JP2022054629A - Exhaust emission control system for internal combustion engine - Google Patents

Abstract

To provide an exhaust emission control system capable of performing DPF regeneration suppressing generation of CO2 and DTI (Drop To Idling).SOLUTION: An exhaust emission control system includes: an oxidation catalyst (DOC) connected to an exhaust pipe of an internal combustion engine; a particulate collection filter (DPF) connected to the exhaust pipe on the downstream side of the oxidation catalyst; an ammonia supply device supplying ammonia into the exhaust pipe on the upstream side of the particulate collection filter or on the upstream side of the oxidation catalyst; and a control section controlling the ammonia supply device so that first amount of ammonia is supplied into the exhaust pipe during regeneration of the particulate collection filter and second amount of ammonia that is larger than the first amount is supplied into the exhaust pipe during regeneration of the particulate collection filter and when an excessive temperature rise of the particulate collection filter is detected or predicted.SELECTED DRAWING: Figure 3

Description

The present invention relates to a DPF regeneration technique in an exhaust purification system of an internal combustion engine.

Conventionally, as an exhaust purification device for an internal combustion engine such as a diesel engine, an oxidation catalyst (DOC: Diesel Oxidation Catalyst), a diesel particulate filter (DPF: Diesel Particulate Filter), and a selective reduction catalyst (SCR: Selective Catalystic Reduction) are provided. Is known (see, for example, Patent Document 1).

DOC oxidizes most of the organic components contained in the soot in the exhaust gas and purifies HC and CO. In the following, soot may be referred to as particulate matter (PM: Particulate Matter).

The DPF is provided after the DOC and collects PM in the exhaust. The collected PM is deposited on the DPF. When the amount of PM deposited is equal to or greater than a predetermined value, DPF regeneration is performed. The DPF regeneration is performed, for example, by injecting fuel to the exhaust upstream side of the DOC and burning it in the DOC to raise the temperature of the exhaust gas and burning the PM deposited in the DPF (see, for example, Patent Document 2). ..

The SCR is provided after the DPF. In SCR, ammonia generated by hydrolyzing urea water injected into the exhaust pipe with the heat of the exhaust is reduced by reducing NOx in the exhaust to nitrogen (N2) by the action of a catalyst. To.

Further, a technique of supplying ammonia into an exhaust pipe instead of urea water is also known (see, for example, Patent Document 3).

Special Table 2010-591459 Gazette Japanese Unexamined Patent Publication No. 2011-069323 Japanese Unexamined Patent Publication No. 2013-124569

By the way, since the temperature rise of the exhaust gas for the conventional DPF regeneration is performed by direct injection of unburned fuel into the exhaust pipe or post-injection into the engine as described above, there is a drawback that a large amount of CO2 is generated. be.

Further, when performing DPF regeneration, it is required to suppress the occurrence of DTI (Drop To Idling). Hereinafter, DTI will be briefly described.

During DPF regeneration, it is in the following state.
・ The exhaust temperature is raised by post injection.
-Unburned fuel (hydrocarbon HC) is supplied into the exhaust pipe from the post injection or the fuel injection valve in the exhaust pipe.
-By burning unburned fuel in the DOC, the inlet temperature of the DPF is raised to the PM combustion temperature by O2.

During such DPF regeneration, for example, when fuel injection in the engine is stopped due to deceleration from high load operation (= O2 is thin), fresh air having a high O2 concentration flows into the DOC and DPF under the condition that the flow velocity is slow. , A phenomenon occurs in which PM explosively burns in the DPF. This phenomenon is called DTI.

When DTI occurs, the DPF is in an overheated state, and as a result, the DPF carrier may be cracked or melted, or the catalyst carried on the DPF may be deteriorated.

As a first method of preventing DTI, a method of suppressing the DPF inlet temperature during PM regeneration can be considered. However, if this method is adopted, the DPF regeneration time becomes long, so that there are drawbacks such as deterioration of convenience and large fuel consumption.

As a second method of preventing DTI, a method of suppressing the amount of PM accumulated in the DPF can be considered. However, if this method is adopted, the frequency of PM regeneration increases, so that there are drawbacks that fuel consumption increases and lubricating oil dilutes.

The present invention has been made in consideration of the above points, and provides an exhaust gas purification system capable of performing DPF regeneration in which the generation of CO2 and DTI is suppressed.

One aspect of the exhaust gas purification system for an internal combustion engine of the present invention is:
An exhaust purification system that purifies the exhaust gas of an internal combustion engine.
An oxidation catalyst connected to the exhaust pipe of the internal combustion engine and
A particle collection filter connected to the exhaust pipe on the downstream side of the oxidation catalyst,
An ammonia supply device that supplies ammonia into the exhaust pipe on the upstream side of the particle collection filter or on the upstream side of the oxidation catalyst.
When the particle collection filter is regenerated, a first amount of ammonia is supplied into the exhaust pipe, and when the particle collection filter is regenerated and an excessive temperature rise of the particle collection filter is detected or predicted, the exhaust gas is exhausted. A control unit that controls the ammonia supply device so that a second amount of ammonia, which is larger than the first amount, is supplied into the pipe.
To prepare for.

According to the present invention, DPF regeneration in which the generation of CO2 and DTI is suppressed can be performed.

The figure which showed the main part structure of the exhaust gas purification system of Embodiment 1. A flowchart used to explain the DPF regeneration control according to the first embodiment. The figure which showed the main part structure of the exhaust gas purification system of Embodiment 2. A flowchart used to explain the DPF regeneration control according to the second embodiment. A flowchart used to explain the DPF regeneration control according to the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1> Embodiment 1
<1-1> Configuration of Exhaust Gas Purification System FIG. 1 is a diagram showing a configuration of a main part of the exhaust gas purification system according to the first embodiment. In the present embodiment, an embodiment in which the present invention is applied to the exhaust gas purification system 100 of the diesel engine 10 will be described. However, the exhaust purification system according to the present embodiment can be applied not only to the exhaust purification system 100 of the diesel engine 10 but also to the exhaust purification system of a gasoline engine.

The exhaust purification system 100 is mounted on a vehicle such as a truck, and purifies NOx in the exhaust gas of the engine 10.

The engine 10 includes, for example, a combustion chamber, a fuel injection device that injects fuel in the combustion chamber, an engine ECU that controls the fuel injection device, and the like (not shown). The engine 10 generates power by burning and expanding a mixture of fuel and air in a combustion chamber. The engine 10 is connected to an intake pipe 20 that introduces air into the combustion chamber and an exhaust pipe 30 that discharges the exhaust gas after combustion discharged from the combustion chamber to the outside of the vehicle.

The exhaust purification system 100 includes an oxidation catalyst (DOC: Diesel Oxidation Catalyst) 101, a particle particulate filter (DPF: Diesel Particulate Filter) 102, and a selective catalytic reduction (SCR: Selective Catalytic Reduction) 103. The exhaust gas purification system 100 may have LNT (Lean NOx Trap) or the like as a catalyst in addition to SCR103 or in place of SCR.

DOC101 is formed by supporting rhodium, platinum or the like on a carrier made of aluminum oxide, metal or the like. DOC101 oxidizes and removes unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust, heats and raises the exhaust gas with the reaction heat at this time, and oxidizes NO in the exhaust to NO2.

The DPF 102 is composed of a filter with a catalyst, and collects particulate matter (PM: Particulate Matter) contained in the exhaust gas, and burns and removes the collected and accumulated PM.

The SCR 103 has, for example, a cylindrical shape and has a honeycomb carrier made of ceramic. A catalyst such as zeolite or vanadium is supported or coated on the wall surface of the honeycomb. The SCR 103 occludes ammonia and selectively reduces and purifies NOx from the exhaust gas by the occluded ammonia.

The exhaust purification system 100 includes an ammonia supply device 110 that supplies ammonia into the exhaust pipe 30. The ammonia supply device 110 includes a high-pressure tank 111, a shutoff valve 112, a pressure reducing valve 113, a flow control valve 114, 115, and an ammonia injection port that can store ammonia in a liquid phase state (that is, in a liquefied ammonia (liquefied NH3) state). It has 116 and 117.

Further, the exhaust gas purification system 100 has an ECU (Electronic Control Unit) 130. The ECU 130 controls the operation of the exhaust gas purification system 100.

The ECU 130 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input port, an output port, and the like. The functions described later in the ECU 130 are realized, for example, by the CPU referring to a control program and various data stored in a ROM, RAM, or the like. However, the function is not limited to processing by software, and of course, it can be realized by a dedicated hardware circuit.

The ECU 130 communicates with the engine ECU (not shown) of the engine 10 to control them and acquire their states.

The ECU 130 functions as a control unit that controls the supply of ammonia into the exhaust pipe 30 by the ammonia supply device 110.

A temperature sensor 141 is provided near the entrance of the DOC 101. Further, a temperature sensor 142 is provided near the entrance of the DPF 102. The temperature sensor 141 detects the temperature of the exhaust gas flowing into the DOC 101. The temperature sensor 142 detects the temperature of the exhaust gas flowing into the DPF 102.

The ECU 130 inputs the temperature information detected by the temperature sensors 141 and 142, and controls the opening degree of the isolation valve 112 and the flow control valve 115 based on the temperature information, thereby injecting the ammonia from the ammonia injection port 117. Control the amount of ammonia.

<1-2> DPF regeneration control Next, the DPF regeneration control according to the present embodiment will be described.

First, before giving a detailed explanation, the principle of DPF regeneration according to the present embodiment will be described.

When soot is deposited on the DPF 102, the exhaust pressure rises and causes problems such as deterioration of fuel efficiency. Therefore, DPF regeneration is performed in which the soot is burned so as not to exceed the accumulated amount determined in advance in an experiment or the like. Conventionally, when the exhaust temperature to the DPF does not reach, for example, 500 ° C or higher, which enables combustion of soot, unburned fuel is supplied to the DOC, and the exhaust temperature is raised by oxidation and heat generation (combustion). Is generally done, but if this is done, CO2 will be generated.

If soot that cannot be burned by NO2 is deposited on the DPF 102, the exhaust pressure rises and causes deterioration of fuel efficiency. Therefore, conventionally, it is generally practiced to raise the exhaust temperature to 500 ° C. or higher by burning fuel and to burn soot by O2. At this time, CO2 is generated by the reaction of C + O2 → CO2. In addition, CO2 is also generated by the combustion of fuel.

In consideration of this, in the present embodiment, ammonia is supplied into the exhaust pipe 30 on the upstream side of the DOC 101, and this ammonia is burned by the DOC 101 to promote DPF regeneration, thereby generating CO2. It can be reduced.

The DPF regeneration by supplying ammonia in this embodiment can be used in combination with the conventional DPF regeneration by fuel combustion. For example, the exhaust temperature is raised by conventional fuel combustion until the exhaust temperature at which ammonia can be burned in the DOC 101, and then the DPF regeneration by supplying ammonia is switched. As a result, CO2 generated during DPF regeneration can be reduced.

Here, there are the following two reactions for removing PM (soot) deposited on DPF102.

(1) PM combustion by O2 in an environment with a high exhaust temperature (for example, 500 ° C or higher)

(2) PM combustion due to the reaction of 2NO2 + 2C → 2CO2 + N2 at an appropriate exhaust temperature (for example, around 300 ° C)

The conventional DPF regeneration by fuel combustion mainly relies on the reaction of (1). On the other hand, the DPF regeneration by supplying ammonia in the present embodiment mainly promotes the reaction of (2).

When ammonia is supplied to DOC101 under the condition that ammonia is oxidizable in DOC101, a reaction of 4NH3 + 7O2 → 4NO2 + 6H2O occurs in DOC101, and NO2 is generated. This NO2 is used for the PM combustion reaction of (2) above in DPF102.

Here, in general, NO2 is generated by DOC101 from NO contained in the exhaust gas from the engine, and this is used for the PM combustion reaction of (2) above. In the present embodiment, by supplying ammonia to DOC101, more NO2 can be given to DPF102, and as a result, the reaction of (2) above is further promoted.

FIG. 2 is a flowchart provided for explaining the DPF regeneration control according to the present embodiment. The flowchart of FIG. 2 is executed by the ECU 130.

When the ECU 130 starts DPF regeneration, in step S11, the temperature of the temperature sensor 141 determines whether or not the temperature at which ammonia can be oxidized in the DOC 101. This temperature is, for example, about 250 ° C.

When the ECU 130 obtains an affirmative result in step S11 (step S11; YES), the ECU 130 proceeds to step S12. In step S12, the ECU 130 determines whether or not the temperature of the temperature sensor 142 is in a temperature range suitable for burning the deposited particles in the DPF 102. This temperature range is, for example, 300 ° C to 350 ° C.

When the ECU 130 obtains an affirmative result in step S12 (step S12; YES), the ECU 130 proceeds to step S13. The ECU 130 supplies ammonia to the DOC 101 in step S13. Specifically, the ECU 130 supplies ammonia to the DOC 101 by injecting ammonia from the ammonia injection port 117 by controlling the isolation valve 112 and the flow rate adjusting valve 115 to be in the open state.

Next, in step S14, the ECU 130 determines whether or not the PM removal amount in the DPF 102 exceeds the target amount, and if it exceeds the target amount (step S14; YES), ends the DPF regeneration control and targets. If the value is not exceeded (step S14; NO), the process returns to step S11.

If a negative result is obtained in step S11 or step S12, the ECU 130 moves to step S15 and requests temperature adjustment. For example, the ECU 130 requires the engine ECU (not shown) to raise the temperature of the exhaust gas by the engine. Further, for example, when an electric heater for raising the temperature of the exhaust pipe 30 is provided, the temperature may be adjusted by the electric heater. In short, the temperature is adjusted so that a positive result can be obtained in steps S11 and S12 by some means.

Here, when affirmative results are obtained in steps S11 and S12 and ammonia is supplied to DOC101 in step S13, as described above, a reaction of 4NH3 + 7O2 → 4NO2 + 6H2O occurs in DOC101, and 2NO2 + 2C → 2CO2 + N2 in DPF102. PM combustion by the reaction is performed.

As a result, efficient DPF regeneration can be performed while suppressing the generation of CO2.

<1-3> Summary As described above, according to the present embodiment, the oxidation catalyst (DOC101) connected to the exhaust pipe 30 of the internal combustion engine and the exhaust pipe 30 connected to the exhaust pipe 30 downstream of the oxidation catalyst are connected. A particle collection filter (DPF102), an ammonia supply device 110 that supplies ammonia into the exhaust pipe 30 upstream of the oxidation catalyst, and a first temperature sensor 141 that detects the temperature of the exhaust gas flowing into the oxidation catalyst. , The exhaust pipe 30 by the ammonia supply device 110 based on the temperature detected by the second temperature sensor 142 that detects the temperature of the exhaust gas flowing into the particle collection filter and the first and second temperature sensors 141 and 142. By providing a control unit (ECU 130) for controlling the supply of ammonia to the inside, it is possible to realize an exhaust gas purification system 100 capable of effectively performing DPF regeneration while suppressing the generation of CO2.

Further, according to the present embodiment, since the ammonia supply device 110 is shared by the DOC 101 and the SCR 103, it is possible to suppress an increase in the size of the exhaust gas purification system. However, the SCR 103 may be configured to supply urea water instead of ammonia.

<2> Embodiment 2
<2-1> Configuration of Exhaust Gas Purification System FIG. 3 is a diagram showing a configuration of a main part of the exhaust gas purification system according to the second embodiment, in which the same reference numerals are given to the portions corresponding to those in FIG.

Compared with the exhaust gas purification system 100 (FIG. 1) of the first embodiment, the exhaust gas purification system 200 (FIG. 3) of the present embodiment has the ammonia of the high pressure tank 111 in the state of ammonia gas via the pressure reducing valve 113. In addition to the first supply system for supplying the exhaust pipe 30, there is a second supply system for supplying the ammonia of the high pressure tank 111 to the exhaust pipe 30 in the state of a liquid phase.

Specifically, the first supply system supplies the vaporized ammonia gas after the pressure reducing valve 113 to the exhaust pipe 30 from the ammonia injection port 117. On the other hand, the second supply system supplies liquid phase ammonia from the injector 118 to the exhaust pipe 30. As a result, a large amount of ammonia can be supplied into the exhaust pipe 30 from the second supply system as compared with the first supply system.

Further, in the exhaust gas purification system 200, information on the operating state of the internal combustion engine is input to the ECU 130. The operating state of this internal combustion engine corresponds to the amount of depression of the accelerator. In other words, it can be said that the operating state of the internal combustion engine is the operating load of the internal combustion engine. The larger the accelerator depression amount, the higher the load operation state of the internal combustion engine. The ECU 130 inputs information on the accelerator depression amount from, for example, an ECU (not shown) that controls the entire vehicle.

The ECU 130 controls the opening degree of the isolation valve 112 and the flow control valve 115 based on the operating state of the internal combustion engine and the temperature detected by the temperature sensors 141 and 142 to control the opening degree of the shutoff valve 112 and the flow control valve 115 to control the opening degree of the ammonia injection port 117 and the injector. Controls the amount of ammonia ejected from 118.

<2-2> DPF regeneration control Next, the DPF regeneration control according to the present embodiment will be described.

As described above, during DPF regeneration, for example, when fuel injection in the engine is stopped by deceleration from high load operation (= O2 is thin), that is, the state of the internal combustion engine is changed from the high load operation state to the low load operation state. In the case of a sudden change to DOC101 and DPF102, fresh air having a high O2 concentration flows into the DOC101 and DPF102 at a slow flow velocity, so that a phenomenon in which PM explosively burns in the DPF102, so-called DTI (Drop To Idling), occurs.

In consideration of this, in the present embodiment, the O2 increased during the sudden change in the operating state as described above is forcibly consumed by the supply of ammonia (NH3), and the O2 flowing into the DPF 102 is reduced to reduce the DTI. Suppress.

Here, the ammonia supplied into the exhaust pipe 30 from the injector 118 or the ammonia injection port 117 consumes O2 by the reaction of NH3 + O2 → N2 + H2O (coefficients are ignored) in the DOC101. By this reaction, O2 flowing into DPF 102 can be reduced. This makes it possible to suppress the explosive PM combustion in the DPF 102.

One feature of the DPF regeneration control of the present embodiment is that a first amount of ammonia is supplied into the exhaust pipe 30 during DPF regeneration, and an excessive temperature rise of the DPF is detected or predicted during DPF regeneration. The point is that a second amount of ammonia, which is larger than the first amount, is supplied into the exhaust pipe 30.

Since DTI occurs suddenly when the operating state suddenly changes, there is a possibility that the suppression of DTI cannot be made in time only by supplying ammonia from the first supply system that supplies ammonia gas. Therefore, in the present embodiment, when DTI is likely to occur (that is, when an excessive temperature rise of DPF 102 is detected or predicted), liquefied ammonia is injected in order to supply a large amount of ammonia into the exhaust pipe 30. Two supply systems are provided. Of course, when DTI is likely to occur (that is, when an overheating of the DPF is detected or predicted), ammonia may be supplied not only from the second supply system but also from the first supply system.

Here, there are, for example, two methods for predicting that DTI is likely to occur. The first method is a method of predicting based on the operating state of the internal combustion engine. The second method is a method of predicting based on the temperature of the temperature sensor 142.

FIG. 4 is a flowchart used to explain the DPF regeneration control using the first method. The flowchart of FIG. 4 is executed by the ECU 130. The flowchart of FIG. 4 is performed during the period when the DPF regeneration is already performed.

The ECU 130 determines in step S21 whether or not the internal combustion engine has suddenly changed from the high load operation state to the low load operation state during the DPF regeneration period.

When the affirmative result is obtained in step S21 (step S21; YES), the ECU 130 proceeds to step S22 and injects a large amount of ammonia from the second supply system (injector 118).

As a result, it is possible to quickly suppress the excessive temperature rise of the DPF when the operation of the internal combustion engine suddenly changes.

FIG. 5 is a flowchart used to explain the DPF regeneration control using the second method. The flowchart of FIG. 5 is executed by the ECU 130. The flowchart of FIG. 5 is performed during the period when the DPF regeneration is already performed.

During the DPF regeneration period, the ECU 130 determines in step S31 whether the temperature of the temperature sensor 142 is higher than the temperature range suitable for burning the deposited particles in the DPF 102.

When the affirmative result is obtained in step S31 (step S31; YES), the ECU 130 proceeds to step S32 and injects a large amount of ammonia from the second supply system (injector 118).

As a result, it is possible to quickly suppress the excessive temperature rise of the DPF when the operation of the internal combustion engine suddenly changes.

<2-3> Summary As described above, according to the present embodiment, the first amount of ammonia is supplied into the exhaust pipe 30 during the DPF regeneration, and the DPF 102 is overheated during the DPF regeneration. When detected or predicted, the exhaust pipe 30 is supplied with a second amount of ammonia, which is larger than the first amount, so that DPF regeneration in which the generation of CO2 and DTI is suppressed can be performed. It will be like.

Further, the ammonia supply device 110 supplies the first amount of ammonia into the exhaust pipe 30 in the gas phase state, while supplying the second amount of ammonia into the exhaust pipe 30 in the liquid phase state. As a result, a large amount of ammonia can be supplied into the exhaust pipe 30 as a second amount, so that DTI can be quickly suppressed.

The above-mentioned embodiments 1 and 2 are merely examples of the embodiment of the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. That is, the present invention can be implemented in various forms without departing from its gist or its main features.

In the above-described embodiment, the case where the injector 118 that supplies a second amount of ammonia larger than the first amount is provided on the upstream side of the DOC 101 is described, but the injector 118 is provided on the downstream side of the DOC 101 and of the PDF 102. It may be provided on the upstream side. Even when arranged in this way, it is possible to prevent the rapid combustion of PM accumulated in the DPF 102. Under temperature conditions where DTI is a concern, combustion of ammonia is possible without a catalyst by appropriately setting spray conditions and the like.

The present invention can be widely used as a DPF regeneration technique for an exhaust purification system.

10 Diesel engine (engine)
20 Intake pipe 30 Exhaust pipe 100, 200 Exhaust purification system 101 DOC (oxidation catalyst)
102 DPF (Diesel Particulate Filter)
103 SCR (selective reduction catalyst)
110 Ammonia supply device 111 High pressure tank 112 Shutoff valve 113 Pressure reducing valve 114, 115 Flow control valve 116, 117 Ammonia injection port 118 Injector 130 ECU (control unit)
141, 142 Temperature sensor

Claims (6)

An exhaust purification system that purifies the exhaust gas of an internal combustion engine.
An oxidation catalyst connected to the exhaust pipe of the internal combustion engine and
A particle collection filter connected to the exhaust pipe on the downstream side of the oxidation catalyst,
An ammonia supply device that supplies ammonia into the exhaust pipe on the upstream side of the particle collection filter or on the upstream side of the oxidation catalyst.
When the particle collection filter is regenerated, a first amount of ammonia is supplied into the exhaust pipe, and when the particle collection filter is regenerated and an excessive temperature rise of the particle collection filter is detected or predicted, the exhaust gas is exhausted. A control unit that controls the ammonia supply device so that a second amount of ammonia, which is larger than the first amount, is supplied into the pipe.
Exhaust purification system equipped with. The ammonia supply device supplies the first amount of ammonia into the exhaust pipe in a gas phase state, while supplying the second amount of ammonia into the exhaust pipe in a liquid phase state.
The exhaust purification system according to claim 1. The ammonia supply device is
A high-pressure tank that can store ammonia in a liquid phase,
A first supply system that supplies ammonia in the high-pressure tank to the exhaust pipe in the form of ammonia gas via a pressure reducing valve, and
A second supply system that supplies ammonia in the high-pressure tank in a liquid phase to the exhaust pipe,
Equipped with
The first amount of ammonia is supplied to the exhaust pipe via the first supply system.
The second amount of ammonia is supplied to the exhaust pipe at least through the second supply system.
The exhaust purification system according to claim 1. The control unit
When the operating state of the internal combustion engine suddenly changes from the high load operating state to the low load operating state based on the operating state of the internal combustion engine, the second amount of ammonia is supplied by the ammonia supply device.
The exhaust gas purification system according to any one of claims 1 to 3. A first temperature sensor that detects the temperature of the exhaust gas flowing into the oxidation catalyst, and
A second temperature sensor that detects the temperature of the exhaust gas flowing into the particle collection filter, and
Further prepare
The control unit
The temperature of the first temperature sensor is a temperature at which ammonia can be oxidized in the oxidation catalyst, and the temperature of the second temperature sensor is a temperature range suitable for combustion of deposited particles in the particle collection filter. In this case, the ammonia supply device is controlled to supply the first amount of ammonia into the exhaust pipe on the upstream side of the oxidation catalyst.
The temperature of the first temperature sensor is a temperature at which ammonia can be oxidized in the oxidation catalyst, and the temperature of the second temperature sensor is a temperature range suitable for combustion of deposited particles in the particle collection filter. When the temperature is higher than the above, the ammonia supply device controls to supply the second amount of ammonia into the exhaust pipe on the upstream side of the oxidation catalyst.
The exhaust gas purification system according to any one of claims 1 to 3. A selective reduction catalyst is connected to the exhaust pipe on the downstream side of the particle collection filter.
The ammonia supply device supplies ammonia to the selective reduction catalyst in addition to the inside of the exhaust pipe on the upstream side of the oxidation catalyst.
The exhaust purification system according to any one of claims 1 to 5.

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