JP2006194088A - Regeneration method for nox storage catalyst and exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a regeneration method for NOx storage catalyst for regenerating NOx storage catalyst efficiently while catching NOx in exhaust gas continuously and to provide an exhaust emission control device. <P>SOLUTION: In this regeneration method for NOx storage catalyst provided in the exhaust emission control device for the internal combustion engine, NOx in exhaust gas is eliminated in a region for letting exhaust gas pass by controlling a flow passage of exhaust gas flowing into the NOx storage catalyst to let a part of NOx storage catalyst pass selectively, and reducing agent is introduced to reduce NOx absorbed into the NOx storage catalyst, let it react, and remove it in a region for preventing exhaust gas from passing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for regenerating an NO _x storage catalyst and an exhaust purification device for an internal combustion engine. In particular, the present invention relates to a regeneration method for an NO _x storage catalyst and an exhaust purification device for an internal combustion engine that can efficiently regenerate the NO _x storage catalyst while collecting NO _x in the exhaust gas.

Conventionally, in exhaust gas discharged from an internal combustion engine such as a diesel engine, particulate matter (hereinafter, referred to as PM) and nitrogen oxides (hereinafter, referred to as NO _X), etc. are included. Therefore, as a post-processing device for an internal combustion engine, to collect NO _X and _the NO _X storage catalyst with the primary objective, a diesel particulate filter (hereinafter referred to as a main purpose of collecting the PM, referred to as DPF ) To purify the exhaust gas.
Among these, in the NO _x storage catalyst, the catalyst may become clogged with the collected NO _x or the like with time, and the purification rate of the exhaust gas may decrease. Therefore, even during operation of the internal combustion engine, it is necessary to regenerate the NO _x storage catalyst by removing the NO _x adsorbed on the NO _x storage catalyst through a reduction reaction.

As shown in FIG. 7, as an exhaust gas purifying device for an engine capable of regenerating such NO _X storage catalyst, as shown in FIG. 7, a NO _X storage catalyst 124 provided in the exhaust pipe of the engine and a hydrocarbon-based liquid provided upstream thereof. a liquid injection nozzle 129 which can inject, a bypass pipe 138 which bypasses the the NO _X storing catalyst 124, the exhaust control valve 141, 142 for adjusting the flow rate of the exhaust gas flowing respectively in the NO _X storage catalyst 124 and bypass tube 138, the An exhaust gas purification device for an engine including the same is disclosed (see Patent Document 1).
More specifically, at the time of reproduction of the NO _X storage catalyst, passing a large portion of the exhaust gas bypass pipe, and with adjusting the exhaust gas regulating valve to flow a portion of the exhaust gas in the NO _X storage catalyst, the liquid from the liquid injection nozzle By injecting NOx, the excess air ratio in the exhaust gas at the inlet of the NO _x storage catalyst is reduced and the ratio of the reducing agent is increased, so that the adsorbed NO _x can be decomposed into N ₂ etc. is there.
JP 2002-349236 A (Claims Fig. 1)

However, the engine exhaust gas purification device disclosed in Patent Document 1 tries to regenerate the entire surface of the catalyst at a time when the NO _x storage catalyst is regenerated, and is a reduction for use in the decomposition of NO _x. There was a problem that a large amount of the agent was consumed, resulting in deterioration of fuel consumption. Further, at the time of reproduction of the NO _X storage catalyst, most of the exhaust gas, in order to bypass the _the NO _X storage catalyst, a problem that in the exhaust gas discharged from the engine during which it is impossible to collect NO _X There was also.
On the other hand, in order to regenerate the NO _x storage catalyst, there is also a method of increasing the fuel injection amount in the engine cylinder to make the air-fuel ratio of the exhaust gas rich, but this method also causes deterioration of fuel consumption, There is a problem in that it is difficult to control the operating state of the engine because a sudden torque fluctuation may occur in the engine output.

Accordingly, the inventors of the present invention have made diligent efforts to change the exhaust gas flow path through which the NO _X storage catalyst passes when the NO _X storage catalyst is regenerated, so that the exhaust gas can be used as one of the NO _X storage catalysts. The NO _x storage catalyst is efficiently regenerated while trapping NO _x in the exhaust gas by introducing a reducing agent and partially regenerating the NO _x storage catalyst while passing through the section. The present invention has been completed by finding out that it can be achieved.
That is, an object of the present invention is to provide an NO _X storage catalyst that can regenerate the NO _X storage catalyst while repairing NO _X in the exhaust gas by controlling the exhaust gas passage in the NO _X storage catalyst. A regeneration method and an exhaust gas purification apparatus for an internal combustion engine are provided.

According to the present invention, there is provided a method for regenerating an NO _x storage catalyst provided in an exhaust purification device for an internal combustion engine,
By controlling the flow path of the exhaust gas flowing into the NO _X storage catalyst, by selectively passing a portion of the NO _X storage catalyst,
While purifying NO _x in the exhaust gas in the region through which the exhaust gas passes,
In a region which does not pass through the exhaust gas, and introducing a reducing agent, a reproduction method of the NO _X storage catalyst, characterized in that the removal by reduction reaction NO _X adsorbed in the NO _X storage catalyst.
In the present invention, the region through which exhaust gas passes means a region through which most exhaust gas flows, and the region through which exhaust gas does not pass means a region through which almost no exhaust gas flows. Therefore, as a result, some exhaust gas may flow even in a region where the exhaust gas is not allowed to pass.

In carrying out the regeneration method of the NO _x storage catalyst of the present invention, it is preferable to selectively pass a part of the NO _x storage catalyst while switching the exhaust gas passage position in the oxidation catalyst.

In carrying out the regeneration method of the NO _x storage catalyst of the present invention, it is preferable to introduce a fuel overconcentration gas as a reducing agent.

In carrying out the regeneration method of the NO _x storage catalyst of the present invention, it is preferable to introduce the reducing agent by flame injection with a burner or fuel injection with an injector.

Another aspect of the present invention is an exhaust purification device that is provided in an exhaust passage of an internal combustion engine and includes a NO _x storage catalyst for purifying NO _{x in} exhaust gas,
The exhaust gas flowing into the NO _X storage catalyst, a flow path control means for selectively passing a portion of the _the NO _X storage catalyst,
The region which does not pass through the exhaust gas, by introducing a reducing agent, a reducing agent supply means for removing by reduction reaction NO _X adsorbed in the NO _X storage catalyst,
An exhaust emission control device for an internal combustion engine characterized by comprising:

  In configuring the exhaust emission control device of the present invention, the flow path control means is preferably a flow path control valve.

In configuring the exhaust gas purification apparatus for an internal combustion engine of the present invention, it is preferable that the reducing agent supply means is disposed between the flow path control means and the NO _x storage catalyst.

  In configuring the exhaust gas purification apparatus for an internal combustion engine according to the present invention, it is preferable that the reducing agent supply means is a burner or an injector.

According to the reproducing method of the NO _X storage catalyst of the present invention, when reproducing _the NO _X storage catalyst, the exhaust gas is partially passed through _the NO _X storage catalyst, in the area for passing exhaust gas, the exhaust gas The NO _x storage catalyst can be regenerated in a region where the exhaust gas is not allowed to pass while the inside NO _x is collected.
In addition, since the NO _x storage catalyst is partially regenerated in this way, it can be regenerated using a small amount of a reducing agent. For example, even when fuel is used as the reducing agent, the fuel consumption is reduced. Can be prevented from becoming significantly worse.

Further, in the method for regenerating the NO _X storage catalyst of the present invention, the entire surface of the NO _X storage catalyst is covered with a small amount of reducing agent by passing a part of the NO _X storage catalyst while switching the passage position of the exhaust gas. it is possible to uniformly reproduced, it is possible to prevent variations in the temperature of the NO _X storage catalyst.

Further, in the regeneration method of the NO _x storage catalyst of the present invention, by using the fuel overconcentrated gas as the reducing agent, the engine fuel can be used as it is without reducing the fuel consumption significantly.

Further, according to the regeneration method of the NO _x storage catalyst of the present invention, CO, CO ₂ , and HC as the NO _x reducing agent can be efficiently used by using the engine fuel by introducing the reducing agent by a predetermined method. Can be supplied to.

According to the exhaust gas purification apparatus for an internal combustion engine of the present invention, the exhaust gas can be partially passed through the NO _x storage catalyst by including the predetermined flow path control means and the reducing agent supply means. In addition, since the reducing agent can be introduced into the region where the exhaust gas is not allowed to pass, the NO _x storage catalyst can be efficiently regenerated while collecting the NO _x in the exhaust gas. A purification device can be provided.

In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the passage control valve is provided as the passage control means, so that the exhaust gas passage in the NO _x storage catalyst can be changed with a simpler configuration.

Further, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the reducing agent supply means is arranged at a predetermined location to locally regenerate the NO _x storage catalyst in an area where the exhaust gas is not allowed to pass through in a fuel-rich state. Can be made.

In the exhaust gas purification apparatus for an internal combustion engine of the present invention, the predetermined reducing agent supply means is provided, so that the NO _x reducing agent can be efficiently supplied using the engine fuel as it is.

Hereinafter, with reference to the drawings, the method of reproducing _the NO _X storage catalyst according to the present invention, and will be specifically described embodiment relates to an exhaust purification device of the _the NO _X storage catalyst regeneration process can be carried out the internal combustion engine. However, this embodiment shows one aspect of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.

1. Exhaust Purification Device (1) Basic Configuration An exhaust purification device for an internal combustion engine according to the present invention is provided in an exhaust passage 20 of an internal combustion engine 51 as shown in FIGS. a exhaust gas purification device 10 comprising the NO _X storing catalyst 11 for purifying the NO _X, the exhaust gas flowing into the NO _X storage catalyst, for selectively passing a portion of the the NO _X storing catalyst 11 the flow path control means 13, to a region which does not pass through the exhaust gas, by introducing a reducing agent, a reducing agent supply means 15 for removing by reduction reaction nO _X adsorbed in the nO _X storing catalyst The exhaust gas purification apparatus 10 for an internal combustion engine is characterized by comprising: Here, FIG. 1 (a) is a diagram schematically showing the exhaust purification device 10 of the present invention, and FIG. 1 (b) is a view of the exhaust purification device 10 from the direction of the arrow in FIG. 1 (a). It is the schematic in the case.

The exhaust purification apparatus 10 is an apparatus for purifying exhaust gas mainly by adsorbing NO _X contained in the exhaust gas D exhausted from the internal combustion engine 51 to the NO _X storage catalyst 11. Furthermore, NO has been adsorbed on the NO _X storing catalyst _X is by reduction using a reducing agent such as CO (carbon monoxide) and HC (raw gas), N ₂ (nitrogen), water (H ₂ O ), Carbon dioxide (CO ₂ ), etc., and discharged.
By implementing the present invention, it is possible to effectively purify NO _x in the exhaust gas. However, regarding PM contained in the exhaust gas, for example, in the internal combustion engine, the fuel injection timing is delayed. By controlling in this way, the amount of PM in the exhaust gas can be effectively reduced.

(2) Internal combustion engine As the internal combustion engine 51 that discharges the exhaust gas indicated by the arrow D in FIG. 1, a diesel engine or a gasoline engine is typical. It is suitable to target diesel engines that must be regenerated.

(3) Exhaust passage The exhaust passage 20 is connected to an exhaust port 22 of the internal combustion engine, and an exhaust purification member such as a NO _x storage catalyst is disposed in the middle thereof. The cross-sectional shape of the exhaust passage 20 is not particularly limited as long as it is an exhaust passage 20 such as a circle, an ellipse, or a prism.

(4) NO _x storage catalyst The NO _x storage catalyst 11 is arranged in the middle of the exhaust passage 20 and is a catalyst for adsorbing NO _x contained in the exhaust gas and promoting the NO _x reduction reaction. is there. That is, NO and NO ₂ contained in the exhaust gas are collected by the catalyst, and the reduction reaction with the reducing agent introduced is promoted, and NO _x is efficiently converted into N ₂ , H ₂ O, and CO ₂ . Disassemble and discharge.
Such NO _x storage catalyst is not particularly limited, and known ones such as strontium or barium as active ingredients on a porous carrier, alkaline earth metals such as magnesium, cerium and lanthanum, etc. Those containing rare earth metals, noble metals such as platinum and rhodium can be used.

Further, the NO _x storage catalyst 11 may be variable in its arrangement position, such as being rotatable about the flow direction of the exhaust gas as a rotation axis, or being movable in the front-rear direction with respect to the flow direction of the exhaust gas. preferable. In other words, the exhaust gas flow path in the NO _x storage catalyst can be switched and the distance between the flow path control means and the NO _x storage catalyst can be changed with the exhaust gas flow path fixed. It is preferable.
The reason for this is that the exhaust gas passage position and passage area of the NO _X storage catalyst can be easily changed by changing the arrangement position of the NO _X storage catalyst together with the switching of the exhaust gas passage position by the flow path control means described later. This is because it can be controlled.
Therefore, it is possible to efficiently regenerate the NO _x storage catalyst while collecting NO _x contained in the exhaust gas.

(5) the flow path control means also on the upstream side of the NO _X storage catalyst 11 in the exhaust passage 20, the exhaust gas flowing into the NO _X storage catalyst 11, for selectively passing a portion of the NO _X storage catalyst 11 A flow path control means 13 is provided. That is, most of the exhaust gas is allowed to pass through only a part of the NO _x storage catalyst 11 to continuously collect NO _{x in} the exhaust gas, while almost no exhaust gas is allowed to pass through the other areas. In this way, the NO _x storage catalyst can be regenerated at the same time.
As such a flow path control means, for example, as shown in FIG. 2A, it is preferable to use a flow path control valve 13 including a fan member 17 that can rotate around a rotation shaft 18. This is because such a flow path control valve can easily control the flow path of the exhaust gas with a relatively simple configuration.

More specifically, in a normal state in which the amount of NO _x adsorbed on the NO _x storage catalyst is small, the flow direction of the exhaust gas D is controlled through the flow path control valve 13 as shown in FIG. Placed in parallel. Then, since the exhaust gas D flows into the entire surface of the NO _X storage catalyst 11, the entire surface of the NO _X storage catalyst 11 can be used to efficiently collect NO _{X in} the exhaust gas.
On the other hand, when the amount of NO _x trapped by the NO _x storage catalyst 11 increases and it is necessary to regenerate the NO _x storage catalyst, the flow control valve 13 is exhausted as shown in FIG. The gas D is disposed in an oblique direction with respect to the flow direction of the gas D. As a result, most of the exhaust gas D selectively passes through a part of the NO _x storage catalyst 11. Therefore, in the region through which the exhaust gas D passes, the NO _x in the exhaust gas D can be continuously collected although the passage area is small. On the other hand, in the region where the exhaust gas D hardly passes, the NO _x storage catalyst 11 can be regenerated using a reducing agent described later.
A specific method for regenerating the NO _x storage catalyst will be described later.

(6) the reducing agent supply means also reducing agent supply means 15, to decompose the NO _X adsorbed in the NO _X storing catalyst 11, in order to reproduce _the NO _X storage catalyst 11, a reducing agent such as HC and CO It is a means that is introduced upstream of the NO _X storage catalyst 11 and flows into the catalyst 11. By introducing such a reducing agent, a NO _X adsorbed in the NO _X storage catalyst, N ₂ and H ₂ O, is decomposed into CO ₂ and the like can be discharged, while purifying the exhaust gas, The NO _X storage catalyst can be efficiently regenerated.
The reducing agent supply means is not particularly limited as long as it can supply CO, HC, or the like as a reducing agent. For example, incomplete combustion gas containing a large amount of CO or HC can be supplied. A burner, an injector capable of injecting mist-like fuel (HC), or the like can be used.

For example, as shown in FIG. 3, as a reducing agent supply means, an injector 60 for supplying high-pressure fuel, a first air introduction pipe 61 for mixing air with high-pressure fuel, and the supplied fuel are heated. A fuel evaporation device 63 for evaporating the fuel, an orifice 65 for diffusing and evaporating the vaporized and vaporized fuel, a second air introduction pipe 67 for taking in air for assisting the combustion of the fuel, and the fuel Preferably, the burner 50 includes a fuel ignition device 69 for igniting into combustion gas.
This is because the burner 50 can be reduced in size as compared with, for example, a premixed type burner, and the unburned gas contained in the incomplete combustion gas to be injected is configured as described above. This is because the amount of HC and CO can be easily controlled.
More specifically, in such a burner, the fuel is diffused and injected by the diffusion type orifice 65 so that the fuel at the center does not touch the air taken in from the second air introduction pipe 67. Can be incompletely burned. Therefore, it is possible to inject fuel with HC and CO contained in the combustion gas.
When focusing on the reduction efficiency of NO _x , it has been found that the higher the CO content than the HC, the higher the reduction efficiency.

3 preferably further includes an oxidation catalyst 66 for oxidizing the incomplete combustion gas injected from the burner 50. The reason is that by providing the oxidation catalyst 66, HC in the incomplete combustion gas burned at the predetermined air-fuel ratio in the burner 50 can be oxidized, and CO can be efficiently generated.
More specifically, since the incomplete combustion gas injected from the burner 50 includes a predetermined amount of heat and HC, normally, a part of HC causes incomplete combustion due to residual heat, and a small amount of CO is generated. appear. However, by providing the oxidation catalyst 66 on the downstream side of the burner 50, the oxidation catalyst 66 is activated by the amount of heat in the incomplete combustion gas, and HC and a small amount of oxygen in the incomplete combustion gas are oxidized. Can cause incomplete combustion and efficiently generate CO. Therefore, the regeneration efficiency of the NO _x storage catalyst can be remarkably improved by utilizing the amount of heat in the incomplete combustion gas, CO, and the remaining HC.

Such reducing agent supply means is preferably arranged between the flow path control means 13 and the NO _x storage catalyst 11.
The reason for this is that, by configuring in this way, the reducing agent can be introduced only into the region where the exhaust gas in the NO _x storage catalyst does not pass through, and only this region is locally brought into the fuel overconcentration state. This is because the NO _x storage catalyst can be efficiently regenerated with a small amount of fuel.
For example, when the flow rate control means is the above-described flow rate control valve 13, as shown in FIG. 2, between the position of the rotating shaft 18 of the rotatable fan member 17 and the NO _x storage catalyst 11, It is preferable that the reducing agent is disposed in the direction of the rotating shaft 18.
This is because, by arranging the thus reducing agent supply means, when reproduction of the NO _X storage catalyst, even in a state of being inclined in either direction Ogitai member, in a region where the exhaust gas hardly flows This is because a reducing agent can be supplied.

(7) Lambda sensor It is preferable that a lambda sensor is provided between the supply port of the reducing agent supply means and the NO _x storage catalyst.
The reason for this is that when the engine fuel gas (HC) is used as the reducing agent in the region where the NO _X storage catalyst is regenerated, the air-fuel ratio of the incomplete combustion gas flowing into the NO _X storage catalyst is measured. This is because the amount of reducing agent supplied from the reducing agent supply means is controlled based on the measured value. Therefore, the reducing agent can be supplied so that the air-fuel ratio at which the NO _x reduction reaction is most efficiently performed is achieved.

(8) Control means Although not shown, it is preferable that a control means for determining the position of the flow path control means 13 is provided. This is because, for example, the position of the flow path control means is determined so that the exhaust gas passes through the entire surface or a part of the NO _X storage catalyst according to the elapsed time, and the NO _X storage catalyst. This is for controlling the passage position to be switched at a predetermined timing even when exhaust gas is allowed to pass through a part of the exhaust gas.
Thus, NO with the entire surface of the _X storage catalyst can be uniformly reproduced, prevents the temperature of the NO _X storage catalyst partially varies it can be made entirely uniform temperature. In addition, since the NO _x storage catalyst can be regenerated at a predetermined timing as the engine operation time elapses, the purification efficiency of NO _x in the exhaust gas can be improved.

(9) Other In addition, in the middle of the exhaust passage, there is a temperature sensor for measuring the temperature of the exhaust gas, an oxidation catalyst for raising the NO _x storage catalyst to the activation temperature early, or in the exhaust gas. A diesel particulate filter (DPF) or the like for adsorbing PM may be provided.

2. The method of reproducing _the NO _X storage catalyst Next, with reference to FIGS. 4 to 6, in the exhaust purification apparatus having the above structure will be described in detail reproducing method of the NO _X storage catalyst. In the following description, an example using a diesel engine as an internal combustion engine will be described.

First, in a normal state where the amount of NO _x adsorbed on the NO _x storage catalyst is small and the catalyst does not need to be regenerated, the exhaust gas flow path is controlled by the flow path control means so that the NO _x storage catalyst. The exhaust gas is allowed to flow into the entire surface. In this state, in order to be able to adsorb the NO _X in the exhaust gas using the entire surface of _the NO _X storage catalyst, decomposing NO _X in the efficient exhaust gas can be discharged.
For example, when the flow control valve 13 including the rotatable fan member 17 is used as the flow control means, the flow control is performed so as to be parallel to the flow direction of the exhaust gas D as shown in FIG. By disposing the valve 13, the exhaust gas D can be caused to flow into the entire surface of the NO _x storage catalyst 11 without changing the flow of the exhaust gas D by the flow rate control valve 13.

Next, as the amount of NO _x adsorbed on the NO _x storage catalyst increases with the passage of time and the NO _x storage catalyst needs to be regenerated, the flow path of the exhaust gas is changed by the flow rate control means, While most of the exhaust gas is selectively passed through a part of the NO _x storage catalyst, almost no exhaust gas is allowed to pass through the other parts.
For example, when the above-described flow path control valve 13 is used as the flow path control means, as shown in FIG. 4B, the flow control valve is inclined so as to be inclined with respect to the flow direction of the exhaust gas D. 13 is arranged. By doing so, the exhaust gas D hardly flows into the region B, while the passage area of the exhaust gas D is small in the region A through which most of the exhaust gas D passes, NO _X in the gas D can be continuously collected.

Next, as shown in FIG. 4C, the reducing agent 16 is introduced by the reducing agent supply means 15 into the region B where the exhaust gas D hardly flows. Then, in such region B, and the density of the reducing agent 16 is high, the NO _X adsorbed in the NO _X storing catalyst 11 efficiently decomposed into N ₂ and H ₂ O, etc., it was drained The NO _x storage catalyst 11 can be efficiently regenerated.
For example, when the above-described flow control valve 13 is used, by introducing incomplete combustion gas containing HC or CO as the reducing agent 16 to the region B, the region B is locally in a fuel rich state. Therefore, the NO _x storage catalyst 11 can be regenerated by efficiently decomposing NO _x adsorbed on the NO _x storage catalyst 11 into N ₂ , H ₂ O, and CO ₂ .

Here, it is preferable to introduce the reducing agent 16 using the burner 50 as shown in FIG.
This is because the temperature of the NO _x storage catalyst 11 is raised to the activation temperature or higher by the amount of heat of the high-temperature incomplete combustion gas, while HC or CO contained in the exhaust from the burner is used as the NO _x reducing agent 16. This is because the NO _x storage catalyst 11 can be regenerated very efficiently. Moreover, since the combustion system of the burner itself exists independently of the internal combustion engine, fuel and air can be mixed and burned at a desired concentration in the burner independently of the operating state of the internal combustion engine. On the other hand, the burner combustion state also has no possibility of affecting the operation state of the internal combustion engine.

More specifically, when the content of HC in the exhaust gas from the burner becomes, for example, a value less than 0.1 vol%, the NO _X reducing agent is insufficient and the regeneration efficiency of the NO _X storage catalyst may be reduced. is there. On the other hand, if the content of HC in the exhaust from the burner exceeds, for example, 5 vol%, the temperature of the exhaust from the burner is also reduced, and the temperature of the catalyst cannot be sufficiently raised, Similarly, the regeneration efficiency of the NO _x storage catalyst may decrease.
Similarly to HC, CO oxidized by incomplete combustion due to residual heat or the like can also be used as a reducing agent for NO _x . Even in this case, when the content of CO in the exhaust gas from the burner becomes, for example, a value less than 0.001 vol%, the NO _X reducing agent may be insufficient and the regeneration efficiency of the NO _X storage catalyst may decrease. is there. On the other hand, if the content of carbon monoxide in the combustion gas exceeds 10 vol%, for example, the temperature of the exhaust gas from the burner is also lowered in correlation, so the temperature of the catalyst cannot be sufficiently increased, The regeneration efficiency of the NO _x storage catalyst may be reduced.

Accordingly, since it is possible to significantly improve the regeneration efficiency when reproducing _the NO _X storage catalyst, it is preferably set to a value within the range of the content of CO in the exhaust from the burner 0.01～9Vol%, More preferably, the value is within the range of 0.1 to 8 vol%. Similarly, the HC content in the exhaust gas from the burner is preferably set to a value in the range of 0.1 to 4.5 vol%, and more preferably set to a value in the range of 0.15 to 4 vol%. .
It has been found that it is more efficient to use CO than HC when considering reduction efficiency.

Further, the relationship among the air-fuel ratio (−) in the exhaust from the burner, the contents of CO and HC (vol%) in the exhaust from the burner, and the temperature of the exhaust from the burner will be described.
Here, FIG. 5 shows the lambda value (−) as the air-fuel ratio in the exhaust from the burner connected to the upstream side of the NO _X storage catalyst, and the contents of CO and HC in the exhaust from the burner (vol%). It is a figure which shows the relationship between and the temperature of the exhaust_gas | exhaustion from a burner. In FIG. 5, line A shows the characteristic relationship between the lambda value and CO, line B shows the characteristic relationship between the lambda value and HC, and line C shows the lambda value and the exhaust from the burner. The relationship between the temperature and the temperature is shown.

  As can be easily understood from FIG. 5, if the air-fuel ratio (lambda value) of the exhaust gas from the burner is a value within a predetermined range, a predetermined amount of CO and HC are included. That is, for example, when the lambda value is about 0.9, the amount of CO and HC contained in the exhaust gas from the burner can be about 0.001 vol%, respectively. When the lambda value is about 0.5, the amount of CO contained in the exhaust gas from the burner can be about 7.5 vol%, and the amount of HC can be about 5 vol%. Further, when the lambda value is set to 0.4 or less, it can be understood that the amount of CO and HC contained in the exhaust gas from the burner increases as the value decreases.

If the air-fuel ratio (lambda value) in the exhaust from the burner is a value within a predetermined range, the temperature of the exhaust from the burner is a value in the range of 250 to 1,200 ° C. That is, for example, when the lambda value is about 0.9, the temperature of the exhaust gas from the burner can be about 800 ° C. When the lambda value is about 0.5, the temperature of exhaust from the burner can be about 450 ° C. Furthermore, when the lambda value is set to a value of 0.4 or less, the temperature of the exhaust gas from the burner decreases as the value decreases, but it tends to gradually become flat.
Accordingly, the air-fuel ratio (lambda value) in the exhaust from the burner is preferably a value within the range of less than 0.1 to 1.0, and more preferably within the range of 0.15 to 0.8. More preferably, the value is in the range of 0.2 to 0.6. By incomplete combustion so that such air-fuel ratio, a predetermined amount of CO, or HC against _the NO _X storage catalyst, can be made to flow at a high temperature of 250~1,200 ℃, NO _X This is because the storage catalyst can be regenerated very efficiently.
The air-fuel ratio of the exhaust gas from the burner can be measured using a lambda sensor, or can be calculated from the amount of fuel and air used.

As described above, after playing a portion of the NO _X storage catalyst, in turn, to an already was regenerated _the NO _X storage catalytic region, as in turn, flowing a large portion of the exhaust gas flow rate Control the control means. As a result, the exhaust gas hardly flows in the region including the portion where the NO _X storage catalyst has not been regenerated.
For example, when the above-described flow path control valve 13 is used, as shown in FIG. 6A, the flow control valve 13 is inclined in the direction opposite to the previously inclined direction with respect to the flow direction of the exhaust gas D. Thus, the flow path control valve 13 is arranged. By arranging in this way, most of the exhaust gas D passes through the region B ′ including the already regenerated portion in the NO _x storage catalyst, and in the region A ′ including the portion that has not been regenerated, Exhaust gas D hardly flows.

Then, as shown in FIG. 6B, in the same manner as described above, the reducing agent 16 is introduced into the region A ′ in which the exhaust gas D hardly flows, so that NO in the region A ′ is obtained. _{The X} storage catalyst 11 can be regenerated. In this way, the entire surface of the NO _X storage catalyst 11 is regenerated by switching the passage of the exhaust gas D in the NO _X storage catalyst 11 a plurality of times.
Thereafter, as shown in FIG. 6 (c), by'll return the flow control means 13 to the initial position, the adsorption of NO _X contained in the exhaust gas D by using the entire surface of the NO _X storing catalyst 11, which is reproduced The normal operation state can be performed.
Needless to say, even during playback of the NO _X storage catalyst, since the exhaust gas passes through the portion of the NO _X storage catalyst, is continuously collected of the NO _X in the exhaust gas line It has been broken.

Note that by switching the passing position of the exhaust gas in _the NO _X storage catalyst, the _the NO _X storage catalyst in order to sequentially reproduced part by part, in addition to a method of switching the flow path control means as described above, _the NO _X storage catalyst Can also be implemented by rotating the flow direction of the exhaust gas around the rotation axis.
Also, by changing the distance between the flow path control means and _the NO _X storage catalyst, by switching the like passage area of the exhaust gas in _the NO _X storage catalyst, it is possible to change the playback position in _the NO _X storage catalyst.

Thus, according to the regeneration method of the NO _x storage catalyst of the present invention, the setting of the flow rate control means is switched and the exhaust gas passage in the NO _x storage catalyst is periodically changed, so that the NO _x in the exhaust gas is changed. While collecting _X continuously, the NO _x storage catalyst can be regenerated efficiently at the same time.
In addition, by regenerating the NO _x storage catalyst in this way, a fuel rich state can be locally generated in a small volume range, and the NO _x storage catalyst can be regenerated. The amount of reducing agent consumed can be reduced to a small amount.

(A) And (b) is the side view and top view which respectively show the exhaust emission control device which concerns on this invention. (A)-(c) is a figure provided in order to demonstrate the flow-path control means which concerns on this invention. It is a figure which shows the burner as a reducing agent supply means which can be used for the exhaust gas purification apparatus of this invention. (A) ~ (c) is a view for explaining the reproducing method of the NO _X storage catalyst of the present invention (Part 1). It is a figure which shows the relationship between the lambda value in the exhaust_gas | exhaustion of a burner as a reducing agent supply means, CO amount, HC amount, and exhaust temperature. (A) ~ (c) is a view for explaining the reproducing method of the NO _X storage catalyst of the present invention (Part 2). It is a figure which shows the conventional engine exhaust gas apparatus.

Explanation of symbols

10: exhaust gas purification device, 11: NO _X storage catalyst 13: passage control means (channel control valve), 15: reducing agent supply means, 16: reducing agent, 17: Ogitai member, 18: rotary shaft, 20 : Exhaust passage, 50: burner, 51: internal combustion engine

Claims (8)

A method for regenerating an NO _x storage catalyst provided in an exhaust gas purification apparatus for an internal combustion engine,
By controlling the flow path of the exhaust gas flowing into the _the NO _X storage catalyst, by selectively passing a portion of the _the NO _X storage catalyst,
While purifying NO _x in the exhaust gas in the region through which the exhaust gas passes,
A method for regenerating a NO _x storage catalyst, wherein a reducing agent is introduced and NO _x adsorbed on the NO _x storage catalyst is reduced and removed in a region where the exhaust gas does not pass. The method for regenerating a NO _x storage catalyst according to claim 1, wherein a part of the NO _x storage catalyst is selectively passed while switching a passage position of the exhaust gas in the oxidation catalyst. The method for regenerating an NO _x storage catalyst according to claim 1 or 2, wherein a fuel over-concentration gas is introduced as the reducing agent. The method for regenerating an NO _x storage catalyst according to any one of claims 1 to 3, wherein the reducing agent is introduced by flame injection using a burner or fuel injection using an injector. In an exhaust gas purification apparatus that is provided in an exhaust passage of an internal combustion engine and includes a NO _x storage catalyst for purifying NO _{x in} exhaust gas,
The exhaust gas flowing into the _the NO _X storage catalyst, a flow path control means for selectively passing a portion of the _the NO _X storage catalyst,
The region which does not pass through the exhaust gas, by introducing a reducing agent, a reducing agent supply means for removing NO _X adsorbed in the _the NO _X storage catalyst by reduction reaction,
An exhaust emission control device for an internal combustion engine, comprising:   The exhaust purification device for an internal combustion engine according to claim 5, wherein the flow path control means is a flow path control valve. The exhaust gas purification apparatus for an internal combustion engine according to claim 5 or 6, wherein the reducing agent supply means is disposed between the flow path control means and the NO _x storage catalyst.   The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 5 to 7, wherein the reducing agent supply means is a burner or an injector.

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