JPH09141044A - Nitrogen oxides removing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove NOx at a high efficiency by colliding a flue gas with a duct sidewall plate to turn the direction and to transiently retain at a corona discharge generating part in a gas introducing pipe zone. SOLUTION: The flue gas duct is composed of a pair of cathode plates 1a and 1b made of metal and parallel flat plate electrodes and a pair of sidewall plates 1c composed of insulating materials and the flue gas G is passed through the flue gas duct. A discharge treating section D is formed in a zone opposed to the cathodes 1a and 1b and the metal made gas introducing pipe 2 having many nozzle electrodes 3, which are airtightly part through the sidewall plate 1d and have opened tips, is arranged near the center of the discharge treating section D. The flue gas G is collided with the sidewall plates 1c to turn the direction when introduced from the upstream side of an inlet into the duct and is transiently retained in the vicinity of the gas introducing pipe 2 with nozzle electrode, where corona discharge is generated. By adding a trace quantity of an NH3 -containing gas thereinto, the chemical reaction is accelerated and the flue gas is effectively denitrificated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an additive gas injection type discharge type NOx removing device.

[0002]

2. Description of the Related Art For example, nitrogen oxides (hereinafter referred to as NOx) contained in flue gas discharged into the atmosphere from a thermal power plant, a refuse incinerator, an automobile tunnel, etc., in the form of acid rain, etc. The impact on environmental damage poses a serious problem today. In order to deal with this problem, a NOx removal device such as an electron beam system or a discharge system has recently been proposed and attracted attention.

Particularly in the case of the discharge method, in order to remove NOx, the key point is to efficiently generate radical particles in the discharge treatment chamber. In order to efficiently generate radical particles, it is necessary to increase only the electron energy in the discharge space, which plays a major role in the generation of radical particles, without increasing the energy of the fumes and ions generated by discharge. I have to. For that purpose, electron energy up to about 10 eV is usually required. Therefore, corona discharge having a relatively high electron energy is adopted as the discharge form.

There are various types of electrode structures for causing this corona discharge, and one of them is a NOx removing device using a nozzle electrode. FIG. 10 shows a NOx removing device using such a nozzle electrode with the front plate removed.

In the NOx removing apparatus of FIG. 18, in order to process a large amount of flue gas, cathodes made of a metal having a ground potential, for example, stainless steel, which are arranged as a pair of vertically arranged parallel plate electrodes. Plates 1a, 1b and a pair of side wall plates 1c, 1d made of an insulator (side wall plate 1d on the front side)
Is shown in a removed state) to form a smoke exhaust duct, and the smoke gas G to be treated flows through the smoke exhaust duct. Parallel plate electrodes 1a, 1
The discharge processing chamber D is formed in the opposing region of b. A gas introduction pipe 2 made of metal, for example, stainless steel, which has a large number of nozzle electrodes 3 having airtightly penetrated through a side wall plate 1d (not shown), is arranged at substantially the center of the discharge processing chamber D. . The gas introducing pipe 2 with a nozzle electrode is provided in the discharge processing chamber D to generate a DC corona discharge, and is a cathode plate 1a having a ground potential.
A positive DC voltage is applied from the DC power supply 4 to the gas introduction pipe 2 with b as a reference potential. Further, the additive gas A is supplied to the gas introduction pipe 2 from an additive gas source (not shown), and the additive gas A is ejected from the tip opening of the nozzle electrode 3 into the discharge processing chamber D. As the additive gas A,
Air is the main component, and a small amount of ammonia gas NH ₃
The one mixed with is used.

In the NOx removal device of FIG. 18 having the above structure, a large amount of radical particles are produced by introducing the additive gas A into the corona discharge part C (see FIGS. 19 and 20) near the nozzle electrode 3 where the electron energy is high. To generate NO
The x removal action is better promoted.

Next, a typical reaction process of NOx removal by this NOx removal device will be described. The nitrogen oxides contained in the flue gas G flowing through the flue gas duct due to the radicals generated by the discharge are NO ₂ and N ₂ O.
NH ₄ NO ₃ (aerosol) is generated by the action of NH ₃ contained in the additive gas after being oxidized to ₅ or the like.

NH ₃ in the additive gas is decomposed into radicals such as NH and NH _{2 in the} process of passing through the corona discharge region, and NO + NH ₂ → H ₂ O + N ₂ NO + NH → N ₂ + OH NO + OH + N ₂ → HNO ₂ + N ₂ → (aerosol The chemical reaction directly converts NO into harmless gas and aerosol.

For details of the principle of NOx removal outlined above, refer to, for example, IEEE TRANSACTIONS ON INDUSTORY A
PPLICATIONS, Vol.30, No.4, pp.856-861, "NOx Remo
valby a Pipe with Nozzle-Plate Electrode Corona Di
scharge System "(issued in July 1994).

[0010]

NOx removal apparatus NOx using the gas introduction pipe with nozzle electrode as described above.
At present, the removal performance does not always reach a satisfactory level.

Therefore, an object of the present invention is to provide a more efficient NOx removal device.

[0012]

In order to achieve the above-mentioned object, the NOx removing device according to the invention of claim 1 has a pair of two opposing two of the four surfaces, through which the gas to be treated flows and which is parallel to the longitudinal axis. A discharge treatment chamber whose surface is configured as a cathode plate, a gas introduction pipe arranged in the discharge treatment chamber, a plurality of nozzle electrodes mounted in communication with the gas introduction pipe, and discharge treatment from these nozzle electrodes A little NH in the room
An additive gas containing ₃ is provided with an additive gas supply means for introducing it through a gas introduction pipe, and a pulse voltage generating means for applying a pulse voltage to the nozzle electrode in order to generate a corona discharge between the cathode plate. It is a thing.

The invention of claim 2 is the NO of claim 1.
The x removing device is provided with a DC voltage superposing means for superposing a DC voltage on the pulse voltage generated by the pulse voltage generating means.

The NOx removing device according to the invention of claim 3 is
A discharge processing chamber in which a gas to be processed flows and a pair of two surfaces of the four surfaces parallel to the longitudinal axis which face each other are used as a cathode plate, and the discharge processing chamber is spaced from each other in the direction of the flow of the processing gas in the discharge processing chamber. A plurality of gas introduction pipes arranged at a plurality of positions, a plurality of nozzle electrodes respectively connected to the gas introduction pipes, and an additive gas containing a trace amount of NH ₃ from these nozzle electrodes into the discharge treatment chamber. Is provided via a gas introducing pipe, and a DC voltage generating means for applying a DC voltage to each nozzle electrode in order to generate corona discharge between the cathode plate and.

The invention of claim 4 is the NO of claim 3
In the x removal device, the interval between the plurality of gas introduction pipes is variable.

The NOx removing device according to the invention of claim 5 is
A discharge processing chamber through which the gas to be processed flows, a mesh electrode having a ground potential arranged at at least one of an inlet and an outlet of the gas to be processed in the discharge processing chamber, and a gas introduction pipe arranged in the discharge processing chamber, A plurality of nozzle electrodes attached in communication with the gas introducing pipe, and an additive gas supply means for introducing an additive gas containing a slight amount of NH ₃ into the discharge processing chamber from the nozzle electrodes through the gas introducing pipe. , A DC voltage generating means for applying a DC voltage to the nozzle electrode in order to generate a corona discharge between the mesh electrode and the mesh electrode.

The NOx removing device according to the invention of claim 6 is
A gas to be processed flows, and a discharge processing chamber in which a pair of two surfaces of the four surfaces parallel to the longitudinal axis that face each other are used as a cathode plate, a gas introduction pipe arranged in the discharge processing chamber, and this gas A plurality of nozzle electrodes attached in communication with the introduction pipe, an additive gas supply means for introducing an additive gas containing a slight amount of NH ₃ from these nozzle electrodes into the discharge processing chamber through the gas introduction pipe, and a nozzle A dielectric ring attached to each tip of the electrode and a DC voltage generating means for applying a DC voltage to the nozzle electrode in order to generate a corona discharge between the dielectric plate and the cathode plate.

According to a seventh aspect of the present invention, in the NOx removing device according to the fifth or sixth aspect, a plurality of gas introduction pipes provided with nozzle electrodes are provided at intervals in the flow direction of the gas to be treated. Is.

The invention of claim 8 is the NO of claim 7.
In the x removal device, the interval between the plurality of gas introduction pipes is variable.

According to a ninth aspect of the present invention, the gas to be processed flows through,
Of the four surfaces parallel to the longitudinal axis, a pair of two surfaces facing each other are used as a cathode plate, a discharge treatment chamber, a gas introduction pipe arranged in the discharge treatment chamber, and a gas communication pipe connected to the gas introduction pipe. Corona discharge between the plurality of nozzle electrodes and the additive gas supply means for introducing the additive gas containing a small amount of NH ₃ from these nozzle electrodes into the discharge treatment chamber through the gas introduction pipe, and the cathode plate. In the NOx removal device provided with a DC voltage generating means for applying a DC voltage to the nozzle electrode in order to generate
It is characterized in that it has a curved path shape so that the direction of the flow of the gas to be processed passing through the gas introduction pipe portion is different between the upstream side and the downstream side of the nozzle electrode.

According to a tenth aspect of the present invention, in the NOx removing device according to any one of the third to ninth aspects, in the NOx removing device according to any of the third to ninth aspects, instead of the DC voltage generating means, The gas introducing pipe is provided with a pulse voltage generating means for applying a pulse voltage.

The invention according to claim 11 is the NOx removing device according to any one of claims 3 to 9, further comprising pulse voltage superposing means for superposing the pulse voltage on the DC voltage generated by the DC voltage generating means. Is.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. N according to claim 1 with reference to FIG.
The Ox removing device will be described. Cathode plates 1a, 1b made of a pair of parallel plate electrodes made of metal, for example, stainless steel, and a pair of side wall plates 1c, 1 made of an insulator.
A smoke exhaust duct is formed by d (the side wall plate 1d on the front side is shown in a removed state), and the smoke exhaust gas G that is the gas to be processed flows through the smoke exhaust duct. ing. A discharge processing chamber D is formed in a region where the cathode plates 1a and 1b face each other. A gas introduction pipe 2 made of metal, for example, stainless steel, which has a large number of nozzle electrodes 3 having airtightly penetrated through a side wall plate 1d (not shown), is arranged at substantially the center of the discharge processing chamber D. . Nozzle electrode 3
Is provided for generating a corona discharge in the discharge processing chamber D, communicates with the gas introduction pipe 2, and is electrically connected. A positive pulse voltage is applied from the pulse voltage generating circuit 5 to the nozzle electrode 3 via the gas introduction pipe 2 with the cathode plates 1a and 1b set to the ground potential as reference potentials. Further, the additive gas is supplied to the gas introduction pipe 2 from an additive gas supply device 11 (not shown), and the additive gas is introduced into the discharge processing chamber D through the tip opening of the nozzle electrode 3. As the additive gas, air is the main component,
A mixture of a small amount of ammonia gas NH ₃ is used.

The above components are NOx shown in FIG.
In comparison with the removing device, the components other than the pulse voltage generating circuit 5 are the same. 1 is characterized in that the pulse voltage generating circuit 5
The pulse voltage generated here is not the conventional continuous DC voltage but the nozzle electrode 3 through the gas introduction pipe 2.
Is applied to An example of the configuration of the pulse voltage generation circuit 5 is shown in FIG.
Shown in

The pulse voltage generating circuit 5 in FIG. 2 comprises a DC power supply 51, a charging resistor 52, a charging capacitor 53 and a rotary switch 54. A pulse voltage is generated by repeating charging and discharging of the capacitor 53 by the periodic switching operation of the rotary switch 54, and the pulse voltage is applied to the gas introduction pipe 2. The rotary switch 54 is driven by, for example, a motor (not shown).

The operation of the apparatus shown in FIGS. 1 and 2 is performed as follows. If the resistance value of the charging resistor 52 is R and the capacitance of the charging capacitor 53 is C, the charging capacitor 53 is charged by the DC power supply 51 with a time constant T = RC in the charging mode period in which the rotary switch 54 is in the off position. In the discharge mode period corresponding to the ON position of the rotary switch 54, the output end of the pulse voltage generation circuit 5 is connected to the gas introduction pipe 2. Thus, by repeating the on / off operation of the rotary switch 54 periodically, the positive pulse voltage Vp is applied from the pulse voltage generating circuit 5 to the nozzle electrode 3 as shown in FIG.
The discharge current Id flows.

By pulsing the voltage applied to the nozzle electrode 3 as described above, the voltage is continuously applied to the nozzle electrode 3 as compared with the conventional continuous DC voltage applying system. Therefore, arc discharge having a small electron energy, which is inconvenient for removing NOx, is less likely to occur, and only corona discharge having a large electron energy, which is convenient for removing NOx, can be formed. Therefore, compared with the conventional DC voltage application method, the discharge power is NO.
x can be efficiently consumed for removal.

FIG. 4 shows a NOx removing device according to the second aspect of the invention. In this embodiment, a superposed voltage generation circuit 5A for outputting a voltage (FIG. 6: voltage Vq) in the form of superposing a DC voltage Vo on the output pulse voltage Vd of the pulse voltage generation circuit 5 shown in FIG. 1 is provided. The point is characteristic. That is, as shown in FIG.
A serial capacitor 56 is connected to the output end of the rotary switch 54 in the pulse voltage generating circuit 5 shown in FIG. 1, a shunt reactor 55 is connected to the rotary switch side of the series capacitor 56, and a series reactor 57 is provided on the gas introduction pipe side. The DC power supply 58 has a circuit configuration in which each is connected to a shunt.

The operation of the device of FIG. 4 operates as follows. Charging and discharging of the charging capacitor 53 is performed as already described with reference to FIG. However, in the circuit of FIG. 4, during the discharge mode period, as shown in FIG. 6, the DC voltage obtained from the DC power source 57 via the reactor 58 with respect to the pulse voltage Vd obtained from the charging capacitor 53 via the capacitor 56. A voltage Vq in a form in which the voltage Vo is superimposed is applied. When the pulse voltage Vd is output from the capacitor 53 via the rotary switch 54 and the capacitor 56, the discharge is performed and the discharge current Id is generated.
Flows. Therefore, as shown in FIG. 7, it is considered that the most efficient DC voltage Vo is the voltage value V _{1 at the} instant when the discharge starts. By doing so, the typical current waveform becomes like the current Id shown in FIG. 7.

In this embodiment, in addition to the action and effect of the voltage pulsing, the DC voltage Vo is superposed on the pulse voltage Vd, so that the pulse operation can be realized at a low voltage, and the switching is easy and easy. It has the feature of extending the life of the switching unit.

FIG. 8 shows a NOx removing device according to the third aspect of the invention. In this embodiment, a plurality of gas introduction pipes with nozzle electrodes, for example, two (gas introduction pipe 2a having nozzle electrode 3a and gas introduction pipe 3b having nozzle electrode 3b) are provided. is there. The other components are the same as those in FIG. In this embodiment, a DC voltage is applied from the common DC power supply 4 to the two gas introduction pipes 2a and 2b.

When only one gas introduction pipe 2 is provided as in the conventional device (FIG. 18), it is the value of the NOx removal rate R with respect to the discharge input power P, but as shown in FIG. 9, it is smaller. N for discharge input power P = P ₁
Assuming that the Ox removal rate is R = R ₁ , the discharge input power P ₁
With respect to the minute change amount ΔP ₁ of the discharge input power at
Amount of change in NOx removal rate at x removal rate R = R ₁ (ΔR
₁ ) / (ΔP ₁ ) is larger discharge input power P = P ₂
Assuming that the NOx removal rate for R is R = R ₂ , the change amount (ΔR ₂ ) / (ΔP ₂ of the NOx removal rate at the NOx removal rate R = R _{2 with} respect to the minute change amount ΔP ₂ of the discharge input power P ₂ Compared with ₂ ), the former becomes a characteristic curve with a larger and more convex shape (the curve is more prominent) than the latter.

Therefore, by providing a plurality of gas introduction pipes 2a and 2b, for example, two gas introduction pipes share the discharge input power under the condition that the total discharge input power is the same. By doing so, it is possible to achieve a larger NOx removal rate while halving the discharge input power per unit, and to realize a highly efficient NOx removal apparatus as a whole.

The NOx removing apparatus having the plurality of gas introducing pipes 2a and 2b with nozzle electrodes as described above is also provided with the pulse voltage generating circuit 5 or 5A described with reference to FIGS. 1 to 3 or 4 to 7. As described above, the pulse voltage alone may be applied to the gas introduction pipes 2a and 2b, or a method in which a direct current voltage is superposed thereon may be adopted. By doing so, a highly efficient NOx removal device can be configured for the reason described in the embodiment of FIG.

FIG. 10 shows a NOx removing device according to a fourth aspect. Here, a NOx removal device having two gas introduction pipes 2a and 2b having nozzle electrodes 3a and 3b is shown. The feature of this embodiment is that the gas introduction pipes 2a, 2b are supported by the pipe electrode support bases 8a, 8b having a structure in which the mutual distances can be variably attached, so that the gas introduction pipes 2a, 2b as shown in FIG. The distance K between them is variable.

The distance K between the gas introduction pipes 2a and 2b.
By variably configuring, it becomes possible to control the length of the non-irradiation region N where the exhaust gas is not exposed to the corona discharge. From another perspective, this means that the flue gas G
It has the same meaning as that it becomes possible to control the non-irradiation time during which the flue gas G is not exposed to the corona discharge according to the flow velocity of. Generally, the existence of non-irradiation time is
As shown in the characteristic curves Ra, Rb, Rc of FIG. 12, NOx
It greatly affects the removal rate. Nitrogen oxides are oxidized by the action of radical particles such as O and OH, and NO → N
It becomes O ₂ and is further decomposed into a harmless gas by radical particle reaction and heterogeneous reaction. However,
NO ₂ → N due to the action of radical particles such as O and OH
There is also a reverse reaction process called O. In the presence of the non-irradiation time, the heterogeneous reaction is promoted, NO ₂ is decomposed into a harmless gas, and the amount of NO ₂ is reduced, so that this reverse reaction process can be suppressed.

By varying the distance between the gas introduction pipes in this manner, the non-irradiation time can be optimized according to the flow rate of the exhaust gas, and a highly efficient NOx removal device can be realized.

Further, in the NOx removing device in which the intervals between the plurality of gas introduction pipes with nozzle electrodes are variable as described above, the voltage application method to the gas introduction pipes is changed from direct voltage application to pulse voltage application as described above. It is also effective to apply DC voltage + pulse voltage. As a result, as compared with the conventional DC voltage application, arc discharge having a small electron energy, which is inconvenient for NOx removal, is less likely to occur, and only corona discharge having a large electron energy, which is convenient for NOx removal, is formed. Alternatively, the action and effect of the invention described in claim 2 can be obtained.

FIG. 13 shows a NOx removing device according to a fifth aspect. In this embodiment, applying a DC voltage to the gas introduction pipe 2 from the DC voltage generating circuit 4 to generate corona discharge in the discharge treatment chamber D is the same as in each of the embodiments described above. NOx shown here
In the removing device, the side wall of the duct does not also serve as the electrode having the ground potential, and the duct merely constitutes the flow guide path for the flue gas G, and the discharge treatment chamber D
The mesh electrodes 9a and 9b are arranged at the inlet and the outlet of, respectively. In that case, an insulating upper plate 1e (not shown) and a bottom plate 1f are used instead of the metal cathode plates 1a and 1b. Exhaust gas G here
Is introduced into the discharge processing chamber D through the mesh electrode 9. The gas introducing pipe 2 penetrates the side wall plate 1d via the penetrating ring 8.

According to the embodiment shown in FIG. 13, the corona discharge portion C is formed so as to spread conically from the tip of the nozzle electrode 3 toward the mesh electrode 9 as shown in FIG. It is possible to eliminate the portion where the molecules of the flue gas G are not exposed to the corona discharge. Therefore, it is possible to realize a highly efficient NOx removing device as compared with the case of using the conventional cathode plates 1a and 1b.

Even in the NOx removing device using the mesh electrodes 9a and 9b for the gas introducing pipe 2 with nozzle electrodes, the configuration is such that a plurality of gas introducing pipes with nozzle electrodes and the intervals between the gas introducing pipes with nozzle electrodes are variable. By adopting the configuration described above, a highly efficient NOx removal device can be realized for the reasons described above.

Further, also in the embodiment shown in FIG.
By applying a voltage to the gas introduction pipe 2 from a DC voltage application to a pulse voltage application or a DC voltage + pulse voltage application as described above, the same operation and effect as described above can be achieved.

FIG. 15 shows a NOx removing device according to the sixth aspect. In this embodiment, the dielectric ring 10 is arranged at the tip of the nozzle electrode 3. Dielectric ring 1 is attached to the tip of nozzle electrode 3.
By setting 0, the discharge start voltage is changed from the voltage V ₁₁ in the characteristic curve S1 to the characteristic curve S as shown in FIG.
Voltage V _{12 at} 2. This is because by arranging the dielectric ring 10 at the tip of the metal nozzle electrode 3, singular points having different permittivities are formed at the tip of the nozzle electrode 3 and the electric field strength at the tip of the nozzle electrode 3 is enhanced. This is due to the fact. Thus, the applied voltage can be lowered in order to obtain the same discharge current, that is, to obtain almost the same radical particles, so that a highly efficient NOx removal device can be realized.

Also in this embodiment, it is possible to provide a plurality of gas introduction pipes with nozzle electrodes and to make the intervals between the plurality of gas introduction pipes variable.
Further, as described above, the method of applying a voltage to the gas introduction pipe may be a method of applying a DC voltage to a pulse voltage or a method of applying a superimposed voltage of a form in which a pulse voltage is superimposed on a DC voltage.

FIG. 17 shows a NOx removing device according to claim 9. The embodiment shown in the drawings is a NOx removal device for removing a NOx by applying a DC voltage to the gas introduction pipe 2, and the cathode plates 1a and 1b and the side wall plates 1c and 1d.
The exhaust gas duct made of is configured in a curved path shape such that the flow direction of the exhaust gas G passing through the region of the gas introduction pipe 2 is different between the upstream side and the downstream side of the gas introduction pipe 2. To do.

The flue gas G enters the flue gas duct from the upstream side of the inlet, collides with the abutting portion of the side wall plate 1c and changes the flow direction, and as a result, the flue gas G in the region of the gas introduction pipe 2 is discharged. Change the flow direction. Therefore, the flue gas G is a gas introduction pipe 2 with a nozzle electrode that is generating corona discharge.
After temporarily staying in the vicinity of, the gas will flow toward the outlet on the downstream side of the gas introduction pipe 2. By doing so, the flue gas G is effectively exposed to corona discharge, and the chemical reaction can be promoted to realize a highly efficient NOx removal device.

Also in this embodiment, the method of applying the voltage to the gas introducing pipe 2 can be changed from the application of the DC voltage to the application of the pulse voltage or the application of the DC voltage + the pulse voltage as described above, whereby the voltage application is already performed. It is possible to expect the same actions and effects as described above.

In each of the embodiments shown in FIGS. 1, 4, 8, 10, 15, and 17, the smoke exhaust duct is composed of a metal cathode plate and a side wall plate made of an insulator. Although described, in some cases, the plate body may be made of metal. The DC power supply may be a battery, a rectifier that rectifies an AC voltage to obtain DC, or a DC power supply device having a floating charge type battery that uses both of them together. Further, in order to adjust the voltage, an AC circuit may be interposed and a transformer may be used to roughly adjust to an appropriate voltage, and a voltage adjusting means may be attached to perform fine adjustment.

[0049]

As described in detail above, according to the present invention, the NOx removing device with higher efficiency can be provided by adopting the structure described in each claim.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a NOx removing device according to claim 1 of the present invention with a side wall plate on the front side removed.

FIG. 2 is an electric circuit diagram showing details of a pulse voltage generation circuit in the apparatus of FIG.

FIG. 3 is a diagram showing waveforms of voltage / current of a nozzle electrode in the apparatus of FIG.

FIG. 4 is a perspective view showing the NOx removing device according to claim 2 of the present invention with the side wall plate on the front side removed.

5 is an electric circuit diagram showing details of a voltage generating circuit in the apparatus of FIG.

6 is a diagram showing waveforms of voltage / current of a nozzle electrode in the apparatus of FIG.

7 is a voltage vs. current characteristic diagram of the nozzle electrode in the apparatus of FIG.

FIG. 8 is a perspective view showing the NOx removing device according to claim 3 of the present invention with the side wall plate on the front side removed.

9 is a diagram showing the characteristics of input power versus NOx removal rate in the device of FIG.

FIG. 10 is a perspective view showing a NOx removing device according to claim 4 of the present invention.

FIG. 11 is a diagram for explaining the interval between the discharge electrodes in the device of FIG.

FIG. 12 is a diagram showing a difference in characteristics of input power vs. NOx removal rate depending on the time during which flue gas is exposed to corona discharge in the device of FIG.

FIG. 13 shows a NOx removing device according to claim 5 of the present invention,
The perspective view shown in the state where the upper plate electrode was removed.

14 is a diagram for explaining a corona discharge generation mode of the apparatus of FIG.

FIG. 15 is a perspective view showing an NOx removing device according to claim 6 of the present invention.

16 is a diagram for explaining the relationship between the discharge start voltage and the effect of mounting the dielectric ring in the device of FIG.

FIG. 17 is a perspective view showing a NOx removing device according to claim 9 of the present invention.

FIG. 18 is a perspective view showing a conventional NOx removal device with a side wall plate on the front side removed.

FIG. 19 is a conceptual diagram of the state of occurrence of corona discharge in the device of FIG.

FIG. 20 is a conceptual diagram of the corona discharge occurrence state in the apparatus of FIG. 18 as viewed from the upstream side of the flue gas.

[Explanation of symbols]

 1a, 1b Cathode plate 1c, 1d Side wall plate 1e Upper plate 1f Bottom plate 2, 2a, 2b Gas introduction pipe 3, 3a, 3b Nozzle electrode 4 DC voltage generation circuit 5 Pulse voltage generation circuit 5A Superposed voltage generation circuit 51 DC power supply 52 Charging Resistance 53 Charging capacitor 54 Rotary switch 55, 57 Reactor 56 Series capacitor 58 DC power supply 8 Penetrating ring 8a, 8b Pipe electrode support 9a, 9b Mesh electrode 10 Dielectric ring 11 Additive gas supply device C Corona discharge part D Discharge treatment chamber G Flue gas

Claims (11)

[Claims] 1. A discharge processing chamber in which a gas to be processed flows, and a pair of two surfaces facing each other out of four surfaces parallel to the longitudinal axis are used as a cathode plate, and a gas introduction provided in the discharge processing chamber. A pipe, a plurality of nozzle electrodes attached in communication with the gas introduction pipe, and an additive gas containing a trace amount of NH ₃ from the nozzle electrodes into the discharge treatment chamber,
An NOx removing device comprising: an additional gas supply means introduced through the gas introduction pipe; and a pulse voltage generation means for applying a pulse voltage to the nozzle electrode in order to generate a corona discharge between the cathode plate and the cathode plate. 2. The NOx removing device according to claim 1, further comprising a DC voltage superposing means for superposing a DC voltage on the pulse voltage generated by the pulse voltage generating means. 3. A discharge processing chamber in which a gas to be processed flows, and a pair of two surfaces, which are opposed to each other among four surfaces parallel to the longitudinal axis, are formed as a cathode plate, and the discharge processing chamber is provided with the gas to be processed. A plurality of gas introduction pipes arranged at intervals from each other in the direction of flow, a plurality of nozzle electrodes respectively connected to the gas introduction pipes, and a small amount of the nozzle electrodes from the nozzle electrodes inside the discharge treatment chamber. DC voltage for applying a DC voltage to each nozzle electrode in order to generate a corona discharge between the cathode plate and an additive gas supply means for introducing an additive gas containing NH ₃ through the gas introduction pipe. A NOx removal device having a generation means. 4. The NOx removal device according to claim 3, wherein the interval between the plurality of gas introduction pipes is variable. 5. A discharge processing chamber through which a gas to be processed flows, and a mesh electrode having a ground potential, which is disposed at at least one of an inlet and an outlet of the gas to be processed in the discharge processing chamber,
A gas introduction pipe disposed in the discharge treatment chamber, a plurality of nozzle electrodes connected to the gas introduction pipe, and an additive gas containing a small amount of NH ₃ from the nozzle electrodes into the discharge treatment chamber. An additional gas supply means for introducing the gas through the gas introduction pipe, and a DC voltage generating means for applying a DC voltage to the nozzle electrode in order to generate a corona discharge between the mesh electrode and the N electrode.
Ox removal device. 6. A discharge processing chamber in which a gas to be processed flows, and a pair of two surfaces facing each other out of the four surfaces parallel to the longitudinal axis are cathode plates, and a gas introduction provided in the discharge processing chamber. A pipe, a plurality of nozzle electrodes attached in communication with the gas introduction pipe, and an additive gas containing a trace amount of NH ₃ from the nozzle electrodes into the discharge treatment chamber,
Additive gas supply means introduced through the gas introduction pipe, a dielectric ring attached to each tip of the nozzle electrode, and a direct current to the nozzle electrode to generate a corona discharge between the cathode plate. A NOx removal device comprising a DC voltage generating means for applying a voltage. 7. The NOx removal device according to claim 5 or 6, wherein a plurality of the gas introduction pipes provided with the nozzle electrodes are provided at intervals in the flow direction of the gas to be treated. Removal device. 8. The NOx removal device according to claim 7, wherein the interval between the plurality of gas introduction pipes is variable. 9. A discharge processing chamber in which a gas to be processed flows, and a pair of two surfaces, which are opposed to each other among four surfaces parallel to the longitudinal axis, are formed as a cathode plate, and a gas introduction provided in the discharge processing chamber. A pipe, a plurality of nozzle electrodes attached in communication with the gas introduction pipe, and an additive gas containing a trace amount of NH ₃ from the nozzle electrodes into the discharge treatment chamber,
In an NOx removal device comprising: an additional gas supply means introduced through the gas introduction pipe; and a direct current voltage generation means for applying a direct current voltage to the nozzle electrode in order to generate a corona discharge between the cathode plate. The discharge processing chamber is configured in a curved path shape so that the flow direction of the gas to be processed passing through the gas introduction pipe portion is different between the upstream side and the downstream side of the nozzle electrode. NOx removal device. 10. N according to any one of claims 3 to 9.
In the Ox removing device, a NOx removing device comprising pulse voltage generating means for applying a pulse voltage to the gas introducing pipe, instead of the DC voltage generating means. 11. N according to any one of claims 3 to 9.
A NOx removal device in an Ox removal device, comprising pulse voltage superposition means for superposing a pulse voltage on the DC voltage generated by the DC voltage generation means.