JP3158797B2 - Exhaust gas purification method and exhaust gas purification apparatus using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying method for purifying exhaust gas discharged from a diesel engine or the like and an exhaust gas purifying apparatus using the same.

[0002]

2. Description of the Related Art In recent years, harmful components such as particulates (soot) and nitrogen oxides contained in exhaust gas discharged from trucks, buses, passenger cars and the like equipped with a diesel engine have become a serious environmental problem.

[0003] As a countermeasure, a honeycomb type filter and a foam type filter which collect and burn particulates, and a system which carries various catalysts on these filters to reduce harmful components such as nitrogen oxides have been studied. Have been.

[0004]

However, the operating state of the diesel engine is not constant and has the following disadvantages.

For example, when a diesel engine is started, the temperature of the engine is low, so that the exhaust gas has many particulates. After that, the engine is stabilized and becomes a steady state, and the exhaust gas becomes high in particulate matter and high in dry soot during high temperature. Further, the gas components are different, and the ratios of the SOF components (soluble organic components) are also different. A catalyst that efficiently removes both of these has not been found.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust gas purifying method and an exhaust gas purifying apparatus using the same, in which different filters are used for treating the exhaust gas of a diesel engine depending on the state of the exhaust gas to purify the exhaust gas efficiently. .

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems
The exhaust gas purification method of the present invention measures the temperature of the exhaust gas.
If the temperature is lower than the specified temperature, a catalyst that is active at low temperature
Exhaust gas is purified by the first purification means carried by the
If the temperature is higher than a predetermined temperature, a high-temperature active catalyst is forged.
Exhaust gas by the second purification means carried by the
It is characterized by purifying. Also, the exhaust gas purification of the present invention
The device is equipped with temperature detection means for detecting the exhaust gas temperature,
A first filter supporting an active catalyst on a honeycomb filter
Filter and a high-temperature active catalyst for the foam filter.
And the exhaust gas passage is connected to the first filter.
Passage disconnection for connection to a filter or said second filter
Replacement means and the exhaust gas temperature is measured by the temperature detection means.
If the temperature of the exhaust gas is equal to or lower than a predetermined value,
By driving the road switching means, the first exhaust gas is exhausted.
The exhaust gas temperature is equal to or higher than a predetermined value.
For example, by driving the passage switching means, the exhaust gas is
Control means for allowing the filter to pass through.

[0008] passage switching means available are ones known switchable flow of the exhaust gas by the passage switching means <br/> exhaust gas of the catalyst filter and cold carried in high-temperature catalysts supported filters It is switched so that it flows to either one.

As the temperature detector, a thermocouple, a temperature sensor or the like for directly detecting the temperature of the exhaust gas, or an engine speed sensor or a torque sensor for indirectly detecting the temperature of the exhaust gas can be used.

[0010] The control device controls the valve based on the exhaust gas temperature detected by the temperature detector, and an existing similar device can be used.

As the low-temperature oxidation catalyst, a catalyst in which a platinum group metal or the like is supported on a catalyst carrier is suitable. For example, γ-alumina is used as a support layer and platinum is supported. As the catalyst carrier, there are a pellet type, a honeycomb type, a foam type, and the like. At a low temperature, a filter having a large amount of particulates and a honeycomb type shape is suitable. A catalyst for purifying harmful gas components such as nitrogen oxides may be supported at the same time. The activity of the catalyst varies depending on the temperature, and the catalyst must be used at a temperature suitable for the catalyst in order to increase the efficiency. Can be.

As the high-temperature oxidation catalyst, a catalyst having a perovskite structure which is active at a high temperature is suitable. A catalyst for purifying harmful gas components such as nitrogen oxides may be supported at the same time. As a catalyst carrier, a honeycomb filter may be used, but the amount of particulates is relatively small, so the exhaust gas whose particulates have been reduced due to improvements in diesel engines and fuels, etc. A foam-type filter having a high catalyst-bearing ability and an excellent catalytic effect is suitable because the number of substances increases.

[0013]

With this configuration, a filter and a catalyst suitable for the exhaust gas temperature can be selected, so that the purification efficiency of the diesel exhaust gas can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an exhaust gas purifying method of the present invention and an exhaust gas purifying apparatus using the same will be described.

In the exhaust gas purifying apparatus for diesel engines of this embodiment, when the temperature of the exhaust gas detected by the temperature detecting device is lower than a preset temperature, the valve is operated by the control device to carry the low temperature catalyst. When the exhaust gas passes through the filter portion and the temperature of the exhaust gas is higher than a preset temperature, the valve is operated by the control device so that the exhaust gas passes through the filter portion carrying the high temperature catalyst. The preset temperature is set according to the case because the optimum temperature differs depending on the type of the high-temperature oxidation catalyst and the type of the low-temperature oxidation catalyst.

FIG. 1 is a view showing an exhaust gas purifying apparatus according to one embodiment of the present invention. In FIG. 1, 1 is a diesel engine, 2 is an exhaust manifold provided in the diesel engine 1, 3 is an exhaust pipe connected to the exhaust manifold 2, and the exhaust pipe 3 is divided into an exhaust pipe 4 and an exhaust pipe 5 on the way. ing. Further, casings 6 and 7 are connected to the exhaust pipes 4 and 5, respectively. Filters 8 and 9 are housed in the casings 6 and 7, respectively. A low temperature exhaust gas is passed through the filter 8 and a high temperature exhaust gas is passed through the filter 9. As an example of the filter 8, a filter in which a low-temperature oxidation catalyst (for example, Pt, molybdenum oxide, or the like) is supported on a honeycomb filter can be considered. As an example of the filter 9, a filter in which a high-temperature oxidation catalyst (for example, a lanthanum strontium-based catalyst having a perovskite structure) is supported on a foam-type filter can be considered. In addition, the filters 8 and 9 are not limited to the above-described configurations and materials, but may be any as long as they achieve their respective purposes.

The casing 6 and the casing 7 are made of a material such as stainless steel, for example, and are divided into two semicircular shapes so that the filters 8 and 9 can be easily set. Is set so that there is no leakage. Filters 8, 9 and casing 6,
A cotton-like heat-resistant material 10 is packed between the layers 7 as a buffer material.

Reference numeral 11 denotes a temperature sensor for measuring the temperature of exhaust gas in the exhaust pipe 3. As the temperature sensor 11, for example, a thermocouple made of platinum or the like is used.

Numeral 12 designates a valve for selecting whether the exhaust gas passing through the exhaust pipe 3 flows to the exhaust pipe 4 or the exhaust pipe 5.
3 is a valve 1 based on temperature information from the temperature sensor 11.
2 is a control unit for controlling the control unit 2.

The operation of the exhaust gas purifying apparatus configured as described above will be described below.

First, since the exhaust gas at the time of starting the engine or the like contains a lot of particulates due to its low temperature, it is preferable to purify the exhaust gas with the filter 8. Therefore,
When the control unit 13 detects from the temperature information of the temperature sensor 11 that the temperature of the exhaust gas passing through the exhaust pipe 3 is equal to or lower than a predetermined temperature, the control unit 13 transmits the drive unit 1 as shown in FIGS.
2b. The drive unit 12b moves the passage changing plate 12a according to the signal so that the exhaust gas flowing in the exhaust pipe 3 flows toward the exhaust pipe 4.

When the temperature of the exhaust gas flowing through the exhaust pipe 3 becomes equal to or higher than a predetermined temperature, the particulate component in the exhaust gas decreases, and instead, the harmful gas components, such as nitrogen oxides, increase. Therefore, this exhaust gas is preferably purified by the filter 9. Therefore, when the temperature of the exhaust gas flowing in the exhaust pipe 3 becomes equal to or higher than a predetermined temperature, the control unit 13 detects the temperature through the temperature sensor 11 and sends a signal to the drive unit 12b. Upon receiving the signal, the drive unit 12b moves the passage changing plate 12a so that the exhaust gas from the exhaust pipe 3 flows to the exhaust pipe 5, as shown in FIGS.

As described above, this embodiment focuses on the fact that the components contained in the exhaust gas differ depending on the temperature of the exhaust gas.
By providing the filters 8 and 9 suitable for removing these components in parallel, the life of the filters 8 and 9 can be extended reliably.

Hereinafter, the effect will be described specifically.
First, for comparison, an exhaust gas purifying apparatus using only a honeycomb type filter was manufactured as a sample 1, an exhaust gas purifying apparatus using only a foam type filter was manufactured as a sample 2, and an exhaust gas purifying apparatus of the present example was used as a sample 3. A purification device was prepared. The particulate removal efficiency of each of these samples is shown in (Table 1).

[0025]

[Table 1]

As can be seen from Table 1, the removal efficiency of sample 3 does not deteriorate compared to the other samples.

As described above, the purification efficiency of the particulates contained in the exhaust gas is improved by being oxidized by the catalyst suitable for the temperature of the exhaust gas, and the particulates contained in the exhaust gas are effectively reduced. Purified.

The particulate matter in the exhaust gas was efficiently collected by the honeycomb filter, and the particulate harmful components in the exhaust gas were effectively removed.

The present invention is not limited to the above-described embodiment, but is effective in a wide range of applications.

[0030]

As described above, the exhaust gas purifying method of the present invention is as described above.
And according to the exhaust gas purifying apparatus, it is possible to choose a catalyst suitable for each condition by the exhaust gas temperature is divided catalyst in a low temperature state and a high temperature, it is possible to perform a catalytic action in each optimal conditions Therefore, the catalyst efficiency is improved, and the low-temperature side is not exposed to high temperature, so that a catalyst that deteriorates at high temperature can be used as a low-temperature catalyst, and the amount of nitrogen oxides is higher at high temperature Therefore, it is useful and practical that the purification ability is improved by using a perovskite-based catalyst which can expect oxidation of particulates at the same time as purification of nitrogen oxides as a high-temperature catalyst as a high-temperature catalyst.

Further, by using a honeycomb filter as a low-temperature filter, it is possible to effectively remove a large amount of particulates at a low temperature, and to provide a foam-type filter having an excellent catalytic ability because of a large supporting area on a high-temperature filter. By using it, the catalytic ability can be improved, and harmful gas components that are often present at high temperatures can be efficiently removed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an exhaust gas purifying apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a valve portion of the exhaust gas purifying apparatus according to one embodiment of the present invention.

FIG. 3 is an enlarged view of a valve portion of the exhaust gas purifying apparatus according to the embodiment of the present invention.

FIG. 4 is an enlarged view of a valve portion of the exhaust gas purifying apparatus according to the embodiment of the present invention.

FIG. 5 is an enlarged view of a valve portion of the exhaust gas purifying apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 8, 9 Filter 11 Temperature sensor 12 Valve 12a Passage changing plate 12b Drive unit 13 Control unit

Continuation of the front page (56) References JP-A-4-43808 (JP, A) JP-A-1-108316 (JP, U) JP-A-63-132819 (JP, U) JP-B-6-21542 (JP) , B2) Jikgyo Hei 3-29533 (JP, Y2) (58) Field surveyed (Int. Cl. ⁷ , DB name) F01N 3/02-3/038 F01N 3/08-3/38 F01N 9/00 -11/00

Claims (2)

(57) [Claims] The temperature of exhaust gas is measured. If the temperature is lower than a predetermined temperature, the exhaust gas is purified by a first purifying means in which a low-temperature active catalyst is carried on a honeycomb filter. An exhaust gas purifying method, comprising purifying exhaust gas with a second purifying means in which a high-temperature active catalyst is carried on a foam type filter . 2. A temperature detection means for detecting the exhaust gas temperature, low
The first type in which a catalyst active at a temperature is supported on a honeycomb filter
Filter and high temperature active catalyst foam type filter
Wherein the second filter is担時, the passage of the exhaust gas to the
A passage switching means for connecting the first filter or the second filter, to measure the exhaust gas temperature by said temperature detecting means, the exhaust gas temperature before if a predetermined temperature below
By driving the passage switching means, the first exhaust gas is exhausted.
Filter, and the exhaust gas temperature is equal to or higher than a predetermined temperature.
If so, the passage switching means is driven to discharge exhaust gas.
An exhaust gas purifying device , comprising: a control unit that allows the gas to pass through a second filter .