JP4638452B2 - Electric dust collector - Google Patents

Description

  The present invention relates to an electric dust collection device for an air cleaning device that captures dust that is airborne particles.

In recent years, air purifiers have been widely used in order to keep the air in buildings and vehicles in a clean state at all times. There are various types of air purifiers, ranging from large industrial devices to small household devices. The air purifiers are used alone or mounted inside a device with a blower.
Air purifiers that have become popular in recent years give fine particles in an air current by corona discharge or the like, and collect and remove charged particles by electrostatic force while the charged particles pass through the charge. Therefore, it is called an electrostatic dust collection device.

  The conventional air dust collector electrostatic dust collection device has a ground plate electrode as a counter electrode parallel to the discharge electrode or wire discharge electrode with a sharp tip, and applies a high voltage to the discharge electrode or wire discharge electrode with a sharp tip. In this way, a corona discharge is generated between the electrodes, and an ionization part that charges fine particles in the air is provided, and a collector part or a dust collection filter that collects the fine particles charged in the ionization part is provided downstream of the ionization part. It is removed (see, for example, Patent Document 1).

Japanese Patent No. 3516725 (paragraph 0025, FIG. 2)

In general, an electrostatic dust collection device is composed of an ionization unit that charges floating dust in the air and a collector unit that collects charged floating dust. In order to improve dust collection efficiency, It is important to charge the floating dust in the ionization section and to collect the floating dust charged in the collector section firmly.
Since the conventional electrostatic dust collection device uses conductive metal for the high voltage electrode of the collector portion, spark discharge may occur between the high voltage electrode and the dust collection electrode. Therefore, a method of covering the surface of the high voltage electrode with a resin, a method of forming the high voltage electrode itself with a resin, and adding a conductive material such as carbon black or a metal filler into the resin have been employed. However, when the surface of the high voltage electrode is coated with resin, spark discharge may occur due to deterioration of the coating resin, pinholes, or the like. In addition, when the high voltage electrode itself is made of a resin and a conductive material such as carbon black or a metal filler is added to the resin, a conductive path is locally formed when a certain voltage or more is applied, and a spark is generated. Discharge sometimes occurred. When a spark discharge occurs, unpleasant sound and light are generated, and at the same time, the spark discharge is a localized and intermittent limited discharge, which causes a significant reduction in dust collection efficiency.

  In order to solve this problem, for example, ABS resin, polyester resin, acrylic resin, etc. mixed with hygroscopic resin such as polyamide, poval, acrylate, etc. are used for the high voltage electrode of the collector section. However, a method has been proposed in which the resistance value of the high voltage electrode is controlled by moisture adsorbed on the resin, and the spark discharge is suppressed and the dust collection efficiency is increased by setting the resistance value to a predetermined value. However, in the case of this method, these resins exhibit high water absorption, and the resistance value fluctuates due to the resin adsorbing moisture in the use environment, so that it is difficult to control the resistance value. For example, when controlling with low resistance during drying, the resistance value further decreases in a high humidity environment, and spark discharge is generated. In addition, when the resistance is controlled to be high in a high humidity environment, the resistance further increases during drying, a predetermined resistance value cannot be obtained, and the dust collection efficiency is greatly reduced. For this reason, there has been a problem that stable dust collection efficiency cannot be obtained when the humidity changes greatly between summer and winter for home use.

  The present invention has been made to solve the above-described problems. The first object is to stably obtain high dust collection efficiency without being affected by the environment, and to suppress spark discharge. An electrostatic precipitating device that can be obtained is obtained.

An electrostatic dust collection device according to the present invention includes an ionization unit that generates corona discharge between a discharge electrode and a counter electrode to charge dust in the air, and a dust collection electrode that collects dust charged by the ionization unit And a collector portion having a high voltage electrode as a counter electrode, and the high voltage electrode of the collector portion is integrally formed of an antistatic resin formed by mixing a semiconductive filler and a dispersant in a thermoplastic resin, The volume resistance of the high voltage electrode is 1.0E + 10 Ωcm or more when the applied voltage is 6000 V, the volume resistance of the high voltage electrode is X Ωcm , and the surface resistance is YΩ / □, the value of Y is the value of X It is characterized by being 1/10.

  The electric dust collection device of the present invention has an effect of being able to stably obtain a high dust collection efficiency without being influenced by the environment and further suppressing spark discharge.

Embodiment.
FIG. 1 is an exploded perspective view of an electrostatic precipitator according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the principle of the electrostatic precipitator according to an embodiment of the present invention.
As shown in FIG. 1, the electrostatic dust collecting device includes a casing 1, a discharge electrode 2 integrally provided on a flat plate and provided with a projection having an acute angle, a flat ground (dust collection) electrode 3, and a flat high voltage electrode 4. Consists of. In FIG. 2, an ionization unit 5 that charges dust in the air is formed at the windward portion of the discharge electrode 2 and the ground (dust collection) electrode 3, and a plurality of stacked high voltage electrodes 4 and ground (dust collection) electrodes are stacked. 3, the collector part 6 which collects the dust charged by the ionization part 5 is comprised. The ground (dust collection) electrode 3 is formed by integrating the ground electrode of the ionization unit and the dust collection electrode of the collector unit. The discharge electrode 2 is formed of a metal such as stainless steel, and a protrusion with an acute angle at one end is arranged on one side or both sides on a flat plate. The discharge electrode 2 may be a wire such as a tungsten wire or a tungsten oxide wire. Further, plating by gold plating or the like may be performed. The grounding (dust collecting) electrode 3 is formed of a conductive material such as a conductive resin in which a metal such as stainless steel, carbon fiber, or metal fine particles is kneaded, and has a volume resistance of 1.0E + 0 to 1.0E + 4Ωcm, a surface resistance of 1 It has physical properties of 0.0E + 0 to 1.0E + 4Ω / □. However, 1.0E + 0 represents 1.0 × 10 0 power and 1.0E + 4 represents 1.0 × 10 4th power. Although the ground (dust collection) electrode 3 is integrated in this embodiment, it may be separated by the ionization unit 5 and the collector unit 6 to be a ground electrode and a dust collection electrode, respectively. The high voltage electrode 4 uses a semiconductive resin with a volume resistance of 1.0E + 10 to 1.0E + 15Ωcm in which a semiconductive filler is kneaded and a surface resistance of 1.0E + 9 to 1.0E + 14Ω / □ which is one order lower than the volume resistance. Is done. As the semiconductive filler, one or more of carbon, tin oxide, and zinc oxide may be used. In the case of carbon, it is desirable to use a semiconductive filler having higher resistance and lower conductivity than ordinary carbon black or carbon fiber. Originally, tin oxide and zinc oxide have higher resistance and lower conductivity than conductive materials. These substances are substances that hardly absorb moisture in the environment. As the resin base material for kneading these substances, thermoplastic resins such as ABS resin, polyester resin, acrylic resin, polypropylene resin, PET resin, and polycarbonate resin are desirable. These resins are configured so as to satisfy a predetermined volume resistance by containing about several tens of percent of a semiconductive filler. At this time, since the semiconductive filler has poor dispersibility, it is desirable to use a dispersant in order to uniformly mix the resin. Moreover, you may mix a flame retardant etc. in this resin. When a flame retardant is contained, safety against fire can be improved. Since the resin thus configured can be injection-molded, it can be integrally molded as a high-voltage electrode. Generally, the high-voltage electrode 4 and the ground (dust collection) electrode 3 have a shorter distance between the electrodes and are stacked as much as possible to increase the dust collection area and increase the dust collection efficiency. However, when the distance between the electrodes is shortened, spark discharge occurs in the case of conductors. However, in the present embodiment, since a semiconductive resin in which a semiconductive filler is kneaded into the high voltage electrode 4 is used, it is possible to suppress spark discharge and improve dust collection efficiency. The discharge electrode 2 is connected to an ionization unit high-voltage power supply 7 for supplying a positive or negative high voltage of 1 to 10 kV direct current, and similarly to the high voltage electrode 4 a positive or negative high voltage of 1 to 10 kV direct current is supplied. A collector high voltage power supply 8 is connected. In this embodiment, the ionization unit high-voltage power source 7 and the collector unit high-voltage power source 8 are separate power sources, but a single power source may be used. The ground (dust collecting) electrode 3 is grounded.

Next, the operation will be described.
In the electric dust collection device configured as described above, the dust 9 that has flowed in is charged by corona discharge generated between the projection tip of the discharge electrode 2 and the ground (dust collection) electrode 3 in the ionization unit 5. The charged dust 9 flows into the collector, and is attracted to and attached to the ground (dust collection) electrode 3 by the repulsive force of the high voltage electrode 4 and the suction force of the ground (dust collection) electrode 3. At this time, the high voltage electrode 4 is composed of a semiconductive resin having a volume resistance of 1.0E + 10 to 1.0E + 15 Ωcm and a surface resistance of 1.0E + 9 to 1.0E + 14Ω / □ into which a semiconductive filler is kneaded. The repulsive force and suction force of the high voltage electrode 4 and the ground (dust collection) electrode 3 are maximized, and the dust collection rate is maximized.

Example 1
FIG. 3 shows the applied voltage dependence of the volume resistance value when a hygroscopic resin is used for the high voltage electrode 4 as Conventional Example 1. As the hygroscopic resin, a mixture of ABS resin and several tens of% polyamide was used. In this case, when the temperature in the environment is 25 ° C. and the relative humidity is 50% and 60%, the volume resistance is about 1.0E + 12 Ωcm regardless of the applied voltage. Therefore, since it is a predetermined volume resistance value under these conditions, it is possible to obtain a good dust collection efficiency and to suppress spark discharge. However, when the relative humidity is 80%, the volume resistance is less than about 1.0E + 10 Ωcm, and the resistance value is reduced by two orders of magnitude. Further, when the relative humidity was 90%, the volume resistance was less than about 1.0E + 8 Ωcm, and it was found that there was a concern about the occurrence of spark discharge. At this time, the surface resistance was one order lower than the volume resistance. For example, when the ambient temperature is 25 ° C. and the relative humidity is 50% and 60%, the surface resistance is about 1.0E + 11Ω / □ regardless of the applied voltage. When the relative humidity was 80%, the surface resistance was less than about 1.0E + 9Ω / □. In this case, when there is a change in humidity, moisture is absorbed from the surface, so that the surface resistance is reduced in a shorter time. Since spark discharge occurs on the surface, when the environment changes, the surface resistance may decrease in a short time, and the frequency of occurrence of spark discharge may increase.

  FIG. 4 shows the applied voltage dependence of the volume resistance when a resin obtained by kneading carbon into ABS resin is used for the high voltage electrode 4 as Conventional Example 2. Carbon has a very high conductivity, and its volume resistance is about 1.0E + 1 Ωcm or less. Therefore, it is often used for conductive resins. In order to achieve the volume resistance value according to the present embodiment using carbon, it is necessary to reduce the carbon content, and the content is on the order of several percent. In this case, since carbon hardly absorbs water, the volume resistance value and the surface resistance value are constant regardless of the temperature and humidity in the environment. However, it is very difficult to adjust the carbon content of several percent, and if this value changes even a little, there is a problem that the conductivity changes greatly and the possibility of generating spark discharge becomes high. Further, since carbon is very conductive and easily affected by voltage, increasing the applied voltage greatly reduces the volume resistance value and the surface resistance value, and spark discharge occurs at several kV or more. In FIG. 4, two types of carbon kneaded resins were used, and the dependency of the volume resistance value on the applied voltage when the ambient temperature was 25 ° C. and the relative humidity was 60% was measured. As a result, when the applied voltage is 10 V, the volume resistance value is about 1.0E + 12 Ωcm. By increasing the applied voltage, the volume resistance value is reduced to about 1.0E + 9 Ωcm or less. When a voltage of 4 kV or more is applied, a spark is generated. Discharge occurred. This is because the contained carbon is partially short-circuited by applying a voltage of 4 kV or higher, and a large current flows. In particular, carbon has poor dispersibility and is often distributed in a locally offset manner. Therefore, when a positive or negative high voltage of 1 to 10 kV direct current, which is an applied voltage used as a high voltage electrode of the electric dust collection device, is applied, spark discharge occurs and the dust collection efficiency is greatly reduced. Therefore, it is conceivable that the carbon content is further reduced and the volume resistance value is further increased. However, when the carbon content is further reduced, the physical properties as a semiconductive resin cannot be maintained, which is equivalent to the insulating resin. It becomes impossible to collect dust.

  FIG. 5 shows the applied voltage dependence of the volume resistance value when a resin in which a semiconductive organic filler is kneaded into an ABS resin is used for the high voltage electrode 4 as an example of the present invention. As the semiconductive organic filler, a carbon-based one is used. The volume resistance value was changed by changing the amount of kneading of A1, A2, A3 and the semiconductive organic filler. Here, the relationship of the amount of kneading of the organic filler is A1> A2> A3. In this case, the kneading amount is on the order of several tens of percent. In this case, as in the case of the resin in which carbon is kneaded into the ABS resin in FIG. 4, the volume resistance value shows a constant value regardless of the temperature and humidity in the environment, but the volume resistance value can be increased by increasing the applied voltage. Decrease. However, when a voltage of 1 kV or higher is applied, a substantially constant volume resistance value is exhibited, and when a positive or negative high voltage of 1 to 10 kV actually used is applied, the volume resistance value is substantially constant. At this time, when the kneading amount is A3, the volume resistance value 1.0E + 10 to 1.0E + 15Ωcm and the surface resistance 1.0E + 9 to 1.0E + 14Ω / □ suitable for dust collection can be maintained. It becomes possible to obtain dust efficiency.

FIG. 6 shows the applied voltage dependence of the volume resistance value when a resin in which a semiconductive inorganic filler is kneaded into an ABS resin is used for the high voltage electrode 4. As the semiconductive inorganic filler, tin oxide, zinc oxide or the like is used. The volume resistance value was changed by changing the amount of kneading between B1 and B2 and the semiconductive inorganic filler. Here, the relationship of the amount of kneading of the organic filler is B1> B2. In this case, the kneading amount is on the order of several tens of percent. In this case, the volume resistance value is constant regardless of the temperature and humidity in the environment, similar to the resin kneaded with carbon in the ABS resin in FIG. 4 and the resin kneaded with the semiconductive organic filler in the ABS resin in FIG. Indicates the value of. However, the volume resistance value decreases by increasing the applied voltage. Therefore, when a positive or negative high voltage of DC 1 kV to 10 kV actually used is applied, the volume resistance value suitable for dust collection is 1.0E + 10 to 1.0E + 15Ωcm, the surface resistance is 1.0E + 9 to 1.0E + 14Ω / □. The amount of the semiconductive inorganic filler to be kneaded is controlled so that When this resin is used, spark discharge does not occur and high dust collection efficiency can be obtained.
5 and FIG. 6, the filler kneading amounts A1 to A3 and B1 to B2 are on the order of several tens of percent. Therefore, unlike the adjustment of carbon, if the kneading amount is a little, Even if it changes, there is no big change in conductivity and there is no possibility of generating spark discharge. For this reason, adjustment of the amount of kneading is very easy.

  Next, various properties of the resin used in FIGS. 5 and 6 are shown in FIG. As an example of the voltage condition of 1 kV to 10 kV, the volume resistance value at 6000 V is as shown in FIGS. In the case of the hygroscopic resin shown in FIG. 3, the water absorption rate of the resin is high in order to control the resistance value of the high voltage electrode by the moisture adsorbed on the resin and obtain a predetermined resistance value. The resin used in FIG. 6 has a low water absorption rate. As a result of measuring the weight difference after drying for 24 hours at a temperature of 50 ° C. and then standing at a temperature of 70 ° C. and a relative humidity of 65% for 48 hours, the resin used in FIG. 5 and FIG. I found out. On the other hand, in the case of the hygroscopic resin shown in FIG. 3, the water absorption was 0.7% or more. Therefore, in the case of the resin used in FIG. 5 and FIG. 6, the water absorption rate to the resin is low, and the volume resistance value shows a constant value regardless of the temperature and humidity in the environment.

  When a voltage of 1000 V or higher is applied to one point of the resin used in FIGS. 5 and 6 in an environment where the temperature is 20 ° C. and a relative humidity is 60%, the surface potential of the electrode surface 1 cm or more away from the voltage application point is the applied voltage. It was verified whether it was maintained in the same order. FIG. 8 shows the experimental method. Each resin is used for the high voltage electrode 4, and a high voltage of 1000 V or more from the high voltage power supply 10 is applied to the power supply unit 11 connected to one point of the high voltage electrode 4. At this time, the potential change on the surface of the high voltage electrode 4 was measured with the surface potential meter 12. A probe 13 for measurement is connected to the surface potential meter 12, and the surface potential can be measured by applying the probe 13 to the surface of the high voltage electrode 4. As a result of the measurement, it was found that the surface potential of the same order as the applied voltage was maintained in A2, A3, and B1. In B2, the surface potential is lowered by being 1 cm or more away from the voltage application point. In order to obtain a repulsive force by the high voltage electrode 4 for collecting dust and an attractive force by the ground (dust collecting) electrode 3, a high surface potential of the high voltage electrode 4 is essential, and B2 is a high voltage electrode. It turned out to be unsuitable. As a result of verifying the presence or absence of spark discharge, spark discharge occurred in a humid state in A1, and slightly spark discharge occurred in A2 and B1. In A3 and B2, no spark discharge could be confirmed. In A3 and B2, the high voltage electrode 4 and the ground (dust collection) electrode 3 are contacted (short-circuited), and even if DC positive or negative 10 kV is applied, it is a leakage current of 1 μA or less, resulting in a spark discharge current. I knew it would n’t.

As described above, a predetermined volume resistance value and surface resistance value are obtained by integrally forming the high voltage electrode of the collector portion with an antistatic resin obtained by mixing a semiconductive filler and a dispersant with a thermoplastic resin. This makes it possible to obtain high dust collection efficiency and to suppress spark discharge. In addition, the semiconductive filler mixed with the high voltage electrode of the collector portion is a high voltage by mixing one or more of materials that hardly absorb moisture in the environment, such as carbon, tin oxide, and zinc oxide. The electrode water absorption is set to 0.6% or less by weight difference after standing for 48 hours in a dry state and in an environment with a temperature of 70 ° C. and a relative humidity of 65%. It becomes possible to obtain a resistance value and a surface resistance value, thereby obtaining high dust collection efficiency and suppressing spark discharge.
At this time, the volume resistance of the high voltage electrode in the collector is preferably 1.0E + 10 Ωcm or more when the applied voltage is 6000 V, and the surface resistance is preferably one order lower than the volume resistance. Can be suppressed, and high dust collection efficiency can be obtained. Furthermore, when a voltage of 1000 V or higher is applied to a high voltage electrode in the collector section at a temperature of 20 ° C. and a relative humidity of 60%, the surface potential of the electrode surface 1 cm or more away from the voltage application point is the applied voltage. By controlling so that it is maintained in the same order, it becomes possible to maintain a high potential on the electrode surface, and to obtain a repulsive force due to the high voltage electrode for dust collection and an attractive force due to the ground (dust collecting) electrode. High dust collection efficiency can be obtained.

It is a disassembled perspective view of the electrostatic dust collection device of embodiment of this invention. It is sectional drawing which shows the principle of the electrostatic dust collection device of embodiment of this invention. It is an applied voltage dependence figure of the volume resistance value of the hygroscopic resin of embodiment of this invention. It is an applied voltage dependence figure of the volume resistance value of the carbon kneading resin of embodiment of this invention. It is an applied voltage dependence figure of the volume resistance value of the semiconductive organic filler kneaded resin of embodiment of this invention. It is an applied voltage dependence figure of the volume resistance value of the semiconductive inorganic filler kneaded resin of embodiment of this invention. It is a figure which shows the various characteristics of semiconductive organic filler kneaded resin of embodiment of this invention, and semiconductive inorganic filler kneaded resin. It is a figure which shows the measuring method of the surface potential of embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Casing, 2 Discharge electrode, 3 Grounding (dust collection) electrode, 4 High voltage pole, 5 Ionization part, 6 Collector part, 7 Ionization part high voltage power supply, 8 Collector high voltage power supply, 9 Dust, 10 High voltage power supply, 11 Feeding part , 12 Surface electrometer, 13 probe.

Claims (6)

An ionization unit having a discharge electrode and a ground electrode which is a counter electrode, and charging corona discharge between the discharge electrode and the counter electrode to charge dust in the air;
A high-voltage electrode and a ground electrode that is a counter electrode, and a collector unit that collects dust charged by the ionization unit on the counter electrode,
The high-voltage electrode of the collector part is integrally formed with an antistatic resin formed by mixing a semiconductive filler and a dispersant with a thermoplastic resin,
The volume resistance of the high voltage electrode is 1.0E + 10 Ωcm or more when the applied voltage is 6000 V,
The electrostatic precipitator according to claim 1, wherein when the volume resistance of the high voltage electrode is X Ωcm and the surface resistance is YΩ / □, the value of Y is one tenth of the value of X.   2. The electrostatic precipitator according to claim 1, wherein the semiconductive filler is made of a material that hardly absorbs moisture in the environment. 3. The electric dust collector according to claim 2, wherein the semiconductive filler is composed of one or more of semiconductive carbon , tin oxide, and zinc oxide having lower conductivity than carbon black or carbon fiber. device.   The water absorption rate of the high voltage electrode is 0.6% or less in terms of a weight difference after standing for 48 hours in a dry state and in an environment at a temperature of 70 ° C and a relative humidity of 65%. The electric dust collection device in any one of.   When a voltage of 1000 V or more is applied to a high voltage electrode at a temperature of 20 ° C. and a relative humidity of 60%, the surface potential of the electrode surface 1 cm or more away from the voltage application point is maintained in the same order as the applied voltage. The electrostatic precipitator according to claim 1, wherein   The electrostatic precipitator according to claim 1, wherein the high voltage electrode and the ground electrode are stacked in pairs.

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