JPS59155523A - Filter regenerative apparatus in diesel exhaust fine particulate collecting device - Google Patents

Abstract

PURPOSE:To perform the regeneration of an oxidation catalyst supporting filter stably in a short time by supplying hydrocarbon with excellent reactivity with the catalyst by a structure wherein a device to generate hydrocarbon by reforming or cracking kerosene is provided between a fuel tank and a kerosene injection device. CONSTITUTION:An oxidation catalyst bearing filter 4 is arranged in the midway of an exhaust pipe 3 extending from the exhaust manifold 2 of a diesel engine main body 1. Further, a fuel injection device 5, which opens in the exhaust pipe 3, is installed between the filter 4 and the engine main body 1. In the above-mentioned arrangement, a reforming and cracking device 7 is connected to stainless steel pipes 8 and 9 composing of the by-path of the exhaust pipe 8 so as to let a part of exhaust gas pass through the vessel of the device 7 in order to facilitate to preheat a reaction tank 7' installed in the interior of the device 7. Furthermore, the kerosene sucked up by means of a fuel pump 6 is led in the reaction tank 7' so as to generate hydrocarbon by reforming or cracking with a catalyst layer 7a in order to inject the generated hydrocarbon into exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an exhaust purification device for a diesel engine. ) is physically removed using a suitable collection material such as a fill element (
The present invention relates to a filter regeneration device in an exhaust gas purification device suitable for periodically incinerating exhaust particulates captured by a filter and restoring the function of the filter.

Prior Art Filters used as means for capturing exhaust particulates contained in the exhaust gas of diesel engines include ceramic filters with a three-dimensional mesh structure and wall-through type filters with plugs alternately installed at the exhaust gas inlet and outlet of the cell. Ceramic filters, aluminum-coated metal mesh filters, steel wool filters, and the like are known. However, in these filters, when the amount of captured exhaust particles increases to a certain extent, the back pressure increases, so in order to avoid this, it is necessary to periodically burn the captured exhaust particles to regenerate the filter. The methods of combustion of the exhaust particulates include: (1) raising the exhaust gas temperature to 550 to 600°C or higher, which is the combustion temperature of the exhaust particulates, using intake and exhaust throttles, and (2) raising the combustion temperature of the exhaust particulates using a catalyst. Proposed methods include: 1. Installing a heater or burner at the exhaust gas inlet (before the filter) to ignite exhaust particulates and propagate the combustion.

However, in the method (2), it is possible to raise the exhaust gas temperature to such a high temperature when the vehicle is running at high speed, but it is not possible when the vehicle is running at low speed. Furthermore, in the method (2), a catalyst that can burn exhaust particulates at approximately 250° C., which is the exhaust gas temperature obtained in a normal driving range, has not yet been developed. Furthermore, in method (2), in order to enable filter regeneration in the entire fecal area, there is a problem that the configuration such as control of exhaust gas flow rate and ignition timing or ignition system becomes complicated.

Therefore, the present applicant has proposed another filter regeneration method in which hydrocarbons or carbon monoxide is introduced into the exhaust gas upstream of the filter, and this is combusted by a catalyst supported on the filter, and the exhaust particulates are captured by the generated heat. proposed a method of burning. (See 4! Application No. 57-210576). However, when light oil is used as the hydrocarbon source to be introduced in this method, the reaction between light oil particles and the catalyst is slow, and in order to perform complete regeneration, the light oil injection time is required. There are problems in that it has to be long, it has to be long, and it has to use a fuel injector with good atomization performance.

Purpose of the Invention The present invention has been made to solve the above-mentioned problems, and its purpose is to reform or decompose light oil to be injected into exhaust gas so that it has good reactivity with a catalyst. It is an object of the present invention to provide a filter regeneration device for a diesel exhaust particulate collector that can supply hydrocarbons to increase reaction efficiency and regenerate the filter stably in a short time.

Structure of the Invention In order to achieve the above-mentioned object, the present invention provides a diesel exhaust system that includes an oxidation catalyst-carrying filter installed in the exhaust system of a diesel engine and a device for injecting light oil in a fuel tank into the exhaust pipe on the upstream side. The filter regeneration device in the particulate collector is characterized in that a device for reforming or decomposing light oil to generate hydrocarbons that easily react with the catalyst is provided between the fuel tank and the light oil injection device. be.

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

FIG. 1 shows an experimental embodiment of the present invention, in which a volume of 11 equivalents of palladium was placed as an oxidation catalyst in the middle of the exhaust pipe 3 extending from the exhaust manifold 2 of the diesel engine main body 1. A foam filter 4 carrying 93g is provided. Engine body 1 and foam filter 4
A fuel injection device 5 opening into the exhaust pipe 3 is disposed between the exhaust pipe 3 and the exhaust pipe 3 . This fuel injection device 5 is connected to a fuel tank 10 via a fuel cylinder f6 and a light oil reforming and decomposition device 7, and by opening a valve of the fuel injection device 5, light oil is injected into exhaust gas. It is now possible to do so. The light oil reforming and decomposing device 7 is connected to stainless steel pipes 8 and 9 that constitute the gas passage of the exhaust pipe 3, and a portion of the exhaust gas flows into the container of the light oil reforming and decomposing device 7. The reactor 7' is preheated by passing through the interior of the reactor tank 7'. A catalyst layer 7a is provided inside the reaction tank 7'.

A 300-mesh stainless steel wire mesh 7b supporting the catalyst layer 7a and a stainless steel wool filter 7c are housed therein, while a pipe 11 communicates with the fuel tank 10.
The other side is connected to a fuel injection device 5 via a fuel pump 6 through a pipe 12 .

The light oil pumped up by the fuel pump in this way is introduced into the reaction tank 7' and reformed or decomposed by the catalyst layer 7a to generate hydrocarbons (HC), which are injected into the exhaust gas. It looks like this. Note that 13 is an exhaust gas analyzer for detecting the amount of hydrocarbons (HC) in the exhaust gas during light oil injection, and 14 is a differential pressure gauge for detecting the amount of hydrocarbons (HC) in the exhaust gas collected by the foam filter 4. This is only for detecting the combustion state of particulates.

The results of an operation experiment of this apparatus having the above-mentioned configuration were as follows: The engine 1 was operated for 8 hours at 2000 rpm, and exhaust particulates were collected in the foam filter 4.

At this time, the amount of exhaust particulates adhering to the foam filter 4 was "h+:>x4.xg" for one foam filter.

Next, the fuel pump 6 is operated to pump light oil into the reaction tank 7', and the engine is operated for 30 minutes at 2000 rpm x 9 kg/m1 with an exhaust gas temperature of 390°C, and the reaction tank temperature is reduced to 3.
Decompose the diesel oil at 50°C, then reduce the engine condition to 2.
000 rpm x 3 kg/m and the exhaust gas temperature was set to 200°C. Next, the differential pressure at this time was read, more fuel was injected into the fuel injection device 5 for 5 minutes, and the relationship between the elapsed time and the differential pressure was plotted. The catalyst used for reforming the light oil was a γ-M203 carrier carrying 0.75% by weight of platinum, and the fuel injection amount was 0.5% of the exhaust gas flowing into the Four Thousand Filter 4. %Met.

The experimental results are shown in the solid line in FIG.

The experimental results of the comparative example corresponding to this example are as follows.

The comparative example is the same as the above example except for the point plate in which the light oil is injected directly into the exhaust gas without passing through the reaction tank 7'. Suwachi engine condition 2000 rpm
The engine 1 was operated for 8 hours at 3kli'・m, and the foam filter 4 collected the exhaust particulates.
Individual win, 914.8. F exhaust particulates were attached. This is to make the exhaust particulate collection conditions the same as in the embodiment. Next, set the engine conditions to 2000rpm x 3k17m, exhaust gas temperature 200℃, inject light oil for 5 minutes,
The relationship between elapsed time and differential pressure was plotted. Note that the amount of light oil injected at this time was 0.5% of the exhaust gas flow rate, similar to the example. The results of the experiment are indicated by the broken line in FIG.

As is clear from FIG. 2, the fuel injected into the exhaust gas after introducing light oil into the reaction tank 7' for reformation has high reactivity with the catalyst and should not be introduced into the reaction tank 7'. It can be seen that it is possible to burn the exhaust particulates attached to the filter in a shorter time than when diesel oil is directly injected.

In this example, Pt-AA! is used as the gas oil reforming catalyst.
203 was used, but the catalyst species are not limited to this.
Furthermore, there is no particular restriction as to what the product is.

In the case of this example, considering the reaction conditions, it is thought that a part of the light oil supplied to the reaction tank 7' was injected into the exhaust gas in the form of side chains, rings, or lower straight chains. 14
Compared to light oil, which is made up of straight-chain hydrocarbons that are said to have a carbon content of ~16, if there is some highly reactive hydrocarbon component, it is effective as an ignition source on the filter surface, and the collected exhaust particulates are It is thought to have an effect on combustion.

Effects of the Invention As explained above, the present invention injects light oil to be injected into exhaust gas by specifically reforming or decomposing it to generate hydrocarbons that easily react with the catalyst.
The reactivity between the injected fuel and the catalyst supported on the filter is improved, and the fuel is quickly combusted on the surface of the filter, allowing exhaust particulates adhering to the filter to be combusted in a short period of time.

In addition, the filter regeneration performance is not affected by the atomization performance of the fuel injection device, and stable filter regeneration is possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram of an example that also serves as an experiment of the present invention, and FIG. 2 is a graph showing the experimental results of the same example and a comparative example. 1... Diesel engine body, 3... Exhaust pipe, 4
'... Form filter, 5... Fuel injection device, 6
...Fuel cylinder 7'', 7...Diesel oil improvement/decomposition device, 7
′...Reaction tank, 10...Fuel tank. 11゛1 1A θF2 Figure Fuel, injection time (mLn)

Claims (1)

[Scope of Claims] 1. Filter regeneration in a diesel exhaust particulate collector equipped with an oxidation catalyst-supported filter installed in the exhaust system of a diesel engine and a device for injecting light oil in a fuel tank into the exhaust pipe on the upstream side thereof. A filter regeneration device characterized in that a device for reforming or decomposing light oil to generate hydrocarbons that easily react with a catalyst is provided between the fuel tank and the light oil injection device. 2. The equipment for reforming or decomposing the light oil has a catalyst and -
Claim 1 constituted by a reaction tank containing a wire mesh for supporting the catalyst and metal wool for filtration.
The filter regeneration device described in Section 1. 3. The filter regeneration device according to claim 2, wherein the catalyst is a catalyst in which platinum is supported on a γ-Al2O3 carrier.