JP2022155785A - electric dust collector - Google Patents

Abstract

To provide an electric dust collector that attains weight saving while ensuring dust collection efficiency.SOLUTION: An electric dust collector includes an electrification part 1 in which a charging pole 3 and a grounding pole plate 4 are alternately arranged, and a dust collection part 2 a loading electrode plate 5 and a dust collection pole plate 7 are arrayed alternately and in parallel, with a plurality of open holes 6 being provided in an area of a half of the loading pole plate 5 on the outflow side. Weight saving can be attained by the provision of the open holes 6 in the charging pole plate 5 of the dust collection part 2. Further, a non-uniform electric field is formed in the vicinity of an edge of the opening holes 6 and dust can be collected by gradient force; hence dust collection efficiency can be secured as well.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an electrostatic precipitator that charges suspended particles in the air and collects them by electrostatic force.

Conventionally, this type of electrostatic precipitator applies a high DC voltage to the discharge electrode of the charging section to generate a positive or negative corona, thereby charging the dust passing through the charging section with a positive or negative charge. The charged dust is collected on the surface of the dust collecting electrode plate by electrostatic force due to the high electric field of the dust collecting part having the charging electrode plate to which a DC high voltage is applied and the dust collecting electrode plate connected to the ground. The technology is widely and commonly known (Patent Documents 1 and 2).

In addition, the electrostatic precipitator used for dust removal in road tunnels has become large in order to process a large amount of air.

The principle of electric dust collection, which is a known technology, will be described with reference to FIGS. 7 and 8. FIG. As shown in FIG. 7, the dust collection unit of the electrostatic precipitator is composed of a charging section 101 and a dust collection section 102 . The ventilation direction is from the charging unit 101 to the dust collection unit 102 (from the lower left to the upper right in FIG. 7). As shown in FIG. 8, DC high voltages of -10 kV and -7.2 kV are supplied to the charging section 101 and the dust collection section 102 from a DC power supply 107 and a DC power supply 108, respectively. The charging unit 101 is composed of a discharge electrode plate 103 having thorns for discharge and a ground electrode plate 104 . A DC high voltage of −10 kV is applied to the discharge electrode plate 103 , and a negative corona discharge is generated in the space between the discharge electrode plate 103 and the ground electrode plate 104 . Negative ions generated by this negative corona give negative charge to dust (not shown) in the space, and the dust is negatively charged. The charged dust is collected on the dust collecting electrode plate 106 by Coulomb force due to the electric field formed between the charge electrode plate 105 and the dust collecting electrode plate 106 in the dust collecting portion 102 at the rear stage (dust collection principle). For the sake of simplicity, only two plates are shown for each electrode plate, but in reality, several tens of plate plates are provided for each charging section.

In the dust collection section 102 of such an electric dust collector, the charge electrode plate 105 and the dust collection electrode plate 106 have substantially the same size and shape, and are arranged with respect to the wind direction in order to secure a large dust collection area. They are arranged alternately and in parallel. Then, as described above, an electric field is formed between the charge electrode plate 105 and the dust collection electrode plate 106, and in the case of FIG. will be captured. Since dust is removed by the particles adhering to the surface of the dust collecting electrode plate 106, the larger the area of the dust collecting electrode plate 106, the higher the dust collection efficiency. That is, in order to secure dust collection efficiency, the area of the electrode plate is increased, and the entire electrostatic precipitator is also increased in size and weight.

JP 2014-087734 A JP 2015-33696 A

However, the installation space of the electrostatic precipitator is limited, and it is required to be as small and light as possible from the viewpoint of transportation, on-site construction and maintenance. Therefore, reducing the weight while ensuring dust collection efficiency has been one of the challenges of electrostatic precipitators.

In order to achieve this object, the electrostatic precipitator according to the present invention comprises a charging section in which charging electrode plates and ground electrode plates are alternately arranged, and a collector in which charging electrode plates and dust collection electrode plates are arranged in parallel and alternately. It has a dust part and has a plurality of apertures on the outflow side of the charging electrode plate. This achieves the intended purpose.

According to the present invention, by providing a plurality of openings on the outflow side of the charge electrode plate, the weight of the electrostatic precipitator can be reduced. In addition, a nonuniform electric field is formed in the vicinity of the edge of the aperture of the charge electrode plate, and the particles are attracted to the edge of the aperture where the lines of electric force concentrate, and are adhered and collected. As described above, the effect of reducing the weight of the electrostatic precipitator can be obtained without lowering the dust collection efficiency.

The figure of the dust collection part of the electrostatic precipitator of embodiment of this invention FIG. 2(a) Overall view and (b) enlarged view of the opening portion of the charge electrode plate of the dust collecting portion of the electrostatic precipitator according to the embodiment of the present invention. Schematic diagram of an electrostatic precipitator according to an embodiment of the present invention Fig. 6 is a diagram of a system of positive electric field analysis simulating the dust collecting part (a) of the conventional electrostatic precipitator and the dust collecting part (b) of the electrostatic precipitator according to the embodiment of the present invention. Fig. 3 is a diagram of positive electric field analysis calculation results simulating the dust collecting portion (a) of the conventional electrostatic precipitator and the dust collecting portion (b) of the electrostatic precipitator according to the embodiment of the present invention. The figure showing the re-entrainment suppression process of the dust collecting part of the electric dust collector of Embodiment 1 of the present invention. Diagram of conventional electrostatic precipitator System diagram of a conventional electrostatic precipitator Observation diagram of the dust adhesion state on the surface of the electrode plate in the dust collection part of the conventional electrostatic precipitator

An electrostatic precipitator according to the present invention has a charging section in which charging electrode plates and ground electrode plates are alternately arranged, and a dust collecting section in which charging electrode plates and dust collection electrode plates are arranged in parallel and alternately. The charging electrode plate has a plurality of apertures on the outflow side.

As a result, the weight of each dust collecting electrode plate can be reduced, and the weight of the entire electrostatic precipitator can also be reduced. Also, by providing the charge electrode plate with an aperture, a non-uniform electric field is formed in the vicinity of the edge of the aperture. In the non-uniform electric field region, the lines of electric force are concentrated, and together with the gradient force, dust can be collected with a greater force than in the uniform electric field. This is the reason why a large amount of dust collects at the outflow end of the dust collector. By providing a large number of openings, a large number of non-uniform electric field regions can be created, leading to an improvement in dust collecting performance.

On the other hand, if the dust accumulates due to this non-uniform electric field area and exceeds the limit, the dust will eventually separate and re-scatter. Conventionally, it was thought that when the amount of dust accumulated in the non-uniform electric field area at the outflow side of the dust collecting section exceeded the limit, the dust would eventually separate and scatter again. In the past, techniques have been disclosed for re-collecting re-entrained dust by changing the positions of the outflow side ends of the charging electrode plate and dust-collecting electrode plate, or by providing a new electrode plate for re-entrainment prevention. (Patent Documents 1 and 2). In the dust collecting part of the dust collector according to the present invention, the non-uniform electric field area can be increased, so the dust collection capacity is increased in the non-uniform electric field area, and the dust collection efficiency is maintained. In addition, the re-entrained particles can be charged to the same polarity as the electrode by induction charging and re-entrained, and can be re-collected by the dust collection electrode plate located downwind from the point where they were dispersed. This also contributes to the improvement of dust collection efficiency.

(Embodiment 1)
The electrostatic precipitator according to the present invention comprises a charging section 1 and a dust collecting section 2, as shown in FIG.
The charging section 1 and the dust collecting section 2 are arranged in this order from the inflow side along the ventilation direction. The charging section 1 has a plurality of charging electrodes 3 and a plurality of grounding plates 4, and the charging electrodes 3 and the grounding plates 4 are alternately arranged. The dust collecting part 2 has a plurality of charging electrode plates 5 and a plurality of dust collecting electrode plates 7, and the charging electrode plates 5 and the dust collecting electrode plates 7 are arranged in parallel and alternately.

As shown in FIG. 2, a plurality of apertures 6 are provided in the outflow side 1/2 area of the charging electrode plate 5 . In the present embodiment, the charge electrode plate 5 having a size of about 700×900 mm in length and width has round holes with a diameter of 5 mm arranged in a staggered pattern of 60° round holes at intervals of 8 mm. The number of openings 6 is about 2100. The shape of the opening 6 is not limited to this embodiment, and may be an oval hole or a rectangle, and as long as a non-uniform electric field can be formed, there is no difference in function and effect. The diameter, spacing, and pattern are not limited to this embodiment, and a non-uniform electric field can be formed as long as the diameter of the opening 6 is about 2 mm or more. The ratio of the openings 6 in the charging electrode plate 5 is also the same. In the pattern of this embodiment, the porosity is about 13% in the area where the openings 6 are provided. In this case, the weight of each charging electrode plate 5 can be reduced by 6.5% compared to a flat plate without the openings 6 . When 50 charging electrode plates 5 are used for one electrostatic precipitator, each electrode plate with the above area weighs about 2.0 kg, and the weight of one electrostatic precipitator can be reduced by about 6.5 kg.

As shown in FIG. 3, the charging section 1 includes a plurality of charging electrodes 3, a plurality of ground electrode plates 4, and a DC power source 8 for the charging section. A high voltage is applied to the charging electrode 3 by the DC power source 8 of the charging section. When a high voltage is applied to the charging electrode 3, corona discharge is generated between the grounded electrode plates, and dust flowing in from the inflow side is charged. In the present embodiment, a so-called thorn electrode in which a plurality of thorns are provided on a flat plate is used as the charging electrode 3. However, the charging electrode 3 may be a needle electrode, a wire electrode, or the like, which may be a needle electrode, a wire electrode, or the like. Any form can be used as long as it can be discharged so as to be charged.

A high voltage is applied to the charging electrode plate 5 by the DC power source 9 of the dust collector. In the 1/2 area on the inflow side of the dust collection part 2, that is, in the area where the charge electrode plate 5 is not provided with the openings 6, a uniform uniform electric field region exists between the charge electrode plate 5 and the dust collection electrode plate 7. is formed, whereby the particles charged by the charging section 1 are subjected to Coulomb force and collected by the dust collection electrode plate 7 .

On the other hand, in the 1/2 area on the outflow side of the dust collecting section 2, that is, in the area where the charge electrode plate 5 is provided with the openings 6, the lines of electric force are concentrated near the edges of the openings 6, and the uniform electric field due to the flat plate is generated. A non-uniform electric field region with a higher electric field strength is created (Fig. 3). Since a gradient force acts in the nonuniform electric field region, dust particles are attracted by a stronger force in the vicinity of this region.

A model of a conventional dust collecting part 102 in which a flat charging electrode plate 105 and a dust collecting electrode plate 106 are arranged side by side (Fig. 4(a)), and a charging electrode plate having openings 6 according to the present embodiment. A positive electric field analysis was performed using a dust collection part 2 model in which 5 and a dust collection electrode plate 7 were arranged side by side (Fig. 4(b)), and the respective electric field intensities were compared.

As shown in FIG. 4( a ), the conventional model of the dust collector 102 has one charge electrode plate 105 sandwiched between two dust collection electrode plates 106 .

Further, as shown in FIG. 4(b), the dust collector 2 model of the present embodiment has openings 6 in the charge electrode plate 5 having the same outer shape as the dust collector 102 model of the conventional type. . Both the conventional dust collecting part 102 and the dust collecting part 2 of the present embodiment are 200 mm in the ventilation direction. In addition, although the finite shape is used in FIG. 4, the calculation is performed assuming that the shape continues periodically to infinity in the vertical direction (periodic boundary condition). The length in the ventilation direction was set to such a length that the tendency of the electric field intensity was observed at the central portion. The distance between the collecting electrode plate 106 and the charging electrode plate 105 and between the collecting electrode plate 7 and the charging electrode plate 5 is 9 mm. Considering that a voltage of −7.2 kV is applied to the charge electrode plate 105 and the charge electrode plate 5 by the dust collector DC power supply 9, the voltage boundary conditions are −7.2 kV to the charge electrode plate and The plate was set to 0 kV.

The analysis results are shown in FIG. FIG. 5 is a cross-sectional view of the dust collecting portion 102 and the dust collecting portion 2 as seen from above in the vertical direction, and the intensity of the electric field is indicated by the color density. As shown in FIG. 5(a), in the conventional model dust collection unit 102, it can be seen that the electric field strength is uniform in the space between the flat plates. On the other hand, as shown in FIG. 5(b), in the dust collecting section 2 of the present embodiment, a non-uniform electric field is formed near the edges of the openings 6 of the charging electrode plate 5, and the electric field region is stronger than the uniform electric field. exists in the vicinity of the 6 edges of the aperture. In this region, the electric field intensity is about 9.0×10 ⁵ [V/m].

FIG. 6 is a horizontal cross-sectional view passing through the center of the opening 6 of the charging electrode plate 5 for the dust collecting portion 2 in this embodiment. The action of collecting dust in the charging electrode plate 5 and collecting electrode plate 7 of the present embodiment will be described with reference to FIG.

As described above, a nonuniform electric field stronger than the conventional one is formed near the edge of the aperture 6 . The nonuniform electric field, combined with the gradient force, attracts dust particles with greater force. FIG. 6 shows a state in which dust is intensively collected by the nonuniform electric field in this area. In the region of the inflow side 1/2 of the dust collection section 2, 1) dust that is not sufficiently charged, 2) dust that was once collected in the inflow side 1/2 of the dust collection section 2 and is scattered again, and 3. ) The dust that escapes due to the fluid resistance of the turbulent flow reaches the 1/2 area on the outflow side of the dust collecting section 2 without being collected. In the 1/2 region on the outflow side of the dust collecting portion 2, the inflowing dust can be collected by the nonuniform electric field generated by the openings 6, as described above.

Also, by providing a large number of openings 6, a large number of non-uniform electric field regions can be produced. This increases the volume of dust that can be collected in the nonuniform electric field region. On the other hand, non-uniform electric fields are intensively dust-collected, deposited, and eventually re-entrained. It is known that, when re-scattered, the dust becomes the same polarity as that of the adhering electrode plate due to induction charging, and the dust re-scattered from the vicinity of the opening 6 of the charging electrode plate 5 is negatively charged. Since the re-entrained dust is re-collected by the dust collecting electrode plate 7 located downstream from the re-entrained dust position, it is possible to prevent reduction in dust collection efficiency due to re-entrained dust from the non-uniform electric field region. Therefore, the dust collecting electrode plate 7 is preferably longer than the charging electrode plate 5 in the airflow direction, and is arranged to protrude downstream of the charging electrode plate 5 . With this configuration, dust re-entrained from the outflow side of the charging electrode plate 5 can be collected by the dust collecting electrode plate 7 protruding downstream.

FIG. 9 shows the dust collecting state of the charging electrode plate 105 and the dust collecting electrode plate 106 in the conventional dust collecting portion 102 using flat plate plates (Patent Documents 1 and 2 (patent application filed by the same applicant as the present application). ). Dust also adheres to the charging electrode plate 105 using a flat plate, but the degree of dust adhesion (attachment area to the electrode plate area) is 18% for every quarter of the total length of the electrode plate from the windward side (inflow side). , 10%, 6% and 4%. Also, the degree of adhesion to the dust collecting electrode plate 106 is similarly 56%, 38%, 23%, and 13% for each quarter of the total length of the electrode plate from the windward side (inflow side).

As described above, it can be seen that the dust collection efficiency of the flat plate is greatly reduced on the downstream (outflow) side of the half of the total length. That is, even if a uniform electric field is formed on the outflow side, it does not greatly contribute to dust collection efficiency. is provided. In particular, the charging electrode plate 5 having the same polarity as the charging portion 1 is provided with an opening 6 to collect the dust re-scattered from the dust collection electrode plate 7 and the dust not charged in the charging portion 1. can be done.

Thus, by providing the opening 6 in the region on the outflow side of the charging electrode plate 5, the weight can be reduced. In addition, the openings 6 form a nonuniform electric field, and can collect dust re-scattered from the inflow side and dust that could not be collected. Also, by arranging a large number of openings 6 in a fixed pattern, a large number of non-uniform electric field regions are formed, and the collection capacity in the non-uniform electric field regions increases. Furthermore, there is a re-entrainment prevention process in which the dust re-entrained from the non-uniform electric field region can be re-collected by the dust collecting electrode plate 7 on the downstream side from the re-entrainment position. As described above, the intended problem of reducing the weight while maintaining the dust collection efficiency is solved.

Since the electrode plate used in many electrostatic precipitators can be made lighter and the dust collection efficiency can be ensured, it is particularly useful as a technique used for large-sized electrostatic precipitators.

REFERENCE SIGNS LIST 1 charging section 2 dust collecting section 3 charging electrode 4 grounding electrode plate 5 charging electrode plate 6 aperture 7 dust collecting electrode plate 8 charging section DC power supply 9 dust collecting section DC power supply 101 charging section 102 dust collecting section 103 discharge electrode plate 104 grounding Electrode plate 105 Charge electrode plate 106 Dust collection electrode plate 107 DC power supply 108 DC power supply

Claims (4)

An electrostatic precipitator having a charging section in which charging electrodes and ground electrode plates are alternately arranged, and a dust collection section in which charging electrode plates and dust collection electrode plates are arranged in parallel and alternately,
An electrostatic precipitator in which a plurality of openings are provided in the charging electrode plate of the dust collection section. 2. An electrostatic precipitator according to claim 1, wherein said apertures are provided in at least half of the outflow side of said charging electrode plate. 3. The electrostatic precipitator according to claim 1, wherein said dust collecting electrode plate is longer in the airflow direction than said charging electrode plate and arranged to protrude downstream. The electrostatic precipitator according to any one of claims 1 to 3, wherein the openings are provided in a staggered pattern of 60° round holes with a diameter of 5 mm at intervals of 8 mm.

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