JP5705461B2 - Electric dust collector - Google Patents

Description

  The present invention relates to an electrostatic precipitator configured to remove particulate matter from particulate matter-containing gas such as exhaust gas of an internal combustion engine that contains particulate matter (PM).

Exhaust gas discharged from an internal combustion engine contains NOx, SOx, and harmful substances such as particulate matter containing carbon as a main component. It is known that various human health hazards occur when a human inhales particulate matter into the body by breathing, and development of a particulate matter removing device that efficiently removes particulate matter is desired.
As such a particulate matter removing device, there is a direction in which a filter is installed in the exhaust duct. However, the filter is easily clogged and has problems such as a large pressure loss. On the other hand, the electrostatic precipitator is not clogged and has a small pressure loss.

  For example, as shown in FIG. 8, a discharge electrode 101 and a discharge electrode 101 are provided in the gas flow containing the particulate matter so as to face the discharge electrode 101 as an electric dust collection system. A filtration device 102, a high-voltage power supply 103 that applies a high voltage between the discharge electrode 101 and the filtration device 102, a bleeder fan 104 that adjusts a gas flow that passes through the filtration device 102, and a main blower 105 that sucks exhaust gas Is known (for example, refer to Patent Document 1). Similarly, as shown in FIG. 9, the bleeder 104 is omitted, and instead of this, the gas outlet is divided into two, and a dust drop adjustment damper 110 is provided at each gas outlet. Is also known (see, for example, Patent Document 1).

  Further, as shown in FIGS. 10 and 11, a discharge device 101 in a gas flow containing particulate matter, a filtration device 102 having a counter electrode 107 provided to face the discharge electrode 101, and a discharge electrode There is known a dust removal apparatus including a high voltage power supply 103 that applies a high voltage between the filter 101 and the filtration device 102, and a closed space 108 that is closed in or on the back of the filtration means 102 (see, for example, Patent Document 2). .

Japanese Patent Laid-Open No. 2-63560 JP-A-2-184357

  However, in the conventional example shown in FIG. 8 described in Patent Document 1 described above, the amount of gas passing through the filtration device 102 is adjusted by the extraction blower 104, but the filtration device 102 has a size on the order of submicrons. In order to filter a certain particulate matter, it is necessary to use a sufficiently fine one, so that the pressure loss due to the filtration device 102 becomes large, and the bleed air blower 104 needs to have a large capacity. In this case, if the system is operated for a certain period of time, as shown in FIG. 12, the particulate matter 109 is clogged in the filtration device 102 and clogging occurs, making dust collection impossible. Therefore, the filtration device 102 is frequently replaced. There is an unresolved issue that is necessary for On the other hand, when the capacity of the extraction fan 104 is small, the amount of air passing through the filtration device 102 is small, so that the particulate matter 109 is concentrated near the surface of the filtration device 102 as shown in FIG. In this case, since the collected particulate matter 109 is exposed to the main gas flow, under conditions where the wind speed of the main gas flow is high, the drag of the filter 102 is caused by the drag of the main gas flow. There is an unsolved problem that the particulate matter collected on the surface is peeled off and scattered again.

  Similarly, even in the conventional example shown in FIG. 9 described in Patent Document 1, a blower for extraction can be omitted, but the amount of extraction of the filtration device 102 is adjusted by the pressure loss adjustment damper 110, so that filtration is performed. As the device 102, it is necessary to use a sufficiently fine one in order to filter the particulate matter having a size of the order of submicron. Therefore, the pressure loss due to the filtration device 102 becomes large, and the pressure loss adjusting damper 110 is enlarged. Must be closed. In this case, the pressure loss of the main gas flow caused by the pressure loss adjusting damper 110 becomes large, so that the fan 105 needs to have a large capacity. Further, as shown in FIG. 12, there is an unsolved problem that when the operation is performed for a certain period of time, the filtration device 102 is clogged and dust collection becomes impossible. On the contrary, when the closing amount of the pressure loss adjusting damper 110 is small, the capacity of the blower 105 may be small, but since the amount of air passing through the filtration device 102 is small, the surface of the filtration device 102 as shown in FIG. There is an unsolved problem that the particulate matter 109 collected in the film is peeled off and re-scattering occurs. In addition, the movable mechanism such as the pressure loss adjusting damper 110 has an unsolved problem that the risk of failure is extremely high in high-temperature exhaust gas.

Further, in the conventional example shown in FIG. 10 described in Patent Document 2, the secondary flow caused by the ion wind generated between the discharge electrode 101 and the counter electrode 107 has a maximum wind speed of about 2 m / s. It is necessary to use a filtration device 102 that is sufficiently fine to filter particulate matter having a size on the order of submicrons. Since the pressure loss due to the filtration device 102 is large, only a secondary flow caused by an ion wind can be used. It is difficult for the gas to sufficiently pass through the filtration device 102, and the particulate matter 109 is concentrated and collected near the surface of the filtration device 102 as shown in FIG. In this case, since the collected particulate matter is exposed to the main gas flow, the particulate matter collected on the surface of the filtration device 102 by the drag of the main gas flow under conditions where the wind speed of the main gas flow is high. There is an unsolved problem that the substance 109 is peeled off and re-scattering occurs.
Therefore, the present invention has been made paying attention to the above-mentioned unsolved problems of the conventional example, and does not require a large-capacity bleeder and does not clog and re-scatters even under high wind speed conditions. It is an object of the present invention to provide an electrostatic precipitator that is difficult, exhibits high dust collection performance, and has a low possibility of failure.

In order to achieve the above object, an electrostatic precipitator according to an embodiment of the present invention includes a cylindrical electrode and a discharge electrode disposed at a central portion of the cylindrical electrode, and the inside of the cylindrical electrode. The particulate matter in the dust collection target gas is charged by applying a voltage between the cylindrical electrode and the discharge electrode in a state where the dust collection target gas is allowed to flow to generate corona discharge. An electrostatic precipitator that sucks and collects on the cylindrical electrode side. Then, a through hole for passing the pre-Symbol particulate material prior Symbol tubular electrode together with forming a plurality of, the cylindrical electrode and placed inside a larger cylindrical casing electrode from the cylindrical electrodes, the tubular electrode A collecting space for collecting the particulate matter is formed between the outer surface of the casing electrode and the inner surface of the casing electrode, and a plurality of auxiliary electrodes are disposed in the collecting space, the cylindrical electrode, the casing electrode, The auxiliary electrodes have the same potential .

According to this configuration, the particulate matter in the dust collection target gas is charged by corona discharge generated between the discharge electrode and the cylindrical electrode, and the outer surface of the cylindrical electrode and the inner surface of the casing electrode are passed through the through-hole by Coulomb force. In the collection space formed between the two and the collection space.
Further, since the auxiliary electrode is arranged in the collection space, the allowable limit amount for collecting the particulate matter can be greatly increased by expanding the collection region of the particulate matter.

In the electrostatic precipitator according to another aspect of the present invention, a nozzle that sprays liquid is disposed in the collection space, and the liquid is sprayed from the nozzle to the particulate matter collected in the collection space. Is done.
According to this configuration, the liquid is sprayed from the nozzle in the collection space to wet the particulate matter, and the adsorption force of the particulate matter with the electrode is increased by the surface tension of the liquid, thereby suppressing re-scattering.

  According to the present invention, since the plurality of through holes are formed in the cylindrical electrode in which the discharge electrode is disposed, and the collecting electrode is formed by covering the cylindrical electrode with the casing electrode, the discharge electrode and the cylindrical shape are formed. Corona discharge is generated between the electrodes, the particulate matter is negatively charged, and moved into the collection space through the through hole by Coulomb force, and the particulate matter can be collected in the collection space, It is not necessary to provide a large-capacity extraction blower, and by making the through-hole have a larger diameter than that of the particulate matter, clogging does not occur, and re-scattering is difficult even under high wind speed conditions. It is possible to provide an electric dust collector that can exhibit dust collection performance and is less likely to fail.

It is the perspective view which made the cross section the center part which shows 1st Embodiment of the electrical dust collector which concerns on this invention. It is a schematic diagram which shows the collection state of a particulate matter. It is the perspective view which made the cross section the principal part which shows 2nd Embodiment of the electrostatic precipitator which concerns on this invention. It is sectional drawing on the AA line of FIG. It is a longitudinal cross-sectional view which shows 3rd Embodiment of the electrical dust collector which concerns on this invention. It is a longitudinal cross-sectional view which shows 4th Embodiment of the electrical dust collector which concerns on this invention. It is a cross-sectional view showing a fifth embodiment of the electrostatic precipitator according to the present invention. It is explanatory drawing which shows a prior art example. It is explanatory drawing which shows another prior art example. It is explanatory drawing which shows another prior art example. It is a detailed block diagram of the filtration apparatus of FIG. It is a schematic diagram which shows the collection state of the particulate matter in a filtration apparatus. It is a schematic diagram which shows the re-scattering state of the particulate matter in a filtration apparatus. It is a schematic diagram which shows the re-scattering state of the particulate matter in a filtration apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view with a cross section taken at the center showing the first embodiment of the present invention.
In the figure, reference numeral 1 denotes, for example, particulate matter (PM: Particulate Matter) having a particle size of 100 μm or less, mainly containing carbon contained in the exhaust gas of an internal combustion engine, particularly a diesel engine, in particular, a suspended particle shape having a particle size of 10 μm or less It is an electrostatic precipitator capable of collecting a substance (SPM: Suspended Particulate Matter).

In the electrostatic precipitator 1, a discharge electrode 2 is arranged at the center, and a cylindrical electrode 3 is disposed coaxially with the discharge electrode 2, for example, and the cylindrical electrode 3 is formed in, for example, a rectangular rectangular tube. The casing electrode 4 is surrounded. A space between the discharge electrode 2 and the cylindrical electrode 3 is a gas flow path 7 through which the exhaust gas 6 including the particulate matter 5 passes.
The discharge electrode 2 has a rod-shaped conductor 2a having a circular cross section. On the outer peripheral surface of the rod-shaped conductor 2a, a large number of needle-like electrode portions 2b are formed so as to protrude at a predetermined interval in the axial direction and at a predetermined interval (for example, 90 °) in the circumferential direction.

  The cylindrical electrode 3 is composed of, for example, a cylindrical stainless steel pipe 3a so as to face the needle-like electrode portion 2b of the discharge electrode 2 with a predetermined interval. In the stainless steel pipe 3a, a large number of through holes 3b having a diameter (for example, about several mm) sufficiently larger than the particle diameter of the particulate matter 4 are formed at positions facing the needle-like electrode portion 2b of the discharge electrode 2. A punching pipe is applied.

The casing electrode 4 includes a rectangular frame plate portion 4a having conductivity facing the outer peripheral surface of the cylindrical electrode 3 at a predetermined distance on the outer peripheral side of the cylindrical electrode 3, and both axial ends of the rectangular frame plate portion 4a. It is comprised by the end-plate part 4b which connects between the surface and the axial direction both end surfaces of the cylindrical electrode 3. As shown in FIG. A semi-closed space 8 as a collecting space is formed by the outer peripheral surface of the cylindrical electrode 3 and the inner peripheral surfaces of the square frame plate portion 4 a and the end plate portion 4 b of the casing electrode 4. This semi-closed space 8 communicates with the gas flow path 7 through the through hole 3 a of the cylindrical electrode 3.
Further, between the discharge electrode 2 and the casing electrode 4, there is a high voltage power source 9 for applying a high voltage of about 10 ³ to 10 ⁵ volts, for example, having a positive electrode connected to the casing electrode 4 and a negative electrode connected to the discharge electrode 2. The high-voltage power supply 9 is connected to the positive electrode side and grounded.

Next, the operation of the first embodiment will be described.
By applying a high voltage between the discharge electrode 2 and the cylindrical electrode 3 and the casing electrode 4 from the high-voltage power supply 9, the gas flow path is directed from the tip of the needle electrode portion 2 b of the discharge electrode 2 toward the cylindrical electrode 3. Corona discharge across 7 occurs.
In this state, when an exhaust gas as a particulate matter-containing gas containing particulate matter 5 discharged from an internal combustion engine or the like is caused to flow through the gas flow path 7, the particulate matter 5 is charged by corona discharge. The Coulomb force acts on the particulate matter 5 by the electric field between the discharge electrode 2 and the cylindrical electrode 3 and starts to move toward the cylindrical electrode 3. Since the particulate matter 5 has a mass, it passes through the through-hole 3b of the cylindrical electrode 3 as it is and is guided to the semi-closed space (collection space) 8 by inertia force.

  In this semi-closed space 8, the flow field is very gentle, so that the particulate matter 5 is not easily affected by the flow field, and the particulate matter 5 has its own charge and the potential difference between the cylindrical electrode 3 and the casing electrode 4. 2 is received and collected on the outer peripheral surface of the cylindrical electrode 3 and the inner peripheral surface of the casing electrode 4 as schematically shown in FIG. According to the numerical analysis, compared with the flow rate of the main flow of the exhaust gas in the gas flow path 7, the flow rate is about 1/20 to 1/10 in most of the semi-closed space 8 and locally about 1/4. It has been confirmed.

  Thus, according to the first embodiment, the exhaust gas is simply passed through the gas flow path 7 between the discharge electrode 2 and the cylindrical electrode 3, and there is no need to provide a blower or the like as a bleeder. . Further, since it is not necessary to provide a damper or the like that obstructs the flow of exhaust gas, the pressure loss of exhaust gas can be reduced. Furthermore, since the diameter of the through-hole 3b formed in the cylindrical electrode 3 can be formed to a large diameter regardless of the particle diameter of the particulate matter 5, it is possible to suppress the pressure loss correspondingly. Further, since the particulate matter 5 is collected on the outer peripheral surface of the cylindrical electrode 3 constituting the semi-closed space 8 and the inner peripheral surface of the casing electrode 4, a large amount of particulate matter corresponding to the surface areas of both electrodes 3 and 4 is obtained. 5 can be allowed, and the through-hole 3b is extremely difficult to be clogged, so that it is possible to reliably prevent a collection failure due to clogging. Furthermore, since the flow field of the semi-closed space 8 is small, it is difficult for the particulate matter 5 collected once to re-scatter. In addition, since there are no movable parts such as dampers and blowers, various effects that the possibility of failure is extremely low can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment, the exhaust gas flow rate can be increased.
That is, in the second embodiment, as shown in FIGS. 3 and 4, in the configuration of FIG. 1 in the first embodiment described above, a plurality of, for example, two tubes each having two discharge electrodes 2A and 2B are individually provided. The parallel electrodes 3A and 3B are arranged in parallel in the same plane so as to form a predetermined semi-closed space 8 between them in the direction perpendicular to the axis. And the outer peripheral side of each cylindrical electrode 3A and 3B is covered with the square cylindrical casing electrode 4 at predetermined intervals. In the configuration of FIG. 3, the same reference numerals are given to the portions corresponding to those in FIG.

  In the second embodiment, since the two gas flow paths 7A and 7B are formed by the discharge electrodes 2A and 2B and the cylindrical electrodes 3A and 3B, the exhaust gas flow area is increased and the exhaust gas is increased. The flow rate of can be suppressed. A good collection function of the particulate matter 5 can be exhibited even with a large flow rate of exhaust gas. In this case, when the exhaust gas flow rate for collecting the particulate matter 5 is large, the number of sets of the discharge electrode 2 and the cylindrical electrode 3 may be increased according to the exhaust gas flow rate, and the exhaust gas in the gas flow path 7 is increased. It is possible to appropriately control the flow rate and exhibit good dust collection performance.

Next, a third embodiment of the present invention will be described with reference to FIG.
In the third embodiment, the collection performance of the particulate matter 5 in the semi-closed space 8 is improved.
That is, in the third embodiment, as shown in FIG. 5, the outer peripheral surface excluding the through hole 3 b of the cylindrical electrode 3 and the casing electrode 4 in the semi-closed space 8 constituted by the cylindrical electrode 3 and the casing electrode 4. For example, four auxiliary electrodes 11 are provided radially between the four corners.
According to the third embodiment, since the four auxiliary electrodes 11 are added in the semi-closed space 8, the collection area of the particulate matter 5 can be increased by the surface integral of these auxiliary electrodes 11. For this reason, the collection allowable amount of the particulate matter 5 can be significantly increased as compared with the first embodiment described above.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
Also in the fourth embodiment, the collection performance of the particulate matter 5 in the semi-closed space 8 is improved as in the third embodiment described above.
That is, in the fourth embodiment, as shown in FIG. 6, the auxiliary electrode having four arcs in cross section coaxially with the cylindrical electrode 3 in the semi-closed space 8 constituted by the cylindrical electrode 3 and the casing electrode 4. 12 is formed. Both ends of the auxiliary electrode 12 in the axial direction are connected to the end plate portion 4 b of the casing electrode 4, and are connected to the positive electrode side of the high-voltage power supply 9 through the casing electrode 4.

According to the fourth embodiment, since the four auxiliary electrodes 12 are formed in the semi-closed space 8 as in the third embodiment described above, the amount of the particulate matter 5 by the surface integral of these auxiliary electrodes 11 is increased. The collection area can be increased. For this reason, the collection allowable amount of the particulate matter 5 can be significantly increased as compared with the first embodiment described above.
In the third and fourth embodiments, the case where the auxiliary electrodes 11 and 12 are provided has been described. However, the present invention is not limited to this, and the auxiliary electrode 12 is provided in the middle portion of the auxiliary electrode 11 in the radial direction. May be formed to further increase the collection area of the particulate matter 5.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
In the fifth embodiment, the particulate matter 5 is more reliably collected in the semi-closed space 8.
That is, in the fifth embodiment, as shown in FIG. 7, it is described above except that the nozzles 15 for ejecting the liquid in a mist form are arranged on the end plate portions 4b at both ends in the axial direction of the casing electrode 4, respectively. The configuration is the same as in FIG. 1 in the first embodiment. Therefore, in FIG. 7, the same reference numerals are given to the parts corresponding to those in FIG. 1, and the detailed description thereof will be omitted. Here, as the liquid sprayed from the nozzle 15, water is used when the exhaust gas temperature is low, and oil with a high melting point is used when the exhaust gas temperature is high.

  According to the fifth embodiment, since the liquid is sprayed in the semi-closed space 8 from the nozzle 15 in the form of a mist, the liquid is charged by corona discharge and introduced into the semi-closed space 8 by the Coulomb force. The particulate matter 5 collected on the outer peripheral surface 3 and the inner peripheral surface of the casing electrode 4 is wetted by the liquid mist. For this reason, the adsorption force of the particulate matter 5 to the cylindrical electrode 3 or the casing electrode 4 is increased by the surface tension of the liquid, and the particulate matter 5 is peeled off from the collecting surface of the cylindrical electrode 3 or the casing electrode 4. A great suppression effect against re-scattering can be exhibited.

In the fifth embodiment, the case where the nozzle 15 is added to the first embodiment described above has been described. However, the nozzle 15 may be added to the second to fourth embodiments described above. Good.
Moreover, in the said 1st-5th embodiment, although the case where the particulate matter 5 contained in the exhaust gas discharged | emitted from an internal combustion engine was removed was demonstrated, it is not limited to this, Arbitrary particle | grains The particulate matter can be removed from the particulate matter-containing gas.
Moreover, in the said 1st-5th embodiment, although the case where the casing electrode 4 was a rectangular tube shape was demonstrated, it is not limited to this, The semi-closed space 8 is formed for the cylindrical electrode 3 And can be any shape such as a cylindrical shape or a polygonal cylindrical shape.

Similarly, the cylindrical electrode 3 is not limited to a cylindrical shape, and may be arbitrarily provided that the distance between the inner peripheral surface of the discharge electrode 2 facing the needle electrode portion 2b and the needle electrode portion 2b is equal. It can be made into the shape. That is, for example, when six (or eight) acicular electrode portions 2b are formed on the rod-shaped conductor 2a at intervals of 60 ° (or 45 °) in the circumferential direction, the cylindrical electrode 3 is formed in a hexagonal tube shape (or You may make it form in an octagonal cylinder shape.
Moreover, in the said 1st-5th embodiment, although the case where all the acicular electrode parts 2b of the discharge electrode 2 were protruded in the same direction by the axial direction was demonstrated, it is not limited to this, but acicular The protruding position of the electrode part 2b may be shifted in the circumferential direction at each part in the axial direction.

  DESCRIPTION OF SYMBOLS 1 ... Electric dust collector, 2 ... Discharge electrode, 2a ... Rod-shaped conductor, 2b ... Needle-shaped electrode part, 3 ... Cylindrical electrode, 3a ... Stainless steel pipe, 3b ... Through-hole, 4 ... Casing electrode, 4a ... Square frame board 4, 4 ... end plate, 5 ... particulate matter, 6 ... exhaust gas, 7 ... gas flow path, 8 ... semi-closed space (collection space), 9 ... high-voltage power source, 11, 12 ... auxiliary electrode, 15 ... nozzle

Claims (2)

A cylindrical electrode; and a discharge electrode disposed at a central portion of the cylindrical electrode, and a dust collection target gas is allowed to flow inside the cylindrical electrode, and between the cylindrical electrode and the discharge electrode. An electrostatic precipitator that applies a voltage to generate a corona discharge to charge and collect particulate matter in the dust collection target gas and suck it on the cylindrical electrode side,
A through hole for passing the pre-Symbol particulate material prior Symbol tubular electrode together with forming a plurality of, the cylindrical electrode disposed within the large cylindrical casing electrode than the cylindrical electrode,
A collecting space for collecting the particulate matter is formed between the outer surface of the cylindrical electrode and the inner surface of the casing electrode,
A plurality of auxiliary electrodes are arranged in the collection space,
An electrostatic precipitator , wherein the cylindrical electrode, the casing electrode, and the auxiliary electrode have the same potential . 2. The electrostatic precipitator according to claim 1, wherein a nozzle for spraying liquid is disposed in the collection space, and the liquid is sprayed from the nozzle onto the particulate matter collected in the collection space. .

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