JPH0747223A - Electric field apparatus for gas oxidation - Google Patents

Abstract

PURPOSE:To provide an electric field apparatus for gas oxidation which can generate a uniform plasma regardless of properties of a gas to be treated. CONSTITUTION:By arranging projections 1a and 3a and 1c and 3a of electrodes with the same shape in such a way that they are shifted and not neighbor with each other e.g. on the right side and the left side of a dielectric 2, creeping discharge is generated on the face of the opposite side to the face where the dielectric 2 is brought into contact with the projections 1a, 1c and 3a, namely, the surface of the dielectric with which the electrode is not brought into contact. At the same time, as electrodes 1a, 1d, 1b, 1c, 3a and 3b are arranged to the creeping discharge generating face and an electric voltage being the same polarity as that of the creeping discharge generating face is applied, a space between the creeping discharge generating face and the electrodes arranged so as to surround it, namely, the inside of a cylindrical gas flow path is turned to a glow discharge plasma condition.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an apparatus for oxidizing O ₂ to produce O ₃ for deodorization or improving combustion efficiency, or an exhaust gas treatment apparatus for oxidizing NO _x or SO _x for denitration / desulfurization. The present invention relates to an electric field device for gas oxidation applied to.

[0002]

2. Description of the Related Art FIGS. 7 and 8 are explanatory views of a conventional electric field device for gas oxidation. It will be described taking as an example a case of processing a NO _x in the exhaust gas, for example gas-fired boiler by the device. In FIG. 7, 101 is a reaction vessel of a conventional gas oxidation electric field apparatus, in which passages having a square cross section are arranged adjacent to each other in flight, and insulating ceramics such as alumina porcelain, silicon nitride porcelain, and zirconia porcelain. To form a honeycomb structure. Explaining one tubular passage of this honeycomb structure, it is constituted by four continuous inner walls 102, 103, 104 and 105, and when expanded, it becomes as shown in FIG. Further, the inner walls 102, 103, 104, 105 are border lines 106, 1
The structure is such that it is bent 90 ° by 07, 108, and 109. At one end 110 of the inner wall 102, terminals 111 and 112 connected to a power source 127, and subsequently corona discharge electrodes 113 and 114 made of a conductive film such as tungsten are connected to the surfaces of the inner walls 102, 103, 104 and 105 in parallel at equal intervals. Have been installed.

When the pulsed high voltage having a pulse width of about 1 ns to 1000 ns is applied between the corona discharge electrodes 113 and 114 while introducing the exhaust gas of the gas-fired boiler into the reaction vessel 101 having such a structure, the inner wall surface of the corona discharge electrodes 113 and 114 is applied. A pulse corona discharge is generated in the vicinity to turn the exhaust gas into plasma. Then, the following chemical reactions occur in the exhaust gas turned into plasma. 2O ₂ → O ₃ + 1 / 2O ₂ NO + O ₃ → NO ₂ + O _{2 In the} above chemical reaction formula, O ₂ molecules contained in the exhaust gas are converted into O ₃ by plasma, and O ₃ is NO which is a harmful component.
Is oxidized to NO ₂ . The NO ₂ generated here can be easily removed or detoxified by reduction by alkali cleaning or adsorption with an adsorbent. Therefore, since the corona discharge electrodes 113, 114 can be provided on the inner walls 102, 103, 104, 105 of the tubular passages, they do not require a large space even if they have a three-dimensional structure, and they are small and have a large capacity as an electric field apparatus for gas oxidation. It is being applied to an exhaust gas treatment device for improving the combustion efficiency of various devices involving deodorization and combustion, or removing NO _x and SO _x in exhaust gas discharged from devices involving various combustion.

[0004]

However, the conventional device has the following drawbacks and is very difficult to put into practical use. (1) Since there is only a space between the electrodes, for example, when there is a large amount of water in the gas or the inner wall of the tubular passage 10
If there are water droplets at 2, 103, 104 and 105, the insulation strength between the electrodes may be extremely reduced, arc discharge may occur, and the plasma may become non-uniform and the treatment may become impossible. Therefore, it is easily affected by the properties of the gas to be treated (water content, oil content, etc.). (2) Tubular passage inner walls 102, 103 of the honeycomb structure,
A conductive film of tungsten or the like is used as a discharge electrode for 104 and 105, but the cost of film formation and power supply is very high. (3) Honeycomb structure ceramics is used as the dielectric, but its structure makes maintenance difficult,
If a part of the honeycomb structure should be damaged, it must be replaced and the maintenance cost is very high.

In view of the above-mentioned problems, the present invention generates a uniform plasma which does not need to be completely replaced even if a part of the dielectric is damaged without depositing a line as an electrode as in the prior art. An object is to provide an electric field device for gas oxidation.

[0006]

Means for Solving the Problems The structure of the present invention which achieves the above-mentioned object is as follows: (1) A first step having a plurality of shelves protruding inward from the left and right side walls of a rectangular tubular outer frame toward the inside. Electrodes,
A first comb tooth-shaped electrode having a plurality of steps of shelving protrusions corresponding to the shelving protrusions of the first electrode on both left and right sides of a partition wall that divides the inside of the outer frame into a plurality of left and right sides, and the first and second left and right sides of a flat wall as described above. First
A second comb-tooth-shaped electrode having a plurality of stages of shelf-like protrusions that are alternately offset from the shelf-like protrusions of the electrode and the first comb-tooth-like electrode; and the first electrode and the second comb-tooth-like electrode Of the first comb-teeth-shaped electrode and the second comb-teeth-shaped electrode that are in contact with and are located between the respective shelves of A voltage having a different polarity is applied between the first electrode and the first comb-teeth-shaped electrode and the second comb-teeth-shaped electrode, and (2) inside the inner peripheral wall of the cylindrical outer frame. A first electrode having a plurality of radial projections toward the center, a cylindrical first dielectric body whose outer peripheral wall contacts the tip of the radial projections of the first electrode, and a first dielectric body inside the first dielectric body. It is cylindrical and has radial protrusions on both the outer and inner peripheral walls, and the arc distance between adjacent radial protrusions on the outer peripheral wall side is equal. In addition, the radial projections on the outer peripheral wall side and the radial projections on the outer side electrode are staggered so that the arc distances between the adjacent radial projections on the inner peripheral wall side are equal, and the radial projections on the outer peripheral wall are also taken. One step or two or more steps of which the tip contacts the inner peripheral wall of the cylindrical dielectric
The electrode, the cylindrical second dielectric body whose outer peripheral wall contacts the radial projection on the inner peripheral wall of the second electrode, and the distal end of the radial projection contacting the inner peripheral wall of the second dielectric body, and the base end of the radial projection. All together, the adjacent radial projections have the same circular arc distance, and the third projection has a third electrode in a positional relationship in which the radial projections and the radial projections on the inner peripheral wall of the second electrode are offset from each other. It is characterized in that different polarities are applied to adjacent electrodes sandwiched therebetween.

[0007]

[Function] Since the front surface and the back surface of the dielectric body are provided with misaligned shelf-like projections and radial projections, a creeping discharge is generated on the back surface side of the dielectric surface with which the projection is in contact, and the surface where the creeping discharge is generated is removed. Since a protrusion and a wall are provided so as to surround the same and a voltage having the same polarity as that of the creeping discharge generating surface is applied, the inside of the gas passage is in a glow discharge plasma state. That is, in order to induce glow discharge plasma by creeping discharge on the dielectric surface by generating voltages of different polarities on both sides of the dielectric,
The firing voltage is controlled by the thickness of the dielectric and the distance between the electrodes,
The space between the electrodes is unlikely to be affected by the properties of the gas to be processed, and the dielectric can be easily removed, which facilitates maintenance. Moreover, the electrode is not a film and is easy to manufacture and the cost is significantly low.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will now be described with reference to FIGS. FIG. 1 is an external view of the electric field device of the first embodiment,
2 is a front view of the electrode structure, and FIG. 3 is a side sectional view of the electrode structure. Inside the left and right side walls 1d of the outer frame 1 which is a rectangular tube-shaped body, a plurality of stages of shelf-like projections 1a are provided vertically inside. Further, a partition wall 1b is integrally formed with the outer frame 1 at the central portion on the left and right, and a plurality of stages of shelf-shaped projections 1c corresponding to the shelf-shaped projections 1a of the side wall 1d are provided on both left and right sides of the partition wall 1b. The outer frame 1 and the shelf-like protrusions 1a form a first electrode, and the partition walls 1b and the shelf-like protrusions 1c form a first comb-tooth-like electrode, which are made of a conductor such as aluminum or stainless steel. . On the other hand, a second comb tooth-shaped electrode is provided between the first electrode and the first comb tooth-shaped electrode. The second comb-shaped electrode is composed of a flat wall 3b parallel to the side wall 1d and the partition wall 1b of the outer frame 1 and a shelf-like projection 3a formed on the flat wall 3b in a plurality of vertical steps. It is formed so as to be at a position deviated from the vertical position of the shelf-shaped projections 1d and 1c. Then, the ledges 1 of both the first electrode and the second comb-shaped electrode are formed.
A dielectric 2 made of an insulating material such as glass or ceramics is arranged as a partition so as to be in contact with each of d and 3a, and both the first comb-shaped electrode and the second comb-shaped electrode are arranged. Similar dielectrics 2 are arranged so that the shelves 1c and 3a are in contact with each other. An insulator 4, which is a spacer for vertically fixing the second comb-teeth-shaped electrodes and vertically fixing the dielectric 2 is arranged inside the outer frame 1 and is made of an insulating material such as ceramics or glass.
The power supply 5 has a frequency of several tens of Hz to several tens of KHz and a voltage of several KV to
Alternating voltage such as sine wave or pulse wave of several tens of KV is the first electrode,
It is applied between the first comb-teeth electrode and the second comb-teeth electrode to supply electric power for plasma generation.

While introducing, for example, the exhaust gas of the gas-fired boiler into the inside of the first electrode and the first comb-teeth-shaped electrode, the first electrode, the first comb-teeth-shaped electrode and the second comb-teeth-shaped electrode are separated from each other. When electric power for plasma generation is supplied from the power supply 5, the space between the electrodes and the dielectric 2, that is, the inside of the tubular passage is shown in FIG.
Glow discharge plasma G having a striped pattern shown in (b) is generated. This plasma starts discharge from the vicinity of the contact surface between the dielectric 2 and the tips of the first protrusions 1a, 1c, 3a of the first comb-shaped electrode and the second comb-shaped electrode and the second comb-shaped electrode, and these electrodes and the dielectric Electric discharge is induced in the entire gas in the space inside the tubular passage having the body 2 as the inner wall.

Therefore, the gas introduced into the first electrode and the first comb-teeth electrode becomes a substantially uniform plasma state inside, and gas molecules such as NO _x , N ₂ and O ₂ in the exhaust gas. It is excited and dissociated to be in a chemically active state. As a result, the reaction described below is caused. 2O ₂ → O ₃ + 1 / 2O ₂ NO + O ₃ → NO ₂ + O _{2 In the} above reaction formula, NO, which is the main component of NO _x introduced into the first electrode and the first comb-shaped electrode, is oxidized into NO _2. Indicates that it will be done. Usually, when the exhaust gas treatment of a gas-fired boiler is performed, the target of the exhaust gas purification treatment is NO _x , but its main component is NO. NO has poor reactivity and is difficult to treat, but as described above, when it is oxidized to NO ₂ , it can be easily detoxified by a method such as reduction by alkali washing or an adsorbent with an adsorbent. In addition, the dielectric is placed between electrodes of different polarities, and the electrodes of different polarities are arranged so as to be offset so as not to be adjacent to each other across the dielectric. There is little electric field concentration. Therefore, the discharge electrodes are always insulated from each other by the dielectric, so that a stable plasma state can be maintained without being affected by moisture or oil in the gas. Further, the four surfaces of the inner wall of the tubular passage have a structure in which one surface is surrounded by a dielectric and the other three surfaces are surrounded by conductors of the same potential, which has the effect of flattening the electric field intensity distribution and making the plasma uniform. In addition, a large capacity can be achieved by connecting a large number of electric field devices of this embodiment in parallel, or by extending the shelf-like projections and the dielectrics in the vertical direction to increase the number of tubular passages, thereby increasing the throughput. It is easy to convert. Moreover, the electrode structure is a simple one in which a dielectric is inserted inside a comb-shaped electrode made of metal, maintenance of the dielectric is easy, and the manufacturing cost is low.

A second embodiment according to the present invention will be described with reference to FIGS. 4, 5 and 6. FIG. 4 is a view showing the electric field device of the second embodiment. FIG. 5 is a front view of the electrode structure showing a cross section of the opening, and FIG. 6 is a side view of the electrode structure. The first electrode has a structure in which a plurality of radial projections 11a are projected inside the cylindrical outer wall 11b at equal intervals in the circumferential direction. The first dielectric 21 has a cylindrical shape and also serves as a partition wall, and the tip of the radial projection 11a of the first electrode is in contact with the outside thereof. The second electrode has a plurality of radial projections 12a protruding at equal intervals in the circumferential direction on the outside of the cylindrical partition wall 12b.
The radial projections 1 are also provided on the inner side of the partition wall 12b at equal intervals in the circumferential direction.
A plurality of 2c are projected. The plurality of radial protrusions 12c
Is in contact with the outside of the second dielectric 22 inside thereof.
In addition, in the radial projections 12a projecting outside of the partition wall 12b and the radial projections 12c projecting inside thereof, the distance between each adjacent projection, for example, a certain projection 12a and the adjacent projection 12a is from their tip to tip. The arc distances are equal. Therefore, the number of the protrusions 12c is smaller than the number of the protrusions 12a on the outer side and the inner side of the partition wall 12b. The second dielectric 22 has a cylindrical shape and also serves as a partition, a plurality of radial projections 12c of the second electrode are in contact with the outside thereof, and a plurality of the third electrodes are inside the partition. Projections 13a are in contact with each other. The third electrode joins the plurality of radial protrusions 13a at one end, and the other end, that is, the tip is in contact with the inside of the second dielectric 22, and the distance between the tips of the protrusions 13a is small. They are arranged so that their arc distances are equal.
Further, the projections (for example, 11a and 12a, 12c and 13a) sandwiching the first dielectric body 21 and the second dielectric body 22 are arranged so as not to be adjacent to each other. Furthermore, regarding the arrangement of the radial protrusions, the arc distance between the tips of the adjacent flat plates is substantially constant, and the protruding length of each radial protrusion is also constant. Thus, a large number of fan-shaped opening cross sections are formed as shown in FIG. The first, second, and third electrodes are formed of a metal material (conductor) such as aluminum or stainless steel, and the first and second dielectrics (21
And 22) are formed of an insulating material such as glass or ceramics. Reference numeral 5 denotes a power source, one terminal of which is connected to the first electrode and the third electrode, and the other terminal of which is connected to the second electrode.

When electric power is supplied from the power source 5 to the electrode while introducing the exhaust gas of the gas-fired boiler into the cylindrical electrode, glow discharge plasma is generated in the tubular passage having a fan-shaped cross section, Results The following reactions are triggered. 2O ₂ → O ₃ + 1 / 2O ₂ NO + O ₃ → NO ₂ + O _{2 The} above reaction formula shows that NO, which is the main component of NO _x introduced into the first electrode, is oxidized to NO ₂ . In the second embodiment, the flat plate-shaped dielectric of the first embodiment is replaced by a cylindrical shape, but the principle of plasma generation is common to both the first and second embodiments, and NO _x oxidation is performed. The processing performance is comparable. In the present embodiment, the NO _x oxidation treatment has been described, but it can also be applied to O ₃ generation, CO oxidation to CO _2, and the like. In addition, in both the first and second embodiments,
Further, it can be formed in multiple stages.

[0013]

As described above, according to the present invention, it is possible to realize a compact and low-cost gas oxidation treatment apparatus. Moreover, since maintenance is easy and the capacity can be easily increased, a device for oxidizing O ₂ to produce O ₃ for deodorization and improving combustion efficiency, and a device for NO _x , SO _x , CO, etc. for denitration / desulfurization, etc. The industrial value is extremely high as an electric field device for gas oxidation such as a device for treating exhaust gas.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention.

FIG. 2 is a front view of the first embodiment.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a perspective view of a second embodiment.

FIG. 5 is a front view of the second embodiment.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a perspective view of a conventional example.

FIG. 8 is a development view of FIG. 7.

[Explanation of symbols]

 a, 1c, 3a Shelf-like projection 1b Partition wall 1d Side wall 2 Dielectric material 3b Flat wall 5 Power supply 11a, 12a, 12c, 13a Radial projection 11b Outer wall 12b Partition wall 21,22 Dielectric material

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01D 53/74 B01J 19/00 A 8822-4G 19/08 Z 8822-4G C01B 13/11 A H05H 1/48 9014-2G (72) Inventor Eishiro Sasakawa 1-1 1-1 Atsunoura-machi, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard Co., Ltd.

Claims (2)

[Claims] 1. A first electrode having a plurality of shelves protruding vertically inward from the left and right side walls of a rectangular tubular outer frame, and on both left and right sides of a partition wall that divides the outer frame into a plurality of left and right sides. A first comb-tooth-shaped electrode having a plurality of stages of shelf-shaped protrusions corresponding to the shelf-shaped protrusions of the first electrode, and shelf-shaped protrusions of the first electrode and the first comb-tooth-shaped electrode on both left and right sides of a flat wall. The second comb-teeth-shaped electrode having a plurality of stages of shelf-like projections that are staggered in a staggered manner and the shelf-like projections of the first electrode and the second comb-teeth-like electrode that are in contact with each other And a dielectric that is in contact with and is located between the respective shelf-like protrusions of the first comb-tooth-shaped electrode and the second comb-tooth-shaped electrode. An electric field device for gas oxidation in which voltages of different polarities are applied between two comb-teeth electrodes. 2. A first electrode having a plurality of radial projections from the inner peripheral wall of a cylindrical outer frame toward the inner center, and a cylindrical outer wall contacting the inside of the tips of the radial projections of the first electrode. The first dielectric and a cylindrical inner cylindrical inside of the first dielectric having radial projections on both the outer peripheral wall and the inner peripheral wall, the arc distance between adjacent radial projections on the outer peripheral wall side being equal, and the outer peripheral wall Side radial projections and the radial projections of the electrodes on the outer side thereof are staggered with each other, and the arc distances between the adjacent radial projections on the inner peripheral wall side are equal, and the tip of the radial projection on the outer peripheral wall is a cylindrical dielectric. The one or more steps of the second electrode in contact with the inner peripheral wall of the second electrode, the cylindrical second dielectric having the outer peripheral wall in contact with the radial projections of the inner peripheral wall of the second electrode, and the inner peripheral wall of the second dielectric. The tip of the radial projection comes into contact with the base of this radial projection. All together, the adjacent radial projections have the same circular arc distance, and the radial projections and the third projections are arranged so that the radial projections on the inner peripheral wall of the second electrode are offset from each other. An electrode for gas oxidation in which different polarities are applied to adjacent electrodes.