JP4308066B2 - Engine exhaust purification system - Google Patents

Description

  The present invention relates to a nitrogen oxide (NOx) discharged from a diesel engine, a gasoline engine or the like mounted on a moving vehicle, a reducing agent supplied from a reducing agent storage tank via a reducing agent supply pipe, and an exhaust upstream side of the reduction catalyst. More specifically, the present invention relates to an engine exhaust purification device that performs reduction removal by injection with an injection nozzle, and more specifically, hot water supply piping through which a heating fluid is passed from the outside along at least a portion of the reducing agent supply piping disposed in the reducing agent storage tank. The exhaust gas purifying apparatus for an engine is intended to rapidly thaw the reducing agent frozen in the reducing agent storage tank.

A conventional engine exhaust purification system includes a reduction catalyst disposed in an exhaust system of an engine, an injection nozzle provided to inject a reducing agent upstream of the exhaust of the reduction catalyst, and a reducing agent supply pipe to the injection nozzle. And a reducing agent storage tank capable of supplying the reducing agent stored inside to the injection nozzle. The reducing agent is supplied from the reducing agent storage tank to the injection nozzle via the reducing agent supply pipe, and the injection is performed. NOx is purified by injecting a reducing agent from the nozzle into the exhaust pipe on the exhaust upstream side of the reduction catalyst, and reducing the reaction of the injected reducing agent and NOx in the exhaust with the reduction catalyst (for example, Patent Document 1).
JP 2002-166130 A

  However, in such a conventional engine exhaust purification system, for example, an aqueous urea solution (urea water) as a reducing agent is reduced when the temperature falls below -20 ° C in winter in a cold region such as Hokkaido. There was a problem that it could not be supplied by freezing in the agent storage tank.

  In order to solve such a problem, a system in which the cooling water of the engine is guided to the reducing agent storage tank and the urea water is thawed by the cooling water warmed by the operation of the engine can be considered. However, in such a thawing system, it takes 20 to 30 minutes after the engine is started until the urea water is thawed and is ready to run.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an exhaust emission control device for an engine that addresses such problems and tries to rapidly thaw the reducing agent frozen in the reducing agent storage tank.

In order to achieve the above object, an exhaust emission control device for an engine according to the present invention is provided in an exhaust system of the engine and reduces and purifies nitrogen oxides in exhaust gas with a reducing agent, and an exhaust passage of the exhaust system. A reducing agent having an injection nozzle for injecting the reducing agent on the exhaust upstream side of the reduction catalyst and a reducing agent supply pipe for storing the reducing agent therein and supplying the reducing agent to the injection nozzle. a exhaust gas purification device for an engine, comprising: a storage tank, wherein the reducing agent storage tank, at least a tank portion which pledged in the body before Symbol reducing agent supply pipe hot water supply pipe passing heated fluid from the outside It is provided in a state where it is aligned and joined to the part .

With such a configuration, the reducing agent supply pipe that supplies the reducing agent from the reducing agent storage tank to the injection nozzle that injects the reducing agent to the exhaust upstream side of the reduction catalyst is inserted into at least the tank body of the reducing agent supply pipe. The heated fluid is passed from the outside through the hot water supply pipe provided along the portion and joined to the portion . As a result, at least the reductant that has been frozen in and around the reducing agent supply pipe in the tank body is thawed by the heating fluid in the hot water supply pipe.

The hot water supply pipe is disposed in the tank body so as to pass through a concentration detection unit of a concentration detection device that detects the concentration of the reducing agent. As a result, the frozen reducing agent around the concentration detecting unit of the concentration detecting device that detects the concentration of the reducing agent with the hot water in the hot water supply pipe is thawed.

  The hot water supply pipe is arranged meandering in the tank body. Thereby, the frozen reducing agent in the tank body is thawed by the hot water supply pipe meanderingly arranged in the tank body.

  The hot water supply pipe is provided with fins on the surface of a pipe body. Thereby, the heat transfer efficiency is improved by the fins provided on the surface of the tubular body.

  The heating fluid is an antifreeze. This prevents freezing even when the heated fluid is cooled.

According to the invention which concerns on Claim 1, it is equipped with the hot water supply piping which lets along the part inserted in the reducing agent storage tank of the reducing agent supply piping at least and joins the said portion, and lets a heating fluid pass from the outside. it can, can rapidly thawed frozen reducing agent inside and around the said portion of Motozai supply piping replaced with a heating fluid hot water supply pipe. Therefore, it is possible to injection state of a reducing agent in a short time after engine start.

According to the second aspect of the present invention, the hot water supply pipe is disposed so as to pass through the concentration detection unit of the concentration detection device that detects the concentration of the reducing agent, so that the concentration of the concentration detection device can be increased by the heated fluid. The frozen reducing agent around the detection unit can be thawed. Therefore, the frozen reducing agent can be rapidly thawed so that the reducing agent concentration can be detected in a short time after the engine is started.

  Furthermore, according to the invention which concerns on Claim 3, the hot water supply piping meandered and arrange | positioned in the tank main body, Therefore The frozen reducing agent in a tank main body can be thawed efficiently.

  Furthermore, according to the invention which concerns on Claim 4, the heat transfer efficiency can be improved with a fin by providing the fin on the surface of the tubular body of the hot water supply pipe. Therefore, the thawing speed of the reducing agent can be increased.

  According to the fifth aspect of the present invention, since the heating fluid is an antifreeze liquid, it is possible to prevent the frozen reducing agent from freezing even when the heating fluid cools during thawing.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram showing an embodiment of an engine exhaust gas purification apparatus according to the present invention. This engine exhaust purification device reduces and removes NOx discharged from a diesel engine, a gasoline engine or the like mounted on a moving vehicle using a reducing agent. The exhaust of the engine 1 using gasoline or light oil as fuel is discharged from the exhaust manifold 2 into the atmosphere via an exhaust pipe 3 serving as an exhaust passage. The exhaust purification device is provided in the middle of the exhaust pipe 3, and includes a reduction catalyst 4, an injection nozzle 5, and a reducing agent storage tank (hereinafter simply referred to as a storage tank 6).

  The reduction catalyst 4 is installed in the exhaust pipe 3. The reduction catalyst 4 reduces and purifies NOx in the exhaust gas passing through the exhaust pipe 3 with a reducing agent, and has a honeycomb-shaped cross section made of, for example, ceramic cordierite or Fe—Cr—Al heat resistant steel. A zeolite-type active component is supported on a monolith type catalyst carrier. Then, the active component supported on the catalyst carrier is activated by the supply of the reducing agent, and effectively purifies NOx in the exhaust gas into a harmless substance.

  An injection nozzle 5 is disposed on the exhaust upstream side of the reduction catalyst 4 inside the exhaust pipe 3. The injection nozzle 5 is for injecting a reducing agent, and injects and supplies the reducing agent into the exhaust pipe 3 together with pressure air supplied from a reducing agent supply device 7 controlled by an engine control unit (ECU) (not shown). It is supposed to be. Here, the tip of the injection nozzle 5 is assumed to extend toward the downstream side substantially in parallel with the flow direction A of the exhaust gas, but protrudes at a substantially right angle with the flow direction A of the exhaust gas in the exhaust pipe 3. It may be a thing. The reducing agent supply device 7 is supplied with urea water stored in a storage tank 6 described later through a reducing agent supply pipe 8. The injection nozzle 5 and the reducing agent supply device 7 constitute reducing agent supply means for supplying the reducing agent to the exhaust upstream side of the reduction catalyst 4.

The storage tank 6 includes a reducing agent supply pipe 8 for supplying the reducing agent to the reducing agent supply device 7 and a concentration detecting device 9 for detecting the concentration of the reducing agent. The reducing agent suction port 8a and the concentration detecting unit 9a are tanks. comprising pledged from the bottom 6b until in reaches as the upper wall portion 6c of the tank body 6a into the tank body 6a, also the return pipe 10 for returning a part of the reducing agent has been supplied to the reducing agent supply device 7 into the tank body 6a Is inserted into the tank body 6a from the upper wall 6c of the tank body 6a. And the hot water supply piping 11 which supplies a heating fluid (henceforth hot water) from the outside is provided along the part inserted in the said tank main body 6a of the reducing agent supply piping 8 , and, for example by welding etc. It is joined to the above portion of the reducing agent supply pipe 8.

The hot water supply pipe 11 further extends from the reducing agent suction port 8a of the reducing agent supply pipe 8 and passes through the concentration detecting portion 9a of the concentration detecting device 9 and is meandered in the tank body 6a. The hot water supply pipe 11 has an upper end drawn out of the upper wall 6c of the tank main body 6a to form a water supply port 11a, and a lower end pulled out from the lower side of the tank main body 6a to the outside. 11b is formed. A cock 12 is provided outside the tank body 6a and in front of the drain port 11b so that the flow path of the hot water supply pipe 11 can be opened and closed. Thereby, warm water can be temporarily stored in the warm water supply pipe 11.

  Further, for example, a rubber cap 13 is provided at the water supply port 11 a of the hot water supply pipe 11. Normally, the water supply port 11 a is closed with the cap 13 so that dust and dirt do not enter the hot water supply pipe 11. In this way, clogging of the piping is prevented.

  In this embodiment, for example, a urea aqueous solution (urea water) is used as the reducing agent to be supplied by the injection nozzle 5. The urea water injected and supplied from the injection nozzle 5 is easily hydrolyzed by the exhaust heat in the exhaust pipe 3 and the water vapor in the exhaust to generate ammonia easily. The obtained ammonia reacts with NOx in the exhaust gas in the reduction catalyst 4 and is purified into water and harmless gas. The urea water is a solid or powdery urea aqueous solution, stored in the storage tank 6, and supplied to the reducing agent supply device 7 through the reducing agent supply pipe 8.

Next, the operation of the engine exhaust gas purification apparatus configured as described above will be described.
First, when the urea water in the storage tank 6 is frozen due to cold, the cap 13 of the hot water supply pipe 11 is removed with the cock 12 open, and the water supply port 11a is connected to, for example, a kettle 14 or the like. Pour the warm water as shown by arrow B. And when warm water comes out from the drain outlet 11b as shown by the arrow C, the cock 12 is closed. Then, the warm water is kept in the warm water supply pipe 11 for a while. Thus, it occurs arrows D and heat transfer E direction from the hot water of the hot water supply pipe 11 as shown in FIG. 2, the reducing agent inlet 8a near the reducing agent supply pipe 8 and the surrounding and the reducing agent supply pipe 8 In addition, the frozen urea water around the concentration detector 9a of the concentration detector 9 is rapidly thawed.

  Next, when the heat transfer from the hot water supply pipe 11 occurs sufficiently and the hot water is cooled, the cock 12 shown in FIG. 1 is opened and the cooled hot water is discharged in the direction of arrow C. In addition, if the above-described warm water supply operation is repeated a plurality of times, the urea water in the tank body 6a can be sufficiently thawed. As a result, urea water can be supplied to the reducing agent supply device 7 in a short time after the engine 1 is started. Moreover, if an antifreeze is used as hot water, it will not freeze in the hot water supply pipe 11 even if the hot water is cooled by heat transfer.

  On the other hand, exhaust from the operation of the engine 1 passes from the exhaust manifold 2 via the exhaust pipe 3, passes through the reduction catalyst 4 disposed in the middle of the exhaust pipe 3, and is discharged from the end exhaust port of the exhaust pipe 3 to the atmosphere. Discharged inside. At this time, when urea water can be supplied by the above-described thawing operation of urea water, urea water is injected from the injection nozzle 5 disposed on the exhaust upstream side of the reduction catalyst 4 inside the exhaust pipe 3. . The injection nozzle 5 is led from a storage tank 6 for storing urea water to a reducing agent supply pipe 8 and supplied with the pressure air by the operation of the reducing agent supply device 7. Then, it is injected and supplied into the exhaust gas by the injection nozzle 5. Note that not all of the urea water supplied to the reducing agent supply device 7 is injected and supplied into the exhaust gas, and a part thereof is returned to the tank body 6a by the return pipe 10 without being used.

As described above, according to the present embodiment, the hot water supply pipe 11 through which hot water passes is provided along the portion of the reducing agent supply pipe 8 disposed in the storage tank 6 and the concentration of the reducing agent is detected. By being disposed so as to pass through the concentration detector 9 a of the concentration detector 9, at least the reducing agent supply pipe 8 in the storage tank 9 with the hot water of the hot water supply pipe 11 and the vicinity thereof and the reducing agent supply pipe 8. The frozen urea water around the reducing agent suction port 8a and the concentration detector 9a can be thawed. Therefore, the frozen urea water can be rapidly thawed so that the urea water can be injected in a short time after the engine 1 is started, and the concentration of the urea water can be detected.

The hot water supply pipe 11 may be provided not only with the reducing agent supply pipe 8 provided in the storage tank 6 but also with the return pipe 10. In this case, as shown in FIG. 3, the hot water supply pipe 11 passes from the return pipe 10 provided in the storage tank 6 through the reducing agent supply pipe 8 to pass through the concentration detector 9 a of the concentration detector 9. It is good to arrange so that it may pass.

  FIG. 4 is an enlarged side view of an essential part showing another embodiment of the hot water supply pipe 11. The hot water supply pipe 11 is provided with a large number of fins 15 on the surface of the pipe body, and the heat transfer efficiency is improved by the fins 15.

  In the present embodiment, the cooling water of the engine 1 is guided to a pipe wound around the storage tank 6 and the urea water inside is thawed by the cooling water warmed by the operation of the engine 1. You may use together. As a result, when the engine 1 is started, hot water is supplied from the outside to rapidly thaw the frozen urea water, and thereafter, the urea water can be prevented from being frozen by the cooling water warmed by the operation of the engine 1. .

Further, in the present embodiment, the exhaust purification device provided with the reduction catalyst 4 only on the exhaust downstream side of the exhaust pipe 3 has been described as an example. However, the present invention is not limited to this, and the NO in the exhaust is oxidized on the upstream side of the exhaust. The present invention can also be applied to an exhaust emission control device that includes an oxidation catalyst that oxidizes to produce NO ₂ . And although the example using urea water was demonstrated as a reducing agent, it is not restricted to this, You may use other reducing agents suitable, for example, ammonia aqueous solution, in order to purify | clean exhaust gas.

It is a conceptual diagram which shows embodiment of the exhaust emission purification device of the engine by this invention. It is sectional drawing explaining the heat transfer of warm water supply piping. It is sectional drawing which shows the other example of arrangement | positioning of warm water supply piping. It is a principal part expanded side view which shows the other Example of warm water supply piping.

Explanation of symbols

1 ... Engine 3 ... Exhaust pipe (exhaust passage)
4 ... Reduction catalyst 5 ... Injection nozzle 6 ... Storage tank (reducing agent storage tank)
6a ... Tank body 8 ... Reducing agent supply pipe 9 ... Concentration detector 9a ... Concentration detector 11 ... Hot water supply pipe 15 ... Fin

Claims (5)

A reduction catalyst disposed in the exhaust system of the engine for reducing and purifying nitrogen oxides in the exhaust with a reducing agent;
An injection nozzle for injecting the reducing agent to the exhaust upstream side of the reduction catalyst in an exhaust passage of the exhaust system;
A reducing agent storage tank provided with a reducing agent supply pipe for storing the reducing agent therein and supplying the reducing agent to the injection nozzle;
An exhaust emission control device for an engine equipped with
The reducing agent storage tank, by including in a state in which along the hot water supply pipe passing heated fluid from the outside in at least a tank pledged portion within the body of the previous SL reducing agent supply pipe, is and bonded to the portion An exhaust gas purification device for an engine. 2. The engine exhaust gas purification according to claim 1, wherein the hot water supply pipe is disposed in the tank body so as to pass through a concentration detection unit of a concentration detection device that detects the concentration of the reducing agent. apparatus.   The engine exhaust gas purification apparatus according to claim 1 or 2, wherein the hot water supply pipe meanders in the tank body.   The engine exhaust gas purification apparatus according to any one of claims 1 to 3, wherein the hot water supply pipe is provided with fins on a surface of a pipe body.   The engine exhaust purification device according to any one of claims 1 to 4, wherein the heating fluid is antifreeze.

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