JPH0515509B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field to which the invention pertains] This invention relates to an electrode for an electrostatic precipitator. [Prior art and its problems] An electrostatic precipitator applies an electric charge to powder or mist particles suspended in a gas, and applies an electric field to electrostatically separate and remove them from the gas. Particle processing methods are classified into three types: dry, wet, and mist collection, each with its own characteristics and used depending on each plant. However, from an environmental perspective, dust collectors have a wide range of application, and the physicochemical properties of the gases, dust, fumes, etc. that they handle vary, resulting in a wide variety of corrosive environments. Therefore, the form of corrosion, frequency of occurrence of corrosion, lifespan, etc. of the constituent materials are not uniform, just like the environment. In particular, electrode materials, especially discharge electrodes, have mechanical and chemical strength that can withstand wear and tear due to high temperatures, corrosion, fatigue, sparks, etc.
Moreover, a shape sufficient to cause sufficient corona discharge is required. For example, FIG. 2 shows an example of the structure of a wet electrostatic precipitator, in which a discharge electrode 2 attached to a discharge electrode frame 1
to generate a corona discharge toward the dust collection electrode 5,
This part gives an electric charge to the particles, and the dust collection electrode 5 separates the particles from the gas. The atomizer 3 forms a water film to prevent dust from adhering to the discharge electrode, and the flushing 4 is a cleaning pipe for flowing the collected dust downward together with water. The gas is configured to flow parallel to the electrodes. The material of the discharge electrode 2 is mild steel, corrosion-resistant steel,
Austenitic stainless steel may be used, as well as titanium and tungsten in highly corrosive environments. Furthermore, when collecting sulfuric acid mist, the surface of the discharge electrode 2 may be coated with lead. On the other hand, the material of the dust collection electrode 5 is a mild steel plate or an austenitic stainless steel plate. However, even if such a material is selected, it may be insufficient depending on the environment. For example, in electrostatic precipitators installed in expressway tunnels, the lifespan of the discharge electrodes is shortened in winter in tunnels located in snowy areas. This is because the spraying of antifreeze agents (eg calcium chloride) and the increase in concrete dust due to spiked tires are leading to a shortened lifespan of the discharge electrodes. For example, the short lifespan of titanium (Ti) and tungsten (W), which are highly corrosion-resistant materials, is explained as follows. Since the discharge electrode continuously generates corona discharge, the corona discharge rises in an extremely microscopic range. When calcium chloride or concrete dust adheres to such a discharge electrode, a high-temperature chloride environment or a high-temperature alkaline environment is created, albeit momentarily. This causes the chemical reaction shown in the following equation to accelerate the corrosion damage rate of highly corrosion resistant materials and shorten their lifespan. CaCl ₂ +2H ₂ O→2HCl+Ca(HO) ₂ ...(1) Ti+2HCl→TiCl ₂ +2H ...(2) CaO+H ₂ O→Ca(OH) ₂ ...(3) WO ₃ +Ca(OH) ₂ →CaWO ₄ +H ₂ O... (4) Therefore, the discharge electrode material needs to be chloride resistant, acid resistant, and alkali resistant. In this respect, titanium and tungsten have the disadvantage of lacking chloride resistance and alkali resistance. [Object of the Invention] This invention has been made in view of the above points, and its purpose is to provide an electrostatic precipitator equipped with an electrode that exhibits Takai corrosion resistance in a chloride environment, an alkaline environment, etc. be. [Summary of the Invention] The present invention provides an electrostatic precipitator having a discharge electrode that charges floating particles in the air by corona discharge and a dust collecting electrode that electrostatically collects the charged floating particles. This goal is achieved by coating the surface with a thin film of porous silicon oxide. That is, the surface of a metal material is coated with a thin film of silicon oxide (hereinafter abbreviated as SiO ₂ ), which is an electrically insulating material, and corona discharge is caused through the openings formed in the SiO ₂ thin film to generate electricity. conductivity is maintained, while the porous SiO ₂ thin film acts as a filter against airborne particles such as chlorides and alkaline substances, preventing the airborne particles from coming into direct contact with the metal material inside. It is designed to prevent this from happening. [Embodiments of the Invention] Next, embodiments of the invention will be described based on the drawings. Discharge electrode 2 was adjusted by the following method. The surface of a tungsten wire (φ0.2×800) as drawn was degreased, and a paste containing colloidal SiO ₂ (Atron NSI-500 (manufactured by Nippon Soda)) was applied with a brush. After drying, heat in an electric oven at 400℃ or
It is fired at a temperature of 500℃, and as shown in FIG.
A thin film 12 of SiO ₂ was formed. The SiO ₂ thin film 12 is porous and has openings 13 formed therein. Regarding the dust collection electrode 5, use the same method as the above-mentioned discharge electrode 2 for a mild steel plate or austenitic stainless steel plate.
A thin film of SiO ₂ can be formed. When an electric precipitator is constructed using the discharge electrode 2 and the dust collection electrode 5 prepared in this manner and discharge is caused, a necessary corona discharge occurs. This corona discharge is caused by the _SiO2 thin film on the electrode surface (this is an insulating material)
This is done through an aperture 13 formed in the. When corona discharge occurs, the electrode surface temperature instantaneously increases by several hundred degrees as mentioned above, but at this temperature,
The thin film of SiO ₂ does not react with the metal materials inside it, nor with airborne particles such as calcium chloride or concrete dust. moreover
The apertures 13 formed in the SiO ₂ thin film are sufficiently small that airborne particles cannot pass through the apertures and therefore do not come into contact with the metal material inside. Therefore, metal materials contain chlorides and alkaline substances (e.g. CaO in concrete dust).
This eliminates the occurrence of high-temperature corrosion reactions and exhibits excellent corrosion resistance in these corrosive environments. In addition to the paste baking method described above, SiO ₂ thin films can be produced using
This can also be formed by a CVD method.
In the CVD method, the processing temperature is quite high at 900°C to 1000°C, so the formed film has good adhesion. Another advantage is that the film formation rate is fast. CVD method _SiO2
The film exhibits electrical properties and corrosion resistance comparable to paste-based films. For reference, the images obtained by the above two methods are
Table 1 shows the corrosion resistance of SiO ₂ thin films in a liquid atmosphere. This is the amount of corrosion of a SiO ₂ thin film when immersed in a boiling solution in an acidic or alkaline environment for 24 hours.
This shows that SiO ₂ thin films have good corrosion resistance.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, an electrostatic precipitator includes a discharge electrode that charges floating particles in the air by corona discharge, and a dust collection electrode that electrostatically collects the charged floating particles. In,
Since at least the surface of the discharge electrode is coated with a porous SiO ₂ thin film, corona discharge occurs through the pores in the SiO ₂ thin film, and at the same time, the SiO ₂ thin film acts as a filter for airborne particles. This prevents floating particles from coming into direct contact with the internal metal material, which improves the corrosion resistance of the electrode.
It has become possible to operate the electrostatic precipitator stably over a long period of time in a corrosive environment.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an electrode according to an embodiment of the present invention, and FIG. 2 is a perspective view showing the structure of a wet electrostatic precipitator. 11...Metal material, 12...SiO ₂ thin film, 1
3...Open hole.

Claims (1)

[Scope of Claims] 1. In an electrostatic precipitator having a discharge electrode that charges floating particles in the air by corona discharge and a dust collection electrode that electrostatically collects the charged floating particles, at least the discharge electrode An electrostatic precipitator characterized in that its surface is coated with a porous silicon oxide thin film. 2. The electrostatic precipitator according to claim 1, wherein the silicon oxide thin film is a thin film deposited by a CVD method. 3. The electrostatic precipitator according to claim 1, wherein the silicon oxide thin film is a thin film formed by applying a paste and firing.