JP6804333B2 - Exhaust gas treatment equipment - Google Patents

Description

The present invention relates to an exhaust gas treatment device.

As an exhaust gas treatment device for a diesel engine, an SCR (Selective Catalytic Reduction) system is used to remove NOx (nitrogen oxides) in the exhaust gas. The SCR system uses urea as the reducing agent, in which case the vehicle is equipped with a urea water tank. Urea water is sprayed into the exhaust pipe, and NOx and ammonia (NH ₃ ) generated from urea are mixed. Then, when the exhaust gas of the diesel engine passes through the catalyst device provided in the exhaust pipe, a NOx reduction reaction occurs. As a result, nitrogen, water and carbon dioxide are generated.

Urea water is sprayed by a spray nozzle provided on the upstream side of the catalyst. Conventionally, the amount of urea water sprayed is adjusted to a required amount according to the operating state of the engine and sprayed into the exhaust pipe.

Patent Document 1 below describes that the exhaust gas temperature is controlled to be raised from the engine start to the urea hydrolysis temperature to shorten the time from the engine start until urea water can be added. ..

Japanese Unexamined Patent Publication No. 2010-116858

When the urea water sprayed into the exhaust pipe collides with the inner wall of the pipe at a low temperature of 200 ° C. or lower, urea or other solid matter may be deposited on the inner wall of the pipe. When urea or the like precipitates on the inner wall of the pipe and accumulates, the evaporation of the sprayed urea water and the mixing with the exhaust gas become insufficient, so that the NOx purification performance deteriorates, and the engine performance due to the increase in back pressure and the pipe blockage. May decrease.

Conventionally, it is common to measure the temperature at the inlet of the exhaust gas catalyst device flowing in the exhaust pipe with a temperature sensor, and the precipitation of urea is prevented based on the measured exhaust gas temperature. However, since the temperature of the inner wall of the pipe is not directly measured, whether or not the inner wall of the pipe has reached the temperature at which urea does not precipitate is determined by determining the actual pipe temperature when the engine is driven, based on the exhaust gas temperature and experimental results. I'm guessing. Therefore, the spraying period of urea water is expected to be limited so that the temperature does not decrease, and there is a period during which NOx cannot be removed.
Moreover, since only the exhaust gas temperature is measured, it is not possible to detect that the sprayed urea water droplets unexpectedly adhere to the pipe surface.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust gas treatment apparatus capable of reliably preventing precipitation of urea in an exhaust pipe and improving denitration performance. ..

The exhaust gas treatment device according to one aspect of the present invention is provided in an exhaust pipe through which exhaust gas flows, and is provided with a nozzle for spraying urea water into the exhaust pipe and a nozzle in the exhaust pipe on the downstream side of the exhaust gas flow. It has a catalyst that promotes the reduction reaction of the nitrogen oxide contained in the exhaust gas by ammonia generated from the urea contained in the urea water, and between the catalyst portion through which the exhaust gas flows and the nozzle and the catalyst portion. In the memory, data relating to the relationship between the temperature measuring unit that measures the temperature distribution of the inner wall surface of the exhaust pipe, the operating conditions of the engine that discharges the exhaust gas, and the temperature distribution of the inner wall surface of the exhaust gas is recorded in advance. Based on the data recorded in the storage unit and the storage unit, and the temperature distribution of the inner wall of the exhaust pipe measured by the temperature measuring unit during the operation of the engine, the exhaust pipe of the exhaust pipe during the operation of the engine. Based on the judgment unit that determines the temperature of the inner wall, the mixing unit that is installed on the downstream side of the exhaust gas flow from the nozzle and mixes the exhaust gas and the urea water, and the result determined by the determination unit. A spray control unit for adjusting the mixing unit is provided.

According to this configuration, the temperature distribution of the inner wall of the exhaust pipe between the nozzle and the catalyst unit can be measured by the temperature measuring unit provided between the nozzle and the catalyst unit.
Further, according to this configuration, the temperature distribution of the inner wall of the exhaust pipe measured by the temperature measuring unit during the operation of the engine is compared with the data recorded in advance in the storage unit, so that the exhaust pipe can be operated during the operation of the engine. It is possible to judge the level of temperature occurring on the inner wall.
Further, according to this configuration, since the mixing unit is adjusted based on the temperature distribution of the inner wall of the exhaust pipe measured by the temperature measuring unit, the temperature distribution of the inner wall of the exhaust pipe can be changed.

In the above embodiment, a storage unit in which data relating to the relationship between the operating conditions of the engine that discharges the exhaust gas and the temperature distribution of the inner wall of the exhaust pipe is recorded in advance, the data recorded in the storage unit, and the data. Further provided with a determination unit for determining the temperature of the inner wall of the exhaust pipe during operation of the engine based on the temperature distribution of the inner wall of the exhaust pipe measured by the temperature measuring unit during operation of the engine. May be good.

In the above embodiment, the spray control unit, based on the result of the determination by the determination unit, the nozzle may be adjusted to spray amount of the urea water to be sprayed.

According to this configuration, the amount of urea water sprayed by the nozzle is adjusted based on the temperature distribution of the inner wall of the exhaust pipe measured by the temperature measuring unit, so that the precipitation of urea can be reliably prevented while being prevented. The removal performance of nitrogen oxides can be improved.

In the above aspect, a warning signal regarding urea precipitation on the inner wall of the exhaust pipe may be output based on the result determined by the determination unit.

According to this configuration, for example, when the temperature distribution of the inner wall of the exhaust pipe is maintained below a predetermined temperature, it is informed that urea may be precipitated or the possibility of precipitation is increasing. be able to. As a result, it is possible to promote the inspection regarding the precipitation of urea and prevent the occurrence of troubles.

In the above aspect, the temperature measuring unit has an optical fiber, and the optical fiber may be arranged in a plane along the inner wall of the exhaust pipe.

According to this configuration, the temperature distribution along the length direction of the optical fiber is measured, and since the optical fiber is arranged in a plane along the inner wall of the exhaust pipe, the temperature distribution of the inner wall surface of the exhaust pipe can be measured. Can be measured.

According to the present invention, precipitation of urea in the exhaust pipe can be reliably prevented, and denitration performance can be improved.

It is a block diagram which shows the engine and the exhaust gas treatment apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the temperature measuring part and the control part which concerns on one Embodiment of this invention. It is sectional drawing which shows the arrangement example of the optical fiber which concerns on one Embodiment of this invention. It is sectional drawing which shows the arrangement example of the optical fiber which concerns on one Embodiment of this invention.

As shown in FIG. 1, the exhaust gas treatment device 10 according to the embodiment of the present invention is a device that purifies the exhaust gas discharged from the diesel engine 1 (hereinafter referred to as "engine 1") and releases it to the atmosphere. It is provided in the exhaust pipe 9 through which the exhaust gas flows.

The engine 1 includes a supercharger 2. The supercharger 2 includes a turbine 3 and a compressor 4 coaxially connected to the turbine 3 and driven by the turbine 3. The air discharged from the compressor 4 of the supercharger 2 passes through the air pipe 5 and is supplied to the air cooler 6, and is cooled by the air cooler 6.

The air cooled by the air cooler 6 passes through the intake pipe 8 after the opening degree is controlled by the throttle valve 7, and is sucked into the engine 1 from the intake port provided for each cylinder.

In the engine 1, the high-pressure fuel accumulated by the common rail (accumulator) is sprayed from the fuel spray valve 26 provided for each cylinder at the spray timing and the spray amount controlled by the common rail control device 25. The sprayed high-pressure fuel mixes with the air sucked from the intake port and is burned.

The combustion gas generated by burning the fuel in the engine 1, that is, the exhaust gas, passes through the exhaust collecting pipe 11 in which the exhaust ports provided for each cylinder are gathered, and is supplied to the turbine 3 of the supercharger 2. The exhaust gas is discharged to the exhaust gas treatment device 10 through the exhaust pipe 9 after driving the turbine 3 and becoming a power source for the compressor 4.

Further, the EGR (exhaust gas recirculation) pipe 22 is branched from the middle of the exhaust gas recirculation pipe 11, and a part of the exhaust gas (EGR gas) passes through the EGR pipe 22 and is cooled by the EGR cooler 23, and the EGR gas is discharged. , The flow rate is controlled by the EGR valve 24. The EGR gas that has passed through the EGR pipe 22 joins the air in the intake pipe 8 on the downstream side of the throttle valve 7.

The exhaust gas treatment device 10 includes a DPF system 12 having a pre-stage oxidation catalyst (DOC: Diesel Oxidation Catalyst) 14 and a filter (DPF: Diesel particulate filter) 15, a urea spray nozzle 16, a mixer 17, an SCR catalyst 18, and a post-stage oxidation catalyst 19. The SCR system 13 and the like are provided.

The exhaust gas that has passed through the exhaust pipe 9 and is discharged to the exhaust gas treatment device 10 is supplied to the pre-stage oxidation catalyst 14. Then, the exhaust gas is supplied to the filter 15 after the hydrocarbon component (HC) and carbon monoxide (CO) are purified by the pre-stage oxidation catalyst 14, and the particulate matter (PM) is collected by the filter 15. To.

The pre-stage oxidation catalyst 14 and the filter 15 each have a shape in which a plurality of pores are aggregated (for example, a honeycomb structure), and exhaust gas can pass through. In the filter 15, the holes on the exhaust gas inlet side and the holes on the outlet side are alternately sealed, and the particulate matter is collected when the exhaust gas passes through the wall portion between the holes.

The pre-stage oxidation catalyst 14 is an example of a catalyst unit, and is provided in an exhaust pipe 9 to oxidize a hydrocarbon component in an exhaust gas that has passed through the pre-stage oxidation catalyst 14 by catalytic action. In the pre-stage oxidation catalyst 14, the temperature rises due to the heat generated by oxidation.

The filter 15 is provided in the exhaust pipe 9 and collects particulate matter in the exhaust gas. The filter 15 regenerates by burning the collected particulate matter. In the regeneration treatment, for example, unburned fuel is supplied to the inlet of the pre-stage oxidation catalyst 14 by late post spraying, and the reaction heat (oxidation heat generation) generated by oxidizing the hydrocarbon component in the pre-stage oxidation catalyst 14 causes the filter 15 to receive heat. This is done by burning the collected particulate matter. Water and carbon dioxide produced by burning particulate matter are discharged to the outside from the exhaust outlet pipe 21. As a result, the particulate matter collected by the filter 15 is removed, and the filter 15 is regenerated.

The exhaust gas after the particulate matter is collected by the filter 15 passes through the connecting pipe 30 and is supplied to the SCR catalyst 18 of the SCR system 13. Further, the connecting pipe 30 is provided with a urea spray nozzle 16, and the urea spray nozzle 16 sprays urea water on the exhaust gas. The mixer 17 is an example of a mixing unit, and mixes urea water and exhaust gas. The mixer 17 is composed of a plurality of vanes (blades) provided in a circumferential shape, and the angle of the vanes may be variable, for example.

In the connecting pipe 30, urea in urea water and NOx in exhaust gas are mixed, and NOx reduction reaction occurs in the SCR catalyst 18 and the post-oxidation catalyst 19 by ammonia (NH ₃ ) generated from urea, and nitrogen, water and dioxide are generated. Carbon is generated. The SCR catalyst 18 and the post-stage oxidation catalyst 19 have a structure in which exhaust gas can flow, and promote the reduction reaction of NOx by ammonia generated from urea.

The amount of urea water sprayed by the urea spray nozzle 16 is controlled by the control unit 41.

Ammonia produced by decomposition of urea water is once adsorbed on the SCR catalyst 18, and then reacts with NOx in the exhaust gas, and NOx is reduced to nitrogen. Further, the ammonia that could not react with the SCR catalyst 18 reacts with NOx in the subsequent oxidation catalyst 19, and NOx is reduced to nitrogen. Further, the ammonia adsorbed on the SCR catalyst 18 is desorbed from the SCR catalyst 18 as the temperature rises, and is oxidatively decomposed into nitrogen by the subsequent oxidation catalyst 19.

The temperature measuring unit 31 is installed on the downstream side of the mixer 17 in the connecting pipe 30. As shown in FIG. 2, the temperature measuring unit 31 includes an optical fiber 32, a light source unit 33, a light detecting unit 34, and a temperature calculating unit 35. Pulsed light is incident on the optical fiber 32 from the light source unit 33. The light incident on the optical fiber 32 travels while being scattered inside the optical fiber 32. Of the scattered light, Raman scattered light (Stosk light and anti-Stokes light) has temperature dependence. Therefore, by detecting the intensity of the Raman scattered light, the temperature distribution along the length direction of the optical fiber 32 can be calculated. The temperature calculation unit 35 calculates the temperature distribution along the length direction of the optical fiber 32 based on the intensity of the Raman scattered light detected by the light detection unit 34.

The optical fiber 32 is installed between the mixer 17 and the SCR catalyst 18, and measures the temperature of the inner wall surface of the connecting tube 30 and the temperature distribution of the inner wall surface of the connecting tube 30. The optical fiber 32 is arranged in a plane along the inner wall surface of the connecting tube 30.

For example, as shown in FIG. 3, the optical fiber 32 is arranged in one direction in the middle portion of the arrangement region of the optical fiber 32, for example, parallel to the axial direction of the connection tube 30, and is arranged at the end portion of the arrangement region. , The optical fiber 32 is folded back and arranged so as to be arranged in parallel at the intermediate portion. Further, the optical fiber 32 may be arranged in a spiral shape as shown in FIG. The central axis of the spirally arranged optical fiber 32 is parallel to the connecting tube 30.

The arrangement shape of the optical fiber 32 is recorded in advance in the memory 42, and the correspondence relationship between the position of the optical fiber 32 in the length direction and the position of the optical fiber 32 in the connection tube 30 is specified in advance. The memory 42 is an example of a storage unit. Thereby, the temperature distribution of the inner wall of the connecting tube 30 can be calculated based on the temperature distribution along the length direction of the optical fiber 32.

As shown in FIG. 2, the control unit 41 includes a memory 42, a determination unit 43, a spray control unit 44, and the like. The operation of the control unit 41 is realized by executing a pre-recorded program and using hardware resources such as a CPU.

The memory 42 is an example of a storage unit, and the memory 42 previously records data on the relationship between the operating conditions of the engine 1 that discharges exhaust gas and the temperature distribution of the inner wall of the connecting pipe 30 under normal conditions in each operating condition. Has been done.

The determination unit 43 actually operates the engine 1 based on the above-mentioned data recorded in the memory 42 and the temperature distribution of the inner wall of the connecting pipe 30 measured by the temperature measurement unit 31 during the actual operation of the engine 1. The height of the temperature distribution on the inner wall of the connecting pipe 30 at the time is determined.

The spray control unit 44 adjusts the amount of urea water sprayed by the urea spray nozzle 16 based on the result determined by the determination unit 43. For example, the spray control unit 44 adjusts the opening degree of the flow rate adjusting valve installed in the pipe that supplies urea water to the urea spray nozzle 16. Further, the spray control unit 44 may adjust the vane angle of the mixer 17 based on the result determined by the determination unit 43.

As a result, the amount of urea water sprayed by the urea spray nozzle 16 is adjusted based on the temperature distribution of the inner wall of the connecting pipe 30 measured by the temperature measuring unit 31, so that the precipitation of urea is reliably prevented. At the same time, the removal performance of nitrogen oxides can be improved.

The warning control unit 45 outputs a warning signal regarding urea precipitation on the inner wall of the connecting pipe 30 based on the result determined by the determination unit 43. For example, if the temperature distribution of the inner wall of the connecting pipe 30 is maintained below a predetermined temperature, the warning control unit 45 may have precipitated urea based on the result determined by the determination unit 43. Alternatively, a warning signal is output to the warning display unit as the possibility of precipitation is increasing. As a result, it is possible to promote an inspection regarding the precipitation of urea in the connecting pipe 30 and prevent the occurrence of troubles.

Next, the operation and the effect of the exhaust gas treatment device 10 according to the present embodiment will be described.
The temperature measuring unit 31 measures the temperature of the inner wall on the downstream side of the urea spray nozzle 16 and the mixer 17 in the connecting pipe 30.

Then, based on the data recorded in the memory 42 and the temperature distribution of the inner wall of the connecting pipe 30 measured by the temperature measuring unit 31 during the actual operation of the engine 1, the connecting pipe 30 during the actual operation of the engine 1 The height of the temperature distribution on the inner wall of the engine is judged.

When the temperature distribution of the inner wall of the connecting pipe 30 measured by the temperature measuring unit 31 during the actual operation of the engine 1 is measured and the temperature of the inner wall of the connecting pipe 30 is lowered, the urea sprayed by the urea spray nozzle 16 Reduce or stop the amount of water sprayed. Alternatively, when the temperature distribution of the inner wall of the connecting pipe 30 measured by the temperature measuring unit 31 during the actual operation of the engine 1 is measured and the temperature distribution of the inner wall of the connecting pipe 30 is biased, the vane of the mixer 17 is used. The temperature of the inner wall of the connecting pipe 30 is adjusted so that the temperature distribution is even.

As described above, according to the present embodiment, since the temperature of the inner wall of the connecting pipe 30 is directly measured instead of the temperature of the exhaust gas, the precipitation of urea on the inner wall of the pipe can be reliably prevented. Further, depending on the temperature of the inner wall of the connecting pipe 30, the presence of precipitates on the inner wall of the pipe and the possibility of precipitation of urea on the inner wall of the pipe can be detected with high accuracy. Further, in the conventional case of detecting the temperature of the exhaust gas, the spray amount and the spray period of urea water are expected to be limited so that the temperature does not decrease, but the spray period corresponds to the temperature decrease of the inner wall of the connecting pipe 30. Therefore, the spray amount and spray period of urea water can be increased. As a result, it is possible to improve the denitration performance of the exhaust gas treatment device 10.

1: Diesel engine (engine)
2: Supercharger 3: Turbine 4: Compressor 5: Air pipe 6: Air cooler 7: Throttle valve 8: Intake pipe 9: Exhaust pipe 10: Exhaust gas treatment device 11: Exhaust gas recirculation pipe 12: DPF system 13: SCR system 14: First stage oxidation catalyst 15: Filter 16: Urea spray nozzle 17: Mixer 18: SCR catalyst 19: Second stage oxidation catalyst 21: Exhaust outlet pipe 22: EGR pipe 23: EGR cooler 24: EGR valve 25: Common rail control device 26: Fuel Spray valve 30: Connection tube 31: Temperature measurement unit 32: Optical fiber 33: Light source unit 34: Light detection unit 35: Temperature calculation unit 41: Control unit 42: Memory 43: Judgment unit 44: Spray control unit 45: Warning control unit

Claims (4)

A nozzle provided in the exhaust pipe through which the exhaust gas flows and spraying urea water into the exhaust pipe,
The exhaust pipe has a catalyst provided downstream of the exhaust gas flow from the nozzle and promoting the reduction reaction of nitrogen oxides contained in the exhaust gas by ammonia generated from urea contained in the urea water. The catalyst part through which the exhaust gas flows and
A temperature measuring unit that measures the temperature distribution of the inner wall surface of the exhaust pipe between the nozzle and the catalyst unit,
A storage unit in which data relating to the relationship between the operating conditions of the engine that discharges the exhaust gas and the temperature distribution of the inner wall of the exhaust pipe is recorded in advance, and
Based on the data recorded in the storage unit and the temperature distribution of the inner wall of the exhaust pipe measured by the temperature measuring unit during the operation of the engine, the temperature of the inner wall of the exhaust pipe during the operation of the engine. Judgment part that judges the height of
A mixing section that is installed on the downstream side of the exhaust gas flow from the nozzle and mixes the exhaust gas and the urea water.
A spray control unit that adjusts the mixing unit based on the result determined by the determination unit, and
Exhaust gas treatment device equipped with. The exhaust gas treatment device according to claim 1, wherein the spray control unit adjusts the amount of the urea water sprayed by the nozzle based on the result determined by the determination unit. The exhaust gas treatment apparatus according to claim 1 , which outputs a warning signal regarding urea precipitation on the inner wall of the exhaust pipe based on the result determined by the determination unit. The exhaust gas treatment device according to any one of claims 1 to 3 , wherein the temperature measuring unit has an optical fiber, and the optical fiber is arranged in a plane along an inner wall of the exhaust pipe.

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