JPH01123647A - Controlling method for reverse ionization of electrostatic precipitator - Google Patents

Abstract

PURPOSE:To prevent an improper charging quiescent period from being continued by shortening the charging quiescent period at a prescribed time when the same charting quiescent period is continued by the arbitrarily preset times. CONSTITUTION:In an electrostatic precipitator in which a charging quiescent period such as intermittent charging or reverse ionization control charging is provided to preform intermittent charging and constant current control is performed at a charging time, when the same charging quiescent period is continued by the arbitrarily preset times, the charging quiescent period is shortened at NX1/2f sec (wherein N shows an integer, f shows frequency of an electric source). For example, in case of presetting the allowable number Ns of the same charging quiescent period to 10 and presetting N to 2, when 0.1sec charging quiescent period T1 is continued by 10 times, the period T1 is shortened at NX1/2f sec and controlled at 0.08sec and furthermore when 0.08sec charging quiescent period T2 is continued at 10 times, the period T2 is shortened and controlled at 0.06sec and thereby dust collection efficiency is prevented from being remarkably reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a control method for an electrostatic precipitator that accurately detects a reverse ionization phenomenon and achieves stabilization of constant current control.

[Conventional technology]

The dust collection efficiency of an electrostatic precipitator improves as the voltage applied between the electrodes increases. However, if this applied voltage exceeds the arc starting voltage, the area between the two electrodes will be flanched over, and the dust collection action will no longer be performed, and in the worst case, there is a risk of burning out the equipment.

Therefore, the load control of the electrostatic precipitator is mainly performed so as to continuously apply as high a voltage as possible while minimizing the number of spark occurrences.

However, for dust with extremely high electrical resistance, a corona discharge with a polarity opposite to that of the discharge electrode occurs from the collecting electrode due to dielectric breakdown of the collecting dust support layer on the collecting electrode (hereinafter referred to as reverse ionization). (referred to as a phenomenon). When the reverse ionization phenomenon occurs, only the applied current increases and the applied voltage does not increase, resulting in a significant drop in dust collection efficiency.

In order to suppress this reverse ionization phenomenon, intermittent charging is performed by providing a charging pause period, such as intermittent charging or reverse ionization control charging.

By the way, in the conventional reverse ionization detection control of an electrostatic precipitator, 2
If the bottom value 1 of the next voltage waveform falls below the reverse ionization detection level (regularly updated) several times in a row, it is determined that reverse ionization has occurred, and the charging pause period T3 is changed to T4 (Tz
<74), thereby suppressing back ionization (see Figure 2).

Conversely, if the bottom value 1 of the secondary voltage waveform exceeds the reverse ionization detection level several times in a row, it is determined that no reverse ionization has occurred and there is insufficient charging, and the charging pause period T is changed to T6. ('
rs > T6) By shortening the length, insufficient charging is prevented (see Fig. 3).

Further, if the bottom value 1 of the secondary voltage waveform does not exceed or fall below the reverse ionization detection level several times in a row, the same charging suspension period T is executed (see FIG. 4).

Details of the above can be found in, for example, Japanese Patent Application Laid-Open No. 146746/1983.

[Problem that the invention seeks to solve]

However, in the conventional reverse ionization control method, the reverse ionization phenomenon is continuously detected, and the load body suspension period may become long.

Once the charging pause period becomes longer, most of the charge stored in the capacitance of the electrostatic precipitator is discharged, so the charging current during recharging increases.

Electrostatic precipitators generally perform constant current control, and when performing constant current control, it is necessary to correct the charging current. Due to this correction control (see Fig. 6), the secondary voltage output during the charge output period becomes irregular, and the second half of each charge output period becomes irregular.
The next voltage output becomes smaller (see Figure 5). When the secondary voltage output becomes small, the bottom value 1 of the secondary voltage waveform becomes close to the reverse ionization detection level, which is related to the reverse ionization phenomenon, and the charging pause period T8 is not updated even though it is inappropriate.

This invention was created to solve the above problems, and is a reverse ionization control method for an electrostatic precipitator that can prevent M1 consecutive inappropriate charging pause periods in an electrostatic precipitator that performs constant current control. The purpose is to provide

[Means for solving problems]

The reverse ionization control method of the present invention is applicable to an electrostatic precipitator that performs intermittent charging with a charging pause period such as intermittent charging or reverse ionization control charging, and performs constant current control during charging. If the pause period continues an arbitrarily set number of times, the charging pause period is set to a predetermined time, for example, N.
It is characterized by reducing the time by x%f seconds (N is an integer, f is the power supply frequency).

〔Example〕

The present invention will be explained below based on examples shown in drawings (graphs).

FIG. 1 shows an example of intermittent charging of an electrostatic precipitator using the reverse ionization control method of the present invention, where the vertical axis shows the secondary voltage output value and the horizontal axis shows time.

This invention provides an electrostatic precipitator that performs intermittent charging with a charging pause period, and controls current during charging, and in which the charging pauses when the same charging pause period continues an arbitrarily set number of times. Set the period to Nx〃f seconds (N is an integer, f
is the power supply frequency). For example, the number of times the same charging pause period is allowed in a 50Hz power supply (arbitrary setting) N,
When N is set to 10 and N is set to 2, the charging pause period (TI)
After 10 consecutive 0.1 seconds, there is a charging rest period ('r+
) is shortened by Nx%f seconds to 0.08 seconds (T2), and if the charging pause period (Tz) of 0.08 seconds continues 10 times, the charging pause period (T2) is similarly shortened to 0.06 seconds.
Control in seconds. , [Effect of the invention] In an electrostatic precipitator that performs intermittent charging with a charging pause period and performs constant current control during charging,
If the same charging pause period continues an arbitrarily set number of times, by shortening the charging pause period by NxV2f seconds (N is an integer, f is the power frequency), it is possible to reliably prevent an inappropriate charging pause period from continuing. , it is possible to prevent a significant decrease in dust collection efficiency.

[Brief explanation of the drawing]

Figure 1 is a secondary voltage waveform diagram showing an example of intermittent charging of an electrostatic precipitator using the reverse ionization control method of the present invention;
Figures 2 to 6 show conventional examples, and Figures 2 to 5 show 2
The next voltage waveform diagram and FIG. 6 are current waveform diagrams. 1... Bottom value of secondary voltage waveform, T + ,
T z , T 3 , T 4 , T s , T ?
, T e... Charging pause period, N... Integer (arbitrary setting), f... Power supply frequency, N5...
...Permissible number of times of the same charging pause period (arbitrary setting).

Claims (1)

[Claims] In an electrostatic precipitator that performs intermittent charging with a charging pause period and performs constant current control during charging, when the same charging pause period occurs consecutively an arbitrarily set number of times. A reverse ionization control method for an electrostatic precipitator, characterized by shortening a charging pause period by a predetermined period of time.