JP2010069360A - Electrostatic dust collector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic dust collector which increases the collection efficiency by effectively sending a fine particulate material into the pocket area of electric field zero utilizing ionic air and which prevents the re-scattering by controlling the stripping due to the induction charge of the collected particulate material. <P>SOLUTION: In the electrostatic dust collector in which the gas stream passage to feed a gas containing the particulate material between a discharge electrode and dust collecting electrode that are oppositely arranged is formed and in which high voltage is applied to both electrodes to electrify the particulate material in the gas flowing through the gas stream passage so that it can be collected in the dust collecting electrode, a required number of dust collecting pockets where the space electric field strength in the inner atmosphere to store the particulate material is zero are installed at the opposite face of the dust collecting electrode against the discharge electrode with intervals in the flowing direction of the gas flowing through the gas stream passage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrostatic precipitator used for removing low-resistance particulate matter from gas or air containing fine low-resistance particulate matter such as exhaust gas of a diesel engine or exhaust gas of a road tunnel. About.

  An electric dust collector is useful for removing fine particulate matter contained in diesel exhaust gas, automobile tunnel exhaust gas, and other industrial exhaust gas. The electrostatic precipitator charges the particulate matter in the gas by corona discharge, and draws and collects the charged particulate matter on the dust collecting electrode by Coulomb force.

  In the electrostatic precipitator, when the particle size of the particulate matter is small, the amount of charge is small, so that the acting Coulomb force is weak, so that it is difficult to collect by the dust collecting electrode.

  In order to solve such a problem, in Patent Document 1, a mesh-shaped dust collecting electrode is arranged with a gap inside the case forming the gas flow path, and the gap between the case and the dust collecting electrode is arranged. A dust collection filter is provided adjacent to the dust collection electrode, and a discharge electrode is provided in the gas flow path in the case so as to face the dust collection electrode. The discharge from the discharge electrode charges the particulate matter in the gas. The particulate matter is packed and collected in the pores of the dust collection filter layer by flowing the gas flow between the gas flow path and the dust collection filter layer by the ion wind generated by the discharge. An electrostatic precipitator has been proposed.

  According to the electrostatic precipitator of Patent Document 1, fine particulate matter having a small charge amount can be sent to the dust collecting filter layer on the back side of the mesh dust collecting electrode and collected by ion wind generated at the time of discharge. As a result, fine particulate matter can be collected effectively.

  Moreover, in patent document 2, the uneven | corrugated | grooved part which a particulate matter accumulates on the surface of a dust collection electrode with a metal net, a punching board, etc. is formed, and the particulate matter collected by a dust collection electrode by Coulomb force is the particle | grains of an uneven | corrugated part. There has been proposed an exhaust gas purification apparatus that is held on the dust collecting electrode side by a holding action.

According to the exhaust gas purifying apparatus of Patent Document 2, particulate matter can be efficiently collected by the particle holding action of the uneven portion.
WO2005 / 021161 JP 2006-136766 A

  However, when the particulate matter contained in the gas is a so-called low resistance particulate matter containing a large amount of carbon and contained in diesel exhaust gas and having a low electrical resistivity, it is once collected by the dust collecting electrode. Then, since the electrostatic holding power is lost, there is a problem that a so-called re-scattering phenomenon occurs in which it is pushed back into the gas flow and peels off from the dust collecting electrode and scatters, thereby reducing the collection efficiency of the electrostatic precipitator. The re-scattering phenomenon becomes remarkable in the particulate matter collected by the dust collecting electrode and agglomerated and enlarged. Since re-scattered particles reciprocate between the high voltage electrode (discharge electrode) and the ground electrode (dust collection electrode) during operation of the electrostatic precipitator, the electric field strength in the space between the discharge electrode and the dust collection electrode is reduced. It is lowered by the space charge formed by the scattered particulate matter, and further reduces the dust collection efficiency. In addition, if particulate matter adheres to the discharge electrode with the passage of time, the generation of ions is hindered, so that the amount of charged particles decreases, and this also reduces the dust collection efficiency.

  In recent years, a method has been put into practical use in which the voltage applied between the electrodes of the electrostatic precipitator is a rectangular wave AC voltage to suppress the occurrence of the re-scattering phenomenon. It is difficult to completely suppress this.

  Moreover, in the case of the electric dust collector provided with the mesh-shaped dust collection electrode and dust collection filter which were shown by the said patent document 1, if the collection amount of a dust collection electrode and a dust collection filter increases, it will be clogged and Therefore, in order to solve this problem, the dust collection electrode and the dust collection filter must be regenerated in a comparatively short cycle, and there is a problem that maintenance is troublesome.

  In the exhaust gas purifying apparatus disclosed in Patent Document 2 as well, mechanical peeling is performed periodically to peel off the particulate matter retained by the particle holding action of the uneven portions on the uneven portions on the surface of the dust collecting electrode. There is a problem that a mechanism must be provided. Instead of providing this mechanical exfoliation mechanism, it has been proposed to exfoliate particulate matter in an enlarged state by causing a gas with a high flow rate to flow instantaneously at a predetermined time interval. Not only is it necessary to flow a fast gas instantaneously at a predetermined time interval, but re-scattering occurs due to induction charging of the particulate matter retained in the concavo-convex portion, and this can be completely prevented. There is a problem that can not be.

  In order to solve such a problem, the present invention improves the dust collection efficiency by utilizing the ion wind generated along with the discharge, and completely prevents the re-scattering phenomenon of the collected particulate matter. It is another object of the present invention to provide an electrostatic precipitator capable of extending the electrode regeneration processing cycle.

  In order to solve the above problems, the present invention provides a gas flow path in which a discharge electrode and a dust collection electrode are arranged opposite to each other in a gas flow path for flowing a gas containing particulate matter, and a high voltage is applied to both electrodes. In an electrostatic precipitator that charges and collects particulate matter in the gas flowing through the dust collecting electrode, the surface of the dust collecting electrode that faces the discharge electrode and contacts the gas flow A plurality of dust collection pockets having an internal space for retaining particulate matter collected at intervals in the flow direction of the gas flowing in the gas flow path are provided.

  The discharge electrode according to the present invention is preferably formed with a plurality of discharge portions at substantially the same interval as the dust collection pockets, and these discharge portions are arranged at positions separated from the front ends of the respective dust collection pockets. To do.

  In the present invention, the dust collection pocket may be provided with a gas flow port on the rear wall facing the opening of the internal space. Further, the dust collection pocket is characterized in that it is electrically coupled to the dust collection electrode and has the same electric potential so that the space electric field strength of the internal space is zero.

  According to the present invention, the discharge electrode and the dust collecting electrode are disposed opposite to each other in the gas flow path for flowing the gas containing the particulate matter, and the particles in the gas flowing through the gas flow path by applying a high voltage to both electrodes. In an electrostatic precipitator that is charged with a particulate material and sucked and collected by a dust collecting electrode, the dust collecting electrode faces the discharge electrode and flows in the gas flow path on a surface in contact with the gas flow Since there are a plurality of dust collection pockets with internal spaces that hold particulate matter at intervals in the gas flow direction, the charged particulate matter generates ion wind generated by the Coulomb force and discharge of the discharge electrode. When trapped by the dust collecting electrode and trapped by the dust collecting electrode, it is trapped in the internal space of the dust collecting pocket provided on the surface of the dust collecting electrode. Particulate matter confined in the dust collection pocket is shielded from the gas flow in the gas flow path, and the internal space of the dust collection pocket is charged by the suspended particulate matter because the space electric field strength becomes zero. Is not induced, and no peeling force due to the induced charge is generated, so that re-scattering of the particulate matter can be completely prevented.

  Embodiments of the present invention will be described based on examples shown in the drawings.

  1 to 3 show the construction of an electrostatic precipitator according to an embodiment of the present invention. FIG. 1 is a perspective view including a partial notch, and FIG. 2 is taken along the line II-II in FIG. FIG. 3 is a transverse sectional view, and FIG. 3 is a longitudinal sectional view taken along line III-III in FIG.

1 to 3, the electrostatic precipitator 1 includes a cylindrical main body case 3 that forms a gas flow path 2 having gas inlets 2A and outlets 2B at both ends. In the main body case 3, there is a pair of dust collecting electrodes 4 constituted by flat electrode plates opposed to each other with the gas flow path 2 interposed therebetween, and an intermediate between the pair of dust collecting electrodes 4, 4. A plurality of discharge electrodes 5 erected at predetermined intervals in the gas flow direction are provided.
A number of discharge portions 5A are formed by spine-shaped electrodes projecting from the outer periphery of the discharge electrode 5 toward the dust collection electrode 4. A plurality of dust collection pockets 6 are formed on the surfaces of the dust collection electrodes 4 and 4 facing each other by joining pocket forming members 6A formed by bending a flat plate like a bowl at substantially the same interval as the discharge electrodes 5. .

  The dust collection pocket 6 is surrounded by the pocket forming member 6 </ b> A and the dust collection electrode 4, and forms an internal space shielded from the gas flow flowing through the gas flow path 2. The internal space of the dust collection pocket 6 leads to the gas flow path 2 through an opening on the front end side opposed to the gas flow direction indicated by an arrow in FIG. 2, and holds and confines the particulate matter fed from here.

  Below the main body case 3, a hopper 8 for housing the particulate matter retained in the dust collection electrode 4 and the dust collection pocket 6 is provided integrally with the case 3. The bottom plate 7 that partitions the hopper 8 and the main body case 3 is provided with communication holes 7 </ b> A for communicating the internal space of the dust collection pocket 6 and the inside of the hopper 8 corresponding to all the dust collection pockets 6. (See FIG. 3).

  The gas flow path 2 of the electrostatic precipitator 1 configured as described above is supplied with a gas containing fine particulate matter such as diesel particles (DPM) from the flow path inlet 2A by a blower (not shown). The flow rate is about 10 m / s. In order to remove and purify the particulate matter from the gas flowing in the gas flow path 2, the average electric field strength between the two electrodes from a high voltage power source (not shown) between the dust collecting electrode 4 and the discharge electrode 5 is 2 to 10 kV. A high DC voltage of about / cm is applied.

  Accordingly, a corona discharge is generated in the gas flow flowing between the discharge electrode 5 and the dust collecting electrode 4 to which a high voltage is applied, and the particulate matter in the gas flow is charged by this discharge. Further, when a discharge is generated between the discharge electrode 5 and the dust collection electrode 4, an ion wind is generated in the direction in which the discharge occurs, that is, the direction in which the discharge current from the discharge electrode 5 to the dust collection electrode 4 becomes the largest. And the main fluid field, that is, the streamline of the gas flow in the gas flow path 2 changes. The charged particulate matter is attracted to the dust collecting electrode 4 by the Coulomb force, and the particulate matter flowing along the gas flow line is further deflected by the ion wind in a direction crossing the gas flow to collect the dust collecting electrode. Since it goes to 4 side, it collects favorably by the dust collection electrode 4.

  Details of the movement of the gas flow loaded with particulate matter will be described with reference to FIG.

  FIG. 4 is a diagram for explaining the operation of the present invention. FIG. 4A corresponds to the discharge portions of the discharge electrodes 5 provided at the same intervals as the intervals of the dust collection pockets 6 provided on the dust collection electrode 4. FIG. 2B shows a state in which the dust collection pocket 6 is located close to the front end (upstream side of the gas flow), and FIG. 2 shows a state of being arranged close to the rear end (downstream side of the gas flow) of the upstream dust collecting pocket 6 apart from the front end of the gas.

  First, in the state where the discharge electrode 5 is arranged close to the front end side of the dust collection pocket 6 as shown in (A), three pieces provided on the dust collection electrode 4 (here, one side is omitted). The dust collection pockets 62 and 63 in the dust collection pocket 6 and the discharge electrodes 52 and 53 of the discharge electrode 5 are shown as being in corresponding positions. Discharge electrodes 52 and 53 are arranged close to the front end side where dust collection pockets 62 and 63 are opened, respectively.

  In this state, a high voltage is applied to the dust collection electrode 4 and the discharge electrode 5 while flowing a gas containing particulate matter in the gas flow path 2. The main flow of the gas flowing in the gas flow path 2 is indicated by Vo.

  Further, here, the dust collection pocket 6 is conductively coupled to the dust collection electrode 4 and is at the same potential as the dust collection electrode 4, so that the spine-shaped outer periphery of the discharge electrode 5 having the smallest interval is formed. The discharge current becomes the largest between the discharge portion 5A and the front end of the dust collection pocket 6 on the side where the dust collection pocket 6 is opened, and the ion wind Via is generated here.

  Due to the discharge generated in such a gas flow, the particulate matter contained in the gas flow is charged. Particulate matter having a relatively large particle size and having a strong charge power is attracted by the dust collecting electrode 4 including the dust collecting pocket 6 by Coulomb force, and is retained and confined in the internal space of the dust collecting pocket 6. The fine particulate matter having a relatively small particle size with a relatively weak charge power is carried on the main flow line Vo of the gas, but since the ion wind Via is generated in the direction crossing the main flow line Vo by the discharge, the main gas flow Since this ion wind Via is applied to the line Vo, the direction of the gas stream line in the vicinity of the discharge electrode 5 is deflected toward the dust collecting electrode side 4 as shown by the combined flow Vra in the vector diagram shown in the upper part of FIG. The As a result, the fine particulate matter is also deflected toward the dust collecting electrode 4 side at an upper portion of the dust collecting pocket with an increased flow velocity.

  However, the arrangement of the discharge electrode shown in FIG. 4A is such that the discharge electrode 5 is provided close to the front end of the dust collection pocket 6 (the side facing the gas flow direction, that is, the upstream end). Therefore, the deflection of the gas stream line is small and the flow velocity is increased, so that the effect of confining the particulate matter in the internal space of the dust collection pocket 6 is almost not preferred.

  In order to increase the effect of pushing the particulate matter into the dust collection pocket, as shown in FIG. 4B, the discharge electrodes 52 and 53 are respectively connected to the front ends of the dust collection pockets 62 and 63 at the corresponding positions. It is good to arrange | position from the rear end side of the dust collection pockets 61 and 62 of the upstream from that.

  When the discharge electrodes are arranged in this manner, the distance between the discharge electrodes 52 and 53 and the dust collecting electrode 4 including the dust collecting pocket 6 is the smallest in the dust collecting pockets 62 and 63 at the corresponding positions. Adjacent upstream dust collection pockets 61 and 62 are formed, and discharge occurs near the rear end of the dust collection pocket adjacent to the upstream side, respectively, so that the largest discharge current flows.

  As a result, the flow direction of the ion wind Vib generated in this portion is directed to the upstream side of the gas flow as shown in the vector diagram of FIG. 4B, and thus the main gas flow line Vo flowing in the flow path 2. Is deflected toward the dust collecting electrode 4 at a deep angle as in the combined flow Vrb in the vector diagram. As a result, the main gas flow line Vo in the flow path 2 becomes a synthesis gas flow Vrb and is pushed deeply into the dust collection electrode 4 in front of the entrance (opening portion of the internal space) of each dust collection pocket 6. The charged particulate matter moving along the line is efficiently pushed into the internal space of the dust collection pocket 6 by the synthesis gas flow Vrb, and the effect of pushing the particulate matter into the dust collection pocket 6 can be enhanced. Moreover, the collection efficiency of particulate matter can be further increased.

  Here, since the internal space of the particulate matter in the dust collection pocket 6 is formed by the dust collection electrode 4 and the dust collection pocket forming member 6A having the same potential, the space electric field intensity becomes a region of zero. For this reason, the particulate matter confined in the internal space of the dust collection pocket 6 is discharged through the dust collection electrode 4 and the dust collection pocket 6 to become non-charged. No longer works. In addition, the particulate matter confined in the internal space of the dust collection pocket 6 is blocked from the gas flow flowing through the gas flow path 2 by the dust collection pocket 6 and is not affected by it. As a result, the particulate matter retained in the internal space of the dust collection pocket of the dust collection electrode is confined here, and does not leave and rescatter.

  When the amount of the particulate matter collected in the dust collection pocket increases, it naturally falls from the interior space of the dust collection pocket 6 and is stored in the hopper 8 from the communication hole 7A of the bottom plate 7 of the main body case 1. As a result, the dust collecting electrode 4 can stably continue the trapping action for a long period of time, so that the regeneration processing cycle can be greatly extended.

  In the above-described embodiment, the dust collection pocket provided in the dust collection electrode has a configuration in which the front end and the upper and lower ends are open and the rear end is closed. However, as shown in FIG. By providing minute ventilation holes 6H on the rear end wall and allowing gas to flow through the dust collection pocket 6, the generation of vortex flow in the dust collection pocket 6 can be suppressed. As a result, re-scattering due to the vortex of the particulate matter in the dust collection pocket can be prevented.

  In addition, the discharge electrode 5 used in the present invention may have various shapes as shown in FIGS. 6 (a) to 6 (e).

  The electrode (a) is constituted by a thin line, and the configuration is the simplest. The electrode (b) is obtained by implanting a needle-like discharge part into a rod-like electrode. (C) forms both side surfaces of a flat electrode plate in a sawtooth shape. (D) is a rod-shaped electrode provided with a star-shaped flat plate discharge portion. (E) is a rod-shaped electrode combined with a disc-shaped discharge portion.

  The discharge electrodes used in the present invention are not limited to those shown here, and other shapes can also be used.

It is a perspective view including a partial notch showing the configuration of the electrostatic precipitator according to the embodiment of the present invention. It is a longitudinal cross-sectional view which follows the II-II line | wire of FIG. FIG. 3 is a transverse sectional view taken along line III-III in FIG. 2. It is operation | movement explanatory drawing of this invention. It is sectional drawing which shows the 1st modification of the dust collection pocket part used for this invention. It is a figure which shows the shape of the discharge electrode used for this invention.

Explanation of symbols

1: Electric dust collector 2: Gas flow path 3: Body case 4: Dust collection electrode 5: Discharge electrode 6: Dust collection pocket

Claims (4)

  Disposing a discharge electrode and a dust collecting electrode oppositely in a gas flow path for flowing a gas containing particulate matter, and applying a high voltage to both electrodes to charge the particulate matter in the gas flowing in the gas flow path. In the electrostatic precipitator adapted to be sucked and collected by the dust collecting electrode, an interval in the flow direction of the gas flowing in the gas flow path is opposed to the discharge electrode of the dust collecting electrode and in contact with the gas flow. An electrostatic precipitator comprising a plurality of dust collecting pockets having an internal space for holding particulate matter collected after the storage.   2. The discharge electrode according to claim 1, wherein a discharge portion is formed in the discharge electrode at substantially the same interval as the dust collection pocket, and the discharge portion is disposed at a position separated from an open front end of each dust collection pocket. An electric dust collector characterized by that.   3. The electrostatic precipitator according to claim 1, wherein the dust collection pocket is provided with a gas flow port on a rear wall facing the front end opening.   4. The electric field strength of the internal space according to claim 1, wherein the dust collection pocket is electrically coupled to the dust collection electrode and has the same potential as the dust collection electrode. An electrostatic precipitator characterized by zeroing.

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