TW202039086A - Electric dust collector - Google Patents

Abstract

Provided is an electric dust collector that can effectively collect dust even if a dust collection electrode faces a discharge electrode that does not have a corona discharge portion. The electric dust collector comprises: a first discharge electrode (5) that has a body portion (5c) and a first corona discharge portion (5a) that projects from the body portion (5c) and that is for corona discharges; a second discharge electrode (6) that has a face on which no projections are formed; and a dust collection electrode (4) that is positioned between the first discharge electrode (5) and the second discharge electrode (6) and the first discharge electrode (5) side of which faces the first corona discharge portion (5a). The dust collection electrode (4) is positioned in a direction further away from the first discharge electrode (5) than the center position (CL) between the first discharge electrode (5) and the second discharge electrode (6).

Description

Electric dust collector

The present invention relates to an electric dust collector.

As conventional electric dust collectors, there are known devices having flat dust collectors arranged in parallel along the airflow and a discharge electrode with a corona discharge part arranged in the center. The shape of the corona discharge part of the discharge electrode has a way to ensure the corona discharge by holding the protrusion shape to concentrate the generated electric field, so that the discharge electrode body generates the same electric field concentration structure, such as angular lines or thin piano wires, etc. In general industrial electric dust collectors, in order to ensure stable corona discharge even if the electrodes are contaminated, a structure with a protruding corona discharge part is the mainstream, and this structure is the prerequisite later on.

In the electric dust collector, by applying a high DC voltage between the dust collecting electrode and the discharge electrode, the corona discharge part of the discharge electrode performs stable corona discharge to charge the dust in the airflow. The charged dust is trapped by the dust collector through the movement of the Coulomb force acting on the dust under the electric field between the discharge electrode and the dust collector, which has been explained in the previous dust collection theory.

However, the electric dust collector of Patent Documents 1 and 2 is provided with a plurality of through holes for passing dust, and has a dust collecting electrode in a closed space for collecting dust. In Patent Documents 1 and 2, it is difficult for the collected dust to scatter again by sealing the dust in the closed space through the through hole.

The electric dust collector of Patent Document 3 is provided with a dust collecting electrode including a ground electrode with an aperture ratio of 65% to 85%, and a dust collecting filter layer for trapping gas. By having such a dust collecting electrode, in Patent Document 3, an ion wind is generated in a cross section orthogonal to the airflow to generate a spiral airflow circulating between the discharge electrode and the dust collecting electrode, which becomes an efficient collection Collect dust. In Patent Document 3, although the ion wind is actively used, this situation is mainly for the purpose of collecting dust by the dust collecting filter layer. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 5761461 [Patent Document 2] Japanese Patent No. 5705461 [Patent Document 3] Japanese Patent No. 4823691

[The problem to be solved by the invention]

The dust collection efficiency η of the electric dust collector can be calculated by the well-known Deutsch equation (Equation 1). w is the dust collection index (moving speed of particulate matter), f is the dust collection area per unit gas.

In the above equation (1), the moving speed w of dust (particulate matter) is determined by the relationship between the force caused by the Coulomb force and the viscous resistance of the gas. In the German formula (the above formula (1)), it is assumed that the dust moves from the discharge electrode in the electric field, and the influence of the ion wind on the performance is not directly considered. However, the performance design mentioned before, that is, the distribution of dust concentration is always in the cross section of the dust collection space between the discharge electrode and the dust collector orthogonal to the airflow of the electric dust collector. The ion wind It is thought that a turbulent flow of gas is generated, which is one of the main reasons that the dust concentration becomes uniform.

When a negative electrode is applied between the electrodes, an ion wind is generated as a result of the negative ions generated by the corona discharge on the discharge electrode. In the case of a positive voltage, an ion wind is generated by the positive ions. Hereinafter, in this specification, the consideration is based on an industrial electric dust collector, so although it describes the case where a negative voltage is applied, it is the same even if a positive voltage is applied.

In an electric dust collector with electric clusters arranged along the airflow, the ion wind generated at the discharge electrode flows across the airflow toward the dust collecting electrode. The ion wind reaching the dust collecting pole reverses at the dust collecting pole and changes the flow direction. Accordingly, a spiral turbulent flow is generated between the electrodes.

In the turbulent flow, the airflow from the discharge electrode to the dust collector has the function of transporting dust to the vicinity of the dust collector. The dust transported to the vicinity of the dust collecting pole is finally captured by Coulomb.

However, since the ion wind reversed at the dust collecting pole moves the dust away from the collecting body, that is, the dust collecting pole, it also has the effect of hindering dust collection. Therefore, it is effective to provide an opening in the dust collecting electrode to prevent the reverse of the ion wind.

Patent Document 3 describes an electric dust collector considering the effect of ion wind. However, in this situation, in order to send the ion wind into the filter layer behind the dust collector with the opening, the structure is also complicated for the purpose of collecting dust in a place not affected by the main gas. And dry type is difficult to peel and collect the attached dust.

Furthermore, when the discharge electrode is provided with a corona discharge part protruding from the main body of the discharge electrode, the corona discharge generated from the corona discharge part causes the ion wind and the corona current to flow toward the dust collecting electrode at the same time. In contrast, when the discharge electrode is not provided with a corona discharge part, since corona discharge does not occur between the discharge electrode and the dust collecting electrode, ion wind cannot be used. Furthermore, in the discharge electrode without corona discharge part, the amount of charge in the dust collecting space due to corona current or charged dust is less than that of the corona discharge part, so the electric field intensity near the dust collecting electrode increases It is smaller than the corona discharge side, and the dust collection effect due to the Coulomb force becomes weaker. Therefore, the inventors of the present invention paid attention to the positive use of the dust collecting electrode opposed to the discharge electrode having no corona discharge part.

The present invention was created in view of such circumstances, and its object is to provide an electric dust collector that can effectively collect dust even if it is a dust collector that does not have a discharge electrode of a corona discharge part. [Means to solve the problem]

An electric dust collector related to one aspect of the present invention includes a main body, a first discharge electrode having a first corona discharge portion for corona discharge protruding from the main body, and a surface with no protrusions formed thereon A second discharge electrode, a dust collecting electrode located between the first discharge electrode and the second discharge electrode, the first discharge electrode side facing the first corona discharge portion, and the dust collecting electrode is located higher than the first discharge electrode. The center position between the electrode and the second discharge electrode is further away from the direction of the first discharge electrode.

The first discharge electrode has a first corona discharge portion protruding to face the dust collecting electrode, and the second discharge electrode has a surface on which no protrusion is formed. According to this, it is possible to generate corona discharge from the first corona discharge portion toward the dust collecting electrode to allow ion wind to flow. The second discharge electrode located on the opposite side of the first discharge electrode sandwiching the dust collecting electrode, that is, the second discharge electrode on the opposite side of the first corona discharge part, does not form a protrusion like the first corona discharge part, so there is almost no occurrence Corona discharge. However, since the dust collecting electrode is located farther away from the first discharge electrode than the center of the first discharge electrode and the second discharge electrode, the second discharge electrode and the dust collecting electrode are very close. According to this, the electric field intensity between the second discharge electrode and the dust collecting electrode can be increased, and the dust collection efficiency due to the improvement of the Coulomb force can be improved even at the second discharge electrode. Furthermore, compared with the conventional method in which only the discharge electrodes with corona discharge parts are provided on both sides, this method has the second discharge electrode without protruding parts, which can eliminate the adjacent dust collecting electrodes. The advantage of the interference of ion wind caused by the discharge electrodes. As the dust collecting electrode, for example, a discrete dust collecting electrode in which members having plural rigidities are arranged at specific intervals. As a member having rigidity, for example, a member in which the main body is formed in a tube shape can be cited. In addition, as another type of dust collecting electrode, for example, a flat dust collecting electrode formed as a plate-shaped body having a plurality of through holes can be cited. As the flat dust collecting electrode, for example, punched metal or gold mesh is used.

Furthermore, in the electric dust collector according to one aspect of the present invention, the distance between the first discharge electrode and the dust collecting electrode is set to D1, and the distance between the second discharge electrode and the dust collecting electrode is When the distance of is set to D2, it becomes 1.1≦D1/D2≦2.0.

By setting 1.1≦D1/D2≦2.0, the electric field intensity between the second discharge electrode and the dust collecting electrode can be increased while making the electric field intensity close to the electric field between the first corona discharge part and the dust collecting electrode strength. Compared with the setting of 1.1>D1/D2, the dust collection performance is improved. Unlike the setting of D1/D2>2.0, it can prevent spark discharge.

In addition, in the electric dust collector according to an aspect of the present invention, the dust collecting electrodes are arranged along one direction, and the D1 is the position between the arrangement positions of the first discharge electrode and the dust collecting electrode. The distance, D2 is the distance between the arrangement position of the second discharge electrode and the dust collecting electrode.

The dust collecting electrodes are arranged in one direction. D1 is the distance between the first discharge electrode and the arrangement position of the dust collecting electrode in the vertical direction to the arrangement direction of the dust collecting electrode, and D2 is in the arrangement of the dust collecting electrode. The direction is the distance between the arrangement position of the second discharge electrode and the dust collector in the vertical direction.

Furthermore, in the electric dust collector according to one aspect of the present invention, the electric field intensity between the first discharge electrode and the dust collecting electrode and the electric field intensity between the second discharge electrode and the dust collecting electrode Are set equal.

By making the electric field intensity between the first discharge electrode and the dust collecting electrode equal to the electric field intensity between the second discharge electrode and the dust collecting electrode, compared to placing the dust collecting electrode on the first discharge electrode and the second discharge electrode In the middle of the space, the electric field strength between the second discharge electrode and the dust collector can be increased.

In addition, in the electrostatic precipitator according to one aspect of the present invention, the first discharge electrode sandwiches the main body part, and has a protruding from the main body part on the side opposite to the first corona discharge part. The second corona discharge part for corona discharge is provided with a dust collecting electrode different from the above-mentioned dust collecting electrode so as to face the second corona discharge part.

By having the first corona discharge part and the second corona discharge part on both sides of the main body part of the discharge electrode, it is possible to generate corona discharge toward the dust collecting electrode on both sides to flow the ion wind. [Effects of Invention]

By increasing the intensity of the electric field between the discharge electrode and the dust collecting electrode without the corona discharge part, even in the dust collecting electrode facing the discharge electrode of the corona discharge part, the dust collection can be improved by increasing the Coulomb force Efficient, more effective dust collection.

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

The electric dust collector 1 is used in a thermal power plant that uses coal or the like as a fuel, and collects dust (particulate matter) in combustion exhaust gas introduced from a boiler. Furthermore, the dimensions of the components of the electric dust collector 1 are different from those used in thermal power plants, but they are installed in buildings or underground spaces. Recover tiny particulate matter (for example, PM2.5, etc.) to purify the space in the space.

The electric dust collecting device 1 is provided with plural dust collecting electrodes 4 made of, for example, metal, which is conductive. The dust collecting electrode 4 is formed as a hollow cylindrical circular tube having a circular cross section, and is arranged in an x direction (air flow G direction) orthogonal to the longitudinal direction, that is, the z direction at a predetermined interval. The rows of the dust collecting electrodes 4 arranged in the x direction are arranged in plural rows in the y direction orthogonal to the z direction and the x direction at predetermined intervals. Between each row of the dust collecting electrode 4, the first discharge electrode 5 or the second discharge electrode 6 is arranged in the x-z plane. The first discharge electrodes 5 and the second discharge electrodes 6 are alternately arranged in the y direction.

In FIG. 1, the positions of the mounting frame 5d of the first discharge electrode 5 and the mounting frame 6b of the second discharge electrode 6 are shown. As can be seen from FIG. 2, the dust collecting electrode 4 is shifted from the center position CL between the first discharge electrode 5 and the second discharge electrode 6 arranged in the y direction orthogonal to the direction of the airflow G to the second discharge electrode 6 side. That is, the distance between the dust collecting electrode 4 and the first discharge electrode 5 is greater than the distance between the dust collecting electrode 4 and the second discharge electrode 6.

The dust collecting electrode 4 is grounded. The first discharge electrode 5 and the second discharge electrode 6 are connected to a power source having a negative polarity (not shown). In addition, the power supply connected to the first discharge electrode 5 and the second discharge electrode 6 may have a positive polarity.

As shown in FIG. 2, the first discharge electrode 5 includes a main body portion 5c fixed to the mounting frame 5d, and a plurality of protruding portions (first corona discharge portion) 5a formed as thorns protruding from the main body portion 5c. And a plurality of protruding parts (second corona discharge part) 5b in the shape of thorns protruding from the main body part 5c are provided on the side opposite to the protrusion part 5a with the main body part 5c in between. The main body part 5c is, for example, a round bar with a circular cross section, or a square bar with a square cross section. In addition, the protrusion parts 5a, 5b and the main body part 5c may be connected by separate members by welding or the like, or may be formed by punching a flat plate and formed integrally.

The protruding part 5a is provided so that its front end protrudes toward the dust collecting electrode 4 side of one side, and the protruding part 5b is provided so that its front end protrudes toward the other dust collecting electrode 4 side. The protrusions 5a and 5b are located in the x direction in the direction of the air flow G, and are arranged between the dust collecting electrodes 4. Corona discharge is generated in the protrusions 5a, 5b, and ion wind is generated from the front ends of the protrusions 5a, 5b toward the dust collecting electrode 4 side, respectively.

The second discharge electrode 6 includes a main body portion 6a fixed to the mounting frame 6b. The outer peripheral surface of the second discharge electrode 6 is different from that of the first discharge electrode 5 in that there is no protrusion that protrudes from the main body 6a like the protrusions 5a and 5b. The second discharge electrode 6 has, for example, a round bar with a circular cross-section, or a square bar with a square cross-section. The second discharge electrode 6 is arranged in parallel to the z direction in the axial direction.

As shown in Figures 2 and 3, the center C1 of the dust collecting electrode 4 is offset from the center position CL between the center C2 of the first discharge electrode 5 and the center C3 of the second discharge electrode 6 to the side of the second discharge electrode 6 . Specifically, the dust collecting electrode 4 is moved away from the first discharge electrode 5 having the protrusions 5a, 5b, and is close to the second discharge electrode 6 without the protrusions, and the position is shifted from the center position CL . Therefore, as shown in FIGS. 3 and 4, the distance D1 seen in the y direction between the center C2 of the body portion 5c of the first discharge electrode 5 and the center C1 of the dust collecting electrode 4 is greater than that The distance D2 seen in the y direction between the center C3 of the body portion 6a of the second discharge electrode 6 and the center C1 of the dust collecting electrode 4 is large (D1>D2).

The distance D1 is the distance between the center C2 of the body portion 5c of the first discharge electrode 5 and the center C1 of the dust collecting electrode 4 in the arrangement position. That is, D1 is in the vertical direction (y direction) with respect to the arrangement direction of the dust collecting electrode 4, between the center C2 of the body portion 5c of the first discharge electrode 5 and the arrangement position (center axis) of the dust collecting electrode 4 distance.

The distance D2 is the distance passing through the arrangement position of the center C3 of the body portion 6a of the second discharge electrode 6 and the center C1 of the dust collecting electrode 4. That is, D2 is in the vertical direction (y direction) with respect to the arrangement direction of the dust collecting electrode 4, between the center C3 of the body portion 6a of the second discharge electrode 6 and the arrangement position (center axis) of the dust collecting electrode 4 distance.

Fig. 3 shows a front view of Fig. 1 viewed from the direction of the air flow G. As shown in the figure, the protrusions 5a and 5b are all provided at a predetermined interval in the height direction. Furthermore, the protrusions 5a and the protrusions 5b have different phases, that is, they are alternately arranged at different positions along the z direction of the main body 5c.

FIG. 4 shows the positional relationship when the dust collecting electrode 4 and the first discharge electrode 5 and the second discharge electrode 6 are viewed from above. The interval between the dust collecting electrodes 4 arranged in the direction of the air flow G, that is, in the x direction is set to Pc, and the interval between the first discharge electrode 5 or the second discharge electrode 6 arranged in the x direction is set to Pd. Furthermore, the distance between the dust collecting electrodes 4 arranged in the y direction that is perpendicular to the direction of airflow G is set to 2D1 when the first discharge electrode 5 is in the middle, and the second discharge electrode 6 is in the middle. The distance of the case is set to 2D2. The diameter of the dust collecting electrode 4 is set as Dc.

In this embodiment, the offset position of the dust collecting electrode 4 is the position where the center C1 of the dust collecting electrode 4 shifts from the central position CL to the y direction, and is set at 1.1 by the ratio of the distance D1 to the distance D2 The range of ≦D1/D2≦2.0 is better. The lower limit of D1/D2 is preferably set to 1.2.

FIG. 5 is an enlarged cross section in a position corresponding to the height of the protrusion 5a of the first discharge electrode 5. As shown in FIG. 4 or FIG. 5, the body portion 5c of the first discharge electrode 5 has a circular cross-section, and its diameter is set to Dd1. The length of the protrusion 5a protruding from the main body 5c is set to Lb. As shown in FIG. 4, the main body portion 6a of the second discharge electrode 6 has a circular cross section, and its diameter is set to Dd2.

而且，集塵極4之中心從中央位置CL朝y方向偏移的偏移量Le藉由下式表示。

另外，在圖4及圖5中，雖然表示刺狀之突起部5a或在突起部5b之位置的剖面之例，但是實際上突起部5a、5b所佔據的部分係第1放電極5之一部分，相鄰的兩個突起部5a、5b間之部分佔據第1放電極5之大部分。因此，即使忽略突起部5a、5b之長度Lb而評估L1、L2亦可。When using the various factors shown in Figures 4 and 5, L1 and L2 can be expressed as the following equations.

In addition, the shift amount Le by which the center of the dust collecting pole 4 shifts from the center position CL in the y direction is expressed by the following equation.

In addition, in FIGS. 4 and 5, although the thorn-like protrusion 5a or an example of the cross section at the position of the protrusion 5b is shown, in fact, the portion occupied by the protrusions 5a and 5b is a part of the first discharge electrode 5. , The part between the two adjacent protrusions 5a, 5b occupies most of the first discharge electrode 5. Therefore, even if the length Lb of the protrusions 5a, 5b is ignored, L1, L2 may be evaluated.

The distance between the dust collecting electrodes 4 arranged in the y direction, that is, 2D1 or 2D2, is set to 300 nm or more and 500 nm or less for general generation, for example. However, it can also be set to other sizes in other applications.

Next, using FIGS. 6A to 7B, the effect of the case where the dust collecting electrode 4 is shifted between the first discharge electrode 5 and the second discharge electrode 6 will be described.

Fig. 6A and Fig. 6B show the electric field intensity distribution in the case where the offset is set to 0 without offset, that is, the center C1 of the dust collecting electrode 4 is set on the central position CL. As shown in FIG. 6A, between the protrusions 5a, 5b of the first discharge electrode 5 and the dust collecting electrode 4, as the corona current flows, the electric field intensity near the dust collecting electrode 4 Elma is the negative ions and The space charge effect caused by the electric charge of the charged dust, and the electric field intensity rises relatively large. The electric field intensity (Ecr) of the spark discharge limit in the vicinity of the dust collecting electrode 4 becomes the condition of the maximum electric field intensity that can be applied (E1max≦Ecr).

In addition, as shown in FIG. 6B, because there is no space charge effect as shown in FIG. 6A between the second discharge electrode 6 and the dust collecting electrode 4 without protrusions, the electric field strength rises little, so the dust collecting electrode 4 is near The electric field strength E2max is less than E1max. In addition, since the areas A1 and A2 obtained by integrating the electric field intensity at the distances L1 and L2 respectively correspond to the applied voltage Vo, they are equivalent.

7A and 7B show the electric field intensity distribution between the first discharge electrode 5 and the dust collecting electrode 4 when the dust collecting electrode 4 is shifted from the center position CL, and the second discharge electrode corresponding to this embodiment. The electric field intensity distribution between 6 and the dust collecting electrode 4. Fig. 7A corresponds to Fig. 6A, and Fig. 7B corresponds to Fig. 6B.

As shown in Figs. 7A and 7B, due to the deviation of the electric field intensity between the protrusions 5a, 5b and the dust collecting electrode 4, D1>D2, that is, L1>L2, is If the electric field intensity E1max is the same voltage Vo as in the case of no offset, it is lower than that in Fig. 6A and also smaller than E1ave. (=Vo/L1). In addition, due to the offset, compared to the case of FIG. 6B, L2 becomes smaller, and the average electric field intensity E2ave. becomes larger. Accordingly, the electric field intensity E2max near the dust collecting electrode 4 increases.

Generally speaking, although E1max becomes the operation below the spark discharge limit electric field strength Ecr, the distance L1 between the protrusions 5a and 5b side is increased due to the offset. Therefore, in order to compare with the case of no offset, it becomes more With the same electric field strength as E1max, the applied line voltage Vn itself (Vn>Vo) can be increased, and therefore the maximum electric field strength E2max on the opposite side of the protrusions 5a and 5b can also be increased. In this way, by offsetting and increasing the applied voltage, while maintaining the electric field intensity E1max equal to before the offset, while increasing E2max to the same level, the most effective dust collection near the dust collector 4 can be improved. The electric field strength at the location, and enhance the collection efficiency caused by Coulomb force. In addition, although the distance L1 on the side of the protrusions 5a, 5b where corona discharge is generated by the offset increases, the moving distance of the dust moving during this period increases, but due to the movement of the dust in this part, the main system ion wind, Therefore, a slight increase in the distance of arrival or a decrease in the average electric field intensity on the way will not adversely affect the performance, because the increase in the electric field intensity E2max near the dust collecting electrode 4 of the dust surrounding the second discharge electrode 6 side of the dust collecting electrode 4 Increase, thereby improving performance.

Furthermore, in the present embodiment, compared to the conventional method in which only the discharge electrodes with protrusions (corona discharge parts) are provided on both sides, the second discharge electrode 6 without protrusions is also provided. The advantage of eliminating the interference of ion wind caused by the adjacent discharge electrodes sandwiching the dust collecting electrode 4. That is, since there is no or less ion wind flowing out of the second discharge electrode 6 in the dust collecting electrode 4, the charged dust will not be rolled back toward the first discharge electrode 5 side, and the charged dust can be moved toward the dust collecting electrode. 4 is close. In addition, by providing the protruding portion 5a and the protruding portion 5b so as to be phase shifted, the influence of the ion wind from the side of the second discharge electrode 6 can be further reduced.

The amount of shift (D1/D2 ratio) is preferably adjusted so that the electric field intensity E1max on the side of the first discharge electrode 5 and the electric field intensity E2max on the side of the second discharge electrode 6 are equal. The example of the electric field intensity shown in FIGS. 6A to 7B is an example in which tubular dust collecting electrodes 4 are arranged at intervals, and the description is based on the shortest distance between L1 and L2. As an example of the electrode of the dust collecting electrode 4, there are also mesh-shaped electrodes, so in order to define the offset below, the distance between the arrangement position of the center C1 of the dust collecting electrode 4 and the center C2 of the first discharge electrode 5 D1 and the distance D2 between the arrangement position of the center C1 of the dust collecting electrode 4 and the center C3 of the second discharge electrode 6 are summarized. In this case, even if it is a tubular electrode, since it is not L1 and L2, even if it is evaluated by D1 and D2, the practical range is considered to be slightly equal, so there is no problem.

The range in which the electric field strength of the two becomes equal is, for example, 1.5≦D1/D2≦1.8. However, depending on the operating conditions of the electric dust collector 1 or the conditions of the dust collecting electrode 4, the first discharge electrode 5, or the second discharge electrode 6, the optimum D1/D2 range varies.

The lower limit of the ratio D/D2 between the distance D1 and the distance D2 is, for example, 1.1, and more preferably 1.2. As shown in FIG. 8, it is possible to obtain insights into the changes in the relationship between the flow rate of the air flow G, the amount of offset and the dust collection performance. When the airflow G is relatively fast, if D1/D2 becomes 1.1 or more, the dust collection performance is improved. When the air flow G is compared, if D1/D2 becomes 1.2 or more, the dust collection performance is improved. In this range, when the air flow G is relatively fast, the dust collection performance is surely improved.

In the condition that the flow rate of the airflow G is fast, the Coulomb force has a greater influence, so the increase in electric field strength is affected, and the dust collection performance is improved even at a relatively small offset (for example, 1.1≦D1/D2). In this regard, in the condition of a slow flow rate, the ion wind has a large influence, so in order to improve the dust collection performance by increasing the electric field strength, a larger offset (for example, 1.2≦D1/D2) is required. If it is 1.2≦D1/D2, regardless of the flow rate of the airflow G, the dust collection performance can be improved.

When the offset is too large and the distance between the dust collecting electrode 4 and the second discharge electrode 6 is extremely narrowed, since the electric field intensity near the dust collecting electrode 4 becomes E2max>E1max, it is on the side of the second discharge electrode 6 without protrusions The spark discharge limit intensity of 5A becomes a restrictive condition in operation, and the performance on the side of the first discharge electrode 5 with the protrusions 5a and 5b cannot be exerted, so it is not ideal. Accordingly, it is better to set the maximum offset in the range where E2max does not exceed E1max by much.

Fig. 9 shows an analysis and comparison of the corona discharge side when D1/D2 is changed in an electric dust collector 1 for general industrial use (the side with protrusions 5a, 5b on the body part 5c of the first discharge electrode 5) , That is, the electric field intensity near the dust collecting electrode 4 on the side of the discharge line with thorns, and the electric field intensity near the dust collecting electrode 4 on the electric field side (the side of the second discharge electrode 6, which is the side without thorns) example. The current and voltage which are the operating conditions of the electric dust collector 1 are raised together. In Fig. 9, as the curve moves from the left curve to the right curve, the current and voltage become higher.

In either case, in the case of D1/D2=1, in addition to the distance between the dust collector 4 on the side of the thorn that is closer to the length of the thorn, the space charge electric field increased by the corona current is also added. Therefore, the electric field intensity of the dust collecting electrode 4 on the side with thorns is relatively high. Moreover, as the current increases, the effect of its increase becomes greater, and the value of the electric field intensity becomes higher.

In addition, the case of any of the curves in FIG. 9 shows the tendency that the electric field intensity of the dust collecting electrode 4 on the side without thorns increases unambiguously as D1/D2 increases. Ideally, the point where the electric field strength of the side with thorns and the side without thorns are the same is considered to obtain the most balanced electric field intensity distribution. However, in actual operation, due to the combination of various conditions, the optimal conditions vary. Therefore, even in the test results regarding the improvement of dust collection performance when D1/D2 in FIG. 8 is changed, the optimal point of the extreme dust performance has a certain degree of deviation.

Furthermore, the curve on the right side of Fig. 9 shows that during the operation that increases the current and voltage, especially in the area with large D1/D2 offset, the dust collecting electrode 4 on the side without thorns first exceeds the The spark discharge electric field intensity of the general industrial electric dust collector 1 (although this varies greatly depending on the composition of the gas or the operating temperature conditions, it is generally set at 8kV/cm-12kV/cm), so it is not ideal. More specifically, it is better to set D1/D2≦2.0.

When D1/D2 exceeds 2.0, the electric field intensity on the side of the second discharge electrode 6 reaches the area where spark discharge occurs under normal operating conditions of the electric dust collector 1, or is 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, the upper limit of D1/D2 is preferably set to 2.0.

Next, the operation of the electric dust collector 1 of this embodiment will be explained. In the electric dust collector 1, by applying a negative voltage from the power supply to the first discharge electrode 5 and the second discharge electrode 6, corona discharge is generated at the ends of the protrusions 5a and 5b. The dust contained in the air flow G is charged by corona discharge. In the collection principle of the conventional electrode dust device, although the charged dust is attracted to the grounded dust collecting electrode 4 by the Coulomb force, it becomes trapped on the dust collecting electrode 4, but it is actually caused by the influence of ion wind Great effect.

When corona discharge occurs, negative ions are generated in the vicinity of the protrusions 5a and 5b, and the negative ions move toward the dust collecting electrode 4 by the electric field to generate ion wind. Therefore, when the Coulomb force acts on the dust, the ion wind flowing toward the dust collecting electrode 4 acts to move the dust contained in the air flow G to the vicinity of the dust collecting electrode 4. Moreover, in the area near the dust collecting electrode 4, the Coulomb force is increased by the increase of the electric field strength, and the dust is collected effectively. Furthermore, by arranging the dust collecting electrodes 4 arranged in circular tubes at intervals in the specific airflow G direction, that is, the x direction, a part of the ion wind flowing from the protrusions 5a and 5b toward the dust collecting electrode 4 is allowed to face The back side of the dust collecting electrode 4 leaks. In this way, since the airflow of the ion wind being reversed and separated at the dust collecting electrode 4 can be suppressed, the collection efficiency is improved.

Part of the ion wind that contains dust and flows toward the dust collecting electrodes 4 passes between the dust collecting electrodes 4.

In addition, between the second discharge electrode 6 and the dust collecting electrode 4 that do not have protrusions, as explained using FIG. 7B, by shifting the dust collecting electrode 4 from the center position CL toward the second discharge electrode 6 side, it shrinks The narrow distance between the dust collecting electrode 4 and the second discharge electrode 6 can increase the electric field intensity E2max near the dust collecting electrode 4 on the side of the second discharge electrode 6 compared with no offset. Accordingly, even the dust collecting electrode 4 on the second discharge electrode 6 side effectively collects dust by the Coulomb force. That is, by the ion wind from the side of the first discharge electrode 5, the uncollected dust that wraps around to the back of the dust collecting electrode 4, that is, on the side of the second discharge electrode 6 can be efficiently collected.

The dust collected to the dust collecting pole 4 is stripped and recovered by hammering. Or, even if the dust collecting electrode 4 is moved and the dust is scraped off with a brush, or wet cleaning is acceptable.

With this implementation type, the following effects can be achieved. Since the center C1 of the dust collecting electrode 4 is located at the center position CL between the center C2 of the first discharge electrode 5 and the center C3 of the second discharge electrode 6 further away from the direction of the first discharge electrode 5, the dust collecting electrode 4 It is close to the second discharge electrode 6. Accordingly, the electric field intensity between the dust collecting electrode 4 and the second discharge electrode 6 can be increased, and even the dust collecting electrode 4 on the side of the second discharge electrode 6 can increase the dust collection efficiency due to the Coulomb force.

In the above embodiment, although the example in which the dust collecting electrode 4 is a circular tube has been described, the present invention is not limited to this example. For example, the dust collecting electrode 4 may be a flat dust collecting electrode like a punched metal in which a large number of holes are formed in a flat plate. Alternatively, the dust collecting electrode 4 may be a braided metal mesh (for example, a lock crimp braided metal mesh, etc.) in which metal wires are crossed longitudinally and laterally. The dust collecting electrode 4, the first discharge electrode 5, and the second discharge electrode 6 are arranged as shown in FIGS. 10 to 12. Because the woven metal mesh has a certain aperture ratio and no edges on the surface, the electric field intensity near the dust collecting electrode 4 can be increased. In addition, the metal mesh is not limited to a woven metal mesh, and may be a metal mesh that is arranged in the longitudinal direction and the transverse direction and connects wires of a circular cross-section like a welded metal mesh.

When the electric dust collector 1 is used as an air cleaner for air purification, the time for particles to stay in the device is short, and the particle concentration is also low. In addition, the electric dust collector 1 used in a thermal power plant is different from the one used in air purification. It has a larger scale, longer particle retention time, and higher particle concentration. In the electric dust collector 1 for air purification, when low-concentration particles are passed with a short residence time, due to the effect of the gas circulation generated by the ion wind from the first discharge electrode 5, the dust collector 4 cannot Capture particles.

Therefore, even if the gas blocking plate 7 is provided on the upstream side of the air flow G between the dust collecting electrode 4 and the second discharge electrode 6. Since the air flow G is blocked by the gas blocking plate 7, the flow rate of the air flow flowing between the dust collecting electrode 4 and the second discharge electrode 6 is reduced, the retention time of particles is increased, and the trapping performance by the dust collecting electrode 4 can be improved.

In the case where the dust collecting electrode 4 is a flat dust collecting electrode, as shown in FIG. 13, even if it is set as a folded plate dust collecting electrode in which flat materials such as punched metal or metal mesh are alternately and regularly folded in the direction of air flow G It can be. In this case, the first discharge electrode 5 and the second discharge electrode 6 are offset according to the unevenness of the facing folded plate.

1: Electric dust collector 4: Dust collecting pole 5: The first discharge electrode 5a: Protruding part (1st corona discharge part) 5b: Protruding part (second corona discharge part) 5c: body part 5d: installation frame 6: The second discharge electrode 6a: Main body 6b: Installation frame 7: Gas blocking board C1: (dust collecting pole) center C2: (of the first discharge electrode) center C3: (2nd discharge electrode) center CL: Central location

[Fig. 1] is a perspective view showing an electric dust collector related 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 direction of airflow. [Figure 4] is a plan view showing the positional relationship between the dust collecting electrode and the discharge electrode. [Fig. 5] is a cross-sectional view corresponding to the height position of the protrusion of the discharge electrode. [Fig. 6A] is a graph showing the electric field intensity between the first discharge electrode and the dust collecting electrode in the case of no offset. [Fig. 6B] is a graph showing the electric field intensity between the second discharge electrode and the dust collecting electrode when there is no offset. [Fig. 7A] is a graph showing the electric field intensity between the first discharge electrode and the dust collecting electrode when there is a shift. [Fig. 7B] is a graph showing the electric field intensity between the second discharge electrode and the dust collecting electrode when there is a shift. [Figure 8] is a graph showing the relationship between the dust collection performance index and the offset ratio. [Figure 9] is a graph showing the relationship between the electric field intensity near the dust collecting electrode and the offset ratio. Fig. 10 is a plan view showing a modification of the electric dust collector according to one embodiment of the present invention. [Fig. 11] is a front view of the electric dust collector of Fig. 10 viewed from the direction of airflow. [Fig. 12] is a plan view showing the positional relationship between the dust collecting electrode and the discharge electrode. [Fig. 13] is a plan view showing a modification of the dust collecting electrode.

4: Dust collecting pole

5: The first discharge electrode

5a: Protruding part (1st corona discharge part)

5b: Protruding part (second corona discharge part)

5c: body part

5d: installation frame

6: The second discharge electrode

6a: Main body

6b: Installation frame

C1: (dust collecting pole) center

C2: (of the first discharge electrode) center

C3: (2nd discharge electrode) center

CL: Central location

D1: distance

D2: distance

G: Airflow

Claims (5)

An electric dust collection device with: The first discharge electrode, which has a main body, and a first corona discharge part for corona discharge protruding from the main body; The second discharge electrode, which has a surface without protrusions; and The dust collecting electrode is located between the first discharge electrode and the second discharge electrode, and the first discharge electrode side faces the first corona discharge part, The dust collecting electrode is located in a direction farther from the first discharge electrode than the central position between the first discharge electrode and the second discharge electrode. Such as the electric dust collector described in claim 1, where When the distance between the first discharge electrode and the dust collecting electrode is D1, and the distance between the second discharge electrode and the dust collecting electrode is D2, it becomes 1.1≦D1/D2≦2.0. Such as the electric dust collector described in claim 2, where The above-mentioned dust collecting electrodes are arranged along one direction, The D1 is the distance between the arrangement position of the first discharge electrode and the dust collecting electrode, The above D2 is the distance between the arrangement position of the second discharge electrode and the dust collecting electrode. The electric dust collection device described in any one of claims 1 to 3, wherein The electric field intensity between the first discharge electrode and the dust collecting electrode is equal to the electric field intensity between the second discharge electrode and the dust collecting electrode. The electric dust collection device described in any one of claims 1 to 3, wherein The first discharge electrode has a second corona discharge portion for corona discharge protruding from the main body part on the side opposite to the first corona discharge portion with the main body part in between, so as to be compatible with the second corona discharge part. In the way that the corona discharge part faces each other, a dust collecting electrode different from the above dust collecting electrode is provided.

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