JPH03213165A - Controlling method for current of electric precipitator - Google Patents

Abstract

PURPOSE:To prevent that fine particles are suspended to be discharged to the atmosphere by raising a current to the original value in a predetermined time change ratio after the completion of hammering work. CONSTITUTION:The hammering work completion signal from a hammering instruction contact 16 is inputted to a comparator 14 through an integrator 20. The hammering instruction contact 16 is closed during hammering work to control a main control thyristor 3 through a current controller 15 so that the current average value detected on the basis of the instruction from the comparator 14 is limited to a predetermined small value. When the hammering instruction contact 16 is opened after the completion of hammering work, the integrator 20 outputs a predetermined time change ratio signal and, therefore, a current limit value gradually rises according to said signal to prevent the re-suspension if fine particles. By this method, it can be avoided that fine particles are discharged to the atmosphere.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is directed to current control when returning the current to its original value after dropping fine particles attached to the electrodes of an electrostatic precipitator by hammering. Regarding the method.

[Conventional technology]

FIG. 3 is a circuit diagram showing a conventional example of current control of an electrostatic precipitator.

As shown in Fig. 3, an electric precipitator applies a high DC voltage between a discharge electrode 6 and a dust collection electrode 7, and causes gas containing fine particles to pass between these electrodes. It is well known that fine particles in gas are charged and adsorbed to a dust collecting electrode. Here, 8 is a voltage dividing resistor, which is used to detect the voltage between the discharge electrode 6 and the dust collection electrode 7.

In order to apply a DC high voltage between both electrodes, AC power from the power source 2 is applied to the transformer 4 via the main control thyristor 3, and the AC high voltage taken out from the secondary side of the transformer 4 is applied to the main rectifier. 5 converts it to direct current.

Here, the electrostatic precipitator controls the current flowing through the electrostatic precipitator in accordance with the nature of the gas passing between the two electrodes and the amount or nature of fine particles. The rectifier 12 and the variable setting device 13 detect the current flowing through the electrostatic precipitator at a desired average value.

This average current detection value is led to a comparator 14, which compares it with a separately set current target value (not shown), and provides the comparison result to a current regulator 15. The current y4 moderator 15 outputs a signal for controlling the phase of the main control thyristor 3 so that the detected current value matches the target current value.

If the operation is continued while performing the above-mentioned current control, a large amount of fine particles will adhere to the dust collection electrode 7 and the dust collection efficiency will decrease, so that once a certain amount of fine particles have adhered, they must be removed.

When a large amount of gas is emitted, such as in a thermal power plant, multiple electrostatic precipitators are installed, so the particles adhering to the electrostatic precipitators are removed in turn. After cutting off the gas passing through and reducing the current flowing through it to a predetermined value, collection 111'r! 1 pole 7
The fine particles adhering to the dust collection electrode 7 are dropped down by the hammering operation. Once this hammering operation is completed,
In addition to returning the current flowing through the electrostatic precipitator to its original value,
Gas flow between the electrodes is resumed.

The hammering command contact 16 shown in FIG. 3 is a contact for notifying the control circuit of the electrostatic precipitator whether or not this hammering work is in progress. For example, it is open when the electrostatic precipitator is in normal operation. However, at the start of hammering work, comparator 1 is closed to reduce the detected current value to a predetermined value.
Give instructions to 4.

[Problem to be solved by the invention]

As mentioned above, at the start of hammering work, the current is limited four times so that the current flowing through the electrostatic precipitator is below a predetermined value.
When the hammering work is completed, this current limit is canceled and the current returns to its original value, but when this current limit is canceled, the particles that had fallen and accumulated from the electrode begin to float again, and at this time Since the gas flow has been resumed, these floaters and particles are inconveniently released into the atmosphere from the chimney.

Therefore, an object of the present invention is to prevent the particulates accumulated in the lower part from floating and being released into the atmosphere when the operation of the electrostatic precipitator is restarted after the hammering operation is completed.

[Means to solve the problem]

In order to achieve the above object, the current control method of the present invention includes hammering the electrodes of an electrostatic precipitator that is equipped with a current adjustment means for controlling the current flowing through the electrostatic precipitator in accordance with the load state. In a current control method for an electrostatic precipitator, in which the current is lowered to a predetermined value during work, and the current is returned to the original value after the hammering work is completed, the current is lowered to a predetermined value. It is assumed that the current is increased to its original value at a predetermined rate of change over time.

[Function] This invention provides an integrator in the part where the average value of the current flowing through the electrostatic precipitator is set to a desired value, and when the hammering work is completed and the average value of the current is returned to the original value, the integrator is installed. By causing the current to gradually rise at a predetermined rate of change over time using an integrator, it is possible to avoid the possibility that the particles deposited at the bottom will be resuspended.

【Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
The power supply 2, main control thyristor 3, and
Transformer 4, main rectifier 5, discharge electrode 6, dust collection electrode 7, voltage dividing resistor 8, current detector 11, rectifier 12, variable setting device 13
, the comparator 14, the current regulator 15, and the hammering command contact 16 are the same in name, purpose, and function as in the conventional circuit described in FIG.

In the present invention, the hammering work completion signal from the hammering command contact 16 is input to the comparator 14 via the integrator 20. That is, during hammering work, the hammering command contact 16 is closed and the main control is performed via the current regulator 15 so that the average current value detected based on the command from the comparator 14 is limited to a predetermined small value. Thyristor 3 is controlled at fil L.

When the hammering operation is completed and the hammering command contact 16 is opened, the integrator 20 outputs a signal with a predetermined time rate of change, so that the current limit value gradually increases accordingly.
Prevents particulates from becoming resuspended.

FIG. 2 is an operation waveform diagram showing the operation of the embodiment circuit shown in FIG. 1, and FIG.
The operation of FIG. 2 (b) shows the changes in the current limit value, respectively.

In this FIG. 2, before time t0, the hammer contact 16
is closed and hammering work is being performed, but at time t0, this hammering work is completed and the contact 16 switches from closed to open. The integrator 20 starts its operation upon receiving this open signal from the hammering command contact 16, and after a time T has elapsed, the average current value returns to the original value, for example, 100χ. In this state, the electrostatic precipitator continues to operate, and at time point 11, the hammering command contact 16 closes again to command the start of hammering work.

[Effects of the invention] The attached particles are removed by hammering the dust collecting electrode while blocking the gas containing particles flowing between the discharge electrode and the dust collecting electrode and limiting the current to a predetermined value or less. After this, the gas flow is started and the current is returned to its original value to restart the operation of the electrostatic precipitator. When starting up, according to the present invention, the current is gradually built up by using an integrator, for example, so that fine particles that have fallen and accumulated at the bottom due to the hammering work are lifted up again. This eliminates the risk of floating. Therefore, it is possible to avoid the possibility that suspended particulates will be released into the atmosphere when the gas starts passing through.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an operation waveform diagram showing the operation of the embodiment circuit shown in Fig. 1, and Fig. 3 is a conventional example of current control of an electrostatic precipitator. FIG. 2...'rtzs, 3... Main control cyrisk, 4.
...Transformer, 5...Main rectifier, 6...Discharge electrode, 7
... Dust collection electrode, 8 ... Voltage division resistor, 11 ... Current detector, 12 ... Rectifier, 13 ... Variable setting device, 14
...Comparator, 15...Current regulator, 16...
- Hammering command contact, 20...integrator. Jisumi t. No. Kasumizu

Claims (1)

[Claims] 1) When hammering the electrodes of an electrostatic precipitator that is equipped with a current adjustment means that controls the current flowing through the electrostatic precipitator in accordance with the load condition, the current must be lowered to a predetermined value. , in a current control method for an electrostatic precipitator in which the current is returned to its original value after the hammering operation is completed, the current is increased to the original value at a predetermined rate of change over time after the hammering operation is completed; A current control method for an electrostatic precipitator, characterized by: