JPH0715248B2 - Diesel exhaust gas purification equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to an exhaust gas purifying apparatus for removing particulates (combustible fine particles such as soot) contained in exhaust gas of a diesel engine.

2. Description of the Related Art As an exhaust gas purifying apparatus for purifying exhaust gas by removing particulates discharged from a diesel engine, there is known one in which a heat resistant filter is attached in the middle of an exhaust pipe to filter particulates. The characteristic of this type of device is that it is called "regeneration", and when particulates are deposited to some extent, it is incinerated to regenerate the filter cleanly and can be repeatedly used. In general, diesel engines have low exhaust gas temperatures, so particulates do not burn as they are. Therefore, some means such as raising the exhaust gas temperature or lowering the particulate ignition temperature must be taken.

As one of conventional purification devices capable of performing such regeneration, a heating means is provided upstream of the filter on the engine side, and the heat is used to raise the particulates to the ignition temperature.

Further, it has been attempted to ignite the particulates by the ignition means after continuously depositing the particulates on the filter to an amount capable of self-combustion.

However, in order to raise the particulates in the filter to the ignition temperature, it is necessary to heat the filter and the exhaust gas flowing therein, which requires a large capacity heating means. Therefore, there is a problem that the energy consumed for regeneration is extremely large.

Further, if the particulates are deposited until they self-burn, on the contrary, the combustion will run away after ignition, causing a rapid temperature rise due to the heat generation of the particulates itself, and there is a problem that the filter is damaged.

Therefore, the present invention does not consume a large amount of energy,
Further, the present invention provides a diesel exhaust gas purifying apparatus capable of safely performing regeneration without causing a runaway of particulate combustion.

Means for Solving the Problems And the technical means of the present invention for solving the above problems is to perform regeneration of the filter by using both the electric heater ignition means and the combustor heating means in combination.
That is, first, the amount of particulates deposited on the filter is limited to a region where normal ignition means cannot perform self-combustion. Next, the combustor is operated to heat the filter to raise the temperature to a temperature range where self-combustion occurs even with a small amount of particulates. At this time, the electric heater ignites the particulates deposited on the front surface and inside the filter.

Action The action of the technical means of the present invention is as follows.

That is, according to the above-mentioned means, even if the accumulation of particulates is very small, the condition that the combustor can self-combust particulates will be satisfied. At this time, when a part of the particulates accumulated on the filter is ignited by the electric heater, the combustion starts gently, and the combustion continues to be propagated to the surrounding particulates, and the regeneration is completed. As described above, since the combustion is maintained by the combustor under the condition that the particulates can self-combust, it does not stop as long as the particulates exist.

Further, since the regeneration is performed by depositing a small amount of particulates, there is no possibility that the temperature of the filter abnormally rises due to the amount of heat generated by the particulates and the filter is melted.

Furthermore, since the particulates are not heated to the ignition temperature by heating, a small capacity combustor is sufficient and regeneration can be performed with a small amount of energy consumption. If the amount of exhaust gas flowing into the filter is limited, the capacity of the combustor can be further reduced.

Embodiment Hereinafter, a diesel exhaust gas purification apparatus in one embodiment of the present invention will be described with reference to the accompanying drawings.

The figure shows a vertical cross section of the exhaust gas purifying apparatus, in which 1 has a large number of cells 2a and 2b inside, and one end side of which is plug 3 alternately.
It is a ceramic filter that is closed by. Further, the ceramic filter 1 is wound around a cushioning material 4 having a good heat insulating property, which is obtained by hardening ceramic fibers with an organic binder, and is housed in a cylindrical stainless steel can case 5. Inside the can case 5, the ceramic filter 1 moves back and forth to move the cushioning material 4
The stoppers 6a and 6b are welded to prevent the movement of the stoppers. In addition, an exhaust gas connecting portion 7 having a conical cone shape is formed in the front portion of the can case 5, and an electric heater 8 is provided so that the heating portion may contact the front surface of the ceramic filter 1 on the wall surface thereof. Has been done. Further, a rear portion of the can case 5 is narrowed down into a conical cone shape, and a muffler connecting portion 9 connected to a muffler muffler (not shown) is provided.

On the other hand, the ceramic filter 1 is provided in front of the exhaust gas connecting portion 7.
Equipped with a light oil burner 10 toward the front of the. The light oil burner 10 has a structure in which the atomization nozzle 11 is placed at the center, and the air from the combustion air port 12 flows in the tip direction of the atomization nozzle 11 around the atomization nozzle 11. A spark plug 13 for igniting the atomized combustion with a high-pressure discharge arc is attached near the tip of the atomizing nozzle 11.

An engine exhaust gas introducing pipe 14 is connected to the exhaust gas connecting portion 7 between the ceramic filter 1 and the light oil burner 10. An exhaust pipe 15 of an engine (not shown) is branched into an exhaust gas introduction pipe 14 and an exhaust gas bypass pipe 16. A three-way valve 17 is provided at this branch point. Further, the exhaust gas bypass pipe 16 joins the muffler connecting portion 9 behind the ceramic honeycomb 1. The three-way valve 17 has a structure capable of switching the exhaust gas from the engine to the exhaust gas introduction pipe 14 and the exhaust gas bypass pipe 16 by rotating it.

Next, the operation in this configuration will be described. First, the normal operation of the diesel engine will be described. Three-way valve 17
Is set in a direction in which the engine exhaust pipe 15 communicates with the exhaust gas introduction pipe 14. At this time, the exhaust gas from the engine reaches the front surface of the ceramic filter 1 through the exhaust gas introducing pipe 14. From here, the exhaust gas enters the cell 2a which is open to the front of the ceramic filter 1, where it passes through the cell wall and enters the cell 2b which is open to the rear. At this time, the particulates contained in the exhaust gas cannot pass through the cell wall and are deposited in the cell 2a. On the other hand, the exhaust gas that has been cleaned by removing the particulates enters the muffler connection portion 9 and is discharged to the atmosphere through the muffler muffler.

The work of depositing such particulates is continuously performed for 1 to 2 hours. Then, when the particulates are sufficiently accumulated in the ceramic filter 1 and if the particulates are accumulated more than this, the engine is adversely affected,
The three-way valve 17 is rotated to bring the engine exhaust pipe 15 into communication with the exhaust gas bypass pipe 16. Then, the exhaust gas flows into the exhaust gas bypass pipe 16 and is discharged to the atmosphere through the muffler connecting portion 9.

The light oil burner 10 is operated at the same time as the switching of the three-way valve 17. To operate the light oil burner 10, first, combustion air is blown to the combustion air port 12 by an air pump (not shown). Next, an air compressor (not shown) sends high-pressure air to the atomizing nozzle 11 to atomize the supplied light oil. Spark plug here 13
When the atomized fuel is lit at, the light oil burner 10 starts to burn. The high temperature combustion gas generated by the light oil burner 10 flows into the ceramic filter 1 to heat it and gradually raise the temperature.

When the temperature of the ceramic filter 1 reaches about 500 ° C., the electric heater 8 is energized and the ceramic filter 1
The particulates deposited on the front surface of the fire ignite. After several tens of seconds, when the electric heater 8 is de-energized, the internal particulates are supplied with air and the combustion continues to be propagated to the front surface of the ceramic filter 1 and then to the rear surface thereof. The gas emitted at this time is released to the atmosphere through the muffler muffler.

If this state is maintained for about 10 minutes, all the particulates deposited in the ceramic filter 1 are burned out, and the inside returns to the original clean state.

Then, the light oil burner 10 is stopped, the three-way valve 17 is rotated in the reverse direction, and the flow of the exhaust gas flowing through the exhaust gas bypass pipe 16 is switched to the exhaust gas introduction pipe 14. Then, the normal operation state is restored.

Thus, when incinerating the particulates deposited in the ceramic filter 1, that is, at the time of regeneration, the light oil burner 10 is used as an auxiliary to adjust the combustion conditions, and the electric heater 8 ignites the two heat sources combined method. To regenerate.

EFFECTS OF THE INVENTION The present invention uses a burner as a heat source to heat a ceramic filter to a relatively low temperature to adjust the combustion conditions of particulates during regeneration, and then ignites with an electric heater to deposit a small amount of particulates. However, combustion can be continued and the filter can be regenerated. Therefore, the temperature of the filter does not rise during regeneration, and the purification device has very good durability. Moreover, since the filter is maintained at a low temperature, the energy consumption required for regeneration can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a diesel exhaust gas purifying apparatus according to an embodiment of the present invention. 1 ... Ceramic filter, 3 ... Plug, 5 ... Can case, 8 ... Electric heater, 10 ... Light oil burner, 15 ... Exhaust pipe, 16 ... Exhaust gas bypass pipe, 17 ... Three-way valve.

Claims (3)

[Claims] 1. A can case connected to an exhaust pipe of a diesel engine, a filter which is housed in the can case to collect particulates in exhaust gas, and a combustion gas which is disposed in front of the filter to filter the filter. A diesel exhaust gas purifying apparatus comprising: a heating combustor for heating; and an electric heater for igniting and burning particulates in a filter heated by the combustor. 2. The diesel exhaust gas purifying apparatus according to claim 1, wherein the temperature of the combustion gas generated in the combustor is controlled to 600 ° C. or lower. 3. A bypass pipe that branches exhaust gas of a diesel engine without passing through a filter, and a bypass opening / closing valve that switches the inflow of exhaust gas between the filter and the bypass pipe, and the bypass opening / closing valve when the filter is regenerated. The diesel exhaust gas purification apparatus according to claim 1, wherein the exhaust gas purification apparatus is configured to limit the amount of exhaust gas flowing into the filter.