JPH067704A - Charging method of electric dust collecting apparatus - Google Patents

Abstract

PURPOSE:To improve the efficiency of collecting dust contained in dust- containing gas and the efficiency of collecting submicron particles. CONSTITUTION:Higher current density is made in the dust collecting space in the upper stream side of the dust-containing gas flow than in the dust collecting space in the down stream side by making discharge current running in a plurality of discharge lines 6A, 6B, 6C higher in this order wherein the discharge lines compose a discharge electrode 6. Consequently, since dust in the dust collecting space in the upper stream side is charged with high charge density, high Coulomb force is generated due to the electric field formed in the dust collecting space in the down stream side. As a result, dust is surely captured by the dust collecting electrode while flowing to the down stream side from the upper stream side. Specially, the efficiency of collecting submicron particles is improved by making high current density in the dust collecting space in the upper stream side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging method for an electrostatic precipitator, and relates to an electrostatic precipitator for efficiently collecting dust particles in a dust-containing gas, particularly submicron particles (particle diameter 1 μm or less). It relates to a charging method.

[0002]

2. Description of the Related Art Generally, an electrostatic precipitator collects dust from a dust-containing gas flowing into a charged dust collecting chamber by corona discharge generated between a discharge electrode and a dust collecting electrode provided in the chamber. It is electrostatically adsorbed on the pole and collected. FIG. 7 shows a schematic overall configuration of a typical flat plate type electrostatic precipitator of this type of electrostatic precipitator. In the figure, the output voltage (charging voltage V) from the DC voltage power supply device 42 that generates a high DC voltage is passed through an insulator 44 and a negative discharge electrode 46 formed of a flat plate-shaped discharge line and It is applied between the two dust collecting electrodes 48, 48 of the positive electrode, which are arranged so as to face both surfaces of the discharge electrode 46. As a result, a predetermined corona discharge occurs between the discharge electrode 46 and the dust collecting electrodes 48, 48, and the dust in the dust-containing gas flowing in from the direction shown by the arrow 50 is charged with positive and negative ions. The dust charged with negative ions is collected by the dust collecting electrodes 48, 48. Further, the dust concentration in the charged dust collecting chamber is determined by the discharge electrode 4 on the inlet side into which the dust-containing gas flows.
6 is the highest, and gradually becomes lower along the direction in which the dust-containing gas flows out.

By the way, as shown in the discharge current characteristic diagram of FIG. 8, the discharge current I of the discharge electrode 46 of such an electrostatic precipitator tends to flow more difficult as the dust concentration is higher than the charging voltage V. is there.

[0004]

However, in the electrostatic precipitator provided with the discharge electrode formed of the discharge lines having the same shape, the dust concentration at the inlet side of the charged dust collecting chamber is lower than that at the outlet side. Since it is high, the spark voltage generated between the discharge electrode on the inlet side and the dust collecting electrode is suppressed. As a result, the discharge current discharged from the discharge line on the inlet side becomes small and a large current density cannot be formed in the dust collecting space on the inlet side, so that the charging efficiency of dust in the dust-containing gas deteriorates, and There is a problem that the dust collecting performance of the dust collecting device is lowered. In particular, in the charging of submicron particles (1 μm or less), diffusion charging is predominant, so it is important to increase the current density of the dust collecting space to increase the chance of being charged.

In view of the above problems of the prior art, the present invention forms a larger current density in the dust collecting space on the upstream side of the flow of the dust-containing gas flowing into the dust collecting chamber than on the dust collecting space on the downstream side.
An object of the present invention is to provide a charging method for an electrostatic precipitator, which can improve the electrostatic collection efficiency of the electrostatic precipitator, particularly the submicron particles.

[0006]

In order to solve the above-mentioned problems, a dust-containing gas is caused to flow into a dust-collecting chamber of an electrostatic precipitator, and dust is provided from the dust-containing gas into the dust-collecting chamber. In a charging method of an electrostatic precipitator that electrostatically adsorbs and collects on a dust collecting electrode by corona discharge generated between a discharge electrode composed of a plurality of discharge lines and the dust collecting electrode, it flows into the dust collecting chamber. A discharge current larger than that of the discharge line on the downstream side is applied to the discharge line on the upstream side of the flow of the dust-containing gas, and the current density gradually decreases from the dust collection space on the upstream side to the dust collection space on the downstream side. The dust is charged with a high-density electric charge in the dust collecting space on the upstream side of the dust collecting space on the downstream side.

[0007]

According to the charging method for the electrostatic precipitator of the present invention, a discharge current larger than that of the discharge line on the downstream side is applied to the discharge line on the upstream side of the flow of the dust-containing gas flowing from the dust collecting chamber. A larger current density was formed in the dust collection space of the above than in the dust collection space on the downstream side. As a result, since it is possible to charge the dust with a high-density charge in the dust collecting space on the upstream side, the dust generates a large Coulomb force in the electric field formed in the dust collecting space of the discharge line on the downstream side, It becomes easy to be sucked into the dust collecting electrode.
Therefore, the dust can be reliably collected by the dust collecting electrode while the dust flows from the upstream side to the downstream side. In particular, by increasing the current density of the dust collecting space on the upstream side, the chance of being charged by submicron particles in which diffusion charging is dominant increases, so that a large amount of charge can be charged in a short time. Thereby, the collection efficiency of submicron particles can be improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a charging method for an electrostatic precipitator according to the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 shows a schematic overall structure of an electrostatic precipitator to which a charging method for an electrostatic precipitator according to the present invention is applied. In FIG. 1, an output voltage from a DC voltage power supply device 2 for generating a high-voltage DC voltage is shown. (Charging voltage V) is applied between the plate-shaped negative electrode discharge electrode 6 via the insulator 4 and the two positive electrode dust collecting electrodes 8 disposed opposite to both surfaces of the discharge electrode 6. Is applied.

By the way, the flat plate discharge electrode 6 of this embodiment is composed of discharge lines 6A, 6B and 6C having different core thicknesses, and these discharge lines (6A, 6B, 6).
C) is the discharge lines 6A, 6B, 6 in the order of discharge lines with a thin core wire toward the dust-containing gas flowing in from the direction shown by the arrow 10.
C is provided. That is, the discharge line 6A having the smallest electric resistance is arranged on the side where the dust-containing gas flows in, and the discharge line 6C having the largest electric resistance is arranged on the side where the dust-containing gas flows out. Each of these discharge lines 6A, 6B and 6C has a discharge current characteristic with respect to the charging voltage V shown in FIG. In the figure, the discharge line 6A is a dashed line 60A in the figure.
Discharge current characteristics of the discharge line 6B and 6C are indicated by the broken line 6
The discharge current characteristics of 0B and the solid line 60C are shown respectively. In this way, the discharge lines of the discharge electrode 6 are the discharge lines 6A, 6B, 6C.
A large discharge current flows in this order.

Next, an outline of the operation of the electrostatic precipitator constructed as described above will be described. A predetermined high voltage charging voltage V is applied between the discharge electrode 6 and the dust collecting electrodes 8, 8 from the DC voltage power supply device 2 to generate a predetermined corona discharge, that is, a negative corona. In such a state, ionization of gas molecules progresses, a large number of negative ions and positive ions are generated, the positive ions are immediately neutralized by the discharge electrode 6, and the negative ions move toward the dust collecting electrodes 8 and 8. To run. When the dust-containing gas is made to flow in from the direction indicated by the arrow 10 in the state where the ionization has progressed in this way, the dust in the dust-containing gas is instantaneously charged with positive and negative ions. Among these charged dusts, the charged dusts charged with negative ions are collected by, for example, the dust collecting electrodes 8 in a region of the discharge electrode 6 facing the discharge line 6A, and the charged dusts are charged with positive ions. The charged dust is attracted to the discharge electrode 6 side by the Coulomb force and is neutralized. The charged dust newly charged with negative ions among the neutralized dust is collected by the dust collecting electrodes 8 and 8. In this way, the discharge lines 6A, 6B and 6C of the discharge electrode 6,
The dust in the dust-containing gas passing between the dust collecting electrode 8 and the dust collecting electrode 8 is gradually collected by the dust collecting electrodes 8 and 8 every time negative ions are charged.

In the charging method for the electrostatic precipitator of the present invention, the discharge lines 6A, 6B and 6C are arranged so that a large discharge current flows in that order, so that the discharge lines 6A, 6B,
A large current density is formed in the order of the discharge lines 6A, 6B, and 6C in each dust collecting space of 6C. As described above, when the dust-containing gas is introduced from the direction shown by the arrow 10 in a state where a large current density is formed in the dust collecting space of the discharge line 6A on the upstream side, the dust in the dust-containing gas is charged with a large charge amount. Can be made. As a result, the dust charged with a large amount of charge generates a large Coulomb force in the electric field formed in the dust collecting space of the discharge lines 6B and 6C on the downstream side, and is easily attracted to the dust collecting electrode. The dust collecting electrodes 8 can be reliably collected while flowing from the upstream side to the downstream side. In particular, by increasing the current density in the dust collecting space of the discharge line 6A on the upstream side, the chance of being charged to submicron particles in which diffusion charging is dominant increases, so that a large amount of charge is charged in a short time. be able to. This allows
The collection efficiency of submicron particles can be improved.

Next, the result of comparison of the dust collection efficiency between the conventional dust collector and the dust collector to which the charging method for the dust collector of this embodiment is applied will be described with reference to FIG. In the figure, the horizontal axis represents the charging power P (charging voltage V and discharge current I).
And the vertical axis indicates the coordinate axis of the dust collection efficiency. In the conventional electrostatic precipitator, the spark voltage is suppressed by increasing the dust concentration on the inlet side of the charge precipitating chamber, and the charging power P cannot be set to, for example, the charging power P1 or higher. In the dust collector, the spark voltage is set higher than that of the conventional device, so the charging power P is
The charging power P2 can be set to a value higher than the charging power P1. As described above, the charging voltage V and the discharge current I applied between the discharge electrode and the dust collecting electrode can be set higher than those in the conventional electrostatic precipitator, so that the electric adhesive force acting on the dust layer in the dust-containing gas is reduced. Increase.

In the electrostatic precipitator to which the charging method for the electrostatic precipitator of the above-mentioned embodiment is applied, the discharge electrodes are formed by the discharge lines having different thicknesses in order to improve the collecting efficiency, but the present invention is not limited to this. For example, the discharge electrode may be formed into a rectangular discharge line as shown in FIG. 4, a discharge line with a protrusion 20 as shown in FIG. 5, or a discharge line with a needle 22 as shown in FIG. It may be formed by a discharge line. Further, the discharge electrode may be formed by combining different types of discharge lines so that the discharge current characteristics of the discharge electrode are changed.

[0014]

As described above, according to the charging method for the electrostatic precipitator according to the present invention, the discharge line on the downstream side of the discharge line on the upstream side of the flow of the dust-containing gas flowing from the dust collecting chamber. A larger discharge current was applied to form a larger current density in the upstream side dust collecting space than in the downstream side dust collecting space, and the amount of charges charged on the dust was increased in the upstream side dust collecting space. As a result, a large Coulomb force is applied to the dust in the electric field formed on the downstream side. Therefore,
While the dust flows from the upstream side to the downstream side, it is sucked into the dust collecting electrode and is reliably collected, so that the dust collecting efficiency can be improved, and particularly, the collecting efficiency of the submicron particles in the dust-containing gas. Can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a schematic overall configuration diagram of an electrostatic precipitator to which a charging method for an electrostatic precipitator according to the present invention is applied.

FIG. 2 is a characteristic diagram showing discharge current characteristics of the electrostatic precipitator shown in FIG.

FIG. 3 is a characteristic diagram showing the relationship between charging power and dust collection efficiency.

FIG. 4 is a side view showing the shape of a discharge line in another embodiment of the electrostatic precipitator to which the charging method for the electrostatic precipitator according to the present invention is applied.

FIG. 5 is a side view showing the shape of a discharge line in another embodiment of the electrostatic precipitator to which the charging method for the electrostatic precipitator according to the present invention is applied.

FIG. 6 is a side view showing the shape of a discharge wire in another embodiment of the electrostatic precipitator to which the electrostatic precipitating method according to the present invention is applied.

FIG. 7 is a configuration diagram showing a schematic overall configuration diagram of a conventional electrostatic precipitator.

8 is a characteristic diagram showing discharge current characteristics of a discharge electrode of the electrostatic precipitator shown in FIG.

[Explanation of symbols]

 2 ... DC voltage power supply device 4 ... Insulator 6 ... Discharge electrode 8 ... Dust collecting electrode

Claims (1)

[Claims] 1. A dust-collecting gas is caused to flow into a dust-collecting chamber of an electrostatic precipitator, and dust from the dust-containing gas is provided in the dust-collecting chamber. In a charging method of an electrostatic precipitator that electrostatically adsorbs and collects a dust collecting electrode by corona discharge generated between, a downstream of a discharge line on an upstream side of a flow of dust-containing gas flowing into the dust collecting chamber. A discharge current larger than that of the discharge line on the side to form a gradually smaller current density from the dust collection space on the upstream side to the dust collection space on the downstream side, and the dust collection on the upstream side of the dust collection space on the downstream side. A method for charging an electrostatic precipitator, characterized in that dust is charged with a high-density charge in a space.