JP7063016B2 - Post-processing equipment - Google Patents

Description

The present disclosure relates to an exhaust gas aftertreatment device.

Conventionally, an aftertreatment device including a selective reduction catalyst that reduces nitrogen oxides (NOx) in exhaust gas discharged from an internal combustion engine is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2010-53847

However, for example, when the internal combustion engine is started, the temperature of the exhaust gas is low, so that the temperature does not reach the temperature at which the selective reduction catalyst is activated, and the NOx purification rate may decrease.

An object of the present disclosure is to provide an aftertreatment apparatus capable of improving the NOx purification rate of a selective reduction catalyst even when the temperature of the exhaust gas is low.

The aftertreatment device according to one aspect of the present disclosure is an exhaust gas aftertreatment device in which a selective reduction catalyst is provided in an exhaust pipe through which an exhaust gas discharged from an internal combustion engine flows, and the outer periphery of the exhaust pipe is spirally formed. A heat exchange unit that exchanges heat between the exhaust gas flowing downstream of the internal combustion engine and upstream of the selective reduction catalyst and a liquid, and a gas generated by the heat exchange. A gas pipe through which the pump flows , an oxidation catalyst provided on the upstream side of the selective reduction type catalyst, and a fine particle collection filter provided on the upstream side of the selective reduction type catalyst and on the downstream side of the oxidation catalyst. A urea water injection device provided on the upstream side of the selective reduction type catalyst and downstream of the fine particle collection filter and injecting urea water into the exhaust pipe, and a storage unit for storing the liquid allow the liquid to be pumped. It has a pump that pumps up and sends it to the heat exchange unit, and a drive control device that controls the drive of the pump. The heat exchange unit is provided on the upstream side of the oxidation catalyst, and the gas pipe. The downstream end communicates with the exhaust pipe on the downstream side of the fine particle collection filter and on the upstream side of the urea water injection device, and the drive control device is the oxidation catalyst after the start of the internal combustion engine. When the temperature of the exhaust gas flowing on the upstream side exceeds the lower limit value at which the liquid vaporizes, the driving of the pump is started, and after the driving of the pump is started, it is on the downstream side of the fine particle collection filter. When the temperature of the exhaust gas flowing upstream of the selective reduction type catalyst exceeds the lower limit value at which the selective reduction type catalyst is activated, the driving of the pump is stopped .

According to the present disclosure, the NOx purification rate of the selective reduction catalyst can be improved.

Schematic diagram showing an example of the configuration of the aftertreatment device according to the embodiment of the present disclosure. A flowchart showing an example of the operation of the drive control device according to the embodiment of the present disclosure.

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

First, the configuration of the aftertreatment device 1 according to the embodiment of the present disclosure will be described with reference to FIG. FIG. 1 is a diagram schematically showing an example of the configuration of the aftertreatment device 1 of the present embodiment.

The aftertreatment device 1 is a device mounted on a vehicle to purify exhaust gas discharged from an internal combustion engine (not shown). In the present embodiment, the case where the internal combustion engine is a diesel engine will be described as an example, but the present invention is not limited to this, and the internal combustion engine may be, for example, a gasoline engine. Further, the aftertreatment device 1 can be applied not only to the internal combustion engine of a vehicle but also to a ship or a stationary internal combustion engine.

As shown in FIG. 1, the aftertreatment device 1 includes an exhaust pipe 2, a DOC (Diesel Oxidation Catalyst) 3, a DPF (Diesel Particulate Filter) 4, an SCR (Selective Catalytic Reduction) 5, an ASC (Ammonia Slip Catalyst) 6, and a urea. It has a water injection device 7, temperature sensors 8 and 9, a storage unit 10, a pump 11, a liquid pipe 12a, a heat exchange unit 12b, a gas pipe 12c, and a drive control device 100.

The upstream end (left side in the drawing) of the exhaust pipe 2 is connected to the downstream end of the exhaust manifold 13 of the diesel engine. The exhaust gas discharged from the exhaust manifold 13 flows through the exhaust pipe 2 from the left side to the right side in the figure. In FIG. 1, the solid arrow shown in the exhaust pipe 2 indicates the flow of exhaust gas.

The exhaust pipe 2 is provided with DOC3, DPF4, SCR5, and ASC6 in order from the upstream side thereof.

DOC3 is a catalyst that oxidizes nitric oxide (NO) and hydrocarbons (HC) in exhaust gas. This produces nitrogen dioxide (NO ₂ ) and water. DOC3 corresponds to an example of an "oxidation catalyst".

DPF4 is a filter that collects and removes particulate matter (PM) in exhaust gas. DPF4 corresponds to an example of a "fine particle collection filter".

SCR5 is a catalyst that reduces NOx in exhaust gas to nitrogen by ammonia generated from urea water (details will be described later). SCR5 corresponds to an example of a "selective reduction catalyst". In this embodiment, the case where SCR is used will be described, but the present invention is not limited to this, and other selective reduction catalysts may be used.

ASC6 is a catalyst that oxidizes and decomposes ammonia that cannot be consumed by SCR5. This can prevent ammonia from being discharged into the atmosphere.

The exhaust gas that has passed through the SCR5 and ASC6 is discharged to the outside of the vehicle from the discharge port (not shown).

Note that DOC3, DPF4, and ASC6 may not be provided. Further, instead of the DOC3, another catalyst such as an LNT (Lean NOx Trap) catalyst may be provided.

The urea water injection device 7 is a dosing module provided on the upstream side of the SCR 5 and injects urea water into the exhaust pipe 2. Ammonia is generated from the injected urea water, and this ammonia is supplied to SCR5. The urea water injection amount and the injection timing are controlled by a urea water injection control device (not shown).

The temperature sensor 8 detects the temperature of the exhaust gas flowing upstream of the DOC 3 (hereinafter referred to as the DOC upstream temperature) at any time. Then, the temperature sensor 8 outputs a signal indicating the detected upstream temperature of the DOC (see the arrow of the alternate long and short dash line in the figure) to the determination unit 110 of the drive control device 100.

The temperature sensor 9 detects the temperature of the exhaust gas flowing downstream of the DPF 4 and upstream of the SCR 5 (hereinafter referred to as the SCR upstream temperature) at any time. Then, the temperature sensor 9 outputs a signal indicating the detected upstream temperature of the SCR (see the arrow of the alternate long and short dash line in the figure) to the determination unit 110 of the drive control device 100 described later.

The storage unit 10 stores the liquid. In the present embodiment, the case where the liquid is water will be described as an example, but the present embodiment is not limited thereto. For example, the liquid may be urea water.

When the pump 11 receives a drive start instruction signal (see the arrow of the alternate long and short dash line in the figure) from the control unit 120 of the drive control device 100 described later, the pump 11 starts driving. As a result, the water stored in the storage unit 10 is pumped up and sent out to the heat exchange unit 12b (details will be described later) via the liquid pipe 12a (details will be described later).

Further, when the pump 11 receives a drive stop instruction signal (see the arrow of the alternate long and short dash line in the figure) from the control unit 120 of the drive control device 100 described later, the pump 11 stops the drive. As a result, the pumping of the water stored in the storage unit 10 is stopped.

The liquid pipe 12a is a flow path through which water pumped by the pump 11 flows. In FIG. 1, the dotted arrow shown in the liquid pipe 12a indicates the flow of water.

The upstream end of the liquid pipe 12a is connected to the storage unit 10, and the downstream end of the liquid pipe 12a is connected to the upstream end of the heat exchange unit 12b described later. Further, in the liquid pipe 12a, the pump 11 described above is provided between the storage unit 10 and the heat exchange unit 12b.

The heat exchange portion 12b is provided on the downstream side of the exhaust manifold 13 and on the upstream side of the DOC3. The upstream end of the heat exchange unit 12b is connected to the downstream end of the liquid pipe 12a, and the downstream end of the heat exchange unit 12b is connected to the upstream end of the gas pipe 12c described later.

The heat exchange unit 12b exchanges heat between the exhaust gas discharged from the exhaust manifold 13 and the water flowing in from the liquid pipe 12a to vaporize the water.

The heat exchange portion 12b is provided so as to be in contact with the outer surface of the exhaust pipe 2. Further, the heat exchange unit 12b is a coil type heat exchanger spirally wound around the outer periphery of the exhaust pipe 2.

The gas pipe 12c is a flow path through which water vapor generated by heat exchange in the heat exchange unit 12b flows. In FIG. 1, the dotted arrow shown in the gas pipe 12c indicates the flow of water vapor.

The upstream end of the gas pipe 12c is connected to the downstream end of the heat exchange portion 12b. The downstream end of the gas pipe 12c is connected to the exhaust pipe 2 on the downstream side of the DPF 4 and on the upstream side of the urea water injection device 7. Therefore, the gas pipe 12c communicates with the exhaust pipe 2. Therefore, the water vapor flowing through the gas pipe 12c is mixed with the exhaust gas flowing through the exhaust pipe 2.

The liquid pipe 12a, the heat exchange unit 12b, and the gas pipe 12c may be configured separately or integrally.

The drive control device 100 is a device that controls the drive of the pump 11 (in other words, the start / stop of water supply).

The drive control device 100 has a determination unit 110 and a control unit 120. Although not shown, the drive control device 100 includes, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) containing a control program, a working memory such as a RAM (Random Access Memory), and a working memory. It has a communication circuit and the like. Each function of the determination unit 110 and the control unit 120 is realized by the CPU executing the control program.

The determination unit 110 determines whether or not the DOC upstream temperature detected by the temperature sensor 8 exceeds a predetermined first threshold value.

The first threshold value is the lower limit of the temperature at which the liquid supplied to the heat exchange unit 12b is vaporized. In the present embodiment, the liquid supplied to the heat exchange unit 12b is water, so for example, the first threshold value is 100 ° C.

Further, the determination unit 110 determines whether or not the SCR upstream temperature detected by the temperature sensor 9 exceeds a predetermined second threshold value.

The second threshold is the lower limit of the temperature range in which SCR5 is active. For example, the second threshold is 200 ° C.

For example, after the diesel engine is started, the control unit 120 starts driving the pump 11 when the determination unit 110 determines that the DOC upstream temperature exceeds the first threshold value. Specifically, the control unit 120 outputs a drive start instruction signal for instructing the start of driving of the pump 11 to the pump 11. As described above, the pump 11 that has received the drive start instruction signal starts driving.

Further, the control unit 120 stops the drive of the pump 11 when the determination unit 110 determines that the SCR upstream temperature exceeds the second threshold value after the start of the drive of the pump 11. Specifically, the control unit 120 outputs a drive stop instruction signal for instructing the stop of the drive of the pump 11 to the pump 11. As described above, the pump 11 that has received the drive stop instruction signal stops driving.

The configuration of the aftertreatment device 1 of the present embodiment has been described above.

Next, the operation of the drive control device 100 of the present embodiment will be described with reference to FIG. FIG. 2 is a flowchart showing an example of the operation of the drive control device 100 of the present embodiment. The operation shown in FIG. 2 is started, for example, when the diesel engine is started.

First, the determination unit 110 determines whether or not the temperature on the upstream side of the DOC exceeds the first threshold value (step S101).

If the DOC upstream temperature does not exceed the first threshold (step S101: NO), the flow returns to step S101.

On the other hand, when the DOC upstream temperature exceeds the first threshold value (step S101: YES), the control unit 120 starts driving the pump 11 (step S102).

As a result, the water stored in the storage unit 10 is pumped up. The water flows from the liquid pipe 12a into the heat exchange section 12b and becomes water vapor by heat exchange with the exhaust gas flowing through the exhaust pipe 2. The water vapor flows from the heat exchange unit 12b into the gas pipe 12c, is discharged into the exhaust pipe 2, and mixes with the exhaust gas.

After the driving of the pump 11 is started, the determination unit 110 determines whether or not the SCR upstream temperature exceeds the second threshold value (step S103).

If the SCR upstream temperature does not exceed the second threshold (step S103: NO), the flow returns to step S103. In this case, the driving of the pump 11 is continued.

On the other hand, when the SCR upstream temperature exceeds the second threshold value (step S103: YES), the control unit 120 stops driving the pump 11 (step S104).

As a result, the pumping of water from the storage unit 10 is stopped, and the supply of water to the heat exchange unit 12b is stopped.

The operation of the drive control device 100 of the present embodiment has been described above.

As described in detail so far, the post-treatment device 1 of the present embodiment exchanges heat between the exhaust gas flowing through the exhaust pipe 2 and water, and the heat exchange unit 12b that generates water vapor and the water vapor are SCR5. It has a gas pipe 12c for discharging to the exhaust pipe 2 on the upstream side. As a result, the steam and the exhaust gas are mixed, and the temperature of the exhaust gas rises due to the heat of the steam. Therefore, even when the diesel engine is started, the SCR5 is activated and the NOx purification rate of the SCR5 can be improved.

It should be noted that the present disclosure is not limited to the above-described embodiment, and can be appropriately modified and implemented without departing from the spirit of the present disclosure. Hereinafter, each modification will be described.

[Modification 1]
The installation position of the heat exchange unit 12b is not limited to the position shown in FIG. The heat exchange unit 12b may be provided on the downstream side of the internal combustion engine and on the upstream side of the SCR5. However, as shown in FIG. 1, when the heat exchange unit 12b is provided directly under the internal combustion engine, the water supplied to the heat exchange unit 12b can exchange heat with the high temperature exhaust gas, so that higher temperature steam is generated. Can be made to. Therefore, the heat exchange unit 12b may be provided on, for example, the exhaust manifold 13.

Further, the shape of the heat exchange portion 12b is not limited to the coil type shown in FIG. 1, and may be any other shape.

[Modification 2]
The connection position between the downstream end of the gas pipe 12c and the exhaust pipe 2 is not limited to the position shown in FIG. 1, and may be on the upstream side of the SCR 5. However, as shown in FIG. 1, when the connection position is on the upstream side of the urea water injection device 7, the temperature of the exhaust gas can be raised on the upstream side of the position where the urea water is injected, so that urea can be raised. Can accelerate the hydrolysis of urea.

[Modification 3]
A heat insulating material may be provided so as to cover the outer periphery of the gas pipe 12c. As a result, it is possible to suppress a decrease in the temperature of the water vapor flowing through the gas pipe 12c.

[Modification 4]
In the embodiment, the drive stop condition of the pump 11 is the case where the SCR upstream temperature exceeds the second threshold value, but the drive stop condition of the pump 11 may be further added.

For example, in the aftertreatment device 1 shown in FIG. 1, a sensor that detects the temperature of water vapor flowing through the gas pipe 12c (hereinafter referred to as water vapor temperature) and a side downstream of DPF4 and upstream side of the downstream end of the gas pipe 12c. A sensor for detecting the temperature of the exhaust gas (hereinafter referred to as the temperature directly under the DPF) is provided. The detection results of these sensors are output to the determination unit 110.

After the driving of the pump 11 is started, the determination unit 110 determines whether or not the temperature directly below the DPF is higher than the steam temperature.

When the temperature directly below the DPF is not higher than the steam temperature, the control unit 120 continues to drive the pump 11. On the other hand, when the temperature directly below the DPF is higher than the steam temperature, the control unit 120 stops the driving of the pump 11.

According to this modification, it is possible to prevent the exhaust gas from being cooled by steam having a lower temperature than that.

Each modification example has been described above. In addition, each modification may be carried out in combination as appropriate.

The post-treatment apparatus of the present disclosure is useful in all techniques for purifying exhaust gas using an SCR catalyst.

1 Post-treatment device 2 Exhaust pipe 3 DOC
4 DPF
5 SCR
6 ASC
7 Urea water injection device 8, 9 Temperature sensor 10 Storage section 11 Pump 12a Liquid piping 12b Heat exchange section 12c Gas piping 13 Exhaust manifold 100 Drive control device 110 Judgment section 120 Control section

Claims (3)

An exhaust gas aftertreatment device in which a selective reduction catalyst is provided in the exhaust pipe through which the exhaust gas discharged from the internal combustion engine flows.
A heat exchange unit that is provided by spirally winding the outer periphery of the exhaust pipe and flows on the downstream side of the internal combustion engine and upstream of the selective reduction type catalyst to exchange heat between the exhaust gas and the liquid.
The gas pipe through which the gas generated by the heat exchange flows, and
An oxidation catalyst provided on the upstream side of the selective reduction catalyst and
A fine particle collection filter provided on the upstream side of the selective reduction catalyst and on the downstream side of the oxidation catalyst.
A urea water injection device provided on the upstream side of the selective reduction catalyst and on the downstream side of the fine particle collection filter and injecting urea water into the exhaust pipe.
A pump that pumps the liquid from the storage unit that stores the liquid and sends it to the heat exchange unit.
It has a drive control device that controls the drive of the pump, and has.
The heat exchange unit is
It is provided on the upstream side of the oxidation catalyst and is provided.
The downstream end of the gas pipe
It communicates with the exhaust pipe on the downstream side of the fine particle collection filter and on the upstream side of the urea water injection device.
The drive control device is
After the internal combustion engine is started, when the temperature of the exhaust gas flowing upstream of the oxidation catalyst exceeds the lower limit for vaporization of the liquid, the pump is started to be driven.
When the temperature of the exhaust gas flowing downstream of the fine particle collection filter and upstream of the selective reduction catalyst after the start of driving the pump exceeds the lower limit of activation of the selective reduction catalyst. Stop driving the pump,
Post-processing device. The drive control device is
When the temperature of the exhaust gas flowing downstream of the fine particle collection filter and upstream of the downstream end of the gas pipe is higher than the temperature of the gas flowing through the gas pipe, the driving of the pump is stopped.
The post-processing device according to claim 1 . A heat insulating material is provided on the outer periphery of the gas pipe.
The post-processing apparatus according to claim 1 or 2 .

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