JPS5979025A - Exhaust-gas purifying apparatus for engine - Google Patents

Abstract

PURPOSE:To improve the performance of an exhaust-gas purifying apparatus and to increase its durability, by keeping catlyst type reactor at an optimum temperature by disposing a heat accumulating medium molten at a temperature higher than a prescribed value in the catalyst type reactor disposed at a portion of an exhaust passage or on the upstream side of the same. CONSTITUTION:A catalyst type reactor 2 disposed at an intermediate part of an exhaust passage 1 of an internal combustion engine includes a filter member 3 coated with an oxidizing catalyst. A casing 5 disposed in the manner of surrounding the filter member 3 incorporates therein an intermediate wall 7 which is disposed on the outside of an inner wall member 6 with a prescribed spacing from the same, and the outer surface of the intermediate wall 7 is coated with a heat-insulating material 9. The space formed between the inner wall member 6 and the intermediate wall 7 is changed with a heat accumulating medium 4 consisting of a molten salt of the mixture of lead phosphate, potassium nitriate and sodium cobaltinitrite having a melting point of about 200-300 deg.C or a Teflon type plastics or wood metal having a melting point of about 200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION Misfire I]+1 relates to the improvement of exhaust gas purification and equipment in gasoline engines or diesel engines in which a catalytic reactor is provided in the exhaust passage.

Conventionally, in a gasoline engine, a catalytic reactor is provided in the exhaust passage, and the exhaust gas from the engine is purified by a reaction in the exhaust passage, as shown in Japanese Patent Application Laid-open No. 2003-111002, for example. On the other hand, in order to prevent the reactor from deteriorating due to overheating under high loads, an engine exhaust gas purification device that bypasses the exhaust gas has been proposed, and in order to improve the durability of the reactor, a complex It requires a passage structure and a switching valve.

In diesel engines, for example, as shown in Japanese Patent Application Laid-Open No. 7/3/6, fine particle components such as carbon particles in exhaust gas are collected in order to prevent them from being released into the atmosphere. An exhaust gas purification device in which a filter member is disposed in an exhaust passage, a burner is provided upstream of the filter member, and particulate components collected in the filter member are burned out to eliminate clogging. have been proposed, but the operation of the burner has the disadvantage of increasing fuel consumption.

On the other hand, it is well known that diesel engines use a catalytic reactor in which an oxidation catalyst is attached to a filter component, and the catalyst reacts and the temperature rises from a temperature lower than the combustion start temperature of particulate components. Therefore, it is possible to burn particulate components using the exhaust temperature and the reaction heat of the oxidation catalyst without using a heat source such as a burner, but the exhaust gas temperature is originally low in diesel engines,
Even if an oxidation catalyst is installed, there are a limited number of engine operating conditions in which the reactor reaches the combustion start temperature of the particulate components, and there is a risk that the clogging condition cannot be reliably cleared, resulting in a reduction in reliability. It is low.

In particular, in order to burn out the above-mentioned fine particle components, it is necessary to
It is necessary to hold the temperature at θθ℃ or higher for 60 to 7.20 seconds. If the holding time is short, combustion will not start or combustion will be incomplete. For example, when running through cloth, acceleration and deceleration Since the operation is repeated, the above combustion temperature is exceeded for a short period of time, and combustion often does not occur, making it impossible to sufficiently eliminate clogging.

In view of this, the present invention provides a device in which a catalytic reactor is provided in the exhaust passage, and a storage body containing a heat storage material that melts at a set temperature or higher is placed in the reactor or in the upstream exhaust passage of the reactor. The present invention provides an exhaust gas purification device for an engine that is installed in contact with exhaust gas, maintains a catalytic reactor at an optimum temperature, and improves the purification performance or durability of the reactor.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. This is a catalytic reactor installed in the middle of passage 1. This catalytic reactor 2 has a filter member 6 coated with an oxidation catalyst, and a heat storage material 4 that melts at a set temperature or higher.
The filter member 3 is installed inside an inner wall body 6 that is connected to the front and rear exhaust passages 11, and is formed in a nicomb shape from a porous material such as ceramic. Every other pore along the flow of exhaust gas is closed at the end.
Exhaust gas that has flowed into the open pores at one end passes through the permeable porous partition wall and flows out from the open pores at the other end. The surface of this filter member 6 is coated with an oxidation catalyst made of a noble metal or a base metal, and is configured to oxidize unburned components in the exhaust gas.

Further, in the storage body 5 disposed surrounding the outer periphery of the filter member 6, an inner wall body 7 is disposed outside the inner wall body 6 at a predetermined interval, and the inner wall body 7 and the inner wall body 6 are arranged at a predetermined interval. A heat storage material 4 is housed and sealed between the filter member 6 and the filter member 6 .

1. Heat storage material 4 Older materials include molten salts such as lead phosphate salts with a melting point of around 200 to 300℃ or mixed salts of potassium nitrate and sodium nitrite, or Teflon-based plastics and wood metals with a melting point of around 200℃. (low melting point alloy) etc. are used.

An outer wall 8 is further provided on the outer periphery of the storage body 5, that is, on the outer periphery of the inner wall 7, and a heat insulating material 9 is interposed between the inner wall 7 and the outer wall 8. is provided to prevent heat radiation.

<Example 2> In this example, as shown in FIG. 2, a catalytic reactor 10 having a filter member 6 coated with an oxidation catalyst (same structure as the previous example) is interposed in the exhaust passage 1. Reactor 1
A storage body 11 containing a heat storage material 4 that melts at a predetermined temperature or higher is arranged in the exhaust passage 1 on the upstream side of the exhaust gas passage 1 so as to be in contact with the exhaust gas.

As shown in FIG. 3, this storage body 11 has a container 12 in which the heat storage material 4 is sealed and has a large number of through holes 12a through which exhaust gas flows. The heat storage material 4 is configured to exchange heat with the gas.
is used as in the previous example.

<Embodiment 3> In this example, as shown in FIG. The filter member 14 is configured such that exhaust gas flows from the inner circumferential side to the outer circumferential side of the filter member 14.

Furthermore, a storage body 15 containing a heat storage material 4 that melts at a predetermined temperature or higher is disposed on the inner circumference of the filter member 14 of the reactor 13.

This storage body 15 is a cylindrical container 1 in which a heat storage material 4 is enclosed.
A large number of through-holes 16a are formed in the through-holes 16a through which exhaust gas flows, and heat exchange is performed with the exhaust gas flowing through the through-holes 16a and with the filter member 14.

Next, to explain the operation, if the exhaust gas temperature from the engine fluctuates as shown by the solid line in FIG. 5 depending on the operating state, A.

Although the particulate component combustion temperature TI is exceeded at points B and C,
Since the holding time is short, combustion does not occur, and at points D and F, the temperature is lower than the oxidation reaction start temperature T2 of the catalyst, and the unburned components (HC, CO) are discharged as they are without being burned.

On the other hand, the storage body 5, which houses the heat storage material 4, 11゜1
5, the heat storage material 4 melts at points A, B, and C and stores heat as melting latent heat, and radiates this heat at points E and F. As shown by the broken line, the temperature becomes equal to or higher than the particulate component combustion temperature T1, and the particulate components are burned out and the unburned components are purified by reaction. In addition, by lowering the maximum temperature at points A, B, and C, the reactor 2
, 10°13 is suppressed, and thermal deterioration of the catalyst is prevented. This is particularly noticeable in the embodiments shown in FIGS. 2 and 7 in which the heat storage material storage body is disposed upstream of the filter member 14.

In addition, if the heat storage material 4 is selected so that its melting temperature is higher than the combustion temperature of the particulate component and matches the retention temperature, that is, the set temperature, of the filter member 14, efficient temperature control can be performed.

As explained above, according to the present invention, a storage body containing a heat storage material that melts at a temperature higher than a set temperature is provided in the catalytic reactor or in the upstream exhaust passage of the reactor, thereby optimizing the catalytic reactor. It has the advantage of being able to maintain the temperature, improve the purification performance of the reactor, perform burnout of particulate components and reaction purification of unburned components, and improve durability.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an exhaust gas purification device according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of the second embodiment, and FIG. 3 is a cross-sectional view taken along the line lll-11f in FIG. FIG. 7 is a schematic cross-sectional view of an exhaust gas purification device in Example 3 of the present invention, and FIG. 5 is a curve diagram showing the relationship between exhaust gas temperature and filter temperature.

Claims (1)

[Claims] (1) In an engine equipped with a catalytic reactor in the exhaust passage, a storage body containing a heat storage material that melts at a temperature higher than a set temperature is placed in the reactor or in the upstream exhaust passage of the reactor so that it comes into contact with exhaust gas. An engine exhaust gas purification device featuring a built-in filter.