JP2015024380A - Electric dust collector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a high-rise constitution while maintaining a collection efficiency of dust containing heavy metals, and to reduce a cost of manufacture.SOLUTION: A wet type electric dust collector 1 comprises: a discharge electrode (electrode rod 24 and discharge wire 25), on which a DC high voltage is impressed; and a dust collecting electrode 12 that collects fine particles contained in an exhaust gas discharged out of an exhaust gas generation source by a negative corona discharge generated in a gap from the discharge electrode (electrode rod 24 and discharge wire 25) on the basis of the DC high voltage. The dust collecting electrode 12 is set at a suitable size on the basis of an air quantity containing the exhaust gas and a dust collection efficiency with respect to the fine particles contained in the exhaust gas.

Description

  The present invention relates to an electric dust collector that removes dust and the like from waste gas. In particular, the present invention relates to a wet type electrostatic precipitator capable of increasing the height and maintaining the manufacturing cost while maintaining the dust collection efficiency of dust containing heavy metal.

  Conventionally, wet electrostatic precipitators (see, for example, Patent Documents 1 to 3) remove harmful dust and mist from waste gas generated in waste incineration processes as well as sulfuric acid mist treatment and aluminum refining exhaust gas treatment in the mining industry. It is used for the purpose of collecting. As described above, the wet type electrostatic precipitator is widely used as a useful device from the viewpoint of air pollution prevention and environmental protection.

  To-be-processed waste gas processed with a wet electrostatic precipitator contains harmful substances such as lead, cadmium and arsenic and heavy metals. For this reason, in such a wet electrostatic precipitator, it is required to increase the dust collection efficiency of dust containing harmful substances and heavy metals.

The wet type electrostatic precipitator generally has a dust collecting electrode having a smooth surface composed of two flat plate types or a cylindrical shape such as a cylindrical shape or a rectangular tube shape, and a linear shape provided in the dust collecting electrode. It is comprised so that it may contain.
When fine particles such as dust and mist are removed by such a wet electrostatic precipitator, a high voltage is charged between the discharge electrode side and the grounded collection electrode side. As a result, a strong current electric field is formed between the discharge electrode side and the grounded dust collection electrode side, and a strong corona discharge is generated from the discharge electrode side as the voltage rises. The dust collection space between the two is filled with negative ions and electrons. When exhaust gas is introduced into the dust collection space, dust and mist in the exhaust gas are negatively charged, move toward the dust collection electrode by the Coulomb force with an electrostatic aggregating action, and adhere to the dust collection electrode. The adhering dust or mist loses a negative charge at the dust collecting electrode, is peeled off from the dust collecting electrode by the washing water and its own weight supplied to the dust collecting electrode, and is discharged to the outside of the electric dust collector.
In this way, the wet electrostatic precipitator can collect various types of solids, fine particles such as liquid fine particles, etc. with high dust collection efficiency.

  In such a wet electrostatic precipitator, a technique for increasing the charging voltage between the discharge electrode and the dust collection electrode is known in order to increase the dust collection efficiency of dust containing heavy metals.

JP 2007-196159 A JP 2002-119889 A Japanese Patent Publication No. 6-91965

  However, simply increasing the radix of the wet electrostatic precipitator can improve the dust collection efficiency, but requires a large installation area and increases the number of components. On the other hand, if the installation area is simply reduced, the dust collection efficiency of dust and the like is reduced this time, so that the dust and the like cannot be sufficiently removed from the waste gas. Therefore, it is required to increase the height and reduce the manufacturing cost while maintaining the dust collection efficiency of dust and the like.

  The present invention has been made in view of such a situation, and an object of the present invention is to increase the layer height and reduce the manufacturing cost while maintaining the dust collection efficiency of dust containing heavy metals.

A power supply control device for an electrostatic precipitator according to one aspect of the present invention,
A discharge electrode to which a DC high voltage is applied;
A dust collecting electrode that collects fine particles contained in the exhaust gas discharged from the exhaust gas generation source by negative corona discharge generated between the discharge electrode based on the DC high voltage,
An electric dust collector comprising:
The height of the dust collection electrode is set based on the air volume containing the exhaust gas and the dust collection efficiency for the fine particles contained in the exhaust gas.
It is characterized by that.

  In this case, the height of the dust collection electrode can be further set based on the area and volume of the opening.

  ADVANTAGE OF THE INVENTION According to this invention, while maintaining the dust collection efficiency of the dust containing a heavy metal, while achieving slimming (higher layering), the wet electric dust collector which can aim at reduction of manufacturing cost is realizable. .

It is sectional drawing which shows schematic structure of the wet electric dust collector which concerns on embodiment of this invention. It is a perspective view which shows schematic structure inside the housing of a wet electric dust collector. It is sectional drawing which shows schematic structure of the conventional wet electric dust collector. It is a figure which shows the state which has arrange | positioned two wet electric dust collectors in series. It is a figure which shows the state which slimmed the wet electric dust collector. It is a figure which shows the test result which shows the relationship between the in-machine flow velocity (in-machine gas velocity) (m / s) and K (omega) (apparent particle moving velocity) (m / s) in case sulfuric acid mist is made into object as microparticles | fine-particles. It is a figure which shows the relationship between the in-machine flow velocity (in-machine gas velocity) (m / s) and dust collection efficiency (%) in the case of using sulfuric acid mist as the fine particles. It is a figure which shows the test result which shows the relationship between in-machine flow velocity (in-machine gas velocity) (m / s) and Kω (apparent particle movement velocity) (m / s) when As (arsenic) is used as the fine particles. is there. It is a figure which shows the relationship between the in-machine flow velocity (in-machine gas velocity) (m / s) and dust collection efficiency (%) when As (arsenic) is used as the fine particles.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Configuration of wet electrostatic precipitator]
First, the configuration of the wet electrostatic precipitator 1 will be described with reference to FIG.
FIG. 1 is a cross-sectional view showing a schematic configuration of a wet electrostatic precipitator according to an embodiment of the present invention.
Specifically, FIG. 1 (A) and FIG. 1 (B) are cross-sectional views showing the schematic configuration of the external appearance of the wet type electrostatic precipitator, and are cross-sectional views seen from different directions substantially perpendicular to each other.

  The wet electrostatic precipitator 1 is provided with an upper casing 11, a dust collecting electrode 12 that also functions as a side casing, a lower casing 13, and a frame 14.

  The casing of the wet electrostatic precipitator 1 is configured by combining the upper casing 11, the dust collecting electrode 12, and the lower casing 13 in that order from above. The casing of the wet electrostatic precipitator 1 is fixed by a frame 14 so as to be spaced apart from the ground by a predetermined distance. In the present embodiment, conductive FRP (Fiber Reinforced Plastics) is adopted as the material of the casing of the wet electrostatic precipitator 1.

FIG. 2 is a perspective view showing a schematic configuration inside the housing of the wet electrostatic precipitator 1.
As shown in FIG. 2, an upper grid 21, the above-described dust collecting electrode 12, a lower grid 23, an electrode rod 24, a discharge wire 25, a weight 26, and the like are disposed inside the housing of the wet electrostatic precipitator 1. An upward spray nozzle 27 and a cleaning pipe 28 are provided.

  As shown in FIG. 2, the upper grid 21, the dust collection electrode 12, and the lower grid 23 are spaced apart from each other by a predetermined distance in that order from above, and are substantially parallel to each other in the horizontal direction. It is arranged.

As shown in FIG. 2, the dust collection electrode 12 is configured by repeatedly arranging a plurality of “chambers” with a rectangular tube as a unit (hereinafter, such units are referred to as “chambers”). .
Specifically, hereinafter, one of the substantially horizontal directions is referred to as “vertical direction”, and a direction perpendicular to the vertical direction is referred to as “lateral direction”. In this case, by repeatedly arranging N units in the vertical direction and repeating M units in the horizontal direction (hereinafter referred to as “N × M”), the dust collection electrode 12 is configured.
Here, N and M are arbitrary independent integer values. In the present embodiment, as shown in FIG. 2, the number of “chambers” of the dust collection electrode 12 is N × M = 9 × 9. ing.
Moreover, the chamber of the present embodiment is a square tube having sides with a length of 35 to 50 cm.
In this embodiment, conductive FRP is adopted as the material of the dust collection electrode 12.

In this embodiment, the discharge electrode for the dust collecting electrode 12 is constituted by an electrode rod 24 and a discharge wire 25.
As shown in FIG. 2, the electrode rod 24 is disposed so as to penetrate the center inside of a predetermined “chamber” of the dust collecting electrode 12 in a substantially vertical direction, and has an upper end fixed to the upper grid 21 and a lower end. Is fixed to the lower grid 23.
As shown in FIG. 2, the discharge line 25 is suspended from the upper grid 21 and is disposed so as to penetrate the center inside of a predetermined “chamber” of the dust collecting electrode 12 in a substantially vertical direction. The discharge line 25 is also connected to a weight 26 provided on the upper part of the lower grid 23 so as to have a tension that does not loosen.

  A negative DC high voltage (charge voltage) supplied from the power supply device 2 is directly applied to the electrode rod 24. On the other hand, the negative DC high voltage is applied to the discharge line 25 via the upper grid 21.

  The upward spray nozzle 27 is disposed above the four corners of each “chamber” of the dust collecting electrode 12 and ejects cleaning water flowing through the cleaning pipe 28 as a fine mist in a substantially vertical upward direction. Thereby, fine particles such as mist and dust adhering to the dust collecting electrode 12 can be cleaned and removed.

Next, with reference to FIG. 3, the wet electric dust collector 1 of this embodiment is demonstrated.
FIG. 3 is a cross-sectional view showing a schematic configuration of a conventional wet electrostatic precipitator.
As is clear from comparison between FIG. 1 and FIG. 3, the wet electrostatic precipitator 1 of the present embodiment of FIG. 1 is higher than the conventional wet electrostatic precipitator 100 of FIG. It has been. Hereinafter, the reason will be described with reference to the drawings after FIG.

In recent years, high-efficiency dust collection efficiency is required for wet electrostatic precipitators.
For example, when a dust collection efficiency exceeding 99% is required, the conventional wet electrostatic precipitator 100 (FIG. 4) is designed as shown in FIG. 3) must be connected in series. In addition, the height of the dust collection electrode of the conventional wet electric dust collector 100 shall be 4 m.
FIG. 4 is a view showing a state in which two conventional wet electrostatic precipitators of FIG. 3 are arranged in series.
As shown in FIG. 4A, for example, when two conventional wet electrostatic precipitators 100-1 and 100-2 are installed, twice the installation floor area (installation space) is required. Of course, if N conventional wet electrostatic precipitators 100 (N is an integer greater than or equal to 2) are provided, the installation floor area is required N times.
Therefore, the inventors connect two conventional wet electrostatic precipitators 100-1 and 100-2 in the vertical direction, as shown in FIG. Invented to increase the height to twice the height (8 m height).
Thereby, an installation floor area becomes the same as the case where the one conventional wet electrostatic precipitator 100 is installed.

Furthermore, the present inventors do not simply connect two conventional wet electrostatic precipitators 100-1 and 100-2 in the vertical direction, but increase the height of the dust collecting electrode as shown in FIG. One wet electrostatic precipitator 1 was invented.
FIG. 5 is a view showing a state in which the wet electrostatic precipitator 1 of FIG.
Furthermore, as shown in FIG. 5, if the in-machine gas velocity is increased, it is possible to realize a wet type electrostatic precipitator 1 that is slim (the opening is reduced) with the same dust collection area. In the example of FIG. 5B, the height of the dust collection station is 10 m, which is 2 m higher than 8 m, and slimming is achieved accordingly.
This makes it possible to reduce the cost by reducing the installation floor area (installation space) and the number of parts.

The present inventors conducted the following test in order to verify whether the above-described performance can be achieved by increasing the number of layers.
[Purpose of the test]
(1) In this test, the wet-type electrostatic precipitator 1 of FIG. 1 having a high layer has the performance of dust collection efficiency equivalent to the state in which the conventional wet-type electrostatic precipitators 100-1 and 100-2 are arranged in series. The purpose is to confirm that there is.
(2) Furthermore, this test confirms that the wet electrostatic precipitator can be made taller (slimmed) in the same dust collection area in order to cope with the increase in the gas velocity inside the dust collection electrode. The purpose is to do.

[contents of the test]
A wet electrostatic precipitator (10 m is the wet electrostatic precipitator 1 of the present embodiment in FIG. 1) having a dust collecting electrode with a height of 10 m / 7 m / 4 m was used in this test. With respect to these wet electrostatic precipitators, the in-machine flow velocity (in-machine gas velocity) is 1.0 → 1.5 → 2.0 → 2.4 → 3.7 m / s at a load voltage of 70 kV. It changed to (Max), respectively, measured the sulfuric acid mist density | concentration and As (arsenic) density | concentration, and calculated Komega (apparent particle moving speed) and dust collection efficiency.

[Test results using sulfuric acid mist]
FIG. 6 shows test results showing the relationship between in-machine flow velocity (in-machine gas velocity) (m / s) and Kω (apparent particle movement velocity) (m / s) when sulfuric acid mist is used as the fine particles. FIG.
FIG. 7 is a diagram showing the relationship between the in-machine flow velocity (in-machine gas velocity) (m / s) and the dust collection efficiency (%) when sulfuric acid mist is used as the fine particles.

According to the measurement result of sulfuric acid mist, when the conventional wet electrostatic precipitator 100 (FIG. 3) having a dust collecting electrode with a height of 4 m is used, the in-machine flow velocity at which the Kω value shows the maximum value (peak) is About 1.2 m / s.
On the other hand, when a wet electrostatic precipitator equipped with a dust collecting electrode having a height of 7 m is used, the Kω value shows the maximum value (peak) even when the in-machine flow velocity is about 2.4 m / s. However, there was a tendency to rise linearly.
Similarly, when the wet electrostatic precipitator 1 having a dust collection electrode having a height of 10 m is used, the Kω value shows the maximum value (peak) even when the in-machine flow velocity is about 3.7 m / s. However, there was a tendency to rise linearly.
However, the in-flight flow velocity at which the Kω value is the highest value (peak) exists in the high speed region, and it is estimated that the velocity is higher at 10 m than at 7 m.

As a result of the test, when sulfuric acid mist is used as the fine particles, when the conventional wet electrostatic precipitator 100 having a dust collecting electrode with a height of 4 m is used, the dust collection efficiency is the highest value at Kω. When the in-machine flow velocity (in-machine gas velocity) of 1 m / s was reached, it dropped rapidly.
On the other hand, when the wet electrostatic precipitator provided with a dust collecting electrode having a height of 7 m and the wet electrostatic precipitator 1 of this embodiment provided with a dust collecting electrode having a height of 10 m are used, In contrast, the dust collection efficiency was almost flat even in the region where the in-machine flow velocity (in-machine gas velocity) was high, and did not decrease.

[Test results with As (arsenic)]
FIG. 8 shows test results showing the relationship between the in-machine flow velocity (in-machine gas velocity) (m / s) and Kω (apparent particle movement velocity) (m / s) when As (arsenic) is used as the fine particles. FIG.
FIG. 9 is a diagram showing the relationship between the in-machine flow velocity (in-machine gas velocity) (m / s) and the dust collection efficiency (%) when As (arsenic) is used as the fine particles.

According to the measurement result of As (arsenic), when the wet electrostatic precipitator 1 having a dust collecting electrode with a height of 4 m is used, the in-machine flow velocity at which the Kω value shows the maximum value (peak) is about 0. 0. It was 9 m / s.
On the other hand, when the wet electrostatic precipitator 1 having a dust collecting electrode having a height of 7 m was used, the in-machine flow velocity at which the Kω value showed the highest value (peak) was about 1.5 m / s. .
Similarly, when the wet electrostatic precipitator 1 having a dust collection electrode having a height of 10 m is used, the in-machine flow velocity at which the Kω value shows the maximum value (peak) is about 2.5 to 3.0 m / s. Met.
For the absolute value of the highest value (peak) of the Kω value, either the wet electrostatic precipitator 1 having a dust collecting electrode with a height of 7 m or the wet electrostatic precipitator 1 having a dust collecting electrode with a height of 10 m is used. Even when it was used, it was almost the same as a wet type electrostatic precipitator equipped with a dust collecting electrode having a height of 4 m.

  As a result of the test, when As (arsenic) is used as a fine particle, dust collection is possible even when a wet electrostatic precipitator equipped with a dust collection electrode having a height of 4 m, 7 m, or 10 m is used. The efficiency dropped sharply when Kω exceeded the in-machine flow velocity (in-machine gas velocity) at which the maximum value (peak) was reached.

[Summary]
(1) From the above, it can be seen that the in-machine flow velocity (in-machine gas velocity) at which Kω becomes the maximum value (peak) increases as the height of the dust collection electrode increases.
(2) The dust collection efficiency is kept high to some extent up to the vicinity of the in-machine flow velocity (in-machine gas velocity) where Kω is the maximum value (peak). However, if the in-machine flow velocity (in-machine gas velocity) becomes higher than that, the dust collection efficiency decreases.
(3) Summarizing the above, the height of the dust collection electrode can be calculated by taking the in-machine flow rate (in-machine gas speed, in other words, the volume of air containing exhaust gas) and the dust collection efficiency for fine particles contained in the exhaust gas as parameters. It turned out to be a designable element. That is, it has been found that the height of the dust collection electrode can be set based on the air volume including the exhaust gas and the dust collection efficiency with respect to the fine particles contained in the exhaust gas.

In addition, in the said test, the area of the opening part (bottom surface) of a dust collecting electrode is the wet electric dust collector (10 m is the thing of this embodiment of FIG. 1) provided with the dust collecting electrode of each height of 10m / 7m / 4m. Wet electrostatic precipitator 1) All were the same.
However, as described above with reference to FIG. 5, if the in-machine flow rate (in-machine gas speed, in other words, the air volume including exhaust gas) can be increased, the wet electrostatic dust collection that is slim (the opening is reduced) with the same dust collection area. Realization of the device is also possible.
In other words, the height of the dust collecting electrode can be further set based on the area and volume of the opening (bottom surface).

[Effects of wet electrostatic precipitator of this embodiment]
In summary, the wet electrostatic precipitator 1 (FIG. 1) of the present embodiment can provide the following advantageous effects compared to the conventional wet electrostatic precipitator 100 (FIG. 3). is there.

(1) In the present embodiment, the wet electrostatic precipitator 1 includes a discharge electrode (electrode rod 24 and discharge wire 25) to which a DC high voltage is applied, and a discharge electrode (electrode rod 24 and discharge electrode based on the DC high voltage). And a dust collecting electrode 12 for collecting fine particles contained in the exhaust gas discharged from the exhaust gas generation source by negative corona discharge generated between the electric wire 25) and the electric wire 25). The height of the dust collection electrode 12 is set based on the air volume including the exhaust gas and the dust collection efficiency with respect to the fine particles contained in the exhaust gas.
In this way, by appropriately setting the height of the dust collection electrode 12, it is possible to increase the height and reduce the manufacturing cost while maintaining the dust collection efficiency of dust containing heavy metals.

(2) In the present embodiment, the height of the dust collection electrode 12 can be further set based on the area and volume of the opening (bottom surface).
As a result, while maintaining the dust collection efficiency of heavy metal-containing dust, in addition to increasing the height, it is possible to achieve further slimming (reduction in installation floor area) and to reduce manufacturing costs.

DESCRIPTION OF SYMBOLS 1 ... Wet electrostatic dust collector 11 ... Upper casing 12 ... Dust collection electrode 13 ... Lower casing 14 ... Frame 21 ... Upper grid 23 ... Lower grid 24 ... Electrode Rod 25 ... discharge wire 26 ... weight

Claims (2)

A discharge electrode to which a DC high voltage is applied;
A dust collecting electrode that collects fine particles contained in the exhaust gas discharged from the exhaust gas generation source by negative corona discharge generated between the discharge electrode based on the DC high voltage,
An electric dust collector comprising:
The height of the dust collection electrode is set based on the air volume containing the exhaust gas and the dust collection efficiency for the fine particles contained in the exhaust gas.
An electric dust collector characterized by that. The height of the dust collection electrode is further set based on the area and volume of the opening,
The electrostatic precipitator according to claim 1.

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