JP6729008B2 - Exhaust purification device - Google Patents

Description

The present invention relates to an exhaust emission control device, and more particularly to an exhaust emission control device provided with an injector that injects a reducing agent solution into an exhaust pipe.

Conventionally, as this kind of exhaust emission control device, urea water is injected from an injector into the exhaust pipe, and ammonia (NH ₃ ) generated by hydrolysis from urea water is used as a reducing agent to reduce nitrogen compounds (hereinafter referred to as “nitrogen compound”) contained in the exhaust gas. , NOx) are known to be provided with a selective reduction catalyst (hereinafter referred to as SCR catalyst) (for example, see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 2015-197084 JP, 2015-152009, A

By the way, a general exhaust pipe is formed by bending a plurality of places for reasons such as space restrictions. If an injector is provided on the outside of the bent portion or on the downstream side of the outside of the bent portion, the spray of urea water injected from the injector is affected by the exhaust gas that is drifted to the outside of the bent portion, and the urea water is discharged. May adhere to the inner wall of the exhaust pipe.

In particular, when urea water adheres to the inner wall of the exhaust pipe and accumulates during low load operation of an engine with low exhaust gas temperature, the acid generated in the process of evaporation (vaporization) of urea water with the subsequent rise in exhaust gas temperature There is a problem that causes corrosion of the exhaust pipe.

The technique of the present disclosure aims to effectively prevent corrosion of an exhaust pipe caused by evaporation of urea water.

The technology of the present disclosure includes an exhaust pipe for circulating exhaust gas discharged from an internal combustion engine, an injector provided in the exhaust pipe for injecting a reducing agent solution into the exhaust pipe, and an exhaust gas downstream side of the injector. A carrier that is provided in the exhaust pipe and carries a catalyst that purifies the exhaust gas using the reducing agent solution; and the exhaust gas temperature that changes according to the operating state of the internal combustion engine is the reducing agent solution. The injector is injected into the exhaust pipe so that the reducing agent solution is injected from the injector at an angle at which the reducing agent solution does not adhere to the inner wall of the exhaust pipe with respect to the exhaust gas flow when reaching a predetermined vaporization temperature for starting evaporation. It is characterized in that it is obliquely attached at a predetermined angle.

Further, the exhaust pipe includes a bent portion in at least a part thereof, the injector is attached to the outside of the bent portion of the bent portion, and the reducing agent solution in the exhaust pipe downstream of the bent portion with respect to the pipe axis direction. May be sprayed diagonally.

Further, the injector injects urea water as the reducing agent solution, and the catalyst purifies nitrogen compounds in exhaust gas by using ammonia generated by hydrolysis of the urea water by exhaust heat as a reducing agent. It may be a catalytic reduction catalyst.

According to the technique of the present disclosure, it is possible to effectively prevent corrosion of an exhaust pipe caused by evaporation of urea water.

1 is a schematic overall configuration diagram showing an exhaust emission control device according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a state in which urea water is injected from an injector when the exhaust gas temperature reaches a vaporization temperature at which evaporation of urea water is started in the exhaust emission control device according to the embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a state in which urea water is injected from the injector during high load operation of the engine in the exhaust emission control device according to the embodiment of the present invention.

An exhaust emission control device according to an embodiment of the present invention will be described below with reference to the accompanying drawings. The same parts are designated by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

As shown in FIG. 1, an upstream pipe 12 is connected to an exhaust manifold 11 of a diesel engine (hereinafter simply referred to as engine) 10. The upstream casing 20 is connected to the downstream end of the upstream pipe 12, and the downstream casing 50 is disposed downstream of the upstream casing 20. Further, a discharge pipe 13 for discharging exhaust gas to the atmosphere is connected to the downstream end of the rear casing 40.

The front casing 20 and the rear casing 50 are formed in a substantially cylindrical shape, and are arranged in parallel so that their axes are parallel to each other. The front casing 20 and the rear casing 50 are connected to each other by the first to third connection pipes 30 to 32 arranged between them.

A first oxidation catalyst 21 and a filter 22 are housed inside the front casing 20 in order from the exhaust upstream side via cushion members 23 and 24.

The first oxidation catalyst 21 is formed, for example, by supporting an oxidation catalyst component on the surface of a ceramic carrier such as a honeycomb structure. When the unburned fuel is supplied by the post injection of the engine 10 or the exhaust pipe injection of an exhaust pipe injector (not shown) provided in the upstream pipe 12, the first oxidation catalyst 21 oxidizes the unburned fuel to raise the exhaust temperature.

The filter 22 is formed by, for example, arranging a large number of cells partitioned by porous partition walls along the flow direction of exhaust gas and plugging upstream and downstream sides of these cells alternately. .. The filter 22 collects the particulate matter (PM) in the exhaust gas in the pores and the surface of the partition walls, and when the estimated PM deposition amount reaches a predetermined amount, the filter forced regeneration is performed to burn and remove the PM deposition estimated amount.

The first connecting pipe 30 is an elbow pipe bent in a substantially C-shape whose diameter decreases from the upstream end toward the downstream end, and the downstream end of the front casing 20 is connected to the upstream end thereof. Further, the upstream end of the second connection pipe 31 is connected to the downstream end of the first connection pipe 30. Further, a urea water injector 43 that forms a part of the urea water injection device 40 is attached to the downstream side bent portion 30A of the first connection pipe 30.

The urea water injection device 40 injects (sprays) urea water toward the inside of the urea water tank 41 that stores the urea water, the urea water pump 42 that pumps the urea water from the urea water tank 41, and the second connection pipe 31. And a urea water injector 43. The urea water injected from the urea water injector 43 into the second connection pipe 31 is hydrolyzed by exhaust heat to be produced as ammonia (NH ₃ ), and is supplied to the SCR catalyst 51 on the downstream side as a reducing agent.

The second connection pipe 31 is a substantially cylindrical straight pipe, and is arranged so that its axis is parallel to the axes of the front casing 20 and the rear casing 50. Further, the downstream end of the second connection pipe 31 is connected to the upstream end of the third connection pipe 32.

The third connection pipe 32 is an elbow pipe bent in a substantially C shape whose diameter increases from the upstream end toward the downstream end, and the upstream end of the lower casing 50 is connected to the downstream end thereof.

Inside the rear casing 50, the SCR catalyst 51 and the second oxidation catalyst 52 are housed in order from the exhaust upstream side via the cushion members 53 and 54.

The SCR catalyst 51 is formed by supporting zeolite or the like on the surface of a ceramic carrier such as a honeycomb structure. The SCR catalyst 51 adsorbs ammonia supplied as a reducing agent from the urea water injector 43, and selectively reduces and purifies NOx from the exhaust gas passing by the adsorbed ammonia.

The second oxidation catalyst 52 is formed, for example, by supporting an oxidation catalyst component or the like on the surface of a ceramic carrier such as a honeycomb structure, and has a function of oxidizing ammonia that has slipped downstream from the SCR catalyst 51. ..

Next, the details of the mounting structure of the urea water injector 43 of the present embodiment will be described based on FIG.

In the present embodiment, the urea water injector 43 is provided on the outside of the bent portion of the first connection pipe 30 with a bolt or the like not shown so that the injection axis thereof is inclined at a predetermined angle with respect to the pipe axis direction of the second connection pipe 31. It is attached to 30A.

More specifically, the exhaust gas when the exhaust gas temperature that changes according to the operating state of the engine 10 reaches a predetermined temperature (for example, about 250 to 300° C., hereinafter simply referred to as the vaporization temperature) at which the evaporation of the urea water is started. With respect to the gas flow, the urea water injector 43 causes the spray of urea water that is injected into the second connection pipe 31 to form an angle between the injection axis and the pipe axis direction of the second connection pipe 31. It is attached to the outside 30A of the bent portion so that the inclination angle is such that the inner wall 31A can be advanced linearly without being attached to the inner wall 31A. The predetermined angle may be set to an optimum value depending on the specifications of the engine 10 and the inner diameter of each exhaust pipe.

In this way, by setting the angle between the injection axis of the urea water injector 43 and the tube axis direction of the second connection pipe 31, the engine temperature at which the exhaust gas temperature becomes a predetermined vaporization temperature or lower than the vaporization temperature. In the low load operation state, even if the spray of urea water is affected by the exhaust gas that is drifted to the outside 30A of the bent portion, the spray of urea water does not adhere to the inner wall 31A of the second connecting pipe 31 It follows that it goes along X substantially linearly.

On the other hand, in the high load operation state of the engine 10 in which the exhaust gas temperature is higher than the vaporization temperature range and the exhaust flow velocity is high, as shown in FIG. 3, the spray of urea water injected from the urea water injector 43 bends. Due to the influence of the exhaust gas that is biased to the outside 30A, the second connection pipe 31 is pushed toward the inner wall 31A side. However, during high-load operation of the engine 10 where the exhaust gas temperature becomes high, the hydrolysis of the urea water is promoted by the exhaust heat, so most of the urea water injected from the urea water injector 43 is on the inner wall 31A. Ammonia is generated before it is attached and is supplied to the SCR catalyst 51 on the downstream side.

As described above in detail, according to the exhaust emission control device of the present embodiment, the exhaust gas flow when the exhaust gas temperature that changes according to the operating state of the engine 10 reaches the vaporization temperature at which the evaporation of urea water starts On the other hand, by attaching the urea water injector 43 to the outside 30A of the bent portion so that the urea water spray is sprayed at an angle that does not adhere to the inner wall 31A of the second connection pipe 31, the urea water spray is sprayed on the inner wall 31A. Without adhering, it advances linearly in the second connection pipe 31 along the pipe axis direction X. As a result, it is possible to prevent the urea water from adhering to the inner wall 31A, and it is possible to effectively prevent the corrosion of the second connecting pipe 31 caused by the acid generated in the process of evaporating the urea water.

It should be noted that the present invention is not limited to the above-described embodiments, and can be appropriately modified and carried out without departing from the spirit of the present invention.

For example, although the urea water injector 43 has been described as being provided on the outside 30A of the bent portion, it may be provided on the second connection pipe 31 located immediately downstream of the outside 30A of the bent portion. In this case, the urea water is sprayed at an angle that does not adhere to the inner wall 31A of the second connection pipe 31 with respect to the flow of the exhaust gas that is biased to the outside 30A of the bent portion and flows into the second connection pipe 31. The water injector 43 may be obliquely attached to the second connection pipe 31 at a predetermined angle.

Further, the NOx catalyst is not limited to the SCR catalyst 51 and may be a NOx occlusion reduction type catalyst. In this case, the exhaust pipe injector arranged upstream of the NOx occlusion reduction type catalyst may be attached at an angle at which the spray of unburned fuel is injected without adhering to the inner wall of the exhaust pipe.

Further, the engine 10 is not limited to a diesel engine, but can be widely applied to other engines such as a gasoline engine.

10 Engine 11 Exhaust Manifold 12 Upstream Pipe 20 Pre-stage Casing 21 First Oxidation Catalyst 22 Filter 30 First Connection Pipe 31 Second Connection Pipe 32 Third Connection Pipe 40 Urea Water Injection Device 41 Urea Water Tank 42 Urea Water Pump 43 Urea Water Injector 50 Rear Casing 51 SCR Catalyst 52 Second Oxidation Catalyst

Claims (1)

An exhaust pipe that circulates the exhaust gas emitted from the internal combustion engine;
An injector that is provided in the exhaust pipe and injects urea water into the exhaust pipe,
Wherein provided in the exhaust pipe of the exhaust downstream side of the injector, a carrier carrying a selective reduction catalyst for reducing and purifying nitrogen compounds in the exhaust gas of ammonia generated from the urea water as a reducing agent, a Prepare,
The exhaust pipe is provided with a bent pipe portion on the upstream side of the carrier and a linear straight pipe portion connected to the downstream side of the bent pipe portion,
The injector is attached to the outside of the bent portion of the bent tube portion, and the urea water is injected into the straight tube portion obliquely with respect to the pipe axis direction of the straight tube portion,
The angle formed by the injection axis of the injector and the tube axis direction,
When the temperature of the exhaust gas discharged from the internal combustion engine and biased to the outside of the bent pipe and flowing to the outside reaches a predetermined vaporization temperature for starting the evaporation of the urea water , it is injected into the straight pipe part. An exhaust emission control device, characterized in that the spray of the urea water is set to an angle that advances the spray of urea water along the pipe axis direction without adhering to the inner wall of the straight pipe portion .

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