JP2019118897A - Electrostatic precipitator - Google Patents

Abstract

To provide an electrostatic precipitator efficiently collecting floating fine particles existing in air and suppressing performance deterioration due to the conduction deterioration of a discharge electrode and ozone generation.SOLUTION: In an electrostatic precipitator comprising a charge part 110 charging floating fine particles in air, a steam generating part 120 supplying steam to the charge part 110 and a dust collection part 130 being disposed at the downstream side of the charge part 110 in a ventilation direction and collecting the charged floating fine particles at the charge part 110, the supply rate of steam supplied from the steam generating part 120 to the charge part 110 is 0.20-0.50 mg/min per 1 cmof the cross sectional area of an air duct passing the electrode part of the charge part 110.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrostatic precipitator that collects suspended particles suspended in air.

The electrostatic precipitator is a device that is attached to an electrical product such as an air cleaner or an air conditioner, and purifies air by collecting contaminants such as suspended particles in the air.
In general, such an electrostatic precipitator is a two-stage type including a "charging portion" for charging floating particles by discharge and a "dust collecting portion" for collecting charged floating particles, and has a positive polarity. Alternatively, a high voltage of several kilovolts is applied to generate a corona discharge between the "discharge electrode" to which a high voltage of negative polarity is applied and the "counter electrode" grounded. The floating fine particles in the air introduced into the charging unit are charged to positive or negative polarity due to the occurrence of corona discharge, and are further transported along the flow of air and collected by the dust collection unit.
Although an axial flow fan is widely used for the “air flow generation unit” that generates an air flow for introducing floating particles into the electrostatic precipitator, the air flow itself is a swirling flow under the influence of a propeller fan, so floating There is a variation in the transfer speed of the particles. The floating fine particles having a high transfer speed not only make the collection in the dust collection part difficult but also the charge application in the charging part to be disadvantageous, so the collection efficiency decreases synergistically. In particular, when the amount of processed air per unit time (hereinafter simply referred to as "the amount of processed air") increases, the above tendency becomes remarkable, and the dust collection capacity of the electrostatic precipitator falls sharply. Problems occur.
To solve such a problem, an electricity collector comprising a charging unit provided with first and second charged cells capable of coping with the flow velocity difference of gas and a collecting unit constituted by a collecting electrode to which a high voltage is applied. A proposal regarding a dust device has been made (Patent Document 1).
Although the electrostatic precipitator equipped with such first and second charging cells in the charger can exhibit extremely excellent dust collection ability even when the amount of air treated is large, There is room for improvement in terms of downsizing of the electrostatic precipitator and suppression of ozone generation.
On the other hand, a proposal regarding an electrostatic precipitator equipped with a thin charger in which a sawtooth-shaped or needle-shaped electrode tip crosses the ventilation direction and the electrode tip portion is alternately arranged with other adjacent electrode tip portions (Patent Document 2).
The electrostatic precipitator equipped with such a thin charger can exhibit excellent dust collection performance while improving the miniaturization of the charging portion and the suppression of ozone generation. However, in the discharge electrode having a sawtooth shape or a needle shape, “electricity deterioration” proceeds such that the tip portion is worn down or a nonconductive layer made of oxide is generated depending on the amount of current or time of electric current. Therefore, since the state of corona discharge at the electrode tip portion arranged at a constant interval changes with time, as a result, there is a potential problem that the dust collecting ability of the electrostatic precipitator decreases and ozone generation amount increases. Had.

By the way, in connection with a blower using ion wind, a proposal regarding a discharge electrode in which the amount of generated ions is not easily affected by the consumption of the discharge electrode has been proposed, for example, rounding so that the curvature radius of the tip is equal to or more than the plate thickness. The proposal regarding the discharge electrode which has a protrusion is made | formed (patent document 3).
However, in the case of the same proposal, although the influence of the tip shape of the discharge electrode under the constant voltage condition (-5 kV) on the ion generation ratio has been studied, the reduction of the electrode performance due to the generation amount of ozone and current deterioration. Is not considered. In addition, there is room for consideration in improving the ion generation ratio.
On the other hand, a proposal has also been made to reduce the amount of ozone generation at the time of ion wind generation by a discharge electrode having a projection that is arc-shaped when viewed from the thickness direction (Patent Document 4).
In this case, when a high voltage of negative polarity is applied to the discharge electrode rounded in the thickness direction and discharged under constant current conditions (0.15 mA), the ozone generation amount with respect to the total discharge time is suppressed. . However, as shown in the example of the same proposal, the amount of ozone generation is significantly increased within 100 hours from the start of discharge. This tendency is more remarkable as the radius of curvature of the tip of the projection is smaller, and it is considered that the influence of the current deterioration is strongly suggested. As examined by the present inventors, the discharge electrodes having a plurality of projections often differ in the state of energization deterioration of the respective projections, and the ones that are functioning well and the ones that are not functioning are mixed. It turned out that it was. When such a discharge electrode is diverted to the charging portion of the electrostatic precipitator, the electrification of the suspended particles is uneven even if the amount of energization to the discharge electrode and the amount of ozone generation are stable with the passage of the total discharge time. Are likely to cause a decrease in collection efficiency.
That is, merely specifying the tip shape of the discharge electrode can not solve various problems such as suppression of current flow deterioration of the discharge electrode, stabilization of the amount of generated ions, and suppression of the amount of generated ozone at a high level.

By the way, there has been proposed an electronic air cleaning device provided with a comb-like discharge electrode and a counter electrode of platinum-immersed honeycomb-like ceramic (Patent Document 5).
In this case, although both size reduction and dust collection efficiency are realized by the comb-like electrode and the honeycomb-like counter electrode, the amount of air that can be treated is the ions generated between the comb-like electrode and the honeycomb-like counter electrode It depends on the wind. Therefore, in the case of treating a large amount of air, it is necessary to apply a high voltage between the electrodes, which causes the generation of ozone and the shortening of the life of the discharge electrode.

On the other hand, in order to miniaturize / simplify the collection portion of the electrostatic precipitator, various proposals have been made regarding a gas filter for collecting suspended particles instead of the collection electrode to which a high voltage is applied. ing.
For example, in order to collect suspended particulates, dedicated filters such as HEPA filter and ULPA filter are used. Although these filters are effective in removing suspended particulates, their pressure loss is very high, and they are used as blowers. Etc. will inevitably become large.
On the other hand, it is known to subject an air filter to an electretization treatment for the purpose of adsorbing and removing suspended particles in an air flow by static electricity. For example, electret filters comprising split fibers having a specific fiber width and a film thickness have been proposed (Patent Document 6).
Further, there has been proposed an electret filter obtained by continuously bending or folding an electretized polymer film and laminating the same so as to form a large number of continuous voids (Patent Document 7).
While these gas filters can suppress pressure loss very low, the trapping ability of “inertial collision” and “shuttering effect” is reduced, so trapping of suspended particles is mainly performed by “diffusion” and “ "Electrostatic adsorption" is done. Therefore, although it is possible to process a large amount of air with a small fan as compared with the HEPA filter or the ULPA filter, the collection efficiency is significantly inferior. In particular, when the passing speed of the floating particles is high or the charging state is weak, the collection efficiency of the floating particles becomes extremely low. As described above, in order to improve the performance of the gas filter, it is necessary to simultaneously achieve low pressure loss and high collection efficiency.

JP, 2011-92932, A JP, 2017-13041, A JP, 2000-277235, A JP, 2010-151116, A Japanese Patent Application Laid-Open No. 63-59963 JP-A-6-254320 Japanese Patent Application Laid-Open No. 56-10312

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small-sized electrostatic precipitator excellent in the balance between the collection efficiency of suspended fine particles present in the air and the amount of processed air. .
Furthermore, this invention makes it a subject to provide the electrostatic precipitator by which the performance fall by energization degradation of a discharge electrode and ozone generation were suppressed.

The inventors of the present invention have found that the current flow deterioration of the discharge electrode of the charging portion not only accelerates the generation of ozone but also affects the collection efficiency of the floating fine particles, and in particular, the flat counter electrode In the electrostatic precipitator provided with the arranged charging portion, it was found that the tendency becomes apparent. That is, since the ventilation portion of the charging portion is divided by the counter electrode, even if a portion of the discharge electrode is deteriorated due to discharge, the floating fine particles pass without being charged and the collection efficiency is lowered. It was
The electrostatic precipitator of the present invention is made based on such knowledge, and has the following configuration.
That is, according to the present invention, at least a "charging unit" for charging suspended particles in the air, a "steam generating unit" for supplying water vapor to the charging unit, and a downstream side of the charging unit in the ventilation direction. An electrostatic precipitator comprising a "dust collecting portion" for collecting the floating fine particles charged in the charging portion, wherein a supply speed of the water vapor supplied from the water vapor generating portion to the charging portion corresponds to that of the charging portion. It is characterized in that it is 0.20 to 0.50 mg / min per 1 cm ² of the cross sectional area of the air passage passing through the electrode part.
A water vapor generation unit is provided on the upstream side of the charging unit in the ventilation direction, and water vapor is evaporated in the air flow to supply water vapor to the charging unit at a specific speed, and significantly reduce the amount of ozone generated from the charging unit. Thus, it is possible to suppress the current flow deterioration of the discharge electrode.

Further, in the electrostatic precipitator according to the present invention, the charging unit includes at least a "discharge electrode" to which a high voltage is applied by a high voltage power supply, and a flat plate-like "counter electrode" grounded. Is provided with a plurality of "protruding portions" for discharging at intervals P (mm) (hereinafter simply referred to as "protrusion intervals P"), and the counter electrodes are spaced at intervals G (mm) on both side surfaces of the discharge electrodes. ) (Hereinafter, referred to as “electrode spacing G”) are disposed in parallel, and the projection spacing P and the electrode spacing G satisfy the relationship of 0.5 ≦ P / G ≦ 1.5. preferable.
By using the shapes of the discharge electrode and the counter electrode, it is possible to partition the opening of the charging portion and to identify the relationship between the electrode spacing G and the projection spacing P, thereby enabling suspended particles in the air passing through the charging portion. Charging can be performed uniformly and efficiently. Further, the water vapor supplied to the charging unit also works efficiently.

By the way, the electrostatic precipitator according to the present invention is characterized in that the dust collection unit includes an air filter medium made of a sheet-like or film-like polymer material subjected to electret treatment, and the contact angle of the polymer material with water. The thickness of the air filter medium is preferably 3 mm or more, and the pressure loss at a wind speed of 0.2 m / sec is preferably 60 Pa or less.
By this, the influence of the water vapor supplied from the water vapor generating portion can be minimized, so that the current-carrying deterioration of the discharge electrode can be suppressed without reducing the dust collection efficiency. Moreover, it can contribute also to the cost reduction by thickness reduction and simplification of a collection part.

Furthermore, in the electrostatic precipitator according to the present invention, the air filter medium at least includes a tubular air passage formed by laminating polymer sheets (hereinafter simply referred to as “a structure comprising a tubular air passage”) 60% or more of the opening portion of the tubular air passage occupied in the plane orthogonal to the air flow direction of the air filter medium, and the opening diameter d (mm) of the tubular air passage and the air passage length L It is preferable that (mm) satisfy the relationship of 0.025 ≦ d / L ≦ 0.2.
By making the air filter medium into a structure comprising a tubular air passage, it is possible to achieve both the air throughput and the collection efficiency of suspended particles at a high level. In addition, since condensation of the water vapor supplied from the water vapor generating portion can be prevented, it is possible to suppress the decrease in the effect of the electret treatment of the polymer sheet constituting the tubular air passage. Moreover, it can contribute also to size reduction of a collection part and an airflow generation part.

In addition to the above, in the electric dust collector of the present invention, a non-woven fabric containing 50 mass% or more of film split fibers obtained by processing a polymer film into splits as the air filter medium (hereinafter simply referred to as “film split non-woven fabric It is preferable that the fiber width w (mm) of the film split fiber and the fiber thickness k (mm) satisfy the relationship of 2 ≦ w / k ≦ 5.
By making the air filter medium a non-woven fabric, it is possible to suppress the decrease in the effect of electret treatment in the water vapor atmosphere supplied from the water vapor generation part while suppressing an increase in pressure loss due to the water vapor supplied from the water vapor generation part. Not only can floating particulates be collected efficiently, but it can also contribute to thinning of the collection portion.

  According to the present invention, it is possible to provide a small-sized electrostatic precipitator excellent in the balance between the collection efficiency of the floating fine particles present in the air and the amount of processed air. Furthermore, it is possible to provide an electrostatic precipitator in which performance deterioration due to current flow deterioration of the discharge electrode of the charging portion and generation of ozone are suppressed from the start of use.

Schematic sectional drawing which shows the structure of the electrostatic precipitator which concerns on embodiment of this invention A perspective view (a) and an exploded perspective view (b) of the main part of the charging unit of the electrostatic precipitator External appearance explanatory drawing of the discharge electrode arrange | positioned at a charging part Partially enlarged front view of the electrode (a) and the state of corona discharge of the discharge electrode (b) in order to explain the influence of collection deterioration of the discharge electrode on collection efficiency External appearance explanatory drawing and sectional view of honeycomb structure (a) and corrugated structure (b) used as a structure having a tubular air passage. Conceptual diagram for explaining the structure (direction of split fiber) of the film split nonwoven fabric Table that summarizes the setting conditions and test results of each example and comparative example

  Hereinafter, embodiments of the present invention will be exemplarily described. However, the dimensions, materials, shapes and relative positions of components described in this embodiment should be suitably changed according to the configuration of the apparatus to which the present invention is applied and various conditions. The scope of the present invention is not intended to be limited to the embodiments described below. In the description of the drawings, the same or equivalent elements will be denoted by the same reference symbols, without redundant description.

  Fig.1 (a) is sectional drawing which shows an example of schematic structure of the main part 100 of the electrostatic precipitator based on embodiment of this invention. The direction of air flow is the direction of the arrow (shown), and the main portion 100 focuses on the water vapor generating portion 120 for supplying water vapor to the charging portion 110 around the charging portion 110 that charges suspended particles in air. On the upstream side, a dust collection unit 130 for collecting floating fine particles charged by the charging unit 110 is disposed on the downstream side in the ventilation direction. The main portion 100 is installed in the air flow inside the duct or is used by being connected via the duct, and after charged by the charging unit 110, floating particulates moved from the intake direction are collected by the dust collection unit 130 . Further, the main portion 100 can be used not only by being installed in the air flow, but also by connecting the air flow generation unit 140 as necessary to increase or decrease the air introduction amount to the main portion 100. For example, when the main part 100 is installed inside a home appliance or an office machine, it is possible to remove suspended particles in the air discharged to the outside of the machine as an electric dust collection unit. In addition, when an axial-flow fan equipped with a propeller fan is connected as the air flow generation unit 140 to the main portion 100, a self-supporting indoor electrostatic precipitator can be obtained (see FIG. 1 (b)).

FIG. 2 is a perspective view (a) and an exploded perspective view (b) of the main part of the charging unit 110. The charging unit 110 includes at least a discharge electrode 111 to which a high voltage is applied by a high voltage power supply (not shown) and a flat counter electrode 112 grounded, and the counter electrode 112 is disposed on both sides of the discharge electrode 111. The electrodes are arranged in parallel with a gap G (mm) maintained on the surface and installed in the electrode case 113.
The opening of the charging unit 110 is divided by a flat counter electrode 112 into a length (G × 2) twice as long as the electrode gap G. As a result, it is possible to uniformly charge the suspended particles in the air flow. The electrode gap G is preferably set in the range of 2 to 15 mm. When the electrode gap G is less than 2 mm, the influence of the thickness of the discharge electrode 111 or the counter electrode 112 can not be ignored, and it becomes difficult to secure the opening of the charging portion 110 sufficiently. Further, when it exceeds 15 mm, not only the effect of dividing the opening of the charging portion 110 by the flat counter electrode 112 disappears, but it becomes necessary to apply an unnecessarily high voltage, and the influence of the current deterioration of the electrode Becomes noticeable. By adjusting the number of counter electrodes 112 in order to set the electrode gap G within the above range, the opening of the charging unit 110 can be appropriately divided, which can contribute to the charging of the floating particles.

  The discharge electrode is provided with a plurality of "protrusion portions" for discharge at an interval P (mm), and the projection interval P and the electrode interval G (mm) are 0.5 ≦ P / G ≦ 1.5. It is preferable to set so as to satisfy the relationship. When the P / G value is less than 0.5, the control range of the inter-electrode electrification amount for maintaining the collection state of the floating particulates favorably becomes narrow. If it exceeds 1.5, it will be difficult to uniformly charge the floating fine particles, causing a decrease in collection efficiency and the like.

For example, one having a saw-tooth shape or a needle shape is used as the projection portion. FIG. 3 is an explanatory view of the appearance of the discharge electrode 111 having a sawtooth-shaped protrusion, and the discharge electrode 111 is a flat plate-shaped “base portion”, and the sawtooth-shaped protrusion of height h is spaced by P Have.
A predetermined voltage is applied to the base portion of the discharge electrode 111 from a high voltage power supply (not shown), and a corona is formed at the tip of the projection (hereinafter referred to as "electrode tip") to form suspended particles in the air flow. Charge is applied to it. The degree of electrification to the floating fine particles can be controlled by the amount of electric conduction between the discharge electrode and the counter electrode (hereinafter simply referred to as "the amount of electric conduction between the electrodes").

  When charged particles are given to airborne particulates in the air flow, the electrode tip is worn away while being rounded, and oxidation of constituent materials of the electrode tip and resistance increase by adhesion of chemical substances mixed in the air flow Progress. When such “current degradation” progresses, a larger applied voltage is required to maintain the initial corona formation. The shape of the tip of the electrode greatly contributes to the amount of ozone generation, and for example, in the case of a sawtooth discharge electrode, the tip radius of curvature R of the tip of the electrode exceeds half the thickness of the electrode plate And ozone generation amount doubled. Therefore, the shape of the tip of the electrode is taken into consideration so that the radius of curvature of the tip R of the electrode does not exceed half the thickness of the electrode plate even if the current deterioration progresses, Design.

The degree of energization deterioration of the discharge electrode is often influenced by the tip of the electrode because it is influenced by the amount of electricity supplied between the electrodes, the time of energization, the amount of impurities in the constituent material of the electrode, processing conditions, adhesion frequency of chemical substances, etc. .
Since the discharge electrode provided with the above-mentioned projection part is provided with a plurality of projection parts via the base part on a flat plate, when the projection part to which current degradation has progressed compared with the surroundings is generated, The amount of electrification decreases, and a section where corona formation is unstable partially occurs (see (a) and (b) in FIG. 4). Since the opening of the charging portion is divided by the flat counter electrode, the floating fine particles passing through the section where the protrusion portion where the current deterioration has progressed are not sufficiently charged, and as a result, dust collection is performed. It causes a decrease in efficiency. However, in the present invention, since the water vapor is supplied from the water vapor generation unit 120 to the charging unit 110, not only the generation of ozone is suppressed, but also the progress of the current deterioration is suppressed to prevent the reduction of the dust collection efficiency. Can do.

  The electrostatic precipitator according to the present embodiment includes the water vapor generation unit 120 that supplies water vapor to the charging unit 110, and supplies the water vapor to the charging unit 110, thereby significantly suppressing the amount of ozone generated from the charging unit 110. At the same time, the current supply deterioration of the discharge electrode 111 can be suppressed. In particular, when a high voltage of positive polarity is applied to the discharge electrode 111, the generation amount of ozone can be extremely reduced.

As the humidifying device 121 that can be applied to the water vapor generation unit 120, for example, a small-sized humidifier such as a steam type, an ultrasonic type, a vaporization type (heaterless type), or a hybrid type can be applied. On the other hand, when installed inside a home appliance or an office machine, it is also possible to use the water vapor source existing in those devices. For example, when installed in a printer using an electrophotographic method, the water contained in the printing paper is evaporated using the heating fixing device in the printer, and water vapor is supplied to the charging unit. As a result, not only the water vapor generation source dedicated to the electrostatic precipitator becomes unnecessary, but also the water supply becomes unnecessary, which can contribute to downsizing of the entire apparatus and improvement of usability.
The supply rate of water vapor supplied from the water vapor generation unit 120 to the charging unit 110 is 0.20 to 0.50 mg / minute per 1 cm ² of the cross-sectional area of the air passage passing through the electrode portion of the charging unit 110. Is preferred. If the supply rate of water vapor is less than 0.20 mg, the effect of supplying water vapor is not sufficient, and if it exceeds 0.50 mg / min, it may be caused by excessive moisture in dust collection unit 130 (such as clogging due to dew condensation). This leads to a decrease in collection efficiency.
In the present invention, the supply rate of water vapor is a cut off of the air passage passing through the electrode portion of the charging unit, a value obtained by dividing the amount of transpiration of water introduced into the humidifier by the operation time of the humidifier. It is defined by the value divided by the area.

  Most of the water vapor supplied to the charging unit 110 reaches the dust collection unit 130 with the air flow, but the dust collection unit 130 is an air filter medium made of a sheet-like or film-like polymer material subjected to electret processing. Therefore, it is possible to minimize the influence of water vapor and to prevent a drop in the collection efficiency and the amount of air treated. In particular, the contact angle of the polymer material subjected to the electret treatment to water is 75 ° or more, the thickness of the air filter medium is 3 mm or more, and the pressure loss at a wind speed of 0.2 m / sec is 60 Pa or less A processed air filter medium is preferably used.

In the electret treatment, a polymer is made to have a structure in which charge is held by applying a high voltage to a polymer material or an intermediate of a polymer material while heating and solidifying the polymer material. It is possible to make the material semi-permanently charged.
Even if the polymer sheet or the polymer film subjected to the electret treatment is humidified by the steam transpiration from the steam generation unit 120, the polymer sheet or the polymer film is restored to the charged state only by drying under an air stream. In addition, when immersed in a sparingly soluble organic solvent such as isopropyl alcohol, it is possible to change only the structure for maintaining the charge built up in the polymer material, and to invalidate the electret treatment. Can do.
The charged state of the polymer sheet or polymer film subjected to the electret treatment may be confirmed, for example, by a static electricity measuring instrument (FMX-004) manufactured by SIMCO, a Kelvin probe force microscope (Dimension Edge) manufactured by BRUKER, etc. It is possible.

Examples of materials suitable for electret treatment include thermoplastic resins (such as acrylic resins, polyethylene resins, and ABS resins) which are difficult to pass electricity, and thermosetting resins (such as polyester resins and epoxy resins). However, since the dust collection unit 130 is affected by the water vapor supplied to the charging unit 110, as the polymer material used for the air filter medium, the affinity for water is not reduced because the effect of the electret treatment is not diminished. The low one is preferable, and specifically, it is selected from polymeric materials having a contact angle to water of 75 ° or more. In particular, a polymeric material having a contact angle to water of 80 ° or more is preferable because even if water particles adhere to the surface of the polymeric material, they can be rapidly dried by aeration and can be returned to the original state. Examples of such polymer materials include polypropylene, polyethylene, polyvinylidene fluoride, fluorinated resin, silicone resin and the like, and these can be used alone or in combination. Further, in order to increase the amount of charge retention, it is preferable to provide pores in the polymer material or to contain a charge control agent. Examples of the charge control agent include metal compounds of carboxylic acids such as salicylic acid, naphthoic acid and dicarboxylic acid; polymer type compounds having a sulfonic acid group or a carboxylic acid group in a side chain; boron compounds; urea compounds; silicon compounds; Negatively chargeable charge control agents such as calixarene, quaternary ammonium salts; polymer type compounds having the quaternary ammonium salts in the side chain; guanidine compounds; positively chargeable charge control agents such as imidazole compounds azine compounds etc. You can choose.
What the polymer material which gave the said electret process was processed into a polymer sheet, a polymer film, etc. is applied to an air filter filter medium. At this time, by adjusting the thickness of the air filter to be 3 mm or more and the pressure loss at a wind speed of 0.2 m / sec to be 60 Pa or less, both electrostatic collection and moisture permeability using electret processing can be achieved. I can do it. If the thickness of the air filter medium is less than 3 mm, sufficient collection efficiency can not be obtained, and if the pressure loss exceeds 60 Pa, problems such as condensation of water vapor and reduction in the volume of treated air may occur. is there.

When using the polymer sheet which gave the electret process as an air filter material, it is preferable to laminate | stack a polymer sheet, for example, and process and use it as a structure which has a tubular ventilation path.
As a structure composed of a tubular air passage suitable for the present invention, for example, a honeycomb structure or a corrugated structure as shown in FIG. 5 can be applied. By using a structure having a tubular air passage in the dust collection unit 130, the air flow in the electrostatic precipitator is uniformly distributed and rectified by the structure having the tubular air passage, and therefore, floating in the charging unit 110 The charging of the fine particles is more preferable. As a result, even if the discharge electrode is current-deteriorated, the influence on the collection efficiency of the floating particulates can be minimized. In addition, since a polymer sheet subjected to electret treatment is used, it has a very simple configuration and is in the air stream compared to a two-stage electrostatic collection device that applies a high voltage to both the charging unit and the collection unit. It is possible to electrostatically collect suspended particles of
The structure having the above-mentioned tubular air passage can be manufactured by a known method. For example, in the case of manufacturing a honeycomb structure, an adhesive is linearly formed on both sides of the electret-treated polymer sheet. It is made into a block shape by applying and laminating on. A honeycomb structure can be obtained by cutting the block-like polymer sheet in a direction orthogonal to the application direction of the adhesive and stretching it in the vertical direction. At this time, an arbitrary opening diameter d can be obtained by changing the application width and application interval of the adhesive applied linearly, and the degree of expansion. On the other hand, when manufacturing a corrugated structure, it is possible to manufacture using a corrugator, and while forming the electret-treated polymer sheet in a corrugate shape, the electret treatment in which the top is separately prepared It is bonded to the applied polymer sheet to make a single-sided cardboard. The corrugated structure can be manufactured by cutting the single-faced cardboard after laminating and bonding. At this time, when forming the polymer sheet into a corrugated shape, an arbitrary opening diameter d can be obtained by adjusting the shape and molding conditions. In any case, welding may be performed instead of the adhesive for bonding of the polymer sheet. It is also possible to perform electret treatment immediately before bonding.

In the structure comprising the tubular air passage, the opening portion of the tubular air passage occupied in the plane orthogonal to the air flow direction of the air filter medium is 60 area% or more, and the opening diameter d (mm) of the tubular air passage and the air passage length It is preferable that L (mm) satisfy the relationship of 0.025 ≦ d / L ≦ 0.2 (see FIG. 5), thereby making the air throughput and the collection efficiency of suspended particles compatible at a high level Can do. Further, the opening diameter d of the structure having the tubular air passage is preferably 0.5 to 5 mm. When the opening diameter d is less than 0.5 mm, the pressure loss is large, and it becomes difficult to increase the air throughput. In addition, when the opening diameter d exceeds 5 mm, the opportunity for floating particles in the air to approach the polymer sheet forming the tubular air passage decreases, so the collection efficiency decreases.
The length L of the air passage of the structure having the tubular air passage is preferably 3 mm or more, more preferably 5 to 50 mm, in order to maintain stable collection efficiency, and the length L Is less than 5 mm, the life of the dust collection unit 130 is shortened, and the replacement frequency is increased. Moreover, when the length L exceeds 50 mm, the water vapor supplied by the humidifying device 121 is cooled, and there is a possibility that dew condensation occurs.
The length L of the air passage of the structure having the tubular air passage is set to satisfy the relationship of L> d with respect to the opening diameter d. When L ≦ d, it is difficult for suspended particulates in the air to diffuse into the tubular air passage and to be electrostatically adsorbed, so that sufficient collection efficiency can not be obtained.

It is preferable that the polymer sheet thickness t (mm) which comprises the ventilation path of the structure which has the said tubular ventilation path is 0.1-1.5 mm. When the polymer sheet thickness t is less than 0.1 mm, the strength for forming the tubular air passage is lacking, and it becomes difficult to apply the electret treatment. Also, if it exceeds 1.5 mm, the ratio of the opening of the tubular air passage to the wind receiving surface becomes small, so that the collecting ability is lowered.
In the present invention, the thickness t of the polymer sheet and the opening diameter d constituting the structure having the tubular air passage can be determined by taking an enlarged photograph of the vertical cross section of the tubular air passage (see FIG. 5). Specifically, a magnified picture of the vertical cross section of the tubular air duct is taken into a personal computer etc. and measured using image measurement software, or a method of measuring directly after printing out the magnified picture using a measuring instrument, etc. Thus, the sheet thickness t and the opening diameter d can be determined by respectively averaging the thickness and the opening diameter of 20 or more places randomly extracted. In the present invention, the opening diameter d of the tubular air passage is defined by the diameter of a circle inscribed in the inner wall of the tubular air passage.

  The opening diameter d is preferably selected and combined so as to satisfy d / G = 0.05 to 1 with respect to the distance G between the discharge electrode 111 and the flat counter electrode 112. When d / G is less than 0.05, the charging ability to the floating fine particles is insufficient, and the collecting ability is reduced. In addition, when d / G exceeds 1, the number of tubular ventilation paths with respect to the space partitioned by the flat counter electrode decreases, and therefore, the influence of energization deterioration of the discharge electrode 111 tends to occur.

When a structure having the above-mentioned tubular air passage is applied to the dust collecting portion 130 of the electrostatic precipitator of this embodiment, the length L of the air passage of the structure having the above-mentioned tubular air passage is the above-mentioned tubular air passage. Sufficient air throughput by setting to satisfy the relationship of L / (V × 1,000) ≧ 0.005 with respect to the ventilation velocity V (m / sec) of air introduced into the structure It is possible to secure For example, when the area of the wind receiving surface of the dust collection unit 130 is 100 cm ² , it is possible to process air of about 750 liters to 1 square meter per minute.
The air flow velocity V (m / sec) of air introduced into the structure having a tubular air passage is determined by the surface air velocity of the wind receiving surface, and, for example, a portable anemometer (Crimomaster model 6501-00, probe 6543-21 (manufactured by Nippon Kanomax Co., Ltd.) or the like.

  On the other hand, when using the polymer film which gave the electret process as an air filter material, after using a polymer film as a split fiber, for example, it is preferable to process and use it as a film split nonwoven fabric. By making the air filter medium a non-woven fabric, it is possible not only to capture the floating particles efficiently while suppressing the increase in pressure loss due to water vapor supplied from the water vapor generation part, but also to make the dust collection part thinner. You can contribute.

As a film split nonwoven fabric suitable for the present invention, for example, as shown in FIG. 6 (a), a web in which a part of the film split fibers is disposed in a direction in which the passage of introduced air is not easily impeded I can do it. By using such a film split nonwoven fabric for the dust collection unit 130, the influence of the water vapor supplied from the water vapor generation unit 120 can be minimized.
Generally, a film split fiber is produced by finely cutting a polymer film as a raw material with an opening cutter or the like so that the film width (hereinafter referred to as "fiber width w") is the film thickness (hereinafter referred to as "film width") And “fiber thickness k”). When the polymer film is subjected to electret treatment, the film surface of the fiber tends to be arranged parallel to the surface of the non-woven fabric by laminating such film split fibers to form a web since polarization occurs on the front and back of the film surface. , The passage of air is likely to be impeded (see FIG. 6 (b)). Furthermore, since the adjacent polarized surfaces tend to cancel each other's electrostatic force, the water vapor supplied from the water vapor generation unit 120 may cause the effect of the electret processing to be reduced, or in the worst case, condensation may occur. There is.
However, the film split non-woven film split non-woven fabric used for the air filter medium of the present invention can avoid the above problems by specifying the composition ratio and the cross-sectional shape of the film split fibers constituting the film split non-woven fabric is there.
The film split nonwoven preferably contains at least 50% by weight, more preferably 50 to 90% by weight, of film split fibers obtained by processing a polymer film into splits, and the composition ratio of the film split fibers If the content of the polymer is less than 50% by weight, sufficient collection efficiency can not be obtained because the amount of electret-treated polymer film decreases. Moreover, in addition to the problem of air permeability, when it exceeds 90 weight%, possibility that a malfunction may arise in the intensity | strength maintenance as an air filter medium, etc. increases.
In addition, the film split fiber can collect floating particles efficiently, while suppressing an increase in pressure loss due to water vapor supplied from the water vapor generation part by presenting a specific flat or rectangular shape, and a film It is preferable that the fiber width w (μm) of the split fiber and the fiber thickness k (μm) satisfy the relationship 2 ≦ w / k ≦ 5. When w / k is less than 2, the influence of the treated surface by the opening cutter becomes large, and the dust collection efficiency tends to be reduced. Moreover, when w / k exceeds 5, a pressure loss will become large and ensuring of air permeability will become difficult.
The cross-sectional shape of the film split fiber is preferably flat or rectangular, and the major axis of the film split fiber (hereinafter, referred to as "fiber width") is the minor axis of the polymer film (hereinafter, "film thickness") It is preferable that the composition ratio of the film split fiber occupied in the whole constituent fiber of a film split nonwoven fabric is 50 to 90%. When the fiber width is less than twice the film thickness, the influence of the treated surface by the opening cutter becomes large, and the dust collection efficiency tends to be reduced. Moreover, when it exceeds 5 times, a pressure loss will become large and it will become difficult to ensure air permeability.
In order to reduce pressure loss, it is preferable to use a film split non-woven fabric in combination with a polymer fiber to be an aggregate or a spacer within a range where the composition ratio of the film split fiber satisfies 50 to 90%. You can do it. When the composition ratio of the film split fiber is less than 50%, the amount of the electret-treated polymer film is small, so that sufficient collection efficiency can not be obtained. Moreover, when it exceeds 90%, it will become inconvenient in the intensity | strength maintenance as an air filter medium, etc.
The film split fiber preferably has a fiber thickness k of 3 to 15 μm. In particular, the film thickness of the film split fiber is preferably 3 to 15 μm by mixing one or more types of polymer fibers selected from nylon, rayon, and acetate in a range not exceeding 10% by weight. Furthermore, by mixing one or more types of polymer fibers selected from nylon, rayon and acetate into the film split fiber, it can be used for holding the electret while playing the role of aggregate and spacer. In particular, the non-woven fabric is preferably made of a plurality of polymer fibers different in charge series, and it is possible to compensate for the loss of the electret effect by rubbing at the time of aeration.

By the way, the main part 100 of the electrostatic precipitator of this embodiment is not only installed and used as it is in the air flow, but also the air flow generation unit 140 is connected as needed to introduce the amount of air introduced into the main part 100 It can also be used by increasing or decreasing (see (b) in FIG. 1). For example, when the main part 100 is installed inside a home appliance or an office machine, it is possible to remove suspended particles in the air discharged to the outside of the machine as an electric dust collection unit. In addition, when an axial-flow fan equipped with a propeller fan is connected as the air flow generation unit 140 to the main portion 100, a self-standing indoor electrostatic precipitator can be obtained.
The ventilation direction at this time is the direction of the arrow in the figure, and air containing floating particulates is introduced into the main portion 100 by sucking the air by the air flow generation unit 140, collected after dust collection, and then exhausted. Unlike the swirling flow generated on the discharge side of the blower, the air flow generated on the suction side of the blower is relatively uniform, and therefore, it is possible to preferably remove suspended particles in the air flow. As a result, the swirling flow caused by the propeller fan is made uniform, so that the suspended particles in the air flow passing through the charging unit 110 can be uniformly ionized.
As a blower applied to the airflow generation unit 140, for example, an axial-flow blower equipped with a propeller fan, a centrifugal blower equipped with a multi-blade fan or a turbofan, a mixed-flow blower equipped with a mixed-flow fan, a crossflow fan It is possible to adapt cross flow fans etc. The ventilation direction at this time is the direction of the arrow in the figure, and air containing suspended particles can be sucked by a blower and introduced into the main portion 100.

  Hereinafter, the present invention will be described in detail by examples (and comparative examples), but the present invention is not limited to these examples.

Example 1
Using the self-standing electrostatic precipitator shown in FIG. 1 (b), the collection efficiency of suspended particulates in the air and the rate of ozone emission were evaluated.
In the charging unit 110, flat counter electrodes were disposed in parallel on both sides of the sawtooth discharge electrode. The size of the opening of the charging portion 110 is 80 mm long and 80 mm wide, and the distance G between the discharge electrode and the counter electrode is 5.0 mm, and the opening is 11 counter electrodes (and 10 discharge electrodes). It divided by). The discharge electrode is formed by etching a flat plate (SUS 304) with a thickness of 0.3 mm, and the distance P between the sawtooth-like protrusions is 5.0 mm (P / G = 1.0), and the tip of the electrode tip is The curvature radius R was 50 μm.
For the dust collection unit 130, a corrugated structure obtained by laminating a polypropylene sheet (sheet thickness t = 0.1 mm, contact angle 94 °) subjected to electret processing was used. The opening diameter d of the tubular air passage in the corrugated structure is 0.9 mm, and the air passage length L (filter medium thickness) is 20 mm (d / L = 0.045, opening ratio = 70%, pressure loss = 3 Pa), The area of the air receiving surface was 64 cm ² (the same as the opening of the charging unit 110).
A DC axial flow fan (80 mm × 80 mm × 15 mm) equipped with a propeller fan is used as the air flow generation unit 140 so that the passing wind speed of air introduced into a structure having a tubular air passage is 0.5 m / sec. It was set (L / (V × 1,000) = 0.04). The air throughput at this time was 192 L / min.
When the electrostatic precipitator was in operation, a voltage of positive polarity was applied to the discharge electrode, and the inter-electrode conduction amount was set to 90 μA. In addition, a small-sized ultrasonic humidifier is used for the water vapor generation unit 120, and a supply speed of water vapor supplied from the water vapor generation unit 120 to the charging unit 110 is a cross-sectional area of an air passage through which an electrode portion of the charging unit 110 passes. The adjustment was made to 0.35 mg / min per 1 cm ² (same as the opening).

As a result of evaluating the collection efficiency of suspended particles in air and the emission rate of ozone, the collection efficiency of suspended particles in air is 99% by number, and the emission rate of ozone is less than 1.0 mg / hour. It showed good results.
Furthermore, in order to conduct the influence test of the current flow deterioration of the discharge electrode, the current flow deterioration of the discharge electrode was accelerated by the current flow between the electrodes of 180 μA.
After the discharge electrode was subjected to current flow degradation, the collection efficiency of suspended particles in air and the rate of ozone release were evaluated in the same manner as described above. The collection efficiency of suspended particles in air was 98% by number, and ozone was released The rate was 1.0 mg / hr and remained very good.

  The details of the above results are summarized in the table of FIG. In addition, the measuring method of the collection efficiency of the floating fine particles in the air and the emission rate of ozone, the evaluation standard of a measurement result, and the method of the influence test of the electricity deterioration of a discharge electrode are as follows.

[1. Evaluation of collection efficiency of suspended particles]
The collection efficiency of suspended particulates in the air collected by the electrostatic precipitator is determined by the number concentration of atmospheric dust in the air taken into the electrostatic precipitator and the air in the air exhausted from the electrostatic precipitator. The number concentration of dust was measured for 3 minutes each, and the reduction rate of atmospheric dust was calculated. The collection efficiency of the floating particles thus calculated was evaluated according to the following criteria. A small UFP measuring device (NANOSCAN SMPS NANOPARTICLE SIZER Model 3910, manufactured by TSI Corporation) was used to measure the number concentration of atmospheric dust in the air.
A; 98 number% or more (very good)
B: 95 or more and 98 or less% (good)
C: 80 number% or more and less than 95 number% (this is an acceptable level in the present invention)
D: less than 80% by number (not acceptable in the present invention)

[2. Evaluation of Ozone Emission Rate]
The amount of ozone discharged to the outside of the electrostatic precipitator was calculated by measuring the change in the concentration of ozone generated by the electrostatic precipitator installed in the clean booth during operation to calculate the emission rate. The calculated ozone emission rate was evaluated according to the following criteria. In addition, the ultraviolet absorption type ozone concentration system for low concentration (Model 1100, product made by DYREC Co., Ltd.) was used for the density | concentration measurement of the ozone diffused at the time of operation | use.
A; less than 1.0 mg / hour (very good)
B: 1.0 mg / hour or more and 2.0 mg / hour or less (good)
C: 2.0 mg / hour or more and less than 3.0 mg / hour (this is an acceptable level in the present invention)
D: 3.0 mg / hour or more (this is an unacceptable level in the present invention)

[3. Influence test of current deterioration of discharge electrode]
After conducting electricity for a total of 700 hours with an inter-electrode conduction amount of 1.5 times that in normal use and accelerating the current-carrying deterioration of the discharge electrode, again, the above-mentioned [1. Evaluation of collection efficiency of suspended particles] and [2. Evaluation and Evaluation of Ozone Emission Rate] were carried out.

Example 2
The discharge electrode of the charging unit 110 was replaced, and the curvature radius of the tip of the electrode was changed to 75 μm. In addition, a polypropylene film (film thickness (fiber thickness k) = 10 μm, contact angle 94 °) subjected to electret processing as an air filter material of the dust collection portion 130 is a film split fiber (fiber width w = 43 μm, w / k After setting it as = 4.3, a film split nonwoven fabric (filter material thickness = 3.0 mm, composition ratio of film split fibers = 70 mass%, pressure loss = 20 Pa) was used. Since the thickness of the filter material of the air filter material used in the dust collection unit 130 is thinner than that of the first embodiment, the setting is the same as that of the first embodiment except that readjustment is performed so that the interelectrode current flow amount becomes 120 μA. Then, we conducted a radiation test.
As a result, although the inter-electrode electrification amount is increased, since the water vapor is supplied to the charging unit 110, the amount of floating fine particles can be significantly reduced without increasing the amount of ozone being emitted. In addition, when the influence test of the deterioration of the discharge electrode was conducted, the curvature radius of the tip of the electrode was increased compared to Example 1, so that the floating particles can be stably captured even if the amount of current flowing between the electrodes is increased. It could be collected, but a slight increase in ozone emissions was observed.

Example 3
The discharge electrode of the charging unit 110 was replaced, and the interval P of the sawtooth-shaped projection was changed to 3.5 mm (P / G = 0.7). In addition, a polyethylene film (film thickness (fiber thickness k) = 15 μm, contact angle 101 °) subjected to electret processing as an air filter material of the dust collection portion 130 is a film split fiber (fiber width w = 35 μm, w / k After setting it as = 2.3, one processed into a film split nonwoven fabric (filter medium thickness = 3.0 mm, composition ratio of film split fiber = 53 mass%, pressure loss = 15 Pa) was used. Further, the radiation test was conducted after setting in the same manner as in Example 2 except that the supply rate of the water vapor supplied to the charging unit 110 was readjusted to 0.22 mg / min.
As a result, as compared with Example 2, the amount of ozone released increased as the supply rate of the water vapor supplied to the charging unit 110 became slower. In addition, when the influence test of current flow deterioration of the discharge electrode was carried out, the collection efficiency of suspended particulates decreased and the amount of released ozone further increased, but the interval P of the protruding portion of the charging portion 110 was adjusted to 3.0 mm. As a result, it was possible to achieve both the collection efficiency of suspended particulates and the amount of released ozone at an acceptable level.

Example 4
A film made of polyethylene terephthalate (film thickness (fiber thickness k) = 12 μm, contact angle = 79 °) subjected to electret processing as an air filter material for the dust collection portion 130 is a film split fiber (fiber width w = 60 μm, w / k After setting it as = 5.0), the film split non-woven fabric (filter material thickness = 4.0 mm, composition ratio of film split fiber = 80 mass%, pressure loss = 55 Pa) was used, except that it was used. The radiation test was conducted after setting in the same manner.
As a result, as compared with Example 3, the affinity for water of the air filter medium increased, and the collection efficiency of suspended particulates slightly decreased. However, it was possible to achieve both the collection efficiency of the floating fine particles and the amount of released ozone at an acceptable level, including the results of the influence test of the current-carrying deterioration of the discharge electrode.

Example 5
The discharge electrode of the charging unit 110 was replaced, and the spacing P of the sawtooth-shaped protruding portions was changed to 7.0 mm (P / G = 1.4). Further, the radiation test was conducted after setting in the same manner as in Example 3 except that the supply rate of the water vapor supplied to the charging unit 110 was readjusted so as to be 0.47 mg / min.
As a result, as compared with Example 3, the P / G is large, and the amount of ozone released is reduced as the supply rate of the water vapor supplied to the charging unit 110 is increased, and the air filter has a low affinity for water. By using the filter medium, it was possible to suppress the decrease in the collection efficiency of the floating fine particles to a small extent. In addition, in the influence test of the current-carrying deterioration of the discharge electrode, it was possible to achieve both the collection efficiency of the floating fine particles and the emission amount of ozone at an acceptable level.

Example 6
A radiation test was conducted after setting in the same manner as in Example 5 except that the film split nonwoven fabric used in Example 4 was used as the air filter material of the dust collection portion 130.
As a result, P / G was large compared to Example 4, and the collection efficiency of suspended particulates decreased because the feed rate of water vapor supplied to the charging unit 110 was increased, but the amount of ozone released was significantly reduced. It was possible to
Subsequently, when the influence test of the discharge deterioration of the discharge electrode was carried out, the collection efficiency of suspended particles further decreased. However, by changing the inter-electrode supply amount to 150 μA, the collection efficiency of suspended particles was made to an acceptable level. It was possible to improve and minimize the performance difference before and after the influence test of the discharge deterioration of the discharge electrode.

Example 7
The discharge electrode of the charging unit 110 was replaced, and the spacing P of the sawtooth-shaped protruding portions was changed to 2.5 mm (P / G = 0.5). A corrugated structure (a tubular air passage) obtained by laminating a polyethylene terephthalate sheet (sheet thickness t = 0.1 mm, contact angle 79 °) subjected to electret processing as an air filter material for the dust collection portion 130 As in Example 1, except that the opening diameter d = 0.5 mm, air path length L (filter medium thickness) = 5.0 mm, d / L = 0.10, opening ratio = 75%, pressure loss = 7 Pa) The emission test was conducted after setting to.
As a result, as compared with Example 1, the affinity of the air filter medium to water is increased, and the air passage length L is shortened, so that P / G and the opening diameter d are reduced, thereby collecting the floating fine particles. It was possible to suppress the decrease in efficiency to a small extent. Moreover, when the influence test of the current supply deterioration of the discharge electrode was implemented, the collection efficiency of the floating fine particles and the amount of released ozone could be compatible at an acceptable level. Furthermore, although the amount of current flow between the electrodes was changed to 150 μA, no improvement was seen in the collection efficiency of suspended particulates only by the increase of the amount of released ozone.

Example 8
The discharge electrode of the charging unit 110 was replaced, and the tip radius of curvature R of the electrode tip of the sawtooth-shaped projection was changed to 125 μm. In addition, a corrugated structure (opening of a tubular air passage) obtained by laminating an electret-treated polypropylene sheet (sheet thickness t = 0.2 mm, contact angle 94 °) as an air filter material of the dust collection portion 130 Example 1 except that one processed into an aperture diameter d = 1.2 mm, air path length L (filter material thickness) = 45 mm, d / L = 0.027, aperture ratio = 62%, pressure loss = 2 Pa) was used The emission test was conducted after setting in the same manner as in.
As a result, compared with Example 1, the opening diameter d of the air filter medium was increased, and the opening ratio decreased due to the increase of the sheet thickness t. However, the air passage length L is increased. The reduction of the collection efficiency of the floating particulates could be suppressed to a small extent. In addition, although the amount of ozone emission increases due to the increase of the tip radius of curvature R of the electrode tip, the supply of water vapor to the charging unit 110 can minimize the amount.
Furthermore, when the influence test of current flow deterioration of the discharge electrode was conducted, discharge efficiency was achieved by making the collection efficiency of floating particles and the amount of released ozone compatible with each other at an acceptable level, and by increasing the tip curvature radius R of the electrode tip. It was possible to minimize the performance difference before and after the influence test of the current deterioration of the electrode.

Example 9
The discharge electrode of the charging unit 110 was replaced, the distance P between the sawtooth-shaped protruding portions was 7.0 mm (P / G = 1.4), and the tip radius of curvature R of the electrode tip was changed to 75 μm. In addition, a honeycomb structure (a tubular air passage) obtained by laminating an electret-treated polyethylene sheet (sheet thickness t = 1.5 mm, contact angle = 101 °) as an air filter material of the dust collection portion 130 With an aperture diameter d of 5 mm, an air passage length L (filter material thickness) of 25 mm, d / L of 0.20, an aperture ratio of 79%, and a pressure loss of 1 Pa) The emission test was conducted after setting in the same manner as in Example 1 except that the readjustment was performed as described above.
As a result, the radius of curvature R of the tip of the electrode is larger than in Example 1, and the amount of electrification between the electrodes is also increased. However, since water vapor is supplied to the charging unit 110, the amount of ozone released is small. Was increased to On the other hand, although P / G and the opening diameter d of the air filter medium became large, by lowering the affinity of the air filter medium for water and increasing the amount of electrification between the electrodes, the collection efficiency of suspended particulates was lowered. It was possible to make it an acceptable level.
Subsequently, an influence test of the discharge deterioration of the discharge electrode was conducted, and although the amount of ozone released increased, the collection efficiency of suspended particles and the amount of ozone discharge were compatible at an acceptable level, and the influence of the discharge deterioration of the discharge electrode The performance gap before and after the test could be minimized.

Example 10
The discharge electrode of the charging unit 110 was replaced, and the interval P of the sawtooth-shaped protruding portions was 3.5 mm (P / G = 0.7), and the tip curvature radius R of the electrode tip was changed to 10 μm. Moreover, as an air filter material of the dust collection part 130, what was processed into the meltblown non-woven fabric (filter material thickness = 2.0 mm, contact angle = 94 °, pressure loss = 60 Pa) mainly composed of polypropylene fiber subjected to electret treatment Using. Moreover, after setting similarly to Example 1 except having readjusted so that the amount of electricity_supply between electrodes might be 120 microampere, the diffusion test was done.
As a result, since the air filter material was changed to the meltblown nonwoven fabric, the collection efficiency of the floating fine particles was lowered, but it could be stopped at an acceptable level by using the electret-treated polypropylene fiber.
Subsequently, when the influence test of the deterioration of the discharge electrode was conducted, the discharge electrode with the small tip radius of curvature R at the tip of the electrode was used. The amount of energization was changed to 150 μA. As a result, although the amount of released ozone increased significantly, it was possible to achieve both the collection efficiency of suspended particles and the amount of released ozone at an acceptable level.

  The evaluation results of Examples 2 to 10 are summarized in the table of FIG.

Comparative Example 1
While replacing the discharge electrode of the charging unit 110 and changing the interval P of the sawtooth-like protruding portions to 5.0 mm (P / G = 1.0) and stopping the supply of the water vapor supplied to the charging unit 110 In the same manner as in Example 10, the emission test was conducted. As a result, since the ozone emission amount could not be suppressed to an acceptable level, the water vapor supply rate was readjusted to 0.18 mg / min, and the emission test was resumed.
As a result, it was possible to achieve both the collection efficiency of suspended particulates and the amount of released ozone at an acceptable level.
Subsequently, when the influence test of the current flow deterioration of the discharge electrode was conducted, the collection efficiency of the floating fine particles was lowered. Therefore, similarly to Example 10, the amount of current flow between the electrodes is changed to 150 μA to collect the floating fine particles. However, since the supply rate of the water vapor supplied to the charging unit 110 was not sufficient, the amount of ozone released could not be improved to an acceptable level.

Comparative Example 2
The discharge electrode of the charging unit 110 was replaced, and the radius of curvature of the electrode tip of the sawtooth-shaped projection was changed to 150 μm. Further, the emission test was conducted after setting in the same manner as in Comparative Example 1 except that the supply rate of the water vapor supplied to the charging unit 110 was readjusted so as to be 0.55 mg / min.
As a result, although it was possible to achieve both the collection efficiency of floating particulates and the amount of ozone released at an acceptable level, dew condensation was applied to the air filter medium during the effect test of current-carrying deterioration of the discharge electrode performed thereafter. The test was discontinued as it occurred.

Comparative Example 3
Similar to Comparative Example 1 except that a high-performance air filter (quasi HEPA filter, pressure loss = 200 Pa, filter medium thickness 2.5 mm) mainly composed of glass fiber is used as an air filter medium for the dust collection unit 130 Above, the emission test was done.
As a result, the air treatment amount was significantly reduced, and the air filter medium had dew condensation, so the test was stopped.

Comparative Example 4
The discharge electrode of the charging unit 110 is replaced, and the interval P of the sawtooth-shaped protruding portions is changed to 5.0 mm (P / G = 1.0), and electret treatment is applied as an air filter material of the dust collection unit 130 A film split nonwoven fabric (fiber width w = 60 μm, w / k = 5.0) after making a polyethylene terephthalate film (film thickness (fiber thickness k) = 12 μm, contact angle = 79 °) A radiation test was conducted after setting in the same manner as in Example 5 except that a filter material having a thickness of 4.0 mm, a composition ratio of film split fibers of 40 mass%, and a pressure loss of 12 Pa was used.
As a result, the collection efficiency of suspended particulates did not reach an acceptable level. In addition, the influence test of the energization degradation of the discharge electrode was discontinued.

Comparative Example 5
A corrugated structure (opening of a tubular air passage) obtained by laminating a polyethylene terephthalate sheet (sheet thickness t = 0.1 mm, contact angle 79 °) not subjected to electret processing as an air filter material of the dust collection portion 130 The same as Comparative Example 4 except that the diameter d was 0.5 mm, the air path length L (filter medium thickness) was 5.0 mm, d / L = 0.10, the aperture ratio was 75%, and the pressure loss was 7 Pa). The emission test was conducted after setting to.
As a result, the collection efficiency of suspended particulates did not reach an acceptable level. In addition, the influence test of the energization degradation of the discharge electrode was discontinued.

  The evaluation results of Comparative Examples 1 to 5 are summarized in the table of FIG.

110. . . Charging unit 111. . . Discharge electrode 112. . . Counter electrode 120. . . Water vapor generation part 130. . . Dust collection unit 140. . . Airflow generator G. . . Distance between discharge electrode and counter electrode . . Tubular air passage length P.I. . . Distance between protrusions of discharge electrode d. . . Opening diameter of tubular air passage

Claims (5)

At least a "charging unit" for charging suspended particles in air;
"A steam generation unit" for supplying steam to the charging unit;
And a "dust collection unit" disposed downstream of the charging unit in the flow direction of the charging unit and collecting the floating fine particles charged by the charging unit.
The supply rate of the water vapor supplied from the water vapor generation unit to the charging unit is 0.20 to 0.50 mg / minute per 1 cm ² of the cross-sectional area of the air passage passing through the electrode portion of the charging unit. Electric dust collector characterized by. The charging unit includes at least a “discharge electrode” to which a high voltage is applied by a high voltage power supply, and a flat plate-like “counter electrode” grounded.
The discharge electrode is provided with a plurality of "protrusion portions" for discharge at an interval P (mm), and the counter electrodes are arranged in parallel on both sides of the discharge electrode with an interval G (mm). 2. The electricity according to claim 1, wherein the distance P between the protruding portions and the distance G between the discharge electrode and the counter electrode satisfy the relationship of 0.5 ≦ P / G ≦ 1.5. Dust collector. The dust collection unit includes an air filter medium made of a sheet-like or film-like polymer material subjected to electret treatment,
The contact angle of the polymer material with water is 75 ° or more,
The electrostatic precipitator according to claim 1 or 2, wherein the thickness of the air filter medium is 3 mm or more, and the pressure loss at a wind speed of 0.2 m / sec is 60 Pa or less.   The air filter medium is a structure having at least a tubular air passage formed by laminating polymer sheets, and the opening of the tubular air passage is in a plane orthogonal to the air flow direction of the air filter medium. 60% by area or more, and the opening diameter d (mm) of the tubular air passage and the air passage length L (mm) satisfy the relationship of 0.025 ≦ d / L ≦ 0.2. The electrostatic precipitator as described in 3.   The air filter medium is a non-woven fabric containing at least 50% by mass or more of film split fibers obtained by processing a polymer film into splits, wherein the fiber width w (mm) and the fiber thickness k (mm) of the film split fibers 4. The electrostatic precipitator according to claim 3, wherein the relationship of 2 ≦ w / k ≦ 5 is satisfied.