Marine scrubber system and engine system comprising same

Abstract

The present disclosure relates to a scrubber system for a ship and an engine system including the same. The purpose of the present disclosure is to give consideration to both reduction of the discharge amount of unburned ammonia and reduction of the load of a pump. A scrubber system for a ship, which is connected to a diesel engine capable of combusting ammonia and is configured to purify exhaust gas discharged from the diesel engine, includes a scrubber and a controller that controls the scrubber. The scrubber includes a purge chamber connected to the diesel engine, a nozzle housed in the purge chamber and configured to spray water in the purge chamber in a mist form, a circulation duct configured to circulate the water between the purge chamber and the nozzle, and a supplier configured to supply dilute sulfuric acid to the water circulated through the circulation duct. The controller determines the concentration or amount of the unburned ammonia contained in the exhaust gas, and determines the supply amount of the dilute sulfuric acid supplied by the supplier so as to increase or decrease the supply amount of the dilute sulfuric acid according to the concentration or amount of the unburned ammonia.

Description

Technical Field

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

[0002] Patent Document 1 discloses a diesel engine that mixes fuel oil and gaseous ammonia for combustion. 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 the above Patent Document 1 is, for example, a marine diesel engine. In order to improve the combustion rate of ammonia and reduce unburned ammonia, the marine diesel engine is configured such that the stratification degree of ammonia in the combustion chamber is uniformly distributed over the entire circumference.

[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 having an internal space and a liquid atomizing injection unit that atomizes and injects a liquid into the internal space.

[0005] In addition, the scrubber described in the above Patent Document 2 is, for example, a marine scrubber device. In order to absorb substances in the exhaust gas of a ship, the marine scrubber device is configured to atomize and inject a liquid such as water into the internal space of the reaction tower.

[0006] Patent Document 2: Japanese Published Patent Gazette JP-A-2021-188574

[0007] Patent Document 2: Japanese Published Patent Gazette JP-A-2022-177574 Summary of the Invention

[0008] Technical Problem 1 to be Solved by the Invention

[0009] For a diesel engine that burns ammonia fuel as in the above Patent Document 1, it is required to suppress the ammonia emission amount below a specified reference value by reducing the emission amount of unburned ammonia.

[0010] As a solution to meet this requirement, for example, it can be considered to dissolve unburned ammonia in the water atomized and injected in the scrubber by using a scrubber as in the above Patent Document 2.

[0011] However, generally, a marine scrubber atomizes and injects a large amount of water. Therefore, compared with other uses, a marine scrubber has to use a huge pump, and the load on the pump is also very large. This is disadvantageous in suppressing the operating costs of a ship such as power consumption.

[0012] In order to reduce the load on the pump, although it is possible to consider reducing the amount of water atomized injection, simply reducing the amount of water atomized injection alone may prevent the suppression of unburned ammonia emissions, so it is inappropriate.

[0013] The present disclosure is completed to solve the above technical problems, and its purpose is to balance reducing the emission amount of unburned ammonia and reducing the load on the pump for water atomized injection.

[0014] A technical solution for solving technical problems

[0015] The first aspect of the present disclosure relates to a marine scrubber system that is connected to a diesel engine capable of burning ammonia and is configured to purify the exhaust gas discharged from the diesel engine. The marine scrubber system includes a scrubber and a controller. The scrubber atomizes and injects water into the exhaust gas, and the controller controls the scrubber. The scrubber has a purification chamber, a nozzle, a circulation pipe, and a feeder. The purification chamber is connected to the diesel engine. The nozzle is housed in the purification chamber and atomizes and injects water in the purification chamber. The circulation pipe circulates water between the purification chamber and the nozzle. The feeder supplies an acidic solution to the water circulated via the circulation pipe. The controller determines the concentration or amount of unburned ammonia contained in the exhaust gas, and the controller determines the supply amount of the acidic solution supplied by the feeder in such a way that the supply amount of the acidic solution increases or decreases according to the concentration or amount of unburned ammonia.

[0016] It should be noted that the term "determine" here includes not only determining the concentration or amount of unburned ammonia, but also classifying the magnitude of the concentration or amount of unburned ammonia. For example, in the former concept, it includes processes such as measuring or estimating the concentration or amount of unburned ammonia. In addition, in the latter concept, it includes, for example, processes such as determining the magnitude relationship between the concentration or amount of unburned ammonia and a specified reference value.

[0017] In addition, in the latter concept, it also includes processes that do not directly use the value of the concentration or amount of unburned ammonia but are equivalent to classification according to the concentration or amount of unburned ammonia in terms of results, such as determining whether it is in a mode of injecting ammonia into the cylinder and burning the ammonia.

[0018] According to the first aspect, the feeder supplies an acidic solution to the water circulated via the circulation pipe. As a result, the water atomized and injected from the nozzle will be acidic. By using acidic water to neutralize unburned ammonia, the unburned ammonia can be efficiently treated.

[0019] In addition, the controller according to the first aspect adjusts the supply amount of the acidic solution based on 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 even without spraying a large amount of water in a mist form. Thereby, the amount of water sprayed in a mist form can be suppressed, and the load on the pump for spraying water in a mist form can be reduced.

[0020] In this way, according to the first aspect, both reducing the discharge amount of unburned ammonia and reducing the load on the pump for spraying water in a mist form can be achieved.

[0021] In addition, 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 corresponding to the concentration or amount of unburned ammonia. Thereby, the supply amount of the acidic solution can be suppressed to an appropriate amount without excess.

[0022] In addition, according to the second aspect of the present disclosure, it may also be: the diesel engine can operate in a first mode and a second mode respectively. In the first mode, an oil fuel containing a sulfur compound is burned alone in the cylinder. In the second mode, at least the ammonia and the oil fuel are burned in the same cylinder. The scrubber purifies the exhaust gas generated in the first mode and the second mode respectively. In the first mode, the scrubber causes the water that circulates through the circulation pipe and is sprayed in a mist form from the nozzle to absorb sulfur oxides generated by the oil fuel. And in the second mode, the scrubber uses the water in which the sulfur oxides are dissolved to neutralize the unburned ammonia.

[0023] According to the second aspect, the scrubber serves as both a SOx scrubber for removing sulfur oxides (SOx) from the exhaust gas and a scrubber for removing unburned ammonia from the exhaust gas.

[0024] Here, after the water sprayed in a mist form from the nozzle absorbs SOx, the water (SOx aqueous solution) becomes acidic. It is not necessary to neutralize the acidic water but to circulate it and use this water to neutralize the unburned ammonia. Thereby, the unburned ammonia can be efficiently treated. In this way, it is advantageous in terms of suppressing the usage amount of chemicals such as dilute sulfuric acid required to neutralize the unburned ammonia, and further suppressing the operation cost of the ship.

[0025] In addition, according to the third aspect of the present disclosure, it may also be: in the first mode, the controller sets the supply amount of the acidic solution supplied by the supplier to zero. In the second mode, the controller increases the supply amount of the acidic solution supplied by the supplier as the concentration or amount of the unburned ammonia increases.

[0026] According to the third aspect, the supply amount of the acidic solution can be suppressed to an appropriate amount without excess. In this way, the discharge amount of unburned ammonia can be reduced, and it is possible to reduce the atomized water injection amount and thereby reduce the load on the pump, as well as reduce the supply amount of the acidic solution.

[0027] In addition, according to the fourth aspect of the present disclosure, it may also be that: the marine scrubber system includes a first concentration sensor disposed on a first exhaust pipe connecting the diesel engine and the purification chamber to detect the ammonia concentration in the first exhaust pipe, and the controller based on the detection signal of the first concentration sensor causes the feeder to start supplying the acidic solution when the ammonia concentration in the first exhaust pipe exceeds a specified reference value.

[0028] According to the fourth aspect, the first concentration sensor detects the ammonia concentration immediately before being introduced into the purification chamber of the scrubber. And the controller causes the feeder to start supplying the acidic solution based on the detection signal of the first concentration sensor. By configuring in this way, it is possible to start supplying the acidic solution immediately 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 at a concentration exceeding the specified reference value).

[0029] In addition, according to the fifth aspect of the present disclosure, it may also be that: the marine scrubber system includes a second concentration sensor disposed on a second exhaust pipe connecting the diesel engine and the outside of the ship to detect the ammonia concentration in the second exhaust pipe, and the controller determines the supply amount of the acidic solution supplied by the feeder based on the detection signal of the second concentration sensor.

[0030] According to the fifth aspect, the second concentration sensor detects the ammonia concentration in the exhaust gas discharged from the purification chamber. And 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 supply the acidic solution with the minimum supply amount that can suppress the leakage of unburned ammonia without excess. In this way, the supply amount of the acidic solution can be reduced.

[0031] In addition, according to the sixth aspect of the present disclosure, it may also be that: when the ammonia concentration in the first exhaust pipe is lower than the reference value, the controller causes the feeder to end the supply of the acidic solution.

[0032] According to the sixth aspect, the controller ends 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 has dropped below the reference value. As a result, it is possible to end the supply of the acidic solution at a more appropriate time and more reliably suppress the leakage of unburned ammonia to the outside of the ship (especially at a concentration exceeding the specified reference value).

[0033] In addition, according to the seventh aspect of the present disclosure, it may also be that: the marine scrubber system includes a pH sensor that detects the pH value of the water circulating in the scrubber, and the controller adjusts the supply amount of the acidic solution supplied by the supplier based on the detection signal of the pH sensor.

[0034] According to the seventh aspect, the supply amount of the acidic solution can be suppressed to an appropriate amount without excess. In this way, the discharge amount of unburned ammonia can be reduced, and it is possible to reduce the atomized water spray amount and thus reduce the load on the pump, as well as reduce the supply amount of the acidic solution.

[0035] In addition, the eighth aspect of the present disclosure relates to an engine system. The engine system includes the marine scrubber system and a diesel engine, and the diesel engine is connected to the marine scrubber system and is capable of burning at least the ammonia.

[0036] According to the eighth aspect, the discharge amount of unburned ammonia can be reduced, and it is possible to reduce the supply amount of the acidic solution and the load on the pump for atomized water spray.

[0037] -Effects of the Invention-

[0038] As described above, according to the present disclosure, it is possible to balance both reducing the discharge amount of unburned ammonia and reducing the load on the pump for atomized water spray. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a system diagram exemplarily showing an engine system, a diesel engine, and a marine scrubber system constituting the engine system;

[0040] Figure 2 It is a diagram exemplarily showing the upper structure of an engine body;

[0041] Figure 3 It is a block diagram exemplarily showing the brief structure of a scrubber system;

[0042] Figure 4 It is a flowchart exemplarily showing the processing in the first mode;

[0043] Figure 5A It is a flowchart exemplarily showing the processing in the second mode;

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

[0045] Figure 6 It is a graph exemplarily showing the relationship between the unburned ammonia concentration and the supply amount of dilute sulfuric acid in the second mode;

[0046] Figure 7 is a diagram corresponding to the second embodiment of the marine scrubber system, exemplarily showing Figure 1 ;

[0047] Figure 8 is a diagram corresponding to another modification of the second embodiment, exemplarily showing Figure 7 ;

[0048] -Symbol Explanation-

[0049] 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 - Nozzle; 113 - Circulation pipe; 117 - Feeder; 120 - Controller; 131 - First concentration sensor; 132 - Second concentration sensor; 134 - pH sensor. Detailed Embodiment

[0050] Hereinafter, the 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 is a system diagram exemplarily showing the engine system S, the diesel engine 1 constituting the engine system S, and the marine scrubber system 100.

[0051] <Overall Structure>

[0052] As Figure 1 shown, 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. The engine system S is mounted on large ships such as oil tankers, container ships, and vehicle carriers.

[0053] The engine 1 can at least burn ammonia. The engine 1 is configured as a direct-current scavenging two-stroke cycle engine and serves as a main engine that generates the propulsion force for the above-mentioned ship to navigate. The output shaft of the engine 1 is connected to the 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 pushing the ship forward.

[0054] 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 combusted alone in the cylinder 21; in the second mode, 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.

[0055] More specifically, the engine 1 is configured to be able to perform at least one of mixed combustion using ammonia and the oil fuel together and separate combustion of ammonia when operating in the second mode.

[0056] For example, the engine 1 described in detail below is configured to combust the oil fuel alone in the first mode and combust ammonia and the oil fuel in a mixed manner 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.

[0057] Here, when using the oil fuel and ammonia simultaneously, 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 sulfur oxides generated by the oil fuel, unburned ammonia may also be contained.

[0058] To deal with these 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. The scrubber system 100 includes a so-called wet scrubber 110, which can remove components such as sulfur oxides and unburned ammonia from the exhaust gas.

[0059] Hereinafter, each element constituting the engine system S will be described in turn.

[0060] <Details of the engine 1>

[0061] As Figure 1 shown, the engine 1 includes an engine body 2 having the above-mentioned cylinder 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.

[0062] (1) Engine body 2

[0063] 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. The engine body 2 is configured as a so-called crosshead internal combustion engine in order to achieve its long-stroke design.

[0064] Figure 2 This is a view exemplarily showing the upper structure of the engine body 2. As Figure 2 shown, each 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 Figure 2 the vertical direction of the paper surface here). The cylinder head 24 is fixed to the upper end of the cylinder liner 23 and closes the opening formed at the upper end.

[0065] 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 part of each cylinder head 24 to an exhaust manifold 2b described later. The exhaust valve 26 opens and closes the central part of each cylinder head 24.

[0066] 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.

[0067] One or more (two in the illustrated example) first fuel injection valves 28 are provided on 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.

[0068] One or more second fuel injection valves 29 are also provided on each cylinder 21, preferably the same number as the first fuel injection valves 28 on each cylinder 21 (two in the illustrated example), and 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.

[0069] When the engine 1 operates in the first mode, among the first fuel injection valves 28 and the second fuel injection valves 29, only oil fuel is supplied from the first fuel injection valves 28 into the combustion chamber 27. The oil fuel supplied from the first fuel injection valves 28 burns alone in the combustion chamber 27.

[0070] On the other hand, when the engine 1 operates in the second mode, oil fuel is supplied from the first fuel injection valves 28 into the combustion chamber 27, and ammonia is supplied from the second fuel injection valves 29 into the same combustion chamber 27. The oil fuel and ammonia thus supplied are mixed and burned (co - burned) in the combustion chamber 27.

[0071] By combustion corresponding to each mode, reciprocating motion of the piston 22 is caused. At this time, if the exhaust valve 26 operates to open the combustion chamber 27, the exhaust gas generated by combustion is squeezed into the exhaust relay pipe 25, and air is introduced into the combustion chamber 27 from a scavenging port (not shown).

[0072] In addition, when the piston 22 makes reciprocating motion due to combustion, a crank motion is generated 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.

[0073] Back to Figure 1 , the engine main body 2 also has a scavenging chamber 2a and an exhaust manifold 2b. The scavenging chamber 2a communicates with each combustion chamber 27, and the scavenging chamber 2a temporarily stores air. The exhaust manifold 2b communicates with the combustion chamber 27 via the exhaust relay pipe 25, the exhaust manifold 2b receives the exhaust gas discharged from the combustion chamber 27, and temporarily stores the received exhaust gas, and converts the dynamic pressure of the exhaust gas into static pressure.

[0074] (2) Intake and exhaust system 3

[0075] As Figure 1 shown, the intake and exhaust system 3 has an intake pipe 31 connected to the engine main body 2 via the scavenging chamber 2a, and an exhaust pipe 32 connected to the engine main body 2 via the exhaust manifold 2b.

[0076] The intake pipe 31 communicates with the combustion chamber 27 via the scavenging chamber 2a, and 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 is configured to guide the exhaust gas discharged from the combustion chamber 27.

[0077] Specifically, the exhaust pipe 32 has a first exhaust pipe 32a connecting the engine 1 and the scrubber 110, and a second exhaust pipe 32b connecting the scrubber 110 and the outside of the ship.

[0078] 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 the exhaust gas from the engine 1 to the scrubber 110.

[0079] A first concentration sensor 131 that constitutes the scrubber system 100 together with the scrubber 110 is arranged on the first exhaust pipe 32a. The first concentration sensor 131 detects the ammonia concentration in the first exhaust pipe 32a.

[0080] 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 exhaust gas from the scrubber 110 to the outside of the ship.

[0081] A second concentration sensor 132 that constitutes the scrubber system 100 together with the scrubber 110 is disposed on the second exhaust pipe 32b. The second concentration sensor 132 detects the ammonia concentration in the second exhaust pipe 32b.

[0082] (3) Fuel supply system 4

[0083] 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.

[0084] 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 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.

[0085] For example, when the engine 1 operates in the first mode or the second mode, the first fuel pump 41c operates. Thus, 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 the above-mentioned oil fuel is injected from each first fuel injection valve 28 into the corresponding cylinder 21.

[0086] On the other hand, the second supply system 42 has 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 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.

[0087] 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. Thus, 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 the above-mentioned ammonia is injected from each second fuel injection valve 29 into the corresponding cylinder 21.

[0088] <Details of the scrubber system 100>

[0089] Figure 3 is a block diagram exemplarily showing a brief structure of the scrubber system 100. As Figure 1 and Figure 3 shown, the scrubber system 100 includes a scrubber 110, a controller 120, and a first concentration sensor 131 and a second concentration sensor 132. The scrubber 110 injects water into the exhaust gas in a mist form. The controller 120 controls the scrubber 110, particularly controls the mist injection of water performed by the scrubber 110 (hereinafter, also simply referred to as "the mist injection of water"). The first concentration sensor 131 and the second concentration sensor 132 respectively output detection signals for controlling the scrubber 110 to the controller 120.

[0090] (1) Scrubber 110

[0091] As Figure 1 shown, the scrubber 110 has a scrubber body 111, one or more nozzles 112, a circulation pipe 113, a water pump 114, a branch pipe 115, a centrifuge 116, and a feeder 117. The scrubber 110 is a so-called closed-loop scrubber.

[0092] The scrubber body 111 is a container connected to the engine 1. The scrubber body 111 forms a purification chamber 111a for purifying the exhaust gas with water. Water is injected into the exhaust gas in a mist form in the purification chamber 111a.

[0093] 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 via this other end. The exhaust gas flows into the purification chamber 111a through the first exhaust pipe 32a.

[0094] One end (upstream end) of the second exhaust pipe 32b is connected to the top surface of the purification chamber 111a. The second exhaust pipe 32b communicates with the purification chamber 111a via this one end. The exhaust gas flows out of the purification chamber 111a through the second exhaust pipe 32b.

[0095] One or more nozzles 112 are accommodated in the purification chamber 111a. The nozzles 112 inject water in a mist form in the purification chamber 111a. It should be noted that the number of nozzles 112 is not particularly limited. In Figure 1 the example, for simplicity, only one nozzle 112 is shown.

[0096] Specifically, the nozzle 112 sprays the water (e.g., clean water) circulating in the scrubber 110 in a mist form toward the bottom surface of the purification chamber 111a. After the water sprayed in a mist form from the nozzle 112 moves downward along the packing material (not shown), it falls and accumulates at the bottom of the purification chamber 111a.

[0097] The circulation pipe 113 circulates the water between the purification chamber 111a and the nozzle 112.

[0098] 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 nozzle 112. In order to circulate the water between the purification chamber 111a and the nozzle 112, the circulation pipe 113 forms a passage for sending back the water sprayed in a mist form from the nozzle 112 and accumulated in the purification chamber 111a to the nozzle 112.

[0099] The water pump 114 operates to supply water to the nozzle 112. The water pump 114 is arranged midway in the circulation pipe 113. When the water pump 114 operates, water is sprayed in a mist form from the nozzle 112. This water is sprayed in a mist form toward the exhaust gas that has flowed into the purification chamber 111a. The water sprayed in a mist form is used to absorb the sulfur oxides contained in the exhaust gas and remove the unburned ammonia contained in the exhaust gas.

[0100] Specifically, the water pump 114 is composed of a variable-frequency electric motor. The operation of the motor in the water pump 114 is controlled via an inverter based on a control signal from the controller 120.

[0101] More specifically, when the water pump 114 operates, 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 using this power. The power supply from the inverter to the motor is controlled, for example, by a feedback signal corresponding to the rotational speed of the motor.

[0102] The branch pipe 115 branches off from the circulation pipe 113. The circulation pipe 113 sends a part of the water flowing in the branch pipe 115 into the centrifugal separator 116. The centrifugal separator 116 separates, using centrifugal force, the solid components (sludge), for example, derived from sulfur oxides, from the water. The solid components separated from the water are stored, for example, in a prescribed storage section (so-called sludge tank).

[0103] Specifically, the branch pipe 115 is a tubular member having one end (upstream end) connected to an intermediate portion of the circulation pipe 113 and the other end (downstream end) connected to another portion downstream of this portion (intermediate portion). A part of the water flowing from the circulation pipe 113 into the branch pipe 115 is returned to the circulation pipe 113 after passing through the centrifugal separator 116 or discharged to the outside of the ship via a pipe (not shown).

[0104] The feeder 117 supplies an acidic solution to the water circulating through the circulation pipe 113. An acidic solution refers to a solution having a pH value less than 7. In the present embodiment, dilute sulfuric acid is used as the acidic solution. It should be noted that the acidic solution is not limited to dilute sulfuric acid.

[0105] 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 pressurizes and transports the dilute sulfuric acid stored in the dilute sulfuric acid tank 117a and supplies the dilute sulfuric acid to the purification chamber 111a.

[0106] (4) Controller 120

[0107] (2-1) Brief Structure

[0108] The controller 120 includes a processor, a volatile memory, a non-volatile memory, and an input / output device. In addition to the above-described first concentration sensor 131 and second concentration sensor 132 being electrically connected to the controller 120, Figure 1 and Figure 3 the pH sensor 134 shown, and only Figure 3 the exhaust gas characteristic sensor 135 shown are also electrically connected to the controller 120.

[0109] 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 in the scrubber 110. The pH sensor 134 inputs its detection signal to the controller 120.

[0110] The exhaust gas characteristic sensor 135 detects exhaust gas characteristics other than ammonia concentration (particularly characteristics related to the components contained in the exhaust gas in the first mode). The exhaust gas characteristic sensor 135 inputs its detection signal to the controller 120.

[0111] 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 water pump 114, the centrifuge 116, and the dilute sulfuric acid pump 117c described above. 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.

[0112] For example, in the first mode where only oil fuel is burned, the scrubber 110 according to the present embodiment causes the water that circulates through the circulation pipe 113 and is atomized and sprayed from the nozzle 112 into the purification chamber 111a to absorb sulfur oxides generated by the oil fuel. That is to say, the scrubber 110 functions as a so-called "SO x scrubber" for removing sulfur oxides from the exhaust gas.

[0113] In addition, in the second mode where at least ammonia is burned, the scrubber 110 according to the present embodiment atomizes and sprays water into the same purification chamber 111a as in the first mode, so that unburned ammonia that may be contained in the exhaust gas dissolves in the water. That is to say, the scrubber 110 has both the function of an SO x scrubber and the function of a scrubber for removing unburned ammonia.

[0114] In this way, Figure 1 the scrubber 110 shown is configured to purify the exhaust gas generated in the first mode and the second mode respectively. And, in the present embodiment, the controller 120 that controls such a scrubber 110 is configured to perform processes that contribute to suppressing the discharge of unburned ammonia in the first mode and the second mode respectively.

[0115] Hereinafter, a specific example will be used to illustrate the process related to suppressing the discharge of unburned ammonia.

[0116] (2-2) Specific example of the process in the first mode

[0117] Figure 4 is a flowchart exemplarily showing the process in the first mode.

[0118] First, in Figure 4 step S101, the controller 120 determines whether the engine 1 is operating in the first mode. If the determination is "yes", the controller 120 causes the control process to proceed to step S102. On the other hand, if the determination in step S101 is "no", the controller 120 ends Figure 4 the control process shown and transfers to Figure 5A the process described later shown.

[0119] In step S102, the controller 120 obtains the detection value of the exhaust gas property sensor 135. The detection value obtained in this step S102 includes at least a parameter related to the SOx content in the exhaust gas. Instead of using the exhaust gas property sensor 135, the sulfur (S) content in the fuel may also be detected, and the scrubber system 100 may also be configured to be turned on / off by the crew.

[0120] In the next step S103, the controller 120 determines whether exhaust gas cleaning using the scrubber system 100 is required. This determination is made, for example, by the controller 120 based on the detection value obtained in step S102. When this determination is "yes", the controller 120 advances the control process to step S104. On the other hand, when the determination in step S103 is "no", the controller 120 returns the control process to step S101.

[0121] In step S104, the controller 120 performs atomized water injection using the water pump 114. Specifically, the controller 120 inputs a control signal to the water pump 114 via the frequency converter to drive the water pump 114. The water pump 114 operates, and thereby water is atomized and injected in the purification chamber 111a. This water comes into contact with the exhaust gas flowing into the purification chamber 111a, and thereby SOx is absorbed (captured) from the exhaust gas into the water.

[0122] Here, if SOx is dissolved in water, the SOx becomes sulfate ions in the water. The water containing sulfate ions exhibits acidity corresponding to the ionic concentration of the sulfate.

[0123] Here, in the case of a conventionally known scrubber 110, the acidic water is usually neutralized by supplying an alkaline solution (for example, an aqueous sodium hydroxide solution).

[0124] Compared with this normal situation, the inventors of the present application focused on making the scrubber 110 also serve as a so-called SOx scrubber and a scrubber for removing unburned ammonia from exhaust gas, and newly conceived a method of efficiently removing unburned ammonia in the second mode using acidic water.

[0125] That is, the scrubber 110 according to the present embodiment uses the water in which SOx is dissolved to absorb unburned ammonia while neutralizing the unburned ammonia in the second mode. Thereby, the unburned ammonia that may be generated in the second mode can be efficiently removed.

[0126] In addition, the scrubber 110 according to the present embodiment is configured to supply dilute sulfuric acid to the water circulated in the scrubber 110 using the supplier 117 in the second mode. Thereby, the unburned ammonia can be reliably neutralized regardless of whether SOx is dissolved in the water. Hereinafter, the process related to the supply of dilute sulfuric acid will be referred to as "solution supply process".

[0127] After the processing in step S104 ends, the controller 120 returns the control process to step S102. In this case, the water is continuously sprayed in a mist until the exhaust gas cleaning using the scrubber 110 is no longer required.

[0128] (2-3) Specific example of the processing in the second mode

[0129] Figure 5A And Figure 5B is a flowchart exemplarily showing the processing in the second mode.

[0130] First, in Figure 5A step S201, the controller 120 determines whether the engine 1 is operating in the second mode. If this determination is "yes", the controller 120 causes the control process to proceed to step S202. On the other hand, if the determination in step S201 is "no", the controller 120 ends Figure 5A the control process shown and transfers to Figure 4 the above-mentioned process shown.

[0131] In step S202, the controller 120 obtains the detection value of the first concentration sensor 131. The detection value obtained in this step S202 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 purification chamber 111a, it is sometimes referred to as the "inlet concentration" in the following description.

[0132] In the next step S203, the controller 120 determines whether the inlet concentration obtained in step S202 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 as appropriate according to the need.

[0133] If the determination in step S203 is "yes", the controller 120 causes the control process to proceed to step S204 and determines that the solution supply process should be started. For example, the controller 120 changes the signal value of the signal representing 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 supplier 117 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. On the other hand, if the determination in step S203 is "no", the controller 120 returns the control process to step S201.

[0134] Note that, in the present embodiment, the execution flag for water injection is also used as the execution flag for solution supply processing. That is to say, the controller 120 involved in the present embodiment is configured to start the supply of dilute sulfuric acid by the supplier 117 and the fog-like injection of water by the water pump 114 when the inlet concentration corresponding to the detection signal exceeds a specified reference value based on the detection signal of the first concentration sensor 131.

[0135] In step S205 following step S204, the controller 120 executes solution supply processing. The details of the solution supply processing are as Figure 5B shown. If the control process enters step S205, the controller 120 starts from Figure 5B step S301 of the figure and sequentially executes each process shown in the figure.

[0136] 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 represents the ammonia concentration (especially the concentration of unburned ammonia) in the second exhaust pipe 32b. Since this ammonia concentration is equivalent to the ammonia concentration on the exhaust gas outlet side as viewed from the purification chamber 111a, it is sometimes referred to as the "outlet concentration" in the following description.

[0137] In the next step S302, the controller 120 determines the concentration of unburned ammonia (unburned NH3) contained in the exhaust gas. Specifically, the controller 120 involved in the present embodiment determines the value of the outlet concentration based on the detection signal of the second concentration sensor 132.

[0138] The outlet concentration determined in step S302 is used in the next step S303 to determine the supply amount of dilute sulfuric acid. That is to say, the controller 120 involved in the present embodiment is configured to determine the supply amount of dilute sulfuric acid supplied by the supplier 117 based on the detection signal of the second concentration sensor 132.

[0139] In addition, in the above step S302, the controller 120 may also determine the amount (such as the flow rate) of unburned NH3 contained in the exhaust gas instead of the concentration of unburned NH3 contained in the exhaust gas. For example, this determination can be performed 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.

[0140] In the next step S303, the controller 120 determines the supply amount of dilute sulfuric acid supplied by the supplier 117 in such a way that the supply amount of dilute sulfuric acid increases or decreases according to the concentration of unburned NH3.

[0141] Here, Figure 6It is a graph showing the comparison between the magnitude relationship between the concentration of unburned NH3 in the second mode and the supply amount of dilute sulfuric acid and the supply amount of dilute sulfuric acid in the first mode. The supply amount of dilute sulfuric acid mentioned here corresponds to the target value of the supply amount that should be supplied from the supplier 117 to the purification chamber 111a.

[0142] Figure 6 The solid line L2 in shows the supply amount of dilute sulfuric acid in the second mode in association with the high or low concentration of unburned NH3. As Figure 6 shown by the arrow A2 in, the controller 120 is configured to: in the second mode, increase the supply amount of dilute sulfuric acid supplied by the supplier 117 as the concentration of unburned NH3 increases.

[0143] Figure 6 The dotted line L1 in shows the supply amount of dilute sulfuric acid 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 supply amount of dilute sulfuric acid in the first mode is shown as a straight line parallel to the Figure 6 horizontal axis in, that is, the dotted line L1. As shown by the dotted line L1, in the first mode, the controller 120 sets the supply amount of dilute sulfuric acid supplied by the supplier 117 to zero.

[0144] As Figure 6 shown by the double-headed arrow A1 in, regardless of the high or low concentration of unburned NH3, 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. That is to say, the controller 120 is configured to: in the second mode, make the supply amount of dilute sulfuric acid supplied by the supplier 117 more than that in the first mode.

[0145] It should be noted that in the case of being configured to determine the amount of unburned NH3 instead of the concentration of unburned NH3, the controller 120 can also determine the supply amount of dilute sulfuric acid supplied by the supplier 117 in such a way that the supply amount of dilute sulfuric acid increases or decreases according to the amount of unburned NH3. In this case, the controller 120 can also be configured to: in the second mode, increase the supply amount of dilute sulfuric acid supplied by the supplier 117 as the amount of unburned NH3 increases.

[0146] It should be noted that Figure 6 the shape of the solid line L2 in is just an example. The supply amount of dilute sulfuric acid can change in a stepwise manner, or the supply amount of dilute sulfuric acid can change in a curved manner.

[0147] In the next step S304, the controller 120 drives the dilute sulfuric acid pump 117c to achieve the supply amount determined in step S303. Thus, 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.

[0148] In the next step S305, the controller 120 acquires the detection value of the pH sensor 134. The detection value acquired in this step S305 represents the pH value of the water circulating in the scrubber 110 after being mixed with dilute sulfuric acid.

[0149] In the next steps S306 and S307, the controller 120 adjusts the supply amount of the dilute sulfuric acid supplied by the supplier 117 based on the detection signal of the pH sensor 134.

[0150] Specifically, in step S306, the controller 120 determines whether the pH value acquired in step S305 is below a specified target value. This target value is a value less than 7 and is stored in the controller 120 in advance.

[0151] When the determination in step S306 is "yes", the controller 120 ends Figure 5B the processing shown, and completes the solution supply processing. In this case, the controller 120 causes the control process to proceed from Figure 5B step S306 of Figure 5A to step S206 of

[0152] On the other hand, when the determination in step S306 is "no", the controller 120 causes the control process to proceed from step S306 to step S307, and additionally supplies dilute sulfuric acid (acidic solution). Then, the controller 120 causes the control process to return to step S305. That is, the controller 120 continues to supply dilute sulfuric acid until the pH value reaches below the target value.

[0153] Then, in Figure 5A step S206, the controller 120 performs atomized water injection by driving the water pump 114. Thus, the water mixed with an amount of dilute sulfuric acid corresponding to the concentration of unburned NH3 is atomized and injected from the nozzle 112. By atomizing the water containing dilute sulfuric acid and SOx, unburned NH3 can be neutralized.

[0154] In the next step S207, the controller 120 acquires the inlet concentration again and determines whether the inlet concentration is lower than a specified reference value. This reference value can be the same as the reference value referred to in step S203, for example.

[0155] When the determination in step S207 is "yes", the controller 120 causes the control process to proceed to step S208 and determines that the solution supply process should end. For example, the controller 120 changes the signal value of the signal representing 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 supplier 117 based on the detection signal of the first concentration sensor 131 when the inlet concentration corresponding to the detection signal is lower than the specified reference value.

[0156] On the other hand, when the determination in step S207 is "No", the controller 120 causes the control process to proceed to step S209. In this case, the controller 120 obtains the detection value of the pH sensor 134 in step S209, and determines in the next step S210 whether the obtained detection value is below a specified target value. When the determination in step S210 is "Yes", the controller 120 causes the control process to return to step S206 and performs the atomized water injection. On the other hand, when the determination in step S210 is "No", the controller 120 causes the control process to return to step S205 and performs both the solution supply process and the atomized water injection. In this way, the controller 120 continues to perform the solution supply process and the atomized water injection until the determination in step S207 becomes "Yes".

[0157] <Regarding suppression of unburned NH3 emissions>

[0158] For a diesel engine configured to burn ammonia, it is required to suppress the ammonia emissions below a specified reference value by reducing the amount of unburned ammonia emissions.

[0159] As a solution to meet this requirement, for example, it can be considered to dissolve unburned NH3 in the water atomized in the scrubber by using a so-called scrubber.

[0160] However, as Figure 1 shown, the marine scrubber 110 sprays a large amount of water in an atomized manner. Therefore, compared with other uses, the marine scrubber 110 has to use a huge water pump 114, and the load on the water pump 114, such as the drive current of the water pump 114, is very large. This is disadvantageous in terms of suppressing the operating costs of the ship, such as power consumption.

[0161] In order to reduce the load on the water pump 114, although it can be considered to reduce the atomized water injection amount, if only the atomized water injection amount is simply reduced, it may hinder the suppression of unburned NH3 emissions, so it is not appropriate.

[0162] In contrast, the scrubber 110 according to the above-described embodiment supplies dilute sulfuric acid as an acidic solution to the water circulated through the circulation pipe 113 as Figure 1 and Figure 5B described. As a result, the water atomized and sprayed from the nozzle 112 becomes acidic. By using the acidic water to neutralize the unburned NH3, the unburned NH3 can be efficiently treated.

[0163] In addition, the controller 120 according to the above-described embodiment is as Figure 5BAs shown, the supply amount of dilute sulfuric acid is adjusted 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, even if a large amount of water is not sprayed in a mist form, the emission amount of unburned NH3 can be reduced. Thus, the amount of water sprayed in a mist form can be suppressed, and the load on the water pump 114 for spraying water in a mist form can be reduced.

[0164] In this way, according to the above-described embodiment, both reducing the emission amount of unburned NH3 and reducing the load on the water pump 114 can be achieved.

[0165] In addition, by adjusting the supply amount of dilute sulfuric acid as in the above-described embodiment, the supply amount of dilute sulfuric acid can be made an appropriate amount corresponding to the concentration or amount of unburned NH3. Thus, the supply amount of dilute sulfuric acid can be suppressed to an appropriate amount without being excessive.

[0166] In addition, as referred to Figure 4 、 Figure 5A and Figure 5B As described, the scrubber 110 according to the above-described embodiment also serves as an SOx scrubber for removing SOx from the exhaust gas and a scrubber for removing unburned ammonia from the exhaust gas.

[0167] Here, after the water sprayed in a mist form from the nozzle 112 absorbs SOx, the water (SOx aqueous solution) becomes acidic. It is not necessary to neutralize the acidic water but to circulate it and use the water to neutralize unburned NH3. Thus, unburned NH3 can be efficiently treated. In this way, it is advantageous in reducing the usage amount of chemicals such as dilute sulfuric acid required to neutralize unburned NH3 and further reducing the operating cost of the ship.

[0168] In addition, by changing the supply amount of dilute sulfuric acid in the second mode as Figure 6 shown, the supply amount of dilute sulfuric acid can be suppressed to an appropriate amount without being excessive. In this way, the emission amount of unburned NH3 can be reduced, and reducing the amount of water sprayed in a mist form and further reducing the load on the water pump 114, as well as reducing the supply amount of dilute sulfuric acid, can be achieved.

[0169] In addition, as Figure 1 shown, the first concentration sensor 131 detects the ammonia concentration before the purified chamber 111a of the scrubber 110 is about to be introduced. And, as shown from Figure 5A step S202 to step S204, 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. By configuring in this way, the supply of dilute sulfuric acid can be started immediately when the concentration of 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.

[0170] In addition, as Figure 1 shown, the second concentration sensor 132 detects the ammonia concentration in the exhaust gas discharged from the purification chamber 111a. Further, the controller 120 adjusts the supply amount of the dilute sulfuric acid based on the detection signal of the second concentration sensor 132. With such a configuration, it is possible to supply the dilute sulfuric acid in the minimum amount capable of suppressing the leakage of unburned NH3 without excess. Thus, the supply amount of the dilute sulfuric acid can be reduced.

[0171] In addition, as from Figure 5A steps S207 to S208 shown, the controller 120 ends the supply of the acidic solution based on the detection signal of the first concentration sensor 131. With such a configuration, it is possible to more reliably determine that the ammonia concentration has fallen below the reference value. As a result, it is possible to end the supply of the acidic solution at a more appropriate timing, and reliably suppress the leakage of unburned NH3 to the outside of the ship (especially leakage at a concentration exceeding the specified reference value).

[0172] In addition, as from Figure 5B steps S305 to S307 shown, the controller 120 adjusts the supply amount of the dilute sulfuric acid based on the detection value of the pH sensor 134. Thereby, the supply amount of the dilute sulfuric acid can be suppressed to an appropriate amount without excess. Thus, the discharge amount of unburned NH3 can be reduced, and it is possible to reduce the amount of atomized water spray, thereby reducing the load on the water pump 114, and reducing the supply amount of the dilute sulfuric acid.

[0173] <Second Embodiment>

[0174] In the above-described first embodiment, the exhaust pipe 32 having the first exhaust pipe 32a connecting the engine 1 and the scrubber 110 and the second exhaust pipe 32b connecting the scrubber 110 and the outside of the ship is illustrated, but the present disclosure is not limited to such an exhaust pipe 32. The exhaust pipe 32 may also have an exhaust gas recirculation line.

[0175] Figure 7 is a diagram exemplarily showing a second embodiment of the scrubber system 100 corresponding to Figure 1 . In Figure 7 , elements having the same structure and configuration as those of the first embodiment are given the same reference numerals as those of that embodiment.

[0176] Figure 7 The scrubber system 100’ shown has an exhaust pipe 32’ different from that of the first embodiment. In addition to the first exhaust pipe 32a and the second exhaust pipe 32b configured in the same manner as in the above-described first embodiment, the exhaust pipe 32’ further has a third exhaust pipe 32c constituting a recirculation line.

[0177] 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. In order to repeatedly purify the exhaust gas by means of the scrubber 110, the third exhaust pipe 32c forms a passage for returning the exhaust gas from the second exhaust pipe 32b to the first exhaust pipe 32a.

[0178] A first control valve 133 and an exhaust blower 136 are arranged on the third exhaust pipe 32c. The first control valve 133 and the exhaust blower 136 together with the scrubber 110 constitute a scrubber system 100'. The first control valve 133 is constituted by, for example, an electromagnetic valve that operates based on a control signal from the controller 120, and opens and closes the third exhaust pipe 32c. The exhaust blower 136 is configured to operate, for example, based on a control signal from the controller 120, and generates an exhaust gas flow flowing in the third exhaust pipe 32c.

[0179] When the controller 120 according to the second embodiment determines "No" in step S207, the first control valve 133 is at least temporarily opened, and the exhaust blower 136 is operated. Thereby, the exhaust gas in which unburned NH3 has not been sufficiently removed can be returned to the scrubber 110, and leakage of unburned NH3 to the outside of the ship can be more reliably prevented.

[0180] A modification example 1 of the second embodiment

[0181] It should be noted that the structure according to the second embodiment is not limited to Figure 7 the structure shown. For example, Figure 8 the modification example shown further includes a fourth exhaust pipe 32d that bypasses the scrubber 110.

[0182] 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 Figure 8 shown, the upstream end of the fourth exhaust pipe 32d is located upstream (upstream in the flow direction of the exhaust gas) of the connection portion between the third exhaust pipe 32c and the first exhaust pipe 32a. As shown in the figure, the downstream end of the fourth exhaust pipe 32d is located downstream (downstream in the flow direction of the exhaust gas) of the second concentration sensor 132 and a second control valve 137 described later.

[0183] A third control valve 138 is arranged on the fourth exhaust pipe 32d. The third control valve 138 together with the scrubber 110 constitutes a scrubber system 100'. 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.

[0184] In the case of using the fourth exhaust pipe 32d, the second control valve 137 may be further arranged on the second exhaust pipe 32b. The second control valve 137 and the scrubber 110 together constitute the scrubber system 100'. The second control valve 137 is constituted by, for example, a solenoid valve that operates based on a control signal from the controller 120, and opens and closes the second exhaust pipe 32b.

[0185] <Other embodiments>

[0186] In the above-described first embodiment, it is configured to use the detection value of the second concentration sensor 132 in Figure 5B step S302, but the present disclosure is not limited to such a configuration. Instead of the detection value of the second concentration sensor 132, the detection value of the first concentration sensor 131 may be obtained, or in addition to obtaining the detection value of the second concentration sensor 132, the detection value of the first concentration sensor 131 may also be obtained.

[0187] In addition, in the above-described embodiment, the scrubber 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 scrubber system 100 does not necessarily have to include both the first concentration sensor 131 and the second concentration sensor 132. The scrubber system 100 only needs to include at least one of the first concentration sensor 131 and the second concentration sensor 132.

[0188] Assume that in the case where the scrubber system 100 only has the first concentration sensor 131, it is configured to obtain the detection value of the first concentration sensor 131 in Figure 5B step S301 instead of the detection value of the second concentration sensor 132, and in Figure 5B steps S302 and S303, refer to the inlet concentration instead of the outlet concentration. In such a configuration, the solution supply process can also be immediately started in the same manner as in the above-described embodiment.

[0189] Similarly, in the case where the scrubber system 100 only has the second concentration sensor 132, it is configured to obtain the detection value of the second concentration sensor 132 in Figure 5A step S202 instead of the detection value of the first concentration sensor 131, and in Figure 5A steps S203 and S207, refer to the outlet concentration instead of the inlet concentration. In such a configuration, the water pump 114 can also be driven with the minimum necessary load, which is beneficial to suppressing the operation cost of the ship.

[0190] In addition, in the above-described first and second embodiments, only one dilute sulfuric acid pump 117c is illustrated, but the present disclosure is not limited to such a configuration. For example, a plurality of dilute sulfuric acid pumps 117c may be arranged on the dilute sulfuric acid supply pipe 117b, and the number of operating dilute sulfuric acid pumps 117c may be increased or decreased according to the concentration or amount of ammonia, thereby adjusting the supply amount of dilute sulfuric acid.

[0191] For example, it may be configured such that when the concentration of unburned ammonia is equal to or higher than a specified threshold value, a plurality of (for example, two) dilute sulfuric acid pumps 117c are operated, and when the concentration is lower than the threshold value, only one dilute sulfuric acid pump 117c is operated.

[0192] In addition, in the above-described first to second embodiments, as Figure 1 shown, etc., it is configured to include one or more first fuel injection valves 28 and one or more second fuel injection valves 29 on one cylinder 21, but the present disclosure is not limited to such a configuration. It may also be configured to inject both ammonia and oil fuel from one fuel injection valve (for example, stratified injection).

Claims

1. A marine scrubber system is connected to a diesel engine capable of burning ammonia and is configured to purify the exhaust gas discharged from the diesel engine, characterized in that: The marine scrubber system includes a scrubber and a controller. The scrubber sprays water in a mist form onto the exhaust gas. The controller controls the scrubber. The scrubber has a purification chamber, nozzles, a circulation pipeline, and a feeder. The purification chamber is connected to the diesel engine. The nozzles are housed in the purification chamber and spray water in a mist form therein. The circulation pipeline circulates water between the purification chamber and the nozzles. The feeder supplies an acidic solution to the water circulated through the circulation pipeline. The controller determines the concentration or amount of unburned ammonia contained in the exhaust gas. The controller determines the supply amount of the acidic solution supplied by the feeder in such a way that the supply amount of the acidic solution increases or decreases according to the concentration or amount of the unburned ammonia.

2. The marine scrubber system according to claim 1, characterized in that: The diesel engine can operate in a first mode and a second mode respectively. In the first mode, an oil fuel containing a sulfur compound is burned alone in the cylinder, and in the second mode, at least the ammonia among the ammonia and the oil fuel is burned in the same cylinder. The scrubber purifies the exhaust gas generated in the first mode and the second mode respectively. In the first mode, the scrubber causes the water circulated through the circulation pipeline and sprayed in a mist form from the nozzles to absorb sulfur oxides generated by the oil fuel, and in the second mode, the scrubber uses the water in which the sulfur oxides are dissolved to neutralize the unburned ammonia.

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

4. The marine scrubber system according to any one of claims 1 to 3, characterized in that: The marine scrubber system includes a first concentration sensor arranged on a first exhaust pipe connecting the diesel engine and the purification chamber 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 feeder to start supplying the acidic solution.

5. The marine scrubber system according to claim 4, characterized in that: The marine scrubber system includes a second concentration sensor arranged on a second exhaust pipe connecting the diesel engine and the outside of the ship to detect the ammonia concentration in the second exhaust pipe. The controller determines the supply amount of the acidic solution supplied by the feeder based on the detection signal of the second concentration sensor.

6. The marine scrubber system according to claim 4, characterized in that: When the ammonia concentration in the first exhaust pipe is lower than the reference value, the controller causes the feeder to end the supply of the acidic solution.

7. The marine scrubber system according to claim 1, characterized in that: The marine scrubber system includes a pH sensor that detects the pH value of the water circulating in the scrubber, The controller adjusts the supply amount of the acidic solution supplied by the feeder based on the detection signal of the pH sensor.

8. An engine system, characterized in that: Comprising: The 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.

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