JP2015136683A - Electric dust collecting device and dust collecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric dust collecting device which reduces an ozone generation amount and which can maintain high dust collection performance, and a dust collecting method using the electric dust collecting device.SOLUTION: An electric dust collecting device has: a charging part 10 in which a first discharge electrode 12 has a plurality of first discharge parts 14; a dust collecting part 20 which is installed on a downstream side of the gas of the charging part 10 and which includes a second earth electrode 21 and a second discharge electrode 22; and a voltage generation part 30. A collection plate 40 is installed at an end part located on the downstream side of the gas of the second earth electrode 21. The voltage generation part 30 charges dust by applying positive-polarity voltage to the first discharge electrode 12, the voltage generation part 30 applies the positive-polarity voltage to the second discharge electrode 22, and the second earth electrode 21 and the collection plate 40 collect the charged dust.

Description

  The present invention relates to an electric dust collector, and more particularly, to an electric dust collector installed in a tunnel in which a vehicle travels and a dust collecting method using the same.

  In a long tunnel that penetrates the mountainous area or a tunnel with a large amount of traffic, an air purification system is installed in the tunnel for the purpose of ensuring visibility within the tunnel and improving the environment. FIG. 9 shows an example of a tunnel air purification system. The air purification system 300 is installed in a bypass tunnel 320 branched from a main tunnel 310 in which a vehicle 311 travels or in a ventilation station. In the bypass tunnel 320 and the ventilation station, an air path 340 and a blower 360 are further installed on the downstream side of the air purification system 300, and an auxiliary machine room 330 and an electric room 350 are installed outside the air path 340.

FIG. 10 is an example of an air purification system. Exhaust gas discharged from the vehicle contains nitrogen oxides such as NO ₂ and NO in addition to dust (floating particulate matter, represented as “SPM” in FIG. 10). The air guided to the bypass tunnel 320 flows into the air purification system 300 with dust and nitrogen oxides. The air purification system 300 includes an electrostatic precipitator 301 and a denitration device 302 in order from the gas inlet side in order to remove NO ₂ and SPM.

  Patent document 1 discloses an example of the electrostatic precipitator 301. The electric dust collector of Patent Document 1 includes a charging unit and a dust collecting unit. The charging unit and the dust collecting unit include electrodes in which discharge electrodes and dust collecting electrodes are alternately arranged in parallel. The electrostatic precipitator of Patent Literature 1 generates negative corona discharge in the charging unit to charge the dust negatively, and generates an electric field in the direction of the discharge electrode in the subsequent dust collecting unit. The dust collection electrode attracts the dust collection electrode and collects the dust. By this step, dust is removed from the exhaust gas.

The gas after the dust has been collected is conveyed to a denitration device 302 at the subsequent stage. The denitration apparatus 302 includes an absorbent 303 inside. Nitrogen oxides in the gas are removed from the gas when the absorbent 303 absorbs NO ₂ in the gas when passing through the denitration apparatus 302. The denitration apparatus 302 is, for example, one in which a reaction accelerator is supported on a honeycomb activated carbon carrier.

Among the nitrogen oxides contained in a gas discharged from the vehicle to the environment, regulations are set for NO _2. For this reason, the denitration apparatus 302 installed in the tunnel uses an absorbent carrying a reaction accelerator (for example, KOH) that absorbs NO ₂ . In the absorbent, NO ₂ is removed from the gas by the following reaction formula.
2NO ₂ + 2KOH → KNO ₂ + KNO ₃ + H ₂ O (1)
On the other hand, NO passes through the absorbent 303 and is discharged from the air purification system 300.

Japanese Patent No. 4964515

In the electric dust collector of Patent Document 1, ozone is generated by negative corona discharge. NO in the exhaust gas is oxidized to NO ₂ by ozone. Since the negative corona discharge generates a large amount of ozone, the NO ₂ concentration increases while passing through the electrostatic precipitator. When a denitration apparatus equipped with an NO ₂ absorbent is installed in the subsequent stage, the processing load of the absorbent is increased, and the life of the absorbent is reduced.

  The present invention has been made in view of the above problems, and is an electrostatic precipitator capable of reducing the amount of ozone generated and maintaining high dust collecting performance, and a dust collector using the electrostatic precipitator. It aims to provide a method.

  A first aspect of the present invention is an electrostatic precipitator that collects dust in a gas containing NO, wherein first ground electrodes and first discharge electrodes are alternately arranged substantially in parallel with each other. A charging unit, a dust collecting unit installed downstream of the gas of the charging unit, wherein second ground electrodes and second discharge electrodes are alternately arranged substantially parallel to each other; the charging unit and the collecting unit; A plurality of first discharge electrodes projecting in a direction substantially parallel to the gas flow direction from the downstream and upstream ends of the gas. The second ground electrode and the second discharge electrode have a substantially flat plate shape, and the second ground electrode is disposed at the end located on the downstream side of the gas. A voltage collector that has a collecting plate that collects the dust in the gas, Applying a positive voltage to the first discharge electrode to generate a corona discharge between the first discharge part and the first ground electrode, and applying a positive voltage to the second discharge electrode Then, an electric field directed to the second ground electrode is generated between the second ground electrode and the collecting plate and the second discharge electrode.

  According to a second aspect of the present invention, there is provided a dust collection method for collecting dust in the gas containing NO using the electric dust collector according to the first aspect, wherein the voltage generation unit is the first. A positive voltage is applied to one discharge electrode to generate a positive corona discharge between the first discharge electrode and the first ground electrode, and the dust is positively charged in the charging unit. And the voltage generator applies a positive voltage to the second discharge electrode to generate an electric field toward the second ground electrode between the second discharge electrode and the second ground electrode. The second ground electrode collects the positively charged dust, and the collecting plate separates from the dust remaining in the gas and the second ground electrode into the gas. The scattered dust is collected.

If they contain NO in the gas to be processed in the electric dust collector, NO is oxidized NO ₂ is generated by the ozone generated by corona discharge. For regulating relative NO ₂ which environmental standards to NO ₂ is discharged from the vehicle as described above with provided is provided, there is a case where denitrification apparatus is installed for even NO2 removal tunnel. An increase in NO ₂ increases the load on the denitration device and shortens the life of the absorbent.
Generally, under the same power consumption condition, positive corona discharge is characterized by less ozone generation than negative corona discharge. Therefore, in the present invention, the increase in the NO ₂ concentration is suppressed by charging the dust with positive corona discharge. When a denitration device for removing NO ₂ is provided at the subsequent stage of the electrostatic precipitator of the present invention, the NO ₂ treatment amount in the denitration device is reduced, so that it is possible to suppress a decrease in the life of the absorbent.

  On the other hand, when compared with the same power consumption, the electrostatic precipitator using the positive charge is inferior to the dust collection performance than using the negative charge. In addition, the dust collected by the electrode is re-scattered, so that the dust collection performance of the electric dust collector is reduced. Therefore, in the present invention, a dust collecting part is installed on the earth electrode of the dust collecting part to collect re-scattering particles drifting in the vicinity of the earth electrode, thereby ensuring the same dust collecting performance as that of the negative charge even with the positive charge. It becomes possible to do.

  In the first aspect, the second discharge electrode may have a plurality of second discharge portions protruding in a direction substantially parallel to the gas flow direction at an end located on the downstream side of the gas. preferable.

  By generating corona discharge from the discharge part provided on the discharge electrode of the dust collection part, it is possible to promote the movement of dust toward the ground electrode and the collection plate. As a result, it becomes possible to hold the floating dust including re-scattered dust in the vicinity of the earth pole, and the dust collection efficiency at the earth electrode and the collecting plate can be further improved.

  1st aspect WHEREIN: It is preferable that the porous member is installed in the surface at the side where the said gas collides of the said collection board. By doing so, the holding power of the collided dust increases, so that the dust collection performance can be improved.

1st aspect WHEREIN: It is preferable that the distribution direction of the said gas and the extending direction of the said collection board are substantially orthogonal. Alternatively, the gas flow direction and the extending direction of the collecting plate may form an acute angle. Alternatively, the flow direction of the gas and the extending direction of the collecting plate may form an obtuse angle.
In this case, the distance between the tip of the collecting plate and the earth electrode in the direction from the second earth electrode to the second discharge electrode is the second earth electrode and the second discharge electrode. It is preferable that it is 1/4 or more and 1/2 or less of this distance.

  By providing a collecting plate of such a shape, dust can be collected by the collecting plate without hindering the flow of gas discharged from the dust collecting unit, so that the gas passage region in the dust collecting unit It is possible to improve the dust collection efficiency without a significant increase in pressure loss as in the case where a filter is installed on the entire surface.

  According to a third aspect of the present invention, there is provided an electrostatic precipitator that collects dust in a gas containing NO, wherein the first ground electrodes and the first discharge electrodes are alternately arranged substantially in parallel with each other. A charging unit, a dust collecting unit installed downstream of the gas of the charging unit, wherein second ground electrodes and second discharge electrodes are alternately arranged substantially parallel to each other; the charging unit and the collecting unit; A plurality of first discharge parts projecting substantially parallel to the gas flow direction at both ends of the gas flow direction. The voltage generation unit applies a positive voltage to the first discharge electrode to generate a positive corona discharge between the first discharge unit and the first ground electrode; A negative voltage is applied to the second discharge electrode, and the second discharge electrode is interposed between the second ground electrode and the second discharge electrode. Generating an electric field directed to the discharge electrode.

  A fourth aspect of the present invention is a method of collecting dust in the gas containing NO using the electric dust collector according to the third aspect of the present invention, wherein the voltage generating unit is the A positive voltage is applied to the first discharge electrode to generate a positive corona discharge between the first discharge electrode and the first ground electrode, and the dust is made positive in the charging unit. The voltage generator applies a negative voltage to the second discharge electrode, and an electric field directed toward the second discharge electrode is formed between the second discharge electrode and the second ground electrode. And generating dust that is positively charged by the second discharge electrode.

Also in the 3rd mode and the 4th mode, positive polarity corona discharge is generated in the charging section to suppress the increase in NO ₂ concentration.
Since the discharge electrode of the dust collection portion has a substantially flat plate shape, no corona discharge occurs in the dust collection portion. Since ozone is not generated in the dust collection part, a negative voltage having a high spark voltage is applied to the discharge electrode in this embodiment. By doing so, the electric field strength can be increased, and higher dust collection efficiency can be ensured than when a positive high voltage is applied to the discharge electrode of the dust collection portion.

  It is preferable that the electrostatic precipitator of the first aspect and the third aspect is installed in a tunnel in which the vehicle travels.

Since there is a restriction on the concentration of NO ₂ in the exhaust gas discharged from the vehicle, a denitration device that removes NO ₂ may be installed after the electrostatic precipitator installed in the tunnel. The electrostatic precipitator of the present invention can suppress an increase in NO ₂ concentration accompanying dust charging. Therefore, the use of the electrostatic precipitator of the present invention can achieve the effect of reducing the NO ₂ amount of processing at the subsequent stage of the denitration apparatus, it suppresses the reduction of the service life of the absorber.

According to the present invention, since the generation of ozone is suppressed by charging dust with positive corona discharge in the charging section, it is possible to suppress an increase in NO ₂ concentration in the exhaust gas. As a result, the processing load on the downstream denitration apparatus can be reduced.
When dust is positively charged, the collection performance is lower than when negatively charged. However, in the present invention, the collection plate assists the collection performance, so that high dust collection efficiency can be maintained.
Alternatively, by applying a negative high voltage having a high spark voltage to the discharge electrode in the dust collection unit, as opposed to the charging unit, it is possible to apply a higher electric field than applying a positive high voltage. Collection performance can be increased. As a result, high dust collection efficiency can be maintained.

It is a schematic perspective view of the dust collection unit of the electric dust collector which concerns on 1st Embodiment. It is a schematic plan view of the dust collection unit of the electric dust collector according to the first embodiment. It is a schematic plan view explaining another example of the dust collection unit of the electric dust collector according to the first embodiment. It is a schematic perspective view of the dust collection unit of the electric dust collector which concerns on 2nd Embodiment. It is a schematic plan view of the dust collection unit of the electric dust collector which concerns on 2nd Embodiment. It is a graph explaining the difference in the collection performance by the polarity of dust. It is a graph explaining the difference in the collection performance by the presence or absence of a collection board. It is a schematic perspective view of the dust collection unit of the electric dust collector which concerns on 3rd Embodiment. It is an example of the air purification system for tunnels. It is an example of an air purification system.

[First Embodiment]
An electric dust collector according to a first embodiment of the present invention will be described with reference to the drawings. The electric dust collector of this embodiment is applied to the air purification system illustrated in FIG.
FIG. 1 is a schematic perspective view of a dust collection unit housed in an electric dust collector. FIG. 2 is a plan view of the dust collection unit of FIG. 1 as viewed from above. In FIG. 1, the gas flows in a substantially horizontal direction with respect to the dust collection unit 1. The dust collection unit 1 includes a charging unit 10, a dust collection unit 20 located on the gas downstream side of the charging unit 10, and a voltage generation unit 30.

  The charging unit 10 includes a plurality of ground electrodes (first ground electrodes) 11 and discharge electrodes (first discharge electrodes) 12. The ground electrode 11 and the discharge electrode 12 have a substantially flat plate shape, and are alternately arranged so as to be substantially parallel to each other with a predetermined interval.

  The discharge electrode 12 is provided with a plurality of discharge parts (first discharge parts) 14 at gas gas downstream and upstream ends 13a and 13b. The discharge part 14 is a protrusion protruding from the discharge electrode 12 in a direction substantially parallel to the gas flow direction. 1 and 2, the discharge part 14 is a thorn-shaped protrusion. However, the shape of the discharge part 14 is not limited to this.

  The dust collection unit 20 includes a plurality of ground electrodes (second ground electrodes) 21 and discharge electrodes (second discharge electrodes) 22. The ground electrodes 21 and the discharge electrodes 22 are alternately arranged at predetermined intervals so as to be substantially parallel to each other. The ground electrode 21 and the discharge electrode 22 have a substantially flat plate shape, and the discharge electrode 22 is smaller than the ground electrode 21. In the present embodiment, the discharge portion is not provided in the discharge electrode 22.

  A collecting plate 40 is attached to the ground electrode 21 at an end located on the downstream side of the gas. The collection plate 40 is a plate made of metal such as steel. The collecting plate 40 of FIGS. 1 and 2 has a rectangular cross section. That is, the collection plate 40 extends from the ground electrode 21 in a direction substantially orthogonal to the gas flow direction.

  FIG. 3 is a schematic diagram illustrating another shape example of the collection plate of the present embodiment, and is a plan view of the dust collection unit of FIG. 1 as viewed from above. The collection plate 41 shown in FIG. 3A extends from the ground electrode 21 in a direction that forms an acute angle with the gas flow direction. The collection plate 42 shown in FIG. 3B extends from the ground electrode 21 in a direction that forms an obtuse angle with the gas flow direction.

  A porous member may be installed on the surface of the collection plates 40 to 42 on the gas inflow side. For example, a sponge or a filter is installed.

  When the collecting plates 40 to 42 having the shapes shown in FIGS. 2, 3 (a) and 3 (b) are installed, the gas collides with the gas inflow side surface of the collecting plates 40 to 42, and the end of the ground electrode 21 The gas flow is obstructed at the part. The distance t between the tip of the collecting plates 40 to 42 and the ground electrode 21 in the direction from the ground electrode 21 to the discharge electrode 22 is D / 4 or more, where D is the distance between the ground electrode 21 and the discharge electrode 22. / 2 or less is preferable. If it is less than D / 4, the amount of gas that collides with the collection plates 40 to 42 is small, so that the desired collection efficiency cannot be obtained. On the other hand, if it becomes larger than D / 2, the gas flow area at the discharge port from the dust collecting unit 20 is reduced, so that the pressure loss increases and the dust collected by the increased flow velocity is scattered, Dust collection efficiency decreases.

  The voltage generator 30 is connected to the discharge electrodes 12 and 22 and applies a positive high voltage to the discharge electrodes 12 and 22. The ground electrodes 11 and 21 are grounded.

  In the dust collection unit 1 of the present embodiment, a cleaning unit (not shown) for supplying a cleaning liquid (for example, water) for cleaning the ground electrode 21 and the collection plate 40 above the ground electrode 21 and the collection plate 40. May be installed.

  A method for collecting dust from exhaust gas using the dust collection unit 1 shown in FIGS. Here, a case where an electric dust collector is installed in a tunnel and an exhaust gas generated from a vehicle is treated will be described as an example. However, the electric dust collector of this embodiment is not limited to the case where it is installed in a tunnel, but can also be applied to air purification equipment (such as an indoor air purifier).

The exhaust gas discharged from the vehicle includes dust and nitrogen oxides (NO, NO ₂ ). Exhaust gas containing dust and nitrogen oxide flows into the dust collection unit 1 from the charging unit 10 side.

  The voltage generation unit 30 applies a positive voltage to the discharge electrode 12 of the charging unit 10. When a voltage is applied to the discharge electrode 12, a positive corona discharge is generated between the discharge portion 14 and the ground electrode 11. When the dust passes through the area where the corona discharge is generated, the dust is charged to a positive charge.

Since the exhaust gas contains oxygen, ozone is generated when the exhaust gas passes through the corona discharge. Part of NO contained in the exhaust gas is oxidized to NO ₂ by the generated ozone. That is, when passing through the charging unit 10, the NO ₂ concentration in the exhaust gas increases.

Here, when the distance between the discharge part 14 and the ground electrode 11 is constant, it is generally known that the amount of ozone generated is less in the positive discharge than in the negative discharge. This event depends on the respective discharge characteristics. Accordingly, an increase in NO ₂ concentration is suppressed in the positive corona discharge.

  The voltage generator 30 applies a positive voltage to the discharge electrode 22 of the dust collector 20. Thereby, in the dust collection part 20, the electric field which goes to the earth electrode 21 between the discharge electrode 22, the earth electrode 21, and the collection board 40 generate | occur | produces. In this embodiment, the discharge part is not formed in the discharge electrode 22. For this reason, corona discharge does not occur in the dust collection unit 20.

  The exhaust gas that has passed through the charging unit 10 flows into the dust collecting unit 20 with charged dust and nitrogen oxides. When the exhaust gas flows into the dust collecting unit 20, the positively charged dust is attracted to the earth electrode 21 and is attached to the earth electrode 21 and collected. Thereby, dust is removed from the gas.

  A part of the dust once collected by the earth electrode 21 re-scatters in the gas. The scattered dust is agglomerated and charged. The dust scattered again is collected by the ground electrode 21 again by the electric field between the discharge electrode 22 and the ground electrode 21. On the other hand, dust scattered from the earth electrode 21 on the most downstream side of the gas is collected on the surface of the collection plate 40 where the gas collides. Further, dust that has passed without being collected by the earth electrode 21 is also collected by the collection plate 41. As described above, when the porous member is installed on the surface of the collection plate, the surface area is increased, and thus the collection rate is increased.

Since no corona discharge is generated in the dust collection unit 20, ozone is not generated in the dust collection unit 20. For this reason, the increase in the NO ₂ concentration during passing through the dust collection unit 20 hardly occurs.

  The clean gas (including nitrogen oxides) in which dust is collected passes through the gap between the collection plate 40 and the discharge electrode 22 and is discharged from the dust collection unit 1 and then discharged from the electric dust collector. .

  When the amount of dust attached to the ground electrode 21 and the collection plate 40 increases, the collection efficiency decreases. Therefore, in the electric dust collector of the present embodiment, it is preferable to periodically supply a cleaning liquid from the cleaning unit to the ground electrode 21 and the collecting plate 40 to remove dust from the surface.

[Second Embodiment]
An electric dust collector according to a second embodiment of the present invention will be described with reference to the drawings. The electric dust collector of this embodiment is applied to the air purification system illustrated in FIG.
FIG. 4 is a schematic perspective view of a dust collection unit housed in the electric dust collector according to the second embodiment. FIG. 5 is a plan view of the dust collection unit of FIG. 4 as viewed from above. 4 and 5, the same components as those in FIGS.

  The dust collection unit 101 in the second embodiment has the same configuration as that of the first embodiment except that the discharge electrode 122 of the dust collection unit 120 is different. In addition, the collection board 40 can also be made into the shape shown to Fig.3 (a) or FIG.3 (b).

  The discharge electrode 122 is provided with a plurality of discharge portions (second discharge portions) 124 at an end portion 123 located on the downstream side of the gas. The discharge part 124 is a protrusion protruding from the discharge electrode 122 in a direction substantially parallel to the gas flow direction. 4 and 5, the discharge portion 124 is a thorn-like protrusion, but the shape of the discharge portion 124 is not limited to this.

  A method of collecting dust from exhaust gas using the dust collection unit 101 will be described below. An example will be described in which an electric dust collector is installed in a tunnel and exhaust gas generated from a vehicle is treated. However, the electric dust collector of this embodiment is not limited to the case where it is installed in a tunnel, but can be applied to air purification equipment (such as an indoor air purifier) as in the first embodiment. .

As described in the first embodiment, the dust contained in the exhaust gas is charged positively in the charging unit 10. Further, ozone is generated when the exhaust gas passes through the corona discharge, and a part of NO in the exhaust gas is oxidized to NO ₂ by the ozone.

  The voltage generator 30 applies a positive voltage to the discharge electrode 122 of the dust collector 120. As a result, an electric field directed to the ground electrode 21 is generated between the plate-like portion of the discharge electrode 122 and the ground electrode 21 in the dust collecting portion 120. Further, a positive corona discharge is generated between the discharge portion 124 of the discharge electrode 122 and the ground electrode 21 and the collecting plate 40 located on the gas downstream side.

  The exhaust gas that has passed through the charging unit 10 flows into the dust collecting unit 120. When the exhaust gas flows into the dust collecting unit 120, the positively charged dust is attracted to the ground electrode 21 and is attached to the ground electrode 21 and collected. Thereby, dust is removed from the gas.

  As in the first embodiment, part of the dust collected by the ground electrode 21 is re-scattered into the gas. The dust that has re-scattered is collected by the ground electrode 21 and the collecting plate 40 and removed. In the present embodiment, the movement of dust toward the earth electrode 21 and the collecting plate 40 is promoted by corona discharge from the discharge unit 124. Further, the charge amount of dust is increased by corona discharge, and the collection of dust by the ground electrode 21 and the collection plate 40 on the most downstream side of the gas is promoted.

FIG. 6 is a graph for explaining the difference in collection performance depending on the polarity of dust charged by the charging unit. FIG. 6 was obtained using the electrostatic precipitator having the configuration of the second embodiment. In FIG. 6, the horizontal axis represents the power consumption ratio, and the vertical axis represents the dust collection efficiency ratio.
FIG. 7 is a graph illustrating the difference in collection performance depending on the presence or absence of a collection plate. FIG. 7 was obtained using an electrostatic precipitator having the same configuration as in the second embodiment. In FIG. 7, the horizontal axis represents the power consumption ratio, and the vertical axis represents the dust collection efficiency ratio.

  From FIG. 6, it can be understood that when the power consumption ratio is the same, the dust collection efficiency ratio is reduced when positive charge is applied to the dust at the charging portion, and thus the collection efficiency at the ground electrode is lowered. Further, it can be understood that in order to obtain the same collection efficiency as that in the case of applying a negative charge, it is necessary to increase the voltage applied to the discharge electrode and input power consumption necessary for dust collection.

  From FIG. 7, it can be understood that when the power consumption ratio is the same, the collection efficiency can be improved by installing the collection plate. Moreover, when obtaining the same collection efficiency (dust collection efficiency ratio), it can be understood that the power consumption is smaller when the collection plate is provided.

In order to suppress the NO ₂ concentration increase, it is effective to apply a positive voltage to the discharge electrode of the charging unit. However, as shown in FIG. 6, the collection efficiency is sacrificed by charging the dust to positive polarity. On the other hand, as shown in FIG. 7, since the collection plate has an effect of assisting the collection of dust in the dust collection section, it is possible to maintain high dust collection efficiency.

As described above, in this embodiment, since the increase in NO ₂ concentration after passing through the electrostatic precipitator is suppressed, if the clean gas is guided to the denitration device for removing NO ₂ , the NO ₂ treatment amount in the denitration device is reduced. Therefore, it is possible to suppress the lifetime reduction of the absorbent.

[Third Embodiment]
An electric dust collector according to a third embodiment of the present invention will be described with reference to the drawings. The electric dust collector of this embodiment is applied to the air purification system illustrated in FIG.
FIG. 8 is a schematic perspective view of a dust collection unit accommodated in the electric dust collector according to the third embodiment. In FIG. 8, the gas flows in a substantially horizontal direction with respect to the dust collection unit 201. The dust collection unit 201 includes a charging unit 210, a dust collection unit 220 located on the gas downstream side of the charging unit 210, and a voltage generation unit 230.

  The charging unit 210 has the same configuration as that of the first embodiment. The substantially flat earth electrodes 211 and the discharge electrodes 212 are alternately arranged at predetermined intervals so as to be substantially parallel to each other. The discharge electrode 212 has a discharge part 214.

  The dust collection unit 220 includes a plurality of ground electrodes (second ground electrodes) 221 and discharge electrodes (second discharge electrodes) 222. The ground electrodes 221 and the discharge electrodes 222 are alternately arranged at predetermined intervals so as to be substantially parallel to each other. The ground electrode 221 and the discharge electrode 222 have a substantially flat plate shape, and the discharge electrode 222 is smaller than the ground electrode 221. In the dust collection unit 201, no collecting plate is installed on the ground electrode 221. Further, the discharge portion is not provided in the discharge electrode 222.

  In the third embodiment, the voltage generator 230 includes a first voltage generator 230a and a second voltage generator 230b. The first voltage generator 230 a is connected to the discharge electrode 212 of the charging unit 210 and applies a positive voltage to the discharge electrode 212. The second voltage generator 230 b is connected to the discharge electrode 222 of the dust collector 220 and applies a negative voltage to the discharge electrode 222. The earth electrodes 211 and 221 are grounded.

  In the dust collection unit 201 of the present embodiment, a cleaning unit (not shown) that supplies a cleaning liquid (for example, water) for cleaning the discharge electrode 222 may be installed above the discharge electrode 222.

  A method for collecting dust from exhaust gas using the dust collection unit 201 shown in FIG. 8 will be described below. Here, a case where an electric dust collector is installed in a tunnel and an exhaust gas generated from a vehicle is treated will be described as an example. In addition, the electric dust collector of this embodiment is not limited to the case where it is installed in a tunnel, but can be applied to air purification equipment as in the first embodiment.

The first voltage generator 230 a applies a positive voltage to the discharge electrode 212. As a result, a positive corona discharge is generated between the discharge portion 214 of the discharge electrode 212 and the ground electrode 211. Like the first embodiment, by which the gas passes through a charging unit 210, together with dust is positively charged, a portion of the NO in the exhaust gas is oxidized to NO _2.

  The second voltage generator 230 b applies a negative voltage to the discharge electrode 222 of the dust collector 220. As a result, an electric field directed toward the discharge electrode 222 is generated between the discharge electrode 222 and the ground electrode 221 in the dust collection unit 220. In the present embodiment, no discharge part is formed on the discharge electrode 222. For this reason, corona discharge does not occur in the dust collection unit 220.

  The exhaust gas that has passed through the charging unit 210 flows into the dust collection unit 220 with charged dust and nitrogen oxides. When the exhaust gas flows into the dust collection unit 220, positively charged dust is attracted to the discharge electrode 222 and attached to the discharge electrode 222 and collected. Thereby, dust is removed from the gas. The gas after the dust is removed is discharged from the dust collection unit 201 as a clean gas containing nitrogen oxides, and then discharged from the electric dust collector.

In the present embodiment, positive charging corona discharge is generated in the charging unit 210 to suppress an increase in NO ₂ concentration.
Moreover, since the discharge electrode 222 of the dust collection part 220 is a flat electrode which does not have a discharge part, corona discharge between the earth electrodes 221 does not generate | occur | produce. For this reason, ozone is not generated while passing through the dust collection unit 220. For this reason, a negative voltage having a high spark voltage can be applied to the discharge electrode 222. For this reason, it becomes possible to maintain high dust collection efficiency.

1, 101, 201 Dust collection unit 10, 210 Charging unit 11, 211 Ground electrode (first ground electrode)
12,212 Discharge electrode (first discharge electrode)
14,214 Discharge unit (first discharge unit)
20, 120, 220 Dust collectors 21, 221 Earth electrode (second earth electrode)
22, 122, 222 Discharge electrode (second discharge electrode)
30, 230 Voltage generator 40, 41, 42 Collection plate

Claims (11)

An electric dust collector that collects dust in a gas containing NO,
A charging unit in which the first ground electrode and the first discharge electrode are alternately arranged substantially parallel to each other;
A dust collecting unit installed downstream of the gas of the charging unit, wherein second ground electrodes and second discharge electrodes are alternately arranged substantially parallel to each other;
A voltage generating unit connected to the charging unit and the dust collecting unit,
The first discharge electrode has a plurality of first discharge portions protruding in a direction substantially parallel to the gas flow direction from the downstream and upstream ends of the gas,
The second ground electrode and the second discharge electrode have a substantially flat plate shape,
The second ground electrode has a collecting plate for inhibiting the flow of the gas and collecting the dust in the gas at an end located on the downstream side of the gas,
The voltage generation unit applies a positive voltage to the first discharge electrode to generate a corona discharge between the first discharge unit and the first ground electrode, and the second discharge electrode An electrostatic precipitator that applies a positive voltage to generate an electric field directed to the second ground electrode between the second ground electrode and the collecting plate and the second discharge electrode.   2. The electric current collector according to claim 1, wherein the second discharge electrode has a plurality of second discharge portions projecting in a direction substantially parallel to a flow direction of the gas at an end located on the downstream side of the gas. Dust equipment.   The electrostatic precipitator according to claim 1 or 2, wherein a porous member is installed on a surface of the collecting plate on which the gas collides.   The electric dust collector according to any one of claims 1 to 3, wherein a flow direction of the gas and an extending direction of the collection plate are substantially orthogonal to each other.   The electrostatic precipitator according to any one of claims 1 to 3, wherein the gas flow direction and the extending direction of the collecting plate form an acute angle.   The electric dust collector according to any one of claims 1 to 3, wherein the gas flow direction and the extending direction of the collecting plate form an obtuse angle.   The distance between the tip of the collecting plate and the ground electrode in the direction from the second ground electrode to the second discharge electrode is the distance between the second ground electrode and the second discharge electrode. The electrostatic precipitator according to any one of claims 4 to 6, wherein the electrostatic precipitator is from 1/4 to 1/2. An electric dust collector that collects dust in a gas containing NO,
A charging unit in which the first ground electrode and the first discharge electrode are alternately arranged substantially parallel to each other;
A dust collecting unit installed downstream of the gas of the charging unit, wherein second ground electrodes and second discharge electrodes are alternately arranged substantially parallel to each other;
A voltage generating unit connected to the charging unit and the dust collecting unit,
The first discharge electrode has a plurality of first discharge portions projecting substantially parallel to the gas flow direction at both ends of the gas flow direction,
The voltage generator applies a positive voltage to the first discharge electrode to generate a positive corona discharge between the first discharge part and the first ground electrode, and the second An electric dust collector that applies a negative voltage to the discharge electrode to generate an electric field directed to the second discharge electrode between the second ground electrode and the second discharge electrode.   The electrostatic precipitator according to any one of claims 1 to 8, which is installed in a tunnel in which a vehicle travels. A dust collection method for collecting dust in the gas containing NO using the electric dust collector according to any one of claims 1 to 7,
The voltage generating unit applies a positive voltage to the first discharge electrode to generate a positive corona discharge between the first discharge electrode and the first ground electrode, and thereby in the charging unit. To charge the dust positively,
The voltage generator applies a positive voltage to the second discharge electrode to generate an electric field directed to the second ground electrode between the second discharge electrode and the second ground electrode. The second ground electrode collects positively charged dust,
The dust collection method in which the collection plate collects the dust remaining in the gas and the dust separated from the second ground electrode and scattered in the gas. A method for collecting dust in the gas containing NO using the electrostatic precipitator according to claim 8,
The voltage generating unit applies a positive voltage to the first discharge electrode to generate a positive corona discharge between the first discharge electrode and the first ground electrode, and thereby in the charging unit. To charge the dust positively,
The voltage generator applies a negative voltage to the second discharge electrode to generate an electric field directed to the second discharge electrode between the second discharge electrode and the second ground electrode. A dust collection method for collecting the dust positively charged by the second discharge electrode.

Images