JPH0427910B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for detecting the amount of dust attached to a discharge electrode of an electrostatic precipitator. The present invention relates to a method for detecting the amount of dust attached to a discharge electrode of a dust collector.

[Background of the invention]

The general configuration of an electrostatic precipitator includes a discharge electrode to which a high DC voltage is applied, and a dust collection electrode formed in a flat plate shape and arranged to face the discharge electrode and held at ground potential. It is installed inside a dust collection chamber equipped with a gas flow path.

Ions are generated by corona discharge between the discharge electrode and the dust collecting electrode, and the dust in the dust-containing gas passing between the electrodes is charged, and by the action of the electric field formed between the charged dust and the dust collecting electrode. , dust collection is performed by moving the dust to the dust collection pole. Dust accumulates on the dust collection electrode as the dust collection time passes. If this is left unattended, the dust collection efficiency will decrease, so a method is used in which the dust collection pole is hammered with a hammering device at appropriate time intervals to separate the dust from the dust collection pole surface. The dust that falls due to hammering is collected in a hopper provided outside the dust collection chamber.

On the other hand, also around the discharge electrode, which is the ion supply side, dust caught in the turbulence of the gas flow collides with the discharge electrode, so that dust adheres to the surface thereof. Corona discharge occurs more actively as the discharge electrode becomes thinner, but when its apparent diameter increases due to dust adhesion, the amount of ions generated by the discharge electrode decreases, and the dust in the gas becomes insufficiently charged. .
For this reason, a hammering device is provided not only on the dust collecting electrode but also on the discharge electrode.

The interval at which this discharge electrode is hammered should be determined depending on the dust adhesion situation, but it is usually determined empirically based on the dust concentration of the dust collector inlet gas and the dust particle size at the beginning of operation. It has been set to , and will rarely be changed thereafter.

However, in reality, the characteristics of dust fluctuate due to changes in the operating conditions of the device at the dust source, changes in fuel, and the like. Therefore, when driving for a long time,
Various types of dust fly in the air, and in the case of highly adhesive dust, the diameter of the discharge electrode will be increased. In the case of highly adhesive dust like this, it is necessary to catch the signs that the discharge electrode is becoming enlarged and increase the number of hammer strikes to improve the removal of the dust and prevent the enlargement of the discharge electrode at an early stage. be. The reason for this is that dust that has been attached to the discharge electrode for a long period of time becomes stuck, and it is not possible to remove this by simply increasing the number of hammer strikes.

However, in the past, there was no way to continuously monitor the amount of dust adhering to the discharge electrode, so when the dust adhering to the discharge electrode became fixed to the electrode, even if the voltage was raised to just before the spark voltage, the discharge current remained low. Since the discharge did not reach the set value, it was noticed that the discharge electrode was enlarged.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for detecting the amount of dust attached to a discharge electrode of an electrostatic precipitator, which makes it possible to detect the amount of dust attached to the discharge electrode.

[Summary of the invention]

In order to achieve the above object, the present invention gradually increases the discharge voltage applied to the discharge electrode from the zero level to the set value level at regular intervals, and also reduces the discharge voltage when the discharge current starts flowing during this operation. The enlarged diameter of the discharge electrode is determined by detecting the electrode voltage and substituting this voltage value and the relative density of the gas into a predetermined calculation formula.

〔Example〕

Hereinafter, preferred embodiments of the method for detecting the amount of dust attached to the discharge electrode of an electrostatic precipitator according to the present invention will be described in detail with reference to the accompanying drawings.

Before explaining embodiments, the principle of the present invention will be explained.
As a result of experiments, the inventors confirmed that the corona starting voltage depends on the enlarged diameter of the discharge electrode due to dust adhesion and the gas temperature. By utilizing this, the amount of dust attached to the discharge electrode can be estimated.

The diameter of the discharge electrode is φ, and the relative density of the gas is δ=T ₀ /T・P/P ₀ (1) (T ₀ and P ₀ are the absolute temperature and pressure of the gas based on the reference, and T , P are the actual absolute temperature and pressure of the gas), then the corona starting voltage VC can be approximated by the following formula (where a1, a2, and a3 are constants determined by experiment).

Vc = (a ₁ φδ + a ₂ √)・(a ₃ −lnφ) ………(2) As is clear from equation (1), the corona starting voltage Vc
The enlarged diameter φ of the discharge electrode can be determined by actually measuring the gas temperature T and calculating the equation (2).

Next, an example of the apparatus according to the present invention will be described in detail.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The dust collection chamber 10 is divided into a first section and a second section, and a discharge electrode (not shown) provided in each section is connected to a power source 12 for the first section and a power source 14 for the second section. Each of the power supplies 12 and 14 has a 1-area power supply control panel 1.
Each of the 6th and 2nd ward power control panels 18 is connected,
The voltage applied to the discharge electrode is changed from zero to a predetermined voltage.

Inside the dust collection chamber 10, there is a first section discharge electrode hammering device 20 that hammers the discharge electrode in the first section, which is composed of a combination of a motor and a hammer, and a second section discharge electrode that hammers the discharge electrode in the second section. An electrode hammering device 22 is provided. Furthermore,
Gas temperature detectors 24 and 26 are provided near each of the hammering devices 20 and 22 to detect the gas temperature in the atmosphere. A driving motor (not shown) for each of the hammering devices 20 and 22 is connected to a hammering device control panel 28 .

Power control panels 16 and 18 and hammering device control panel 28
Each of these is connected to a control unit 30 using a microcomputer, and power supply voltage control and hammering intervals are controlled according to a preset program. In addition to the detection voltages Vc1 and Vc2 of the discharge electrodes, detection signals of the gas temperature detectors 24 and 26 are applied to the control unit 30.

The operation of the above configuration will be explained based on FIG. 2. The control unit 30 includes the 1st section power control panel 16
and the second section power control panel 18 are operated alternately at regular intervals. At time t ₀ , the discharge current of the discharge electrode of the first section is reduced to zero by the first section power control panel 16, and from this point on, while gradually increasing the discharge electrode voltage Vc1 of the first section power control panel 16, the discharge current of the first section power supply control panel 16 is reduced to zero. The voltage Vc1 at which the discharge current starts flowing is detected and recorded in the memory within the control unit 30. During this discharge voltage reduction section, the dust collection performance in section 1 temporarily decreases, but the electrostatic precipitator takes into account fluctuations in gas amount and changes in dust properties, sets the worst-case conditions, and then turns on the power. Since the ease of
Normally, the vehicle is driven with plenty of leeway. In other words,
By setting the discharge voltage in the second section to be higher from time _t0 to t2 when the first section is decreasing, the overall dust collection performance of the first section and the second section can be maintained at the planned value. Similarly, when detecting the voltage Vc2 at the beginning of the flow of discharge current in the discharge electrode of the second section, the discharge voltage of the first section is increased from time t2 to t4.

From the corona start voltage obtained in this manner and equation (2), the control unit 30 back-calculates equation (2) to calculate the enlarged diameter φ. The timing at which the hammering device 20 or 22 should be operated is determined from this enlarged diameter φ, and the hammering device control panel 28 is driven.

In addition, in the above configuration, the 1st section and the 2nd section were operated alternately so that the dust collection performance would not deteriorate even during the measurement of the amount of dust attached to the discharge electrode, but only for the measurement of the amount of attached dust. If this is a problem, it is sufficient to control the discharge voltage only in the section where the target discharge electrode is installed, as shown in FIG.

Also, an example was shown in which the dust collection room is divided into two sections, but
The same application is possible even in cases of three or more wards.

Note that if there is no fluctuation in the pressure and temperature (gas density) in the dust collection chamber, the gas temperature detectors 24 and 26 are unnecessary, but by providing them, the accuracy of calculating the amount of attached dust can be improved.

Experimental example 1 Discharge electrode diameter 2.6φ, material carbon steel Dust collection electrode spacing 300mm Discharge electrode spacing 200mm Adhered dust Fly ash (specific electrical resistance 8×10 ¹² Ωcm150℃) The experimental results under the above conditions are shown in Figure 3. It can be seen that this value is almost the same as the calculated value shown by the solid line.

Experimental Example 2 When the diameter of the discharge electrode (carbon steel) was changed and the experiment was conducted without adhering dust, the same tendency as shown in the above figure was shown. Therefore, it was found that equation (2) can be applied regardless of the specific electrical resistance of dust. Note that the constants a ₁ , a ₂ , and a ₃ in equation (2) vary depending on the spacing between the collecting electrodes and the spacing between the discharge electrodes in Experimental Example 1, the composition of the gas to be treated, etc., and are determined experimentally.

〔Effect of the invention〕

As explained above, according to the method for detecting the amount of dust attached to an electrostatic precipitator according to the present invention, the amount of dust attached to the discharge electrode can be easily detected, and the detection can be performed continuously. Furthermore, it is also possible to optimize the hammering interval based on the detected value of the amount of attached dust.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is an operation time chart of the embodiment shown in FIG. 1, and FIG. 3 is an explanatory diagram showing calculated values and experimental values of the amount of dust adhesion. 10...Dust collection room, 12...Power supply for 1 section, 14...
...Power supply for 2nd district, 16...1st district power control panel, 18...
...2nd section power control panel, 20...1st section discharge electrode hammer device, 22...2nd section discharge electrode hammer device, 24, 26...
... Gas temperature detector, 28 ... Hammering device control panel, 3
0...Control unit.

Claims (1)

[Claims] 1 Applying a high voltage to a discharge electrode placed opposite to a dust collection electrode at ground level to generate corona discharge,
In an electrostatic precipitator that collects dust by charging the dust in the gas passing between the electrodes by this corona discharge, the discharge voltage applied to the discharge electrode is set to approximately zero volts, and then the discharge voltage is gradually increased. and detect the discharge electrode voltage at the point when the discharge current starts flowing,
A method for detecting the amount of dust attached to a discharge electrode of an electrostatic precipitator, characterized in that the amount of dust attached to the discharge electrode is detected based on the detected voltage.