JP7109947B2 - A plasma processing apparatus and an exhaust gas purification apparatus using the plasma processing apparatus. - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plasma processing apparatus, and more particularly, to a plasma processing apparatus provided in an exhaust path of an internal combustion engine for activating exhaust gas, and an exhaust gas purifying apparatus using the plasma processing apparatus.

Exhaust gases emitted from internal combustion engines used in automobiles and the like contain harmful substances such as nitrogen oxides (NOx), unburned hydrocarbons (HC), and carbon monoxide (CO). Substance emissions need to be reduced.

The harmful substances are purified by the exhaust purification catalyst, and a method is known in which plasma is generated upstream of the exhaust purification catalyst and the generated radical species activate the exhaust gas to improve the purification efficiency.

In Japanese Patent Laid-Open No. 2009-78266 of Patent Document 1, two metal substrates having a plurality of through holes are arranged in parallel so that the positions of the through holes are aligned, and a voltage is applied between the metal substrates. is applied to generate an electrical discharge, which causes the fluid to pass in a direction perpendicular to the metal substrate.
Further, it is described that the fluid purifying device allows the fluid to pass through without stagnation because the positions of the through holes are aligned with each other.

JP 2009-78266 A

However, since activation of the exhaust gas is performed in the discharge space where the discharge surfaces of the electrodes face each other, in the fluid purification device described in Patent Document 1, the exhaust gas does not need to diffuse into the discharge space. However, if the flow rate of the exhaust gas increases and the flow velocity increases, the exhaust gas cannot be sufficiently activated.

In other words, when the through holes of the two metal substrates are arranged at matching positions, the exhaust gas easily passes through the through holes without passing through the discharge space and passes through the fluid purification device without being activated.

In addition, in order to pass the exhaust gas through the discharge spaces by diffusion, it is necessary to form many discharge spaces in the direction of flow of the exhaust gas.

The present invention has been made in view of such problems of the prior art, and its object is to enable the exhaust gas to be reliably activated regardless of the flow rate of the exhaust gas, and to prevent an increase in pressure loss. It is an object of the present invention to provide a plasma processing apparatus capable of

As a result of intensive studies aimed at achieving the above object, the inventors of the present invention found that the above object can be achieved by providing through-holes of adjacent plate-like electrodes at positions that do not overlap each other in the exhaust gas flow direction. , have completed the present invention.

That is, the plasma processing apparatus of the present invention includes a plurality of plate-shaped electrodes provided in an exhaust passage of an internal combustion engine, and a power supply device for applying a voltage for generating plasma between the plate-shaped electrodes.
Then, the plurality of plate-like electrodes are arranged so that the discharge surfaces face each other in a direction perpendicular to the flow direction of the exhaust gas, and
each of the plurality of plate-like electrodes has a through-hole penetrating in the thickness direction thereof,
The through-holes of adjacent plate-like electrodes are provided at positions that do not overlap each other in the exhaust gas flow direction.

Further, the exhaust gas purifying device of the present invention includes a plasma processing device and an exhaust purifying catalyst downstream of the plurality of plate electrodes of the plasma processing device.
and each of the plurality of plate-like electrodes has a through-hole penetrating in its plate thickness direction,
The through-holes of adjacent plate-shaped electrodes are provided at positions that do not overlap each other in the exhaust gas flow direction,
A combination of two adjacent plate-shaped electrodes arranged immediately before the exhaust purification catalyst,
an upstream plate-shaped electrode having a through hole with a larger opening diameter on the outer side than on the center side;
a plurality of through-holes having an opening diameter smaller than the average opening diameter of the through-holes of the plate-like electrode on the upstream side, and a total opening area of the plurality of through-holes being larger than that of the plate-like electrode on the upstream side; It is characterized by being a combination with a plate-like electrode.

According to the present invention, the through-holes of adjacent plate-like electrodes are provided at positions that do not overlap with each other in the flow direction of the exhaust gas. Therefore, the plasma processing apparatus is capable of both activating the exhaust gas and preventing an increase in pressure loss. can be provided.

1 is a schematic diagram of an internal combustion engine having a plasma processing apparatus of the present invention in an exhaust path; FIG. It is a figure explaining the positional relationship of the through-hole provided in the plate-shaped electrode. It is a figure which shows the state through which exhaust gas passes a discharge space. FIG. 4 is a diagram showing an example of the positional relationship between through holes provided in two plate-like electrodes; It is a figure which shows the example of the through-hole of a plate-shaped electrode. It is a figure which shows the magnitude|size and positional relationship of the through-hole provided in two plate-shaped electrodes. 4 is a diagram showing the positional relationship of through-holes in Example 1 and Comparative Example 1. FIG. 4 is a graph showing HC conversion rate versus power output in Example 1 and Comparative Example 1. FIG.

<Plasma processing device>
A plasma processing apparatus of the present invention will be described in detail.
As shown in FIG. 1, the plasma processing apparatus 1 includes a plurality of plate-like electrodes 11 provided in an exhaust passage 3 of an internal combustion engine 4, and a power supply device that applies a voltage to generate plasma between the plate-like electrodes. 12.

The plate-like electrodes 11 have a surface of a metal substrate covered with a dielectric and have through holes 111 in the plate thickness direction. They are arranged in front of each other with a certain interval so that the discharge surface is perpendicular to the surface. That is, the plate-shaped electrodes are arranged so that the discharge surfaces face each other at a predetermined interval.

Then, an alternating voltage equal to or higher than the discharge start voltage is applied between the adjacent plate-shaped electrodes to generate a dielectric barrier discharge in the discharge space 13 with the discharge surfaces facing each other, and the exhaust gas passing through the discharge space 13 is filtered by the plasma. Activate.

2 and 3 show an example of the layout of the through holes provided in the plate-like electrode.
FIG. 2 is a diagram showing the arrangement of the through holes when the plate electrode is viewed from the upstream side of the exhaust path. In FIG. is shown.
FIG. 3 is a cross-sectional view taken along line AA' in FIG.

In the plasma processing apparatus of the present invention, as shown in FIGS. 2 and 3, the through holes 111 of the adjacent plate-like electrodes 11 are positioned so as not to overlap each other in the flow direction of the exhaust gas indicated by the thick arrows in FIG. is provided. Since the exhaust gas passing through the plasma processing apparatus 1 always passes through the discharge space 13 as indicated by the thin arrow in FIG. 3, the exhaust gas can be reliably activated.

Therefore, even if the flow rate of the exhaust gas increases, there is no need to increase the number of the plate-like electrodes 11 provided in the exhaust path 3, and the pressure loss in the entire plasma processing apparatus 1 does not increase. can be compatible with the prevention of an increase in

In the plate-like electrodes 11, one plate-like electrode 11a of adjacent plate-like electrodes 11a has a plurality of through-holes 111a at positions equidistant from the center of a through-hole 111b provided in the other plate-like electrode 11b. , the plurality of through holes 111a are preferably arranged at regular intervals.

FIG. 4 shows an example of through holes arranged in the above relationship.
In FIG. 4, the through-holes of one plate-like electrode are indicated by dotted lines, and the through-holes of the other plate-like electrode are indicated by solid lines.
Further, the center-to-center distance from the through-hole provided in one plate-like electrode is indicated by a solid line, and the center-to-center distance between the through-holes provided to the other electrode is indicated by a dotted line.

Exhaust gas that has passed through the through-holes of the plate-shaped electrode on the upstream side hits the plate-shaped electrode on the downstream side and flows in all directions along the electrode surface.

The through-holes 111a of one adjacent plate-shaped electrode are arranged with respect to the through-holes 111b provided in the other plate-shaped electrode as shown in FIG. The exhaust gas that has passed through the discharge space 13 flows without stagnation, and the exhaust gas passing through the discharge space 13 is equalized, thereby improving the activation efficiency of the exhaust gas.

The plasma processing apparatus preferably includes a plate-like electrode in which the outer through-hole 111 has a larger opening diameter than the center-side through-hole 111 .
FIG. 5 shows an example of a plate-like electrode in which the opening diameter of the outer through-holes is larger than the opening diameter of the central through-holes.

The exhaust gas flowing through the exhaust path 3 has a flow velocity distribution in the direction perpendicular to the flow direction of the exhaust gas. Specifically, on the outer side near the wall surface of the exhaust path, the flow velocity is reduced by being dragged by the wall surface of the exhaust path, and the flow velocity increases toward the center.

In the plasma processing apparatus 1 of the present invention, the plate-like electrodes 11 are arranged perpendicularly to the flow direction of the exhaust gas, and the opening diameter of the through hole on the center side is small, so that the exhaust gas flowing on the center side The flow is restricted and forced through the outer through-holes with large opening diameters.

Therefore, the flow velocity distribution in the direction perpendicular to the flow direction of the exhaust gas is made uniform, and the activation efficiency of the exhaust gas is improved.

A metal substrate having a dielectric layer on its surface can be used as the plate-shaped electrode.
The metal substrate is not particularly limited as long as it is a conductive material, and for example, stainless steel (SUS), copper, or the like can be used.

As the dielectric, oxide ceramics can be used, such as alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), silica (SiO ₂ ), yttria (Y ₂ O ₃ ), titanate. Examples include simple oxides such as barium (BaTiO ₃ ) and oxides such as composite oxides.

Further, the shape of the through-hole may be straight lines and curved lines as long as there are no corners, but it is preferable that the through holes are formed only by curved lines such as a circle or an ellipse. A uniform dielectric barrier discharge can be generated for a long period of time because the shape of the through-hole is circular.

<Exhaust gas purification device>
Next, the exhaust gas purifier of the present invention will be described in detail.
The exhaust gas purifying device includes the plasma processing device 1 and the exhaust purification catalyst 2 , and the exhaust purification catalyst 2 is arranged downstream of the plurality of plate electrodes 11 .

In the exhaust gas purifying device, it is preferable that the two adjacent plate-like electrodes arranged in front of the exhaust purification catalyst 2 are combined as follows.
the plate-shaped electrode 11a on the upstream side in which the opening diameter of the through hole 111a is larger on the outer side than on the center side;
A plurality of through-holes 111b having an opening diameter smaller than the average opening diameter of the through-holes 111a of the plate-like electrode on the upstream side, and the total opening area of the plurality of through-holes 111b is larger than that of the plate-like electrode on the upstream side. A combination with the plate-like electrode 11b on the downstream side is preferable.
An example of the above combination is shown in FIG. In FIG. 6, the through-hole 111a of the plate-like electrode 11a on the upstream side is indicated by a solid line, and the through-hole 111b of the plate-like electrode 11b on the downstream side is indicated by a dotted line.

Since the combination of the plate-shaped electrode on the upstream side and the plate-shaped electrode on the downstream side is the combination described above, the plate-shaped electrode 11a on the upstream side allows the exhaust gas flowing in the exhaust path to move in the direction perpendicular to the flow direction of the exhaust gas. The flow velocity distribution is made uniform, and the exhaust gas is activated in the discharge space 13 formed between the plate-like electrode 11a on the upstream side and the plate-like electrode 11b on the downstream side.

The plurality of through-holes 111b provided in the plate-like electrode on the downstream side have small and uniform opening diameters, and since they are evenly arranged and the total opening diameter of the through-holes is large, the exhaust gas can flow smoothly. Due to the plate-shaped electrode on the downstream side, the flow velocity distribution of the exhaust gas does not easily change, and the exhaust gas can flow to the exhaust purification catalyst while maintaining a uniform flow velocity distribution.

Therefore, the flow velocity of the exhaust gas flowing through the exhaust purification catalyst is made uniform in the direction perpendicular to the flow direction of the exhaust gas, and the purification efficiency of the exhaust gas is improved.

The exhaust gas purifying catalyst is not particularly limited as long as it has an exhaust gas purifying function. Specifically, it is possible to apply a catalyst component such as a noble metal supported on a monolithic carrier such as a honeycomb carrier.
The catalyst component is not particularly limited, but noble metals such as platinum (Pt), palladium (Pd), rhodium (Rh), and iridium (Ir) are suitable for purifying automobile exhaust gas. be.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples.

Two plate-shaped electrodes were arranged so that the positional relationship of the through-holes was as shown in FIG. 7, power was supplied to the plate-shaped electrodes, and the hydrocarbon conversion rate was measured. In FIG. 7, the through-holes of one plate-like electrode are indicated by solid lines, and the through-holes of the other plate-like electrode are indicated by dotted lines. FIG. 8 shows the measurement results.

From FIG. 8, Example 1, in which the through holes are provided at positions that do not overlap each other, has a large increase in hydrocarbon conversion rate with respect to an increase in power output compared to Comparative Example 1, in which the through holes overlap, and is highly efficient. can be purified.

The plate-like electrodes and the number, size, or shape of the through holes provided in each plate-like electrode can be appropriately changed according to conditions such as the flow rate, flow velocity, and pressure loss of the exhaust gas to be activated. is not limited to the forms described and illustrated in .

REFERENCE SIGNS LIST 1 plasma processing device 11 plate electrode 111 through hole 12 power source device 13 discharge space 2 exhaust purification catalyst 3 exhaust path 4 internal combustion engine

Claims (4)

A plasma processing apparatus comprising: a plurality of plate electrodes provided in an exhaust path of an internal combustion engine;
The plurality of plate-shaped electrodes are arranged in front of each other with the discharge surfaces oriented in a direction perpendicular to the flow direction of the exhaust gas,
each of the plurality of plate-like electrodes has a through-hole penetrating in the thickness direction thereof,
1. A plasma processing apparatus, wherein all through-holes of adjacent plate-like electrodes are provided at positions that do not overlap with each other in the flow direction of exhaust gas. one of the adjacent plate-shaped electrodes has a plurality of through-holes equidistant from the center of the through-hole provided in the other plate-shaped electrode;
2. The plasma processing apparatus according to claim 1, wherein said plurality of through holes are arranged at regular intervals. 3. The plasma processing apparatus according to claim 1, further comprising a plate-like electrode in which the diameter of the through hole on the outer side is larger than the diameter of the through hole on the center side. A plasma processing apparatus having a plurality of plate electrodes in an exhaust path of an internal combustion engine and generating plasma between the electrodes;
An exhaust gas purification device comprising an exhaust purification catalyst on the downstream side of the plate-shaped electrode,
The plasma processing apparatus is the plasma processing apparatus according to any one of claims 1 to 3 ,
A combination of two adjacent plate-shaped electrodes arranged immediately before the exhaust purification catalyst,
an upstream plate-shaped electrode having a through hole with a larger opening diameter on the outer side than on the center side;
a plurality of through-holes having an opening diameter smaller than the average opening diameter of the through-holes of the plate-like electrode on the upstream side, and a total opening area of the plurality of through-holes being larger than that of the plate-like electrode on the upstream side; An exhaust gas purification device characterized by being a combination with a plate-like electrode.

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