JPS6231986B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an unstable charge detection device for an electrostatic precipitator that detects an unstable charge state in an electrostatic precipitator.

[Background Art] Conventionally, dust has been charged using a constant current method so that a discharge current determined in advance empirically is maintained.

However, with this constant current control method, it is difficult to perform stable charging in response to changes in the electrical characteristics of dust, changes in dust type, and changes in exhaust gas properties.For example, dust with high electrical resistivity is collected. When this happens, a reverse ionization phenomenon often occurs, leading to a decrease in dust collection efficiency.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an electrostatic precipitator capable of detecting unstable charging of dust in an electrostatic precipitator. An object of the present invention is to provide an unstable charge detection device for a dust device.

[Summary of the Invention] In order to achieve the above object, an unstable charge detection device for an electrostatic precipitator according to the present invention includes a dust collection detection electrode formed in a cylindrical shape and a dust collection detection electrode provided at the center of the dust collection detection electrode. A discharge detection electrode, a high voltage generator that applies a high voltage between both detection electrodes, and a discharge detection electrode that is collected on the inner circumference of the dust collection detection electrode by moving relatively along the inner circumference of the dust collection detection electrode. The scraper adjusts the thickness of the collected dust to a predetermined value, and the electrostatic precipitator detects an unstable charging state of the dust between the two detection electrodes by determining the pattern of the discharge current flowing between the two detection electrodes. The present invention is characterized by comprising an arithmetic circuit that determines that dust is charged in an unstable state.

In addition, when dust is charged in an unstable state in an electrostatic precipitator, the high voltage for dust collection applied between the collecting electrode and the discharge electrode of the electrostatic precipitator, that is, the dust charging voltage, can be lowered. Since stable charging is possible, reducing the high voltage for dust collection by instructing the charging device that performs this charging in the electrostatic precipitator or its operator to reduce the high voltage for dust collection. It is preferable to configure the arithmetic circuit so as to generate a command.

Furthermore, when an unstable charging state of the dust is detected, the high voltage for detection of the high voltage generator is controlled to be reduced to detect a stable charging voltage, and the dust is stably charged in the electrostatic precipitator based on the stable charging voltage. If the arithmetic circuit is configured to obtain the stable charging voltage target value, the operation for reducing the high voltage for dust collection becomes easy.

A dust layer thickness detector is provided on the inner peripheral surface of the dust collection detection electrode to detect the thickness of the dust layer collected.
If the device is configured so that the detected value is supplied to the arithmetic circuit as a feedback signal for dust thickness adjustment control, the thickness of the dust layer can always be kept accurately constant, resulting in accurate and stable detection operation. It becomes possible.

If a calculation circuit is configured to determine the hammering interval based on the detected value of the dust layer thickness detector and the pattern of the discharge current flowing between the two detection electrodes, this can be used to determine the optimal interval. It is possible to perform hammering with. Note that it is optional to perform this hammering manually or automatically.

[Embodiments of the Invention] Hereinafter, preferred embodiments of the apparatus according to the present invention will be described based on the drawings.

In FIG. 1, gas containing dust generated in a boiler 10 is guided to a chimney 14 by a blower 12 via an electrostatic precipitator 16.

The electrostatic precipitator 16 of this embodiment includes an electrostatic precipitator main body 18 having a precipitator electrode and a discharge electrode (not shown), and a height for collecting dust between the precipitator electrode and the discharge electrode of the electrostatic precipitator main body 18. It is equipped with a charging device 20 that applies a voltage, and a hammering device 22 that hammers the dust collecting electrode.

The charging device 20 has a high voltage reduction command of 100 for dust collection.
The above-mentioned high voltage for dust collection is stabilized by the target value of charging voltage.
102, and the hammering device 22 can be controlled by the hammering command 104.
It is possible to perform hammering by.

The above-mentioned dust collection high voltage reduction command 100, stable charging voltage target value 102, and hammering command 104 are outputted from the unstable charging detection device 24.

In FIG. 1, a bypass flue 28 is formed in the entrance flue 26 of the electrostatic precipitator 16.
The unstable charge detection device 24 is provided in this bypass flue 28.

FIG. 2 explains the configuration of the unstable charge detection device 24. A dust collection detection pole 30 is rotatably inserted in the middle of the bypass flue 28, and the dust collection detection pole 30 is connected to the boiler 10. The exhaust gas 200 is flowing from the left side to the right side of the figure. In addition, dust collection detection electrode 3
0 is grounded.

Further, a belt gear 32 is fitted onto the dust collection detection electrode 30 . A gear 34 is meshed with this belt gear 32, and the gear 34 is connected to its shaft 36,
It is connected to a drive shaft 44 of a motor 42 via pins 8 and 40.

Further, a discharge detection electrode 46 having a sharpened discharge tip directed toward the inner circumferential surface of the dust collection detection electrode 30 is provided at the center inside the dust collection detection electrode 30 . An insulator tube 48 is vertically connected to the downstream passage of the dust collection detection electrode 30, and an insulator 50 in which the base of the discharge detection electrode 46 is embedded is fitted inside the insulator tube 48. Furthermore, a detection high voltage 106 is applied from a high voltage generator 52 to the base end of the discharge detection electrode 46. A conduit 54 is connected to the side surface of the glass tube 48 to which high pressure air for cleaning the tip of the insulator 50 is supplied.

A scraper 5 is installed inside the dust collection detection electrode 30.
6 is provided. This scraper 56 is plate-shaped, and its movement in the radial direction of the dust collection detection electrode 30 is controlled by a scraper moving device 58.

Further, the thickness of the dust layer collected on the dust collection detection electrode 30 is detected by a dust layer thickness detector 60.

Here, the motor 42, the high voltage generator 52,
The scraper moving device 58 and the dust layer thickness detector 60 are connected to an arithmetic circuit 62.

This arithmetic circuit 62 outputs the above-mentioned high voltage reduction command for dust collection.
100, stable charging voltage target value 102, hammer command 104 can be generated, motor 42 and scraper moving device 58
It is possible to control them by supplying a drive current to them.

Further, the high voltage generator 52 is connected to the dust collection detection electrode 3.
0 and a current detector (not shown) for detecting the discharge current between the discharge detection electrodes 46, and a current detection signal 110 thereof is supplied to the arithmetic circuit 62. The dust layer thickness detection value 112 of the dust layer thickness detector 60 is also supplied to this arithmetic circuit 62. The arithmetic circuit 62 also supplies the voltage control signal 114 to the high voltage generator 52 to generate a high voltage for detection.
106 can be controlled to reduce.

The arithmetic circuit 62 is composed of a microcomputer, its input/output circuit, etc., and various fixed data and programs are stored in advance in the ROM of the microcomputer.

The device according to the present invention has the above configuration, and its operation will be explained below.

A constant drive current is supplied from the arithmetic circuit 62 to the motor 42, and the dust collection detection electrode 30 is always driven to rotate at a constant rotation speed.

Further, the high voltage generator 52 uses a high voltage 106 for detecting the reference value according to the voltage control signal 114 of the arithmetic circuit 62.
is applied between the dust collection detection electrode 30 and the discharge detection electrode 46.

As a result, the dust contained in the exhaust gas 200 is charged and collected on the inner peripheral surface of the dust collection detection electrode 30, and a dust layer is formed on the inner peripheral surface of the dust collection detection electrode 30.

The thickness of this dust layer is detected by a dust layer thickness detector 60, and the dust layer thickness detection value 112
is supplied to the arithmetic circuit 62. The arithmetic circuit 62 supplies a drive current according to the dust layer thickness detection value 112 to the scraper moving device 58 , and the scraper moving device 58 drives the scraper 56 in the radial direction of the dust collection detection electrode 30 . The thickness of the dust layer formed inside is adjusted to a predetermined value.

Under the detection conditions set in this way,
That is, under the conditions that the thickness of the dust layer formed inside the dust collection detection electrode 30 is constant and the detection high voltage 106 between the dust collection detection electrode 30 and the discharge detection electrode 46 is constant, the arithmetic circuit 62 is a high voltage generator 52
The pattern of the discharge current flowing between the dust collection detection electrode 30 and the discharge detection electrode 46 is monitored as follows using the current detection signal 110 supplied from the dust collection detection electrode 30 and the discharge detection electrode 46. Detecting unstable charge state of dust.

FIGS. 3 and 4 are flowcharts for explaining this detection operation. In the flowchart of FIG. 3, first an integral calculation is performed, and then a differential calculation is performed as follows.

FIG. 5 shows an example of the characteristic 300 of the discharge current i flowing between the dust collection detection electrode 30 and the discharge detection electrode 46. In the figure, the current i ₀ is the reference current value under the above detection conditions, and the above Integral calculations and differential calculations are repeatedly performed from time t=0 to t=T.

In FIG. 3, it is first determined whether the integral calculation has been completed (step 400).

At this time, if it is determined that the integral calculation has not been completed, a timer is started at time t=0 (step 402).

Next, the discharge current i is sampled and an integral calculation of the following equation is performed (step 404).

P1=∫ ^T ₀ [i(t)−i ₀ ]dt...(1) That is, this integral calculation is performed until time t=T and the timer times up, and when this timer times up, the integral calculation starts. A flag indicating that the process has ended is set (step 408).

When the end of the integral calculation is confirmed by setting the above flag (step 400), the timer is started again (step 410), and then the next differential calculation is performed for the timer time (step 400).
412).

P=di/dt...(2) When it is confirmed that the timer has timed up (step 414), the flag set in step 408 is reset (step 414).
416), the integral calculation is started again.

In this way, integral calculations and differential calculations are constantly performed repeatedly.

In FIG. 4, it is first determined whether the process in FIG. 3 has been performed only once (step 418).

If the process shown in FIG. 3 has been performed two or more times, it is determined whether any of the differential values obtained at step 412 exceeds a set value (step 420).

At this time, if it is determined that none of the differential values exceeds the set value, it is determined whether the integral value obtained in step 404 is greater than or equal to the previous integral value (step 422).

If a negative judgment is made at this time, it is judged that the discharge current i is stable (step 424), and if an affirmative judgment is made, it is judged that the value of the discharge current i is decreasing (step 424). Step 426) is performed.

FIG. 6 shows an example of a typical pattern of discharge current i. When the judgment in step 424 is made, the discharge current changes as shown in A in the figure, and in step 426, the discharge current changes as shown in FIG. When the determination is made, the change has occurred as shown in FIG.

If an affirmative determination is made in step 420, it is determined whether the number of times the differential value exceeds the set value during the timer period T is greater than or equal to a predetermined number of times (step 428). .

If a negative determination is made at this time, it is determined that a spark is generated between the dust collection detection electrode 30 and the discharge detection electrode 46 (step 430).

In this state, the discharge current i is changing as shown in FIG. 6C.

On the other hand, if an affirmative determination is made in step 428, it is determined whether the integral value exceeds a set value (step 432).

If a negative judgment is made in this step 432, it is judged that a reverse ionization phenomenon is partially occurring between the dust collection detection electrode 30 and the discharge detection electrode 46 (step 434), and if it is affirmative. When such a determination is made, it is determined that a full-scale reverse ionization phenomenon has occurred between the two (step 436).

When the determination in step 434 is made, the discharge current i changes as shown in FIG. 6D, and when the determination in step 436 is made, the discharge current i changes as shown in FIG. It's changing.

As described above, the arithmetic circuit 62 includes the dust collection detection electrode 30,
The pattern of the discharge current i flowing between the discharge detection electrodes 46 is monitored, and thereby the unstable charging state of the dust existing between the dust collection detection electrode 30 and the discharge detection electrode 46 (Fig. 6 D, E) is detected. do.

When the determinations in steps 434 and 436 are made, a flag indicating that the charge is unstable is set and the process shown in FIG. 7 is started.

In FIG. 7, it is first determined whether or not a flag indicating charge instability is set (step
438).

Initially, since the flag is set, a positive determination is made, and based on this determination, the arithmetic circuit 62 uses the voltage control signal 114 to slightly lower the detection high voltage 106 of the high voltage generator 52 (step
440).

Furthermore, the judgment of 438 is made again, and step 440
The process continues until the determinations in steps 424, 426, and 430 are made.

After that, judgments are made in steps 424, 426, and 430, and if the flags set in steps 434 and 436 are reset, and a negative judgment is made in step 438, the high voltage for detection at that time is
106 is latched (step 442).

Next, in step 442, the high voltage for detection is latched.
A stable charging voltage target value 102 is calculated based on the value of 106 (step 444).

The stable charging voltage target value 102 obtained in step 444 above corresponds to the value at which the charging voltage applied from the charging device 20 between the dust collection electrode and the discharge electrode of the electrostatic precipitator 16 is optimal. At voltage, the dust between the two electrodes does not become unstable in charge and is always stably charged.

When the stable charging voltage target value 102 is obtained in this way, the high voltage reduction command for dust collection 100 and the stable charging voltage target value 102 are supplied to the charging device 20 (step 446), and finally, in step 442, the voltage is latched. The detection high voltage 106 is set as a control target value (step 448). As a result, the detection high voltage 106 applied between the dust collection detection electrode 30 and the discharge detection electrode 46 is again fixed at a constant value.

Based on the dust collection high voltage reduction command 100 and the stable charging voltage target value 102 obtained as described above,
0 applies a high voltage for dust collection with an optimum value between the dust collection electrode and the discharge electrode of the electrostatic precipitator main body 18, and as a result, the dust is stably charged in the electrostatic precipitator main body 18. The dust is collected on the dust collection electrode of the electrostatic precipitator body 18 with a good dust collection rate.

Finally, hammering control will be explained.

A high voltage for detection is provided in the ROM of the arithmetic circuit 62.
Hammering intervals whose parameters are the thickness of the dust layer formed inside the dust collection detection electrode 30 and the discharge current pattern are stored at 106 predetermined intervals.

Therefore, in FIG. 8, the detection high voltage 106 fixed at step 448 is taken in (step 450).

Next, the dust layer thickness detection value 112 and the step
The determination results of 424, 426, and 430 are imported (step 452).

Further, a hammering interval is read from the ROM based on the data captured in steps 450 and 452 (step 454).

Then, the timer time of the hammering timer is set at the hammering interval, and the operation of the hammering timer is started (step 456).

Thereafter, when the hammering timer times up (step 458), the hammering command 104 is sent to the hammering device 22.
(step 460), and the hammering device 22 hammers the dust collecting electrode of the electrostatic precipitator main body 18.

Finally, when it is confirmed that the determinations in steps 434 and 436 have not been performed (step 462), the processes in steps 456, 458, and 460 are repeated.

Further, if an affirmative determination is made in step 462, this process is stopped.

As described above, hammering is performed at optimal intervals based on the relationship between the thickness of the dust layer and the discharge current pattern.

As explained above, according to this embodiment, it is possible to detect the unstable charging state of dust caused by a change in the electrical characteristics of dust, and furthermore, when detecting the unstable charging state, the charging voltage of the electrostatic precipitator to the dust can be adjusted to an optimal value. Since it can be controlled, it is possible to always collect dust with a good dust collection rate in the electrostatic precipitator.

Furthermore, since the detection of the unstable state of dust charge is carried out under certain detection conditions, stable, accurate, and highly reliable unstable state of dust charge detection operation is possible at all times.

In this embodiment, the control device provided on the charging device 20 and the hammering device 22 side may be provided on the unstable charge detection device 24 side, so that this device can be used not only as a command generation device but also as a control device. suitable.

[Effects of the Invention] As explained above, according to the present invention, it is detected that the dust in the electrostatic precipitator is charged in an unstable state, and accordingly, the dust charge in the electrostatic precipitator is reduced. By adjusting the voltage, the dust can always be charged in a stable state regardless of changes in the electrical characteristics of the dust, and therefore it is possible to collect the dust with a good collection rate.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an electrostatic precipitator system in which the device according to the present invention is used, FIG. 2 is an explanatory diagram of the configuration of the unstable charge detection device 24 in FIG. 1, and FIG.
4 is a flowchart explaining the operation of the unstable charge detection device 24, FIG. 5 is a characteristic explanatory diagram showing an example of discharge current characteristics, and FIG. 6 is a typical pattern of discharge current. FIGS. 7 and 8 are flowcharts illustrating the operation of the unstable charge detection device 24. 16... Electrostatic precipitator, 18... Electrostatic precipitator body, 20... Charging device, 22... Hammering device, 2
8... Bypass flue, 30... Dust collection detection pole, 42
...Motor, 46...Discharge detection electrode, 52...High voltage generator, 56...Scrape, 58...Scrape moving device, 60...Dust layer thickness detector, 6
2... Arithmetic circuit.

Claims (1)

[Claims] 1. A dust collection detection electrode formed in a cylindrical shape through which a part of the exhaust gas that should flow into the inlet side of the electrostatic precipitator passes, a discharge detection electrode provided in the center of the dust collection detection electrode, and a gap between the two detection electrodes. A high voltage generator that applies a high voltage to the dust collection detection electrode is moved relative to the inner peripheral surface of the dust collection detection electrode to maintain the thickness of the dust collected on the inner peripheral surface of the dust collection detection electrode to a predetermined value. By determining the pattern of the discharge current flowing between the scraper to be adjusted and the two detection electrodes, we detect that the dust is unstablely charged in the electrostatic precipitator. An unstable charge detection device for an electrostatic precipitator, comprising: an arithmetic circuit that determines whether a precipitate is present.