JPH0724358A - Operation control of electric dust collector for main exhaust gas from sintering machine - Google Patents

Abstract

PURPOSE:To prevent dust collection efficiency from being lowered because of a reverse ionization phenomenon by statistically processing data on dust concentration after dust collection, and a correlation between peak voltage and bottom voltage between an electric discharge electrode and a dust collection electrode periodically, and control the operation by determining an electric charging cycle to the electric discharge electrode and an electric discharge voltage. CONSTITUTION:A main exhaust gas 5 from a sintering machine is purified by collecting dust from the gas using an electric dust collector 1, and the purified gas 6 is discharged. In this case, the dust concentration of the purified gas 6 is detected using a dust concentration detector, and this detection signal 9 is entered into a calculation controller 7. On the other hand, the voltage between an electric discharge electrode 1-1 and a dust collection electrode 1-2 is detected using a voltage detector 3, and this detection signal 8 is entered into the calculation controller 7. Further, data between the peak voltage of an electric charge voltage signal and the dust concentration of the electric dust collector 1 is analyzed regressively using the calculation controller 7, and thereby, a generating regressive coefficient and a correlation coefficient are determined. In addition, the same processing of the data between the peak voltage and the bottom voltage is also performed. Further it is determined whether a certain electric charge conditions control signal 10 for the electric dust collector 1 should be sent to a power pack 2, i.e., by referring to several cases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control method for an electric precipitator used for collecting the main exhaust gas of a sintering machine,
More specifically, it relates to an operating method for reducing the concentration of dust particles in the exhaust gas from the outlet of the electrostatic precipitator within a set range.

[0002]

2. Description of the Related Art Cyclones have been widely used in dust collectors of sintering machines, but most of them use dry electrostatic precipitators due to stricter pollution regulations.

The dust collection efficiency η of the electrostatic precipitator is represented by η = 1-e- ^{wA / Q} from the Deutsche equation. However, w is the dust moving speed, A is the capacity of the electrostatic precipitator, and Q is the amount of exhaust gas. Here, since the capacity A of the electrostatic precipitator is fixed, the items that change the dust collection efficiency η during operation are the dust moving speed w and the exhaust gas amount Q. The dust moving speed is the speed at which anions formed by corona discharge are charged to dust and are attracted to the dust collector plate, which is the positive electrode, by the Coulomb force.

Conventionally, the following method has been known as a control method for an electrostatic precipitator. (1) A method of hammering the dust collecting electrode intermittently by a hammering device to mechanically remove the accumulated dust on the surface of the dust collecting electrode and increase the dust moving speed W, (2) Deposition on the dust collecting plate The dust collection efficiency η greatly changes depending on the electric resistance value ρd of the dust layer and is represented by ρd = f (water content, temperature). Therefore, the electric resistance value ρd is measured by actually measuring the water content and temperature in the gas. There is a method of calculating and controlling by determining which of the four areas shown below is the area of B, C, or D. Area A (re-scattering, η = 0) Area B (normal, good η) 1 × 10 ⁴ ≦ ρd ≦ 5 × 10
¹⁰ (Ω · cm) C region (frequent sparks, η deterioration) 5 × 10 ⁵ ≦ ρd ≦ 1 × 1
0 ¹¹ (Ω · cm) D region (reverse ionization, η deterioration) 1 × 10 ¹² ≦ ρd (Ω · c
m)

As another method, (3) a method has been proposed in which the most appropriate charge control of an electrostatic precipitator is selectively applied to each of the above four areas to enhance the dust collecting efficiency (Japanese Patent Laid-Open No. 60-60). 94160, etc.). This method focuses on the fact that the apparent resistivity value of dust is greatly affected by temperature and humidity, and by measuring this as a parameter, the apparent resistivity value of dust is calculated to obtain the dust collection electrode. In this method, the charging method is selected by automatically determining the occurrence and state of back corona that generates cations and diffuses into the dust collecting space.

(4) The outlet of the electrostatic precipitator, which detects the concentration of dust particles in the exhaust gas from the outlet of the electrostatic precipitator, and adjusts the charge rate of the electrostatic precipitator that performs intermittent charging when the detected value is out of the set range. A method for controlling the concentration of dust particles in the exhaust gas to be within a set range (see Japanese Patent Laid-Open No. 59-36559), (5) Detecting the spark generation voltage of the electrostatic precipitator, and multiplying the value by a coefficient. Control method for setting peak voltage (see Japanese Patent Laid-Open No. 61-249557), (6) When collecting high-resistance dust, automatic switching between intermittent charging and continuous charging is performed according to the frequent occurrence of sparks. An operation method (see Japanese Patent Laid-Open No. 62-45361) for improving dust efficiency has been proposed.

[0007]

However, the above-mentioned conventional methods have the following drawbacks. That is, (1)
The method of intermittently hammering the dust collecting electrode with the hammering device to mechanically remove the accumulated dust on the surface of the dust collecting electrode and increase the dust moving speed W is to improve the dust collecting efficiency due to fluctuations on the inlet side of the electrostatic precipitator. There is a drawback that η is controlled and is not stable. Also,
(2) The method of (3) measuring the amount of water in the gas and the temperature to calculate the electric resistance value ρd and performing the electric dust collector charging control is as follows.
Since the charge control of the electrostatic precipitator is controlled to be constant in each of the above-mentioned areas, it is not possible to cope with minute fluctuations within the area, and the final output dust concentration in the exhaust gas from the electrostatic precipitator is not directly controlled. There is a drawback that the dust collection efficiency η cannot be accurately grasped.

Further, the method (4) for controlling the charging rate according to the concentration of the dust particles at the outlet of the electrostatic precipitator is limited to the one in which the correlation between the charging conditions and the generation sources of dust particles, dust particles, etc. is known. Therefore, there is a drawback that the optimum control for increasing the dust collection efficiency η of the electrostatic precipitator for the main exhaust gas of the sintering machine cannot be sufficiently performed.

Further, since the control methods (5) and (6) are control based on only the charging state between the discharge electrode and the dust collecting electrode of the electrostatic precipitator, the state of the dust collecting efficiency should be properly grasped. In addition, the control method of (5) cannot cope with the dust collection situation that changes from moment to moment, and the control method of (6) needs to adjust the set value of the switching timer each time. Due to poor responsiveness and the like, each of them has a drawback that the optimum control for increasing the dust collection efficiency η cannot be sufficiently performed as in the case of (4).

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and proposes an operation control method of an electric dust collector for a main exhaust gas of a sintering machine, which can maximize the dust removal efficiency of the electric dust collector. It is what

[0011]

SUMMARY OF THE INVENTION The present invention controls the applied voltage and the application time to prevent the deterioration of the dust collection efficiency due to the reverse ionization phenomenon, so that the dust collection efficiency .eta.
Can be the maximum, that is, a control method that enables an optimal operation that can minimize the dust concentration in the exhaust gas of the electrostatic precipitator outlet, the gist of which is a charging voltage signal between the discharge electrode and the collecting electrode of the electrostatic precipitator, The signal for detecting the dust concentration in the exhaust gas at the outlet of the electric dust collector is taken into the arithmetic and control unit, and the correlation coefficient between the peak voltage of the charging voltage of the electric dust collector and the dust concentration in the exhaust gas at the outlet of the dust collector and the regression coefficient, and the correlation coefficient between the peak voltage and the bottom voltage are calculated. Then, in case 1 below, the charging voltage is increased, in case 2 the charging cycle is shortened, in case 3 the charging cycle is lengthened, in case 4 the electrostatic precipitator is operated to lower the charging voltage. The set value of the charging voltage and the charging period is controlled based on the peak voltage and the magnitude of the population regression coefficient of the dust concentration in the exhaust gas from the dust collector outlet exhaust gas. It is an operation control method of the scan for the electrostatic precipitator. Case 1: The correlation coefficient between the peak voltage and the dust concentration in the exhaust gas from the dust collector exit is negative, and the correlation coefficient between the peak voltage and the bottom voltage is positive. Case 2: The correlation coefficient between the peak voltage and the dust concentration in the exhaust gas from the dust collector exit is negative, and the correlation coefficient between the peak voltage and the bottom voltage is also negative. Case 3: The correlation coefficient between the peak voltage and the dust concentration in the exhaust gas from the dust collector outlet is positive, and the correlation coefficient between the peak voltage and the bottom voltage is also positive. Case 4: The correlation coefficient between the peak voltage and the dust concentration in the exhaust gas from the dust collector outlet is positive, and the correlation coefficient between the peak voltage and the bottom voltage is negative.

[0012]

The basic concept of charging the electrostatic precipitator is as follows. There are the following three types of charging methods for the electrostatic precipitator as shown in the relationship between time and applied voltage as shown in FIG. (a) Continuous charging: A charging method in which a constant voltage is applied to the discharge electrode and the collecting electrode by a general method. (b) Intermittent charging: In continuous charging, when high-resistance dust (typically sintering exhaust gas) accumulates on the collecting electrode, local sparks are generated and high voltage cannot be applied. Because it is the voltage at the time of dielectric breakdown between the electrodes). Therefore, if the applied voltage is momentarily turned off, this phenomenon can be prevented a little, so charging is repeated by turning on and off at intervals of several seconds. This is called an intermittent charging method. (c) Pulse charging: A charging method in which an ON / OFF operation of intermittent charging is turned ON / OFF in the order of microseconds by a switching circuit.

In an electric dust collector that collects high-resistance dust,
As described above, a local spark is likely to occur between the collector electrode and the discharge electrode, and the dust collection efficiency is reduced. This is called the reverse ionization phenomenon. It has been experimentally proved that when this reverse ionization phenomenon occurs, the dust collection efficiency does not increase even if the charging voltage of the electrostatic precipitator is increased, and the bottom voltage decreases immediately after charging. As a measure to prevent the reverse ionization phenomenon, it is considered that the method of lowering the applied voltage or shortening the application time is effective, but in order to always carry out the optimum application, it is possible to accurately judge whether or not the reverse ionization phenomenon has occurred. However, the applied voltage and the applied time must be properly controlled.

In the present invention, the basic concept for determining whether or not the reverse ionization phenomenon has occurred is shown in FIGS. 8 (a) and 8 (b). 8A shows the relationship between the electric precipitator peak voltage and the electric dust collector output side dust concentration, and FIG. 8B shows the relationship between the electric precipitator peak voltage and the electric precipitator bottom voltage.

That is, in FIG. 8A, the correlation coefficient between the peak voltage of the electrostatic precipitator and the dust concentration on the output side of the electrostatic precipitator is negative when the dust concentration on the outgoing side decreases as the peak voltage rises, and the peak voltage rises. If the discharge side dust concentration increases as the temperature rises, the correlation coefficient between the electrostatic precipitator peak voltage and the electrostatic precipitator bottom voltage is determined as shown in FIG. If the bottom voltage becomes negative and the peak voltage increases as the peak voltage increases, it is determined to be positive. When the correlation coefficient between the peak voltage and the dust concentration in the exhaust gas from the dust collector exit and the correlation coefficient between the peak voltage and the bottom voltage are Case 1,
The reverse ionization phenomenon is prevented by increasing the charging voltage, shortening the charging cycle in case 2, controlling the charging cycle in case 3 and decreasing the charging voltage in case 4. It is possible to suppress a decrease in dust collection efficiency. The degree of change in the set value at that time is determined by the magnitude of the population regression coefficient (absolute value) between the peak voltage and the dust concentration. That is, when the population regression coefficient is large, the change range is also large. If the case 4 frequently occurs under the above control, it is determined that the charging status is abnormal, and the maintenance work of the electrostatic precipitator is performed.

As described above, according to the present invention, the applied voltage and the applied time are controlled based on the charged state of the electrostatic precipitator and the dust concentration, so that the reverse ionization phenomenon can be prevented and the deterioration of the dust collecting efficiency can be minimized. Further, in the conventional control method, the feedback factor is a fixed value that is experimentally obtained, whereas in the present invention, the situation that changes from moment to moment is captured and fed back to the electrostatic precipitator operating conditions, so the electrostatic precipitator is accurately controlled. can do.

[0017]

1 is a block diagram showing an example of the construction of an apparatus for carrying out the method of the present invention, 1 is an electrostatic precipitator, 1-1 is a discharge electrode, 1-2 is a dust collecting electrode, 2 is a power pack, 3 Is a voltage detector, 4 is a dust concentration detector, 5 is a main exhaust gas of a sintering machine, 6
Is a cleaning gas, 7 is an arithmetic and control unit (computer),
Reference numeral 8 is an electrostatic precipitator charging voltage signal, 9 is a dust concentration detection signal, and 10 is an electrostatic precipitator charging condition control signal.

The main exhaust gas 5 of the sintering machine is introduced into the electrostatic precipitator 1 to collect dust and is discharged as a cleaning gas 6 thereof. At this time, the dust concentration detector 4 provided on the outlet side of the electrostatic precipitator. The dust concentration in the cleaning gas 6 is detected, and the dust concentration detection signal 9 is input to the arithmetic and control unit 7. At the same time, the electric dust collector charging voltage signal 8 is input to the arithmetic and control unit 7 from the voltage detector 3 which detects the voltage between the discharge electrode 1-1 and the dust collecting electrode 1-2.

The arithmetic and control unit 7 performs a regression analysis between the peak voltage and the dust concentration in the electrostatic precipitator charging voltage signal 8 to obtain a mother regression coefficient and a correlation coefficient. Further, similar processing is performed between the peak voltage and the bottom voltage. Then, the electric dust collector charging condition control signal 10 is sent to the power pack 2
To the power pack 2. The determination for transmitting to the power pack 2 is performed, that is, the determination of Cases 1 to 4 described above is performed. Table 1 shows the determination table by the correlation coefficient, Table 2 shows the contents of the electrostatic precipitator charging condition control signal in each case, and Table 3 shows the set value change range depending on the magnitude of the population regression coefficient.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

That is, when the arithmetic and control unit 7 determines, for example, "case 3", the content of the charge condition control signal is determined to "lengthen the charge cycle", and the degree is determined from the mother regression coefficient of 0.8. Determined as "8Hz". That is, since the reverse ionization phenomenon has occurred, a control signal for increasing the charging period by 8 Hz is transmitted to the power pack 2 of the electrostatic precipitator 1. As a result, the dust concentration in the exhaust gas at the outlet of the electrostatic precipitator 1 can be stabilized at a low level.

Example 1 FIGS. 2 to 6 show the results of the control test of the electrostatic precipitator for the main exhaust gas of the sintering machine under the test conditions shown in Table 4. 2 is a correlation coefficient between peak voltage and dust concentration, a correlation coefficient between peak voltage and bottom voltage, FIG. 3 is a mother regression coefficient, FIG. 4 is an electrostatic precipitator charging voltage, FIG. 5 is an electrostatic precipitator charging cycle, and FIG. 6 shows the dust removal efficiency, respectively. The charging conditions in the conventional method were set to a maximum applied voltage of 50 kv (decreased when reverse ionization occurs) and a constant charging of 15 Hz by pulse charging.

That is, in the present embodiment, the method of the present invention was applied when 3 hours had elapsed after the start of charging by the conventional method. Various detection signals as control conditions at that time were sampled at a pitch of 30 seconds, and an average value for 2 minutes was applied. In addition, 30 data were used for the regression analysis. Therefore, the control was not performed for securing the number of data for one hour after the control switching, and after the lapse of one hour, the first control signal was transmitted to the power pack for control. Subsequently, regression analysis was performed at a 10-minute pitch (the data number is 30 so that the data for the first 10 minutes is deleted), and control was performed.

As is clear from the results shown in FIGS. 2 to 6, according to the method of the present invention, the charging voltage of the electrostatic precipitator is higher than that of the conventional method (constant charging), so that the reverse ionization phenomenon can be suppressed. As a result, the dust removal efficiency could be significantly increased (see FIG. 6).

[0027]

[Table 4]

[0028]

As described above, according to the method of the present invention, the correlation between the dust concentration after dust removal and the peak voltage and bottom voltage between the discharge electrode and the dust collecting electrode is statistically processed periodically. Since the charging period and the charging voltage to the discharge electrode are determined and controlled based on the result, it is possible to effectively prevent the reverse ionization phenomenon that tends to occur especially when collecting high-resistance dust such as sintering main exhaust gas. As a result of being able to increase the charging voltage of the electrostatic precipitator, it is possible to maintain the maximum dust collecting efficiency of the electrostatic precipitator, which has a great effect of significantly reducing the concentration of dust particles in the exhaust gas at the outlet of the electrostatic precipitator. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a device configuration for carrying out the method of the present invention.

FIG. 2 is a diagram showing a correlation coefficient between a peak voltage and a dust concentration and a correlation coefficient between a peak voltage and a bottom voltage in Example 1 of the present invention.

FIG. 3 is a diagram showing a population regression coefficient in the same example.

FIG. 4 is a diagram showing a change in charging voltage of the electrostatic precipitator according to the embodiment.

FIG. 5 is a diagram showing a transition of a pulse charging period of the electrostatic precipitator in the same example.

FIG. 6 is a view showing the dust removal efficiency in the above-mentioned embodiment in comparison with the conventional method.

FIG. 7 is a diagram showing types of charging methods for the electrostatic precipitator.

FIG. 8 is a basic conceptual diagram for determining whether or not the reverse ionization phenomenon of the electrostatic precipitator occurs, (a) is a diagram showing a relationship between the electrostatic precipitator peak voltage and the dust concentration on the output side of the electrostatic precipitator, and (b) is a peak of the electrostatic precipitator. It is a figure which shows the relationship between a voltage and a bottom voltage.

[Explanation of symbols]

 1 Electrostatic Precipitator 1-1 Discharge Electrode 1-2 Dust Collection Electrode 2 Power Pack 3 Voltage Detector 4 Dust Concentration Detector 5 Sinter Machine Main Exhaust Gas 6 Purifying Gas 7 Operation Control Device (Computer) 8 Electrostatic Precipitator Charge Voltage Signal 9 Dust concentration detection signal 10 Electric dust collector charging condition control signal

Claims (1)

[Claims] 1. A peak voltage of the loading voltage of the electric dust collector and the dust in the exhaust gas of the dust collector exit are taken in by a charge control voltage signal between the discharge electrode and the dust collecting electrode of the dust collector and the dust concentration detection signal of the exhaust gas at the dust exit of the dust collector. The concentration correlation coefficient and population regression coefficient, and the peak voltage and bottom voltage correlation coefficients are obtained. In case 1 below, the charging voltage is increased, in case 2 the charging cycle is shortened, and in case 3 In case 4, the electrostatic precipitator is operated and controlled so that the charging cycle is lengthened and the charging voltage is lowered, and the set values of the charging voltage and the charging cycle are the population regression coefficient of the peak voltage and the dust concentration in the exhaust gas from the dust collector outlet. A method for controlling the operation of an electrostatic precipitator for a main exhaust gas of a sintering machine, which is characterized in that it is determined based on the size. Case 1: The correlation coefficient between the peak voltage and the dust concentration in the exhaust gas from the dust collector exit is negative, and the correlation coefficient between the peak voltage and the bottom voltage is positive. Case 2: The correlation coefficient between the peak voltage and the dust concentration in the exhaust gas from the dust collector exit is negative, and the correlation coefficient between the peak voltage and the bottom voltage is also negative. Case 3: The correlation coefficient between the peak voltage and the dust concentration in the exhaust gas from the dust collector outlet is positive, and the correlation coefficient between the peak voltage and the bottom voltage is also positive. Case 4: The correlation coefficient between the peak voltage and the dust concentration in the exhaust gas from the dust collector outlet is positive, and the correlation coefficient between the peak voltage and the bottom voltage is negative.