JP2005013928A - Apparatus for treating exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for treating exhaust gas, the power consumption required to denitration of which is made small so that the cost of the apparatus itself can be reduced. <P>SOLUTION: This apparatus is provided with an insulator-made reaction vessel 27 having an exhaust gas inlet 18 at one end and an exhaust gas outlet 19 at the other end, a plate-shaped electrode 13 which is arranged in the vessel 27 and has a surface 13a formed along the flow direction of exhaust gas G, at least one comblike electrode 14 which is formed by arranging acicular electrodes 20 in a row and arranged in the vessel 27 on at least one plane almost perpendicular to the flow direction of the gas G and the tip part of which is opposed to the surface 13a of the electrode 13 and a high-voltage DC power source 17 for supplying an electric current between the electrodes 13 and 14. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas treatment apparatus that denitrates NOx contained in exhaust gas by a discharge method.
[0002]
[Prior art]
An exhaust gas treatment apparatus for treating NOx in exhaust gas by applying electric discharge has been developed. This apparatus is mainly classified into three types: (1) corona discharge method, (2) pulse discharge method, and (3) glow discharge method. Hereinafter, the prior art of the exhaust gas treatment apparatus in these three methods will be described.
[0003]
(1) Corona discharge method An example of a method using corona discharge is shown in FIG. An exhaust gas inlet 33a is provided on one side of the wet dust collector 33, and an exhaust gas generator 31 and a flow meter 32 are provided below the exhaust gas inlet 33a. The exhaust gas G is introduced into the exhaust gas inlet 33a through the flow meter 32 from the exhaust gas generator 31. A wire-like discharge electrode 34 is provided at the center of the wet dust collector 33, and a negative voltage is applied to the discharge electrode 34 by a DC high voltage generator 35 via a protective resistor 36. . In FIG. 4, a wire-like electrode is assumed, but a rod-like electrode or a plate-like electrode may be used.
[0004]
An outer cylinder electrode 37 is provided on the outer periphery of the discharge electrode 34. The outer cylinder electrode 37 is grounded, and corona discharge is generated between the outer cylinder electrode 37 and the discharge electrode 34. Oxidized NOx is trapped in the circulating liquid tank 38 provided below the wet dust collector 33 by this corona discharge. The treated exhaust gas G is discharged from an outlet 33b provided at the upper part of the outer cylinder electrode 37, and the liquid in the circulating liquid tank 38 is pumped by the pump 39 via the circulation pipe 40 to the outer cylinder electrode. It is sent to the upper part of 37 and circulates in the wet dust collector 33 (for example, refer patent document 1).
[0005]
(2) Pulse Discharge Method An example of a method using the pulse discharge method is shown in FIG. An exhaust gas inlet 42 a is provided at one side lower part of the cylindrical outer cylinder electrode 42. Similarly to the above (1), the exhaust gas G is introduced into the exhaust gas inlet 42a from the exhaust gas generator 31 through the flow meter 32. A wire-like discharge electrode 41 is provided at the center of the outer cylinder electrode 42, and a pulse voltage is applied to the discharge electrode 41 by a power supply 43 for generating a short pulse. The pulse has a rise time of 20 to 100 [ns], a half width of the pulse width of 100 to 500 [ns], and a frequency of several tens to several hundreds [Hz].
[0006]
The polarity of the applied voltage is positive or negative, and a high voltage having a peak voltage of about 60 [kV] is applied. Since the outer cylinder electrode 42 is grounded, a high electric field that rises quickly is generated between the outer cylinder electrode 42 and the discharge electrode 41. As a result, only electrons are accelerated at high speed, and the electrons collide with the exhaust gas G to accelerate the reaction, thereby removing NOx. The treated exhaust gas G is discharged from an outlet 42b provided at the upper part of the outer cylinder electrode 42 (see, for example, Patent Documents 2 and 3).
[0007]
(3) Glow discharge method An example of a method using the glow discharge method is shown in FIG. An exhaust gas inlet 51 a is provided on one side of the plasma reactor 51. Similarly to the above (1), the exhaust gas G is introduced into the exhaust gas inlet 51a through the flow meter 32 from the exhaust gas generation unit 31. In the discharge part of the reaction device 51, parallel plate electrodes 52, 53 arranged vertically opposite to each other, and a dielectric or semiconductor 55 are provided on the other electrode 53. One electrode 52 is grounded, and the other electrode 53 is applied with an alternating high voltage from a high frequency power source 54.
[0008]
NOx contained in the exhaust gas G is processed by plasma generated between the dielectric 55 and the electrode 52. The treated exhaust gas G is exhausted from an outlet 51b provided on the other side of the plasma reactor 51. In addition, the technique which makes it easy to discharge by providing a protrusion in an electrode is disclosed (for example, refer patent document 4).
[0009]
[Patent Document 1]
JP 2001-210448 A [Patent Document 2]
JP 2002-052309 A [Patent Document 3]
JP 2001-113118 A [Patent Document 4]
Japanese Patent Laid-Open No. 10-015336
[Problems to be solved by the invention]
While the above-described conventional techniques have many advantages, there are problems with each method. For example, the power consumption required for denitration is too large (several Wh / Nm ³ or more).
[0011]
In particular, in the pulse discharge method, the energy loss at the time of pulse generation is large. In addition, since the atmospheric pressure glow discharge method has a small electrode gap of 2 to 3 mm, the amount of exhaust gas that can be processed is limited.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problems of the prior art, the present invention includes an insulating reaction vessel having an exhaust gas inlet at one end and an exhaust gas outlet at the other end, and is disposed in the reaction vessel. A flat plate electrode having a surface formed along a flow direction of exhaust gas, and at least one comb-shaped electrode in which needle electrodes are arranged in a line, the needle electrode being in the reaction container and exhausted A comb electrode disposed in at least one plane substantially perpendicular to the gas flow direction and having a tip thereof provided opposite to the plane of the plate electrode; and between the plate electrode and the comb electrode And a direct current power source for supplying current.
[0013]
Also, an insulating reaction vessel having an exhaust gas inlet at one end and an exhaust gas outlet at the other end, and a metal mesh disposed in the reaction vessel and having a surface substantially perpendicular to the direction in which the exhaust gas flows An electrode and a needle electrode disposed in the reaction vessel, located on the downstream side of the metal mesh electrode, and arranged in at least one row on a surface substantially parallel to the surface of the metal mesh electrode, the tip of the needle electrode And a comb-shaped electrode provided so as to face the surface of the metal mesh electrode, and a DC power source for supplying a current between the metal mesh electrode and the comb-shaped electrode.
[0014]
According to the present invention, when a positive high-voltage DC voltage is applied to the comb electrode, a sheet-like streamer discharge is generated between the flat plate electrode and the comb electrode. Exhaust gas is introduced from the inlet and flows across the streamer discharge section. Therefore, collision of electrons in the discharge with exhaust gas generates molecular dissociation, O ₃ and O necessary for oxidation reaction, and the like. NOx reacts and is removed efficiently. In this way, NOx in the exhaust gas is efficiently removed with a simple device.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an exhaust gas treatment apparatus according to the present invention will be described below with reference to FIGS.
[0016]
FIG. 1 shows a first embodiment of the present invention. The exhaust gas treatment device is provided with a blower 11 for sucking exhaust gas and a discharge treatment device 12 into which exhaust gas G is introduced from the blower 11. The discharge treatment device 12 is provided with a reaction vessel 27 made of an insulator that has a hollow shape and allows the exhaust gas G to pass therethrough. An exhaust gas inlet 18 is provided at one end (blower side) of the reaction vessel 27. An exhaust gas outlet 19 is provided at the other end facing the exhaust gas inlet 18. A flat plate electrode 13 is provided in a suspended state in the upper part of the reaction vessel 27, and the flat plate electrode 13 is provided with a surface 13 a formed along the direction in which the exhaust gas G flows. . A fixed terminal (not shown) is provided outside the central portion of the plate electrode 13, and the fixed terminal is connected to ground.
[0017]
A comb-shaped electrode 14 is provided at a lower portion of the reaction vessel 27 in a plane orthogonal to the direction in which the exhaust gas G flows. As shown in FIGS. 2 (a) and 2 (b), the comb-shaped electrode 14 includes needle electrodes 20 arranged in a line at equal intervals. The tip of the needle of the comb electrode 14 is arranged upward so as to face the surface 13 a of the flat plate electrode 13. The lower part of the comb-shaped electrode 14 is solidified by an insulating spacer 15, and the tip of the comb-shaped electrode 14 is disposed so as to protrude from the upper end of the insulating spacer 15. The insulating spacer 15 functions so that the exhaust gas G passes only through the discharge part when properly grounded. The comb-shaped electrode 14 is connected to the positive electrode of the high-voltage DC power source 17 through the protective resistor 16.
[0018]
In the present embodiment, the thickness and pitch length of the needle electrode 20 of the comb-shaped electrode 14 are 0.8 mm, and the length of the needle-shaped portion of the comb-shaped electrode 14 (length in the depth direction in FIG. 1). Is about 100 mm, and the distance between the tip of the needle-like portion of the comb-shaped electrode 14 and the plate electrode 13 is about 10 mm. The exhaust gas treatment apparatus is configured with a discharge area of 20 × 1 cm ² and four electrode stages. Here, the discharge area refers to the area of the portion where discharge occurs in the plate electrode when the discharge generated from the comb electrode reaches the plate electrode, and the number of electrode stages refers to the number of comb electrodes (number of sets). Say.
Further, the type of exhaust gas G to be treated is [air + NO (3 ppm) + H ₂ O (1%)], the flow rate of the exhaust gas G is 22.8 Nm ³ / h, and the flow rate of the exhaust gas G in the discharge section is 3. 17 m / s.
[0019]
In the above-described configuration, when a positive DC high voltage of about 10 kV is applied from the high-voltage DC power supply 17, streamer discharge is generated between the individual needle-like tips and the plate electrode 13 in the comb-shaped electrode 14. It becomes like this. When this streamer discharge reaches the flat plate electrode 13 from the needle-like tip of the comb electrode 14 and emits electrons, the electric field becomes weak, resulting in a pulsed discharge of several kHz.
[0020]
The exhaust gas G supplied by the blower 11 flows so as to cross the sheet-like streamer discharge section. When the electrons being discharged collide with the exhaust gas G, molecular dissociation, O ₃ , O, and the like necessary for the oxidation reaction occur, and NOx in the exhaust gas G is efficiently oxidized and decomposed.
[0021]
When the relationship between the power consumption and the denitration rate in the present embodiment is compared with that of the prior art, it has been found that the denitration performance is high despite the low power consumption compared to the prior art.
[0022]
FIG. 3 shows a second embodiment of the present invention. The exhaust gas G is sucked by the blower 11 and introduced into the discharge treatment device 21. The discharge treatment device 21 is provided with a reaction vessel 27 made of an insulator that has a hollow shape and allows the exhaust gas G to pass therethrough, and an exhaust gas inlet 24 is provided at one end (blower side) of the reaction vessel 27. An exhaust gas outlet 25 is provided at the other end facing the exhaust gas inlet 24. A metal mesh electrode 22 is provided inside the reaction vessel 27, and a surface 22a that is substantially orthogonal to the direction in which the exhaust gas G flows is formed on the metal mesh electrode. Furthermore, a comb-shaped electrode 23 provided on a surface substantially parallel to the surface 22 a is disposed inside the reaction vessel 27 on the downstream side of the metal mesh electrode 22. The comb-shaped electrode 23 is configured by arranging the needle-like needle electrodes 20 arranged at equal intervals with the tip thereof in the upstream direction of the exhaust gas G (the direction facing the surface 22a). The metal mesh electrode 22 is connected to the ground via a fixed terminal (not shown).
[0023]
The exhaust gas G flowing in from the exhaust gas inlet 24 passes through the mesh of the metal mesh electrode 22 and is guided to the space between the surface 22a of the metal mesh electrode 22 and the comb-shaped electrode 23. It will flow downward and pass through the discharge part. The exhaust gas G is guided to the exhaust gas outlet 25 by the hood 26 that covers the rear portion of the reaction vessel 27 and is discharged.
[0024]
The comb-shaped electrode 23 is configured by arranging the needle electrodes 20 at equal intervals in the direction perpendicular to the paper surface of FIG. The comb-shaped electrode 23 is connected to the positive electrode of the high-voltage DC power source 17 through the protective resistor 16. In the present embodiment, the length of the needle-like portion of the comb-shaped electrode 23 (the length in the depth direction in FIG. 3) is about 1000 mm, and the distance between the tip of the comb-shaped electrode 23 and the metal mesh electrode 22 is about 10 mm. It is said.
[0025]
In the above configuration, when a positive DC high voltage of about 10 kV is applied from the high-voltage DC power supply 17, streamer discharge is generated between the individual needle-like tips and the metal mesh electrode 22 in the comb-shaped electrode 23. It becomes like this. When this streamer discharge reaches the metal mesh electrode 22 from the needle-like tip and emits electrons, the electric field becomes weak, resulting in a pulsed discharge of several kHz.
[0026]
The exhaust gas G supplied by the blower 11 is introduced into the reaction vessel 27, passes through the metal mesh electrode 22, and flows so as to cross the sheet-shaped streamer discharge portion generated by the comb-shaped electrode 23. It has become. When the electrons in discharge and the exhaust gas G collide, molecular dissociation, O ₃ , O, and the like necessary for the oxidation reaction occur, and NOx in the exhaust gas G reacts efficiently and is oxidatively decomposed. .
[0027]
As in the first embodiment, when the relationship between the power consumption and the denitration rate in this embodiment is compared with that of the prior art, high denitration performance is exhibited despite the low power consumption compared to the conventional one. I found out.
[0028]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention.
For example, in FIG. 1, the comb-shaped electrodes 14 are arranged in one row with respect to the flow direction of the exhaust gas G. However, when the amount of exhaust gas to be processed increases, it is arranged in a plurality of rows (multiple rows). By doing so, the effect of improving the processing capability can be obtained. Similarly, in the second embodiment, the comb-shaped electrodes 23 are arranged in one row. However, when the amount of exhaust gas G to be processed increases, the same effect can be obtained by arranging in a plurality of rows. Can be obtained.
[0029]
【The invention's effect】
As described above, the exhaust gas treatment apparatus according to the present invention includes an insulating reaction vessel having an exhaust gas inlet at one end and an exhaust gas outlet at the other end, and is disposed in the reaction vessel. A flat plate electrode having a surface formed along the flow direction of the gas and at least one comb-shaped electrode in which the needle electrode is arranged in a line, the needle electrode being in the reaction vessel and containing exhaust gas. A comb-shaped electrode disposed in at least one plane substantially perpendicular to the flowing direction and having a tip thereof provided opposite to the plane of the plate electrode; and a current between the plate electrode and the comb-shaped electrode. Since the DC power supply is provided, NOx can be efficiently removed with a simple device.
[0030]
Also, an insulating reaction vessel having an exhaust gas inlet at one end and an exhaust gas outlet at the other end, and a metal mesh disposed in the reaction vessel and having a surface substantially perpendicular to the direction in which the exhaust gas flows An electrode and a needle electrode disposed in the reaction vessel, located on the downstream side of the metal mesh electrode, and arranged in at least one row on a surface substantially parallel to the surface of the metal mesh electrode, the tip of the needle electrode Since the portion includes a comb-shaped electrode provided facing the surface of the metal mesh electrode, and a DC power source for supplying a current between the metal mesh electrode and the comb-shaped electrode, similarly, The apparatus can efficiently remove NOx.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an exhaust gas processing apparatus according to a first embodiment of the present invention.
FIG. 2A is a front view of a comb-shaped electrode according to an embodiment of the present invention, and FIG. 2B is an enlarged view of a main part showing an A portion of FIG.
FIG. 3 is a structural cross-sectional view schematically showing an exhaust gas processing apparatus according to a second embodiment of the present invention.
FIG. 4 is a cross-sectional view schematically showing an exhaust gas treatment apparatus according to a conventional corona discharge method.
FIG. 5 is a cross-sectional view schematically showing an exhaust gas treatment apparatus according to a conventional pulse discharge method.
FIG. 6 is a cross-sectional view schematically showing an exhaust gas processing apparatus according to a conventional glow discharge method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Blower 12 Discharge treatment apparatus 13 Flat plate electrode 13a Surface 14 Comb electrode 15 Insulating spacer 16 Protection resistance 17 High voltage DC power supply 18 Exhaust gas inlet 19 Exhaust gas outlet 20 Needle electrode 21 Discharge treatment apparatus 22 Metal mesh electrode 22a Surface 23 Comb electrode 24 Exhaust gas inlet 25 Exhaust gas outlet 26 Hood 27 Reaction vessel 31 Exhaust gas generator 32 Flow meter 33 Wet electrostatic precipitator 33a Exhaust gas inlet 33b Exhaust gas outlet 34 Wire-shaped discharge electrode 35 DC high voltage generator 36 Protection resistance 37 Outer cylinder electrode 38 Circulating fluid 39 Pump 40 Circulating pipe 41 Wire-shaped discharge electrode 42 Outer cylinder electrode 42a Exhaust gas inlet 42b Exhaust gas outlet 43 Short pulse generating power supply 51 Plasma reactor 51a Exhaust gas inlet 51b Exhaust gas outlets 52, 53 Parallel Flat electrode 54 High frequency power supply 55 Dielectric or half Body G exhaust gas

Claims (2)

An insulator reaction vessel having an exhaust gas inlet at one end and an exhaust gas outlet at the other end;
A plate electrode disposed in the reaction vessel and having a surface formed along the direction in which the exhaust gas flows;
At least one comb electrode in which needle electrodes are arranged in a line, the needle electrode being arranged in at least one plane in the reaction vessel and substantially perpendicular to the direction in which the exhaust gas flows; A comb-shaped electrode whose tip is provided to face the surface of the plate electrode;
A DC power source for supplying a current between the flat plate electrode and the comb electrode;
An exhaust gas treatment apparatus comprising: An insulator reaction vessel having an exhaust gas inlet at one end and an exhaust gas outlet at the other end;
A metal mesh electrode disposed in the reaction vessel and having a surface substantially perpendicular to the direction in which the exhaust gas flows;
The needle electrode is disposed in the reaction vessel, is located on the downstream side of the metal mesh electrode, and is arranged in at least one row on a surface substantially parallel to the surface of the metal mesh electrode, and a tip portion of the needle electrode A comb-shaped electrode provided facing the surface of the metal mesh electrode;
A direct current power source for supplying a current between the metal mesh electrode and the comb electrode;
An exhaust gas treatment apparatus comprising:

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