JP2022044263A - Reducing agent supply system, reducing agent supply control device, and reducing agent supply control method - Google Patents

Abstract

To provide a reducing agent supply system, a reducing agent supply control device and a reducing agent supply control method enabling efficient supply of a reducing agent.SOLUTION: A reducing agent supply system includes: a supply source storing a liquid reducing agent; a supply device supplying the reducing agent to an upstream side of an exhaust gas purification material in an exhaust pipe in which exhaust gas flows; a pressure reduction valve executing pressure reduction for converting the liquid reducing agent caused to flow out from the supply source into a gaseous reducing agent; and a supply pipe that connects the supply source with the supply device, has the pressure reduction valve and supplies either the liquid reducing agent or the gaseous reducing agent to the supply device.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a reducing agent supply system, a reducing agent supply control device, and a reducing agent supply control method.

Conventionally, a technique for purifying exhaust gas discharged from an internal combustion engine by a catalyst is known.

For example, Patent Document 1 describes a system provided with a urea water injection device (also referred to as an injector or a dosing module) and an SCR (Selective Catalytic Reduction) catalyst in order from the upstream side in an exhaust pipe through which exhaust gas flows. It has been disclosed.

In this system, urea water (an example of a precursor) injected into an exhaust pipe from a urea water injection device is hydrolyzed by the heat of the exhaust gas. Ammonia gas (an example of a reducing agent) generated thereby is supplied to the SCR catalyst. Then, in the SCR catalyst, NOx in the exhaust gas is reduced to nitrogen.

On the other hand, for example, Patent Document 2 discloses a system for supplying ammonia gas as a reducing agent instead of urea water into an exhaust pipe on the upstream side of the SCR catalyst.

Japanese Unexamined Patent Publication No. 2009-138737 Japanese Unexamined Patent Publication No. 2013-124569

All of the conventional systems described above have room for improvement in terms of efficient supply of reducing agents.

An object of one aspect of the present disclosure is to provide a reducing agent supply system, a reducing agent supply control device, and a reducing agent supply control method capable of realizing efficient supply of a reducing agent.

The reducing agent supply system according to one aspect of the present disclosure comprises a supply source for storing the liquid reducing agent, a supply device for supplying the reducing agent to the upstream side of the exhaust gas purifying material in the exhaust pipe through which the exhaust gas flows, and the supply source. A pressure reducing valve that executes depressurization to change the discharged liquid reducing agent into a gaseous reducing agent, the supply source and the supply device are connected, and the pressure reducing valve is provided, and the liquid reducing agent or the gas is provided. It has a supply pipe for supplying any of the reducing agents to the supply device.

The reducing agent supply control device according to one aspect of the present disclosure includes a supply source for storing the liquid reducing agent, a supply device for supplying the reducing agent to the upstream side of the exhaust gas purifying material in the exhaust pipe through which the exhaust gas flows, and the supply source. A pressure reducing valve that executes depressurization to change the liquid reducing agent from the above into a gaseous reducing agent, the supply source and the supply device are connected, and the pressure reducing valve is provided, and the liquid reducing agent or the above. It is used in a system provided with a supply pipe for supplying any of the gaseous reducing agents to the supply device, and the temperature of the exhaust gas on the upstream side of the exhaust gas purifying material or the temperature of the exhaust gas purifying material itself is predetermined. A determination unit for determining whether or not the temperature is below the threshold, and when the temperature is less than the threshold, the pressure reducing valve is made to execute the depressurization, and when the temperature is not less than the threshold, the pressure reducing valve is made to perform the depressurization. It has a control unit that does not execute the above.

The reducing agent supply control method according to one aspect of the present disclosure includes a supply source for storing the liquid reducing agent, a supply device for supplying the reducing agent to the upstream side of the exhaust gas purifying material in the exhaust pipe through which the exhaust gas flows, and the supply source. A pressure reducing valve that executes depressurization to change the liquid reducing agent from the above into a gaseous reducing agent, the supply source and the supply device are connected, and the pressure reducing valve is provided, and the liquid reducing agent or the above. It is used in a system provided with a supply pipe for supplying any of the gaseous reducing agents to the supply device, and the temperature of the exhaust gas on the upstream side of the exhaust gas purifying material or the temperature of the exhaust gas purifying material itself is predetermined. It is determined whether or not it is below the threshold, and if the temperature is less than the threshold, the pressure reducing valve is made to perform the depressurization, and if the temperature is not less than the threshold, the pressure reducing valve is not made to perform the depressurization. ..

According to the present disclosure, an efficient supply of a reducing agent can be realized.

Schematic diagram showing a configuration example of the reducing agent supply system and its peripheral portion according to the embodiment of the present disclosure. A block diagram showing a configuration example of the reducing agent supply control device according to the embodiment of the present disclosure. A flowchart showing an operation example of the reducing agent supply control device according to the embodiment of the present disclosure. Schematic diagram showing a configuration example of the reducing agent supply system and its peripheral portion according to the modified example of the present disclosure.

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

First, the components of the reducing agent supply system 100 of the present embodiment and its peripheral portions will be described with reference to FIG. FIG. 1 is a schematic diagram showing a configuration example of the reducing agent supply system 100 and its peripheral portion.

Each component (referenced) shown in FIG. 1 is mounted on, for example, a vehicle (for example, a bus, a truck, etc.) (not shown). The internal combustion engine (not shown) mounted on the vehicle may be a diesel engine or a gasoline engine. The internal combustion engine is not limited to the internal combustion engine of a vehicle, and may be, for example, an internal combustion engine of a ship or a stationary internal combustion engine.

The exhaust pipe 1 is a pipe through which the exhaust gas discharged from the internal combustion engine flows. The arrow shown in the exhaust pipe 1 indicates the flow direction of the exhaust gas. Therefore, the injection device 2, the temperature sensor 3, and the SCR catalyst 4 are provided in the exhaust pipe 1 in order from the upstream side in the flow direction of the exhaust gas.

Although not shown, the upstream end of the exhaust pipe 1 is connected to an exhaust manifold provided in the internal combustion engine. Further, although not shown, the downstream end of the exhaust pipe 1 may face the atmosphere or may be connected to an exhaust diffuser or the like.

The SCR catalyst 4 may be housed in a catalyst converter (also referred to as a catalyst casing) connected to the exhaust pipe 1. Further, the catalytic converter may include an injection device 2 and a temperature sensor 3.

The injection device 2 (an example of a supply device) is, for example, a device capable of injecting either liquid ammonia or gaseous ammonia onto the upstream side of the SCR catalyst 4 in the exhaust pipe 1. The injection device 2 is controlled by the reducing agent supply control device 200 (see FIG. 2), which will be described later. The injection device 2 is one of the components of the reducing agent supply system 100.

The temperature sensor 3 is provided on the upstream side of the SCR catalyst 4 (specifically, near the inlet of the SCR catalyst 4). The temperature sensor 3 periodically detects the temperature of the exhaust gas at the inlet of the SCR catalyst 4 (hereinafter, also simply referred to as the temperature of the exhaust gas) and notifies the reducing agent supply control device 200 (see FIG. 2) described later.

In the present embodiment, the case where the temperature sensor 3 is provided near the inlet of the SCR catalyst 4 and detects the temperature of the exhaust gas at the inlet of the SCR catalyst 4 will be described as an example, but the present invention is not limited to this. For example, the temperature sensor 3 may be provided at a position where the temperature of the SCR catalyst 4 itself can be detected, and the temperature of the SCR catalyst 4 itself may be detected. In this specification, the temperature of the exhaust gas at the inlet of the SCR catalyst 4 is regarded as synonymous with the temperature of the SCR catalyst 4 itself.

The SCR catalyst 4 (an example of an exhaust gas purifying material) is a catalyst that reduces NOx in exhaust gas to nitrogen by ammonia.

An ASC (Ammonia Slip Catalyst), which is a catalyst for oxidizing and decomposing ammonia that could not be consumed by the SCR catalyst 4, may be provided on the downstream side of the SCR catalyst 4.

The reducing agent supply system 100 includes an injection device 2, a first supply pipe 5, an ammonia storage unit 6, and a pressure reducing valve 7. Further, as a component of the reducing agent supply system 100, the reducing agent supply control device 200 described later may be included.

The first supply pipe 5 is a pipe that connects the injection device 2 and the ammonia storage unit 6. Liquid ammonia (an example of a liquid reducing agent) stored in the ammonia storage unit 6 flows through the first supply pipe 5 from the ammonia storage unit 6 toward the injection device 2.

The ammonia storage unit 6 (an example of a supply source) is a tank for storing liquid ammonia.

The pressure reducing valve 7 is provided in the first supply pipe 5. The pressure reducing valve 7 performs depressurization (hereinafter referred to as vaporization depressurization) for changing liquid ammonia flowing through the first supply pipe 5 from the ammonia storage unit 6 toward the injection device 2 into gaseous ammonia. Further, the pressure reducing valve 7 adjusts the pressure to stabilize the injection amount of ammonia in the injection device 2. The pressure reducing valve 7 is controlled by the reducing agent supply control device 200 (see FIG. 2) described later.

The components of the reducing agent supply system 100 and its peripheral portions have been described above.

Next, the configuration of the reducing agent supply control device 200 of the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration example of the reducing agent supply control device 200.

The reducing agent supply control device 200 shown in FIG. 2 is a device that controls the injection device 2 and the pressure reducing valve 7 shown in FIG.

Although not shown, the reducing agent supply control device 200 includes, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) containing a control program, and a working memory such as a RAM (Random Access Memory). And so on. The function of the reducing agent supply control device 200 described below is realized by the CPU reading the control program from the ROM and executing it on the RAM. For example, the reducing agent supply control device 200 is realized by an ECU (Electronic Control Unit).

As shown in FIG. 2, the reducing agent supply control device 200 has a determination unit 210 and a control unit 220.

The determination unit 210 determines whether or not the temperature of the exhaust gas notified from the temperature sensor 3 is less than a predetermined threshold value.

If the temperature of the exhaust gas at the inlet of the SCR catalyst 4 (which may be the temperature of the SCR catalyst 4 itself as described above) is less than the threshold value, the liquid ammonia is changed to gaseous ammonia (an example of a gaseous reducing agent) by depressurization. The value at which the pressure reducing valve 7 is controlled is determined based on the results of experiments and the like conducted in advance. For example, the threshold value may be the lower limit of the active temperature range of the SCR catalyst 4.

When the determination unit 210 determines that the temperature of the exhaust gas is below the threshold value, the control unit 220 controls the pressure reducing valve 7 so as to execute the vaporization depressurization described above. As a result, gaseous ammonia flows downstream of the pressure reducing valve 7 of the first supply pipe 5, and the gaseous ammonia is supplied to the injection device 2.

On the other hand, when the determination unit 210 determines that the temperature of the exhaust gas is not less than the threshold value, the control unit 220 does not cause the pressure reducing valve 7 to execute vaporization and depressurization. As a result, liquid ammonia flows downstream of the pressure reducing valve 7 of the first supply pipe 5, and the liquid ammonia is supplied to the injection device 2. In this case, the pressure reducing valve 7 does not perform vaporization and depressurization, but may adjust the pressure to stabilize the injection amount of ammonia in the injection device 2.

Further, the control unit 220 controls the injection device 2 so as to inject the ammonia (either gaseous ammonia or liquid ammonia) supplied to the injection device 2 into the exhaust pipe 1. For example, the control unit 220 determines the injection amount based on the temperature of the exhaust gas notified from the temperature sensor 3, and causes the injection device 2 to inject the ammonia of the injection amount.

The injection amount may be determined based on a parameter other than the temperature of the exhaust gas flowing upstream of the SCR catalyst 4. The parameters include, for example, the flow rate of the exhaust gas flowing upstream of the SCR catalyst 4, the pressure of the exhaust gas flowing upstream of the SCR catalyst 4, the amount of NOx in the exhaust gas flowing upstream of the SCR catalyst 4, or the injection device. Examples include the pressure of the ammonia supplied to 2. It is assumed that these parameters are detected by a sensor (not shown) and notified to the control unit 220.

The configuration of the reducing agent supply control device 200 has been described above.

Hereinafter, the operation of the reducing agent supply control device 200 will be described with reference to FIG. FIG. 3 is a flowchart showing an operation example of the reducing agent supply control device 200.

This operation example is started, for example, when the temperature of the exhaust gas at the inlet of the SCR catalyst 4 becomes a predetermined value (for example, the lower limit value of the active temperature range of the SCR catalyst 4) or more. The process of determining whether or not the temperature of the exhaust gas at the inlet of the SCR catalyst 4 is equal to or higher than a predetermined value is performed by, for example, the determination unit 210.

First, the determination unit 210 determines whether or not the temperature of the exhaust gas notified from the temperature sensor 3 is below the threshold value (step S1).

When the temperature of the exhaust gas is less than the threshold value (step S1: YES), the control unit 220 controls the pressure reducing valve 7 so as to execute vaporization and depressurization (step S2).

As a result, the liquid ammonia flowing from the ammonia storage unit 6 toward the injection device 2 through the first supply pipe 5 is changed to gaseous ammonia at the pressure reducing valve 7. Then, the gaseous ammonia is supplied to the injection device 2.

On the other hand, when the temperature of the exhaust gas is not less than the threshold value (step S1: NO), the flow proceeds to step S3.

In this case, since the vaporization depressurization is not executed in the pressure reducing valve 7, the liquid ammonia flowing from the ammonia storage unit 6 toward the injection device 2 and flowing through the first supply pipe 5 is supplied to the injection device 2 as it is.

Next, the control unit 220 controls the injection device 2 so as to inject the ammonia supplied to the injection device 2 into the exhaust pipe 1 (step S3).

As a result, either gaseous ammonia or liquid ammonia is injected from the injection device 2 into the exhaust pipe 1 on the upstream side of the SCR catalyst 4.

The operation of the reducing agent supply control device 200 has been described above.

As described above, in the reducing agent supply system 100 of the present embodiment, the liquid ammonia is directly or the liquid ammonia is changed to the gaseous ammonia from the ammonia storage unit 6 for storing the liquid ammonia to the injection device 2. It is characterized by having a supply configuration. Therefore, since the reducing agent supply system 100 can selectively supply ammonia having different phases to the injection device 2, efficient supply of ammonia can be realized.

Further, the SCR catalyst 4 has a characteristic that the NOx purification rate is highest in the active temperature range of the SCR catalyst 4 (for example, 250 ° C. to 400 ° C.), but decreases outside the active temperature range. I have something to have. With respect to this characteristic, the reducing agent supply control device 200 of the present embodiment has different phases of ammonia based on the temperature of the exhaust gas on the upstream side of the SCR catalyst 4 (synonymous with the temperature of the SCR catalyst 4 itself as described above). That is, it is characterized in that it controls to supply either gaseous ammonia or liquid ammonia to the injection device 2.

Specifically, when the exhaust gas is at a low temperature (for example, a temperature below the threshold value), the reducing agent supply control device 200 changes the liquid ammonia into gaseous ammonia and injects the gaseous ammonia into the exhaust pipe 1. As a result, it is possible to suppress a decrease in the temperature of the exhaust gas on the upstream side of the SCR catalyst 4. On the other hand, when the exhaust gas has a high temperature (for example, a temperature equal to or higher than the threshold value), the reducing agent supply control device 200 injects liquid ammonia into the exhaust pipe 1. As a result, it is possible to suppress an excessive rise in the temperature of the exhaust gas on the upstream side of the SCR catalyst 4.

Therefore, the reducing agent supply control device 200 can maintain an appropriate temperature of the exhaust gas on the upstream side of the SCR catalyst 4, and can realize efficient NOx purification in the SCR catalyst 4. Therefore, the reducing agent supply control device 200 can realize an efficient supply of ammonia that contributes to efficient NOx purification.

It should be noted that the present disclosure is not limited to the description of the above embodiment, and various modifications can be made without departing from the spirit of the present embodiment. Hereinafter, a modified example will be described.

[Modification 1]
In the embodiment, the case where the reducing agent supply system 100 includes only the first supply pipe 5 has been described as an example, but the present invention is not limited thereto.

Another configuration example of the reducing agent supply system 100 will be described with reference to FIG. FIG. 4 is a schematic diagram showing a configuration example of the reducing agent supply system 100 of this modification and its peripheral portion. In FIG. 4, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 4, the reducing agent supply system 100 includes a second supply pipe 8, a third supply pipe 9, a first isolation valve 10, and a second isolation valve 11 in addition to the components shown in FIG. ..

The third supply pipe 9 is connected to the ammonia storage unit 6. One end of the first supply pipe 5 is connected to the injection device 2, and the other end of the first supply pipe 5 is connected to the third supply pipe 9. Similarly, one end of the second supply pipe 8 is connected to the injection device 2, and the other end of the second supply pipe 8 is connected to the third supply pipe 9.

The first isolation valve 10 is provided in the first supply pipe 5. More specifically, the first isolation valve 10 is provided in the first supply pipe 5 on the upstream side of the pressure reducing valve 7. The second isolation valve 11 is provided in the second supply pipe 8. The first isolation valve 10 and the second isolation valve 11 are controlled to be in an open state or a closed state by, for example, the control unit 220 of the reducing agent supply control device 200.

When the determination unit 210 determines that the temperature of the exhaust gas is below the threshold value, the control unit 220 controls the first isolation valve 10 to be in the open state and the second isolation valve 11 to be in the closed state. Further, the control unit 220 controls the pressure reducing valve 7 so as to execute vaporization and depressurization. As a result, the liquid ammonia discharged from the ammonia storage unit 6 flows through the first supply pipe 5 and changes to gaseous ammonia at the pressure reducing valve 7. Then, the gaseous ammonia is supplied to the injection device 2.

On the other hand, when the determination unit 210 determines that the temperature of the exhaust gas is not less than the threshold value, the control unit 220 controls the first isolation valve 10 to be in the closed state and the second isolation valve 11 to be in the open state. As a result, the liquid ammonia discharged from the ammonia storage unit 6 flows through the second supply pipe 8 and is supplied to the injection device 2. At this time, the control unit 220 does not cause the pressure reducing valve 7 to execute vaporization and depressurization.

In the second supply pipe 8, a pressure reducing valve may be provided on the downstream side of the second isolation valve 11. This makes it possible to adjust the pressure to stabilize the injection amount of liquid ammonia in the injection device 2.

[Modification 2]
In the embodiment, the case where the reducing agent supply system 100 has an injection device 2 capable of injecting either gaseous ammonia or liquid ammonia has been described as an example, but the present invention is not limited thereto.

For example, the reducing agent supply system 100 may separately have an injection device capable of injecting only gaseous ammonia into the exhaust pipe 1 and an injection device capable of injecting only liquid ammonia into the exhaust pipe 1.

In that case, the first supply pipe 5 shown in FIG. 1 may be bifurcated, one may be connected only to the former injection device, and the other may be connected only to the latter injection device. Further, in the case of the first embodiment described above (see FIG. 4), the first supply pipe 5 may be connected only to the former injection device, and the second supply pipe 8 may be connected only to the latter injection device.

[Modification 3]
In the embodiment, the case where the device for supplying ammonia into the exhaust pipe 1 is the injection device 2 has been described as an example, but the present invention is not limited to this.

For example, the reducing agent supply system 100 may have a flow rate adjusting valve (an example of a supply device) capable of adjusting the amount of ammonia supplied into the exhaust pipe 1 instead of the injection device 2.

In that case, the flow rate adjusting valve may be controlled by, for example, the reducing agent supply control device 200. For example, the control unit 220 determines the supply amount of ammonia supplied from the flow rate adjusting valve into the exhaust pipe 1 based on a predetermined parameter, so that the determined supply amount of ammonia is supplied into the exhaust pipe 1. The opening time and opening time of the flow rate adjusting valve may be controlled.

The above parameters include, for example, the temperature of the exhaust gas flowing on the upstream side of the SCR catalyst 4, the flow rate of the exhaust gas flowing on the upstream side of the SCR catalyst 4, the pressure of the exhaust gas flowing on the upstream side of the SCR catalyst 4, and the upstream side of the SCR catalyst 4. Examples include the amount of NOx in the flowing exhaust gas, the pressure of ammonia supplied to the flow control valve, and the like. Further, it is assumed that these parameters are detected by various sensors and notified to the control unit 220.

The flow rate adjusting valve may be provided in the first supply pipe 5 and used in combination with the injection device 2.

[Modification 4]
In the embodiment, the case where the SCR catalyst 4 is used as the exhaust gas purifying material has been described as an example, but the present invention is not limited to this.

For example, instead of the SCR catalyst 4, an exhaust gas purifying material in which an SCR catalyst and a filter for collecting particulate matter in the exhaust gas are integrated may be used. Examples of the exhaust gas purifying material include SDPF (also referred to as SCR-Filter) used when the internal combustion engine is a diesel engine.

The modified example has been described above. The above-mentioned modifications may be realized by combining them as appropriate.

The reducing agent supply system, the reducing agent supply control device, and the reducing agent supply control method of the present disclosure are useful in the technique of supplying the reducing agent to the upstream side of the exhaust gas purifying material in the flow path of the exhaust gas.

1 Exhaust pipe 2 Injection device 3 Temperature sensor 4 SCR catalyst 5 1st supply pipe 6 Ammonia storage 7 Pressure reducing valve 8 2nd supply pipe 9 3rd supply pipe 10 1st isolation valve 11 2nd isolation valve 200 Reducing agent supply control device 210 Judgment unit 220 Control unit

Claims (5)

A source for storing the liquid reducing agent and
A supply device that supplies a reducing agent to the upstream side of the exhaust gas purifying material in the exhaust pipe through which the exhaust gas flows,
A pressure reducing valve for performing depressurization that changes the liquid reducing agent from the source into a gaseous reducing agent, and
It has a supply pipe that connects the supply source and the supply device, is provided with the pressure reducing valve, and supplies either the liquid reducing agent or the gaseous reducing agent to the supply device.
Reducing agent supply system. Further having a reducing agent supply control device for controlling the pressure reducing valve,
The reducing agent supply control device is
It is determined whether or not the temperature of the exhaust gas on the upstream side of the exhaust gas purifying material or the temperature of the exhaust gas purifying material itself is less than a predetermined threshold value.
If the temperature is below the threshold, the pressure reducing valve is made to perform the depressurization.
If the temperature is not less than the threshold, the pressure reducing valve is not allowed to perform the pressure reduction.
The reducing agent supply system according to claim 1. The liquid reducing agent is liquid ammonia.
The gaseous reducing agent is gaseous ammonia.
The exhaust gas purifying material is an SCR (Selective Catalytic Reduction) catalyst.
The reducing agent supply system according to claim 1 or 2. A source for storing the liquid reducing agent and
A supply device that supplies a reducing agent to the upstream side of the exhaust gas purifying material in the exhaust pipe through which the exhaust gas flows,
A pressure reducing valve for performing depressurization that changes the liquid reducing agent from the source into a gaseous reducing agent, and
Used in a system including a supply pipe that connects the supply source and the supply device and is provided with the pressure reducing valve and supplies either the liquid reducing agent or the gaseous reducing agent to the supply device. Be,
A determination unit for determining whether or not the temperature of the exhaust gas on the upstream side of the exhaust gas purifying material or the temperature of the exhaust gas purifying material itself is less than a predetermined threshold value.
It has a control unit that causes the pressure reducing valve to perform the depressurization when the temperature is below the threshold value, and does not cause the pressure reducing valve to execute the depressurization when the temperature is not below the threshold value.
Reducing agent supply control device. A source for storing the liquid reducing agent and
A supply device that supplies a reducing agent to the upstream side of the exhaust gas purifying material in the exhaust pipe through which the exhaust gas flows,
A pressure reducing valve for performing depressurization that changes the liquid reducing agent from the source into a gaseous reducing agent, and
Used in a system including a supply pipe that connects the supply source and the supply device and is provided with the pressure reducing valve and supplies either the liquid reducing agent or the gaseous reducing agent to the supply device. Be,
It is determined whether or not the temperature of the exhaust gas on the upstream side of the exhaust gas purifying material or the temperature of the exhaust gas purifying material itself is less than a predetermined threshold value.
If the temperature is below the threshold, the pressure reducing valve is made to perform the depressurization.
If the temperature is not less than the threshold, the pressure reducing valve is not allowed to perform the pressure reduction.
Reducing agent supply control method.

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