JPH0671196A - Method for application of pulse voltage in electric dust collector - Google Patents

Abstract

PURPOSE:To provide a method for application of pulse voltage in an electric dust collector capable of maintaining high dust collecting performance to collect the dusts having a high electrical resistivity without causing the occurrence of back discharge phenomenon. CONSTITUTION:DC voltage VD is set at a value slightly below corona discharge initiating voltage Vc and then overlapped by pulse voltage Vp. The pulse voltage Vp is applied with a predetermined period of application time tp and non- application time ts and is so controlled as to be intermittently applied to the discharge electrode only during the application time tp. The number of repeated application (pulse train) of the pulse voltage Vp during the application time tp is controlled so as to be the number necessary to obtain the discharge current required for dust collection. Upon intermittent application of the pulse train, therefore, the back discharge phenomenon likely to occur during the application is eliminated during the non-application time ts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a pulse voltage to an electrostatic precipitator, and more particularly to a method for applying a pulse voltage to an electrostatic precipitator for collecting high electric resistivity dust.

[0002]

2. Description of the Related Art If high electric resistivity dust is collected by an electrostatic precipitator, a reverse ionization phenomenon may occur and the dust collecting performance may be deteriorated. The reverse ionization phenomenon is a voltage drop due to the discharge current flowing into the dust layer collected and accumulated at the dust collecting electrode exceeds the breakdown voltage of the dust layer, and the ions ionized in the dust layer collect dust. It is a phenomenon that is released into space.

In order to prevent such a reverse ionization phenomenon, for example, it is necessary to reduce the discharge current or make the distribution of the discharge current flowing into the surface of the dust collecting electrode uniform. as to the discharge electrode of the electrostatic precipitator conventionally, there is a method of continuously applied DC high voltage pulse waveform obtained by superposing a high-pressure pulse voltage V _P to the DC voltage V _D shown in FIG. This method utilizes the characteristic that uniform discharge occurs when the DC high voltage is applied to the discharge electrode. The DC voltage V _D is set to be slightly higher than the corona discharge starting voltage V _C.

[0004]

However, in the conventional pulse voltage application method for the electrostatic precipitator, even if a slight DC discharge current flows when the electric resistivity of the dust exceeds 5 × 10 ¹³ Ω · cm. There is a drawback that a reverse ionization phenomenon occurs. Therefore, as a means to eliminate such problems,
A method has been proposed in which the voltage applied to the discharge electrode is set to be equal to or lower than the corona discharge, and the corona discharge is discharged from the discharge electrode only at the moment when the pulse voltage is applied. ), The supply amount of ions is insufficient, and the discharge current distribution becomes non-uniform when the pulse repetition rate is set to 1000 p / s in order to satisfy the supply amount of ions, so that the reverse ionization phenomenon is likely to occur. There are drawbacks.

The present invention has been made in view of the above circumstances and provides an air precipitator capable of collecting high electric resistivity dust while maintaining high dust collection performance without causing a reverse ionization phenomenon. An object is to provide a pulse voltage application method.

[0006]

In order to achieve the above-mentioned object, the present invention applies a high DC voltage obtained by superimposing a high voltage pulse voltage to a DC voltage to the discharge electrode of an electrostatic precipitator,
In a method of applying a pulse voltage to an electrostatic precipitator in which dust is collected by a dust collecting electrode of the electrostatic precipitator, a pulse train in which the pulse voltage is controlled to have a predetermined number of repetitions is interrupted at a predetermined cycle And is applied to the discharge electrode.

[0007]

The feature of the present invention is that the reverse ionization which is attempted to occur during the application of the pulse train is performed by intermittently applying the pulse train in which the pulse voltage is controlled to the predetermined number of repetitions in the predetermined cycle to the discharge electrode. The phenomenon is to be extinguished in a dwell time between pulse trains. As a result, the high electric resistivity dust can be collected while maintaining the high dust collection performance without causing the reverse ionization phenomenon.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a pulse voltage applying method for an electrostatic precipitator according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of an electrostatic precipitator 10 to which a pulse voltage applying method for an electrostatic precipitator according to the present invention is applied.

The electric dust collector 10 has a dust collecting space 12
The discharge electrode 14 and the dust collecting plate 16 are arranged in the space, and the discharge electrode 14 and the dust collecting plate 16 are arranged alternately at a predetermined interval in the depth direction in the drawing. A pulse voltage generator 20 and a DC high voltage power source 2 are connected to the discharge electrode 14 via a support insulator 18.
And 2 are connected. In addition, the pulse voltage generator 2
0 and the DC high-voltage power supply 22 are controlled by the control unit 24 so that the applied voltage waveform shown in FIG. 2 is applied to the discharge electrode 14. That is, the control unit 24 sets the DC voltage V _D from the DC high-voltage power supply 22 to be slightly lower than the corona discharge start voltage V _C , and the pulse voltage generation unit 2 sets the DC voltage V _D to the DC voltage V _D.
The pulse voltage V _P from 0 is controlled so as to be superposed. In addition, the control unit 24 controls the pulse voltage V _P to be intermittently applied to the discharge electrode for the application time tp at a predetermined cycle with the application time tp and the rest time ts as one cycle. The number of repetitions (pulse train) in the application time tp of V _P is controlled to be the number of repetitions necessary to obtain the discharge current necessary for collecting dust.

Therefore, according to this embodiment, the pulse voltage V _P is applied intermittently in the pulse train.
The reverse ionization phenomenon that was about to occur during application disappears during the rest time ts. As a result, the high electric resistivity dust can be collected while maintaining the high dust collection performance without causing the reverse ionization phenomenon. Next, a preferred method of operating the pulse voltage application method for the electrostatic precipitator according to the present invention will be described.

As an electrostatic precipitator, a corona discharge starting voltage V _C
When a type of 22 to 25 kW is used, the DC voltage V _D is set to 20 kW. And the pulse voltage V
_P is set to 20 to 50 kW, and the cycle of the application time tp and the rest time ts is set to 5 to 50 c / s. Further, the application time tp is set to 0.5ts <tp <3ts. This is because if the application time tp is abnormal for 3 ts, the reverse ionization phenomenon is likely to occur, and if it is 0.5 ts or less, it becomes difficult to secure the required number of pulses for obtaining the discharge current. Furthermore, the number of repetitions (pulse train) of the pulse voltage V _{P at} the application time tp is larger than in the conventional case in order to secure the required number of pulses due to the intermittent pulse train. For example, in the conventional case, 200 p / s is preferable 2-5 in the present invention
Double to 400 to 1000 p / s.

Then, the application time tp + the rest time ts is 1
Cycle to 10 c / s, application time tp to 0.05 se
When the pulse repetition rate is set to c and the pulse repetition rate is set to 600 p / s, the pulse number of the pulse train is 30 pulses. In this way, by setting the period of the pulse train and conducting an experiment to collect high electric resistivity dust, the reverse ionization phenomenon did not occur,
It was possible to collect high electrical resistivity dust while maintaining high dust collection performance.

[0013]

As described above, according to the pulse voltage application method for the electrostatic precipitator according to the present invention, the pulse train is intermittently applied to the discharge electrode of the electrostatic precipitator, and an attempt is made to occur during the application. Since the reverse ionization phenomenon is made to disappear during the rest time of the pulse train, it is possible to collect the high electrical resistivity dust while maintaining the high dust collection performance without causing the reverse ionization phenomenon.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of an electrostatic precipitator to which a pulse voltage applying method for an electrostatic precipitator according to the present invention is applied.

FIG. 2 is an explanatory view showing a pulse applied voltage set by a pulse voltage applying method for an electrostatic precipitator according to the present invention.

FIG. 3 is an explanatory diagram showing a conventional pulse applied voltage.

[Explanation of symbols]

10 ... Electrostatic precipitator 14 ... Discharge electrode 16 ... Dust collector 20 ... Pulse voltage generator 22 ... DC high-voltage power supply 24 ... Controller V _C ... Corona discharge starting voltage V _D ... DC voltage V _P ... Pulse voltage tp ... Applied Time ts ... Rest time

Claims (1)

[Claims] 1. An electric precipitator for collecting dust at a dust collecting electrode of the electric precipitator by applying a high direct current voltage obtained by superposing a high voltage pulse voltage on a direct current voltage to a discharge electrode of the electric precipitator. In the pulse voltage applying method, the pulse train in which the pulse voltage is controlled to have a predetermined number of repetitions is intermittently applied to the discharge electrode at a predetermined cycle, and the pulse is applied to the electrostatic precipitator. Voltage application method.