TW202012047A - Electric dust collector - Google Patents

Abstract

Provided is an electric dust collector that can effectively collect dust even at a dust collecting electrode on the side opposite to a corona discharge unit. The invention comprises: a discharge electrode (5) that has a main unit (5b) and a projection (5a) for corona discharge projecting from the main unit (5b); a discharge side dust collecting electrode (4a) that is located on the projection (5a) side; and an opposite side dust collecting electrode (4b) that is located on the side opposite to the discharge side dust collecting electrode (4a) with the discharge electrode (5) therebetween; wherein the center (C1) of the main unit (5b) of the discharge electrode (5) is located further from the discharge side dust collecting electrode (4a) than the central position (CL) between the discharge side dust collecting electrode (4a) and the opposite side dust collecting electrode (4b).

Description

Electric dust collector

The invention relates to an electric dust collector.

As a conventional electric dust collector, a plate-shaped dust collector electrode arranged in parallel along the air flow and a discharge electrode having a corona discharge part arranged at the center thereof are known. Regarding the shape of the corona discharge part of the discharge electrode, there is a structure in which the discharge electrode body generates the same concentration of the electric field by having a protruding shape to concentrate the electric field to ensure the corona discharge, such as a corner line or a thin piano wire, but In general industrial dust collectors, even if the electrodes are contaminated, a stable corona discharge is ensured. Therefore, a structure having a protruding corona discharge portion is the mainstream, and this structure is assumed as a premise below.

In the electric dust collecting device, by applying a high DC voltage between the dust collecting electrode and the discharge electrode, a stable corona discharge is carried out at the corona discharge part of the discharge electrode to charge the dust in the airflow. The previous dust collection theory explained that charged dust is trapped by the dust collector due to the action of the Coulomb force acting on the dust under the electric field between the discharge electrode and the dust collector.

However, the electric dust collectors of Patent Documents 1 and 2 include a dust collector, which has a plurality of through holes for passing the dust, and a closed space for trapping the dust inside. In Patent Documents 1 and 2, the enclosed dust is sealed in the closed space through the through hole, so that the collected dust is not easily scattered.

The electric dust collector of Patent Document 3 includes a dust collector including a ground electrode having an opening ratio of 65% to 85%, and a dust collection filter layer for trapping gas. By having such a dust collecting electrode, in Patent Document 3, ion wind is generated in a cross section orthogonal to the air flow, and a spiral air flow circulating between the discharge electrode and the dust collecting electrode is generated and efficiently collected dust. In Patent Document 3, although ion wind is actively used, the purpose of this example is mainly to collect dust with a dust collection filter layer. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 5671461 [Patent Document 2] Japanese Patent Publication No. 5705461 [Patent Document 3] Japanese Patent Publication No. 4823691

[Problems to be solved by the invention]

The dust collection efficiency η of the electric dust collector can be calculated by the following well-known odd formula (equation (1)). w is the dust collection index (movement speed of particulate matter), and f is the dust collection area per unit gas volume.

In the above formula (1), the moving speed w of dust (particulate matter) is determined by the relationship between the force of the Coulomb force and the viscosity resistance of the gas. In the multi-odd formula (formula (1) above), it is assumed that dust moves from the discharge electrode in the electric field, and the effect of ion wind on performance is not directly considered. However, before the performance design, it is mentioned that the distribution of dust concentration is usually based on the same premise as the cross section of the dust collecting space between the discharge electrode and the dust collecting electrode orthogonal to the airflow of the electric dust collecting device. One of the main reasons why the gas is chaotic and the dust concentration is the same.

When a negative voltage is applied between the electrodes by the ion wind system, negative ions are generated by the corona discharge of the discharge electrode, and those generated as a result are generated by positive ions in the case of positive voltage. In the following, in this specification, industrial electric dust collectors are taken as the basis, so examples of applying negative voltages are described, and the same applies to positive voltages.

In an electric dust collecting device with electrode groups arranged along the airflow, the ion wind generated by the discharge electrode flows in a manner crossing the airflow toward the dust collecting electrode. The ion wind reaching the dust collecting pole is reversed by the dust collecting pole, and the flow direction is changed. As a result, a spiral turbulent flow is generated between the electrodes.

In the turbulent flow, the flow from the discharge electrode toward the dust collecting electrode has the effect of sending the dust to the vicinity of the dust collecting electrode. The dust sent to the dust collecting pole is finally collected by Coulomb.

However, the ion wind reversed by the dust-collecting pole moves the dust in a direction away from the collecting body, that is, the dust-collecting pole, so it also acts as a hindrance to dust collection. Therefore, it is more effective to provide an opening in the dust collecting pole to prevent the ion wind from reversing.

Patent Document 3 describes an electric dust collector that also considers the effect of ion wind. However, in this example, the structure for sending ion wind to the filter layer behind the dust collecting electrode with an opening is aimed at collecting dust at a location not affected by the main gas, and the structure is also complicated, and is dry. It is difficult to peel off and collect attached dust during operation.

In addition, the corona discharge generated by the corona discharge part protruding from the body part of the discharge electrode causes the ion wind to flow to the dust collecting electrode side along with the corona current, but the discharge electrode is not provided with corona discharge Between the dust-collecting poles on the opposite side of the part, the ion wind cannot be used because there is no corona discharge. In addition, on the opposite side of the area where the corona discharge part is not provided, the corona current or the amount of charge in the dust collecting space of the charged dust is less than that of the corona discharge part, so the increase in the electric field strength near the dust collecting pole and the corona discharge part The dust collection effect of the Coulomb force is also weakened compared to the side. Therefore, the inventors focused on actively using the dust collecting electrode on the opposite side of the corona discharge part.

The present invention has been completed in view of such circumstances, and its object is to provide an electric dust collector that can effectively collect dust on the opposite side of the corona discharge part. [Technical means to solve the problem]

An electric dust collector according to an aspect of the present invention includes: a discharge electrode having a body portion and a corona discharge portion for corona discharge protruding from the body portion; a discharge side dust collector electrode located at the corona discharge portion Side; and the opposite side dust collector electrode, which is located on the opposite side of the discharge side dust collector electrode through the discharge electrode; and the center of the body portion of the discharge electrode is located more than the discharge side dust collector electrode and the opposite side dust collector The central position between the electrodes is further away from the above-mentioned discharge side dust collecting electrode.

The discharge electrode has a corona discharge portion that protrudes only toward the discharge side dust collecting electrode of one of the dust collecting electrodes. Thereby, the corona discharge from the corona discharge part only to the discharge side dust collecting electrode can cause the ion wind to flow. This method can make the interference of the ion wind between the discharge electrode opposed to the dust collector electrode disappear due to the flow of ion wind on both sides due to the corona discharge parts on both sides of the common discharge electrode. Advantage. However, the dust collecting electrode located on the opposite side of the discharge side dust collecting electrode via the discharge electrode, that is, the opposite side of the corona discharge part, does not face the corona discharge part, so that corona discharge hardly occurs. However, since the center of the body portion of the discharge electrode is located further away from the discharge side dust collection electrode than the center position between the discharge side dust collection electrode and the opposite side dust collection electrode, the body portion of the discharge electrode is close to the opposite side dust collection electrode . In this way, the electric field strength between the body portion of the discharge electrode and the dust collecting electrode on the opposite side can be increased, and the dust collection efficiency can also be improved in the electrode on the opposite side due to the increase in Coulomb force. The center of the body portion of the discharge electrode is preferably positioned more than 10 mm away from the opposite side of the dust collecting electrode when the distance between the discharge side dust collecting electrode and the opposite side dust collecting electrode is 300 mm or more and 500 mm or less, for example. As the dust collecting electrode, for example, a discrete-type dust collecting electrode in which a plurality of rigid members are arranged at specific intervals is cited. As a member having rigidity, for example, a member whose body portion is in the shape of a catheter is cited. In addition, as another type of dust collecting electrode, for example, a flat plate dust collecting electrode provided with a plate-like body having a plurality of through holes is cited. As the flat dust collector, for example, punched metal or metal mesh is used.

Furthermore, in an electric dust collector of one aspect of the present invention, the distance between the center of the body portion of the discharge electrode and the discharge side dust collection electrode is D1, and the center of the body portion of the discharge electrode When the distance from the dust collecting electrode on the opposite side is D2, it is set to 1.1≦D1/D2≦2.0.

By setting 1.1≦D1/D2≦2.0, the electric field strength between the body part of the discharge electrode and the opposite side dust collecting electrode can be increased, and the electric field strength can be made close to the electric field between the corona discharge part and the electrode side dust collecting electrode strength. Compared with the case of 1.1>D1/D2, the dust collection performance is improved. Unlike the case of D1/D2>2.0, it can prevent the occurrence of spark discharge.

Furthermore, in an electric dust collector of one aspect of the present invention, the discharge side dust collection electrode and the opposite side dust collection electrode are arranged in one direction, respectively, and the D1 is the center of the body portion of the discharge electrode and the discharge side The distance between the arrangement positions of the dust collecting electrodes, D2 is the distance between the center of the body portion of the discharge electrode and the arrangement position of the opposite dust collecting electrodes.

The discharge-side dust-collecting electrode and the opposite-side dust-collecting electrode are respectively arranged in one direction, D1 is the arrangement direction relative to the discharge-side dust-collecting electrode, the center of the body of the discharge electrode and the discharge-side dust-collecting electrode are arranged in the vertical direction The distance between them, D2 is the distance between the center of the body of the discharge electrode and the arrangement position of the opposite dust collecting pole in the vertical direction relative to the arrangement direction of the opposite dust collecting pole.

Furthermore, in an electric dust collector of one aspect of the present invention, the electric field strength between the discharge electrode and the discharge side dust collector electrode is equal to the electric field strength between the discharge electrode and the opposite side dust collector electrode.

By making the electric field strength between the discharge electrode and the discharge side dust collecting electrode equal to the electric field strength between the discharge electrode and the opposite side dust collecting electrode, the center of the body of the discharge electrode can be positioned between the two dust collecting electrodes In the center, increase the electric field strength between the discharge electrode and the electrode on the opposite side.

Furthermore, in an electric dust collector of one aspect of the present invention, the front end of the corona discharge portion is located closer to the opposite side than the center position between the discharge side dust collecting electrode and the opposite side dust collecting electrode Dust pole side.

By making the front end of the corona discharge part closer to the opposite side of the dust collecting electrode than the central position between the two dust collecting electrodes, the electric field strength between the corona discharge part and the discharge side dust collecting electrode can be reduced and the discharge can be increased The electric field strength between the body of the electrode and the electrode on the opposite side. [Effect of invention]

By increasing the electric field strength between the body of the discharge electrode and the opposite side dust collecting electrode, the dust collecting efficiency can be improved by the improvement of the Coulomb force in the opposite side electrode, even if it is the opposite side dust collecting electrode, it can be further effective To collect dust.

Hereinafter, an embodiment of the electric dust collector of the present invention will be described with reference to the drawings.

The electric dust collector 1 is used for, for example, coal-fired thermal power generation equipment to collect dust (particulate matter) in fuel exhaust gas discharged from a boiler. In addition, the size of each component of the electric dust collector 1 is different from that of thermal power generation equipment. It is installed in a building or underground space, etc., and collects fine particulate matter (such as PM2.5, etc.) to purify the air in the space.

The electric dust collector 1 includes a plurality of conductive dust collector electrodes 4 made of metal, for example. The dust collecting pole 4 is a circular duct having a hollow cylindrical shape with a circular cross section, and is arranged at a predetermined interval in the x direction (air flow G direction) orthogonal to the z direction, which is the longitudinal direction. The rows of the dust-collecting poles 4 arranged in the x direction are arranged in parallel at a certain interval in the y direction orthogonal to the z direction and the x direction, and are arranged in parallel. Between each row of the dust collecting electrode 4, a discharge electrode 5 is arranged in the x-z plane. In FIG. 1, the position of the mounting frame 5c of the discharge electrode 5 is shown. As can be seen from FIG. 1, the discharge electrode 5 is deviated from the central position CL between the dust collecting electrodes 4 arranged in the y direction orthogonal to the air flow G direction to one of the dust collecting electrodes 4 side (the right side in the y direction in FIG. 1) shift.

The dust collector 4 is grounded. The discharge electrode 5 is connected to a power source having a negative polarity (not shown). In addition, the power source connected to the discharge electrode 5 may also have a positive polarity.

As shown in FIG. 2, the discharge electrode 5 includes a body portion 5b fixed to the mounting frame 5c, and a plurality of protruding portions (corona discharge portions) 5a protruding from the body portion 5b. The protrusion 5a is provided so as to protrude toward the front end only on the dust collecting electrode 4 side of one. The protrusion 5a is arranged between the dust collecting pole 4 in the x direction of the air flow G direction. A corona discharge is generated in the protrusion 5a, and ion wind is generated from the front end of the protrusion 5a toward the opposing dust collecting electrode 4 side.

As shown in FIG. 2, the center C1 of the body portion 5 b of the discharge electrode 5 is offset from the center position CL between the dust collecting electrodes 4. Specifically, the center C1 of the body portion 5b of the discharge electrode 5 is away from the dust collecting electrode 4 facing the protrusion 5a (hereinafter, this dust collecting electrode 4 is referred to as "discharge side dust collecting electrode 4a") And, it is displaced from the central position CL so as to approach the dust collecting electrode 4 on the opposite side of the protrusion 5a (hereinafter, this dust collecting electrode 4 is referred to as "the opposite side dust collecting electrode 4b"). Therefore, the distance D1 viewed along the y direction between the center C1 of the main body portion 5b and the center C2 passing through the discharge side dust collecting electrode 4a is greater than the center C1 along the main body portion 5b and the center passing through the opposite side dust collecting electrode 4b The distance D2 (D1>D2) observed in the y direction between the arrangement positions of C3. In addition, since the discharge electrode 5 and the dust collecting electrode 4 are alternately arranged in the y direction, in one dust collecting electrode 4, the protruding portion 5a side is the discharge side dust collecting electrode 4a, and the opposite side of the protruding portion 5a is the opposite side dust collecting electrode 4b.

The distance D1 is the distance between the arrangement position of the center C1 of the body portion 5b of the discharge electrode 5 and the center C2 of the dust collecting electrode 4a passing through the discharge side. That is, D1 is between the center C1 of the main body portion 5b of the discharge electrode 5 and the arrangement position (center axis) of the discharge side dust collector 4a in a direction perpendicular to the arrangement direction of the discharge side dust collector 4a Distance.

The distance D2 is the distance between the center C1 of the body portion 5b of the discharge electrode 5 and the arrangement position of the center C3 passing through the dust collecting electrode 4b on the opposite side. That is, D2 is between the center C1 of the main body portion 5b of the discharge electrode 5 and the arrangement position (center axis) of the opposite side dust collecting electrode 4b in a direction (y direction) perpendicular to the arrangement direction of the opposite side dust collecting electrode 4b Distance.

The front end of the protrusion 5a is arranged, for example, when the distance from the center of the body portion 5b of the discharge electrode 5 to the front end of the discharge portion, that is, Dd/2+Lb (see FIG. 4B) is set to less than 30 mm, preferably about 20 mm In this case, it is located closer to the opposite side of the dust collecting electrode 4b than the center position CL.

As described above, since the protrusions 5a are oriented in one direction and are arranged between the dust collecting electrodes 4 in the x direction, the ion wind from the protrusions 5a toward the discharge side dust collecting electrodes 4a is oriented in substantially the same direction, which can avoid ions Wind interference.

Fig. 3 is a front view of Fig. 1 viewed from the direction of the air flow G. As shown in the figure, the protrusions 5a are provided at specific intervals in the height direction.

4A shows the positional relationship when the dust collecting electrode 4 and the discharge electrode 5 are viewed from above. Let the interval of the dust collecting electrodes 4 arranged in the x direction of the airflow G be Pc, and the interval of the discharge electrodes 5 arranged in the x direction be Pd. In addition, the interval between the dust collecting electrodes 4 arranged in the y direction is set to 2D. Let the diameter of the dust collecting electrode 4 be Dc.

In this embodiment, the offset position of the discharge electrode 5, that is, the position where the center of the body portion 5b of the discharge electrode 5 is displaced from the central position CL in the y direction, it is preferable to set the ratio of the distance D1 to the distance D2 to 1.1≦D1 /D2≦2.0. It is better to set the lower limit of D1/D2 to 1.2.

The distance between the front end of the protrusion 5a of the discharge electrode 5 and the side surface of the nearest discharge side dust collecting electrode 4a is set to L1, and the body portion 5b on the opposite side of the protrusion 5a of the discharge electrode 5 and the nearest opposite dust collecting electrode The distance between the sides of 4b is set to L2. In addition, the curve drawn between the discharge electrode 5 and the dust collecting electrode 4 shown in FIG. 4A is a power line.

FIG. 4B shows an enlarged cross-section of a height position corresponding to the protrusion 5a of the discharge electrode 5. As shown in the figure, the body portion 5b of the discharge electrode 5 has a circular cross section, and its diameter is set to Dd. The length of the protrusion of the protrusion 5a protruding from the body 5b is set to Lb.

且，放電極5之本體部5b之中心自中央位置CL向y方向移位之偏移量Le由下式表示。

另，圖4A及圖4B中顯示有刺狀之突起部5a之位置之剖面之例，但實際上突起部5a所佔部分為放電極5之一部分，相鄰二個突起部5a間之部分佔放電極5之大部分。因此，亦可忽視突起部5a之長度Lb而評估L1、L2。If the parameters shown in FIGS. 4A and 4B are used, L1 and L2 can be expressed as follows.

Moreover, the offset Le of the center of the body portion 5b of the discharge electrode 5 displaced from the central position CL in the y direction is expressed by the following formula.

In addition, FIGS. 4A and 4B show an example of a cross section of the position of the thorn-shaped protrusion 5a, but actually the portion occupied by the protrusion 5a is a part of the discharge electrode 5, and the portion between the two adjacent protrusions 5a Most of the discharge electrode 5. Therefore, the length Lb of the protrusion 5a can be ignored and L1 and L2 can be evaluated.

The distance 2D between the dust collecting electrodes 4 arranged in the y direction is set to 300 mm or more and 500 mm or less for general industrial use, for example. However, in other applications, it can also be set to other sizes.

Next, the effect of the case where the discharge electrode 5 is shifted will be described using FIGS. 5A to 6B.

FIGS. 5A and 5B show the electric field intensity distribution when there is no offset with the offset Le=0, that is, when the body portion 5b of the discharge electrode 5 is disposed at the central position CL. As shown in FIG. 5A, the corona current flows between the protruding portion 5a and the discharge-side dust collecting electrode 4a, and the electric field intensity E1max near the discharge-side dust collecting electrode 4a is due to the negative ions existing in the space and the space charge of the charged dust And rise. The electric field intensity (Ecr) of the spark discharge limit near the discharge side dust collecting electrode 4a becomes the condition of the maximum applied maximum electric field intensity (E1max≦Ecr).

On the other hand, as shown in FIG. 5B, since there is no increase in space charge as shown in FIG. 5A between the opposite side of the protruding portion 5a and the opposite side dust collecting electrode 4b, the electric field intensity E2max near the opposite side dust collecting electrode 4b Less than E1max. In addition, the areas A1 and A2 that integrate the electric field strength with the distances L1 and L2 correspond to the applied voltage Vo, respectively, and thus become equal values.

6A and 6B show the electric field intensity distribution between the discharge electrode 5 and the dust collecting electrode 4 corresponding to the present embodiment, and in the case where the discharge electrode 5 is shifted from the central position CL. 6A corresponds to FIG. 5A, and FIG. 6B corresponds to FIG. 5B.

As shown in FIGS. 6A and 6B, the electric field strength between the protruding portion 5a and the discharge side dust collecting electrode 4a becomes L1>L2 or D1>D2 due to the offset, so if the electric field intensity E1max near the discharge side dust collecting electrode 4a is The voltage Vo, which is the same as the case without offset, is further lower than that in FIG. 5A, and E1ave. (=Vo/L1) also becomes smaller. On the other hand, due to the offset, L2 is smaller than in the case of FIG. 5B, and the average electric field strength E2ave. becomes larger, which can increase the electric field strength E2max near the opposite dust collecting electrode 4b.

Generally speaking, the E1max during operation is less than the spark discharge limit electric field strength Ecr, but the distance on the protrusion side becomes longer due to the offset, so the electric field strength becomes the same as the original E1max compared to the case without offset. Therefore, the applied line voltage Vn itself (Vn>Vo) can be increased, and the maximum electric field intensity E2max on the side opposite to the protrusion can be further increased. In this way, by increasing the applied voltage while shifting, the electric field strength E1max is maintained equal to that before the shift, and E2max is increased to the same level as E1max, thereby improving the dust collection effect near the dust collector. The electric field strength of the part and improve the collection efficiency according to the Coulomb force. In addition, due to the offset, the distance of the corona discharge side becomes larger, and the moving distance of the dust moving between them becomes larger, but the movement of the dust in this part mainly depends on the ion wind, so the reaching distance slightly increases or the average electric field strength in the middle The reduction will not negatively affect the performance, and may be due to the increase in the electric field strength E2max near the opposite side dust collecting electrode 4b of the dust bypassing the dust collecting electrode 4b on the back side of the discharge side dust collecting electrode 4a Improve performance.

The offset Le is preferably adjusted so that the electric field intensity E1max of the discharge side dust collecting electrode 4a and the electric field intensity E2max of the opposite side dust collecting electrode 4b are equal. The examples of the electric field intensity shown in FIGS. 5A to 6B are examples in which the duct-shaped dust collecting electrodes 4 are arranged at intervals, and are described based on the shortest distances of L1 and L2. As an example of the electrode of the dust collecting electrode 4, there are mesh-shaped electrodes, etc., so the following is the defined offset, and the arrangement position passing through the centers C2, C3 of the dust collecting electrode 4 and the center C1 of the discharge electrode 5 The distances, D1 and D2, are described together. In this case, even if it is a catheter-shaped electrode, even if it is evaluated by D1, D2 instead of L1, L2, it can be regarded as approximately equal in the practical range, so there is no obstacle.

The range in which the electric field strengths of the two are equal is, for example, 1.5≦D1/D2≦1.8. However, the optimal range of D1/D2 varies according to the operating conditions of the electric dust collector 1 or the conditions of the dust collecting electrode 4 or the discharge electrode 5.

The lower limit of the ratio D1/D2 between the distance D1 and the distance D2 is, for example, 1.1, and more preferably 1.2. As shown in FIG. 10, the insight that the relationship between the offset and the dust collection performance changes according to the flow velocity of the air flow G is obtained. When the airflow G is relatively fast, if D1/D2 becomes 1.1 or more, the dust collection performance is improved. When the airflow G is relatively slow, if D1/D2 becomes 1.2 or more, the dust collection performance is improved, and within this range, when the airflow G is relatively fast, the dust collection performance is indeed improved.

Under the condition that the flow rate of the airflow G is faster, the increase in the electric field strength is affected due to the greater Coulomb force. Even with a small offset (for example, 1.1≦D1/D2), the dust collection performance is also improved. On the contrary, under the condition of slow flow velocity, the influence of ion wind is greater, so the dust collection performance is improved due to the increase of the electric field strength, and a larger offset is required (for example, 1.2≦D1/D2). If 1.2≦D1/D2, the dust collection performance can be improved regardless of the flow rate of the airflow G.

If the offset is too large, the electric field strength near the dust collecting electrode on the opposite side becomes E2max>E1max, and the electric field strength of the spark discharge limit on the opposite side of the corona discharge part becomes the operational constraint, and the performance on the corona discharge side cannot be exerted , Which is not good. Therefore, it is preferable to set the maximum offset within a range where E2max does not greatly exceed E1max.

FIG. 11 shows the corona discharge side when the D1/D2 is changed in the general industrial electric dust collector 1 (the side where the body 5b of the discharge electrode 5 has the protrusion 5a, that is, the side where the discharge line is thorny ) The electric field strength near the discharge side dust collecting electrode 4a and the electric field side near the dust collecting electrode 4b on the opposite side of the electric field side (the side where the body portion 5b of the discharge electrode 5 does not have the protrusion 5a, ie, the non-thorn side) Examples of strength analysis and comparison. The current and voltage which are the operating conditions of the electric dust collector 1 are raised together. In FIG. 11, as the graph from left to right progresses, the current voltage becomes higher.

In any case, when D1/D2=1, not only the discharge side dust collector 4a on the thorn side is closer due to the length of the thorn, but also the electric field rises due to the space charge of the corona current As a result, the electric field intensity of the discharge side dust collecting electrode 4a on the barbed side is high. Moreover, as the current increases, its rising effect becomes larger, and the electric field intensity value becomes higher.

On the other hand, the situation in any of the graphs in FIG. 11 also shows that as D1/D2 increases, the electric field intensity of the dust collecting electrode 4b on the opposite side of the non-barbed side increases uniformly. Ideally, the point where the electric field strength on the barbed side and the non-barbed side coincide is the most balanced distribution of electric field strength. However, in actual operation, due to the combination of various conditions, the optimal conditions have changed. Therefore, in the test results related to the improvement of the dust collection performance when D1/D2 in FIG. 10 is changed, even if it is the optimal point of the dust collection performance, there is a certain degree of deviation.

In addition, in the graph on the right side of FIG. 11, even when the current and voltage increase, especially in the area with a large offset D1/D2, the dust collector 4b on the opposite side of the non-barbed side will first exceed the general industrial use. The electric field intensity of the spark discharge of the electric dust collector 1 (although there is a large difference depending on the composition of the gas or the operating temperature condition, it is usually set to 8 kV/cm to 12 kV/cm), which is not good. More specifically, it is preferably D1/D2≦2.0.

If D1/D2 exceeds 2.0, the electric field intensity on the opposite side of the dust collecting electrode 4b reaches the area where spark discharge occurs under normal operating conditions of the electric dust collecting device 1, or close to the reached value. Therefore, it is difficult to operate stably due to the restriction of the operating conditions of the electric dust collector 1. Therefore, it is preferable to set the upper limit of D1/D2 to 2.0.

Next, the operation of the electric dust collector 1 of this embodiment will be described. In the electric dust collector 1, by applying a negative electrode to the discharge electrode 5 from a power source, a corona discharge is generated at the front end of the protrusion 5a. The dust contained in the airflow G is charged by corona discharge. According to the previous collection principle of the electric dust collector, the charged dust is attracted to the grounded dust collector 4 due to the Coulomb force, and is trapped on the dust collector 4, but in reality, the influence of ion wind exerts A greater effect.

When a corona discharge occurs, negative ions are generated in the vicinity of the protrusion 5a, and the negative ions move toward the dust collecting electrode 4 by an electric field to generate ion wind. Therefore, while the Coulomb force acts on the dust, the ion wind flowing toward the dust collecting electrode 4 acts so that the dust contained in the air flow G moves to the vicinity of the discharge side dust collecting electrode 4a. In addition, in the area near the dust collecting electrode 4a on the discharge side, the Coulomb force is increased by the increase of the electric field strength, and the dust is effectively collected. In addition, the dust collecting electrode 4 which is a circular duct is arranged at a certain air flow direction G, that is, in the x direction with a space therebetween, so that a part of the ion wind flowing from the protrusion 5a to the discharge side dust collecting electrode 4a is allowed to reach the dust collecting electrode 4 The back side escapes. As a result, the flow of ion wind that reverses and deviates from the dust collecting electrode 4 can be suppressed, so the collection efficiency is improved.

Part of the ion wind that contains dust and flows toward the dust collecting pole 4 passes between the dust collecting poles 4. Since the ion wind is oriented in one direction, it will not interfere with each other.

On the other hand, between the dust collecting electrode 4b on the opposite side to the opposite side of the protrusion 5a, as explained using FIG. 6B, by displacing the discharge electrode 5 from the center position CL, the vicinity of the dust collecting electrode 4b on the opposite side can be made The electric field strength E2max increases compared with no offset. Thereby, the dust collecting pole 4b on the opposite side to the opposite side of the protrusion 5a also efficiently collects dust by the Coulomb force. That is, the uncollected dust that bypasses the dust collecting electrode 4b on the back side of the dust collecting electrode 4, that is, the back side of the dust collecting electrode 4, can be efficiently collected by the ion wind.

The dust collected by the dust collecting pole 4 is stripped and recovered by thrashing. Alternatively, the dust collector can be moved and wiped off with a brush or wet cleaning.

According to this embodiment, the following effects can be exerted. Since the center of the body portion 5b of the discharge electrode 5 is located further away from the direction of the discharge side dust collecting electrode 4a than the center position CL between the discharge side dust collecting electrode 4a and the opposite side dust collecting electrode 4b, the body portion 5b of the discharge electrode 5 and The dust collecting pole 4b on the opposite side approaches. Thereby, the electric field strength between the body portion 5b of the discharge electrode 5 and the opposite side dust collecting electrode 4b can be increased, and the dust collecting efficiency can also be improved by the Coulomb force in the opposite side electrode 4b.

In addition, in the above-mentioned embodiment, as the configuration of the discharge electrode 5, the protrusion 5a is provided to the body portion 5b having a circular cross section, but as shown in FIG. 7A, it may also be configured to have a rectangular cross section The corner bar 5b' is provided with a protrusion 5a. Alternatively, as shown in FIG. 7B, it may be formed through a flat plate, and the protrusion 5a and the body 5b'' are integrally formed.

Moreover, as shown in FIGS. 8A and 8B, instead of the dust collecting electrode 4 as the above-mentioned circular duct, a flat metal dust collecting electrode 4'like a punching metal in which a plurality of holes are formed in a flat plate may be used. Or, as shown in FIGS. 9A and 9B, a bent plate-shaped dust collecting electrode 4'' which alternately and regularly folds back a metal-like flat plate formed with a plurality of holes in the direction of the air flow G may be used. In this case, the protrusion 5a of the discharge electrode 5 is shifted according to the unevenness of the oppositely bent plate.

In addition, the dust collecting electrode 4 may also be a braided metal mesh (for example, a lock crimped braided metal mesh, etc.) in which metal wires are crossed in the longitudinal direction and the transverse direction. Since the braided metal mesh has a certain aperture ratio and the surface has no edges, the electric field intensity near the dust collecting electrode 4 can be similarly increased. In addition, the metal mesh is not limited to the woven metal mesh, but may also be a wire cross-sectionally arranged and connected in a longitudinal direction and a lateral direction like a welded metal mesh.

When the electric dust collector 1 is used as an air washer during air purification, the particles stay in the device for a short time and the particle concentration is low. On the other hand, the electric dust collector 1 used in thermal power generation equipment is different from the one used for air purification. It has a larger scale, a longer particle retention time, and a higher particle concentration. In the electric dust collector 1 for air purification, if low-concentration particles are passed through with a short residence time, the particles cannot be captured by the effect of the gas circulation generated by the ion wind from the protrusion 5a of the discharge electrode 5 To dust collector 4.

Therefore, as shown in FIG. 12, it is preferable to provide the gas cutoff plate 6 on the upstream side of the air flow G between the dust collecting electrode 4 b on the opposite side and the discharge electrode 5. By blocking the airflow G with the gas cutting plate 6, the flow rate of the airflow flowing between the dust collecting electrode 4b on the opposite side and the discharge electrode 5 can be reduced, the retention time of the particles passing through the dust collecting electrode 4 can be extended, and the collection performance can be improved.

1: Electric dust collector 2D: interval 4: dust collector 4': Flat dust collector 4'': Bending plate-shaped dust collector 4a: Dust collector on the discharge side 4b: Dust collector on opposite side 5: discharge electrode 5a: Protruding part (corona discharge part) 5b: Body part 5b': corner stick 5b'': Body part 5c: Installation frame 6: Gas cut-off board A1, A2 area C1: (of the body of the discharge electrode) center C2: Center C3: Center CL: Central location D1: distance D2: distance Dc: diameter Dd: diameter E1ave.: Average electric field strength E1max: electric field strength E2ave.: average electric field strength E2max: electric field strength G: Airflow f: dust collection area L1: distance L2: distance Lb: protrusion length Le: offset Pc: interval Pd: interval Vn: apply line pressure Vo: applied voltage w: dust collection index x: direction y: direction z: direction η: dust collection efficiency

FIG. 1 is a perspective view showing an electric dust collector according to an embodiment of the present invention. FIG. 2 is a plan view of the electric dust collector of FIG. 1 viewed from above. FIG. 3 is a front view of the electric dust collector of FIG. 1 viewed from the air flow direction. 4A is a plan view showing the positional relationship between the dust collecting electrode and the discharge electrode. 4B is a cross-sectional view corresponding to the height position of the protrusion of the discharge electrode. FIG. 5A is a graph showing the electric field strength between the discharge side discharge electrode and the dust collecting electrode without deviation. FIG. 5B is a graph showing the electric field strength between the discharge electrode and the dust collecting electrode on the opposite side in the case of no offset. 6A is a graph showing the electric field strength between the discharge side discharge electrode and the dust collecting electrode in the case of deviation. 6B is a graph showing the electric field intensity between the discharge electrode and the dust collecting electrode on the opposite side in the case of deviation. 7A is a front view showing a variation of the discharge electrode. FIG. 7B is a front view showing another modification of the discharge electrode. FIG. 8A is a plan view showing a variation of the dust collecting pole. FIG. 8B is a front view showing a variation of the dust collecting pole. Fig. 9A is a plan view showing another variation of the dust collecting electrode. FIG. 9B is a front view showing other modified examples of the dust collecting pole. Fig. 10 is a graph showing the relationship between the dust collection performance index ratio and the offset ratio. Fig. 11 is a graph showing the relationship between the electric field intensity near the dust collecting pole and the offset ratio. 12 is a plan view showing an electric dust collector according to an embodiment of the present invention.

4: dust collector

4a: Dust collector on the discharge side

4b: Dust collector on opposite side

5: discharge electrode

5a: Protruding part (corona discharge part)

5b: Body part

5c: Installation frame

C1: (of the body of the discharge electrode) center

C2: Center

C3: Center

CL: Central location

D1: distance

D2: distance

G: Airflow

x: direction

y: direction

Claims (5)

An electric dust collector, including: The discharge electrode has a body part and a corona discharge part for corona discharge protruding from the body part; A dust collecting electrode on the discharge side, which is located on the side of the corona discharge portion; and The dust collector on the opposite side is located on the opposite side of the dust collector on the discharge side through the discharge electrode; and The center of the body portion of the discharge electrode is located further away from the discharge side dust collecting electrode than the center position between the discharge side dust collecting electrode and the opposite side dust collecting electrode. As in the electric dust collector of claim 1, where The distance between the center of the body of the discharge electrode and the discharge side dust collector is D1, and the distance between the center of the body of the discharge electrode and the opposite dust collector is D2 , Set to: 1.1≦D1/D2≦2.0. As in the electric dust collector of claim 2, where The discharge-side dust-collecting pole and the opposite-side dust-collecting pole are arranged in one direction respectively; The D1 is the distance between the center of the body of the discharge electrode and the arrangement position of the discharge side dust collector; The D2 is the distance between the center of the body portion of the discharge electrode and the arrangement position of the dust collector on the opposite side. The electric dust collector according to any one of claims 1 to 3, wherein the electric field strength between the discharge electrode and the discharge side dust collection electrode is equal to the electric field strength between the discharge electrode and the opposite side dust collection electrode. The electric dust collector according to any one of claims 1 to 3, wherein the front end of the corona discharge portion is located closer to the opposite side than the center position between the discharge side dust collecting electrode and the opposite side dust collecting electrode Dust collector side.

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