JPH0427908B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling corona discharge current in an electrostatic precipitator.

Electrostatic precipitators, which are generally used in air purifiers, etc., consist of a charging section and a dust collection section. After the dust in the dust-containing air is charged in the charging section, it is transferred to an electric field formed in the dust collection section. The dust is guided and collected on an electrode plate with a polarity opposite to that of the dust, and corona discharge is used to charge the dust.

In the electrostatic precipitator method, the method in which the corona discharge in the charging part and the formation of the electric field in the dust collecting part are performed using the same power source is called the single-stage charging method, and the method in which they are performed using separate power supplies is called the two-stage charging method. In this case, corona discharge is usually carried out by applying a high voltage between a discharge electrode provided in the flow path of dust-containing air and an electrode facing the discharge electrode.

The dust collection performance of an electrostatic precipitator depends not only on the structural factors of the device and the strength of the electric field in the dust collection section, but also on the amount of charge and flow velocity of the dust. Depends on concentration and corona discharge current.

Therefore, it is extremely important to control the corona discharge current in accordance with the dust concentration and flow rate in an electrostatic precipitator.

Conventionally, methods commonly used to control the discharge current in corona discharge include switching the voltage of a high-voltage power supply and changing the distance between the discharge electrode and the opposing electrode.

The method of switching the voltage of the high-voltage power supply is that in the one-stage charging method, the voltage applied to the dust collection section is also changed at the same time, so it is impossible to control only the discharge current.
In this case, a two-stage charging system with a more complex structure had to be used.

In electrostatic precipitators, local flow velocity fluctuations and dust concentration fluctuations sometimes occur in the flow path that forms the charged part, and in this case, the discharge current in each part varies depending on the flow velocity and dust concentration. If this was done by switching the voltage of the high-voltage power supply to control this, high-voltage circuits with different voltages would converge, which was very troublesome.

Furthermore, the method of controlling the discharge current by changing the distance between the discharge electrode and the counter electrode means changing the design of the charging section, which is very complicated.

The object of the present invention is to eliminate the above-mentioned drawbacks of the conventional discharge current control method, and to provide an electrostatic precipitator that can control the discharge current extremely easily without changing the voltage of the high-voltage power supply or the distance between the discharge electrode and the counter electrode. An object of the present invention is to provide a method for controlling discharge current in a device.

1, 2, and 3 are diagrams for explaining the basic principle of the present invention. Then, a needle-shaped discharge electrode 3 having a diameter smaller than the diameter of the tip surface is protruded from the tip surface of a rod-shaped second electrode 4' disposed parallel to the inner wall of the electrode 1'. ' and the discharge electrode 3 by applying a high voltage between the discharge electrode 3 and the discharge electrode 3.
It has been discovered that when a corona discharge is caused from the protruding end 6 of a needle, the discharge current I becomes smaller as the discharge needle becomes shorter, as shown in FIG. 1b.

FIG. 2a shows the device shown in FIG.
However, in this case as well, as shown in Figure 2b, the discharge current I during corona discharge is
It decreases as the length L becomes shorter.

Next, the device shown in FIG. 3a is the same as the device shown in FIG.
The protruding end 6 of the hemispherical porous plate 12 is located at the center of the hemispherical porous plate 12. In this case as well, the discharge current I changes with the length L of the discharge electrode 3, as shown in FIG. 3b. There is.

In this way, when a needle-shaped discharge electrode is caused to protrude from the tip surface of a member having a diameter larger than the diameter of the discharge electrode to cause corona discharge, the discharge current is equal to or less than the length L of the discharge electrode. It is thought that the reason why L decreases as L becomes shorter is that the steep potential gradient formed at the sharp tip of the discharge electrode becomes gentler due to the influence of the tip surface as L decreases.

The present invention has been made based on the above findings, and details thereof will now be explained based on examples.

FIG. 4a is a side cross-sectional view of an electrostatic precipitator according to an embodiment of the present invention, FIG. 4b is an enlarged cross-sectional view of the discharge element 15 in FIG. 4a, and FIG. FIG. 3 is a perspective view of the device of FIG.

In these figures, inside each of the cylindrical dust collecting electrodes 1 of a dust collecting member 13 formed by integrally molding a plurality of cylindrical dust collecting electrodes 1 forming a flow path 2 for dust-containing air, A needle-shaped discharge electrode 3 is arranged along the flow path 2, and a terminal 8 connected to the dust collection member 13 and the discharge electrode 3
When a high-voltage power source (not shown) is connected between the terminal 9 and the terminal 9, a corona discharge is generated from the protruding end 6 of the discharge electrode 3 toward the inner surface of the dust collection electrode 1.

The discharge electrode 3 is formed integrally with the tip of an electrode base 14, and a cylindrical member 5 whose tip portion has a larger diameter than the diameter of the discharge electrode 3 is slidably fitted into the electrode base 14. The discharge element 15 is formed by sliding the member 5 up and down, so that the length L of the discharge electrode 3 can be changed.

A flat permeable perforated plate 12 made of wire mesh is provided in the opening 11 on the inflow side of the dust collecting electrode 1 constituting the dust collecting member 13, and the protruding end 6 of each discharge electrode is provided with a permeable perforated plate 12. It is arranged to be located at a certain distance from 12.

Now, in these air purifiers equipped with the electrostatic precipitator of the present invention shown in FIGS. 4 and 5, the length L of the discharge electrode 3 is constant and the flow path formed in the dust collection electrode 1. If the flow velocity of the dust-containing air sent to the air filter 2 differs in proportion to the arrows shown in Figure 4, the air is not purified because the dust collection electrode in the part where the flow velocity is high is insufficient. Although the dust removal rate as a machine was low, the cylindrical member 5 was slid and the L of the part where the flow velocity was high was
When L was made larger and L was made smaller in the portion where the flow velocity was low, the dust removal rate of the air purifier was significantly improved, although the discharge voltage and total discharge current remained the same.

This is because, as explained at the beginning, the excess discharge current in the portions where the flow rate is low is suppressed, and the discharge current in the portions where the flow rate is high is increased.

FIG. 6a is a side sectional view of an electrostatic precipitator according to another embodiment of the present invention, and FIG. 6b is a perspective view of the discharge element 15.

In the dust collector of this embodiment, a dust collecting member 13 is formed by integrally molding a plurality of cylindrical dust collecting electrodes 1 forming a flow path 2 for dust-containing air. In this case, a discharge electrode 3 attached integrally to the tip of a repulsion electrode 4 is arranged along the flow path, and the diameter of the tip surface of the discharge electrode that needs to control the discharge current is A discharge element 15 is formed by fitting a disk-shaped member 5 having a diameter larger than the diameter of the discharge electrode 3 into the discharge electrode 3 at its center.

By sliding the member 5 up and down along the discharge electrode 3, the length L of the discharge electrode 3 can be changed.

A hemispherical permeable perforated plate 12 is provided at the opening on the inflow side of the dust collection electrode 1, and the protruding end 6 of each discharge electrode is positioned at the center of the hemisphere of the permeable perforated plate 12. It's summery.

Now, when operating an air purifier equipped with this electrostatic precipitator, when the disk-shaped member 5 for adjusting the discharge electrode length L was removed, it showed excellent dust removal performance, but the structure of the air purifier The dust concentration at the dust collection electrode in the upper center was high, and it was low at the periphery.

Therefore, when the disk-shaped member 5 was fitted into the discharge electrode 3 in the area where the dust concentration was low to reduce the discharge electrode length L, the total discharge current decreased, but there was no change in the dust removal rate.

This means that the discharge current in the area where the dust concentration was low was initially excessive.

Next, FIG. 7 is also a sectional view of an embodiment of the present invention, and in this figure, the cylindrical dust collecting electrode 1 of the dust collecting member 13 constituted by a plurality of cylindrical dust collecting electrodes 1 is shown. forms a flow path 2 for dust-containing air introduced from the direction of the arrow.

A needle-shaped discharge electrode 3 is arranged inside each of the cylindrical dust collecting electrodes 1 along a flow path 2, and each discharge electrode 3
is connected to the terminal 9 via the discharge electrode attachment member 16.

Each of the plurality of pipe-shaped repulsion electrodes 4 attached to the repulsion electrode mounting member 17 has a tip portion 5 having a diameter larger than the diameter of the discharge electrode 3, and the discharge electrode 3 protrudes from the center of the tip portion. By changing the gap d between the discharge electrode mounting member 16 and the repulsion electrode mounting member 17, the repulsion electrode 4 can be removed from the protruding end 6 of the discharge electrode.
The distance L to the tip of can be changed.

The repulsion electrode 4 and the discharge electrode 3 are electrically connected, and when a high voltage is applied between the terminal 8 connected to the dust collection member 13 and the terminal 9 connected to the discharge electrode mounting member 16, each discharge electrode protrudes. Corona discharge is generated from the end 6 toward the inner wall of the dust collecting electrode 1.

In this electrostatic precipitator, an insulating holding member 18 is provided between the dust collecting member 13 and the repulsion electrode mounting member 17.
By changing the height of the repulsion electrode mounting member 17 and the distance d between the repulsion electrode mounting member 17 and the discharge electrode mounting member 16, the length L of the discharge electrode 3 changes, and as explained at the beginning, discharge can be performed without changing the discharge voltage or the distance between the electrodes. As the current changes,
According to the present invention, it is possible to respond to changes in the air purifier's processing air volume and dust concentration without changing the design or converting parts.

In the present invention, the member 5 for changing the length L of the discharge electrode is not only the member 5 described in the above embodiment, but also the member 5 for changing the length L of the discharge electrode.
As shown in Figure a, a
The coil 5 may have a larger diameter than the discharge electrode 3.

When the tip of the repulsive electrode 4 is used as the member 5, the eighth
As shown in Figure b, if the repulsion electrode 4 is made hollow and the discharge electrode 3 is inserted into the hole 7 provided at its tip, the repulsion electrode 4 can also serve as the base of the discharge electrode, and in this case, after determining L, The base of the hole 7 can also be fixed by caulking or the like.

As explained above, when the present invention is used, it is possible to easily change only the discharge current under a constant discharge voltage without switching the power supply voltage or changing the distance between electrodes in corona discharge. The power source is simplified, high-voltage circuits with different voltages do not converge, and fluctuations in flow velocity and dust concentration can be accommodated without the need for complicated means such as changing the design of the discharge section.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 are diagrams for explaining the principle underlying the present invention. FIG. 4 is a sectional view of one embodiment of the present invention, and FIG. 5 is a perspective view thereof. 6a and b are a sectional view and a partial perspective view of another embodiment of the present invention, FIG. 7 is a sectional view of still another embodiment, and FIG. 8 is a partially enlarged sectional view of a discharge electrode. It is. 1... Cylindrical dust collecting electrode, 1'... Cylindrical electrode, 2...
...Flow path, 3... Needle discharge electrode, 4... Repulsion electrode,
4'... Rod-shaped second electrode, 5... Member, 6... Projecting end, 7... Hole, 8... Terminal, 9... Terminal, 10...
... Ammeter, 11 ... Opening, 12 ... Air permeable porous plate, 13 ... Dust collection member, 14 ... Electrode base, 15
...Discharge element, 16...Discharge electrode mounting member,
17... Repulsion electrode mounting member, 18... Holding member.

Claims (1)

[Claims] 1. A cylindrical dust collecting electrode 1 forming a flow path 2 for dust-containing air.
A needle-shaped discharge electrode 3 is arranged inside the flow path 2, and a high voltage is applied between the cylindrical dust-collecting electrode 1 and the discharge electrode 3 to cause a corona discharge from the protruding end 6 of the discharge electrode 3. In an electrostatic precipitator for performing this, the discharge electrode 3 is made to protrude from a member 5 whose tip surface diameter is at least larger than the diameter of the discharge electrode 3, and the distance L from the protruding end 6 of the discharge electrode 3 to the member 5 is changed. A method for controlling discharge current in an electrostatic precipitator characterized by controlling discharge current. 2. A method for controlling a discharge current in an electrostatic precipitator according to claim 1, wherein the length L of the needle discharge electrode 3 is changed in accordance with the flow velocity of the flow path 2. 3. A method for controlling a discharge current in an electrostatic precipitator according to claim 1, wherein the length L of the needle discharge electrode 3 is changed in accordance with the dust concentration in the dust-containing air flowing through the flow path 2. 4. Any one of claims 1 to 3, wherein the member 5 has a larger diameter than the discharge electrode 3 and is a tip portion of a repulsion electrode 4 disposed along the flow path 2. A method for controlling discharge current in an electrostatic precipitator.