JP3465234B2 - Ionization section of electric dust collector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric dust collector, and more particularly to an improvement in a discharge electrode in an ion part. 2. Description of the Related Art An electrostatic precipitator includes an ionizing section for generating corona discharge between a discharge electrode and a counter electrode, and a dust collecting section for collecting the charged dust. FIG. 10 is a perspective view showing an ionization section of a conventional dust collector disclosed in, for example, Japanese Patent Application Laid-Open No. 5-184969. In the figure, 21 is a discharge electrode and 22 is a counter electrode. The discharge electrode 1 is a metal plate in which a plurality of projections 21a are stamped and formed at both ends in the longitudinal direction at a predetermined interval.
1 is arranged so that its plate surface is orthogonal to the flow direction of the wind, and is configured such that the plurality of protrusions 21 a face the counter electrode 2. As described above, since the discharge electrodes 21 are arranged so as to be orthogonal to the flow direction of the wind, the plurality of discharge electrodes 21 can be integrally formed by stamping from one metal plate, and the plate thickness can be reduced. Can be. [0003] Because of the configuration described above, FIG.
As shown in the figure, the distance between the discharge electrode 21 and the counter electrode 2 is always kept constant even if the discharge electrode 21 is warped, stable discharge is performed, and the discharge electrode 21 has a thin slope. Therefore, the concentration of charges on the tip of the discharge electrode 21 increases, and the dust collection efficiency can be improved. [0004] Since the corona current greatly depends on the shape of the electrodes, the distance between the electrodes, and the like, the shape of the discharge electrode and the counter electrode must be appropriately adjusted in order to apply a large ion current at a constant voltage. Need to be In the ionization section of the above-mentioned conventional electric precipitator, the particles containing the dust particles are charged by the passage of the air containing the dust particles through the place where the corona current flows (the location indicated by the dotted line in the figure). 2
1a, a corona current flows from the tip of the discharge electrode 21a.
Is orthogonal to the air flow, particles passing between the protrusions 21a (locations other than the dotted lines in the figure) pass without being charged, and there is a problem that the dust collection efficiency is reduced. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. By optimizing the shape of the electrodes and the distance between the electrodes, a high and stable corona current at a constant voltage and a high particle charge can be obtained. To obtain a high dust collection rate due to efficiency, to obtain energy saving, and to obtain an ionization unit of an electric precipitator that can obtain quietness (sound is generated by current pulsation) by stable corona current without pulsation. With the goal. The ionization section of the electric precipitator according to the present invention charges dust by corona discharge generated between a flat counter electrode and a discharge electrode along an air flow. In the ionization section of an electric dust collector that collects dust
L-shaped bending at the upstream end of the air flow of the discharge electrode
And a plurality of protrusions are provided along the air flow on the downstream side of the air flow, and when the distance between the protrusions is P and the distance between the opposing electrodes is D, D / 5 ≦ P ≦ D is satisfied. When the distance between the upstream end of the air flow of the counter electrode and the tip of the protrusion is A, and the width of the counter electrode in the air flow direction is B, -2B / 3 ≦ A ≦ 0 is satisfied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a cross-sectional configuration diagram showing a schematic configuration of a general two-stage charged dust collector, FIG. 2 is a perspective view of a main part of an ionization unit according to the first embodiment, FIG. 3 is an electrode detailed view of the ionization unit, and FIG. FIG. 5 is a graph showing the relationship between the applied voltage and the discharge current, and FIG. 6 is a graph showing the relationship between the applied voltage and the discharge current when the pitch between the discharge electrodes is changed. As shown in FIG. 1, the electrostatic precipitator includes an ionization unit 1 for charging dust flowing in by corona discharge, and a collector unit 2 for adsorbing the charged dust to a ground electrode by Coulomb force. Collector part 2
Has a plurality of plate-like high voltage electrodes 5 and a dust collecting electrode plate 6 grounded alternately arranged in parallel. A DC power source 7 supplies a voltage of several kV between the counter electrode 3 and the discharge electrode 4 of the ionization unit 1.
To several KV. In FIG. 2, the ionization section 1 comprises a plurality of counter electrodes 3 arranged in parallel with each other and grounded, a casing 3a for supporting the counter electrodes 3, and a discharge electrode 4 disposed therebetween. 4a is a projection, 4b is a bent portion having an L-shaped cross section, 11 is a spacer made of an insulating member such as an insulator, and is a spacer which is electrically insulated from the counter electrode 3 to keep an interval. Is attached by screws 12 or the like via a spacer 11. FIG. 3A is a sectional view of the discharge electrode 4 and the counter electrode 3 in the ionization section 1, and FIG. 3B is a side view of the discharge electrode 4 and the counter electrode 3 in the ionization section. In the figure, A is the tip of the projection 4a of the discharge electrode 4 and the counter electrode 3
B is the width of the counter electrode 3 in the air flow direction, P is the interval (pitch) between the protrusions 4a of the discharge electrode 4, and D is the distance between the counter electrodes 3. The distance A is defined as positive (0) in the airflow upstream direction and negative in the downstream direction, with the air inlet end of the counter electrode 3 as the reference (0). Since the corona current greatly depends on the shape of the electrodes, the distance between the electrodes, and the like, the relationship between the applied voltage between the discharge electrode 4 and the counter electrode 3 and the corona current is examined by changing the distance P between the protrusions 4a of the discharge electrode 4. The results obtained will be described below. As an example, B = 18 mm, D = 25 mm
The interval (pitch) P between the protrusions 4a of the discharge electrode 4 is
Experiments were conducted on the state of the corona current when the applied voltage was 4 to 9 KV for three types of D / 5 ≦ P ≦ D, D / 5> P and P> D. The results are shown in FIGS. FIG.
4A is a cross-sectional view showing a state of a corona current flowing between the discharge electrode 4 and the counter electrode 3, FIG. 4B is a side view showing a state of a corona current flowing between the discharge electrode 4 and the counter electrode 3, and FIG. (C) is a bottom view of the state of the corona current flowing between the discharge electrode 4 and the counter electrode 3 as viewed from the downstream of the airflow. As can be seen from FIGS. 4B and 4C, P
In the case of> D, the density of the corona current is low with respect to the air flow path, and there are many portions where dust passes without being charged. D / 5
If> P, corona currents interfere with each other. D / 5 ≦ P ≦
In the case of D, the density of the corona current is high, the corona current does not interfere, and the state is good. In the case of D / 5> P, the corona currents interfere with each other. FIG. 5 shows the result of measuring the state of change of the corona current at this time. FIG. 5A is a diagram showing the state of the applied voltage and the corona current when D / 5 ≦ P ≦ D, and FIG.
It is a figure showing the case of 5> P. As can be seen from the figure, D
When / 5> P, pulsation occurs in the corona current, but D / 5
When ≤P≤D, the corona current is stable without pulsation. FIG. 6 shows VI characteristics summarizing the above results. As can be seen from the figure, the corona current for the same applied voltage is D / 5 ≦ P when the applied voltage is 4 to 5.5 KV.
≦ D (solid circle) and P> D (solid square) have the same corona current, but are higher than D / 5> P (x mark), and the applied voltage is 5.
For 5 to 8.5 KV, D / 5 ≦ P ≦ D (black circle), P> D
(Black squares), D / 5> P (marked by X), and the corona current for the same applied voltage was highest when D / 5 ≦ P ≦ D. As described above, in the case of D / 5> P, the pitch is narrow and the corona currents flowing from the projections interfere with each other, so that the current is pulsated and becomes unstable, and the current value decreases. As a result, the charging efficiency is reduced and the dust collection efficiency is reduced. In addition, pulsation generates shoe noise, and the amount of generated ozone tends to increase. Also, P
In the case of> D, the pitch is wide and the corona current density is low, so that the corona current decreases and the charging efficiency decreases, so that the dust collection efficiency decreases. However, when D / 5 ≦ P ≦ D, the corona current is high, the corona current is stable without pulsation, the charging efficiency is increased, and the dust collection rate is increased. In addition, it was confirmed that the relationship between P and D was the same as that described above even with dimensions other than the example of B = 18 and D = 25 mm. As described above, the distance between the protrusions of the discharge electrode is D
By setting / 5 ≦ P ≦ D, the corona current can be increased and stabilized at a constant voltage, and the charging efficiency can be increased.
Therefore, the dust collection rate can be increased. Further, since the voltage for obtaining the predetermined current can be reduced, energy can be saved, and furthermore, there is no pulsation, no sound is generated, and noise can be reduced. In addition, since the air inlet end of the discharge electrode is formed as an L-shaped bent portion, the discharge electrode does not warp, and the distance between the discharge electrode and the counter electrode can be kept constant. Furthermore, as can be seen from the current density distribution (FIG. 4), arranging the protrusions horizontally makes it possible to reduce the sparse portion of the current density by the length of the protrusions, rather than arranging them vertically. it can. Embodiment 2 FIG. In the present embodiment, the protrusion 4a
The relationship between the applied voltage between the discharge electrode 4 and the counter electrode 3 and the corona current was obtained by experiment to find the appropriate range of A by changing the distance A between the tip of the electrode and the upper end of the air flow of the counter electrode 3. is there. FIG. 7 is a detailed view of the electrodes of the ionization unit of the electrostatic precipitator according to the second embodiment, FIG. 8 is a diagram showing the discharge state of the ionization unit, and FIG. FIG. 9 is a characteristic diagram of an applied voltage and a discharge current when a distance A to an end is changed. For example, B = 18 mm, D = 25 mm, P
= 8, the tip of the projection 4a of the discharge electrode 4 and the counter electrode 3
The distance A from the upstream end of the airflow is −2B / 3 ≦ A ≦
For three types of 0, A> 0 and -2B / 3> A, the state of the corona current when the applied voltage was 4 to 10 KV was tested. The results are shown in FIGS. FIG. 8 (a)
Discharge electrode 4 and counter electrode 3 when −2B / 3 ≦ A ≦ 0
FIG. 9B is a cross-sectional view showing a state of a corona current flowing therebetween.
FIG. 8C is a cross-sectional view showing the state of the corona current flowing between the discharge electrode 4 and the counter electrode 3 when A> 0, and FIG.
FIG. 4 is a cross-sectional view of a state of a corona current flowing between the discharge electrode 4 and the counter electrode 3 when 3> A. In the figure, the air upstream direction is positive and the downstream direction is negative with reference to the air inlet side end of the counter electrode 3. As can be seen from the figure, FIG.
In the case of 2B / 3> A, the ion current from the tip of the projection 4a generates a component directed to the counter electrode 3 in the direction of the airflow by about 45 degrees due to the corner curvature of the tip. If it enters the inside of the counter electrode 3 too much, the current decreases. Further, since the collector portion 2 is located downstream, the current flows into the dust collecting electrode plate 6 of the collector portion 2 and the current as the ionization portion 1 decreases. When A> 0 shown in FIG. 8B,
The current decreases as A increases. FIG. 8 (a)
In the case of −2B / 3 ≦ A ≦ 0, the density of the corona current distribution is high and the state is good. Next, B = 18 mm, D = 25 mm, P =
As 8, -2B / 3 ≦ A ≦ 0, A> 0, A = 0 and −
The relationship between the applied voltage and the corona current was tested for four types of 2B / 3> A. The result is shown in FIG. As can be seen, the corona current for the same applied voltage is -2B
/ 3 ≦ A ≦ 0 (black circle), A = 0A (triangle), −2B / 3
> A (square black), A> 0 (rhombic black).
Thus, the corona current for the same applied voltage is −
The case where 2B / 3 ≦ A ≦ 0 is the highest, and since the charging efficiency is high, the dust collection efficiency is the highest. As described above, the distance A between the tip of the projection of the discharge electrode and the upstream end of the air flow of the counter electrode is set to -2B / 3 ≦
By setting A ≦ 0, the corona current can be increased and stabilized at a constant voltage, the charging efficiency can be increased, and the dust collection rate can be increased. In addition, since the voltage can be reduced, energy can be saved. As described above, in the ionization section of the electric precipitator which charges and collects dust by corona discharge generated between the flat counter electrode and the discharge electrode along the air flow. L-shaped at the upstream end of the air flow of the discharge electrode
Is provided, and a plurality of protrusions are provided along the air flow on the downstream side of the air flow. When the distance between the protrusions is P and the distance between the opposed electrodes is D, D / 5 ≦ P ≦ D is satisfied, and the distance between the upstream end of the air flow of the counter electrode and the tip of the protrusion is A, and the width of the counter electrode in the air flow direction is B, -2B / 3 ≦ A ≦
Since 0 is satisfied, the corona current is high, the corona current is stable without pulsation, the charging efficiency is increased, and the dust collection rate can be increased. In addition, since the voltage can be reduced, energy can be saved, and furthermore, there is no pulsation, no sound is generated, and noise can be reduced. Further, the discharge electrode is not warped, and the distance between the discharge electrode and the counter electrode can be kept constant. [0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional configuration diagram showing a schematic configuration of a general two-stage charged dust collector. FIG. 2 is a perspective view of a main part of an ionization unit of the electric dust collector according to Embodiment 1 of the present invention. FIG. 3 is a detailed electrode diagram of an ionization unit of the electric precipitator according to Embodiment 1 of the present invention. FIG. 4 is a diagram showing a discharge state of an ionization unit of the electric dust collector according to Embodiment 1 of the present invention. FIG. 5 is a characteristic diagram showing a relationship between an applied voltage and a discharge current of an ionization unit of the electric dust collector according to Embodiment 1 of the present invention. FIG. 6 is a characteristic diagram of an applied voltage and a discharge current of the ionization unit of the electric dust collector according to Embodiment 1 of the present invention. FIG. 7 is a detailed electrode diagram of an ionization section of the electric precipitator according to Embodiment 2 of the present invention. FIG. 8 is a diagram showing a discharge state of an ionization unit of the electric dust collector according to Embodiment 2 of the present invention. FIG. 9 is a characteristic diagram of an applied voltage and a discharge current of an ionization unit of an electric dust collector according to Embodiment 2 of the present invention. FIG. 10 is a perspective view of an ionization unit of a conventional electric dust collector. FIG. 11 is a diagram showing a discharge state of an ionization unit of a conventional electric precipitator. [Description of Signs] 1 Ionization part, 3 counter electrode, 4 discharge electrode, 4a
Projection, 4b bent part.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-310251 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B03C 3/00-3/88

Claims (1)

(1) An ionization unit of an electric precipitator for charging and collecting dust by corona discharge generated between a flat counter electrode and a discharge electrode along an air flow. An L-shaped bend at the upstream end of the air flow of the discharge electrode
And a plurality of protrusions are provided along the air flow on the downstream side of the air flow, and when the distance between the protrusions is P and the distance between the opposing electrodes is D, D / 5 ≦ P ≦ D is satisfied. When the distance between the upstream end of the air flow of the counter electrode and the tip of the protrusion is A, and the width of the counter electrode in the air flow direction is B, -2B / 3 ≦ A An ionization unit of an electric precipitator characterized by satisfying ≦ 0.