JP2007046516A - Exhaust gas treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PM removing filter made of low cost material, resistant to clogging of PM and blockage of ash and not requiring bypass piping and large scale means such as backwashing and heating combustion, and an exhaust gas treatment device using the same. <P>SOLUTION: In this exhaust gas treatment device, filter units formed by laminating two or more platelike filters through spacers are provided in an exhaust gas channel. The filter units are so formed that the wall surfaces of the platelike filters are arranged at right angles to the exhaust gas channel so that exhaust gas is supplied from an oblique direction to the opening parts of the filter units, and sealing plates are provided to partition between the adjacent filter units. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas treatment apparatus using an exhaust gas purification catalyst, and in particular, an exhaust gas treatment apparatus and an exhaust gas treatment including a PM removal filter that can efficiently remove particulate matter (PM) contained in diesel engine exhaust gas with low pressure loss. It is about the method.

Diesel engine (DE) is one of the most efficient types of internal combustion engines. It has low CO ₂ emissions per unit output and can be used with low-quality fuels such as heavy oil. In recent years, DE has been reviewed from the viewpoint of preventing global warming, and therefore, it is spreading as automobiles and stationary power generation facilities.

On the other hand, DE's exhaust gas, which uses light oil or heavy oil as fuel, has a lot of particulate matter (PM) in which unburned hydrocarbons and soot are integrated, and has become a social problem as a cause of pollution. For this reason, research and development related to PM removal has been promoted in various areas such as engines and automobile manufacturers. Nitrogen monoxide (NO) in exhaust gas is supported by a filter having excellent removal performance, a pre-catalyst and an oxidation catalyst supported on the filter. ) Is nitrogen dioxide (NO ₂ ), and PM is burned to research and develop a PM filter (DPF) that can prevent clogging due to PM accumulation (Patent Document 1).

Many of these prior arts filter exhaust gas through a thin wall of porous ceramic of several μm, and are made of plate-like or cylindrical metal or ceramic sintered filters, honeycomb-like ceramic porous body cells A filter made by alternately filling in, a fine metal wire woven fabric, and the like are known. Furthermore, in order to prevent or alleviate the clogging, these filters have a function of oxidizing NO to NO ₂ and a function of burning the accumulated PM (Patent Literature). 2 and 3).

The above prior art has high PM collection performance and excellent performance. However, when using light oil or heavy oil as fuel, or when using it for stationary power generation facilities, the following problems are encountered: There is.
(1) It is a filter material based on the basic principle of filtering PM through fine pores. The pressure loss during gas passage is large, and the characteristics of highly efficient DE are often impaired.
(2) Ash in fuel or engine oil accumulates in the pores of the filter material, causing clogging, resulting in a short filter life.
(3) When a large amount of PM flows in temporarily, it is likely to become clogged, and there are many things that require major measures such as installing bypass piping, backwashing, and heating and burning PM.
Industrial Environment Management Association, Environmental Management Vol.37, p441-449 JP-A-1-318715 In response to this, a filter for removing particulate matter in which multiple plate-like nets are stacked has been proposed to reduce the load on wall flow type filters. Although it is used as a prefilter for reducing the exhaust gas temperature, an increase in the differential pressure of the prefilter cannot be avoided under conditions where the exhaust gas temperature is low, and the apparatus becomes large if the units are arranged in a plane in order to change the filtration area There is a problem.

  The object of the present invention is to eliminate the above-mentioned problems, to be composed of an inexpensive material, to be strong against clogging of PM and blockage of ash, and to eliminate the need for bypass piping, large-scale means such as backwashing and heating combustion. An object of the present invention is to provide a removal filter and an exhaust gas treatment apparatus using the filter.

In order to achieve the above object, the invention claimed in the present application is as follows.
(1) An exhaust gas treatment apparatus in which a filter unit in which a plurality of plate-like filters are stacked via a spacer is installed in an exhaust gas flow path, and the exhaust gas is directed to an opening of the filter unit. The plate-like filter wall surface is disposed at a right angle to the exhaust gas flow path so as to be supplied from an oblique direction, and a seal plate for partitioning between adjacent filter units is provided. Exhaust gas treatment equipment.
(2) An exhaust gas treatment apparatus in which a plurality of filter units in which a plurality of plate-like filters are stacked via spacers are installed in parallel to the exhaust gas flow path, wherein the exhaust gas is exhausted from the filter unit. A seal that is arranged so that the wall surface of the plate-like filter is perpendicular to the exhaust gas flow path so as to be supplied from an oblique direction with respect to the opening, and that partitions between the farthest ends of adjacent filter units An exhaust gas treatment apparatus comprising a plate.
(3) The direction of the seal plate is changed so that the rotating shaft provided swingably in the center and the flow path to which the exhaust gas is supplied are alternately switched between adjacent filters. The apparatus as described in (1) which has a switching means.
(4) The apparatus according to any one of (1) to (3), wherein the plate filter is a metal lath plate.
(5) The exhaust gas containing particulate matter is supplied to the apparatus described in (3), and after a predetermined time has passed, the direction of the seal plate is switched so that the direction of gas flow in the filter unit is reversed. An exhaust gas treatment method characterized by treating for a predetermined time.
[Action]
First, it will be described how the laminated structure of plate-like nets used in the present invention functions as a DPF.

Conventionally, when exhaust gas is supplied to a laminated structure of plate-like nets, the exhaust gas flows from an edge portion (end) where the plate-like nets are stacked. An oxidation catalyst is supported on the plate network. When the exhaust gas flows into the laminated structure, a part of the particulate matter (PM) in the exhaust gas collides with the mesh by inertial collision and accumulates on the surface of the mesh. On the other hand, NO contained in the exhaust gas is oxidized to NO ₂ by a catalyst having oxidation activity, and this NO ₂ continuously oxidizes and burns PM mainly composed of carbon to CO ₂ as shown in the formula (1), so that the filter The pressure loss is prevented from increasing over time.

2NO ₂ + C → CO ₂ + 2NO (1)
In the known wall flow honeycomb DPF in which the channels of the honeycomb molded body are alternately filled, all porous walls are used as filter media, so PM is deposited on all porous wall surfaces. The exhaust gas containing NO in the gas passes through the accumulated PM portion, and then comes into contact with the porous wall on which the oxidation catalyst is supported to generate NO ₂ . For this reason, the contact between PM and NO ₂ is not necessarily good, and PM cannot be burned efficiently.

On the other hand, in the present invention, the filter unit is arranged so that the wall surface of the plate filter is perpendicular to the gas flow path, and the flow path is partitioned by the partition plate 3, whereby the gas is opened in the filter unit. As a result, the contact frequency between the PM in the gas and the filter is increased, and the PM removal performance is improved. More specifically, FIG. 2 is a plan sectional view for explaining the operation of the filter unit used in the exhaust gas treatment apparatus of the present invention. In FIG. When arranged so as to be parallel to the exhaust gas flow path 4, (b) is arranged so that the wall surface of the plate filter is perpendicular to the exhaust gas flow path 4, and between the side walls of the exhaust gas flow path. The case of the present invention partitioned by the partition plate 3 is shown. In the case of the present invention of FIG. 2B, the exhaust gas is supplied obliquely to the opening of the filter unit. In the case of the present invention, it increased to 70%. Further, in the case of a diesel engine having a PM concentration of about 30 mg / m ^{3 in} exhaust gas, it was confirmed that 70% or more of PM can be removed by using a reactor as shown in FIG. This is presumably because the collision frequency between the PM in the exhaust gas and the filter material is increased by supplying it obliquely as shown in FIG.

  In FIG. 3, a plurality of filter units are arranged in parallel and in multiple stages on the cross section of the exhaust gas flow path, the other cross section of the filter unit is shielded by a partition plate, and the number of filter units is changed to change the inlet gas velocity. It is a figure which shows the relationship between an inlet gas velocity and PM removal rate in a case. In the case where the filter unit is arranged in parallel to the exhaust gas flow path (a) and in the case where the filter unit is arranged at a right angle (b), increasing the inlet gas velocity increases the effect of inertial collision with the filter. Although the purification performance increases, if it exceeds a certain flow rate, when it is arranged in parallel (a), the PM once deposited is re-scattered and the PM purification performance is reduced, but when arranged at right angles (b), It turns out that there is no such thing.

  According to the present invention, it is possible to provide an exhaust gas treatment apparatus having a highly efficient PM removal filter with a small pressure loss. The reactor can be made compact, and by switching the flow path, low load operation can be handled without increasing the differential pressure. Further, by applying the filter used in the present invention to the pre-filter of the denitration apparatus, the life of the expensive post-filter can be extended and the economic effect is great.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory diagram for explaining the outline of the present invention. As shown in FIG. 1 (a), a plate-like filter 1 used in the present invention is a plate-like reticulated base material 1 carrying a catalyst component, and the filter unit 2 of the present invention comprises the plate-like filter 1 as shown in FIG. It consists of many laminated via spacers. In the figure, arrows indicate the inflow direction of exhaust gas. As shown in FIG. 1 (b), a plurality of exhaust gas treatment apparatuses of the present invention are installed in parallel to the exhaust gas flow path 4, and the filter unit 2 is connected to the exhaust gas flow path 4 with the plate-like filter 1. A sealing plate 3 is provided to partition between the farthest ends of adjacent filter units so that the wall surfaces are arranged at right angles and exhaust gas is supplied from an oblique direction to the opening of the filter unit. Is. In the drawing, (c) shows a front view of (b).

In FIG. 1 (b), the exhaust gas flows from the top to the bottom in the figure, and is introduced into the filter unit 2 obliquely along the partition plate 3, where a part of the PM is collected and NO in the gas is removed. It burns with NO ₂ produced by oxidation, and particulate matter is removed. Since the removal performance of the particulate matter changes depending on the area of the filter, the number of filter units can be changed depending on the required removal performance. Moreover, the reactor can be made compact by providing a large number of filter units in the cross section of the flow path.

FIG. 4 is an explanatory view of an exhaust gas treatment apparatus showing another embodiment of the present invention. The difference between this device and the device shown in the filter in which a plurality of plate-like nets 1 in FIG. 1B are stacked is that the seal plate 3 that divides between the farthest ends of adjacent filter units is located at the center. The rotating shaft 6 is provided, and switching means for changing the direction of the seal plate is provided so that the flow path to which the gas is supplied is alternately switched between adjacent filters. In FIG. 4 (a), the exhaust gas flows from the top to the bottom in the figure, and the particulate matter is removed in the same manner as in FIG. 1 (b), but it is filtered as in low load operation where the exhaust gas temperature is low. When the differential pressure increases, the partition plate 3 is switched as shown in FIG. 4 (b) to flow the gas through the flow path of the adjacent filter unit, and the gas is introduced to the filter surface where the amount of PM accumulated is small. As a result, the production of NO ₂ can be promoted and the PM combustion efficiency can be increased. Thus, by periodically switching the gas flow, it is possible to prevent an increase in the differential pressure during low load operation under low temperature conditions.

  In the embodiment shown in FIG. 4, the partition plate 3 is provided with a rotating shaft 6 so that the partition plate 3 can be rotated. As an alternative, the partition plate 3 is fixed in parallel to the exhaust gas flow, and the filter unit 2 is used. A rotating shaft may be provided in the filter unit itself so that the exhaust gas is introduced into the opening from the oblique direction, and the filter unit may be rotated until it contacts the partition plate.

  The exhaust gas treatment apparatus of the present invention can be made compact by providing a plurality of filter units in parallel or in multiple stages in the exhaust gas flow path according to the purpose of exhaust gas treatment. In addition to being used as a single device, the present invention is particularly suitably used as a pre-filter for a conventional wall flow type PM removal device, for example, a diesel particulate filter device.

Explanatory drawing for demonstrating the outline | summary of this invention. The plane sectional view for explaining the operation of the filter unit used for the exhaust gas treatment apparatus of the present invention. The figure which shows the relationship between an inlet gas velocity and PM removal rate. Explanatory drawing of the waste gas processing apparatus which shows the other Example of this invention.

Explanation of symbols

1: plate filter, 2: filter unit, 3: partition plate, 4: exhaust gas flow path, 6: rotating shaft.

Claims (5)

An exhaust gas treatment apparatus in which a filter unit in which a plurality of plate-like filters are stacked via a spacer is installed in an exhaust gas flow path, wherein the exhaust gas from an oblique direction with respect to the opening of the filter unit An exhaust gas treatment is provided, wherein a seal plate is provided so that a wall surface of the plate-like filter is perpendicular to the exhaust gas flow path and is partitioned between adjacent filter units. apparatus. An exhaust gas treatment apparatus in which a plurality of filter units in which a plurality of plate-like filters are laminated via a spacer are installed in parallel to an exhaust gas flow path, wherein the filter unit is configured so that exhaust gas is at the opening of the filter unit. On the other hand, a seal plate is provided so that the wall surface of the plate-like filter is perpendicular to the exhaust gas flow path so as to be supplied from an oblique direction, and partitions between the farthest ends of adjacent filter units. An exhaust gas treatment apparatus characterized by being made. The seal plate includes a switching means for changing the direction of the seal plate so that a rotating shaft provided in a swingable manner in a central portion and a flow path to which the exhaust gas is supplied are alternately switched between adjacent filters. The apparatus of claim 1 comprising: The apparatus according to claim 1, wherein the plate filter is a metal lath plate. The exhaust gas containing particulate matter is supplied to the apparatus according to claim 3, and after a predetermined time has passed, the direction of the seal plate is switched so that the direction of gas flow in the filter unit is reversed, and the processing unit performs processing for a predetermined time. An exhaust gas treatment method comprising:

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