- Email: [email protected]
Matching between generator and reactor for producing pulsed corona discharge
Journal of
ELECTROSTATIC Journal
of Electrostatics
44 (1998) 41-45
Matching between generator and reactor for producing pulsed corona discharge Zhu Yimin, Wang Rongyi Institute of Electrostatics,
Dalian University
of Technology,
Dalian II 6023, P. R. China
Abstract
The matching between generator and reactor is a crucial aspect in optimizing the pulsed corona discharge. Several methods can be adopted to reach the matching, reducing inductance in discharge circuit, regulating relative humidity of flue gas, and paralleling a suitable condenser with the reactor. The detail of the matching discussed in this paper is based on experimental results and the theories of streamer formation as well. The matching not only makes the injection of pulsed energy effective, but also promotes the formation of pulsed streamer in the reactor. Keywords:
1.
Pulsed corona discharge; Pulsed generator; Pulsed corona reactor; Matching
Introduction:
Pulsed corona discharge, as a novel technology, is being researched for the control of gaseous pollutants ,and so on. It is considered as a prospective method in removing SO, and NO,. In this process, the pulsed corona characteristics should be necessarily optimized. Up to now, many projects have been launched in researching the factors that influence the pulsed corona characteristics[l-31. However, due to slowness of systematic researches, the optimum characteristics have not been touched. The 0304-3886/98/$19.00 0 Elsevier PII SO304-3886(98)00020-S
Science
B.V:
All rights reserved
42
Zhu Yimin, Wang Rongyi/Journal
OfElectrostatics
44 (1998) 41-4.5
matching, which serves all pulsed energy from the generator to the reactor, is vital to realize the optimum pulsed corona characteristics. However, the detailed discussion on the matching realization and the roles it plays in forming the pulsed streamer has not been presented.
2. Experiments
and results
L
D
RSGS
ti 3 8
X
-7 c,---Reactor __ -
Fig. 1. Discharge circuit for producing pulsed corona
Fig. 1 shows a discharge circuit for producing pulsed corona discharge. After the pulse forming condenser C, discharged, the formed pulsed energy is injected into the reactor via rotary spark gap switches and transmission line, and pulsed corona discharge is produced in the reactor. Meanwhile, a high-voltage DC power provides the reactor with a DC bias voltage. The pulsed voltage and current are measured by Iwatsu model HV-P60 voltage and Tektronix model A6303 Am 503s current probes respectively, and the pulse waveforms are recorded by a Hewlett-Packard 54503A digital memory oscilloscope. Experiments are conducted on wire cylinder reactor (DlOOmm) with one emitting wire (1 m), and the C, value of 200-500 pF. Several methods to reach the matching through the experiments mainly follow. The principle condition is that the C, value should be greater than 3 C, (C, is the value of nominal condenser of the reactor). On a small scale, the matching is easily reached on a minimized inductance basis (fig. 2). However, the minimal inductance is not sufficient for industrial application in future. With a DC bias voltage, the same results are obtained like those in the reference [4] (fig. 3). By paralleling a suitable condenser with the reactor or regulating relative humidity of flue gas, the satisfactory results are fulfilled as shown in fig.
Zhu Yimin, Wang Rongyi/Journal of Electrostatics 44 (1998) 41-45
43
4 and 5 respectively.
200nsldiv Fig. 2. Pulse waveforms while is low in inductance: peak value of pulsed voltage 47KV; rise time of voltage 40ns; peak value of pulsed current 64.6A; rise time of current 50ns; pulse duration Sons.
200nsldiv Fig. 3. Pulse waveforms with DC bias voltage: peak value of pulsed voltage 46.7KV; rise time of voltage 40ns; peak value of pulsed current 66.6A; rise time of current 50ns; pulse duration 1OOns; DC voltage 17KV.
1OOns/div Fig. 4. Pulse waveforms
the reactor is paralleled with a suitable condenser:
peak value of
44
Zhu Yimin. Wang Rongyi/Journal of Electrostatics 44 (1998) 41-45
pulsed voltage 50KV; rise time of voltage 40ns; peak value of pulsed current 70A; rise time of current 50ns; pulse duration 70ns.
500nsIdiv Fig. 4. Pulse waveforms under high relative humidity: peak value of pulsed voltage 49.3KV; rise time of voltage 79ns; peak value of pulsed current 65.5A; rise time of current 89ns; pulse duration 300ns.
3. Discussion With regard to the experimental data, in each case the pulsed voltage waveforms are characterized with high valued tail in small oscillation. Thus, the matching reduces the energy consumption in the pulse transmission. Meanwhile, as illustrated in fig. 2-5, steep rise fronts in the pulsed current are observed, and almost approach to those in the pulsed voltage. It indicates that the matching has promoted the formation of the pulsed streamer. In the process of the streamer formation, there are different phases of the streamer evolution such as an avalanche, expansion-contraction space-charge phase (SCP), filamentary streamer phase (FSP) and so on [5]. In order to reach the FSP, it is necessary to promote the transition between these phases. The DC corona discharge can provide copious space charges, so a DC bias voltage promotes the transition of the pulse streamer evolution, namely, effectively promotes the formation of the pulse streamer. However, except for fig. 3, no DC bias voltage can be found in the other experiments before the formation of the pulsed streamer. In fig. 2 due to the low inductance in the discharge circuit, the C, can immediately provides the reactor with pulsed energy, and the pulsed voltage tail hold small oscillation. A suitable
Zhu Yimin. Wang Rongyi/Journal of Electrostatics 44 (1998) 41-45
45
condenser CL paralleled with the reactor may result in (CL+ Cl) tending to C,. This servers to save time in forming the pulsed streamer and to choke oscillation on the pulse tail as well (fig. 4). The high relative humidity conduces to absorbing and attaching electrons and ions more [6]. Therefore, this premise makes it much effective to inject pulsed energy into the reactor. The space field keeps being relatively high to the order of microseconds (fig. 5).
4. Conclusions In this work the following conclusions have been drawn: The matching has been reached by minimizing the inductance in the discharge circuit, using a DC bias voltage [4], regulating the relative humidity of flue gas, and paralleling a suitable condenser with the reactor. The matching not only saves energy in the pulse transmission process, but also promotes the formation of the pulse streamer.
Acknowledgments
This research is financially supported by The National Natural Science Foundation of China for the key project “SO, and NO, removal from flue gas by pulsed corona discharge”. References
111 S. Masuda, Pulse corona induced plasma chemical process: a horizon of new plasma chemical technologies, Pure & Appl. Chem., 60 (1988) 727-73 1. PI Massimo Rea, Evaluation of pulse voltage generators, IEEE Tran. Ind. Appl., 3 l(3) (1995) 507-512. [31 Tomio Fujii et al., Pulse corona characteristics, IEEE Tran. Ind. Appl., 29( 1) (1993) 98102. [41 Yan Keping et al., Matching between voltage pulse generator and reactor for producing low temperature plasma by positive pulse corona, Proc. of 2nd Int. Conf. Applied Electrostatics, Beijing, (1993) 122-127. 151 P. A. Vitello et al., Multi-dimensional modeling of the dynamic morphology of streamer corona, Non-Thermal Plasma Techniques for Pollution Control, B. M. Penetrante and S. E. Schultheis(Ed.), G34(A) (1993) 249-271. [61 Mazen abdel Salam, Positive wire-to-plane corona as influenced by atmospheric humidity, IEEE Tran. Ind. Appl., IA-21(l) (1985) 35-40.
ELECTROSTATIC Journal
of Electrostatics
44 (1998) 41-45
Matching between generator and reactor for producing pulsed corona discharge Zhu Yimin, Wang Rongyi Institute of Electrostatics,
Dalian University
of Technology,
Dalian II 6023, P. R. China
Abstract
The matching between generator and reactor is a crucial aspect in optimizing the pulsed corona discharge. Several methods can be adopted to reach the matching, reducing inductance in discharge circuit, regulating relative humidity of flue gas, and paralleling a suitable condenser with the reactor. The detail of the matching discussed in this paper is based on experimental results and the theories of streamer formation as well. The matching not only makes the injection of pulsed energy effective, but also promotes the formation of pulsed streamer in the reactor. Keywords:
1.
Pulsed corona discharge; Pulsed generator; Pulsed corona reactor; Matching
Introduction:
Pulsed corona discharge, as a novel technology, is being researched for the control of gaseous pollutants ,and so on. It is considered as a prospective method in removing SO, and NO,. In this process, the pulsed corona characteristics should be necessarily optimized. Up to now, many projects have been launched in researching the factors that influence the pulsed corona characteristics[l-31. However, due to slowness of systematic researches, the optimum characteristics have not been touched. The 0304-3886/98/$19.00 0 Elsevier PII SO304-3886(98)00020-S
Science
B.V:
All rights reserved
42
Zhu Yimin, Wang Rongyi/Journal
OfElectrostatics
44 (1998) 41-4.5
matching, which serves all pulsed energy from the generator to the reactor, is vital to realize the optimum pulsed corona characteristics. However, the detailed discussion on the matching realization and the roles it plays in forming the pulsed streamer has not been presented.
2. Experiments
and results
L
D
RSGS
ti 3 8
X
-7 c,---Reactor __ -
Fig. 1. Discharge circuit for producing pulsed corona
Fig. 1 shows a discharge circuit for producing pulsed corona discharge. After the pulse forming condenser C, discharged, the formed pulsed energy is injected into the reactor via rotary spark gap switches and transmission line, and pulsed corona discharge is produced in the reactor. Meanwhile, a high-voltage DC power provides the reactor with a DC bias voltage. The pulsed voltage and current are measured by Iwatsu model HV-P60 voltage and Tektronix model A6303 Am 503s current probes respectively, and the pulse waveforms are recorded by a Hewlett-Packard 54503A digital memory oscilloscope. Experiments are conducted on wire cylinder reactor (DlOOmm) with one emitting wire (1 m), and the C, value of 200-500 pF. Several methods to reach the matching through the experiments mainly follow. The principle condition is that the C, value should be greater than 3 C, (C, is the value of nominal condenser of the reactor). On a small scale, the matching is easily reached on a minimized inductance basis (fig. 2). However, the minimal inductance is not sufficient for industrial application in future. With a DC bias voltage, the same results are obtained like those in the reference [4] (fig. 3). By paralleling a suitable condenser with the reactor or regulating relative humidity of flue gas, the satisfactory results are fulfilled as shown in fig.
Zhu Yimin, Wang Rongyi/Journal of Electrostatics 44 (1998) 41-45
43
4 and 5 respectively.
200nsldiv Fig. 2. Pulse waveforms while is low in inductance: peak value of pulsed voltage 47KV; rise time of voltage 40ns; peak value of pulsed current 64.6A; rise time of current 50ns; pulse duration Sons.
200nsldiv Fig. 3. Pulse waveforms with DC bias voltage: peak value of pulsed voltage 46.7KV; rise time of voltage 40ns; peak value of pulsed current 66.6A; rise time of current 50ns; pulse duration 1OOns; DC voltage 17KV.
1OOns/div Fig. 4. Pulse waveforms
the reactor is paralleled with a suitable condenser:
peak value of
44
Zhu Yimin. Wang Rongyi/Journal of Electrostatics 44 (1998) 41-45
pulsed voltage 50KV; rise time of voltage 40ns; peak value of pulsed current 70A; rise time of current 50ns; pulse duration 70ns.
500nsIdiv Fig. 4. Pulse waveforms under high relative humidity: peak value of pulsed voltage 49.3KV; rise time of voltage 79ns; peak value of pulsed current 65.5A; rise time of current 89ns; pulse duration 300ns.
3. Discussion With regard to the experimental data, in each case the pulsed voltage waveforms are characterized with high valued tail in small oscillation. Thus, the matching reduces the energy consumption in the pulse transmission. Meanwhile, as illustrated in fig. 2-5, steep rise fronts in the pulsed current are observed, and almost approach to those in the pulsed voltage. It indicates that the matching has promoted the formation of the pulsed streamer. In the process of the streamer formation, there are different phases of the streamer evolution such as an avalanche, expansion-contraction space-charge phase (SCP), filamentary streamer phase (FSP) and so on [5]. In order to reach the FSP, it is necessary to promote the transition between these phases. The DC corona discharge can provide copious space charges, so a DC bias voltage promotes the transition of the pulse streamer evolution, namely, effectively promotes the formation of the pulse streamer. However, except for fig. 3, no DC bias voltage can be found in the other experiments before the formation of the pulsed streamer. In fig. 2 due to the low inductance in the discharge circuit, the C, can immediately provides the reactor with pulsed energy, and the pulsed voltage tail hold small oscillation. A suitable
Zhu Yimin. Wang Rongyi/Journal of Electrostatics 44 (1998) 41-45
45
condenser CL paralleled with the reactor may result in (CL+ Cl) tending to C,. This servers to save time in forming the pulsed streamer and to choke oscillation on the pulse tail as well (fig. 4). The high relative humidity conduces to absorbing and attaching electrons and ions more [6]. Therefore, this premise makes it much effective to inject pulsed energy into the reactor. The space field keeps being relatively high to the order of microseconds (fig. 5).
4. Conclusions In this work the following conclusions have been drawn: The matching has been reached by minimizing the inductance in the discharge circuit, using a DC bias voltage [4], regulating the relative humidity of flue gas, and paralleling a suitable condenser with the reactor. The matching not only saves energy in the pulse transmission process, but also promotes the formation of the pulse streamer.
Acknowledgments
This research is financially supported by The National Natural Science Foundation of China for the key project “SO, and NO, removal from flue gas by pulsed corona discharge”. References
111 S. Masuda, Pulse corona induced plasma chemical process: a horizon of new plasma chemical technologies, Pure & Appl. Chem., 60 (1988) 727-73 1. PI Massimo Rea, Evaluation of pulse voltage generators, IEEE Tran. Ind. Appl., 3 l(3) (1995) 507-512. [31 Tomio Fujii et al., Pulse corona characteristics, IEEE Tran. Ind. Appl., 29( 1) (1993) 98102. [41 Yan Keping et al., Matching between voltage pulse generator and reactor for producing low temperature plasma by positive pulse corona, Proc. of 2nd Int. Conf. Applied Electrostatics, Beijing, (1993) 122-127. 151 P. A. Vitello et al., Multi-dimensional modeling of the dynamic morphology of streamer corona, Non-Thermal Plasma Techniques for Pollution Control, B. M. Penetrante and S. E. Schultheis(Ed.), G34(A) (1993) 249-271. [61 Mazen abdel Salam, Positive wire-to-plane corona as influenced by atmospheric humidity, IEEE Tran. Ind. Appl., IA-21(l) (1985) 35-40.