SE408761B - CIRCUIT COUPLING FOR ELECTROSTATIC DUST SEPARATOR - Google Patents

Description

_ 160226341 » 2 the electrodes of the dust collector formed the capacitor, back to the storage capacitor for re-storage in this.

This makes it possible to reduce the energy and power consumption required for charging the electrical condensate ptorn, represented by the electrostatic precipitator, by recovering the energy input to it. 7 Pulse voltage driven electrostatic precipitators are first and mainly advantageous in the following respects: The charging of the particles is improved, because of the voltage peak value can be increased without increasing the mean value of the voltage and thereby the number of estimates. By varying the pulse amplitude and the pulse frequency, it becomes possible to control the emission current independently of the main electric field so that the current load of the dust layer on the collection electrode can be adapted to the radiation limit, which determined by the “resistivity of dust.

The non-uniform current distribution in conventional dust separators give rise to re-radiation on the collected dust is highly resistant. By using pulse voltage driven dust separators with three electrodes, a very uniform current distribution can be kept over the collecting electrode when using extremely short voltages high amplitude pulses, as these pulses can produce an electron cloud with a high charge density and thereby a high expansion effect. Thereby an improved distribution over the collection electrode of the emission generated by each individual emission electrode sion current.

Another well-known problem with conventional, electrostatic dust collectors consist of a few percent of the dust collector volume but can add almost 100% of the dust collector current due to differences in gas or radiative condition differences _ _ inside the dust collector. By using pulses, one can be uniform distribution over the entire dust collector section is obtained independently of local gas and re-emission conditions, as the emission current at pulses of short duration and high amplitude are determined by the work by releasing the charge carriers from the emission electrode. This touches a lot on the emission electrode but only a little on the surrounding one gases. '_ In operation, a dust collector with two electrodes can be made of electric point of view is considered equivalent to a capacitor, which is parallel or connected in series with a resistor, which is why it is connected to the dust collector the energy emitted can be divided into an active and a reactive part¿ "_Éill- 7602263-1 3 the supply of active energy is an irreversible process, while the supply, of reactive energy can be considered as a reversible process. With the methods known hitherto, however, it has not been possible to recover the significant energy stored in an electrostatic the capacitance of dust collectors during a pulse, without this energy has instead converted to useless heat.

The quantitative size of this unnecessary energy consumption can be calculated using the formula (1) Erå - G- (vš-vf) (1) where C = capacitance V2 = peak voltage V1 = starting voltage The corresponding effect can be calculated by the formula (2) Q = v- E (2) where V = pulse rate.

Below are some examples of estimated energy and power operation at different capacitance and voltage values: Table la (two-electrode system) l 2 2 4 C nF 70 150 70 150 Vm kV, 50 50 50 50 Vp kV "20 20 100 100 E Joule 85 180 700 1500 Q kw 55 75 280 600 where C = dust separator_capacitance Và = DC voltage Vp = superimposed pulse voltage E = energy consumption for a single charge Q = power consumption (at a pulse frequency of 400 Hz).

Table lb ' (three-electrode system) 1 2 3 4 5 CEH No. 100 160 - 160 ~ 160 160- _ CEU No. 30 80 80 80 80 Vhu kV 50 50 50 50 50 \ VÉU kV 50 50 50 50 30 Vp kV 50 20 50 100 50 'E J 240 150 500 1600 660 _ - _ Q kw 95 5 _50 * g200Wg 640 265 76022634 hrs where CEH = emission auxiliary electrode capacitance CEU = emission collection electrode capacitance VHU = DC voltage between auxiliary electrode and collector electrode VÉU = DC voltage between the emission electrode and the collection electrode Vp = superimposed pulse voltage E = energy consumption for a single charge Q = power consumption (at a pulse frequency of 400 Hz).

As can be seen from the tables, the power consumption is large dust collectors (larger collection electrode area than 2500 m) at high pulse voltages to between 200 and 600 kW. Since a conventional dust collectors only use 10% of this power it is obvious that the pulse operation of electrostatic precipitators can not be used on an industrial scale for economic reasons unless they the energy of individual pulses is recovered in an efficient way.

In addition to reducing the energy of the electrostatic precipitator The invention also aims at ensuring extinguishing one of the corona discharges after each pulse.

To control the charging current and for three-electrode systems even the current distribution across the collection electrode is in itself it is necessary to be able to regulate the time function of the corona current.

The emission current does not only depend on the dust separator voltage instantaneous value but also on whether an ionized plasma is present in advance in the immediate vicinity of the emission electrode, since 1 this In this case, the trend towards new ionisation will increase so that new carriers will be generated at a relatively low field strength. One further feature of the invention is thus that the extinguishing of the corona discharge can be ensured by lowering the voltage where the main voltage for a short time interval after each pulse.

The invention is described in more detail below with reference to attached drawing, in which Fig. 1 shows a wiring diagram above a circuit connection for an electrostatic precipitator according to a first embodiment of the invention, Fig. 2 shows a circuit cupf for an electrostatic precipitator according to a second embodiment embodiment of the invention, Fig. 3 shows a circuit connection for a 7602263-1 5 electrostatic precipitator according to a third embodiment of the Fig. U shows a circuit connection for an electrostatic separator according to a fourth embodiment of the invention, Fig. 5 shows a circuit connection for an electrostatic precipitator according to a fifth embodiment of the invention and Fig. 6 shows a circuit coupling for an electrostatic precipitator according to a sixth embodiment of the invention.

In Fig. 1, 1 denotes a charging circuit for a storage con- densifier 7. 2 denotes a discharge circuit in which pulses are generated race and the circuit 2 forms an oscillation circuit for these together with the circuit denoted by 3.

From a voltage source 4, which may be single-phase or multiphase, a single-phase or multiphase alternating voltage is obtained, which is rectified by means of a rectifier 5 (which may, for example, consist of a single-phase or multiphase bridge coupling). A coil 6 isolates the DC source from the current transients from the pulse generator and allows direct current supply of a electrode combination 16 representing the emission electrode and the collecting electrode in an electrostatic precipitator, for example of the well-known type used as a gas filter to separate dust particles from a flowing gas. The capacitor 7 is a capacitor, from which the energy of the pulses is taken and to which the energy after returned. energy, which is consumed during each pulse partly 1 the corona discharge To start the generator and compensate for it and in part as losses in components and conductors, it is necessary to be able to supply the capacitor with new energy. limiting resistor 8 and a coil 9. 10 denotes a thyristor, which can be ignited by means of an ignition circuit (not shown). Then the oscillating the charge of the capacitor 7 via a pulse transformer 12 with a primary winding 13 and a secondary winding 14 to a capacitor 15__ and the electrode combination 16 and back to the capacitor 7 via a diode (or diode combination) 11, the conduction direction of which is opposite thyristor conduction direction. The oscillation period is determined by the pulse the short-circuit inductance of the transformer 12 and the capacitors 7 and 15 capacitance and the 16 capacitance of the electrode assembly. Condensate This is done via a current tower 15 is arranged in the generator in order to avoid direct current through 7602263-1 6 the secondary winding lb of the pulse transformer 12, and must be adjusted accordingly relative to the capacitance of the electrode combination 16 to pulse voltage convergence the liquidity is divided between the two capacitances in an appropriate ratio. the.

Fig. 1 also shows the use of the circuit 1 for supplying an additional electrode combination 17, which may represent auxiliary the electrode and the collecting electrode in a three-electrode separator (comparator for Fig. 5).

In Fig. 2, 20 denotes a charging circuit for a capacitor 25, while 21 denotes a discharge circuit in which the pulses are generated, wherein the circuit 21 together with the circuit 22 represents the circuit, in which the pulses oscillate. ._ _ 25 denotes a source of a high DC voltage, which source The positive terminal is grounded so that a negative voltage can be drawn from the source. A coil 24 insulates the voltage source 25 from the current transients from the pulse generator. Denoted by 25 is a capacitor, from which the energy of the pulses is taken and to which the energy after returned. To start the generator and compensate for the e- energy, which is consumed during each pulse partly in the corona discharge and partly as losses in components and conductors, it is necessary to supply new energy to the capacitor. This is done with the help of a charging network consisting of a current limiting resistor 26 and a coil 27. When overshoot occurs in a spark gap 28 between two spark electrodes 5A and 55, the charge of the capacitor 25 oscillates via spark gap 28 and a coil 52 of a capacitor 51 and an electrode combiner nation 55, representing an electrostatic precipitator, and then back to the capacitor 25 via a diode (or diode combo nation) 29. The estimate in the spark gap 28 can be achieved ~ either by adjusting the spark gap for self-discharge at a predetermined threshold voltage or by providing some form of trigger of the spark gap, for example by exposing the spark gap to ultraviolet lett_lJus. If the spark gap is self-discharging, the oscillation must be be so strong that the gap is not recharged after the pulse voltage: _ oscillated back to the capacitor 25. For this type of spark gap, the pulse frequency is determined by the time constant of the charge the mains 26, 27 and the capacitor 25. A coil 50 is used to hold one side of the spark gap Grounded with respect to the direct current but isolated row from ground at sufficiently high frequencies. Capacitor 51 in- gàr_i the generator in order to avoid direct current from the direct voltage the source through the coil 50 and must be so Adjusted relative to the electrode 7 the capacitance of the combination 33 that the pulse voltage amplitude is divided between the two capacitances according to an appropriate ratio. The period for the oscillation generated by flashing in the spark gap 28 is determined by the inductance of the coil 32 and the capacitance of the capacitors 25 and 31 and the capacitance of the electrode combination 33.

In Fig. 3, 40 denotes a source of high DC voltage, which source positive terminal is grounded so that a negative voltage can be taken from the source. This voltage is supplied via a coil 41 to a electrode combination 51, representing an electrostatic precipitator year, thereby determining the mean value of the voltage across it electrostatic precipitator. A coil 41 was used to insulate voltage source 40 from the current transmitting during the pulse generation. enter. 43 denotes a capacitor from which the energy of the pulse the ones are taken out and in which the energy is stored. In contrast to the pulse the generators according to Figs. 1 and 2 own the pulse generation according to Fig. 3 room independent of the DC supply 51 of the separator 51. In the circuit according to Fig. 3, a separate DC source 42 was used to charge the storage the capacitor 43 at the start of the generator and for compensation for it energy, which is consumed during each pulse partly in the corona discharge and partly as losses in components and conductors. The voltage source 42 positive terminals are grounded, so a negative voltage can be drawn from the voltage source in question. A coil 44 was used as well to limit the current (current increase) from the direct current source 42 to the capacitor satator 43 as for isolating the voltage source from the pulse generation occurring current transients. When a thyristor combination 45 was lit, oscillates the charge of the capacitor 43 via a pulse transformer 47 with a primary winding 48 and a secondary winding 49 to a capacitor so ooh avskngaron 51 and back ein capacitor uïvio oioakombi- nation 46, whose direction of conduction is opposite to that of the thyristor combination line direction. The period of oscillation is determined by that of the pulse transformer 47 short-circuit inductance and the capacitance of capacitors 43 and 50 and the capacitance of the separator 51. Capacitor 50 is included in the generator 1 and to avoid direct current through the secondary transformer 47 of the pulse transformer 47. winding 49 and must be adjusted so relative to the capacitance of the separator 51 that the pulse voltage amplitude is divided between the two capacitances according to an appropriate relationship.

In Fig. 4, 60 denotes a pulse generator of, for example, the type as described in connection with Fig. 2 or 3. As shown in FIG Fig. 4, the pulse generator 60 is connected between a direct current source 61 and vèååzez-1 1 7602263-1 8 the emission electrode 65 1 an electrostatic precipitator 62 and can either be self-feeding as shown in Fig. 2 or require one separate supply source as shown in Fig. 5. The DC source positive terminal is Grounded as well as the dust collector collector rod 64, so that a negative voltage is applied to the emission electrode.

In Fig. 5, 70 denotes a pulse generator of the type, for example as described in connection with Fig. 1. As shown in Figs the pulse generator 70 is connected between a direct current source 71 and the emission the electrode 75 in an electrostatic precipitator 72 and can either be self-feeding as shown in Fig. 1 or require a separate power supply. An auxiliary electrode 74 in the dust collector 72 is connected directly to the direct current source 71 and the potential difference between the auxiliary electrode 74 and the emission electrode 75 therefore comes to consist of the pulse voltage. Because the direct current source is negative terminal is grounded together with the collecting electrode 75 in the dust the disconnector, both the emission and auxiliary electrodes are charged positively voltage.

In Fig. 6, 80 denotes a pulse generator, for example, of that type as described in connection with Fig. 2 or 5. As shown in FIG In the figure, the pulse generator 80 is connected between a direct current source 81 and the emission electrode 85 in an electrostatic precipitator 82 and can either be self-feeding as shown in Fig. 2 or require a separate feed source as shown in Fig. 5. Dust removal the disconnector also has an auxiliary electrode 84, which is connected to a paired direct current source 86, so the potential difference between the auxiliary rod 84 and the emission electrode 85 will be equal to the pulse voltage superimposed on a DC voltage. Because both direct current sources positive terminals are grounded together with the dust collector 85, both the emission and auxiliary electrodes will be taken with negative voltage.

The embodiments described with reference to the drawing above are intended only to exemplify the invention and are in no way limiting the scope of the invention. _ _ By appropriate arrangements, the pulse generators described above can be also used to feed a plurality of dust separator sections, whereby one only needs to use a single pulse generator to feed an electrostatic precipitator consisting of several sections.

Claims (5)

7602263-1 9 Patent claims l. Circuit breaker for electrostatic precipitator, comprising a DC circuit (4,5) for generating a DC voltage supplied to the capacitor (16) formed by the electrode separator electrodes, a pulse generator with a storage capacitor (7) for generating pulses, and inductive means (13, 14) connected between the storage capacitor (7) and the capacitor (16) formed by the dust collector electrodes for transmitting to the dust collector electrodes pulses which are superimposed on the direct voltage, characterized by an LC oscillation circuit formed by the storage capacitor. (7), the inductive means (13, 14) and the capacitor (16) formed by the electrodes of the dust collector, and non-linear electrical components (10, 11) for controlling the LC oscillation circuit, which non-linear electrical components (10, ll) are arranged to transmit a substantial part of the energy which during each pulse is transmitted to and stored in the capacitor formed by the electrodes of the dust collector n (16), return to the storage capacitor (7) for re-storage in this. Circuit breaker according to claim 1, characterized in that the non-linear electrical components comprise a pulse initiating means (10) with a line direction and an electric valve (II) with the opposite line direction. 3. A circuit connection according to claim 2, characterized in that the self-inductance of the LC oscillating circuit consists of a secondary winding (14) of a pulse transformer (12). Circuit connection according to Claim 2, characterized in that the self-inductance of the LC oscillation circuit consists of a series circuit comprising two coils (30, 32), one of which (32) is connected in the supply line of the dust collector, while the other is shunted by a spark gap (28) in series with a voltage source. Circuit switching according to one of Claims 2 to 4, characterized in that the LC oscillation circuit is tuned to resonance at a frequency which has approximately the pulse as half-wave. PROMISED PUBLICATIONS: Germany 2 253 601 '