Exhaust emission control device

Abstract

To provide an exhaust emission control device capable of stopping an engine at any timing without waiting for completion of decomposition treatment of ammonia.SOLUTION: An exhaust emission control device 1 includes: a first catalyst 4 disposed in an exhaust flow passage 3 connected to an ammonia engine 2; a second catalyst 5 disposed downstream of the first catalyst 4; a temperature detection section that detects a temperature of the second catalyst 5; an electric heater 6 that heats the second catalyst 5; a determination section 12 that determines whether or not the amount of ammonia adsorbed to the second catalyst 5 is a predetermined specified amount or less while the ammonia engine 2 is stopped; a temperature determination section 14 that determines whether or not the temperature of the second catalyst 5 detected by the temperature detection section is a decomposition activation temperature or higher; and a heating control section 15 that turns on the electric heater 6 when a determination that the amount of the ammonia adsorbed to the second catalyst 5 is not the specified amount or less is made and a determination that the temperature of the second catalyst 5 is not the decomposition activation temperature or higher is made.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas purification device. [Background technology]

[0002] Known as an exhaust purification device is, for example, the technology described in Patent Document 1. The exhaust purification device described in Patent Document 1 is provided with a three-way catalyst that is disposed in an exhaust pipe connected to an ammonia engine and purifies ammonia, NOx, and hydrogen in the exhaust, and an SCR catalyst that is disposed in the exhaust pipe downstream of the three-way catalyst and purifies NOx in the exhaust using ammonia as a reducing agent. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-167823 Summary of the Invention [Problem to be solved by the invention]

[0004] In some exhaust gas purification devices, a second catalyst having an ammonia adsorption function and an ammonia decomposition function is disposed downstream of a first catalyst, which is a three-way catalyst. In this case, when the temperature of the second catalyst is low, unburned ammonia that has passed through the first catalyst is adsorbed by the second catalyst. When the temperature of the second catalyst subsequently rises to its decomposition activation temperature, the ammonia adsorbed by the second catalyst is decomposed into hydrogen and nitrogen.

[0005] However, if the ammonia engine is stopped before the ammonia decomposition process in the second catalyst is completed, the next time the ammonia engine is started, ammonia will already be adsorbed in the second catalyst, and the unburned ammonia may not be adsorbed completely in the second catalyst. In this case, the ammonia will flow through the exhaust pipe and be discharged. Therefore, after the ammonia engine is started, it cannot be stopped until the ammonia decomposition process in the second catalyst is completed.

[0006] An object of the present invention is to provide an exhaust gas purification device that can stop the engine at any timing without waiting for the completion of the ammonia decomposition process. [Means for solving the problem]

[0007] (1) One aspect of the present invention is an exhaust purification device that purifies exhaust gas generated by an engine, the device comprising: a first catalyst disposed in an exhaust flow path connected to the engine and having a function of oxidizing and reducing ammonia and NOx contained in exhaust gas flowing through the exhaust flow path; a second catalyst disposed in the exhaust flow path downstream of the first catalyst and having a function of adsorbing and decomposing ammonia that has passed through the first catalyst; a temperature detection unit that detects the temperature of the second catalyst; a heater that heats the second catalyst; a determination unit that determines whether, when the engine is stopped, the amount of ammonia adsorbed on the second catalyst is equal to or less than a predetermined amount; a temperature determination unit that determines whether the temperature of the second catalyst detected by the temperature detection unit is equal to or greater than a decomposition activation temperature at which ammonia can be decomposed; and a heating control unit that turns on the heater when the determination unit determines that the amount of ammonia adsorbed on the second catalyst is not equal to or less than the predetermined amount and the temperature determination unit determines that the temperature of the second catalyst is not equal to or greater than the decomposition activation temperature.

[0008] In this exhaust gas purification device, during normal engine operation, ammonia that passes through the first catalyst is adsorbed onto the second catalyst, and the ammonia adsorbed onto the second catalyst is decomposed when the second catalyst is heated. When the engine is stopped, a determination is made as to whether the amount of ammonia adsorbed onto the second catalyst is equal to or less than a specified amount, and whether the temperature of the second catalyst is equal to or higher than the decomposition activation temperature. If the amount of ammonia adsorbed onto the second catalyst is greater than the specified amount and the temperature of the second catalyst is lower than the decomposition activation temperature, the heater is turned on. The heater then directly heats the second catalyst. When the temperature of the second catalyst rises to the decomposition activation temperature, the ammonia adsorbed onto the second catalyst is decomposed. Therefore, even if the decomposition process of the ammonia adsorbed onto the second catalyst is not completely completed when the engine is stopped, the ammonia adsorbed onto the second catalyst is removed by forcibly heating the second catalyst with the heater. This allows the engine to be stopped at any time without waiting for the ammonia decomposition process to be completed.

[0009] (2) In the above (1), the exhaust purification device may further include a heating time measurement unit that measures whether the heating of the second catalyst has continued for a certain period of time or more, and the heating control unit may turn off the heater when the heating time measurement unit measures that the heating of the second catalyst has continued for a certain period of time or more.

[0010] In this configuration, it is measured whether the heating of the second catalyst has continued for a certain period of time or more. If the heating of the second catalyst has continued for a certain period of time or more, the decomposition of ammonia in the second catalyst will progress sufficiently. Furthermore, if the heating of the second catalyst has continued for a certain period of time or more, the heater is turned off, thereby sufficiently removing the ammonia adsorbed in the second catalyst and reducing the power consumption of the heater.

[0011] (3) In the above (1) or (2), a fan for promoting exhaust of decomposition gas of ammonia may be disposed downstream of the second catalyst in the exhaust passage.

[0012] In such a configuration, the fan disposed in the exhaust flow path promotes the diffusion of hydrogen contained in the decomposition gas of ammonia produced by the decomposition of ammonia, so that the hydrogen is quickly exhausted to the outside.

[0013] (4) In any one of the above (1) to (3), the exhaust flow path may extend so that an exhaust port for exhausting the decomposition gas of ammonia to the outside is located above the second catalyst.

[0014] In this configuration, hydrogen, which is lighter than air and contained in the decomposition gas of ammonia produced by the decomposition of ammonia, flows more easily toward the exhaust port, facilitating the diffusion of hydrogen, which allows the hydrogen to be quickly exhausted to the outside. [Effects of the Invention]

[0015] According to the present invention, the engine can be stopped at any timing without waiting for the completion of the ammonia decomposition process. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic configuration diagram showing an exhaust gas purification device according to a first embodiment of the present invention. [Figure 2] 2 is a block diagram showing a control system of the exhaust purification device shown in FIG. 1. FIG. [Figure 3] 3 is a flowchart showing a processing procedure executed by the ECU shown in FIG. 2. [Figure 4] FIG. 6 is an enlarged view of a main part showing a second catalyst and an exhaust flow path of an exhaust purification device according to a second embodiment of the present invention. [Figure 5] FIG. 10 is an enlarged view of a main part showing a second catalyst and an exhaust flow path of an exhaust purification device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0018] (First embodiment) Fig. 1 is a schematic diagram showing an exhaust gas purification device according to a first embodiment of the present invention. In Fig. 1, the exhaust gas purification device 1 of this embodiment is mounted on a vehicle (not shown). The exhaust gas purification device 1 is a device that purifies exhaust gas generated from an ammonia engine 2.

[0019] The ammonia engine 2 is an engine that uses ammonia (NH3) as fuel. At this time, hydrogen (H2) may be mixed with the ammonia as a combustion aid to make the flame-retardant ammonia more combustible. A tubular exhaust flow path 3, which serves as a flow path for exhaust gas, is connected to the ammonia engine 2. The exhaust flow path 3 is a flow path through which exhaust gas generated from the ammonia engine 2 flows toward an exhaust port 3d (see FIG. 5).

[0020] The exhaust purification device 1 includes a first catalyst 4, a second catalyst 5, an electric heater 6 (heater), temperature sensors 8 and 9, and an ECU (Electronic Control Unit) 11.

[0021] The first catalyst 4 is disposed in an exhaust flow path 3 connected to an ammonia engine 2 (engine). That is, the first catalyst 4 is connected to the ammonia engine 2 via the exhaust flow path 3. The first catalyst 4 is a catalyst that has the function of oxidizing and reducing ammonia and NOx (nitrogen oxides) contained in the exhaust gas flowing through the exhaust flow path 3. The first catalyst 4 is, for example, a three-way catalyst. The first catalyst 4 has, for example, a cylindrical shape with its axis aligned in the direction in which the exhaust flow path 3 extends.

[0022] The second catalyst 5 is disposed downstream of the first catalyst 4 in the exhaust flow path 3. The second catalyst 5 is a catalyst that has the function of adsorbing and decomposing ammonia that has passed through the first catalyst 4. Examples of catalytic species that can be used for the second catalyst 5 include ruthenium (Ru), rhodium (Rh), cobalt (Co), iron (Fe), and nickel (Ni). The second catalyst 5 has, for example, a cylindrical shape with its axis aligned in the direction in which the exhaust flow path 3 extends.

[0023] The electric heater 6 is disposed around the second catalyst 5 so as to surround the second catalyst 5. The electric heater 6 is, for example, an electric heater that is in contact with the second catalyst 5. The electric heater 6 is a heater that heats the second catalyst 5. Note that the heater is not particularly limited to an electric heater, and may be, for example, a type that heats by irradiating microwaves.

[0024] The temperature sensor 8 is a sensor that detects the temperature of a portion of the exhaust passage 3 between the first catalyst 4 and the second catalyst 5. In other words, the temperature sensor 8 is a sensor that detects the temperature on the inlet side of the second catalyst 5.

[0025] The temperature sensor 9 is a sensor that detects the temperature of a portion of the exhaust passage 3 downstream of the second catalyst 5. In other words, the temperature sensor 9 is a sensor that detects the temperature of the outlet side of the second catalyst 5.

[0026] The ECU 11 is composed of a CPU, RAM, ROM, an input / output interface, etc. As shown in Fig. 2, the ECU 11 has a determination unit 12, a temperature estimation unit 13, a temperature determination unit 14, a heating control unit 15, and a heating time measurement unit 18.

[0027] The determination unit 12 determines whether the amount of ammonia adsorbed on the second catalyst 5 is equal to or less than a predetermined specified amount while the ammonia engine 2 is stopped. The specified amount may be, for example, zero or a numerical value close to zero.

[0028] If the amount of ammonia adsorbed on the second catalyst 5 is equal to or less than the specified amount, there is no need to perform decomposition treatment of the adsorbed ammonia. However, if the amount of ammonia adsorbed on the second catalyst 5 exceeds the specified amount, the amount of adsorption of ammonia is large, so it is necessary to heat the second catalyst 5 using the electric heater 6 and perform decomposition treatment of the ammonia.

[0029] The temperature estimation unit 13 estimates the temperature of the second catalyst 5 based on the detection values ​​of the temperature sensors 8 and 9. The temperature estimation unit 13 cooperates with the temperature sensors 8 and 9 to form a temperature detection unit that detects the temperature of the second catalyst 5. In other words, the temperature detection unit detects the temperature of the second catalyst 5.

[0030] The temperature determination unit 14 determines whether the temperature of the second catalyst 5 estimated by the temperature estimation unit 13 is equal to or higher than the ammonia decomposition activation temperature. That is, the temperature determination unit 14 determines whether the temperature of the second catalyst 5 detected by the temperature detection unit is equal to or higher than the ammonia decomposition activation temperature. The decomposition activation temperature is the temperature at which ammonia can be decomposed, and differs depending on the catalyst type of the second catalyst 5.

[0031] The heating control unit 15 controls the electric heater 6 to be turned on when the judgment unit 12 judges that the amount of ammonia adsorbed on the second catalyst 5 is not equal to or less than a specified amount and the temperature judgment unit 14 judges that the temperature of the second catalyst 5 is not equal to or higher than the decomposition activation temperature.

[0032] The heating control unit 15 turns off the electric heater 6 when the heating time measurement unit 18, which will be described later, determines that heating of the second catalyst 5 has continued for a certain period of time or more. The heating control unit 15 may also turn off the electric heater 6 based on the temperature of the second catalyst 5 detected by the temperature detection unit. Furthermore, the heating control unit 15 may also turn off the electric heater 6 based on both the heating time and the temperature of the second catalyst 5.

[0033] The heating time measurement unit 18 measures whether the heating of the second catalyst 5 has continued for a certain period of time or more. The certain period of time refers to the time from when the temperature of the second catalyst 5 reaches or exceeds the decomposition activation temperature until ammonia is sufficiently decomposed. The heating of the second catalyst 5 continuing for a certain period of time or more means that the temperature of the second catalyst 5 continues to be at or above the decomposition activation temperature for a certain period of time or more by heating the second catalyst 5.

[0034] 3 is a flowchart showing a processing procedure executed by the ECU 11. This processing is executed, for example, when a user turns off the ignition switch of the vehicle. The user is, for example, the driver of the vehicle. When the ignition switch is turned off, an engine stop signal is input to the ECU 11.

[0035] 3, the ECU 11 first determines whether or not an engine stop signal has been input to the ECU 11 (step S101). When the ECU 11 determines that an engine stop signal has not been input to the ECU 11, the ECU 11 ends this process.

[0036] When the ECU 11 determines that the engine stop signal has been input to the ECU 11, it determines whether the amount of ammonia adsorbed to the second catalyst 5 is equal to or less than a specified amount (step S102).

[0037] For example, the amount of ammonia adsorbed to the second catalyst 5 is estimated based on the temperature on the inlet side of the second catalyst 5 and the mixture ratio of the exhaust gas obtained separately, and the time until the ammonia is removed is estimated from the amount of ammonia. Therefore, the ECU 11 determines whether the process of removing the ammonia adsorbed to the second catalyst 5 is completed by determining whether a certain time has elapsed. In other words, the ECU 11 determines whether the amount of ammonia adsorbed to the second catalyst 5 is equal to or less than a specified amount by determining whether a certain time has elapsed.

[0038] When the ECU 11 determines that the amount of ammonia adsorbed in the second catalyst 5 is equal to or less than the specified amount, the ECU 11 ends this process. When the ECU 11 determines that the amount of ammonia adsorbed in the second catalyst 5 is not equal to or less than the specified amount, the ECU 11 acquires the detection values ​​of the temperature sensors 8 and 9 (step S103). Then, the ECU 11 estimates the temperature of the second catalyst 5 based on the detection values ​​of the temperature sensors 8 and 9 (step S104).

[0039] Next, the ECU 11 determines whether the temperature of the second catalyst 5 is equal to or higher than the decomposition activation temperature (step S105). When the ECU 11 determines that the temperature of the second catalyst 5 is equal to or higher than the decomposition activation temperature, the ECU 11 ends this process.

[0040] When the ECU 11 determines that the temperature of the second catalyst 5 is not equal to or higher than the decomposition activation temperature, the ECU 11 turns on the electric heater 6 to start heating the second catalyst 5 (step S106).

[0041] Thereafter, the ECU 11 determines whether the heating of the second catalyst 5 has continued for a certain period of time or more since the heating of the second catalyst 5 started (step S107).

[0042] The ECU 11 repeatedly executes step S107 until it determines that the heating of the second catalyst has continued for a certain period of time or more. When it determines that the heating of the second catalyst has continued for a certain period of time or more, the ECU 11 turns off the electric heater 6, stops heating the second catalyst 5 (step S108), and ends this process.

[0043] Here, the determination unit 12 executes steps S101 and S102. The temperature estimation unit 13 executes steps S103 and S104. The temperature determination unit 14 executes step S105. The heating control unit 15 executes steps S106 and S108. The heating time measurement unit 18 executes step S107.

[0044] In conventional exhaust gas purification devices, the second catalyst is heated using the heat of the exhaust gas while the ammonia engine is running. By heating the second catalyst, it is possible to raise the temperature to a decomposition activation temperature sufficient to decompose the unburned ammonia adsorbed on the second catalyst. When the ammonia engine is running, exhaust gas continuously flows through the second catalyst. Therefore, the heat keeps the second catalyst at its decomposition activation temperature. As a result, the unburned ammonia undergoes a decomposition reaction in the second catalyst, decomposing the unburned ammonia into hydrogen and nitrogen.

[0045] However, when the ammonia engine is stopped, the flow of exhaust gas stops, and the heating of the second catalyst by the heat of the exhaust gas also stops. Because the supply of heat to the second catalyst is thus cut off, the temperature of the second catalyst drops, making it difficult for the decomposition reaction of unburned ammonia to occur in the second catalyst. Therefore, if the ammonia engine is stopped before the decomposition process of unburned ammonia is complete, unburned ammonia may remain in the second catalyst. As a result, the next time the ammonia engine is started, unburned ammonia will already be adsorbed on the second catalyst 5, reducing the amount of unburned ammonia that can be adsorbed, and unburned ammonia that is not adsorbed on the second catalyst may be released into the atmosphere.

[0046] In contrast, in this embodiment, when the ammonia engine 2 is stopped, it is determined whether the amount of ammonia adsorbed on the second catalyst 5 is equal to or less than a specified amount, and whether the temperature of the second catalyst 5 is equal to or higher than the decomposition activation temperature. When the amount of ammonia adsorbed on the second catalyst 5 is greater than the specified amount and the temperature of the second catalyst 5 is lower than the decomposition activation temperature, the electric heater 6 is turned on. The second catalyst 5 is then directly heated by the electric heater 6. When the temperature of the second catalyst 5 rises to the decomposition activation temperature, the ammonia adsorbed on the second catalyst 5 is decomposed. Therefore, even if the decomposition process of the ammonia adsorbed on the second catalyst 5 is not completely completed when the ammonia engine 2 is stopped, the ammonia adsorbed on the second catalyst 5 is removed by forcibly heating the second catalyst 5 with the electric heater 6. This allows the ammonia engine 2 to be stopped at any time without waiting for the ammonia decomposition process to be completed.

[0047] In this embodiment, it is also measured whether the heating of the second catalyst 5 has continued for a certain period of time or longer. When the heating of the second catalyst 5 has continued for a certain period of time or longer, the decomposition of ammonia in the second catalyst 5 has progressed sufficiently. By measuring the duration of heating, it is possible to determine the time during which the second catalyst 5 has maintained the ammonia decomposition activation temperature. This ensures that sufficient time is available for the decomposition of ammonia. Furthermore, when the heating of the second catalyst 5 has continued for a certain period of time or longer, the electric heater 6 is turned off, thereby sufficiently removing the ammonia adsorbed to the second catalyst 5 and conserving the power consumed by the electric heater 6.

[0048] In addition, in this embodiment, the size of the exhaust gas purification device 1 can be reduced, and the cost can be reduced. X The occurrence of can be suppressed.

[0049] (Second embodiment) 4 is an enlarged view of a main portion of an exhaust purification device 1A according to a second embodiment of the present invention, showing the second catalyst 5 and the exhaust flow path 3. The exhaust purification device 1A differs from the exhaust purification device 1 according to the first embodiment in that it is provided with a fan 3A. The other configuration of the exhaust purification device 1A is the same as that of the exhaust purification device 1. Therefore, explanations of components other than the fan 3A will be omitted.

[0050] A fan 3A is disposed downstream of the second catalyst 5 in the exhaust flow path 3 of the exhaust purification device 1A to promote the exhaust of hydrogen and nitrogen, which are decomposition gases of ammonia. The fan 3A is disposed inside the tubular exhaust flow path 3. Specifically, the fan 3A has a plurality of blower blades 3a. The plurality of blower blades 3a are attached to the exhaust flow path 3 so as to be rotatable around the center of a circular cross section perpendicular to the extension direction of the exhaust flow path 3. The fan 3A is connected to a power supply device (not shown) and is controlled by the ECU 11.

[0051] As described above, in this embodiment, the fan 3A is disposed in the exhaust flow path 3 downstream of the second catalyst 5. When the ammonia engine 2 is stopped, the flow of gas in the exhaust flow path 3 also stops, so even if the ammonia adsorbed on the second catalyst 5 is decomposed as in the first embodiment, the decomposition gases, hydrogen and nitrogen, remain in the exhaust flow path 3. Therefore, by driving the fan 3A disposed in the exhaust flow path 3 for a predetermined time after the ammonia engine 2 is stopped, the diffusion of hydrogen contained in the decomposition gas of ammonia generated by the decomposition of ammonia is promoted, and the hydrogen is quickly exhausted to the outside.

[0052] (Third embodiment) 5 is an enlarged view of a main portion of the second catalyst 5 and exhaust flow path 3 of an exhaust purification device 1B according to a third embodiment of the present invention. The exhaust flow path 3 of the exhaust purification device 1B extends so that an exhaust port 3d for discharging decomposition gas of ammonia to the outside is located above the second catalyst 5. The rest of the configuration of the exhaust purification device 1B is the same as that of the exhaust purification device 1. Therefore, a description of overlapping content will be omitted.

[0053] Specifically, the exhaust flow path 3 has, between the second catalyst 5 and the exhaust port 3d, a horizontal section 3c that is aligned along the horizontal direction and an inclined section 3b that is inclined relative to the horizontal throughout. The inclined section 3b is provided in a portion of the exhaust flow path 3 that is downstream of the second catalyst 5. The horizontal section 3c and the inclined section 3b are adjacent to each other. The horizontal section 3c is connected to the second catalyst 5. The inclined section 3b includes the exhaust port 3d. The length of the inclined section 3b in the extension direction is longer than the length of the horizontal section 3c in the extension direction.

[0054] In the above, the molecular weight of hydrogen produced by the decomposition of ammonia is sufficiently smaller than the average molecular weight of air. Therefore, hydrogen is lighter than air and tends to rise upward.

[0055] As described above, in this embodiment, the inclined portion 3b of the exhaust flow path 3 is inclined relative to the horizontal. The inclined portion 3b includes the exhaust port 3d. The exhaust port 3d is located higher than the second catalyst 5. When the ammonia engine 2 stops, the flow of gas in the exhaust flow path 3 also stops. As a result, the decomposition gas of ammonia adsorbed on the second catalyst 5 remains in the exhaust flow path 3 as in the first embodiment, but hydrogen, which is lighter than air and is contained in the decomposition gas of ammonia produced by the decomposition of ammonia, is more likely to flow toward the exhaust port 3d. This promotes the diffusion of hydrogen, allowing the hydrogen to be quickly exhausted to the outside.

[0056] In the third embodiment described above, the portion of the exhaust flow path 3 downstream of the second catalyst 5 has an inclined portion 3b, but this is not particularly limited to this form, and for example, the exhaust flow path 3 may extend vertically to the exhaust port 3d.

[0057] The present invention is not limited to the above embodiment. For example, in the above embodiment, the temperature of the second catalyst 5 is estimated using the temperature sensor 8 that detects the temperature on the inlet side of the second catalyst 5 and the temperature sensor 9 that detects the temperature on the outlet side of the second catalyst 5. However, the present invention is not particularly limited to this configuration, and the temperature of the second catalyst 5 may be detected directly. Furthermore, the temperature of the second catalyst 5 may be estimated based on the history of state quantities such as the rotation speed and load of the ammonia engine 2 and the ambient temperature.

[0058] In the above embodiment, when the electric heater 6 is turned on and heating of the second catalyst 5 continues for a certain period of time or more, the electric heater 6 is turned off to terminate the process of decomposing the ammonia adsorbed on the second catalyst 5. However, this is not a limitation. For example, the temperature of the second catalyst 5 may be estimated based on the detection values ​​of the temperature sensors 8, 9, etc. while the electric heater 6 is heating, and the ON / OFF of the electric heater 6 may be controlled so that the temperature of the second catalyst 5 does not rise to a temperature unsuitable for decomposing ammonia. Alternatively, for example, the temperature of the second catalyst 5 may be estimated based on the detection values ​​of the temperature sensors 8, 9, etc. while the electric heater 6 is heating, and the process of decomposing ammonia may be terminated if the decomposition activation temperature continues for a certain period of time or more. In this case, the power consumption of the electric heater 6 can be reduced while the ammonia adsorbed on the second catalyst 5 can be more reliably removed.

[0059] Furthermore, in the above embodiment, the first catalyst 4 is a three-way catalyst, but is not limited to this form, and the first catalyst 4 may be any catalyst that has the function of oxidizing and reducing NH3 and NOx, for example.

[0060] Furthermore, although the exhaust purification device 1 in the above embodiment is mounted on a vehicle, the configuration is not particularly limited thereto, and for example, the exhaust purification device 1 may be mounted on a ground-based power generation device or the like. [Explanation of symbols]

[0061] 1, 1A, 1B...exhaust gas purification device, 2...ammonia engine (engine), 3...exhaust flow path, 3A...fan, 4...first catalyst, 5...second catalyst, 6...electric heater (heater), 8...temperature sensor (temperature detection unit), 9...temperature sensor (temperature detection unit), 12...judgment unit, 13...temperature estimation unit (temperature detection unit), 14...temperature judgment unit, 15...heating control unit, 18...heating time measurement unit.

Claims

1. An exhaust purification device that purifies exhaust gas generated from an engine, a first catalyst disposed in an exhaust passage connected to the engine and having a function of oxidizing and reducing ammonia and NOx contained in the exhaust gas flowing through the exhaust passage; a second catalyst disposed downstream of the first catalyst in the exhaust flow path and having a function of adsorbing and decomposing ammonia that has passed through the first catalyst; a temperature detection unit that detects the temperature of the second catalyst; a heater for heating the second catalyst; a determination unit that determines whether an amount of ammonia adsorbed on the second catalyst is equal to or less than a predetermined amount while the engine is stopped; a temperature determination unit that determines whether the temperature of the second catalyst detected by the temperature detection unit is equal to or higher than a decomposition activation temperature at which the ammonia can be decomposed; an exhaust purification device comprising: a heating control unit that turns on the heater when the judgment unit determines that the amount of ammonia adsorbed on the second catalyst is not equal to or less than the specified amount and when the temperature judgment unit determines that the temperature of the second catalyst is not equal to or higher than the decomposition activation temperature.

2. a heating time measurement unit that measures whether the heating of the second catalyst has continued for a certain period of time or more; 2. The exhaust gas purification device according to claim 1, wherein the heating control unit turns off the heater when the heating time measurement unit measures that the heating of the second catalyst has continued for a certain period of time or more.

3. 2. The exhaust purification device according to claim 1, further comprising a fan disposed in the exhaust passage downstream of the second catalyst for promoting exhaust of the decomposition gas of ammonia.

4. 2. The exhaust purification device according to claim 1, wherein the exhaust flow path extends so that an exhaust port for discharging the decomposition gas of ammonia to the outside is located above the second catalyst.

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