JPH0249914A - Exhaust gas purifying method for diesel engine - Google Patents

Abstract

PURPOSE:To suppress variation in the operating condition by heating and incinerating carbonaceous particulates collected by a filter, thereby reproducing filter, sucking the combustion gas generated at this time, returning to the suction side of engine, and therein shifting gradually the positions of a heating means and a sucking means. CONSTITUTION:Soot and dust of the exhaust gas, which has flowed into an exhaust gas purifier 3 from an outlet smoke duct 6 of a Diesel engine 2, are collected while passing through a filter 13, and this purified gas is passed through a filter outlet smoke duct 7 to be exhausted to the silencer side. In this purifier 3, a vertically moving regenerative gas suction device 10 is provided downstream the filter 13. Current is supplied to an electric heater 12 upstream the filter 13 corresponding to the position of the suction device 10 on the surface of filter 13, and thereby the exhaust gas is heated up to the temp. necessary for oxidation of the soot and dust, and thus regeneration of the filter is made. The gas incl. secondary pollutional substances generated at this time of regeneration is sucked by the suction device 10 and circulated back to the suction pipe 5 of engine 2 via the suction pipe 8.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for purifying exhaust gas from a diesel engine, and more particularly to a method for purifying exhaust gas from a diesel engine suitable for regenerating a filter for removing soot and dust from exhaust gas. .

[Conventional technology]

The development of diesel engines has a long history, and improvements made to date have made it possible to use heavy oil as fuel, and the technology has almost reached maturity as an internal combustion engine with a high power conversion ratio. However, the disadvantage of diesel engines is that the exhaust gas contains nitrogen oxides and soot.

This occurs due to the high heat during combustion, and as the efficiency of the engine increases, it tends to occur more frequently, making it difficult to suppress its occurrence.

Recently, due to the problem of air pollution in urban areas, there is a tendency to regulate the exhaust gas generated from internal combustion engines for automobiles, private power generation, etc., and it is necessary to reduce soot and dust in the exhaust gas from diesel engines as well. As techniques for removing soot and dust, methods using an electric precipitator, a method using a cyclone, and a method using a filter have been proposed, and a method using a filter has been put into practical use due to the performance and size of the device.

When soot and dust in exhaust gas is captured and removed by a filter, the filter gradually becomes clogged, so a regeneration process is required to remove the clogged soot and dust. A regeneration method unique to diesel exhaust gas treatment involves burning and eliminating clogged soot and dust. The soot and dust on the filter is usually oxidized and erased at a temperature of 500° C. or higher. It is also possible to lower the oxidation temperature if a catalyst is present. Therefore, if the filter can be maintained at a temperature above a certain level, it is possible to simultaneously collect and eliminate soot and dust. However, in reality, it is difficult to maintain a constant temperature above a certain level, and there is also the problem of deterioration of the catalyst.Soot and dust are collected and the clogged filter is artificially heated and burned to regenerate it. There are many things.

When a filter clogged with soot and dust is heated and regenerated, volatile substances such as tar adsorbed on carbon particles evaporate and the temperature rises, which then ignites, and then incomplete combustion generates carbon monoxide, etc. Complete combustion occurs after the temperature rises further. Polynuclear aromatic compounds generated in this process are harmful and even carcinogenic, and when released into the atmosphere, they cause secondary pollution.

[Problem to be solved by the invention] In the method proposed in Japanese Patent Application Laid-open No. 60-20491°3, which was proposed as a method for removing harmful volatile components generated during filter regeneration, a noble metal catalyst downstream of the filter is used. An oxidation method is used.

However, with the above conventional technology that uses a catalyst, once the catalyst surface is covered with tar when the exhaust gas temperature drops and is cut off from oxygen in the exhaust gas, even if the temperature rises to the temperature where it can be oxidized, only volatile matter in the exhaust gas remains. However, there was a problem that the tar on the surface of the catalyst was difficult to oxidize, and the performance deteriorated with long-term use.

Japanese Patent Application Laid-Open No. 59-77021 adopts a method in which a filter clogged with soot in engine exhaust gas is incinerated with combustion gas from a separately installed burner, and the incinerated gas is supplied to the diesel engine population. This solves the problem of pollution caused by combustion gas and the above issues. However, in this method, the soot and dust are incinerated over the entire filter at once, so the engine inlet gas composition during incineration varies significantly compared to when no soot and dust is incinerated, making it difficult to maintain a uniform operating condition of the diesel engine. was difficult.

[Means to solve the problem]

The problems with the conventional technology described above are the process of collecting carbonaceous particles in the exhaust gas of a diesel engine with a filter, the process of heating the filter that has collected the carbonaceous particles to incinerate the carbonaceous particles, and the process of incinerating the carbonaceous particles. Carbon'1. In a diesel engine exhaust gas purification method that includes a step of sucking combustion gas containing heavy particles and a step of returning the sucked combustion gas to the inlet intake pipe of the diesel engine, the incineration step and the suction step are performed in the same part of the filter. This problem is solved by a method for purifying exhaust gas of a diesel engine, which is characterized by sequentially moving the exhaust gas on the filter while performing the cleaning on each section.

[Effect]

In the present invention, the positions of the heating means and the means for suctioning the gas generated by heating are moved little by little on the surface of the filter, so that the filter removes soot and dust and oxidizes and removes the soot and dust clogging the filter in a steady state. . therefore,
The gas composition and flow rate returned to the diesel engine after being used for regeneration are also constant, and the operation of the diesel engine is also maintained constant. Harmful components in the gas after being used for regeneration are combusted with other fuels in a diesel engine and rendered harmless.

〔Example〕

FIG. 1A is an overall system diagram of one embodiment of the present invention. In FIG. 1A, 1 is an air cleaner, 2 is a diesel engine, 3 is an exhaust gas purifier, 4 is a silencer, 5 is an intake pipe, 6
7 is a diesel outlet flue, 7 is a filter outlet flue, 8 is a suction pipe, and 9 is a suction gas adjustment valve. Figure 1B shows
FIG. 1A is an enlarged explanatory view of the exhaust gas purifier shown in FIG. 1A. In FIG. 1, exhaust gas generated by a diesel engine 2 has soot and dust removed by an exhaust gas purifier 3 equipped with a filter 13, and is discharged into the atmosphere through a muffler 4.

As a feature of the present invention, a suction pipe 8 is installed to suck in a portion of the exhaust gas from the exhaust gas purifier 3 and recycle it to the inlet of the diesel engine 2. In the suction pipe 8, since the inlet of the diesel engine 2 has a negative pressure and the outlet has a positive pressure, the exhaust gas is constantly recycled by adjusting the gas flow rate using the suction gas adjustment valve.

In Fig. 1B, the exhaust gas that has flowed into the exhaust gas purifier 3 from the diesel outlet flue 6 passes through the filter 13, where soot and dust is collected and purified. be discharged.

A feature of this embodiment is that there is a regeneration gas suction device 10 that moves up and down, and the electric heater 12 upstream of the filter 13 corresponding to the position of the regeneration gas suction device 10 on the surface of the filter 13 is activated, and the electric heat is applied to the filter I3. The inflowing gas is heated to the temperature required for oxidizing the soot and dust and passed through the filter 13. The gas containing secondary pollutants generated during regeneration is sucked in by the regeneration gas suction device 10, and is then sent to the diesel engine 2 through the suction pipe 8. It is returned to the inlet (intake pipe 5). Regeneration gas suction device 1
The filter I3 in the non-active portion of 0 is not heated and is used for exhaust gas purification, and is not regenerated until the regeneration gas suction device 10 is moved to that location.

Another embodiment of the exhaust gas purifier according to the present invention is shown in FIG. In this embodiment, the regeneration gas suction device 10 is fixed at a fixed position, and the filter 13 rotates and moves around the filter rotation axis 15. LPG gas pipe 1 as a heating source
The high-temperature gas generated by the high-temperature gas generator 17 using the LPG gas from the tube furnace 8 and the combustion air from the combustion air pipe 19 is used, and as the high-temperature gas generator 17, in addition to a normal burner, a catalytic burner is also convenient. It is.

Note that when implementing the present invention, in order to localize the oxidation on the filter 13, it is necessary to regenerate the filter 13 while the accumulation of soot and dust is small. If a large amount of dust accumulates in the filter 13 and oxidizes after forming a thick layer, combustion may expand due to heat generation.

〔Effect of the invention〕

According to the present invention, secondary pollutants generated during filter regeneration can be incinerated without using an oxidation catalyst or an in-line burner and without changing the operation of the diesel engine. Furthermore, as a side effect, the filter ventilation pressure loss does not fluctuate.

[Brief explanation of the drawing]

FIG. 1A is an overall system diagram of an embodiment of the present invention, FIG. 1B is an enlarged view of the exhaust gas purifier of FIG. 1A, and FIG. 2 is an exhaust gas purifier of another embodiment of the present invention. It is an enlarged view of. 1...Air cleaner, 2...Diesel engine, 3.
... Exhaust gas purifier, 4... Silencer, 5... Intake pipe, 6... Diesel outlet flue, 7... Filter outlet flue, 8... Suction pipe, 9... Suction gas adjustment valve, 10... Combustion gas suction device, 11... Suction device moving device, 12... Electric heater, 13... Filter. Agent Patent Attorney Takeshi Kawakita Filter rotary shaft rotary drive machine High temperature gas generator LPG gas pipe Combustion air pipe Air cleaner Diesel engine exhaust gas purifier Silencer Suction pipe Diesel outlet Flue Filling outlet Flue Suction pipe Suction gas adjustment Valve combustion gas suction device] 3: Filter Fig. 1A Fig. 1B

Claims (1)

[Claims] (1) The process of collecting carbonaceous particles in the exhaust gas of a diesel engine with a filter, the process of heating the filter that has collected the carbonaceous particles to incinerate the carbonaceous particles, and the combustion of the incinerated carbonaceous particles. In a diesel engine exhaust gas purification method comprising a step of sucking gas and a step of returning the sucked combustion gas to the inlet intake pipe of the diesel engine, the above-mentioned incineration step and suction step are performed on the same part of the filter. A method for purifying exhaust gas from a diesel engine, characterized by moving the exhaust gas sequentially over a filter.