JPH0199657A - Method for controlling charging rate of electrostatic precipitator - Google Patents

Abstract

PURPOSE:To obtain optimum dust collection performance by controlling the charging rate so that minimum value per one cycle of voltage is regulated to maximum value at a time of normal charge and controlling the charging rate so that minimum value per one cycle of voltage is regulated to maximal value at the time of generating reverse ionization. CONSTITUTION:In a charging rate controlling method of an electrostatic precipitator having an intermittent charge function, a charging rate is controlled so that minimum value per one cycle of voltage is regulated to maximum value at a time of normal charge. Further, the charging rate is controlled so that minimum value per one cycle of voltage is regulated to maximal value at the time of generating reverse ionization. As a result, optimum performance can be obtained at every electric source units without necessitating an external equipment such as a soot and dust monitor. Minimum value per one cycle of voltage waveform is made to a monotonous decreasing function at a time of normal charge and further characteristics having maximal value in a range of <=1/3 charging rate are utilized at a time for generating reverse ionization and charting rate control can be made rapid by performing control correspondent to respective states.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrostatic precipitator (hereinafter referred to as B) having an intermittent charging function.
(abbreviated as P) relates to a rate control method for a load.

[Conventional technology]

In the conventional BP with intermittent charging function, the charging rate is set to 1.
The main method is to monitor the entire EP outlet concentration and find the optimum conditions without manually changing the charging rate.In addition, there is also a known method, as shown in Figure 6, which is automated in combination with a soot and dust monitor. ing.

In the case shown in FIG. 6, since the optimal value of the intermittent charging rate changes depending on the dust conditions, the charging rate is changed so that the amount of soot and dust monitored at the BP outlet is minimized. As shown in Figure 3, intermittent charging is a charging method in which the current is turned on and off periodically in accordance with the commercial frequency, and the charging rate T is defined as charging time T1 and pause time T. time, r=
=T, /T, +T.

It is expressed in

However, this case has disadvantages in that a medium monitor is required at the outlet of the BP and that individual power supply units cannot be optimally adjusted.

On the other hand, a method for setting the optimum load for each power supply device based on the voltage waveform of each power supply category is to use the voltage peak value Vp.
A control method has been devised to maximize the product VPXVm of the average value of voltage and Vm, and a correlation with dust collecting performance has also been confirmed. However, in this case, for dust that causes back ionization, lowering the charge rate can suppress back ionization, even though the dust collection performance is high.

Since the higher the charge rate, the higher the average voltage, a phenomenon in which ViVpXVm increases depending on the dust conditions has been observed, and there have been cases where reverse ionization has been incompletely suppressed and optimal adjustment cannot be obtained.

In FIG. 6, 10 is a BP, 1z is a power supply unit, 12 is a control device, and 14 is a dust collection monitor.

[Problem that the invention seeks to solve]

In general, in EP for coal-fired boilers, etc., the electrical resistance of the dust to be collected varies depending on the operating conditions such as the coal used and the operating temperature, and the effectiveness of conventional charging methods varies significantly. As a countermeasure to this problem, intermittent charging can suppress the decline in multiplicity due to the reverse ionization phenomenon when the dust to be collected has a high resistance, and has been put into practical use, but the optimal setting value varies depending on the dust conditions. It has been confirmed that this occurs (see Figure 4).

However, in order to automatically set the optimal conditions for intermittent charging in response to these condition fluctuations, the soot layer monitor signal is required, as conventionally the medium concentration signal at the C and EP outlet has been fed back. Also, since multiple power supply units were controlled with uniform set values, it was not possible to optimally adjust each power supply.

As a result of investigating the relationship between performance and voltage waveform under various dust conditions, the present invention focused on the fact that there is a certain relationship between the charge rate of intermittent charging of EP and the smallest value of the BP voltage waveform for each cycle. The optimum charging rate for intermittent charging can be set automatically, reliably and quickly for each power supply device without the need for a media monitor or external control unit. The present invention aims to provide a method for controlling the charge rate of BP.

[Means for solving problems]

The charging rate control method for BP according to the present invention is a method for controlling the charging rate for EP having an intermittent charging function.

During normal charging, the charge rate is controlled so that the minimum value per cycle of voltage becomes the maximum value, and when reverse ionization occurs, the charge rate is controlled so that the minimum value per cycle of voltage becomes the maximum value. It is special to do so. That is, in the present invention, as a means for setting the charge rate of one intermittent charge, in the case of dust conditions such that the smallest value Vb of each cycle of the voltage waveform causes reverse ionization, normal charge is set as the charge rate changes. Focusing on the fact that it is a monotonically decreasing function in the case of , and that it takes an extremely thick value below a certain charge rate during reverse ionization, Load 1! The rate is set. For example, Fig. 5 shows the charge rate and Vb under various dust conditions.
Although the relationship between O values is shown, optimal dust collection performance can be obtained by setting the charge rate such that Vb takes the maximum value or local maximum value under each dust condition.

[Effect]

For example, as shown in FIG. 3, when reverse ionization occurs.

Because the apparent corona resistance of EP becomes smaller, the rate of decrease of the voltage waveform per unit time is large.

The minimum voltage value Vb per cycle of continuous charging is smaller than that during normal charging.

However, by lowering the υ charge rate through intermittent charging, the average current decreases, which makes it possible to suppress reverse ionization, which increases the apparent corona resistance and reduces the drop in voltage per unit time. .

As a result, Vb increases.

Based on the above principles, the relationship between the charge rate of intermittent charging and dust collection, and the minimum value Vb during one cycle of the voltage waveform are summarized under various dust conditions.

For example, as shown in FIG. 5, it has been found that the highest performance as shown in FIG. 4 can be achieved when Vb takes a maximum value or a local maximum value.

In other words, since reverse ionization does not occur with medium-low resistance dust, s
Vb shows a monotonically decreasing curve as the charge rate decreases9
．． Performance is also a monotonically decreasing function, but in the case of dust that causes reverse ionization, Vb is not necessarily a load, and the military setting coincides with the optimal performance adjustment point of EP.

Therefore, by changing the charging rate during operation and setting it at the point where it takes the maximum value or local maximum value.

No external equipment such as a dust monitor is required, and the best performance can be obtained for each power supply unit.

In addition, during normal charging, the minimum value Vb of voltage per cycle υ becomes a monotonically decreasing function by lowering the charging rate γ, but by using compensation for operating conditions that cause reverse ionization, normal Distinguish between charging and reverse ionization state, set the maximum value within the charging rate setting range when normal charging occurs, and set Vb when reverse ionization occurs.
By performing floating control such that the maximum charge rate is achieved, the optimum charge rate can be quickly set without scanning the entire charge rate setting range.

Here, the maximum value line within the charging rate setting range is usually r = 1'5I
: However, if there is room for performance, it goes without saying that γ may be set to 1/2, 2/3, etc. in consideration of energy saving.

Also, the number of sparks in BP is 1! There are cases where this occurs.

At that time, Vb becomes OKV, but there is no point in increasing the detection accuracy of b''b by excluding such abnormal voltages and by sampling a plurality of vb and detecting cvb.

〔Example〕

8g1 is a diagram showing an example of a power supply configuration used to carry out the method of the present invention, and FIG. 2 is a diagram showing an example of a flowchart of operation control according to an embodiment of the present invention.

In FIG. 1, an alternating current power supply AC is supplied to a thyristor circuit 1, and is inputted from the same circuit to a high voltage transformer 2. A DC high voltage is supplied from the secondary side of the transformer 2 to the BP 4 via the rectifier 3 .

The signals of the current detector 5 and the voltage detector 6 are transmitted to the control unit 7
The control device 8 controls the thyristor circuit 1 to set the optimum charging rate by determining the operating state of the BP 4 by the microcomputer unit 9, thereby setting a predetermined charging rate. Can be set.

FIG. 2 shows a flowchart of the control method according to the present invention, and basically, under conditions where back ionization occurs, the charge rate r =
Since it is operated at 1/3 or less, Vb only needs to be controlled to take the maximum value. Therefore, as long as there are no significant changes in operating conditions, it is necessary to always control Vb to take the maximum value using 70-ting control. , there is no need to scan the entire charging rate setting range.

On the other hand, during normal charging, vb becomes a monotonically decreasing function, so from the initial value γ = 1/4 (continuous charge 'fhL) to γ
Since it is possible to determine whether the condition is normal charging or reverse ionization by covering the point 1 which exceeds =1/3, there is no need to check the conditions below that point. Therefore, the charging state can be determined without significantly reducing the high dust collection efficiency during normal charging.

That is, due to the characteristic that vb takes a monotonically decreasing function value during normal charging, prompt and optimal control is possible by changing the control method based on each state.

Note that the change from normal charging to reverse ionization occurs when the operating conditions change significantly, but in that case, the flow is such that it is possible to escape from each state.

Next, the operation of one embodiment of the method of the present invention will be explained based on the flowchart shown in FIG.

In the method of the present invention, the current charging rate r and the minimum value Vb of voltage per cycle υ are periodically monitored. is the operating mode during normal charging. Here, set the load rate r to γ=1.2/3゜1/2, 1/3, t/
s, 1/7, 1/11, 1/21, 1/31
, 1/61.

shall be.

At this time, if BP is in a normal charged state, as % r decreases (for example, r = 1 → 2/3 → 1/2 → 1/3
), the minimum value Vb of one cycle of each waveform is single γ = 115
), if it continues to decrease monotonically, then 1
It is determined that this charging is in a normal charging state, and the optimum setting value r for normal charging is set to r=1, and one cycle of control is completed.

On the other hand, if vb tends to increase during this process.

It is determined that this is under the charging condition of reverse ionization, and γ is set to be lowered by one rank. In general, if the opposite occurs, γ
Since Vb tends to increase near = 172 or γ = 1/3, the setting at this time is γ = Next, after a certain period of time, control is again performed for optimal adjustment, but in this case, If the charge is the same normal charge as at the beginning, it is determined in the same manner as the first time.

On the other hand, even if charging is normal at first, due to changes in operating conditions, E
If P is moving to reverse ionization conditions.

This is because Vb improves in the process of decreasing r.

finish.

In addition, when the reverse ionization state continues, +V
The control immediately shifts to setting b to an extremely thick value.

In other words, compare the previous Vb and the current Vb,
The charging rate is constantly raised or lowered in a direction that is higher than the previous vb. For example, by multiplying γ by 1/11, it is controlled so that it approaches the maximum value.

In this case, an attempt is made to further lower r, resulting in a setting of r=1/21, but in this case, the next control determines that Vb has decreased compared to the previous one, so γ is increased in the next setting. Therefore, 70-ting control is performed near r=x10.

In other words, control is performed to constantly aim for r=1/11.

Also, when normal charging is restored from reverse i1m, Vbrl
The arrow loop moves to the normally charged loop.

〔Effect of the invention〕

According to the present invention, the following effects can be achieved.

(1) In an EP that has an intermittent charging function, the charging rate setting can be determined and optimized based on the minimum value per cycle of the voltage waveform, without the need for a top monitor. Optimum adjustment can be made for each power supply unit.

(2) In the above, the minimum value per cycle of the voltage waveform is a monotonically decreasing function when normal charging occurs, and when reverse ionization occurs, it has an extremely thick value in the region where the charging rate is 1/3 or less, and each state is Speeding up the control is possible by controlling according to the situation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a power supply used to carry out the method of the present invention, and FIG.
Figure 3 is a diagram showing the flow of the method of making a skein. Figure 4 shows a comparative example of continuous charging and intermittent charging regarding the relationship between EP charging state and current/voltage waveform. Figure 4 shows the relationship between charge rate and dust collection for 1 intermittent charging for each dust condition. 5 is a diagram showing the relationship between the minimum voltage value vb per cycle at that time and the charging rate, and FIG. 6 is a diagram for explaining an example of a conventional method for setting intermittent charging. DESCRIPTION OF SYMBOLS 1... Thyristor circuit, 4... BP, 5... Current detector, 6... Voltage detector, 7... Control unit. Applicant's agent Patent attorney Takehiko Suzue 1st Ren, accent 1t γ・8 1pzu2ru=-= Business t r-=3/3-q4+'kotori-i Figure 6

Claims (1)

[Claims] In a charging rate control method for an electrostatic precipitator having an intermittent charging function, during normal charging, the charging rate is controlled so that the minimum value per cycle of voltage becomes the maximum value, and when reverse ionization occurs, the charging rate is controlled so that the minimum value per cycle of voltage becomes the maximum value. A charge rate control method for an electrostatic precipitator, characterized in that the charge rate is controlled so that the minimum value of the hit becomes the maximum value.