Marine SCR (Selective Catalytic Reduction) system and engine system comprising same

Abstract

The present invention relates to a marine SCR system and an engine system including the same, and aims to reduce the discharge amount of unburned ammonia and suppress the degradation of a catalyst part at the same time. A marine SCR system, which is connected to an engine capable of combusting ammonia and is configured so as to remove exhaust gas discharged from the engine, comprises: a catalyst module having a plurality of reaction cells that form a flow path for the exhaust gas and promote a reaction of unburned ammonia; the catalyst module allows unburned ammonia discharged from the engine to flow in together with exhaust gas containing the unburned ammonia, the unit number variable mechanism changes the number of reaction units among the plurality of reaction units through which the unburned ammonia flowing into the catalyst module passes, and the controller controls the unit number variable mechanism. The controller determines the concentration or amount of unburned ammonia contained in the exhaust gas, and determines the number of reaction cells so as to increase or decrease the number of reaction cells according to the concentration or amount of unburned ammonia.

Description

Technical Field

[0001] The present disclosure relates to a marine SCR system and an engine system including the marine SCR system. Background Art

[0002] Patent Document 1 discloses a diesel engine that burns a mixture of fuel oil and gaseous ammonia. Specifically, the diesel engine includes a combustion chamber and a fuel injection mechanism that injects fuel oil and ammonia into the combustion chamber.

[0003] In addition, the diesel engine described in Patent Document 1 above is, for example, a marine diesel engine. In order to increase the combustion rate of ammonia and reduce unburned ammonia, the marine diesel engine is configured to make the stratification degree of ammonia in the combustion chamber uniformly distributed over the entire circumference.

[0004] On the other hand, Patent Document 2 discloses an exhaust gas treatment device that is applied to a marine diesel engine as an example of a marine SCR system. Here, the marine diesel engine to which the exhaust gas treatment device is applied is particularly an ammonia-fueled engine that burns a mixture of ammonia fuel and fossil fuel for driving.

[0005] Specifically, the exhaust gas treatment device described in Patent Document 2 above includes a mixer and a reactor having a catalyst layer. Here, the mixer mixes the exhaust gas with a reducing agent and sends them into the reactor. The reactor selectively performs a reduction reaction of nitrogen oxides in the exhaust gas received from the mixer with the reducing agent by the action of the catalyst.

[0006] In addition, the exhaust gas treatment device described in Patent Document 2 above separates a liquid containing ammonia from the ammonia-containing drain, and burns the liquid containing ammonia in an oxidation reactor. The exhaust gas treatment device uses the unburned ammonia component remaining after this combustion as a reducing agent mixed with the exhaust gas.

[0007] Patent Document 1: Japanese Patent Laid-Open Gazette No. 2021-188574

[0008] Patent Document 2: Japanese Patent Laid-Open Gazette No. 2023-120082 Summary of the Invention

[0009] -Technical Problem to be Solved by the Invention-

[0010] For a diesel engine that burns ammonia fuel as in Patent Document 1 above, it is required to suppress the ammonia emission amount below a specified reference value by reducing the emission amount of unburned ammonia.

[0011] As a solution to meet this requirement, for example, it can be considered to make the unburned ammonia react with nitrogen oxides in the exhaust gas by using a marine SCR system as in Patent Document 2 above.

[0012] However, marine SCR systems typically have to process a large amount of exhaust gas. Therefore, compared with other applications (such as automobiles), marine SCR systems have to use a huge catalyst section. In the case of using a huge catalyst section, replacing the catalyst section not only takes a lot of man-hours, but also the cost required for its replacement is very high.

[0013] In order to reduce the above-mentioned man-hours and costs, it is possible to consider suppressing the deterioration of the catalyst section to achieve its long life. However, so far, there is no known technical solution that can take into account both long life and suppression of unburned ammonia emissions.

[0014] The present disclosure is completed to solve the above-mentioned technical problems, and its purpose is to take into account both reducing the amount of unburned ammonia emissions and suppressing the deterioration of the catalyst section.

[0015] -Technical solutions for solving technical problems-

[0016] The first aspect of the present disclosure relates to a marine SCR system that is connected to a diesel engine capable of burning ammonia and is configured to remove unburned ammonia discharged from the diesel engine. The marine SCR system includes a catalyst module, a variable unit number mechanism, and a controller. The catalyst module has a plurality of reaction units that form a flow path for exhaust gas and promote the reaction of unburned ammonia. The catalyst module allows unburned ammonia discharged from the diesel engine to flow in together with the exhaust gas containing the unburned ammonia. The variable unit number mechanism changes the number of reaction units through which the unburned ammonia flowing into the catalyst module among the plurality of reaction units. The controller controls the variable unit number mechanism. The controller determines the concentration or amount of unburned ammonia contained in the exhaust gas, and the controller determines the number of reaction units in such a way that the number of reaction units is increased or decreased according to the concentration or amount of the unburned ammonia.

[0017] According to the first aspect, the variable unit number mechanism adjusts the number of reaction units (reaction unit number) through which the unburned ammonia passes according to the concentration or amount of unburned ammonia contained in the exhaust gas. By setting the number of reaction units corresponding to the concentration or amount of unburned ammonia, it is possible to remove unburned ammonia without using all the reaction units. Thus, it is possible to suppress the deterioration of the reaction units and further suppress the deterioration of the catalyst section.

[0018] In this way, according to the first aspect, it is possible to take into account both reducing the amount of unburned ammonia emissions and suppressing the deterioration of the catalyst section.

[0019] In addition, according to the second aspect of the present disclosure, it may also be that the controller increases the number of reaction units as the concentration or amount of the unburned ammonia increases.

[0020] According to the second aspect, the number of reaction units can be suppressed to an appropriate amount commensurate with the concentration or amount of unburned ammonia, without excess. Thereby, the discharge amount of unburned ammonia can be reduced, and the deterioration of the catalyst section can be suppressed.

[0021] Further, according to the third aspect of the present disclosure, it may also be that: the catalyst module has a plurality of catalyst sections connected in parallel or in series with respect to the flow direction of the exhaust gas, and the unit number variable mechanism is configured to change the number of catalyst sections through which the unburned ammonia passes among the plurality of catalyst sections, and the controller increases the number of catalyst sections as the concentration or amount of the unburned ammonia increases.

[0022] According to the third aspect, the controller changes the number of reaction units by changing the number of catalyst sections (the number of catalyst sections) through which the unburned ammonia passes. Thereby, since it is only necessary to change the flow path to each catalyst section, the number of reaction units can be easily changed without providing a complicated mechanism for a specific catalyst section.

[0023] Further, in the case where the number of reaction units is configured to be changed through the number of catalyst sections, the degree of deterioration of each catalyst section is generally different in each catalyst section. In this case, as long as the reaction unit is replaced in units of catalyst sections, the maintainability of the marine SCR system can be improved.

[0024] Further, according to the fourth aspect of the present disclosure, it may also be that: the controller controls the unit number variable mechanism based on the number of catalyst sections set corresponding to the concentration or amount of the unburned ammonia and the combination of catalyst sections set corresponding to the number of catalyst sections, and the controller updates the correspondence between the number of catalyst sections and the combination of catalyst sections on the occasion of a specified condition.

[0025] According to the fourth aspect, by presetting the combination of catalyst sections through which the unburned ammonia passes for each number of catalyst sections and configuring to update this setting under specified conditions, the degree of deterioration of each catalyst section can be made uniform. Thereby, it is advantageous in suppressing the deterioration of the catalyst section.

[0026] Further, according to the fifth aspect of the present disclosure, it may also be that: the marine SCR system includes a first concentration sensor arranged on a first exhaust pipe connecting the diesel engine and the catalyst module, detecting the ammonia concentration in the first exhaust pipe, and the controller, based on the detection signal of the first concentration sensor, when the ammonia concentration in the first exhaust pipe exceeds a specified reference value, causes the unburned ammonia to start flowing into the catalyst module.

[0027] According to the fifth aspect, the first concentration sensor detects the ammonia concentration before it is introduced into the catalyst module. And, the controller causes the unburned ammonia to start flowing into the catalyst module based on the detection signal of the first concentration sensor. With such a configuration, it is possible to immediately start the inflow of unburned ammonia when the concentration of unburned ammonia increases. It is possible to more reliably suppress the leakage of unburned ammonia to the outside of the ship (especially leakage at a concentration exceeding a specified reference value).

[0028] In addition, according to the sixth aspect of the present disclosure, it may also be that: the marine SCR system includes a second concentration sensor disposed on a second exhaust pipe connecting the catalyst module to the outside of the ship, and detects the ammonia concentration in the second exhaust pipe, and the controller determines the number of reaction units through which the unburned ammonia passes in the catalyst module based on the detection signal of the second concentration sensor.

[0029] According to the sixth aspect, the second concentration sensor detects the ammonia concentration immediately after it is discharged from the catalyst module. And, the controller adjusts the number of reaction units based on the detection signal of the second concentration sensor. With such a configuration, it is possible to set the number of reaction units to the minimum number of reaction units that can suppress the leakage of unburned ammonia without excess. As a result, it is possible to suppress the deterioration of the catalyst part without hindering the reduction of the discharge amount of unburned ammonia.

[0030] In addition, according to the seventh aspect of the present disclosure, it may also be that: when the ammonia concentration in the second exhaust pipe is lower than the reference value, the controller ends the inflow of unburned ammonia into the catalyst module.

[0031] According to the seventh aspect, the controller ends the inflow of unburned ammonia into the catalyst module based on the ammonia concentration immediately after it is discharged from the catalyst module. With such a configuration, it is possible to more reliably determine that the ammonia concentration in the exhaust gas discharged from the catalyst module has fallen below the reference value. As a result, it is possible to end the inflow of unburned ammonia into the catalyst module at a more appropriate time, and it is possible to more reliably suppress the leakage of unburned ammonia to the outside of the ship (especially leakage at a concentration exceeding a specified reference value).

[0032] In addition, according to the eighth aspect of the present disclosure, it may also be that: the marine SCR system includes a bypass pipe and a bypass valve. The bypass pipe connects the diesel engine to the outside of the ship in a way that bypasses the catalyst module. The bypass valve is electrically connected to the controller. The bypass valve opens and closes the bypass pipe. When the ammonia concentration in the first exhaust pipe connecting the diesel engine to the catalyst module is below a specified reference value, the controller opens the bypass valve, so that the unburned ammonia bypasses the catalyst module through the bypass pipe. When the ammonia concentration in the first exhaust pipe exceeds the reference value, the controller closes the bypass valve, so that the unburned ammonia flows into the catalyst module.

[0033] In addition, according to the ninth aspect of the present disclosure, it may also be that the marine SCR system includes a bypass pipe and a bypass valve. The bypass pipe connects the diesel engine to the outside of the ship in a way that bypasses the catalyst module. The bypass valve is electrically connected to the controller. The bypass valve opens and closes the bypass pipe. When the ammonia concentration in the first exhaust pipe is below the reference value, the controller opens the bypass valve, so that the unburned ammonia bypasses the catalyst module via the bypass pipe. When the ammonia concentration in the first exhaust pipe exceeds the reference value, the controller closes the bypass valve, so that the unburned ammonia flows into the catalyst module.

[0034] It should be noted that the term "opening the valve" here not only includes the action of making the opening degree of the bypass valve fully open, but also includes all actions of adjusting its opening degree in the opening direction. Similarly, the term "closing the valve" here not only includes the action of making the opening degree of the bypass valve fully closed, but also includes all actions of adjusting its opening degree in the closing direction.

[0035] According to the eighth and ninth aspects, by appropriately opening and closing the bypass valve or adjusting its opening degree based on the ammonia concentration, more precise control commensurate with the ammonia concentration can be achieved.

[0036] In addition, the tenth aspect of the present disclosure relates to an engine system. The engine system may also include the marine SCR system and a diesel engine. The diesel engine is connected to the marine SCR system and the diesel engine can at least burn ammonia.

[0037] According to the tenth aspect, it is possible to balance the reduction of the discharge amount of unburned ammonia and the suppression of the deterioration of the catalyst part.

[0038] - Effects of the Invention -

[0039] As described above, according to the present disclosure, it is possible to balance the reduction of the discharge amount of unburned ammonia and the suppression of the deterioration of the catalyst part. Description of the Drawings

[0040] Figure 1 It is a system diagram exemplarily showing an engine system, a diesel engine, and a marine SCR system constituting the engine system;

[0041] Figure 2 It is a diagram exemplarily showing the upper structure of the engine body;

[0042] Figure 3 It is a block diagram exemplarily showing the brief structure of the marine SCR system;

[0043] Figure 4is a system diagram exemplarily showing the structure of a marine SCR system;

[0044] Figure 5A is a flowchart exemplarily showing the processing in the second mode;

[0045] Figure 5B is a flowchart exemplarily showing the processing in the second mode;

[0046] Figure 5C is a flowchart exemplarily showing the processing in the second mode;

[0047] Figure 5D is a flowchart exemplarily showing the processing in the second mode;

[0048] Figure 6 is a graph showing the relationship between the concentration of unburned NH3 and the number of reaction units in the second mode;

[0049] Figure 7 is a diagram showing an example of the first control map;

[0050] Figure 8 is a diagram for explaining the update of the first control map;

[0051] Figure 9 is a diagram showing a modified example of the backflow prevention mechanism and Figure 4 the corresponding diagram;

[0052] Figure 10 is a diagram showing the second embodiment of the SCR system and Figure 4 the corresponding diagram;

[0053] Figure 11 is a diagram exemplarily showing the first control map in the second embodiment.

[0054] -Symbol Explanation-

[0055] S - Engine system; 1 - Diesel engine; 2 - Engine main body; 21 - Cylinder; 3 - Intake and exhaust system; 32 - Exhaust pipe; 32a - First exhaust pipe; 32b - Second exhaust pipe; 100 - Marine SCR system; 110 - SCR device; 111 - Exhaust gas flow pipe; 111d - Bypass pipe; 115 - Catalyst module; 115a - Reaction unit; 116 - Catalyst part; 116a - First catalyst part; 116b - Second catalyst part; 116c - Third catalyst part; 117 - Unit number variable mechanism; 117d - Bypass valve; 120 - Controller; 131 - First concentration sensor; 132 - Second concentration sensor; M1 - First control map; T1 - First reference value (reference value). Detailed Embodiment

[0056] Hereinafter, a first embodiment (hereinafter simply referred to as "embodiment") of the present disclosure will be described based on the drawings. It should be noted that the following description is only an example. Figure 1 It is a system diagram exemplarily showing an engine system S, a diesel engine 1 and a marine SCR system 100 constituting the engine system S.

[0057] <Overall Structure>

[0058] As Figure 1 shown, the engine system S includes a diesel engine (hereinafter also simply referred to as "engine") 1 and a marine SCR system (hereinafter also simply referred to as "SCR system") 100 connected to the engine 1. The engine system S is mounted on large ships such as tankers, container ships, and vehicle carriers.

[0059] The engine 1 can at least burn ammonia. The engine 1 is configured as a direct-current scavenging two-stroke cycle engine and is used as a main engine that generates propulsion force for the above-mentioned ship to navigate. The output shaft of the engine 1 is connected to a propeller (not shown) of the ship via a propeller shaft (not shown). When the engine 1 operates, the output of the engine 1 is transmitted to the propeller, thereby propelling the ship forward.

[0060] Specifically, the engine 1 can operate in a first mode and a second mode respectively. In the first mode, the sulfur-containing oil fuel is burned alone in the cylinder 21; in the second mode, at least ammonia among ammonia and the oil fuel is burned in the same cylinder 21. The engine 1 can operate in the first mode or the second mode by switching from the first mode to the second mode or from the second mode to the first mode. In the present embodiment, fossil fuels such as heavy oil are used as the oil fuel. The fossil fuel can be any fuel that can be refined from crude oil.

[0061] More specifically, the engine 1 is configured to be able to perform at least one of the mixed combustion of ammonia and oil fuel and the separate combustion of ammonia when operating in the second mode.

[0062] For example, the engine 1 described in detail below is configured to burn the oil fuel alone in the first mode and burn ammonia and the oil fuel in the second mode. It should be noted that the first mode is not essential. The engine 1 only needs to be able to operate in the second mode at least.

[0063] Here, when configured to burn ammonia, it can be envisioned that in the exhaust gas discharged from the cylinder 21 (especially the exhaust gas before being discharged to the outside of the ship), in addition to containing so-called nitrogen oxides, unburned ammonia may also be contained.

[0064] In order to remove the contaminants in the exhaust gas, the SCR system 100 according to this embodiment is configured to remove the unburned ammonia discharged from the diesel engine 1. The SCR system 100 includes an SCR device 110. By using this device 110, the unburned ammonia reacts with nitrogen oxides, so that the unburned ammonia can be removed from the exhaust gas.

[0065] Hereinafter, each element constituting the engine system S will be described in turn.

[0066] <Details of the engine 1>

[0067] As Figure 1 shown, the engine 1 includes an engine body 2 having the above-described cylinders 21, an intake and exhaust system 3, and a fuel supply system 4. The intake and exhaust system 3 and the fuel supply system 4 are respectively connected to the engine body 2.

[0068] (1) Engine body 2

[0069] As Figure 1 shown, the engine body 2 has a plurality of (only three are shown in Figure 1 ) cylinders 21. The engine body 2 is a two-stroke engine and is provided in the engine room of the ship. In order to achieve its long stroke, the engine body 2 is configured as a so-called crosshead internal combustion engine.

[0070] Figure 2 is a view exemplarily showing the upper structure of the engine body 2. As Figure 2 shown, the cylinder 21 houses a piston 22. Each cylinder 21 is composed of a cylinder liner 23 and a cylinder head 24. Here, the cylinder liner 23 functions as an inner cylinder extending in the vertical direction (corresponding to the vertical direction of the paper surface in Figure 2 ). The cylinder head 24 is fixed to the upper end of the cylinder liner 23 and closes the opening formed at the upper end.

[0071] Each cylinder 21 of the engine body 2 also has an exhaust relay pipe 25 and an exhaust valve 26. Here, the exhaust relay pipe 25 connects the central portion of each cylinder head 24 to an exhaust manifold 2b described later. The exhaust valve 26 opens and closes the central portion of each cylinder head 24.

[0072] Moreover, a combustion chamber 27 is defined in each cylinder 21 by the inner wall of each cylinder 21 and the top surface of the piston 22. One or more first fuel injection valves 28 and one or more second fuel injection valves 29 are provided on the cylinder head 24 corresponding to each combustion chamber 27.

[0073] One or more (two in the illustrated example) first fuel injection valves 28 are provided for each cylinder 21 and are respectively connected to a first supply system 41. Each first fuel injection valve 28 is arranged in a posture facing the interior of the combustion chamber 27 and is configured to inject oil fuel from its injection port.

[0074] One or more second fuel injection valves 29 are also provided for each cylinder 21. Preferably, the same number (two in the illustrated example) of second fuel injection valves 29 as the first fuel injection valves 28 are provided for each cylinder 21, and they are respectively connected to a second supply system 42. Each second fuel injection valve 29 is arranged in a posture facing the interior of the combustion chamber 27 and is configured to inject ammonia from its injection port.

[0075] When the engine 1 operates in the first mode, only the first fuel injection valve 28 among the first fuel injection valve 28 and the second fuel injection valve 29 supplies oil fuel into the combustion chamber 27. The oil fuel supplied from the first fuel injection valve 28 burns alone in the combustion chamber 27.

[0076] On the other hand, when the engine 1 operates in the second mode, oil fuel is supplied from the first fuel injection valve 28 into the combustion chamber 27, and ammonia is supplied from the second fuel injection valve 29 into the same combustion chamber 27. The oil fuel and ammonia thus supplied are mixed and burned (co-combusted) in the combustion chamber 27.

[0077] The reciprocating motion of the piston 22 is caused by the combustion corresponding to each mode. At this time, if the exhaust valve 26 operates to open the combustion chamber 27, the exhaust gas generated by the combustion is expelled into the exhaust relay pipe 25, and air is introduced into the combustion chamber 27 from a scavenging port (not shown).

[0078] In addition, when the piston 22 makes a reciprocating motion due to combustion, a crank motion occurs via a piston rod, a crosshead, etc., and the crankshaft rotates with this crank motion. The rotation of the crankshaft causes the propeller of the ship to rotate via a propeller shaft. The propeller of the ship rotates, thereby propelling the ship forward.

[0079] Returning to Figure 1 , the engine body 2 also has a scavenging box 2a and an exhaust manifold 2b. The scavenging box 2a communicates with each combustion chamber 27 and temporarily stores air. The exhaust manifold 2b communicates with the combustion chamber 27 via the exhaust relay pipe 25, receives the exhaust gas discharged from the combustion chamber 27, temporarily stores the received exhaust gas, and converts the dynamic pressure of the exhaust gas into static pressure.

[0080] (2) Intake and exhaust system 3

[0081] As Figure 1 shown, the intake and exhaust system 3 has an intake pipe 31 connected to the engine body 2 via the scavenging box 2a and an exhaust pipe 32 connected to the engine body 2 via the exhaust manifold 2b.

[0082] The intake pipe 31 communicates with the combustion chamber 27 via the scavenging chamber 2a, and the intake pipe 31 is configured to introduce air into the combustion chamber 27. The exhaust pipe 32 communicates with the combustion chamber 27 via the exhaust manifold 2b, and the exhaust pipe 32 is configured to guide the exhaust gas discharged from the combustion chamber 27.

[0083] Specifically, the exhaust pipe 32 has a first exhaust pipe 32a connecting the engine 1 and the SCR device 110 and a second exhaust pipe 32b connecting the SCR device 110 and the outside of the ship.

[0084] The first exhaust pipe 32a is a tubular member having one end (upstream end) connected to the engine 1 and the other end (downstream end) connected to the SCR device 110. The first exhaust pipe 32a forms a passage for guiding the exhaust gas from the engine 1 to the SCR device 110.

[0085] A first concentration sensor 131 that constitutes the SCR system 100 together with the SCR device 110 is arranged on the first exhaust pipe 32a. The first concentration sensor 131 detects the ammonia concentration in the first exhaust pipe 32a.

[0086] The second exhaust pipe 32b is a tubular member having one end (upstream end) connected to the SCR device 110 and the other end (downstream end) connected to the outside of the ship. The second exhaust pipe 32b forms a passage for guiding the exhaust gas from the SCR device 110 to the outside of the ship.

[0087] A second concentration sensor 132 that constitutes the SCR system 100 together with the SCR device 110 is arranged on the second exhaust pipe 32b. The second concentration sensor 132 detects the ammonia concentration in the second exhaust pipe 32b.

[0088] (3) Fuel supply system 4

[0089] As Figure 1 shown, the fuel supply system 4 has a first supply system 41 and a second supply system 42. The first supply system 41 supplies oil fuel to each first fuel injection valve 28. The second supply system 42 supplies ammonia to each second fuel injection valve 29.

[0090] Specifically, the first supply system 41 has a first fuel tank 41a, a first fuel supply pipe 41b, and a first fuel pump 41c. The first fuel tank 41a stores oil fuel. The first fuel supply pipe 41b connects the first fuel tank 41a and each first fuel injection valve 28. The first fuel pump 41c is arranged on the first fuel supply pipe 41b. The first fuel pump 41c pressurizes and transports the oil fuel stored in the first fuel tank 41a and supplies the oil fuel to the first fuel injection valve 28.

[0091] For example, when the engine 1 operates in the first mode or the second mode, the first fuel pump 41c operates. As a result, the oil fuel stored in the first fuel tank 41a is supplied to each first fuel injection valve 28 via the first fuel supply pipe 41b, and is injected from each first fuel injection valve 28 into the corresponding cylinder 21.

[0092] On the other hand, the second supply system 42 includes a second fuel tank 42a, a second fuel supply pipe 42b, and a second fuel pump 42c. The second fuel tank 42a stores ammonia. The second fuel supply pipe 42b connects the second fuel tank 42a with each second fuel injection valve 29. The second fuel pump 42c is arranged on the second fuel supply pipe 42b. The second fuel pump 42c pressurizes and transports the ammonia stored in the second fuel tank 42a, and supplies the ammonia to the second fuel injection valve 29.

[0093] For example, when the engine 1 operates in the second mode, in addition to the first fuel pump 41c operating, the second fuel pump 42c also operates. As a result, the ammonia stored in the second fuel tank 42a is supplied to each second fuel injection valve 29 via the second fuel supply pipe 42b, and is injected from each second fuel injection valve 29 into the corresponding cylinder 21.

[0094] <Details of the SCR system 100>

[0095] Figure 3 is a block diagram exemplarily showing the brief structure of the SCR system 100, Figure 4 is a system diagram exemplarily showing the structure of the SCR system 100. As Figure 3 shown, the SCR system 100 includes the above-mentioned SCR device 110, a controller 120, a first concentration sensor 131, and a second concentration sensor 132.

[0096] Here, the SCR device 110 causes unburned ammonia (NH3) in the exhaust gas to react with nitrogen oxides (NO x ) in the exhaust gas as well, to remove the unburned NH3 from the exhaust gas. The controller 120 controls the SCR device 110, particularly controls the unit number variable mechanism 117 described later. The first concentration sensor 131 and the second concentration sensor 132 respectively output detection signals for controlling the unit number variable mechanism 117 to the controller 120.

[0097] (1) SCR device 110

[0098] As Figure 4 shown, the SCR device 110 includes an exhaust gas flow pipe 111, a mixer 113, the above-mentioned catalyst module 115, a unit number variable mechanism 117, and a backflow prevention mechanism 119.

[0099] Here, the catalyst module 115 functions as a reactor for Selective Catalytic Reduction (SCR). The catalyst module 115 has a plurality of reaction units 115a that form a flow path for the exhaust gas and promote the reaction of unburned NH3. The catalyst module 115 is configured to allow the unburned NH3 discharged from the engine 1 to flow in together with the exhaust gas containing the unburned NH3.

[0100] In addition, the catalyst module 115 has a plurality of catalyst parts 116, and each of the plurality of catalyst parts 116 has a plurality of reaction units 115a. These plurality of catalyst parts 116 are connected in parallel or in series with respect to the flow direction of the exhaust gas. Each catalyst part 116 is composed of a so-called SCR catalyst, a slip catalyst, and the like.

[0101] In particular, in the present embodiment, the three catalyst parts 116 are connected in parallel with respect to the flow direction of the exhaust gas. Hereinafter, these plurality of catalyst parts 116 may sometimes be referred to as a first catalyst part 116a, a second catalyst part 116b, and a third catalyst part 116c.

[0102] In addition, the unit number variable mechanism 117 has a plurality of control valves. Hereinafter, these plurality of control valves may sometimes be referred to as a first inlet valve 117a, a second inlet valve 117b, a third inlet valve 117c, and a bypass valve 117d.

[0103] In addition, the backflow prevention mechanism 119 has a plurality of control valves. Hereinafter, these plurality of control valves may sometimes be referred to as a first outlet valve 119a, a second outlet valve 119b, and a third outlet valve 119c.

[0104] (1-1) Exhaust gas circulation pipe 111

[0105] The exhaust gas circulation pipe 111 extends in a manner of relaying between the first exhaust pipe 32a and the second exhaust pipe 32b, and is configured to guide the exhaust gas flowing in from the first exhaust pipe 32a to the catalyst module 115 and guide the exhaust gas discharged from the catalyst module 115 to the second exhaust pipe 32b.

[0106] That is to say, it can be regarded that: the first exhaust pipe 32a connects the engine 1 to the catalyst module 115 via the exhaust gas circulation pipe 111. Similarly, it can be regarded that: the second exhaust pipe 32b connects the catalyst module 115 to the outside of the ship via the exhaust gas circulation pipe 111.

[0107] Specifically, the exhaust gas circulation pipe 111 has a first circulation pipe 111a, a second circulation pipe 111b, a third circulation pipe 111c, and a bypass pipe 111d.

[0108] The first flow pipe 111a is a tubular member having one end (upstream end) connected to the downstream end of the first exhaust pipe 32a and the other end (downstream end) connected to the upstream end of the second exhaust pipe 32b.

[0109] On the first flow pipe 111a, a mixer 113, a first inlet valve 117a, a first catalyst section 116a, and a first outlet valve 119a are arranged in sequence from the upstream side.

[0110] The bypass pipe 111d connects the engine 1 to the outside of the ship so as to bypass the catalyst module 115. In particular, the bypass pipe 111d according to the present embodiment connects the engine 1 to the outside of the ship via the first exhaust pipe 32a and the second exhaust pipe 32b.

[0111] Specifically, the bypass pipe 111d has one end (upstream end) connected to the first connection portion P1 and the other end (downstream end) connected to the second connection portion P2. The first connection portion P1 is located in the middle of the first flow pipe 111a, and the second connection portion P2 is located in the middle of the first flow pipe 111a and downstream of the first connection portion P1.

[0112] Here, the first connection portion P1 is downstream of the mixer 113 and upstream of the first inlet valve 117a on the first flow pipe 111a. The second connection portion P2 is downstream of the first outlet valve 119a on the first flow pipe 111a.

[0113] In addition, a bypass valve 117d described later is arranged on the bypass pipe 111d.

[0114] With respect to the flow direction of the exhaust gas, the second flow pipe 111b is connected in parallel with the first flow pipe 111a and the bypass pipe 111d.

[0115] Specifically, the second flow pipe 111b has one end (upstream end) connected to the third connection portion P3 and the other end (downstream end) connected to the fourth connection portion P4. The third connection portion P3 is located in the middle of the bypass pipe 111d, and the fourth connection portion P4 is located in the middle of the bypass pipe 111d and downstream of the third connection portion P3.

[0116] Here, the third connection portion P3 is upstream of the bypass valve 117d on the bypass pipe 111d. The fourth connection portion P4 is downstream of the bypass valve 117d on the bypass pipe 111d.

[0117] On the second flow pipe 111b, a second inlet valve 117b, a second catalyst section 116b, and a second outlet valve 119b are arranged in sequence from the upstream side.

[0118] The third flow pipe 111c is connected in parallel with the first flow pipe 111a, the second flow pipe 111b, and the bypass pipe 111d with respect to the flow direction of the exhaust gas.

[0119] Specifically, the third flow pipe 111c has one end (upstream end) connected to the fifth connection part P5 and the other end (downstream end) connected to the sixth connection part P6. The fifth connection part P5 is located in the middle of the bypass pipe 111d, and the sixth connection part P6 is located in the middle of the bypass pipe 111d and downstream of the fifth connection part P5.

[0120] Here, the fifth connection part P5 is downstream of the third connection part P3 on the bypass pipe 111d and upstream of the bypass valve 117d. The sixth connection part P6 is downstream of the bypass valve 117d on the bypass pipe 111d and upstream of the fourth connection part P4.

[0121] On the third flow pipe 111c, a third inlet valve 117c, a third catalyst part 116c, and a third outlet valve 119c are arranged in sequence from the upstream side.

[0122] (1 - 2) Mixer 113

[0123] The mixer 113 is an exhaust pipe configured to inject a reducing agent into the exhaust gas to mix them and vaporize the reducing agent mixed into the exhaust gas. In the present embodiment, urea water is used as the reducing agent injected into the exhaust gas.

[0124] Specifically, as Figure 4 shown, the mixer 113 according to the present embodiment has a mixing pipe 113a through which the exhaust gas flows and a nozzle 113b arranged inside the mixing pipe 113a and injecting urea water into the exhaust gas. The nozzle 113b is electrically connected to the controller 120, and the nozzle 113b injects urea water based on a control signal from the controller 120. The urea water injected into the exhaust gas becomes NH3 through vaporization.

[0125] In addition, as will be described later, in the NH3 used in the present embodiment, in addition to the NH3 derived from urea water in the first mode, it also contains unburned NH3 derived from ammonia fuel in the second mode. The urea water injected from the nozzle 113b as described above is related to the former NH3.

[0126] (1 - 3) Catalyst module 115

[0127] The catalyst module 115 promotes a chemical reaction on the reaction unit 115a by bringing the exhaust gas containing NH3 into contact with the reaction unit 115a. Thereby, at least NH3 is removed from the exhaust gas. Each catalyst part 116 constituting the catalyst module 115 functions as a so - called reactor in the SCR device 110.

[0128] The reaction unit 115a that constitutes each catalyst part 116 is composed of a honeycomb structure through which exhaust gas flows. On each unit wall that constitutes the honeycomb structure, for example, zeolite that captures NH3 and a metal that reacts with NH3 (for example, a metal that reduces NO with NH3 as a reducing agent) are supported. x The metal).

[0129] In addition, the first catalyst part 116a, the second catalyst part 116b, and the third catalyst part 116c are connected in parallel with respect to the flow direction of the exhaust gas as described above. In the present embodiment, these catalyst parts 116 are each configured as an SCR catalyst that reduces NO with NH3 as a reducing agent. x The SCR catalyst.

[0130] (1-4) Unit number variable mechanism 117

[0131] The unit number variable mechanism 117 is configured to change the number of reaction units 115a through which NH3 flowing into the catalyst module 115 passes among a plurality of reaction units 115a (hereinafter, also referred to as "the number of reaction units"). It should be noted that the "NH3" mentioned here refers to NH3 contained in the exhaust gas. Especially in the second mode, the "NH3" mentioned here corresponds to unburned NH3 that may be contained in the exhaust gas.

[0132] In particular, the unit number variable mechanism 117 according to the present embodiment is configured to change the number of catalyst parts 116 through which the unburned ammonia passes among a plurality of catalyst parts 116 (hereinafter, also referred to as "the number of catalyst parts").

[0133] Specifically, as described above, the unit number variable mechanism 117 has a plurality of control valves. The plurality of control valves include a first inlet valve 117a, a second inlet valve 117b, a third inlet valve 117c, and a bypass valve 117d.

[0134] The first inlet valve 117a, the second inlet valve 117b, the third inlet valve 117c, and the bypass valve 117d are each composed of, for example, a solenoid valve. The first inlet valve 117a, the second inlet valve 117b, the third inlet valve 117c, and the bypass valve 117d are each electrically connected to the controller 120.

[0135] The first inlet valve 117a operates based on a control signal from the controller 120, thereby opening and closing the first flow pipe 111a. If the first inlet valve 117a opens the first flow pipe 111a, the exhaust gas is allowed to flow into the first catalyst part 116a. If the first inlet valve 117a closes the first flow pipe 111a, the flow of the exhaust gas into the first catalyst part 116a is restricted.

[0136] The second inlet valve 117b operates based on a control signal from the controller 120, thereby opening and closing the second flow pipe 111b. If the second inlet valve 117b opens the second flow pipe 111b, exhaust gas is allowed to flow into the second catalyst section 116b. If the second inlet valve 117b closes the second flow pipe 111b, the inflow of exhaust gas into the second catalyst section 116b is restricted.

[0137] The third inlet valve 117c operates based on a control signal from the controller 120, thereby opening and closing the third flow pipe 111c. If the third inlet valve 117c opens the third flow pipe 111c, exhaust gas is allowed to flow into the third catalyst section 116c. If the third inlet valve 117c closes the third flow pipe 111c, the inflow of exhaust gas into the third catalyst section 116c is restricted.

[0138] The bypass valve 117d operates based on a control signal from the controller 120, thereby opening and closing the bypass pipe 111d. If the bypass valve 117d opens the bypass pipe 111d, the exhaust gas can bypass the catalyst module 115. If the bypass valve 117d closes the bypass pipe 111d, the flow of exhaust gas through the bypass pipe 111d is restricted.

[0139] For example, in a state where the bypass valve 117d is closed, if all of the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c are opened, the exhaust gas will pass through all of the first catalyst section 116a, the second catalyst section 116b, and the third catalyst section 116c. The number of reaction units through which the exhaust gas (specifically, unburned NH3 contained in the exhaust gas) passes becomes the maximum value N3. This maximum value N3 is as described later Figure 6 shown. At this time, the number of catalyst sections defined as above becomes the maximum value, which is 3.

[0140] In addition, in a state where the bypass valve 117d is opened, if all of the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c are closed, the number of reaction units through which the exhaust gas passes becomes the minimum value (=0) as Figure 6 shown. The number of catalyst sections at this time becomes the minimum value, which is 0.

[0141] In addition, in a state where the bypass valve 117d is closed, if one of the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c is opened, the exhaust gas will pass through one of the first catalyst section 116a, the second catalyst section 116b, and the third catalyst section 116c. As Figure 6 shown, the number of reaction units through which the exhaust gas passes becomes a first intermediate value N1 that is closer to the minimum value than to the maximum value. The number of catalyst sections at this time is 1.

[0142] Further, in a state where the bypass valve 117d is closed, if two of the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c are opened, the exhaust gas will pass through two of the first catalyst section 116a, the second catalyst section 116b, and the third catalyst section 116c. As Figure 6 shown, the number of reaction units through which the exhaust gas passes becomes a second intermediate value N2 that is closer to the maximum value than to the minimum value. The number of catalyst sections at this time is 2.

[0143] Further, in a state where the bypass valve 117d is opened, if at least one of the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c is opened, the flow direction of the exhaust gas will be split and pass through the catalyst module 115 and the bypass pipe 111d respectively.

[0144] (1 - 5) Backflow prevention mechanism 119

[0145] The backflow prevention mechanism 119 is configured to prevent the exhaust gas that has passed through the catalyst module 115 or the bypass pipe 111d from flowing back.

[0146] As described above, the backflow prevention mechanism 119 has a plurality of control valves. The plurality of control valves include a first outlet valve 119a, a second outlet valve 119b, and a third outlet valve 119c.

[0147] The first outlet valve 119a, the second outlet valve 119b, and the third outlet valve 119c are each constituted by, for example, a solenoid valve. The first outlet valve 119a, the second outlet valve 119b, and the third outlet valve 119c are each electrically connected to the controller 120.

[0148] The first outlet valve 119a operates based on a control signal from the controller 120 to open and close the first flow pipe 111a. If the first outlet valve 119a opens the first flow pipe 111a, the exhaust gas is allowed to flow out from the first catalyst section 116a. If the first outlet valve 119a closes the first flow pipe 111a, the outflow of the exhaust gas from the first catalyst section 116a is restricted, and the backflow of the exhaust gas into the first catalyst section 116a is restricted.

[0149] The second outlet valve 119b operates based on a control signal from the controller 120 to open and close the second flow pipe 111b. If the second outlet valve 119b opens the second flow pipe 111b, the exhaust gas is allowed to flow out from the second catalyst section 116b. If the second outlet valve 119b closes the second flow pipe 111b, the outflow of the exhaust gas from the second catalyst section 116b is restricted, and the backflow of the exhaust gas into the second catalyst section 116b is restricted.

[0150] The third outlet valve 119c operates based on a control signal from the controller 120, thereby opening and closing the third flow pipe 111c. If the third outlet valve 119c opens the third flow pipe 111c, the exhaust gas is allowed to flow out from the third catalyst section 116c. If the third outlet valve 119c closes the third flow pipe 111c, the outflow of the exhaust gas from the third catalyst section 116c is restricted, and the backflow of the exhaust gas into the third catalyst section 116c is restricted.

[0151] (2) Controller 120

[0152] (2-1) Brief structure

[0153] The controller 120 includes a processor, a volatile memory, a non-volatile memory, and an input / output device. The controller 120 is electrically connected to the first concentration sensor 131 and the second concentration sensor 132 described above.

[0154] The controller 120 generates a control signal based on the detection signals input from these sensors, and inputs the control signal to, for example, the mixer 113, the unit number variable mechanism 117, and the backflow prevention mechanism 119. Thereby, the controller 120 controls each part represented by the unit number variable mechanism 117. The controller 120 purifies the exhaust gas by inputting a control signal to each part of the SCR system 100, so that the SCR device 110 purifies the exhaust gas.

[0155] Figure 1 The shown SCR device 110 is configured to purify the exhaust gas generated in the first mode and the second mode, respectively. For example, in the first mode of burning oil fuel alone, the SCR device 110 according to the present embodiment makes the NO x react with NH3 derived from the aqueous urea solution to purify the NO x .

[0156] Specifically, in the first mode, the controller 120 fully opens the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c in a state where the bypass valve 117d is closed. On this basis, the controller 120 appropriately injects the aqueous urea solution from the nozzle 113b of the mixer 113.

[0157] In addition, in the second mode of burning at least ammonia, the SCR device 110 according to the present embodiment makes the unburned NH3 that may be contained in the exhaust gas react with the NO x derived from the exhaust gas to purify the unburned NH3. At this time, the controller 120 according to the present embodiment performs a process that helps to suppress the discharge of unburned NH3 by appropriately controlling the unit number variable mechanism 117 described above. Hereinafter, this process will be referred to as the "unburned NH3 purification process".

[0158] Hereinafter, the processes related to the purification treatment of unburned NH3 will be described using specific examples.

[0159] (2-2) Specific examples of the processes in the second mode

[0160] Figure 5A , Figure 5B , Figure 5C and Figure 5D are flowcharts exemplarily showing the processes in the second mode.

[0161] First, in Figure 5A step S101, the controller 120 determines whether the engine 1 is operating in the second mode. If the determination is "yes", the controller 120 advances the control process to step S102. On the other hand, if the determination in step S101 is "no", the controller 120 transfers from the Figure 5A shown control process to the Figure 5B shown control process and starts the processes applicable to the first mode.

[0162] Specifically, when the determination in Figure 5A step S101 is "no", the controller 120 closes the bypass valve 117d in Figure 5B step S201. In the next step S202, the controller 120 controls the unit number variable mechanism 117. Specifically, in step S202, the controller 120 opens all the inlet valves constituting the unit number variable mechanism 117, that is, the controller 120 opens all of the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c.

[0163] In addition, in step S203 following step S202, the controller 120 controls the backflow prevention mechanism 119. Specifically, in step S203, the controller 120 opens all the outlet valves constituting the backflow prevention mechanism 119, that is, the controller 120 opens all of the first outlet valve 119a, the second outlet valve 119b, and the third outlet valve 119c.

[0164] If step S203 ends, the controller 120 ends the control process continuing from Figure 5A to Figure 5B . It should be noted that Figure 5B the steps of

[0165] can also be rearranged in order, or two or more steps can be performed simultaneously. Figure 5AWhen the determination in step S101 is "Yes", the controller 120 obtains the detection value of the first concentration sensor 131 in step S102 of this figure. The detection value obtained in step S102 represents the ammonia concentration (especially the concentration of unburned ammonia) in the first exhaust pipe 32a. Since this ammonia concentration is equivalent to the ammonia concentration on the exhaust gas inlet side as viewed from the catalyst module 115, in the following description, this ammonia concentration is sometimes referred to as the "inlet concentration".

[0166] It should be noted that in the above step S102, instead of the detection value of the first concentration sensor 131, the detection value of the second concentration sensor 132 can be obtained, or in addition to obtaining the detection value of the first concentration sensor 131, the detection value of the second concentration sensor 132 can also be obtained.

[0167] In the next step S103, the controller 120 determines whether the inlet concentration obtained in step S102 exceeds a specified reference value. This reference value is, for example, a limit value specified by laws and regulations, etc., and is stored in the controller 120 in advance. The controller 120 reads this reference value appropriately as needed. An example of the reference value is as shown by T1 described later Figure 6 shown.

[0168] When the determination in step S103 is "Yes", the controller 120 causes the control process to enter step S104 and determines that the unburned NH3 purification process should be started. For example, the controller 120 changes the signal value of the signal representing the execution flag of the unburned NH3 purification process. As described later, the unburned NH3 purification process is a process that occurs with the inflow of unburned NH3 into the catalyst module 115.

[0169] That is to say, based on the detection signal of the first concentration sensor 131, when the inlet concentration corresponding to this detection signal exceeds the specified reference value (T1), the controller 120 involved in this embodiment starts the inflow of unburned NH3 into the catalyst module 115.

[0170] On the other hand, when the determination in step S103 is "No", the controller 120 causes the control process to transfer to Figure 5C step S301. In this case, the controller 120 opens the bypass valve 117d in Figure 5C step S301. In the next step S302, the controller 120 controls the unit number variable mechanism 117. Specifically, in step S302, the controller 120 closes all the inlet valves constituting the unit number variable mechanism 117, that is to say, the controller 120 closes the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c all.

[0171] In addition, in step S303 following step S302, the controller 120 controls the anti-backflow mechanism 119. Specifically, in step S303, the controller 120 closes all the outlet valves constituting the anti-backflow mechanism 119. That is to say, the controller 120 closes the first outlet valve 119a, the second outlet valve 119b, and the third outlet valve 119c all together.

[0172] If step S303 ends, the controller 120 ends the control process starting from Figure 5A continuing to Figure 5C . It should be noted that Figure 5C the steps of

[0173] can also be rearranged in order, or two or more steps can be carried out simultaneously. Figure 5D Also, returning to step S104, in step S105 following this step, the controller 120 performs unburned NH3 purification processing. The details of the unburned NH3 purification processing are as Figure 5D shown. If the control process enters step S105, the controller 120 starts from

[0174] step S401 of

[0175] and sequentially performs each process shown in this figure. First, in step S401, the controller 120 obtains the detection value of the second concentration sensor 132. The detection value obtained in this step S401 represents the ammonia concentration (especially the concentration of unburned NH3) in the second exhaust pipe 32b. Since this ammonia concentration is equivalent to the ammonia concentration on the exhaust gas outlet side as seen from the catalyst module 115, in the following description, this ammonia concentration is sometimes referred to as the "outlet concentration".

[0176] It should be noted that in the above step S401, the detection value of the first concentration sensor 131 can be obtained instead of the detection value of the second concentration sensor 132, or the detection value of the first concentration sensor 131 can be obtained in addition to the detection value of the second concentration sensor 132.

[0177] In the next step S402, the controller 120 determines the concentration of unburned NH3 contained in the exhaust gas. Specifically, the controller 120 according to the present embodiment determines the value of the outlet concentration based on the detection signal of the second concentration sensor 132.

[0178] In addition, in the above step S402, the controller 120 may also determine the amount (e.g., flow rate) of unburned NH3 contained in the exhaust gas to replace the concentration of unburned NH3 contained in the exhaust gas. This determination can be performed, for example, by combining the detection signals from at least one of the first concentration sensor 131 and the second concentration sensor 132 with the detection signal of a flow rate sensor capable of detecting the overall flow rate of the exhaust gas.

[0179] In the next step S403, the controller 120 determines the number of reaction units in such a manner that the number of reaction units increases or decreases according to the concentration of unburned NH3. As described above, the controller 120 according to the present embodiment regards the detection value of the second concentration sensor 132 as the concentration of unburned NH3. In addition, the number of reaction units according to the present embodiment is changed by the number of the above catalyst parts.

[0180] That is to say, the number of reaction units according to the present embodiment is adjusted by the number (= the number of catalyst parts) of the catalyst parts 116 through which unburned NH3 passes among the first catalyst part 116a, the second catalyst part 116b, and the third catalyst part 116c, and it increases or decreases discretely according to the number of the catalyst parts.

[0181] Here, Figure 6 is a graph showing the relationship between the concentration of unburned NH3 and the number of reaction units in the second mode. As shown on the right side of the paper of this graph, Figure 6 the vertical axis can also be regarded as the number of catalyst parts proportional to the number of reaction units. In the case of regarding it in this way, the vertical axis is any one of the values 0, 1, 2, and 3 starting from the minimum value.

[0182] Figure 6 The solid line L2 of Figure 6 shows the relationship between the number of reaction units (the number of catalyst parts) and the high or low concentration of unburned NH3 in the second mode. As shown by the arrow A1 of Figure 6 , the controller 120 is configured such that in the second mode, the number of reaction units increases as the concentration of unburned NH3 increases. If the number of reaction units increases, the number of catalyst parts also increases accordingly. Therefore, it can also be said that the controller 120 is configured to increase the number of catalyst parts as the concentration of unburned NH3 increases.

[0183] Figure 6 The dotted line L1 of Figure 6 shows the number of reaction units (the number of catalyst parts) in the first mode. In the first mode, although the discharge amount of unburned NH3 is originally zero, in order to clarify the magnitude relationship with the solid line L2, the dotted line L1 is shown as a straight line parallel to the Figure 6 horizontal axis of Figure 6 . As shown by the dotted line L1, the controller 120 sets the number of reaction units and the number of catalyst parts to the maximum value in the first mode.

[0184] It should be noted that when it is configured to determine the amount of unburned NH3 instead of the concentration of unburned NH3, the controller 120 can also determine the number of reaction units and the number of catalyst parts in such a way that the number of reaction units and the number of catalyst parts are increased or decreased according to the amount of unburned NH3. In this case, the controller 120 can also be configured to increase the number of reaction units and the number of catalyst parts as the amount of unburned NH3 increases in the second mode.

[0185] In the next step S404, the controller 120 reads the first control map M1 (refer to Figure 7 ), and the first control map M1 defines the relationship between the number of reaction units or the number of catalyst parts corresponding to the concentration of unburned NH3 and the combination of the catalyst parts 116 set corresponding to the number of catalyst parts. The "combination of catalyst parts 116" mentioned here refers to the combination of the catalyst parts 116 among the plurality of catalyst parts 116 through which the unburned NH3 should pass.

[0186] The first control map M1 related to this embodiment is a map defined by associating the current number of catalyst parts with the control parameters of the unit number variable mechanism 117. The control parameters defined in the first control map M1 refer to a parameter list that defines whether each control valve constituting the unit number variable mechanism 117 is opened or closed.

[0187] Figure 7 An example of the first control map M1 is shown. For example, when the number of catalyst parts is 3, the controller 120 reads the following control parameters: the control parameters are defined to open (open) all the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c and close (close) the bypass valve 117d.

[0188] In step S405, the controller 120 queries the number of catalyst parts determined in step S403 with the first control map M1 read in step S404. The controller 120 determines the control parameters of the unit number variable mechanism 117 corresponding to the number of catalyst parts at this moment.

[0189] In step S406, the controller 120 inputs a control signal to the bypass valve 117d to close it. The process of step S406 can also be carried out together with the next step S407, or the process of step S406 can be carried out immediately after the judgment in Figure 5A step S103 is "yes", and then step S104 is carried out.

[0190] In step S407, the controller 120 controls the variable number of units mechanism 117 based on the control parameters determined in step S405. Specifically, the controller 120 opens or closes the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c according to the first control map M1.

[0191] It should be noted that when the first inlet valve 117a is open, the first outlet valve 119a is open; on the other hand, when the first inlet valve 117a is closed, the first outlet valve 119a is closed. Similarly, when the second inlet valve 117b is open, the second outlet valve 119b is open; on the other hand, when the second inlet valve 117b is closed, the second outlet valve 119b is closed. When the third inlet valve 117c is open, the third outlet valve 119c is open; on the other hand, when the third inlet valve 117c is closed, the third outlet valve 119c is closed.

[0192] For example, as Figure 6 shown, when the concentration of unburned NH3 is 0 or more and below the first reference value T1, both the number of reaction units and the number of catalyst parts are zero as the minimum value. In this case, the judgment in step S103 is "no", and the process described by Figure 5C is executed. The first reference value T1 mentioned here is an example of the "reference value" in the present embodiment.

[0193] In addition, as Figure 6 shown, when the concentration of unburned NH3 exceeds the first reference value T1 and is below the second reference value T2, the number of reaction units becomes the first intermediate value N1, and the corresponding number of catalyst parts becomes 1. In this case, the controller 120 only opens the first inlet valve 117a and the first outlet valve 119a, and only introduces unburned NH3 into the first catalyst part 116a.

[0194] In addition, as Figure 6 shown, when the concentration of unburned NH3 exceeds the second reference value T2 and is below the third reference value T3, the number of reaction units becomes the second intermediate value N2, and the corresponding number of catalyst parts becomes 2. In this case, the controller 120 opens the first inlet valve 117a and the first outlet valve 119a, the second inlet valve 117b and the second outlet valve 119b, and introduces unburned NH3 into the first catalyst part 116a and the second catalyst part 116b.

[0195] In addition, as Figure 6As shown, when the concentration of unburned NH3 exceeds the third reference value T3, the number of reaction units becomes N3, and the corresponding number of catalyst parts becomes the maximum value of 3. In this case, the controller 120 opens the first inlet valve 117a and the first outlet valve 119a, the second inlet valve 117b and the second outlet valve 119b, and the third inlet valve 117c and the third outlet valve 119c, and introduces unburned NH3 into the first catalyst part 116a, the second catalyst part 116b, and the third catalyst part 116c.

[0196] If the process of step S407 ends, the controller 120 ends Figure 5A the process of step S105, and makes the control process enter step S106.

[0197] In step S106, the controller 120 acquires the outlet concentration again, and determines whether the outlet concentration is lower than a specified reference value. This reference value can be equal to the reference value (T1) referred to in step S103, for example.

[0198] When the determination in step S106 is "yes", the controller 120 makes the control process enter step S107, and determines that the purification process of unburned NH3 should end. For example, the controller 120 changes the signal value of the signal indicating the execution flag of the purification process of unburned NH3.

[0199] That is to say, based on the detection signal of the second concentration sensor 132, when the outlet concentration corresponding to the detection signal is lower than the specified reference value (T1), the controller 120 involved in the present embodiment stops the inflow of unburned NH3 into the catalyst module 115.

[0200] On the other hand, when the determination in step S106 is "no", the controller 120 makes the control process return to step S105. The controller 120 continues the purification process of unburned NH3 until the determination in step S106 becomes "yes". During the purification process of unburned NH3, the controller 120 Figure 5D changes the number of reaction units in real time through the processes of step S402 and step S403, and thus changes the number of catalyst parts.

[0201] It should be noted that, as described above Figure 5D the controller 120 is configured to control the unit number variable mechanism 117 based on the combination of the number of catalyst parts set corresponding to the concentration or amount of unburned NH3 and the catalyst parts set corresponding to the number of catalyst parts.

[0202] Here, the controller 120 updates the correspondence relationship between the number of catalyst parts and the combination of catalyst parts on the occasion of specified conditions. This update is achieved by changing Figure 7performed according to the first control map M1 shown. For example, the controller 120 involved in the present embodiment automatically updates the first control map M1 regularly. For example, this automatic update is performed by the controller 120 whenever the operation in the second mode has been carried out for a specified period. The specified condition may also be input by the crew's operation.

[0203] Figure 8 is a diagram for explaining the update of the first control map M1. As Figure 8 shown, whenever the operation in the second mode has been carried out for a specified period, the controller 120 updates the first control map M1 to the second control map M2. Whenever the operation in the second mode has been carried out for a specified period, the controller 120 updates the second control map M2 to the third control map M3. Whenever the operation in the second mode has been carried out for a specified period, the controller 120 updates the third control map M3 to the first control map M1.

[0204] The update objects in the first control map M1 are limited to the control parameters related to the opening and closing of the first inlet valve 117a, the second inlet valve 117b, and the third inlet valve 117c related to the catalyst module 115, and the first outlet valve 119a, the second outlet valve 119b, and the third outlet valve 119c corresponding to each inlet valve. As Figure 8 shown, the control parameters related to the opening and closing of the bypass valve 117d are excluded from the update objects in the first control map M1.

[0205] <Regarding Suppression of Unburned NH3 Emission>

[0206] For a diesel engine configured to burn ammonia, it is required to suppress the ammonia emission below a specified reference value by reducing the amount of unburned ammonia emission.

[0207] As a solution to meet this requirement, for example, it can be considered to react unburned NH3 with NO in the exhaust gas by using a so-called SCR device. x react.

[0208] However, as Figure 1 shown, the marine SCR device 110 usually has to process a large amount of exhaust gas. Therefore, compared with other uses (such as automobiles), the marine SCR system 100 has to use a huge catalyst section. In the case of using a huge catalyst section, replacing the catalyst section not only takes a lot of man-hours, but also the economic cost required for its replacement is very high.

[0209] In order to reduce the above-mentioned man-hours and costs, it can be considered to suppress the deterioration of the catalyst section to achieve its long life. However, so far, there is no known technical solution that can take into account both long life and suppression of unburned NH3 emission.

[0210] In this regard, the variable number of units mechanism 117 involved in the above-described embodiment is as follows Figure 5D in steps S402 to S407, Figure 6 and Figure 7 as shown, the number of reaction units 115a through which the unburned NH3 contained in the exhaust gas passes (the number of reaction units) is adjusted according to the concentration or amount of the unburned NH3. By setting the number of reaction units corresponding to the concentration or amount of the unburned NH3, it is possible to remove the unburned NH3 without using all of the reaction units 115a. Thus, it is possible to suppress the deterioration of the reaction units 115a and further suppress the deterioration of each catalyst section 116.

[0211] In this way, according to the above-described embodiment, it is possible to achieve both reducing the discharge amount of unburned NH3 and suppressing the deterioration of the catalyst module 115.

[0212] In addition, by adjusting the number of reaction units as Figure 6 shown, it is possible to suppress the number of reaction units to an appropriate number commensurate with the concentration or amount of the unburned NH3 without excess. Thus, it is possible to reduce the discharge amount of unburned NH3 and suppress the deterioration of the catalyst module 115.

[0213] In addition, as Figure 6 and Figure 7 shown, the controller 120 changes the number of reaction units by changing the number of catalyst sections (the number of catalyst sections) through which the unburned NH3 passes. Thus, since it is only necessary to change the flow path to each catalyst section 116, it is possible to easily change the number of reaction units without providing a complicated mechanism to a specific catalyst section 116.

[0214] In addition, in the case where the number of reaction units is changed through the number of catalyst sections, the degree of deterioration of each catalyst section 116 is generally different in each catalyst section 116. In this case, it is only necessary to replace the reaction unit 115a in units of the catalyst section 116, and the maintainability of the marine SCR system 100 can be improved.

[0215] In addition, as Figure 7 and Figure 8 shown, by presetting the combination of the catalyst sections 116 through which the unburned NH3 passes for each number of catalyst sections and configuring to update the setting under specified conditions, it is possible to make the degree of deterioration of each catalyst section 116 uniform. Thus, it is advantageous in suppressing the deterioration of the catalyst module 115.

[0216] In addition, as Figure 1 shown, the first concentration sensor 131 detects the ammonia concentration immediately before being introduced into the catalyst module 115. And, as from Figure 5AAs shown in steps S102 to S104, the controller 120 causes the unburned NH3 to start flowing into the catalyst module 115 based on the detection signal of the first concentration sensor 131. With this configuration, the unburned NH3 can start flowing immediately when the concentration of the unburned NH3 increases. The leakage of unburned NH3 to the outside of the ship (especially leakage at a concentration exceeding a specified reference value) can be more reliably suppressed.

[0217] In addition, as Figure 1 shown, the second concentration sensor 132 detects the ammonia concentration immediately after being discharged from the catalyst module 115. And, as described in steps S401 to S403 of Figure 5D , the controller 120 adjusts the number of reaction units based on the detection signal of the second concentration sensor 132. With this configuration, the number of reaction units can be set to the minimum number of reaction units that can suppress the leakage of unburned NH3 without being excessive. Thereby, the deterioration of the catalyst unit 116 can be suppressed without hindering the reduction of the discharge amount of unburned NH3.

[0218] In addition, as shown in steps S106 to S107 of Figure 5A , the controller 120 causes the inflow of unburned NH3 into the catalyst module 115 to end based on the ammonia concentration immediately after being discharged from the catalyst module 115. With this configuration, it is possible to more reliably determine that the ammonia concentration in the exhaust gas discharged from the catalyst module 115 is lower than the reference value. As a result, the inflow of unburned NH3 into the catalyst module 115 can end at a more appropriate time, and the leakage of unburned NH3 to the outside of the ship (especially leakage at a concentration exceeding a specified reference value) can be more reliably suppressed.

[0219] In addition, as Figure 6 and Figure 7 shown, by appropriately opening, closing, or adjusting the opening degree of the bypass valve 117d based on the ammonia concentration, more precise control commensurate with the ammonia concentration can be achieved.

[0220] It should be noted that the term "valve opening" in this embodiment not only includes the action of making the opening degree of the bypass valve 117d fully open, but also includes all actions of adjusting its opening degree in the opening direction. Similarly, the term "valve closing" in this embodiment not only includes the action of making the opening degree of the bypass valve 117d fully closed, but also includes all actions of adjusting its opening degree in the closing direction. This is the same in the following modified examples and other embodiments.

[0221] <Modification example of the anti-backflow mechanism 119>

[0222] In the above-described embodiment (the first embodiment), control valves such as the first outlet valve 119a are used as the backflow prevention mechanism 119, but the backflow prevention mechanism 119 is not limited to control valves. Gas injection may also be used as the backflow prevention mechanism 119.

[0223] Figure 9 is a diagram corresponding to a modified example of the backflow prevention mechanism 119. Figure 4 In Figure 9 elements having the same structure and configuration as Figure 4 are given the same reference numerals as in this embodiment.

[0224] Figure 9 The exemplified SCR device 110 shown includes a second backflow prevention mechanism 119' using gas injection, instead of the first backflow prevention mechanism 119 using a control valve. The second backflow prevention mechanism 119' has a first gas supplier 119a', a second gas supplier 119b', and a third gas supplier 119c'.

[0225] The first gas supplier 119a' is located at a position between the first inlet valve 117a and the first catalyst section 116a on the first flow pipe 111a. The first gas supplier 119a' supplies gas to this position. By supplying gas in a state where the first inlet valve 117a is closed, backflow of exhaust gas in the first flow pipe 111a is thereby suppressed. The supply timing of the gas supplied by the first gas supplier 119a' may be set to be the same as the closing timing of the first outlet valve 119a.

[0226] The second gas supplier 119b' is located at a position between the second inlet valve 117b and the second catalyst section 116b on the second flow pipe 111b. The second gas supplier 119b' supplies gas to this position. By supplying gas in a state where the second inlet valve 117b is closed, backflow of exhaust gas in the second flow pipe 111b is thereby suppressed. The supply timing of the gas supplied by the second gas supplier 119b' may be set to be the same as the closing timing of the second outlet valve 119b.

[0227] The third gas supplier 119c' is located at a position between the third inlet valve 117c and the third catalyst section 116c on the third flow pipe 111c. The third gas supplier 119c' supplies gas to this position. By supplying gas in a state where the third inlet valve 117c is closed, backflow of exhaust gas in the third flow pipe 111c is thereby suppressed. The supply timing of the gas supplied by the third gas supplier 119c' may be set to be the same as the closing timing of the third outlet valve 119c.

[0228] The second backflow prevention mechanism 119' may replace Figure 4It can be used with the first anti-backflow mechanism 119 shown, or it can be used together with the first anti-backflow mechanism 119. By using the first anti-backflow mechanism 119 and the second anti-backflow mechanism 119' together, it is possible to more reliably prevent the backflow of exhaust gas.

[0229] <Second Embodiment>

[0230] In the above-described embodiment (the first embodiment), a structure in which a plurality of catalyst parts (three catalyst parts 116 in the first embodiment) are connected in parallel with respect to the flow direction of the exhaust gas is illustrated, but the present disclosure is not limited to such a structure. The plurality of catalyst parts may also be connected in series with respect to the flow direction of the exhaust gas.

[0231] Figure 10 is a diagram corresponding to an exemplary second embodiment of the SCR system Figure 4 In Figure 10 For elements having the same structure and configuration as Figure 4 the same symbols as those in this embodiment are given. In addition, the description that overlaps with the above first embodiment is appropriately omitted.

[0232] (1) SCR device 110'

[0233] In the SCR system 100' according to the second embodiment, the structure of its SCR device 110' is different from the structure according to the first embodiment. Specifically, as Figure 10 shown, the SCR device 110' according to the second embodiment includes an exhaust gas flow pipe 111', a mixer 113, a catalyst module 115', and a unit number variable mechanism 117'. The structure of the mixer 113 is the same as that of the first embodiment.

[0234] In addition, the catalyst module 115' has a plurality of catalyst parts 116', and the plurality of catalyst parts 116' each have a plurality of reaction units 115a'. These plurality of catalyst parts 116' are connected in series with respect to the flow direction of the exhaust gas.

[0235] Particularly in the second embodiment, three catalyst parts 116' are connected in series with respect to the flow direction of the exhaust gas. Hereinafter, these plurality of catalyst parts 116' may sometimes be referred to as a first catalyst part 116a', a second catalyst part 116b', and a third catalyst part 116c'.

[0236] In addition, similarly to the first embodiment, the unit number variable mechanism 117' has a plurality of control valves. Hereinafter, similarly to the first embodiment, these plurality of control valves may sometimes be referred to as a first inlet valve 117a', a second inlet valve 117b', a third inlet valve 117c', and a bypass valve 117d'.

[0237] (1-1) Exhaust gas flow pipe 111’

[0238] The exhaust gas flow pipe 111’ extends in a way that relays between the first exhaust pipe 32a and the second exhaust pipe 32b, and is configured to guide the exhaust gas flowing in from the first exhaust pipe 32a to the catalyst module 115’ and guide the exhaust gas discharged from the catalyst module 115’ to the second exhaust pipe 32b.

[0239] That is to say, it can be regarded as: the first exhaust pipe 32a connects the engine 1 to the catalyst module 115’ via the exhaust gas flow pipe 111’. Similarly, it can be regarded as: the second exhaust pipe 32b connects the catalyst module 115’ to the outside of the ship via the exhaust gas flow pipe 111’.

[0240] Specifically, similar to the first embodiment, the exhaust gas flow pipe 111’ has a first flow pipe 111a’, a second flow pipe 111b’, a third flow pipe 111c’ and a bypass pipe 111d’.

[0241] The first flow pipe 111a’ is a tubular member having one end (upstream end) connected to the downstream end of the first exhaust pipe 32a and the other end (downstream end) connected to the upstream end of the second exhaust pipe 32b.

[0242] On the first flow pipe 111a’, a mixer 113, a first inlet valve 117a’, a first catalyst part 116a’, a second catalyst part 116b’ and a third catalyst part 116c’ are arranged in sequence from the upstream side.

[0243] The bypass pipe 111d’ connects the engine 1 to the outside of the ship in a way that bypasses the catalyst module 115’. In particular, the bypass pipe 111d’ involved in this embodiment connects the engine 1 to the outside of the ship via the first exhaust pipe 32a and the second exhaust pipe 32b.

[0244] Specifically, the bypass pipe 111d’ has one end (upstream end) connected to the first connection part Q1 and the other end (downstream end) connected to the second connection part Q2. The first connection part Q1 is located in the middle of the first flow pipe 111a’, and the second connection part Q2 is located in the middle of the first flow pipe 111a’ and downstream of the first connection part Q1.

[0245] Here, the first connection part Q1 is downstream of the mixer 113 and upstream of the first inlet valve 117a’ on the first flow pipe 111a’. The second connection part Q2 is downstream of the third catalyst part 116c’ on the first flow pipe 111a’.

[0246] In addition, a bypass valve 117d’ described later is arranged on the bypass pipe 111d’.

[0247] The second flow pipe 111b' extends in a manner that connects the first flow pipe 111a' and the bypass pipe 111d'. Specifically, the second flow pipe 111b' has one end (upstream end) connected to the third connection part Q3 and the other end (downstream end) connected to the fourth connection part Q4. The third connection part Q3 is located in the middle of the bypass pipe 111d', and the fourth connection part Q4 is located in the middle of the first flow pipe 111a' and downstream of the first connection part Q1.

[0248] Here, the third connection part Q3 is upstream of the bypass valve 117d' on the bypass pipe 111d'. The fourth connection part Q4 is between the first catalyst part 116a' and the second catalyst part 116b' on the first flow pipe 111a'.

[0249] A second inlet valve 117b' is arranged on the second flow pipe 111b'.

[0250] The third flow pipe 111c' extends in a manner that connects the first flow pipe 111a' and the bypass pipe 111d'. Specifically, the third flow pipe 111c' has one end (upstream end) connected to the fifth connection part Q5 and the other end (downstream end) connected to the sixth connection part Q6. The fifth connection part Q5 is located in the middle of the bypass pipe 111d', and the sixth connection part Q6 is located in the middle of the first flow pipe 111a' and downstream of the fourth connection part Q4.

[0251] Here, the fifth connection part Q5 is downstream of the third connection part Q3 on the bypass pipe 111d' and upstream of the bypass valve 117d'. The sixth connection part Q6 is between the second catalyst part 116b' and the third catalyst part 116c' on the first flow pipe 111a'.

[0252] A third inlet valve 117c' is arranged on the third flow pipe 111c'.

[0253] (1-2) Catalyst module 115'

[0254] The catalyst module 115' promotes the chemical reaction on the reaction unit 115a' by bringing the exhaust gas containing NH3 into contact with the reaction unit 115a'. As a result, at least NH3 is removed from the exhaust gas. Each catalyst part 116' constituting the catalyst module 115' functions as a so-called reactor in the SCR device 110. The reaction unit 115a' constituting each catalyst part 116' is the same as that in the above first embodiment.

[0255] Further, the first catalyst section 116a', the second catalyst section 116b', and the third catalyst section 116c' are connected in series with respect to the flow direction of the exhaust gas as described above. In the second embodiment, these catalyst sections 116' are each configured to reduce NO using NH3 as a reducing agent. x SCR catalyst.

[0256] (1-3) Unit number variable mechanism 117'

[0257] Similar to the first embodiment described above, the unit number variable mechanism 117' is configured to change the number of reaction units 115a' (the number of reaction units) through which the NH3 flowing into the catalyst module 115' passes among the plurality of reaction units 115a'.

[0258] The unit number variable mechanism 117' according to the second embodiment is configured to change the number of catalyst sections 116' (hereinafter also referred to as "the number of catalyst sections") through which the unburned ammonia passes among the plurality of catalyst sections 116'.

[0259] Specifically, the unit number variable mechanism 117' has a plurality of control valves as described above. The plurality of control valves include a first inlet valve 117a', a second inlet valve 117b', a third inlet valve 117c', and a bypass valve 117d'. The structures of these control valves are the same as those in the first embodiment.

[0260] The first inlet valve 117a' operates based on a control signal from the controller 120 to open and close the first flow pipe 111a'. If the first inlet valve 117a' opens the first flow pipe 111a', the exhaust gas is allowed to flow into the first catalyst section 116a', the second catalyst section 116b', and the third catalyst section 116c'. If the first inlet valve 117a' closes the first flow pipe 111a', the inflow of the exhaust gas into the first catalyst section 116a' is at least restricted.

[0261] The second inlet valve 117b' operates based on a control signal from the controller 120 to open and close the second flow pipe 111b'. If the second inlet valve 117b' opens the second flow pipe 111b', the exhaust gas is allowed to flow into the second catalyst section 116b' and the third catalyst section 116c'. If the second inlet valve 117b' closes the second flow pipe 111b', the inflow of the exhaust gas into the second catalyst section 116b' is at least restricted.

[0262] The third inlet valve 117c’ operates based on a control signal from the controller 120, thereby opening and closing the third flow pipe 111c’. If the third inlet valve 117c’ opens the third flow pipe 111c’, exhaust gas is allowed to flow into the third catalyst unit 116c’. If the third inlet valve 117c’ closes the third flow pipe 111c’, the inflow of exhaust gas into the third catalyst unit 116c’ is restricted.

[0263] The bypass valve 117d’ operates based on a control signal from the controller 120, thereby opening and closing the bypass pipe 111d’. If the bypass valve 117d’ opens the bypass pipe 111d’, the exhaust gas can bypass the catalyst module 115’. If the bypass valve 117d’ closes the bypass pipe 111d’, the flow of exhaust gas through the bypass pipe 111d’ is restricted.

[0264] For example, in a state where the bypass valve 117d’ is closed, if only the first inlet valve 117a’ is opened, the exhaust gas will pass through all of the first catalyst unit 116a’, the second catalyst unit 116b’, and the third catalyst unit 116c’. The number of reaction units through which the exhaust gas (specifically, unburned NH3 contained in the exhaust gas) passes becomes the maximum value N3. This maximum value N3 is as described above Figure 6 shown. At this time, the number of catalyst units becomes the maximum value, which is 3.

[0265] In addition, in a state where the bypass valve 117d’ is opened, if all of the first inlet valve 117a’, the second inlet valve 117b’, and the third inlet valve 117c’ are closed, the exhaust gas will not pass through any of the first catalyst unit 116a’, the second catalyst unit 116b’, and the third catalyst unit 116c’. As Figure 6 shown, the number of reaction units through which the exhaust gas passes becomes the minimum value (=0). At this time, the number of catalyst units becomes the minimum value, which is 0.

[0266] In addition, in a state where the bypass valve 117d’ is closed, if only the second inlet valve 117b’ is opened, the exhaust gas will pass through the second catalyst unit 116b’ and the third catalyst unit 116c’. As Figure 6 shown, the number of reaction units through which the exhaust gas passes becomes a second intermediate value N2 that is closer to the maximum value than to the minimum value. At this time, the number of catalyst units is 2.

[0267] In addition, in a state where the bypass valve 117d’ is closed, if only the third inlet valve 117c’ is opened, the exhaust gas will only pass through the third catalyst unit 116c’. As Figure 6 shown, the number of reaction units through which the exhaust gas passes becomes a first intermediate value N1 that is closer to the minimum value than to the maximum value. At this time, the number of catalyst units is 1.

[0268] In addition, in a state where the bypass valve 117d’ is already opened, if at least one of the first inlet valve 117a’, the second inlet valve 117b’, and the third inlet valve 117c’ is opened, the flow direction of the exhaust gas will split and pass through the catalyst module 115’ and the bypass pipe 111d’ respectively.

[0269] (2) Controller 120

[0270] Similar to the first embodiment, the controller 120 according to the second embodiment performs unburned NH3 purification processing. Except for the processing related to the anti-backflow mechanism 119, the outline of the unburned NH3 purification processing is the same as that Figures 5A to 5D shown in the processing.

[0271] That is to say, the controller 120 determines the number of reaction units in such a way that the number of reaction units increases or decreases according to the concentration or amount of unburned NH3. Regarding Figure 6 the content shown is also the same as that of the first embodiment.

[0272] Similar to the first embodiment, the controller 120 is configured such that in the second mode, the number of reaction units increases as the concentration of unburned NH3 increases. In other words, the controller 120 is configured to increase the number of catalyst units as the concentration of unburned NH3 increases.

[0273] The main difference between the processing according to the second embodiment and the processing according to the first embodiment lies in Figure 5D the details of the control map (the first control map M1) read in step S404. Figure 11 Exemplarily, the first control map M1’ according to the second embodiment is shown. This difference stems from the fact that the relationship between the opening and closing states of the first inlet valve 117a’ etc. and the number of catalyst units achieved thereby is different from that of the first embodiment as described above.

[0274] According to the second embodiment, similar to the first embodiment, it is possible to balance both reducing the emission amount of unburned NH3 and suppressing the deterioration of the catalyst module 115.

[0275] In addition to this, regarding various advantages related to the first concentration sensor 131 and the second concentration sensor 132, and various advantages related to the relationship between the concentration or amount of unburned NH3 and the number of reaction units (the number of catalyst units), it is also possible to enjoy them in the same way as the first embodiment.

[0276] <Other Embodiments>

[0277] In the above-described embodiment, the SCR system 100 including the first concentration sensor 131 and the second concentration sensor 132 is illustrated, but the present disclosure is not limited to such a configuration. The SCR system 100 does not necessarily include both the first concentration sensor 131 and the second concentration sensor 132.

[0278] Assume that in the case where the SCR system 100 includes only the first concentration sensor 131, it is configured to obtain the detection value of the first concentration sensor 131 instead of the detection value of the second concentration sensor 132 in Figure 5D step S401, and refer to the inlet concentration instead of the outlet concentration in Figure 5A step S106. In such a configuration, it is also possible to immediately introduce unburned NH3 into the catalyst module 115 in the same manner as in the above-described embodiment.

[0279] Similarly, in the case where the SCR system 100 includes only the second concentration sensor 132, it is configured to obtain the detection value of the second concentration sensor 132 instead of the detection value of the first concentration sensor 131 in Figure 5A step S102, and refer to the outlet concentration instead of the inlet concentration in Figure 5A step S103. In such a configuration, it is also possible to set the number of reaction units to the minimum number of reaction units that can suppress the leakage of unburned NH3 without excess. Thus, it is possible to suppress the deterioration of the catalyst part 116 without hindering the reduction of the discharge amount of unburned NH3.

[0280] In addition, when performing processing based on the ammonia concentration as shown in Figure 6 and Figure 7 , it is not necessary to use the detection signals of the first concentration sensor 131 and the second concentration sensor 132. For example, the concentration of unburned NH3 may be estimated based on various data, and the bypass valve 117d may be appropriately opened, closed, or its opening degree may be adjusted based on the estimation result.

Claims

1. A marine SCR system is connected to a diesel engine capable of burning ammonia and is configured to remove unburned ammonia discharged from the diesel engine, characterized in that: The marine SCR system includes a catalyst module, a variable cell number mechanism, and a controller. The catalyst module has a plurality of reaction cells that form a flow path for exhaust gas and promote the reaction of unburned ammonia. The catalyst module allows unburned ammonia discharged from the diesel engine to flow in together with the exhaust gas containing the unburned ammonia. The variable cell number mechanism changes the number of reaction cells through which the unburned ammonia flowing into the catalyst module among the plurality of reaction cells. The controller controls the variable cell number mechanism. The controller determines the concentration or amount of unburned ammonia contained in the exhaust gas. The controller determines the number of reaction cells in such a way that the number of reaction cells increases or decreases according to the concentration or amount of unburned ammonia.

2. The marine SCR system according to claim 1, characterized in that: The controller increases the number of reaction cells as the concentration or amount of unburned ammonia increases.

3. The marine SCR system according to claim 2, characterized in that: The catalyst module has a plurality of catalyst parts connected in parallel or in series with respect to the flow direction of the exhaust gas. The variable cell number mechanism is configured to change the number of catalyst parts through which the unburned ammonia passes among the plurality of catalyst parts. The controller increases the number of catalyst parts as the concentration or amount of unburned ammonia increases.

4. The marine SCR system according to claim 3, characterized in that: The controller controls the variable cell number mechanism based on the number of catalyst parts set corresponding to the concentration or amount of unburned ammonia and the combination of catalyst parts set corresponding to the number of catalyst parts. The controller updates the correspondence between the number of catalyst parts and the combination of catalyst parts on the occasion of a specified condition.

5. The marine SCR system according to claim 1, characterized in that: The marine SCR system includes a first concentration sensor arranged on a first exhaust pipe connecting the diesel engine and the catalyst module to detect the ammonia concentration in the first exhaust pipe. Based on the detection signal of the first concentration sensor, when the ammonia concentration in the first exhaust pipe exceeds a specified reference value, the controller causes the unburned ammonia to start flowing into the catalyst module.

6. The marine SCR system according to claim 5, characterized in that: The marine SCR system includes a second concentration sensor arranged on a second exhaust pipe connecting the catalyst module and the outside of the ship to detect the ammonia concentration in the second exhaust pipe. The controller determines the number of reaction cells through which the unburned ammonia passes in the catalyst module based on the detection signal of the second concentration sensor.

7. The marine SCR system according to claim 6, characterized in that: When the ammonia concentration in the second exhaust pipe is lower than the reference value, the controller causes the inflow of unburned ammonia into the catalyst module to end.

8. The marine SCR system according to any one of claims 1 to 4, characterized in that: The marine SCR system includes a bypass pipe and a bypass valve. The bypass pipe connects the diesel engine to the outside of the ship in a way that bypasses the catalyst module. The bypass valve is electrically connected to the controller, and the bypass valve opens and closes the bypass pipe. When the ammonia concentration in the first exhaust pipe connecting the diesel engine to the catalyst module is below a specified reference value, the controller opens the bypass valve, so that the unburned ammonia bypasses the catalyst module via the bypass pipe. When the ammonia concentration in the first exhaust pipe exceeds the reference value, the controller closes the bypass valve, so that the unburned ammonia flows into the catalyst module.

9. The marine SCR system according to any one of claims 5 to 7, characterized in that: The marine SCR system includes a bypass pipe and a bypass valve. The bypass pipe connects the diesel engine to the outside of the ship in a way that bypasses the catalyst module. The bypass valve is electrically connected to the controller, and the bypass valve opens and closes the bypass pipe. When the ammonia concentration in the first exhaust pipe is below the reference value, the controller opens the bypass valve, so that the unburned ammonia bypasses the catalyst module via the bypass pipe. When the ammonia concentration in the first exhaust pipe exceeds the reference value, the controller closes the bypass valve, so that the unburned ammonia flows into the catalyst module.

10. An engine system, characterized in that: The engine system includes: The marine SCR system according to claim 1; and A diesel engine, which is connected to the marine SCR system and the diesel engine can at least burn the ammonia.

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