JP4637531B2 - Ceramic member for exhaust gas treatment and exhaust gas treatment device - Google Patents

Description

  The present invention relates to an exhaust gas treatment apparatus for an internal combustion engine or an external combustion engine, and in particular, treats suspended particulate matter, nitrogen oxides, hydrocarbons and the like in the exhaust gas.

Conventionally, light oil and heavy oil have been used as fuel for internal combustion engines such as diesel engines and gas turbines, and external combustion engines such as generators and boilers, but suspended particulate matter (hereinafter also referred to as SPM), nitrogen oxidation objects (hereinafter, also referred to as NO _X) and hydrocarbon (hereinafter, also referred to as HC) is disadvantageously generated. There are concerns that SPM may cause health damage such as carcinogenicity, NO _X causes acid rain and photochemical smog, and HC has been reported to have adverse effects on human bodies and animals and plants. Yes. For this reason, exhaust gas treatment apparatuses that can treat SPM, NOx, and HC harmlessly have been developed. This conventional exhaust gas treatment apparatus is shown in FIG. In this figure, reference numeral 12 denotes an insulating member, and 13 denotes an electrode. The insulating member 12 and the electrode 13 basically constitute an exhaust gas treatment device 11.

  The insulating member 12 is a corrugated sheet made of a heat-resistant material such as a ceramic sheet, and also has a function of holding the electrodes 13 at a predetermined interval. The electrode 13 is made of a conductive plate such as aluminum (Al) or stainless steel (SUS).

  The insulating member 12 and the electrode 13 described above are stacked in a plurality of stages to constitute the exhaust gas processing device 11. Then, by connecting the electrode 13 to the power supply device 14 and applying a high-voltage AC voltage to the electrode 13, plasma is generated between the electrodes 13, and the exhaust gas of the internal combustion engine or the external combustion engine is transferred to the insulating member 12 and the electrode 13 is passed (see, for example, Patent Document 1 below).

In a short time, this plasma decomposes NOx contained in the exhaust gas, oxidizes SPM, decomposes HC to CO ₂ , and releases it as harmless exhaust material to the atmosphere.
Japanese Patent Laid-Open No. 2003-336519

  However, in the conventional configuration, it is difficult to process the insulating member 12 into a predetermined corrugated shape, the height dimension of the wave front of the insulating member 12 varies, or a thin portion occurs in the insulating member 12 and cracks occur. In some cases, damage such as If the height of the insulating member 12 varies, or if the insulating member 12 is damaged by a crack or the like, the interval between the electrodes 13 cannot be maintained at a predetermined interval, and the plasma is stably generated between the electrodes 13. It may be difficult to generate. As a result, there has been a problem that SPM, NOx, and HC contained in the exhaust gas cannot be completely processed.

  There is also a problem that the cost required for processing the insulating member 12 is high and is not suitable for mass production.

  Accordingly, the present invention has been completed in view of the above-mentioned conventional problems, and its object is to make the suspended particulate matter, nitrogen oxides and hydrocarbons contained in the exhaust gas harmless, and to be inexpensive and mass-produced. It is an object of the present invention to provide an exhaust gas processing ceramic member and an exhaust gas processing apparatus suitable for the above.

The present invention includes a ceramic substrate, and a plurality of conductor plates for applying a DC pulse voltage or an AC voltage, which are arranged on the respective upper and lower main surfaces of the ceramic substrate and face each other with the ceramic substrate interposed therebetween. The main surface of the ceramic substrate is provided with a groove having a quadrangular cross section as an exhaust gas flow path, and the groove is formed on the upper main surface of the ceramic substrate and has a central axis and a lower main groove. It is characterized in that the central axes of those formed on the surface are provided in parallel to each other so as not to overlap in plan view .

  In the exhaust gas treatment ceramic member of the present invention, preferably, the groove is provided in a straight line.

  In the ceramic member for exhaust gas treatment according to the present invention, preferably, the groove is formed by grinding the ceramic substrate.

The present invention also provides the ceramic member for exhaust gas treatment, and a conductive plate for applying a high-voltage DC pulse voltage or a high-voltage AC voltage disposed so as to be in contact with the upper and lower main surfaces of the exhaust gas treatment ceramic member, respectively. And an exhaust gas processing apparatus characterized by comprising:

  In the exhaust gas processing ceramic member of the present invention, the upper and lower main surfaces of the ceramic substrate are formed with grooves having a quadrangular cross section as an exhaust gas flow path. The thickness dimension of the exhaust gas can be reduced within a specified range and the cross section is a square-shaped groove. In addition, plasma can be generated uniformly at all sites in the groove, and suspended particulate matter, nitrogen oxides, and hydrocarbons in the exhaust gas of the internal combustion engine and the external combustion engine can be efficiently processed. Further, the production of the exhaust gas treating ceramic member becomes easy, and it can be made inexpensive and suitable for mass production.

  In the exhaust gas treating ceramic member of the present invention, preferably, the groove is formed so that the central axis of the groove formed on the upper main surface of the ceramic substrate and the central axis of the lower main surface do not overlap in plan view. Thus, the plasma is more stably generated in the groove, and the exhaust gas can be effectively prevented from staying in the groove. Then, suspended particulate matter, nitrogen oxides and hydrocarbons in the exhaust gas can be treated more efficiently.

  Furthermore, in the exhaust gas processing ceramic member of the present invention, preferably, since the groove is provided in a straight line shape, the flow resistance is small and a large amount of exhaust gas can be processed efficiently without stagnation.

  In the exhaust gas treating ceramic member of the present invention, preferably, the groove is formed by grinding the ceramic substrate, so that the groove inner surface becomes rough and the groove inner surface floats in the exhaust gas. Particulate matter, nitrogen oxides and hydrocarbons are likely to adhere appropriately and plasma is more likely to be generated. As a result, the suspended particulate matter, nitrogen oxides and hydrocarbons in the exhaust gas can be treated even better.

  The exhaust gas treatment device of the present invention comprises a high-pressure DC pulse voltage or a high-voltage AC voltage arranged so as to be in contact with the upper and lower main surfaces of the exhaust gas treatment ceramic member of the present invention and the exhaust gas treatment ceramic member, respectively. By providing an application conductor plate, it is possible to efficiently treat suspended particulate matter, nitrogen oxides and hydrocarbons in the exhaust gas using the ceramic member for exhaust gas treatment of the present invention. It is cheap and suitable for mass production.

  The exhaust gas processing ceramic member and the exhaust gas processing apparatus of the present invention will be described in detail below. FIG. 1 is a sectional view showing an example of an embodiment of an exhaust gas treatment apparatus of the present invention. In this figure, 2 is a ceramic member for exhaust gas treatment (hereinafter also referred to as a ceramic member), 3 is a conductor plate, and the ceramic member 2 and the conductor plate 3 basically constitute an exhaust gas treatment device 1. The

  As shown in FIG. 1, the exhaust gas processing ceramic member 2 of the present invention has a plurality of grooves 2a each having a quadrangular cross section as an exhaust gas flow path formed on both upper and lower main surfaces of a ceramic substrate.

  Further, as shown in FIG. 1, the exhaust gas treatment apparatus 1 of the present invention is disposed so as to abut on the exhaust gas treatment ceramic member 2 of the present invention and the upper and lower main surfaces of the exhaust gas treatment ceramic member 2 respectively. And a conductive plate 3 for applying a high-voltage DC pulse voltage or a high-voltage AC voltage.

The ceramic member 2 of the present invention is made of ceramics such as alumina (Al ₂ O ₃ ) sintered body, aluminum nitride (AlN) sintered body, silicon nitride (Si ₃ N ₄ ) sintered body. With this configuration, since the dielectric strength of the ceramic member 2 is high, the conductor plates 3 can be reliably insulated from each other by the ceramic member 2 and the conductor plates 3 can be held at a predetermined interval. Then, plasma is generated between the conductor plates 3 arranged so as to be in contact with the upper and lower main surfaces of the ceramic member 2, respectively, but the ceramic member 2 made of ceramic having high heat resistance is sandwiched between the conductor plates 3. Accordingly, the ceramic member 2 is not deformed or deteriorated by heat at the time of plasma generation, and the interval between the conductive plates 3 contacting the upper and lower main surfaces of the ceramic member 2 is kept constant so that the plasma can be stably generated. Can be generated.

If the ceramic member 2 is made of, for example, an Al ₂ O ₃ sintered material, the raw material powder such as Al ₂ O ₃ , silicon oxide (SiO ₂ ), magnesium oxide (MgO), calcium oxide (CaO) is used. A suitable organic binder, solvent, plasticizer, dispersant, etc. are mixed and added to form a slurry, and a ceramic green sheet (ceramic raw sheet) is formed by adopting a doctor blade method or a calender roll method. Thereafter, the ceramic green sheet is appropriately punched, and a plurality of ceramic green sheets are laminated and fired at a temperature of about 1600 ° C.

  The groove 2a is provided by forming a punch to be the groove 2a when the ceramic green sheet is punched, or is provided with a square cross section by grinding the fired ceramic substrate.

  The cross-sectional shape of the groove 2a may be a rectangular shape such as a rectangle, a square, or a trapezoid. Preferably, the rectangle and the square have the same width on the upper surface and the lower surface of the groove. It is sufficient that the flow rate is stable and easy to process reliably.

  By processing the ceramic member 2 in this manner, the thickness dimension between the upper and lower main surfaces of the ceramic member 2 can be reduced within a predetermined dimension range, and the dimension of the groove 2a can be set within the predetermined dimension range. It can be processed into a state with little variation.

  Preferably, the dielectric strength of the ceramic member 2 is 10 kV / mm or more. If the dielectric strength of the ceramic member 2 is less than 10 kV / mm, since the dielectric strength of the ceramic member 2 is too small, dielectric breakdown is likely to occur, and plasma may not be generated in the groove 2a.

  Then, by incorporating this ceramic member 2 into the exhaust gas treatment device and using it, it becomes possible to generate plasma uniformly in all the parts in the groove 2a, and an external combustion engine such as an internal combustion engine, a generator, a boiler or the like. It is possible to efficiently treat suspended particulate matter, nitrogen oxides and hydrocarbons in the exhaust gas. In addition, the ceramic member 2 can be easily manufactured, and can be inexpensive and suitable for mass production.

  In the ceramic member 2, preferably, a plurality of grooves 2a are provided in parallel with each other so that the central axis of the upper main surface and the central axis of the lower main surface do not overlap in plan view. It is good to have. With this configuration, the wall portion made of a dielectric between the groove 2a on one side main surface and the groove 2a adjacent thereto faces the bottom surface portion of the groove 2a on the opposite main surface. A strong electric field is applied to this bottom surface portion of the groove 2a, plasma is generated more stably in the groove 2a, and the grooves 2a are formed in parallel to each other, so that the flow resistance of each groove 2a. Therefore, it is possible to effectively prevent the exhaust gas from staying in the groove 2a. Then, SPM, NOx and HC in the exhaust gas can be processed more efficiently.

  The central axis of the groove 2a formed on the upper main surface and the central axis of the groove 2a formed on the lower main surface are the central axis of the groove 2a formed on the upper main surface on the lower main surface. The groove 2a is preferably arranged so as to be the center of the central axis of the adjacent groove 2a. Moreover, it is preferable that the width of the groove 2a formed on the upper main surface and the interval between the central axes be the same as the width of the groove 2a formed on the lower main surface and the interval between the central axes. As a result, the electric field generated in the groove 2a formed in the upper main surface and in the groove 2a formed in the lower main surface is the same, and the groove 2a formed in the upper main surface and the lower main surface The plasma generated in the groove 2a formed on the surface can be the same.

  More preferably, the groove 2a is provided linearly in the above configuration. As a result, the resistance (flow path resistance) acting on the exhaust gas flowing through the groove 2a is reduced, so that a large amount of exhaust gas can be efficiently processed without stagnation.

  In addition, the groove 2a is preferably provided so that a portion with a lower gas pressure is larger than a portion with a high cross-sectional area where the gas pressure of the exhaust gas supplied to the ceramic member 2 is high. By adjusting the cross-sectional area of the groove 2a in this way, the flow resistance of the groove 2a between the high gas pressure portion and the low gas pressure portion can be adjusted, and the flow rate of the exhaust gas can be adjusted over the entire surface of the ceramic member 2. Can be adjusted to the same extent.

  Preferably, in the ceramic member 2, the groove 2a is formed by grinding a fired ceramic substrate. With this configuration, the inner surface of the groove 2a becomes a rough surface, and suspended particulate matter, nitrogen oxides, and hydrocarbons in the exhaust gas are appropriately attached to the inner surface of the groove 2a, and the residence time in the groove 2a is long. Thus, it is easy to be surely processed in the groove 2a, and plasma is more easily generated from the tip of the rough surface. As a result, the SPM, NOx, and HC in the exhaust gas can be treated even better.

  When such a groove | channel 2a is formed by grinding process, it is preferable that the surface roughness becomes 1-10 micrometers in arithmetic mean roughness (Ra). With this configuration, suspended particulate matter, nitrogen oxides, and hydrocarbons in the exhaust gas can be appropriately attached to the inner surface of the groove 2a, and plasma can be further easily generated. Further, SPM, NOx and HC in the exhaust gas can be further reliably processed. When Ra <1 μm, the surface of the groove 2a becomes too smooth, so that SPM, NOx and HC are difficult to adhere, and the processing efficiency is lowered. If Ra> 10 μm, the surface of the groove 2a becomes too rough, so that the discharge generated in the groove 2a becomes non-uniform, and the exhaust gas processing efficiency decreases. The groove 2a may be ground using a surface grinder or the like.

  Preferably, the groove 2a has a depth of 0.5 to 10 mm. With this configuration, the exhaust gas can be easily ventilated and plasma can be generated stably, and the exhaust gas processing efficiency can be made extremely efficient. If the depth of the groove 2a is less than 0.5 mm, since the groove 2a is too shallow, the flow rate of the exhaust gas is reduced and the throughput of the exhaust gas is reduced. On the other hand, if the depth of the groove 2a exceeds 10 mm, the groove 2a is too deep, so that the distance between the electrodes 3 is increased and plasma is hardly generated.

  The width of the groove 2a is preferably 3 mm or more. If the width of the groove 2a is less than 3 mm, the width of the groove 2a is too narrow, so that the flow rate of the exhaust gas is reduced and the processing amount of the exhaust gas is reduced.

  The conductive plate 3 is made of a conductive plate 3 such as Al or SUS, and is manufactured in a predetermined shape by applying a conventionally known metal processing method such as rolling or punching to a metal ingot.

  The thickness of the conductor plate 3 is preferably 1 to 5 mm. If the thickness of the conductor plate 3 is less than 1 mm, the thickness of the conductor plate 3 is too thin, so that it is likely to be deteriorated when plasma is generated. On the other hand, if the thickness of the conductor plate 3 exceeds 5 mm, the thickness of the conductor plate 3 is too thick and the unit itself becomes heavy and difficult to handle.

  The above exhaust gas treatment device 1 is not limited to a single structure in which the conductive plate 3 is disposed so that the upper and lower main surfaces of the single ceramic member 2 are in contact with each other, and usually a plurality of conductive plates 3 are laminated. Thus, the exhaust gas processing apparatus 1 is configured in which the ceramic member 2 is sandwiched between the conductor plates 3. And it connects to the power supply device 4 so that a voltage may be applied to the mutually opposing conductor plates 3, and the high AC voltage or the high DC pulse voltage for generating a plasma is applied to the conductor plate 3 by applying. In addition to generating plasma between the conductor plates 3, exhaust gas generated from an internal combustion engine such as a diesel engine or a gas turbine or an external combustion engine such as a generator or a boiler is passed between the ceramic member 2 and the conductor plate 3.

In a short time, NOx contained in the exhaust gas is decomposed by this plasma, SPM is oxidized, HC is decomposed into CO ₂ and released into the atmosphere as an innocuous exhaust material to living organisms. .

  The power supply device 4 is a voltage generator such as a multivibrator, and generates a high-voltage AC voltage or a high-voltage DC pulse voltage with a voltage of 1000 to 10000 V and a frequency of 100 Hz to 10 KHz. Here, the waveform generated by the power supply device 4 is not particularly limited, but a rectangular wave is preferable. That is, if the waveform of the power supply device 4 is a rectangular wave, the waveform becomes a pulse shape when rectified, and the electrostatic dust collecting action is effectively exhibited. Further, when the waveform of the power supply device 4 is a rectangular wave, there is an advantage that plasma rises quickly because the voltage rises sharply.

  In addition, this invention is not limited to the example of the above embodiment, It does not have any trouble in making various changes within the range which does not deviate from the summary of this invention. For example, a ceramic substrate having a metallized layer formed on the surface may be used instead of the conductor plate 3. Further, a metallized layer may be formed on the upper surface of the wall portion between the grooves 2a, and the ceramic member 2 may be joined to the conductor plate 3 via a brazing material or the like. Thereby, it is possible to prevent the exhaust gas flowing through the groove 2a from leaking out of the groove 2a.

It is sectional drawing which shows an example of embodiment of the exhaust-gas processing apparatus of this invention. It is sectional drawing which shows the example of the conventional exhaust gas processing apparatus.

Explanation of symbols

1: Exhaust gas treatment device 2: Ceramic member for exhaust gas treatment 2a: Groove 3: Conductor plate

Claims (4)

A ceramic substrate;
A plurality of conductor plates for DC pulse voltage or AC voltage application, arranged on each of the upper and lower main surfaces of the ceramic substrate and facing each other across the ceramic substrate;
The main surface of the ceramic substrate is provided with a groove having a square cross section as an exhaust gas flow path ,
The groove is provided in parallel to each other so that a central axis of the ceramic substrate formed on the upper main surface and a central axis of the lower main surface do not overlap in plan view. A ceramic member for exhaust gas treatment. 2. The ceramic member for exhaust gas treatment according to claim 1 , wherein the groove is provided in a straight line shape. 3. The exhaust gas processing ceramic member according to claim 1 , wherein the groove is formed by grinding the ceramic substrate. 4. A ceramic member for exhaust gas treatment according to any one of claims 1 to 3,
A high-pressure DC pulse voltage or a high-voltage AC voltage application conductor plate disposed so as to be in contact with the upper and lower main surfaces of the exhaust gas processing ceramic member, respectively. apparatus.

Images