JP3846541B2 - NOx adsorbent regeneration device and regeneration method - Google Patents

Description

【００５２】
実施例１及び比較例１から、ＮＯｘ吸着手段を反転するときは、１０−１５モードを走行できる回数が約２倍に増えている。即ち、実施例１ではＮＯｘ吸着材のＳに対する耐久性が２倍になったことを意味する。
また、実施例３及び比較例２から、ＮＯｘ吸着手段を反転することにより、１０−１５モードを走行できる回数が約２倍に増えていることがわかる。これは、ＮＯｘ吸着手段を反転することによって、ＮＯｘ吸着材から脱離したＳの再吸着が防止されたためであると考えられる。
更に、実施例３及び参考例３から、ＮＯｘ吸着手段を反転しても、Ｓの脱離温度が本発明の好適範囲でないときは、１０−１５モードを走行できる回数が約１／３になることがわかる。これは、６００℃未満の温度では脱離されるＳが少ないためと考えられる。
【００５３】
【発明の効果】
以上説明してきたように、本発明によれば、内燃機関等の排気流路に設置したＮＯｘ吸着手段を流通する排気ガスの流れ方向を、適切に切り換えることとしたため、硫黄被毒を受けたＮＯｘ吸着材のＮＯｘ吸収性能の低下を抑制し、長期に亘りＮＯｘを効率良く吸収（トラップ）することが可能となるＮＯｘ吸着材再生装置、再生方法及び排気ガス浄化装置を提供することができる。
【図面の簡単な説明】
【図１】 ガス流制御手段の一例であるＮＯｘ吸着手段反転装置の概略図である。
【図２】 ガス流制御手段の一例であって、排気ガスの流通方向を順方向（ａ）及び逆方向（ｂ）に制御する際の概略を示す図である。
【図３】 排気ガスの流通方向を制御するフローチャートである。
【符号の説明】
１ エンジン
１０ 排気流路（本流路）
１１ バイパス流路（下流側）
１２ バイパス流路（上流側）
２０ ＮＯｘ吸着手段（触媒）
２１ ＮＯｘ吸着手段反転装置（回動軸）
３０ 弁１
３１ 弁２
３２ 弁３
３３ ＮＯｘセンサー
３４ コントローラー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a NOx adsorbent regeneration device and a regeneration method, and more particularly to a method for regenerating NOx adsorbent poisoned by sulfur (S) contained in gasoline or lubricating oil, and more particularly, an automobile ( NOx adsorbents installed to purify hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) in exhaust gas discharged from internal combustion engines such as gasoline and diesel and boilers Etc. are preferably used.
[0002]
[Prior art]
In recent years, demand for fuel-efficient vehicles has increased due to the problem of depletion of petroleum resources and global warming, and the development of lean burn vehicles has attracted attention for gasoline vehicles. In such a lean burn automobile, the exhaust gas atmosphere becomes an oxygen excess atmosphere (lean state) compared to the theoretical air combustion state (stoichi) during lean burn running, but when a normal three-way catalyst is applied in the lean state, There is a problem that the NOx purification action becomes insufficient due to the influence of excessive oxygen.
[0003]
For this reason, a catalyst capable of purifying NOx even when oxygen is excessive has been developed. For example, Japanese Patent Laid-Open No. 5-168860 discloses a catalyst in which Pt and lanthanum are supported on a porous carrier, and the exhaust gas is A catalyst is described in which NOx is absorbed when oxygen is excessive (lean region), and the absorbed NOx is released and purified when stoichiometric.
[0004]
[Problems to be solved by the invention]
However, since sulfur is contained in the fuel and the lubricating oil, and this sulfur is discharged into the exhaust gas as an oxide, the NOx absorbent is poisoned by sulfur (this is referred to as “sulfur poisoning”). As a result, the NOx absorption performance is reduced.
As a method for preventing this sulfur poisoning, Japanese Patent Application Laid-Open No. 6-58138 discloses that a sulfur trap catalyst is disposed in front of a NOx absorption catalyst, and sulfur oxide is absorbed by the sulfur trap catalyst in a lean region. A method for preventing sulfur oxide from flowing into the absorption catalyst is disclosed.
In JP-A-7-217474, sulfur poisoning to some extent is unavoidable, and the adsorbed sulfur is desorbed by setting the NOx absorption catalyst to a high temperature (air-fuel ratio A / F in a rich state) at regular intervals. And a method for recovering the performance of the NOx absorption catalyst is disclosed.
[0005]
However, in the method disclosed in Japanese Patent Laid-Open No. 6-58138, the sulfur trap catalyst is saturated by the sulfur oxide absorbed, and the sulfur oxide further flows into (adsorbs) the NOx absorption catalyst, There was a problem that sulfur poisoning would occur.
Further, in the method disclosed in Japanese Patent Application Laid-Open No. 7-217474, the front side of the NOx occlusion catalyst is not used unless the NOx occlusion catalyst undergoes thermal degradation during the desorption operation of sulfur. The sulfur desorbed from the NOx is adsorbed on the rear side of the NOx storage catalyst, and the sulfur adsorption amount of the NOx storage catalyst as a whole is hardly changed, and there is a problem that poisoning is not alleviated.
[0006]
The present inventors have been made in view of such problems of the prior art, and the object of the present invention is to suppress a decrease in the NOx absorption performance of the NOx adsorbent that has been subjected to sulfur poisoning. It is an object of the present invention to provide a NOx adsorbent regeneration device, a regeneration method, and an exhaust gas purification device that can efficiently absorb (trap) NOx.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-described problems, the present inventors have appropriately switched the flow direction of the exhaust gas flowing through the NOx adsorbing means installed in the exhaust flow path of the internal combustion engine or the like. Has been achieved, and the present invention has been completed.
[0008]
That is, the NOx adsorbent regeneration apparatus according to the present invention includes a NOx adsorbing means in which a NOx adsorbent that adsorbs nitrogen oxide is supported on a carrier, and a gas flow control means for controlling the flow direction of exhaust gas to the NOx adsorbing means. With
The gas flow control means includes rotation means capable of reversing the NOx adsorption means about a rotation axis perpendicular to the exhaust gas flow direction, and the exhaust gas flow direction is determined by the NOx adsorption means. The NOx adsorbent regenerator can be switched in the forward direction from one end side to the other end side of the carrier or in the reverse direction from the other end side to the one end side.
2. The gas flow control means comprises: a main flow path that passes through the NOx adsorption means; a bypass flow path that bypasses the NOx adsorption means and communicates from one end side to the other end side of the carrier; And a valve for opening and closing the passage and the bypass passage.
[0009]
Further, in a preferred embodiment of the NOx adsorbent regenerator of the present invention, the gas flow control means is configured such that the gas flow control means bypasses the NOx adsorption means and the NOx adsorption means bypasses one end side to the other end side of the carrier. And a bypass channel that communicates with the main channel and a valve that opens and closes the main channel and the bypass channel.
[0011]
Furthermore, in another preferred embodiment of the NOx adsorbent regeneration method according to the present invention, the NOx adsorbent of the NOx adsorbing means is subjected to sulfur poisoning and the nitrogen oxide absorption performance is switched. It is characterized by being performed when
[0012]
In another preferred embodiment of the NOx adsorbent regenerator of the present invention, when the flow direction of the exhaust gas is switched, the exhaust gas is stoichiometrically rich and the NOx adsorbing means is heated to 600 ° C. or higher. It is characterized by that.
[0013]
Furthermore, in another preferred embodiment of the NOx adsorbent regenerator of the present invention, the NOx adsorbent contains at least one element selected from the group consisting of alkali metals, alkaline earth metals, rare earths and transition metals. It is characterized by doing.
[0014]
Furthermore, the NOx adsorbent regeneration method of the present invention is a NOx adsorbent regeneration method using the NOx adsorbent regeneration apparatus,
By reversing the NOx adsorption means, the exhaust gas flow direction is supplied while switching the forward direction from one end side to the other end side of the carrier in the NOx adsorption means or the reverse direction from the other end side to the one end side. It is characterized by that.
[0015]
Further, the preferred form of the NOx adsorbent regeneration method of the present invention is to switch the flow direction of the exhaust gas when the NOx adsorbent of the NOx adsorbing means is subjected to sulfur poisoning and the nitrogen oxide absorption performance is lowered. It is characterized by performing.
[0016]
Furthermore, the exhaust gas purification apparatus of the present invention is an exhaust gas purification apparatus comprising the NOx adsorbent regeneration device installed in an exhaust gas flow path of a lean burn internal combustion engine,
The carrier in the NOx adsorbing means is further supported with a catalyst component having an exhaust gas purifying ability.
[0017]
[Action]
In the NOx adsorbent regenerator of the present invention, the exhaust gas flowing through the NOx adsorbing means can be switched so as to flow from the reverse direction. Therefore, the NOx adsorbent regenerator that can use the NOx adsorbing means for a long period of time can be obtained by using the portion of the NOx adsorbing material that is carried on the NOx adsorbing means that is relatively low in sulfur poisoning as needed.
In the preferred form of the NOx adsorbent regeneration method of the present invention, when the flow direction of the exhaust gas is switched, the exhaust gas is stoichiometrically rich and the NOx adsorbing means is heated to 600 ° C. or higher. Therefore, the sulfur content related to sulfur poisoning on the NOx adsorbent can be effectively desorbed and removed, and the NOx adsorbent can be more reliably regenerated.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the NOx adsorbent regeneration apparatus and the regeneration method of the present invention will be described in detail.
As described above, the NOx adsorbent regeneration apparatus according to the present invention includes a NOx adsorbing means that supports a NOx adsorbent that adsorbs nitrogen oxides on a carrier, and a gas flow control that controls the flow direction of exhaust gas to the NOx adsorbing means. Means.
[0019]
Here, examples of the NOx adsorbent that is a constituent component of the NOx adsorbing means include alkali metals, alkaline earth metals, rare earths, transition metals, and materials containing any combination thereof.
In addition, as a carrier for supporting these NOx adsorbents, a monolithic carrier such as a monolithic carrier (honeycomb structure or the like) made of a heat resistant material is preferable. For example, a ceramic carrier such as cordierite, a ferrite stainless steel, or the like Metal ones can be used. Further, the NOx adsorbing material may be formed by supporting the NOx adsorbing material on a granular or pellet-shaped carrier and filling these into a container. When using a monolithic structure type carrier, a plurality of carriers and a tandem arrangement may be used. In this case, it is necessary to handle a carrier group arranged in a tandem as one carrier.
[0020]
On the other hand, the gas flow control means controls the flow direction of the exhaust gas to the NOx adsorption means. That is, the flow direction of the exhaust gas can be switched in the forward direction from one end side to the other end side of the carrier in the NOx adsorbing means, or in the reverse direction from the other end side to the one end side.
[0021]
In the present invention, as the gas flow control means, the NOx adsorbing means is provided with a rotating means capable of reversing around a rotation axis perpendicular to the exhaust gas flow direction, and the exhaust gas flow direction The NOx adsorbent is regenerated by supplying exhaust gas while appropriately switching between. At this time, the distribution direction can be switched based on a signal from the sensor or a predetermined time as described later.
Specifically, as shown in FIG. 1, a rotation shaft 21 can be installed as a rotation unit, and the front and rear of the NOx adsorption unit 20 can be reversed. At this time, inversion can be performed automatically or manually.
[0022]
Further, the gas flow control means includes a main flow path that passes through the NOx adsorption means, a bypass flow path that bypasses the NOx adsorption means and communicates from one end side to the other end side of the carrier, A valve for opening and closing the bypass channel can be provided.
Specifically, as shown in FIG. 2 , the exhaust passage 10, which is an example of the main passage connected to the engine 1, bypasses the NOx adsorption means 20 (NOx adsorbent) carried on the carrier. The gas flow control means which connects the two bypass flow paths 11 and 12 and provides the valves 30-32 in the connection site | part of the exhaust flow path 10 and the bypass flow paths 11 and 12 can be illustrated. This gas flow control means shuts off the bypass flow passages 11 and 12 with valves 30 to 32 as shown in FIG. When exhaust gas can be circulated only through the passage 10 and exhaust gas is to be circulated in the opposite direction, a part of the exhaust passage 10 is blocked by the valves 30 to 32 as shown in FIG. Thus, the flow direction of the exhaust gas can be changed through the bypass flow paths 11 and 12. Further, although not installed in this example, a valve can be further provided at a connection portion with the exhaust gas passage 10 on the downstream side of the bypass passage 11. Further, these valves can be opened and closed by the controller 34.
[0023]
Needless to say, the exhaust passage 10 is not limited to a straight line, and the NOx adsorption means 20 (carrier) can be installed in correspondence with the shape of the exhaust passage. Further, the “one end side” and the “other end side” of the “bypass channel communicating from one end side to the other end side” of the carrier are strictly the exhaust channel portions on the front and rear sides of the one end structure type carrier. Means.
[0024]
Further, the switching of the exhaust gas flow direction by the gas flow control means is preferably performed when the NOx adsorbent of the NOx adsorption means is subjected to sulfur poisoning and the nitrogen oxide absorption performance is lowered.
[0025]
For example, it is effective to switch the flow direction of the exhaust gas when the NOx concentration released into the atmosphere becomes higher than the NOx emission allowable amount (sensor output N> NOx emission allowable concentration Nlim). Here, “N” is the NOx concentration indicated by the NOx sensor (33 in FIG. 2 ).
As another method, the NOx emission amount per unit time calculated from the engine operating conditions is integrated to estimate the NOx amount adsorbed on the NOx adsorbent, and if this estimated NOx amount exceeds a predetermined amount, the exhaust gas The distribution direction may be switched.
[0026]
Here, when the NOx adsorbent is subjected to sulfur poisoning (hereinafter abbreviated as “S poison”) by the sulfur component contained in the fuel, the NOx adsorbent is at one end (front side) to the other end (rear side). Sulfur (S) tends to be adsorbed in order toward the surface. This also applies to the absorption of NOx, and more NOx and S are absorbed on the front side of the NOx adsorbent, and the amount of these absorptions is less on the rear side.
[0027]
The reason why S is adsorbed on the NOx adsorbent can be considered as follows.
S (SO2 in exhaust gas) contained in the fuel or the like is a precious metal (Pt, Pd, Rh, etc.) contained in a catalyst (such as a three-way catalyst) that is normally installed under an oxygen excess condition (lean condition). Oxidized by catalysis, it may be absorbed as a sulfate by NOx adsorbent (alkali, alkaline earth metal or rare earth). Since this reaction is very stable, sulfates are generated in order from the point where S contacts in the NOx adsorbent, and are strongly adsorbed by the NOx adsorbent.
[0028]
Therefore, in such S poisoning, a concentration gradient occurs in the amount of S adsorbed before and after the NOx adsorbent, and the amount of S adsorbed may increase toward the front side (upstream side) of the adsorbent. That is, in the portion where S has been adsorbed, S, which is an impurity, is strongly adsorbed on the active point of the NOx adsorbent, and the NOx adsorbent activity is reduced or lost. NOx cannot be absorbed as far as the front side.
On the other hand, even if the front side of the NOx adsorbent is subjected to considerable S poisoning, the rear side of the NOx adsorbent is hardly adsorbing S and is in a state of higher activity than the front side of the NOx adsorbent. . However, since the entire NOx adsorbent is subjected to S poisoning, it is difficult to sufficiently absorb NOx in the exhaust gas.
[0029]
Therefore, in the present invention, the flow direction of the exhaust gas can be switched when the NOx adsorbent of the NOx adsorbing means is subjected to sulfur poisoning and the nitrogen oxide absorption performance is lowered. As a result, the use period of the NOx adsorbent can be greatly extended, so that the NOx absorption performance is maintained over a long period of time.
That is, one end of the NOx adsorbing means that has become unable to exhibit the NOx absorption performance due to the adsorption of S is the rear side having a relatively small influence on the NOx absorption performance, and the NOx absorption performance is sufficiently exhibited with almost no S adsorbed. The NOx absorption performance can be regenerated by reversing the flow direction of the exhaust gas on the NOx adsorbent so that the other end that can be used is the front side that has a large influence on the NOx absorption performance. Typically, the durability of the NOx adsorbent with respect to S can be increased by 1.8 to 2 times.
The switching of the flow direction can be repeated as long as a suitable NOx absorption capacity can be maintained, and there is a difference depending on the degree of sulfur poisoning and the presence or absence of sulfur desorption operation, but one NOx adsorbent. On the other hand, the heat treatment at less than 600 ° C. can be switched about once, whereas the heat treatment at 600 ° C. or higher can be further switched about five times. Further, the concentration gradient of S adsorbed on the NOx adsorbent, for example, is remarkably manifested when traveling about 5000 km in an exhaust gas purification device installed in an automobile engine.
[0030]
Further, in the present invention, when the flow direction of the exhaust gas is switched, the exhaust gas is preferably stoichiometrically rich and the NOx adsorbing means is preferably heated to 600 ° C. or higher. As a result, the NOx adsorbent is adsorbed. The desorbed S can be desorbed and the NOx adsorbent can be regenerated. An example of the heating means at this time is an electric heater.
[0031]
Further, as described above, after switching the exhaust gas flow direction, a large amount of S is adsorbed on the downstream side (rear side) with respect to the exhaust gas flow direction on the NOx adsorbent. When S is desorbed, it is removed from the NOx adsorbing means without being adsorbed again by the NOx adsorbing material, so that the S adsorbing amount is easily reduced by the entire NOx adsorbing means. At this time, if a sulfur trap catalyst or the like is disposed in the exhaust passage, the release of the S component to the outside can be prevented.
[0032]
In addition to the above S desorption operation, as the desorption operation of S adsorbed on the NOx adsorbent, the air-fuel ratio is made rich to stoichiometric without reversing the front and rear of the NOx adsorbent that receives the exhaust gas, There is a method of raising the temperature to about 600 ° C., but in this method, S desorbed from the front side of the NOx adsorbent (catalyst) is re-adsorbed to the rear side of the adsorbent due to the concentration gradient of the S adsorption amount. The adsorbed S cannot be removed as desired.
In addition, there are a method of further enriching the air-fuel ratio A / F and a method of raising the circulating exhaust gas to a high temperature up to 700 ° C. or higher. However, the method of further enriching the A / F cannot obtain the fuel efficiency improvement effect. In addition, the method of setting the exhaust gas to a high temperature of 700 ° C. or higher is not preferable from the viewpoint of thermal durability because the NOx adsorbent is likely to be activated and deteriorated by sintering.
On the other hand, in the present invention, the NO poisoning of the NOx adsorbent can be released as described above, and the NOx absorption performance can be regenerated and sustained more reliably. Further, since the above-described re-adsorption of S does not easily occur during the desorption operation of S, the desorption of S can be achieved if the temperature of the exhaust gas is at least 600 ° C.
[0033]
The above-described representative example of the switching control of the exhaust gas flowing to the NOx adsorbing means (carrier), that is, the operation of the NOx adsorbing material rotating means ( FIG. 1 ) and the exhaust gas detouring means ( FIG. 2 ) generically is preferably carried out, typically it can be performed according to the flowchart shown in FIG. It is assumed that the S desorption operation performed in the following flowchart is performed under conditions of an exhaust gas temperature of 600 ° C. to 650 ° C., an air-fuel ratio of 13.5 to 14.6, and a time of 5 minutes.
[0034]
Hereinafter, explaining the flow chart shown in FIG. 3 (A) to the order of steps. This flow chart relates to the NOx adsorbent turning means ( FIG. 1 ).
First, in step 1 (hereinafter abbreviated as [S1]), it is determined whether N> Nlim. If the result of this determination is No, the NOx absorption amount of the NOx adsorbent has not yet reached the allowable absorption limit amount, so that the exhaust gas flow is continued as it is [S2].
On the other hand, when it is Yes, the concentration of NOx released into the atmosphere becomes high, so that the rotation means of the NOx adsorption means is activated at the same time as N> Nlim [S3].
[0035]
After [S3], it is determined again whether N> Nlim. If the result of this determination is No, the NOx absorption amount has not yet reached the allowable absorption limit amount, so that the exhaust gas flow continues as it is [S4].
On the other hand, when [Yes] is [S5], since the concentration of NOx released into the atmosphere becomes high, N> Nlim, and at the same time, the S desorption operation is performed to desorb S in the NOx adsorbent. Performed [S6].
[0036]
Next, FIG. 3 (B) shows that when the exhaust gas bypass means shown in FIG. 2 is operated, the valves 30 to 32 are opened (only the main flow path is circulated) (FIG. It is a flowchart which judges when using a bypass flow path (FIG. (B)). Note that “F” in the flowchart indicates the number of times the detour means is operated.
[0037]
The flowchart shown in FIG. 3B will be described below in the order of steps.
First, in [S10], 1 is added to F which is the operation frequency parameter. Next, it is determined whether the value of F is even or odd [S11]. If F is an even number as a result of this determination, the state shown in FIG. 2A , that is, the valve in the exhaust passage 10 is opened, and the exhaust gas flows through the NOx adsorbing means from the forward direction [S12]. . On the other hand, when F = odd, the state shown in FIG. 2B, that is, a part of the exhaust gas flow path 10 is blocked by the valve, and the exhaust gas is switched to flow through the bypass flow path. The adsorbent is distributed from the opposite direction [S13].
Incidentally, in the flowchart in FIG. 3 (B), incorporating S1 and S2 shown in FIG. 3 (A), can be a reference for bypass operations poisoning of sulfur.
[0038]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.
[0039]
In the following examples and comparative examples, an exhaust gas purification device in which an exhaust gas purification component is further carried on the NOx adsorption means having a NOx adsorbent carried on a carrier is used. That is, Ba was supported on 20 wt%, Pd was supported on 5 wt%, and Rh was supported on 1 wt% Al ₂ O ₃ , and this was coated on a honeycomb carrier. Moreover, the thermal durability shown below was performed before use.
[0040]
[Durability]
The exhaust gas purification device was mounted on the exhaust system of an engine with a displacement of 4400 cc, the NOx adsorbent inlet temperature was 650 ° C., and the engine was operated for 50 hours. At this time, the S concentration in gasoline was set to 3 ppm or less.
[0041]
Example 1
The exhaust gas purification device was mounted on the exhaust system of an engine with a displacement of 2000 cc and the S concentration in gasoline was 300 ppm, and the 10-15 mode was repeatedly run until N> Nlim. When N> Nlim, the NOx adsorbing means was removed, attached with the front and rear reversed, and the 10-15 mode was run repeatedly until N> Nlim again. At this time, the NOx adsorbing means was removed, and the attachment with the front and rear reversed was performed manually.
[0042]
( Reference Example 1 )
The same operation as in Example 1 was repeated except that the NOx adsorption means was not reversed and the flow direction of the exhaust gas was switched using the bypass flow path as shown in FIG .
[0043]
( Example 2 )
The same operation as in Example 1 was repeated except that the NOx adsorption means was reversed using the NOx adsorption means reversing device (rotating shaft) 21 shown in FIG .
[0044]
( Example 3 )
The exhaust gas purification device was installed in the exhaust system of an engine with a displacement of 2000 cc and the S concentration in gasoline was 300 ppm, and the 10-15 mode was repeatedly run until N> Nlim according to the flowchart of FIG .
When N> Nlim, the NOx adsorbing means is removed, and the front and rear are reversed, and the temperature is 600 ° C., the air-fuel ratio is 14.6, the time is 5 minutes, and the S concentration in gasoline is 3 ppm or less. The separation operation was performed (1).
Thereafter, the S concentration in the gasoline was set to 300 ppm, and the 10-15 mode was repeated until N> Nlim again (2).
The operation of (1) and the running of (2) were repeated until N <Nlim was not reached even when the S desorption operation was performed. The removal of the NOx adsorbing means at this time and the attachment with the front and rear reversed were performed manually.
[0045]
( Reference Example 2 )
The same operation as in Example 3 was repeated except that the NOx adsorption means was not reversed and the flow of the exhaust gas was switched using a bypass as shown in FIG .
[0046]
( Example 4 )
The same operation as in Example 3 was repeated except that the NOx adsorption means was reversed using the NOx adsorption means reversing device 21 shown in FIG .
[0047]
(Comparative Example 1)
The exhaust gas purification device was installed in the exhaust system of an engine with a displacement of 2000 cc and the S concentration in gasoline was 300 ppm, and the 10-15 mode was repeatedly run until N> Nlim. Further, the NOx adsorption means was not reversed. Except for this, the same operation as in Example 1 was repeated.
[0048]
(Comparative Example 2)
The same operation as in Example 3 was repeated except that the NOx adsorption means was not reversed.
[0049]
( Reference Example 3 )
The same operation as in Example 3 was repeated except that the temperature during the S desorption operation was 550 ° C.
[0050]
[Evaluation]
In the above examples and comparative examples, the number of times the vehicle was able to travel by repeating the 10-15 mode until the NOx conversion rate became 65% or less was compared. The results are shown in Table 1. The NOx conversion rate when N <Nlim was 68 to 70%.
[0051]
[Table 1]

[0052]
From Example 1 and Comparative Example 1, when the NOx adsorption means is reversed, the number of times that the vehicle can travel in the 10-15 mode has increased approximately twice. That is, in Example 1, it means that the durability of the NOx adsorbent with respect to S is doubled.
In addition, it can be seen from Example 3 and Comparative Example 2 that the number of times that the vehicle can travel in the 10-15 mode is increased approximately twice by inverting the NOx adsorption means. This is considered to be because the re-adsorption of S desorbed from the NOx adsorbent was prevented by inverting the NOx adsorption means.
Furthermore, from Example 3 and Reference Example 3 , even if the NOx adsorption means is reversed, if the desorption temperature of S is not within the preferred range of the present invention, the number of times that the vehicle can travel in the 10-15 mode is about 1/3. I understand that. This is presumably because there is little S desorbed at temperatures below 600 ° C.
[0053]
【The invention's effect】
As described above, according to the present invention, the flow direction of the exhaust gas flowing through the NOx adsorbing means installed in the exhaust flow path of the internal combustion engine or the like is appropriately switched, so that the NOx that has received sulfur poisoning. It is possible to provide a NOx adsorbent regeneration device, a regeneration method, and an exhaust gas purification device that can suppress NOx absorption performance of the adsorbent and efficiently absorb (trap) NOx over a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic view of a NOx adsorbing means reversing device as an example of a gas flow control means.
FIG. 2 is an example of gas flow control means, and is a diagram showing an outline when controlling the flow direction of exhaust gas in a forward direction (a) and a reverse direction (b).
FIG. 3 is a flowchart for controlling the flow direction of exhaust gas.
[Explanation of symbols]
1 Engine 10 Exhaust flow path (main flow path)
11 Bypass channel (downstream side)
12 Bypass channel (upstream side)
20 NOx adsorption means (catalyst)
21 NOx adsorption means reversing device (rotating shaft)
30 Valve 1
31 Valve 2
32 Valve 3
33 NOx sensor 34 Controller

Claims (10)

A NOx adsorbing means carrying a NOx adsorbent for adsorbing nitrogen oxides on a carrier; and a gas flow control means for controlling the flow direction of exhaust gas to the NOx adsorbing means,
The gas flow control means includes rotation means capable of reversing the NOx adsorption means about a rotation axis perpendicular to the exhaust gas flow direction, and the exhaust gas flow direction is determined by the NOx adsorption means. The NOx adsorbent regenerator can be switched in the forward direction from one end side to the other end side of the carrier or in the reverse direction from the other end side to the one end side.   The gas flow control means includes a main flow path that passes through the NOx adsorption means, a bypass flow path that bypasses the NOx adsorption means and communicates from one end side to the other end side of the carrier, and the main flow path and the bypass flow path. The NOx adsorbent regeneration apparatus according to claim 1, further comprising a valve that opens and closes the valve.   3. The NOx according to claim 1, wherein the exhaust gas flow direction is switched when the NOx adsorbent of the NOx adsorbing means is subjected to sulfur poisoning and the nitrogen oxide absorption performance is lowered. Adsorbent recycling device.   The exhaust gas is stoichiometrically rich when the exhaust gas flow direction is switched, and the NOx adsorption means is heated to 600 ° C or higher. The NOx adsorbent regeneration device described.   The NOx adsorbent contains at least one element selected from the group consisting of alkali metals, alkaline earth metals, rare earths, and transition metals. The NOx adsorbent regeneration device described. A NOx adsorbent regeneration method using the NOx adsorbent regeneration apparatus according to any one of claims 1 to 5,
By reversing the NOx adsorption means, the exhaust gas flow direction is supplied while switching the forward direction from one end side to the other end side of the carrier in the NOx adsorption means or the reverse direction from the other end side to the one end side. NOx adsorbent regeneration wherein the.   7. The NOx adsorbent regeneration method according to claim 6, wherein switching of the exhaust gas flow direction is performed by changing the flow direction of the exhaust gas.   The NOx according to claim 6 or 7, wherein the switching of the exhaust gas flow direction is performed when the NOx adsorbent of the NOx adsorbing means is subjected to sulfur poisoning and the nitrogen oxide absorption performance is lowered. Adsorbent regeneration method.   The exhaust gas is made stoichiometric to rich when the exhaust gas flow direction is switched, and the NOx adsorption means is heated to 600 ° C. NOx adsorbent regeneration method. An exhaust gas purification device comprising the NOx adsorbing material regeneration device according to any one of claims 1 to 5 installed in an exhaust gas flow path of a lean burn internal combustion engine,
An exhaust gas purifying apparatus, wherein the carrier in the NOx adsorption means further carries a catalyst component having an exhaust gas purifying ability.

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