JPS5998747A - Electric dust collecting apparatus - Google Patents

Abstract

PURPOSE:To effectively collect dust bypassing a dust collecting space, by providing a raised wool like fiber filter to the post stage of an electric dust collecting part. CONSTITUTION:A filter 7 formed by assembling a filter constituted of a raised wool like fiber is provided to the post stage of a dust collecting section. In this case, charged dust and non-charged dust are simultaneously enter the filter 7 but this filter 7 is charged by collecting the charged dust. Whereby, a strong electric field is formed around raised fibers and the non-charged dust can be collected in a high dust collecting rate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic precipitator suitable for treating exhaust gas discharged from places.

Conventionally, electrostatic precipitators have been mainly used as dust collectors for sources that emit large volumes of exhaust gas, such as thermal power plants. Among electrostatic precipitators, flat plate electrostatic precipitators have been adopted. This will be explained below with reference to FIG. The electrostatic precipitator mainly consists of a discharge electrode 1, a dust collection electrode 2, a high voltage power supply, a hammering device, a hopper 3, and a dispersion plate 4.
and a binocular noise prevention plate 5. discharge electrode l
A high DC voltage, usually of negative polarity, is applied from a high voltage power supply to the insulator 6 for high voltage insulation, so that the gas flow velocity within the corona insulating device is made uniform.

be introduced. The dust that enters the dust collection space composed of the discharge electrode 1 and the dust collection electrode 2 collides with the electric charge generated by the corona discharge and becomes charged particles, which are then turned into charged particles by the Coulomb force and ionic wind caused by the electric field in the dust collection space. The dust is transported to the vicinity of the dust collection site.

The dust is collected extremely well by Coulomb force. The dust collected in the dust collector is brushed off at regular intervals and sent to hopper 3.
will be collected. At this time, in order to maintain high dust collection performance, it is necessary to maintain a large amount of charge generated by corona discharge, and as a discharge electrode, an electrode with a shape that facilitates current flow is used. In addition, the high voltage applied to the discharge electrode l is the voltage immediately before spark discharge, and is usually 40 mm.
A relatively high voltage is being applied. The discharge electrode 1 to which such a high voltage is applied is insulated from the casing by the insulator 6, but in the dust collection space, it is insulated by the exhaust gas dielectric strength. However, the dielectric strength of the exhaust gas varies depending on the distance between the high voltage part and the grounded dust collection electrode and casing.

The insulation distance from the casing is set to be greater than the distance between the discharge electrode and the dust collection electrode. Therefore, there is a space between the discharge electrode and the casing where no dust can collect.

The dust passing through this section is collected and goes directly to the next section. In an electrostatic precipitator, a large number of bypass prevention plates 5 are used to prevent such bypass. However, even in this case, there is a drawback that it is difficult to completely prevent bypass due to the relationship with the insulation distance from the discharge electrode.

This drawback becomes a factor that greatly affects the dust collection performance of the dust collector in the case of coal-fired power plant exhaust gas treatment which requires high dust collection performance. Taking the example of a coal-fired power plant as an example, it is as follows. in general.

Is the dust concentration in coal-fired power plant exhaust gas 20? /m3N
If 1% of the total pi·ξs exists, the dust collection performance will be 99% and the exit dust concentration will be 0.2 m3N, but recent electrostatic precipitators are required to have dust collection performance higher than 99%. However, it is clear that this will not be possible.

An object of the present invention is to provide an electrostatic precipitator that effectively collects dust that has bypassed a dust collection space.

As mentioned above, in electrostatic precipitators that require high performance, the upper limit of dust collection performance was considered to be the amount of dust that passes through the dust collection space. As a method to prevent this piston, a low-pressure ventilation loss type filter made of a filtration material with naps on the entire cross section of the bypass prevention plate installed in each section of the electrostatic precipitator is proposed. By installing a filter and collecting charged particles that could not be collected in the dust collection space, a surface potential is generated on the filter, and the dust that has bypassed the dust collection space is collected using dielectric force. be. A specific example will be described below.

Figure 2 shows the appearance of the filter used in the experiment, which was manufactured by fixing the nap filter 12 to the support frame 11.
The processing gas flows from the upper part of the support frame 11 and flows toward the nap filter. As can be seen from Figure 2, this filter has a different structure from conventional filters, and the collection mechanism of the filter is different. In other words, since conventional filters utilize the blocking effect of the filter member and also utilize the filtration effect of the dust layer formed on the filter surface, even at a filtration speed of about 15 (7), the ventilation loss is large. Versus e, 2nd
The filter shown in the figure utilizes the dielectric force generated in the raised part by collecting by inertial collision and collecting charged dust, so even at a flow velocity of about 1 m/s, the draft is as low as several wnAq. It has the characteristic of being a loss. For example, FIG. 3 shows an example of the results of an experiment conducted using the filter shown in FIG.

A shows the collection efficiency when collecting ordinary dust, and shows the collection efficiency due to inertial force, and it can be seen that it improves as the filtration rate increases. B.

C is a type of dust that gives a charge to the dust and collects the charged dust, and when charged dust is collected, the collection performance is dramatically improved to 94.95%. It can be seen that the collection efficiency decreases as the speed increases.Also, the difference between B and C is when the amount of charge applied to the dust is changed.
C has a larger amount of charge than B. In the case of C, it can be seen that the collection efficiency is 95% or more at a filtration rate of 1 m/s, and the ventilation loss is about several mm Aq.

In this way, the filter shown in Figure 2 removes charged dust.
It has become clear that even at a filtration rate of about m/s, it exhibits a high collection efficiency of 95% or more and has the characteristics of low ventilation loss.

In order to take advantage of the above-mentioned features, the present invention is designed to effectively collect charged dust that could not be collected in the previous section at the rear of each section of the electrostatic precipitator, as shown in Figure 2 at the separation between each section. By installing the filter shown in the figure, it is intended to efficiently collect dust that has bypassed the dust collection space in the previous section.

Two embodiments of the present invention will be described below with reference to FIG. 1st
The difference from the conventional example shown in the figure is that after the exhaust gas containing the dust collected is uniformized by the dispersion plate 4,
When the dust passes through the dust collection space, which is composed of the discharge electrode 1 and the dust collection electrode 2, it is charged by corona discharge and becomes charged dust.

The dust is collected by the Hecoulomb force. The charged dust that is not collected here and the uncharged dust that has bypassed the dust collection space are partially collected by the filter 7 and enter the subsequent section. At this time, filter 7
Charged dust and uncharged dust enter at the same time.

By collecting electrically charged dust, the entire filter becomes electrically charged, that is, has a potential. In this state, the raised part repels reciprocally and spreads out into space due to the repulsive force caused by the same charges, like the foil of an electroscope. In this state, the nap is very thin and forms a strong electric field around the nap, so if uncharged dust enters, it will stick to the nap due to gradient force. be captured. In this way, uncharged particles can be collected with a high dust collection rate, which prevents bypassing of the flat plate type dust collector and improves dust collection performance.

According to the present invention, charged dust that has bypassed the dust collection space can be collected, so bypass can be prevented.
It has the effect of improving dust collection performance.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a flat plate type electrostatic precipitator, Fig. 2 is a perspective view of a filter used in the present invention, Fig. 3 is a characteristic diagram of the filter shown in Fig. 2, and Fig. 4 is an implementation of the present invention. FIG. 3 is a vertical cross-sectional view of an example. l...discharge electrode 2...dust collection electrode 5...
Bypass prevention plate 7...filter.

Claims (1)

[Claims] (1) A discharge electrode to which a high voltage is applied, and a discharge electrode opposite thereto. An electrostatic precipitator equipped with an electrostatic precipitator made of a grounded precipitate electrode, characterized in that a filter made of napped woolen fiber is provided downstream of the electrostatic precipitator. Electrostatic precipitator. 2. The electrostatic precipitator according to claim 1, wherein the filter is made of raised woolen fibers.