JP2010131515A - Electrostatic precipitator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic precipitator which minimizes amounts of NOx and ozone generated for solving such a problem in conventional electrostatic precipitators removing SPM (suspended particle matters) in the atmospheric air on the road that harmful gas components, NOx and ozone, are generated and increased by corona discharge, a basic principle of electrostatic precipitation. <P>SOLUTION: The electrostatic precipitator 1 is of a parallel-plain-plate structure in which a metal-made discharge plate 2 having plural splinter electrodes and an active-carbon-fiber-made earth electrode plate 3 molded into a flat plate shape are alternately arranged, impresses DC or AC high voltage, and by promoted discharge from the active-carbon-fiber, ozone and NOx generated by the corona discharge are promptly adsorbed by the active carbon fiber, thus minimizing the amount of NOx and generated ozone. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric dust collection system for removing suspended particulate matter (SPM) in exhaust gas along a motorway.

Over the past decade, environmental awareness has increased, suspended particulate matter (SPM) and nitrogen oxides (NOx) of nitrogen oxides, and NO ₂ along the congested motorway roads in large cities. (Nitrogen dioxide) and NO (Nitrogen mono-oxide) have been studied in various places (Non-Patent Documents 1 to 6). In the background, in the residential area near the road where traffic is congested, the environmental standard (the daily average value of SPM is 0.1 mg / m ³ or less, the daily average value of NO ₂ is 0.04 to 0.06 ppm or less) ) May not be achieved, and its reports (Non-Patent Documents 4, 6, and 7) Has been made. The proportion of NO ₂ in NOx in the roadside atmosphere (ppm ratio) is generally about 20% to 50%, and the rest is said to be NO. This is also shown in the actual measurement result (Non-Patent Document 8).

  A report (Non-patent Document 9) by the Environmental Regeneration and Maintenance Organization shows that SPM in the roadside atmosphere can be removed using an electric dust collector.

  Here, what should not be overlooked is that NOx is generated by corona discharge used in the electrostatic precipitator. Several studies (Non-Patent Documents 10 and 11) have been published, and the following points have been reported.

・ Positive charge produces more NOx than negative charge ・ NOx produced by DC corona is mostly NO ₂ Also, ozone (O ₃ ) is produced by corona discharge of electrostatic precipitator ( Non-Patent Documents 12 and 13), which react with NO in the roadside atmosphere to generate NO ₂ that is more toxic than NO (Non-Patent Documents 9 and 14).

  In addition, a study has been reported in which NOx in the roadside atmosphere is removed by ventilation through a slit of activated carbon fiber ACF (Activated Carbon Fiber) (Non-patent Document 15).

In addition, an electrostatic precipitator that removes SPM in the roadside atmosphere and a slit of activated carbon fiber ACF that removes NOx are combined and arranged in parallel to the wind flow, aiming to achieve SPM removal and NOx removal simultaneously. Studies on purification systems have been reported (Non-patent Document 8).
Nishimatsu Construction Technical Report June 2003 issue Fujita Technology Research Report November 2003 Annual Report of Hazama Research December 2002 Kawasaki City Institute for Pollution Research Annual Report December 2001 Abstracts of Annual Meeting of Japan Society for Atmospheric Environment 1999 Journal of the Japan Institute of Energy January 1998 Journal of the Japan Society for Atmospheric Environment April 2007 issue Environmental Restoration and Conservation Organization: Survey and Research Digest Collection for Environmental Improvement, June 2008 Issue Environmental Restoration and Conservation Organization: FY2005 Survey and Research Results Collection on Environmental Improvement December 2006 Atmospheric Environment 1996 Journal of Imaging Science May 1988 Issue Journal of the electrostatic society march 2006 IEEJ Plasma Research Material 2006 6th Conference of the French Electrostatics Society 2008 Environmental Restoration and Conservation Organization: FY 2004 Survey and Research Results on Environmental Improvement December 2005

  FIG. 9 shows a configuration of a typical one-stage electrostatic precipitator 101. The metal discharge plate 102 having the thorn electrode and the metal ground electrode plate 103 are alternately arranged while maintaining an equal interval to form a parallel plate structure. The high voltage generator 104 applies an AC or DC high voltage to each discharge plate 102. Each ground electrode plate 103 is grounded. In the electrostatic precipitator 101 having such a configuration, the high voltage applied to the discharge plate 102 causes corona discharge of the thorn electrode that becomes a strong electric field, and the corona between the thorn electrode and the adjacent ground electrode plate. A discharge space is formed. At this time, since the surface of the ground electrode plate 103 is a smooth metal surface and there is no protrusion such as a thorn that can be a field of a strong electric field, a corona discharge of reverse polarity generated from the ground electrode plate 103 toward the discharge plate. Does not occur. The dust in the air ventilated by the electric dust collector 101 is charged by corona discharge and collected on the surface of the ground electrode plate 103 by Coulomb force. In this way, the corona discharge of the electrostatic precipitator collects dust, but on the other hand, the corona discharge, which is the basic principle of electrostatic precipitator, generates more NOx and ozone that are harmful gas components. There was a problem of letting it go.

  Here, the electric dust collector that removes the SPM in the roadside atmosphere has been required to be able to suppress the generation amount of NOx and ozone to the minimum.

  In order to solve the above-mentioned problems, the electrostatic precipitator of the present invention has a parallel plate structure in which metal discharge plates having a plurality of thorn electrodes and ground electrode plates of activated carbon fibers formed into a flat plate shape are alternately arranged. Then, a high voltage of direct current or alternating current is applied.

  With this configuration, the generation amount of NOx and ozone is reduced.

  An electrostatic precipitator that can suppress the generation amount of NOx and ozone to the minimum can be realized.

  The electrostatic precipitator according to the first embodiment of the present invention has a parallel plate structure in which a metal discharge plate having a plurality of thorn electrodes and a ground electrode plate of activated carbon fiber formed into a flat plate shape are alternately arranged. A DC or AC high voltage is applied to the discharge plate. Therefore, a strong electric field space can be formed between the discharge plate and the ground electrode plate. That is, since the metal discharge plate is in a strong electric field, corona discharge can be generated from the barb electrodes (that is, protrusions) of the discharge plate. On the other hand, since the fiber of the activated carbon fiber forming the ground electrode plate is also a protrusion in a strong electric field, corona discharge having a polarity opposite to that of the discharge plate can be generated from the activated carbon fiber. Here, since the former corona discharge has a larger discharge current than the latter corona discharge, the former will be referred to as main corona discharge and the latter as sub-corona discharge. In the same electrostatic precipitator, corona discharges having opposite polarities (positive corona discharge and negative corona discharge) can be simultaneously generated from each of the discharge plate and the ground electrode plate by using one high-voltage power supply. In order to improve the SPM removal rate of the electrostatic precipitator, it can be said that it is better to increase the discharge current due to the main corona discharge because the charging ability to the dust is increased. Ozone and NOx are generated as described in the background art. However, paying attention to the secondary corona discharge from the activated carbon fiber, it has been clarified through experiments that the generation of ozone and NOx is suppressed.

  Table 1 shows the amount of NOx increase, the amount of ozone generated and the amount of collection when a high voltage is applied to a certain electrostatic precipitator and only main corona discharge is generated and when main corona discharge and sub-corona discharge are generated simultaneously. It is the result of experimenting how dust efficiency changes.

  That is, in the discharge from the activated carbon fiber (in this case, the secondary corona discharge), the generated ozone and NOx are immediately adsorbed by the activated carbon fiber, so that the generation of ozone and NOx can be suppressed in the secondary corona discharge. In the electrostatic precipitator that generates the main corona discharge and the sub corona discharge at the same time, the target value of the SPM removal rate can be achieved by the main corona discharge, and the generation of ozone and NOx can be suppressed by the sub corona discharge. .

  The electrostatic precipitator according to the second embodiment of the present invention constitutes a grounding electrode plate by attaching activated carbon fibers to both surfaces of a metal flat plate. Since activated carbon fiber is attached to the surface of a strong metal flat plate as a base material, vibration of the ground electrode plate due to ventilation can be suppressed. That is, re-scattering of dust collected on the ground electrode plate can be suppressed. Moreover, since suppressing mechanical vibration suppresses fluctuation (vibration) of the electric field strength, spark discharge (spark) can be suppressed and dust collection efficiency can be stabilized.

  The electrostatic precipitator according to the third embodiment of the present invention constitutes a ground electrode plate by attaching activated carbon fibers to a part of both surfaces of a metal flat plate. Sub-corona discharge is generated from the portion where the activated carbon fiber is pasted, and no sub-corona discharge is generated from the portion where the metal surface is exposed without being pasted. Therefore, the discharge current value of the sub-corona discharge can be adjusted by adjusting the area where the activated carbon fiber is pasted, so that the dust collection efficiency can be adjusted.

  The electrostatic precipitator according to the fourth embodiment of the present invention is composed of a portion where the activated carbon fiber is pasted on the metal base material of the ground electrode plate and a portion where the activated carbon fiber is not pasted, and the activated carbon fiber is not pasted. The ground electrode plate has a plurality of thorn protrusions arranged on the exposed metal portion. The discharge current value of the secondary corona discharge can be adjusted by adjusting the area where the protrusions are provided. Therefore, the dust collection efficiency can be adjusted.

  The electrostatic precipitator according to the fifth embodiment of the present invention constitutes a grounding electrode plate by sandwiching both surfaces of activated carbon fibers with a metal wire mesh. Since the activated carbon fibers are sandwiched by a strong wire mesh, vibration of the ground electrode plate due to ventilation can be suppressed, and dust collection efficiency can be stabilized. Further, since the wire rod of the wire mesh itself becomes a protrusion, the sub-corona discharge from the ground electrode plate can be generated not only from the activated carbon fiber but also from the wire mesh. That is, the discharge current of the secondary corona discharge can be increased, and the dust collection efficiency can be improved.

The electrostatic precipitator according to the sixth embodiment of the present invention has a configuration of a ground electrode plate in which a part of a metal wire mesh is cut out. A discharge current density of missing parts off the wire mesh [mA / mm ^2], since the discharge current density of the portion not cut [mA / mm ^2] is a difference, by adjusting the area of cutting out, sub The discharge current value of corona discharge can be adjusted. Therefore, the dust collection efficiency can be adjusted.

  The electrostatic precipitator according to the seventh embodiment of the present invention includes a grounding electrode plate on which activated carbon fibers are attached and a discharge plate on which activated carbon fibers are attached to a part of the surface. . Since the activated carbon fiber is attached to a part of the discharge plate surface, the discharge current value of the main corona discharge can be adjusted. Therefore, the dust collection efficiency can be adjusted.

  The electrostatic precipitator according to the eighth embodiment of the present invention has a structure of a discharge plate in which activated carbon fibers are bonded to the entire surface of both surfaces of a metal discharge plate. Since the fiber of the activated carbon fiber becomes a protrusion and most of the main corona discharge and sub-corona discharge occur, it is possible to efficiently suppress the generation amounts of ozone and NOx.

  The electrostatic precipitator according to the ninth embodiment of the present invention includes a ground electrode plate in which both sides of the activated carbon fiber are sandwiched between metal wire meshes, both sides of the activated carbon fiber are sandwiched between metal wire meshes, and ends of the wire mesh are The discharge plate is configured as described above. Since the ground electrode plate and the discharge plate can be manufactured using a material having a high degree of processing freedom such as activated carbon fiber and wire mesh, the manufacturing cost can be reduced.

  The electrostatic precipitator according to the tenth embodiment of the present invention has a parallel plate structure in which a discharge plate in which activated carbon fibers are pasted on both surfaces of a metal discharge plate and metal grounding electrode plates are alternately arranged. Thus, a high DC voltage is applied. Since activated carbon fiber is used for the discharge plate, the amount of ozone and NOx generated by the main corona discharge can be efficiently suppressed.

  In the electric dust collector according to the eleventh embodiment of the present invention, the discharge plates having both ends of the activated carbon fiber sandwiched between metal wire meshes and the wire mesh end portions as thorn electrodes and metal ground electrode plates are alternately arranged. A parallel plate structure applies a high DC voltage. Since activated carbon fiber is used for the discharge plate, the amount of ozone and NOx generated by the main corona discharge can be efficiently suppressed.

  The electrostatic precipitator according to the twelfth embodiment of the present invention uses a discharge plate using activated carbon fibers and a ground electrode plate having a plurality of thorns. Since activated carbon fiber is used for the discharge plate, the amount of ozone and NOx generated by the main corona discharge can be efficiently suppressed. Moreover, since the sub-corona discharge from the ground electrode plate can be generated, the discharge current value can be increased. That is, since the charging ability can be increased, dust collection efficiency can be improved.

  The electrostatic precipitator according to the thirteenth embodiment of the present invention has a parallel plate structure in which a metal discharge plate having a plurality of thorn electrodes and a ground electrode plate having a plurality of thorn electrodes are alternately arranged, A high voltage is applied. Since the main corona discharge from the discharge plate and the sub-corona discharge from the ground electrode plate can be generated simultaneously, the discharge current value can be increased. That is, since the charging ability can be increased, dust collection efficiency can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
FIG. 1 is a configuration diagram of an electrostatic precipitator according to this embodiment. In the one-stage electrostatic precipitator 1, metal discharge plates 2 having thorn electrodes and ground plates 3 made of activated carbon material formed into a flat plate shape are alternately arranged while maintaining an equal interval. Forming a structure. The discharge plate 2 is provided with a thorn protruding toward the upstream side in the air passage direction. This figure shows an example in which one discharge plate 2 and two grounding electrode plates 3 are alternately arranged. However, the number is not limited to this number, and a plurality of discharge plates 2 and a plurality of discharge plates 2 are arranged. The grounding electrode plates 3 are alternately arranged in parallel to form the electrostatic precipitator 1. (The same applies to the following embodiments.) The high voltage generator 4 applies an AC or DC high voltage to the discharge plate 2. The ground electrode plate 3 is grounded. In the electrostatic precipitator 1 having such a configuration, corona discharge is generated in the vicinity of the thorn electrode that becomes a field of a strong electric field due to the high voltage applied to the discharge plate 2. (Main corona discharge) On the other hand, the surface of the ground electrode plate 3 is not smooth because it is activated carbon fiber. Accordingly, corona discharge (sub-corona discharge) having a polarity opposite to that of the thorn electrode is generated. FIG. 2 (main / sub-corona discharge phase diagram) shows a state when the corona discharge is viewed from directly above the electrostatic precipitator 1. In FIG. 2, the main corona discharge emitted from the tip of the thorn is indicated by a solid arrow, and the sub-corona discharge emitted from the activated carbon fiber is indicated by a broken arrow.

(Example 2)
FIG. 3 is a configuration diagram of an electric dust collector according to the present embodiment. Activated carbon fiber 6 is attached to the entire surface of both surfaces of metal plate 5 to constitute grounding electrode plate 3. The discharge plate 2 has thorns on the windward side as in the first embodiment. With such a configuration, the aspect of main corona discharge (solid arrow) and sub-corona discharge (broken arrow) is the same as in FIG.

(Example 3)
FIG. 4 is a configuration diagram of an electrostatic precipitator according to this embodiment. Activated carbon fiber 6 is attached to a part of both surfaces of metal plate 5 to constitute ground electrode plate 3. The discharge plate 2 has thorns on the windward side as in the first embodiment. With such a configuration, the aspect of the main corona discharge is the same as that in FIG. 2 with respect to the discharge when a high voltage is applied, but the sub-corona discharge (broken arrow) is limited to the portion where the activated carbon fiber 6 is attached. Has occurred.

Example 4
FIG. 5 is a configuration diagram of an electrostatic precipitator according to the present embodiment. Fig.5 (a) is the figure which looked at the grounding electrode plate 3 from the horizontal direction of the electrostatic precipitator, and FIG.5 (b) is a top view of the electrode plate part of an electrostatic precipitator. The discharge plate 2 has thorns on the windward side as in the first embodiment. The ground electrode plate 3 is configured by attaching activated carbon fibers 6 to a part of both surfaces of a metal plate 5. Furthermore, a thorn electrode is punched and provided on a bare metal portion where the activated carbon fiber is not attached. (A portion in FIG. 5) This thorn has a shape protruding upstream with respect to the air passage direction. With such a configuration, the aspect of the main corona discharge is the same as in FIG. 2 for the discharge when a high voltage is applied, but the sub-corona discharge has a portion where the activated carbon fiber 6 is attached and a punched thorn electrode. It is generated from the portion A provided.

(Example 5)
FIG. 6 is a configuration diagram of an electrostatic precipitator according to the present embodiment. Activated carbon fibers 6 are attached to both surfaces of the metal plate 5 to constitute the ground electrode plate 3. Further, the activated carbon fiber 6 is attached to part of both surfaces of the metal plate 5 to constitute the discharge plate 2. The discharge plate 2 has thorns on the windward side as in the first embodiment. With such a configuration, the aspect of the main corona discharge at the tip of the thorn of the discharge plate 2 is not different from that in FIG. 2 with respect to the discharge when a high voltage is applied, but from the activated carbon fiber 6 attached to the discharge plate 2. The main corona discharge has also occurred.

(Example 6)
FIG. 7 is a configuration diagram of an electrostatic precipitator according to this embodiment. Activated carbon fiber 6 is attached to the entire surface of both surfaces of metal plate 5 to form discharge plate 2. Further, the ground electrode plate 6 is composed of only the metal plate 5. The discharge plate 2 has thorns on the windward side as in the first embodiment. With such a configuration, the main corona discharge of the discharge plate 2 is generated from the tip of the thorn and the entire surface of the discharge plate 2 with respect to the discharge when a high voltage is applied.

(Example 7)
FIG. 8 is a configuration diagram of an electrostatic precipitator according to the present embodiment. FIG. 8A is a diagram of the grounding electrode plate 3 viewed from the lateral direction of the electrostatic precipitator, and FIG. 8B is a plan view of the electrode plate portion of the electrostatic precipitator. The discharge plate 2 has thorns on the windward side as in the first embodiment. The grounding electrode plate 3 is composed only of the metal plate 5, and a thorn electrode is punched and provided on the flat surface portion (A portion). This thorn has a shape protruding toward the upstream side in the air passage direction. With such a configuration, the aspect of the main corona discharge is the same as that in FIG. 2 with respect to the discharge when a high voltage is applied, but the sub-corona discharge is generated from the portion A provided with the punched barb electrode. .

  The present invention is an electrostatic precipitator that can efficiently suppress the increase in NOx and ozone that are increased by the electrostatic precipitator, and is suitable for purification of exhaust gas along an automobile road.

FIG. 1 is a configuration diagram of an electric dust collector according to a first embodiment of the present invention. Main / sub-corona discharge phase diagram by the electrostatic precipitator of the first embodiment Main / sub corona discharge phase diagram by electric dust collector of the second embodiment Main / sub corona discharge phase diagram by electric dust collector of the third embodiment Configuration diagram of electrostatic precipitator of the fourth embodiment (a) Diagram of ground electrode plate, (b) Phase diagram of main / sub corona discharge Main sub-corona discharge phase diagram by electric dust collector of the fifth embodiment Main / sub-corona discharge phase diagram by electric dust collector of the sixth embodiment Electric dust collector configuration diagram of the seventh embodiment (a) Ground electrode plate diagram, (b) Main / sub corona discharge phase diagram Configuration of conventional single-stage electrostatic precipitator

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric dust collector 2 Discharge plate 3 Grounding electrode plate 4 High voltage generator 5 Metal plate 6 Activated carbon fiber

Claims (13)

A parallel plate structure in which a metal discharge plate having a plurality of thorn electrodes and a ground electrode plate made of activated carbon fibers formed into a flat plate shape are alternately arranged, and a DC or AC high voltage is applied. Dust collector. 2. The electrostatic precipitator according to claim 1, wherein activated carbon fibers are attached to both surfaces of a metal flat plate to form a ground electrode plate. The electrostatic precipitator according to claim 2, wherein activated carbon fibers are attached to a part of both surfaces of a metal flat plate to form a ground electrode plate. The electrostatic precipitator according to claim 3, wherein the ground electrode plate has a plurality of thorn protrusions disposed on the exposed metal portion. 2. The electrostatic precipitator according to claim 1, wherein a ground electrode plate is formed by sandwiching both sides of the activated carbon fiber with a metal wire mesh. 5. The electrostatic precipitator according to claim 4, wherein a ground electrode plate is formed by cutting out a part of the metal wire mesh. The electrostatic precipitator according to claim 1, wherein activated carbon fibers are attached to a part of the discharge plate. The electrostatic precipitator according to claim 7, wherein the discharge plate has activated carbon fibers attached to the entire surface of both sides. The electrostatic discharge device according to any one of claims 1 to 6, wherein the discharge plate includes both sides of the activated carbon fiber sandwiched between metal wire meshes and ends of the wire mesh are barbed electrodes. A parallel plate structure in which a discharge plate with activated carbon fibers pasted on both sides of a metal discharge plate and metal grounding electrode plates are alternately arranged, and a high current of DC is applied. Dust equipment. It is characterized by applying a high DC voltage with a parallel plate structure in which both sides of the activated carbon fiber are sandwiched by metal wire mesh and the discharge plate with the wire mesh end part as a thorn electrode and metal ground electrode plates are arranged alternately. Electric dust collector. The electrostatic precipitator according to claim 10 or 11, wherein a ground electrode plate having a plurality of thorns is used. An electrostatic precipitator that applies a high DC voltage with a parallel plate structure in which a metal discharge plate having a plurality of thorn electrodes and a ground electrode plate having a plurality of thorn electrodes are alternately arranged.

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