JPH0655099A - Wet type electrostatic dust precipitation method - Google Patents

Abstract

PURPOSE:To automatically clean dust precipitation electrodes at a low cost by utilizing the water flow films formed by washing water without stopping the dust precipitation operation. CONSTITUTION:The bottom end side of a conductive flat plate 10 for forming the water flow films is pendently provided with net-like bodies 11, 12. The water flow films Wa formed by radiating the washing water W from a washing nozzle 13 to the flat plate 10 are allowed to flow down the net-like bodies 11, 12 as it is. The particles electrified negative are captured by such water flow films Wa.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet type for purifying exhaust gas from various exhaust gas treatment devices, particularly exhaust gas discharged in a state in which oily mist and dust as particles and tar and water are mixed. The present invention relates to an electric dust collecting method.

[0002]

As is well known, in a wet electrostatic precipitator,
Direct current high voltage is applied to the dust collecting electrode (positive electrode) and discharge electrode (negative electrode), which are arranged facing each other to generate corona discharge, and negatively charge the rectified exhaust gas particles taken in from the gas inlet. The exhaust gas is collected and collected by the dust collecting electrode, whereby the exhaust gas is purified and discharged.

When purifying exhaust gas with such a dust collector, if the particles collected by the dust collector are merely oily mist, even if they adhere to the surface of the dust collector, the viscosity of the oil Unless the value is extremely high, most of the particles fall naturally from the dust collecting electrode and can be used well.

However, when oily mist and dust or tar are collected at the dust collecting electrode at the same time, that is, when these are mixed to form a paste or grease, dust is collected. Once collected on the pole, it will stick to the dust collection pole with little spontaneous fall. It is difficult to remove the washing water when it is emitted, and the dust collecting capability is significantly reduced. For example, the exhaust gas generated at a metal press working site, a work site where a plasticizer is kneaded into resin or rubber, or the like often produces the above-mentioned paste-like particles.

With respect to the dirt on the dust collecting electrode, in the dry type electric dust collecting device, the operation is stopped and the dust collecting electrode is manually washed, but this takes a lot of time and labor. , It is necessary to take measures to automatically clean the dust collecting electrode.

Conventionally, as a method for automatically cleaning the dust collecting electrode,
There is one shown in FIGS. 6 and 7. The one shown in FIG. 6 is
A rod-shaped discharge electrode 62 was inserted through a pipe-shaped dust collecting electrode 61,
This is an example of application to a so-called concentric cylinder type wet electrostatic precipitator, in which a water reservoir 63 is provided above the dust collecting electrode 61, and the wash water W in the water collecting reservoir 63 is overwhelmed from the upper end of the dust collecting electrode 61. -The water flow film Wa formed by flowing it down
Therefore, the negatively charged particles are collected before they are attached to the inner peripheral surface of the dust collecting electrode 61.

On the other hand, FIG. 7 shows an example of application to a so-called flat-plate type wet electrostatic precipitator using a flat plate-shaped dust collecting electrode 71 and a rod-shaped discharge electrode 72. From above and from the front, respectively, cleaning sprays 73, 7
4, the cleaning water W is radiated to collect the negatively charged particles on the water flow film Wa formed along the surface of the dust collecting electrode 71.

[0008]

However, in the former case described above, the dust collecting electrode 61 originally has a pipe-shaped dust collecting area.
The dust collecting ability is low only on the inner peripheral surface of the above, and the spaces between the dust collecting electrodes 61 are wasteful spaces. Particularly, if the water surface level for overflowing the wash water W in the water reservoir 63 into the dust collecting electrode 61 is not set with high accuracy, the uniform water flow film W will be obtained.
a cannot be obtained, in other words, the setting conditions are complicated, the manufacturing cost is considerably high, and it is difficult to positively adopt it.

Further, when fresh water is always used as the cleaning water W, the dust collecting electrode 61 is hard to get dirty,
When the cleaning water W is circulating water, the oil component that has emulsified gradually adheres to the inner peripheral surface of the dust collecting electrode 61 over time, and it becomes difficult to maintain a good water flow film for a long period of time.

Further, in the latter case of the above-mentioned prior art, since the dust collecting electrode 71 and the discharge electrode 72 are set close to each other at the same place, the cleaning water W prevents the cleaning electrodes W and W from being short-circuited. The amount of W radiation must be restricted and emitted. Further, even if the cleaning water W is allowed to flow down to the flat plate-shaped dust collecting electrode 71, it is difficult to form a uniform water flow film Wa from top to bottom due to the influence of the surface tension or the distortion of the surface of the dust collecting electrode 71. . Even if the water flow film Wa is formed, it is hard to be stable, and therefore it is possible to surely prevent the above-mentioned paste-like or grease-like particles from adhering to the dust collecting electrode 71. There is no guarantee.

The present invention has been made in order to solve the above-mentioned conventional problems, and can exert an excellent cleaning effect by utilizing a water flow film of cleaning water without stopping the dust collecting operation. Moreover, it is an object of the present invention to provide a wet electrostatic precipitating method that can be implemented at low cost.

[0012]

In order to achieve the above-mentioned object, the present invention relates to an exhaust gas which is vertically arranged with a discharge electrode and is negatively charged by corona discharge between the discharge electrode and the discharge electrode. The dust collecting electrode that collects particles is composed of a conductive flat plate for forming a water flow film and a mesh-like body that is vertically installed on the lower end side of the flat plate, and is provided above the dust collecting electrode for cleaning. While irradiating washing water from the nozzle to the flat plate to form a water flow film that spreads downward, this water flow film is allowed to flow down to the mesh body as it is,
As a result, the negatively charged particles are collected on the water flow film formed on the surface of the dust collecting electrode.

[0013]

In the present invention, particles in the exhaust gas taken in from the outside are negatively charged by the corona discharge generated between the discharge electrode and the dust collecting electrode and attracted to the dust collecting electrode side. At this time, since cleaning water is radiated from the cleaning nozzle to the conductive flat plate in the dust collecting electrode, the water flow film formed on this conductive flat plate spreads and flows down to the mesh body, and continues to the lower side as it is. Becomes Therefore, even if the negatively charged particles are mixed with oily mist or dust, they are collected before they adhere to the dust collecting electrode.
An effective cleaning action can be automatically performed while continuing the dust collecting operation.

Further, when the washing water is circulating water, even if the emulsified oil component in the washing water adheres to the line portion of the reticulate body, it does not hinder the formation of a safe water flow film. Further, since the water flow film can be formed relatively easily, it is advantageous to manufacture the device at low cost.

[0015]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an apparatus to which the wet electrostatic precipitating method of the present invention is applied, and FIG. 2 is a schematic plan configuration diagram showing an electrode arrangement state of the apparatus.

1 and 2, a gas inlet 2 for taking in exhaust gas G1 from the outside is formed in a lower side wall of the casing 1 and a purified gas G is formed in an upper wall thereof.
A gas outlet 3 for discharging 2 is formed. Reference numeral 4 denotes a rectifying plate which is horizontally arranged in the lower part of the casing 1 and allows the exhaust gas G1 to flow at a constant flow rate upward, and 5 denotes a dust collecting portion set above the rectifying plate 4. .

In the dust collecting section 5, a plurality of plate-shaped dust collecting electrodes 6 arranged vertically and a plurality of rod-shaped discharge electrodes 7 arranged vertically corresponding to the dust collecting electrodes 6 are provided. By applying a high voltage of direct current between the both electrodes 6 and 7, corona discharge is generated to negatively charge the particles in the exhaust gas G1. Reference numeral 8 is a drain discharge port formed on the lower wall of the casing 1.

The structure of the dust collecting electrode 6 is shown in FIGS. 3 and 4. In both figures, 10 is a flat plate formed of a conductive material, for example, a metal plate in a horizontally long rectangular shape, and is adapted to form a water flow film by receiving the irradiation of washing water described later. On the lower side of the flat plate 10, a net-like body having a size longer than the length of the flat plate 10 in the longitudinal direction, for example, two wire nets 11 and 12 is vertically installed so as to face each other. The dust collecting electrode 6 is composed of the flat plates 10 and 11.

Reference numeral 13 denotes a plurality of cleaning nozzles which are located above the dust collecting electrode 6 and are arranged in parallel in the width direction.
The cleaning water W is emitted to Reference numeral 14 is a pipe for supplying the cleaning water W to each cleaning nozzle 13.

Next, a dust collecting method using the above apparatus will be described. When a direct current high voltage is applied between the dust collecting electrode 6 and the discharge electrode 7, corona discharge is generated between the two electrodes 6 and 7. On the other hand, the flow rate of the exhaust gas G1 taken into the casing 1 from the gas inlet 2 is constrained by the straightening plate 4 to rise and reach the dust collecting section 5. The particles in the exhaust gas G1 are negatively charged by the corona discharge and are attracted to the dust collecting electrode 6 side.

On the other hand, when the cleaning water W is radiated from the cleaning nozzle 13 to the conductive flat plate 10 of the dust collecting electrode 6, the cleaning water W hits the flat plate 10 and spreads downwardly.
Then, it moves to the wire nets 11 and 12 as it is and flows down.

The water film Wa formed on the flat plate 10 is
It is uniform up to about 30 to 50 cm in the vertical direction, but if it flows down by about 1 m, it will be cut vertically, so it is necessary to transfer the water flow film Wa to the wire nets 11 and 12 before the film is cut. Therefore, it is desirable that the length of the flat plate 10 in the vertical direction is about 30 cm so that the water film Wa can be maintained.

The water flow film Wa formed by the flat plate 10 and spreading downward moves to the wire nets 11 and 12 and flows down, and a water film is formed in the line and space of both wire nets 11 and 12, and they are continuous, so that the water flow The film Wa is evenly held up to the lower ends of the wire nets 11 and 12. If, for example, wire meshes 11 and 12 having a wire diameter of 10 mm and a wire diameter of 1 mm are used, the wire meshes 11 and 12 will be approximately 3
A water flow film Wa having a length up to m is formed.

Since the water flow film Wa naturally becomes the positive electrode through the conductive flat plate 10, the negatively charged particles are attached to the dust collecting electrode 6 before the water flow film Wa.
The purified exhaust gas G2 is discharged from the gas outlet 3 while being trapped in the air flow and discharged from the drain discharge port 8, and the dust collecting electrode 6 can be automatically cleaned while continuing the dust collecting operation. .

As described above, since a stable water flow film Wa can be formed, even particles formed by mixing oil-like mist with dust or the like to form a paste form do not adhere to the dust collecting electrode 6, A stable water flow film Wa can be obtained which can be collected and removed by the water flow film Wa, has a relatively simple structure, and only needs to appropriately adjust the radiation amount of the wash water W.
Since the design condition of the device is simple, it can be realized at low cost.

As an example for obtaining the stable water flow film Wa, for example, in a device having a dust collection efficiency of 90% for exhaust gas of 600 m ³ / min, the total length of the dust collection electrode 6 in the width direction is about About 60 m is required, but 3 for this dust collecting electrode 6.
A stable water flow film Wa can be formed by supplying the wash water W of m ³ / min at a pressure of 1.5 Kg / cm ² by a 15 KW pump.

By the way, when circulating water is used as the cleaning water W, even if the emulsified oil component in the circulating water adheres to the wire nets 11 and 12, it is
Since it is the portion of the line 12 and does not hinder the generation of the stable water flow film Wa, it can be used as the cleaning water W for a long period of time. In particular, with the wash water W whose surface tension is reduced by using soap or other surface active agent, it becomes possible to form a more stable water flow film Wa and to operate for a longer time.

In the above example, the two metal nets 11, 1
I explained using 2 but this may be one,
Further, if a small metal mesh of 3 mm between the both wire meshes 11 and 12 or a cloth 15 is hung vertically to the lower end side of the flat plate 10 as shown in FIG. 5, a more stable water flow film Wa of 4 to 5 m can be obtained.
Or it can be extended to longer lengths. Also,
As the net-like body, in addition to the wire nets 11 and 12, expanded metal or synthetic resin can be appropriately selected and used.

[0029]

As described above, according to the present invention, a net is vertically provided on the lower end side of the conductive flat plate for forming a water flow film to form a dust collecting electrode, and the cleaning water from the cleaning nozzle is supplied. Since the water flow film is formed by radiating to the flat plate and the water flow film is made to flow down to the mesh body, a long water flow film is easily formed continuously in the longitudinal direction, which allows the oily mist to be dusted. Even particles that are mixed with the like are collected in the water flow film.

Therefore, the dust collecting electrode is automatically cleaned while continuing the dust collecting operation, and the stable water flow film can be maintained even when the cleaning water is circulating water. Furthermore, the setting conditions for forming a water flow film are simple,
There is an effect that can be realized at low cost. Further, according to the present invention, when the exhaust gas containing the oily mist is treated, even if sparks are generated during corona discharge, the wash water always flows down in the form of a stable water film, so that it is ignited. That's not it.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus to which a wet electrostatic precipitating method of the present invention is applied.

FIG. 2 is a schematic plan view showing an arrangement state of electrodes of the above apparatus.

FIG. 3 is a cross-sectional view showing a structure of a dust collecting electrode of the above device.

FIG. 4 is a side view showing a configuration of the dust collecting electrode.

FIG. 5 is a cross-sectional view showing another example of the dust collecting electrode.

FIG. 6 is a cross-sectional view of a main part showing an example of a conventional wet electrostatic precipitating method.

FIG. 7 is a cross-sectional view of a main part showing another conventional wet electrostatic precipitating method.

[Explanation of symbols]

 6 Dust collecting electrode 7 Discharge electrode 10 Conductive flat plate 11, 12, 15 Net body 13 Cleaning nozzle G1 Exhaust gas W Cleaning water Wa Water flow film

Claims (1)

[Claims] 1. A dust collecting electrode, which is disposed vertically with a discharge electrode and collects particles in exhaust gas that are negatively charged by corona discharge between the discharge electrode and the discharge electrode, is used as a conductive film for forming a water flow film. Water film that spreads downward by irradiating cleaning water from the cleaning nozzle disposed above the dust collecting electrode to the flat plate, which is composed of a transparent flat plate and a mesh-like body vertically provided on the lower end side of the flat plate. Is formed, and this water film is allowed to flow down to the mesh body as it is,
Thus, the wet electrostatic precipitating method is characterized in that the water-charged film formed on the surface of the dust collecting electrode collects the negatively charged particles.