JPS6029304B2 - Charging method of electrostatic precipitator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charging method for a dust collector that collects dust having a high specific electrical resistance, and particularly to a charging method for an electrostatic precipitator suitable for use under changing smoke exhaust conditions. .

In general, a dust collector is a collector that separates solid particles from the gas at the feeding end of powder or granules, a device that separates particles of active ingredients from process gas, or a device that separates solid components from reaction gas. It refers to equipment that separates and collects so-called fine molecules in gas, including those used to remove them to create clean gas.

Generally speaking, electrostatic precipitation involves generating a corona discharge using a high DC voltage, charging particles in the gas (discharge electrode part), and separating the charged particles from the gas by electric force in the Kameba (dust collection). This refers to a particle electrostatic collection system with a mechanism (extreme). Electrostatic precipitation is a particularly effective dust collection method for ultrafine particles because the speed of separation and movement of particles in the submicron range does not drop as sharply as the sedimentation speed due to gravity or centrifugal force. The electrode section of a conventional electrostatic precipitator has a configuration as shown in FIG.

That is, a plurality of linear discharge electrodes 1 are provided in a row at predetermined intervals, and plate-shaped dust collection electrodes 2 are provided with a required gap between the discharge electrodes 1 provided in the row. The discharge electrode 1 and the dust collection electrode 2 are respectively installed inside the workpiece 3 outside the dust collector. Further, the dust collection electrode 3 is grounded via a ground wire 5, and a high voltage line 4 is connected to the discharge electrode 1. In such a configuration, a high voltage obtained by superimposing a pulse or an alternating current on a negative direct current is applied to the discharge electrode 1 via the high voltage line 4.

Then, a negative corona discharge is generated from the discharge electrode 1. Due to the discharge, electrons and negative ions move to the dust collecting electrode 2 which is at ground potential. During the movement of electrons and negative ions, the dust in the flue gas is charged. This negatively charged dust is collected on the dust collecting electrode 2 by the electric field created by the discharge electrode 1 and the collecting electrode 2. At this time, once the exhaust gas conditions such as the type of dust, temperature, concentration, and flow rate are determined, the current-voltage characteristics are uniquely determined.

Taking fly ash, which is generated in coal-fired boilers as a high-resistance dust, as an example, it is often used as a countermeasure against fluctuating loads. Therefore, the load fluctuations of coal-fired boilers are also large. In order to respond to this load fluctuation without reducing the bag dust rate, for example, as shown in Figure 2, the current-voltage characteristic that shows the optimum dust collection efficiency when the dust concentration changes from a high state to a low state is necessary. changes from a to b. Therefore, in order to collect dust without reducing the dust collection rate, the current should be l.
It must be decreased from o to 1. That is, the operating state shifts from point A to point B in Figure 2, and the operating voltage changes from Vo to V. It changes to Onaka. In order to follow such fluctuations in the power supply with a single power supply, the response speed is slow and a large margin is required. Furthermore, for high-resistance dust, it is necessary to perform fine current control, and in order to perform this over a wide range, the control system itself has to be very large. It also has the disadvantage of exceeding the power supply capacity and control range, making it uncontrollable. An object of the present invention is to provide a charging method for an electrostatic precipitator that can finely control discharge current over a wide range. The present invention
The discharge electrodes are divided into a plurality of groups, and the electrodes in each group are selectively charged with three types of voltages: a voltage obtained by superimposing a pulse voltage or an AC voltage on a DC voltage, a DC voltage, and an uncharged voltage depending on the smoke exhaust conditions. In addition, by changing the pulse voltage liquid peak value: pulse width, repetition frequency, alternating current peak value, alternating current charge, and pause time, the discharge current is finely controlled.

Examples of the present invention will be described below.

FIG. 3 shows an embodiment of the invention.

In the figure, 10 is a discharge electrode, and 11 is a dust collection electrode.

This discharge electrode 10 is divided into a 1st group and a 0th group, the 1st group is connected to the power supply section P, and the 0th group is connected to the power supply section P2, as shown in Table 1. A voltage in such a mode is applied. The discharge electrodes 10 are divided into groups 1 and n, with every other discharge electrode 10 or a plurality of discharge electrodes 10 in one duct along the flow of exhaust gas. In this case, 1
The number of discharge electrodes in the group and the number of discharge electrodes in the group B may be the same or different, and can be selected depending on the fluctuation range. table
1 Charging voltage mode By dividing the discharge electrode into two groups as described above and applying the voltage in the mode shown in Table 1, the current-voltage characteristic C of the first group is obtained as shown in Figure 4.
, the current-voltage characteristic d of the 0 group, and the current-voltage characteristic e of the sum thereof.By keeping the charging mode of the 1 group constant and changing the charging mode of the B group, the diagonal line in Fig. 4 can be obtained. Current control can be performed in the region shown by .

Now, if the voltage Vo is fixed, the current which was 12 at the operating point C of the first group is operated at the point D of the B group, and the dust collector as a whole will be operated at the point E, and a current of 13 will flow. By performing group voltage control as described above, it is possible to sufficiently respond to large load fluctuations, and by using pulses and alternating current, fine control can be performed. In addition, by applying the above voltage mode in correlation with the flow rate and the ionization electrode pitch, it is possible to uniformly charge the dust, and it is possible to uniformly attach the dust to the dust collecting electrode, which is particularly likely to occur with high-resistance dust. Local abnormal electric fields can be prevented, that is, locally generated total insulation breakdown can be prevented. Furthermore, even if a total breakdown occurs, it is only necessary to temporarily suspend charging for the voltage of that group, and other groups are still charged, so the temporary dust collection rate that occurs by temporarily suspending charging of the entire system as in the past In other words, an abnormal increase in exhaust dust can be prevented. f, g related to DC + AC in Table 1
This is the case where the charging time phase of the alternating current superimposed on the direct current is different, as shown in FIGS. 5A and 5B.

Even if this exchange is a pulse, the illusion remains the same. Furthermore, although the case where the ionizing electrode group is divided into two groups has been described here, the effect remains the same even if the ionizing electrode group is divided into three or more groups.

Therefore, according to this embodiment, it is possible to finely control the electrostatic precipitator over the entire range of changes in smoke exhaust conditions, and prevent uniform charging of high-resistance dust as well as local abnormal electric fields. In other words, it is possible to prevent total path failure that occurs locally.

Further, according to this embodiment, even if a complete circuit breakdown occurs, it is only necessary to temporarily suspend the voltage of that group, and it is possible to prevent a temporary abnormal increase in the amount of discharged dust. As explained above, according to the present invention, discharge current can be finely controlled over a wide range.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the electrode part of an electrostatic precipitator, FIG. 2 is a current-voltage characteristic diagram in a secondary type electrostatic precipitator, and FIG. 3 is an electrode connection diagram dividing the ionizing electrodes of the present invention into groups. Fig. 4 is a current-voltage characteristic diagram showing the effects of the present invention, and Fig. 5 is a DC +
It is a figure which shows two types of lightning voltage modes with different alternating current. Explanation of symbols, 1... Ionization electrode, 2... Bonito collecting electrode, 3
...The outside of the dust collector. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A plurality of discharge electrodes that apply a voltage obtained by superimposing a pulse voltage or an alternating current voltage to a DC voltage to cause corona discharge and supply ions into a space, and a plurality of discharge electrodes that are provided opposite to the discharge electrodes to remove dust. In an electrostatic precipitator having a dust collection electrode for adhesion and collection, the discharge electrode is divided into a plurality of groups, and three modes are applied: a voltage obtained by superimposing a pulse voltage or an AC voltage on a DC voltage, a DC voltage, and an uncharged voltage. A charging method for an electrostatic precipitator, characterized in that each of the divided discharge electrode groups is charged with one of the following according to smoke exhaust conditions. 2. The charging method for an electrostatic precipitator according to the invention as set forth in claim 1, wherein the voltage mode can be changed over time.