JP2012117487A - Particulate filter with catalyst, exhaust gas purification and discharge system, catalyst arrangement part ratio calculation method, and catalyst arrangement part ratio calculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently suppress a change of regeneration performance irrespective of the accumulation of an internal combustion residue, in a particulate filter with a catalyst.SOLUTION: The particulate filter 16 with the catalyst has a PM oxide catalyst which is held by a filter body 27 and oxidizes and removes a particulate having carbon as a main component. The particulate filter 16 has a catalyst coating part 30 which is arranged at an exhaust inlet side, and in which the oxide catalyst is arranged, and a catalyst non-coating part 32 which is arranged at an exhaust outlet side, and in which the oxide catalyst is not arranged. The particulate filter is regulated so that a partial coating ratio X being a ratio of the length of the catalyst coating part 30 with respect to the whole length and a regeneration ratio E generated by the removal of the particulate may satisfy a prescribed relationship.

Description

  The present invention relates to a particulate filter with a catalyst, which is supported on a honeycomb structure and includes an oxidation catalyst for oxidizing and removing particulate matter which is exhaust particulate mainly composed of carbon, an exhaust gas purification / exhaust system, a ratio of catalyst arrangement parts The present invention relates to a calculation method and a catalyst arrangement portion ratio calculation device.

  In exhaust gas discharged from an internal combustion engine, for example, a diesel engine, particulates (PM), which are exhaust particulates mainly composed of soot made of carbon, and combustion residues such as ash, that is, ash, are included. For this reason, conventionally, for example, in a diesel engine exhaust gas exhaust structure, it has been considered to provide a diesel particulate filter, that is, a DPF, to remove particulates and combustion residues.

  Further, the particulates accumulated in the DPF must be burned and removed when a predetermined amount is reached to recover the back pressure of the filter, that is, the DPF needs to be regenerated. For this reason, an oxidation catalyst DOC (Diesel Oxidation Catalyst) capable of oxidizing harmful components such as HC and CO in the exhaust gas and fuel is disposed upstream of the DPF, and the exhaust path upstream of the DOC is passed after a predetermined period. It has been practiced to inject fuel, raise the temperature of exhaust gas by the oxidation heat of the fuel, burn and remove particulates accumulated in the DPF, and regenerate the DPF. Also, an oxidation catalyst (hereinafter sometimes referred to as a PM oxidation catalyst) for lowering the particulate oxidation temperature is provided in the DPF, and fuel is injected upstream of the DOC when a predetermined period of time elapses. Therefore, it is also considered that the particulates are burned and removed at a relatively low temperature. In this way, when the PM oxidation catalyst is provided in the DPF, the amount of fuel added can be reduced because the combustion of the particulates is performed at a low temperature. In the entire specification and claims, “upstream” and “downstream” mean upstream and downstream of the flow of exhaust gas discharged from the internal combustion engine, respectively.

  Patent Document 1 discloses a structure of an exhaust gas purification apparatus for an internal combustion engine, in which the amount of catalyst supported on a DPF formed in a honeycomb cylindrical shape is larger on the upstream side, which is an exhaust gas inlet, than on the downstream side. In addition, a structure is described in which more catalyst is supported on the exhaust gas inflow side of the partition provided between the plurality of flow paths in the DPF than on the outflow side. As a result, it is said that these are oxidized and removed more actively at the inlet end of the DPF having a high exhaust concentration and a large amount of particulates. Further, since particulates are reduced at the outlet end, it is said that oxidation removal is performed by a corresponding amount of catalyst material.

Further, in Patent Document 2, as an exhaust particulate reduction device structure, an oxidation catalyst capable of oxidizing harmful components such as HC and CO in exhaust in order from an upstream side to a downstream side in an exhaust passage, and particulates such as carbon particles. The structure which provides the filter apparatus which can collect can be described. The filter member provided in the filter device divides a plurality of cells in a lattice shape by partition walls, and exhaust gas flowing into the upstream side flows from one cell to the other cell through the partition walls and is discharged from the filter member. I am doing so. In addition, a catalyst layer carrying a catalyst metal is coated on both sides of the partition wall. Further, the catalyst metal supported on the downstream portion of the filter member is supported more than the catalyst metal supported on the upstream portion. Thereby, it is said that the removal performance of carbon particles can be enhanced at a downstream portion of the filter member where the regeneration performance deteriorates due to the deposition of compound particles, which are ash mainly composed of components other than carbon, and can be configured at low cost. Further, when a noble metal is used as the catalyst metal, it is said that NO can be easily converted to NO ₂ . Further, the catalyst layer contains an alkali metal, and the supported amount of the alkali metal is increased in the upstream portion than in the downstream portion.

  Further, Patent Document 3 discloses an exhaust gas purification device, which is a first purification unit having a metal honeycomb structure on which a first oxidation catalyst is supported, and a second oxidation unit disposed downstream of the first purification unit. An exhaust gas purification device is described that includes a second purification unit having a particulate filter on which a catalyst is supported. The particulate filter is said to have a relatively large amount of the second oxidation catalyst supported on the upstream side than on the downstream side. This makes it possible to activate the catalyst efficiently and to purify the exhaust gas efficiently.

  Further, by setting the region where the amount of the second oxidation catalyst supported is relatively large from the upstream side of the particulate filter to the region of 20 to 80% of the length in the axial direction of the particulate filter, It is said that the catalyst is disposed in the upstream portion where the exhaust gas is more easily contacted than the case where the exhaust gas is uniformly dispersed and supported, and the effect on the purification performance due to the pressure loss and catalyst deterioration of the exhaust gas can be suppressed.

  Non-Patent Document 1 describes a physical model for expressing an oxidation mechanism of particulates inside a DPF provided with a PM oxidation catalyst.

Non-Patent Document 2 describes the simulation of soot oxidation in a DPF using a plurality of channels. Non-Patent Document 2 describes that the filter ages due to the accumulation of ash on the filter, and that the thickness and ash mass ratio of the ash layer in the filter are related to the ash function Jash. Further, in Non-Patent Document 2, Jash is a step function that depends on the local shear stress and the maximum temperature Tmax experienced by the filter wall. the Jash when boundary temperature Tcr is greater than a 0, Jash otherwise is as to be a constant value J _0. Furthermore, it is recommended that the exhaust gas temperature does not exceed the boundary temperature Tcr of 1050 ° C. in terms of ensuring that the non-sticky ash is transferred to the downstream end of the filter. When the boundary temperature Tcr exceeds 1050 ° C., sticky ash is supposed to be deposited along the wall of the filter.

JP 2001-207836 A JP 2004-239197 A JP 2009-57922 A

A.G. Konstandopoulos, M. Kostoglou, "Periodically Reversed Flow Regeneration of Diesel Particulate Traps", USA, 1999, SAE Tech. Paper No. 1999-01-0469 A.G.Konstandopoulos, M. Kostoglou, P. Housiada, N. Vlachos, and D. Zarvalis, "Multichannel Simulation of Soot Oxidation in Diesel Particulate Filters", USA, 2003, SAE Tech. Paper No. 2003-01-0839

  As previously considered, when a configuration in which a PM oxidation catalyst is provided on the DPF by coating is adopted, it is possible to reduce the amount of fuel required for particulate combustion, that is, filter regeneration. There is sex. However, in addition to particulates, exhaust gas discharged from the engine contains ash, an element that causes ash, which is a combustion residue that cannot be removed in the normal filter regeneration process. Is deposited in the filter, the effect of the PM oxidation catalyst is hindered, and the regeneration performance of the filter may be reduced. In particular, the DPF has two flow path groups, an upstream flow path group and a downstream flow path group, which are partitioned by a plurality of cell walls that are partition walls, and the upstream flow path group is downstream on the downstream side. When the downstream flow path group includes a honeycomb structure whose upstream side is blocked by the upstream plug, combustion residues such as ash are present on the exhaust outlet end side of the upstream flow path group. May accumulate.

  Therefore, in the conventional DPF, the regeneration performance of the filter is high at the start of use, and the regeneration performance is greatly deteriorated as combustion residues such as ash (hereinafter referred to as ash) accumulate due to repeated regeneration. there is a possibility. For this reason, it can be considered that the amount of fuel added necessary for regeneration of the filter during deposition is added as a fixed amount during regeneration corresponding to the case where ash or the like has accumulated to some extent in the filter. The amount of fuel added is too large, which not only causes the temperature inside the filter to overheat, but also causes fuel consumption to deteriorate as a maintenance cost.

  On the other hand, it is conceivable to change the amount of fuel added to regenerate the filter according to the amount of ash accumulated in the filter, but this requires a detection and control mechanism for the amount of ash accumulated. This leads to an increase in the cost of the post-processing system. It is also conceivable to change the fuel addition amount necessary for regeneration of the filter by performing control according to the travel distance without detecting the ash accumulation amount. However, the properties of ash-causing substances such as oil vary widely depending on the region, and it is difficult to estimate the amount of ash deposition from the travel distance. Therefore, to realize a DPF provided with a PM oxidation catalyst, which has a regenerative performance with little or no change such as a constant regenerative performance regardless of accumulation of ash or the like in the filter. Is desired.

  On the other hand, in the case of the configurations described in Patent Documents 1 and 3, the accumulation of ash or the like in the filter is not considered. In the case of the configurations described in Patent Documents 1 and 3, the amount of catalyst supported on the upstream side of the filter is larger than that on the downstream side, but it is not possible to provide a catalyst non-arrangement part that does not provide a catalyst on the downstream side of the filter. Not considered. For this reason, when a catalyst is also provided on the downstream side of the filter, when the catalyst is a PM oxidation catalyst, the performance of the PM oxidation catalyst is hindered by ash or the like, and the regeneration performance of the filter may be lowered. On the other hand, it is conceivable to provide a region with a small amount of catalyst in the entire area of the filter. However, in this case, the regeneration performance of the filter itself deteriorates and the original purpose cannot be achieved. For this reason, realization of a means capable of suppressing performance degradation due to ash or the like while maintaining reproduction performance is desired.

In the case of the configuration described in Patent Document 2, the amount of noble metal catalyst is increased on the downstream side of the filter from the upstream side in consideration of the accumulation in the filter such as ash, and on the downstream side where the ash accumulation amount is large. By promoting the conversion of NO in the exhaust gas to NO ₂ , the deterioration of the DPF regeneration performance due to the accumulation of ash is suppressed using the oxidation of particulates by NO ₂ . However, this method not only increases the cost due to an increase in the amount of noble metal used, but also the NO emission amount varies depending on the operating state of the engine, so that the regeneration performance of the filter may greatly change due to the accumulation of ash or the like. .

  In the case of the configuration described in Patent Document 2, in consideration of the accumulation of ash or the like on the downstream side of the filter, the amount of alkali metal supported on the upstream side of the filter is larger than that on the downstream side. However, with this method, the amount of alkali metal supported can be reduced, but the alkali metal that is the PM oxidation catalyst is also supported on the downstream side of the filter, and the regeneration performance of the filter greatly changes due to the accumulation of ash or the like. there is a possibility. Further, Patent Document 2 does not mention a catalyst loading form that is optimal for the regeneration performance of the DPF, such as an alkali metal loading distribution.

  The particulate filter with catalyst, the exhaust gas purification / discharge system, the catalyst arrangement portion ratio calculation method, and the catalyst arrangement portion ratio calculation device according to the present invention are the particulate filter provided with an oxidation catalyst, regardless of the accumulation of combustion residues inside. An object is to efficiently suppress a change in reproduction performance.

The particulate filter with catalyst according to the present invention is a plurality of flow paths partitioned from each other by a plurality of cell walls, and is divided into two flow path groups, an upstream flow path group and a downstream flow path group. A plurality of channels, wherein the upstream channel group is closed at the downstream side by a downstream plug, and the downstream channel group is blocked at the upstream side by an upstream plug. A particulate filter having a catalyst structure, and a particulate filter with a catalyst, which is supported on the honeycomb structure and an oxidation catalyst for oxidizing and removing exhaust particulates mainly composed of carbon. And a catalyst disposition portion where the oxidation catalyst is disposed on the exhaust inlet side, and a catalyst non-arrangement portion where the oxidation catalyst is not disposed on the exhaust outlet side with respect to the length direction. Against the total length of the road The catalyst arrangement ratio, which is the ratio of the length of the catalyst arrangement portion, is assumed to be X, the regeneration rate by removal of exhaust particulates is assumed to be E, the regeneration rate assuming that the catalyst arrangement ratio is 0 is assumed to be E0, and the catalyst arrangement ratio is assumed to be 1. When the playback rate is E1,
0 <X <1 (1)
−δE ≦ E−E0− (E1−E0) × X ≦ δE (2)
δE = (E1-E0) × 0.1 (3)
It is a particulate filter with a catalyst characterized by satisfying all of the above. In the present specification and claims as a whole, “regeneration rate” refers to the ratio of the weight of particulates burned by regeneration to the total weight of particulates (PM) that are exhaust particulates before filter regeneration. .

  According to the particulate filter with catalyst according to the present invention, even when combustion residues such as ash accumulate on the downstream side of the honeycomb structure, the regeneration rate changes up to a certain accumulation amount regardless of the accumulation amount of the combustion residue. Is substantially constant, and the change in the reproduction rate can be suppressed. Moreover, the range of the period etc. which can suppress the change of the reproduction rate can be enlarged sufficiently.

  In the particulate filter with catalyst according to the present invention, preferably, (E1−E0) X = E−E0 is satisfied.

  The exhaust gas purification / discharge system according to the present invention includes the particulate filter with catalyst according to the present invention, and a supply unit that supplies fuel to the upstream side of the particulate filter with catalyst, and further passes through the particulate filter with catalyst. The maximum temperature of the exhaust gas is regulated so as to be equal to or lower than a preset boundary temperature for suppressing the stickiness of the combustion residue contained in the exhaust gas. More preferably, the boundary temperature is 1050 ° C.

  According to the above configuration, the combustion residue easily accumulates on the exhaust outlet side of the particulate filter, so that the change in the regeneration performance of the particulate filter can be suppressed more efficiently.

  Further, the catalyst arrangement portion ratio calculation method according to the present invention is a plurality of flow paths partitioned from each other by a plurality of cell walls, and is divided into two flow path groups, an upstream flow path group and a downstream flow path group. A honeycomb structure having a plurality of divided flow paths, wherein the upstream flow path group is closed at the downstream side by a downstream plug, and the downstream flow path group is closed at the upstream side by an upstream plug. A particulate filter with a catalyst, comprising a honeycomb structure that is peeled, and an oxidation catalyst that is carried on the honeycomb structure and oxidizes and removes exhaust particulates mainly composed of carbon, the honeycomb structure comprising: A particulate filter with catalyst, which is provided on the exhaust inlet side with respect to the length direction and where the oxidation catalyst is disposed, and a catalyst non-arrangement portion which is provided on the exhaust outlet side with respect to the length direction and where the oxidation catalyst is not disposed. Against In order to maintain the regeneration rate E due to the removal of the fine particles in the vicinity of a desired value, a calculation for calculating a catalyst arrangement ratio X, which is a ratio of the length of the catalyst arrangement portion with respect to the total length of the upstream flow path of the honeycomb structure, using a computer A method for storing a regeneration rate catalyst ratio relationship between a regeneration rate E and a catalyst arrangement ratio X obtained in advance in a storage unit, a step of receiving the regeneration rate E, and a regeneration rate from the received regeneration rate E. A method for calculating a catalyst arrangement portion ratio of a particulate filter with a catalyst, comprising: obtaining a catalyst arrangement ratio X in accordance with a catalyst ratio relationship; and outputting the acquired catalyst arrangement ratio X.

  According to the catalyst arrangement portion ratio calculating method according to the present invention, the optimum value of the catalyst arrangement ratio of the particulate filter with catalyst can be calculated efficiently, so that the optimum value can be used regardless of the accumulation of combustion residues inside. Therefore, it is possible to realize a particulate filter with a catalyst that can efficiently suppress a change in regeneration performance.

  Further, the catalyst arrangement portion ratio calculating apparatus according to the present invention includes a plurality of flow paths that are partitioned from each other by a plurality of cell walls, and includes two flow path groups, an upstream flow path group and a downstream flow path group. A honeycomb structure having a plurality of divided flow paths, wherein the upstream flow path group is closed at the downstream side by a downstream plug, and the downstream flow path group is closed at the upstream side by an upstream plug. A particulate filter with a catalyst, comprising a honeycomb structure that is peeled, and an oxidation catalyst that is carried on the honeycomb structure and oxidizes and removes exhaust particulates mainly composed of carbon, the honeycomb structure comprising: A particulate filter with catalyst, which is provided on the exhaust inlet side with respect to the length direction and where the oxidation catalyst is disposed, and a catalyst non-arrangement portion which is provided on the exhaust outlet side with respect to the length direction and where the oxidation catalyst is not disposed. Against A calculation device for calculating a catalyst arrangement ratio X, which is a ratio of the length of the catalyst arrangement portion to the entire length of the upstream flow path of the honeycomb structure, in order to maintain the regeneration rate E by removal of the fine particles in the vicinity of a desired value. A storage unit that stores in advance a regeneration rate catalyst ratio relationship between the regeneration rate E and the catalyst arrangement ratio X determined in advance, a receiving unit that receives the regeneration rate E, and a regeneration rate catalyst ratio from the regeneration rate E received by the receiving unit A catalyst placement portion ratio calculation device for a particulate filter with a catalyst, comprising: a ratio acquisition unit that acquires a catalyst placement ratio X according to a relationship; and an output unit that outputs the acquired catalyst placement ratio X. .

  According to the catalyst arrangement portion ratio calculating apparatus according to the present invention, the optimum value of the catalyst arrangement ratio of the particulate filter with catalyst can be calculated efficiently, so that the optimum value is used for the accumulation of the combustion residue inside. Therefore, it is possible to realize a particulate filter with a catalyst that can efficiently suppress a change in regeneration performance.

  According to the particulate filter with catalyst, the exhaust gas purification / discharge system, the catalyst arrangement portion ratio calculation method, and the catalyst arrangement portion ratio calculation device according to the present invention, in the particulate filter provided with the oxidation catalyst, the accumulation of combustion residues inside Regardless of this, changes in playback performance can be efficiently suppressed.

It is a lineblock diagram of an exhaust gas purification exhaust system of an embodiment of the invention. It is a schematic perspective view which shows the structure of the particulate filter with a catalyst of embodiment of this invention. FIG. 3 is a schematic diagram for explaining a catalyst coated portion and a catalyst uncoated portion of the particulate filter of FIG. 2. In the particulate filter with catalyst according to the embodiment of the present invention, simulation is performed to obtain the relationship between the partial coat ratio X and the regeneration ratio, and three types of analysis models with different partial coat ratios X are used. It is a figure which shows the simulation result which was done by the relationship between the accumulation state of an ash, and a regeneration rate. It is a figure which shows the simulation result of FIG. 4 by the relationship with the generalized value. FIG. 6 is a diagram for explaining a method of using the relationship of FIG. 5 and obtaining an effective partial coat ratio from a required reproduction rate in order to suppress a change in the reproduction rate. It is a figure for demonstrating an example of a mode that a partial coat ratio is calculated | required according to a request | requirement reproduction | regeneration rate using the relationship of FIG. It is a figure which shows the analysis result which calculated | required the change of the regeneration rate by ash deposition with the analysis model using the partial coat ratio obtained from FIG. In the particulate filter with catalyst according to the embodiment of the present invention, it is a diagram showing the relationship between the partial coat ratio X and the regeneration rate. It is a figure which shows the structure of the computer which is a catalyst arrangement | positioning part ratio calculation apparatus of embodiment of this invention. It is a figure which shows the catalyst arrangement | positioning part ratio calculation method of embodiment of this invention.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows an overall configuration of an exhaust gas purification / discharge system including a particulate filter with a catalyst according to an embodiment of the present invention.

  As shown in FIG. 1, the exhaust gas purification / discharge system of the present embodiment is connected to a diesel engine (hereinafter simply referred to as an engine) 10 that is an internal combustion engine, and fuel is combusted in a combustion chamber of the engine 10. Used to discharge the generated exhaust gas to the outside. In the exhaust gas purification / exhaust system, an exhaust gas passage 12 including an exhaust pipe is connected to an exhaust manifold (not shown) of the engine 10, and the exhaust gas passage 12 allows the exhaust gas purification device 14 and a particulate with catalyst having a PM oxidation catalyst. A filter (hereinafter simply referred to as DPF) 16 is connected in order from the upstream side to the downstream side. In the exhaust gas path 12, a fuel-supplied supply unit 18 is provided between the exhaust manifold and the exhaust gas purification device 14. In the fuel supply unit 18, the fuel is supplied from the fuel supply unit 20, and the fuel is mixed with the exhaust gas flowing through the exhaust gas path 12. The exhaust gas after the fuel mixing is sent to the exhaust gas purification device 14 on the downstream side.

  The exhaust gas purification device 14 has an oxidation catalyst support structure called DOC, and supports a catalyst containing an oxidation catalyst in a honeycomb structure that does not block the upstream and downstream ends. The exhaust gas purification device 14 has a function of purifying NOx, hydrocarbon (HC), etc. in the exhaust gas.

  The exhaust gas that has passed through the exhaust gas purification device 14 is sent to the DPF 16. The DPF 16 is exhaust particulates contained in the exhaust gas of the engine 10, and collects particulate matter (particulate matter) and combustion residues such as ash (hereinafter referred to as ash) and the like, and collects the particulates. Used for removal by oxidation, ie combustion.

  As shown in FIG. 2, the DPF 16 is a honeycomb-type filter body that is a honeycomb structure formed in a honeycomb shape having a plurality of flow paths 24 and 26 separated from each other by partition walls 22 that are a plurality of cell walls. 27 and a PM oxidation catalyst carried on the filter main body 27. The plurality of flow paths 24 and 26 are divided into two flow path groups, a flow path 24 that is an upstream flow path group and a flow path 26 that is a downstream flow path group. The upstream channel 24 is closed by the downstream plug 28 on the downstream side (right side in FIG. 2), and the downstream channel 26 is upstream on the upstream side (left side in FIG. 2). The plug 29 is blocked. A honeycomb having a checkerboard cross section is formed by the plurality of flow paths 24 and 26. A part of the upstream channel 24 is surrounded by the downstream channel 26, and a part of the downstream channel 26 is surrounded by the upstream channel 24. The DPF 16 allows the exhaust gas to pass through the partition wall 22 but prevents the exhaust gas from passing through the upstream and downstream plugs 28 and 29. The DPF 16 is generally cylindrical in FIG. 2, but is not limited to such a configuration.

  The exhaust gas flowing in the direction of arrow α in FIG. 2 is sent into the DPF 16 from the opening of the upstream flow path 24, sent to the downstream flow path 26 through the pores provided in the partition wall 22, and It is discharged to the outside from the opening of the flow path 24. Since the particulates contained in the exhaust gas hardly pass through the partition wall 22, they are collected in the DPF 16. For this reason, it becomes possible to purify the exhaust gas passing through the DPF 16.

  In addition, excessive accumulation of particulates in the DPF 16 increases the pressure loss and causes performance deterioration. For this reason, in the DPF 16, fuel is periodically supplied to the exhaust gas path 12 (FIG. 1) by the fuel supply unit 20 (FIG. 1). The fuel is mixed in the exhaust gas, sent to the exhaust gas purification device 14, and oxidized or burned in the exhaust gas purification device 14, so that the temperature of the exhaust gas rises and the heated exhaust gas is sent to the DPF 16. Unburned fuel is also sent to the DPF 16. For this reason, the PM oxidation catalyst is supported on the base material constituting the filter main body 27 directly or via a carrier, so that the fuel can be oxidized by the DPF 16, that is, burned to further raise the temperature of the exhaust gas. When the temperature of the exhaust gas rises and reaches, for example, 600 degrees or more, it becomes possible to burn and remove the particulates accumulated in the DPF 16. Further, the particulate oxidation temperature can be lowered by the PM oxidation catalyst, and the particulate can be burned and removed at a relatively low temperature. For this reason, in the DPF 16 of the present embodiment, the PM oxidation catalyst is supported on the base material constituting the honeycomb filter body 27. That is, the DPF 16 is configured such that regeneration by burning and removing the particulates is performed by supplying fuel from the fuel supply unit 20. In addition, although the material of a base material is not limited, For example, the base material etc. which consist of ceramics, such as a cordierite, a silicon carbide, and a mullite, can be used.

  The PM oxidation catalyst is a catalyst in which a noble metal such as Pt or Pd is supported on a carrier made of a metal oxide such as alumina. Moreover, the aggregate which consists of a silver particle used as a nucleus and a ceria microparticle with an average primary particle diameter of 1-100 nm covering the circumference | surroundings of a silver particle can also be used as PM oxidation catalyst. The silver particles may be one using silver alone, but an alloy composed of two or more metals of silver and a metal other than silver can also be used. Furthermore, part of the silver particles may form an oxide or may form a compound with another element. When a part of silver particles forms an oxide or a compound, the silver content is preferably 0.3% by mass or more. Silver particles and ceria fine particles themselves are primary particles, and secondary particles formed by covering the former with the latter are aggregates.

  Such silver particles function as an oxygen release material. Such silver particles make it possible to incorporate oxygen atoms into a reaction system that efficiently oxidizes particulates and the like. In addition, the silver particles may function as an oxygen-containing substance capturing material. The ceria fine particles also act as a reducing agent, can move the oxygen active species generated by the silver particles, and function as an oxygen active transfer material. The received oxygen active species can move through the ceria fine particles and reach the adsorbed particulates.

  In the aggregate, in order to increase the mobility of the oxygen active species in the ceria fine particles and more effectively prevent the ceria particles from coarsening, rare earth elements other than Ce such as La and Nd, Zr, Y, More preferably, it further contains at least one additive component selected from the group consisting of Al and Si.

  The average particle size of the aggregate is not particularly limited, but is preferably 0.05 to 0.5 μm, and more preferably 0.07 to 0.2 μm. If the average particle diameter is less than the above lower limit, the contact between the oxygen-containing substance and the silver particles tends to be inhibited. On the other hand, if it exceeds the above upper limit, the contact between the ceria fine particles and the particulates tends to be inhibited.

  Such aggregates preferably have high dispersibility, and 60% by volume or more of all aggregates may have a particle size in the range of the above average particle size ± 50%. preferable. The shape of the aggregate is not limited, but is preferably spherical.

  Further, in the present embodiment, as shown in FIG. 3, the DPF 16 is provided on the engine side, that is, on the exhaust inlet side (right side in FIG. 3) with respect to the length direction, and the PM oxidation catalyst is placed on the partition wall 22 (FIG. 2). The catalyst coating part 30 which is the catalyst arrangement | positioning part arrange | positioned, and the catalyst non-coating part 32 which is provided in the exhaust outlet side (left side of FIG. 3) regarding the length direction and where a PM oxidation catalyst is not arranged is provided. That is, the DPF 16 is catalyst coated at a predetermined partial coating ratio X described later with respect to the total length L in the axial direction (left and right direction in FIG. 3) that is the longitudinal direction from the exhaust inlet end (left end in FIG. 3) on the upstream side. A portion 30 is provided. In the catalyst coating unit 30, the partition wall 22 is provided with a PM oxidation catalyst by coating.

  That is, the catalyst coat portion 30 is provided in the region indicated by the length Lc in FIG. 3, and the PM oxidation catalyst is disposed substantially uniformly on the catalyst coat portion 30. Further, a portion downstream from the catalyst coating portion 30 is a catalyst non-coating portion 32 that is a catalyst non-arrangement portion where no PM oxidation catalyst is provided. As described above, in the DPF 16, the PM oxidation catalyst is concentratedly arranged only on the upstream catalyst coat portion 30. Conversely, the PM oxidation catalyst is not coated on the exhaust inlet side by a predetermined length portion preset from the exhaust outlet end (right end in FIG. 3) of the DPF 16. The ratio Lc of the length Lc of the catalyst coat portion 30 provided from the upstream end to each partition wall 22 (FIG. 2) of the DPF 16 is the ratio of the length Lc to the total length of the upstream flow path 24 (FIG. 2) of the filter body 27. The partial coat ratio X, which is the ratio of the length of the portion 30, is substantially the same for each partition 22. This partial coat ratio X is set, that is, set according to the required reproduction rate. This will be described in detail later.

  Preferably, the PM oxidation catalyst provided in the catalyst coat portion 30 of the DPF 16 is composed of the above-described silver particles serving as the nucleus and ceria fine particles having an average primary particle diameter of 1 to 100 nm covering the periphery of the silver particles. Aggregates are used.

  Preferably, the maximum temperature Tmax of the exhaust gas that passes through the DPF 16 is regulated so as to be equal to or lower than a preset boundary temperature Tcr for suppressing the adhesion of ash or the like contained in the exhaust gas (Tmax ≦ Tcr). Yes. For this reason, the maximum temperature Tmax is regulated by various controls such as engine control. For example, when cordierite is used for the base material of the DPF 16, the boundary temperature Tcr is set to 1050 ° C.

  Further, the partial coating ratio X of the PM oxidation catalyst is set according to the required regeneration rate that is the required regeneration performance, that is, the regeneration performance that is set. The “regeneration rate” is a regeneration rate due to the removal of particulates in the DPF 16, and the particulates in the DPF 16 after the particulates are burned and removed by regeneration with respect to the weight of the particulates in the DPF 16 before regeneration. The ratio of weight.

  Next, from the required regeneration performance, the DPF 16 in which the partial coating ratio X, which is the catalyst arrangement portion ratio, the method for setting the partial coating ratio X, that is, the calculation method, and the apparatus used for calculating the field are used. Will be explained. First, in order to obtain the partial coat ratio X corresponding to the reproduction performance set in the present embodiment, the inventor changes the partial coat ratio X in three types of 0, 53, 1, and 0.75, The relationship between the accumulation state of the ash in the DPF 16 and the regeneration rate was obtained by simulation.

In this simulation, a cylindrical shape having an outer diameter of 16 cm and an axial length of 10 cm has a cell pitch per square inch (= 6.45 cm ² ), that is, the number of channels per cross-sectional area of one square inch is 300. And an analysis model having a DPF 16 in which the thickness of the partition wall 22 (FIG. 2) is 12 milliinches (= 30.5 × 10 ⁻³ cm). In this analysis model, the PM oxidation catalyst is arranged in the DPF 16 from the exhaust inlet side, and the partial coating ratio X, which is the length ratio with respect to the entire length of the arrangement portion of the PM oxidation catalyst, is set to 0, 53, 1,. Three types of analysis models with 75 different types were used. Such an analysis model was created by a conventionally known analysis method as described in Non-Patent Document 1 above. For example, it is assumed that the flow paths 24 and 26 (FIG. 2) in the DPF 16 include a first layer that is affected by the catalyst coating and a second layer in which a large amount of soot accumulated on the first layer is disposed. Then, thermal oxidation and oxidation by catalyst coating in each layer were calculated. Moreover, it calculated using the aggregate which consists of said ceria microparticles | fine-particles with an average primary particle diameter of 1-100 nm which covers the circumference | surroundings of silver particle | grains and the silver particle as a PM oxidation catalyst.

  And with respect to these analysis models, the change in the regeneration performance due to the accumulation of ash was analyzed by simulation of the regeneration analysis of DPF 16 by the thermal fluid analysis software STAR-CD manufactured by CD-adapco. In the following description, elements equivalent to those shown in FIGS. 1 to 3 are denoted by the same reference numerals. FIG. 4 shows the result of this simulation. In this simulation, according to the above-mentioned Non-Patent Document 2, ash is deposited in the DPF 16 so as to gradually and uniformly fill the flow paths 24 and 26 from the exhaust outlet end of the filter body 27 toward the exhaust inlet side. In the DPF 16, the particulates cannot enter the area where the ash is accumulated. In FIG. 4, the ash tip position is the position of the ash surface that is the exhaust inlet side end of the ash that gradually accumulates from the exhaust outlet end of the filter body 27 toward the exhaust inlet side. Thus, ash exists only in the outlet side direction, and no ash exists in the inlet side direction.

  From the simulation results shown in FIG. 4, when the ash tip position is in the catalyst uncoated portion 32 shown as “catalyst uncoated region” in FIG. 3, the change in the regeneration performance of the filter body 27 due to ash accumulation is as follows. I understand that it is small. It can also be seen that the regeneration performance of the filter body 27 is drastically reduced when the amount of ash deposited increases and the tip position enters the catalyst coat portion 30 shown as “catalyst coat region” in FIG. This is considered to be due to the fact that even when the PM oxidation catalyst is provided in the portion where the ash is deposited, the contact property between the PM oxidation catalyst and the particulates is lowered and the particulate oxidation reaction is inhibited.

  From the knowledge obtained from the results of FIG. 4, the present inventor has shown that the relationship between the regeneration rate of the DPF 16 and the ash tip position when the partial coat ratio X of the DPF 16 is a general value is as shown in FIG. I thought. In FIG. 5, the ash tip position is taken on the horizontal axis, the regeneration rate of the DPF 16 is taken on the vertical axis, and the total length of the filter body 27 of the DPF 16 is L. In this case, when the partial coat ratio X is 1, the regeneration rate of the DPF 16 increases linearly as the ash tip position approaches the exhaust outlet side from the exhaust inlet end. Further, when the axial length of the catalyst coat portion 30 is Lc, that is, when the partial coat ratio X is Lc / L, as the tip of the ash approaches the exhaust outlet end side from the exhaust inlet side end, the ash The regeneration rate of the DPF 16 is the same as that in the case of X = 1 until the tip position of L is Lc, but the regeneration rate is maintained at a constant value when the tip position of the ash is between Lc and L.

  From the results shown in FIG. 5, the present inventor has obtained a DPF 16 that satisfies the required regeneration rate and can reduce deterioration in regeneration performance due to ash when the tip position of ash or the like is in the catalyst uncoated portion 32 of FIG. It came to think about the method of determining the partial coat ratio to realize.

  This will be described in detail with reference to FIG. 6. When the partial coating ratio X is 0, that is, when the filter body 27 has no portion coated with the PM oxidation catalyst, the regeneration rate of the DPF 16 is E0, and the partial coating ratio X Is 1, that is, the regeneration rate of the DPF 16 when the PM oxidation catalyst is coated over the entire length of the filter body 27 is E1. In this case, assuming that the regeneration rate required for the DPF 16 is E, from the relationship shown in FIG. 6, a graph showing the intersection of the point P1 where the partial coating ratio X is 1 and the regeneration rate is E1, and the horizontal axis and the vertical axis. It is possible to obtain the partial coat ratio X when the reproduction rate is E on the straight line Q connecting with the origin of. That is, the partial coat required to be set by the DPF 16 from the point that the straight line T drawn parallel to the vertical axis intersects the horizontal axis at the intersection of the straight line S and the straight line Q passing through E on the vertical axis in FIG. A ratio X is determined.

Next, simulation of an application example using the method of determining the partial coat ratio of the filter main body 27 from the relationship of FIG. 6 will be described. This simulation was performed using the same analysis model as in the simulation shown in FIG. That is, even in this simulation, a cylindrical shape with an outer diameter of 16 cm and an axial length of 10 cm has a cell pitch per square inch (= 6.45 cm ² ), that is, the number of flow channels per cross-sectional area of 1 square inch. Was set to 300, and an analysis model having a DPF 16 in which the partition wall 22 (FIG. 2) had a thickness of 12 milliinches (= 30.5 × 10 ⁻³ cm) was used. Then, two types of models in which the value of the partial coat ratio X was varied between 0 and 1 in this analysis model were created, and the regeneration performance of the DPF 16 was evaluated by the thermal fluid analysis software STAR-CD. FIG. 7 shows the simulation result.

  As is clear from the simulation results of FIG. 7, when the partial coat ratio X is 0, the regeneration rate E0 of the DPF 16 is 55.2%, and when the partial coat ratio X is 1, the regeneration rate E1 of the DPF 16 is 97.2. %. Therefore, when the reproduction rate is 85% as the required reproduction performance, the partial coat ratio X satisfying the required reproduction rate is calculated, and as a result, a value of 0.72 is obtained as the partial coat ratio X as shown in FIG. It was.

  Therefore, next, an analysis model of DPF 16 having a partial coat ratio X of 0.72 (X = 0.72) was created, and a simulation for analyzing the change in the regeneration performance due to ash deposition was performed. FIG. 8 shows the result of this simulation. As is apparent from the results of FIG. 8, in the analysis model of X = 0.72, the regeneration performance is improved until the tip position of the ash is the length from the exhaust inlet end of the catalyst uncoated portion 32 to 100 mm to 72 mm. It was confirmed that the regeneration rate could be maintained at a constant level regardless of the accumulation of ash.

  And from this knowledge, this inventor considered DPF16 which set the partial coat ratio X which is the optimal catalyst arrangement | positioning part ratio from the reproduction | regeneration performance requested | required. FIG. 9 is a diagram showing the relationship between the partial coat ratio X and the regeneration rate in the DPF of the present embodiment. In FIG. 9, the method for obtaining the straight line Q is the same as the method for obtaining the straight line Q in FIG. The present inventor not only makes the straight line Q coincide with the straight line Q but also a partial coating ratio in a range in the vicinity of the straight line Q, that is, a portion between the straight lines L1 and L2 arranged on both sides of the straight line Q in FIG. Even when the relationship between X and the regeneration rate E is established, it is considered that the regeneration rate of the DPF 16 can be maintained almost constant regardless of the accumulation of ash in the filter body 27.

That is, in the present embodiment, the partial coat ratio, which is the ratio of the length of the catalyst coat section 30 to the total length of the upstream flow path 24 of the filter body 27, is X, and the regeneration ratio by the removal of particulates in the DPF 16 is E. When the reproduction rate assuming that the partial coat ratio is 0 is E0, and the reproduction rate assuming that the partial coat ratio is 1 is E1,
0 <X <1 (1)
−δE ≦ E−E0− (E1−E0) × X ≦ δE (2)
δE = (E1-E0) × 0.1 (3)
The relationship between the regeneration rate E and the partial coat ratio X is regulated so that all of the above are satisfied. Therefore, when the relationships (1) to (3) are satisfied, the relationship between the reproduction rate E and the partial coat ratio X is in the range indicated by the arrow A between the straight lines L1 and L2 in FIG. It will be.

  Preferably, the relationship between the reproduction rate E and the partial coat ratio X is regulated so as to satisfy (E1-E0) X = E-E0. In this case, the relationship between the reproduction rate E and the partial coat ratio X is on the straight line Q in FIG.

  Further, in order to determine the partial coat ratio X set from the required reproduction rate E using such a relationship, that is, to calculate the partial coat ratio X, the following partial coat ratio calculation device and partial coat ratio calculation Use the method. FIG. 10 shows a computer which is a partial coat ratio calculation apparatus according to the present embodiment, and FIG. 11 shows a partial coat ratio calculation method using this computer.

  As shown in FIG. 10, the computer 34 is a calculation device, and has a function of calculating the partial coat ratio X in order to maintain the regeneration rate E by removing the particulates in the vicinity of the desired value with respect to the DPF 16. Have. The computer 34 stores a storage unit 36 that stores the regeneration rate catalyst ratio relationship between the regeneration ratio E and the partial coat ratio X obtained in advance as shown in FIG. A receiving unit 38 that receives the reproduction rate E in accordance with an operation of a unit (not shown). Further, the computer 34 obtains, that is, calculates the partial coat ratio X corresponding to the regeneration rate E from the regeneration rate E received by the receiving unit 38 according to the regeneration rate catalyst ratio relationship stored in the storage unit 36. An acquisition unit 40 and an output unit 42 such as a display for outputting the acquired partial coat ratio X are provided.

  Further, as shown in FIG. 11, the partial coat ratio calculation method uses the above-mentioned computer for calculating the partial coat ratio X in order to maintain the regeneration rate E by the removal of the particulate matter in the vicinity of the desired value with respect to the DPF 16. 34 (FIG. 10). In this calculation method, the storage step of storing the regeneration ratio catalyst ratio relationship between the regeneration ratio E and the partial coat ratio X obtained in advance as data such as a map in the storage unit 36 (FIG. 10), the user's keyboard, etc. A receiving step of receiving the reproduction rate E by the receiving unit 38 (FIG. 10) according to the operation of the input unit. Further, the calculation method uses the ratio acquisition unit 40 (see FIG. 10) to obtain the partial coat ratio X corresponding to the regeneration rate E from the regeneration rate E received by the receiving unit 38 in accordance with the regeneration rate catalyst ratio relationship stored in the storage unit 36. ), That is, a ratio acquisition step of calculating, and an output step of outputting the acquired partial coat ratio X by the output unit 42 (FIG. 10) such as a display.

  According to the DPF 16, exhaust gas purification / discharge system, partial coat ratio calculation method, and partial coat ratio calculation apparatus of the present embodiment, regardless of the accumulation of ash or the like in the DPF 16 provided with the PM oxidation catalyst, Changes in playback performance can be efficiently suppressed. That is, according to the DPF 16 of the present embodiment, even when ash or the like is deposited on the downstream side of the filter body 27, the regeneration rate change is made substantially constant up to a certain accumulation amount regardless of the accumulation amount of ash or the like. The rate change can be suppressed. Moreover, the range of the period etc. which can suppress the change of the reproduction rate can be enlarged sufficiently.

  Further, according to the exhaust gas purification / discharge system of the present embodiment, the DPF 16 and the fuel supply unit 20 that supplies fuel to the upstream side of the DPF 16 are provided, and the maximum temperature Tmax of the exhaust gas that passes through the DPF 16 is the exhaust gas. It is regulated so as to be not more than a preset boundary temperature Tcr (for example, not more than 1050 ° C.) for suppressing adhesiveness such as ash contained therein. For this reason, ash and the like are easily deposited on the exhaust outlet side of the upstream flow path 24 of the filter main body 27, so that the change in the regeneration performance of the DPF 16 can be suppressed more efficiently. Note that such a DPF 16 is formed by coating a PM oxidation catalyst only on a portion corresponding to the catalyst coating portion 30 by, for example, immersing a particulate filter before providing the PM oxidation catalyst in a slurry of the PM oxidation catalyst. create. In this case, not only the upstream flow path 24 of the DPF 16 but also the downstream flow path 26 is provided with the catalyst coat portion 30 whose arrangement ratio is similarly regulated on the exhaust inlet side. However, in the present invention, it is not always necessary to regulate the arrangement ratio of the catalyst coat portion in the downstream channel 26.

  In addition, according to the partial coat ratio calculation method and the partial coat ratio calculation apparatus of the present embodiment, the optimum value of the partial coat ratio X of the DPF 16 can be calculated efficiently. DPF 16 that can efficiently suppress the change in the regeneration performance can be realized by design or the like regardless of the accumulation of the material. That is, it is possible to design the DPF 16 in which the regeneration rate does not substantially change until ash or the like is deposited to a certain amount. In addition, the amount of ash and the like accumulated until the regeneration rate decreases can be estimated in advance according to the required regeneration rate. Therefore, it is almost always possible to replace the DPF 16 within a period of time sufficient to reach the amount of deposition. It becomes possible to regenerate the DPF 16 at a regeneration rate that does not change.

DESCRIPTION OF SYMBOLS 10 Diesel engine, 12 Exhaust gas path, 14 Exhaust gas purification apparatus, 16 Particulate filter (DPF), 18 Fuel supply part, 20 Fuel supply part, 22 Partition, 24, 26 Flow path, 27 Filter main body 27, 28 Downstream plug , 29 upstream side plug, 30 catalyst coated part, 32 catalyst uncoated part, 34 computer, 36 storage part, 38 receiving part, 40 ratio obtaining part, 42 output part.

Claims (5)

A honeycomb structure having a plurality of flow paths partitioned from each other by a plurality of cell walls and divided into two flow path groups, an upstream flow path group and a downstream flow path group There,
In the upstream flow path group, the downstream side is blocked by the downstream stopper,
The downstream flow path group includes a honeycomb structure in which the upstream side is closed by the upstream side plug,
A particulate filter with catalyst, which is supported on a honeycomb structure and includes an oxidation catalyst for oxidizing and removing exhaust particulates mainly composed of carbon,
The honeycomb structure includes a catalyst arrangement portion provided on the exhaust inlet side with respect to the length direction and in which the oxidation catalyst is arranged, and a catalyst non-arrangement portion provided on the exhaust outlet side with respect to the length direction and in which the oxidation catalyst is not arranged. ,
Assuming that the catalyst arrangement ratio, which is the ratio of the length of the catalyst arrangement portion to the total length of the upstream flow path of the honeycomb structure, is X, the regeneration ratio by removing exhaust particulates is E, and the regeneration ratio assuming that the catalyst arrangement ratio is 0 When E0 is assumed and the regeneration rate assuming that the catalyst arrangement ratio is 1 is E1,
0 <X <1 (1)
−δE ≦ E−E0− (E1−E0) × X ≦ δE (2)
δE = (E1-E0) × 0.1 (3)
Particulate filter with catalyst characterized by satisfying all of the above. The particulate filter with catalyst according to claim 1,
(E1-E0) A particulate filter with a catalyst satisfying X = E-E0. A particulate filter with catalyst according to claim 1 or 2,
A supply unit for supplying fuel to the upstream side of the particulate filter with catalyst,
Further, the maximum temperature of the exhaust gas that passes through the particulate filter with catalyst is regulated so as to be equal to or lower than a preset boundary temperature for suppressing the stickiness of the combustion residue contained in the exhaust gas. Exhaust gas purification and exhaust system. A honeycomb structure having a plurality of flow paths partitioned from each other by a plurality of cell walls and divided into two flow path groups, an upstream flow path group and a downstream flow path group There,
In the upstream flow path group, the downstream side is blocked by the downstream stopper,
The downstream flow path group includes a honeycomb structure in which the upstream side is closed by the upstream side plug,
A particulate filter with catalyst, which is supported on a honeycomb structure and includes an oxidation catalyst for oxidizing and removing exhaust particulates mainly composed of carbon,
The honeycomb structure includes a catalyst placement portion that is provided on the exhaust inlet side in the length direction and on which the oxidation catalyst is disposed, and a catalyst non-placement portion that is provided on the exhaust outlet side in the length direction and on which the oxidation catalyst is not disposed. In order to maintain the regeneration rate E by the removal of exhaust particulates in the vicinity of a desired value with respect to the particulate filter with catalyst, the catalyst arrangement which is the ratio of the length of the catalyst arrangement part to the total length of the upstream flow path of the honeycomb structure A calculation method for calculating the ratio X using a computer,
Storing the regeneration rate catalyst ratio relationship between the regeneration rate E and the catalyst arrangement ratio X determined in advance in a storage unit;
Receiving a playback rate E;
Obtaining the catalyst arrangement ratio X from the received regeneration ratio E according to the regeneration ratio catalyst ratio relationship;
And a step of outputting the obtained catalyst arrangement ratio X. A method for calculating the catalyst arrangement ratio of the particulate filter with catalyst. A honeycomb structure having a plurality of flow paths partitioned from each other by a plurality of cell walls and divided into two flow path groups, an upstream flow path group and a downstream flow path group There,
In the upstream flow path group, the downstream side is blocked by the downstream stopper,
The downstream flow path group includes a honeycomb structure in which the upstream side is closed by the upstream side plug,
A particulate filter with catalyst, which is supported on a honeycomb structure and includes an oxidation catalyst for oxidizing and removing exhaust particulates mainly composed of carbon,
The honeycomb structure includes a catalyst placement portion that is provided on the exhaust inlet side in the length direction and on which the oxidation catalyst is disposed, and a catalyst non-placement portion that is provided on the exhaust outlet side in the length direction and on which the oxidation catalyst is not disposed. In order to maintain the regeneration rate E by the removal of exhaust particulates in the vicinity of a desired value with respect to the particulate filter with catalyst, the catalyst arrangement which is the ratio of the length of the catalyst arrangement part to the total length of the upstream flow path of the honeycomb structure A calculation device for calculating the ratio X,
A storage unit that stores in advance a regeneration rate catalyst ratio relationship between the regeneration rate E and the catalyst arrangement ratio X that are obtained in advance;
A receiving unit for receiving the playback rate E;
A ratio acquisition unit that acquires a catalyst arrangement ratio X according to a regeneration rate catalyst ratio relationship from the regeneration rate E received by the receiving unit;
An output unit for outputting the obtained catalyst arrangement ratio X. A catalyst arrangement part ratio calculation apparatus for a particulate filter with a catalyst, comprising:

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