JPH07155641A - Electrostatic precipitator - Google Patents

Abstract

PURPOSE:To provide an electrostatic precipitator by which high dust collection efficiency is obtained by providing a plurality of dust-collecting spaces. CONSTITUTION:An electrostatic precipitator is equipped with a first dust- collecting space S1 and a second dust-collecting space S3 or the like. The first dust-collecting space S1 is arranged on the upstream side of gas flow and has dust-collecting electrode 1a arranged in a first interval. The second dust- collecting space S3 is arranged on the downstream side of gas flow and has dust-collecting electrodes 1c arranged in a second interval wider than the first interval. When the dust-collecting space is arranged at >=3, the interval of the dust-collecting electrodes is widened wider as these are arranged on the downstream side of gas flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic precipitator, and more particularly to an electrostatic precipitator having a plurality of dust collecting spaces.

[0002]

2. Description of the Related Art An electrostatic precipitator includes, for example, a linear discharge electrode and a dust collecting electrode arranged around the discharge electrode.

When a DC voltage is applied between the discharge electrode and the dust collecting electrode, the electric field formed between the two electrodes becomes stronger near the discharge electrode. As the applied voltage is increased, local dielectric breakdown occurs near the discharge electrode, and bipolar ions (including electrons) are generated. These ions are accelerated by the electric field and move toward the electrodes of opposite polarity.

When the ions collide with dust in the gas, the dust is charged and the dust particles are moved to the electrode. In this way, dust particles are captured on the surface of the dust collecting electrode and the discharge electrode. Since the location where the dielectric breakdown occurs is near the discharge electrode, most of the dust particles are captured on the dust collecting electrode where the electric charge travels long.

For example, when a negative voltage is applied, negatively charged dust particles near the discharge electrode are discharged to the dust collecting electrode.
The positively charged dust moves to the discharge electrode. The dust that positively withstands electricity is neutralized by the negative ions or electrons that are generated next, and the trapping on the discharge electrode is generally very small with respect to the dust collecting electrode, but dust aggregation may occur. Then, the adhesion to the discharge electrode may increase.

The voltage at which local dielectric breakdown occurs is called the corona starting voltage. Further, as the voltage is increased, a spark is generated between the discharge electrode and the dust collecting electrode, and most of the current will flow through the spark. The voltage at this time is called a spark starting voltage (spark point). If sparks are generated, current flows unnecessarily, and the dust collection efficiency is significantly reduced.

Electrostatic precipitating takes place in the corona discharge region between the corona onset voltage and the spark point. Generally, in order to form a high potential gradient (electric field gradient) between the discharge electrode and the dust collecting electrode, the applied voltage is controlled near the spark point. In general, control is performed to detect the number of sparks and the spark frequency and adjust the applied voltage below the spark point.

FIG. 3 shows an example of the structure of a conventional electrostatic precipitator. 3A shows a plan view and FIG. 3B shows an elevation view. The first section S1, the second section S2, and the third section S3 of the dust collecting space are arranged side by side,
It is surrounded by a common wall to form a gas flow passage. The dust collecting electrodes 21 are arranged in parallel in these dust collecting spaces, and a plurality of discharge electrodes 22 are arranged between the dust collecting electrodes as shown in FIG. Is suspended in.

These discharge electrodes 22 are connected to a DC power source 26 via an insulator 32 arranged in an insulator chamber 31. The combination of the dust collecting electrode 21 and the discharge electrode 22 is arranged independently in each section, and is connected to the DC power supply 26 independent of each other.

An inlet duct 23 is connected to a gas upstream side of the dust collecting space via a rectifying plate 25, and an outlet duct 24 is connected to a downstream side of the dust collecting space. In addition, a hopper 29 is arranged below each dust collecting section.

When dust is deposited on the surfaces of the dust collecting electrode and the discharge electrode, a hammering device (not shown) is energized to strike the dust collecting electrode and the discharge electrode to remove the dust accumulated on the surface in the hopper 29. Drop it on.

First section S1 and second section S
In the second and third sections S3, the dust collecting electrodes 21 are arranged at equal intervals and the electrode configurations are almost the same. Regarding the polarity of the DC power supply, generally, a DC power supply having a negative polarity is used in terms of stability of corona current and dust collection performance.

That is, a voltage having a negative polarity with respect to the dust collecting electrode 21 is applied to the discharge electrode 22. However, when ozone generation is disliked, such as for air conditioning, a direct current power source of positive polarity is used.

When clean air containing no dust is flowing in such a dust collecting space, a constant electric field strength and a constant corona current can be maintained at both the entrance and the exit of the dust collecting space. When dust comes in, it becomes difficult for the corona current to flow. At this time, since the dust is gradually captured on the electrode surface as the gas flows, the dust concentration in the exhaust gas decreases toward the downstream side, and the corona current easily flows.

When the constant voltage control is performed by the continuous charging method, the maximum value of the applied voltage is determined at the entrance of the dust collecting space where the dust concentration is high. Even if the constant voltage control is performed, the corona current value is determined at the entrance of the dust collecting space.

Under such a circumstance, if collective charging control is performed over the entire dust collecting space, the same voltage is applied to spaces having different dust concentrations and different corona discharge regions, which results in high dust collecting performance. Can't get Therefore, optimization is achieved by performing charge control for each section.

Considering the collection of dust, the particle size is large,
Dust with low electric resistance is easily captured at the entrance of the dust collection space. When such dust is collected, the remaining exhaust gas has a fine particle size and remains a dust component having high electric resistance.
That is, the harder the dust gets, the more it enters the exit side of the dust collecting space. Therefore, the dust collecting space arranged on the downstream side of the gas flow passage is controlled so that the dust component having a small particle diameter and high electric resistance is collected as efficiently as possible.

Here, generally considering the dust collecting performance, in order to improve the dust collecting efficiency, (1). How to apply corona current (how to increase the charge amount of dust particles) (2). The two most important points are how to maintain a large potential gradient between the discharge electrode and the dust collection electrode (how to form a significant unequal electric field).

At the entrance of the dust collecting space having a high dust concentration, for example, the first section in the configuration of FIG. 3, it is important to pass a large corona current to increase the amount of dust charge.
At the outlet of the dust collecting space where the dust concentration is low, in the third section in the configuration of FIG. 3, it is preferable to increase the supply voltage and keep the potential gradient large.

[0020]

As described above,
In the conventional electrostatic precipitator, the distance between the collecting electrodes is kept constant. In order to improve the dust collection efficiency, the dust collection space is divided into multiple sections, each of which is controlled by an independent power source. However, the maximum voltage was almost determined by the distance between the dust collecting electrodes, and the degree of freedom in control was limited.

An object of the present invention is to provide an electrostatic precipitator capable of obtaining high dust collecting efficiency.

[0022]

The electrostatic precipitator of the present invention comprises:
A first dust collecting space that is arranged on the upstream side of the gas flow and has dust collecting electrodes that are arranged at a first gap, and a second gap that is arranged on the downstream side of the gas flow and that is wider than the first gap. And a second dust collecting space having a dust collecting electrode arranged at.

[0023]

In the first dust collecting space, since the distance between the dust collecting electrodes is set to be narrow, it becomes easy to flow a large corona current even if the dust concentration is high.

In the second dust collecting space, since the distance between the dust collecting electrodes is set wide, a high potential gradient can be set. By flowing a large corona current in the first dust collecting space, the charge amount of dust particles can be increased. By giving a large potential gradient to the charged dust particles in the second dust collecting space, it becomes possible to efficiently collect even small dust particles.

[0025]

FIG. 1 schematically shows an electrostatic precipitator according to an embodiment of the present invention. The dust collecting space container 11 has an inlet duct 3 for gas inflow on the left side and an outlet duct 4 for gas outflow on the right side. A rectifying plate 5 is provided between the inlet duct 3 and the dust collection space to supply the inflowing gas in a laminar flow to the dust collection space.

The dust collecting space is divided into a first section S1, a second section S2 and a third section S3.
In the first section S1 on the most upstream side, the dust collecting electrodes 1a are arranged at the narrowest electrode intervals. In the second section S2, the space between the dust collecting electrodes 1b is slightly widened.
In the third section S3, the distance between the dust collecting electrodes 1c is further widened.

In FIG. 1, the discharge electrode is not shown. FIG. 2 schematically shows an electrode arrangement in each dust collecting space shown in FIG. The dust collecting electrodes 1 on the flat plate are arranged and installed in parallel with each other. The discharge electrodes 2 are arranged in parallel between the adjacent dust collecting electrodes 1. In the configuration shown, the discharge electrode 2 is a linear electrode, and the weight 8 is suspended and arranged vertically.

The discharge electrode 2 is connected to the negative electrode of the DC power supply 6. The distance between the discharge electrodes 2 is x, and the distance between the dust collecting electrodes 1 is y.
Then, the ratio of x / y is set to 1 or a value slightly lower than 1.

As shown in FIG. 1, a plurality of dust collecting electrodes are arranged in parallel in each section of the discharge space. A plurality of discharge electrodes are arranged between the adjacent dust collecting electrodes as shown in FIG. The basic structure of the discharge electrode and the dust collecting electrode is the same, but the first section, the second section, and the third section are the same.
In the section, the distance y between the dust collecting electrodes and the distance x between the discharge electrodes are set to gradually increase in the gas flow direction.

For example, the dust collecting electrode spacing is set to about 200 mm in the first section, the dust collecting electrode spacing is set to about 300 mm in the second section, and the dust collecting electrode spacing is set to about 400 mm in the third section.

Although the linear discharge electrode and the flat plate-shaped dust collecting electrode structure are shown, various modifications can be made to the structure of the dust collecting electrode and the structure of the discharging electrode. Using a self-supporting electrode as the discharge electrode,
It is also possible to use a structure that does not use weights or a structure that surrounds each discharge electrode as a collecting electrode. However, the basic configuration is the same, and the term "dust collecting electrode interval" used herein refers to the minimum value when the distance between the adjacent dust collecting electrodes passing through the discharge electrode is measured.

Further, in the electric dust collector of FIG. 1, a hopper as shown in FIG. 3 is provided in the lower portion thereof, and a hammering device for hitting the dust collecting electrode or the discharge electrode is also provided. Normally, a high voltage can be applied at the entrance of the dust collecting space due to the high dust concentration, but the corona current value can be kept low.
At the outlet of the dust collection space, the low dust concentration causes
High voltage and large corona current can be achieved.

Considering the function of the electrostatic precipitator, it is desirable to flow a large corona current in order to charge the dust at the entrance of the dust collecting space. At the outlet of the dust collecting space, since the dust is already charged, the corona current may be low, and a high potential gradient is desirable for the dust collecting action. In an electrostatic precipitator using the same electrode structure, these requirements are difficult to meet.

That is, in order to obtain a large corona current, it is preferable to narrow the distance between the dust collecting electrodes, but if the distance between the dust collecting electrodes is narrowed, the applied voltage will decrease. If the distance between the dust collecting electrodes is wide, a high voltage can be obtained, but the corona current will be reduced.

As shown in FIG. 1, when the distance between the dust collecting electrodes is narrowed in the gas upstream portion of the dust collecting space, a large corona current can be obtained and the dust particles can be efficiently charged. Further, a high potential gradient can be set by setting a large distance between the dust collecting electrodes on the gas downstream side.

In the structure of FIG. 1, when a high corona current is obtained by applying a voltage corresponding to the distance between the dust collecting electrodes between the collecting electrode and the discharge electrode, which are arranged at a narrow interval in the first section, the dust in the gas is removed. The particles are effectively charged. Dust particles of relatively large size and low resistance are collected in the first section.

In the second section, the dust collecting electrode interval is widened and a higher voltage is applied. Since a certain amount of dust is collected in the first section, the corona current easily flows, and a relatively high corona current can be obtained even if the distance between the dust collecting electrodes is widened.

Further, since the distance between the dust collecting electrodes is widened and a higher voltage is applied, a higher potential gradient is obtained, and dust particles having a smaller particle size and dust particles having a higher resistance are also collected in the second section. It

In the third section, the distance between the dust collecting electrodes is further widened, and a higher voltage is applied between the dust collecting electrode and the discharge electrode. In the third section, the dust collecting electrode interval may be widened so that it becomes more difficult for the corona current to flow.

The dust particles flowing in from the upstream are the first
Since the sections S1 and the second sections S2 have already been charged, it is possible to efficiently collect dust if a high potential gradient is applied to the third section without further charging. Further, by providing a high potential gradient, it is possible to efficiently collect high-resistance dust particles, which are difficult to collect, and smaller dust particles.

Assuming that the arrangement of the dust collecting electrode and the discharge electrode in the second section S2 corresponds to that of the conventional electrostatic precipitator, the dust collecting electrode interval in the first section S1 becomes narrow and the electrode surface area of the dust collecting electrode increases. is doing. Since the distance between the dust collecting electrodes is narrowed, a larger corona current can be passed, and the electrode surface of the dust collecting electrode is expanded, so that the dust collecting performance is improved.

In the third section S3, the distance between the dust collecting electrodes is widened and the voltage between the dust collecting electrode and the discharge electrode is increased. By increasing the applied voltage, a higher potential gradient can be obtained, and high resistance and dust collection of fine particles can be efficiently performed. Further, since it is not necessary to pass the corona current unnecessarily, it is possible to reduce the current consumption by suppressing the current value.

The configurations of the dust collecting electrode and the discharge electrode can be variously changed. For example, the number of dust collecting electrodes can be increased or decreased according to the size of the dust collecting space. Further, if there are a plurality of dust collecting sections arranged in the gas flow passage, the number may be variously changed according to the dust collecting performance, the property of the inlet gas, and the like. Further, the method of applying voltage to the electrodes can be selected from various charging methods such as continuous charging, intermittent charging, pulse charging and the like.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various changes, improvements, combinations and the like can be made.

[0045]

The dust collecting space is divided into a plurality of sections,
By increasing the distance between the dust collecting electrodes in each section in accordance with the gas flow direction, it is possible to perform charge control suitable for the properties (concentration, physical properties) of dust.

Since dust can be collected according to the properties of the dust (concentration, physical properties, charge amount) in each section,
It can be made smaller than the conventional electrostatic precipitator. Since it is possible to operate the electrostatic precipitator at the optimum voltage and current in each section, it is possible to eliminate wasteful current consumption and reduce power consumption.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of an electrostatic precipitator according to an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing an electrode configuration example in the electrostatic precipitator of FIG.

FIG. 3 is a plan view and an elevation view schematically showing a configuration of an electrostatic precipitator according to a conventional technique.

[Explanation of symbols]

 S Dust collection section 1 Dust collection electrode 2 Discharge electrode 3 Inlet duct 4 Outlet duct 5 Rectifier plate 6 DC power supply 8 Weight 11 Dust collection space container

Claims (2)

[Claims] 1. A first dust collecting space, which is arranged on the upstream side of the gas flow and has dust collecting electrodes arranged at a first interval, and a first dust collecting space, which is arranged on the downstream side of the gas flow, from the first interval. An electrostatic precipitator having a second dust collecting space having dust collecting electrodes arranged at wide second intervals. 2. A first DC power supply capable of supplying a first voltage value and a first current value for the first dust collecting space, and a first DC power source for the second dust collecting space. The electrostatic precipitator according to claim 1, further comprising a second DC power supply capable of supplying a second voltage value higher than the voltage value and a second current value lower than the first current value.