JPS63267456A - Electric dust-collector - Google Patents

Abstract

PURPOSE:To prevent deterioration of dust collection efficiency by comparing a detection value of charging voltage with a set value of starting voltage for corona discharge, and automatically applying DC high voltage between a discharging electrode and a dust collection electrode intermittently or continuously in accordance with the comparison result. CONSTITUTION:A charging voltage from a power supply circuit 4 to be applied between a discharging electrode 10 and a dust collection electrode 12 is detected by a charging voltage detector 22. Then this detected value and the set value of a starting voltage for corona discharge which is set beforehand by a corona starting voltage setting device 24 are compared with a comparator 26 to detect the generation of deionization. A power supply means is controlled by a charging system selector 28 which operates based on the comparison results of the comparator 26. When the deionization does not generate, DC high voltage is continuously applied between the electrodes 10, 14, while the DC high voltage is intermittently applied between the electrodes 10, 14, when the deionization generates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic precipitator, and more particularly to an electrostatic precipitator that is capable of collecting high-resistance dust.

[Conventional technology]

Generally, in electrostatic precipitators, it is known that when the electrical resistance of dust increases, abnormal discharge called a reverse ionization phenomenon occurs, significantly reducing dust collection performance. This is because when the charged dust adhering to the collecting rM electrode plate in the dust collecting chamber has a high resistance, electrical dielectric breakdown occurs in the dust layer due to poor charge release from the dust layer, and ions generated by this dielectric breakdown This neutralizes the electric charge in the dust collection space.

One of the measures to suppress the occurrence of this reverse ionization phenomenon is a method of intermittently applying a charging voltage between the discharge electrode and the dust collection electrode (hereinafter abbreviated as an intermittent charging method). This is intended to alleviate the decline in blood collection performance.

By the way, the electrical equivalent circuit of an electrostatic precipitator is represented by a parallel circuit of a capacitor C and a resistor R, as shown in FIG.

Here, the capacitor C corresponds to the capacitance between the discharge electrode and the dust collection electrode of the dust collection chamber, and the resistance R corresponds to the discharge resistance between the electrodes. For this reason, the discharge time constant (CXR) becomes small. Therefore, when a charging voltage is intermittently applied between the discharge electrode and the dust collection electrode, if no reverse ionization phenomenon occurs, the charging voltage changes as shown by the solid line 40 in FIG. A large constant discharge occurs. On the other hand, when a reverse ionization phenomenon occurs, the time constant of the circuit becomes small, so that the corona starting voltage is lowered when charging is stopped, as shown by the broken line 42 in FIG. It is known that as a result, the dust collection performance decreases at a rate approximately commensurate with the time during which the load 2g pressure is not applied, that is, the charging pause time. For this reason, considering that the electrical resistance of dust changes greatly depending on the temperature of the exhaust gas being processed, the amount of moisture in the gas, the components of the dust, etc., we can monitor the occurrence of reverse ionization phenomena associated with changes in the electrical resistance of dust in real time. It is necessary to detect and select an optimal charging method for the device, that is, to switch between a continuous charging method in which a charging voltage is continuously applied and an intermittent charging method.

Therefore, conventionally, as shown in the charging voltage waveform shown in FIG. 4, the bottom value of the charging voltage when the reverse ionization phenomenon shown by the solid line 44 does not occur and the bottom value of the charging voltage when the reverse ionization phenomenon shown by the broken line 46 has occurred. It has been proposed to focus on the fact that there is a difference in the bottom value of the charging voltage, determine the presence or absence of reverse ionization from this bottom value, and automatically select the charging method.

However, although the presence or absence of back ionization in a device operating with a continuous charging method can be detected from the bottom value of the charging voltage, it is possible to detect the occurrence of back ionization in a device operating with an intermittent charging method. There is a problem in that detection accuracy is poor because the bottom value of the charging voltage decreases only by a small amount due to the effect of suppressing reverse ionization due to charging. For this reason, in devices operating in an intermittent charging mode, it is not possible to appropriately switch from intermittent charging to continuous charging in order to prevent blood collection performance from deteriorating when the reverse ionization phenomenon stops occurring. There is a problem.

The present invention has been made in view of the above circumstances, and it is possible to detect the occurrence of reverse ionization phenomenon with high accuracy even during operation using the intermittent charging method, and when the occurrence of the reverse ionization phenomenon has stopped, the intermittent charging method can be stopped. The object of the present invention is to provide an electrostatic precipitator having a function of automatically switching to continuous charging mode operation.

[Means for solving problems]

In order to achieve the above object, the present invention applies a DC high voltage between a discharge electrode and a dust collection electrode provided in a dust collection chamber to generate a corona discharge, and collects electricity by the corona discharge. In the dust collector, corona start voltage setting means sets a starting voltage of corona discharge generated between the electrodes, power supply means outputs a DC high voltage applied between the electrodes, and detects the voltage between the electrodes. voltage detection means;
a comparison means for comparing a detection value of the voltage detection means with a set value of the starting voltage of the corona discharge, and a comparison signal which receives a comparison signal from the comparison means and determines that the detection value of the voltage detection means is the corona start voltage setting; If the detected value of the voltage detecting means is higher than the set value of the voltage detecting means, the power supply means is controlled so that the DC high voltage is continuously output from the power supply means, and the comparison signal indicates that the detected value of the voltage detecting means is the corona starting voltage. and a selection means for controlling the power supply means so that the DC high voltage is intermittently outputted from the power supply means when the voltage is lower than the set value of the setting means. ing.

[Effect]

The present invention detects a direct current high voltage from a power supply means applied between a discharge electrode and a collecting electrode by a voltage detection means, and detects a corona discharge voltage set in advance in a corona start voltage setting means. The occurrence of reverse ionization is detected by comparing the starting voltage with the set value of the starting voltage by the comparing means. The power supply means is controlled by the selection means operated based on the comparison result of the comparison means so that when no reverse ionization occurs, a DC high voltage is continuously applied between the electrodes; When reverse ionization occurs, a high DC voltage is intermittently applied between the electrodes. In this way, by automatically causing corona discharge continuously or intermittently depending on whether or not reverse ionization occurs, it is possible to prevent blood collection performance from deteriorating.

〔Example〕

Hereinafter, preferred embodiments of the electrostatic precipitator according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows the basic configuration of an electrostatic precipitator according to the present invention. 8, and a collecting chamber 1 in which a discharge electrode 10 and a blood collecting bridge 12 are provided.
It is composed of 4.

The power supply circuit 4 of the charge control device 8 includes a power control element 16 such as Cyrisk that controls the phase of the AC voltage from the AC power supply 2;
A transformer 1 that boosts the AC voltage from the power control element 16
8, and a rectifier 20 that rectifies the AC high voltage from the transformer 18 into a DC high voltage (charged voltage).

The DC high voltage from the rectifier 20 is applied to the discharge electrode 1 of the dust collection chamber 14.
0 and the blood collection electrode 12.

The power control element 16 outputs an alternating current voltage when an output signal from an intermittent charging signal generator 30 (described later) is input manually;
It is configured not to output AC voltage when no input is received. Incidentally, the power control element 16 is controlled to start by a drive circuit (not shown).

On the other hand, the control circuit 6 of the charge control device 8 includes a charge voltage detector 22 that detects the charge voltage applied between the discharge electrode 10 and the dust collection electrode 12 of the collection chamber 14, and a charge voltage detector 22 that detects the start voltage of corona discharge. The corona start voltage setter 24 to be set, the comparator 26 that compares the levels of the signals from the charging voltage detector 22 and the corona start voltage setter 24, and the power control element 16 of the power supply circuit 4 are turned on and off. It is comprised of an intermittent charging signal generator 30 that outputs a control signal, and a charging method switch 28 that controls supply of the output signal from the intermittent charging signal generator 30 to the power control element 16.

The charging voltage detector 22 consists of two resistors 32 and 34, whereby a detection signal representing the charging voltage divided by the resistors 32 and 34 is input to the comparator 26.

The comparator 26 compares the level of the detection signal from the charging voltage detector 22 and the output signal from the corona start voltage setter 24 set to a signal level corresponding to the start voltage of corona discharge, and inverts the detection signal in the dust collection chamber 14. This is a circuit for checking whether ionization is occurring. If reverse ionization occurs in the collection chamber 14 and the detected value of the charging voltage detector 22 is lower than the set value of the corona start voltage setter 24, no signal is output from the comparator 26 to the charging method switch 28. It has become. On the other hand, the occurrence of reverse ionization has stopped in the dust collection chamber 14, and the detected value of the charging voltage detector 22 has changed to the corona start voltage setting device 2.
When the value becomes higher than the set value of 4, a signal is output from the comparator 26 to the charging method switch 28.

The charging method switch 28 includes a switch 8w1 and the like that is turned on and off based on the output signal from the comparator 26. The switch sw1 is closed when the output signal from the comparator 26 is not input, so that the output signal from the intermittent charging signal generator 24 is inputted to the power control element 16, and the output signal from the comparator 26 is inputted. When inputted, it becomes an open state and cuts off the output signal from the intermittent charging signal generator 24.

The intermittent charging signal generator 30 outputs, for example, a constant cycle drive signal for operating the power control element 16 intermittently. As a result, a charging voltage is intermittently applied between the discharge electrode 10 and the dust collection electrode 12 in the dust collection chamber 14, thereby suppressing the reverse ionization phenomenon.

Next, the operation of the electrostatic precipitator constructed as described above will be described.

After the device is started, for example, by a continuous charging method, the power control element 16 is controlled to start based on a control signal from a drive circuit (not shown), and accordingly, the power supply voltage from the AC power supply 2 is phase-controlled and The voltage is stepped up by a transformer 18 and rectified by a rectifier 20, and the discharge electrode 10 and the dust collection electrode 12 are
is applied between the electrodes. The charging voltage applied between the electrodes 10.12 is constantly detected by a charging voltage detector 22, which supplies a signal corresponding to the charging voltage to the comparator 20. Therefore, if it is detected that reverse ionization has occurred based on the level comparison result between the output signal from the charging voltage detector 22 and the output signal from the corona start voltage setting device 24, the comparator 22 determines whether the charging method The charging method switch 28 is controlled to switch from the continuous charging method to the intermittent charging method. That is, comparator 2
The output signal from 6 is no longer input to the charging method switch 28, and the switch SWI changes from the open state to the closed state. When the switch SW1 is closed, a drive signal is supplied from the intermittent charging signal generator 30 to the power control element 16. As a result, a charging voltage is intermittently applied from the power supply circuit 4 between the discharge electrode 10 and the dust collection electrode.

On the other hand, when it is detected that the generation of back ionization has stopped based on the comparison result of the comparator 26, a signal is outputted from the comparator 26 to the charging method switch 28. The switch SWI is opened by the signal from the comparator 26, so that the drive signal from the intermittent charging signal generator 30 is not supplied to the power control element. As a result, the device returns from intermittent charging mode to continuous charging mode.

In this way, in the electrostatic precipitator of this embodiment, the charging voltage applied between the discharge electrode 10 and the collecting electrode 12 is detected and compared with the corona start voltage, and as a result of this comparison, the charging voltage is If the charging voltage is lower than the corona starting voltage, it is determined that reverse ionization has occurred, and the system is operated in an intermittent charging method to suppress reverse ionization, and if the charging voltage is higher than the corona starting voltage, no reverse ionization has occurred. It is determined that the battery is configured to operate in a continuous charging mode. As a result, when the generation of back ionization stops during operation with the intermittent charging method, the intermittent charging method automatically switches to the continuous charging method, so even if the generation of back ionization has stopped, the operation with the intermittent charging method will continue. Dust collection performance will not deteriorate due to continued use.

〔Effect of the invention〕

As explained above, according to the electrostatic precipitator according to the present invention, the detected value of the charging voltage and the set value of the starting voltage of corona discharge are compared, and the discharge electrode and the dust collecting electrode are adjusted according to the comparison result. Since the structure was configured so that high DC voltage was automatically applied intermittently or continuously between the electrodes, the occurrence of back ionization was stopped during operation with DC voltage being applied intermittently between the electrodes. At this time, the DC high voltage is automatically switched from an intermittent application method to a continuous application method, which prevents the dust collection performance from deteriorating.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the overall configuration of an electrostatic precipitator according to the present invention, Fig. 2 is an electric circuit diagram showing an electrical equivalent circuit of a basic electrostatic precipitator, and Figs. 3 and 4 are FIG. 3 is an explanatory diagram showing an example of a voltage waveform of a charging voltage. 2... AC power supply, 10... discharge electrode, 12...
- Dust collection electrode, 16... Power control element, 18.
...Transformer, 20...Rectifier, 22...Charging voltage detector, 24...Corona start voltage setting device, 26
...Comparator, 28...Charging method switching device, 30.
...Intermittent charging signal generator. Applicant: Hitachi Plant Construction Co., Ltd. 2. Interchangeable T system 10..Discharge electrode 12-response, waist pole 161L
Force control cable ÷ old transformer 20
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24-FOIMON LIEL! &2! ! 26 Comparison 8 28 Book T7 Type Shilto Protector 30 - Missing Charged Signal Helmet Generator Diagram 2

Claims (1)

[Scope of Claims] An electrostatic precipitator in which a DC high voltage is applied between a discharge electrode and a dust collection electrode provided in a dust collection chamber to generate corona discharge, and dust collection is performed by the corona discharge, corona start voltage setting means for setting the start voltage of corona discharge generated between the electrodes; power supply means for outputting a DC high voltage applied between the electrodes; voltage detection means for detecting the voltage between the electrodes; Comparing means for comparing the set value of the starting voltage of the corona discharge with the detected value of the voltage detecting means; and a comparison signal that receives a comparison signal from the comparing means and determines that the detected value of the voltage detecting means is the corona starting voltage setting. If the detected value of the voltage detecting means is higher than the set value of the voltage detecting means, the power supply means is controlled so that the DC high voltage is continuously output from the power supply means, and the comparison signal indicates that the detected value of the voltage detecting means is the corona starting voltage. and a selection means for controlling the power supply means so that the DC high voltage is intermittently outputted from the power supply means when the voltage is lower than the set value of the setting means. Electrostatic precipitator.