JP2010029827A - Electric dust collector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric duct collector of a small size ensuring a sufficient dust collecting capacity as an electric dust collector by ensuring the quantity of corona discharges with suppressing occurrence of spark discharges, with avoiding increase in the size of the whole electric dust collector. <P>SOLUTION: A discharge electrode 21 for causing a corona discharge and a grounding electrode 22 connected to the ground are arranged in parallel with an air flow direction. The discharge electrode 21 comprises an insulation substrate 31 having an electric insulation property, a resistor 33 having an electric resistance value, a needle electrode 34 and an electric conduction section 32. A high voltage is fed to the electric conduction section 32 provided on the electric insulation substrate 31. If electric discharges are caused in a quantity exceeding a specified value between the needle electrode 34 and the insulation substrate 31 at a certain site, the needle electrode 34 and the electric conduction section 32 at the site are insulated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  Conventionally, this type of electrostatic precipitator is known as follows, and will be described with reference to FIG. 8 (see, for example, Patent Document 1).

  As shown in FIG. 8, a plane ground electrode 81 is provided in parallel with the air flow, and a discharge electrode 84 including a support 82 and a plurality of needle-like electrodes 83 is provided in parallel therewith. By supplying a voltage to the discharge electrode 84, a corona discharge is generated between the ground electrode 81 and the discharge electrode 84, and the suspended particulate matter in the air is charged and collected.

  The ground electrode 81 is made of a metal such as steel, stainless steel, or aluminum. In general, the needle-shaped electrode 83 is made of steel or stainless steel. However, in consideration of corrosion and corrosion resistance, metals such as titanium, iridium, platinum, rhodium, and tungsten, and alloys thereof may be used.

At this time, the inter-electrode distance between the needle electrode 83 and the discharge electrode 84 in the ground electrode 81 is 30 mm, and the voltage applied to the needle electrode 83 is 18 kV.
JP 59-59258 A

  In such a conventional electrostatic precipitator, if the distance between the ground electrode and the discharge electrode is too small, spark discharge occurs frequently and the original precipitator performance of the electrostatic precipitator cannot be obtained. If the distance between the electrodes is increased, the problem can be solved, but the corona discharge amount of the entire electrostatic precipitator is reduced, which also leads to a decrease in the precipitator performance of the electrostatic precipitator.

  The conventional electrostatic precipitator increases the distance between the electrodes to a distance where spark discharge does not occur frequently and arranges a plurality of discharge electrodes in the air flow direction to ensure the corona discharge as a whole and maintain the dust collection performance. ing. Accordingly, the planar ground electrode is also enlarged in the air flow direction.

  As a result, the size of the electrostatic precipitator as a whole has increased and the weight has become heavier, so that it has been necessary to secure the space of the installation place and to withstand the strength against the load. In addition, the increase in the size of the electrostatic precipitator in the direction in which air flows increases the pressure loss, which requires a large amount of power for the blower.

  The present invention solves such a conventional problem, and by suppressing the continuous occurrence of spark discharge, the size of the entire electrostatic precipitator can be reduced, and the amount of corona discharge can be secured. An object of the present invention is to provide an electrostatic precipitator capable of sufficiently securing the dust collecting performance as an electrostatic precipitator while being small in size.

  In order to achieve the above object, the electrostatic precipitator of the present invention is arranged so that a discharge electrode for generating corona discharge and a ground electrode connected to the ground are parallel to the air flow direction, and the discharge electrode is electrically connected. A conductive portion provided on the insulating substrate, wherein the conductive portion includes a conductive insulating portion, a needle-like electrode, and a conductive portion, and a plurality of the needle-like electrodes are connected so as to be connected in parallel from the conductive portion. Is supplied with a high voltage from the high voltage generating means, and when a corona discharge exceeding a specified level occurs between the one needle electrode and the insulating base, the one needle electrode and the high voltage The generation means is insulated.

  By this means, when a spark discharge occurs between one needle-like electrode and the insulating base, it is possible to eliminate the continuous spark discharge by insulating only the needle-like electrode and the high voltage generating means.

  Another means is that a resistor is provided between the conductive portion and the needle-like electrode protruding from the insulating substrate.

  By this means, the occurrence of spark discharge is prevented.

  Another means is that a plurality of resistors and needle-like electrodes are connected so as to be connected in parallel from the conductive portion provided on the insulating substrate of the discharge electrode.

  By this means, the corona discharge amount can be ensured.

  Another means is that the suspended particulate matter is charged and collected by corona discharge generated between the discharge electrode and the ground electrode, and connected to the ground and the charged electrode to which high voltage is supplied from the high voltage generating means downstream A plurality of the collected dust collecting electrodes are arranged in parallel with the air flow direction, and the charged suspended particulate matter is collected by an electric field generated between the charged electrode and the dust collecting electrode. is there.

  By this means, the dust collection performance of the electric dust collector can be improved.

  Another means is to set the electric resistance value of the resistor to 10 MΩ to 200 MΩ.

  By this means, spark discharge can be prevented appropriately.

  Another means uses a chip resistor having a square plate shape without a metal lead wire as a resistor.

  By this means, the electrostatic precipitator can be reduced in size.

  Another means uses ceramics as the material of the resistor.

  By this means, it is possible to use one having an electric resistance value / capacitance in a region not available on a commercially available chip resistor.

  Another means is that the ceramic has an electric resistance adjusted by mixing at least iron oxide or carbon particles.

  By this means, the electrical resistance value of the ceramic can be easily adjusted.

  Another means is to mold the periphery of the resistor with an insulating resin.

  By this means, it is possible to prevent a short-circuit phenomenon from occurring through the creeping surface or space of the resistor when the potential difference between both ends of the resistor increases.

  Another means is that a through hole is provided in an insulating substrate where a resistor is provided.

  By this means, it becomes easy to mold the surface of the resistor facing the insulating substrate with the insulating resin.

  Another means is that the insulating substrate is a glass epoxy substrate in which a glass nonwoven fabric and a glass cloth are overlapped and impregnated with an epoxy resin.

  By this means, the warpage of the insulating substrate can be reduced, the corona discharge can be generated uniformly, and the dust collection performance of the electric dust collector can be stabilized.

  Another means is that the material of the insulating substrate is ceramics.

  By this means, the durability of the insulating substrate against ozone or the like can be further increased.

  Another means is that the tip of the needle electrode has a tip diameter R of 0.3 mm or less.

  By this means, the amount of corona discharge can be increased and the performance of the electrostatic precipitator can be improved.

  As another means, the needle-like electrode is a round bar having a thickness of φ0.3 to 1.0 mm.

  By this means, even if the tip of the needle electrode is durablely deteriorated due to corona discharge and the tip disappears, the thickness of the needle electrode does not change, so the amount of corona discharge can be maintained, and electric dust collection is possible. The dust collection performance of the machine can be maintained for a long time.

  Another means is that the material of the needle-like electrode is stainless steel.

  By this means, it is possible to prevent the needle-like electrode from becoming brittle due to oxidation and being easily damaged.

  Another means is that the material of the needle-like electrode is tungsten.

  By this means, deterioration due to corona discharge at the tip of the needle electrode can be suppressed, and durability can be improved.

  Another means is that the interelectrode distance D between the discharge electrode and the ground electrode and the pitch P between adjacent needle electrodes are in a relationship of 0.4D ≦ P ≦ 1.4D.

  By this means, a corona discharge can be ensured in a space-saving manner, and the electrostatic precipitator can be reduced in size and the dust collection performance can be maintained.

  Another means is that the distance D between the discharge electrode and the ground electrode and the length J at which the tip of the needle electrode protrudes from the insulating substrate have a relationship of 0.8D ≦ J ≦ 1.4D. .

  By this means, a corona discharge can be ensured in a space-saving manner, and the electrostatic precipitator can be reduced in size and the dust collection performance can be maintained.

  ADVANTAGE OF THE INVENTION According to this invention, the electric dust collector which has the effect of preventing dust generation | occurrence | production continuously and ensuring dust collection performance, performing size reduction can be provided.

  Moreover, the occurrence of spark discharge can be prevented.

  In addition, the electrical resistance value of the resistor can be easily adjusted.

  Moreover, the short circuit phenomenon which generate | occur | produces at the both ends of a resistor can be prevented.

  Further, corona discharge can be generated uniformly.

  In addition, the durability of the electrostatic precipitator can be increased.

  According to a first aspect of the present invention, a discharge electrode for generating a corona discharge and a ground electrode connected to the ground are arranged in parallel with a direction in which air flows, and the discharge electrode is electrically insulative. A certain insulating substrate, a needle electrode, and a conductive portion are provided, a plurality of the needle electrodes are connected so as to be connected in parallel from the conductive portion, and a high voltage is generated in the conductive portion provided on the insulating substrate. When a high voltage is supplied from the means and a corona discharge exceeding a specified level is generated between the needle-like electrode at one place and the insulating base, the needle-like electrode at one place and the high-voltage generating means are insulated. It is possible to prevent the continuous generation of spark discharge, and the distance between the discharge electrode and the ground electrode can be reduced, so the size is reduced and the amount of corona discharge can be increased. Effect of improved performance A.

  According to the second aspect of the present invention, a resistor is provided between the conductive portion and the needle-like electrode protruded from the insulating substrate. When the discharge electrode and the ground electrode are separated from each other, the resistor is provided. The current tends to flow through the electrode, but if the current increases as it approaches, the resistor will make it difficult for the current to flow, so spark discharge can be prevented and the distance between the discharge electrode and the ground electrode can be reduced. Therefore, the size can be reduced and the amount of corona discharge can be increased, so that the dust collection performance is improved.

  According to the third aspect of the present invention, a plurality of resistors and needle-like electrodes are connected so as to be connected in parallel from the conductive portion provided on the insulating substrate of the discharge electrode, and the amount of corona discharge is increased. And has the effect of improving dust collection performance.

  According to a fourth aspect of the present invention, the suspended particulate matter is charged and collected by corona discharge generated between the discharge electrode and the ground electrode, and a high voltage is supplied downstream from the high voltage generating means. A plurality of electrodes and dust collecting electrodes connected to the ground are arranged in parallel to the air flow direction, and the charged suspended particulate matter is captured by the electric field generated between the charged electrodes and the dust collecting electrodes. Since the collecting action by the Coulomb force is increased, the dust collecting performance of the electric dust collector is improved.

  According to the fifth aspect of the present invention, the electric resistance value of the resistor is 10 MΩ to 200 MΩ, and when the discharge electrode and the ground electrode are separated from each other, a current easily flows in the resistor, but approaches. Thus, when the current increases, it becomes difficult for the resistor to flow the current, so that spark discharge can be appropriately prevented.

  The invention according to claim 6 of the present invention uses a chip resistor having a square plate shape without a metal lead wire as the resistor, and since the size of the resistor is small, the insulation of the discharge electrode is used. Since the size of the conductive substrate can be reduced, the electrostatic precipitator can be reduced in size.

  In the invention according to claim 7 of the present invention, ceramic is used as the material of the resistor, and it is possible to use one having an electric resistance value / capacitance in a region not available in a commercially available chip resistor. The current can be controlled more accurately.

  The invention according to claim 8 of the present invention is such that the ceramic has an electric resistance value adjusted by mixing at least iron oxide or carbon particles, and has an effect that the electric resistance value of the ceramic can be easily adjusted. .

  The invention according to claim 9 of the present invention is the one in which the periphery of the resistor is molded with an insulating resin, and when the potential difference becomes large at both ends of the resistor, the short circuit phenomenon occurs through the creeping surface or space of the resistor. It has the effect | action that it can prevent generating.

  According to a tenth aspect of the present invention, a through hole is provided in an insulating substrate where a resistor is installed, and an insulating resin is also provided on the surface of the resistor facing the insulating substrate. It has the effect that it becomes easy to mold with.

  According to the eleventh aspect of the present invention, the insulating substrate is a glass epoxy substrate in which a glass nonwoven fabric and a glass cloth are overlapped and impregnated with an epoxy resin, and warping of the insulating substrate is reduced. Thus, the corona discharge can be uniformly generated, and the dust collection performance of the electric dust collector can be stabilized.

  According to the twelfth aspect of the present invention, the material of the insulating substrate is ceramic, and has the effect that the durability of the insulating substrate against ozone or the like can be further increased.

  According to the thirteenth aspect of the present invention, the tip of the needle electrode has a tip diameter R of 0.3 mm or less, which can increase the amount of corona discharge and increase the performance of the electrostatic precipitator. Has an effect.

  According to the fourteenth aspect of the present invention, the needle-like electrode is a round bar having a diameter of 0.3 to 1.0 mm, and the tip of the needle-like electrode is deteriorated by corona discharge and the tip disappears. However, since the thickness of the needle electrode does not change, the corona discharge amount can be maintained, and the dust collection performance of the electric dust collector can be maintained for a long period of time.

  According to the fifteenth aspect of the present invention, the needle-shaped electrode is made of stainless steel, and has an effect of preventing the needle-shaped electrode from becoming brittle and easily damaged by oxidation.

  According to the sixteenth aspect of the present invention, the material of the needle-like electrode is tungsten, so that deterioration due to corona discharge at the tip of the needle-like electrode can be suppressed, and the durability can be improved.

  In the invention according to claim 17 of the present invention, the inter-electrode distance D between the discharge electrode and the ground electrode and the pitch P between the adjacent needle-like electrodes have a relationship of 0.4D ≦ P ≦ 1.4D, Corona discharge can be secured in a space-saving manner, and the electric dust collector can be reduced in size and the dust collection performance can be maintained.

  According to the eighteenth aspect of the present invention, the distance D between the discharge electrode and the ground electrode and the length J at which the tip of the needle electrode protrudes from the insulating substrate are in a relationship of 0.8D ≦ J ≦ 1.4D. Thus, corona discharge can be secured in a space-saving manner, and the electric dust collector is reduced in size and has an effect of maintaining dust collection performance.

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

(Embodiment 1)
FIG. 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 view of a charging unit and a dust collecting unit according to Embodiment 1 of the present invention, and FIG. It is a detailed view of the discharge electrode in Form 1.

  As shown in FIG. 1, a charging unit 1 for charging suspended particulate matter in the air and a dust collecting unit 2 for collecting the charged suspended particulate matter are provided, and downstream of the dust collecting unit 2, The duct 3 is provided with a blower (an axial flow blower in the first embodiment) which is a blowing means 4 for drawing air containing suspended particulate matter. The high voltage generating means 5 for supplying a high voltage to the charging section 1 and the dust collecting section 2 is a DC high-voltage power supply in the first embodiment, and the current detecting means 7 and the controller 6 are electrically connected.

  Next, the operation in FIG. 1 will be described. The air containing the suspended particulate matter that has flowed into the duct 3 due to the suction of the blower is charged by the suspended particulate matter due to corona discharge when passing through the charging portion 1, and is collected by the Coulomb force of the electric field of the dust collection portion 2. The dust is collected and removed by the dust electrode 24 and becomes clean air, which is discharged from the blower to the outside. At this time, a DC high voltage (for example, -8 kV to the charging unit 1 and -8 kV to the dust collecting unit 2) is supplied from the high voltage generating means 5 to the charging unit 1 and the dust collecting unit 2, and these controls are performed. Is performed by the controller 6.

  FIG. 2 is a perspective configuration diagram of the charging unit 1 and the dust collecting unit 2. The charging unit 1 includes a discharge electrode 21 for applying a high voltage and a ground electrode 22 connected to the ground in the air flow direction (arrow direction). Stacked in parallel, the dust collector 2 has a charging electrode 23 for applying a high voltage and a dust collecting electrode 24 (for example, a stainless steel plate) connected to the ground 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 21 and the ground electrode 22 of the charging unit 1 and the gap between the charge electrode 23 and the ground electrode 22 of the dust collection unit 2 as indicated by arrows. The suspended particulate matter in the air is charged to a negative potential by corona discharge (minus discharge in the first embodiment) generated between the first electrode 21 and the ground electrode 22, and the charged electrode 23 (this embodiment) Due to the electric field generated between the negative electrode in form 1 and the positive electrode in the first embodiment (positive electrode in the first embodiment), the suspended particulate matter charged to a negative potential adheres to the dust collection electrode (positive electrode) by Coulomb force. It is collected.

  FIG. 3 is a detailed view of the discharge electrode 21, and an electrically conductive portion 32 (copper stay in the first embodiment) is provided on one side of an electrically insulating substrate 31. A high voltage is applied to the conductive portion 32 from the high voltage generating means 5. If the insulating substrate 31 is warped, the distance between the needle electrode 34 and the ground electrode 22 will be different, and the amount of corona discharge generated will be uneven. Therefore, it is desirable that the insulating substrate 31 is not warped. . Moreover, since it may wash | clean using surfactant and water, it must be the material which can endure them.

  Therefore, in this Embodiment 1, the glass epoxy board | substrate which overlap | superposed the glass nonwoven fabric and the glass cloth and impregnated the epoxy resin is used. A resistor 33 having an electric resistance value on the surface of the insulating substrate 31 (in the first embodiment, a chip resistor having a square plate shape without a metal lead wire is used, and the electric resistance value is 50 MΩ) The conductive portion 32 and the resistor 33 are electrically connected and fixed by soldering. A conductive wire pattern 36 is installed between the conductive portion 32 and the resistor 33.

  Similarly, the needle electrode 34 is connected to the resistor 33 in series by soldering. At this time, the tip of the needle electrode 34 protrudes from the insulating substrate 31. In the first embodiment, as shown in FIG. 3, only one end of the needle electrode 34 protrudes from the insulating substrate 31, but both ends of the needle electrode 34 may protrude from the insulating substrate 31. . In the unlikely event that the needle electrode 34 and the ground electrode 22 are close to each other, the discharge current increases, the potential difference between both ends of the resistor 33 increases, and there is a possibility that a short circuit occurs through the surface of the resistor 33 or through the space. Further, the resistor 33 is molded with an insulating resin (silicone resin in the first embodiment) so that the resistor 33 can withstand a collected substance, a surfactant, water, etc., and the resistor 33 is corroded or short-circuited. Is preventing.

  Further, a through hole 35 is formed in the insulating substrate 31 where the resistor 33 is installed, so that it can be easily molded on the back side (insulating substrate 31 side) of the resistor 33 without a gap. .

  Next, the configuration of the needle electrode 34 in FIG. 3 will be described. In the first embodiment, the needle-shaped electrode 34 is made of stainless steel that can prevent oxidation compared to steel and the like. The diameter gradually decreases toward the tip, and the tip has a tip diameter R of 0.3 mm or less (preferably 20 μm or less). Then, a sufficient amount of corona discharge can be secured. Since the amount of corona discharge becomes smaller at R 0.3 mm or more, the number of needle-shaped electrodes 34 must be increased to maintain the dust collection performance, and the apparatus becomes large.

  For this reason, the distance (pitch) between the adjacent needle-shaped electrodes 34 and the length protruding from the insulating substrate 31 must be set in the optimum range because corona discharge interferes or the discharge amount becomes too small. I must. The range was obtained from the next experiment.

  In the experiment, first, using one acicular electrode 34, the protrusion length from the insulating substrate 31 was changed, and the discharge current was measured. At this time, the stainless steel plate connected to the ground facing the needle electrode 34 is arranged in parallel, the distance D between the electrodes is 15 mm, a high DC voltage of -8.0 kV is applied to the needle electrode 34, and the needle at that time The tip diameter of the electrode 34 is R20 μm.

  The result is shown in FIG. As for the relationship between the interelectrode distance D and the protrusion length J, 0.8D ≦ J ≦ 1.4D is the optimum range, and a protrusion length of 15 mm at which the discharge current value reaches a peak is desirable. If it is 90% or more of the peak value of the discharge current, the relationship between the size of the electrostatic precipitator and the corona discharge amount can be maintained exactly. The lower limit of the protruding length at this time is 12 mm (0.8 times the interelectrode distance D) from FIG. On the other hand, if the length is longer than 1.4D, the current is not increased, but the needle-like electrode 34 becomes longer, so the size of the electrostatic precipitator increases.

  Based on this result, the distance between the electrodes was fixed to 15 mm and the protruding length was 15 mm, the pitch between the adjacent needle electrodes 34 was changed, and the discharge current at that time was measured. Similarly, the applied voltage to the needle electrode 34 was −8.0 kV, the needle electrode 34 was fixed at a width of 120 mm, and the needle electrode 34 was placed by changing the pitch within the width. Therefore, this result represents the discharge current per length (120 mm).

  The result is shown in FIG. The optimum range of the relationship between the inter-electrode distance D between the needle electrode 34 and the ground electrode 22 and the pitch P between the adjacent needle electrodes 34 is 0.4D ≦ P ≦ 1.4D. A pitch of 10 mm at which the discharge current peaks is desirable. If it is 90% or more of the peak value of the discharge current, the relationship between the size of the electrostatic precipitator and the corona discharge amount can be maintained exactly. The pitch of 6 mm to 21 mm is 90 μA or more, which is 90% of the peak value of 67 μA. If the diameter is less than 6 mm, the needle-shaped electrodes 34 are too dense to increase the weight, and the number of resistors 33 increases accordingly, so there is no cost merit.

  Next, in Embodiment 1, an operation capable of maintaining the performance of the electrostatic precipitator while reducing the size of the electrostatic precipitator will be described. Usually, the discharge electrode 21 is a thin metal wire of 1 mm or less, for example, has a needle-like shape, and the resistor 33 is not used. In this state, when the distance between the discharge electrode 21 and the ground electrode 22 is reduced, a spark discharge is generated from a certain distance. When a spark discharge occurs, the electric resistance value of air approaches 0, and the applied voltage of the discharge electrode 21 also approaches 0. For this reason, the generation of corona discharge stops, the suspended particulate matter in the air cannot be charged, and the dust collection performance deteriorates.

  Further, if the distance between the discharge electrode 21 and the ground electrode 22 is too large, the amount of corona discharge is extremely reduced, and the dust collection performance is deteriorated. Based on these, the conventional electrostatic precipitator approaches the discharge electrode 21 in the direction in which the air flows in order to reduce the distance between the discharge electrode 21 and the ground electrode 22 to a marginal distance where no spark discharge occurs and to secure a corona discharge amount. There were multiple numbers. Along with this, the size of the ground electrode 22 also increases in the direction in which air flows, so that the overall size and weight have increased.

  Therefore, in the present invention, the acicular electrode 34 that generates corona discharge and the resistor 33 are connected in series. As a result, a voltage drop occurs in the resistor 33 portion according to Ohm's law. When the distance between the discharge electrode 21 and the ground electrode 22 is increased, the current flowing through the resistor 33 is reduced, so that the voltage drop at the resistor 33 is reduced, and a sufficient voltage for corona discharge is secured at the tip of the needle electrode 34. Is done.

  As the distance between the discharge electrode 21 and the ground electrode 22 is reduced, the amount of current flowing through the resistor 33 increases, so that the voltage drop in the resistor 33 increases and the tip of the needle electrode 34 is connected to the discharge electrode 21. The voltage decreases as the distance from the ground electrode 22 decreases. Since spark discharge does not occur even when the distance is reduced, the distance between the discharge electrode 21 and the ground electrode 22 can be reduced, and the amount of corona discharge per needle electrode 34 can be increased. It is not necessary to provide the discharge electrode 21 and it is possible to reduce the size. At this time, since the corona discharge amount is maintained, the dust collection performance is maintained without decreasing.

  Next, the results of experiments on the difference between the spark discharge generation distance and the discharge current when the electrical resistance value of the resistor 33 is changed will be described. In the experiment, a stainless steel plate is connected to the ground, and the needle electrode 34 has a tip diameter of 20 μm. The needle electrode 34 is arranged so as to be perpendicular to the stainless steel plate, and the tip of the needle electrode 34 and the stainless steel plate The distance was set to 15 mm. A resistor is electrically connected to the acicular electrode 34, and a DC high voltage of -8.0 kV is applied to the primary side of the resistor.

  FIG. 6 (right axis) shows the discharge current when the value of the resistor is changed. Further, the distance between the tip of the needle electrode 34 and the stainless steel plate is shortened, and the distance when the spark discharge is generated is defined as the spark discharge generation distance. The result is also shown in FIG. 6 (left axis). From this result, when the resistance value is increased, the discharge current is decreased, and the spark discharge generation distance is shortened accordingly.

  When the resistor 33 is inserted, the discharge current is reduced, but the spark discharge generation distance is shortened. Therefore, the distance between the discharge electrode 21 and the ground electrode 22 can be shortened. When the distance is shortened, the discharge current is increased. It is not necessary to dispose a plurality of discharge electrodes 21 in the flowing direction, and the discharge current can be maintained while realizing miniaturization, so that the dust collection performance can be maintained. With respect to an appropriate resistance value, if it is less than 10 MΩ, there is almost no difference in the spark discharge generation distance when the resistance value is 0.

  In addition, when it is larger than 200 MΩ, the discharge current continues to decrease as estimated from the graph of FIG. 6, but the decrease in the spark discharge generation distance has almost disappeared. However, it is difficult to reduce the size. For this reason, the resistance value is appropriately in the range of 10 MΩ to 200 MΩ.

  As shown in FIG. 3, in the present invention, the spark discharge generation distance can be shortened. However, in the unlikely event that an electrically conductive object comes flying, it is considered that the acicular electrode 34 and the ground electrode 22 Is short-circuited, an abnormal current flows and heat is generated in the short-circuit portion, and a load is applied to the transformer of the high-voltage generating means 5, so that the current has a certain threshold value (in the first embodiment, a normal corona discharge current value). Since the conductor pattern 36 connecting the conductive portion 32 and the resistor 33 is disconnected when the value exceeds 10), only one shorted needle electrode 34 stops supplying high voltage. It is supposed to be.

  In some cases, the current detection means 7 detects that the current has exceeded a certain threshold value (set to a value 10 times the normal corona discharge current value in the first embodiment), and supplies the current to the acicular electrode 34. It is also possible to cut off the supply of high voltage.

(Embodiment 2)
FIG. 7 is a detailed view of the discharge electrode 21 in Embodiment 2 of the present invention. Description of the same parts as those in Embodiment 1 is omitted. In the present embodiment, zirconia ceramics is used for the resistor 33, and the needle electrode 34 is made of tungsten and is a round bar having a thickness of φ0.5 mm.

  By mixing a conductive filler such as iron oxide or carbon into ceramics, the resistance value can be easily adjusted.

  The durability of the needle-shaped electrode 34 can be improved by using tungsten as the material for the needle-shaped electrode 34 and a round bar having a thickness of 0.3 to 1.0 mm. By using tungsten, it is possible to reduce the strong oxidizing action at the tip of the acicular electrode 34 due to the occurrence of corona discharge, and by using a round bar whose thickness does not change, the acicular electrode 34 should be used. Even if the tip is oxidized and the length of the needle-like electrode 34 is shortened, the thickness does not change, so that the ability close to the initial state can be continuously generated. No need to replace. If the thickness of the needle-shaped electrode 34 is less than φ0.3 mm, the strength is weakened so that the needle electrode 34 bends immediately and contacts the ground electrode 22 to cause a short circuit.

  On the other hand, if it is larger than φ1.0 mm, the amount of corona discharge is reduced, and sufficient dust collection performance cannot be ensured.

  In the second embodiment, both ends of the needle electrode 34 are protruded from the insulating substrate 31. However, by doing so, the amount of corona discharge can be doubled. This method can also be used in the first embodiment, and dust collection performance can be further improved.

  The present invention is effective as an air cleaning method in the case where a flammable substance is contained in airborne particulate matter in the air, and while ensuring dust collection efficiency, the occurrence of spark discharge is suppressed and the apparatus is downsized. It is intended to provide an electrostatic precipitator that can be used.

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 discharge electrode Graph showing the experimental results of the protrusion length and discharge current of the needle electrode Graph showing the experimental results of the pitch and discharge current of the needle electrode Graph showing experimental results when changing the spark discharge generation distance and discharge current resistance Detailed view showing the discharge electrode of Embodiment 2 of the present invention Figure showing a conventional electrostatic precipitator

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging part 2 Dust collection part 3 Duct 4 Blowing means 5 High voltage generation means 6 Controller 7 Current detection means 21 Discharge electrode 22 Ground electrode 23 Charging electrode 24 Dust collection electrode 31 Insulating substrate 32 Conductive part 33 Resistor 34 Needle shape Electrode 35 Through hole 36 Conductor pattern

Claims (18)

A discharge electrode for generating corona discharge and a ground electrode connected to the ground are arranged in parallel with the direction of air flow, and the discharge electrode is an electrically insulating insulating substrate, a needle electrode, and a conductive part. A plurality of the needle-like electrodes are connected so as to be connected in parallel from the conductive portion, and the conductive portion provided on the insulating substrate is supplied with a high voltage from a high voltage generating means, and is at least one place When a corona discharge exceeding a specified level occurs between the needle-shaped electrode and the insulating substrate, an electric dust collector that insulates the needle-shaped electrode where the corona discharge exceeds the specified level from the high voltage generating means. Machine. 2. The electric dust collector according to claim 1, wherein a resistor is provided between the conductive portion and the needle-like electrode protruding from the insulating substrate. 3. The electric dust collector according to claim 2, wherein a plurality of resistors and needle-like electrodes are connected so as to be connected in parallel from the conductive portion provided on the insulating substrate of the discharge electrode. A charged electrode in which suspended particulate matter is charged and collected by corona discharge generated between the discharge electrode and the ground electrode, and a high voltage is supplied from a high voltage generating means downstream thereof, and a dust collection electrode connected to the ground A plurality of the particles are arranged in parallel with the air flow direction, and the charged suspended particulate matter is collected by an electric field generated between the charged electrode and the dust collecting electrode. Electric dust collector. The electric dust collector according to any one of claims 2 to 4, wherein an electric resistance value of the resistor is 10 MΩ to 200 MΩ. 6. The electric dust collector according to claim 2, wherein a chip resistor having a square plate shape without a metal lead wire is used as the resistor. 6. The electrostatic precipitator according to claim 2, wherein the resistor is made of ceramic. The electric dust collector according to claim 7, wherein the electrical resistance value of the ceramic is adjusted by mixing at least iron oxide or carbon particles. 9. The electrostatic precipitator according to claim 2, wherein the periphery of the resistor is molded with an insulating resin. The electrostatic precipitator according to any one of claims 2 to 9, wherein a through-hole is provided in an insulating substrate where a resistor is installed. The electric dust collector according to any one of claims 1 to 10, wherein the insulating substrate is a glass epoxy substrate in which a glass nonwoven fabric and a glass cloth are overlapped and impregnated with an epoxy resin. The electric dust collector according to claim 1, wherein a material of the insulating substrate is ceramics. The electrostatic precipitator according to any one of claims 1 to 12, wherein the tip of the needle electrode has a tip diameter R of 0.3 mm or less. The electrostatic precipitator according to any one of claims 1 to 12, wherein the needle-like electrode is a round bar having a diameter of 0.3 to 1.0 mm. The electrostatic precipitator according to any one of claims 1 to 14, wherein a material of the needle electrode is stainless steel. The electrostatic precipitator according to any one of claims 1 to 14, wherein a material of the needle-like electrode is tungsten. The electrostatic precipitator according to any one of claims 1 to 16, wherein an inter-electrode distance D between the discharge electrode and the ground electrode and a pitch P between adjacent needle electrodes are in a relationship of 0.4D ≦ P ≦ 1.4D. 18. The distance D between the discharge electrode and the ground electrode and the length J from which the tip of the needle electrode protrudes from the insulating substrate have a relationship of 0.8D ≦ J ≦ 1.4D. Electric dust collector.

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