JP6752736B2 - Electrostatic precipitator - Google Patents

Description

The present invention relates to an electrostatic precipitator.

As a conventional electrostatic precipitator, a device including a flat plate-shaped dust collecting electrode arranged in parallel along a gas flow and a discharge electrode having a sharp shape arranged in the center thereof is known.

In the electrostatic precipitator, a high DC voltage is applied between the dust collecting electrode and the discharge electrode, and a stable corona discharge is performed on the discharge electrode to charge the dust in the gas flow. Conventional dust collection theory explains that charged dust is collected by the Coulomb force acting on the dust under the electric field between the discharge electrode and the dust collection electrode.

By the way, the electrostatic precipitators of Patent Documents 1 and 2 are provided with a plurality of through holes for passing dust, and are provided with a dust collecting electrode having a closed space for collecting dust inside. In Patent Documents 1 and 2, the collected dust is made difficult to re-scatter by confining the dust in a closed space through the through hole.

The electrostatic precipitator of Patent Document 3 includes a dust collecting electrode including an earth electrode having an aperture ratio of 65% to 85% and a dust collecting filter layer for collecting gas. By providing such a dust collecting electrode, in Patent Document 3, an ionic wind is generated in a cross section orthogonal to the gas flow, and a spiral gas flow circulating between the discharge electrode and the dust collecting electrode is generated. , I try to collect dust efficiently. In Patent Document 3, ionic wind is actively used, but the purpose of this case is to collect dust mainly in the dust collecting filter layer.

Japanese Patent No. 5761461 Japanese Patent No. 5705461 Japanese Patent No. 4823691

The dust collection efficiency η in the electrostatic precipitator can be calculated by the following well-known Deutsche's mathematical formula (Equation (1)). w is the dust collection index (movement speed of particulate matter), and f is the dust collection area per unit gas amount.
η = 1-exp (−w × f) ・ ・ ・ (1)

In the above formula (1), the moving speed w of dust (particulate matter) is determined by the relationship between the force due to Coulomb force and the viscous resistance of gas. According to Deutsche's formula (formula (1) above), dust moves from the release electrode in the electric field, and ion wind is not directly considered in terms of its effect on performance. However, there is a precondition that the dust concentration, which is the premise of the performance design, is always uniform in the dust collection space between the discharge electrode and the dust collection electrode, and the ion wind causes gas turbulence. It is considered as one of the factors that make the dust concentration uniform.

When a negative voltage is applied between the electrodes, the ionic wind generates negative ions due to corona discharge at the discharge electrode, and as a result, it is generated, and in the case of a positive voltage, it is generated by positive ions. Hereinafter, a case where a negative voltage is applied will be described in order to consider an industrial electrostatic precipitator as a base, but the same applies even if it is positive.

The ionic wind generated at the discharge electrode flows across the gas flow toward the dust collecting electrode. The ionic wind that has reached the dust collecting electrode reverses at the dust collecting electrode and changes the flow direction. This creates a spiral turbulence between the electrodes.

Of the turbulent flow, the flow from the discharge electrode to the dust collecting electrode has the effect of carrying dust to the vicinity of the dust collecting electrode. The dust carried to the vicinity of the dust collection electrode is finally collected by Coulomb force.

However, the ionic wind inverted at the dust collecting electrode moves the dust away from the dust collecting electrode, which is a collector, and therefore has an action of inhibiting dust collection.

Patent Document 3 describes an electrostatic precipitator in consideration of the effect of ionic wind. However, in this case, the structure is such that ion air is sent to the filter layer behind the dust collecting electrode having an opening, and the purpose is to collect dust in a place that is not affected by the main gas. It was complicated, and it was difficult to remove and recover the adhered dust by the dry method.

The present invention has been made in view of such circumstances, and pays attention to the ionic wind which has not been considered in the conventional electrostatic precipitator, and suppresses the alienation action of the ionic wind which reduces the dust collecting effect. It is an object of the present invention to provide an electrostatic precipitator capable of increasing the dust collection efficiency.

In order to solve the above problems, the electrostatic precipitator according to the present invention employs the following means.
That is, in the electrostatic precipitator according to one aspect of the present invention, a casing having a gas inlet portion into which gas flows in and a gas outlet portion in which the gas is discharged to the outside is formed, and a plurality of openings are formed. A dust collecting electrode provided parallel to the gas flow direction of the gas flowing from the gas inlet portion to the gas outlet portion in the casing, and a discharge electrode arranged in parallel with the dust collecting electrode. The plurality of the dust collecting electrodes and the plurality of the discharging electrodes are alternately arranged in a direction orthogonal to the gas flow direction, and the discharging electrodes are only one of the facing dust collecting electrodes. A plurality of corona discharge portions for corona discharge projecting toward the dust collecting electrode are continuously provided in the gas flow direction.

By providing a plurality of openings in the dust collecting electrode, it is allowed that a part of the ion wind flowing from the discharge electrode toward the dust collecting electrode escapes to the back side of the dust collecting electrode. As a result, it is possible to suppress the flow in which the ionic wind is reversed at the dust collecting electrode and separated.
The discharge electrode has a plurality of corona discharge portions for corona discharge projecting toward the dust collection electrode of only one of the facing dust collection electrodes in succession in the gas flow direction. As a result, ion wind can flow from a plurality of corona discharge portions continuous in the gas flow direction toward only one of them, so that interference of ion wind from adjacent corona discharge portions in the gas flow direction can be reduced as much as possible. The dust collection efficiency can be improved.
Examples of the dust collecting electrode include a discrete dust collecting electrode in which a plurality of rigid members are arranged at predetermined intervals in the gas flow direction. Examples of the rigid member include a pipe-shaped member. Further, as another type of dust collecting electrode, for example, a flat plate dust collecting electrode in which one plate-shaped body having a plurality of through holes is provided along the gas flow direction can be mentioned. As the flat plate dust collecting electrode, for example, punching metal is used.

Further, in the electrostatic precipitator according to one aspect of the present invention, the plurality of dust collecting electrodes and the plurality of the discharging electrodes are alternately arranged in a direction orthogonal to the gas flow direction, and the gas flow direction. In the predetermined region, all of the corona discharge portions of each of the discharge electrodes project in the same direction.

When a plurality of dust collecting electrodes and a plurality of discharging electrodes are alternately arranged in a direction orthogonal to the gas flow direction, all the corona discharge portions are directed in the same direction in a predetermined region of the gas flow direction. Protrude. As a result, the ionic wind is directed in a uniform direction across the plurality of dust collecting electrodes in the entire predetermined region, the interference of the ionic wind is suppressed, and the dust collecting efficiency can be improved.

Further, in the electrostatic precipitator according to one aspect of the present invention, in the downstream region downstream of the predetermined region, all of the corona discharge portions of the discharge electrodes are directed in the other direction opposite to the one direction. Protrude.

In the downstream region downstream of the predetermined region, all the corona discharge portions project in the opposite direction to the corona discharge portion in the predetermined region. As a result, the dust collection efficiency can be further improved by changing the direction of the ion wind biased in one direction in the predetermined region to the other direction in the downstream region.

According to the electrostatic precipitator of the present invention, it is possible to suppress the ion wind from separating from the dust collecting electrode and improve the dust collecting efficiency.

It is sectional drawing which showed the electrostatic precipitator which concerns on one Embodiment of this invention. It is a partially enlarged view which showed the arrow view of AA of FIG. It is sectional drawing which showed the modification of the arrangement of the corona discharge part. It is sectional drawing which showed the other modification of the arrangement of the corona discharge part. It is a cross-sectional view which showed the deformation example of the outer shape of the cross section of the pipe member of a dust collecting electrode. It is sectional drawing which showed the electrostatic precipitator using the channel member. It is sectional drawing which showed the electrostatic precipitator using the flat plate type dust collecting electrode. It is a partially enlarged view which showed the mesh belt.

Hereinafter, an embodiment of the electrostatic precipitator according to the present invention will be described with reference to the drawings.

FIG. 1 shows a cross-sectional view of the electrostatic precipitator according to the present embodiment. In FIG. 1, the gas flow G is a horizontal flow and flows from the left side to the right side of the paper.

The electrostatic precipitator 1 includes a plurality of dust collecting poles 4 arranged along the gas flow G in the casing 2, a plurality of discharging electrodes 5 arranged in parallel with the dust collecting pole 4, and a power source ( (Not shown) and.
The casing 2 includes a gas inlet portion 2a, a main body portion 2b, and a gas outlet portion 2c. The gas flowing in from the gas inlet portion 2a is guided to the main body portion 2b to collect dust, and then is discharged to the outside from the gas outlet portion 2c.

The dust collecting electrodes 4 and the discharging electrodes 5 provided on the main body 2b of the casing 2 are alternately arranged in a direction orthogonal to the gas flow G. The electrostatic precipitator 1 shown in FIG. 1 is schematically shown, and the sizes and the number of installations of the discharge electrode 5 and the dust collection electrode 4 are not limited to the illustrated example.

The dust collecting electrode 4 and the discharging electrode 5 are separated from each other and electrically insulated from each other. The release electrode 5 is also insulated from the casing 2. The dust collecting electrode 4 is grounded, and a power supply is connected to the discharge electrode 5 (not shown). The discharge electrode 5 is located at an intermediate position between adjacent dust collecting electrodes 4.

The dust collecting pole 4 is a discrete dust collecting pole in which a plurality of pipe members 4a are arranged at predetermined intervals in the flow direction of the gas flow G. Each pipe member 4a is made of a rigid metal. Each pipe member 4a is arranged in the vertical direction (vertical direction on the paper surface) so that the axis line is orthogonal to the gas flow G. By fixing each of the pipe members 4a arranged in the gas flow G direction using a common frame, each dust collecting electrode 4 has an independent configuration.

The discharge electrode 5 is arranged so as to be sandwiched between the dust collecting electrodes 4. Each of the release electrodes 5 has a mounting base material 7 and a plurality of corona discharge portions 8. The mounting base material 7 is a rod-shaped or plate-shaped member made of a conductive material. The mounting base material 7 is arranged substantially parallel to the facing dust collecting poles 4.

The corona discharge unit 8 generates a corona discharge by applying a voltage to the discharge electrode 5. The corona discharge portion 8 is a protrusion fixed to the mounting base material 7 so as to protrude toward the facing dust collecting electrode 4, and has a tapered tip. As shown in FIG. 2, a plurality of corona discharge units 8 are arranged in a direction orthogonal to the gas flow G, that is, in a height direction. Each corona discharge unit 8 is arranged so as to be located at the center of adjacent pipe members 4a in the gas flow G direction. However, the position of the corona discharge unit 8 in the gas flow G direction is not limited.

As shown in FIG. 1, the inside of the casing 2 is formed by separating the upstream region S1 and the downstream region S2 in the gas flow G direction. That is, a region in which the dust collecting electrode 4 and the discharging electrode 5 are not provided is formed between the upstream region S1 and the downstream region S2.
The dust collecting electrode 4 and the discharging electrode 5 in the upstream region S1 and the dust collecting electrode 4 and the discharging electrode 5 in the downstream region S2 are arranged on the same straight line in the gas flow G direction. Has been done. The present invention is not limited to the fact that the dust collecting poles 4 and the discharging electrodes 5 are arranged on the same straight line as described above, and the dust collecting poles 4 and the discharging electrodes 5 in the upstream region S1 are included. On the other hand, the dust collecting electrode 4 and the discharging electrode 5 in the downstream region S2 may be arranged so as to be offset in a direction orthogonal to the gas flow G direction.

All of the corona discharge portions 8 in the upstream region S1 are attached in the same direction, that is, facing upward on the paper surface. On the other hand, all of the corona discharge portions 8 in the downstream region S2 are attached in the direction opposite to the upstream region S1, that is, in the direction on the paper surface.

A shielding plate 3a is fixed to the casing 2 at the upstream corner portion in the direction in which the corona discharge portion 8 of the upstream region S1 is directed. Further, a shielding plate 3b is fixed to the casing 2 at the upstream corner portion in the direction in which the corona discharge portion 8 of the downstream region S2 is directed.
The shielding plates 3a and 3b block the gas from flowing between the casing 2 and the dust collecting electrode 4 adjacent to the casing 2, and guide the gas to flow between the other dust collecting electrode 4 and the discharge electrode 5.
The roles of the shielding plates 3a and 3b are only auxiliary roles, and the mounting method and size thereof are not particularly limited, and the shielding plates 3a and 3b may be omitted.

Although not shown, the electrostatic precipitator 1 is provided with a hammering device for peeling off particulate matter adhering to the dust collecting electrode 4. The hammering device has a hammer, and when the hammer strikes the dust collecting electrode 4, the particulate matter adhering to the surface is peeled off and removed by vibration.
The method for removing the particulate matter from the dust collecting electrode 4 is not limited to hammering using a hammering device. For example, the particulate matter may be removed from the dust collecting electrode 4 by blowing a gas onto the particulate matter collected in the dust collecting electrode 4 or by irradiating a sound wave with a sonic horn. .. Further, the particulate matter may be removed from the dust collecting electrode 4 by cleaning with a cleaning liquid performed by a wet electrostatic precipitator.

Next, the operation of the electrostatic precipitator 1 of the present embodiment will be described.
In the electrostatic precipitator 1, by applying a voltage to the discharge electrode 5, a corona discharge is generated at the tip of the corona discharge unit 8. The particulate matter contained in the gas stream is charged by the corona discharge. According to the collection principle of the conventional electrostatic precipitator, the charged particulate matter is attracted to the dust collection electrode 4 by the Coulomb force and is collected on the dust collection electrode 4. The influence of ion wind has a large effect.

When a corona discharge is generated, negative ions are generated near the corona discharge portion 8, and the negative ions move toward the dust collecting electrode 4 by the electric field, and an ion wind is generated. The ionic wind flowing toward the dust collecting electrode 4 acts to move the particulate matter contained in the gas stream to the vicinity of the dust collecting electrode 4. As a result, the particulate matter having a small particle size and being hard to be charged can be carried into the region where the Coulomb force acts, so that the collection efficiency is improved.

A part of the ionic wind containing the particulate matter and flowing toward the dust collecting electrode 4 passes between the pipe members 4a of the dust collecting electrode 4.
In the upstream region S1, all of the corona discharge portions 8 are directed in one direction (upward in FIG. 1), so that the ion wind is directed in one direction and the gas flow is indicated by an arrow in the entire upstream region S1. As shown in FIG. 1, it faces diagonally upward.
On the other hand, in the downstream region S2, since all of the corona discharge portions 8 are directed in the opposite direction (downward in FIG. 1), the ion wind is directed in the opposite direction, and the gas flow is the entire downstream region S2. Then, as shown by the arrow, it faces diagonally downward in FIG.

According to this embodiment, the following effects are exhibited.
By providing a plurality of openings between the pipe members 4a of the dust collecting electrode 4, a part of the ion wind flowing from the discharge electrode 5 toward the dust collecting electrode 4 is allowed to escape to the back side of the dust collecting electrode 4. As a result, it is possible to suppress the flow in which the ion wind is reversed at the dust collecting electrode 4 and separated.
The discharge electrode 5 is provided with a plurality of corona discharge portions 8 projecting toward the dust collection electrode 4 of only one of the facing dust collection electrodes 4 continuously in the gas flow G direction. As a result, ion air can flow from a plurality of corona discharge units 8 continuous in the gas flow G direction toward only one of them, so that ion wind interference from adjacent corona discharge units 8 in the gas flow direction is possible. The dust collection efficiency can be improved by reducing the amount.

A plurality of dust collecting electrodes 4 and a plurality of discharging electrodes 5 are arranged alternately in a direction orthogonal to the gas flow G direction, and all of the upstream region S1 and the downstream region S2 in the gas flow G direction are arranged. The corona discharge portion 8 of the above is projected in the same direction. As a result, the ion wind is directed in a uniform direction across the plurality of dust collecting poles 4 in the entire regions S1 and S2, the interference of the ion wind is suppressed, and the dust collecting efficiency can be improved. ..

In the downstream region S2 downstream of the upstream region S1, all the corona discharge portions 8 project in the direction opposite to the corona discharge portion 8 in the upstream region S1. As a result, the dust collection efficiency can be further improved by changing the direction of the ion wind biased in one direction in the upstream region S1 to the other direction in the downstream region S2.

FIG. 3 shows a modified example of the orientation of the corona discharge unit 8. In the embodiment shown in FIG. 1, the direction of the corona discharge unit 8 is changed between the upstream region S1 and the downstream region S2, but the present invention is not limited to this. For example, as shown in FIG. 3, the corona discharge unit 8 is continuously directed in only one direction (upward in FIG. 3) over a predetermined section in the gas flow G direction (three consecutive in FIG. 3). ), And then the corona discharge unit 8 may be continuously provided in the opposite direction (downward in FIG. 3). Even with such an arrangement of the corona discharge unit 8, it is possible to suppress the interference of the ion wind due to the influence of the adjacent corona discharge unit 8, and the ions are formed in the direction intersecting the gas flow G over the plurality of dust collecting electrodes 4. The wind can flow. Therefore, as in the other modification shown in FIG. 4, two consecutive corona discharge units 8 may be alternately directed in opposite directions.

In FIG. 5, the outer shape of the cross section of the pipe member 4a of the dust collecting electrode 4 is not limited to the circular shape. For example, as shown in FIG. 5 (a), a substantially square pipe member 4b with R at the corner may be used, or as shown in FIG. 5 (b), a rectangular pipe with R at the corner. The member 4c may be used, or as shown in FIG. 5C, the channel member 4d having a substantially U-shaped concave shape may be used. That is, when a discrete dust collecting electrode 4 using a plurality of rod-shaped members is adopted, the pipe members 4a, 4b, 4c and the channel member 4d have a moment of inertia of area of a predetermined value or more so as to secure rigidity. It suffices to have a cross section.

FIG. 6 shows an example in which the concave channel member 4d shown in FIG. 5C is arranged. As shown in the figure, the corona discharge unit 8 is arranged so as to face the convex side of the channel member 4d. By arranging in this way, the ionic wind from the corona discharge portion 8 can easily escape to the back surface side of the channel member 4d. Each corona discharge unit 8 is arranged so as to be located at the center of adjacent channel members 4d in the gas flow G direction. However, the position of the corona discharge unit 8 in the gas flow G direction is not limited.

FIG. 7 shows a case where the dust collecting electrode 4 is formed of a flat plate 4e using a punching metal or the like instead of the discrete dust collecting electrode 4 using a plurality of rod-shaped members. Through holes 4e1 having substantially the same shape are uniformly formed in the flat plate 4e. The shape of the through hole 4e1 may be circular, oval or polygonal. Even with such a flat plate-shaped dust collecting electrode 4, the ion wind can be flowed in a direction orthogonal to the gas flow G direction to pass through the dust collecting electrode 4 as in the above-described embodiment.

Further, as the dust collecting electrode 4, a mesh belt may be used as shown in FIG. The mesh belt has flexibility in which fine metal wires are woven into a plane. The mesh belt is endlessly wound around a plurality of rotating members (rotational drive rollers) so that the mesh belt is appropriately moved between the gas flow path and the outside thereof. Dust adhering to the mesh belt is removed by a brush outside the gas flow path.

1 Electrostatic precipitator 2 Casing 2a Gas inlet 2b Main body 2c Gas outlet 3a, 3b Shielding plate 4 Dust collector 4a, 4b, 4c Pipe member 4d Channel member 4e Flat plate 5 Discharge electrode 7 Mounting base material 8 Corona discharge part G gas flow S1 upstream area (predetermined area)
S2 downstream area

Claims (3)

A casing having a gas inlet portion into which the gas flows in and a gas outlet portion in which the gas is discharged to the outside.
A plurality of openings are formed, and a dust collecting electrode provided in parallel along the gas flow direction of the gas flowing from the gas inlet portion to the gas outlet portion in the casing.
A discharge electrode arranged in parallel with the dust collecting electrode and
With
The plurality of dust collecting electrodes and the plurality of discharging electrodes are alternately arranged in a direction orthogonal to the gas flow direction.
The discharge electrode is an electrostatic precipitator having a plurality of corona discharge portions for corona discharge projecting toward the dust collection electrode of only one of the facing dust collection electrodes in the gas flow direction. In certain regions of the previous SL gas flow direction, all of the corona discharge unit of each of the discharge electrodes, an electric dust collector of claim 1 projecting toward the same direction. The electrostatic precipitator according to claim 2, wherein in the downstream region downstream of the predetermined region, all of the corona discharge portions of the discharge electrodes project in the other direction opposite to the one direction.

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