JP2005226458A - Method and device for treating diesel exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for treating diesel exhaust gas capable of providing high denitration performance in various temperature zone. <P>SOLUTION: A method comprising oxidizing part of nitrogen monoxide in an exhaust gas to nitrogen dioxide by passing part or whole of the exhaust gas through an oxidation catalyst 4 after removing particulate matter in the exhaust gas discharged from a diesel engine 1 with a filter 3, and reducing and removing nitrogen oxide in the exhaust gas by passing the exhaust gas through a denitration catalyst 11 after injecting ammonia or ammonia precursor 10 into the exhaust gas. Quantity of the exhaust gas passing through the oxidation catalyst 4 is controlled to keep mole ratio of nitrogen oxide to carbon dioxide in the exhaust gas before passing through the denitration catalyst 11 reversibly at 1:1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a diesel exhaust gas purification method and apparatus, and more particularly to a method and apparatus for efficiently removing nitrogen oxides in exhaust gas discharged from a diesel engine even in a low temperature range.

  Diesel engines are widely used in cogeneration systems, automobiles, generators, etc. Recently, due to the growing interest in protecting the global environment, regulations on exhaust gas emitted from these engines have been strengthened. Usually, a three-way catalyst (Japanese Examined Patent Publication No. Sho 56-27295) that simultaneously oxidizes carbon monoxide (CO) and hydrocarbons (HC) and reduces NOx is used as a catalyst for purifying automobile exhaust gas. In the case of a burn engine or a diesel engine, there is a problem that it is difficult to purify NOx with a general three-way catalyst because of an oxygen-excess atmosphere. Therefore, for the purification of these exhaust gases, the following method, (1) a method of removing particulate oxide (hereinafter sometimes referred to as PM) with a filter and then removing nitrogen oxides, (2) Many methods such as a method of reducing NOx using a hydrocarbon as a reducing agent on a catalyst carrying a noble metal such as Pt (Japanese Patent Laid-Open No. 5-103985) and (3) a method of using a NOx storage catalyst have been proposed.

Among the above techniques, the method (1) is such that the particulate matter (PM) in the exhaust gas discharged from the diesel engine 1 is first filtered (diesel particulate filter, hereinafter referred to as DPF) as in the flow shown in FIG. Part of NO is oxidized to NO ₂ by the oxidation catalyst component collected at 3 and supported by the DPF and / or the oxidation catalyst provided in the previous stage of the DPF (Equation (1)), and the reactivity with soot is more than oxygen After burning the soot with high NO ₂ to render the soot harmless to carbon dioxide (formula (2)), an NH ₃ precursor such as NH ₃ or urea is added from the reducing agent injection nozzle 5, and a denitration catalyst 6 is a method of catalytically reducing nitrogen oxides to harmless nitrogen and water, and studies aiming at practical use are being conducted as a method that can reliably remove PM and NOx.
NO + 1 / 2O ₂ → NO ₂ (1)
C + 2NO ₂ → CO ₂ + 2NO (2)
JP-A-5-103985

This denitration method is a method that has been widely used for boiler exhaust gas treatment in conventional power plants and the like. In addition to a titanium oxide-based denitration catalyst, a catalyst in which an active component is ion-exchanged with zeolite is used. However, the exhaust gas temperature of diesel automobiles that frequently start and stop the engine is as low as 200 to 300 ° C., and sufficient low-temperature activity cannot be obtained with the above catalyst. For this reason, NO ₂ generated by the oxidation catalyst for removing soot in the upstream is used to perform denitration (NO (3)) faster than NO-only deNOx (NO (4)). Improvement of activity is being studied.
NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O (3)
NO + NH ₃ + 1 / 4O ₂ → N ₂ + 3 / 2H ₂ O (4)

However, most of the NO ₂ produced by the oxidation catalyst is consumed by burning and removing soot by DPF (Equation (2)), so that sufficient NO ₂ required for the reaction (Equation (3)) is obtained on the denitration catalyst. I can't. In order to improve this, the present inventors have proposed a method in which an oxidation catalyst for generating NO ₂ is provided upstream of the denitration catalyst downstream of the particulate matter removal filter (soot removal means) (Japanese Patent Application 2002- 305503). By adopting this method, even if NO ₂ is consumed for soot combustion, NO ₂ is generated by the oxidation catalyst installed in the previous stage of the denitration catalyst, so the denitration reaction according to (Equation (3)) can be performed. Thus, high denitration activity can be obtained even at low temperatures, and it is effective as a method for preventing a reduction in NOX outflow at low temperatures.

However, the above-described oxidation catalyst installation method does not consider the following points, and it has been found that further improvement is necessary.
FIG. 6 is a graph showing an example of temperature dependence of the oxidation activity (change rate of NO to NO ₂ ) of the oxidation catalyst. Under conditions where the exhaust gas temperature is relatively low (approximately 300 ° C or less), the oxidation activity of the oxidation catalyst is not so high, and most of the NO ₂ produced on the oxidation catalyst of the soot removal means is used for soot combustion. The molar ratio of NO ₂ and NO in the latter stage (NO ₂ / NO molar ratio) is much less than 1. Therefore, if an oxidation catalyst is installed in the subsequent stage and the NO ₂ / NO molar ratio is set to around 1, an early denitration reaction (formula (3)) can be performed on the subsequent denitration catalyst, and the activity is greatly improved. can do. However, when the exhaust gas temperature is high (approximately 300 ° C or higher), the oxidation activity of the oxidation catalyst is high, so the amount of NO ₂ produced on the oxidation catalyst of the soot removal means is large, and even after being used for soot combustion The NO ₂ / NO molar ratio is kept high. Therefore, when an oxidation catalyst is further installed in the subsequent stage, NO is further oxidized to NO ₂ by passing through it, and the NO ₂ / NO molar ratio in the previous stage of the denitration catalyst exceeds 1, and this time the reverse In addition, a slow denitration reaction (formula (5)) or N ₂ O production reaction (formula (6)) with NO ₂ and NH ₃ proceeds.

3NO ₂ + 4NH ₃ → 7 / 2N ₂ + 6H ₂ O (5)
NO ₂ + NH ₃ + 1 / 4O ₂ → N ₂ O + 3 / 2H ₂ O (6)
Since the denitration reaction of (Formula (5)) is slow, not only the NOx removal rate decreases, but also NO _{2, which} is more harmful than NO, flows out to the downstream. In addition, N ₂ O produced by (Formula 6) is also a global warming substance, and its emission is not preferable.

  An object of the present invention is to provide a diesel exhaust gas treatment method and apparatus capable of solving the above problems and obtaining high denitration performance in any temperature range.

The invention claimed in the present application is as follows.
(1) In the method for treating exhaust gas discharged from a diesel engine, after removing particulate matter in the exhaust gas with a filter, passing part or all of the exhaust gas through an oxidation catalyst, A method of oxidizing a part of the mixture into nitrogen dioxide and then injecting ammonia or an ammonia precursor into the exhaust gas and then passing the denitration catalyst to reduce and remove nitrogen oxides in the exhaust gas. A method for treating exhaust gas, characterized in that the amount of exhaust gas passed through the oxidation catalyst is controlled so that the molar ratio of nitrogen oxides to nitrogen dioxide in the exhaust gas before being allowed to be as much as possible is 1: 1. .

(2) The method for controlling the molar ratio of nitrogen oxides to nitrogen dioxide in the exhaust gas to be as much as possible is a ratio controlled by the temperature of the exhaust gas passed through the oxidation catalyst. (1) The method of description.
(3) Before the particulate matter in the exhaust gas is removed by a filter, the exhaust gas is passed through an oxidation catalyst, or the filter carries an oxidation catalyst component (1) or ( 2) The method described.

(4) The method of removing particulate matter in the exhaust gas with a filter is a method of passing a diesel particulate filter (DPF) or a method of passing a DPF carrying an oxidation catalyst component (1) to (3 ) Any one of the methods.
(5) In an exhaust gas treatment apparatus having a flue of exhaust gas discharged from a diesel engine, a particulate matter filter device, a reducing agent injection means, and a denitration catalyst device sequentially provided along the gas flow direction of the flue, An oxidation catalyst device is provided between the particulate matter filter device and the reducing agent injection means. The oxidation catalyst device is provided at a right angle to the gas flow direction, and does not carry the catalyst. An exhaust gas treatment apparatus comprising: a section; and a section switching means for introducing a gas flow introduced into the oxidation catalyst device into any of the sections.

(6) The apparatus according to (5), wherein the section switching unit further includes a control unit that controls switching of a gas flow to each section by temperature.
(7) When the exhaust gas temperature is lower than a predetermined value, the control means passes the section carrying the oxidation catalyst, and when the exhaust gas temperature is higher than the predetermined value, the control means supports the oxidation catalyst. (6) The apparatus according to (6), characterized in that the exhaust gas is controlled to pass through a non-existing section.

  (8) The particulate matter removing filter device includes a diesel particulate filter (DPF), a DPF that is preceded by an oxidation catalyst layer, a DPF that carries an oxidation catalyst component, an oxidation catalyst layer, and an oxidation catalyst component. The apparatus according to any one of (5) to (7), which is any one of supported DPFs.

  In the method of the present invention, when the exhaust gas after the particulate matter (PM) in the exhaust gas is removed in advance is passed through the oxidation catalyst layer, the oxidation catalyst layer is loaded with several oxidation catalysts in the gas flow direction. And a catalyst layer provided with unsupported sections, and the gas flow into each section is controlled by switching according to, for example, the exhaust gas temperature according to the exhaust gas temperature. The gas is switched by, for example, a sector provided at the gas inlet of the oxidation catalyst layer, but other switching means may be used. The switching temperature cannot be determined unconditionally because the oxidation ability varies depending on the catalyst used, but as a rough guideline, when a noble metal-supported catalyst is used as the oxidation catalyst, the oxidation activity tends to increase from about 300 ° C. Therefore, good results can be obtained by setting the temperature to be switched to around 300 ° C. When the exhaust gas temperature is lower than the set temperature, the section carrying the oxidation catalyst is passed, and when the set temperature is high, the section not carrying the oxidation catalyst is passed.

Further, instead of dividing the section supporting the oxidation catalyst and the section not supporting the section, sections each supporting two types of catalysts having different oxidation catalyst capabilities may be used. In that case, when the temperature is low, the section having a high oxidizing power is passed, and when the temperature is low, the section having a low oxidizing power is passed.
The temperature measurement position may be the gas temperature in the vicinity of the oxidation catalyst layer inlet or the temperature inside the catalyst layer, and may be predicted by measuring the exhaust gas temperature at the engine outlet or the exhaust gas temperature at the DPF outlet.

Any method can be used to remove PM from diesel exhaust gas, but soot is collected and burned in the diesel particulate filter (DPF) cell, and an oxidation catalyst is placed in the previous stage to remove part of the NO. A method of oxidizing PM collected in DPF by NO ₂ at a low temperature after being oxidized to NO ₂ , a method of burning PM with an oxidation catalyst component also supported on DPF, and a combination of these methods However, any other method may be used as long as it is a method for removing PM from exhaust gas. Here, the DPF is a flow-through type honeycomb filter that is alternately clogged, and the gas entering from the gas flow path in the inlet portion passes through the filter wall, soot in the gas is collected, and the adjacent gas flow It has a structure in which gas flows out from the road.

It is preferable that the injection position of the denitration reducing agent is at the latter stage of the oxidation catalyst. This is to prevent ammonia or ammonia precursor (for example, urea) as a reducing agent from being oxidized to NOx by the oxidation catalyst.
The oxidation catalyst used in the present invention is not particularly limited as long as it is a catalyst capable of oxidizing NO to NO _2. For example, at least one kind of noble metal such as platinum, palladium, iridium, rhodium is titania, zirconia, alumina. For example, a catalyst in which a catalyst component loaded on a cordierite honeycomb structure or the like is loaded on is suitable. Further, the denitration catalyst may be any catalyst that is usually used for denitration, for example, a catalyst in which a denitration active component such as vanadium or tungsten is loaded on titanium oxide, copper, iron, cerium, or the like. Suitable is a catalyst in which a zeolite obtained by ion-exchange of a transition metal is supported on a cordierite honeycomb structure or the like.

  According to the first to eighth aspects of the present invention, high NOx removal performance can be obtained even when the exhaust gas temperature is low in exhaust gas treatment of diesel vehicles or the like in which start and stop frequently occur.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flowchart showing an embodiment of the method of the present invention. In FIG. 1, exhaust gas discharged from the diesel engine 1 passes through an exhaust pipe 21 and is introduced into a particulate matter removal filter device (DPF) 3 through an oxidation catalyst device 2. In the oxidation catalyst device 2, nitrogen oxide (NO) in the exhaust gas is oxidized to NO ₂ according to the above-described equation (1). Next, the exhaust gas that has passed through the oxidation catalyst device 2 is guided to the DPF 3 and PM in the exhaust gas is collected in the DPF filter, and at the same time, is oxidized by NO _{2 in} the gas according to the formula (2), and CO ₂ Become.

  The exhaust gas continues to pass through the exhaust pipe 22 and is guided to the oxidation catalyst device 4. The oxidation catalyst device 4 is provided with a flow-through type honeycomb catalyst, but the cross section is a gas as shown in FIG. Section 5 supporting the oxidation catalyst, section 6 not supporting the oxidation catalyst, and section switching means (sector 8) for introducing the gas flow into one of the sections 5 and 6 provided so as to be perpendicular to the flow direction. ).

  FIG. 3 is a development view of the above oxidation catalyst device. The honeycomb catalyst provided in the exhaust gas flue is divided into an oxidation catalyst supporting section 5 and an oxidation catalyst non-supporting section 6 in a radial section, and the exhaust gas inlet thereof. The section is provided with a sector 8 having an opening and a closing portion having a shape matching the cross section of the section so as to be rotatable around its central axis and in contact with the front surface of the section. Any mechanism may be used for switching (turning) the sector 8 as long as it is a known mechanism. For example, as shown in FIG. The same principle mechanism can be used to change. In FIG. 4, the sector switching device 12 moves up and down, the shaft 14 connected to the connecting rod 13 rotates the sector 8, and stops the sector 8 at the positions of the oxidation catalyst supporting section 5 and the catalyst non-supporting section 6, respectively. Let

Switching of the gas inflow to the sections 5 and 6 by the sector 8 can be controlled by a temperature sensor 9 installed at the oxidation catalyst layer inlet. For example, when the temperature is 300 ° C. or lower, exhaust gas is allowed to flow through section 5. In section 5, a part of NO in the exhaust gas is oxidized to NO ₂ by the supported oxidation catalyst component. When the temperature is 300 ° C. or higher, exhaust gas is introduced into section 6. In Section 6, since no oxidation catalyst is supported, NO in the exhaust gas is not oxidized to NO ₂ . In the present invention, if the sections 5 and 6 have the same volume, the pressure loss does not change even if the exhaust gas is switched to each section. For example, a method of bypassing the oxidation catalyst and leading to the downstream denitration catalyst layer 10 Compared to the above, there is an advantage that problems such as a load on the apparatus due to a change in pressure loss do not occur. FIG. 5 shows an example in which sections 5 and 6 have the same volume and are divided and arranged.

For example, urea water, which is a reducing agent, is injected into the exhaust gas from the reducing agent injection device 10 into the exhaust gas that has passed through the oxidation catalyst device 4 and led to the denitration catalyst layer 11 at the subsequent stage. In the denitration catalyst layer 11, and the NO and NO ₂ is always NO ₂ / NO molar ratio is near 1, and is controlled so as not to exceed 1, so that any early denitration reaction in the temperature range (3 equation) is Mainly proceeds to obtain a high NOx removal rate. In addition, it is possible to prevent NO ₂ from flowing out due to NO ₂ excess and N ₂ O from flowing out due to the reaction between NO ₂ and NH ₃ .

FIG. 7 is a diagram showing a basic flow when the PM removing means is the DPF oxidation catalyst device 12 carrying the oxidation catalyst component in the embodiment of FIG. 1 and the oxidation catalyst device 2 is not installed. In this case, the collection of soot in DPF 12, oxidation to NO ₂ NO, the further combustion by NO ₂ in the PM are performed simultaneously. The subsequent flow is the same as in the first embodiment.
FIG. 8 is a diagram showing a basic flow in which the DPF 3 is the DPF oxidation catalyst device 12 carrying the oxidation catalyst component in the embodiment of FIG. In this case, oxidation of first to the oxidation catalyst device 2 by a NO NO ₂ occurs, the collection of soot in DPF, oxidation to NO ₂ in NO, further combustion by NO ₂ in the PM are performed simultaneously. The subsequent flow is the same as in the first embodiment.
FIG. 9 shows an embodiment in which the oxidation catalyst 2 placed in front of the PDF 3 is omitted from FIG.

[Example 1]
Exhaust gas discharged from a 25 Kw diesel engine using light oil (50 ppm S content in the fuel) as fuel was treated according to the flow chart of FIG. The exhaust gas discharged from the diesel engine 1 passes through the flue 21, and the oxidation catalyst layer 2 as an oxidation catalyst device (volume 1.2L, carrier material; cordierite, honeycomb cell number 300cpsi, porosity 30%, catalyst component; Introduced into Pt alumina (Pt loading time 1.5g / L). When the load is low such as when the engine is started, the exhaust gas temperature is about 300 ° C., and in the oxidation catalyst layer 2, approximately 30% of NO is oxidized to NO ₂ due to the oxidation action of the noble metal component supported on the catalyst. When the engine load is high and the exhaust gas temperature is as high as 300 ° C. or higher, approximately 50% of NO is oxidized to NO ₂ . Next, the exhaust gas that has passed through the oxidation catalyst layer 2 is led to DPF 3 (volume 2.5 L, carrier material: cordierite, number of cells 300 cpsi, porosity 60%) to collect soot. The soot in the gas is collected on the filter wall of the DPF 3 and at the same time is oxidized according to the formula (2) by the NO ₂ generated in the gas to become CO ₂ . The exhaust gas that has passed through the DPF 3 is then guided to the oxidation catalyst device 4 according to the present invention. As shown in FIG. 2, the oxidation catalyst device 4 has a section 5 supporting a catalyst component (volume 0.6 L, support material: cordierite, honeycomb cell number 300 cpsi, porosity 30%, catalyst component: Pt alumina (Pt support) 1.5g / L)) and unsupported section 6 (volume 0.6L, carrier material: cordierite, honeycomb cell number 300cpsi, porosity 30%). When the exhaust gas temperature is low, the NO ₂ content in the exhaust gas flowing into the oxidation catalyst layer 4 is low, about 10%, and the exhaust gas is led to section 5 by the sector 8, and about 20% of NO on the catalyst is NO. Oxidized to ₂ . On the other hand, when the exhaust gas temperature is high, the NO ₂ content in the exhaust gas flowing into the oxidation catalyst layer 4 is about 40%, the exhaust gas is led to the section 6 by the sector 8, and NO oxidation on the catalyst does not occur. As it is, it is led to the downstream denitration catalyst layer 4.

After that, the exhaust gas passes through the denitration catalyst layer 11 (catalyst component: Ti-WV system, volume 2.5 L, carrier material: cordierite, number of cells 400 cpsi, porosity 30%), and is injected into the upstream of the catalyst layer 11 NOx in exhaust gas is catalytically reduced by a reducing agent (for example, urea aqueous solution, urea concentration 35 wt%). In any temperature range, NO and NO ₂ coexist on the NOx removal catalyst 11 at a NO ₂ / NO molar ratio of about 1, and therefore the reaction of the formula (3) proceeds faster than NO alone. As a result, nitrogen oxides are rendered harmless by nitrogen.

[Test Example 1]
Alumina sol (Alumina sol 520, manufactured by Nissan Chemical Co., Ltd.) and water are mixed, and 1 liter of an aqueous solution containing 15% alumina is prepared. A flow-through cordierite carrier (300 cpsi) 100 x 100 mm (50 mm length) ), And the operation of draining by air blow was repeated twice, followed by drying in air at 150 ° C. for 5 hours and baking at 500 ° C. for 2 hours. The resulting support was impregnated with an aqueous solution of dinitrodiammine platinum, drained by air blow, dried in air at 150 ° C. for 5 hours, and calcined at 550 ° C. for 2 hours. The amount of platinum supported per volume was 2 g / liter. An oxidation catalyst was obtained.

  Titanium oxide, tungsten oxide, ammonium metavanadate, oxalic acid and water were kneaded with a kneader to form a paste, which was extruded and granulated, dried, and then fired at 500 ° C. for 2 hours. The obtained granulated product was pulverized to 150 μm or less to obtain a denitration catalyst powder (Ti / W / V = 89/5/6). Denitration catalyst powder and water were mixed with a stirrer to prepare a slurry with a slurry concentration of 35%, which was impregnated with a flow-through cordierite carrier (600 cpsi) 100 x 100 mm (50 mm length), and drained by air blow The post-drying process was repeated three times, followed by calcination at 500 ° C. for 2 hours to obtain a denitration catalyst.

Using a flow-type reactor, an oxidation catalyst (8 cells x 8 cells) and a denitration catalyst (8 x 8 cells) are set in parallel in the gas flow direction, and a reducing agent (NH) is placed between the oxidation catalyst and the denitration catalyst. ₃ ) was injected and the denitration rate was measured under the conditions shown in Table 1.
[Test Example 2]
Only the denitration catalyst was used without the oxidation catalyst of Test Example 1, and thereafter the denitration rate was measured in the same manner as in Test Example 1.

The results of Test Examples 1 and 2 are shown together in Table 2. In Test Example 1, that is, when an oxidation catalyst is present in the upstream of the denitration catalyst, the denitration rate at 200 ° C. is high, but the denitration rate at 400 ° C. is lower than 200 ° C. In contrast, in the case of Test Example 2, that is, in the case of only the denitration catalyst, the denitration rate at 200 ° C. is low, but the denitration rate at 400 degrees is rather higher than in Test Example 1.
From this test example, it is clear that the denitration rate of the downstream denitration catalyst can always be kept high by controlling the amount of exhaust gas that passes through the oxidation catalyst according to the exhaust gas temperature.

  In the treatment of exhaust gas containing a large amount of particulate matter such as diesel automobiles, the exhaust gas can be treated at a high NOx removal rate even in a low temperature region along with the removal of particulate matter.

The figure which shows the basic flow of the waste gas processing of this invention. Explanatory drawing of the oxidation catalyst used for this invention. The expanded view which shows the Example of the oxidation catalyst apparatus used for this invention. Explanatory drawing which shows the control mechanism of the oxidation catalyst apparatus used for this invention. Explanatory drawing of the oxidation catalyst used for this invention. Graph showing the relationship between the rate of change from NO by the exhaust gas temperature and the oxidation catalyst into NO _2. The flowchart which shows the Example of the waste gas processing of this invention. The flowchart which shows the Example of the waste gas processing of this invention. The flowchart which shows the Example of the waste gas processing of this invention. The flowchart which shows an example of the conventional exhaust gas processing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 2 ... Oxidation catalyst, 3 ... DPF, 4 ... Oxidation catalyst, 5 ... Oxidation catalyst carrying section, 6 ... Oxidation catalyst non-carrying section, 8 ... Sector, 9 ... Temperature sensor, 10 ... Reducing agent injection device, DESCRIPTION OF SYMBOLS 11 ... Denitration catalyst, 12 ... Sector switching device, 13 ... Connecting rod, 14 ... Crankshaft, 21-23 ... Exhaust pipe.

Claims (8)

In a method for treating exhaust gas discharged from a diesel engine, particulate matter in exhaust gas is removed by a filter, and then a part or all of the exhaust gas is passed through an oxidation catalyst to remove a part of nitrogen monoxide in the exhaust gas. A method of oxidizing nitrogen dioxide and then injecting ammonia or an ammonia precursor into the exhaust gas and then passing through a denitration catalyst to reduce and remove nitrogen oxides in the exhaust gas before passing through the denitration catalyst. A method for treating exhaust gas, characterized in that the amount of exhaust gas passed through the oxidation catalyst is controlled so that the molar ratio of nitrogen oxides to nitrogen dioxide in the exhaust gas is as much as possible as 1: 1. The method for controlling the molar ratio of nitrogen oxides and nitrogen dioxide in the exhaust gas to a ratio of 1: 1 as much as possible is controlled by the temperature of the exhaust gas passed through the oxidation catalyst. The method according to claim 1. 3. The method according to claim 1, wherein the particulate matter in the exhaust gas is passed through an oxidation catalyst before the particulate matter is removed by a filter, or the filter carries an oxidation catalyst component. . The method of removing particulate matter in the exhaust gas with a filter is a method of passing a diesel particulate filter (DPF) or a method of passing a DPF carrying an oxidation catalyst component. The method described. In an exhaust gas treatment apparatus having a flue for exhaust gas discharged from a diesel engine and a particulate matter filter device, a reducing agent injection means, and a denitration catalyst device that are sequentially provided along the gas flow direction of the flue, the particulate matter An oxidation catalyst device is provided between the material filter device and the reducing agent injection means, and the oxidation catalyst device includes a section that supports the oxidation catalyst and a section that does not support the catalyst, provided at right angles to the gas flow direction. An exhaust gas treatment apparatus comprising: a section switching means for introducing a gas flow introduced into the oxidation catalyst device into any of the sections. 6. The apparatus according to claim 5, wherein the section switching means further comprises control means for controlling switching of gas flow to each section by temperature. When the exhaust gas temperature is lower than a predetermined value, the control means passes the section that does not support the oxidation catalyst when the exhaust gas passes through the section that supports the oxidation catalyst. 7. The apparatus according to claim 6, wherein the apparatus controls the exhaust gas to pass therethrough. The particulate matter removing filter device includes a diesel particulate filter (DPF), a DPF having an oxidation catalyst layer placed thereon, a DPF carrying an oxidation catalyst component, a DPF carrying an oxidation catalyst layer and carrying an oxidation catalyst component. The device according to any one of claims 5 to 7, which is any one of the following.

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