JP6333697B2 - Electric dust collector - Google Patents

Description

  The present invention relates to an electric dust collector including a discharge electrode that performs corona discharge and a dust collection electrode that is disposed to face the discharge electrode.

  An electric dust collector removes soot and dust particles (also called dust, particulate matter, etc.) contained in exhaust gas or air before releasing them from a chimney or the like to the atmosphere. The electric dust collector includes a discharge electrode, a dust collection electrode disposed opposite to the discharge electrode, etc., and generates a corona discharge between the two electrodes by applying a high voltage to the discharge electrode so that exhaust gas etc. The particles contained in are charged. The charged particles are attracted to the dust collecting electrode by the electric field formed between both electrodes, and are collected on the electrode plate.

JP 2002-361117 A

  The dust collection electrode of the electric dust collector is a plate-like member and is generally installed in parallel to the gas flow. However, in order to improve the collection efficiency, it is necessary to increase the area of the dust collection electrode. At that time, since there is a limit to spreading the plate-like member in the height direction, it is necessary to increase the length in the depth direction, and the apparatus size in the gas flow direction becomes large. In that case, structural design difficulties arise, and equipment placement difficulties due to an increase in installation area occur.

  On the other hand, a breathable plate (hereinafter referred to as a “breathable member”) with uniform gap distribution over the entire surface, such as a metal mesh or punching metal, is installed in a direction perpendicular to the gas flow to collect dust. Sometimes used as a pole to collect dust. However, since the air-permeable member has a gap in the corona discharge range of the discharge electrode that can charge the particles most efficiently, the charged particles may slip through and the collection efficiency may be reduced.

  In addition, as shown in Patent Document 1, a plate-shaped member (hereinafter referred to as “plate-shaped member”) of a dust collecting electrode that does not have air permeability may be installed in a direction substantially orthogonal to the gas flow. In this case, the apparatus size in the gas flow direction can be shortened. However, when an attempt is made to improve the collection efficiency of the electric dust collector in which the plate-like member of the dust collecting electrode is installed in a direction substantially perpendicular to the gas flow, the following discharge event occurs. That is, if the dust collection area is increased in order to improve the collection efficiency, the opening is narrowed and the gas flow rate is increased. As a result, the amount of dust passing through the gas increases and the pressure loss increases. Up to now, regarding the electric dust collector that installs the plate-like member of the dust collection electrode in the direction almost orthogonal to the gas flow, the knowledge about the proper arrangement for improving the collection efficiency of the dust collection electrode and the discharge electrode is Not obtained.

  The present invention has been made in view of such circumstances, and it is possible to improve the collection efficiency when the plate-like member of the dust collection electrode is installed in a direction substantially orthogonal to the gas flow. An object of the present invention is to provide a simple electric dust collector.

In order to solve the above problems, the electrostatic precipitator of the present invention employs the following means.
That is, the electrostatic precipitator according to the present invention has a protruding discharge thorn, has a discharge electrode for performing corona discharge, and a plate-like member having no air permeability, and is disposed to face the discharge thorn. And a plate surface of the plate-like member of the dust collection electrode is disposed substantially orthogonal to a gas flow flowing toward the dust collection electrode, and the discharge electrode is disposed on the dust collection electrode. On the other hand, it is installed on the upstream side of the gas flow, discharges to the upstream surface of the plate-like member of the dust collecting electrode, and between the ends of the two adjacent plate-like members installed in the same plane When the distance is a and the width of the plate member is W,
0.1 ≦ a / (a + W) ≦ 0.5
The relationship is established.

  According to this configuration, the discharge electrode having the protruding discharge thorn performs corona discharge, and the particles included in the gas flow are collected by the dust collection electrode having the plate-like member. At this time, since the plate-like member does not have air permeability, it is difficult for particles to re-scatter, and the plate-like member is disposed almost orthogonal to the gas flow flowing toward the dust collecting electrode. The size can be shortened. Moreover, since the aperture ratio represented by a / (a + W) is in the range of 10% to 50%, the collection efficiency is high.

In the above invention, when the distance between the tip of the discharge barb of the discharge electrode and the plate-like member of the dust collection electrode is d,
0.5d ≦ W ≦ 2.0d
It is better to further establish the relationship.

  When the width W of the plate-like member is 1.0 d which is equal to the distance d between the tip of the discharge spike and the plate-like member, a result is obtained that the optimum value covers the range affected by the corona discharge. Therefore, by setting the upper limit value of the width W of the plate-shaped member to 2.0d, it is possible to prevent the current density from being excessively lowered, and by setting the lower limit value of the width W of the plate-shaped member to 0.5d, The collection efficiency can be increased without increasing the number of members 7 installed.

In the above invention, the distance between the tip of the discharge barb of the discharge electrode and the plate-like member of the dust collection electrode is d, and the distance in the height direction between two adjacent discharge barbs is H. When
0.3d ≦ H ≦ 2.0d
It is better to further establish the relationship.

  When the width W of the plate-like member is 1.0 d which is equal to the distance d between the tip of the discharge spike and the plate-like member, a result is obtained that the optimum value covers the range affected by the corona discharge. Therefore, by setting the upper limit value of the width W of the plate-like member to 2.0 d, it is possible to prevent the current density from being excessively lowered, and by setting the lower limit value of the width W of the plate-like member to 0.3 d, corona discharge The collection efficiency can be increased without causing too much interference in the generation area.

  In the above invention, a second discharge electrode is further provided on the downstream side of the gas flow with respect to the dust collection electrode, and the second discharge electrode is a downstream surface of the plate-like member of the dust collection electrode. Or the second discharge electrode may be provided on an extension of a gas passage portion formed between two adjacent plate-like members installed in the same plane. It may be provided.

  According to this configuration, since the particles are already charged on the upstream side of the plate-like member, it is effective by performing discharge toward the downstream surface of the plate-like member by the second discharge electrode. Particles can be collected.

  In the above-mentioned invention, it further includes a second dust collecting electrode installed on the downstream side of the gas flow with respect to the dust collecting electrode, and the second dust collecting electrode is the same as the dust collecting electrode installed in the same plane. You may provide on the extension of the gas passage part formed between the two said plate-shaped members adjacent.

  According to this configuration, since the particles that have passed through the upstream dust collection electrode flow toward the second dust collection electrode, it is possible to easily lead to the influence range of the corona discharge by the discharge electrode of the next stage. .

  The said invention WHEREIN: You may further provide the partition plate which block | closes the clearance gap between the said plate-shaped member of the said dust collection electrode, and the inner surface of a casing.

  According to this configuration, since the gap between the plate-like member and the inner surface of the casing is blocked by the partition plate, it is possible to prevent uncharged particles from passing through the gap and collect the dust with the dust collection electrode. Particles that are not removed can be reduced.

  The said invention WHEREIN: The said plate-shaped member of the said dust collection electrode may be arrange | positioned according to the upper end part of a hopper, and may be equipped with the structure which plugs up the clearance gap between the said plate-shaped member and the upper end part of the said hopper.

  According to this configuration, since the gap between the plate-like member and the upper end of the hopper is closed, the gas passing above the hopper can be reduced, and the collection efficiency can be increased.

  According to the present invention, when the plate-like member of the dust collection electrode is installed in a direction substantially orthogonal to the gas flow, the collection efficiency can be improved.

It is a longitudinal cross-sectional view which shows the electric dust collector which concerns on one Embodiment of this invention. It is a cross-sectional view which shows the electrostatic precipitator which concerns on one Embodiment of this invention. It is a perspective view which shows the discharge electrode and dust collection electrode of the electric dust collector which concern on one Embodiment of this invention. It is a front view which shows the dust collection electrode of the electrical dust collector which concerns on one Embodiment of this invention, and also shows the position of a discharge thorn. It is a cross-sectional view which shows the 1st modification of the electric dust collector which concerns on one Embodiment of this invention. It is a transverse cross section showing the 2nd modification of an electric dust collector concerning one embodiment of the present invention. It is a transverse cross section showing the 3rd modification of an electric dust collector concerning one embodiment of the present invention. It is a graph which shows the relationship between a collection coefficient ratio and operation time. It is a graph which shows the relationship between a pressure loss ratio and operation time. It is a cross-sectional view which shows the discharge thorn and plate-shaped member of the electric dust collector which concerns on one Embodiment of this invention. It is a perspective view of a discharge electrode and a dust collection electrode of an electric dust collector concerning one embodiment of the present invention. It is a graph which shows the relationship between a collection coefficient and an aperture ratio. It is a graph which shows the relationship between the current density on a dust collection electrode, and the ratio of the width | variety of a plate-shaped member and the distance between a discharge thorn and a plate-shaped member. It is a graph which shows the relationship between the current density on a dust collection electrode or a collection coefficient, and the ratio of the space | interval of the height direction of a discharge thorn and the distance between a discharge thorn and a plate-shaped member. It is a front view which shows the dust collection electrode of the 4th modification of the electrical dust collector which concerns on one Embodiment of this invention, and also shows the position of a discharge thorn. It is a transverse cross section showing the 5th modification of an electric dust collector concerning one embodiment of the present invention. It is a transverse cross section showing the 6th modification of an electric dust collector concerning one embodiment of the present invention. It is a cross-sectional view which shows the 7th modification of the electric dust collector which concerns on one Embodiment of this invention. It is a cross-sectional view which shows the electrostatic precipitator which concerns on one Embodiment of this invention. It is a perspective view which shows the electric dust collector which concerns on one Embodiment of this invention.

Hereinafter, an electric dust collector according to an embodiment of the present invention will be described with reference to the drawings.
The electric dust collector according to the present embodiment is installed in an exhaust gas treatment facility provided in a flue on the downstream side of an industrial combustion facility such as a coal-fired or heavy oil-fired power plant or an incinerator, for example. Further, the dust collector can be used not only for industrial combustion equipment but also for air purification equipment filters (for example, clean room air conditioning filters, virus removal filters, etc.). In the following, for the sake of explanation, the electric dust collector 1 installed in the exhaust gas treatment facility will be described.

  As shown in FIGS. 1 to 4, the electrostatic precipitator 1 includes a discharge electrode 2 that charges particles to remove particles such as dust and mist, and a dust collection electrode that is disposed to face the discharge electrode 2. 3 etc. The discharge electrode 2 and the dust collection electrode 3 are installed in the casing 4. Note that the electric dust collector 1 shown in FIGS. 1 to 4 is schematically shown, and the sizes and the number of installed discharge electrodes 2 and dust collection electrodes 3 are not limited to the illustrated example.

  The discharge electrode 2 has a mounting material 5 and a discharge thorn 6. The discharge thorn 6 is installed on the attachment material 5 and protrudes in the direction from the attachment material 5 toward the dust collection electrode 3. In the discharge electrode 2 shown in FIG. 2, the tip direction represents the tip direction of the discharge thorn 6. For example, as shown in FIG. 2, the discharge thorn 6 is installed on the upstream side of the gas flow with respect to the dust collection electrode 3. As will be described later, as shown in FIG. 1 and the like, the discharge spikes 6 may be provided on both surfaces of the dust collection electrode 3, and in this case, provided on the upstream side and the downstream side with respect to one dust collection electrode 3. It is done.

  The axial direction of the attachment member 5 is perpendicular to the gas flow at the inlet of the electrostatic precipitator 1. Here, the gas flow of the electric dust collector 1 which concerns on this embodiment is a perpendicular | vertical direction with respect to the gravity direction, for example. In addition, this invention is not limited to this example, It can apply also to the electrostatic precipitator in which the gas flow was parallel or inclined with respect to the gravity direction, and is not influenced by the gas flow direction.

  The dust collection electrode 3 has a plate-like member 7 formed of a metal plate or the like, and is installed facing the discharge electrode 2. The plate-like member 7 of the dust collection electrode 3 is a plate having no air permeability on the plate surface and having conductivity, for example, a metal plate.

  The plate surface of the plate-like member 7 of the dust collection electrode 3 is arranged substantially orthogonal to the gas flow flowing toward the dust collection electrode 3. Further, the discharge barb 6 of the discharge electrode 2 is placed opposite to the plate member 7 so that the influence range of the corona discharge is appropriately distributed in the plate member 7 of the dust collection electrode 3. For example, when there is one discharge thorn 6 in the width direction of the plate-like member 7, the discharge thorn 6 is arranged at the center in the width direction of the plate-like member 7.

  The discharge electrode 2 and the dust collection electrode 3 are spaced apart from each other and are electrically insulated. The discharge electrode 2 is connected to a high voltage power source (not shown). When a high voltage is applied to the discharge electrode 2, corona discharge occurs at the discharge electrode 2. The particles contained in the exhaust gas or the air are charged by the corona discharge, and the charged particles are attracted to the dust collection electrode 3 by the Coulomb force and collected on the plate-like member 7 which is an electrode plate.

The electric dust collector 1 is provided with a striking device (not shown) for peeling particles adhering to the dust collecting electrode 3. The hammering device has a hammer. When the hammer strikes the dust collecting electrode 3, particles attached to the surface are peeled and removed by vibration.
In addition, the removal method from the plate-shaped member 7 of the dust collection electrode 3 of particles is not limited to the strike using a strike device. For example, the particles may be removed from the plate-like member 7 by a method of blowing a gas to the particles collected on the plate-like member 7 or a method of irradiating a sound wave using a sonic horn. Further, the particles may be removed from the plate-like member 7 by cleaning with a cleaning liquid as is performed in a wet electrostatic precipitator.

  A hopper 8 is attached to the lower part of the casing 4. The hopper 8 receives particles separated from the dust collection electrode 3 of the electric dust collector 1 by hitting. The hopper 8 is provided with a particle discharging device (not shown) for discharging the accumulated particles.

Next, the dust collection electrode 3 according to this embodiment will be described.
For example, as shown in FIGS. 3 and 4, the plate-like member 7 of the dust collecting electrode 3 is a long member having a rectangular shape in front view.

  For example, as shown in FIG. 2, the plate-like member 7 is a flat plate having no bent portion in the cross-sectional shape. The plate-like member 7 is a plate without air permeability. Thereby, the plate-like member 7 has higher mechanical strength than a gas-permeable member such as a wire mesh or punching metal. For example, when removing particles collected on the surface of the plate-like member 7 of the dust collecting electrode 3, durability can be improved even when hitting or vibrating the plate-like member 7. Further, unlike the air-permeable member such as a wire mesh, the plate-like member 7 is not clogged under a condition where the particle concentration is high, so that the performance with time does not deteriorate. The manufacturing cost of the plate-like member 7 can also be reduced as compared with a breathable member such as a wire mesh.

  It is desirable that the plate-like member 7 of the dust collecting electrode 3 has a width and a height so as to be within a range affected by corona discharge generated in front of the discharge thorn 6. That is, as shown in FIG. 3, since there is no gas passage 9 between the two plate-like members 7 within the range of corona discharge, there is little slipping of charged particles and less re-scattering. The dotted line in FIG. 3 schematically shows the range of influence of corona discharge.

A plurality of plate-like members 7 of the dust collecting electrode 3 are arranged in parallel so as to be within the same plane, and an opening portion through which gas passes , that is, a gas passage portion 9, is provided between the two plate-like members 7. Is formed. The shape of the gas passage portion 9 is a rectangle when the shape of the plate-like member 7 when viewed from the front is a rectangle.

  The plate-like member 7 is arranged in a plurality of stages from the upstream side to the downstream side of the gas flow. As shown in FIG. 2, the plate member 7 on the upstream side, that is, the plate member 7 on the upstream side is arranged so that the entire surface overlaps in front view. Thereby, since the gas passage part 9 becomes the same position over several steps, it can suppress the raise of a pressure loss.

  As described above with reference to FIG. 2 and the like, the discharge electrode 2 is installed on the dust collection electrode 3. The discharge electrode 2 is installed on the upstream side of the gas flow, and the upstream side of the plate-like member 7 provided on the downstream side. It is essential to discharge the discharge thorn 6 toward the surface. This is because the discharge thorn 6 is not discharged toward the upstream side surface of the plate-like member 7 provided on the downstream side, and the discharge thorn 6 is applied only to the downstream side surface of the plate-like member 7 provided on the upstream side. This is because the particle collection efficiency is extremely low in the case of discharging toward the surface.

  However, as shown in FIG. 2, the single-sided discharge that discharges toward the upstream surface of the plate member 7 is performed in two stages in the gas flow direction, and the upstream of the plate member 7 as shown in FIG. When the case of performing double-sided discharge that discharges toward both the downstream side and the downstream side in one stage in the gas flow direction, the collection efficiency was the same. That is, if the particles are already charged on the upstream side of the plate-like member 7, it is possible to effectively collect the particles by performing discharge toward the downstream surface of the plate-like member 7. .

  Therefore, from the viewpoint of space saving of the electrostatic precipitator 1, the number of stages of the dust collection electrode 3 is reduced when the double-sided discharge is installed in a plurality of stages rather than the case where the single-sided discharge is installed in a plurality of stages. Particles can be collected without taking up much space and without reducing the collection efficiency. For example, the collection efficiency when the single-sided discharge is performed in four stages and the double-sided discharge is performed in two stages is substantially the same.

  Moreover, as shown in FIG. 5, also about the discharge electrode 2, the discharge thorn 6 can be installed toward both upstream and downstream. That is, the discharge directed to both the downstream surface of the first-stage plate member 7 and the upstream surface of the second-stage plate member 7 can be executed from one discharge electrode 2.

  In addition, this invention is not limited to this example, As shown in FIG.6 and FIG.7, the several plate-shaped member 7 may be staggered. That is, the plate member 7 on the upstream side, that is, the plate member 7 on the upstream side with respect to the plate member 7 on the upstream side may be arranged at a position corresponding to the substantially central portion of the gas passage portion 9 on the front stage side in a front view. As a result, although the pressure loss increases, the particles that have passed through the gas passage 9 can be easily guided to the influence range of the corona discharge by the discharge electrode 2 in the next stage.

  Further, in the above-described embodiment, as shown in FIG. 2 and the like, the discharge electrode 2 is disposed so as to face the discharge thorn 6 so as to be substantially at the center in the width direction of the plate-like member 7 of the dust collection electrode 3. However, the present invention is not limited to this example. For example, as shown in FIG. 7, when performing discharge toward the downstream surface of the plate-like member 7, the discharge electrode 2 may be provided also in the central portion of the gas passage portion 9. This makes it possible to collect dust that has passed through the dust collection electrode 3 and improve the collection efficiency.

  The distance a between the two plate-like members 7 of the dust collecting electrode 3 and the distance d between the discharge thorn 6 and the plate-like member 7 will be described later.

  FIG. 8 is a graph showing the relationship between the collection coefficient ratio and the operation time, and FIG. 9 is a graph showing the relationship between the pressure loss ratio and the operation time. When a metal mesh is used for the dust collection electrode of the electric dust collector (comparative example: broken line), and when a plate member of a metal plate is used for the dust collection electrode as in this embodiment (this example: solid line). Are comparing.

  In the comparative example using a wire mesh, the pressure loss increases with an increase in the operation time, and slipping due to particles passing through the wire mesh occurs, and the distance between the wire mesh and the dust is short, so re-scattering increases. As a result, the collection efficiency decreases. On the other hand, in the present Example using the plate-shaped member of a metal plate, it can drive | operate stably, without a performance falling in both pressure loss and collection efficiency.

  Next, the arrangement of the discharge barb 6 of the discharge electrode 2 and the plate-like member 7 of the dust collection electrode 3 according to this embodiment will be described. Below, as shown in FIG.10 and FIG.11, let the distance between the edge parts of the adjacent two plate-shaped members 7 installed in the same plane be a, and the front-end | tip of the discharge thorn 6 of the discharge electrode 2 and The distance between the dust collecting electrode 3 and the plate-like member 7 is d, the distance between two adjacent discharge spikes 6 is L, the width of the plate-like member 7 is W, and the height direction of the discharge spike 6 Was set to H.

  As an example of experimental conditions, the distance d between the tip of the discharge barb 6 of the discharge electrode 2 and the plate-like member 7 of the dust collection electrode 3 is 130 mm, and the distance L between two adjacent discharge barbs 6 is as follows. In the case of 150 mm, the current is relatively strong, and the region where the particles adhere densely is a substantially circular region having a diameter of about 130 mm. From this, the influence of the adjacent discharge thorns 6 cannot be ignored. However, as schematically shown in FIG. 3, the diameter is approximately equal to the distance d between the tip of the discharge thorns 6 and the plate member 7. It can be said that this indicates that the circular region as described above may be considered as a range affected by corona discharge.

On the other hand, as shown in FIG. 12, the test results show that the maximum value of the collection efficiency is in the range where the aperture ratio is 20% or more and 35% or less. Before the experiment, when the aperture ratio was about 10%, it was predicted that the collection efficiency would be maximized, but actually, the maximum value was obtained with an aperture ratio larger than expected. Considering the range in which the maximum value of the collection efficiency exists, the desirable aperture ratio is assumed to be in the range of 10% to 50%. Thereby, it can collect in the state where collection efficiency is high.
This is expressed as follows.
0.1 ≦ a / (a + W) ≦ 0.5 (Formula 1)

FIG. 13 shows the current density on the dust collecting electrode 3 and the position (the width (W) of the plate-like member 7 and the discharge thorn 6 and the plate-like member 7) from the position directly below (0 point) the discharge thorn 6 on the plate-like member 7. It is a graph which shows a relationship with ratio (W / d) between distance (d) between. As described above, when the width W is 1.0 d, the width W is an optimal value that covers the range affected by the corona discharge. On the other hand, the upper limit value of the width W is set to 2.0d so that the current density does not decrease too much, and the lower limit value of the width W is set to 0.5d in consideration of the number of the plate-like members 7 installed.
This is expressed as follows.
0.5d ≦ W ≦ 2.0d (Formula 2)

From the relationship between the interval L between adjacent discharge spikes 6, the interval a between adjacent plate members 7, and the width W of the plate members 7,
L = a + W (Formula 3)
The relationship holds.

Therefore, the above equation 1 is
1 / 9W ≦ a ≦ 1.0W (Formula 4)
And considering equation 2,
1 / 18d ≦ a ≦ 2.0d (Formula 5)
The relationship is established.

Furthermore, Equation 1 above can be expressed as
10 / 9W ≦ L ≦ 2.0W (Formula 6)
And considering equation 2,
5 / 9d ≦ L ≦ 4.0d (Formula 7)
The relationship holds.

FIG. 14 shows an average current density ratio or a collection coefficient ratio on the dust collecting electrode 3, a distance (H) in the height direction of the discharge thorn 6, and a distance (d) between the discharge thorn 6 and the plate-like member 7. It is a graph which shows the relationship with ratio (H / d). Regarding the interval H, a circular region having a diameter that is approximately equal to the distance d between the tip of the discharge thorn 6 and the plate-like member 7 may be considered as a corona discharge generation area. The optimum value is 1.0 d, similar to the optimum value of the width W described above. On the other hand, the upper limit value of the interval H is set to 2.0 d so that the collection efficiency does not decrease too much and the current density on the plate-like member 7 does not decrease too much so that the corona discharge generation area does not interfere too much. The lower limit value of the interval H is 0.3d.
This is expressed as follows.
0.3d ≦ H ≦ 2.0d (Formula 8)

Next, the relationship between the aperture ratio and the collection coefficient will be described in more detail with reference to FIGS. FIG. 12 is a graph showing the relationship between the collection coefficient ratio and the aperture ratio.
According to the experimental results, the collection efficiency is almost the maximum when the aperture ratio is in the range of 25% or more and 30% or less, and the collection efficiency is lowered even if the aperture ratio is larger or smaller than this range. In particular, when the aperture ratio is less than 10% or exceeds 50%, the collection efficiency is less than 85%, and the collection cannot be performed efficiently.

  In the present embodiment, the plate surface of the plate-like member 7 of the dust collection electrode 3 is disposed substantially orthogonal to the gas flow flowing toward the dust collection electrode 3. When shifting from a condition in which the area of the plate-like member 7 per unit gas amount is narrow to a condition in which the area of the plate-like member 7 is increased, a region in which particles can be collected increases, and the collection efficiency increases.

  On the other hand, when the area of the plate-like member 7 increases, the opening area of the gas passage portion 9 decreases, so that the flow velocity of the gas flow increases. As a result, particles accompanying the gas flow are not collected by the plate-like member 7, but particles flowing out downstream increase, and the collection efficiency decreases.

  Since these rejection events exist, as shown in FIG. 12, the collection efficiency is almost the maximum when the aperture ratio is in the range of 25% to 30%, and the aperture ratio is larger or smaller than this range. It is estimated that the result that the collection efficiency decreases was obtained.

  The experiment confirmed how the dust collection area per unit gas amount and the aperture ratio, that is, the passing gas flow velocity at the opening, affect the collection efficiency. As parameters, (1) aperture ratio, (2) number of electrode stages, (3) gas amount, and (4) electrode shape (rectangular, circular, etc.) were set. In order to determine an appropriate aperture ratio range, the contribution of each parameter to the collection efficiency was evaluated.

  As a result of the experiment, it was confirmed that the relationship of FIG. 12 was established between the aperture ratio per electrode stage under the condition of a constant gas amount and the collection efficiency regardless of the electrode shape.

  FIG. 13 shows the current density distribution ratio on the dust collecting electrode 3 and the position from the position directly below (0 point) the discharge barb 6 on the plate member 7 (the width (W) of the bar plate member 7 and the discharge barb 6 and the plate bar). It is a graph which shows the relationship with the ratio (W / d) with the distance (d) between the members 7). According to this graph, it can be seen that the current density becomes maximum at a position directly below the discharge thorn 6 and decreases as it goes to the end side of the plate-like member 7.

  The current density is about 1/5 of the maximum value at the position of + d or −d immediately below the discharge thorn 6 (0 point). The current density is almost zero at a position + 2d or −2d immediately below the discharge thorn 6 (0 point). Therefore, since it is necessary to secure a current for suppressing re-scattering of particles, the upper limit of the width W of the plate-like member 7 is 2d.

  On the other hand, if the width W of the plate-like member 7 is reduced with respect to the distance d between the discharge thorn 6 and the plate-like member 7, the number of installed plate-like members 7 increases. In the large-sized electrostatic precipitator 1, if the number of installations is large, it becomes difficult to maintain the installation accuracy of the discharge electrode 2 and the dust collection electrode 3 at a predetermined level or more. Therefore, it is reasonable to set the lower limit of the width W of the plate-like member 7 to 0.5d.

FIG. 14 shows an average current density ratio or a collection coefficient ratio on the dust collecting electrode 3, a distance (H) in the height direction of the discharge thorn 6, and a distance (d) between the discharge thorn 6 and the plate-like member 7. It is a graph which shows the relationship with ratio (H / d).
According to this experimental result, when the interval H in the height direction of the discharge thorn 6 is too narrow, adjacent discharge areas interfere with each other, and the discharge current decreases. On the other hand, if the interval H in the height direction of the discharge thorn 6 is too wide, the area where the discharge current does not flow on the plate member 7 increases. In either case, when the applied voltage is set to be the same, the average current density is reduced and the collection efficiency is reduced. In general, the higher the current density, the higher the particle collection efficiency. Therefore, it is desirable to select the interval H in the height direction of the discharge thorn 6 that increases the average current density.

  The optimum value is H / d = 1.0 where the current density coefficient ratio and the collection efficiency ratio are the highest. Despite the above-described assumption, according to the experimental results obtained by the inventors, the change in the collection coefficient ratio was small even when the average current density was changed. For example, even if the interval H in the height direction of the discharge thorn 6 is narrowed and the current density ratio is reduced to about 0.6, the collection coefficient ratio is reduced only to about 0.9. Therefore, the distance (H) in the height direction of the discharge thorn 6 and the ratio (H / d) of the distance (d) between the discharge thorn 6 and the plate-like member 7 are set in the range of 0.3 to 2.0.

Next, a modification of the electric dust collector 1 according to this embodiment will be described.
In the embodiment described above, the front view shape of the plate member 7 is rectangular, but as shown in FIG. 15, the front view shape of the plate member 7 may be circular.
In this case, the discharge electrodes 2 are installed at equal intervals in the vertical direction and the horizontal direction on the plane. The arrangement relationship between the discharge barb 6 of the discharge electrode 2 and the plate-like member 7 of the dust collection electrode 3 is the same as when the plate-like member 7 has a rectangular shape when viewed from the front. Note that the width W of the plate-like member 7 in the above description is read as the diameter W of the circular portion of the plate-like member 7 when the shape of the plate-like member 7 when viewed from the front is circular.

  Further, as shown in FIG. 16, the plate-like member 7 may be shaped like a grooved steel having a bent portion near the end in the cross-sectional shape. Further, as shown in FIG. 17, the plate-like member 7 may have a shape curved in the width direction (for example, a letter shape of a cross section U). By having such a shape, the plate-like member 7 can improve the strength as compared with the case where it is a flat plate having no bent portion. In particular, in the case of a large-sized electrostatic precipitator 1, the length of the plate-like member 7 is advantageous. Moreover, the re-scattering of the collected particle | grains can be prevented by arrange | positioning so that the center part of the plate-shaped member 7 may be dented in the downstream. Furthermore, compared to a simple flat plate, when particles collected by striking or the like are dropped, the particles are easily guided downward in the direction of gravity, so that they are less likely to rescatter.

Next, with reference to FIG. 18, a modified example of the arrangement relationship between the discharge electrode 2 and the dust collection electrode 3 inside the casing 4 will be described.
The above-described arrangement relationship between the discharge electrode 2 and the dust collection electrode 3 is also applied to the case where a plurality of plate-like members 7 and the blocking plate 10 are arranged in a U-shaped cross section in the casing 4 of the dust collection device 1. it can. In this case, the plate surface of the plate-like member 7 is parallel to the gas inflow direction and the outflow direction of the inlet portion and the outlet portion of the casing 4 of the apparatus. However, since the gas passage portion 9 is formed between two adjacent plate-like members 7, the gas flow flowing toward the dust collection electrode 3 is substantially orthogonal to the plate surface of the plate-like member 7. It will be. That is, even when the plurality of plate-like members 7 and the blocking plate 10 are arranged in the casing 4 of the electric dust collector 1 so as to have a U-shaped cross section, the plate surface of the plate-like member 7 is not dust-collected. It is arranged substantially orthogonal to the gas flow flowing toward the electrode 3.

When the plurality of plate-like members 7 and the blocking plates 10 are arranged in the casing 4 of the electric dust collector 1 so as to have a U-shaped cross-section, the discharge electrode 2 has two plate-like members facing each other. 7, the discharge thorn 6 is provided toward both plate-like members 7.
Although only the discharge from the upstream side is shown in the figure, it is possible to improve the performance by installing the discharge electrode 2 toward the plate member 7 on the downstream side of the gas flow and discharging from the downstream side. It is.

Next, with reference to FIG.19 and FIG.20, the structure which prevents the collection leak to the downstream of particle | grains is demonstrated.
In the electric dust collector 1, the plate member 7 of the dust collecting electrode 3 has a longitudinal direction parallel to the vertical direction. In order to improve the particle collection efficiency, the plate-like member 7 is desirably arranged as follows.

  That is, as shown in FIG. 19, it is necessary to provide a predetermined space between the inner surface of the casing 4 of the electrostatic precipitator 1 and the discharge electrode 2 so as to be electrically insulated. 11 is produced. Therefore, between the inner wall surface 4a of the side wall of the electric dust collector 1 and the side end portion 7a of the plate-like member 7, or between the inner upper surface of the electric dust collector 1 and the upper end portion of the plate-like member 7 (not shown). The partition plate 12 is installed in By installing the partition plate 12 on the upstream side of the gas flow, it becomes possible to suppress slipping of a gas containing uncharged particles, and to reduce particles that are not collected.

  Moreover, as shown in FIG. 20, the clearance gap formed between both can be eliminated by arrange | positioning the lower end part 3a of the plate-shaped member 7 according to the upper end part 8a of the hopper 8. As shown in FIG. As a result, the gas passes only through the gas passage 9 near the lower end of the plate-like member 7. Further, the gas passing above the hopper 8 without passing through the dust collection electrode 3 can be reduced, and the collection efficiency can be increased.

  In addition, the electric dust collector 1 which concerns on this embodiment is not only installed independently, but it is also possible to combine with other types of dust collectors, or to integrate with other types of dust collectors.

DESCRIPTION OF SYMBOLS 1 Electric dust collector 2 Discharge electrode 3 Dust collector electrode 4 Casing 5 Mounting material 6 Discharge spike 7 Plate-shaped member 8 Hopper 9 Gas passage part

Claims (6)

A discharge electrode having a protruding discharge thorn and performing corona discharge;
A plate-like member having no air permeability, and a dust collecting electrode installed opposite to the discharge thorn;
With
The plate surface of the plate-like member of the dust collection electrode is disposed substantially orthogonal to the gas flow flowing toward the dust collection electrode,
The discharge electrode is installed on the upstream side of the gas flow with respect to the dust collection electrode, and discharges to the upstream surface of the plate-like member of the dust collection electrode,
When the distance between the ends of the two adjacent plate-like members installed in the same plane is a and the width of the plate-like member is W,
0.1 ≦ a / (a + W) ≦ 0.5
Is established ,
An electric dust collector comprising a structure in which the plate-like member of the dust collection electrode is arranged in accordance with an upper end portion of a hopper and closes a gap between the plate-like member and the upper end portion of the hopper . When the distance between the tip of the discharge barb of the discharge electrode and the plate member of the dust collection electrode is d,
0.5d ≦ W ≦ 2.0d
The electric dust collector according to claim 1, wherein When the distance between the tip of the discharge barb of the discharge electrode and the plate-shaped member of the dust collection electrode is d, and the distance in the height direction between two adjacent discharge barbs is H,
0.3d ≦ H ≦ 2.0d
The electrostatic precipitator according to claim 1 or 2, wherein the relationship is further established. A second discharge electrode installed on the downstream side of the gas flow with respect to the dust collection electrode;
The second discharge electrode is provided at a position for discharging the downstream surface of the plate-like member of the dust collection electrode.
Alternatively, the second discharge electrode is provided on an extension of a gas passage portion formed between two adjacent plate-like members installed in the same plane. The electric dust collector described in 1. A second dust collecting electrode installed on the downstream side of the gas flow with respect to the dust collecting electrode;
The said 2nd dust collection electrode is provided on extension of the gas passage part formed between the two said plate-shaped members of the said dust collection electrode installed in the same plane. The electric dust collector of any one of Claims.   The dust collector according to any one of claims 1 to 5, further comprising a partition plate that closes a gap between the plate-like member of the dust collection electrode and an inner surface of the casing.

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