Marine scrubber system and engine system including the same

Abstract

To enable both reduction of emissions of unburned ammonia and reduction of a pump load.SOLUTION: A marine scrubber system 100 that is connected to a diesel engine 1 enabling combustion of ammonia and is configured to purify exhaust gas discharged from the diesel engine 1 includes a scrubber 110 and a controller for controlling the scrubber 110. The scrubber 110 includes: a purification chamber 111a connected to the diesel engine 1; a spray nozzle 112 accommodated in the purification chamber 111a and spraying water in the purification chamber 111a; circulation piping 113 for circulating water between the purification chamber 111a and the spray nozzle 112; and a supply device 117 for supplying diluted sulfuric acid to the water circulating via the circulation piping 113. The controller determines a concentration or amount of unburned ammonia included in exhaust gas, and decides a supply amount of the diluted sulfuric acid by using the supply device 117 so as to increase / decrease in accordance with the concentration or amount of the unburned ammonia.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a marine scrubber system and an engine system including the same.

Background Art

[0002] Patent Document 1 discloses a diesel engine that mixes and burns fuel oil and gaseous ammonia. Specifically, this diesel engine includes a combustion chamber and a fuel injection means for injecting fuel oil and ammonia into the combustion chamber.

[0003] Further, the diesel engine according to Patent Document 1 is, for example, a marine diesel engine. This marine diesel engine is configured to uniformly distribute the stratification degree of ammonia in the combustion chamber over the entire circumference in order to increase the combustion rate of ammonia and reduce unburned ammonia.

[0004] On the other hand, Patent Document 2 discloses a scrubber (scrubber device) as an example of a marine scrubber system. Specifically, the scrubber disclosed in Patent Document 2 includes a reaction tower in which an internal space is formed and a liquid spraying unit for spraying a liquid in the internal space.

[0005] Further, the scrubber according to Patent Document 2 is, for example, a marine scrubber device. This marine scrubber device is configured to spray a liquid such as water into the internal space of the reaction tower in order to capture substances in the exhaust gas of the ship.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In a diesel engine that burns ammonia fuel as in Patent Document 1, it is required to reduce the emission amount of unburned ammonia so that the emission amount is within a predetermined standard value or less.

[0008] As a measure to meet such demands, for example, by using a scrubber such as Patent Document 2, it is conceivable to dissolve unburned ammonia in the water sprayed in the scrubber.

[0009] However, generally, a marine scrubber sprays a huge amount of water. Therefore, a marine scrubber has to use a huge pump compared with other applications, and the load on the pump also becomes huge. This is inconvenient in suppressing the running cost of a ship such as power.

[0010] Although it is conceivable to reduce the amount of water sprayed to reduce the load on the pump, simply reducing the amount of water sprayed arbitrarily is inconvenient because it may interfere with suppressing the emission of unburned ammonia.

[0011] The present disclosure has been made in view of such points, and an object thereof is to achieve both reduction in the emission amount of unburned ammonia and reduction in the load on the pump for water spraying.

Means for Solving the Problems

[0012] A first aspect of the present disclosure relates to a marine scrubber system connected to a diesel engine capable of burning ammonia and configured to purify exhaust gas discharged from the diesel engine. The marine scrubber system includes a scrubber that sprays water into the exhaust gas and a controller that controls the scrubber. The scrubber includes a purification chamber connected to the diesel engine, a spray nozzle housed in the purification chamber and spraying water in the purification chamber, a circulation pipe that circulates water between the purification chamber and the spray nozzle, and a supplier that supplies an acidic solution to the water circulating through the circulation pipe. The controller determines the concentration or amount of unburned ammonia contained in the exhaust gas and determines the supply amount of the acidic solution by the supplier so as to increase or decrease according to the concentration or amount of the unburned ammonia.

[0013] Note that the term "determination" as used herein includes, in addition to determining the concentration or amount of unburned ammonia, classifying the magnitude of the concentration or amount of unburned ammonia. For example, the former concept includes processes such as measuring or estimating the concentration or amount of unburned ammonia. The latter concept includes, for example, a process of determining the magnitude relationship between the concentration or amount of unburned ammonia and a predetermined reference value.

[0014] Furthermore, the latter concept includes processes that correspond to classifications according to the concentration or amount of unburned ammonia, such as determining whether or not to operate in a mode of injecting and burning ammonia into the cylinder, without directly using the value of the concentration or amount of unburned ammonia.

[0015] According to the first aspect, the scrubber supplies an acidic solution to the water circulating through the circulation pipe. As a result, the water sprayed from the spray nozzle will tend to be acidic. By neutralizing unburned ammonia with acidic water, unburned ammonia can be efficiently treated.

[0016] Furthermore, the controller according to the first aspect adjusts the supply amount of the acidic solution according to the concentration or amount of unburned ammonia contained in the exhaust gas. By supplying an amount of the acidic solution corresponding to the concentration or amount of unburned ammonia, the discharge amount of unburned ammonia can be reduced without spraying a large amount of water. As a result, the amount of water sprayed can be suppressed, and the load on the pump for water spraying can be reduced.

[0017] Thus, according to the first aspect, it is possible to achieve both reduction in the discharge amount of unburned ammonia and reduction in the load on the pump for water spraying.

[0018] Furthermore, by adjusting the supply amount of the acidic solution as in the first aspect, the supply amount of the acidic solution can be made an appropriate amount commensurate with the concentration or amount of unburned ammonia. As a result, the supply amount of the acidic solution can be suppressed to an appropriate amount without being excessive.

[0019] Also, according to the second aspect of the present disclosure, the diesel engine can be operated in each of a first mode in which an oil fuel containing a sulfur component is burned alone in a cylinder and a second mode in which at least the ammonia among the ammonia and the oil fuel is burned in the same cylinder, and the scrubber purifies the exhaust gas generated in each of the first mode and the second mode. In the first mode, sulfur oxides resulting from the oil fuel are absorbed by water that circulates through the circulation pipe and is sprayed from the spray nozzle, and in the second mode, the unburned ammonia is neutralized by water in which the sulfur oxides are dissolved.

[0020] According to the second aspect, the scrubber also serves as an SO x scrubber for removing sulfur oxides (SO x ) from the exhaust gas and a scrubber for removing unburned ammonia from the exhaust gas.

[0021] Here, when water sprayed from the spray nozzle absorbs SO x , the water (SOx The aqueous solution will tend to be on the acidic side. By circulating the acidic water without neutralizing it and using the water for neutralizing unburned ammonia, unburned ammonia can be efficiently treated. This can suppress the amount of chemicals required for neutralizing unburned ammonia, such as dilute sulfuric acid, and thus is advantageous in suppressing the running cost of the ship.

[0022] Also, according to the third aspect of the present disclosure, in the first mode, the controller may set the supply amount of the acidic solution by the supplier to zero, and in the second mode, as the concentration or amount of the unburned ammonia increases, increase the supply amount of the acidic solution by the supplier.

[0023] According to the third aspect, the supply amount of the acidic solution can be suppressed to an appropriate amount without being excessive. By doing so, while reducing the discharge amount of unburned ammonia, it is possible to reduce the water spray amount, and thus the load on the pump, and reduce the supply amount of the acidic solution.

[0024] Also, according to the fourth aspect of the present disclosure, the marine scrubber system is provided with a first concentration sensor disposed in a first exhaust pipe connecting the diesel engine to the purification chamber, for detecting the ammonia concentration in the first exhaust pipe, and the controller may start the supply of the acidic solution by the supplier when the ammonia concentration in the first exhaust pipe exceeds a predetermined reference value based on the detection signal of the first concentration sensor.

[0025] According to the fourth aspect, the first concentration sensor detects the ammonia concentration immediately before being introduced into the purification chamber of the scrubber. Then, the controller starts the supply of the acidic solution by the supplier based on the detection signal of the first concentration sensor. By configuring in this way, the supply of the acidic solution can be started without delay as soon as the concentration of unburned ammonia increases. Leakage of unburned ammonia to the outside of the ship (especially leakage at a concentration exceeding a predetermined reference value) can be more reliably suppressed.

[0026] Further, according to a fifth aspect of the present disclosure, the marine scrubber system includes a second concentration sensor disposed in a second exhaust pipe connecting the diesel engine to the outside of the ship, for detecting the ammonia concentration in the second exhaust pipe, and the controller determines the supply amount of the acidic solution by the supplier based on the detection signal of the second concentration sensor.

[0027] According to the fifth aspect, the second concentration sensor detects the ammonia concentration in the exhaust gas discharged from the purification chamber. Then, the controller adjusts the supply amount of the acidic solution based on the detection signal of the second concentration sensor. By configuring in this way, it is possible to set the supply amount to the minimum amount that can suppress the leakage of unburned ammonia without supplying the acidic solution excessively. As a result, the supply amount of the acidic solution can be reduced.

[0028] Further, according to a sixth aspect of the present disclosure, the controller may terminate the supply of the acidic solution by the supplier when the ammonia concentration in the first exhaust pipe falls below the reference value.

[0029] According to the sixth aspect, the controller terminates the supply of the acidic solution based on the ammonia concentration in the exhaust gas discharged from the diesel engine. By configuring in this way, it is possible to more reliably determine that the ammonia concentration is below the reference value. As a result, the supply of the acidic solution can be terminated at a more appropriate timing, and the leakage of unburned ammonia to the outside of the ship (especially the leakage at a concentration exceeding a predetermined reference value) can be more reliably suppressed.

[0030] Further, according to a seventh aspect of the present disclosure, the marine scrubber system includes a pH sensor for detecting the pH value of the water circulating through the scrubber, and the controller may adjust the supply amount of the acidic solution by the supplier based on the detection signal of the pH sensor.

[0031] According to the seventh aspect, the supply amount of the acidic solution can be suppressed to an appropriate amount without being excessive. By doing so, it is possible to reduce the discharge amount of unburned ammonia while realizing a reduction in the water spray amount and thus the load on the pump, and a reduction in the supply amount of the acidic solution.

[0032] Further, the eighth aspect of the present disclosure relates to an engine system. This engine system may include the marine scrubber system and at least the diesel engine capable of burning the ammonia, which is connected to the marine scrubber system.

[0033] According to the eighth aspect, it is possible to reduce the discharge amount of unburned ammonia while realizing a reduction in the supply amount of the acidic solution and a reduction in the load on the pump for water spraying.

Advantages of the Invention

[0034] As described above, according to the present disclosure, it is possible to achieve both a reduction in the discharge amount of unburned ammonia and a reduction in the load on the pump for water spraying.

Brief Description of the Drawings

[0035]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6

Figure 7

Figure 8

MODE FOR CARRYING OUT THE INVENTION

[0036] Hereinafter, a first embodiment of the present disclosure (hereinafter simply referred to as "embodiment") will be described with reference to the drawings. Note that the following description is illustrative. FIG. 1 is a system diagram illustrating an engine system S, a diesel engine 1 constituting the engine system S, and a marine scrubber system 100.

[0037] <Overall Configuration> As shown in FIG. 1, the engine system S includes a diesel engine (hereinafter also simply referred to as "engine") 1 and a marine scrubber system (hereinafter also simply referred to as "scrubber system") 100 connected to the engine 1. This engine system S is mounted on a large ship such as an oil tanker, a container ship, or an automobile carrier.

[0038] The engine 1 is capable of burning at least ammonia. This engine 1 is configured as a uniflow scavenging two-stroke one-cycle engine and is used as a main engine that generates a propulsive force for operating the ship. 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, its output is transmitted to the propeller, and the ship is propelled.

[0039] Specifically, the engine 1 can operate in each of a first mode in which the oil fuel containing sulfur is combusted alone in the cylinder 21 and a second mode in which at least ammonia among ammonia and the oil fuel is combusted 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, a fossil fuel such as heavy oil is used as the oil fuel. The fossil fuel may be any fuel that can be refined from crude oil.

[0040] More specifically, the engine 1 is configured to be capable of performing at least one of co-combustion using both ammonia and the oil fuel and single combustion of ammonia during operation in the second mode.

[0041] For example, the engine 1 described in detail below is configured to combust the oil fuel alone in the first mode and to co-combust ammonia and the oil fuel in the second mode. Note that the first mode is not essential. The engine 1 only needs to be operable in at least the second mode.

[0042] Here, when the oil fuel and ammonia are used in combination, it is assumed that the exhaust gas discharged from the cylinder 21 (particularly, the exhaust gas before being discharged outside the ship) may contain unburned ammonia in addition to sulfur oxides resulting from the oil fuel.

[0043] To cope with those exhaust gas components, the scrubber system 100 according to the present embodiment is configured to purify the exhaust gas discharged from the diesel engine 1. This scrubber system 100 includes a so-called wet scrubber 110 and can remove components such as sulfur oxides and unburned ammonia from the exhaust gas.

[0044] Hereinafter, each element constituting the engine system S will be described in order.

[0045] <Details of the engine 1> As shown in FIG. 1, the engine 1 includes an engine body 2 having the aforementioned 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 each connected to the engine body 2.

[0046] (1) Engine body 2 As shown in FIG. 1, the engine body 2 has a plurality (only three are illustrated in FIG. 1) of cylinders 21. The engine body 2 is a two-stroke engine and is installed in the engine room of a ship. This engine body 2 is configured as a so-called crosshead type internal combustion engine in order to achieve its long stroke.

[0047] FIG. 2 is a diagram illustrating the upper structure of the engine body 2. As shown in FIG. 2, each cylinder 21 houses a piston 22. Each cylinder 21 is composed of a cylinder liner 23 and a cylinder cover 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 FIG. 2). The cylinder cover 24 is fixed to the upper end portion of the cylinder liner 23 and closes the opening formed at the upper end portion thereof.

[0048] The engine body 2 further has, for each cylinder 21, an exhaust relay pipe 25 and an exhaust valve 26. Here, the exhaust relay pipe 25 connects the central portion of each cylinder cover 24 and an exhaust manifold 2b described later. The exhaust valve 26 opens and closes the central portion of each cylinder cover 24.

[0049] And a combustion chamber 27 is partitioned for each cylinder 21 by the inner wall of each cylinder 21 and the top surface of the piston 22. One or a plurality of first fuel injection valves 28 and one or a plurality of second fuel injection valves 29 are provided in the cylinder cover 24 corresponding to each combustion chamber 27.

[0050] The first fuel injection valve 28 is provided one or more (two in the illustrated example) for each cylinder 21, and is respectively connected to the first supply system 41. Each first fuel injection valve 28 is arranged in a posture facing the inside of the combustion chamber 27, and is configured to inject oil fuel from its injection port.

[0051] The second fuel injection valve 29 is also provided one or more, preferably the same number as the first fuel injection valve 28 (two in the illustrated example) for each cylinder 21, and is respectively connected to the second supply system 42. Each second fuel injection valve 29 is arranged in a posture facing the inside of the combustion chamber 27, and is configured to inject ammonia from its injection port.

[0052] During the operation of the engine 1 in the first mode, among the first and second fuel injection valves 28 and 29, only the first fuel injection valve 28 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.

[0053] On the other hand, during the operation of the engine 1 in the second mode, oil fuel is supplied into the combustion chamber 27 from the first fuel injection valve 28, and ammonia is supplied into the same combustion chamber 27 from the second fuel injection valve 29. The oil fuel and ammonia thus supplied burn in a mixed manner (mixed combustion) in the combustion chamber 27.

[0054] The reciprocating motion of the piston 22 is caused by the combustion corresponding to each mode. At this time, when the exhaust valve 26 operates to release the combustion chamber 27, the exhaust generated by the combustion is pushed out into the exhaust relay pipe 25, and air is introduced into the combustion chamber 27 from a scavenging port (not shown).

[0055] Further, when the piston 22 reciprocates due to combustion, a crank motion is generated via a piston rod, a crosshead, etc., and the crankshaft rotates according to the crank motion. The rotation of the crankshaft rotates the propeller of the ship via a propeller shaft. When the propeller of the ship rotates, the ship is propelled.

[0056] Returning to FIG. 1, the engine body 2 further has a scavenging trunk 2a and an exhaust manifold 2b. The scavenging trunk 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 discharged from the combustion chamber 27, temporarily stores the received exhaust, and converts the dynamic pressure of the exhaust into static pressure.

[0057] (2) Intake and Exhaust System 3 As shown in FIG. 1, the intake and exhaust system 3 has an intake pipe 31 connected to the engine body 2 via the scavenging trunk 2a and an exhaust pipe 32 connected to the engine body 2 via the exhaust manifold 2b.

[0058] The intake pipe 31 communicates with the combustion chamber 27 via the scavenging trunk 2a and is configured to guide air into the combustion chamber 27. The exhaust pipe 32 communicates with the combustion chamber 27 via the exhaust manifold 2b and is configured to guide the exhaust discharged from the combustion chamber 27.

[0059] Specifically, the exhaust pipe 32 has a first exhaust pipe 32a connecting the engine 1 to the scrubber 110, a second exhaust pipe 32b connecting the scrubber 110 to the outside of the ship, and a third exhaust pipe 32c connecting the second exhaust pipe 32b to the first exhaust pipe 32a.

[0060] 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 scrubber 110. The first exhaust pipe 32a forms a passage for guiding exhaust from the engine 1 to the scrubber 110.

[0061] A first concentration sensor 131 that constitutes the scrubber system 100 together with the scrubber 110 is disposed in the first exhaust pipe 32a. The first concentration sensor 131 detects the ammonia concentration in the first exhaust pipe 32a.

[0062] The second exhaust pipe 32b is a tubular member having one end (upstream end) connected to the scrubber 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 scrubber 110 to the outside of the ship.

[0063] A second concentration sensor 132 that constitutes the scrubber system 100 together with the scrubber 110 is disposed in the second exhaust pipe 32b. The second concentration sensor 132 detects the ammonia concentration in the second exhaust pipe 32b.

[0064] (3) Fuel supply system 4 As shown in FIG. 1, 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.

[0065] 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 to each first fuel injection valve 28. The first fuel pump 41c is disposed in the first fuel supply pipe 41b. The first fuel pump 41c pumps the oil fuel stored in the first fuel tank 41a and supplies it to the first fuel injection valve 28.

[0066] For example, when the engine 1 is operating 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.

[0067] 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 to each second fuel injection valve 29. The second fuel pump 42c is disposed in the second fuel supply pipe 42b. The second fuel pump 42c pumps the ammonia stored in the second fuel tank 42a and supplies it to the second fuel injection valve 29.

[0068] For example, when the engine 1 is operating in the second mode, in addition to the first fuel pump 41c, the second fuel pump 42c 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.

[0069] <Details of the scrubber system 100> FIG. 3 is a block diagram illustrating a schematic configuration of the scrubber system 100. As shown in FIGS. 1 and 3, the scrubber system 100 includes a scrubber 110, a controller 120, and first and second concentration sensors 131 and 132. The scrubber 110 sprays water into the exhaust gas. The controller 120 controls the scrubber 110, particularly the spraying of water by the scrubber 110 (hereinafter, also simply referred to as "water spraying"). The first and second concentration sensors 131 and 132 output detection signals for controlling the scrubber 110 to the controller 120, respectively.

[0070] (1) Scrubber 110 As shown in FIG. 1, the scrubber 110 includes a scrubber main body 111, one or more spray nozzles 112, a circulation pipe 113, a water pump 114, a branch pipe 115, a centrifuge 116, and a feeder 117. This scrubber 110 is a so-called closed-loop scrubber.

[0071] The scrubber main body 111 is a container connected to the engine 1. The scrubber main body 111 forms an exhaust purification chamber 111a with water. The water spray to the exhaust is to be carried out within this purification chamber 111a.

[0072] The other end (downstream end) of the first exhaust pipe 32a is connected to the side wall portion of the purification chamber 111a. The first exhaust pipe 32a communicates with the purification chamber 111a through its other end. Exhaust flows into the purification chamber 111a through the first exhaust pipe 32a.

[0073] One end (upstream end) of the second exhaust pipe 32b is connected to the ceiling surface of the purification chamber 111a. The second exhaust pipe 32b communicates with the purification chamber 111a through its one end. Exhaust flows out from the purification chamber 111a through the second exhaust pipe 32b.

[0074] One or more spray nozzles 112 are accommodated in the purification chamber 111a. The spray nozzles 112 spray water within the purification chamber 111a. Note that the number of spray nozzles 112 is not particularly limited. In the example of FIG. 1, only one spray nozzle 112 is shown for simplicity.

[0075] Specifically, the spray nozzles 112 spray the water (for example, clean water) circulating in the scrubber 110 toward the bottom surface of the purification chamber 111a. The water sprayed from the spray nozzles 112 moves downward along a filler (not shown) and then falls and accumulates at the bottom of the purification chamber 111a.

[0076] The circulation pipe 113 circulates water between the purification chamber 111a and the spray nozzles 112.

[0077] Specifically, the circulation pipe 113 is a tubular member having one end (upstream end) connected to the bottom of the purification chamber 111a and the other end (downstream end) connected to the spray nozzle 112. The circulation pipe 113 forms a passage for sending back the water sprayed from the spray nozzle 112 and accumulated in the purification chamber 111a to the spray nozzle 112 in order to circulate water between the purification chamber 111a and the spray nozzle 112.

[0078] The water pump 114 is driven to supply water to the spray nozzle 112. The water pump 114 is disposed in the middle of the circulation pipe 113. When the water pump 114 is driven, water is sprayed from the spray nozzle 112. This water is sprayed toward the exhaust gas flowing into the purification chamber 111a. The sprayed water is used for absorbing sulfur oxides contained in the exhaust gas and removing unburned ammonia contained in the exhaust gas.

[0079] Specifically, the water pump 114 is constituted by an inverter-type motor. The driving of the motor in the water pump 114 is controlled via an inverter based on a control signal from the controller 120.

[0080] More specifically, when driving the water pump 114, the controller 120 inputs an operation command (control signal) to the inverter. The inverter that has received the operation command supplies power to the motor of the water pump 114 and drives the motor with the power. The power supply from the inverter to the motor is controlled by, for example, a feedback signal corresponding to the rotational speed of the motor.

[0081] The branch pipe 115 branches off from the circulation pipe 113. The circulation pipe 113 feeds a part of the water flowing through the branch pipe 115 into the centrifuge 116. The centrifuge 116 separates, for example, solid components (sludge) derived from sulfur oxides from the water by centrifugal force. The solid components separated from the water are stored, for example, in a predetermined storage section (so-called sludge tank).

[0082] Specifically, the branch pipe 115 is a tubular member having one end (upstream end) connected to an intermediate part of the circulation pipe 113 and the other end (downstream end) connected to another part located downstream of that part (intermediate part). A part of the water flowing from the circulation pipe 113 into the branch pipe 115 passes through the centrifugal separator 116 and then is sent back to the circulation pipe 113 or discharged outside the ship through a pipe (not shown).

[0083] The feeder 117 supplies an acidic solution to the water circulating through the circulation pipe 113. The acidic solution refers to a solution having a pH value less than 7. In this embodiment, dilute sulfuric acid is used as the acidic solution. Note that the acidic solution is not limited to dilute sulfuric acid.

[0084] Specifically, the feeder 117 includes a dilute sulfuric acid tank 117a, a dilute sulfuric acid supply pipe 117b, and a dilute sulfuric acid pump 117c. The dilute sulfuric acid tank 117a stores dilute sulfuric acid. The dilute sulfuric acid supply pipe 117b connects the dilute sulfuric acid tank 117a to the purification chamber 111a. The dilute sulfuric acid pump 117c pumps the dilute sulfuric acid stored in the dilute sulfuric acid tank 117a and supplies it to the purification chamber 111a.

[0085] (2) Controller 120 (2-1) Schematic configuration The controller 120 has a processor, a volatile memory, a non-volatile memory, and input / output devices. In addition to the aforementioned first concentration sensor 131 and second concentration sensor 132, the pH sensor 134 shown in FIGS. 1 and 3 and the exhaust property sensor 135 shown only in FIG. 3 are electrically connected to this controller 120.

[0086] The pH sensor 134 is attached to the scrubber main body 111 and detects the pH value of the water stored in the purification chamber 111a and circulating through the scrubber 110. The pH sensor 134 inputs its detection signal to the controller 120.

[0087] The exhaust property sensor 135 detects exhaust properties other than the ammonia concentration (particularly, the properties related to the exhaust components in the first mode). The exhaust property sensor 135 inputs its detection signal to the controller 120.

[0088] Based on the detection signals input from those sensors, the controller 120 generates a control signal and inputs the control signal to, for example, the aforementioned water pump 114, centrifuge 116, dilute sulfuric acid pump 117c, first control valve 133, and second control valve 136. By inputting the control signal to each part of the scrubber system 100, the controller 120 causes the scrubber 110 to purify the exhaust gas.

[0089] For example, in the first mode in which the oil fuel is burned alone, the scrubber 110 according to the present embodiment causes sulfur oxides resulting from the oil fuel to be absorbed by water that circulates through the circulation pipe 113 and is sprayed from the spray nozzle 112 into the purification chamber 111a. That is, this scrubber 110 functions as a so-called "SO x scrubber" configured to remove sulfur oxides from the exhaust gas.

[0090] In addition, in the second mode in which at least ammonia is burned, the scrubber 110 according to the present embodiment dissolves unburned ammonia that may be contained in the exhaust gas in water by spraying water into the same purification chamber 111a as in the first mode. That is, this scrubber 110 has both the function as an SO x scrubber and the function as a scrubber for removing unburned ammonia.

[0091] As described above, the scrubber 110 illustrated in FIG. 1 is configured to purify the exhaust gas generated in each of the first mode and the second mode. And in the present embodiment, the controller 120 that controls such a scrubber 110 is configured to execute processing that contributes to suppressing the emission of unburned ammonia in each of the first mode and the second mode.

[0092] Hereinafter, the process for suppressing the emission of unburned ammonia will be described using a specific example.

[0093] (2-2) Specific Example of the Process in the First Mode FIG. 4 is a flowchart illustrating the process in the first mode.

[0094] First, in step S101 of FIG. 4, the controller 120 determines whether the engine 1 is operating in the first mode. If this 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 ends the control process shown in FIG. 4 and proceeds to the flowchart described later in FIG. 5A.

[0095] In step S102, the controller 120 acquires the detection value of the exhaust property sensor 135. The detection value obtained in this step S102 includes at least a parameter related to the content of SO x in the exhaust gas. Instead of using the exhaust property sensor 135, the sulfur (S) content in the fuel may be detected, or the crew may be configured to perform the on / off operation of the scrubber system 100.

[0096] In the subsequent step S103, the controller 120 determines the necessity of exhaust gas cleaning by the scrubber system 100. This determination is made by the controller 120, for example, based on the detection value obtained in step S103. If this determination is YES, the controller 120 advances the control process to step S104. On the other hand, if the determination in step S103 is NO, the controller 120 returns the control process to step S101.

[0097] In step S104, the controller 120 executes water spraying by the water pump 114. Specifically, the controller 120 inputs a control signal to the water pump 114 via an inverter to drive it. When the water pump 114 is driven, water is sprayed in the purification chamber 111a. When this water comes into contact with the exhaust gas flowing into the purification chamber 111a, SO x is absorbed (captured) from the exhaust gas into the water.

[0098] Here, when SO x dissolves in water, that SO x becomes sulfate ions in the water. The water containing sulfate ions will exhibit acidity according to its ion concentration.

[0099] Here, in the case of the conventionally known scrubber 110, it was common practice to neutralize the water inclined to the acidic side by supplying an alkaline solution (for example, an aqueous sodium hydroxide solution).

[0100] In contrast to such common practice, the inventors of the present application focused on the fact that the scrubber 110 serves as both a so-called SO x scrubber and a scrubber for removing unburned ammonia from the exhaust gas, and newly conceived a mechanism that can efficiently remove unburned ammonia in the second mode with water inclined to the acidic side.

[0101] That is, in the second mode, the scrubber 110 according to the present embodiment absorbs unburned ammonia while neutralizing it with water in which SO x has dissolved. Thereby, unburned ammonia that may be generated in the second mode can be efficiently removed.

[0102] Furthermore, in the second mode, the scrubber 110 according to the present embodiment is configured to supply dilute sulfuric acid to the water circulating in the scrubber 110 by the supplier 117. Thereby, regardless of whether SO x has dissolved or not, unburned ammonia can be surely neutralized. Hereinafter, the process related to the supply of dilute sulfuric acid is referred to as "solution supply process".

[0103] When the process of step S104 is completed, the controller 120 returns the control process to step S102. In this case, the water spraying continues until the exhaust cleaning by the scrubber 110 becomes unnecessary.

[0104] (2-3) Specific Example of Processing in the Second Mode FIGS. 5A and 5B are flowcharts illustrating the processing in the second mode.

[0105] First, in step S201 of FIG. 5A, the controller 120 determines whether or not the engine 1 is operating in the second mode. If this determination is YES, the controller 120 advances the control process to step S202. On the other hand, if the determination in step S201 is NO, the controller 120 ends the control process shown in FIG. 5A and shifts to the aforementioned flow shown in FIG. 4.

[0106] In step S202, the controller 120 acquires the detection value of the first concentration sensor 131. The detection value acquired in this step S202 indicates the ammonia concentration (particularly, the concentration of unburned ammonia) in the first exhaust pipe 32a. Since this ammonia concentration corresponds to the ammonia concentration on the exhaust inlet side as viewed from the purification chamber 111a, it may be referred to as the "inlet concentration" in the following description.

[0107] In the subsequent step S203, the controller 120 determines whether or not the inlet concentration acquired in step S202 exceeds a predetermined reference value. This reference value is, for example, a regulated value defined by laws and regulations, and is stored in the controller 120 in advance. The controller 120 is configured to appropriately read this reference value as needed.

[0108] If the determination in step S203 is YES, the controller 120 advances the control process to step S204 and determines that the solution supply process should be started. For example, the controller 120 changes the signal value of a signal indicating the execution flag of the solution supply process. That is, the controller 120 according to the present embodiment is configured to start the supply of dilute sulfuric acid by the feeder 117 when the inlet concentration corresponding to the detection signal exceeds a predetermined reference value based on the detection signal of the first concentration sensor 131. On the other hand, if the determination in step S203 is NO, the controller 120 returns the control process to step S201.

[0109] Note that the execution flag of the solution supply process also serves as the execution flag of water injection in this embodiment. That is, the controller 120 according to the present embodiment is configured to start the supply of dilute sulfuric acid by the feeder 117 and the water spray by the water pump 114 when the inlet concentration corresponding to the detection signal exceeds a predetermined reference value based on the detection signal of the first concentration sensor 131.

[0110] In step S205 following step S204, the controller 120 executes the solution supply process. The details of the solution supply process are as shown in FIG. 5B. When the control process advances to step S205, the controller 120 executes each process shown in the figure in order from step S301 in FIG. 5B.

[0111] First, in step S301, the controller 120 acquires the detection value of the second concentration sensor 132. The detection value acquired in this step S301 indicates the ammonia concentration (particularly, the concentration of unburned ammonia) in the second exhaust pipe 32b. Since this ammonia concentration corresponds to the ammonia concentration on the exhaust outlet side as seen from the purification chamber 111a, it may be referred to as the "outlet concentration" in the following description.

[0112] In the subsequent step S302, the controller 120 determines the concentration of unburned ammonia (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.

[0113] The outlet concentration determined in step S302 is used to determine the supply amount of dilute sulfuric acid in the subsequent step S303. That is, the controller 120 according to the present embodiment is configured to determine the supply amount of dilute sulfuric acid by the feeder 117 based on the detection signal of the second concentration sensor 132.

[0114] Also, in step S302, instead of the concentration of unburned NH3 contained in the exhaust gas, the controller 120 may determine the amount (for example, flow rate) of unburned NH3 contained in the exhaust gas. This determination can be executed, for example, by combining the detection signal 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 flow rate of the entire exhaust gas.

[0115] In the subsequent step S303, the controller 120 determines the supply amount of dilute sulfuric acid by the feeder 117 so as to increase or decrease according to the concentration of unburned NH3.

[0116] Here, FIG. 6 is a graph showing the magnitude relationship between the concentration of unburned NH3 and the supply amount of dilute sulfuric acid in the second mode in comparison with the supply amount of dilute sulfuric acid in the first mode. The supply amount of dilute sulfuric acid referred to here corresponds to the target value of the supply amount to be supplied from the feeder 117 to the purification chamber 111a.

[0117] The solid line L2 in FIG. 6 shows the supply amount of dilute sulfuric acid in the second mode in association with the level of the concentration of unburned NH3. As shown by the arrow A2 in FIG. 6, in the second mode, the controller 120 is configured to increase the supply amount of dilute sulfuric acid by the feeder 117 as the concentration of unburned NH3 increases.

[0118] The dashed line L1 in FIG. 6 indicates the supply amount of dilute sulfuric acid in the first mode. In the first mode, although the emission amount of unburned NH3 is zero from the start, the dashed line L1 is shown as a straight line parallel to the horizontal axis of FIG. 6 in order to clarify the magnitude relationship with the solid line L2. As shown by the dashed line L1, the controller 120 sets the supply amount of dilute sulfuric acid by the supplier 117 to zero in the first mode.

[0119] As suggested by the double-headed arrow A1 in FIG. 6, the supply amount of dilute sulfuric acid in the second mode is set to be higher than the supply amount of dilute sulfuric acid in the first mode regardless of the level of the concentration of unburned NH3. That is, the controller 120 is configured to increase the supply amount of dilute sulfuric acid by the supplier 117 in the second mode as compared with the first mode.

[0120] Note that when configured to determine the amount instead of the concentration of unburned NH3, the controller 120 may determine the supply amount of dilute sulfuric acid by the supplier 117 so as to increase or decrease according to the amount of unburned NH3. In that case, the controller 120 may be configured to increase the supply amount of dilute sulfuric acid by the supplier 117 as the amount of unburned NH3 increases in the second mode.

[0121] Note that the shape of the solid line L2 in FIG. 6 is merely an example. The supply amount of dilute sulfuric acid may be changed stepwise or curvilinearly.

[0122] In the subsequent step S304, the controller 120 drives the dilute sulfuric acid pump 117c so as to realize the supply amount determined in step S303. As a result, an amount of dilute sulfuric acid (acidic solution) corresponding to the concentration of unburned NH3 is supplied to the water accumulated in the purification chamber 111a.

[0123] In the subsequent step S305, the controller 120 acquires the detection value of the pH sensor 134. The detection value acquired in this step S305 indicates the pH value of the water circulating through the scrubber 110 after the dilute sulfuric acid is mixed.

[0124] In subsequent steps S306 and S307, the controller 120 adjusts the supply amount of dilute sulfuric acid by the feeder 117 based on the detection signal of the pH sensor 134.

[0125] Specifically, in step S306, the controller 120 determines whether the pH value obtained in step S305 is less than or equal to a predetermined target value. This target value is a value less than 7 and is pre-stored in the controller 120.

[0126] If the determination in step S306 is YES, the controller 120 ends the process shown in FIG. 5B and completes the solution supply process. In this case, the controller 120 advances the control process from step S306 in FIG. 5B to step S206 in FIG. 5A.

[0127] On the other hand, if the determination in step S306 is NO, the controller 120 advances the control process from step S306 to step S307 and additionally supplies dilute sulfuric acid (acidic solution). After that, the controller 120 returns the control process to step S305. That is, the controller 120 continues to supply dilute sulfuric acid until the pH value becomes less than or equal to the target value.

[0128] Thereafter, in step S206 of FIG. 5A, the controller 120 drives the water pump 114 to perform water spraying. As a result, water mixed with an amount of dilute sulfuric acid corresponding to the concentration of unburned NH3 is sprayed from the spray nozzle 112. By spraying water containing dilute sulfuric acid and SO x it is possible to neutralize unburned NH3.

[0129] In subsequent step S207, the controller 120 acquires the inlet concentration again and determines whether the inlet concentration is below a predetermined reference value. This reference value may be the same as the reference value referred to in step S203, for example.

[0130] If the determination in step S207 is YES, the controller 120 advances the control process to step S208 and determines that the solution supply process should end. For example, the controller 120 changes the signal value of a signal indicating the execution flag of the solution supply process. That is, the controller 120 is configured to end the supply of dilute sulfuric acid by the feeder 117 when the inlet concentration corresponding to the detection signal is below a predetermined reference value based on the detection signal of the first concentration sensor 131.

[0131] On the other hand, if the determination in step S207 is NO, the controller 120 advances the control process to step S209. In this case, the controller 120 acquires the detection value of the pH sensor 134 in step S209, and in the subsequent step S210, determines whether the acquired detection value is less than or equal to a predetermined target value. If the determination in step S210 is YES, the controller 120 returns the control process to step S206 to perform water spraying. On the other hand, if the determination in step S210 is NO, the controller 120 returns the control process to step S205 and performs both the solution supply process and water spraying. In this way, the controller 120 continues the solution supply process and water spraying until the determination in step S207 becomes YES.

[0132] <Regarding suppression of unburned NH3 emissions> For a diesel engine configured to burn ammonia, it is required to reduce the emission amount of unburned ammonia so that the emission amount is within a predetermined reference value or less.

[0133] As a measure to meet such a demand, for example, by using a so-called scrubber, it is conceivable to dissolve unburned NH3 in the water sprayed in the scrubber.

[0134] However, as exemplified in FIG. 1, the marine scrubber 110 sprays a huge amount of water. Therefore, the marine scrubber 110 has to use a huge water pump 114 compared to other applications, and the load on the water pump 114, such as the drive current of the water pump 114, also becomes extremely large. This is inconvenient in terms of suppressing the running costs of the ship, such as power.

[0135] To reduce the load on the water pump 114, although it is conceivable to reduce the amount of water sprayed, simply reducing the spray amount arbitrarily is inconvenient because it may interfere with the suppression of unburned NH3 emissions.

[0136] On the other hand, as described with reference to FIGS. 1 and 5B, the scrubber 110 according to the embodiment supplies dilute sulfuric acid as an acidic solution to the water circulated through the circulation pipe 113. As a result, the water sprayed from the spray nozzle 112 will tend to be on the acidic side. By neutralizing unburned NH3 with acidic water, the unburned NH3 can be efficiently treated.

[0137] Furthermore, as exemplified in FIG. 5B, the controller 120 according to the embodiment adjusts the supply amount of dilute sulfuric acid according to the concentration or amount of unburned NH3 contained in the exhaust gas. By supplying an amount of dilute sulfuric acid corresponding to the concentration or amount of unburned NH3, the emission amount of unburned NH3 can be reduced without spraying a large amount of water. As a result, the amount of water sprayed can be suppressed, and the load on the water pump for water spraying, that is, the water pump 114, can be reduced.

[0138] Thus, according to the embodiment, it is possible to achieve both a reduction in the emission amount of unburned NH3 and a reduction in the load on the water pump 114.

[0139] Furthermore, by adjusting the supply amount of dilute sulfuric acid as in the embodiment, the supply amount of dilute sulfuric acid can be made an appropriate amount corresponding to the concentration or amount of unburned NH3. As a result, the supply amount of dilute sulfuric acid can be kept at an appropriate amount without being excessive.

[0140] Also, as described with reference to FIGS. 4, 5A, and 5B, the scrubber 110 according to the embodiment removes SO from the exhaust gas. x It will also serve as a scrubber for removing SO from the exhaust gas. x and a scrubber for removing unburned ammonia from the exhaust gas.

[0141] Here, when water sprayed from the spray nozzle 112 absorbs SO, x the water (aqueous SO solution) will tend to be acidic. By circulating the acidic water without neutralization treatment and using the water for neutralizing unburned NH3, unburned NH3 can be efficiently treated. This is advantageous in suppressing the amount of chemicals required for neutralizing unburned NH3, such as dilute sulfuric acid, and thus reducing the running cost of the ship. x

[0142] Also, as illustrated in FIG. 6, by changing the supply amount of dilute sulfuric acid in the second mode, the supply amount of dilute sulfuric acid can be suppressed to an appropriate amount without being excessive. This can reduce the amount of unburned NH3 emissions while reducing the water spray amount and thus the load on the water pump 114, as well as reducing the supply amount of dilute sulfuric acid.

[0143] Also, as illustrated in FIG. 1, the first concentration sensor 131 detects the ammonia concentration immediately before being introduced into the purification chamber 111a of the scrubber 110. Then, as illustrated from step S202 to step S204 in FIG. 5A, the controller 120 starts the supply of dilute sulfuric acid by the supplier 117 based on the detection signal of the first concentration sensor 131. With this configuration, the supply of dilute sulfuric acid can be started without delay as soon as the concentration of unburned NH3 increases. Leakage of unburned NH3 to the outside of the ship (especially leakage at a concentration exceeding a predetermined reference value) can be more reliably suppressed.

[0144] ​Also, as illustrated in FIG. 1, the second concentration sensor 132 detects the ammonia concentration in the exhaust gas discharged from the purification chamber 111a. Then, the controller 120 adjusts the supply amount of dilute sulfuric acid based on the detection signal of the second concentration sensor 132. By configuring in this way, it is possible to set the supply amount to the minimum amount capable of suppressing the leakage of unburned NH3 without supplying dilute sulfuric acid excessively. Thus, the supply amount of dilute sulfuric acid can be reduced.

[0145] Also, as illustrated from step S207 to step S208 in FIG. 5A, the controller 120 terminates the supply of the acidic solution based on the detection signal of the first concentration sensor 131. By configuring in this way, it is possible to more reliably determine that the ammonia concentration is below the reference value. As a result, the supply of the acidic solution can be terminated at a more appropriate timing, and the leakage of unburned NH3 to the outside of the ship (especially the leakage at a concentration exceeding a predetermined reference value) can be more reliably suppressed.

[0146] Also, as illustrated from step S305 to step S307 in FIG. 5B, the controller 120 adjusts the supply amount of dilute sulfuric acid based on the detected value of the pH sensor 134. Thereby, the supply amount of dilute sulfuric acid can be suppressed to an appropriate amount without being excessive. Thus, while reducing the discharge amount of unburned NH3, it is possible to reduce the spray amount of water, and thus the load on the water pump 114, and also reduce the supply amount of dilute sulfuric acid.

[0147] <Second Embodiment> In the first embodiment, the exhaust pipe 32 having the first exhaust pipe 32a connecting the engine 1 to the scrubber 110 and the second exhaust pipe 32b connecting the scrubber 110 to the outside of the ship was illustrated, but the present disclosure is not limited to such an exhaust pipe 32. The exhaust pipe 32 may have an exhaust gas recirculation line.

[0148] FIG. 7 is a diagram corresponding to FIG. 1 illustrating a second embodiment of the scrubber system 100. In FIG. 7, elements having the same configuration and structure as those in the first embodiment are denoted by the same reference numerals as those in the said embodiment.

[0149] The scrubber system 100’ illustrated in FIG. 7 has an exhaust pipe 32’ different from that of the first embodiment. This exhaust pipe 32’ has a third exhaust pipe 32c that constitutes a recirculation line in addition to a first exhaust pipe 32a and a second exhaust pipe 32b configured in the same manner as in the first embodiment.

[0150] The third exhaust pipe 32c is a tubular member having one end (upstream end) connected to the second exhaust pipe 32b and the other end (downstream end) connected to the first exhaust pipe 32a. The third exhaust pipe 32c forms a passage for sending the exhaust gas from the second exhaust pipe 32b back to the first exhaust pipe 32a in order to repeatedly purify the exhaust gas by the scrubber 110.

[0151] A first control valve 133 and an exhaust blower 136 are arranged in the third exhaust pipe 32c. The first control valve 133 and the exhaust blower 136 constitute the scrubber system 100’ together with the scrubber 110. The first control valve 133 is constituted by an electromagnetic valve that operates based on, for example, a control signal from the controller 120, and opens and closes the third exhaust pipe 32c. The exhaust blower 136 is configured to operate based on, for example, a control signal from the controller 120, and generates an exhaust gas flow flowing through the third exhaust pipe 32c.

[0152] When it is determined as NO in step S207, the controller 120 according to the second embodiment opens the first control valve 133 at least temporarily and operates the exhaust blower 136. Thereby, the exhaust gas in which unburned NH3 has not been sufficiently removed can be sent back to the scrubber 110, and the leakage of unburned NH3 to the outside of the ship can be more reliably prevented.

[0153] -Modification of the Second Embodiment- Note that the configuration according to the second embodiment is not limited to that illustrated in FIG. 7. For example, the modification shown in FIG. 8 further includes a fourth exhaust pipe 32d that bypasses the scrubber 110.

[0154] The fourth exhaust pipe 32d is a tubular member having one end (upstream end) connected to the first exhaust pipe 32a and the other end (downstream end) connected to the second exhaust pipe 32b. As shown in FIG. 8, the upstream end of the fourth exhaust pipe 32d is located upstream (upstream in the exhaust flow direction) of the connection portion between the third exhaust pipe 32c and the first exhaust pipe 32a. As shown in the same figure, the downstream end of the fourth exhaust pipe 32d is located downstream (downstream in the exhaust flow direction) of the second concentration sensor 132 and a second control valve 137 described later.

[0155] A third control valve 138 is disposed in the fourth exhaust pipe 32d. The third control valve 138 constitutes a scrubber system 100' together with the scrubber 110. The third control valve 138 is constituted by, for example, an electromagnetic valve that operates based on a control signal from the controller 120, and opens and closes the fourth exhaust pipe 32d.

[0156] When the fourth exhaust pipe 32d is used, a second control valve 137 may be further disposed in the second exhaust pipe 32b. The second control valve 137 constitutes a scrubber system 100' together with the scrubber 110. The second control valve 137 is constituted by, for example, an electromagnetic valve that operates based on a control signal from the controller 120, and opens and closes the second exhaust pipe 32b.

[0157] <Other Embodiments> In the first embodiment, the detected value of the second concentration sensor 132 was used in step S302 of FIG. 5B, but the present disclosure is not limited to such a configuration. Instead of the detected value of the second concentration sensor 132, or in addition to the detected value of the second concentration sensor 132, the detected value of the first concentration sensor 131 may be acquired.

[0158] In addition, in the above-described embodiment, the scrubber system 100 including the first and second concentration sensors 131 and 132 has been illustrated. However, the present disclosure is not limited to such a configuration. It is not essential for the scrubber system 100 to include both the first and second concentration sensors 131 and 132. The scrubber system 100 may include at least one of the first concentration sensor 131 and the second concentration sensor.

[0159] If, for example, the scrubber system 100 includes only the first concentration sensor 131, in step S301 of FIG. 5B, the detected value of the first concentration sensor 131 may be acquired instead of the second concentration sensor 132, and in step S207 of FIG. 5A, the inlet concentration may be referred to instead of the outlet concentration. Even in such a configuration, similar to the above-described embodiment, the solution supply process can be started without delay.

[0160] Similarly, if the scrubber system 100 includes only the second concentration sensor 132, in step S202 of FIG. 5A, the detected value of the second concentration sensor 132 may be acquired instead of the first concentration sensor 131, and in step S203 of FIG. 5A, the outlet concentration may be referred to instead of the inlet concentration. Even in such a configuration, the water pump 114 can be driven with a minimum necessary load, which is advantageous for suppressing the running cost of the ship.

[0161] In addition, in the first and second embodiments, only one dilute sulfuric acid pump 117c has been illustrated. However, the present disclosure is not limited to such a configuration. For example, a plurality of dilute sulfuric acid pumps 117c may be arranged in the dilute sulfuric acid supply pipe 117b, and the supply amount of dilute sulfuric acid may be adjusted by increasing or decreasing the number of operating dilute sulfuric acid pumps 117c according to the concentration or amount of ammonia.

[0162] For example, when the concentration of unburned ammonia is equal to or higher than a predetermined threshold value, a plurality of (for example, two) dilute sulfuric acid pumps 117c may be driven, and when the concentration is lower than the threshold value, only one dilute sulfuric acid pump 117c may be driven.

[0163] Also, in the first and second embodiments, as illustrated in FIG. 1 and the like, for each cylinder 21, one or a plurality of first fuel injection valves 28 and one or a plurality of second fuel injection valves 29 were separately provided. However, the present disclosure is not limited to such a configuration. It may be configured to inject both ammonia and oil fuel from one fuel injection valve (for example, stratified injection).

Explanation of Reference Numerals

[0164] S engine system 1 Diesel engine 2 Engine body 21 Cylinder 3 Intake and exhaust system 32 Exhaust pipe 32a First exhaust pipe 32b Second exhaust pipe 100 Marine scrubber system 110 Scrubber 111 Scrubber body 111a Purification chamber 112 Spray nozzle 113 Circulation pipe 117 Feeder 120 Controller 131 First concentration sensor 132 Second concentration sensor 134 pH sensor

Claims

1. A marine scrubber system connected to a diesel engine capable of burning ammonia and configured to purify the exhaust gas discharged from the diesel engine, a scrubber that sprays water into the exhaust gas, and a controller that controls the scrubber, wherein the scrubber includes a purification chamber connected to the diesel engine, a spray nozzle housed in the purification chamber and spraying water in the purification chamber, a circulation pipe that circulates water between the purification chamber and the spray nozzle, and a feeder that supplies an acidic solution to the water circulating through the circulation pipe, and the controller determines the concentration or amount of unburned ammonia contained in the exhaust gas, and determines the supply amount of the acidic solution by the feeder so as to increase or decrease according to the concentration or amount of the unburned ammonia characterizing the marine scrubber system.

2. In the marine scrubber system according to claim 1, the diesel engine is operable in each of a first mode in which an oil fuel containing sulfur is burned alone in a cylinder and a second mode in which at least the ammonia among the ammonia and the oil fuel is burned in the same cylinder, and the scrubber purifies the exhaust gas generated in each of the first mode and the second mode, and in the first mode, sulfur oxides caused by the oil fuel are absorbed by water circulating through the circulation pipe and sprayed from the spray nozzle, and in the second mode, the unburned ammonia is neutralized by water in which the sulfur oxides are dissolved characterizing the marine scrubber system.

3. In the marine scrubber system according to claim 2, the controller sets the supply amount of the acidic solution by the feeder to zero in the first mode, and increases the supply amount of the acidic solution by the feeder as the concentration or amount of the unburned ammonia increases in the second mode characterizing the marine scrubber system.

4. In the marine scrubber system according to any one of claims 1 to 3, it is provided with a first concentration sensor disposed in a first exhaust pipe connecting the diesel engine to the purification chamber and detecting the ammonia concentration in the first exhaust pipe, When the ammonia concentration in the first exhaust pipe exceeds a predetermined reference value based on the detection signal of the first concentration sensor, the controller starts the supply of the acidic solution by the supplier. A marine scrubber system characterized by the above.

5. In the marine scrubber system according to claim 4, A second concentration sensor is provided which is arranged in a second exhaust pipe connecting the diesel engine to the outside of the ship and detects the ammonia concentration in the second exhaust pipe. Based on the detection signal of the second concentration sensor, the controller determines the supply amount of the acidic solution by the supplier. A marine scrubber system characterized by the above.

6. In the marine scrubber system according to claim 4, When the ammonia concentration in the first exhaust pipe falls below the reference value, the controller ends the supply of the acidic solution by the supplier. A marine scrubber system characterized by the above.

7. In the marine scrubber system according to claim 1, A pH sensor is provided which detects the pH value of the water circulating through the scrubber. Based on the detection signal of the pH sensor, the controller adjusts the supply amount of the acidic solution by the supplier. A marine scrubber system characterized by the above.

8. A marine scrubber system according to claim 1, and a diesel engine connected to the marine scrubber system and capable of burning at least the ammonia. An engine system characterized by the above.

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