WO2024075552A1 - Engine system and ship - Google Patents

Abstract

This engine system comprises: an engine which is driven by methane as a fuel; a supercharger which supplies air to the engine by being driven by emission gas discharged from an exhaust section of the engine; a discharge pipe through which emission gas discharged from the supercharger passes; a first oxidation processing unit into which emission gas is introduced via the discharge pipe and in which a first methane oxidation catalyst is housed; a supercharger bypass pipe which causes a portion of the emission gas discharged from the exhaust section to bypass the supercharger and merge into the discharge pipe; and a second oxidation processing unit which is provided in the middle of the supercharger bypass pipe and in which a second methane oxidation catalyst is housed.

Description

Engine systems, ships

The present disclosure relates to an engine system, a marine vessel.
This application claims priority to Japanese Patent Application No. 2022-159920, filed in Japan on October 4, 2022, the contents of which are incorporated herein by reference.

Catalytic converters are known that oxidize the methane contained in engine exhaust gas. In engine systems equipped with a turbocharger, such catalytic converters are often placed downstream of the turbocharger in the exhaust gas discharge direction.

Patent Document 1 discloses an engine system (reciprocating piston internal combustion engine) that includes an engine, a supercharger (exhaust gas turbocharger), and a catalytic converter. The supercharger is driven by exhaust gas from the engine and supplies air to the engine. A line equipped with a catalytic converter is provided between the engine and the supercharger. Exhaust gas from the engine is passed through the line equipped with the catalytic converter. The catalytic converter is a methane oxidation catalytic converter, and oxidizes methane contained in the exhaust gas.

JP 2015-214970 A

When methane is used as engine fuel, the exhaust gas may contain unburned methane. For this reason, before the exhaust gas is discharged into the atmosphere, the unburned methane contained in the exhaust gas must be oxidized using a methane oxidation catalyst. On the other hand, in engine systems equipped with a turbocharger, it is desirable to efficiently drive the turbocharger using exhaust gas discharged from the engine.

In contrast, in the configuration described in Patent Document 1, when gas is used as fuel, exhaust gas discharged from the engine is supplied to the turbocharger via a catalytic converter. When the exhaust gas passes through the catalytic converter, it comes into contact with a methane oxidation catalyst in the catalytic converter, and the methane contained in the exhaust gas is oxidized. Because the catalytic converter acts as a flow resistance to the flow of exhaust gas, a pressure loss occurs in the exhaust gas that reaches the turbocharger via the catalytic converter, leading to a decrease in the drive efficiency of the turbocharger.

The present disclosure has been made to solve the above problems, and aims to provide an engine system and ship that can effectively oxidize the unburned methane contained in exhaust gas and prevent a decrease in the drive efficiency of the turbocharger.

In order to solve the above problems, the engine system according to the present disclosure includes an engine, a turbocharger, an exhaust pipe, a first oxidation treatment unit, a turbocharger bypass pipe, and a second oxidation treatment unit. The engine is driven by methane as fuel. The turbocharger is driven by exhaust gas discharged from an exhaust section of the engine to supply air to the engine. Exhaust gas discharged from the turbocharger flows through the exhaust pipe. The first oxidation treatment unit is introduced with the exhaust gas via the exhaust pipe. The first oxidation treatment unit contains a first methane oxidation catalyst. The turbocharger bypass pipe causes a portion of the exhaust gas discharged from the exhaust section to bypass the turbocharger and merge with the exhaust pipe. The second oxidation treatment unit is provided midway through the turbocharger bypass pipe. The second oxidation treatment unit contains a second methane oxidation catalyst.

The vessel disclosed herein is equipped with an engine system as described above.

The engine system and ship disclosed herein can effectively oxidize the unburned methane contained in the exhaust gas and prevent a decrease in the drive efficiency of the turbocharger.

FIG. 1 is a side view of a vessel including an engine system according to a first embodiment of the present disclosure. 1 is a diagram showing a configuration of an engine system according to a first embodiment of the present disclosure. FIG. FIG. 2 is a diagram showing an example of the relationship between the temperature of exhaust gas and the methane oxidation rate in the first methane oxidation catalyst and the second methane oxidation catalyst provided in the engine system according to the first embodiment of the present disclosure. FIG. 2 is a diagram showing the flow of exhaust gas when methane is used as fuel in the engine system according to the first embodiment of the present disclosure. 2 is a diagram showing the flow of exhaust gas when heavy oil is used as fuel in the engine system according to the first embodiment of the present disclosure. FIG. FIG. 4 is a diagram showing a configuration of an engine system according to a second embodiment of the present disclosure.

First Embodiment
Hereinafter, an engine system and a ship according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 6.
(Vessel configuration)
1, the ship 1 of the first embodiment includes at least a hull 2 and an engine system 10A. Examples of the type of ship 1 include a bulk carrier, a carrier for liquefied gas such as liquefied natural gas (LNG), carbon dioxide, or ammonia, a ferry, a roll-on/roll-off ship (RO-RO ship), a pure car & truck carrier (PCTC), and a passenger ship.

(Hull configuration)
The hull 2 has a pair of side walls 3A, 3B, a bottom wall 4, an upper deck 5, and a bottom deck 6, which form the outer hull of the hull. The side walls 3A, 3B have a pair of side wall shells that form the left and right sides, respectively. The bottom wall 4 has a bottom wall shell that connects the side walls 3A, 3B. The pair of side walls 3A, 3B and the bottom wall 4 form the outer hull of the hull 2 in a U-shape in a cross section perpendicular to the bow-stern direction Da. The upper deck 5 illustrated in the first embodiment is a full-length deck exposed to the outside. The bottom wall 6 is provided inside the hull 2 and forms a double bottom together with the bottom wall shell. The hull 2 has a superstructure 7 having a living area formed on the upper deck 5 on the stern 2b side, for example. The position and size of the superstructure 7 can be changed as appropriate.

(Engine system configuration)
FIG. 2 is a diagram showing a configuration of an engine system according to the first embodiment of the present disclosure.
The engine system 10A is provided within the hull 2.
As shown in FIG. 2, the engine system 10A mainly includes an engine 20A, a turbocharger 30, a first oxidation treatment unit 40, and a second oxidation treatment unit 50.

The engine 20A is provided within the hull 2. Examples of the engine 20A include a main engine that generates driving force to propel the hull 2, and an engine that drives a generator that supplies power to the hull 2. The engine 20A is driven by burning fuel. The engine 20A emits exhaust gas generated by burning fuel. The engine 20A used in this first embodiment is capable of switching between methane and heavy oil as fuel. Examples of heavy oil include heavy oil A and heavy oil C.

Engine 20A includes an engine body 21 and an exhaust section 22. Engine body 21 has, for example, multiple cylinders (not shown). A mixture of fuel and air is introduced from the outside into each cylinder of engine body 21 via an intake section (not shown). The mixture is combusted in each cylinder. The engine body 21 is driven by the combustion of the mixture in each cylinder. In addition, engine body 21 exhausts exhaust gas generated by the combustion of the mixture in each cylinder to the outside via exhaust section 22.

The exhaust section 22 discharges exhaust gas from each cylinder of the engine body 21 to the turbocharger 30 and the first oxidation treatment section 40. The exhaust section 22 is equipped with a connecting pipe 23 and a manifold 24. The connecting pipes 23 are provided corresponding to each of the multiple cylinders. Each connecting pipe 23 connects the exhaust port (not shown) of each cylinder to the manifold 24. Exhaust gas flows into the manifold 24 from the multiple connecting pipes 23. The manifold 24 collects the exhaust gas discharged from the multiple connecting pipes 23 and sends it to the turbocharger 30 and the first oxidation treatment section 40.

The turbocharger 30 is connected to the end of the manifold 24 downstream in the exhaust gas flow direction. A portion of the exhaust gas flowing through the manifold 24 is introduced into the turbocharger 30. The turbocharger 30 has a compressor (not shown) that supplies air to the engine 20A, and an exhaust turbine (not shown). The exhaust turbine (not shown) of the turbocharger 30 converts the energy of the exhaust gas discharged from the exhaust section 22 into rotational energy. The compressor (not shown) is driven by this rotational energy. The exhaust gas that has passed through the turbocharger 30 is discharged into the exhaust pipe 102.

The exhaust pipe 102 forms a flow path that guides the exhaust gas discharged from the turbocharger 30. In other words, the exhaust gas discharged from the turbocharger 30 flows through the exhaust pipe 102. One end of the exhaust pipe 102 is connected to the discharge port (not shown) of the turbocharger 30. The exhaust pipe 102 illustrated in this first embodiment extends upward from the turbocharger 30 in the vertical direction Dv. The other end of the exhaust pipe 102 is connected to the first oxidation treatment unit 40.

The first oxidation treatment unit 40 performs a process to oxidize the methane contained in the exhaust gas. The exhaust gas is introduced into the first oxidation treatment unit 40 via an exhaust pipe 102. The exhaust gas introduced into the first oxidation treatment unit 40 includes at least the exhaust gas discharged from the turbocharger 30. The first oxidation treatment unit 40 has a housing 41 and a first methane oxidation catalyst 42.

The housing 41 forms the outer shell of the first oxidation treatment unit 40. In this first embodiment, the housing 41 extends in the vertical direction Dv. The other end of the exhaust pipe 102 is connected to the lower end of the housing 41. Meanwhile, the exhaust duct 43 is connected to the upper end of the housing 41. The exhaust duct 43 leads to the funnel 9 shown in FIG. 1. The funnel 9 in this first embodiment is provided on the upper deck 5 on the stern 2b side of the hull 2, has a cylindrical shape extending in the vertical direction Dv, and extends so as to protrude upward from the upper deck 5.

As shown in FIG. 2, the first methane oxidation catalyst 42 is housed in a housing 41. This first methane oxidation catalyst 42 oxidizes the unburned methane contained in the exhaust gas. The first methane oxidation catalyst 42 includes, for example, a catalyst carrier and an active component made of palladium particles or the like fixed to the catalyst carrier.

The second oxidation treatment unit 50 is provided midway through the turbocharger bypass pipe 103. The second oxidation treatment unit 50 performs a process to oxidize the methane contained in the exhaust gas flowing through the turbocharger bypass pipe 103.

The turbocharger bypass pipe 103 allows a portion of the exhaust gas discharged from the exhaust section 22 to bypass the turbocharger 30 and merge with the exhaust pipe 102. A first end 103a of the turbocharger bypass pipe 103 is connected to the exhaust section 22. The first end 103a is connected downstream in the exhaust gas flow direction within the manifold 24 from the position where the multiple connection pipes 23 are connected to the manifold 24 of the exhaust section 22. A second end 103b of the turbocharger bypass pipe 103 is connected to the exhaust pipe 102.

The pipe diameter (inner diameter) D2 of the turbocharger bypass pipe 103 is set based on the exhaust gas flow rate required to drive the turbocharger 30 to feed air to the engine 20A. The exhaust gas flow rate required to drive the turbocharger 30 is determined based on the set value (design value) of the air flow rate to be fed to the engine 20A. The turbocharger bypass pipe 103 is introduced with exhaust gas at a flow rate that is the difference between the exhaust gas flow rate discharged from the engine 20A and the exhaust gas flow rate required to drive the turbocharger 30. In other words, the turbocharger bypass pipe 103 is introduced with the surplus exhaust gas required by the turbocharger 30 out of the exhaust gas discharged from the engine 20A. For this reason, the pipe diameter (inner diameter) D2 of the turbocharger bypass pipe 103 is smaller than the pipe diameter D1 of the exhaust pipe 102.

The exhaust gas discharged from the exhaust section 22 of the engine 20A is introduced into the second oxidation treatment section 50 via the turbocharger bypass pipe 103. The second oxidation treatment section 50 has a housing 51 and a second methane oxidation catalyst 52.

The housing 51 forms the outer shell of the second oxidation treatment unit 50. In this first embodiment, the housing 51 extends in the vertical direction Dv. The upstream portion 103p of the turbocharger bypass pipe 103 is connected to the lower end of the housing 51. The downstream portion 103q of the turbocharger bypass pipe 103 is connected to the upper end of the housing 51.

The second methane oxidation catalyst 52 is accommodated in the housing 51. The second methane oxidation catalyst 52 oxidizes the unburned methane contained in the exhaust gas. The second methane oxidation catalyst 52 comprises, for example, a catalyst carrier and an active component made of palladium particles or the like fixed to the catalyst carrier. In this first embodiment, the first methane oxidation catalyst 42 and the second methane oxidation catalyst 52 contain the same active component.

FIG. 3 is a graph showing an example of the relationship between the temperature of exhaust gas and the methane oxidation rate in the first methane oxidation catalyst and the second methane oxidation catalyst provided in the engine system according to the first embodiment of the present disclosure.
As shown in Fig. 3, in the first methane oxidation catalyst 42 and the second methane oxidation catalyst 52, the higher the exhaust gas temperature, the higher the methane oxidation rate. For this reason, it is preferable to oxidize unburned methane in a region where the exhaust gas temperature is as high as possible. In this first embodiment, by making the concentration of catalytic components in the second methane oxidation catalyst 52 higher than the concentration of catalytic components in the first methane oxidation catalyst 42, the efficiency of the methane oxidation treatment can be further improved, and the total amount of active components in the first methane oxidation catalyst 42 and the second methane oxidation catalyst 52 combined can be reduced.

Also, as shown in FIG. 2, a valve 60A is provided in the upstream portion 103p of the turbocharger bypass pipe 103, which is located upstream of the second oxidation treatment unit 50 in the exhaust gas flow direction. The valve 60A opens and closes the flow path of the exhaust gas from the exhaust unit 22 to the turbocharger bypass pipe 103. The opening of the valve 60A is adjusted according to the amount of exhaust gas required for the turbocharger 30.

The engine system 10A in this first embodiment further includes a first oxidation treatment unit bypass pipe 105 and a switching unit 110. The first oxidation treatment unit bypass pipe 105 forms a flow path for exhaust gas that bypasses the first oxidation treatment unit 40. One end of the first oxidation treatment unit bypass pipe 105 branches off from the exhaust pipe 102. The other end of the first oxidation treatment unit bypass pipe 105 merges with the exhaust duct 43.

The switching unit 110 switches the introduction destination of the exhaust gas discharged from the turbocharger 30 between the exhaust pipe 102 and the first oxidizer bypass pipe 105. The switching unit 110 has a first switching valve 111 and a second switching valve 112. The first switching valve 111 is disposed in the exhaust pipe 102 between a portion to which one end of the first oxidizer bypass pipe 105 is connected and the first oxidizer 40. The second switching valve 112 is disposed in the first oxidizer bypass pipe 105. The first switching valve 111 and the second switching valve 112 may be opened and closed by remote control or the like.
The engine system 10A in the first embodiment is equipped with the first oxidation treatment unit bypass pipe 105 and the switching unit 110 as described above, so that the destination of the exhaust gas can be switched from the first oxidation treatment unit 40 to the first oxidation treatment unit bypass pipe 105. As a result, the exhaust gas discharged from the turbocharger 30 to the exhaust pipe 102 can bypass the first oxidation treatment unit 40 and reach the exhaust duct 43.

As shown in Figures 1 and 2, the engine 20A, turbocharger 30, and second oxidation treatment unit 50 of the engine system 10A are housed, for example, in an engine room 2k provided in the hull 2. The exhaust pipe 102 and the downstream portion 103q of the turbocharger bypass pipe 103 extending upward from the second oxidation treatment unit 50 penetrate the deck 8 provided above the engine room 2k and extend to the upper layer within the hull 2. The first oxidation treatment unit 40 illustrated in this embodiment is disposed in the upper engine room 2j formed above the deck 8. However, the location of the first oxidation treatment unit 40 is not limited to being disposed in the upper engine room 2j.

FIG. 4 is a diagram showing the flow of exhaust gas when methane is used as fuel in the engine system according to the first embodiment of the present disclosure.
As shown in Fig. 4, in the engine system 10A, when methane is used as fuel for the engine 20A, the valve 60A and the first changeover valve 111 are opened, and the second changeover valve 112 is closed. A part of the exhaust gas discharged from the exhaust section 22 of the engine 20A is introduced into the turbocharger 30 from the manifold 24 of the exhaust section 22. The turbocharger 30 is driven by the exhaust gas introduced into the turbocharger 30, and air is supplied to the engine 20A. The exhaust gas discharged from the turbocharger 30 to the exhaust pipe 102 is lowered in temperature by performing work to supply air to the engine 20A.

The remaining (excess) portion of the exhaust gas discharged from the exhaust section 22 of the engine 20A flows from the manifold 24 into the turbocharger bypass pipe 103. The exhaust gas that flows into the turbocharger bypass pipe 103 is introduced into the second oxidation treatment section 50. In the second oxidation treatment section 50, the second methane oxidation catalyst 52 oxidizes the unburned methane contained in the introduced exhaust gas. The temperature of the exhaust gas that has passed through the second oxidation treatment section 50 rises due to the oxidation of the unburned methane in the second oxidation treatment section 50.

The exhaust gas that has passed through the turbocharger 30 and the exhaust gas that has passed through the second oxidation treatment unit 50 join together in the exhaust pipe 102. Since the temperature of the exhaust gas that has passed through the second oxidation treatment unit 50 has increased due to the oxidation treatment, the temperature of the mixed gas (exhaust gas) in which the exhaust gas that has passed through the turbocharger 30 and the exhaust gas that has passed through the second oxidation treatment unit 50 are mixed is higher than the temperature of the exhaust gas alone discharged from the turbocharger 30.

The exhaust gas whose temperature has been raised in this way is introduced into the first oxidation treatment unit 40 from the exhaust pipe 102. In the first oxidation treatment unit 40, the unburned methane contained in the exhaust gas is oxidized by the first methane oxidation catalyst 42. The exhaust gas that has passed through the first oxidation treatment unit 40 is released into the atmosphere from the funnel 9 through the exhaust duct 43.

FIG. 5 is a diagram showing the flow of exhaust gas when heavy oil is used as fuel in the engine system according to the first embodiment of the present disclosure.
5, in the engine system 10A, when heavy oil is used as fuel for the engine 20A, the valve 60A and the first switching valve 111 are closed, and the second switching valve 112 is opened. All exhaust gas discharged from the exhaust section 22 of the engine 20A is introduced into the turbocharger 30 from the manifold 24 of the exhaust section 22. The turbocharger 30 is driven by the exhaust gas introduced into the turbocharger 30, and air is supplied to the engine 20A. The exhaust gas discharged from the turbocharger 30 flows from the exhaust pipe 102 into the first oxidizer bypass pipe 105, bypasses the first oxidizer 40, and is released into the atmosphere from the funnel 9 through the exhaust duct 43.

(Action and Effect)
In the engine system 10A and the ship 1 of the first embodiment, exhaust gas discharged from the exhaust section 22 of the engine 20A is sent to the turbocharger 30 and the turbocharger bypass pipe 103. The turbocharger 30 is driven by the exhaust gas and supplies air to the engine 20A. The exhaust gas discharged from the turbocharger 30 flows through the exhaust pipe 102. The exhaust gas discharged from the turbocharger 30 to the exhaust pipe 102 is lowered in temperature by performing work to supply air to the engine 20A.

Meanwhile, the exhaust gas sent to the turbocharger bypass pipe 103 is introduced into the second oxidation treatment unit 50. The second oxidation treatment unit 50 oxidizes the unburned methane contained in the introduced exhaust gas using the second methane oxidation catalyst 52. As the unburned methane is oxidized, the exhaust gas sent out from the second oxidation treatment unit 50 has a higher temperature than the exhaust gas introduced into the second oxidation treatment unit 50. The exhaust gas discharged from the second oxidation treatment unit 50 passes through the turbocharger bypass pipe 103 and merges with the exhaust pipe 102.

The exhaust gas is introduced into the first oxidation treatment unit 40 through the exhaust pipe 102. The exhaust gas introduced into the first oxidation treatment unit 40 is a mixture of the exhaust gas discharged from the turbocharger 30 and the exhaust gas discharged from the second oxidation treatment unit 50, which join together in the exhaust pipe 102. The exhaust gas discharged from the second oxidation treatment unit 50 is hotter than the exhaust gas discharged from the turbocharger 30, so the exhaust gas mixed with the exhaust gas discharged from the turbocharger 30 and the exhaust gas discharged from the second oxidation treatment unit 50 is hotter than the exhaust gas discharged from the turbocharger 30. This makes it possible to increase the temperature of the exhaust gas introduced into the first oxidation treatment unit 40 compared to a case in which the turbocharger bypass pipe 103 and the second oxidation treatment unit 50 are not provided.

The higher the temperature of the exhaust gas introduced into the first methane oxidation catalyst 42, the higher the oxidation rate of methane, making it possible for the first oxidation treatment unit 40 to efficiently oxidize methane.

Moreover, the second oxidation treatment unit 50 is provided midway through the turbocharger bypass pipe 103, and is not provided between the exhaust section 22 and the turbocharger 30. Therefore, the exhaust gas discharged from the exhaust section 22 is directly fed to the turbocharger 30. Therefore, a decrease in the drive efficiency of the turbocharger 30 is suppressed.
As a result, it is possible to satisfactorily oxidize the unburned methane contained in the exhaust gas, and to suppress a decrease in the drive efficiency of the turbocharger 30.

In the first embodiment, the engine is further provided with a valve 60A that opens and closes the flow path of the exhaust gas from the exhaust section 22 to the turbocharger bypass pipe 103.
As a result, by opening and closing the valve 60A, it is possible to interrupt the supply of exhaust gas from the exhaust section 22 to the second oxidation treatment section 50. Therefore, when heavy oil is used as the fuel for the engine 20A and oxidation treatment of unburned methane in the second oxidation treatment section 50 is not necessary, the supply of exhaust gas to the second oxidation treatment section 50 can be stopped.

In the first embodiment, the engine 20A can be fueled by switching between methane and heavy oil.
As a result, when methane is used as fuel, by opening the valve 60A, the unburned methane contained in the exhaust gas can be oxidized sequentially by the second oxidation treatment unit 50 and the first oxidation treatment unit 40.

In addition, when heavy oil is used as fuel and the exhaust gas does not contain unburned methane, the valve 60A can be closed and the exhaust gas can be sent only to the turbocharger 30 without being sent to the second oxidation treatment unit 50. This allows the turbocharger 30 to be driven efficiently. In addition, when heavy oil is used as fuel, the sulfur contained in the exhaust gas can be prevented from reaching the second oxidation treatment unit 50, and the impact on the second methane oxidation catalyst 52 can be reduced.

In the first embodiment, the switching unit 110 can switch the introduction destination of the exhaust gas discharged from the turbocharger 30 between the exhaust pipe 102 and the first oxidizer bypass pipe 105 .
As a result, for example, when methane is used as the fuel, the switching unit 110 causes the exhaust gas discharged from the turbocharger 30 to be introduced into the first oxidation treatment unit 40 via the exhaust pipe 102, so that the unburned methane contained in the exhaust gas can be oxidized in the first oxidation treatment unit 40, as described above.
On the other hand, when heavy oil whose exhaust gas does not contain unburned methane is used as fuel, the switching unit 110 causes the exhaust gas discharged from the turbocharger 30 to be introduced into the first oxidation treatment unit bypass pipe 105, so that the exhaust gas is not introduced into the first oxidation treatment unit 40 and can be efficiently discharged through the first oxidation treatment unit bypass pipe 105.

Furthermore, in the first embodiment, the capacity of the turbocharger 30 is set according to the flow rate of air to be supplied to the engine 20A. When methane is used as fuel, the surplus exhaust gas discharged from the exhaust section 22 that is not supplied to the turbocharger 30 is introduced into the turbocharger bypass pipe 103. In addition, by making the pipe diameter (inner diameter) D2 of the turbocharger bypass pipe 103 smaller than the pipe diameter (inner diameter) D1 of the exhaust pipe 102, it can be made to correspond to the flow rate of exhaust gas introduced into the turbocharger bypass pipe 103. This ensures the capacity of the turbocharger 30 while efficiently oxidizing the unburned methane contained in the exhaust gas.

In addition, in the first embodiment, the temperature of the exhaust gas introduced into the first oxidation treatment unit 40 is lower than the temperature of the exhaust gas introduced into the second oxidation treatment unit 50, and the efficiency of oxidation treatment of the unburned methane contained in the exhaust gas is higher in the second oxidation treatment unit 50 than in the first oxidation treatment unit 40. However, in the first embodiment, by making the concentration of the catalytic components of the second methane oxidation catalyst 52 higher than the concentration of the catalytic components of the first methane oxidation catalyst 42, the efficiency of the methane oxidation treatment can be further increased, and the total amount of active components in the first methane oxidation catalyst 42 and the second methane oxidation catalyst 52 combined can be reduced.

Furthermore, in the first embodiment, the first methane oxidation catalyst 42 and the second methane oxidation catalyst 52 contain the same active component. This allows the first oxidation treatment unit 40 and the second oxidation treatment unit 50 to be manufactured efficiently.

(Modification of the first embodiment)
In the above first embodiment, the engine system 10A is provided in the boat 1, but the engine system 10A is not limited to being provided in the boat 1. The engine system 10A can also be applied to engine systems used in various facilities on land, for example.

Second Embodiment
Next, a second embodiment of the engine system according to the present disclosure will be described. Since the second embodiment differs from the first embodiment only in a part of the configuration of the engine system, the same parts as those in the first embodiment are denoted by the same reference numerals and will not be described again.
(Engine system configuration)
FIG. 6 is a diagram showing a configuration of an engine system according to a second embodiment of the present disclosure.
As shown in FIG. 6, an engine system 10B illustrated in the second embodiment includes an engine 20B, a turbocharger 30, a first oxidation treatment unit 40, and a second oxidation treatment unit 50.

Engine 20B emits exhaust gases generated by burning fuel. The engine 20B illustrated in this embodiment uses only methane as fuel.

The turbocharger 30 is connected to an end of the manifold 24 on the downstream side in the flow direction of the exhaust gas. A portion of the exhaust gas flowing through the manifold 24 is introduced into the turbocharger 30. The turbocharger 30 in this second embodiment is a high-efficiency turbocharger that is more efficient than a turbocharger used in a general engine system that uses only methane as fuel. As a result, the flow rate of the exhaust gas from the engine 20B exceeds the flow rate of the exhaust gas required by the turbocharger 30, and as in the first embodiment, an excess of exhaust gas may occur.
Exhaust gas discharged from the turbocharger 30 flows through the exhaust pipe 102 .

The exhaust gas is introduced into the first oxidation treatment unit 40 via the exhaust pipe 102. The exhaust gas introduced into the first oxidation treatment unit 40 is a mixture of the exhaust gas discharged from the turbocharger 30 and the exhaust gas discharged from the second oxidation treatment unit 50.

The second oxidation treatment section 50 is provided midway through the turbocharger bypass pipe 103. The turbocharger bypass pipe 103 allows a portion of the exhaust gas discharged from the exhaust section 22 to bypass the turbocharger 30 and merge with the exhaust pipe 102.

Exhaust gas is introduced into the second oxidation treatment unit 50 via a turbocharger bypass pipe 103 .
The turbocharger bypass pipe 103 is provided with a valve 60B in an upstream portion 103p located upstream of the second oxidation treatment unit 50 in the exhaust gas flow direction.

Note that the engine system 10B in this second embodiment does not include the first oxidation treatment unit bypass pipe 105 and the switching unit 110 of the engine system 10A exemplified in the first embodiment above.

In this type of engine system 10B, a portion of the exhaust gas discharged from the exhaust section 22 of the engine 20B is introduced into the turbocharger 30 through the manifold 24 of the exhaust section 22. The exhaust gas introduced into the turbocharger 30 drives the turbocharger 30, supplying air to the engine 20B.

The valve 60B is adjusted in opening depending on the rotation speed of the engine 20B, the rotation speed of the turbocharger 30, etc. Specifically, when the flow rate of exhaust gas from the engine 20B exceeds the flow rate of exhaust gas required by the turbocharger 30 and an excess of exhaust gas is generated, the valve 60B is opened at an opening according to the excess. The valve 60B may be always open while the engine 20B is operating, or when no excess of exhaust gas is generated, the valve 60B may be fully closed. When the valve 60B is open, the remaining part (excess) of the exhaust gas discharged from the exhaust section 22 of the engine 20B flows from the manifold 24 into the turbocharger bypass pipe 103. The exhaust gas that flows into the turbocharger bypass pipe 103 is introduced into the second oxidation treatment unit 50. In the second oxidation treatment unit 50, the second methane oxidation catalyst 52 oxidizes the unburned methane contained in the introduced exhaust gas.

The exhaust gas that has passed through the turbocharger 30 and the exhaust gas that has passed through the second oxidation treatment unit 50 join together in the exhaust pipe 102. The exhaust gas that has passed through the second oxidation treatment unit 50 has a higher temperature due to the oxidation process than the exhaust gas introduced into the second oxidation treatment unit 50. Therefore, the temperature of the mixed gas (exhaust gas) in which the exhaust gas that has passed through the turbocharger 30 and the exhaust gas that has passed through the second oxidation treatment unit 50 are mixed is higher than the temperature of the exhaust gas that has passed through the turbocharger 30. The exhaust gas with the increased temperature is introduced from the exhaust pipe 102 to the first oxidation treatment unit 40. In the first oxidation treatment unit 40, the first methane oxidation catalyst 42 oxidizes the unburned methane contained in the introduced exhaust gas. The exhaust gas that has passed through the first oxidation treatment unit 40 is released into the atmosphere from the funnel 9 through the exhaust duct 43.

(Action and Effect)
In the engine system 10B of the second embodiment, as in the first embodiment, it is possible to effectively oxidize the unburned methane contained in the exhaust gas and suppress a decrease in the drive efficiency of the turbocharger 30.

Other Embodiments
Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not deviate from the gist of the present disclosure are also included.
The configurations of the engine systems 10A, 10B shown in the above embodiments are merely examples, and the configurations of the various components can be modified as appropriate.
Furthermore, the uses of the engine systems 10A and 10B are not limited in any way and the engine systems 10A and 10B can be used for a variety of purposes.

<Additional Notes>
The engine systems 10A, 10B and the boat 1 described in each embodiment can be understood, for example, as follows.

(1) The engine system 10A, 10B according to the first aspect includes an engine 20A, 20B driven by methane as fuel, a turbocharger 30 that is driven by exhaust gas discharged from the exhaust section 22 of the engine 20A, 20B to supply air to the engine 20A, 20B, an exhaust pipe 102 through which the exhaust gas discharged from the turbocharger 30 flows, a first oxidation treatment section 40 into which the exhaust gas is introduced via the exhaust pipe 102 and which contains a first methane oxidation catalyst 42, a turbocharger bypass pipe 103 that causes a portion of the exhaust gas discharged from the exhaust section 22 to bypass the turbocharger 30 and merge with the exhaust pipe 102, and a second oxidation treatment section 50 that is provided midway through the turbocharger bypass pipe 103 and contains a second methane oxidation catalyst 52.

In this engine system 10A, 10B, exhaust gas discharged from the exhaust section 22 of the engine 20A, 20B is sent to a turbocharger 30 and a turbocharger bypass pipe 103. The turbocharger 30 is driven by the exhaust gas and supplies air to the engines 20A, 20B. The exhaust gas discharged from the turbocharger 30 flows through an exhaust pipe 102. The exhaust gas discharged from the turbocharger 30 to the exhaust pipe 102 has a lowered temperature by performing work to supply air to the engines 20A, 20B.
The exhaust gas sent to the turbocharger bypass pipe 103 is introduced into the second oxidation treatment unit 50. The second oxidation treatment unit 50 oxidizes the unburned methane contained in the introduced exhaust gas by a second methane oxidation catalyst 52. As the unburned methane is oxidized, the temperature of the exhaust gas sent out from the second oxidation treatment unit 50 is increased. The exhaust gas discharged from the second oxidation treatment unit 50 is passed through the turbocharger bypass pipe 103 and merges with the exhaust pipe 102.
A mixture of exhaust gas discharged from the turbocharger 30 and exhaust gas discharged from the second oxidation treatment unit 50, which have joined together inside the exhaust pipe 102, is introduced into the first oxidation treatment unit 40 through an exhaust pipe 102. Since the exhaust gas discharged from the second oxidation treatment unit 50 has a higher temperature than the exhaust gas discharged from the turbocharger 30, the temperature of the exhaust gas introduced into the first oxidation treatment unit 40 is higher. The first methane oxidation catalyst 42 has a higher oxidation rate of methane as the temperature of the exhaust gas introduced therein is higher. Therefore, methane can be efficiently oxidized in the first oxidation treatment unit 40.
In addition, the second oxidation treatment unit 50 is provided midway through the turbocharger bypass pipe 103, and is not provided between the exhaust section 22 and the turbocharger 30. Therefore, the exhaust gas discharged from the exhaust section 22 is directly fed to the turbocharger 30. Therefore, a decrease in the drive efficiency of the turbocharger 30 is suppressed.
As a result, it is possible to satisfactorily oxidize the unburned methane contained in the exhaust gas, and to suppress a decrease in the drive efficiency of the turbocharger 30.

(2) The engine system 10A, 10B according to the second aspect is the engine system 10A, 10B of (1), further comprising a valve 60A, 60B that opens and closes the flow path of the exhaust gas from the exhaust section 22 to the turbocharger bypass pipe 103.

As a result, by opening and closing the valves 60A and 60B, the flow path of the exhaust gas from the exhaust section 22 to the turbocharger bypass pipe 103 is opened and closed, and the supply of exhaust gas from the exhaust section 22 to the second oxidation treatment section 50 can be interrupted. Therefore, when oxidation treatment of the unburned methane contained in the exhaust gas in the second oxidation treatment section 50 is not necessary, the supply of exhaust gas to the second oxidation treatment section 50 can be stopped.

(3) The engine system 10A according to the third aspect is the engine system 10A of (2), in which the engine 20A switches between using methane and heavy oil as fuel.

As a result, when methane is used as fuel, by opening the valve 60A, the unburned methane contained in the exhaust gas can be oxidized sequentially in the second oxidation treatment unit 50 and the first oxidation treatment unit 40.
Furthermore, when heavy oil is used as fuel, the exhaust gas does not contain unburned methane. Therefore, by closing the valve 60A, the exhaust gas can be sent only to the turbocharger 30 without being sent to the second oxidation treatment unit 50. This allows the turbocharger 30 to be driven efficiently. Furthermore, when heavy oil is used as fuel, the sulfur content contained in the exhaust gas can be prevented from reaching the second oxidation treatment unit 50, and the second methane oxidation catalyst 52 can be prevented from being adversely affected.

(4) The engine system 10A according to the fourth aspect is the engine system 10A according to (3), further comprising a first oxidation treatment unit bypass pipe 105 that causes the exhaust gas discharged from the turbocharger 30 to bypass the first oxidation treatment unit 40, and a switching unit 110 that switches the introduction destination of the exhaust gas discharged from the turbocharger 30 between the exhaust pipe 102 and the first oxidation treatment unit bypass pipe 105.

This allows the switching unit 110 to switch the introduction destination of the exhaust gas discharged from the turbocharger 30 between the exhaust pipe 102 and the first oxidizer bypass pipe 105 .
When methane is used as the fuel, the switching unit 110 introduces the exhaust gas discharged from the turbocharger 30 into the exhaust pipe 102, whereby the unburned methane contained in the exhaust gas can be oxidized sequentially in the second oxidation treatment unit 50 and the first oxidation treatment unit 40.
In addition, when heavy oil is used as fuel, the exhaust gas does not contain unburned methane. Therefore, by using the switching unit 110 to introduce the exhaust gas discharged from the turbocharger 30 into the first oxidizer bypass pipe 105, the exhaust gas can be efficiently discharged through the first oxidizer bypass pipe 105 without being sent to the first oxidizer 40.

(5) The engine system 10A, 10B according to the fifth aspect is any one of the engine systems 10A, 10B of (1) to (4), in which the pipe diameter D2 of the turbocharger bypass pipe 103 is smaller than the pipe diameter D1 of the exhaust pipe 102.

In this configuration, the capacity of the turbocharger 30 is set according to the flow rate of air to be supplied to the engines 20A, 20B. In this case, the turbocharger bypass pipe 103 is introduced with the surplus exhaust gas discharged from the exhaust section 22 that is not supplied to the turbocharger 30. By making the pipe diameter D2 of the turbocharger bypass pipe 103 smaller than the pipe diameter D1 of the exhaust pipe 102, it is possible to make it correspond to the flow rate of exhaust gas introduced into the turbocharger bypass pipe 103. This ensures the capacity of the turbocharger 30 while efficiently oxidizing the unburned methane contained in the exhaust gas.

(6) The engine system 10A, 10B according to the sixth aspect is any one of the engine systems 10A, 10B according to (1) to (5), in which the second methane oxidation catalyst 52 has a higher concentration of catalytic components than the first methane oxidation catalyst 42.

In this configuration, the temperature of the exhaust gas introduced into the first oxidation treatment unit 40 is lower than the temperature of the exhaust gas introduced into the second oxidation treatment unit 50. As a result, the efficiency of the oxidation treatment of the unburned methane contained in the exhaust gas is higher in the second oxidation treatment unit 50 than in the first oxidation treatment unit 40. By making the concentration of the catalytic components of the second methane oxidation catalyst 52 higher than the concentration of the catalytic components of the first methane oxidation catalyst 42, the efficiency of the oxidation treatment of methane can be further increased, and the total amount of active components in the first methane oxidation catalyst 42 and the second methane oxidation catalyst 52 combined can be reduced.

(7) The seventh aspect of the engine system 10A, 10B is any one of the engine systems 10A, 10B of (1) to (6), in which the first methane oxidation catalyst 42 and the second methane oxidation catalyst 52 contain the same active component.

This allows the first oxidation treatment section 40 and the second oxidation treatment section 50 to be manufactured efficiently.

(8) The vessel 1 according to the eighth aspect is equipped with any one of the engine systems 10A described in (1) to (7).

This makes it possible to provide a ship 1 equipped with an engine system 10A that can effectively oxidize the unburned methane contained in the exhaust gas and suppress a decrease in the driving efficiency of the turbocharger 30.

The engine system and ship disclosed herein can effectively oxidize the unburned methane contained in the exhaust gas and prevent a decrease in the drive efficiency of the turbocharger.

Reference Signs List 1... Ship 2... Hull 2b... Stern 2j... Upper engine room 2k... Engine room 3A, 3B... Ship side 4... Ship bottom 5... Upper deck 6... Bottom deck 7... Superstructure 8... Deck 9... Funnel 10A, 10B... Engine system 20A, 20B... Engine 21... Engine body 22... Exhaust section 23... Connection pipe 24... Manifold 30... Turbocharger 40... First oxidation treatment section 41... Housing 42... First methane oxidation catalyst 43... Exhaust duct 50... Second oxidation treatment section 51... Housing 52... Second methane oxidation catalyst 60A, 60B... Valve 102... Discharge pipe 103... Turbocharger bypass pipe 103a... First end 103b... Second end 103c... Intermediate position 103p... Upstream section 103q... Downstream section 105: First oxidation treatment unit bypass pipe 110: Switching unit 111: First switching valve 112: Second switching valve D1, D2: Pipe diameter Da: Bow-stern direction Dv: Up-down direction

Claims (8)

1. an engine powered by methane;
   a turbocharger that is driven by exhaust gas discharged from an exhaust portion of the engine to supply air to the engine;
   An exhaust pipe through which exhaust gas discharged from the turbocharger flows;
   a first oxidation treatment unit into which the exhaust gas is introduced via the exhaust pipe and which accommodates a first methane oxidation catalyst;
   a turbocharger bypass pipe that causes a portion of the exhaust gas discharged from the exhaust portion to bypass the turbocharger and join the exhaust pipe;
   a second oxidation treatment unit provided in the turbocharger bypass pipe and accommodating a second methane oxidation catalyst;
   An engine system comprising:
2. 2. The engine system according to claim 1, further comprising a valve for opening and closing a flow path of the exhaust gas from the exhaust to the turbocharger bypass pipe.
3. 3. The engine system according to claim 2, wherein the engine switches between using methane and heavy oil as fuel.
4. a first oxidation treatment unit bypass pipe for causing the exhaust gas discharged from the turbocharger to bypass the first oxidation treatment unit;
   4. The engine system according to claim 3, further comprising a switching unit that switches a destination of the exhaust gas discharged from the turbocharger between the exhaust pipe and the first oxidation treatment unit bypass pipe.
5. 3. The engine system according to claim 1, wherein a pipe diameter of the supercharger bypass pipe is smaller than a pipe diameter of the exhaust pipe.
6. 3. The engine system according to claim 1, wherein the second methane oxidation catalyst has a higher concentration of catalytic components than the first methane oxidation catalyst.
7. 3. The engine system according to claim 1, wherein the first methane oxidation catalyst and the second methane oxidation catalyst contain the same active component.
8. A ship comprising the engine system according to claim 1 or 2.

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