JP2009208041A - Electric precipitator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly durable electric precipitator which generates corona discharge and prevents spark discharge from generating. <P>SOLUTION: An electric precipitator is provided with a charged part 21, a dust collecting part 31, a blower 2 and a high voltage electric source 3. A semi-conducting electric plate 28 designed by a semi-conducting ceramic of which the electric resistance per unit area of the electric current flowing in a width direction is 10<SP>8</SP>-10<SP>10</SP>Ω cm<SP>2</SP>is located on the surface of a ground electrode 23 of the charged part 21. Then, a discharge electrode 22 of the charged part 21 is constituted of a plurality of a needle-shaped electrodes 27 projecting from a supporting part 26 arranged in parallel to the ground electrode 23. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric dust collector for collecting airborne particulate matter and cleaning the air.

  Conventionally, this kind of electrostatic precipitator is known, for example, as disclosed in Patent Document 1. Hereinafter, the electric dust collector will be described with reference to FIGS. 8 and 9. FIG.

As shown in FIG. 8, the electric dust collector includes a charging unit 81, a dust collector 82, a blower fan 83, and an electronic control box 84, and controls a high voltage power source and an electric dust collector (not shown) in the electronic control box 84. A controller (not shown) is provided. As shown in FIG. 9, the charging unit 81 and the dust collection unit 82 have a discharge electrode 91 connected to a high-voltage power supply and a grounded electrode 92 that are connected to a high-voltage power source alternately and in parallel without contacting each other. It is arranged with an interval of. Similarly, a load electrode plate 93 connected to a high voltage power source and a grounded electrode plate 94 connected to a high voltage power source are alternately arranged in parallel at a constant interval without contacting each other. Yes. By applying a high voltage from a high-voltage power supply, the charging unit 81 generates a corona discharge between the discharge electrode 91 to which the high voltage is applied and the grounded electrode 92 to charge the suspended particulate matter in the air. In the dust collector 82, the charged suspended particulate matter adheres to the ground electrode plate 94 due to the electric field generated between the load electrode plate 93 connected to the high voltage power source and the grounded electrode plate 94. By being collected, airborne particulate matter can be removed and air can be purified.
Japanese Patent Laid-Open No. 2-114286

  In such a conventional electrostatic precipitator, the discharge electrode 91 connected to the high voltage power source of the charging unit 81 to which a high voltage is applied, the ground electrode 92 grounded, and the load connected to the high voltage power source of the dust collector 82. Since the electrode plate 93 and the grounded electrode plate 94 that are grounded face each other with the conductor exposed, spark discharge may occur depending on the applied voltage and the temperature and humidity conditions of the space. When a spark discharge occurs during operation, the combustible material adhering to the ground electrode 92 of the charging unit 81 and the ground electrode plate 94 of the dust collection unit 82 is partially abnormally overheated, and the ground electrode 92 and the ground electrode plate 94 are heated. Due to the deformation, there is a problem that the durability life is shortened.

  An object of the present invention is to solve such a conventional problem and to provide a highly durable electric dust collector that prevents the occurrence of spark discharge while ensuring a corona discharge amount. .

In order to achieve the above object, the electric dust collector of the present invention includes a charging unit, a dust collecting unit, a blower, and a high-voltage power source, and has an electric resistance per unit area of 10 ⁸ to 10 for a current flowing in the thickness direction. ^A semiconductive plate made of ¹⁰ Ω · cm ² of semiconductive ceramic is disposed on the surface of the ground electrode of the charging portion.

  By this means, corona discharge is generated in the charging portion to charge the suspended particulate matter in the air, and spark discharge can be prevented to ensure durability.

  Another means is that the semiconductive plate is made of a semiconductive ceramic whose main component is at least one of zirconium oxide, silicon carbide, and titanium oxide.

  Thereby, the electrical resistance per unit area of the semiconductive ceramic for preventing spark discharge can be easily adjusted.

  Another means is that the semiconductive plate is made of a semiconductive ceramic containing 63% or more of zirconium oxide, 30% or more of ferric oxide, and 5% or less of yttrium oxide.

  Thereby, the electrical resistance per unit area of the semiconductive ceramic for preventing spark discharge can be optimized.

  Another means is that the semiconductive plate is made of a semiconductive ceramic having a thickness of 0.5 to 5 mm.

  Thereby, the electrical resistance per unit area of the semiconductive ceramic for preventing spark discharge can be optimized.

  Another means is that the semiconductive plate is fixed to the ground electrode of the charging unit with an insulating screw.

  Thereby, it is possible to reliably fix the semiconductive plate to the ground electrode of the charging unit while preventing spark discharge with certainty.

  Another means is that the semiconductive plate is attached to the ground electrode of the charging portion with a conductive adhesive or a conductive heat welding film.

  Accordingly, the semiconductive plate can be reliably fixed to the ground electrode of the charging unit while securing the current value of the corona discharge.

  Another means is that the ground electrode of the charging unit is a conductive film, and the semiconductive plate is affixed to the conductive film with a conductive adhesive or a conductive heat welding film.

  Thereby, the ground electrode can be reduced in weight.

  Another means is that the discharge electrode of the charging unit is composed of a support part arranged in parallel to the ground electrode and a plurality of needle-like electrodes protruding from the support part.

  Thereby, the efficiency of corona discharge is improved, and even when the same amount of corona discharge is obtained at the charging portion, the voltage applied to the charging portion can be lowered, and spark discharge can be reliably prevented.

  Another means is that the semiconductive plates are divided into approximately the same number as the tips of the opposing needle electrodes, and the gaps between the adjacent semiconductive plates are filled with an insulator.

  Thereby, manufacture of a semiconductive board can be performed easily and cost can be reduced.

  Another means is that the radius of the curved surface of the tip of the needle electrode is 0.1 mm or less.

  Thereby, the efficiency of corona discharge can be further improved.

  The other means is that the protrusion length H from the support portion of the needle-like electrode is H / D = 0.5 to 1. with respect to the distance D between the discharge electrode and the ground electrode arranged in parallel with the charging portion. 5 is set.

  Thereby, the efficiency of corona discharge can be further improved.

  Another means is that the needle pitch P of the adjacent needle-like electrodes arranged on one support portion is P / D = 1 with respect to the distance D between the discharge electrode arranged in parallel with the charging portion and the ground electrode. It is set in the range of .0 to 1.5.

  Thereby, the efficiency of corona discharge can be further improved.

  Another means is that the voltage applied to the charging unit supplied from the high voltage power source is controlled so that the current flowing as a corona discharge between the discharge electrode and the ground electrode of the charging unit has a predetermined value. It is.

  As a result, the corona discharge current is optimized in the charging unit, and an unnecessarily high applied voltage is not applied, so that spark discharge can be reliably prevented.

  Another means is to apply the applied voltage Va so that the difference K = Vm−Va between the withstand voltage Vm of the semiconductive plate and the applied voltage Va applied to the charging unit supplied from the high-voltage power supply always keeps a predetermined value or more. Is limited.

  Thereby, since the voltage beyond a withstand voltage is not applied to a semiconductive plate, the spark discharge resulting from the dielectric breakdown of a semiconductive plate can be prevented reliably.

Another means is that an insulating plate made of a resin film or an insulating ceramic having an electric resistance per unit area with respect to a current flowing in the thickness direction of 10 ¹⁰ Ω · cm ² or more is used for the load electrode plate of the dust collecting portion. It is arranged on the surface.

  Thereby, not only the charging part but also the spark discharge of the dust collecting part can be prevented and the durability can be ensured.

  Another means is to apply the applied voltage Vb so that the difference K = Vn−Vb between the withstand voltage Vn of the insulating plate and the applied voltage Vb to the dust collector supplied from the high-voltage power supply always keeps a predetermined value or more. Is limited.

  Thereby, since the voltage beyond a withstand voltage is not applied to an insulating board, the spark discharge resulting from the dielectric breakdown of an insulating board can be prevented reliably.

  ADVANTAGE OF THE INVENTION According to this invention, after ensuring the corona discharge amount enough, generation | occurrence | production of spark discharge can be prevented and a highly durable electric dust collector can be provided.

  In addition, it is possible to reliably prevent the spark discharge and secure the current value of the corona discharge, and to securely fix the semiconductive plate to the ground electrode of the charging unit.

  In addition, the efficiency of corona discharge is improved, and even when the same amount of corona discharge is obtained in the charging portion, the applied voltage to the charging portion can be lowered, and the corona discharge current is optimized so that an unnecessary high applied voltage is not applied. Therefore, spark discharge can be reliably prevented.

  Further, not only the charging portion but also the spark discharge of the dust collection portion is prevented, and the effect of ensuring the durability is also exhibited.

  In addition, since a voltage higher than the withstand voltage is not applied to the semiconductive plate and the insulating plate, there is an effect that the spark discharge caused by the dielectric breakdown is surely prevented.

According to the first aspect of the present invention, a semiconductive plate made of a semiconductive ceramic having an electric resistance per unit area of 10 ⁸ to 10 ¹⁰ Ω · cm ² with respect to a current flowing in the thickness direction is used as a charging portion. By disposing on the surface of the ground electrode, corona discharge is generated in the charging portion to charge the suspended particulate matter in the air, and spark discharge is prevented and durability is ensured.

  According to a second aspect of the present invention, the semiconductive plate is made of a semiconductive ceramic whose main component is at least one of zirconium oxide, silicon carbide, and titanium oxide. The semiconductive ceramic has an effect that the electric resistance per unit area can be easily adjusted.

  The invention according to claim 3 of the present invention is such that the semiconductive plate is made of a semiconductive ceramic containing 63% or more of zirconium oxide, 30% or more of ferric oxide, and 5% or less of yttrium oxide, thereby causing a spark discharge. This has the effect of optimizing the electric resistance per unit area of the semiconductive ceramics for preventing the above.

  The invention according to claim 4 of the present invention is that the semiconductive plate is made of a semiconductive ceramic having a thickness of 0.5 to 5 mm, so that the semiconductive ceramic for preventing spark discharge is provided. It has the effect of optimizing the electrical resistance per unit area.

  According to a fifth aspect of the present invention, the semiconductive plate is fixed to the ground electrode of the charging unit by an insulating screw, so that spark discharge is reliably prevented, and then the semiconductive plate is connected to the ground electrode of the charging unit. It has the effect | action of fixing to a certain.

  In the invention according to claim 6 of the present invention, the semiconductive plate is adhered to the ground electrode of the charging portion with a conductive adhesive or a conductive heat welding film, thereby ensuring a current value of corona discharge. The semiconductive plate is reliably fixed to the ground electrode of the charging unit.

  According to the seventh aspect of the present invention, the ground electrode of the charging portion is a conductive film, and the semiconductive plate is attached to the conductive film with a conductive adhesive or a conductive heat welding film. Therefore, the ground electrode can be reduced in weight.

  The invention according to claim 8 of the present invention is such that the discharge electrode of the charging portion is constituted by a support portion arranged in parallel to the ground electrode and a plurality of needle-like electrodes protruding from the support portion, whereby corona discharge Even when the same corona discharge amount is obtained at the charging portion, the voltage applied to the charging portion can be lowered and spark discharge can be reliably prevented.

  According to the ninth aspect of the present invention, the semiconductive plate is divided into approximately the same number as the tips of the opposing needle-like electrodes, and the gap between the adjacent semiconductive plates is filled with an insulating material. The conductive plate can be easily manufactured, and the cost can be reduced.

  The invention according to claim 10 of the present invention has the effect of further improving the efficiency of corona discharge by setting the radius of curvature of the tip of the needle electrode to 0.1 mm or less.

  According to the eleventh aspect of the present invention, with respect to the distance D between the discharge electrode arranged in parallel to the charging portion and the ground electrode, the protrusion length H from the support portion of the needle electrode is H / D = 0. By being set to the range of 5-1.5, it has the effect | action which further improves the efficiency of a corona discharge.

  According to the twelfth aspect of the present invention, the needle pitch P of the adjacent needle-like electrodes arranged on one supporting portion is P with respect to the distance D between the discharge electrode arranged in parallel to the charging portion and the ground electrode. By being set in the range of /D=1.0 to 1.5, it has the effect of further improving the efficiency of corona discharge.

  According to the thirteenth aspect of the present invention, the voltage applied to the charging unit supplied from the high voltage power source is such that the current flowing as a corona discharge between the discharge electrode and the ground electrode of the charging unit becomes a predetermined value. By being controlled, the corona discharge current is optimized in the charging portion, and an unnecessary high applied voltage is not applied, so that spark discharge can be reliably prevented.

  According to the fourteenth aspect of the present invention, the difference K = Vm−Va between the withstand voltage Vm of the semiconductive plate and the applied voltage Va to the charging unit supplied from the high voltage power source is always kept at a predetermined value or more. Since the applied voltage Va is limited to the above, since the voltage higher than the withstand voltage is not applied to the semiconductive plate, the spark discharge due to the dielectric breakdown of the semiconductive plate is surely prevented.

According to a fifteenth aspect of the present invention, there is provided an insulating plate made of a resin film or insulating ceramic having an electric resistance per unit area of 10 ¹⁰ Ω · cm ² or more with respect to a current flowing in the thickness direction. By arranging on the surface of the load electrode plate, not only the charging part but also the spark discharge of the dust collecting part is prevented, and the durability is ensured.

  According to the sixteenth aspect of the present invention, the difference K = Vn−Vb between the withstand voltage Vn of the insulating plate and the voltage Vb applied to the dust collector supplied from the high-voltage power supply always ensures a predetermined value or more. When the applied voltage Vb is limited, the insulating plate is not applied with a voltage higher than the withstand voltage, so that spark discharge caused by dielectric breakdown of the insulating plate is reliably prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
1 is a cross-sectional configuration diagram of an electric dust collector according to Embodiment 1 of the present invention, FIG. 2 is a perspective configuration diagram of a charging unit and a dust collector according to Embodiment 1 of the present invention, and FIG. 3 is an embodiment of the present invention. 3A is a detailed view of the charging unit in Embodiment 1, FIG. 3A is a plan view taken in the direction of arrow A in FIG. 2, FIG. 3B is a sectional view taken in the direction of arrow B in FIG. 2, and FIG. It is sectional drawing of the dust collection part load electrode plate in the form 1.

  As shown in FIG. 1, a duct 1 is provided with a charging unit 21 that charges floating particulate matter in the air, and a dust collecting unit 31 that collects the charged suspended particulate matter. A blower 2 for drawing air containing suspended particulate matter into the duct 1 is provided downstream. Reference numeral 3 denotes a high voltage power source that supplies a high voltage to the charging unit 21 and the dust collecting unit 31, and is electrically connected to the current detector 4 and the controller 5.

  Next, the operation in FIG. 1 will be described. The air containing the suspended particulate matter that has flowed into the duct 1 due to the suction of the blower 2 is charged by the suspended particulate matter due to corona discharge when passing through the charging portion 21, and is caused by the Coulomb force of the electric field of the dust collection portion 31. It is collected and removed by the electrode plate, becomes clean air, and is discharged from the blower 2 to the outside. At this time, a DC high voltage (for example, −8 kV to the charging unit 21 and −8 kV to the dust collecting unit 31) is supplied from the high-voltage power supply 3 to the charging unit 21 and the dust collecting unit 31, and these controls are controlled. This is done by the vessel 5.

  FIG. 2 is a perspective configuration diagram of the charging unit 21 and the dust collecting unit 31. The charging unit 21 includes a discharge electrode 22 for applying a high voltage and a ground electrode 23 connected to the ground in parallel to the air flow direction (arrow direction). The dust collector 31 has a load electrode plate 32 for applying a high voltage and a ground electrode plate 33 (for example, a stainless steel plate) connected to the ground, which are stacked in parallel to the air flow direction (arrow direction). Has been placed. In FIG. 2, air flows through the gap between the discharge electrode 22 and the ground electrode 23 of the charging unit 21 and the gap between the load electrode plate 32 and the ground electrode plate 33 of the dust collection unit 31 as indicated by arrows. The suspended particulate matter in the air is charged to a negative potential by corona discharge (negative discharge in the first embodiment) generated between the discharge electrode 22 and the ground electrode 23, and the load electrode plate 32 ( The floating particulate matter charged to a negative potential due to the electric field generated between the negative electrode in the first embodiment and the ground electrode plate 33 (the positive electrode in the first embodiment) causes the ground electrode plate 33 (the positive electrode) by the Coulomb force. ) And collected.

3 is a detailed view of the charging unit. FIG. 3A is a plan view as viewed from the direction of the arrow A, and FIG. 3B is a plan view of the discharge electrode 22 viewed from the direction A. FIG. 3 is a cross-sectional view of the discharge electrode 22 and the ground electrode 23 viewed from the direction B in FIG. As shown in the plan view of FIG. 3 (a), a plurality of discharge electrodes 22 (two in the first embodiment) are arranged from the upstream portion 24 to the downstream portion 25 in the air flow direction. A plurality of needle-like electrodes 27 (stainless steel needles as an example) protrude from 26 (stainless steel plate as an example) and are attached by welding or the like. Further, as shown in the cross-sectional view in the direction of arrow B in FIG. 3B, the electric resistance per unit area with respect to the current flowing in the thickness direction is 10 ⁸ to 10 on the surface of the ground electrode 23 (stainless steel plate as an example). ^A semiconductive plate 28 made of ¹⁰ Ω · cm ² of semiconductive ceramic is disposed. In the first embodiment, the semiconductive plate 28 is fixed to the ground electrode 23 by an insulating screw 41. The reason for using the insulating screw 41 is that if it is fixed to the ground electrode 23 with a conductive screw, a spark discharge may occur between the conductive screw and the needle electrode 27, and this is prevented. Because. That is, by using the insulating screw 41, it is possible to reliably prevent the spark discharge and securely fix the semiconductive plate 28 to the ground electrode 23.

  Here, the effect | action which prevents a spark discharge by arrange | positioning the semiconductive board 28 on the surface of the ground electrode 23 is demonstrated. Normally, if the ground electrode 23 is made of a conductive stainless steel sheet, when the dielectric breakdown of air occurs during corona discharge, the electrical resistance of the air at that point approaches zero as much as possible, and the current concentrates. Flow spark discharge occurs. On the other hand, when the semiconductive plate 28 is arranged on the surface of the ground electrode 23, even if the dielectric breakdown of air occurs during corona discharge and the electrical resistance of the air at that location approaches zero as much as possible, the semiconductive plate 28 is disposed. Since the resistance of the plate 28 is in series, there is little difference in resistance value compared to the resistance of other locations (air resistance + semiconductive plate resistance), the current is dispersed and concentrated in one location, and the spark does not flow. The occurrence of discharge can be prevented. At this time, if the electrical resistance of the semiconductive plate 28 is too large, corona discharge cannot be sufficiently performed. If it is too small, the effect of dispersing the above-described current and preventing spark discharge is lost.

The physical property of the semiconductive plate 28 is generally a volume resistivity representing the electric resistance (resistance of electricity flowing per unit volume (Ω · cm)), which correlates with the effect of preventing spark discharge. The thickness of the conductive plate 28 is also related. That is, in essence, the resistance per unit area against the current flowing in the thickness direction of the semiconductive plate 28 (that is, the value obtained by multiplying the volume resistivity by the thickness. Hereinafter, the area resistivity (Ω · cm ² ) It is important to set a proper range. The present inventors have found that it is optimal to set the value of the sheet resistivity to 10 ⁸ to 10 ¹⁰ Ω · cm ² . This range is, for example, that the volume resistivity is 2 × 10 ⁹ to 2 × 10 ¹¹ Ω · cm for the semiconductive plate 28 of 0.5 mm, and the volume resistivity is 2 × 10 5 for the semiconductive plate 28 of 5 mm. It corresponds to ^{8 to} 2 × 10 ¹⁰ Ω · cm.

Any material can be used for the semiconductive plate 28 as long as the above-described sheet resistivity can be obtained. However, when a resin material is used, the polymer material deteriorates with time when a high voltage is applied, and eventually the dielectric breakdown occurs. In the present invention, semiconductive ceramics are used because there is a possibility that the desired function is not achieved. Although it is difficult to adjust the electrical resistance of ceramics, a desired sheet resistivity of 10 ⁸ to 10 ¹⁰ Ω · cm ² can be obtained by using a ceramic mainly composed of at least zirconium oxide, silicon carbide, or titanium oxide. Obtainable. The most suitable material contains zirconium oxide 63% or more, ferric oxide 30% or more, and yttrium oxide 5% or less. The thickness of the semiconductive plate 28 at this time is optimally 0.5 to 5 mm. This is because if it is thinner than 0.5 mm, it is difficult to mold the ceramic, and if it is thicker than 5 mm, it is necessary to reduce the volume resistivity, and it is difficult to adjust the electrical resistance with ceramics.

  Next, the configuration of the needle electrode 27 will be described. As shown in FIG. 3, the discharge electrode 22 has a plurality of protruding needle-like electrodes 27 arranged in the longitudinal direction on the end face of a support portion 26 arranged in parallel to the ground electrode 23, and the tip of the needle is sharp. As a result, the charge of corona discharge is concentrated, and the corona discharge efficiency can be improved. The radius of the curved surface at the tip of the needle electrode 27 is preferably 0.1 mm or less. Thereby, even when the same corona discharge amount is obtained by the charging unit 21, the voltage applied to the charging unit 21 can be lowered, and the spark discharge can be further reliably prevented. In the first embodiment, with respect to the distance D between the discharge electrode 22 and the ground electrode 23, the protruding length H of the needle electrode 27 from the support portion 26 is in the range of H / D = 0.5 to 1.5. Is set to Further, the needle pitch P of the adjacent needle-like electrodes 27 arranged on one support portion 26 with respect to the distance D between the discharge electrode 22 and the ground electrode 23 is in the range of P / D = 1.0 to 1.5. Is set to If the values of H / D and P / D are too large, the density per unit area of the corona discharge is lowered and the corona discharge efficiency is lowered, and if it is too small, the needle-like electrode 27 and the support portion 26 are in contact with each other. Corona discharge efficiency decreases because the discharge between the electrodes interferes. The present inventors have found that the efficiency of corona discharge is the best in the ranges of H / D = 0.5 to 1.5 and P / D = 1.0 to 1.5. Thereby, the efficiency of the corona discharge is further improved, and even when the same corona discharge amount is obtained in the charging unit 21, the voltage applied to the charging unit 21 can be further reduced, and the spark discharge can be further reliably prevented. .

  Next, control of applied voltage to the charging unit 21 by the high-voltage power supply 3 will be described. As shown in FIG. 1, a current detector 4 is connected to the high-voltage power source 3, and in order to make the corona discharge amount appropriate, the current supplied to the charging unit 21 is measured by the current detector 4, The voltage applied to the charging unit 21 is controlled by the controller 5 so as to be a value of 10 (10 mA as an example). Thereby, since the corona discharge current is optimized in the charging unit 21 and an unnecessarily high applied voltage is not applied, spark discharge can be reliably prevented. In the first embodiment, the difference K = Vm−Va between the withstand voltage Vm of the semiconductive plate 28 and the applied voltage Va applied to the charging unit 21 supplied from the high voltage power source is always kept at a predetermined value or more. The applied voltage Va is limited. For example, when the withstand voltage of the semiconductive ceramic as the semiconductive plate 28 is Vm = 15 kV, by controlling the applied voltage to Va ≦ 10 kV, K = Vm−Va always has a safety factor of 5 kV or more. Can be secured. The higher the safety factor, the better. However, it depends on the withstand voltage related to the physical properties of the semiconductive ceramic, and a reasonable numerical value is determined in consideration of the cost. Thereby, since the voltage beyond a withstand voltage is not applied to the semiconductive board 28, the spark discharge resulting from the dielectric breakdown of the semiconductive board 28 can be prevented reliably.

FIG. 4 is a cross-sectional view of the load electrode plate 32 of the dust collection portion 31. With reference to FIG. 4, means for preventing the spark discharge of the dust collection portion 31 will be described. On the surface of the load electrode plate 32 (as an example, a stainless steel plate) of the dust collecting portion 31, a resin film (an example of an electrical resistance (area resistivity) per unit area with respect to a current flowing in the thickness direction is 10 ¹⁰ Ω · cm ² or more. Insulating plate 34 made of, for example, PET, PP, PVDF, etc.) or insulating ceramics (alumina as an example) is disposed. The insulating plate 34 may be fixed to the ground electrode plate 33 with an insulating screw as in the charging unit 21 of FIG. 3, or may be a heat welding film 35 (either insulating or conductive as shown in FIG. 4). ) May be fixed to the ground electrode plate 33. Normally, if the load electrode plate 32 is made of a conductive stainless steel cloth, when the dielectric breakdown of the air occurs, the electric resistance of the air at that location approaches zero as much as possible, and the current flows intensively and spark discharge occurs. Occurs. On the other hand, when the insulating plate 34 is disposed on the surface of the load electrode plate 32, even if the insulation breakdown of the air occurs and the electric resistance of the air at that location approaches zero as much as possible, the resistance of the insulating plate 34 is reduced. Because it is in series, there is little difference in resistance compared to the resistance of other locations (air resistance + insulation plate resistance), and the current is dispersed and concentrated in one location, preventing the occurrence of spark discharge without flowing current be able to. The role of the dust collecting portion 31 is to cause charged floating particulate matter to adhere to and collect on the ground electrode plate 33 by Coulomb force due to the electric field generated between the load electrode plate 32 and the ground electrode plate 33. Unlike the portion 21, it is not necessary to perform corona discharge. Therefore, if the area resistivity of the insulating plate 34 is 10 ¹⁰ Ω · cm ² or more, the dust collecting portion 31 also has an effect of preventing spark discharge.

  In the first embodiment, the difference K = Vn−Vb between the withstand voltage Vn of the insulating plate 34 and the voltage Vb applied to the dust collection portion 31 supplied from the high-voltage power supply always ensures a predetermined value or more. The applied voltage Vb is limited. For example, when the withstand voltage of the insulating plate 34 is Vn = 25 kV, the safety factor of K = Vn−Vb can always be 15 kV or more by controlling the applied voltage to Vb ≦ 10 kV. The higher the safety factor, the better. However, it depends on the withstand voltage related to the physical properties of the insulating plate 34, and a reasonable numerical value is determined in consideration of the cost. Thereby, since the voltage beyond a withstand voltage is not applied to the insulating board 34, the spark discharge resulting from the dielectric breakdown of the insulating board 34 can be prevented reliably.

  With the above configuration, the corona discharge amount is sufficiently secured and the dust collection efficiency is increased, and then a spark discharge is generated during operation, and the combustible material adhering to the ground electrode 23 and the ground electrode plate 33 is partially abnormally overheated. Since the ground electrode 23 and the ground electrode plate 33 are not deformed by heat, the durability of the electrostatic precipitator can be improved.

(Embodiment 2)
FIG. 5 is a detailed view of the charging unit of the electric dust collector according to the second embodiment of the present invention, FIG. 5 (a) is a plan view in the direction of arrow A in FIG. 2, and FIG. 5 (b) is B in FIG. It is direction arrow sectional drawing. The same components as those in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 5, the semiconductive plate 28 is attached to the ground electrode 23 of the charging unit 21 with a conductive heat welding film 51. Alternatively, instead of the conductive heat welding film 51, a conductive adhesive may be used. The reason why the conductive material is used as the pasting means is that a current necessary for corona discharge in the charging unit 21 needs to flow to the ground electrode 23. In this method, the semiconductive plate 28 can be affixed by automated equipment as compared with the fastening by screws, so that the manufacturing cost in mass production can be reduced. Thereby, the semiconductive plate 28 can be securely fixed to the ground electrode 23 while ensuring the current value of the corona discharge.

(Embodiment 3)
6 is a detailed view of the charging unit of the electrostatic precipitator according to Embodiment 3 of the present invention. FIG. 6 (a) is a plan view in the direction of the arrow A in FIG. 2, and FIG. 6 (b) is B in FIG. It is direction arrow sectional drawing. The same components as those in FIGS. 1 to 3 and FIG.

  As shown in FIG. 6, the semiconductive plate 28 is divided into approximately the same number as the tips of the opposing acicular electrodes 27, and a gap between adjacent semiconductive plates 28 is filled with an insulator 61. The semiconductive ceramic used as the semiconductive plate 28 is generally difficult to form a thin plate shape having a large area, and the production yield can be improved and the manufacturing cost can be reduced by dividing the semiconductive ceramic into a small area. However, if the semiconductive plate 28 is divided, the conductive ground electrode 23 is exposed in the gap, so that spark discharge may occur in that portion. Therefore, in the third embodiment, the insulator 61 (silicon as an example) is filled in the gap between the adjacent semiconductive plates 28. The reason why the number of divisions of the semiconductive plate 28 is substantially the same as the number of the tips of the opposing acicular electrodes 27 is that the corona discharge current does not flow to a location where the corona discharge current density is far from the tips of the acicular electrodes 27. This is because the reduction in the amount of corona discharge is minimized by disposing the insulator 61.

(Embodiment 4)
7 is a detailed view of the charging unit of the electrostatic precipitator according to Embodiment 4 of the present invention. FIG. 7 (a) is a plan view in the direction of arrow A in FIG. 2, and FIG. 7 (b) is B in FIG. It is direction arrow sectional drawing. The same components as those in FIGS. 1 to 3 and FIG.

  As shown in FIG. 7, the semiconductive plate 28 is affixed to the ground electrode 23 of the charging unit 21 by a conductive heat welding film 51. Or you may affix with a conductive adhesive instead of the electroconductive heat welding film 51. FIG. Here, in the fourth embodiment, a conductive film 71 (conductive PVDF, 100 μm as an example) is used as the ground electrode 23. When a semiconductive ceramic of 0.5 to 5 mm is used as the semiconductive plate 28, since the semiconductive plate 28 becomes a rigid body and maintains strength, the ground electrode 23 only needs to have a function of conducting electricity. By using the thin conductive film 71 even if it is not used, the ground electrode 23 can be reduced in weight.

  The present invention is effective as an air cleaning method in the case where a flammable substance is contained in airborne particulate matter, and is highly durable without causing spark discharge while ensuring dust collection efficiency. An electric dust collector is provided.

Sectional block diagram which shows the electric dust collector of Embodiment 1 of this invention Perspective configuration diagram of the charging unit and dust collection unit Detailed view of the charging unit ((a) plan view in the direction of arrow A in FIG. 2, (b) cross-sectional view in the direction of arrow B in FIG. 2) Cross-sectional view of the dust collector electrode plate 2A and 2B are detailed views of the charging unit showing the electrostatic precipitator according to Embodiment 2 of the present invention ((a) a plan view in the direction of arrow A in FIG. 2, (b) a cross-sectional view in the direction of arrow B in FIG. 2). FIG. 4 is a detailed view of a charging unit showing an electric dust collector according to Embodiment 3 of the present invention ((a) a plan view in the direction of arrow A in FIG. 2 and (b) a cross-sectional view in the direction of arrow B in FIG. 2). FIG. 4 is a detailed view of a charging unit showing an electric dust collector according to Embodiment 4 of the present invention ((a) a plan view in the direction of arrow A in FIG. 2 and (b) a cross-sectional view in the direction of arrow B in FIG. 2). Cross-sectional configuration diagram of a conventional electrostatic precipitator Diagram showing the principle of a conventional electrostatic precipitator

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Blower 3 High voltage power supply 21 Charging part 22 Discharge electrode 23 Ground electrode 26 Support part 27 Needle-like electrode 28 Semiconductive plate 31 Dust collection part 32 Load electrode plate 33 Grounding electrode plate 34 Insulation plate 41 Insulating screw 51 Thermal welding film 61 Insulation 71 Conductive film

Claims (16)

The discharge electrode and the ground electrode are stacked in parallel with the air flow direction to charge the floating particulate matter in the air, and the load electrode plate and ground electrode plate are stacked in parallel with the air flow direction. A dust collection unit that collects suspended particulate matter in the air charged by the charging unit, a blower that allows air containing suspended particulate matter to flow into the charging unit and the dust collection unit, and a suspended particulate matter A high-voltage power supply that supplies a high voltage to the charging unit and the dust collection unit, and an electric resistance per unit area with respect to a current flowing in a thickness direction is 10 ⁸ to 10 ¹⁰ Ω · cm ² . An electrostatic precipitator in which a semiconductive plate made of semiconductive ceramic is disposed on the surface of the ground electrode of the charging unit. 2. The electric dust collector according to claim 1, wherein the semiconductive plate is made of a semiconductive ceramic containing at least one of zirconium oxide, silicon carbide, and titanium oxide as a main component. 2. The electric dust collector according to claim 1, wherein the semiconductive plate is made of a semiconductive ceramic containing 63% or more of zirconium oxide, 30% or more of ferric oxide, and 5% or less of yttrium oxide. The electrostatic precipitator according to claim 1, wherein the semiconductive plate is made of semiconductive ceramic having a thickness of 0.5 to 5 mm. The electric dust collector according to claim 1, wherein the semiconductive plate is fixed to the ground electrode of the charging unit by an insulating screw. 5. The electric dust collector according to claim 1, wherein the semiconductive plate is affixed to the ground electrode of the charging unit by a conductive adhesive or a conductive heat welding film. The electrostatic precipitator according to claim 6, wherein the ground electrode of the charging unit is a conductive film, and the semiconductive plate is attached to the conductive film with a conductive adhesive or a conductive heat welding film. The electrostatic precipitator according to any one of claims 1 to 7, wherein the discharge electrode of the charging unit includes a support part disposed in parallel with the ground electrode and a plurality of needle-like electrodes protruding from the support part. 9. The electric dust collector according to claim 8, wherein the semiconductive plate is divided into approximately the same number as the tip of the opposing needle electrodes, and a gap between the semiconductive plates is filled with an insulator. The electric dust collector according to claim 8 or 9, wherein the needle-like electrode has a curved surface radius of 0.1 mm or less. The protrusion length H from the support portion of the needle electrode is set in the range of H / D = 0.5 to 1.5 with respect to the distance D between the discharge electrode and the ground electrode arranged in parallel with the charging portion. The electric dust collector according to claim 8. For the distance D between the discharge electrode and the ground electrode arranged in parallel to the charging unit, the needle pitch P of the adjacent needle electrodes arranged on one support unit is P / D = 1.0 to 1.5 The electric dust collector according to any one of claims 8 to 10, which is set to a range. The voltage applied to the charging unit supplied from the high-voltage power supply is controlled so that a current flowing as a corona discharge between the discharge electrode and the ground electrode of the charging unit has a predetermined value. The electric dust collector described in Crab. 14. The applied voltage Va is limited so that the difference K = Vm−Va between the withstand voltage Vm of the semiconductive plate and the applied voltage Va applied to the charging unit supplied from the high-voltage power supply always maintains a predetermined value or more. The electric dust collector described. ^2. An insulating plate made of a resin film or insulating ceramic having an electric resistance per unit area of 10 ¹⁰ Ω · cm ² or more with respect to a current flowing in the thickness direction is arranged on the surface of the load electrode plate in the dust collecting portion. The electric dust collector in any one of -14. 16. The applied voltage Vb is limited so that the difference K = Vn−Vb between the withstand voltage Vn of the insulating plate and the applied voltage Vb applied to the dust collector supplied from the high-voltage power supply always maintains a predetermined value or more. The electric dust collector described.

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