JP3139221B2 - Power control method of electric dust collector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power control method for an electric precipitator, and more particularly to an electric power control method for applying a high voltage between a discharge electrode and a precipitating electrode provided in a dust collecting chamber of the electric precipitator. The present invention relates to a power control method for a dust collector.

[0002]

2. Description of the Related Art An electric dust collector is widely used in industry as a device for collecting dust in combustion gas discharged from various combustion furnaces for petroleum and coal. And, the dust collecting performance of the electric dust collector depends on the electric resistivity of the dust to be collected. When the electric resistivity exceeds 10 ¹² Ωcm, discharge occurs from the dust on the dust collecting electrode toward the discharge electrode. There has been a problem that the so-called reverse ionization phenomenon significantly reduces dust collection performance. As a countermeasure for this, a pulse charging method in which a pulse voltage from a pulse power supply is superimposed on a DC base voltage from a DC bias power supply has been proposed as a high-voltage power supply device for an electrostatic precipitator. With this pulse charging method, the dust collection performance during the reverse ionization phenomenon in which the electrical resistivity exceeds 10 ¹² Ωcm has been improved compared to the conventional DC charging using only a DC voltage.

[0003]

However, the conventional electric precipitator that performs pulse charging has a constant power supply applied between the discharge electrode and the precipitating electrode even during the reverse ionization phenomenon. As a result, there is a problem that efficient dust collection performance cannot be obtained during the reverse ionization phenomenon, and that there is waste in terms of power consumption.

[0004] The inventors of the present invention have obtained the following findings through various experiments. That is, even when charging is performed by the pulse charging method, as shown in FIG. 2, the dust collection performance in a normal state in which the reverse ionization phenomenon does not occur is improved with an increase in the power supplied to the electric dust collector, and the discharge is performed. When the electric current is 0.2-0.
It shows the highest dust collection performance when the supply power is 5 mA / m ² . On the other hand, the dust collection performance at the time of the reverse ionization phenomenon gradually increases with an increase in the supplied power, and thereafter decreases conversely. The maximum dust collection performance is 0.05 mA / m in discharge current.
^This is the time when the supply power is 2. For this reason, it is necessary to change the supply power supplied to the electrostatic precipitator to control the discharge current to obtain an efficient dust collection performance between the normal state and the reverse ionization phenomenon.

As shown in FIG. 3, in a normal state and a reverse ionization phenomenon, a discharge characteristic represented by an applied voltage and a discharge current applied between the discharge electrode and the dust collection electrode draws different curves, The difference between the curves can be regarded as the difference between the slopes of the discharge characteristic curves. That is, from FIG. 3, the slope at the normal time is represented by ΔI ₁ / ΔV, and the slope at the time of the reverse ionization phenomenon is Δi ₂
/ ΔV.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power control method for an electric dust collector that improves the collection performance of the electric dust collector and saves energy.

[0007]

According to the present invention, in order to achieve the above object, a high voltage of a pulse charging system in which a pulse voltage is superimposed on a DC base voltage is applied between a discharge electrode and a dust collection electrode of an electrostatic precipitator. In the power control method of the electrostatic precipitator applied to the discharge electrode, a discharge characteristic curve is obtained from an applied voltage and a discharge current applied between the discharge electrode and the dust collection electrode, and a voltage change of the applied voltage in the discharge characteristic curve is obtained. The slope of the discharge characteristic curve is calculated from the current change of the discharge current with respect to the discharge characteristic curve, and the calculated slope and the discharge characteristic curve at the time of the reverse ionization phenomenon or the non-reverse ionization phenomenon determined in advance are used as the reference of the discharge characteristic curve. It is characterized by comparing the gradient with the gradient to determine whether the gradient is during reverse ionization or non-reverse ionization, and controlling the magnitude of the discharge current based on the determined result.

[0008]

According to the present invention, even when a pulse charging method in which a pulse voltage is superimposed on a DC base voltage is employed, the dust collection of the electrostatic precipitator is performed in the normal state (when the reverse ionization phenomenon is not performed) and in the reverse ionization phenomenon. The performance varies greatly depending on the power supplied to the electrostatic precipitator, that is, the magnitude of the discharge current. This was achieved by the knowledge that the discharge characteristics represented by the applied voltage and discharge current applied between the discharge electrode and the dust collection electrode draw different curves in the normal state and in the case of the reverse ionization phenomenon. We were able to.

According to the present invention, a discharge characteristic curve is obtained from an applied voltage and a discharge current applied between the discharge electrode and the dust collection electrode, and the discharge characteristic curve with respect to a change in the applied voltage of the discharge characteristic curve. The slope of the discharge characteristic curve is calculated from the current change of the discharge current, and the slope and the reference slope of at least one of the discharge characteristic curves at the time of the reverse ionization phenomenon or the non-reverse ionization phenomenon determined in advance. In comparison, it is determined whether the inclination is a reverse ionization phenomenon or a non-reverse ionization phenomenon. The magnitude of the discharge current is controlled based on the result of the determination. For example, when the determination result is not the reverse ionization phenomenon, the discharge current is 0.2 to 0.5 mA /
m ² . If the result of the determination is a reverse ionization phenomenon, the discharge current value is controlled to be 0.05 mA / m ² .

As a result, it is possible to obtain an efficient dust collection performance according to the normal state and the reverse ionization phenomenon.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the power control method for an electric dust collector according to the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a circuit diagram showing an embodiment of a high-voltage power supply device used in the power control method for an electric dust collector according to the present invention. As shown in FIG. 1, the high-voltage power supply includes a DC base voltage generating circuit 10 for mainly generating a DC base voltage, a pulse voltage generating circuit 12 for generating a pulse voltage, and a coupling capacitor 14 for superimposing a pulse voltage on the DC base voltage. A measuring circuit 16 for sequentially measuring an applied voltage and a discharging current applied between the discharge electrode and the dust collecting electrode, obtaining a discharge characteristic curve from the measured values in the measuring circuit 16, calculating a slope thereof, and calculating the slope. It is determined whether the slope is normal or reverse ionization by comparing with a reference slope of a discharge characteristic curve obtained in a normal state (electric resistivity is smaller than 10 ¹² Ωcm, that is, when there is no reverse ionization). It comprises an arithmetic unit 17 and a gate control circuit 18 for increasing or decreasing the voltage of the DC base voltage generation circuit 10 according to an instruction from the arithmetic unit 17.

In the DC base voltage generating circuit 10, a first AC power supply 24 is connected to a primary coil side of a first transformer 28 via a first thyristor 26 to form a first AC power supply circuit. are doing. Further, a second thyristor 30 connected to the first thyristor 26 in a direction opposite to that of the first thyristor 26 is provided in parallel with the first thyristor 26. Then, the first and second thyristors 26, 30
Of the gate control circuit 18
It is connected to the. This allows the gate control circuit 18 to switch the first and second thyristors to increase or decrease the voltage of the first AC power supply circuit. A rectifier circuit is formed on the secondary coil side of the first transformer 28 by the four diode bridges 32, 32,... And the first reactor 34, and a predetermined DC base voltage is obtained. The rectifier circuit includes the current transformer 2
2, a gate control circuit 1 for controlling a discharge current value discharged between a discharge electrode (not shown) of the electrostatic precipitator 20 and the precipitating electrode.
Feedback to 8

In the pulse voltage generating circuit 12, a second AC power supply 36 is connected to a primary coil side of a second transformer 40 via a third thyristor 38 to form a second AC power supply circuit. ing. Further, the third thyristor 3
4th thyristor 4 connected in the reverse direction to 8
2 are arranged in parallel with the third thyristor 38. A pulse circuit is formed on the secondary coil side of the second transformer 40, and four diode bridges 4 are provided.
, 44, and the second reactor 46 perform a phase angle control and rectification of an AC power supply voltage, and are charged to a predetermined DC voltage. A power supply capacitor 48 and an intermediate tap between the power supply capacitor 48 and a primary coil of the pulse transformer 50 are provided. A fifth thyristor 52 disposed between the power supply capacitor 48 and the other terminal of the primary coil of the pulse transformer 50, the fifth thyristor 52 being capable of conducting in the direction of discharging the electric charge stored in the power supply capacitor 48; And a sixth thyristor 54 connected to the fifth thyristor 52 in the opposite direction of conduction.
The gate terminals 52A and 54A of the fifth and sixth thyristors 52 and 54 are connected to a second gate control circuit 56. With the circuit configuration of the pulse voltage generation circuit 12, a rectangular wave pulse voltage having an arbitrary pulse width can be obtained, and the electric charge stored in the electric precipitator 20 can be efficiently collected in the power supply capacitor 48.

The pulse voltage is superimposed on the DC base voltage and applied to the discharge electrode of the electrostatic precipitator 20 by the coupling capacitor 14 connected to the secondary coil of the pulse transformer 50. Next, the operation of the power control method for the electric precipitator of the present invention configured as described above will be described.
Note that, as described in the related art, the present invention employs a pulse charging method in which a pulse voltage is superimposed on a DC base voltage. The performance greatly differs depending on the supply power supplied to the electrostatic precipitator 20, that is, the magnitude of the discharge current. In addition, the fact that the discharge characteristic curve expressed by the applied voltage applied between the discharge electrode and the dust collection electrode and the discharge current differs between the normal state and the reverse ionization phenomenon was obtained. The operation and effect of the present invention will be described on the premise of this. As described above, the reference slope of the normal discharge characteristic curve is input to the computing unit 17 in advance. That is, the reference inclination is ΔI ₁ / ΔV shown in FIG. The discharge current in the normal state is 0.2 to 0.5 mA / m ^2.
The voltage of the DC base voltage generation circuit 10 is adjusted by the gate control circuit 18 so that

When the operation of the electric precipitator 20 is started, the pulse voltage generated by the pulse voltage generation circuit 12 is:
DC base voltage generating circuit 10 by coupling capacitor 14
Superposed on the DC base voltage generated by the
Are applied to the discharge electrodes. At the same time, in the measurement circuit 16, the applied voltage and the discharge current applied between the discharge electrode and the dust collection electrode are measured and sequentially input to the arithmetic unit 17. Next, arithmetic unit 1
In step 7, a discharge characteristic curve is obtained from the applied voltage and the discharge current measured by the measurement circuit 16, and the slope of the discharge characteristic curve is calculated, and is compared with a previously input reference slope. When the slope is larger than the reference slope, it is determined that the reverse ionization phenomenon has occurred, and the gate control circuit 18 controls the gate control circuit 18 to decrease the voltage of the first AC power supply circuit in accordance with an instruction from the calculator 17. In addition, the power supplied from the high-voltage power supply to the electrostatic precipitator 20 is reduced to reduce the discharge current value. The discharge current value at this time is
Is fed back to the gate control circuit 18 from
In the gate control circuit 18, the discharge current value is 0.05 mA /
The power supplied to the electric precipitator 20 is controlled so as to be m ² .

If the slope calculated by the computing unit 17 is the same as the reference slope, it is determined that the operation is normal, and the discharge current is set to 0.2, which is the discharge current value at the start of the electric precipitator 20. to maintain the ~0.5mA / m ^2. As described above, in the power control method for the electrostatic precipitator according to the present invention, it is determined whether the current is normal or the time of the reverse ionization phenomenon, and the magnitude of the discharge current is controlled based on the determination result. That is, the power supplied from the high-voltage power supply to the electric precipitator 20 is changed so that the discharge current provides an efficient dust collection performance. As a result, efficient dust collection performance can be obtained in both normal and reverse ionization phenomena, so that the collection performance of the electric dust collector 20 can be improved, and the collection efficiency with respect to power consumption is improved. It saves energy.

In this embodiment, the slope of the discharge characteristic curve at normal time is set as the reference slope, but the slope at the time of reverse ionization may be set as the reference slope.

[0018]

As described above, according to the power control method for an electric precipitator according to the present invention, it is determined whether a non-reverse ionization phenomenon (normal) or a reverse ionization phenomenon, and based on the determination result. Thus, the magnitude of the discharge current is controlled. That is, the power supplied to the electric precipitator is changed so that the discharge current is such that an efficient precipitating performance is obtained. This allows
Efficient dust collection performance can be obtained in both normal and reverse ionization phenomena, so that the collection performance of the electrostatic precipitator can be improved and the collection efficiency with respect to power consumption can be improved, thereby saving energy.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a high-voltage power supply device used in a power control method for an electric dust collector according to the present invention.

FIG. 2 is a dust collection characteristic diagram comparing the relationship between the power supplied to an electric dust collector and the dust collection performance in pulse charging in a normal state and a reverse ionization phenomenon.

FIG. 3 is a comparison diagram of a discharge characteristic curve in a normal state and a discharge characteristic curve in a reverse ionization phenomenon.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... DC base voltage generation circuit 12 ... Pulse voltage generation circuit 14 ... Coupling capacitor 16 ... Measurement circuit 17 ... Calculator 18 ... Gate control circuit 20 ... Electric precipitator 22 ... Current transformer

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B03C 3/00-3/88

Claims (2)

(57) [Claims] 1. A power control method for an electrostatic precipitator, wherein a high voltage of a pulse charging system in which a pulse voltage is superimposed on a DC base voltage is applied between the discharge electrode and the precipitating electrode of the electric precipitator. Calculating a discharge characteristic curve from an applied voltage and a discharge current applied between the dust collection electrode, and calculating a slope of the discharge characteristic curve from a change in the discharge current with respect to a change in the applied voltage in the discharge characteristic curve. The calculated slope is compared with a reference slope of at least one of the discharge characteristic curves at the time of the reverse ionization phenomenon or at the time of the non-reverse ionization phenomenon obtained in advance, and the slope is at the time of the reverse ionization phenomenon or non-reverse. A power control method for an electric dust collector, comprising: determining whether an ionization phenomenon has occurred; and controlling the magnitude of the discharge current based on a result of the determination. 2. When the determination result is not the reverse ionization phenomenon, the discharge current is controlled so as to be 0.2 to 0.5 mA / m ^2, and when the determination result is the reverse ionization phenomenon, the discharge current is controlled. ^{2. The} method according to claim 1, wherein the current value is controlled to be 0.05 mA / m < ² >.