JPH11216390A - Dry electric precipitator and operation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry electric precipitator in which a re-scattering preventing dust collecting electrode suppressing the re-scattering amt. of dust at a time of hammering is incorporated. SOLUTION: In a dry electric precipitator internally divided into a plurality of sections in relation to a gas flow direction and constituted by arranging many sets of combinations of discharge electrodes and plate-shaped dust collecting electrodes 1 in the respective sections, a combination of re-scattering preventing dust collecting electrode parts 2 and discharge electrodes 3 is arranged in the rear stage of the final section to perform two-stage dust collection. The re-scattering preventing dust collection electrode parts 2 are formed by arranging a plurality of chute-shaped dust collection electrodes in one row in the gas flow direction and the chute-shaped dust collection electrodes have trough-shaped parts having an almost U-shaped cross section extending up and down and the projected parts of the trough-shaped parts are arranged in the gas flow direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry electric precipitator and a method of operating the same, and more particularly to a dry electric precipitator having a dust collecting electrode structure for suppressing re-scattering of dust particles when collecting dust particles by hammering. And its operation method.

[0002]

2. Description of the Related Art Combustion exhaust gas using coal, heavy oil, etc. as fuel,
In addition, dust removal from combustion exhaust gas from refuse incinerators, sintering furnaces, and the like is generally performed by a dry electric dust collector (hereinafter, referred to as an electric dust collector). With increasing environmental protection activities in recent years, there has been a demand for invisible smoke emission, and there is an urgent need to improve the performance of electric dust collectors.

[0003] In general, dust collected by a dust collecting electrode in an electric dust collector is separated and dropped by hammering the dust collecting electrode to collect the dust. However, a part of the dust separated when hammered is entrained in the gas flow and discharged from the outlet of the electrostatic precipitator. This phenomenon is called the re-dispersion phenomenon due to hammering and causes visible smoke from the chimney. Therefore, achieving invisible smoke emission is important for improving the performance of the electric dust collector.

FIG. 12 shows a schematic diagram of a general electric dust collector. Two dust collection poles 101 are arranged facing each other in parallel with the gas flow,
The discharge electrodes 102 are provided at predetermined intervals at these intermediate portions. Utilizing corona discharge generated by applying a negative high voltage between the collection electrode 101 and the discharge electrode 102,
The dust in the exhaust gas is collected by the dust collecting electrode 101.

[0005] An industrial electric precipitator is constructed by combining a number of basic structures shown in Fig. 12 in the lateral direction and in the gas flow direction. FIG. 13 and FIG. 14 are views of a general configuration of an industrial electric dust collector viewed from above and from the side, respectively. The number of combinations of the basic configuration in FIG.
Depending on the dust content and the required dust collection performance, the gas flow direction is divided into sections 1 to n (FIGS. 13 and 14).
3 sections).

In FIG. 13, a gas rectifying plate 103 is disposed on the gas inlet side of the dust collection chamber 100,
In FIG. 12, a number of basic configurations are arranged. In addition,
In FIG. 13, the discharge electrodes are not shown.

In FIG. 14, a DC high-voltage power supply 104 is provided for each section, and power is applied to the discharge electrode 102 through an insulator 106 disposed in an insulator chamber 105. A weight 107 is provided below each discharge electrode 102. A hopper 108 is provided below the dust collecting electrode 101.

The collection of the dust collected by the dust collecting electrode 101 of each section is performed by hitting a part of the dust collecting electrode 101 with a hammer, that is, by so-called hammering. Dust separated from the dust collecting electrode 101 by hammering falls into the hopper 108 and is collected. However, part of the dust separated by the hammer is entrained in the gas stream as re-scattered dust, and is discharged as visible smoke from the chimney.

Until now, the required value of the dust collection performance in the exhaust gas of a coal-fired boiler was 100 to 200 mg / m ³ N as the dust concentration at the outlet of the electric dust collector, so that the influence of the re-scattered dust on the visualization of the flue gas was small. It was not necessary to consider. However, in recent years, the required value has been increased to 30 mg / m ³ N, and even to 10
mg / m ³ N, and the influence of re-scattered dust cannot be ignored. The effect of these performance requirements on the exit dust content due to re-scattered dust will be described with reference to FIGS.

FIG. 15 shows a high dust concentration (100 to 200).
mg / m ³ N), and FIG. 16 shows a low dust concentration (30 mg).
/ M ³ N, shows an example of the correspondence) to less than 10mg / m ³ N. In the case of a high dust concentration, the proportion of the re-scattered amount is small and the influence on the exit dust concentration is small. On the other hand, in the case of low dust concentration, the ratio of the re-scattered amount to the outlet dust concentration is large, and the re-scattered dust at the time of hammering is discharged from the chimney as a puff and is captured as visible smoke.

Normally, an electric dust collector is designed in consideration of the amount of re-scattering on the basis of the performance at the time of hammering. That is, FIG.
The average dust concentration at the outlet indicated by the broken line in FIG. 6 corresponds to the design value (required value). Therefore, as the required value of the electric dust collection performance increases, the effect of the re-scattered amount on the outlet dust concentration becomes remarkable. For this reason, in order to satisfy the design value, it is necessary to increase the size of the apparatus, which has caused an increase in cost. Further, it is difficult to completely suppress re-dispersion of dust by the current hammering method.

The following two methods have been proposed as prior art methods effective in preventing dust re-scattering under such circumstances. The first method is a method called a damper closed method, and the second method is a method in which a movable dust collecting electrode is adopted in the last section and is scraped off with a brush (hereinafter, referred to as a movable electrode method).

[0013]

In the damper closed system, as shown in FIG. 17, each section of the electrostatic precipitator is divided into a plurality of chambers so as to form a plurality of parallel gas flows, and an inlet and an outlet (flue portion). An entrance damper 111 and an exit damper 112 are provided so that the entrance and exit of each chamber can be opened and closed, respectively. Then, by closing the inlet damper 111 and the outlet damper 112 of the chamber to be hammered (the first chamber in FIG. 17), the hammering is performed with the gas flow shut off.

FIG. 17 shows the case of four rooms,
One of these chambers is not collecting dust because the gas flow is shut off during hammering. Therefore, when designing, it is necessary to ensure the dust collection performance required only in three chambers. In other words, an extra chamber is required to prevent dust re-scattering, so that the entire apparatus becomes large. In recent years, boilers for coal-fired power generation have been increasing in size from 500 to 1,000,000 KW, and the length in the height direction of a dust collecting electrode of an electric dust collector used for the boiler reaches over 10 m. Therefore, the damper also becomes inevitably long and frequent (once / one to ten hours).
Therefore, there is a concern about the durability of the entire apparatus, including the seal unit and the drive unit. Further, there is a possibility that the pressure change due to the opening / closing operation of the damper may make the combustion state of the boiler unstable.

On the other hand, in the moving electrode system, as shown in FIG. 18, a plurality of dust collecting electrodes 120 are formed in a caterpillar shape by a link chain 121, and are driven by a lower wheel 122 and a driving wheel 123. The discharge electrode 124 is arranged in a caterpillar space. At a position close to the lower wheel 122, a rotating brush 125 that scrapes dust from both surfaces of the dust collecting electrode 120 is provided.

In this movable electrode system, since the dust collecting electrode 120 is moved like a caterpillar, a driving unit is required, and since there are many moving mechanism components in the dust-containing gas, mechanical failure is caused. And concerns about maintenance.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dry electric precipitator incorporating a re-scatter prevention dust collecting electrode for suppressing the amount of re-scatter of dust during hammering.

Another object of the present invention is to provide an operation method suitable for the above-mentioned dry electric precipitator.

[0019]

A dry electric precipitator according to the present invention is constructed such that the inside of the precipitator is divided into a plurality of sections with respect to the gas flow direction, and a number of combinations of discharge electrodes and precipitating electrodes are arranged in each section. In the dry type dust collector consisting of
A two-stage dust collection is performed by arranging a combination of a re-scattering prevention type dust collection electrode and a discharge electrode at a stage subsequent to the final section, and the re-scattering prevention type dust collection electrode includes a plurality of chute type collection electrodes. Are arranged in a line in the flow direction of the gas, and the chute-type dust collection electrode has a gutter-like portion having a substantially U-shaped cross section extending in a vertical direction, and the flow of the gas flows through the convex side of the gutter-like portion. It is characterized by being arranged toward.

It is preferable that the chute-type dust collecting electrode is installed so as to be inclined in a direction opposite to the gas flow direction.

It is preferable that the chute-type dust collecting electrode has a left-right symmetric cross-sectional shape composed of a cylindrical body having two trough-like portions having a substantially U-shaped cross section.

It is preferable that a fin having a substantially T-shaped cross section is combined with the chute-type dust collecting electrode at the rearmost part of the re-scattering prevention type dust collecting electrode.

The chute-type dust collecting electrodes for each row in the re-scattering prevention type dust collecting electrode are connected via a connecting member.
A hammer is provided at at least one location.

Further, an opening is provided below the chute-type dust collecting electrode at the rearmost part of the re-scattering prevention type dust collecting electrode so that dust that separates and slides down above the drop-type dust collecting electrode may fall directly below. Can be

It is preferable to form a fin-shaped portion for preventing spark at the end of the gutter-shaped portion of the chute-type dust collecting electrode.

According to the present invention, there is also provided a dry-type electrostatic precipitator in which the inside of the precipitator is divided into a plurality of sections in the gas flow direction, and a plurality of combinations of discharge electrodes and precipitating electrodes are arranged in each section. A combination of a re-scatter-prevention type dust collecting electrode and a discharge electrode is disposed at a stage subsequent to the final section, and the re-scatter-prevention type dust collecting electrode comprises a plurality of chute type dust collecting electrodes arranged in a line in the gas flow direction. The chute-type dust collecting electrode has a gutter-like portion having a substantially U-shaped cross section extending in a vertical direction, and the convex side of the gutter-like portion is arranged to face the flow of the gas. The chute-type dust collecting electrode for each row in the re-scattering prevention type dust collecting electrode is connected via a connecting member, and at least one of the chute-type dust collecting electrodes is provided with a hammering device. And the chute type dust collecting electrode by the hammering device. Performed at a plurality of times intervals lighter hammering against, then dry electrostatic precipitator operating method which is characterized in that the strong hammering than the lighter hammering is provided.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the relationship between a general method of hammering a dust collecting electrode and a dust re-scattering phenomenon will be described. The hammering method includes uncharged hammering in which charging between the discharge electrode and the dust collection electrode is stopped and hammering is performed, and charged hammering in which the charging is performed in a charged state. The charged hammer includes a method in which the applied voltage is applied in a normal dust collection state and a method in which the applied voltage is reduced. Here, the former is referred to simply as charged hammering, and the latter is referred to as low charged hammering.

The dust particles collected by the dust collection electrode are separated by an electric force F = qE (q: charge amount of the dust particles, E: electric field strength between the discharge electrode and the collection electrode) and an inherent adhesion force of the dust particles. ,
It is compacted and held on the dust collection electrode surface. Usually, since hammering is performed by charged hammering, a hammering force (acceleration) that overcomes the above-described electric force is required. When hammered, most of the dust particles are separated from the dust collecting electrode in an agglomerated form (cake shape) and collected in a lower hopper, but a part is entrained in the gas flow.

FIG. 19 is a schematic diagram showing the behavior of dust particles during hammering.
Shown in When the dust collection electrode is hammered, most of the dust falls from point A to point B as an aggregated dust group, and is collected in a lower hopper. Each dust particle behaves differently depending on its physical properties (particle size, mass, adhesion between particles, electrical resistivity). That is, there are two types: those that fall off the surface of the dust collecting electrode while being separated and re-collected each time they are hammered, and those that are directly carried out of the dust collecting electrode. Among them, the dust particles moving from the point A to the point C are collected in the lower hopper, but the dust particles moving from the point A to the point D are carried out of the dust collecting pole. Therefore, the dust particles moving to the points D and E are carried out to the outlet of the electrostatic precipitator.

In the present invention, dust particles or a group of dust particles (including a cake) moving to points D and E
Is defined as rescattered particles. Although it depends on the physical properties of the dust particles, in general, if the amount of dust accumulated on the surface of the dust collection electrode (thickness of the dust attached to the dust collection electrode) increases, the amount of re-dispersion tends to increase. The ratio (re-scattered amount / dust accumulation amount) tends to decrease.

The hammering is performed for each dust collecting electrode in order to minimize the amount of re-scattering. The time interval of hammering is determined in consideration of both the dust collecting performance at the time of hammering and the amount of re-scattering. Usually, the thickness of the dust adhering layer on the surface of the dust collecting electrode is 1 to 5 mm.
Is determined assuming the time to reach.

Next, the elucidation of the re-scattering phenomenon due to hammering at the time of charged hammering will be described. Figure 2 shows the re-scattering phenomenon caused by hammering
This will be described with reference to FIGS. These figures are obtained by examining the behavior of particles re-scattered by hammering while changing the applied voltage. FIG. 20 shows the average electric field intensity between the discharge electrode and the dust collection electrode: E
(Here, the applied voltage is defined as a value obtained by dividing the distance between the discharge electrode and the dust collection electrode) by 4 KV / cm, and FIG. 21 shows 3 KV / c.
m, FIG. 22 is 2 KV / cm, and FIG. 23 is 0 KV / cm
The behavior of the re-scattered particles at the time of (uncharged) is shown.

When the average electric field strength is 4 KV / cm, hammering causes dust particles to fly out from the surface of the dust collecting electrode toward the discharge electrode, and to be collected by the dust collecting electrode again just in a semicircular shape. Gathered. When the average electric field intensity is 3 KV / cm, the distance until re-collection by the dust collection electrode becomes longer, and when the average electric field intensity becomes 2 KV / cm, the particles are hardly re-collected and re-scattered. Was observed. On the other hand, with uncharged hammering (0 KV / cm), no flyout of dust particles from the dust collection electrode surface was observed.

This phenomenon is considered as follows. In the charged state, the collected dust particles are induced with a reverse charge (positive charge) with respect to the negatively charged ions generated from the discharge electrode.
Therefore, it is thought that the dust particles are affected by the high voltage of the negative polarity and become positive electrodes by the electric attraction moment when they leave the dust collection electrode by hammering, move toward the discharge electrode, and jump out into the gas flow. Can be

On the other hand, in the uncharged state, the electric charge of the dust particles flows to the dust collecting electrode (earth), and the dust particles are in a positive / negative zero charge state. In this case, it is considered that the dust particles that have left the dust collecting electrode by hammering do not jump into the gas flow because they are not affected by the electric field. The average electric field strength of the electrostatic precipitator is operated at 2-3 KV / cm. Since this corresponds to the average electric field strength shown in FIGS. 21 and 22, it is considered that this is an operating condition in which a part of the dust particles are re-scattered by hammering. From these results, the following can be considered.

A. By adjusting the average electric field intensity between the discharge electrode and the dust collection electrode, the re-collection distance of the re-scattered dust particles can be adjusted.

B. It is possible to adjust the average electric field intensity between the discharge electrode and the dust collection electrode, suppress the electric attraction force, and reduce dust particles entrained in the gas flow.

C. Unscattered dust can be prevented by uncharged hammering.

However, in the case of hammering with the current actual machine, hammering without charging is the opposite of dust in the exhaust gas (dust that has not yet been collected at the collecting electrode, hereinafter referred to as primary particles). ) Are not collected. As a result, the dust collecting performance is reduced, so that the electric dust collector having the current structure cannot perform uncharged hammering.

The present invention provides a re-scattering prevention type dust collecting electrode based on the behavior of the re-scattered dust particles described above, and an embodiment will be described below.

FIG. 1 shows the basic structure of an electric dust collector according to the present invention.
Shown in In the present invention, a re-scattered particle re-collection section is provided at a stage subsequent to the final section (third section in FIG. 1) of the electric precipitator in which the ordinary dust collection electrode 1 is disposed. This re-scattered particle re-collection section is characterized by disposing a re-scatter prevention type dust collecting electrode section 2 and a discharge electrode 3 to minimize re-scattered particles. The re-scatter-prevention type dust collecting electrode portion 2 has a length equal to or less than half the reference length of the dust collecting electrode 11 (in FIG. 1, the length of the first or second section in the gas flow direction of the dust collecting electrode). However, it is not limited to this numerical value. The re-scatter-prevention type dust collecting electrode portion 2 collects dust not collected in the preceding stage dust collecting electrode 1 and additionally collects the dust collecting electrode 1.
It is for collecting the re-scattered dust at the time of hammering. The re-scattering prevention type dust collecting electrode portion 2 is configured by arranging a plurality of chute type collecting electrodes described later in series in the gas flow direction. A well-known hammering device is provided in each of the dust collecting electrode 1 and the re-scattering prevention type dust collecting electrode portion 2. Dust is collected by these hammering devices individually. That is, hammering is not performed simultaneously in the dust collecting electrode 1 and the re-scattering prevention type dust collecting electrode 2 in the same section. In particular, hammering in the re-scattering prevention type dust collecting electrode unit 2 will be described later in detail.

FIG. 2 shows a cross-sectional shape of the chute-type dust collecting electrode 12 constituting the re-scattering prevention type dust collecting electrode portion 2 in FIG. In FIG. 2, a chute-type dust collecting electrode 12 has two gutter-shaped portions 12-1 having portions that are gently curved from upstream to downstream so as to slightly block a gas flow, and the gutter-shaped portions 12.
And a tubular body 12-2 formed so as to expand in a direction perpendicular to the gas flow from -1 to the downstream side and connecting the two gutter-shaped parts 12-1 so that they are symmetrical. It is molded into. Thus, the gutter-shaped portion 12-
A space is formed on the back side of the device 1 so as not to receive the gas flow directly. In other words, the gutter-shaped portion 12-1 forms a dust collecting groove on the leeward side of the gas flow.
In addition, a fin portion 12-3 for preventing spark is formed at the tip of the gutter-shaped portion 12-1 on the side opposite to the cylindrical body.
This is because if a part of the electrode is sharpened somewhere, a spark is likely to occur there. Further, as will become clear later, the entire chute type dust collecting electrode 12 is formed so as to be inclined in the opposite direction to the gas flow. The plurality of chute-type dust collection electrodes 12 are arranged so as to form a row in parallel with the gas flow, and are configured to apparently act as a single dust collection electrode. The plurality of chute type dust collecting electrodes 12 are connected by a connecting member extending from the frontmost portion to the rearmost portion for each row, and a well-known hammering device is provided at a front end and a rear end of the connecting member. The reason for such a shape will be described.

At the beginning of 1920, a dust collecting electrode having a flat plate (hereinafter, referred to as a curved dust collecting electrode) was used for collecting low-resistance dust. Since the low-resistance dust loses its electric charge as soon as it is collected by the dust collection electrode, it has a weak adhesive force and is easily entrained in the gas flow. As a result, the performance is significantly reduced,
In the worst case, it falls to the point where dust collection is impossible. When a normal flat-type dust collection electrode is used to collect such low-resistance dust,
Since the dust collecting surface is smooth, the separated dust particles are entrained in the gas flow. The solution to this problem is the curved dust collection electrode. Other dust collecting electrodes for low-resistance dust include a mesh type, a perforated plate type, a pocket type, and a finned electrode. It has been confirmed that these dust collection electrodes have inferior dust collection performance as compared with the curved dust collection electrodes, and because of their complicated shapes, they are hardly used as dust collection electrodes in ordinary electric dust collectors.

In the present invention, the following measures and improvements are added to the curved dust collecting electrode, and a new operation method is adopted to prevent re-scattering of dust and improve the performance of the electric dust collector. .

A. The normal final section has a two-stage dust collection system, a normal precipitating pole is provided, and a chute-type precipitating pole is used at the rear. Alternatively, in the case where a section for re-collecting re-scattered particles is provided in addition to the final section, only the chute-type dust collecting electrode is provided alone. In the case of single installation, it is as shown in FIG.

B. The method of hammering the chute type dust collection electrode is performed for each row as follows. When the dust has begun to be collected to some extent, first, a hammer is used with a weak hammer using a hammering device in front of a row of chute type dust collecting electrodes. This is done several times at appropriate time intervals depending on the deposition conditions. Thereafter, for the purpose of peeling off the dust from the entire row of the chute-type dust collecting electrodes, the hammering is performed with a strong hammer using a hammering device on the rear side of the row of the chute-type dust collecting poles. This is called a two-stage hammering method. It is sufficient that the hammering device is provided at at least one position, and the position is not limited to only the front or the rear.

C. The chute type dust collecting electrode is installed at an angle to the gas flow to avoid entrainment by the gas flow when the dust is separated, and the gutter-shaped part has a structure to slide off the separated dust when hammering. Has become.

The features of the chute-type dust collecting electrode according to the present invention will be described below. For comparison, FIG. 3 shows a dust collecting state of a conventional flat-type dust collecting electrode, and FIG. 4 shows a dust collecting state of a chute-type dust collecting electrode according to the present invention. In the case of the plate-type dust collecting electrode of FIG. 3, as described with reference to FIGS. 19 to 23, when the dust collecting electrode is hammered, a part of the dust particles are entrained in the gas flow and re-scatter.

On the other hand, as shown in FIG. 4, a plurality of chute-type dust collecting electrodes 12 are arranged in a line in the direction of gas flow, and apparently form a single dust collecting electrode. I try to suppress the phenomenon. FIG. 5 is a view of the plurality of chute-type dust collecting electrodes 12 viewed from the side. As shown in FIG. 5, each chute-type dust collecting electrode 12 is installed so as to be inclined so as to have an inclination angle θ in a direction opposite to the gas flow.

FIGS. 6 and 7 are schematic diagrams of the chute-type dust collecting electrode 12 during dust collection and hammering. The dust particles in the gas flow are charged and collected intensively by the strong high electric field between the fin portion 12-3 of the protruding round tip of the chute-type dust collection electrode 12 and the discharge electrode (FIG. 6 (a)). )). In addition, since corona discharge is also performed in portions other than the fin portion 12-3, dust particles that have not been collected in the fin portion 12-3 are collected on almost all areas other than the fin portion 12-3. (Referred to as a main electrode portion) (FIG. 6B)
State after elapse). The dust particle layer deposited on the fin portion 12-3 is deposited at a position slightly away from the main electrode portion, and adheres intensively in a small area. When the deposition proceeds as it is, it falls naturally due to the gravitational action acting on the dust particle layer. If the hammer is not hammered in such a situation, the dust collecting performance is extremely deteriorated. Therefore, the chute type dust collecting electrode 12 is hammered lightly in a state where the dust is collected to some extent. In the case of light hammering, as shown in FIG. 7A, the dust particle layer particularly deposited on the fin portion 12-3 falls. On the other hand, in the case of normal hammering, as shown in FIG.
The dust particle layer deposited on the main electrode portion in almost the entire area other than the above falls.

FIG. 8 is a schematic view showing the gas flow around the chute dust collecting electrode 12. As shown in FIG. The gutter-shaped portion 12-1 forms a dust collection groove on the leeward side of the gas flow. Therefore, the phenomenon that the dust particles adhered to the main electrode portion collapse due to the gas flow velocity and accompany the gas flow is eliminated, and a small secondary vortex due to the gas flow is generated in the dust collecting groove. Since the vortex is at a lower pressure than the gas flow, it helps the dust particles fall into the dust collecting groove by hammering.

As shown in FIG. 7A, when hammered with a light force, the dust particles are easily separated and do not return to the gas flow, but are attracted to the positive polarity of the chute type dust collecting electrode 12. And fall into the dust collecting groove. The hammering force in this case may be less than half of the normal hammering force.

When the dust particles of the fin portion 12-3 are separated, the separated dust particles are collected in the dust collecting groove and the main electrode portion by the gas flow and the electrostatic force. In other words, it can be said that light hammering is performed to agglomerate the dust particles separated from the fin portion 12-3 on the main electrode portion. In this way, by aggregating the dust particles and increasing the particle diameter, the gravitational action at the time of collecting the dust is enhanced, and it is possible to suppress re-scattering. Therefore, in the following, light hammering is called auxiliary hammering.

After performing the auxiliary hammering several times, the dust particles collected on the main electrode portion of the chute-type dust collecting electrode 12 by the usual hammering are removed. Here, as described above, the separated dust particles have previously been agglomerated by auxiliary hammering, so that the particle diameter is large and can be collected without being entrained in the gas flow. The dust particles collected at the rear part of the main electrode part are entrained in the gas flow by ordinary hammering.
It is collected in 2-3, and agglomerated and collected by the same hammering operation.

As shown in FIG. 5, the chute type dust collecting electrode 1
2 has an inclination angle θ for the following reason. Normal,
In a dust collection electrode installed at right angles to the gas flow, dust separated by hammering is affected by the gas flow until it reaches the hopper, and there is a concern that some agglomeration may be lost and dispersed.

On the other hand, by making the chute type dust collecting electrode 12 have an inclination angle θ as in the present invention, the fallen dust is received by the dust collecting groove formed by the gutter-shaped portion 12-1, and the inner surface is slid. It becomes possible to collect while. Therefore, dust separated by ordinary hammering can be collected without being dispersed in the gas stream. Although the inclination angle θ is determined by the physical properties of the dust particles, the processing gas conditions, and the like, it is selected in the range of 3 to 15 degrees (preferably, about 6 degrees). However, if the chute-type dust collection electrode 12 is inclined, a portion where the end of the installed chute-type dust collection electrode 12 (a part close to the exit flue) is interrupted in the gas flow space apart from the hopper may appear. In this state, the chute-type dust collection electrode 12 at the end
Hammering would result in the dispersion of dust particles in the gas flow space. In order to prevent this, the trailing chute type dust collecting electrode 12 has the following structure.

Referring to FIG. 9, an opening 12-5 is provided in the dust collecting groove of the gutter-shaped portion 12-2 of the chute dust collecting electrode 12 at the end. Then, the dust that slides in the dust collecting groove is moved through the opening 1.
It falls from 2-5 to the hopper just below it. In addition to this
A substantially T-shaped special fin 20 as shown in FIG. The fin 20 allows the chute-type dust collecting electrode 12 at the end and the fin 2
A secondary vortex is generated between 0 and 0, and the entrainment of the dust particles separated from the trailing chute-type dust collecting electrode 12 into the gas flow can be further reduced. In other words, the fins 20
It acts to prevent blow-through of dust particles separated from the chute-type dust collecting electrode 12 at the end. The fins 20 are also provided with fin portions 20-1 for spark prevention at both ends thereof. Note that the fin 20 in FIG. 10 is an example of a case where the fin 20 is attached to the chute-type dust collecting electrode 12 at the end, and the size and shape are not limited to this.

FIG. 11 is a schematic view of the chute-type dust collecting electrode 12 at the end when collecting dust particles.

The effect of suppressing re-scattering of dust according to the present invention will be described based on embodiments. In the embodiment, the conventional flat-type dust collecting electrode and the chute-type dust collecting electrode of the present invention (re-scattering prevention type dust collecting electrode) are used.
For, the dust collection performance and the re-scattered amount were compared and evaluated. The specifications of the used electrostatic precipitator are shown in Table 1 below, and the test conditions are shown in Table 2.

[0060]

[Table 1]

[0061]

[Table 2]

The electric precipitator used in the embodiment has the structure shown in FIG. 4, and the conventional precipitator as a comparative example has a flat plate type and has a normal electric precipitator as shown in FIG. 3 or FIG. It is a structure of a dust collector.

Table 3 shows the dust collection performance test results of the chute-type dust collection electrode according to the present invention and the flat plate-type dust collection electrode of the comparative example.

[0064]

[Table 3]

From the test results shown in Table 3, it was confirmed that the re-scattering prevention type dust collecting electrode according to the present invention was improved in dust collecting performance by up to 10% as compared with the conventional type. The reason for the improvement in dust collection performance is that the chute type dust collection electrode can secure more dust collection area with the same installation length (length in the gas flow direction) than the flat type. Conceivable.

Next, a comparison was made between the chute type dust collecting electrode and the flat plate type dust collecting electrode with respect to the amount of re-scattering when hammering was performed.
Table 4 shows the results. Note that the measurement of the re-scattered amount was performed by installing a laser scattering dust concentration meter at the outlet of the dust collector. In this measuring instrument, the re-scattered dust amount is displayed as a cpm value (count / min), and the larger the cpm value, the larger the re-scattered dust amount.

[0067]

[Table 4]

From the test results, the amount of re-scattering by hammering was 1/10 or less for the re-scatter prevention type dust collecting electrode compared to the conventional dust collecting electrode. It was confirmed that it was extremely effective in preventing re-scattering.

The electric dust collector using the chute-type dust collecting electrode of the present invention can be miniaturized by minimizing re-scattering by hammering and suppressing re-scattering of separated dust during dust collection. Furthermore, as the greatest effect, the possibility of achieving invisible smoke emission has increased.

The measures for preventing re-scattering at the time of hammering of the dust collecting pole have been described above. At the time of hammering of the discharge electrode, a small amount of re-scattering occurs compared to the amount of re-scattering at the time of hammering of the dust collecting pole. However, it goes without saying that the present invention also effectively acts to prevent re-scattering at the time of hammering the discharge electrode. Although the above description is directed to an electric dust collector for exhaust gas in a coal-fired boiler, the present invention is also effective for electric dust collectors for iron making, cement, heavy oil combustion, orimulsion combustion, and the like. Can be widely used, and the more re-scattered dust is, the more effective it is.

In FIG. 2, two gutter-like portions 12 are shown.
Since the portion having -1 is a tubular shape that gradually expands along the flow direction of the gas flow, it is referred to as a tubular body 12-2 for convenience, but this portion 12-2 is not a tubular body, It may be plate-shaped.

[0072]

As described above, by using the chute-type dust collecting electrode of the present invention, it is possible to extremely effectively prevent re-scattering of dust particles by hammering without providing a special driving device. Can be. Therefore, the electric dust collector according to the present invention can be downsized compared to the conventional type, and the visibility of smoke exhaustion due to re-scattered dust at the time of hammering can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a basic configuration of a dry electric dust collector according to the present invention.

FIG. 2 is a view showing a cross-sectional shape of a chute type dust collecting electrode used in the present invention.

FIG. 3 is a cross-sectional view showing a dust collecting state in a normal plate-shaped dust collecting electrode for comparison with the present invention.

FIG. 4 is a cross-sectional view showing an arrangement of a plurality of chute-type dust collecting electrodes and a dust collecting state according to the present invention.

FIG. 5 is a diagram showing a plurality of chute-type dust collecting electrodes according to the present invention as viewed from the side (FIG. A) and a diagram showing a cross section taken along line AA of FIG.

FIG. 6 is a cross-sectional view (FIG. A) showing an initial dust collection state on the chute-type dust collecting electrode according to the present invention, and a cross-sectional view (FIG. B) showing a dust collection state after a lapse of time.

FIG. 7 is a cross-sectional view (FIG. A) for explaining a state of dust peeling when light hammering is performed on the chute-type dust collecting electrode according to the present invention, and dust when normal hammering is performed. FIG. 4 is a transverse cross-sectional view (FIG. B) for explaining a peeled state of FIG.

FIG. 8 is a cross-sectional view for explaining a gas flow in the vicinity of a chute-type dust collecting electrode according to the present invention.

FIG. 9 is a partial side view (FIG. A) for explaining the shape of the lower portion at the rearmost part of the chute-type dust collecting electrode according to the present invention, and a view (FIG. B) viewed from the direction of arrow A in FIG.

FIG. 10 is a cross-sectional view for explaining blow-through preventing fins combined with the last part of the chute-type dust collecting electrode according to the present invention.

11 is a partial side view (FIG. 10A) and a cross-sectional view (FIG. 10B) for explaining the operation of the blow-through prevention fin shown in FIG.

FIG. 12 is a cross-sectional view for describing a basic configuration of a conventional dry electric dust collector.

FIG. 13 is a cross-sectional view for explaining an arrangement of dust collecting electrodes in a conventional dry electric dust collector.

FIG. 14 is a longitudinal sectional view showing an internal configuration of a conventional dry electric precipitator.

FIG. 15 is a characteristic diagram for explaining the influence of re-scattering of dust due to hammering in a conventional dry electric dust collector under a high dust concentration.

FIG. 16 is a characteristic diagram for explaining the effect of dust re-scattering due to hammering in a conventional dry electric dust collector under a low dust concentration.

FIG. 17 is a cross-sectional view for explaining the operation of a conventional dry electric precipitator of a damper closed type.

FIG. 18 is a perspective view (FIG. A) and a side view (FIG. B) illustrating a conventional dry-type electrostatic precipitator of a movable electrode type.

FIG. 19 is a diagram for explaining the behavior of dust particles at the time of hammering a dust collecting pole.

FIG. 20 is a diagram for explaining the behavior of re-scattered dust particles under an electric field of 4 KV / cm.

FIG. 21 is a diagram for explaining the behavior of re-scattered dust particles under an electric field of 3 KV / cm.

FIG. 22 is a diagram for explaining the behavior of re-scattered dust particles under an electric field of 2 KV / cm.

FIG. 23 is a view for explaining the behavior of the re-scattered dust particles at the time of uncharged hammering.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 101 Dust collection electrode 2 Re-scattering prevention type dust collection electrode 3, 102 Discharge electrode 12 Chute type dust collection electrode 12-1 Gutter-like part 12-2 Cylindrical body 12-3, 20-1 Fin part 20 Fin 100 Dust chamber 103 Gas rectifier

Claims (8)

[Claims] 1. A dry type electrostatic precipitator in which the inside of a precipitator is divided into a plurality of sections in the gas flow direction, and a plurality of combinations of discharge electrodes and precipitating electrodes are arranged in each section. A combination of a scattering prevention type dust collecting electrode and a discharge electrode is arranged to perform two-stage dust collection, and the re-scattering prevention type dust collecting electrode is configured to divide a plurality of chute type dust collecting electrodes into a flow direction of the gas. The chute-type dust collecting electrode has a gutter-like portion having a substantially U-shaped cross section extending in the vertical direction, and the convex side of the gutter-like portion is arranged facing the flow of the gas. A dry-type electrostatic precipitator, characterized in that: 2. The dry type electrostatic precipitator according to claim 1, wherein the chute type dust collecting electrode is installed so as to be inclined in a direction opposite to a flow direction of the gas. 3. The chute-type dust collection electrode is substantially U-shaped in cross section.
The dry type electrostatic precipitator according to claim 2, wherein the dust collector has a symmetrical cross-sectional shape comprising a cylindrical body having two U-shaped trough-shaped portions. 4. The dry-type electric device according to claim 3, wherein a fin having a substantially T-shaped cross section is combined with the chute-type dust collection electrode at the rearmost part of the re-scattering prevention type dust collection electrode. Dust collector. 5. The chute-type dust collecting electrode for each row in the re-scattering prevention type dust collecting electrode portion is connected via a connecting member, and a hammer is provided at at least one position. The dry electric dust collector according to claim 4, wherein 6. An opening is provided at a lower portion of the last chute-type dust collecting electrode in the re-scattering prevention type dust collecting electrode for dropping the dust which is separated and slid down at an upper portion from the lower portion. The dry electric precipitator according to claim 5, wherein 7. The dry type electrostatic precipitator according to claim 1, wherein a fin-shaped portion for preventing spark is formed at an end of the gutter-shaped portion of the chute type dust collecting electrode. 8. A dry type electrostatic precipitator comprising: a plurality of sections inside a precipitator which are divided into a plurality of sections with respect to a gas flow direction, and a plurality of combinations of discharge electrodes and plate-shaped precipitating poles arranged in each section; A combination of a re-scattering prevention type dust collecting electrode portion and a discharge electrode is arranged at a stage subsequent to the section, and the re-scattering prevention type dust collecting electrode portion is configured by arranging a plurality of chute type dust collecting electrodes in a line in the gas flow direction. The chute-type dust collecting electrode has a gutter-like portion having a substantially U-shaped cross section extending in a vertical direction, and the convex side of the gutter-like portion is arranged toward the flow of the gas. A chute-type dust collecting electrode for each row in the re-scattering prevention type dust collecting electrode portion is connected via a connecting member, and at least one of the chute type dust collecting electrodes is a method for operating a dry type electric dust collector comprising a hammering device, A light hammer for the chute type dust collecting electrode by the hammering device. A method for operating a dry-type electrostatic precipitator, comprising: hitting a plurality of times at intervals, and thereafter performing a hammering stronger than the light hammering.