JPH0578389B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrostatic precipitator using round dust collecting electrodes, and more particularly to an electrostatic precipitator in which the arrangement pitch of the dust collecting electrodes is improved. [Conventional technology] Conventional electrostatic precipitator (hereinafter abbreviated as EP)
, the dust resistance increases and its specific resistance value becomes 10 ¹¹
If it exceeds ~10 ¹² [Ω-cm], dielectric breakdown occurs within the dust layer deposited on the dust collection electrode, a so-called reverse ionization phenomenon, resulting in a significant drop in collection performance.
For this reason, when handling high-resistance dust such as EP for coal-fired power plants or sintering machines, the EP capacity is generally increased to compensate for the decrease in collection performance. Various attempts have been made to counter high-resistance dust, one of which is the two-stage EP, which is widely used in air purifiers, etc., which collects dust using a charged part that charges the dust and a high electric field. Attempts have been made to generally apply a method of suppressing reverse ionization by reducing the current as much as possible in the high electric field area and the dust collecting area. However, in this case as well, it is difficult to suppress reverse ionization of the charged part of the dust, and various methods have been tried. For example, a method uses a pipe as a dust collection electrode and cools the electrode by flowing water through the pipe to lower the electrical resistance of the dust and suppress reverse ionization. There is a third electrode method that attempts to suppress reverse ionization by providing three electrodes and absorbing ions of opposite polarity generated during reverse ionization. In addition, a particle charging device called a boxer charger (Japanese Patent Application No. 106,400/1982) has also been devised, which uses charge control techniques to apply only an electric charge to dust without causing reverse ionization. but,
All of these methods have not been put into practical use because they are difficult to implement on a commercial scale for general industry. Therefore, the present inventors developed a dust collection electrode with a round shape or an equivalent shape, with the aim of giving as much charge to the dust as possible in the charging part and obtaining high dust collection efficiency by combining it with the dust collection part in the latter stage. The electrical characteristics formed by the combination of an array of polygons (usually quadrilaterals) and a discharge electrode placed at the center of the polygons are similar to those on a flat plate parallel to the gas flow direction. Unlike the combination of a dust collection electrode and a row of discharge electrodes arranged in the center, we focused on the superiority of focusing only on the property of giving charge to dust, and used round dust collection electrodes. proposed an electric dust collector (Japanese Patent Application No. 59-66286). By using this round dust collection electrode, the current density on the surface of the dust collection electrode is made uniform and the electric field strength on the surface of the dust collection electrode is improved, thereby increasing the dust collection efficiency per the same dust collection area and charging the dust. It has been confirmed through tests that the ability to provide dust is superior to that of the conventional method in which dust collection electrodes are arranged parallel to the gas flow direction. Figures 7a and b and Figure 8 compare the case of using the round dust collecting electrode proposed in Japanese Patent Application No. 59-66286 and the case of using the conventional parallel plate dust collecting electrode. a,
As shown in Fig. 7b, the current density distribution characteristics are different from the current density with the conventional electrode combination (1b+2b) shown in Fig. 7b, as shown in Fig. 7a.
A very uniform current density is obtained on the surface of a. In addition, in the equal electric field strength line and the electric field intensity distribution at the shortest point between the discharge electrode and the dust collection electrode, in the conventional electrode configuration shown in Figure 8b, there is a portion Pb with high electric field strength only in the vicinity of the discharge electrode 1b. However, in the electrode configuration of the round dust collection electrode shown in Figure a, a portion Pa having high electric field strength can be formed not only near the discharge electrode 1a but also near the dust collection electrode 2a. There is. [Problems to be Solved by the Invention] However, when adopting this method of round dust collecting electrodes, the discharge electrode is formed of a polygonal (generally quadrangular) shape composed of round dust collecting electrodes. It is necessary to configure the discharge electrode in the center, and in the case of conventional discharge electrodes, the arrangement and support method are difficult. For example, FIG. 9 shows an example in which the discharge electrode is supported in the vertical direction, but the discharge electrode 1 passes through the support part 7 of the dust collecting electrode 2, and the insulation distance is the longest at the penetration part of the discharge electrode 1. Since the length is shortened, the operating voltage is controlled by the dielectric breakdown voltage of the penetration portion. Furthermore, even when the discharge electrode 1 is assembled into a frame and supported horizontally, the insulation distance between the discharge electrode mounting frame 3 and the dust collection electrode 2 becomes the shortest, as shown in FIG. There is a drawback that the breakdown voltage is lower than the breakdown voltage. The present invention has been made in consideration of the above circumstances, and its purpose is to realize a discharge electrode that can exhibit the characteristics of a round dust collection electrode without reducing the operating voltage. An object of the present invention is to provide an electrostatic precipitator that can ensure the uniformity of surface current density and high electric field density inherent to dust electrodes. [Means for Solving the Problems] The present invention is characterized in that an electric dust collector generates a corona discharge between a dust collection electrode and a discharge electrode, and attracts dust particles to the dust collection electrode. The dust collection electrode is formed into a round shape, and the discharge electrode is formed into a wide shape, with both lines of the wide part of the wide discharge electrode facing the gas flow direction, and the mounting frame of the discharge electrode is oriented perpendicular to the gas flow. In addition, the reference pitch of the arrangement of round dust collecting electrodes in the gas flow direction is made longer than the reference pitch in the direction perpendicular to the gas flow by a length approximately equal to the width of the discharge electrode. [Function] By using a wide type discharge electrode, oriented the mounting frame of the discharge electrode in the direction perpendicular to the gas flow, and making the reference pitch of the round dust collection electrode as long as the width of the discharge electrode in the gas flow direction, the discharge can be improved. There is no drop in operating voltage due to spark discharge between the electrode mounting frame and the dust collecting electrode. Further, the gas flow is not disturbed due to the use of the wide discharge electrode. [Effects of the Invention] According to the present invention, there is no reduction in operating voltage due to spark discharge between the discharge electrode mounting frame and the dust collection electrode, and there is no disturbance in gas flow due to the use of a wide electrode. The current density and electric field strength distribution on the surface of the round dust collecting electrode are made uniform, and the merits of ensuring the uniformity of current density and high electric field strength on the surface of the round dust collecting electrode, which are inherent to the round dust collecting electrode, are fully realized. You can make use of it. [Examples] Hereinafter, details of the present invention will be explained with reference to illustrated examples. Fig. 1 is a plan view showing the main part configuration of an electrostatic precipitator according to an embodiment of the present invention, Fig. 2 is a perspective view thereof, and Fig. 3 is a perspective view showing the relationship between the discharge electrode and its mounting frame. It is a diagram. In the figure, the discharge electrode 1 has a width in the gas flow direction (width is ld),
In addition, the mounting frame 3 of the discharge electrode 1 is arranged in the direction perpendicular to the gas flow, and the arrangement of the round dust collection electrode 2 surrounding the discharge electrode 1 is arranged in the direction perpendicular to the gas flow with respect to the reference electrode pitch _l1 in the direction perpendicular to the gas flow. The reference electrode pitch l ₂ is set to be approximately the same length as l ₁ + ld, and the distance lw from the tip of the discharge electrode 1 to the tip 5 of the dust collection electrode 2 is the distance between the discharge electrode mounting frame 3 and the dust collection electrode 2. In the relationship of the shortest distance lmin with , set so that lmin/lw≧0.7. In addition, when the reference polygon is a triangle as shown in Figure 5 a and b, one side of the equilateral triangle is the reference dimension.
Using the height ls when l ₁ , the reference electrode pitch l ₂ in the gas flow direction is set to be approximately the same length as ls + ld, and set so that lmin/lw≧0.7. It goes without saying that the shape of the discharge electrode 1 is not limited to the flat bar type shown in FIG. 4a, but may also be a discharge electrode with spikes as shown in FIG. 4b. The device configured in this way operates as follows. By using a widthwise type discharge electrode as the discharge electrode 1, lmin/lw≧0.7 can be achieved, and a drop in operating voltage due to spark discharge between lmin can be prevented. Specifically, the first
In the figure, the diameter lc of the round dust collecting electrode 2 is 60 [mm] (equivalent to 50A in piping nominal), and the diameter of the discharge electrode mounting frame 3 is
When lf = 34 [mm] (equivalent to 25A), it is expressed as lmin = (l ₂ - lf - lc) x 1/2, and if we set l ₂ = l ₁ + ld, then lmin = (l ₁ + ld - 94)×1/2. Generally, the dimension perpendicular to the gas flow is 300
If l ₁ = 300 [mm] to take a value close to [mm], then lmin103 + ld/2, and on the other hand, with the above value, the distance lw between the tip of the discharge electrode 1 and the tip 5 of the collecting electrode 2 is

[C] becomes. Therefore, ld is 5 to 10, which is the same as that of conventional discharge electrodes.
[mm], lmin/lw≒0.58 can only be secured, but by setting ld≧50[mm], lmin/lw≧0.7 can be achieved. According to the test results, the distance ls (S is a subscript indicating spark discharge) at which a spark discharge occurs in a high-resistance dust atmosphere is the following: a part with an edge, such as the discharge electrode 1, and a part without an edge, such as the discharge frame 3. Although it changes depending on the state of dust adhesion, approximately lmins (discharge frame): lws (discharge line) = 1:0.7 to 0.85, so by ensuring lmin/lw≧0.7, the original discharge line The operating voltage can be maintained up to the spark breakdown voltage of the dust collecting electrode. On the other hand, when lmin/lw<0.7, a spark discharge occurs at lmin between the discharge frame 3 and the dust collection electrode 2, which causes a drop in the operating voltage and makes it impossible to take advantage of the characteristics of the original round dust collection electrode. I can't. In the above example, when a conventional piano wire discharge electrode is used, lmin/lw≧0.58, so compared to the case of lmins/lws×0.7, the operating voltage is 0.58/0.7=0.83 times, or about 20 [%] compared to the original operating voltage. By supporting the mounting frame 3 of the discharge electrode 1 in the direction perpendicular to the gas flow, the width direction (wide part) of the discharge electrode 1 is
It is possible to have this in the direction of the gas flow, and it is possible to prevent disturbances in the gas flow caused by the wide electrode. In Figure 1, when the discharge electrode mounting frame 3 is arranged in the same direction as the gas flow as in the conventional EP, the gas flow direction is the Y direction, but in this case the discharge electrode 1
The larger the width of ld, the more it acts in the direction of obstructing the gas flow, which causes a decrease in performance.However, in the present invention, since the gas flow direction is in the X direction, even if the ld of the discharge electrode 1 is made large, the gas There is no flow disturbance and no performance deterioration occurs. By setting l ₂ to the same length as l ₁ +ld, even if a wide discharge electrode 1 is used, the uniformity of the electric field strength distribution and current density on the surface of the collecting electrode can be maintained. If the basic dimension l ₁ in the direction perpendicular to the gas flow and the reference dimension l ₂ in the gas flow direction are equal in FIG. It has been confirmed that the performance is good both experimentally and theoretically. On the other hand, when a wide type discharge electrode 1 (width length ld) is used as shown in the operation, the distance between the tip of the discharge electrode 1 and the dust collecting electrode 2 is (l) in the gas flow direction, as shown in Figure 6b. ₂ −ld)/2, and l ₁ /2 in the direction perpendicular to the gas flow, and by taking l ₂ to the same length as l ₁ + ld,
The respective distances are approximately the same in both the gas flow direction and the perpendicular direction. As a result, in Figure 6a,
Electric lines of force similar to those when l ₁ = l ₂ are obtained, and the uniformity of the electric field strength distribution and current density on the surface of the dust collecting electrode is maintained. In this way, according to the device of this embodiment, the wide type discharge electrode 1 is used, the mounting frame 3 of the discharge electrode 1 is oriented perpendicular to the gas flow direction, and the reference pitch of the round dust collection electrode 2 is oriented in the gas flow direction. By making the discharge electrode 1 as long as the width thereof, a drop in operating voltage due to spark discharge between the discharge electrode mounting frame 3 and the dust collection electrode 2 does not occur. Further, the gas flow is not disturbed due to the use of the wide discharge electrode 1. Therefore, according to the device of this embodiment, there is no drop in operating voltage due to spark discharge between the discharge electrode mounting frame 3 and the dust collecting electrode 2, and the gas flow is disturbed due to the use of the wide electrode. By making the current density and electric field strength distribution uniform on the surface of the round dust collecting electrode, and making use of the merits of ensuring the uniformity of current density and high electric field strength on the surface of the round dust collecting electrode, which is inherent to the round dust collecting electrode. be able to. Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of the drawing]

Figures 1 and 2 show the main parts of an electrostatic precipitator according to an embodiment of the present invention. Figure 1 is a plan view, Figure 2 is a perspective view, and Figure 3 is a discharge electrode. A perspective view showing the relationship with the mounting frame, Figures 4a and b are side views showing the shape of the discharge electrode, Figures 5a and b are plan views showing the arrangement of the dust collecting electrodes, and Figures 6a and b. 1 is a schematic diagram showing the relationship between the dust collection electrode and the lines of electric force, and FIGS. 7 to 10 are diagrams for explaining the conventional apparatus, respectively. DESCRIPTION OF SYMBOLS 1... Discharge electrode, 2... Dust collecting electrode, 3... Discharge electrode mounting frame, 4... Dust collecting electrode support part, 5... Dust collecting electrode tip, 6... Connection part.

Claims (1)

[Claims] 1. In an electric dust collector that generates a corona discharge between a dust collection electrode and a discharge electrode and attracts dust particles to the dust collection electrode, the dust collection electrode is formed into a round shape, and the discharge electrode is formed into a wide shape, both lines of the wide part of the wide discharge electrode are oriented in the gas flow direction, and the mounting frame of the discharge electrode is oriented in the direction perpendicular to the gas flow, and the gas flow of the arrangement of round dust collecting electrodes is An electrostatic precipitator characterized in that the reference pitch in the direction is longer than the reference pitch in the direction perpendicular to the gas flow by a length substantially equal to the width of the discharge electrode.