KR20030056542A - Electric Dust Collector Controlling the Risistivity of Exhaust Gas - Google Patents

Abstract

PURPOSE: Provided is an electrical dust collector with specific-resistance control function of exhaust gas to corrosion of equipment and temperature decrease of the gas, to reduce environmental pollution, and increase efficiency of entire dust collection by preliminarily charging the dust. CONSTITUTION: The dust collector(1) comprises inlet(20) for exhaust gas, dust collection part(40) and outlet(60), an equipment(50) to introduce oxygenated water and low-temperature plasma device(33) mounted lower than the equipment(50). The equipment(50) has an injection nozzle(3) located on the inlet(20), a metering pump(31) to supply the oxygenated water to the nozzle(3) and a connection line(34). The plasma device(33) has a discharge pole(42), a ground pole(41) and positive poles(41,42), and pulsing device(43) to apply voltage to the poles.

Description

Electric Dust Collector Controlling the Risistivity of Exhaust Gas}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic precipitator capable of adjusting the resistivity of exhaust gas, and more particularly, to an electrostatic precipitator for converting high resistivity dust into a normal resistivity dust by oxidizing SO ₂ gas contained in the exhaust gas.

Performance of electrostatic precipitators is dependent largely by the specific resistance (Resistivity) value of the particles contained in the exhaust gas, wherein the specific resistance value of the low specific resistance according to the dust collection efficiency ^{(Low Resistivity: 10 4 ~10 7} Ω / cm), the top specific resistance ( Normal Resistivity: 10 ⁷ ~ ^{10 10} Ω / cm), and High Resistivity:> 10 ¹⁰ Ω / cm.

Particles of low resistivity are easily charged in the dust collector and collected in the dust collecting plate, and then immediately lose electrical performance and are neutralized and re-spread. Therefore, while the dust collection and re-scattering process is easily repeated, the number of particles that are not collected and finally discharged to the outside increases the collection performance.

On the other hand, high-resistance particles are very difficult to charge, and once charged and attached to the dust collecting electrode, they do not lose their electrical properties to form dust layers without being exhausted. Moreover, the continuous dust deposition ultimately results in back corona, whereby the dust layer attached to the dust collector is scattered again and discharged to the outside. In this case, the dust collection performance may be reduced to 50% or less in severe cases.

The specific resistance value of the particles is influenced by the concentration of sulfur contained in the fuel. As the sulfur content increases, the specific resistivity progresses to high resistivity. In order to convert the low resistivity or high resistivity particles having low collection efficiency into the normal resistivity which is well collected, various methods such as injecting additives into the exhaust gas or controlling the temperature are applied.

On the other hand, the conventional apparatus for converting particles of high resistivity into particles of normal resistivity can be broadly classified into a device for injecting SO ₃ gas into an inlet of the electrostatic precipitator and a device for injecting sulfuric acid or an additive.

An apparatus for injecting SO ₃ gas is shown in FIG. 1 (a). In this conventional apparatus, before the exhaust gas 4 flows into the electrostatic precipitator 40, the nozzle 3 is provided inside the inlet 20 to inject SO ₃ gas. Here, the SO ₃ gas is generated by oxidizing sulfur dioxide generated by burning sulfur with the catalyst device 11. For this process, it is composed of a sulfur reservoir 13 for storing sulfur, a sulfur combustion device 12, and a catalyst device 11 for oxidizing at least 90% of SO ₂ gas generated during combustion. The SO ₃ gas generated here is injected in the range of 10 ppm to 15 ppm with respect to the total amount of the exhaust gas 4. This conventional SO ₃ gas injector has a problem of explosion due to the operation of the combustion device, and the entire equipment is easily aged because of the use of corrosive combustion gas. In addition, there was a need to periodically exchange expensive oxidation catalysts used for SO ₂ oxidation. In addition, while SO ₃ artificially injected into the exhaust gas in the process has the effect of increasing the dust collection efficiency, since the harmful gas is made and injected, the problem of environmental pollution could be intensified. Moreover, the injected SO ₃ gas is easily converted to sulfuric acid and is present in the vapor and aerosol state. In the presence of an excess of aerosolic sulfuric acid, corrosion occurs inside the plant or is not collected and is discharged through the chimneys, thus providing visible smoke. (Visible Flume, a specific phenomenon of sulfuric acid aerosols) and other forms of environmental problems such as acidification of the soil in the surrounding area may occur.

On the other hand, sulfuric acid or additive injector is shown in Figure 1 (b). Sulfuric acid or additives are stored in the reservoir 22 and injected into the injection nozzle 3 using the injection pump 21, and are injected at the same position as the aforementioned SO ₃ gas. In this case, the steam conversion rate should be maintained at least 10 ppm. According to this process, the overall equipment is simplified and the initial investment cost and operating cost are low, but it is necessary to keep the exhaust gas above the dew point temperature to prevent corrosion. In order to solve such a problem, a method of preheating before spraying was prepared, but nevertheless, partial corrosion at low temperature after spraying was inevitable. In addition, sulfuric acid is already widely used as a chemical, it is easy to purchase, but is classified as a strong acid is difficult to handle, there is a problem such as increasing the moisture and the temperature of the exhaust gas when diluted and used. In addition, since the boiling point of sulfuric acid is more than 290 ° C, most of the sulfuric acid was present as a sulfuric acid aerosol to corrode the equipment. On the other hand, additives other than sulfuric acid, which can control high resistivity dust while minimizing corrosion problems, have been used, but the price was too expensive.

The present invention has been made to solve the above problems, an object of the present invention is to provide an electrostatic precipitator that can prevent the corrosion of the device and the temperature drop of the exhaust gas, minimize the environmental pollution, and at the same time increase the dust collection efficiency have.

Figure 1 (a) is a schematic configuration diagram showing an example of a conventional electrostatic precipitator.

Fig. 1 (b) is a schematic block diagram showing still another example of a conventional electrostatic precipitator.

2 (a) is a block diagram of an electrostatic precipitator according to the present invention.

FIG. 2 (b) is a perspective view showing the low temperature plasma apparatus in FIG. 2 (a) in detail.

※ Explanation of Major Drawings

1 ... electrostatic precipitator

2. Power supply of electrostatic precipitator

3. Spray nozzle

4. Exhaust gas

11 ... Catalyst

12 ... sulfur burner

13 ... sulfur storage

21 ... Dosing Pump

22 ... sulfuric acid or additive storage

31 ... Dosing Pump

32 ... hydrogen peroxide reservoir

33. Low Temperature Plasma Equipment

41 ... (-) earth electrode

42 ... (+) discharge

43 ... High Voltage Pulse Supply

In order to achieve the above object, the present invention oxidizes the SO ₂ gas contained in the exhaust gas through hydrogen peroxide injection and low temperature plasma generation to increase the SO ₃ and H ₂ SO ₄ concentration to increase the resistance of the high resistivity dust. At the same time, the dust is converted to dust, and the dust is precharged to improve the efficiency of the conventional dust collector. The specific structure is as follows.

The electrostatic precipitator according to the present invention is composed of an inlet, an electrostatic precipitator, and an outlet of an exhaust gas, and includes a device for injecting hydrogen peroxide water into the inlet, and a low temperature plasma apparatus installed downstream from the hydrogen peroxide water injector at the inlet. It is characterized in that the configuration.

Here, the hydrogen peroxide injection device is composed of a nozzle for injection disposed in the inlet, a metering pump and a connection pipe for supplying hydrogen peroxide from the hydrogen peroxide reservoir to the injection nozzle.

The low temperature plasma apparatus is characterized by comprising a pulse supply device for applying a high voltage to a positive discharge electrode, a ground electrode, and a positive electrode of (-).

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

2 (a) shows the configuration of the electrostatic precipitator according to the present invention. In general, the inlet 20 of the exhaust gas, the electrostatic precipitator 40 and the outlet 60 is the same as the conventional electrostatic precipitator.

While the exhaust gas 4 passes, hydrogen peroxide water is injected into the inlet 20 by the hydrogen peroxide water injection device 50. The hydrogen peroxide water injector 50 includes a nozzle 34 for injection disposed in the inlet 20, a connecting pipe 34 connected from the hydrogen peroxide reservoir 32 to the nozzle 3 for injection, and the connector It is comprised by the metering pump 31 provided in the middle of 34. Accordingly, the hydrogen peroxide water in the hydrogen peroxide reservoir 32 is injected into the inlet 20 through the injection nozzle 3 by the metering pump 31. As such, the hydrogen peroxide water injected into the inlet 20 is easily converted into OH radical peroxygen atoms (O) to oxidize some SO ₂ gas in the exhaust gas into SO ₃ and H ₂ SO ₄ .

On the other hand, a lower temperature plasma apparatus 33 is installed downstream of the hydrogen peroxide water injection device 50 at the inlet 20, so that the oxidation rate can be increased, thereby reducing the amount of hydrogen peroxide water used. As shown in FIG. 2 (b), the low temperature plasma apparatus 33 supplies a high voltage pulse for applying a high voltage in the form of a pulse to the (+) electrode 42, the (-) ground electrode 41 and the anode. Device 43. When the high voltage in the form of pulse is applied between the (+) discharge electrode 42 and the (-) ground electrode 41 in the high voltage pulse supply device 43, a corona is formed between the anodes to generate a plasma. When hydrogen peroxide water and exhaust gas 4 pass through the plasma space, oxidation is accelerated (sulfur oxide removal process by low temperature plasma has already been proposed in many research data, and the contents of Korean Patent No. 213812 are described in detail. Is disclosed).

Since the exhaust gas passing through the low temperature plasma apparatus 33 has a short residence time and a small amount of energy delivered to the exhaust gas, the oxidation performance of SO ₂ gas is 10% or less, but by adjusting the injection concentration of hydrogen peroxide solution therein, Oxidation performance can be raised to 10%. For the 10% oxidation efficiency of the SO ₂ contained in the exhaust gas (low-sulfur fuel, and the SO2 emission concentration 150ppm~200ppm, 10% of the initial SO2 concentration of SO3 is oxidized with H ₂ SO ₄ shows a 15ppm~20ppm Can be maintained at 10ppm to 20ppm, the same as SO ₃ or sulfuric acid vapor which must be injected to reduce the dust resistivity value. Summarizing the series of reaction process is shown in the following reaction formula.

H ₂ O ₂ → H ₂ O + O

H ₂ O, H ₂ O ₂ → (plasma) OH, O

SO ₂ + O → SO ₃

SO ₂ + H ₂ O, OH → H ₂ SO ₄

SO ₃ + H ₂ O → H ₂ SO ₄

Another function of the low temperature plasma apparatus 33 is to increase the dust collection performance of attaching and removing the dust collector finally attached to the dust collecting plate by applying electrical charge to the dust in advance. Dust is generally charged by the negative electric charge present in the space charge between the dust collecting plate and the discharge electrode, and is collected by the dust collecting plate which has a positive (+). The dust collecting form of the electrostatic precipitator is field charged and diffused charged. In the plasma apparatus, the charge performance of the fine particles may be improved since the dust is mostly charged by accumulated discharge and corona discharge.

According to the present invention having the above configuration, the following effects can be achieved.

First, compared to the case of the conventional sulfuric acid injection, the boiling point of hydrogen peroxide water is very low at 152 ℃, 10ppm ~ 20ppm injection can be converted to most of the vapor state to prevent the corrosion of the device and the temperature drop of the exhaust gas.

Second, since the SO ₂ gas from the exhaust gas is oxidized and used, the environmental pollution can be greatly reduced compared to the SO ₃ injection or sulfuric acid injection process, which is an artificial harmful gas injection process.

Third, by additionally installing a low-temperature plasma apparatus, it is possible to reduce the amount of hydrogen peroxide water used, and to increase the overall dust collection efficiency by precharging dust.

Claims (3)

In the electrostatic precipitator 1 composed of the inlet 20 of the exhaust gas, the electrostatic precipitator 40 and the outlet 60, A device (50) for injecting hydrogen peroxide water into the inlet (20); Electrostatic precipitator characterized in that it comprises a low-temperature plasma apparatus 33 installed downstream from the hydrogen peroxide water injection device 50 in the inlet (20). The method of claim 1, The hydrogen peroxide water injection device 50, the injection nozzle (3) disposed in the inlet 20, and a metering pump for supplying hydrogen peroxide water from the hydrogen peroxide reservoir 32 to the injection nozzle (3) ( 31) and the electrostatic precipitator, characterized in that composed of a connecting pipe (34). The method according to claim 1 or 2, The low temperature plasma apparatus 33 includes a pulse supply device 43 for applying a high voltage to the discharge electrode 42 of (+), the ground electrode 41 of (-), and the anodes 41 and 42. Electrostatic precipitator characterized in that.