JPH0685891B2 - Method and apparatus for cleaning electrostatic precipitator - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method for cleaning an electrostatic precipitator for removing soot and dust accumulated in a dust collecting passage in an electrostatic precipitator, and an apparatus for carrying out this method.

[Prior art]

The electrostatic precipitator is already known as a device for cleaning the air containing soot and dust. This is a device that uses a corona discharge to apply an electric charge to soot particles in the air, and applies a Coulomb force to the charged particles to collect them on a dust collecting electrode plate. Since the collected soot and dust accumulates in the dust collecting passage, it is necessary to wash off the accumulated soot and dust at regular intervals. Since this dust removal is always associated with the electrostatic precipitator, how efficiently the electrode plate can be cleaned is a very important issue for the electrostatic precipitator as well as the dust collection efficiency. Especially in recent years, due to the pursuit of improved dust collection efficiency and downsizing of equipment, the electrode plate spacing has been reduced to 10
It has been narrowed down from mm to several mm, and removal of the collected dusts between the electrode plates arranged at such a narrow interval has become a major issue. A mechanical method has long been known as a means for removing soot and dust. This involves disposing a scraper, a brush, etc. between the electrode plates, and moving them up and down during cleaning to scrape off soot and dust, but there are many problems such as complicated structure and maintenance of insulation during normal operation. There is an air cleaning system as a solution to such a problem. This is one in which pressurized air is blown to the collected dust to blow it off. For example, there is an electric dust collector shown in Japanese Patent Publication No. 57-16864. This dust collector is for treating gas containing non-adhesive dust, and the non-adhesive dust accumulated in the dust collection passage is blown off with a jet stream with both ends of the dust collection passage closed. As a result, the non-adhesive dust discharged in a dispersed state in which the particles are aggregated and coarsened in the dust collecting passage is discharged to the outside of the apparatus main body and collected. Such an air cleaning method has many excellent points such as the simplicity of the device and the ease of discharging the removed dust to the outside of the machine in comparison with the above-mentioned mechanical method, and the current main method is to It is often used in ventilation systems. However, as described in Japanese Patent Publication No. 57-16864, the air cleaning method is effective for removing non-adhesive soot dust, but has a drawback that the cleaning power is weak for tacky soot dust. There is. Therefore, a problem has recently arisen even when it is used in the automobile tunnel. In other words, with the spread of spiked tires, the winter road surface is scraped off and concrete dust is generated, which adheres to the tires and combines with snow-melting agents such as calcium chloride brought into the tunnel to form clay-like particles, which results in electrostatic dust collection. Increasing numbers of cases are being collected by devices. If the air pollution in the automobile tunnel is solely due to the exhaust gas from the automobile, the soot and dust is mainly graphite and does not show tackiness to a particular problem. The water cleaning method is effective for soot and dust that is sticky and cannot be completely removed by the air cleaning method. This is to remove soot and dust by spraying pressurized water instead of air, and the cleaning power of water having a large mass is significantly larger than that of air. However, this water washing method wets the dust collector to which a high voltage is applied, so it cannot be operated as it is after cleaning, and the dust collector must be dried before restarting operation. There is. If a high voltage is applied to the dust collecting part with incomplete drying,
Electric discharge occurs between the electrode plates via water droplets. As a result, the electrode plates are thermally deformed, and in some cases, the electrode plates come into contact with each other to cause a short circuit. As for the insulators, the current flowing through the wetting of the surface causes the insulators to be locally heated and cracked, or when the current value is large, the protective breaker operates and the dust collector stops operating. May lead to. Therefore, in the case of the water washing method, it is necessary to pay sufficient attention to the drying after washing. Conventionally, as the drying means,
An air blower installed to guide polluted air to the electric dust collector was used, and the electrodes, insulators, etc. were dried by the air blow by this air blower. However, in such simple ventilation drying, it takes a long time until the operation is restarted, and during that time, a loss of electric power is large due to the operation of the large-capacity blower. For example, looking at the dust collector for the above-mentioned automobile tunnel, the cleaning time itself takes only a few minutes, but when ventilation drying is performed at a wind speed of about 7 m / s, it takes 60 minutes or more before operation can be restarted. . The present invention has been made under such circumstances, and the electric dust collector is washed with water by taking an effective means for removing water droplets when the electric dust collector is washed with a water washing method. It is an object of the present invention to provide a method for cleaning an electrostatic precipitator which can be restarted in a short time thereafter, and a device suitable for carrying out the method.

[Means for solving problems]

As a result of repeating various experiments, the inventors have blown pressurized air to the electrode plate wet by washing with water and blowing off the water droplets attached to the electrode plate, prior to ventilation drying by a blower. Was found to be extremely effective in shortening the time of subsequent ventilation drying. Therefore, the method for cleaning an electrostatic precipitator of the present invention comprises a step of spraying water pressurized toward a dust collecting passage of the electric precipitator to remove soot and dust accumulated in the dust collecting passage, A step of blowing pressurized air to the electrode plate forming the dust collecting passage to blow away water droplets adhering to this electrode plate, a step of blowing air through the dust collecting passage, and a voltage is gradually applied between the electrode plates during blowing. And a step of applying the voltage while boosting the voltage. The step of blowing air through the dust collecting passage is preferably started at the same time as the air blowing in the preceding step, but it is not necessarily limited to this. That is, during the air spraying process,
Or even if it starts after that, it cannot serve. Further, a voltage shall be applied between the electrode plates at the start of the blowing process by the blower. In that case, it is dangerous to immediately apply the rated voltage during normal operation, and it is necessary to gradually increase the voltage from a very low voltage. At that time, it is preferable to count the number of discharges generated by the wetting of the electrode plate and control the voltage so that the number of discharges per unit time falls within an allowable range that does not damage the electrode plate. Next, the cleaning device for the electrostatic precipitator of the present invention collects the water injected from the water injection mechanism and the water injection mechanism for spraying pressurized water to the dust collection passage and discharges it out of the machine. A drainage mechanism, an air blow mechanism for blowing pressurized air to the electrode plates forming the dust collecting passage, and a means for gradually increasing the voltage applied between the electrode plates are provided. Here, the water injection mechanism includes a fountain nozzle, a wash water pump, a water pipe, a solenoid valve, and the like. Furthermore, the air blow mechanism includes an air nozzle, an air blow compressor, air piping, a solenoid valve, and the like. The drainage mechanism is composed of a water pan at the bottom of the dust collecting unit, a water pipe for guiding the waste water collected by the water pan to the outside of the machine. It is preferable that the nozzles or the pipes in the water injection mechanism and the air blow mechanism are used in common. If water droplets remain on the tip of the nozzle of the water injection mechanism or locally on the pipe, the passage may be blocked due to freezing in cold regions.
However, if both nozzles or pipes are also used, residual water is air-purged in the air spraying process, and the above connection can be prevented. The accumulation of soot and dust naturally adheres not only to the dust collecting passage in the dust collecting part, but also to the electrode plate of the charging part for giving a charge to the soot and dust particles, the discharge wire, or the insulator. Therefore, it is naturally desirable to add cleaning to the charging section and the insulator.

[Work]

According to the present invention, after the pressurized water is sprayed on the dust collected in the dust collecting passage, the pressurized air is blown to the electrode plate forming the dust collecting passage prior to the air blow by the blower. By this air blowing, first, the water droplets adhering to the electrode plate are instantaneously blown off, and the electrode plate surface is simply wet. Further, the air supplied from the air compressor is hot air that is drier than the atmosphere, and the air in the dust collecting passage is replaced by this, so that the water vapor on the electrode plate surface is effectively evaporated. However, it is not rational to try to dry the inside of the dust collection unit only with air blow, and after the air blowing process for a certain time, a blower process with a blower is provided to dry the entire dust collection unit. To seek. In addition, at that time, by applying voltage while gradually increasing the voltage between the electrode plates, the water droplets remaining on the electrode plates are repelled by the spark discharge, and the insulator surface is dried by the Joule heat of the current flowing through the wetting of the insulator surface. Promote.

【Example】

An embodiment of the present invention will be described below when the present invention is applied to an electrostatic precipitator for purifying air in an automobile tunnel. First, FIG. 2 shows an outline of a ventilation facility for an automobile tunnel, in which polluted air in the roadway space of the automobile tunnel 100 is introduced from an intake port 101 in a side wall into a bypass 102 in which an electric dust collector is installed. The air that has been introduced into and cleaned is blown out into the roadway space from the air supply port 103. The bypass 102 is divided into a dust collecting chamber 104, an air passage 105, a blower chamber 106, and a discharge duct 107. Furthermore, the dust collecting chamber 104 and the wind 105 are divided into two chambers on the left and right by the central partition wall 108. The electric dust collecting device 1 and the blower 3 are installed in each of these chambers so that they can be operated independently. It has become. Further, except for the dust collecting chamber 104, the air passage 105, the blower chamber 106, and the discharge duct 107 are all provided by utilizing only the upper half of the bypass space partitioned by the partition wall 109, and the lower half is supplemented. It is used as a machine room 110, an electric room 111, and a work room 112. By the way, the electric dust collectors installed in the left and right chambers of the dust collecting chamber 104 are each composed of six dust collecting units 2 each having a treatment air volume of 15 m ³ / s, and as a whole 90 m ³
It has a treated air volume of / s. 3 is a blower with a motor output of 300kW, 1 for each of the left and right air passages
They are installed one by one. By operating the blower 3, the polluted air sucked from the roadway space as indicated by the arrow 4 passes through the dust collector 1 at a wind speed of about 7 m / s to be cleaned, and as shown by the arrow 5 Is discharged. The auxiliary equipment room 110 is provided with a wash water storage tank 6, a wash water pump 7, a waste water tank 8, and a water treatment device 9. The cleaning water sent to the electrostatic precipitator 1 by the water supply pipe 10 is temporarily stored in the waste water tank 8 via the drain pipe 11 after cleaning the dust collecting passage and the like as described later, and further sent to the water treatment device 9. After being cleaned and purified, it is released. The water treatment device 9 may be provided outside the illustrated ventilation equipment. The sludge cake generated from the water treatment device 9 is carried out of the work room 112 by car. Reference numeral 12 is an air blow compressor for blowing pressurized air to the electrostatic precipitator after washing with water as described later. In the electric room 111, there are installed a high voltage generation panel for generating a DC high voltage applied to the electrostatic precipitator, a dust collector control panel for controlling the entire dust collector, a blower panel, a transformer panel, etc. There is. Next, FIG. 1 shows a time chart in the case of cleaning the electrostatic precipitator by the method of the present invention in the ventilation equipment. The cleaning water pump 7 and the air blow compressor 12 are used for spraying water to the dust collecting passage and spraying air to the electrode plate.
The treated air volume is 15m ³
Two dust collection units 2 of / s, that is, treated air volume of 30
It is carried out in pairs of m ³ / s. Therefore, in the case of the embodiment shown in FIG. 2, the steps of water spraying and air spraying are performed three times in sequence with two dust collecting units 2 each, and then all the units are collectively blown by the blower 3. As shown in FIG. 1, the water spraying process is carried out for 1 minute and the air spraying process is carried out for 3 minutes for each set of two dust collecting units. For 6 dust collection units divided into 3 groups, when the water spraying and air spraying processes are completed, the air blowing process is performed for 10 minutes. This blowing step may be started at the same time as the third air blowing step or in the middle thereof. It is effective to accelerate the drying by applying a voltage from the high voltage generator to the dust collecting portion or the charging portion of the dust collecting device at the time of starting the blowing process or during the blowing process. That is, even if water droplets locally remain on the electrode plate after air blowing, the water droplets are repelled by the spark discharge and removed by applying the above voltage. In addition, an electric current flows through the wetting remaining on the insulator surface, and the Joule heat accelerates the drying of the insulator surface. However, this voltage needs to be gradually increased as shown in FIG. 1, and if the operating voltage is immediately applied, there is a risk of causing damage to the electrode plate due to excessive discharge or generation of an excessive short-circuit current. As a means of gradually increasing the voltage, there is a method of counting the number of sparks and controlling the voltage so that the number of times per unit time is a previously confirmed allowable value, for example, about 40 to 50 times per minute or less. Conceivable. In the embodiment of FIG. 1, the time required from the start of the cleaning work to the resumption of operation is 22 minutes. On the other hand, when the same electrostatic precipitator was tested by the conventional method, it took 60 minutes or more for drying when the water spraying step was carried out 3 times for each 1 minute and then immediately moved to the air blowing step. It takes about 70 minutes from the start of cleaning to the restart of operation.
That is, it was three times or more that of the method of the present invention. In the above-mentioned embodiment, water spraying and air spraying are each performed three times.
This is only an example, and if the capacity of the wash water pump, air blow compressor, etc. is increased so that it can be done only once, the effect of shortening the time of the blowing process can be further utilized. . 3 and 4 show the dust collection unit 2. The dust collecting unit 2 has a vertical, horizontal, and height dimensions of about 2 m, and a single unit has a treated air volume of 15 m ³ / s. The dust collecting apparatus 1 shown in FIG. 2 is configured by using six dust collecting units 2 for each of the left and right air passages. In the dust collecting unit 2, 13 is a dust collecting portion that collects soot and dust, and 14 is a charging portion that gives electric charges to the dust collecting particles in the preceding stage. And this dust collection unit 2 is this dust collection part
A total of four sets, each of which is formed by vertically stacking a set of 13 and a charging unit 14 in two rows, are further arranged in two rows on the left and right. In the dust collecting part 13, as shown by cutting out a part of FIG. 3 and FIG. 4, a large number of the ground potential dust collecting plates 15 and the opposite high potential plates 16 are alternately arranged in parallel. Placed,
A dust collecting passage 17 having a width of 6 mm is formed between the electrode plates 15 and 16. The high-potential electrode plate 16 is attached to a rod 18 that penetrates the dust collecting electrode plate 15 with a gap. The rod 18 is fixed to a high-voltage support plate 19, and the high-voltage support plate 19 is a support insulator. It is supported by a side plate 21 having a ground potential via 20. Pole plate
From the high voltage generator 23 to the power supply insulator 22, DC 5.5kV
Is applied. In this case, the charging unit 14 is configured by a discharge line 25 stretched between a plurality of ground potential electrodes 24 arranged in parallel at intervals of 40 mm, and the discharge line 25 is provided with a support insulator 27 from a high voltage generator 26. DC 11kV is applied via. The discharge line 27 is supported by a support insulator (not shown). Reference numeral 28 is a cleaning pipe for spraying pressurized water onto the dust collecting passage 17. The cleaning pipes 28 are provided horizontally and vertically in eight stages facing the inlet side 29 of the contaminated air and the outlet side 30 of the cleaning air with the dust collecting portion 13 and the charging portion 14 interposed therebetween. ing. A large number of nozzles 31 are horizontally attached to the cleaning pipe 28. This nozzle ejects fluid in a conical shape, and is designed so as to sufficiently satisfy the cleaning range required for each nozzle. The cleaning pipe 28 and the nozzle 31 are used for both water spraying and air spraying. The cleaning pipe 28 is connected to the cleaning water pump 7 via the solenoid valve V1 and to the air blow compressor 12 via the solenoid valve V3. It is connected. 32-35 are nozzles for cleaning the insulator. That is, 32 is for cleaning the support insulator 20 (FIG. 4) of the dust collecting part 13,
33 is for cleaning the supporting insulator 22 of the dust collecting part 13, 34 is for cleaning the power feeding insulator 27 of the charging part 14, and 35 is for cleaning the supporting insulator (not shown) of the charging part. These insulator cleaning nozzles are adapted to eject a fluid in a flat shape so as to match the shape of a cylindrical insulator. The insulator cleaning nozzles 32 to 35 are connected to the cleaning water pump 7 and the air blow compressor 12 via electromagnetic valves V2 and V4 by an insulator cleaning pipe 36. 37 and 38 are damper doors on the air inlet side 29 and the air outlet side 30, respectively. Each of them has a damper 40 that opens and closes around a vertical shaft 39 as a fulcrum, and a wire net 41 for preventing foreign matter from entering and electric shock, and further supports a nozzle mounting portion of the dust collecting portion cleaning pipe 28. Also, the damper door 37 on the air inlet side is shown in FIG. 3 so that it is convenient for the internal inspection of the dust collection unit 2.
It can be opened and closed as indicated by the dashed line. 42 is a water pan installed at the bottom of the dust collection unit 2.
It is connected to the drain pipe 11 at some point. Further, 43 is a side wall of the dust collecting unit, and 44 is a ceiling plate. When cleaning the dust collecting apparatus 1 including the dust collecting unit 2 as described above, the damper 40 is closed, the washing water pump 7 is started, and the solenoid valves V1 and V2 are opened to perform water washing for 1 minute.
The water pressure is about 3 kg / cm ² , and the cleaning water ejected from the dust collecting portion cleaning nozzle 31 cleans the dust collecting passage 17 and the charging portion 14. Further, the cleaning water simultaneously ejected from the insulator cleaning nozzles 32 to 35 cleans the support insulator 20 of the dust collecting portion, the power feeding insulator 22, and the support insulator (not shown) of the charging portion and the power feeding insulator 21. Following water washing, solenoid valves V3 and V4 are opened and air is blown for 3 minutes. The air pressure is about 2 kg / cm ² , and the air jetted at the speed of sound from the same nozzles 31 to 35 as when washing with water immediately blows off the water droplets attached to the electrode plates, insulators, and the like. Further, by this air blowing, the water remaining in the pipe and the nozzle outlet is removed by the air purge. In the case of the embodiment shown in FIG. 2, the above-mentioned spraying of water and air is sequentially repeated three times with two dust collecting units 2 as a set. After that, open the damper 40 and start the blower 3 to remove dust.
Ventilates 13 and charging section 14. As a result, the entire dust collecting unit is dried. At the same time, the dust collecting part 13
And a high voltage generator while gradually increasing the voltage to the charging unit 14.
A high voltage from 23 and 26 is applied to accelerate drying. In order to prevent water from splashing outside the machine during water spraying and air spraying, the damper 40 is provided to close the dust collecting unit, but it is not necessary to completely close it. , Even with the eliminator left open, which also functions as a rectifier when blowing air, another step is not supported. In particular, when the dust collecting portion cleaning pipes 28 are arranged to face each other as in the illustrated embodiment, the jetted waters collide with each other and fall into the central portion of the dust collecting unit, which further reduces scattering to the outside. .

EFFECTS OF THE INVENTION According to the present invention, after the dust collecting passage is washed with water, pressurized air is blown to the electrode plate to which water droplets are attached to remove the water droplets first, and then air is blown between the electrode plates. Since the dust collecting portion is dried by applying the voltage, the time of the air blowing step can be significantly shortened as compared with the conventional method in which the air is blown as it is after washing with water. Therefore, it is possible to complete the cleaning work in a short time while adopting the water cleaning method having a large cleaning effect, and it is possible to actively cope with the removal of the sticky soot and dust.

[Brief description of drawings]

FIG. 1 is a time chart showing an embodiment of the method of the present invention, FIG. 2 is a perspective view showing the outline of an automobile tunnel ventilation facility equipped with an electric dust collector using the apparatus of the present invention, and FIG. FIG. 4 is a plan view of the inside of the electrostatic precipitator unit, and FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1: Dust collector, 2: Dust collector unit, 3: Blower, 6: Water tank, 7: Wash water pump, 8: Waste water tank, 10: Water supply pipe, 11: Drain pipe, 12: Air blow compressor, 13: Collection Dust part, 14: charging part, 17: dust collecting passageway, 28: cleaning pipe, 31: dust collecting part cleaning nozzle, 32-35: insulator cleaning nozzle, 36: insulator cleaning pipe.

Claims (2)

[Claims] 1. A step of spraying water pressurized toward a dust collecting passage of an electrostatic precipitator to remove soot and dust accumulated in the dust collecting passage, and an electrode plate forming the dust collecting passage. A step of blowing pressurized air to blow off water droplets attached to the electrode plate, and a step of blowing air through the dust collecting passage,
A method for cleaning an electrostatic precipitator, comprising the step of applying a voltage between the electrode plates while gradually increasing the pressure during air blowing. 2. An electrostatic precipitator comprising a dust collecting passage and a blower for introducing air containing dust and soot into the dust collecting passage, wherein a water injection mechanism for spraying pressurized water to the dust collecting passage. A drainage mechanism that collects the water injected from the water injection mechanism and discharges it out of the machine; an air blow mechanism that blows pressurized air to the electrode plate that forms the dust collecting passage; And a means for gradually increasing the voltage applied to the cleaning apparatus for the electrostatic precipitator.