JPH0117418B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to electrical technology, and more particularly to a method and apparatus for supplying current to an electrostatic precipitator for high resistance dust.

PRIOR ART Achieving higher separation efficiency and reliability of electrostatic precipitators for high resistance dust removal is an important issue when performing the removal of suspended particles from gases using electrostatic precipitation methods. . Due to the high electrical resistance of the dust, many electrostatic precipitators used in power plants, metallurgical industry, cement industry, and chemical industry are unable to provide the desired separation efficiency. Along with that, frequent breakdowns,
And the high fatigue degree of the vibration mechanism when removing the dust layer collected on the electrodes affects the reliability and service life of the electrostatic precipitator.

During gas cleaning operation, dust particles are charged by a negative corona discharge generated in the interelectrode gap, i.e. in the gap between the corona generating electrode and the dust collection electrode, and are deposited on the dust collection electrode. It will be done. The electrical resistivity of the collected dust is
Higher than 10 ⁸ Ω, a charge is accumulated on the surface of the collected dust layer under the action of the corona discharge current, while inside the layer the electric field strength is
An electric field of about 20 kV/Ω is formed, which causes breakdown in the dust layer. In this case, a reverse corona discharge occurs in the breakdown region on the dust collection electrode, from which ions with a polarity opposite to that of the corona-generating electrode are emitted into the interelectrode gap. The positively charged ions neutralize the negative charge on the particles, thereby reducing the charge, or
or even reverse its polarity, which also considerably reduces the velocity of the particles moving to the collection electrode and worsens the separation efficiency.

The existence of reverse corona discharge in electrostatic precipitators is
This results in a voltage drop across the high-resistance dust layer and a reduction in the electrical strength of the interelectrode gap, which reduces the electric field strength and thereby reduces the dust separation efficiency.

The high resistivity of high-resistance dust also causes the creation of a dust layer that is difficult to remove from the electrode. Removing such dust build-up requires greater vibratory shock forces and higher repetition frequencies of electrode oscillations. This adversely affects the reliability of the operation of the vibration mechanism and ultimately impairs the dust separation efficiency as a whole.

Currently, the higher efficiency of electrostatic precipitators in removing high-resistance dust from gas is mainly achieved by reducing the electrical resistance of the collected dust layer, and this reduction in electrical resistance For example,
This is achieved by treating and conditioning the gas to be purified with chemical reagents such as NH ₃ , SO ₃ etc. Collecting Fly Ash Dust” Freight Review,
1977, 12, pp. 7-11, and Mayer-
Schwinning G., Rennhack R., "New Knowledge on Splattering Bodies and Fog Droplets" Hemy Ingenieur Technique 1980, 52, No. 5, pp. 375-383) Also, at high temperatures of 300° to 400° This is achieved by static purification of the gas (Matts S., "Cold Side Dust Collector", Journal of the Air Pollution Control Association, 1975, 25, No. 2, pp. 146-148), and
White HJ, “Electrostatic Precipitation of Fly Ash,” Journal of the Air Pollution Control Association, 1977, 27, No. 3, 206.
(See pages ~217). This gas regulation does not completely eliminate the reverse corona discharge, but only partially weakens it, and also involves the consumption of large amounts of chemical reagents. Moreover, the reagents also cause air pollution. Purifying gas at high temperatures leads to an increase in the volume of purified gas and also requires the use of high temperature electrostatic precipitators, which also makes the cost of gas cleaning operations higher. It leads to doing. Regulation of the gas to be purified with the aid of chemical reagents and high temperatures is only used in the limited field of temperature and physicochemical properties of dust;
It does not completely solve the problem of improving the efficiency of removing high resistance dust from gases by electrostatic precipitators.

The unfavorable influence that the high electrical resistance of the collected dust has on the collection efficiency can be reduced by using a special mode of current supply to the electrostatic precipitator. Various variants of pulsed current supply to electrostatic precipitators are currently being developed, for example in the USSR (Shwarts ZP, Device for supplying current to electrostatic precipitators, USSR Inventor's Certificate No. 575629). , classification B03C
3/68, C05T 1/22, 1977, Publication No. 37, and Shwarts ZL, Nagorny BB, Gonozov A.
In the United States (Komar KS, Feldman
PL, Middle HJ, Shubert C., Results of the First Practical Experiments in Pulsed Dust Collection, Ind. Annual Meeting, Cleveland, OH, 1979, Cont. Cer New York 1979, 1333-37), and in West Germany (West Germany). Patent Application No. 2713675 International Classification B03C
(See 3/66) has been developed. In the case of pulsed voltage supply mode, partial discharges in the dust layer occur in the intervals between supply pulses, which reduce the probability of breakdown of the layer and also reduce the reverse corona discharge. However, the pulsed current supply does not completely eliminate the reverse corona discharge and only allows the amount of residual dust in the gas after electrostatic precipitation to be reduced by a factor of two on average. In addition, this type of voltage supply does not solve the problem of the difficulty of removing the dust layer from the electrodes.

It is known that an electrostatic precipitator is supplied with an asymmetric alternating current voltage at a commercial frequency.
Obtained by superimposing a 50Hz alternating voltage (West German Patent No. 1206397, International Classification B03C 3/38).
In this current supply method, the dust layer accumulates a negative charge on its surface during a half period of a negative voltage and is discharged during a subsequent half period of a positive voltage, reducing its amplitude. The use of asymmetric voltage helps reduce the reverse corona discharge intensity and the adhesion of the dust layer on the electrode.

A disadvantage of the above-described method of supplying an asymmetrical voltage to an electrostatic precipitator is that the particles are not sufficiently charged because they are alternately recharged to opposite polarity at a frequency of 50 Hz. In this case, the duration in the field of corona discharge of one polarity does not exceed 0.01 seconds. Furthermore, during the positive half-cycle of the asymmetric voltage, the strength of the electric field in the electrostatic precipitator is lower than during the negative half-cycle. These factors adversely affect the efficiency of static purification operations and cause asymmetric voltages to not be used in practice for the purposes mentioned above.

A method is known in which an electrostatic precipitator is supplied with a voltage of reverse polarity (USSR Inventor's Certificate No. 548315, International Classification B03C 3/38), which completely eliminates reverse corona discharges and also reduces the Provides self-cleaning of the dust electrode.

In this method, the polarity of the supply voltage is periodically reversed so that the particles are sufficiently charged during a corona discharge at each polarity, and then effectively placed in an electric field and deposited on the dust layer. The charge on the layer never reaches its critical value, thereby preventing breakdown in the layer. Periodically reversing the charge of the high-resistance dust layer prevents the occurrence of reverse corona discharges and enables dust collection efficiencies as high as those obtained with low-resistivity dust deposition.

Furthermore, since the charge is neutralized when the polarity is reversed, the electrical component of adhesion is reduced, and when the deposited dust layer reaches a certain thickness, the dust layer flakes off and falls off, but The dust collecting electrode is then self-cleaned. This self-cleaning phenomenon makes it possible to eliminate vibration mechanisms.

FIG. 1 shows a photograph of a dust layer formed on the surface of a dust collection electrode of an electrostatic precipitator, and the dust collector is supplied with a voltage whose polarity is periodically reversed. And the dust collector is not equipped with a vibration mechanism. FIG. 2 is a diagram schematically representing the photographing of electrodes. Photographs of the electrodes are taken using a camera 111 placed at a certain angle to the dust collecting electrode 112 (FIGS. 1 and 2).
A corona generating electrode 113 and a tubular frame 114 for attaching the corona generating electrode 113 are positioned between them.

The photograph in FIG. 1 shows a portion 115 of the clean surface of the dust-collecting electrode 112 where the dust layer has flaked off and fallen, and a portion 116 of the electrode surface with a dust layer approximately 1 cm thick. The fall of the deposited dust due to gravity occurs periodically as the thickness of each part of the dust layer increases. The dust layer thus formed does not interfere with the accumulation of particles and, if necessary, can be completely dropped by impacting the dust collection electrode.

When using a supply voltage of reverse polarity for high resistance dust separation in an electrostatic precipitator, the separation efficiency is
The electrical resistivity of the separated dust and the strength of the corona discharge are increased.

However, there are significant technical difficulties when using the above-described method in electrostatic precipitators for industrial applications. Due to the capacitance of the dust collector and the inductance of the power supply, a significant overvoltage is generated in the power supply circuit, which causes a breakdown in the power supply circuit and prevents the operation of the power supply. .

Object and Structure of the Invention The present invention provides a method and apparatus for supplying voltage to a high resistance dust electrostatic precipitator,
The method and device make it possible to prevent overvoltage occurrences in the power supply circuit, thereby increasing the operational reliability of the device.

The object of the invention is achieved by the following method.
That is, the method is a method for supplying a voltage to a high-resistance dust electrostatic precipitator having a dust collection electrode and a corona generation electrode while periodically reversing the polarity of the supply voltage, and in this method according to the present invention, The supply voltage is applied intermittently to the electrostatic precipitator, with the interruption of the voltage supply occurring simultaneously with the reversal of the supply voltage polarity, and the reversal of the supply voltage polarity is at the beginning of the interruption of the voltage supply. It is delayed.

Such a method prevents overvoltages and thus breakdowns in the power supply circuit, thereby increasing the reliability of the equipment implementing the method.

The highest separation efficiency in a precipitator is achieved by maintaining the supply voltage at a pre-breakdown level during the periods between voltage-free intervals, which reduces the amount of dust deposited on the electrostatic precipitator's collection electrode. by measuring the electrical potential of the dust layer applied to the electrostatic precipitator and varying the voltage applied to the electrostatic precipitator in proportion to the measured potential, thereby increasing the electrical potential applied to the precipitator. The supply voltage is made to correspond to the pre-breakdown voltage.

Variations of the method according to the invention are possible, in which the duration of the voltage supply in each polarity within the period between the voltage-free intervals is such that the amount of time the voltage is deposited on the dust collection electrodes of the dust collector is It is selected depending on the electric field strength within the dust layer.

The aforementioned objects of the invention are also achieved by the following device. That is, the device is a device for supplying voltage to a high-resistance dust electrostatic precipitator having a dust collection electrode and a corona generation electrode, and the device according to the present invention includes a step-up transformer, and one of the step-up transformers. A switchgear connected in series to a thyristor-type controller arranged in a secondary winding circuit, a secondary winding circuit of the transformer, and an electrostatic precipitator, the switchgear being connected in antiparallel to each other. a regulating unit comprising a protection unit, made in the form of two transit pentodes, each of which is provided with a control solenoid having an axis perpendicular to the axis of the corresponding pentode; The control unit is connected to an input terminal of the thyristor type controller, and the protection unit includes a thyristor element, and the control unit has a main oscillator, and one output terminal of the main oscillator is connected to the input terminal of the protection unit. The thyristor element includes one connected to the control electrode of the thyristor element, the other output terminal of which is connected to the control solenoid of the transit pentode via a flip-flop and a power amplifier.

Such a configuration of the device implementing the method proposed by the invention is such that the pentode is most advantageously used, has relatively small dimensions and low cost. , ensuring high operational reliability. In addition, the high internal dynamic resistance of the transit pentode limits the magnetizing current of the electrostatic precipitator and also reduces the spark discharge energy in the event of a breakdown, which is also the case when high power supplies are used. Eliminates the possibility of burnout of the corona-generating electrode, which can occur as a result of breakdown.

For the purpose of adjusting the duration of the voltage application period in each polarity, the device proposed in the invention can be provided with four voltage pickups, each of which has one lead. a comparator circuit having an input terminal connected to the other lead of the voltage pickup, the control unit being connected to the input terminal of the comparator circuit. a function generator, and a regulating unit is a pulse converter arranged in a circuit between the protection unit and the thyristor-type controller and an output terminal of the function generator in the control unit. Includes things connected to.

A variant is also possible in which the supply voltage is maintained at a pre-breakdown level during the period between voltage-free intervals, the device having one lead connected to the dust collection electrode of the dust collector. and in which the control unit includes a function generator having an input connected to the other lead of the voltage pickup, and the regulating unit is a pulse converter and in which the control unit includes a function generator having an input connected to another lead of the voltage pickup. arranged in a circuit between the protection unit and the thyristor type controller and having one input terminal connected to the function generator in the control unit.

The above object is also achieved by providing the following apparatus for implementing the method proposed in the invention. That is, the device comprises two step-up transformers, each having a thyristor-type controller located in the primary winding circuit of the transformer;
two high-voltage rectifiers, each having two high-voltage leads of reactive polarity, each placed in parallel with the secondary winding of the corresponding transformer, one of which is grounded; , two serially connected transit pentodes, each having a control solenoid, the axis of each control solenoid being perpendicular to the axis of the corresponding pentode;
one of the pentodes has a lead wire electrically connected to the electrostatic precipitator and the other transit pentode;
The other lead wire is electrically connected to the lead wire of the high voltage rectifier, the regulating unit is equipped with a protection unit, and is connected to the input terminal of the thyristor type controller, and the protection unit is connected to the input terminal of the thyristor type controller. A control unit including a main oscillator having a thyristor element, the main oscillator having two output terminals connected to the control electrodes of the thyristor element in the protection unit, and a third output terminal of the main oscillator. connected to the control solenoid of the corresponding transit pentode via a flip-flop and a power amplifier.

In this case, two variants are possible.

In a first variant, the series connection of the transit pentodes is carried out by connecting the cathode of one pentode to the anode of the other, the common connection point being connected to the dust collector. , the anode of the first pentode is connected to the negative high voltage lead of one high voltage rectifier whose positive high voltage lead is grounded, and the cathode of the other pentode is connected to The negative high voltage lead wire is connected to the positive high voltage lead wire of the other grounded high voltage rectifier.

In another variant of the device proposed by the invention, the series connection of the pentodes is carried out via one high-voltage rectifier, the anode of the one pentode being connected to its positive terminal. The high voltage lead is connected to the negative lead of the corresponding high voltage rectifier that is grounded, and the cathode of the same pentode is connected to the other high voltage rectifier that has the negative lead that is grounded through the other Connected to the positive high voltage lead of the voltage rectifier,
The other pentode is placed in a circuit including the high voltage rectifier and ground, and has its anode connected to the negative high voltage lead of the high voltage rectifier.

The above objects of the present invention are achieved by providing the following device for supplying voltage to a high resistance dust electrostatic precipitator having a dust collecting electrode and a corona generating electrode. That is, the device according to the invention comprises a power supply having two high voltage leads of opposite polarity, a high voltage switch having a control coil and connected to the dust collector, and a lead connected to the dust collector. a control unit comprising two series-connected diodes, the other lead of the field strength transducer being connected to the common connection point lead of the diodes; , the other lead of the diode is connected to a comparator circuit, and the control unit also includes a power amplifier, the power amplifier having an input terminal connected to the output terminal of the comparator circuit, and the corresponding an output terminal of the amplifier connected to the corresponding control coil of the high voltage switch.

Embodiments The invention will now be described with reference to embodiments illustrated in the accompanying drawings.

The device for carrying out the method proposed by the invention is represented in block diagram form in FIG. 2, a power supply 1 having a series circuit composed of a step-up transformer 3 and a high voltage rectifier 4, and a switchgear 5 connected to the power supply 1 and also connected to an electrostatic precipitator 6.
The voltage supply status is controlled by a control unit 7 which is connected to the switching device 5 and to the regulating unit 2.

When the voltage supply to the electrostatic precipitator is carried out according to the above block diagram, an alternating voltage at commercial frequency (in this particular case) from the 380V power supply line is applied to the regulating unit 2; In , the alternating voltage is regulated to a level determined according to the specified voltage and current supply of the electrostatic precipitator 6, after which the alternating current voltage is adjusted to a level determined according to the specified voltage and current supply of the electrostatic precipitator 6.
and then rectified by a high voltage rectifier 4. The switching device 5 periodically reverses the polarity of the voltage thus rectified, and alternately applies a positive or negative voltage to the corona generating electrode.

The waveform, amplitude and length of the voltage signal at each polarity are adjusted with the help of the control unit 7 and are selected to optimal values depending on the nature of the separated dust, in particular the electrical resistance of said dust. . In this case, a positive/negative inverted voltage having a square waveform of 1 Hz and equal voltage signal length in each polarity is used.

The reversal of voltage polarity when a voltage is applied to an electrostatic precipitator according to the method proposed by the present invention is shown by the signal waveform diagram in FIG. 6, and this reversal is performed as follows. Ru. For example, when a voltage of positive polarity and amplitude U ₊ is applied to the dust collector, an AC voltage of 50 Hz and amplitude U ₁ is applied to the primary winding of step-up transformer 3. If the polarity of the supply voltage is reversed, the primary winding of the transformer 3 is disconnected from the power supply line at time τ ₁ so that the precipitator is deenergized. Since no supply current flows from the power supply, the capacity of the dust collector 6 is discharged by the corona discharge current, and the voltage across the dust collector 6 changes from U ₊ to a residual value U′ ₊ close to the initial corona discharge voltage.
descend to

At time τ ₂ the dust collector 6 is disconnected from one polarity lead “a” of the source and connected to the opposite polarity lead “b” at time τ ₃ . At the moment when the dust collector 6 is connected to the opposite polarity lead wire "b", the capacity of the dust collector 6 is completely discharged and the voltage across the dust collector drops to zero value. Then, at a certain time τ ₄ , the primary winding of the transformer 3 is reconnected to the power supply line to reenergize the dust collector 6, but this time the dust collector is connected to the negative pole. It is supplied with a voltage U _- .

Reversing the voltage polarity from negative U _- to positive U ₊ is done in the same manner as described above. At time τ ₅ the transformer 3 is disconnected from the power line, then at time τ ₆ the dust collector is disconnected from lead “b” and at time τ ₇ the dust collector is connected to lead “a”. and then at time τ ₈ the transformer 3 is reconnected to the power line.

Such a polarity reversal is carried out periodically with the aid of the control unit 7 according to a preset program. The length of the interval between switching operations and the corresponding repetition frequency are such that the length of the voltage signal at each polarity corresponds to the time required for the potential of the dust layer to reach its critical value and cause breakdown, i.e. The time is selected so as not to exceed a time sufficient to cause a reverse corona discharge in the dust collector 6.

By disconnecting the primary winding of the transformer 3 from the power supply line, the reversal of voltage polarity at the dust collector 6 occurs smoothly and without voltage surges and current inrushes, thereby preventing overvoltages in the supply circuit. do.

In order to minimize the time consumption required for switching, the intervals τ ₁ - _{τ 3} and τ ₅ - _{τ 7} are chosen as short as possible, with a minimum potential difference applied to the high-voltage switchgear 5. be done. For this purpose, the connection of the precipitator to the opposite polarity lead at time τ ₃ is delayed by 1/2 period to 3/2 period. That is, there is a delay of 0.01 to 0.03 seconds after the power is disconnected from the power line. During this time,
As the capacity of the dust collector 6 is discharged by the corona discharge current, the voltage across the dust collector drops from U ₊ to U′ ₊ (approximately half). This prevents the occurrence of a double overvoltage across the switchgear 5 when the dust collector is connected to the power supply leads of opposite polarity at time τ ₃ . The time interval τ ₂ −τ ₃ also does not exceed more than one half period, and if an inertialess electronic switch is used, the time interval τ ₂ −τ ₃
can be equal to zero.

In this case, while reversing the supply voltage polarity,
The total duration of the voltage-free state of the dust collector does not exceed 0.05 seconds, which corresponds to a loss of time of less than 5% at a switching repetition rate of 1 Hz.

To improve the efficiency of using reverse voltage, the potential between the corona generating electrode and the dust layer on the collecting electrode of the electrostatic precipitator is pre-broken down during the period between the voltage-free intervals. - Must be maintained at pre-breakdown level. This measures the potential of the dust layer,
This is accomplished by adjusting the voltage applied to the dust collector in proportion to the measured value of the potential.

The block diagram of FIG. 4, illustrating a variant of the method proposed by the invention, includes a power supply 1 in a series circuit comprising a regulating unit 2, a step-up transformer 3 and a high-voltage rectifier 4. Equipped with. The block diagram further includes a switching device 5 connected to the power supply 1 and connected to the dust collector 6, and a control unit 7. The output of the control unit 7 is connected to the switching device 5 and the regulating unit 2. In addition, one or several voltage pickups are mounted on the dust collection electrode of the dust collector to provide a feedback in the supply circuit for controlling the operating conditions, the voltage pickups being connected to the top of the dust layer. It has an output adapted to measure the electrical potential and connected to the control unit 7.

The signal received from the pickup 8 is proportional to the voltage drop across the dust layer, which signal is converted in the control unit 7 and then in the regulation unit 2.
and is transmitted to the opening/closing device 5.

Each time the supply voltage polarity is reversed, the dust layer initially has an accumulated charge as a result of the corona discharge of the previous polarity. Therefore, the potential of the dust layer is negative with respect to the potential across the corona-generating electrode, to which a voltage of opposite polarity is already applied, and therefore the potential difference between the corona-generating electrode and the dust layer Increase absolute value.

In order to prevent breakdown in the air gap between the electrodes, which can occur when supply voltages of opposite polarity are applied (see Figure 4), the amplitude of the supply voltage applied to the precipitator is initially reduced. be done. The dust layer is then recharged and new charges of opposite polarity are accumulated, increasing the potential of the same polarity and increasing the amplitude of the supply voltage. This results in
A maximum voltage difference is continuously maintained on both sides of the gas flow path in the gap between the electrodes, the potential difference corresponding to the pre-breakdown voltage, thereby maintaining the maximum electric field strength and thus the gas cleaning ability. Improve.

In another variant of the method proposed by the invention (FIG. 5), the length of the supply voltage signal in each polarity, which is applied to the dust collector in the period between the voltage-free intervals, is It is selected depending on the electric field strength in the dust layer deposited on the dust collection electrode of the machine 6.

A block diagram illustrating a variation of the proposed method is shown in FIG. As before, the block diagram shows a power supply 1 with two high voltage leads "a" and "b", a switchgear 5,
It includes an electrostatic precipitator 6 and a control unit 7. In this case, the switchgear is an electromagnetic switch with control coils 9 and 10, and the pickup 8 attached to the dust collector is connected to the coils 9 and 10 of the switchgear 5.
10 via a control unit 7.

According to this variant, the signal from the transducer 8 is proportional to the electric field strength in the dust layer deposited on the dust collection electrode of the dust collector 6 and is applied to the control unit 7. When the electric field strength in the dust layer reaches a pre-breakdown level, a control signal is generated in the control unit 7, which control signal is applied to the control coils 9, 10 of the switchgear 5 to cause a reversal of the voltage polarity. thereby preventing breakdown in the dust layer on the dust collecting electrode and occurrence of reverse corona discharge in the dust collector.

The method proposed in the present invention using a positive/negative supply voltage is an electrostatic precipitator YI2-4- installed after a rotary kiln for burning magnesite.
37 in the fourth section (the last section when looking in the direction of gas flow). Two supply units ATΦ-400 fitted with thyristor type voltage regulators were used as sources of reverse polarity voltages. A high voltage of negative polarity was applied from the output of one unit, and a high voltage of positive polarity was applied from the output of the other unit. The high voltage leads of both units of opposite polarity were connected to the dust collector via an electromagnetic switch. The switch was operated with the aid of an automatic control unit that makes it possible to adjust the length of the voltage signal of each polarity.

Signals from the control unit were applied to the control coil of the high voltage switchgear and to the power regulator to disconnect the unit from the power line.

By disconnecting the unit from the power line, no overvoltage occurred in the dust collector's supply circuit when the supply voltage was switched.
Compared to the prior art methods that utilize DC voltage as the supply voltage, the method proposed by the present invention reduces the amount of dust remaining after passing through the electrostatic precipitator by 2 to 2.
It was possible to reduce it by 2.5 times. When the electrostatic precipitator was supplied with an inverted voltage, the vibrating mechanism was turned off and the dust deposited on the electrodes fell off due to gravity.

By monitoring the amount of residual dust in the gas after processing with a dust collector using optical dust counting, it is possible to detect secondary scattering of dust when a voltage of reverse polarity is supplied to the electrostatic precipitator. It has been found that entrainment, i.e. the secondary entrainment that occurs during vibration of the collecting electrode in prior art methods using a unipolar voltage supply, does not occur.

A device for supplying voltage to electrostatic precipitators for high-resistance dust is proposed for carrying out the method of the invention, which device comprises a thyristor-type control arranged in each case in the primary winding circuit of the corresponding transformer. two step-up transformers 11 and 12 (FIGS. 7 and 8) with a voltage regulator 13 or 14 respectively, a regulating unit 15;
and 16, a high voltage bridge rectifier 17, 18 with positive and negative high voltage leads respectively, a transit pentode 19, 2 arranged in series in the supply circuit of the electrostatic precipitator 21.
0, and a control unit.

The thyristor controllers 13, 14, made in the form of two anti-parallel connected thyristors, and the regulating units 15 and 16 are connected to the power supply unit ATφ.
(A.Aliev, “Agregatou Pitanya Electrofiltrob” M.1980 Gosenergoizdat,
It is constructed in the same manner as shown in the block diagram on page 96). Adjustment units 15 and 16
each includes a protection unit 23, 24, which is adapted to disconnect the device from the power supply line in the event of a breakdown in the electrostatic precipitator, in the general case. Protection unit 2
3,24 at least one thyristor key (thyristor element, not shown in the drawings) coupled to a thyristor adapted to disconnect the device from the power supply line in response to an external control signal;
has.

Control unit 22 includes a main oscillator 25, a flip-flop 26 and power amplifiers 27,28. The two output terminals of the main oscillator 25 are connected to the control lines of the thyristor elements in the protection units 23, 24, and the third output terminal of the main oscillator is connected to the input terminal of a flip-flop 26, which Control solenoid 2 of the transit pentode 19, 20 whose output terminal corresponds to
It is connected to lead wires 9 and 30 via power amplifiers 27 and 28.

The transit pentode tubes 19 and 20 (Fig. 7) are
The electrostatic precipitator 21 is connected such that the cathode of the transit pentode 19 is connected to the corona generating electrode of the electrostatic precipitator 21 and the anode of the same pentode is connected to the negative high voltage lead wire of the high voltage rectifier 17. located within the supply circuit of the transit pentode 20
has its cathode connected to the positive high voltage lead wire of the high voltage rectifier 18, and its anode connected to the corona generating electrode of the dust collector 21. in this case,
The positive lead wire of high voltage rectifier 17 and the negative lead wire of high voltage rectifier 18 are grounded.

A variant of the device proposed by the invention is possible, in which a transit pentode 20 (FIG. 8) is arranged in the supply circuit of the dust collector 21 between the high-voltage rectifier 18 and ground. , the anode of the transit pentode 20 is connected to the negative lead of the high voltage rectifier 18, and the cathode of the pentode is grounded. A positive lead wire of the high voltage rectifier 18 is connected to a corona generating electrode of the dust collector 21 . Such a configuration of the device is simpler and
and improve operational reliability.

The variant device illustrated in FIGS. 7 and 8 operates in the following manner. For example, a high voltage of negative polarity is applied from the lead wire of the rectifier 17 to the electrostatic precipitator 21 via the transit pentode 19. Before switching the high voltage, the main oscillator 2 of the control unit 22
A thyristor controller 13, responsive to a signal applied from 5 to the input terminal of a protection unit 23 in the regulating unit 15, disconnects the transformer 11 from the supply line. Next, the power amplifier 2 of the control unit 22
In response to signals applied to control solenoids 29 and 30 from 7 and 28, transit pentode 1
9 is made non-conducting, and the transit pentode 20
is turned on and then a signal from the main oscillator 25 of the control unit 22 is applied to the protection unit 24 of the regulating unit 16, the thyristor controller 14 connects the transformer 12 to the supply line, in this case At , a positive supply voltage is applied from the rectifier 18 to the dust collector.

This configuration of a device for supplying a voltage with reversed polarity and full-wave rectification to a dust collector is as follows:
Provides the maximum value of voltage and current applied to the dust collector. However, this variant requires the use of two step-up transformers and two rectifying bridges, which makes the device larger in size, heavier in weight and higher in cost. Furthermore, each transformer only operates during only 50% of the total operating time of the dust collector, which is more uneconomical.

If the desired separation efficiency can be achieved with a supply voltage and current below the maximum value,
It is advisable to use a device of simpler construction, which supplies the dust collector with an inverted voltage, but a half-wave rectified wave. In this case, the device comprises a step-up transformer 31 comprising a thyristor-type voltage regulator 32 arranged in series in the primary winding circuit of the transformer, a regulating unit 33, and a cathode, Transit pentodes 35, 36 with anodes and corresponding control solenoids with leads c, d,
A switchgear 34 is provided, comprising a control solenoid having a control solenoid whose axis is perpendicular to the axis of its corresponding pentode. The transit pentode tubes 35 and 36 of the switchgear 34 are in an antiparallel relationship, and both are arranged in series in a circuit between the secondary winding of the step-up transformer 31 and the electrostatic precipitator 39. In this case, two variants are possible, as explained below.

A first variant is shown in FIG. In this modification, one terminal of the secondary winding of the step-up transformer 31 is connected to a switchgear 34 that is directly connected to an electrostatic precipitator 39 .

In the second modification shown in FIG.
One terminal of the secondary winding of step-up transformer 31 is directly connected to electrostatic precipitator 39, and the other terminal of the winding is connected to grounded switchgear 34.

The regulating unit 33, as in the previously described variant, includes a protection unit 40 whose output terminal is connected to the input terminal of the thyristor controller 32 and which includes a thyristor element. .

This variant device also includes a control unit 41 incorporating a master oscillator 42, a flip-flop 43, and power amplifiers 44 and 45.
One output terminal of the main oscillator 42 is connected to the protection unit 4.
The other output terminal of the oscillator is connected to the input terminal of a flip-flop 43. The output terminal of flip-flop 43 is connected to the leads of power amplifiers 44 and 45. Lead wire c ¹ of the power amplifier 44,
d ¹ is the control solenoid 3 of the transit pentode 35
7, and the lead wires e ¹ and f ¹ of the power amplifier 45 are connected to the transit pentode 36.
The control solenoid 38 is connected to lead wires e and f of the control solenoid 38.

The modified apparatus shown in FIGS. 9 and 10 operates as follows.

The control solenoids 37 and 38 are connected to the control unit 41
A supply current is alternately applied from power amplifiers 44 and 45. When supply current flows through solenoid 37 and solenoid 38 is in a no-current state, transit pentode 35 is non-conducting;
On the other hand, the transit pentode 36 is conductive, and the corona generating electrode is supplied with a positive voltage. When current flows through the control solenoid 38 and the control solenoid 37 is in a no-current state, the corona generating electrode of the precipitator 39 is supplied with a negative polarity voltage. In this case, each transit pentode operates as a half-wave rectifier and voltage switch.

Before switching the voltage, the thyristor controller 32, responsive to a signal applied to the protection unit 40 from the main oscillator 42 of the control unit 41, disconnects the step-up transformer from the supply line and after the switching operation is completed. , the transformer 31 is reconnected to the power line.

The transit pentodes 35, 36, which have a high internal dynamic resistance, allow the supply current to be limited in the event of a breakdown, thereby preventing arcing and thus reducing the voltage in the electrostatic precipitator. Improve supply conditions.

caused by changes in the properties of the dust-laden gas stream,
The reduction in precipitator load resistance increases the voltage drop across the transit pentode, which causes excessive power. Therefore, adjusting the supply voltage with the aid of feedback to reduce the voltage across the transit pentode would be useful to prevent excessive power consumption of the power supply.

In FIG. 11, a device configuration is shown in which feedback control is used internally to minimize the voltage drop across the transit pentode. In addition, the device also includes transit pentode tubes 35, 36.
includes voltage pickups 46, 47, 48, 49 attached to the anode and cathode sides of the. The control unit 41 includes a pickup 46,
It incorporates a comparison circuit 50 adapted to compare the signals received from 47, 48 and 49 with a reference voltage, and a function generator 51. The regulation unit 33 includes a pulse converter 52, which can be used to regulate the voltage in response to an external control signal.

Voltage pickups 46, 47, 48 and 49
is connected to the input of a comparison circuit 50 whose output terminal is connected via a function generator 51 to the input terminal of a pulse converter 52 in the control unit 23.

For example, in the event of an overvoltage across the transit pentode 35, an increase in the difference in the signals from the voltage pickups 46, 47 will generate a control signal at the output of the comparator circuit 50 in the control unit 41, The signal is applied to pulse converter 52. In this case, with the help of the thyristor controller 32, the regulating unit 33 reduces the supply voltage applied to the device, which in effect
5. Prevent excessive voltage from occurring at both ends.

The operating principle of the device using feedback control is shown in FIG. 12, which shows the voltage-current characteristics of the transit pentode 35 or 36 (curve 1) and the load characteristics of the electrostatic precipitator 39 (curve 2, 3) is shown. When the device is in operation, the voltage at the output terminals of the transformer 31, the transit pentode 35 or 36
A current whose value depends on the current limit level at and on the load characteristics of the dust collector 39 flows through the supply circuit of the dust collector.

The optimal operating condition for the device is one in which the current in the precipitator 39 is at a maximum current I _nax and the voltage drop across the corresponding transit pentode is minimal. This situation at the supply voltage E corresponds to a corresponding point A where the curve 1 of the voltage supply characteristic and the curve 2 of the dust collector load characteristic intersect each other.

If the load increases due to a decrease in the resistance of the dust collector 49, the operating point moves to point B, in which case the current in the supply circuit is reduced by the transit pentode across which an excessive voltage drop occurs. Since the current value is limited, it does not increase. Depending on the voltage drop detected by the corresponding voltage pickup connected to the control unit 41, the transformer 31
The voltage across the primary winding and the output terminal voltage decreases, thereby reducing the rectified voltage at the device output to a value
Reduce E to ¹ . In this case, the operating point is again at its position A, in which case no excessive voltage and power dissipation in the transit pentode occurs. This eliminates overheating of the device and increases its operational reliability.

FIG. 13 shows a variant of the device, which is suitable for implementing a variant of the method in which the supply voltage during the no-voltage interval is maintained at a pre-breakdown level.

This modified device (FIG. 9) also includes a voltage pickup 53, one lead of which is connected to the dust collection electrode of the dust collector 39. Control unit 41 further includes a function generator 54 having an input terminal connected to the other lead of voltage pickup 53. The regulating unit 33 includes a pulse converter 55, which
The protection unit 40 and the thyristor type controller 32
and one input terminal thereof is connected to the function generator 54.

In this variant, the polarity of the voltage applied to the corona-generating electrode is periodically reversed in response to a signal from the master oscillator 42, which signal is converted in a flip-flop 43 and
4 and 45, the polarity reversal is performed with the aid of transit pentode tubes 35, 36 having control solenoids 37, 38, respectively. After each reversal of the supply voltage polarity, the dust layer on the dust collection electrode is recharged and the potential on the surface of the dust layer increases again. With the increase in the potential, the signal from the pickup 53 increases proportionally to the potential, which signal is transmitted via the function generator 54 to the pulse converter 55 in the regulating unit 33 and to the controller 32. , causing the supply voltage to increase proportionally to the signal from the pickup to the pre-breakdown level. Maintaining the supply voltage at a maximum level allows an increase in the electric field strength in the electrostatic precipitator, thereby increasing its efficiency.

A variant of the device shown in FIG. 14 is such that the length of the supply voltage pulse in each polarity between the voltage-free intervals is selected depending on the electric field strength in the dust layer deposited on the dust collection electrode. , is intended to implement a variant of the method proposed in the invention.

This modified device includes a power source 56 having two high voltage output terminals of opposite polarity, and a dust collector 5.
8, the dust collector 58 comprises at least one field strength transducer 59 mounted on the dust collection electrode of the dust collector.

Source 56 includes components similar to those shown in FIGS. 3 and 4. The switch 57 includes control coils 60 and 61. Transducer 59
are diodes 63, 64, comparison unit 65,
and to control coils 60, 61 via a control unit 62 including power amplifiers 66, 67. This transducer 59 is a diode 6
3 and 64 to the input terminals of a comparator unit 65, the output terminals of which are connected via power amplifiers 66, 67 to coils 60, 61 of switch 57. The output terminal of control unit 62 is also connected to the input terminal of supply source 56.

The device described above operates as follows. When the strength of the electric field in the dust layer increases to a predetermined level that does not exceed the pre-breakdown level, a signal is applied from transducer 59 to comparator circuit 65 via diode 63, and converts the signal into a reference voltage. After comparison, comparison circuit 65 generates a control signal. This control signal, after being amplified by power amplifier 66, is applied to the input of supply source 56 to isolate it from the power supply line during polarity reversal operations in a manner similar to that described above, and also:
The control signal is applied to coil 60 of switch 57, which operates to reverse the polarity of the supply voltage applied to dust collector 58 in response to the signal. After the reversal operation is completed, the electric field strength within the dust layer increases with opposite polarity. When the intensity reaches its predetermined value, the transducer 59 is applied to the comparator circuit 65 via the diode 64.
The signal from the power supply 56 reverses the polarity of the supply voltage simultaneously with the disconnection of the power supply 56 from the power supply line. In this way, the polarity of the supply voltage is periodically reversed with a repetition frequency of polarity reversal, which repetition frequency depends on the rate of increase of the electric field strength in the dust layer deposited on the collection electrode of the electrostatic precipitator. will be determined.

Adjusting the voltage of polarity reversal according to the strength of the electric field in the dust layer improves the dust cleaning efficiency. This is because by reversing the voltage polarity before the electric field strength within the dust layer reaches its critical level, breakdown and reverse corona discharge within the dust layer is prevented.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the corona-generating electrode and dust-collecting electrode portions, showing self-cleaning of the dust-collecting electrode from a layer of dust deposited on the dust-collecting electrode according to a prior art method; FIG. 2 is a top view schematically showing the corona generating electrode and dust collecting electrode of FIG. 1, and FIG. 3 is a block diagram of an apparatus for carrying out the method of supplying voltage to an electrostatic precipitator according to the present invention. FIG. 4 shows a block diagram of an apparatus for carrying out one modification of the method of the invention, FIG. 5 shows a block diagram of an apparatus for carrying out another modification of the method of the invention, and FIG. are signal waveform diagrams when the polarity of the supply voltage is reversed according to the present invention, and Figures 7 and 8 are two signal waveform diagrams of a certain device that supplies voltage to an electrostatic precipitator according to the present invention. A circuit diagram of a modified example is shown, and the ninth, tenth, eleventh, and first
Figure 3 shows a circuit diagram of another modification of the device for supplying voltage to an electrostatic precipitator according to the present invention, and Figure 12 shows the voltage-current characteristics of the transit pentode (curve 1) and the dust collector. Machine load characteristics (curves 2 and 3)
FIG. 14 represents a circuit diagram of a further device for supplying voltage to an electrostatic precipitator according to the invention. 1,56...power supply, 2,15,16,33...
Adjustment unit, 3, 11, 12, 31... Step-up transformer, 4, 17, 18... High voltage rectifier, 5, 3
4... Switchgear, 6, 21, 39, 58... Electrostatic precipitator, 7, 22, 41, 62... Control unit, 8, 46, 47, 48, 49, 53... Voltage pickup, 9, 10, 60, 61... Control coil, 13, 14... Thyristor type controller, 1
9, 20, 35, 36...transit pentode,
23, 24, 40...protection unit, 25, 42
... Main oscillator, 26, 43 ... Flip-flop, 27, 28, 44, 45, 66, 67 ... Power amplifier, 29, 30, 37, 38 ... Control solenoid, 32 ... Thyristor type voltage controller, 5
0, 65... Comparison circuit, 51, 54... Function generator, 52, 55... Pulse converter, 57... High voltage switch, 59... Field strength transducer, 63, 64... Diode.

Claims (1)

[Claims] 1. A method for supplying voltage to a high-resistance dust electrostatic precipitator having a dust collection electrode and a corona generation electrode while periodically reversing the polarity of the supply voltage, wherein the supply voltage is is applied intermittently to the dust collector, the interruption of the voltage supply is performed simultaneously with the polarity reversal of the supply voltage, and the reversal of the polarity of the supply voltage is delayed with respect to the start of the interruption of the voltage supply. A method for supplying voltage to an electrostatic precipitator for high-resistance dust. 2. The duration of the interruption of the voltage supply is 0.01 or more.
A method according to claim 1, characterized in that the time is 0.05 seconds. 3. The supply voltage is maintained at a pre-breakdown level during the period between the voltage supply interruption times, and the maintenance at the pre-breakdown level is carried out by measuring the potential of the dust layer on the dust collection electrode of the electrostatic precipitator;
by adjusting the voltage supplied to the electrostatic precipitator in proportion to the measured potential;
3. Method according to claim 1, characterized in that the voltage applied to the electrostatic precipitator is thereby made to correspond to a pre-breakdown voltage. 4. The duration of applying voltages of each polarity to the electrostatic precipitator during the period between voltage supply interruptions depends on the electric field strength within the dust layer on the dust collection electrode of the electrostatic precipitator. 3. A method according to claim 1 or 2, characterized in that the method is selected. 5. A device for supplying voltage to a high-resistance dust electrostatic precipitator having a dust-collecting electrode and a corona-generating electrode, the device comprising: a step-up transformer 31; a thyristor type controller 32, a switchgear 34 connected in series to the secondary winding of the transformer 31 and the circuit of the electrostatic precipitator, the switchgears being connected in antiparallel to each other; A protective unit made in the form of two transit pentodes and comprising control solenoids 37 and 38, respectively, the axes of which are perpendicular to the axis of the corresponding pentode. a regulating unit 33 with 40 connected to the input terminal of the thyristor controller 32, the protection unit 40 comprising a thyristor element; and a control unit 41 with a main oscillator 42, One output terminal of the main oscillator 42 is connected to the control electrode of the thyristor element in the protection unit 40, and the other output terminal is connected to the transit pentode 35, 36 via a flip-flop 43 and power amplifiers 44, 45. The control solenoid 3
An apparatus for supplying voltage to an electrostatic precipitator for high-resistance dust, characterized in that it is connected to 7 and 38. 6 4 voltage pickups 46, 47, 48,
49, each of which has one lead connected to a corresponding pentode 35 or 3.
6, the control unit 41 connects the voltage pickups 46, 47, 4
The adjustment unit 33 includes a comparator circuit 50 having an input terminal connected to the other lead wire of the comparator circuit 50 and a function generator 51 connected to the input terminal of the comparator circuit 50; and arranged in the circuit between the protection unit 40 and the thyristor type controller 32 and within the control unit 4
6. The device according to claim 5, further comprising: one connected to the output terminal of one of the function generators 51. 7 Voltage pickup 5 having one lead wire connected to the dust collecting electrode of the electrostatic precipitator 39
3, the control unit includes a function generator 54 having an input terminal connected to the other lead of the voltage pickup 53, the regulating unit 33 being a pulse converter 55, characterized in that it includes a function generator arranged in the circuit between the unit 40 and the thyristor controller 32, one input terminal of which is connected to the function generator 54 in the control unit 41. Apparatus according to claim 5. 8. A device for supplying voltage to a high-resistance dust electrostatic precipitator having a dust collecting electrode and a corona generating electrode, the device comprising: two step-up transformers 11 and 12, thyristor type controllers 13, 14; , each of which is arranged in the primary winding circuit of the transformer 11, 12, respectively; two high voltage rectifiers 17, 18, each of which is arranged in the secondary winding circuit of the corresponding transformer 11, 12; two series-connected transit pentodes 1 having two high-voltage leads arranged in parallel with the windings and of opposite polarity, one of which is grounded;
9, 20, each of which has a control solenoid 2.
9 and 30, respectively, the axis of each control solenoid being perpendicular to the axis of the corresponding transit pentode, and electrically connected to the electrostatic precipitator 21 and the other transit pentode. and a lead wire electrically connected to the high voltage lead wire of one of the high voltage rectifiers 17, 18, a regulating unit 15, 16, each of which has a corresponding protection. a control unit 22 comprising units 23, 24 and connected to the input terminals of the thyristor type controller 13 or 14, each of which has a thyristor element; and a control unit 22 comprising a main oscillator 25; The oscillator has its two output terminals connected to the control electrodes of the thyristor elements in the protection units 23, 24, and its third output terminal connected to the corresponding transit pentode via a flip-flop 26 and power amplifiers 27, 28. A device for supplying voltage to an electrostatic precipitator for high resistance dust, characterized in that it comprises: connected to said control solenoids 29, 30 of pipes 19, 20. 9. The series connection of the transit pentodes 19, 20 is carried out by connecting the cathode of one of the pentodes to the anode of the other pentode, the common connection point being connected to the electrostatic precipitator. The anode of the first transit pentode 19 is connected to the negative high voltage lead of one high voltage rectifier 17, the positive high voltage lead of which is connected to ground, and the other transit pentode 20
9. The apparatus of claim 8, wherein the cathode of is connected to the positive high voltage lead of the other high voltage rectifier 18 whose negative high voltage lead is grounded. 10 The series connection of the transit pentodes 19 and 20 is made through one of the high voltage rectifiers 18, and the anode of the one transit pentode 19 has its positive high voltage lead wire grounded. The cathode of the transit pentode 19 is connected to the negative lead of the corresponding high voltage rectifier 17.
the other high voltage rectifier 18 whose negative lead is grounded via the other transit pentode 20;
The other pentode 20 is placed in a circuit consisting of the high voltage rectifier 18 and ground, and is connected to the negative high voltage lead of the high voltage rectifier 18. 9. The device according to claim 8, characterized in that: 11. A device for supplying voltage to a high-resistance dust electrostatic precipitator having a dust-collecting electrode and a corona-generating electrode, the device comprising: a power source 56 having two high-voltage leads of opposite polarity; and a control coil 60, 61. a high voltage switch 57 having and connected to the corona generating electrode of the electrostatic precipitator, a field strength transducer 59 mounted on the collecting electrode in the electrostatic precipitator 58, and each other. Two diodes 6 connected in series
3,64, the control unit 62 comprising:
a common connection point of the diode leads is connected to a lead of the field strength transducer 59;
The other lead of the diode is connected to a comparator circuit 65 and the control unit also connects a power amplifier 6
6, 67, the input terminals of the power amplifiers 66, 67 are connected to the output terminals of the comparator circuit 65, and the output terminals of the corresponding power amplifiers 66, 67 are connected to the corresponding control coil 60 of the high voltage switch 57. ,6
An apparatus for supplying voltage to an electrostatic precipitator for high-resistance dust, characterized in that it is connected to 1.