JPS6197056A - Charging method of electrical dust precipitator - Google Patents

Abstract

PURPOSE:To operate an electrical dust precipitator in high dust collecting efficiency and low electric power consumption by changing a charge process to perform the judgment operation and selecting the charge process excellent in dust collecting efficiency. CONSTITUTION:While operating an electrical dust precipitator in a continuous charge process, it is changed over into a short time-intermittent charge process and the elemental values PW(C) and PW(I) of consumed electric power in each charge process are measured before and after the changeover. Then PW(C).r is calculated from the elemental value of the consumed electric power in the continuous charge process and PW(C).r is compared with the elemental value of consumed electric power in the intermittent charge process to compare the size of PW(I) and PW(C).r. The continuous charge process is selected in PW (I)<PW(C).r and the intermittent charge process is selected in PW(I)>PW(C).r. By this method, the electrical dust precipitator is operated under the conditions of high dust collecting efficiency and low electric power, consumption.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to a method of charging an electrostatic precipitator, and a method of charging an electrostatic precipitator that selects a charging method and operates the electrostatic precipitator in order to increase dust collection efficiency. Chiru.

``Prior art'' In a dry type electrostatic precipitator, a voltage is applied between a discharge electrode and a dust collection electrode to cause a corona discharge to create an electric charge, and a gas containing dust is flowed in to charge the dust and connect it to the dust collection electrode. The dust is electrostatically attached to the surface. The dust contained in the gas and sent in in this manner is collected by a dry electrostatic precipitator.

In this case, the apparent electrical resistance of the dust is
When it exceeds 1011Ω・cs, the potential gradient within the dust layer collected by the dust collecting electrode increases, causing dielectric breakdown within the dust layer and causing a reverse ionization phenomenon in which positive ions are supplied from the dust layer. There are things to do.

When such a reverse ionization phenomenon occurs, the negative ions that contribute to dust collection are neutralized by positive ions, so that most of the discharge current becomes a reactive current, which significantly reduces the dust collection efficiency. Power consumption in the electrostatic precipitator also increases.

Figure 1 is a relationship curve between secondary voltage and secondary current, with the secondary voltage V applied to the electrodes of an electrostatic precipitator taken on the groove axis and the secondary current obtained at that time taken on the vertical axis. Curve A is a relationship curve obtained when only air flows through the electrostatic precipitator. The relationship curve between secondary voltage and secondary current obtained by flowing the gas to be treated into the electrostatic precipitator from this state is the first
As shown in B in the figure, there is a tendency for the secondary current to increase for the same secondary voltage compared to when only air is allowed to flow in. Furthermore, the relationship curve C shown in Fig. 1 is a relationship curve between the secondary voltage and the secondary current when a reverse ionization phenomenon occurs in the electrostatic precipitator during operation.
(There is a tendency for the secondary current value to suddenly reach an excessive value of 1 (-°) with fit.

Generally, if a reverse ionization phenomenon occurs while an electrostatic precipitator is operated in the continuous charging mode, if the charging method of the secondary voltage between the discharge electrode and the collecting electrode is switched to the intermittent charging method, the electrostatic precipitator will It is known that it is possible to reduce power consumption eM and prevent a decrease in dust collection efficiency.

However, this is true when a significant reverse ionization phenomenon occurs in the electrostatic precipitator during operation, and the operation is carried out under complete reverse ionization conditions. If an intermittent charging method is used in the absence of significant reverse ionization phenomena such as excessive reactive current flowing, the dust collection efficiency of the electrostatic precipitator may be lower than when a continuous charging method is used. Conventionally, it has not been quantitatively understood under what operating conditions the intermittent charging method can improve dust collection efficiency and reduce power consumption.

Therefore, the operation of the electrostatic precipitator is constantly monitored, and after confirming the operating condition where the relationship between the secondary voltage and secondary current is clearly recognized as shown by curve C in Figure 1, the operation is switched to the intermittent charging method. You can do it.

However, since the conditions for the switching cannot be quantitatively determined, it is difficult to quickly and accurately confirm the conditions for the occurrence of the reverse ionization phenomenon under which the charging method should be switched. In addition, the dust concentration on the outlet side of the electrostatic precipitator is continuously monitored, and it is possible to switch to the intermittent charging method based on changes in this concentration, but even in this case, it is difficult to understand the complete quantitative relationship. In the past, even if the charging method of the electrostatic precipitator was switched to the intermittent charging method, by the time the switch was made, the operation had already been continued for a long time with low dust collection efficiency, which was wasteful. Switch the charging method of the electrostatic precipitator to the intermittent charging method after a certain amount of power has been consumed and the switching is not effective, or before a significant reverse ionization phenomenon occurs that causes excessive reactive current to flow. This may lead to a decrease in dust collection efficiency.

``Problems to be Solved by the Invention'' ゛ This invention quickly and accurately grasps that the reverse ionization phenomenon occurs under the conditions under which the charging method should be changed in the operation of a dry electrostatic precipitator, and changes the charging method. The object of the present invention is to provide a charging method for an electrostatic precipitator that allows the electrostatic precipitator to be charged at appropriate operating times.

If the electrical resistance log P of the dust of the electrostatic precipitator is plotted on the horizontal axis, and the secondary voltage or secondary current is plotted on the vertical axis, and the relationship between them is shown, the relationship curve shown in FIG. 2 is obtained. In the figure, the normal discharge region, E is called the corona discharge suppression region, and F is called the reverse ionization region. Previously, it was believed that intermittent charging could improve the dust collection efficiency of an electrostatic precipitator only in the reverse ionization region F, but as a result of research by the inventors, the predetermined judgment conditions were also satisfied in regions other than the reverse ionization region F. We have found that it is possible to improve the dust collection efficiency of an electrostatic precipitator by using By checking whether or not the dry electrostatic precipitator is operated by switching between continuous charging and intermittent charging in accordance with the determination conditions, it is possible to operate the dry electrostatic precipitator at the optimum dust collection efficiency at all times.

``Structure of the Invention'' In this invention, during the operation of a dry electrostatic precipitator, the voltage charging method for charging the discharge electrode for a predetermined judgment operation time is selected from among a continuous charging method and an intermittent charging method with a charging rate γ. Switch to a charging method that does not. PW(C)γ obtained from the power consumption element PW(C) in the continuous charging method and the power consumption element PW(I) in the intermittent charging method before and after this switching are compared.

By this comparison, P W (I) < P W (C)
・If γ is determined, the continuous charging method is selected, and P W
When it is determined that (I)>P W (C)·r, the intermittent charging method is selected, the electrostatic precipitator is charged, and the electrostatic precipitator continues to operate.

``Example'' Hereinafter, a method for charging an electrostatic precipitator according to the present invention will be described in detail based on an example using the drawings.

FIG. 4 shows an example of a circuit used to carry out the method of charging an electrostatic precipitator according to the present invention, in which an output signal from a commercial AC power source 11 is applied to the primary side of a transformer 13 via a thyristor 12. The secondary side of the transformer 13 is connected to a discharge electrode 15 via a rectifier 14, and this discharge electrode 15 is disposed opposite to a dust collection electrode 16 of an electrostatic precipitator, and the dust collection electrode 16 is grounded.

A secondary voltmeter 17 and a secondary ammeter 18 are connected to the secondary side of the converter 13, respectively, so that the secondary voltage and secondary current can be detected. Further, a wattmeter 19 is connected to the output terminal of the commercial AC power supply 11. On the other hand, the output of the intermittent charging control circuit 20 is given to the thyristor control circuit 21, and the output of the thyristor control circuit 21 is supplied to the thyristor 120.
A voltage is applied to the control terminal 22.

The output signal of the commercial AC power supply 11 is transferred to the transformer 13 (#) 20
The voltage is increased to ~100 KV, and this increased output signal is charged between the discharge electrode 15 and the dust collection electrode 16 to induce corona discharge.

The electrostatic precipitator used in this invention is configured to be able to switch between continuous charging mode and intermittent charging mode, and the switching is performed by an intermittent charging control circuit 20, a thyrisk control circuit 21, and a thyristor 12, as will be described later. .

FIGS. 3(a) and 3(b) d are diagrams respectively showing the voltage waveform and current waveform during intermittent charging in the charging method of the electrostatic precipitator of the present invention, where the horizontal axis is the time axis, and the voltage waveforms are plotted at each cycle time T. Intermittent charging is performed.

That is, during the charging time t1 from the start point of the period time T, the secondary voltage V
is charged between the discharge electrode 15 and the dust collecting electrode, and thereafter charging with the secondary voltage V is stopped during the charging pause time t2. The period time T and the charging time t1 of the secondary voltage are selected depending on the physical and chemical conditions of the processing gas and dust flowing into the electrostatic precipitator, such as gas composition, gas pressure, gas temperature, and dust particle size. In the intermittent charging method, intermittent charging is performed every cycle time T. In this case, the average secondary voltage and average secondary current during the charging time represent the average secondary voltage and average secondary current during the charging time t1, and in the state γ
=1.

The intermittent charging control circuit 20 in FIG. 4 provides the thyristor control circuit 21 with a control signal having a predetermined cycle time T and charging time t1 depending on the operating conditions of the electrostatic precipitator. The output signal of the thyristor control circuit 21 is applied to the control terminal 22 to control the thyristor 12, and a secondary voltage signal as shown in FIG. 3(a) is generated from the secondary side of the transformer 13 via the rectifier 14. This secondary voltage signal is applied to the discharge electrode 15 of the electrostatic precipitator.

Power consumption element value ff during continuous charging: PW (C), power consumption element li during intermittent charging! , P W (I), charging rate r, the average secondary voltage during the charging time t1 is V, and the average secondary current is Q, the following equations are obtained, respectively.

pw(c)=v・engine・・・・・・・−・・・・
(1) PW (I) = V・Work・γ ・・・・・・・・・
...(2) The inventors operated the electrostatic precipitator at various charging rates, conducted research on the relationship between power consumption, power consumption element values, and dust collection efficiency obtained in each case, and conducted actual measurements. As a result of the analysis, the power consumption element value is proportional to the amount of power consumption, and the relationship between the dust collection efficiency η and the charging rate r is shown in Figures 5 (a), (b), and (C), respectively. It turns out that there is a three-pronged posture. The dust collection efficiency η in this case is defined by the ratio of the dust content in the gas measured at the inlet and outlet sides of the electrostatic precipitator.

Figures 5 (a), (b), and (C) show the electrostatic precipitator operated with the charge rate γ set to 0.25 and when γ set to 1.0 with continuous charging, respectively. The dust collection efficiency η was measured for the case. Fifth
Figure (a) shows that the charging rate is 02 when operating in the continuous charging method.
The dust collection efficiency η is higher than that when operating with the intermittent charging method at a charging rate of 0.5, and in FIG. The dust collection efficiency η is lower than that of Further, in FIG. 5(C), the dust collection efficiency does not change between the continuous charging method and the intermittent charging method at a charging rate of 0.25.

The inventors believe that this is because the discharge state is subtly affected by the electric resistance f of dust near the boundaries of the normal discharge region D, corona discharge suppression region E, and reverse ionization region F in Figure 2. This has been clarified as a result of actual measurements and analysis of the actual measurement data.

On the other hand, Fig. 6 shows the relationship between the power consumption element value and the charging rate actually measured by the inventors, and the continuous charging state γ = 1.0.
The power consumption element value pw=v・cm was measured using the average secondary voltage and average secondary current during operation at
C) point P is obtained. Next, a straight line is created by connecting this point P to the origin of the coordinate system. These straight lines represent the theoretical VIr that can be realized by maintaining the continuous charging conditions as they are. In other words, if the electrostatic precipitator that is currently operating in the continuous charging method is switched to the intermittent charging method, theoretically the power consumption element at this time (@ PW should be on these straight lines. The power consumption element values P'W(I) obtained by switching the internal electrostatic precipitator to intermittent charging mode with a charging rate of 0.25 are 8 in Figure 6 (a), (b), and (C), respectively. It becomes a point.

Figure 6 (a) When operating in the intermittent charging method with fl charging rate of 0.25 η power consumption element value during operation in continuous charging method with charging rate of 1.0 is multiplied by the charging rate. This is the case when the value is less than the value obtained. (b) shows that the power consumption element for one shift during operation in the intermittent charging method with a charging rate of 0.25 is 1.
This is a case where the power consumption element value during operation in the continuous charging method, which is 0, is larger than the value obtained by multiplying the charging rate. This is a case where the power element value is approximately equal to the value obtained by multiplying the power consumption element value during operation in the continuous charging method with a charging rate of 1.0 by the charging rate.

As a result of research by the inventors and actual measurements based on the research, Figure 6<
Corresponding to each of the states a>, (b), and (C), there is a certain relationship between the dust collection efficiency of the electrostatic precipitator obtained when operating with the continuous charging method and when operating with the intermittent charging method. It was confirmed that there is. That is, there is a difference between FIG. 5, which shows the dust collection efficiency η of the electrostatic precipitator obtained when operating with each charging method, and FIG. 6, which shows the power consumption element values when operating with each charging method. a).

It was revealed that (b) and (C) correspond to each other. The charge rate is 0.1 to 0 according to the inventors.
．． It is certain that this correspondence condition is satisfied within the range of 5°.

Therefore, according to this invention, during operation of the electrostatic precipitator,
Power consumption element when operating with continuous charging method [Theoretical power consumption element when operating with intermittent charging method obtained based on 1 shift and actual power consumption element obtained when operating with intermittent charging method] I can do the first shift. Therefore, based on this determination result, the charging method of the electrostatic precipitator currently in operation can be switched to a charging method that provides high dust collection efficiency, and the electrostatic precipitator can be operated.

That is, while the electric dust machine is operating in the continuous charging method, the operation is switched to the intermittent charging method for a short time, and the power consumption element value P W (
C) and PW(I)i are measured. Next, PW(C)r is calculated from the power consumption element value obtained during operation in the continuous charging method, and compared with the power consumption element value obtained during operation in the intermittent charging method, PW(I)<PW( C) γ, or P W (I)> P W (C) γ.

As a result, a determination result of PW(I)<PW(C)γ is obtained, and if it is determined that the state corresponds to FIG. 6(a), then in this case, continuous charging Since the dust collection efficiency is higher when operating in the continuous charging mode, which is the conventional operating state, the judgment result is P W (I) > P W (C)r. If it is determined that the state corresponds to FIG. 6(b), the fifth
As shown in Figure (b), since the intermittent charging method has better dust collection efficiency, the intermittent charging method is used. In this case, the electrostatic precipitator is operated while maintaining the switching state that was used to directly compare the power consumption elements.

If the judgment result is PW(1)=PW(C)・r, depending on the processing gas conditions and operating conditions of the electrostatic precipitator, intermittent charging method may be more efficient in collecting dust, or continuous charging method may be more efficient. There are cases where the dust collection efficiency is 75i better when operating at . In this case, PW(I)=P during trial operation of the electrostatic precipitator
In the case of W (C), which charging method provides higher dust collection efficiency is set in advance in accordance with the processing gas conditions and the operating conditions of the electrostatic precipitator.

Therefore, if PW (I) = PW (C) is obtained as a result of the determination, it is determined whether to operate the electrostatic precipitator with continuous charging method or with intermittent charging method in accordance with the preset conditions. is determined and the operation is performed using that charging method.

In this way, the charging method during operation of the electrostatic precipitator is switched for a determined operation time during operation, and the power consumption factor when operating with different charging methods before and after switching, that is, when operating with continuous charging method and intermittent charging method. PW(I) and PW(C)γ obtained from these are compared to determine which charging method will provide the highest dust collection efficiency. The battery is operated using a charging method. In this case, if the intermittent charging method is used, the charging rate used in the measurement at the time of the determination operation is used.

The interval between the determination operations performed by changing the charging method is determined depending on the processing gas conditions and the operating conditions of the electrostatic precipitator. According to the inventors' research and actual measurements based on the research, it has been found that it is sufficient to perform the judgment operation every 1 to 2 hours when the processing gas conditions and the electrostatic precipitator operating conditions do not change. . However, if the processing gas conditions fluctuate drastically, it is necessary to perform the determination operation every 10 to 30 minutes.

In addition, the judgment operation time for switching the charging method to obtain the power consumption element (@) and performing the judgment operation based on this requires at least 1 second until the charging state is stabilized, and it is necessary to switch the charging method frequently. Several seconds are required when performing this judgment operation.If this judgment operation time is too long, the dust collection efficiency of the electrostatic precipitator may decrease during this judgment operation.
It is necessary to avoid a determination operation time of 0 seconds or more.

The value of the charge rate r used in the determination operation is 0.1 to 0.5. When the charge rate γ is γ<0,1, it is often impossible to maintain the dust collection efficiency in an optimum state, and when γ>0.5, the energy saving effect may not be obtained. One-sided saturation was avoided with the hysteresis curve of 1 and 2, and IUJ was applied to Vl.
Although the minimum value of about 11 L for pumping is a half cycle, in the present invention, the charging time t1 and the charging pause time t2 can be treated as a unit of one AC cycle or an integral multiple thereof.

In this invention, P'W (C) r from the power consumption element in the continuous charging method, direct calculation of power consumption element by switching operation of the above charging method, measurement of secondary voltage, secondary current]
calculation, PW(I) and PW obtained before and after switching
(C) Operations such as comparison with γ and selection of charging method based on determination based on the comparison result can be performed using a microcomputer system.

For example, the actual operating conditions in which the present invention was applied to a dry electrostatic precipitator having a processing capacity of 200,000 rn''/H for treating exhaust gas generated from a dolomite calcining kiln were as follows.

In this case, the gas temperature on the inlet side is approximately 220°C.

The dust concentration was 6-12y/m8. When operating in the continuous charging method with γ = 1.0, the secondary voltage and secondary current are 54.2 KV and 266 mA, respectively, and in this case P
W(C) = 14.4 VA.

γ for 3 seconds while operating the electrostatic precipitator in continuous charging mode.
= 0.25 When the charging method was changed to the intermittent charging method and the entire operation was performed, the secondary voltage and secondary current were each 50
．． 4KV and 421.7 rn A and Natsu 7 to this case PW(I)=50.4X421.7X0.25=5.
31VA, and P W (C) X r = 14.
4X0.25=3,6 VA. Comparing these two results, P W (I) > p w (c) γ was obtained, so that from then on, operation was performed in an intermittent charging method with a charging rate γ = 0.25.

The secondary voltage and secondary current obtained while operating a similar electrostatic precipitator with an intermittent charging method of γ = 0.25 were 55 KV, respectively.
, 256 mA. In this case P W (I) = 55x
256x0.25=3.52VA, 3 seconds r=
1.0 and operated in continuous charging mode, the secondary voltage and secondary current were each 56 KV.

It became 225mA.

In the case of Kono, PW(C)=18.2VA,! : &su, PW(
C) γ = 18.2 From then on, the electrostatic precipitator is operated using the continuous charging method.

"Effects of the Invention" According to this invention, it is possible to quantitatively understand the occurrence of a remarkable reverse ionization phenomenon that requires switching of the charging method in a dry electrostatic precipitator during operation, and to determine whether the operation with any charging method will result in high dust collection. It is possible to determine whether efficiency can be achieved and operate the electrostatic precipitator in a state with high dust collection efficiency.

This determination operation is as simple as switching the charging method of the electrostatic precipitator to a different method than the one currently in operation for a short period of time during operation, and then comparing and calculating the values obtained based on the power consumption factors before and after the switch. This determination operation immediately determines which charging method has the best dust collection effect.

By selecting a charging method based on this determination result, it is possible to perform operation using a charging method that provides a good dust collection effect, and the power consumption can also be reduced.

As explained in detail above, according to the present invention, the charging method of the electrostatic precipitator that is in operation is changed, and the judgment operation is performed.
8: Select a charging method with excellent dust collection efficiency based on the judgment operation and enjoy electric sleep under conditions of high dust collection efficiency and low power consumption.8! It becomes possible to provide a charging method for an electrostatic precipitator that can be operated.

[Brief explanation of the drawing]

Figure 1 shows the relationship curve between secondary voltage and secondary current during operation in an electrostatic precipitator, where A is the relationship curve obtained when only air is flowing, and B is the relationship curve obtained when gas is flowing. The relationship curve C obtained is the relationship curve obtained in the state where the reverse ionization phenomenon occurs, Figure 2 is a diagram showing the relationship between the electrical resistance value of dust and the secondary voltage and secondary current in an electrostatic precipitator, and Figure 3 ) b) is a diagram showing the secondary voltage waveform and secondary current waveform during intermittent charging of the electrostatic precipitator, FIG. 4 is a block diagram showing an example of a control circuit used for carrying out the present invention, and FIG.
Figures (a), (b), (C) are diagrams showing the relationship between charge rate and dust collection efficiency, and Figure 6 (a), (b), (
C) is a diagram showing the relationship between charging rate and power consumption element (direct). 11: commercial AC power supply, 12: thyristor, 13: transformer, 14: rectifier, 15: discharge electrode, 16: dust collection electrode, 1
7: Secondary voltmeter, 18 Secondary ammeter, 19: Wattmeter, 2
0: Intermittent charge control circuit, 21: Cyrisk control circuit, T
: cycle time, '1: charging time, t2: charging pause time, r
: Charging rate, PW (C): Power consumption element during continuous charging,
p w (r): Power consumption during intermittent charging. Agent Takuya Kusano 1 Tuga 20 LogP 3rd Enrei 4 O 5 times (a) (b) (c) Half 6 En

Claims (1)

[Claims] (1) During operation of the dry electrostatic precipitator, switch the charging method of the voltage applied between the discharge electrode and the dust collecting electrode to a charging method that is currently not being charged, from among a continuous charging method and an intermittent charging method with a charging rate γ, PW(C) obtained from the power consumption element value PW(C) in the continuous charging method before and after this switching.
Compare γ with the power consumption element value PW(I) in the intermittent charging method, select the continuous charging method when PW(I)<PW(C)・γ, and select PW(I)>PW(C)・γ. Now, a method for charging an electrostatic precipitator in which an intermittent charging method with a charging rate γ is selected to charge the dry electrostatic precipitator and continue its operation.