009-240908 A

Takeshi Karino, “Behavior of powder particles: Theory and practice”, Industrial Technology Center, 1977, p. 371-376

In Patent Document 2, exhaust gas after passing through an economizer and an exhaust gas cleaning device is recirculated from the turbocharger turbine, not the exhaust gas immediately after the outlet of the turbocharger turbine. As a result, the economizer and the exhaust gas cleaning device pass through the economizer regardless of whether or not EGR is performed. Therefore, exhaust heat recovery by the economizer is performed without waste, and it is not necessary to control the exhaust gas cleaning device according to the EGR rate. It is excellent in that point.
In the configuration described in Patent Document 2, since SOx and PM are sufficiently removed by the exhaust gas cleaning device, there is no problem in the properties of the exhaust gas for performing EGR, and further when the exhaust gas is recirculated. It was thought that there was no need to install a cleaning device.

Further, in the wet two-stage flue gas desulfurization apparatus of Patent Document 3, the venturi scrubber mainly removes soot, which is the main component of PM, and the desulfurization absorption tower mainly removes SOx. However, the wet two-stage flue gas desulfurization device has a large pressure loss because it is necessary to increase the gas flow velocity at the throat portion of the venturi, and when it is installed in a low pressure line downstream of the turbocharger turbine outlet of the internal combustion engine, A blower for discharging is essential after the device. Therefore, if the wet two-stage flue gas desulfurization device of Patent Document 3 is applied to Patent Document 2, all exhaust gases discharged from the internal combustion engine (flow into the EGR path after passing through the wet two-stage flue gas desulfurization device) A large capacity blower is required to flow all exhaust gases.
Further, since the venturi scrubber is provided in addition to the desulfurization absorption tower, there is a problem that the apparatus size is large, the chimney size of the ship is increased, and there is a problem that the design of the ship must be changed.

Various types of wet collection devices (exhaust gas cleaning devices) are known as shown in Non-Patent Document 1, but a device that can remove both SOx and PM theoretically and practically. The existence was not known.
In particular, when sufficient removal of SOx is required, for example, the SOx removal rate [percentage of SOx amount in exhaust gas at the outlet with respect to the SOx amount in exhaust gas at the inlet of the exhaust gas cleaning device] is 95% or more. It is thought that it is necessary to secure a time for SOx to be dissolved in the liquid by increasing the contact time between the absorption liquid (for example, water, seawater, etc. and their aqueous solution) flowing through the exhaust gas cleaning device and the exhaust gas containing SOx. Therefore, it was generally considered that a packed tower type scrubber (desulfurization absorption tower of Patent Document 3) was necessary.
On the other hand, since the venturi scrubber increases the flow rate of the exhaust gas by venturi, it was considered that the contact time between the liquid and SOx could not be sufficiently secured and SOx could not be removed efficiently.

The present invention has been made in view of such circumstances, and provides a ship equipped with an internal combustion engine that can perform EGR with exhaust gas from which not only SOx but also impurities such as PM are reliably removed. The purpose is to do.
Moreover, it aims at providing the ship provided with the internal combustion engine which can reduce the installation space of an exhaust-gas cleaning apparatus as much as possible.
Moreover, it aims at providing the ship provided with the internal combustion engine which can reduce the blower capacity | capacitance for forcedly ventilating exhaust gas as much as possible.

In order to solve the above problems, the ship of the present invention employs the following means.
That is, a ship according to the present invention is a supercharger having an internal combustion engine body for propulsion of a ship, a turbine driven by exhaust gas from the internal combustion engine body, and a compressor connected to the turbine and compressing intake air. An exhaust gas path through which exhaust gas from the internal combustion engine body is guided, an EGR path branched from a branch point of the exhaust gas path, and leading a part of the exhaust gas to the intake path of the internal combustion engine body, It is provided with an EGR exhaust gas cleaning device provided in the EGR path and serving as a venturi scrubber.

As a result of intensive studies by the inventors, it has been found that the venturi scrubber has the ability to remove SOx as well as impurities such as PM. Therefore, a venturi scrubber was adopted as an EGR exhaust gas cleaning device provided in the EGR path. Thereby, not only impurities such as PM but also SOx can be removed through the EGR path during EGR operation.
Since a venturi scrubber is provided in the EGR path, it is sufficient to provide an EGR blower with a capacity corresponding to the amount of exhaust gas flowing through the EGR path, even if the pressure loss caused by the venturi scrubber is compensated. The blower capacity can be reduced as compared with the case where a blower is provided for the total amount of exhaust gas.
Further, the venturi scrubber is smaller in size than a general scrubber such as a desulfurization absorption tower, so that the installation space can be reduced as much as possible. Further, the venturi scrubber can be installed on the internal combustion engine main body as an accessory of the internal combustion engine main body, and can be made more compact, and the design of the installation location of the internal combustion engine main body as a ship need not be changed. There is a merit.
The EGR path may be branched from the upstream side of the turbocharger turbine (high pressure EGR), or may be branched from the downstream side of the turbocharger turbine (low pressure EGR).

  Further, in the ship of the present invention, exhaust gas cleaning for removing sulfur oxides in exhaust gas between the turbine and the branch point and between the branch point and the EGR exhaust gas cleaning device. A device is not provided.

An exhaust gas cleaning device such as a desulfurization absorption tower for removing sulfur oxide is provided between the turbine and the branch point, and between the branch point and the EGR exhaust gas cleaning device, that is, upstream of the EGR exhaust gas cleaning device. Since it is not provided, installation space can be reduced.
Moreover, it is good also as not providing an exhaust-gas cleaning apparatus not only in the upstream of an EGR exhaust-gas cleaning apparatus but in the exhaust-gas path | route downstream from a branch point. Even if the exhaust gas cleaning device is not provided in the exhaust gas path downstream of the branch point, the SOx can be removed by the venturi scrubber provided in the EGR path. In the path, so-called sulfuric acid dew point corrosion due to condensation as sulfuric acid in the low temperature portion does not occur.

  Further, in the ship of the present invention, the exhaust gas path is provided with an exhaust heat recovery device that recovers heat from the exhaust gas, and the EGR path is branched from the upstream side of the exhaust heat recovery device. Features.

  Since the EGR path is branched from the upstream side of the exhaust heat recovery device, the pressure loss of the piping can be reduced compared to the case of branching from the downstream side of the exhaust heat recovery device arranged near the chimney of the ship. The exhaust gas can be guided to the EGR exhaust gas cleaning device which is a venturi scrubber while keeping the pressure of the exhaust gas high. Thereby, the load of an EGR blower can be reduced and a venturi scrubber can be operated efficiently. Moreover, since it can branch from the internal combustion engine main body vicinity, the piping length of an EGR path | route can be shortened significantly and it can be made still more compact.

  Further, in the ship of the present invention, an exhaust heat recovery device that is provided in the exhaust gas path and recovers heat from the exhaust gas, and is provided in the exhaust gas path and downstream of the exhaust heat recovery device, the exhaust gas And an exhaust gas cleaning device for removing sulfur oxide in the exhaust gas cleaning device, wherein the EGR path is branched from the downstream side of the exhaust heat recovery device and the exhaust gas cleaning device.

In addition to the exhaust gas cleaning device provided in the exhaust gas path, an EGR exhaust gas cleaning device is further provided in the EGR path. Thereby, impurities such as PM mainly composed of soot and dust that have not been sufficiently removed by the exhaust gas cleaning device and SOx can be reliably removed by the EGR exhaust gas cleaning device. In this configuration, since SOx is removed by the exhaust gas cleaning device and then passes through the EGR exhaust gas cleaning device, the SOx removal effect can be further enhanced.
The EGR exhaust gas cleaning device is mainly intended to remove impurities such as PM in the exhaust gas after most of the SOx is removed, so it can be further downsized and installed on the internal combustion engine body. In addition, the utility associated with the apparatus can be reduced.
An exhaust gas cleaning device typically includes a desulfurization absorption tower.

Furthermore, in the ship of the present invention, the exhaust gas cleaning device is a scrubber that sprays water,
A common waste water treatment device for treating waste water from the exhaust gas cleaning device and the EGR exhaust gas cleaning device is provided.

  The waste water from the exhaust gas treatment device that is a scrubber and the EGR exhaust gas treatment device that is a venturi scrubber is treated by a common waste water treatment device. Thereby, the installation space of a waste water treatment apparatus can be omitted and waste water treatment can be performed efficiently.

  Furthermore, in the ship according to the present invention, the EGR path may be guided to the upstream side of the compressor. Alternatively, the EGR path may be led downstream of the compressor and upstream of the air cooler. Alternatively, the EGR path may be led to the downstream side of the air cooler.

  Since the venturi scrubber is adopted as the EGR exhaust gas cleaning device provided in the EGR path, not only impurities such as PM but also SOx can be sufficiently removed in the EGR path during the EGR operation. As a result, the compressor of the supercharger and the internal combustion engine main body are not adversely affected.

It is a schematic structure figure showing a 1st embodiment of a ship of the present invention. It is the schematic block diagram which showed 2nd Embodiment of the ship of this invention.

[First Embodiment]
A first embodiment according to the present invention will be described below with reference to FIG.
FIG. 1 shows a schematic configuration around a diesel engine (internal combustion engine) 1 provided in a ship.
The diesel engine 1 includes a diesel engine main body (hereinafter simply referred to as an “engine main body”) 3 that is a main engine for marine propulsion, a supercharger 5 that is driven by exhaust gas from the engine main body 3, and a supercharger. 5 is provided with an EGR system 7 which performs a low pressure EGR by recirculating a part of the exhaust gas led from 5 to the engine body 3.

The engine body 3 is a marine two-cycle diesel engine, and for example, a uniflow type that is scavenged in one direction so as to supply air from below and exhaust upward is adopted. The output from the engine body 3 is directly connected to the screw propeller via a propeller shaft (not shown).
An exhaust port of a cylinder portion 9 (only four cylinders are shown as an example in FIG. 1) of each cylinder of the engine body 3 is connected to an exhaust static pressure tube 11 as an exhaust gas collecting tube. The exhaust static pressure pipe 11 is connected to the inlet side of the turbine 5a of the supercharger 5 via the first exhaust path L1.

  On the other hand, the scavenging port of each cylinder part 9 is connected to the scavenging trunk 13, and the scavenging trunk 13 is connected to the compressor 5b of the supercharger 5 via the scavenging path K1. An air cooler 15 as an intercooler is installed in the scavenging path K1.

  The supercharger 5 includes a turbine 5a and a compressor 5b. The turbine 5a and the compressor 5b are coaxially connected by a rotating shaft 5c. The turbine 5a is driven by exhaust gas from the engine body 3, and the turbine work obtained by the turbine 5a is transmitted to the compressor 5b through the rotating shaft 5c. The compressor 5b sucks outside air (air) or a mixture of outside air and recirculation gas and raises the pressure to a predetermined scavenging pressure.

The exhaust gas after the turbine work is given by the turbine 5a flows out to the second exhaust path L2. An economizer (exhaust heat recovery device) 21 is connected to the second exhaust path L2. The economizer 21 generates steam by the exhaust gas from the engine body 3. The generated steam is used in various places on the ship.
A branch point 17 is provided on the upstream side of the economizer 21, and the EGR route L3 branches from the branch point 17. The EGR path L3 is provided with an EGR valve 19 for performing EGR. The opening degree of the EGR valve 19 is adjusted by a control unit (not shown). The EGR valve 19 is fully opened when the engine body 3 is operated to perform EGR, and is fully closed when EGR is not performed. However, the present invention is not limited to this embodiment, and the valve opening degree of the EGR valve 19 may be appropriately adjusted according to the operating state.

A venturi scrubber (EGR exhaust gas cleaning device) 25 is connected to the downstream side of the EGR valve 19 provided in the EGR path L3.
The venturi scrubber 25 removes not only impurities such as PM contained in the exhaust gas but also SOx by spraying a liquid such as water on the exhaust gas flowing through the EGR path L3. The venturi scrubber 25 is installed in the vicinity of the engine body 3 or on the engine body 3. In such an arrangement, the venturi scrubber 25 is smaller in size than a general scrubber such as a desulfurization absorption tower (for example, the venturi scrubber has a diameter of about 1/5 to 1/2 that of a general scrubber, This is possible because the height is about one-third to one-half and is configured to be a size that can be mounted on the engine body 3).

The venturi scrubber 25 includes a venturi scrubber main body 25a and a gas-liquid separator 25b connected to the venturi scrubber main body 25a.
The venturi scrubber main body 25a includes an upper large-diameter portion 25c provided vertically above, a reduced taper portion 25d provided below the upper large-diameter portion 25c, and having a flow path cross-sectional area gradually decreasing in the flow direction, and a reduced taper portion 25d. A throat portion 25e provided below, an enlarged taper portion 25f provided below the throat portion 25e and having a channel cross-sectional area gradually increasing in the flow direction, and a lower large diameter portion provided below the enlarged taper portion 25f. 25g.
The upper large-diameter portion 25c is provided with a spray nozzle 25h, and an absorbing liquid such as water or an aqueous solution is sprayed from the spray nozzle 25h toward the connection position between the reduced taper portion 25d and the throat portion 25e. The absorbing liquid sprayed from the spray nozzle 25h is effectively diffused and mixed by increasing the flow rate of the exhaust gas at the throat portion 25e of the venturi scrubber body 25a to remove not only impurities such as PM but also SOx. To do.

In the gas-liquid separator 25b, moisture contained in the exhaust gas led from the venturi scrubber main body 25a is removed. A mist separator 25i for removing mist remaining in the exhaust gas is provided at the outlet of the gas-liquid separator 25b, and the separated mist is collected in the gas-liquid separator 25b.
The gas-liquid separator 25b may be a cyclone method in which the gas and liquid are separated by turning the exhaust gas instead of the method using a mist separator.

  An EGR blower 27 is provided on the downstream side of the gas-liquid separator 25b. The EGR blower 27 is rotationally driven by an electric motor 29 whose frequency is variable by an inverter. The EGR blower 27 is used to compensate for the pressure loss of the exhaust gas that is generated when the EGR valve 19 and the venturi scrubber 25 pass through the piping constituting the EGR path L3.

  A mixer 39 is provided on the downstream side of the EGR blower 27. In the mixer 39, the recirculated exhaust gas and air are mixed. The mixed gas (only air when EGR is not performed) mixed in the mixer 39 is guided to the suction port of the compressor 5b through the air supply path K2. Further, an EGR cooler (not shown) may be provided on the EGR path. In this case, for example, the EGR cooler is installed downstream of the EGR blower.

Next, operation | movement of the ship provided with the diesel engine 1 of the said structure is demonstrated.
When the ship uses EGR, such as when navigating in a sea area where exhaust gas NOx regulations are strict (emission control area (ECA)), the EGR valve 19 is opened. Thus, before the exhaust gas guided from the engine body 3 to the turbine 5a through the first exhaust path L1 passes through the economizer 21, it is branched at the branch point 17 and flows to the EGR system 7. The remaining exhaust gas Then, after flowing through the second exhaust path L2 and passing through the economizer 21, it is discharged from a chimney (not shown) to the atmosphere.

  The exhaust gas flowing through the EGR system 7 flows through the venturi scrubber 25 through the EGR valve 19 as a recirculation gas. The exhaust gas from which not only impurities such as PM but also SOx is removed by the venturi scrubber 25 is guided to the EGR blower 27, and the exhaust gas pressurized to a predetermined pressure by the EGR blower 27 is guided to the mixer 39. In the mixer 39, the air and the exhaust gas are mixed and guided to the intake port of the compressor 5b through the intake path K2. The mixture of air and exhaust gas pressurized by the compressor 5b is guided to the air cooler 15 through the scavenging path K1, cooled by the air cooler 15, and then guided to the scavenging trunk 13.

Below, the test result which confirmed that SOx was removed by a venturi scrubber is demonstrated. As described above, the venturi scrubber is generally known to effectively remove impurities such as PM by increasing the flow rate and enhancing the diffusion of the absorption liquid, but it is also effective for removing SOx. I found a new thing.
Table 1 below shows the composition of the exhaust gas at the venturi scrubber inlet, and Table 2 shows the composition of the exhaust gas at the venturi scrubber outlet. In each table, No. 1 to No. 8 indicate the test number of each sampling, and sampling was performed 8 times in total.
The venturi scrubber used in the test has a maximum gas flow rate of 50 to 80 m / s at the throat and a liquid-gas ratio (absorbed liquid spray amount [kg] / standard state converted gas flow rate [Nm3]) of 0.5 to 2.0 kg / Nm3. The specification was used. The nozzle of the venturi scrubber was a single fluid nozzle, and the spray angle was 80-100 °.
The exhaust gas used for the test was the actual exhaust gas of a marine two-cycle diesel engine. The fuel used was A heavy oil, and the sulfur content in the A heavy oil was 0.71 wt%. The engine speed was 105 rpm, which is the rated speed. Gas property analysis was performed using a gas analyzer PG-250 manufactured by HORIBA, Ltd. NOx was analyzed by atmospheric pressure chemiluminescence, SOx and CO2 were analyzed by a non-dispersive infrared absorption method, and O2 was analyzed by zirconia oxygen. Measurement was performed with a meter.

  From the above test results, it can be seen that the venturi scrubber can significantly remove SOx. In particular, the fact that NOx, CO2, and O2 cannot be removed significantly but only SOx can be removed is a new finding that has not been conventionally known.

As mentioned above, according to the ship provided with the diesel engine 1 of this embodiment, there exist the following effects.
Since the venturi scrubber 25 is adopted as the EGR exhaust gas cleaning device provided in the EGR path, not only impurities such as PM but also SOx can be removed in the EGR path L3 during the EGR operation. Thereby, the compressor 5b and the engine main body 3 are not adversely affected.
Since the venturi scrubber 25 is provided in the EGR path L3, it is sufficient to provide the EGR blower 27 having a capacity corresponding to the amount of exhaust gas flowing through the EGR path L3 even when the pressure loss caused by the venturi scrubber 25 is compensated. The blower capacity can be reduced as compared with the case where the blower is provided for the entire amount of exhaust gas discharged from the engine body 3.
Moreover, since the venturi scrubber 25 is smaller in size than a general scrubber such as a desulfurization absorption tower, the installation space can be reduced. In addition, the venturi scrubber 25 can be installed on the engine body 3 as an accessory of the engine body 3 and can be made more compact, and the design of the installation location of the engine body 3 as a ship can be changed. There are good benefits.

Since an exhaust gas cleaning device for removing sulfur oxides is not provided in the second exhaust path L2, which is an exhaust gas path, installation space can be reduced.
Further, even if no exhaust gas cleaning device is provided in the second exhaust path L2, SOx can be removed by the venturi scrubber 25 provided in the EGR path L3, so that the intake path of the engine body 3 is recirculated by the exhaust gas. In this case, so-called sulfuric acid dew point corrosion is not caused by condensation as sulfuric acid at a low temperature part.

  Since the EGR path L3 is branched from the upstream side of the economizer 21, the pressure loss of the piping can be reduced as compared with the case of branching from the downstream side of the economizer 21 arranged near the chimney of the ship. The exhaust gas can be guided to the venturi scrubber 25 while keeping the pressure high. Thereby, the load of the EGR blower 27 can be reduced, and the venturi scrubber 25 can be operated efficiently. Moreover, since it can branch from the engine main body 3 vicinity, the piping length of the EGR path | route L3 can be shortened significantly, and it can be made still more compact.

[Second Embodiment]
Next, a second embodiment according to the ship of the present invention will be described. This embodiment is different from the first embodiment in that a desulfurization absorption tower 23 is provided in the second exhaust path L2. Other common configurations are denoted by the same reference numerals and description thereof is omitted.

An economizer (exhaust heat recovery device) 21 and a desulfurization absorption tower (exhaust gas cleaning device) 23 are sequentially connected to the second exhaust path L2.
The desulfurization absorption tower 23 is a packed tower type scrubber, for example, and removes SOx contained in the exhaust gas by spraying an absorption liquid such as water or an aqueous solution to the exhaust gas. As will be described later, since the exhaust gas guided to the EGR path L3 is guided after passing through the desulfurization absorption tower 23, SOx is sufficiently removed, and the venturi scrubber 25 mainly remains with impurities such as PM. SOx removal is performed.
The desulfurization absorption tower 23 is applied when a fuel containing a sulfur content equal to or greater than the regulation value in the SOx regulation sea area (for example, 1.0% or more) is used as the fuel for the engine body 3.

A branch point 17 ′ is provided on the downstream side of the desulfurization absorption tower 23, and the EGR path L 3 branches from this branch point 17 ′. The point that the EGR valve 19, the venturi scrubber 25, and the EGR blower 27 are provided in the EGR path L3 is the same as in the first embodiment.
Waste water from the venturi scrubber 25 is treated by the same waste water treatment device (not shown) as the desulfurization absorption tower 23 described above. That is, waste water from the desulfurization absorption tower 23 and the venturi scrubber 25 is processed by a common waste water treatment device.

Next, operation | movement of the ship provided with the diesel engine 1 of the said structure is demonstrated.
When the ship uses EGR, such as when navigating in a sea area where exhaust gas NOx regulations are strict (emission control area (ECA)), the EGR valve 19 is opened. Thus, after the exhaust gas guided from the engine body 3 to the turbine 5a through the first exhaust path L1 passes through the economizer 21 and the desulfurization absorption tower 23, it is branched at the branch point 17 ′ and flows to the EGR system 7 side. The remaining exhaust gas flows through the second exhaust path L2, and is discharged from a chimney (not shown) to the atmosphere.

  The exhaust gas flowing through the EGR system 7 flows through the venturi scrubber 25 through the EGR valve 19 as a recirculation gas. The venturi scrubber 25 removes impurities such as PM and SOx that has not been removed by the desulfurization absorption tower 23. The exhaust gas that has passed through the venturi scrubber 25 is guided to the EGR blower 27, and the exhaust gas pressurized to a predetermined pressure by the EGR blower 27 is guided to the mixer 39. In the mixer 39, the air and the exhaust gas are mixed and guided to the intake port of the compressor 5b through the intake path K2. The mixture of air and exhaust gas pressurized by the compressor 5b is guided to the air cooler 15 through the scavenging path K1, cooled by the air cooler 15, and then guided to the scavenging trunk 13.

As mentioned above, according to the ship provided with the diesel engine 1 of this embodiment, there exist the following effects.
In addition to the desulfurization absorption tower 23 provided in the second exhaust path L2, a venturi scrubber 25 is further provided in the EGR path L3. Thereby, impurities such as PM that have not been sufficiently removed by the desulfurization absorption tower 23 and the remaining SOx can be reliably removed by the venturi scrubber 25. Thereby, the compressor 5b and the engine main body 3 are not adversely affected.
Further, the venturi scrubber 25 mainly aims to remove impurities such as PM and remaining SOx in the exhaust gas after passing through the desulfurization absorption tower 23, so that it is further downsized compared to the venturi scrubber of the first embodiment. In addition, it is possible to reduce the utility associated with the apparatus.

  The waste water from the desulfurization absorption tower 23 and the venturi scrubber 25 was treated with a common waste water treatment device. Thereby, the installation space of a waste water treatment apparatus can be omitted and waste water treatment can be performed efficiently.

Since the EGR is performed by branching from the branch point 17 ′ on the downstream side of the economizer 21 and the exhaust gas of the entire amount passes through the economizer 21 regardless of whether the EGR is performed or not, the exhaust heat recovery by the economizer 21 is performed. Is effectively done without waste.
Further, since the EGR is performed by branching from the branch point 17 ′ on the downstream side of the desulfurization absorption tower 23, the desulfurization absorption tower 23 is passed regardless of whether or not the EGR is performed. Therefore, the desulfurization is performed according to the EGR rate. There is no need to control the absorption tower 23.
Further, since the entire amount of exhaust gas passes through the desulfurization absorption tower 23, it is not necessary to use expensive low S component fuel (for example, sulfur content is 1.0% or less) even when a ship navigates the SOx restricted sea area.

  Since the exhaust gas after passing through the desulfurization absorption tower 23 and being cooled is guided to the EGR valve 19 and the venturi scrubber 25, high temperature resistant members are not used as components of the EGR valve 19 and the venturi scrubber 25. good. Furthermore, since the exhaust gas temperature is low, water vapor contained in the exhaust gas can be reduced, the mist diameter can be increased, and the mist recovery rate at the mist separator 25i can be increased. Thereby, the blades of the EGR blower 27 and the blades of the compressor 5b can be protected, and the maintenance cycle can be lengthened.

  Further, the exhaust gas is not recirculated by branching immediately after the turbine 5a of the supercharger 5, but the exhaust gas is recirculated from the branch point 17 ′ on the downstream side of the desulfurization absorption tower 23, and the EGR path It was decided to make it longer. As a result, the mist and steam accompanying the desulfurization absorption tower 23 can be removed while the exhaust gas flows through the EGR path L3, the blades of the EGR blower 27 and the blades of the compressor 5b can be protected, and the maintenance cycle is further increased. Can be long.

In the above-described embodiments, the low-pressure EGR that branches the EGR path L3 from the downstream side of the turbine 5a has been described. However, the present invention is not limited to this, for example, the upstream side of the turbine 5a. It may be a high pressure EGR branched from the first exhaust path L1.
Further, in each of the above-described embodiments, the downstream side of the EGR path L3 is the upstream side of the compressor 5b. However, the present invention is not limited to this. For example, the downstream side of the compressor 5b and the air The downstream side of the EGR path L3 may be connected to the upstream side of the cooler 15, or the downstream side of the EGR path L3 may be connected to the downstream side of the air cooler 15.
In the second embodiment shown in FIG. 2, the branch point 17 ′ is positioned downstream of the desulfurization absorption tower 23, but may be upstream of the economizer 21, and the economizer 21 and the desulfurization absorption tower 23 It may be between.

1 Diesel engine (internal combustion engine)
3 Engine body (Internal combustion engine body)
5 Supercharger 5a Turbine 5b Compressor 7 EGR system 11 Exhaust static pressure pipe 13 Scavenging trunk 15 Air cooler 19 EGR valve 21 Economizer (exhaust heat recovery device)
23 Desulfurization absorption tower (exhaust gas cleaning device)
25 Venturi scrubber (EGR exhaust gas cleaning device)
27 EGR blower L1 First exhaust path L2 Second exhaust path L3 EGR path K1 Scavenging path

Claims (8)

An internal combustion engine body for ship propulsion,
A turbine driven by exhaust gas from the internal combustion engine body, and a supercharger having a compressor coupled to the turbine and compressing intake air;
An exhaust gas path through which exhaust gas from the internal combustion engine body is guided;
An EGR path branched from a branch point of the exhaust gas path and guiding a part of the exhaust gas to the intake path of the internal combustion engine body;
An EGR exhaust gas cleaning device provided in the EGR path and serving as a venturi scrubber;
A ship characterized by comprising:   An exhaust gas cleaning device for removing sulfur oxide in the exhaust gas is not provided between the turbine and the branch point, and between the branch point and the EGR exhaust gas cleaning device. The ship according to claim 1, wherein The exhaust gas path is provided with an exhaust heat recovery device that recovers heat from the exhaust gas,
The ship according to claim 1 or 2, wherein the EGR path is branched from an upstream side of the exhaust heat recovery apparatus. An exhaust heat recovery device that is provided in the exhaust gas path and recovers heat from the exhaust gas;
An exhaust gas cleaning device provided in the exhaust gas path for removing sulfur oxides in the exhaust gas;
With
The ship according to claim 1, wherein the EGR path is branched from a downstream side of the exhaust heat recovery device and the exhaust gas cleaning device. The exhaust gas cleaning device is a scrubber that sprays water,
The ship according to claim 4, comprising a common waste water treatment device for treating waste water from the exhaust gas cleaning device and the EGR exhaust gas cleaning device.   The ship according to any one of claims 1 to 5, wherein the EGR path is led to an upstream side of the compressor. An air cooler for cooling the compressed air compressed by the compressor is provided downstream of the compressor,
The ship according to any one of claims 1 to 5, wherein the EGR path is led downstream of the compressor and upstream of the air cooler. An air cooler for cooling the compressed air compressed by the compressor is provided downstream of the compressor,
The ship according to any one of claims 1 to 5, wherein the EGR path is led to a downstream side of the air cooler.

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