Electrostatic precipitator

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

[0001] The present invention relates to an electrostatic precipitator that charges airborne particles and collects them by electrostatic force.

Background Art

[0002] Conventionally, in this type of electrostatic precipitator, a DC high voltage is applied to the discharge electrode of the charging section to generate positive or negative corona, and the dust passing through the charging section is charged with a positive or negative charge. A technique of collecting the charged dust on the surface of the dust collecting electrode plate by electrostatic force in a high electric field of a dust collecting section having a charged electrode plate to which a DC high voltage is applied and a dust collecting electrode plate connected to the ground is widely known (Patent Documents 1 and 2).

[0003] And the electrostatic precipitator used for dust removal in a road tunnel was large in size in order to process a large amount of air.

[0004] The known electrostatic precipitation principle will be described with reference to FIGS. 7 and 8. 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 section 101 to the dust collection section 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 from DC power sources 107 and 108 to the charging section 101 and the dust collection section 102, respectively. The charging section 101 is composed of a discharge electrode plate 103 having barbs for discharge and a ground electrode plate 104. A DC high voltage of -10 kV is applied to the discharge electrode plate 103, and negative corona discharge occurs in the space between the discharge electrode plate 103 and the ground electrode plate 104. Negative ions generated by this negative corona give negative charges to dust (not shown) in the space, and the dust is negatively charged. The charged dust is collected on the dust collection electrode plate 106 by Coulomb force in the electric field formed between the charged electrode plate 105 and the dust collection electrode plate 106 in the subsequent dust collection section 102 (dust collection principle). For simplicity, only two plates of each electrode plate are drawn, but in reality, each electrode plate in the charging section is composed of dozens of plates.

[0005] In the dust collection section 102 of such an electrostatic precipitator, in order to secure a large dust collection area, the charging electrode plates 105 and the dust collection electrode plates 106 are arranged alternately and parallel to each other with respect to the wind direction, using electrode plates of substantially the same size and shape. And as described above, an electric field is formed between the charging electrode plates 105 and the dust collection electrode plates 106. In the case of Figure 6 (negative charging), negatively charged particles will adhere to and be collected by the dust collection electrode plates 106. Since dust is removed by particles adhering to the surface of the dust collection electrode plates 106 in this way, the larger the area of the dust collection electrode plates 106, the higher the dust collection efficiency. That is, in order to ensure the dust collection efficiency, as the area of the electrode plates increases, the entire electrostatic precipitator also becomes larger and heavier.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the installation space of the electrostatic precipitator is limited, and in terms of transportation, on-site construction, and maintenance, it is required to be as small and light as possible. Therefore, achieving weight reduction while ensuring the dust collection efficiency has been one of the problems of the electrostatic precipitator.

Means for Solving the Problems

[0008] And in order to achieve this object, the electrostatic precipitator according to the present invention has a charging section in which charging electrode plates and grounding electrode plates are arranged alternately, and a dust collection section in which charging electrode plates and dust collection electrode plates are parallel and arranged alternately. Along the ventilation direction of the charged electrode plate, no plurality of apertures are provided in the region of the inflow side 1 / 2 of the total length of the charged electrode plate, and along the ventilation direction of the charged electrode plate, a plurality of apertures are provided in the region on the outflow side rather than the region of the inflow side 1 / 2 of the charged electrode plate. 。This achieves the intended object.

Effects of the Invention

[0009] According to the present invention, by providing a plurality of apertures on the outflow side of the charged electrode plate, the electrostatic precipitator can be made lighter. Further, an unequal electric field is formed in the vicinity of the aperture edge of the charged electrode plate, and particles are attracted to the aperture end where the electric lines of force concentrate, and are adhered and collected. From the above, the effect of reducing the weight of the electrostatic precipitator without reducing the dust collection efficiency can be obtained.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0011] The electrostatic precipitator according to the present invention has a charging part in which charged electrode plates and grounded electrode plates are alternately arranged, and a dust collection part in which charged electrode plates and dust collection electrode plates are parallel and alternately arranged in parallel. The charged electrode plate has a plurality of apertures on the outflow side.

[0012] As a result, the weight per dust collecting electrode plate becomes lighter, and furthermore, the entire electrostatic precipitator is also lightened. Also, by providing openings in the charging electrode plates, an uneven electric field is formed in the vicinity of the opening edges. In the uneven electric field region, the electric field lines are concentrated, and combined with the gradient force, dust can be collected with a greater force than in a uniform electric field. This is why a large amount of dust accumulates at the outflow side end of the dust collecting section. By providing a large number of openings, a large number of such uneven electric field regions can be created, leading to an improvement in the dust collecting ability.

[0013] On the other hand, when dust accumulates in this uneven electric field region and exceeds the limit, it will eventually peel off and re-disperse. Conventionally, it was considered that when the dust accumulated in the uneven electric field region at the outflow side end of the dust collecting section exceeded the limit amount, it would eventually peel off and re-disperse. Conventionally, techniques for re-collecting re-dispersed dust have been disclosed by changing the positions of the outflow side ends of the charging electrode plate and the dust collecting electrode plate, or by newly providing an electrode plate for preventing re-dispersion (Patent Documents 1 and 2). In the dust collecting section of the dust collector according to the present invention, since the number of uneven electric field regions can be increased, the dust collecting capacity increases in the uneven electric field region, and the dust collecting efficiency is maintained. Also, the re-dispersed particles are charged to the same polarity as the electrode by induced charging and re-disperse, and can be re-collected by the dust collecting electrode plate downstream of the point of dispersion. This also contributes to an improvement in the dust collecting efficiency.

[0014] (Embodiment 1) As shown in FIG. 1, the electrostatic precipitator according to the present invention includes a charging section 1 and a dust collecting section 2. They are arranged in the order of the charging section 1 and the dust collecting section 2 from the inflow side along the ventilation direction. The charging section 1 has a plurality of charging electrodes 3 and a plurality of ground electrode plates 4, and the charging electrodes 3 and the ground electrode plates 4 are arranged alternately. Also, the dust collecting section 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 parallel to each other and alternately.

[0015] As shown in Fig. 2, a plurality of apertures 6 are provided in the outflow side 1 / 2 region of the charging electrode plate 5. In the present embodiment, on the charging electrode plate 5 with vertical and horizontal sizes of approximately 700×900 mm, round holes with a diameter of 5 mm are arranged in a staggered pattern with a 60° pitch and an 8 mm interval. The number of apertures 6 is approximately 2100. Note that the shape of the apertures 6 is not limited to this embodiment, and may be oblong holes or rectangles. As long as an uneven electric field can be formed, there is no difference in the action and effect. Note that the diameter, interval, and pattern are not limited to this embodiment either. As long as the diameter of the aperture 6 is about 2 mm or more, an uneven electric field can be formed. The same applies to the ratio of providing the apertures 6 on the charging electrode plate 5. In the pattern of this embodiment, the porosity in the region where the apertures 6 are provided is about 13%. Therefore, if the apertures 6 are provided in 1 / 2 of the entire charging electrode plate 5 (when the apertures 6 are provided only on the downstream side), the charging electrode plate 5 can reduce the mass per sheet by 6.5% compared to the case of a flat plate without the apertures 6. When 50 charging electrode plates 5 are used per electrostatic precipitator, the electrode plates of the above area are approximately 2.0 kg per sheet, and the weight of each electrostatic precipitator can be reduced by about 6.5 kg.

[0016] Also, as shown in Fig. 3, the charging unit 1 includes a plurality of charging electrodes 3, a plurality of grounding electrode plates 4, and a charging unit DC power supply 8. A high voltage is applied to the charging electrodes 3 by the charging unit DC power supply 8. When a high voltage is applied to the charging electrodes 3, corona discharge occurs between the grounded grounding electrode plates, charging the dust flowing in from the inflow side. In the present embodiment, the charging electrode 3 is described using a so-called barbed electrode in which a plurality of barbs are provided on a flat plate. However, the charging electrode 3 may be in any form that can discharge to charge the incoming particles, such as a needle electrode or a wire electrode.

[0017] Also, a high voltage is applied to the charging electrode plate 5 by the dust collection unit DC power supply 9. In the inflow side 1 / 2 region of the dust collection unit 2, that is, in the region of the charging electrode plate 5 where the apertures 6 are not provided, a uniform and equal electric field region is formed between the charging electrode plate 5 and the dust collection electrode plate 7. As a result, the particles charged by the charging unit 1 receive a Coulomb force and are collected on the dust collection electrode plate 7.

[0018] On one hand, in the outflow side half region of the dust collection part 2, that is, in the region where the apertures 6 are provided in the charged electrode plate 5, electric lines of force concentrate near the edges of these apertures 6, forming an unequal electric field region with a higher electric field strength than the uniform electric field by the flat plate (Fig. 3). Since a gradient force acts in the unequal electric field region, dust is attracted with a stronger force near this region.

[0019] Using a conventional dust collection part 102 model (Fig. 4(a)) in which the flat charged electrode plate 105 and the dust collection electrode plate 106 are arranged in parallel, and a dust collection part 2 model (Fig. 4(b)) in which the charged electrode plate 5 having the aperture 6 and the dust collection electrode plate 7 of this embodiment are arranged in parallel, a positive electric field analysis was performed and the electric field strengths of each were compared.

[0020] As shown in Fig. 4(a), the conventional dust collection part 102 model is formed by sandwiching one charged electrode plate 105 between two dust collection electrode plates 106.

[0021] Also, as shown in Fig. 4(b), the dust collection part 2 model of this embodiment is a charged electrode plate 5 with the same outer shape as the conventional dust collection part 102 model, provided with apertures 6. Both the conventional dust collection part 102 and the dust collection part 2 of this embodiment have a length of 200 mm in the ventilation direction. Also, although shown as a finite shape in Fig. 4, calculations were performed assuming periodic continuation to infinity in the vertical direction (periodic boundary conditions). Note that the length in the ventilation direction was set to a length where the tendency of the electric field strength can be observed in the central part. The inter-electrode distances between each dust collection electrode plate 106 and charged electrode plate 105, and between the dust collection electrode plate 7 and charged electrode plate 5 are 9 mm. Considering applying a voltage of -7.2 kV to the charged electrode plate 105 and the charged electrode plate 5 by the dust collection part DC power supply 9, as the voltage boundary conditions, -7.2 kV was set for the charged electrode plate and 0 kV for the dust collection electrode plate.

[0022] The analysis results are shown in Fig. 5. Fig. 5 is a cross-sectional view of the dust collection part 102 and the dust collection part 2, respectively, seen from directly above in the vertical direction, and shows the electric field strength with the shade of color. As shown in Fig. 5(a), it can be seen that in the dust collection part 102 of the conventional model, 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 collection part 2 of the present embodiment, an unequal electric field is formed near the edge of the aperture 6 of the charged electrode plate 5, and it can be confirmed that a stronger electric field region exists near the edge of the aperture 6 than the equal electric field. In this region, the electric field strength is about 9.0×10 5 [V / m].

[0023] Fig. 6 is a horizontal cross-sectional view passing through the center of the aperture 6 of the charged electrode plate 5 for the dust collection part 2 in the present embodiment. Using Fig. 6, the dust collection action of the charged electrode plate 5 and the dust collection electrode plate 7 in the present embodiment will be described.

[0024] As described above, an unequal electric field with a stronger electric field is formed near the edge of the aperture 6 compared to the prior art. The unequal electric field combines with the gradient force to attract dust with a greater force. Fig. 6 illustrates the state in which dust is intensively collected by the unequal electric field in this region. In the inflow side 1 / 2 region of the dust collection part 2, 1) dust that has not been sufficiently charged, 2) dust that has once been collected in the inflow side 1 / 2 of the dust collection part 2 and re-dispersed, and 3) dust that has escaped due to the fluid resistance of the turbulent flow reach the outflow side 1 / 2 region of the dust collection part 2 without being collected. In the outflow side 1 / 2 region of the dust collection part 2, as described above, the inflowing dust can be collected by the unequal electric field due to the aperture 6.

[0025] In addition, by providing a large number of apertures 6, a large number of non-uniform electric field regions can be generated. As a result, the capacity of dust that can be collected in the non-uniform electric field regions increases. On the other hand, in the non-uniform electric field, dust is intensively collected, deposited, and eventually re-dispersed. When re-dispersing, it is known that it becomes the same polarity as the electrode plate to which it adheres by induced charging. Dust re-dispersed from the vicinity of the edge of the aperture 6 of the charged electrode plate 5 is negatively charged. Since this re-dispersed dust is re-collected by the dust collecting electrode plate 7 on the downstream side from its re-dispersion position, it is possible to prevent a decrease in the dust collection efficiency due to re-dispersion from the non-uniform electric field region. Therefore, the dust collecting electrode plate 7 is preferably longer in the ventilation direction than the charged electrode plate 5 and is arranged to protrude downstream of the charged electrode plate 5. With this configuration, dust re-dispersed from the outflow side of the charged electrode plate 5 can be collected by the dust collecting electrode plate 7 protruding downstream.

[0026] FIG. 9 shows the dust collection states of the charged electrode plate 105 and the dust collecting electrode plate 106 in a conventional dust collecting section 102 using flat electrode plates (cited from Patent Documents 1 and 2 (patent applications by the same applicant as this application)). Although dust also adheres to the charged electrode plate 105 using flat electrode plates, the degree of adhesion (the adhesion area in the electrode plate area) is 18%, 10%, 6%, and 4% for every 1 / 4 of the total length of the electrode plate from the upwind side (inflow side). Also, the degree of adhesion to the dust collecting electrode plate 106 is 56%, 38%, 23%, and 13% for every 1 / 4 of the total length of the electrode plate from the upwind side (inflow side).

[0027] As described above, it can be seen that in the flat electrode plate, the dust collection efficiency significantly decreases on the downstream (outflow) side beyond 1 / 2 of the total length. That is, even if a uniform electric field is formed on the outflow side, it does not significantly contribute to the dust collection efficiency. Therefore, in this embodiment, the aperture 6 is provided so as to form a non-uniform electric field in this downstream 1 / 2 region. In particular, the aperture 6 is provided in the charged electrode plate 5 having the same polarity as the polarity to be charged in the charging section 1, and it is possible to collect dust re-dispersed from the dust collecting electrode plate 7 and dust that was not charged in the charging section 1.

[0028] Thus, by providing the apertures 6 in the region on the outflow side of the charged electrode plate 5, weight reduction can be achieved. Further, due to these apertures 6, an uneven electric field is formed, and dust that has re-dispersed from the inflow side and dust that could not be collected can be collected. Also, by arranging a large number of apertures 6 in a certain pattern, a large number of uneven electric field regions are formed, increasing the collection capacity in the uneven electric field regions. Furthermore, there is a re-dispersion prevention process in which dust re-dispersed from the uneven electric field region can be re-collected by the dust collection electrode plate 7 on the downstream side from the re-dispersion position. As described above, while maintaining the dust collection efficiency, the intended problem of achieving weight reduction is solved. By doing so, dust that has re-dispersed from the inflow side and dust that could not be collected can be collected. Also, by arranging a large number of apertures 6 in a certain pattern, a large number of uneven electric field regions are formed, increasing the collection capacity in the uneven electric field regions. Furthermore, there is a re-dispersion prevention process in which dust re-dispersed from the uneven electric field region can be re-collected by the dust collection electrode plate 7 on the downstream side from the re-dispersion position. As described above, while maintaining the dust collection efficiency, the intended problem of achieving weight reduction is solved.

Industrial Applicability

[0029] Since it is possible to reduce the weight of the electrode plates frequently used in electrostatic precipitators and ensure the dust collection efficiency, it is particularly useful as a technology for use in large electrostatic precipitators.

Explanation of Reference Numerals

[0030] 1 Charging section 2 Dust collection section 3 Charging electrode 4 Ground electrode plate 5 Charged electrode plate 6 Aperture 7 Dust collection electrode plate 8 DC power supply for charging section 9 DC power supply for dust collection section 101 Charging section 102 Dust collection section 103 Discharge electrode plate 104 Ground electrode plate 105 Charged electrode plate 106 Dust collection electrode plate 107 DC power supply 108 DC power supply

Claims

1. In an electrostatic precipitator having a charging section in which charging electrodes and a grounded electrode plate are alternately arranged, and a dust collection section in which charged electrode plates and dust collection electrode plates are parallel and alternately arranged in parallel, along the ventilation direction of the charged electrode plate, no plurality of apertures are provided in a region of the inflow side 1 / 2 of the entire length of the charged electrode plate, along the ventilation direction of the charged electrode plate, a plurality of apertures are provided in a region on the outflow side rather than the region of the inflow side 1 / 2 of the charged electrode plate, electrostatic precipitator.

2. The electrostatic precipitator according to claim 1, wherein the apertures are provided in a region of the outflow side 1 / 2 of the charged electrode plate.

3. The electrostatic precipitator according to claim 1 or 2, wherein the dust collection electrode plate is longer than the charged electrode plate in the ventilation direction and is arranged to protrude downstream.

4. The electrostatic precipitator according to any one of claims 1 to 3, wherein the apertures are provided in a pattern of round holes with a diameter of 5 mm at intervals of 8 mm and a 60° stagger pattern of round holes.

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