JP3295505B2 - Electrostatic precipitator, discharge electrode used therefor, and method for preventing deterioration of discharge electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic precipitator, a discharge electrode used in a dust particle charging section thereof, and a method for preventing deterioration of the discharge electrode.

[0002]

2. Description of the Related Art As an electrostatic precipitator for removing dust in the air, a charging function for generating a corona discharge between a discharge electrode and a counter electrode to charge the dust in the air, and a method for discharging the charged dust. 2 of dust collection function that collects dust by electrostatic force
A configuration that collects dust by three functions is known. The dust collection characteristics of an electric dust collector with this configuration are almost proportional to the current of corona discharge used for particle charging.However, considering design aspects such as safety, it is important to pass more discharge current at the lowest possible voltage. It is. Since corona discharge is generated by the formation of an uneven electric field, the discharge portion of the discharge electrode must have a large curvature and effectively form an uneven electric field. As a discharge electrode satisfying this requirement, there are known a thin electrode made of metal (linear electrode) and an electrode having a metal discharge needle portion (needle electrode).

[0003] A conventional electric precipitator having such a configuration will be described below using examples. FIG. 4 shows a charging section of a conventional electric precipitator provided with a needle type discharge electrode. The electrostatic precipitator is provided with a charging unit upstream of the flow of air to be cleaned and a dust collecting unit (not shown) downstream. In the figure, 1 is a discharge electrode, 2 is a counter electrode, and both electrodes 1 and 2 are alternately arranged at an appropriate interval. The discharge electrode 1 is formed of a strip-shaped metal plate having a plurality of needle-like protrusions 1a formed at appropriate intervals.
When a high voltage of, for example, (+) is applied to the discharge electrode 1 and the opposite electrode 2 is grounded, a remarkably uneven electric field is formed in the vicinity of the needle-like projections 1a of the discharge electrode, so that the needle-like projections 1a are discharged. Corona discharge is generated as a part, and the dust in the passing airflow is charged.

FIG. 5 shows a charging section of a conventional electric precipitator provided with linear electrodes. 3 is a linear discharge electrode, 4
Is a counter electrode. The discharge electrode 3 is pulled at both ends by a support component, a spring body, or the like so as to keep a predetermined interval from the counter electrode 4. When a high voltage is applied between the discharge electrode 3 and the counter electrode 4 in the same manner as in the example of FIG. 4, the entire discharge electrode 3 facing the counter electrode 4 becomes a discharge portion, and corona discharge occurs. By this discharge, the dust is charged by the same mechanism as in the example of FIG.

On the other hand, the dust collecting portion has a configuration in which a voltage is applied between the dust collecting electrode and the counter electrode which are disposed opposite to each other at an appropriate interval, and one of the dust collecting electrode and the counter electrode in this configuration. Are also used as a counter electrode of a charging unit, and a filter made of a filter material made of permanently charged fibers called an electret. The dust charged by the charging unit is collected by the dust collection unit disposed on the downstream side.

[0006]

The discharge portion of the discharge electrode of the conventional electrostatic precipitator is deteriorated by wear due to a rise in temperature due to corona discharge and collision of plasma. Therefore, there are the following problems. First, in the needle electrode, the shape of the tip of the needle, which is the discharge portion, changes to a shape with a small curvature due to abrasion, and an uneven electric field cannot be effectively formed, so that corona discharge hardly occurs. As a result, there is a problem that the dust collection characteristics are deteriorated due to a decrease in the discharge current, and safety is impaired due to an increase in the discharge voltage or occurrence of abnormal discharge. In the linear electrode, abrasion deterioration of the wire material causes a decrease in strength and disconnection, stopping discharge,
Further, there is a problem that a short circuit is caused by contact of the wire with the counter electrode.

Accordingly, the present invention provides an electric precipitator which is capable of preventing wear and deterioration of a discharge portion, has a long service life, has high safety, and has excellent corrosion resistance, and a discharge electrode and a discharge electrode used therefor. An object of the present invention is to provide a method for preventing deterioration of a product.

[0008]

In order to solve the above-mentioned problems, the present invention firstly generates a corona discharge between at least one pair of discharge electrodes and a counter electrode, and the corona discharge is generated in the air by the corona discharge. An electrostatic precipitator which collects dust by charging dust particles, wherein the surface of at least a portion of the discharge electrode where corona discharge is generated has a carbon content of 0.2% by weight.
The following iron-based alloy as a base material, the Al and Cr on the substrate
The gist is to form a treatment film provided with an oxide layer.

Secondly, in the above-mentioned first configuration, the ratio of Al to Cr contained in the treatment film is 3-7: 10.
２５25 (weight ratio).

Third, in the above first or second configuration, the gist of the present invention is that the thickness of the treatment film is 1 μm to 500 μm.

Fourth, a corona discharge is generated between at least one set of discharge electrodes and a counter electrode, and the corona discharge charges the dust particles in the air to collect the dust. At least the surface of a portion where corona discharge is generated is made of an iron-based alloy having a carbon content of 0.2% by weight or less, and an oxide layer made of Al and Cr is formed on the base material.
The gist of the present invention is to form the treatment film provided .

Fifth, in the fourth configuration, the ratio of Al to Cr contained in the treatment film is 3-7: 10.
２５25 (weight ratio).

Sixth, in the above-described fourth or fifth configuration, the gist of the present invention is that the thickness of the treatment film is 1 μm to 500 μm.

Seventh, a corona discharge is generated between at least one set of discharge electrodes and a counter electrode, and the corona discharge charges the dust particles in the air to collect the dust, thereby preventing the deterioration of the discharge electrodes in the electric precipitator. Method, at least a surface of a portion of the discharge electrode that causes corona discharge,
The content of carbon as a base material of 0.2 wt% or less of iron-based alloys, and summarized in that to form a <br/> conversion coating oxide layer of Al and Cr on the base material is provided .

Eighth, in the above-mentioned seventh structure, the ratio of Al to Cr contained in the treatment film is 3-7: 10.
２５25 (weight ratio).

Ninth, in the seventh or eighth configuration, the gist of the present invention is that the thickness of the treatment film is 1 μm to 500 μm.

[0017]

In the above construction, firstly, the base material is made of an iron-based alloy having a carbon content of 0.2% by weight or less, whereby A
l and a part of Cr diffuses into the substrate, and Al and Cr
Formation of conversion coating oxide layer is provided consisting of is effectively performed. The treated film provided with an oxide layer composed of Al and Cr is excellent in heat resistance, corrosion resistance, and has high hardness. Is achieved.

Second, Al and Cr contained in the treated film
By setting the ratio to 3 to 7:10 to 25 (weight ratio), a high-hardness treated film suitable for mass production and having excellent heat resistance and corrosion resistance can be obtained most effectively.

Third, the thickness of the treatment film is 1 μm to 50 μm.
When the thickness is set to 0 μm, the effect of the treatment is not sufficient when the thickness is 1 μm or less, and when the thickness is 500 μm or more, the insulating effect of the oxide layer appears, so that the discharge hardly occurs. Therefore, the thickness of the treatment film is limited to the above range.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, the same or equivalent members as those in FIG. 4 are denoted by the same reference numerals as those described above, and redundant description will be omitted. In this embodiment, as shown in FIG. 1, a treatment film containing an oxide layer of Al and Cr is formed on at least the surface of the discharge electrode 1 where corona discharge is generated. Reference numeral 9 denotes a treatment film forming portion. Hereinafter, the method of forming the treatment film and the operation thereof will be described in detail. In order to form a treatment film containing an oxide layer of Al and Cr on the surface of a steel or stainless steel substrate as an iron-based alloy having a carbon content of 0.2% by weight or less in the discharge portion of the discharge electrode 1, The following method is used. First, an Al—Cr layer is formed on a substrate surface by a molten salt method or a plating method.
The substrate is heated to about 900 to 900 ° C. to diffuse Al and Cr into the substrate, and subsequently heated to the same temperature in an oxidizing atmosphere to oxidize the surface of the remaining Al—Cr layer. FIG. 2 shows the configuration of the processing film 8 formed by the above processing. Reference numeral 5 denotes an oxide layer on the surface, which is made of an oxide of Al and Cr. Reference numeral 6 denotes a diffusion layer, which is a portion where Al and Cr are diffused into the base material.
The r component is reduced and the base material component is increased. 7 is a base material layer. The ratio of the thickness of each layer after the treatment is usually an oxide layer: a diffusion layer to 1: 1.
2. The properties of the treatment film 8 formed by this treatment are to be excellent in heat resistance and corrosion resistance and to have high hardness. When this treatment film 8 is formed on the discharge part, it is less susceptible to wear deterioration due to discharge, and it is possible to prevent deterioration of discharge characteristics.

In the present embodiment, the reason why the carbon content of the base material 7 needs to be 0.2% by weight or less is as follows.
This is because the presence of carbon exceeding 2% by weight hinders the diffusion of Al and Cr into the inside of the base material 7 during the present treatment, making it impossible to form an effective film. Further, the ratio of Al to Cr in the treatment film 8 refers to the weight ratio of the content of Al and Cr in the oxide layer 5 and the diffusion layer 6 formed by this treatment. The reason that this ratio is limited to 3-7: 10-25 (weight ratio) is as follows.
This is because this ratio is suitable for mass production of the processed product, and the effect of the processing can be obtained most effectively. Further, the treatment film thickness refers to the sum of the oxide layer 5 and the diffusion layer 6, and this film thickness is limited to 1 μm to 500 μm because the film thickness is 1 μm.
If it is less than m, the effect of the treatment is not sufficient, and if it is more than 500 μm, the insulating effect of the oxide layer 5 appears and it becomes difficult to discharge. However, depending on the shape of the electrodes, the distance between the electrodes, the discharge conditions, and the like, the optimum film thickness range varies within a narrower range, and in most cases, the film thickness is optimum when the film thickness is several μm to several tens μm.

Next, the operation and effect of this embodiment will be described in comparison with a conventional example. The conventional example is a needle type electrode shown in FIG. 4 and uses SUS304 as a material. This embodiment, the needle tip is the discharge portion of the conventional example is obtained by forming the treatment film 8 is oxidized layer 5 made of Al and Cr provided. In this embodiment, since the substrate 7 is made of stainless steel, only the treatment film 8 was formed. The ratio of Al to Cr in the treatment film 8 was 5:20, and the total thickness of the oxide layer 5 and the diffusion layer 6 was 35 μm. FIG.
Table 1 shows that the present embodiment and the conventional example have an applied voltage of 3.5.
This figure shows the change over time of the discharge current and the state of the tip of the needle when corona discharge is continued at kV and a distance between the electrodes of 6 mm. FIG.
The solid line is the present embodiment, and the broken line is the conventional example.

[0023]

[Table 1] As is clear from FIG. 3 and Table 1, in the discharge electrode according to the present embodiment, the deterioration of the needle tip, which is the discharge portion, was smaller than in the conventional example, and a high discharge current was maintained for a longer period.
As described above, when the discharge electrode of the present embodiment is applied to a needle electrode, the discharge portion hardly wears, a high discharge current is maintained for a long period, and abnormal discharge does not occur. That is, by providing the electric precipitator with the discharge electrode of the present embodiment, high dust collecting characteristics can be maintained for a long period of time, and a safe electric precipitator free from an increase in discharge voltage and abnormal discharge can be realized.

The effect is the same when the present embodiment is applied to a linear discharge electrode. The effect is the same. A high discharge current is maintained for a long period of time, and the strength of the electrode is hardly reduced due to abrasion. Accordingly, it is possible to realize an excellent dust collector that maintains high dust collection characteristics for a long time and has no disconnection or short circuit of the discharge electrode. Furthermore, since the treated film of the present embodiment has corrosion resistance, the electric dust collector of the present embodiment is excellent in a corrosive environment. Further, the surface treatment of this embodiment is an excellent treatment method which has a sufficient effect and is inexpensive at low cost as compared with the SiC film formation by the CVD method described in JP-A-63-130149.

[0025]

As described above, according to the present invention,
First, the surface of the portion to generate at least the corona discharge at the discharge electrodes, the content of carbon as a base material of 0.2 wt% or less of the iron-based alloys, Al and Cr Tona on this substrate
Since that oxide layer was formed conversion coating is provided, heat resistance, excellent corrosion resistance, are prevented wear deterioration treatment film having a high hardness by effectively formed by discharge in the discharge unit, high safety and long life Further, it is possible to realize a discharge electrode having excellent corrosion resistance and an electric dust collector.

Second, Al and Cr contained in the treated film
Is 3-7: 10-25, it is possible to reliably obtain a treated film that is suitable for mass production, has excellent heat resistance and corrosion resistance, and has high hardness.

Third, the thickness of the treatment film is 1 μm to 500 μm.
μm, the effect of the treatment is sufficiently obtained and the heat resistance,
A treatment film having excellent corrosion resistance and high hardness can be reliably obtained, and the insulating action of the oxide layer is suppressed, so that corona discharge can be effectively generated.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a charging unit in an embodiment of an electric dust collector according to the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a treatment film in the above embodiment.

FIG. 3 is a diagram showing a change over time of a discharge current in the above-mentioned embodiment together with a comparative example.

FIG. 4 is a perspective view showing a charging unit provided with a conventional needle-type discharge electrode.

FIG. 5 is a perspective view showing a charging section provided with a conventional linear discharge electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge electrode 2 Counter electrode 5 Oxide layer 6 Diffusion layer 7 Base material 8 Treatment film 9 Surface treatment part of discharge electrode

────────────────────────────────────────────────── (5) References JP-A-63-162052 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B03C 3/00-3/88

Claims (9)

(57) [Claims] 1. An electrostatic precipitator for generating corona discharge between at least one set of discharge electrodes and a counter electrode, and charging and collecting dust particles in the air by the corona discharge,
A surface of at least a portion of the discharge electrode where corona discharge is generated is made of an iron-based alloy having a carbon content of 0.2% by weight or less, and an oxide layer made of Al and Cr is provided on the base material. An electrostatic precipitator characterized by forming a treated film. 2. The electrostatic precipitator according to claim 1, wherein the ratio of Al to Cr contained in the treatment film is 3 to 7:10 to 25 (weight ratio). 3. The treatment film has a thickness of 1 μm to 500 μm.
3. The electrostatic precipitator according to claim 1, wherein m is m. 4. A discharge electrode of an electric precipitator for generating a corona discharge between at least one set of discharge electrodes and a counter electrode, and charging and collecting dust particles in the air by the corona discharge. The surface of the portion where corona discharge is generated is made of an iron-based alloy having a carbon content of 0.2% by weight or less, and an oxide layer made of Al and Cr is provided on the base material .
A discharge electrode for an electrostatic precipitator, comprising a treated film formed thereon. 5. The discharge electrode according to claim 4, wherein the ratio of Al to Cr contained in the treatment film is 3 to 7:10 to 25 (weight ratio). 6. The treatment film has a thickness of 1 μm to 500 μm.
The discharge electrode of the electric precipitator according to claim 4, wherein m is m. 7. A method for preventing deterioration of a discharge electrode in an electric precipitator in which a corona discharge is generated between at least one set of discharge electrodes and a counter electrode, and the corona discharge charges and collects dust particles in the air. The surface of at least a portion of the discharge electrode that generates corona discharge is made of an iron-based alloy having a carbon content of 0.2% by weight or less, and an oxide layer made of Al and Cr is formed on the substrate. A method for preventing deterioration of a discharge electrode for an electrostatic precipitator, comprising forming a treatment film provided with a coating. 8. The prevention of deterioration of a discharge electrode for an electrostatic precipitator according to claim 7, wherein the ratio of Al to Cr contained in the treatment film is 3-7: 10-25 (weight ratio). Law. 9. The treatment film has a thickness of 1 μm to 500 μm.
The method for preventing deterioration of a discharge electrode for an electrostatic precipitator according to claim 7 or 8, wherein m is m.