JP2959190B2 - Dust removal method of electric precipitator for motorway tunnel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing dust from an electric dust collector for purifying air in a motorway tunnel, and more particularly, to removing dust collected on a dust collecting electrode of the electric dust collector. The present invention relates to a method for determining the arrival of time.

[0002]

2. Description of the Related Art FIG. 2 is a schematic longitudinal sectional view of an electric precipitator for purifying air in a motorway tunnel, and FIG. 3 is an enlarged front view of the precipitator. In the figure, reference numeral 1 denotes a bypass passage leading to a motorway tunnel (not shown), and an electric precipitator is installed in the bypass passage 1. Reference numeral 3 denotes a casing of the electric precipitator, and reference numeral 2 denotes a blower provided at a rear end of the casing 3. A 'is returned to the tunnel from the rear end of the casing 3 through the bypass passage 1 again.

[0003] Reference numeral 8 denotes a dust collecting unit provided in the casing 3, which has dust collecting electrodes composed of a plurality of ground electrode plates 20 and high voltage electrode plates 21 which are alternately arranged as shown in FIG. 3. I have. A high voltage is applied to the high voltage electrode plate 21 from the power supply 6. Reference numeral 7 denotes a charging unit, which is arranged on the upstream side of the dust collection unit 8. Reference numeral 9 denotes an air blow nozzle, which is disposed downstream of the dust collecting unit 8, injects compressed air supplied from the compressor 10 through the air blow line 11 toward the dust collecting unit 8, and captures the dust on the dust collecting electrodes 20 and 21. The collected dust is blown down into the casing 3 and removed. The blown-down dust passes from a discharge plenum 12 at the bottom of the casing 3 to a dust collection line 1.
4 and collected by the dust separation and collection device 13. Dampers 4 and 5 for opening and closing the front and rear openings of the casing 3, respectively, open when collecting dust and close when collecting dust.

As shown in FIG. 3, a ground electrode plate 20 is supported by a frame 19 of a dust collecting unit 8 and a high voltage electrode plate 21 is provided.
Are fixed to the high voltage electrode 18. The high-voltage electrode 18 is fixed to the electrode support bar 16, and the electrode support bar 16 is fixed to the insulator 15. Further, the insulator 15 is provided with a frame 19.
Is fixed to a mounting table 17 fixed to the mounting table 17. The compressed air from the air blow line 11 is also injected into the insulator 15 to blow off the dust accumulated there.

[0005]

When the amount of dust collected by the dust collecting electrodes 20 and 21 exceeds a certain limit value in the electric dust collector having such a configuration, the collected dust is left in the air. The so-called re-scattering phenomenon of scattering occurs, and the dust collection rate decreases. Therefore, in the case of continuous operation, the dust collected on the dust collecting electrode is removed during the operation. In that case, conventionally, a constant operation time considered appropriate by using a long time timer is generally measured, and dust is removed each time the operation time elapses.

However, the state of dust accumulation at the dust collecting electrode is affected by the degree of contamination of the air in the tunnel due to traffic volume in the tunnel, weather conditions, and the like, and is not suitable for the conventional method of mechanically removing dust at regular intervals. It was difficult to get the timing. Therefore, the present invention provides an electric dust collector for a motorway tunnel that can remove dust at an appropriate timing in accordance with the actual dust accumulation state at the dust collecting electrode and can increase the operation efficiency of the electric dust collector. It is an object of the present invention to provide a method for removing dust.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention obtains the dust collection rate of an electric dust collector for each particle size of the dust, and determines the time to remove the dust from the result. And At this time, it is preferable to remove the dust when the dust collection rate of the dust having a particle size of a certain level or more extremely deteriorates.

[0008]

[Effect] The dust collection rate of the electric dust collector gradually decreases as the dust accumulates on the dust collection electrode. However, especially when the dust amount exceeds a certain limit value, the dust collection rate is significantly reduced due to the re-scattering phenomenon described above. I do. Therefore, by observing the change in the dust collection rate and selecting the point at which the dust collection rate greatly decreases to remove the accumulated dust, it is possible to set an appropriate cleaning timing that is not affected by the operating conditions of the electric dust collector. Obtainable.

By the way, the dust collection rate of an electric dust collector for a motorway tunnel is generally calculated based on the mass concentration. The target of this dust collection rate is set to, for example, 80%, and this is reduced to, for example, 60% or less. If they do, they take some action. However, if the dust collection electrode is cleaned with such a dust collection rate as a guide, the dust collection rate becomes apparent while the collection of relatively heavy dust, in other words, dust having a large particle diameter, is achieved to some extent. Since the cleaning time is improved, the cleaning timing may be delayed. By the way, the particle size of the dust in the air inside the motorway tunnel is
It is known that a large number of fine particles having a size of 0.3 μm or less occupy a large number. However, the collection performance of the electrostatic precipitator in the fine particle size range is particularly deteriorated due to accumulation of dust. In that case, the dust collection rate by the mass concentration does not decrease so much, but scattering of fine dust is not preferable from the viewpoint of air purification.

Therefore, the inventors repeated experiments on a method of determining a time to remove dust from the dust collecting electrode from a change in the dust collecting rate based on the number concentration. As a result, the dust gradually accumulates on the dust collecting electrode, and when the amount exceeds a certain limit value, the dust collection rate of the dust having a certain particle size, for example, 1 μm or more, is extremely reduced, and depending on the experimental conditions, the dust collecting rate is extremely low. It has been found that a phenomenon in which the rejection rate is apparently zero or negative occurs. In that case, the dust collection rate based on the mass concentration described above often indicates a value equal to or higher than a predetermined value.

The above phenomenon has been further considered,
The following causes were confirmed. That is, when the dust amount of the dust collecting electrode exceeds a certain limit value, the dust collecting ability generally decreases for each particle size, and particularly, the fine dust having a large degree of decrease of 1 μm or less passes through the dust collecting electrode. In the process of being discharged from the electrostatic precipitator, a so-called agglomeration phenomenon occurs in which some dust particles are aggregated, and the equivalent particle size becomes larger than the original particle size. For this reason, the number concentration having a particle diameter of 1 μm or more on the downstream side of the electric dust collector increases, and the dust collection rate apparently decreases extremely.

Further, the aggregated fine particles are small in weight because of their small particle size, and the dust collection rate by mass concentration does not immediately decrease. When the change in the dust collection rate is observed depending on the number concentration, when the entire particle size range is measured collectively, the total dust count itself is greatly reduced due to the aggregation of the fine particles, so that the apparent dust collection rate is increased. Therefore, it is necessary to measure the number concentration for each particle size and check the dust collection rate of a certain size or more.

[0013]

An embodiment of the present invention will be described below with reference to FIG. The same parts as those in the conventional example are denoted by the same reference numerals, and description thereof will be omitted. In the figure, a dust suction port 23 of a particle counter 22 is disposed at a stage subsequent to the blower 2 in order to measure the amount of dust in the air discharged from the electric dust collector for each particle size. As is well known, the particle counter 22 measures the number concentration of particles floating in the air in a floating state by a light scattering method,
This is a device having a function of counting the number of particles for each particle size. For example, the number of particles in unit volume air can be counted for each particle size range of 0.3 to 0.5, 0.5 to 1, 1-2, and 2 to 5 μm.

The suction force of the particle counter 22 itself is generally weak, and cannot be directly sucked by the wind speed of an electric precipitator for a motorway tunnel, which is usually 5 to 7 m / s, so that a desiccator is used by another pump 25 using a sampling hose 24. , And the dust in the desiccator 26 is measured by the particle counter 22. In order to calculate the dust collection rate, it is necessary to measure the number concentration of dust in the air before dust collection, but in the illustrated embodiment, the particle counter 22 is installed only at the subsequent stage of the electric dust collector,
The measurement before dust collection is performed by the charging unit 7 and the dust collection unit 8
The application of the voltage is stopped. Needless to say, a particle counter may be separately installed in front of the electric precipitator.

Under such a configuration, the number concentration of dust before and after dust collection by an electric dust collector is measured for each particle size,
For example, a phenomenon in which the dust collection rate of dust having a particle diameter of 1 μm or more is extremely reduced is captured. Here, the extreme decrease means a case where the dust collection rate is zero, close to it, or negative. When such a phenomenon occurs, as described above, in addition to the reduction of the dust collection rate of dust having a particle diameter of 1 μm or more, the dust collection rate of fine dust having a particle diameter of less than 1 μm significantly decreases. It can be considered that the fine dust that has passed through the dust electrode is aggregated into particles having an equivalent particle size of 1 μm or more. In such a case, the amount of accumulated dust on the dust collection electrode exceeds a certain limit, and it may be considered that it is time to stop the operation of the electric dust collector and remove the accumulated dust. it can.

[0015]

According to the present invention, it is determined that the dust deposited on the dust collecting electrode has exceeded the limit value because the dust collection rate of the dust having a particle size of a certain level or more is extremely reduced. As a result, the electric precipitator can be cleaned in a timely manner to improve the operation efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an electric precipitator for explaining an embodiment of the present invention.

FIG. 2 is a schematic vertical sectional view of an electric precipitator for explaining a conventional example.

FIG. 3 is an enlarged front view of the dust collecting unit in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dust collection unit 2 Blower 7 Charging unit 8 Dust collection unit 22 Particle counter

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takeo Takahashi 1-1-1, Tanabe-Nita, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (56) References JP-A-62-279852 (JP, A) JP-A-62-242838 (JP, A) JP-A-62-183863 (JP, A) JP-A-62-6660 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B03C 3 / 00-3/88

Claims (2)

(57) [Claims] A dust collection rate of an electric dust collector for purifying air in a motorway tunnel is determined for each particle size of dust, and from the result, the dust collected on a dust collecting electrode of the electric dust collector is determined. A dust removal method for an electric dust collector for a motorway tunnel, characterized by determining a time to remove the dust. 2. The electric motor for a motorway tunnel according to claim 1, wherein a point in time when the dust collection rate of the dust having a particle diameter of a certain level or more is extremely deteriorated is a time when the dust of the dust collecting electrode is removed. How to remove dust from dust collector.