JP2007216117A - Exhaust gas treatment apparatus, catalyst molding to be used for the same, and manufacturing method of catalyst molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particulate substance removing apparatus preventing increase of discharged NO<SB>2</SB>in back washing operation at a high load time, and lowering cost by reducing the amount of noble metals. <P>SOLUTION: An exhaust gas treatment apparatus is provided with the catalyst molding carrying a catalyst 6 to increase oxidizing power sequentially or stepwise, with a pair of a porous corrugated plate 1 and a porous flat plate 2 as a basic unit, in the diagonal direction 5 of a crossing angle from a side 4 where two planes orthogonal to the ridgeline of the adjacent corrugated plates of the molding 3 formed by stacking the basic units so that they cross each other; exhaust gas inlet passages 7A, 7B communicating with two faces orthogonal to the ridgeline of the corrugated plates, respectively ; exhaust gas outlet passages 8A, 8B communicating with other two faces orthogonal to the ridgeline of the corrugated plates; partition plates 9A, 9B cutting off the exhaust gas inlet passages 7A, 7B from the outlet passages 8A, 8B; and selector valves 10A, 10B alternately switching the exhaust gas flow-in and flow-out to and from the inlet passages 7A, 7B or 8A, 8B communicating with the two faces. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device, and more particularly to an exhaust gas purification device suitably used for removing particulate matter (PM) contained in exhaust gas from an internal combustion engine such as a diesel engine, a catalyst molded body used in the device, and a method for producing the same.

In general, the PM removal technology in diesel exhaust gas is aimed at filtering through a thin wall of porous ceramics, and a plate or cylindrical metal or ceramic sintered filter, honeycomb ceramic porous gas A diesel particulate filter (DPF) or the like in which one of the inflow portion or the discharge portion is alternately sealed by adjacent cells is widely used. In addition, an oxidation catalyst is supported on these, so that nitric oxide (NO) in exhaust gas is oxidized to nitrogen dioxide (NO ₂ ), and soot is efficiently burned from a low temperature so as to prevent soot clogging for a long time. Many studies have been made (Patent Document 1). Furthermore, it is possible to efficiently oxidize and remove PM by carrying more catalyst on the upstream side, which is the inlet of exhaust gas, than on the downstream side, and more catalyst on the inflow side of the filter wall than on the outflow side. However, there is still a problem with respect to the reduction of the life due to the accumulation of ash.
JP-A-60-235620 JP 2001-207836 A

In order to solve the above-mentioned problem, the present inventors have a basic unit of a pair of a porous corrugated plate and a porous flat plate carrying an exhaust gas purification catalyst (oxidation catalyst), and corrugated ridge lines of the porous corrugated plate are alternately arranged. A molded body laminated so as to be orthogonal to each other, and a side surface perpendicular to the corrugated plate ridge line of the molded body and adjacent to each other to seal the porous corrugated plate through the porous flat plate An exhaust gas purifying apparatus having a switching valve for switching between the inflow path and / or the outflow path of the exhaust gas, which is provided with a closing valve for forming an inflow path and an outflow path of the exhaust gas in between. (Japanese Patent Application No. 2004-263889). This device has a high PM removal rate and can remove unburned soot and ash accumulated inside the DPF, so there is no clogging, long life, and a compact device that can be operated from low loads. Although possible, there has been a demand for an apparatus that takes into account the prevention of an increase in the outlet NO ₂ in the backwash operation at higher loads and the reduction in cost by reducing the amount of noble metal in the supported catalyst.

In order to achieve the above object, the invention claimed in the present application is as follows.
(1) A molded body in which a pair of porous corrugated plates and porous flat plates are used as basic units and are laminated so as to be alternately orthogonal, and two surfaces perpendicular to the ridgelines of adjacent corrugated sheets of the molded body are From the intersecting side, the catalyst molded body on which the catalyst is supported so that the oxidizing power increases sequentially or stepwise in the diagonal direction with respect to the intersecting angle and the two surfaces perpendicular to the ridgeline of the corrugated plate communicate with each other. An exhaust gas inlet channel, an exhaust gas outlet channel communicating with the other two surfaces orthogonal to the ridgeline of the corrugated plate, and an exhaust gas inlet channel and an outlet channel provided so as to be orthogonal to the ridgeline of the corrugated plate An exhaust gas treatment apparatus, comprising: a partition plate for shutting off; and a switching valve for alternately switching exhaust gas inflow and exhaust gas exhaust to an exhaust gas flow path communicating with the two surfaces.
(2) A molded body in which a pair of porous corrugated plates and porous flat plates are used as basic units, and these are laminated so as to be orthogonal to each other, and two surfaces perpendicular to the ridgelines of adjacent corrugated sheets of the molded body are The catalyst molded body used in the method according to (1), wherein the catalyst is supported so that the oxidizing power increases sequentially or stepwise from the intersecting side in a direction diagonal to the intersecting angle.
(3) From the intersecting sides of the two surfaces perpendicular to the ridgeline of the adjacent corrugated plate of the molded body laminated with the pair of porous corrugated plates and the porous flat plate as the basic unit and alternately intersecting each other, (1) The method for producing a molded catalyst according to (2), wherein the catalyst slurry is impregnated so as to increase the oxidizing power of the catalyst sequentially or stepwise in the diagonal direction and then dried and fired.

According to the present invention, particulate matter (PM) in exhaust gas is removed with a low-cost and compact device, and backwashing for improving durability is performed without increasing the amount of NO ₂ at the outlet. It is possible to prevent the occurrence of secondary disasters such as yellow smoke.

  FIG. 1 is a perspective view showing a basic unit of a filter constituting the catalyst molded body used in the present invention, FIG. 2 is a perspective view of the catalyst molded body of the present invention, and FIG. 3 is a catalyst to the catalyst molded body of the present invention. FIG. 4 is an explanatory view showing an embodiment of the exhaust gas treatment apparatus of the present invention. As shown in FIG. 1, the exhaust gas purifying apparatus of the present invention is a molded body 3 (FIG. 3) in which a pair of porous corrugated plates 1 and porous flat plates 2 are used as basic units and are laminated so as to be alternately orthogonal. Then, the catalyst 6 is formed so that the oxidizing power increases sequentially or stepwise from the side 4 where two surfaces perpendicular to the ridgeline of the adjacent corrugated sheet of the molded body 3 intersect each other in the crossing angle and the diagonal direction 5. , The exhaust gas inlet passages 7A and 7B communicating with two surfaces orthogonal to the ridge line of the corrugated plate, and the exhaust gas outlet communicating with the other two surfaces orthogonal to the ridge line of the corrugated plate, respectively. The flow paths 8A and 8B, the partition plates 9A and 9B that block the exhaust gas inlet flow paths 7A and 7B and the outlet flow paths 8A and 8B, and the exhaust gas flow paths 7A and 7B or 8A and 8B communicating with the two surfaces. Switching valves 10A and 10B for alternately switching exhaust gas inflow and exhaust gas exhaust To.

Referring to FIG. 4, the flow of the exhaust gas E is changed from the exhaust gas inlet channel 7A to the outlet channel 8A or from the exhaust gas inlet channel 7B to the outlet channel 8B by the switching valves 10A and 10B. The gas flowing in from the inlet A surface is discharged from the outlet C surface, and the gas flowing in from the inlet B surface is discharged from the outlet D surface through the catalyst molded body (DPF) 3 so that it can be efficiently discharged into the exhaust gas. PM can be collected. At this time, the soot contained in the gas is filtered and removed on the surface of the porous flat plate and deposited. The deposited soot is oxidized by the oxidation catalyst attached to the catalyst molded body (DPF) 3 or oxidized by the oxidation catalyst. It is oxidatively decomposed by the released NO ₂ . Thereafter, the remaining unburned matter and ash can be back-washed by switching the flow passages with the switching valves 10A and 10B, and discharged together with the exhaust gas. Further, the exhaust gas can be discharged from one or both of the outlet surfaces C and D by the switching valve 10B, but even when discharging from both surfaces, some of the soot particles in the gas are collected by diffusion inside the DPF. Can burn and remove. Furthermore, odor components such as hydrocarbons in the gas can be decomposed, and operation with a very low pressure loss becomes possible. On the other hand, soot collected by DPF3 undergoes oxidative decomposition according to the following formula 1 very efficiently from a low temperature, and can quickly regenerate DPF.

2NO ₂ + C (煤) → CO ₂ + 2NO (1 set)
In the present invention, the method of oxidizing and decomposing the catalyst in contact with soot in the presence of oxygen is efficient. Therefore, as shown in FIG. 3, increasing the oxidation activity of the catalyst upstream of the exhaust gas of DPF 3 It becomes a very effective means for the reproduction of. That is, when regeneration by DPF backwashing is performed, in the present invention, backwashing is always possible with the oxidizing power of the inflow portion being high, and stable operation at low cost is possible.

Hereinafter, the present invention will be described in detail by way of examples.
[Example 1]
Crossed corrugated honeycomb made of silica alumina fiber nonwoven fabric with a thickness of 0.2mm (corrugated sheet pitch 3.3mm, flat plate spacing 1.9mm, manufactured by NICHIAS, outer dimensions 150mm x 150mm x 150mm), 15% TiO ₂ sol (Ishihara Sangyo Co., Ltd.) After impregnation, the liquid was drained by air blow and dried at 150 ° C. After immersing in dinitrodiammine platinum solution (Tanaka Kikinzoku Kogyo Co., Ltd.) and adsorbing and supporting a specified amount of Pt on the entire surface, draining, drying and firing at 500 ° C. for 2 hours, Pt loading 0.05 g / L A DPF with an oxidation catalyst (conventional specification) was prepared. On the other hand, after impregnation with a dinitrodiammine platinum solution adsorbs and supports a specified amount of Pt on the entire surface, the dinitrodiammine platinum solution prepared separately intersects two surfaces perpendicular to the ridgeline of the adjacent corrugated plate of the catalyst molded body. Immerse only half of the catalyst from the side in the diagonal direction, that is, so that the gas inflow and outflow surfaces of the catalyst molded body are slanted, and then drain, dry, and calcinate at 500 ° C. for 2 hours. The oxidation catalyst molded body (DPF) having a Pt loading of 0.05 g / L was prepared.

[Example 2]
As shown in FIG. 4, the catalyst molded body (DPF) of the present invention is arranged in a flue of diesel engine exhaust gas equivalent to 25 kW using LSA heavy oil as fuel so that the upstream oxidizing power becomes high, and the switching valves 4 and 5 FIG. 5 and FIG. 6 show the results of evaluation performed under the conditions of low load (DPF inlet temperature of about 300 ° C.) and high load operation (DPF inlet temperature of about 390 ° C.).

[Comparative Example 1]
The test was conducted in the same manner as in Example 2, except that the DPF was a conventional DPF in which the catalyst was uniformly supported on the catalyst compact. A result is combined with FIG.5 and FIG.6.
From the results of FIG. 5, there is almost no increase in the differential pressure over time in both the example and the comparative example, and when viewed from the differential pressure of the DPF of the present invention at the time of low load, it can be made slightly lower than before. I understand that. In FIG. 6, the NO ₂ concentration at the DPF outlet in the present invention is very low, and it is possible to prevent the generation of yellow smoke due to the increase in the outlet NO ₂ particularly at high loads. This is thought to be because the generation of harmful gases such as NO ₂ and SO ₃ at the DPF outlet during backwashing can always be kept low.

The perspective view which shows the basic unit of the filter which comprises the catalyst molded object used for this invention. The perspective view of the catalyst molded object of this invention. The top view which shows the support state of the catalyst to the catalyst molded object of this invention. Explanatory drawing which shows one Example of the waste gas processing apparatus of this invention. The figure which shows the change of the differential pressure | voltage of DPF in an Example and a comparative example. It shows the change of the DPF outlet NO ₂ in Examples and Comparative Examples.

Explanation of symbols

1. 1. corrugated plate element; Flat element, 3. DPF block, 4. Sides, 5. Diagonal direction, 6. Catalyst, 7A, 7B. Exhaust gas inlet channel, 8A, 8B. Exhaust gas outlet channel, 9A, 9B. Partition plate, 10A. Gas flow path switching valve (inflow side), 10B. Gas flow switching valve (outflow side).

Claims (3)

A molded body in which a pair of porous corrugated plates and porous flat plates are used as a basic unit and are laminated so as to be orthogonal to each other, and the sides intersecting two surfaces perpendicular to the ridgelines of adjacent corrugated sheets of the molded body From the crossing angle and the diagonal direction, the catalyst molded body on which the catalyst is supported so that the oxidizing power increases sequentially or stepwise, and the exhaust gas inlet flow respectively communicating with the two surfaces orthogonal to the ridgeline of the corrugated plate An exhaust gas outlet channel communicating with each of the other two surfaces orthogonal to the ridgeline of the corrugated plate, and a partition for blocking the exhaust gas inlet channel and the outlet channel provided to be orthogonal to the ridgeline of the corrugated plate An exhaust gas treatment apparatus comprising: a plate; and a switching valve that alternately switches exhaust gas inflow and exhaust gas to an exhaust gas passage communicating with the two surfaces. A molded body in which a pair of porous corrugated plates and porous flat plates are used as a basic unit and are laminated so as to be orthogonal to each other, and the sides intersecting two surfaces perpendicular to the ridgelines of adjacent corrugated sheets of the molded body The catalyst molded body used in the method according to claim 1, wherein the catalyst is supported so that the oxidizing power increases sequentially or stepwise in a direction diagonal to the crossing angle. From the intersecting sides of the two surfaces perpendicular to the ridgeline of the adjacent corrugated sheet of the molded body in which the pair of porous corrugated sheets and the porous flat plate are used as the basic unit and are alternately laminated, 3. The method for producing a catalyst molded body according to claim 2, wherein the catalyst slurry is impregnated so as to increase the oxidizing power of the catalyst sequentially or stepwise in a diagonal direction, and then dried and fired.

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