JP2016200114A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote the hydrolysis of urea water by keeping a site where the urea water is added at a high temperature.SOLUTION: An exhaust emission control device 100 according to one embodiment of this invention includes a casing 2, first and second partition plates 21, 22 forming in the casing an exhaust passage 10 which is turned back in a S-shape, a selective catalyst reduction type NOx catalyst 33 provided in the exhaust passage for reducing nitrogen oxide, an exhaust gas collision plate 20 formed by the first partition plate or the second partition plate to cause the collision of exhaust gas in the exhaust passage upstream of the NOx catalyst, and addition means 40 for adding urea water toward the exhaust gas collision plate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas purification apparatus, and more particularly to an apparatus for purifying exhaust gas of an engine (internal combustion engine).

  Generally, exhaust gas from a diesel engine includes nitrogen oxide (NOx), particulate matter (PM), and the like. Therefore, vehicles equipped with diesel engines are equipped with a selective catalytic reduction type NOx catalyst (SCR: Selective Catalytic Reduction) for purifying NOx in exhaust gas, a particulate filter for collecting particulate matter, etc. An exhaust gas purification device is installed. In particular, for NOx, a urea SCR that reduces and purifies NOx by combining urea water addition and a selective catalytic reduction type NOx catalyst has attracted attention.

  Patent Document 1 discloses a urea water pipe that passes through a part of an exhaust passage formed inside a purification device and then passes through an oxidation catalyst and opens downstream thereof, and ammonia generated in the urea water pipe. An exhaust gas purification device provided with a disk-shaped diffusion plate for mixing the exhaust gas and the exhaust gas is disclosed.

JP 2011-012564 A

  Urea SCR purifies NOx in exhaust gas by a reaction in which ammonia generated by hydrolysis of urea water acts as a reducing agent in the presence of a NOx catalyst. In order to promote the hydrolysis of urea water and efficiently generate ammonia, it is preferable to keep the urea water addition site at a high temperature.

  Accordingly, the present invention has been made in view of such circumstances, and an object thereof is to provide an exhaust gas purifying apparatus capable of promoting the hydrolysis of urea water by maintaining the urea water addition site at a high temperature. .

According to one aspect of the invention,
An exhaust gas purification device installed in an exhaust pipe of an engine,
A casing,
First and second partition plates that form an exhaust passage that is folded into an S-shape in the casing;
A selective catalytic reduction type NOx catalyst provided in the exhaust passage for reducing nitrogen oxides;
An exhaust gas collision plate formed by the first partition plate or the second partition plate, for causing exhaust gas to collide upstream of the NOx catalyst in the exhaust passage;
Adding means for adding urea water toward the exhaust gas collision plate;
An exhaust gas purifying apparatus characterized by comprising:

  Preferably, the addition means adds the urea water toward the back surface of the gas collision surface of the exhaust gas collision plate.

  According to the present invention, an excellent effect is exhibited that the urea water addition site can be maintained at a high temperature to promote hydrolysis of urea water.

1 is a schematic view of an exhaust gas purification device according to an embodiment of the present invention. It is the schematic of the exhaust gas purification apparatus which concerns on other embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view of an exhaust gas purifying apparatus according to an embodiment of the present invention. The exhaust gas purification device 100 is installed in an exhaust pipe 1 of an engine (internal combustion engine) and is a post-treatment device (post-treatment silencer) for purifying the exhaust gas (indicated by arrow G) of the engine before releasing it into the air. It is. The engine is a multi-cylinder compression ignition internal combustion engine mounted on a vehicle, that is, a diesel engine.

  The exhaust gas purification apparatus 100 according to the present embodiment includes a box-shaped casing 2 and an exhaust passage 10 that is formed in the casing 2 and is folded back into an S shape. The exhaust passage 10 is formed by first partition plates 21 and second partition plates 22 arranged alternately in the casing 2, so as to change the flow direction of the exhaust gas in two stages and in an S shape. It has become. That is, in the casing 2, the exhaust passage 10 is defined by the upstream portion 10A, the midstream portion 10B, and the downstream portion 10C, and the flow of the exhaust gas is changed by 180 ° to the midstream portion 10B so as to fold back the upstream portion 10A. Further, the flow of the exhaust gas is turned 180 ° to the downstream portion 10C so as to turn the middle flow portion 10B.

  An oxidation catalyst (DOC: Diesel Oxidation Catalyst) 31 and a particulate filter (hereinafter referred to as “DPF”) 32 are disposed in the upstream portion 10A. Further, a NOx catalyst 33 and an ammonia oxidation catalyst 34 are disposed in the downstream portion 10C.

The oxidation catalyst 31 oxidizes and purifies unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust gas. The oxidation catalyst 31 has a function of heating and raising the temperature of the exhaust gas with heat generated during oxidation of HC and CO. The oxidation catalyst 31 has oxidizes NO in the exhaust to NO _2, also the function of increasing the NO ₂ concentration in the exhaust gas.

  The DPF 32 collects and removes particulate matter (PM) contained in the exhaust gas. In this embodiment, a so-called wall flow type DPF 32 is used in which openings at both ends of a honeycomb-shaped heat-resistant substrate are alternately closed in a checkered pattern. However, any type of filter that physically collects PM can be used, such as a mesh-shaped foam shape. The DPF 32 is a so-called continuous regeneration type DPF with a catalyst in which a noble metal (catalyst) such as Pt is supported on the inner wall thereof. In this case, during normal operation of the engine, HC in the exhaust gas supplied to the DPF is oxidized and burned by catalytic action, and at this time, PM accumulated in the DPF is burned and removed. The DPF 32 is an oxidation catalyst (DOC: Diesel Oxidation Catalyst) that oxidizes and purifies particulate matter (PM) and unburned components (hydrocarbon HC and carbon monoxide CO) in exhaust gas. Also good.

  The NOx catalyst 33 is a catalyst for purifying nitrogen oxide NOx in the exhaust gas. The NOx catalyst 33 is a selective catalytic reduction type NOx catalyst (SCR: Selective Catalytic Reduction), and can continuously reduce NOx when a reducing agent is added.

The ammonia oxidation catalyst 34 is a catalyst that generates N ₂ by oxidizing ammonia (NH ₃ ) that has not been consumed in the reduction of NOx by the NOx catalyst 33.

  In the illustrated example, the casing 2 has a rectangular parallelepiped shape, the exhaust passage 10 has a square sectional shape, and the oxidation catalyst 31, the DPF 32, the NOx catalyst 33, and the ammonia oxidation catalyst 34 have circular sectional shapes. It is not limited to. In the present embodiment, the clearance of the exhaust passage 10 on the outer peripheral side of the oxidation catalyst 31 or the like is closed by a closing plate or the like so that exhaust gas does not flow through the clearance.

  An exhaust gas collision plate 20 for causing exhaust gas to collide is provided upstream of the NOx catalyst 33 in the exhaust passage 10 in the casing 2. In particular, in the exhaust gas purification apparatus 100 according to the present embodiment, the inlet portion 11 for introducing the exhaust gas from a direction perpendicular to the longitudinal direction of the upstream portion 10A is provided at the upstream end portion of the upstream portion 10A. The exhaust gas collision plate 20 is formed by inclining and protruding a part of the first partition plate 21 at the position of the upstream end of the upstream portion 10A into the middle flow portion 10B. Therefore, the exhaust gas collision plate 20 faces the inlet portion 11. The exhaust gas flowing in from the inlet portion 11 collides with the gas collision surface 20A, which is the surface of the exhaust gas collision plate 20, and bends at a right angle toward the downstream side. At this time, the exhaust gas collision plate 20 is heated by the exhaust gas, and the temperature of the exhaust gas collision plate 20 is raised to a high temperature about the temperature of the exhaust gas.

  Incidentally, an addition means or addition valve 40 for adding urea water as a reducing agent is provided in the exhaust passage 10 upstream of the NOx catalyst 33. In the exhaust gas purification apparatus 100 according to the present embodiment, the addition means or the addition port of the addition valve 40 is provided on the exhaust gas collision plate 20 so that the urea water collides with the back surface 20B of the gas collision surface 20A of the exhaust gas collision plate 20. It is directed to the back surface 20B. When urea water is added, urea water is hydrolyzed and ammonia is generated. This ammonia reacts with NOx in the NOx catalyst 33 to reduce NOx.

  In addition, as a constituent material of the casing 2, the 1st partition plate 21, and the 2nd partition plate 22 of the exhaust gas purification apparatus 100 which concerns on this embodiment, heat resistant materials, such as stainless steel and Cr-Mo steel, act, for example. It is preferable.

  Next, with reference to FIG. 1, the operation of the exhaust gas purifying apparatus 100 according to the present embodiment will be described. Exhaust gas flows from the exhaust pipe 1 of the engine into the exhaust passage 10 (upstream portion 10A) in the casing 2 through the inlet portion 11. When the exhaust gas flows into the casing 2, the exhaust gas collides with the exhaust gas collision plate 20, and the flow direction is bent at a right angle. At this time, the exhaust gas collision plate 20 is heated by the exhaust gas.

The exhaust gas that has flowed into the casing 2 passes through the exhaust passage 10 in the order of the upstream portion 10A, the midstream portion 10B, and the downstream portion 10C. The exhaust gas first passes through the oxidation catalyst 31, whereby unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust gas are oxidized and purified. The oxidation catalyst 31 heats and raises the temperature of the exhaust gas with the heat generated during the oxidation of HC and CO. Further, the oxidation catalyst 33 oxidizes NO in the exhaust to NO ₂ and increases the concentration of NO ₂ in the exhaust gas.

  Next, the exhaust gas flows into the DPF 32, and particulate matter (PM) contained in the exhaust gas is collected and removed.

  The exhaust gas that has passed through the DPF 32 is folded at an opening formed on the downstream side of the first partition plate 21 in the upstream portion 10A, and is turned 180 ° from the upstream portion 10A to the midstream portion 10B. At the downstream end of the midstream portion 10B, the exhaust gas collision plate 20 protrudes inward. The exhaust gas also collides with the back surface 20B of the exhaust gas collision plate 20, and the exhaust gas collision plate 20 is further heated by the exhaust gas.

  An addition valve 40 for adding urea water toward the back surface 20B of the exhaust gas collision plate 20 is provided at the downstream end of the middle flow portion 10B. The addition valve 40 adds urea water toward the back surface 20B of the exhaust gas collision plate 20 held at a high temperature about the temperature of the exhaust gas, and causes the urea water to collide with the back surface 20B of the exhaust gas collision plate 20. Therefore, hydrolysis of urea water is promoted and ammonia is efficiently generated.

  Next, the exhaust gas containing at least one of urea water and ammonia is folded back 180 ° in an opening formed on the downstream side of the second partition plate 22 in the middle flow portion 10B, and then flows from the middle flow portion 10B to the downstream portion 10C. Turned around. And it passes through the NOx catalyst 33 in the downstream portion 10C. The NOx catalyst 33 reduces the NOx with high reduction efficiency by using ammonia efficiently generated by the addition and collision of urea water to the exhaust gas collision plate 20.

Ammonia (NH ₃ ) that has not been consumed in the reduction of NOx by the NOx catalyst 33 is oxidized in contact with the ammonia oxidation catalyst 34, and release into the atmosphere is suppressed. The exhaust gas that has passed through the ammonia oxidation catalyst 34 bends in the flow direction at a right angle and is discharged from the casing 2 into the exhaust pipe 1 through the outlet portion 12.

  As described above, the exhaust gas purification apparatus 100 according to the present embodiment includes the exhaust gas collision plate 20 with which the exhaust gas collides, and the exhaust gas collision plate 20 (particularly the gas collision surface 20A) held at a high temperature by the exhaust gas. The urea water is added toward the rear surface 20B). Therefore, according to the exhaust gas purification apparatus 100 according to this embodiment, the exhaust gas collision plate 20 serving as the urea water addition site can be held at a high temperature to promote the hydrolysis of the urea water. Demonstrate.

  Next, another embodiment of the present invention will be described. FIG. 2 is a schematic view of an exhaust gas purification device 200 according to another embodiment.

  In the exhaust gas purification apparatus 200 according to the present embodiment, the second partition plate 22 that divides the midstream portion 10B and the downstream portion 10C of the exhaust passage 10 discharges by a part of the upstream end of the midstream portion 10B. A gas collision plate 220 is formed. The exhaust gas collision plate 220 is formed by causing a part of the second partition plate 22 at the position of the upstream end portion of the midstream portion 10B to be inclined and chamfered into the midstream portion 10B. Thereby, when the flow of the exhaust gas is changed by 180 ° from the upstream portion 10A of the exhaust passage 10 to the middle flow portion 10B, the exhaust gas collides with the collision surface 220A of the exhaust gas collision plate 220.

  Further, in the exhaust gas purification apparatus 200, an addition means or addition valve 240 for adding urea water toward the collision surface 220A of the exhaust gas collision plate 220 is provided at the upstream end portion of the midstream portion 10B of the exhaust passage 10. It has been.

  The exhaust gas purification apparatus 200 includes an exhaust gas collision plate 220 that collides with exhaust gas, and urea water is added toward the collision surface 220A of the exhaust gas collision plate 220 held at a high temperature by the exhaust gas. Therefore, the exhaust gas collision plate 220 as the urea water addition site is maintained at a high temperature, and the excellent effect of promoting the hydrolysis of the urea water is exhibited.

  Note that the configurations of the above-described embodiments can be combined partially or wholly unless there is a particular contradiction. The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Exhaust pipe 2 Casing 10 Exhaust passage 20, 220 Exhaust gas collision plate 21 1st partition plate 22 2nd partition plate 33 NOx catalyst 40, 240 Addition means 100, 200 Exhaust gas purification apparatus

Claims (2)

An exhaust gas purification device installed in an exhaust pipe of an engine,
A casing,
First and second partition plates that form an exhaust passage that is folded into an S-shape in the casing;
A selective catalytic reduction type NOx catalyst provided in the exhaust passage for reducing nitrogen oxides;
An exhaust gas collision plate formed by the first partition plate or the second partition plate, for causing exhaust gas to collide upstream of the NOx catalyst in the exhaust passage;
Adding means for adding urea water toward the exhaust gas collision plate;
An exhaust gas purification apparatus comprising:   The exhaust gas purification device according to claim 1, wherein the adding means adds the urea water toward a back surface of a gas collision surface of the exhaust gas collision plate.

Images