JP4703309B2 - Exhaust gas treatment apparatus, treatment method thereof, and automobile - Google Patents

Description

  The present invention relates to an exhaust gas treatment apparatus that treats harmful substances contained in exhaust gas by discharge, a treatment method thereof, and an automobile.

  From the viewpoint of environmental conservation, it is strongly required to decompose harmful substances contained in automobile exhaust gases, decompose harmful substances contained in gas discharged from factories, or treat deodorized gases containing malodorous components. It has been.

  As this type of device, an adsorption method using activated carbon or the like is known as one of methods for removing harmful substances in gas or performing deodorization.

  In addition, a method using electric discharge has recently attracted attention (see, for example, Patent Documents 1 and 2). Compared with the adsorption method, this method using discharge has the advantage that it is not necessary to replace the adsorbent and the processing cost can be reduced.

However, there are drawbacks that various components are contained in the exhaust gas or the gas temperature becomes high, so that the discharge tends to become unstable. As one means for solving this problem, there is a discharge system called barrier discharge (dielectric barrier discharge). A typical electrode configuration of this barrier discharge system is shown in FIG. An AC voltage is applied to the two plate electrodes 3 and 5 from the high-frequency power source 4 to generate a discharge between the two electrodes 3 and 5. By this discharge, the exhaust gas 6 flowing between the plate electrodes 3 and 5 is treated.
JP-A-2-258014 JP-A-6-178914

  However, in the above-described conventional barrier discharge method, in order to reduce the applied voltage between the two flat plate electrodes 3 and 5, it is necessary to narrow the distance between the two electrodes 3 and 5. On the other hand, if the interval between the two electrodes 3 and 5 facing each other is narrowed, the capacitance between the electrodes facing each other increases. When the capacitance increases, the reactive current flowing from the power source increases, and there is a problem that the power supply device becomes large and expensive.

  The present invention has been made in order to solve the above-described problems, and maintains discharge stably even under gas conditions in which discharge tends to become unstable, thereby reducing the applied voltage of discharge and reducing the capacitance between electrodes. It is an object of the present invention to provide an exhaust gas treatment apparatus, a treatment method thereof, and an automobile that can reduce the size and cost of a power source.

In order to achieve the above object, in the exhaust gas treatment apparatus of the present invention, a first flat plate electrode having a dielectric, and a plurality of voids that are disposed to face the first flat plate electrode and that penetrate therethrough are provided. An AC voltage is applied between the first plate electrode and the second plate electrode; and an exhaust gas supply means for flowing exhaust gas between the first plate electrode and the second plate electrode; a power supply device for treating an exhaust gas flow between said first plate electrode by discharging to the second plate electrodes, have a, the elongated hole of the second plurality of elliptical flat plate electrode or rectangular The long hole is arranged so that the long axis direction of the long hole is substantially parallel to the flow direction of the exhaust gas .
In the exhaust gas treatment apparatus of the present invention, the second plate electrode is composed of a plurality of thin wires arranged substantially in parallel with each other, and further arranged so as to be substantially parallel to the flow direction of the exhaust gas. It is characterized by that.

In order to achieve the above object, in the gas treatment method of the present invention, an exhaust gas treatment method using a second flat plate electrode provided with a plurality of through holes facing the first flat plate electrode having a dielectric. An exhaust gas is allowed to flow between the first plate electrode and the second plate electrode, an alternating voltage is applied between the first plate electrode and the second plate electrode, and the discharge is performed. The exhaust gas supplied between the first flat plate electrode and the second flat plate electrode is treated, and the gap provided in the second flat plate electrode is a plurality of elliptical or rectangular slots, and this The long axis direction of the long hole is arranged substantially parallel to the flow direction of the exhaust gas .

  According to the exhaust gas treatment apparatus and the treatment method of the present invention, the discharge can be stably maintained even under gas conditions where the discharge is likely to be unstable, thereby reducing the applied voltage of the discharge and reducing the capacitance between the electrodes, The power supply can be reduced in size and cost.

  Hereinafter, embodiments of an exhaust gas treatment apparatus and a treatment method thereof according to the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

  FIG. 1 is a perspective view showing a configuration of an exhaust gas treatment apparatus according to an embodiment of the present invention. As shown in this figure, a typical embodiment of an exhaust gas treatment apparatus using a discharge method called barrier discharge (dielectric barrier discharge) is shown. The exhaust gas treatment apparatus using this discharge method is composed of two opposing first plate electrodes 13 and second plate electrodes 11.

  As shown in FIG. 2, one first flat plate electrode 13 is manufactured, for example, by sandwiching an electrode plate 13 a between dielectrics 19 and 19. Here, the flat plate electrode 13 produced by sandwiching one electrode plate 13a between the dielectrics 19 and 19 is used. However, it is not always necessary to sandwich the electrode plate 13a with the dielectric 19 if the discharge can be stably generated. It is important that the capacitance between the electrodes 11 and 13 can be reduced and the pressure loss due to the gas flow 15 can be reduced. A conductive wire 18 is connected to the electrode plate 13a.

  The second flat plate electrode 11 facing this is formed with a plurality of elongated holes 16 which are a plurality of through holes in the surface of the flat plate electrode 11 in order to reduce capacitance and pressure loss. The shape of the elongated hole 16 is an elongated hole such as an ellipse or a rectangle, and is further arranged so that the major axis direction of the elongated hole 16 is substantially parallel to the flow direction of the exhaust gas 15 flowing between the electrodes 11 and 13. Yes.

  Conductive wires 18 and 18 are connected to the two plate electrodes 11 and 13 from a high-frequency power source 14 which is a power supply device, and an AC voltage is applied thereto. In the state where the exhaust gas 15 flows between the electrodes 11 and 13 as shown by the arrows, discharge occurs when this AC voltage is applied.

  In principle, the shape of the long hole 16 opened in the electrodes 11 and 13 may be any shape as long as the substantial area of the electrode is reduced. For example, a plurality of round holes may be formed or a plurality of square holes may be formed. In short, it is sufficient that the substantial area of the electrode is reduced. However, in order to have the effect of reducing the capacitance between the electrodes 11 and 13 facing each other, the effect that the capacitance is reduced unless the diameter of the hole is sufficiently larger than the distance between the electrodes. Not enough. In order to obtain the effect of reducing the electrostatic capacity, the diameter and size of the hole are practically required to be several times or more the distance between the electrodes.

  In addition, the shape of the hole may be any shape in principle if the purpose is only to reduce the capacitance between the opposed flat plate electrodes 11 and 13. However, in order to allow the exhaust gas 15 to flow between the narrow electrodes 11 and 13, it is desirable to reduce the pressure loss of the discharge part as much as possible. In order to reduce the pressure loss due to the flow of the exhaust gas, it is better to increase the distance between the plate electrodes 11 and 13, but the discharge voltage becomes higher and the power supply device 14 becomes larger.

  For this purpose, it is necessary to reduce the distance between the electrodes. As described above, in order to reduce the pressure loss due to the flow of the exhaust gas 15 even at a distance between narrow electrodes, it is necessary to devise the shape of the hole. If a rod or plate is placed in the flow of the exhaust gas 15, vortices are generated before and after the rod or plate, causing pressure loss. For this purpose, as shown in this figure, the shape of the plurality of elongated holes 16 provided in the electrodes is an elongated hole such as an ellipse or a rectangle, and the major axis direction of the elongated holes 16 is the flow direction of the gas flowing between the electrodes. Make them almost parallel.

  Further, as the constituent material of the electrodes 11 and 13, it is preferable to use a metal having high corrosion resistance such as stainless steel, Inconel and Hastelloy.

  In the present embodiment configured as described above, the electrodes 11 and 13 are configured by an electrode in which a plurality of long holes 16 are formed in at least one flat plate electrode. By forming in this way, the vortex generated by the exhaust gas 15 is only before and after the elongated hole, the amount of vortex generation can be suppressed to the minimum, and the pressure loss can be reduced. In this way, it is possible to obtain an electrode configuration that can suppress capacitance even when the distance between the two electrodes 11 and 13 facing each other is narrowed.

  According to the present embodiment, vortices are generated only before and after the long hole 16, and the amount of vortices generated can be minimized and pressure loss can be reduced. In this way, the substantial electrode area related to the electrodes 11 and 13 is reduced, and the capacitance between the opposing electrodes can be reduced. In this way, the discharge can be stably maintained even under gas conditions where the discharge is likely to be unstable, whereby the applied voltage of the discharge can be lowered and the capacitance between the electrodes can be lowered. In this way, the power supply can be reduced in size and cost. Further, the exhaust gas treatment apparatus and the treatment method can be applied to exhaust gas treatment and deodorization treatment in various fields including automobile exhaust gas treatment.

  Further, in this embodiment, the plate electrode 13 produced by sandwiching one electrode plate 13a between the dielectrics 19 and 19 is used. However, it is not always necessary to sandwich the electrode plate 13a with the dielectric 19 if the discharge is stable. It is important that the capacitance between the plate electrodes 11 and 13 can be reduced and the pressure loss can be reduced.

  FIG. 3 is a perspective view showing a configuration of an exhaust gas treatment apparatus according to another embodiment of the present invention. This figure shows a configuration in which the plate electrode 11 having the configuration shown in FIG. 1 is replaced with an electrode 12 constituted by linear thin wires 17, and a configuration different from that shown in FIG. 1 will be mainly described.

  As shown in this figure, the exhaust gas treatment apparatus by the barrier discharge method is composed of two flat plate electrodes 12 and 13. One plate electrode 13 is produced by being sandwiched between dielectrics 19 and 19 shown in FIG. For example, the other 12 of the two plate electrode electrodes is composed of a linear thin wire 17 or a rod in order to reduce the capacitance. The linear thin wires 17 are arranged in parallel to the opposing flat plate electrodes 13, and the thin wires 17 are arranged in parallel to each other. Further, the fine wires 17 are arranged so that the direction of the thin wires 17 is substantially parallel to the direction of the gas flow 15.

  Even when the plate electrode 12 is constituted by the thin wires 17, the shape of the constitution is not particularly limited. In short, it is sufficient that the substantial area of the electrode is reduced. For example, an electrode may be made by arranging a plurality of straight thin wires or thin bars, or may be made of a mesh-like metal material.

  Note that if the interval between the thin wires 17 and the roughness of the mesh are not sufficiently larger than the distance between the electrodes 12 and 13, the effect of reducing the electrostatic capacity cannot be sufficiently obtained. Specifically, in order to obtain a sufficient effect, the distance between the electrodes 12 and 13 needs to be several times as large as the distance between the thin wires 17 arranged side by side.

  In the present embodiment configured as described above, by configuring so that the direction of the fine line 17 is arranged substantially parallel to the flow direction of the exhaust gas 15, the vortex due to the flow of the exhaust gas can be obtained only by the support portions at both ends fixing the fine line 17. Will occur. In this way, the amount of vortex generated by the flow of the exhaust gas 15 can be minimized, and the pressure loss can be reduced. Further, by using an electrode composed of the thin wire 17 as at least one of the electrodes 12 and 13, the capacitance can be reduced even if the distance between the two opposing electrodes is reduced.

  According to this Embodiment, the substantial electrode area which concerns on the electrodes 12 and 13 becomes small, and the electrostatic capacitance between the electrodes which oppose can be made small. In this way, the discharge can be stably maintained even under gas conditions where the discharge is likely to be unstable, thereby reducing the voltage applied to the discharge and reducing the capacitance between the electrodes, thereby reducing the size and cost of the power supply. Can be achieved.

  FIG. 4 is a perspective view showing a configuration of an exhaust gas treatment apparatus according to still another embodiment of the present invention. This figure shows an embodiment configured by arranging a plurality of plate electrodes 11 and 13 having the configuration shown in FIG. 1 in parallel, and the configuration different from that shown in FIG. 1 will be mainly described.

  As shown in FIG. 4, this multistage exhaust gas treatment apparatus is configured by arranging five stages of exhaust gas treatment apparatuses composed of two opposing flat plate electrodes 11 and 13. For example, one plate electrode 13 is manufactured by sandwiching an electrode plate 13a between dielectrics 19 and 19, as shown in FIG. The flat plate electrode 11 facing this is manufactured by opening a plurality of elongated holes 16 in the electrode 11 in order to reduce the capacitance and pressure loss. The exhaust gas treatment apparatus configured as described above is multi-stage so that the flat plate electrodes 11 having a plurality of holes and the flat plate electrodes 13 produced by sandwiching the flat plate electrode plates 13a between the plates of the dielectrics 19 and 19 are alternately opposed to each other. It is configured by stacking. Exhaust gas 15 flows between the flat plate electrodes 11 and 13.

  In the present embodiment, a large amount of exhaust gas 15 can be processed. As shown in FIG. 1, each exhaust gas treatment apparatus is connected to a conductive wire 18 from a high frequency power supply 14 and applied with an AC voltage. For this reason, in the state which the exhaust gas 15 is flowing between the electrodes 11 and 13 as shown by the arrow, all the plate electrodes 11 having a plurality of holes have the same potential. In addition, the plate electrode 13 formed between the dielectrics 19 has the same potential.

  Further, when the capacity of the power source is small, a part of a plurality of stacked plate electrodes 11 formed by sandwiching a plurality of perforated plate electrodes 11 and dielectric plates 19 so as to alternately face each other is set as one set. A block may be connected to a power source, and another block may be connected to another power source. Alternatively, each set of the plate electrode 11 formed by sandwiching the plate electrode 11 having a plurality of holes and the dielectric 19 may be connected to different power sources.

  Further, in the present embodiment, instead of the plate electrode 11 formed by opening a plurality of elongated holes 16 shown in FIG. 1, the plate electrode 12 constituted by the thin wires 17 shown in FIG. The plate electrodes 13 may be stacked in multiple stages so as to alternately face each other. Also in this case, the exhaust gas flows between the plate electrodes 12 and 13.

  With such a configuration, it becomes possible to treat a large amount of exhaust gas.

  Moreover, in order to increase the processing amount of the exhaust gas 15, it is necessary to increase the discharge input in the discharge part. For this purpose, it is necessary to increase the discharge current. One way to increase the discharge current is to increase the frequency of the power supply. However, if the frequency is increased, the plasma characteristics may change, and the exhaust gas treatment performance may change. The optimum frequency value is considered to be several hundred Hz to several tens kHz.

  When the frequency is fixed, the discharge current is substantially determined by the size of the area of the electrode plate 13 a sandwiched between the dielectrics 19 constituting the plate electrode 11. The area of the plate electrode 11 that is not covered with the dielectric 19 has little influence. That is, the current density is limited by the dielectric 19.

  From this point of view, it is desirable that the substantial area of the plate electrode 11 not covered with the dielectric 19 is reduced and the area of the plate electrode 13 sandwiched between the dielectrics 19 is not reduced.

  Further, by adopting the plate electrode 11 formed by opening a plurality of long holes 16 in the electrode or the plate electrode 12 formed by the thin wires 17, the substantial electrode area is reduced without changing the size of the entire electrode. can do. By reducing the electrode area, the capacitance between the plate electrodes 11 and 12 and the plate electrode 13 can be reduced.

  FIG. 5 is a graph showing the calculation result of the electric field strength in the vicinity of the flat plate electrode of FIG.

  In order to reduce the size of the power supply, it is effective to lower the discharge voltage. One method for reducing the discharge voltage when the distance between the electrodes is constant is to increase the electric field in the vicinity of the electrodes. Consider the electric field near this electrode.

  In this figure, the circles indicate calculation examples of the electric field strength in the vicinity of the thin wire 17 related to the plate electrode 12 configured by arranging the thin wire 17 side by side. As a comparative example, ● indicates a calculation example of the electric field strength related to a combination of a conventional flat plate electrode and a flat plate electrode. From this figure, it can be seen that the electric field strength of the plate electrode 12 configured by arranging the thin wires 17 in parallel can obtain a higher electric field twice or more than the electric field strength of the combination of the conventional plate electrode and the plate electrode. I understand.

  According to the present embodiment, in the discharge type exhaust gas treatment apparatus according to the barrier discharge method, by increasing the electric field in the vicinity of the electrode, the discharge is stably maintained even under gas conditions where the discharge tends to become unstable. Further, the power supply can be reduced in size and cost by lowering the applied voltage for discharging and lowering the capacitance between the plate electrodes. For this reason, it becomes possible to apply to various exhaust gas treatments and deodorization treatments including automobile exhaust gas treatment.

  Furthermore, the present invention is not limited to the above-described embodiments, and the thin wire constituting the second flat plate electrode 12 may be changed to a stainless steel wire mesh. Various modifications can be made without departing from the scope of the invention.

The perspective view which shows the structure of the waste gas processing apparatus of embodiment of this invention. The perspective view which shows the structure manufactured by pinching | interposing the flat electrode of FIG. 1 with a dielectric material. The perspective view which shows the structure of the exhaust gas processing apparatus of other embodiment of this invention. The perspective view which shows the structure of the waste gas processing apparatus of further another embodiment of this invention. The graph which shows the calculation result of the electric field strength concerning the flat-plate electrode vicinity by the thin wire | line of FIG. The perspective view which shows the structure of the conventional waste gas processing apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11, 12 ... 2nd flat plate electrode, 13 ... 1st flat plate electrode, 13a ... Electrode plate, 14 ... High frequency power supply, 15 ... Exhaust gas, 16 ... Long hole, 17 ... Fine wire, 18 ... Conductor, 19 ... Dielectric.

Claims (4)

A first plate electrode having a dielectric;
A second flat plate electrode arranged opposite to the first flat plate electrode and provided with a plurality of penetrating gaps;
Exhaust gas supply means for flowing exhaust gas between the first plate electrode and the second plate electrode;
A power supply apparatus for treating exhaust gas flowing between the first plate electrode and the second plate electrode by applying an AC voltage between the first plate electrode and the second plate electrode to cause discharge.
Have
A plurality of elliptical or rectangular long holes are formed in the second flat plate electrode, and the long axis direction of the long holes is arranged substantially parallel to the flow direction of the exhaust gas;
An exhaust gas treatment apparatus characterized by.   2. The exhaust gas treatment apparatus according to claim 1, wherein the first flat plate electrode and the second flat plate electrode are configured to be stacked in multiple stages so as to face each other. An exhaust gas treatment method using a second flat plate electrode provided with a plurality of air gaps facing the first flat plate electrode having a dielectric,
Flowing exhaust gas between the first plate electrode and the second plate electrode;
An alternating voltage is applied between the first flat plate electrode and the second flat plate electrode for discharging, and the exhaust gas supplied between the first flat plate electrode and the second flat plate electrode is treated,
The gap provided in the second plate electrode is a plurality of elliptical or rectangular long holes, and the long axis direction of the long holes is arranged substantially parallel to the flow direction of the exhaust gas. Exhaust gas treatment method .   An automobile comprising the exhaust gas treatment apparatus according to claim 1.

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