WO2020036185A1

WO2020036185A1 - Electric dust collector

Info

Publication number: WO2020036185A1
Application number: PCT/JP2019/031901
Authority: WO
Inventors: 一隆富松; 加藤　雅也; 上田　泰稔
Original assignee: 三菱日立パワーシステムズ環境ソリューション株式会社
Priority date: 2018-08-15
Filing date: 2019-08-14
Publication date: 2020-02-20
Also published as: TW202012047A; TWI742415B

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 present invention relates to an electric precipitator.

As a conventional electric dust collecting device, there is known an electric dust collecting device including a plate-shaped dust collecting electrode arranged in parallel along a gas flow and a discharge electrode having a corona discharge portion arranged in the center thereof. The shape of the corona discharge part of the discharge electrode has a protruding shape to cause the concentration of the electric field to secure corona discharge, and a structure that causes the discharge electrode body to generate a uniform electric field concentration, for example, a square wire However, most industrial electric precipitators have a structure with a protruding corona discharge section in order to ensure stable corona discharge even if the electrodes are contaminated. Assume the structure.

In the electrostatic precipitator, the dust in the gas flow is charged by applying a high DC voltage between the precipitating electrode and the discharge electrode and performing a stable corona discharge at the corona discharge portion of the discharge electrode. The conventional dust collection theory explains that the charged dust is collected by the dust collecting electrode by the action of Coulomb force acting on the dust under the electric field between the discharge electrode and the dust collecting electrode.

電気 By the way, the electric precipitators of

Patent Documents

1 and 2 are provided with a plurality of through holes for passing dust, and a dust collecting electrode having a closed space for collecting dust therein. In

Patent Documents

1 and 2, trapped dust is hardly re-scattered by confining dust in a closed space via the through hole.

電気 The electric dust collector of Patent Document 3 includes a dust collecting electrode including a ground electrode having an aperture ratio of 65% to 85%, and a dust collecting filter layer for collecting gas. According to Patent Document 3, by providing such a dust collecting electrode, an ion wind is generated in a cross section orthogonal to the gas flow, and a spiral gas flow circulating between the discharge electrode and the dust collecting electrode is generated. , To collect dust efficiently. In Patent Literature 3, ion wind is positively used, but the purpose of this case is to collect dust mainly in the dust filter layer.

Japanese Patent No. 5761461 Japanese Patent No. 5705461 Japanese Patent No. 4823691

The dust collection efficiency η in the electric dust collector can be calculated by the following well-known Deutsche equation (Equation (1)). w is a dust collecting index (moving speed of particulate matter), and f is a dust collecting area per unit gas amount.
η = 1−exp (−w × f) (1)

式 In the above equation (1), the moving speed w of the dust (particulate matter) is determined to be determined by the relationship between the Coulomb force and the viscous resistance of the gas. In Deutsche's formula (formula (1)), it is assumed that dust moves in the electric field from the discharge electrode, and the ion wind is not directly considered in affecting the performance. However, the premise of the performance design is that the dust concentration distribution is always uniform in the cross section of the dust collection space between the discharge electrode and the collection electrode perpendicular to the gas flow of the electric precipitator. The ion wind is considered as one of the factors that cause the turbulence of the gas to make the dust concentration uniform.

Ion wind is generated by corona discharge at the discharge electrode when a negative voltage is applied between the electrodes, and as a result, the ion wind is generated by positive ions at a positive voltage. Hereinafter, in the present specification, a case in which a negative voltage is applied will be described in order to consider an industrial dust collector as a base, but the same applies to a case where the voltage is positive.

では In the electric precipitator in which the electrode group is arranged along the gas flow, the ion wind generated at the discharge electrode flows across the gas flow toward the precipitating electrode. The ion wind that reaches the dust collection electrode reverses its flow at the dust collection electrode and changes its flow direction. This causes a spiral turbulence between the electrodes.

のうち Of the turbulent flow, the flow from the discharge electrode to the dust collection electrode has the effect of carrying dust to the vicinity of the dust collection electrode. The dust carried to the vicinity of the dust collection pole is finally collected by Coulomb force.

イオン However, the ion wind reversed at the dust collection electrode moves dust in a direction away from the collection electrode, which is a collecting body, and thus has an effect of obstructing dust collection. Therefore, it is effective to provide an opening in the dust collecting electrode and 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 case, the structure is such that the ion wind is sent to the filter layer behind the dust collecting electrode having an opening, and the purpose is to collect dust at a location not affected by the main gas. It was complicated, and it was difficult to separate and collect the adhered dust by the dry method.

In addition, the corona discharge generated from the corona discharge portion protruding from the main body of the discharge electrode causes the ion wind to flow along with the corona current toward the dust collection electrode side, but the collector on the opposite side of the discharge electrode where the corona discharge portion is not provided. Since no corona discharge occurs between the dust electrode and the dust electrode, the ion wind cannot be used. On the other side, where the corona discharge section is not provided, the amount of electric charge in the dust collection space due to corona current and charged dust is smaller than that in the corona discharge section, so that the electric field strength rises near the dust collection electrode. It is smaller than the part side, and the dust collecting action by Coulomb force is weak. For this reason, the present inventors paid attention to the active use of the dust collection electrode on the opposite side of the corona discharge part.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an electric precipitator capable of effectively collecting dust even at a dust collection electrode on the opposite side of a corona discharge unit. And

The electrostatic precipitator according to one aspect of the present invention has a discharge electrode having a main body portion and a corona discharge portion for corona discharge protruding from the main body portion, and a discharge-side dust collection electrode located on the corona discharge portion side. An opposite-side dust collecting electrode located on the opposite side of the discharge-side dust collecting electrode with respect to the discharge electrode, wherein the center of the main body of the discharging electrode is configured to have the discharge-side dust collecting electrode and the opposite-side collecting electrode. It is located farther from the discharge-side dust collection electrode than the center position between the dust electrode and the dust collection electrode.

The discharge electrode has a corona discharge portion protruding only toward one of the dust collection electrodes on the discharge side. Thereby, corona discharge can be caused to flow from the corona discharge section toward only the discharge-side dust collection electrode, and ionic wind can flow. This method eliminates the interference of ion wind between the discharge electrode and the discharge electrode opposite to each other with the dust collection electrode in between, as compared with the method in which the normal discharge electrode has corona discharge parts on both sides and the ion wind flows on both sides. There are benefits that can be.
However, the opposite side of the discharge-side dust collecting electrode with respect to the discharge-side dust collecting electrode, that is, the opposite side of the dust collecting electrode located on the opposite side of the corona discharge portion does not face the corona discharge portion, so that corona discharge hardly occurs. However, since the center of the main body of the discharge electrode is located in a direction 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 main body of the discharge electrode is The dust collection electrode on the opposite side will come closer. This makes it possible to increase the electric field intensity between the main body of the discharge electrode and the opposite side dust collecting electrode, and also to increase the dust collecting efficiency of the opposite side electrode by improving the Coulomb force.
For example, when the distance between the discharge-side dust collection electrode and the opposite-side dust collection electrode is 300 mm or more and 500 mm or less, the center of the main body of the discharge electrode is located 10 mm or more away from the opposite-side dust collection electrode. It is preferred that
Examples of the dust collecting electrode include a discrete dust collecting electrode in which a plurality of rigid members are arranged at predetermined intervals. As a member having rigidity, for example, a member having a pipe-shaped main body may be used. Further, as another type of dust collecting electrode, for example, a flat plate dust collecting electrode having a plate-like body having a plurality of through holes is exemplified. As the flat-plate dust collecting electrode, for example, a punching metal or a wire mesh is used.

Further, in the electric dust collecting apparatus according to one aspect of the present invention, the distance between the center of the main body of the discharge electrode and the discharge-side dust collecting electrode is D1, and the distance between the center of the main body of the discharge electrode and Assuming that the distance to the opposite side dust collecting electrode is D2, the relation is 1.1 ≦ D1 / D2 ≦ 2.0.

By setting 1.1 ≦ D1 / D2 ≦ 2.0, the electric field strength between the main body of the discharge electrode and the opposite dust collection electrode is increased, and the electric field strength is increased by the corona discharge unit and the discharge side dust collection. It can approach the electric field strength between the poles. As compared with the case where 1.1 と> とする D1 / D2, the dust collection performance is improved, and unlike the case where D1 / D2> 2.0, generation of spark discharge can be prevented.

Further, in the electric dust collecting apparatus according to one aspect of the present invention, the discharge side dust collecting electrode and the opposite side dust collecting electrode are respectively arranged along one direction, and the D1 is a main body of the discharge electrode. D2 is the distance between the center and the arrangement position of the discharge-side dust collection electrode, and D2 is the distance between the center of the main body of the discharge electrode and the arrangement position of the opposite-side dust collection electrode.

The discharge-side dust collecting electrode and the opposite-side dust collecting electrode are arranged along one direction, respectively. D1 is a center of the main body of the discharge electrode and a discharge side in a direction perpendicular to the arrangement direction of the discharge-side dust collecting electrodes. D2 is the distance between the arrangement position of the dust collection electrodes, and D2 is the distance between the center of the main body of the discharge electrode and the arrangement position of the opposite dust collection electrodes in a direction perpendicular to the arrangement direction of the opposite collection electrodes. Is the distance.

Further, in the electric dust collector according to one aspect of the present invention, the electric field strength between the discharge electrode and the discharge-side dust collection electrode, and the electric field strength between the discharge electrode and the opposite-side dust collection electrode. Are equivalent.

By making the electric field strength between the discharge electrode and the discharge-side dust collection electrode equal to the electric field strength between the discharge electrode and the opposite-side dust collection electrode, the center of the main body of the discharge electrode is set to the both collection electrodes. The electric field strength between the discharge electrode and the opposite electrode can be increased as compared with the case where the electric field is located at the center between the discharge electrodes.

Further, in the electric dust collecting apparatus according to one aspect of the present invention, the tip of the corona discharge unit is located on the opposite side of the dust collecting electrode from the center position between the discharge side dust collecting electrode and the opposite side dust collecting electrode. It is located on the extreme side.

By lowering the electric field strength between the corona discharge part and the discharge-side dust collection electrode by positioning the tip of the corona discharge part on the opposite side of the dust collection electrode from the center position between the two dust collection electrodes, The electric field strength between the main body of the discharge electrode and the opposite electrode can be increased.

By increasing the electric field intensity between the main body of the discharge electrode and the opposite dust collecting electrode, the dust collecting efficiency can be increased by improving the Coulomb force in the opposite electrode as well. Can be collected more effectively.

FIG. 1 is a perspective view showing an electric precipitator according to an embodiment of the present invention. It is the top view which looked at the electric precipitator of Drawing 1 from the upper part. It is the front view which looked at the electric precipitator of Drawing 1 from the gas flow direction. It is the top view which showed the positional relationship between the dust collection electrode and the discharge electrode. It is a cross-sectional view of the height position corresponding to the protrusion part of a discharge electrode. It is the figure which showed the electric field strength between the discharge side discharge electrode and the dust collection electrode in the case of no offset. It is the figure which showed the electric field intensity between the opposite discharge electrode and the dust collection electrode in the case of no offset. It is the figure which showed the electric field intensity between the discharge side discharge electrode and the dust collection electrode in the case of having an offset. It is the figure which showed the electric field intensity between the opposite discharge electrode and the dust collection electrode in the case of having an offset. It is the front view which showed the modification of the discharge electrode. It is the front view which showed the other modification of the discharge electrode. It is the top view which showed the modification of a dust collection electrode. It is the front view which showed the modification of a dust collection electrode. It is the top view which showed the other modification of a dust collection electrode. It is the front view which showed the other modification of a dust collection electrode. It is a graph which shows the relationship between a dust collection performance index ratio and an offset ratio. It is a graph which shows the relationship between the electric field intensity near a dust collection electrode, and offset ratio. FIG. 1 is a plan view showing an electric precipitator according to one embodiment of the present invention.

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

The electric dust collector 1 is used in, for example, a thermal power plant using coal or the like as a fuel, and collects dust (particulate matter) in combustion exhaust gas guided from a boiler. In addition, although the size of each component is different from that for the thermal power plant, the electric precipitator 1 is installed in a building, an underground space, or the like, and collects fine particulate matter (for example, PM2.5 or the like) to form a space. Purify the air inside.

The electric dust collecting apparatus 1 includes a plurality of conductive dust collecting electrodes 4 made of, for example, metal. The dust collecting electrodes 4 are formed as hollow cylindrical pipes having a circular cross section and arranged at predetermined intervals in an x direction (gas flow G direction) orthogonal to the longitudinal z direction. Have been. A plurality of rows of the dust collecting electrodes 4 arranged in the x direction are provided in parallel at predetermined intervals in the y direction orthogonal to the z direction and the x direction. Discharge electrodes 5 are arranged in the xz plane between each row of the dust collection electrodes 4. 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 located on one dust collection electrode 4 side (the right side in the y direction in FIG. 1) from the center position CL between the dust collection electrodes 4 arranged in the y direction orthogonal to the gas flow G direction. Offset.

塵 The dust collection electrode 4 is grounded. The discharge electrode 5 is connected to a power source having a negative polarity (not shown). The power supply connected to the discharge electrode 5 may have a positive polarity.

As shown in FIG. 2, the discharge electrode 5 includes a main body 5b fixed to the mounting frame 5c, and a plurality of barbed protrusions (corona discharge parts) 5a protruding from the main body 5b. . The protruding portion 5a is provided so as to protrude toward the tip only on one dust collection electrode 4 side. The projection 5a is arranged so as to be located between the dust collection electrodes 4 in the x direction which is the gas flow G direction. Corona discharge is generated at the protrusion 5a, and ion wind is generated from the tip of the protrusion 5a toward the opposing dust collection electrode 4 side.

中心 As shown in FIG. 2, the center C1 of the main body 5b of the discharge electrode 5 is offset from the center position CL between the dust collection electrodes 4. Specifically, the center C1 of the main body 5b of the discharge electrode 5 is in a direction away from the dust collecting electrode 4 to which the protrusion 5a faces (hereinafter, this dust collecting electrode 4 is referred to as a "discharge-side dust collecting electrode 4a"). In addition, the position is shifted from the center 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 “opposite side dust collecting electrode 4b”). Therefore, the distance D1 in the y direction between the center C1 of the main body 5b and the arrangement position passing through the center C2 of the discharge-side dust collecting electrode 4a is the center of the center C1 of the main body 5b and the center of the opposite side dust collecting electrode 4b. It is larger than the distance D2 as viewed in the y direction between the array position passing through C3 (D1> D2). Since the discharge electrode 5 and the dust collection electrode 4 are alternately arranged in the y direction, the projection 5a side of one dust collection electrode 4 becomes the discharge side dust collection electrode 4a, and the opposite side of the projection 5a is formed. It becomes the dust collecting electrode 4b on the opposite side.

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

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

When the distance from the center of the main body 5b of the discharge electrode 5 to the front end of the discharge portion, that is, Dd / 2 + Lb (see FIG. 4B) is less than 30 mm, preferably about 20 mm, the tip of the protrusion 5a is located at the center. It is arranged to be located on the opposite side of the dust collecting electrode 4b from the position CL.

As described above, by arranging the projection 5a in one direction and arranging it between the dust collection electrodes 4 in the x direction, the ion wind from the projection 5a to the discharge-side dust collection electrode 4a is directed in substantially the same direction. In addition, interference of ion wind can be avoided.

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

FIG. 4A shows a positional relationship between the dust collection electrode 4 and the discharge electrode 5 in a plan view.
The interval between the dust collecting electrodes 4 arranged in the x direction which is the gas flow G direction is Pc, and the interval between the discharge electrodes 5 arranged in the x direction is Pd. The interval between the dust collecting electrodes 4 arranged in the y direction is 2D. The diameter of the dust collecting electrode 4 is Dc.

In the present embodiment, the offset position of the discharge electrode 5, that is, the position where the center of the main body 5b of the discharge electrode 5 is shifted from the center position CL in the y direction is such that the ratio of the distance D1 and the distance D2 is 1.1 ≦ D1 / It is preferable to set D2 ≦ 2.0. More preferably, the lower limit of D1 / D2 is set to 1.2.

The distance between the tip of the protruding portion 5a of the discharge electrode 5 and the side surface of the nearest discharge-side dust collecting electrode 4a is L1, The distance from the side surface is L2.
In addition, the curve drawn between the discharge electrode 5 and the dust collection electrode 4 shown in FIG. 4A is a line of electric force.

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

Using the specifications shown in FIGS. 4A and 4B, L1 and L2 can be expressed as in the following equations.
L1 = ((D1-Dd / 2-Lb) ² + (Pd / 2) ² ) ^0.5 -Dc / 2
L2 = (D2 ² + (Pd / 2) ² ) ^0.5 −Dc / 2−Dd / 2
Then, an offset amount Le in which the center of the main body 5b of the discharge electrode 5 is shifted from the center position CL in the y direction is represented by the following equation.
Le = (D1-D2) / 2
4A and 4B show an example of a cross section at the position of the barb-shaped protrusion 5a, but the portion occupied by the protrusion 5a is actually a part of the discharge electrode 5, and The portion between the two protrusions 5a occupies most of the discharge electrode 5. Therefore, L1 and L2 may be evaluated ignoring the length Lb of the protrusion 5a.

2D, which is the distance between the dust collecting electrodes 4 arranged in the y direction, is, for example, 300 mm or more and 500 mm or less for general industrial use. However, other dimensions may be used for other applications.

Next, the operation and effect when the discharge electrode 5 is offset will be described with reference to FIGS. 5A to 6B.

5A and 5B show the electric field intensity distribution when there is no offset with the offset amount Le = 0, that is, when the main body 5b of the discharge electrode 5 is provided at the center position CL. As shown in FIG. 5A, as the corona current flows between the protrusion 5a and the discharge-side dust collecting electrode 4a, the electric field intensity E1max near the discharge-side dust collecting electrode 4a becomes negative with the negative ions existing in the space and the charged ions. It rises with the space charge of the dust. The electric field intensity (Ecr) at the limit of the spark discharge near the discharge-side dust collecting electrode 4a is the condition of the maximum applicable electric field intensity (E1max ≦ Ecr).

On the other hand, as shown in FIG. 5B, there is no lifting due to space charge as shown in FIG. 5A between the opposite side of the protrusion 5a and the opposite side dust collecting electrode 4b, so the electric field intensity near the opposite side dust collecting electrode 4b. E2max is smaller than E1max.
Note that the areas A1 and A2 obtained by integrating the electric field strengths with the distances L1 and L2 each have the same value because they correspond to the applied voltage Vo.

6A and 6B show the electric field intensity distribution between the discharge electrode 5 and the dust collection electrode 4 when the discharge electrode 5 is offset from the center position CL, which corresponds to the present embodiment. 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 protrusion 5a and the discharge-side dust collecting electrode 4a is set to L1> L2 or D1> D2 due to the offset. If the electric field strength E1max near 4a is the same voltage Vo as that without offset, it will be lower than that in FIG. 5A, and E1ave. (= Vo / L1) will also be smaller. On the other hand, the offset makes L2 smaller than in the case of FIG. 5B and increases the average electric field strength E2ave. Thus, the electric field strength E2max near the opposite dust collecting electrode 4b can be increased.

Generally, the operation is performed with E1max being equal to or less than the spark discharge limit electric field intensity Ecr. Can increase the applied linear pressure Vn itself (Vn> Vo), so that the maximum electric field strength E2max on the side opposite to the protrusion can be further increased. In this way, by offsetting and increasing the applied voltage, the electric field strength E1max is maintained at the same level as before the offset, while E2max is increased to the same level as E1max, so that the most dust collection near the dust collection pole can be achieved. It is possible to increase the electric field strength of an effective field and increase the collection efficiency by Coulomb force. By offsetting, the distance on the corona discharge side increases, and the moving distance of dust moving between them increases.However, the movement of dust in this part is mainly due to ionic wind, so the distance of arrival slightly increases. The electric field intensity E2max 電界 near the opposite dust collecting electrode 4b of the dust that has flowed into the opposite dust collecting electrode 4b on the back side of the discharge dust collecting electrode 4a does not become negative in the performance. It is possible to increase the performance by increasing.

It is preferable that the offset amount Le is adjusted so that the electric field intensity E1max of the discharge-side dust collecting electrode 4a is equal to the electric field intensity E2max of the opposite-side dust collecting electrode 4b. The example of the electric field strength shown in FIGS. 5A to 6B is an example in which the pipe-shaped dust collecting electrodes 4 are arranged at intervals, and the shortest distances at L1 and L2 are described as a base. As an example of the electrode of the dust collecting electrode 4, there is a mesh-shaped electrode or the like. The distances D1 and D2 are collectively described. In this case, even if the electrode is in the form of a pipe, even if it is evaluated not by L1 and L2 but by D1 and D2, it can be considered that they are almost equivalent in a practical range, and there is no problem.

{The range in which the electric field intensities of both are equal is, for example, 1.5} ≦ {D1 / D2} ≦ {1.8. However, the optimum range of D1 / D2 varies depending on the operating conditions of the electric dust collector 1 and the conditions of the dust collecting electrode 4 or the discharge electrode 5.

下限 The lower limit of the ratio D1 / D2 of the distance D1 and the distance D2 is, for example, 1.1, and more preferably 1.2. As shown in FIG. 10, it has been found that the relationship between the offset amount and the dust collection performance changes depending on the flow velocity of the gas flow G. When the gas flow G is relatively fast, if D1 / D2 is 1.1 or more, the dust collection performance is improved. When the gas flow G is relatively slow, the dust collection performance is improved when D1 / D2 is 1.2 or more. In this range, when the gas flow G is relatively fast, the dust collection performance is definitely improved. .

Under the condition where the flow velocity of the gas flow G is high, the influence of the Coulomb force is greater, and the dust collection performance is improved even with a relatively small offset amount (for example, 1.1 ≦ D1 / D2) due to the increase in the electric field strength. I do. On the other hand, under the condition where the flow velocity is slow, the influence of the ion wind is large, so that a larger offset amount (for example, 1.2 ≦ D1 / D2) is required to improve the dust collection performance by increasing the electric field strength. Become. If 1.2 ≦ D1 / D2, dust collection performance can be improved regardless of the flow velocity of the gas flow G.

If the offset amount is too large, the electric field intensity E2max> E1max near the dust collection electrode on the opposite side will be reached, and the spark discharge limit electric field intensity on the opposite side of the corona discharge section will be a constraint on operation, and the performance on the corona discharge side will be exhibited. It is not preferable because it becomes impossible. Therefore, it is desirable that the maximum offset amount is set in a range where E2max does not greatly exceed E1max.

FIG. 11 shows an electric precipitator 1 for general industry, in which the corona discharge side (the side having the projecting portion 5a on the main body 5b of the discharge electrode 5, that is, the barb on the discharge wire) when D1 / D2 is changed. And the opposite side of the electric field side (the side where the main body 5b of the discharge electrode 5 does not have the protrusion 5a, that is, the side without the barb). The example which analyzed and compared the electric field intensity near 4b is shown. The current and voltage as operating conditions of the electrostatic precipitator 1 were both increased. In FIG. 11, the current and the voltage increase from the left graph to the right graph.

In any case, when D1 / D2 = 1, the discharge-side dust collecting electrode 4a on the side where the barb is located is closer to the barb by the length of the barb, and the electric field is raised by the space charge due to the corona current. Is added, the electric field strength of the discharge-side dust collecting electrode 4a on the side with the thorn is higher. Then, as the current increases, the effect of lifting increases, and the value of the electric field strength increases.

On the other hand, in any of the graphs of FIG. 11, as D1 / D2 increases, the electric field intensity of the opposite side of the dust collecting electrode 4b on the side without the thorns tends to uniquely increase. Ideally, the point where the electric field intensity on the side with the barbs and the electric field intensity on the side without the barbs match is considered to be the most balanced electric field intensity distribution. However, in actual operation, various conditions are compounded, and the optimum conditions vary. For this reason, even in the test result regarding the improvement of the dust collection performance when D1 / D2 is changed in FIG. 10, the optimum point of the dust collection performance has some degree of variation.

Further, in the graph on the right side of FIG. 11, that is, in the operation in which the current and the voltage are increased, especially in a region where the offset amount D1 / D2 is large, the spark electric field intensity ( This largely depends on the gas composition and the operating temperature conditions, but is usually set to 8 kV / cm to 12 kV / cm.) Is not preferred.
More specifically, it is desirable that D1 / D2 ≦ 2.0.

When D1 / D2 exceeds 2.0, the electric field strength on the opposite side of the dust collecting electrode 4b reaches or reaches a region where spark discharge occurs under the normal operation conditions of the electric dust collecting device 1. Become closer to Therefore, the stable operation becomes difficult due to the restriction of the operating conditions of the electric precipitator 1. Therefore, the upper limit of D1 / D2 is preferably set to 2.0.

Next, the operation of the electric precipitator 1 of the present embodiment will be described.
In the electrostatic precipitator 1, by applying a negative voltage from the power supply to the discharge electrode 5, corona discharge is generated at the tip of the projection 5a. The dust contained in the gas flow G is charged by corona discharge. According to the collecting principle of the conventional electric dust collector, the charged dust is attracted to the dust collecting electrode 4 grounded by Coulomb force and collected on the dust collecting electrode 4. Is greatly influenced by ion wind.

(4) When corona discharge occurs, negative ions are generated near the protrusion 5a, and the negative ions move toward the dust collection electrode 4 by an electric field, thereby generating ion wind. Therefore, simultaneously with the Coulomb force acting on the dust, the ionic wind flowing toward the dust collecting electrode 4 acts to move the dust contained in the gas flow G to the vicinity of the discharge-side dust collecting electrode 4a. Then, in the region near the discharge-side dust collecting electrode 4a, the Coulomb force is increased by the increase in the electric field strength, and dust is effectively collected. In addition, by arranging the dust collecting electrodes 4 in the form of circular pipes at intervals in the x direction, which is the direction of the predetermined gas flow G, one of the ion winds flowing from the protrusions 5a toward the discharge-side dust collecting electrodes 4a is reduced. The part is allowed to come off to the back side of the dust collecting electrode 4. This can suppress the flow of the ion wind that is reversed at the dust collection electrode 4 and moves away from the dust collection electrode 4, thereby improving the collection efficiency.

一部 A part of the ion wind including dust and flowing toward the dust collection electrode 4 passes between the dust collection electrodes 4. Since the ion winds are directed in one direction, they do not interfere with each other.

On the other hand, as described with reference to FIG. 6B, the discharge electrode 5 is offset from the center position CL between the opposite side of the projection 5 a and the opposite side of the dust collection electrode 4 b, so that Can be increased as compared with the case where there is no offset. As a result, dust is collected effectively by the Coulomb force on the opposite side of the dust collection electrode 4b opposite to the protrusion 5a. That is, it is possible to efficiently collect the uncollected dust that has circulated to the opposite side of the dust collecting electrode 4b due to the ion wind.

ダスト The dust collected by the dust collecting electrode 4 is separated and collected by hammering. Alternatively, a method in which the dust collecting electrode is moved to scrape off dust with a brush, or a wet cleaning may be employed.

According to the present embodiment, the following operation and effect can be obtained.
Since the center of the main body 5b of the discharge electrode 5 is located farther from 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 discharge electrode 5 and the opposite side of the dust collecting electrode 4b come closer. Thereby, the electric field intensity between the main body 5b of the discharge electrode 5 and the opposite dust collecting electrode 4b can be increased, and the dust collecting efficiency by the Coulomb force can also be increased in the opposite dust collecting electrode 4b.

In the above-described embodiment, the configuration of the discharge electrode 5 is such that the projection 5a is provided on the main body 5b having a circular cross section. However, as shown in FIG. 7A, the cross section is rectangular. It is good also as a structure which provided the projection part 5a in the square rod 5b 'made. Alternatively, as shown in FIG. 7B, a flat plate may be formed by punching, and the protrusion 5a and the main body 5b ″ may be integrally formed.

As shown in FIGS. 8A and 8B, instead of the above-described dust collecting electrode 4 having a circular pipe shape, a plate-like dust collecting electrode 4 'such as a punching metal having a large number of holes formed in a flat plate may be used. Alternatively, as shown in FIGS. 9A and 9B, a flat plate such as a punching metal having a large number of holes may be formed into a folded plate-shaped dust collecting electrode 4 ″ which is alternately and regularly folded in the gas flow G direction. In this case, the projection 5a of the discharge electrode 5 is offset according to the unevenness of the opposing bent plate.

Furthermore, the dust collecting electrode 4 may be a woven wire mesh (for example, a rock crimp woven wire mesh) in which metal wires are crossed in the vertical and horizontal directions. Since the woven wire mesh has a constant aperture ratio and no edges on the surface, the electric field intensity in the vicinity of the dust collection electrode 4 can be uniformly increased. The wire mesh is not limited to a woven wire mesh, but may be a wire mesh having a circular cross-section, such as a welded wire mesh, arranged in the vertical and horizontal directions.

(4) When the electrostatic precipitator 1 is used as an air purifier for air purification, the time that particles stay in the device is short, and the particle concentration is low. On the other hand, the electrostatic precipitator 1 used in a thermal power plant has a large scale, a long period of staying particles, and a high particle concentration, unlike the case where it is used for air purification. In the electrostatic precipitator 1 for air purification, when low-concentration particles are passed for a short residence time, the particles are transferred to the dust collection electrode 4 by the effect of gas circulation generated by the ion wind from the projection 5a of the discharge electrode 5. Can't collect.

Therefore, as shown in FIG. 12, a gas blocking plate 6 may be provided on the upstream side of the gas flow G between the opposite side dust collecting electrode 4b and the discharge electrode 5. Since the gas flow G is hindered by the gas blocking plate 6, the flow rate of the gas flow flowing between the opposite side dust collecting electrode 4b and the discharge electrode 5 is reduced, and the residence time of the particles passing through the dust collecting electrode 4 is increased. , The collection performance can be improved.

DESCRIPTION OF SYMBOLS 1 Electric dust collector 4 Dust collection electrode 4a Discharge side dust collection electrode 4b Opposite side dust collection electrode 5 Discharge electrode 5a Projection (corona discharge part)
5b Main body 5c Mounting frame 6 Gas blocking plate C1 Center CL (of main body of discharge electrode) Center position

Claims

A discharge electrode having a main body and a corona discharge portion for corona discharge protruding from the main body,
A discharge-side dust collecting electrode located on the corona discharge unit side,
An opposite-side dust collecting electrode located on the opposite side of the discharge-side dust collecting electrode across the discharge electrode,
With
An electrostatic precipitator in which the center of the main body of the discharge electrode is located farther from the discharge-side dust collector than a center position between the discharge-side dust collector and the opposite-side dust collector. .
When the distance between the center of the main body of the discharge electrode and the discharge-side dust collecting electrode is D1, and the distance between the center of the main body of the discharge electrode and the opposite-side dust collecting electrode is D2. ,
1.1 ≦ D1 / D2 ≦ 2.0
The electric precipitator according to claim 1, wherein
The discharge side dust collection electrode and the opposite side dust collection electrode are respectively arranged along one direction,
D1 is a distance between the center of the main body of the discharge electrode and the arrangement position of the discharge-side dust collection electrodes,
The electrostatic precipitator according to claim 2, wherein the D2 is a distance between a center of the main body of the discharge electrode and an arrangement position of the opposite side dust collection electrode.
The electric field intensity between the discharge electrode and the discharge-side dust collection electrode is equal to the electric field intensity between the discharge electrode and the opposite-side dust collection electrode. An electric precipitator according to any one of the preceding claims.
The tip of the corona discharge part is located on the opposite side dust collection electrode side from the center position between the discharge side dust collection electrode and the opposite side dust collection electrode. An electric precipitator according to claim 1.