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The effect of an external DC electric field on bipolar charged aerosol agglomeration
ARTICLE IN PRESS
Journal of Electrostatics 65 (2007) 82–86 www.elsevier.com/locate/elstat
The effect of an external DC electric field on bipolar charged aerosol agglomeration Baihe Tan, Lianze Wang, Xiangrong Zhang Department of Engineering Mechanics, Tsinghua University, Beijing, 100084, China Received 22 November 2005; accepted 6 July 2006 Available online 2 August 2006
Abstract A direct-current (DC) electric field was exerted in a bench-scale electrostatic precipitator (ESP) to induce the agglomeration of bipolar charged aerosol particles. The test aerosol particles were generated from water with an atomizer and their average diameter was 7.71 mm. A phase doppler anemometer (PDA) was used to measure the size distribution and the number concentration of the particles. Systematic experiments were conducted to investigate the agglomeration efficiency of the system. The percentage decrease in number of sub-micron sized particles was found to be about 10.7%. r 2006 Elsevier B.V. All rights reserved. Keywords: Agglomeration; Aerosol; Bipolar charge; Electrostatic precipitator; Corona
1. Introduction An electrostatic precipitator (ESP) is one of the most commonly used particle collectors from stack emission for preventing air pollution. In the ESP, particles are charged by corona discharge and then collected by a strong electric field perpendicular to the main gas flow. As we know, the total mass collection efficiency of a well-designed ESP can be above 99%. However, the penetration of sub-micron particles may still be as high as 15% [1] due to their low charging efficiency of corona chargers. So now more and more attention has been put on the removal of these small particles. Bipolar agglomeration in a direct-current (DC) electric field (DC-agglomeration) is such a method to increase the collection efficiency of small particles. The principle of DCagglomeration is presented in Fig. 1. Particles are first charged by the bipolar corona discharges. Next they enter the agglomeration chamber with a DC electric field. The direction of the DC field intensity is determined by the relative position of the two discharge electrodes. In such an electric field the particles with opposite charges can be Corresponding author.
E-mail address: [email protected] (B. Tan). 0304-3886/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.elstat.2006.07.002
forced to move towards each other and agglomerate more efficiently. Then the larger particles are easily removed by a conventional ESP. Recently, Wang et al. [2] have developed an analytical solution for the coagulation coefficient of bipolarly charged particles with an external DC electric field. The result showed that an external electric field played an important part in the agglomeration process. Several authors have already studied electrical agglomeration through experiments. Kobashi [3] studied the particle agglomeration induced by alternating electric field in a parallel plate agglomerator. The agglomeration caused a concentration reduction of approximately 30% in the particle size range of 0.3–2 mm. Watanabe and Suda [4,5] used a so-called quadrupole agglomerator. It is based on an electrical quadrupole field to focus charged particles in the middle of the quadrupole [6]. Their results suggested that the agglomeration caused a 20% concentration reduction for particles under 1 mm. Hautanen et al. [7] used both parallel plate and quadrupole agglomerators. They found the sub-micron particle concentration had a reduction of 4–8%. Laitinen et al. [8] observed the effect of bipolar charging on the agglomerate efficiency of a parallel plate agglomerator. The decrease in number concentration of sub-micron sized particles was between 17% and 19%.
ARTICLE IN PRESS B. Tan et al. / Journal of Electrostatics 65 (2007) 82–86
83
FLOW
Corona Charger
Agglomerator
Electrostatic Precipitator
Fig. 1. The principle of flue gas particle removal with an external DC electric field. Particles are first charged by the bipolar corona discharges. Next they enter the agglomeration chamber with a DC electric field, where the particles with opposite charges can be forced to move towards each other and agglomerate more efficiently. Then the larger particles are easily removed by a conventional ESP.
The purpose of our work is to find out the effect of an external DC electric field on the efficiency of a parallel plate agglomerator. Particle size distributions were measured with a phase doppler anemometer (PDA).
Aerosol Inlet
Atomizer
2. Experimental system
A
2.1. Principle A
The efficiency of an agglomeration system is affected by several processes, such as the losses of particles to the walls, the particles charging and coagulation. In order to separate the contribution of the DC electric field from the total efficiency, the transmission efficiency (Z) is used to calculate the reduction efficiency (r), which often acts as the performance standard of an agglomerator. An assumption is made that the different processes do not affect each other and the total transmission efficiency with the DC electric field is Zon ¼ Zwall Zbi ZDC ,
(1)
where Zwall represents the transmission efficiency from the losses of particles to the walls, Zbi from the effect of bipolar corona charging and ZDC from the agglomeration induced by the DC electric field. When the DC voltage is off, the total transmission efficiency becomes Zoff ¼ Zwall Zbi .
Computer
Agglomerator PDA DC Source
Pump Aerosol Outlet Fig. 2. Agglomerator test system. The aerosol generator, high voltage source and pump are shown on the left. The measurement system is shown on the right.
(2)
The total reduction efficiencies of the system with the DC electric field (ron) and without the DC electric field (roff) are ron ¼ 1 Zwall Zbi ZDC ,
(3)
roff ¼ 1 Zwall Zbi .
(4)
Combining Eqs. (3) and (4) the reduction efficiency of the bipolar charged particles caused by the DC electric field (rDC) can be estimated as
rDC ¼ 1 ZDC ¼ 1
Corona Charger
Zon 1 ron ¼1 . Zoff 1 roff
(5)
2.2. Experimental setup Fig. 2 shows the diagram of the experimental system. It was mainly consisted of a particle generator, a corona charger, an agglomerator and a PDA. Test particles were generated by an atomizer and charged by bipolar corona discharges. Then the particles entered the DC electric field of an agglomeration chamber, where their number concentrations and size distributions were measured with a PDA. The test particles were generated from water with a commercial atomizer (TSI 6 jet Atomizer Model 9306). Their initial number concentration and mass concentration distributions are shown in Fig. 3. The count median diameter was 7.71 mm and the mass median diameter was 10.82 mm.
ARTICLE IN PRESS B. Tan et al. / Journal of Electrostatics 65 (2007) 82–86
Numberconcentration Δn/Δlogdp (cm-3)
1000
1000 Number Mass
900
900
800
800
700
700
600
600
500
500
400
400
300
300
200
200
100
100
0
100
101
Mass concentration Δm/Δlogdp (g/m3)
84
0 102
Diameter (μm)
Current (mA)
Fig. 3. Particle number and mass concentration distributions of aerosols generated by the TSI 6 jet atomizer. Number distribution and mass distribution are measured with the PDA system.
0.15
0.1
0.05
-15
-10
-5
0
0
5
10
15
Voltage (kV) -0.05
length, and width of the agglomerator were 100, 200, and 100 mm, respectively. The residence time in the agglomerator was 0.2 s. The number concentrations and size distributions of the test particles were measured with a PDA. The sampling points were set in a cross-section just after the agglomeration chamber. The distance between every two sampling points was 10 mm. On every sampling point 3000 groups of sampling data were obtained. Each measurement was carried out twice and the average results were used to calculate the reduction efficiency. Two different combinations of positive and negative discharge voltages were considered (+4, 10 and +5, 13 kV).
-0.1
3. Results -0.15
-0.2 Fig. 4. Current–voltage characteristics of the corona chargers.
The aerosol particles were charged in two separate corona charger chambers. Each chamber consisted a discharge electrode (diameter 1.8 mm) between two metal plates. The height, length, and width of the corona charger were 100, 100, and 100 mm, respectively. The residence time in the charger was 0.1 s. The I–V characteristics of the charger are shown in the Fig. 4. The bipolar charged particles were induced to agglomerate in a parallel-plate agglomerator. The DC voltage was exerted on the two parallel plates. The electric field intensity in the agglomerator was 1.6 kV cm1. The height,
The electrical agglomeration of the bipolarly charged aerosol particles in a DC electric field was observed. The particles of sub-micron size had higher reduction rates than the particles of several-micron size. And the higher discharge voltage could increase the effect of the DC electric field on the reduction of small particles. Fig. 5 shows the reduction in the number concentrations of the smaller particles (under 4 mm). When the DC voltage is off, the reduction percentage of the sub-micron sized particles is 3.5% at the lower discharge voltages (+4, 10 kV). And at the higher discharge voltages (+5, 13 kV) the reduction is 14.8%. When the DC voltage is on, the agglomerator causes an 8.8% reduction in the particles of sub-micron size at lower discharge voltages and a 24.0% reduction at higher discharge voltages. Fig. 6 shows the contribution of the DC electric field to the reductions of the smaller particles (under 4 mm). At lower discharge voltages the maximum reduction
ARTICLE IN PRESS B. Tan et al. / Journal of Electrostatics 65 (2007) 82–86
Reduction in number concentration (%)
35 Discharge Voltages (+4kV,-10kV) (+4kV,-10kV) (+5kV,-13kV) (+5kV,-13kV)
30
25
DC off on off on
20
10
5
0.5
1
1.5
2
2.5 3 3.5 4
Diameter (μm) Fig. 5. Reduction in the number concentration of bipolar charged particles.
Reduction in number concentration (%)
16 Discharge Voltages (+4kV,-10kV) (+5kV,-13kV)
14 12 10 8 6 4 2 0
efficiency caused by the DC electric is 5.5%. And at the higher discharge voltages the maximum reduction efficiency is 10.7%. Table 1 shows the count median diameter of aerosol particles under different electric condition. At higher discharge voltages (+5, 13 kV), the count median diameter increases about 3.7% due to the effect of the DC electric field. 4. Discussion
15
0
85
0.5
1
1.5
2
2.5 3 3.5 4
Diameter (μm) Fig. 6. Reduction in the number concentration of bipolar charged particles caused by the DC electric field.
Table 1 The count median diameter of aerosol particles under different electric condition Mean diameter (mm)
Discharge voltages
DC voltage
7.71 7.84 7.98 8.12 8.42
(+0 kV, (+4 kV, (+4 kV, (+5 kV, (+5 kV,
Off Off On Off On
0 kV) 10 kV) 10 kV) 13 kV) 13 kV)
The external DC electric field improved the electrical agglomeration of the small particles. This result agreed with the study of Wang et al. [2] qualitatively. The quantitative comparison of the experiments and the theoretical solution needs more accurate and more detailed data. In this study the test particles were generated from water with an atomizer. This is a simple way to produce the steady aerosol flow and the water has the advantage of being non-toxic and always keeping spherical droplets with nearly unit density. Furthermore, the water droplet has a larger charge capacity (er ¼ 80.7) and can holds more charge due to the field charging under the same corona discharge condition, which is very useful for the submicron particles. The study of Schwinning [9] on the wettype ESP has already showed that the use of water droplets as agglomeration nuclei can be possible. The size distribution and the number concentration of the particles were measured with a PDA. The PDA works dependent on laser. This method has no effect on the fluid field and the agglomeration of particles. And the size of the sampling point makes the measurement of the details in the fluid field become possible. The assumption that the agglomeration of the particles, charging effect and the wall losses do not affect each other is only an approximation. In fact these and some other different processes taking place in the agglomerator may be dependent upon each other. However, the main goal of this study was to evaluate the effect of the DC electric field. The changes of the other agglomeration processes can all be attributed to the DC electric field. 5. Conclusion This research shows that electrical agglomeration could be one of the possible methods to decrease the number concentration of small particles. With the effect of DC electric field, the percentage of sub-micron sized particles decreased 10.7% and the count median diameter of particles increased 3.7%. Acknowledgements This project was supported by the National Natural Science Foundation of China (no. 10472057) and the Tsinghua Basic Science Foundation (no. Jc2001033).
ARTICLE IN PRESS 86
B. Tan et al. / Journal of Electrostatics 65 (2007) 82–86
References [1] S. Ylatalo, E. Kauppinen, J. Hautanen, J. Joutsensaari, P. Ahonen, T. Lind, J. Jokiniemi, M. Kilpelainen, On the determination of electrostatic precipitator efficiency by differential mobility analyzer, European Aerosol Conference, Oxford, J. Aerosol Sci. 23 (1) (1992) 795–798. [2] L.Z. Wang, X.R. Zhang, K.Q. Zhu, An analytical expression for the coagulation coefficient of bipolarly charged particles by an external electric field with the effect of Coulomb force, J. Aerosol Sci. 36 (2005) 1050–1055. [3] M. Kobashi, Particle agglomeration induced by alternating electric fields, Ph.D. Thesis, Stanford University, 1979. [4] T. Watanabe, An electrostatic agglomeration apparatus with multipole electrodes, Criepi Report ET 880 1988.
[5] T. Watanabe, T. Suda, Submicron-size carbonic particle agglomeration by an electrostatic agglomeration apparatus, in: S. Masuda, K. Takahashi (Eds.), Proceedings of the Third International Aerosol Conference, vol. 2, Kyoto, Japan, 1990, pp. 749–752. [6] S. Masuda, K. Fujibayashi, On electrodynamics of charged dust particles under an AC quadrupole electric field—theoretical treatment, J. Inst. Electrical Eng. Japan 90 (1970) 861–869. [7] J. Hautanen, M. Kilpelainen, E. Kauppinen, J. Jokiniemi K. Lehtinen, Electrical agglomeration of aerosol particles in alternating electric field, Aerosol Sci. Technol. 22 (1995) 181–189. [8] A. Laitinen, J. Hautanen, J. Keskinen, E. Kauppinen, J. Jokiniemi, K. Lehtinen, Bipolar charged aerosol agglomeration with alternating electric field in laminar gas flow, J. Electrostat. 38 (1996) 303–315. [9] G.M. Schwinning, Proceedings of the Seventh International Conference on Electrostatic Precipitation, Korea, 1998, pp. 522–533.
Journal of Electrostatics 65 (2007) 82–86 www.elsevier.com/locate/elstat
The effect of an external DC electric field on bipolar charged aerosol agglomeration Baihe Tan, Lianze Wang, Xiangrong Zhang Department of Engineering Mechanics, Tsinghua University, Beijing, 100084, China Received 22 November 2005; accepted 6 July 2006 Available online 2 August 2006
Abstract A direct-current (DC) electric field was exerted in a bench-scale electrostatic precipitator (ESP) to induce the agglomeration of bipolar charged aerosol particles. The test aerosol particles were generated from water with an atomizer and their average diameter was 7.71 mm. A phase doppler anemometer (PDA) was used to measure the size distribution and the number concentration of the particles. Systematic experiments were conducted to investigate the agglomeration efficiency of the system. The percentage decrease in number of sub-micron sized particles was found to be about 10.7%. r 2006 Elsevier B.V. All rights reserved. Keywords: Agglomeration; Aerosol; Bipolar charge; Electrostatic precipitator; Corona
1. Introduction An electrostatic precipitator (ESP) is one of the most commonly used particle collectors from stack emission for preventing air pollution. In the ESP, particles are charged by corona discharge and then collected by a strong electric field perpendicular to the main gas flow. As we know, the total mass collection efficiency of a well-designed ESP can be above 99%. However, the penetration of sub-micron particles may still be as high as 15% [1] due to their low charging efficiency of corona chargers. So now more and more attention has been put on the removal of these small particles. Bipolar agglomeration in a direct-current (DC) electric field (DC-agglomeration) is such a method to increase the collection efficiency of small particles. The principle of DCagglomeration is presented in Fig. 1. Particles are first charged by the bipolar corona discharges. Next they enter the agglomeration chamber with a DC electric field. The direction of the DC field intensity is determined by the relative position of the two discharge electrodes. In such an electric field the particles with opposite charges can be Corresponding author.
E-mail address: [email protected] (B. Tan). 0304-3886/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.elstat.2006.07.002
forced to move towards each other and agglomerate more efficiently. Then the larger particles are easily removed by a conventional ESP. Recently, Wang et al. [2] have developed an analytical solution for the coagulation coefficient of bipolarly charged particles with an external DC electric field. The result showed that an external electric field played an important part in the agglomeration process. Several authors have already studied electrical agglomeration through experiments. Kobashi [3] studied the particle agglomeration induced by alternating electric field in a parallel plate agglomerator. The agglomeration caused a concentration reduction of approximately 30% in the particle size range of 0.3–2 mm. Watanabe and Suda [4,5] used a so-called quadrupole agglomerator. It is based on an electrical quadrupole field to focus charged particles in the middle of the quadrupole [6]. Their results suggested that the agglomeration caused a 20% concentration reduction for particles under 1 mm. Hautanen et al. [7] used both parallel plate and quadrupole agglomerators. They found the sub-micron particle concentration had a reduction of 4–8%. Laitinen et al. [8] observed the effect of bipolar charging on the agglomerate efficiency of a parallel plate agglomerator. The decrease in number concentration of sub-micron sized particles was between 17% and 19%.
ARTICLE IN PRESS B. Tan et al. / Journal of Electrostatics 65 (2007) 82–86
83
FLOW
Corona Charger
Agglomerator
Electrostatic Precipitator
Fig. 1. The principle of flue gas particle removal with an external DC electric field. Particles are first charged by the bipolar corona discharges. Next they enter the agglomeration chamber with a DC electric field, where the particles with opposite charges can be forced to move towards each other and agglomerate more efficiently. Then the larger particles are easily removed by a conventional ESP.
The purpose of our work is to find out the effect of an external DC electric field on the efficiency of a parallel plate agglomerator. Particle size distributions were measured with a phase doppler anemometer (PDA).
Aerosol Inlet
Atomizer
2. Experimental system
A
2.1. Principle A
The efficiency of an agglomeration system is affected by several processes, such as the losses of particles to the walls, the particles charging and coagulation. In order to separate the contribution of the DC electric field from the total efficiency, the transmission efficiency (Z) is used to calculate the reduction efficiency (r), which often acts as the performance standard of an agglomerator. An assumption is made that the different processes do not affect each other and the total transmission efficiency with the DC electric field is Zon ¼ Zwall Zbi ZDC ,
(1)
where Zwall represents the transmission efficiency from the losses of particles to the walls, Zbi from the effect of bipolar corona charging and ZDC from the agglomeration induced by the DC electric field. When the DC voltage is off, the total transmission efficiency becomes Zoff ¼ Zwall Zbi .
Computer
Agglomerator PDA DC Source
Pump Aerosol Outlet Fig. 2. Agglomerator test system. The aerosol generator, high voltage source and pump are shown on the left. The measurement system is shown on the right.
(2)
The total reduction efficiencies of the system with the DC electric field (ron) and without the DC electric field (roff) are ron ¼ 1 Zwall Zbi ZDC ,
(3)
roff ¼ 1 Zwall Zbi .
(4)
Combining Eqs. (3) and (4) the reduction efficiency of the bipolar charged particles caused by the DC electric field (rDC) can be estimated as
rDC ¼ 1 ZDC ¼ 1
Corona Charger
Zon 1 ron ¼1 . Zoff 1 roff
(5)
2.2. Experimental setup Fig. 2 shows the diagram of the experimental system. It was mainly consisted of a particle generator, a corona charger, an agglomerator and a PDA. Test particles were generated by an atomizer and charged by bipolar corona discharges. Then the particles entered the DC electric field of an agglomeration chamber, where their number concentrations and size distributions were measured with a PDA. The test particles were generated from water with a commercial atomizer (TSI 6 jet Atomizer Model 9306). Their initial number concentration and mass concentration distributions are shown in Fig. 3. The count median diameter was 7.71 mm and the mass median diameter was 10.82 mm.
ARTICLE IN PRESS B. Tan et al. / Journal of Electrostatics 65 (2007) 82–86
Numberconcentration Δn/Δlogdp (cm-3)
1000
1000 Number Mass
900
900
800
800
700
700
600
600
500
500
400
400
300
300
200
200
100
100
0
100
101
Mass concentration Δm/Δlogdp (g/m3)
84
0 102
Diameter (μm)
Current (mA)
Fig. 3. Particle number and mass concentration distributions of aerosols generated by the TSI 6 jet atomizer. Number distribution and mass distribution are measured with the PDA system.
0.15
0.1
0.05
-15
-10
-5
0
0
5
10
15
Voltage (kV) -0.05
length, and width of the agglomerator were 100, 200, and 100 mm, respectively. The residence time in the agglomerator was 0.2 s. The number concentrations and size distributions of the test particles were measured with a PDA. The sampling points were set in a cross-section just after the agglomeration chamber. The distance between every two sampling points was 10 mm. On every sampling point 3000 groups of sampling data were obtained. Each measurement was carried out twice and the average results were used to calculate the reduction efficiency. Two different combinations of positive and negative discharge voltages were considered (+4, 10 and +5, 13 kV).
-0.1
3. Results -0.15
-0.2 Fig. 4. Current–voltage characteristics of the corona chargers.
The aerosol particles were charged in two separate corona charger chambers. Each chamber consisted a discharge electrode (diameter 1.8 mm) between two metal plates. The height, length, and width of the corona charger were 100, 100, and 100 mm, respectively. The residence time in the charger was 0.1 s. The I–V characteristics of the charger are shown in the Fig. 4. The bipolar charged particles were induced to agglomerate in a parallel-plate agglomerator. The DC voltage was exerted on the two parallel plates. The electric field intensity in the agglomerator was 1.6 kV cm1. The height,
The electrical agglomeration of the bipolarly charged aerosol particles in a DC electric field was observed. The particles of sub-micron size had higher reduction rates than the particles of several-micron size. And the higher discharge voltage could increase the effect of the DC electric field on the reduction of small particles. Fig. 5 shows the reduction in the number concentrations of the smaller particles (under 4 mm). When the DC voltage is off, the reduction percentage of the sub-micron sized particles is 3.5% at the lower discharge voltages (+4, 10 kV). And at the higher discharge voltages (+5, 13 kV) the reduction is 14.8%. When the DC voltage is on, the agglomerator causes an 8.8% reduction in the particles of sub-micron size at lower discharge voltages and a 24.0% reduction at higher discharge voltages. Fig. 6 shows the contribution of the DC electric field to the reductions of the smaller particles (under 4 mm). At lower discharge voltages the maximum reduction
ARTICLE IN PRESS B. Tan et al. / Journal of Electrostatics 65 (2007) 82–86
Reduction in number concentration (%)
35 Discharge Voltages (+4kV,-10kV) (+4kV,-10kV) (+5kV,-13kV) (+5kV,-13kV)
30
25
DC off on off on
20
10
5
0.5
1
1.5
2
2.5 3 3.5 4
Diameter (μm) Fig. 5. Reduction in the number concentration of bipolar charged particles.
Reduction in number concentration (%)
16 Discharge Voltages (+4kV,-10kV) (+5kV,-13kV)
14 12 10 8 6 4 2 0
efficiency caused by the DC electric is 5.5%. And at the higher discharge voltages the maximum reduction efficiency is 10.7%. Table 1 shows the count median diameter of aerosol particles under different electric condition. At higher discharge voltages (+5, 13 kV), the count median diameter increases about 3.7% due to the effect of the DC electric field. 4. Discussion
15
0
85
0.5
1
1.5
2
2.5 3 3.5 4
Diameter (μm) Fig. 6. Reduction in the number concentration of bipolar charged particles caused by the DC electric field.
Table 1 The count median diameter of aerosol particles under different electric condition Mean diameter (mm)
Discharge voltages
DC voltage
7.71 7.84 7.98 8.12 8.42
(+0 kV, (+4 kV, (+4 kV, (+5 kV, (+5 kV,
Off Off On Off On
0 kV) 10 kV) 10 kV) 13 kV) 13 kV)
The external DC electric field improved the electrical agglomeration of the small particles. This result agreed with the study of Wang et al. [2] qualitatively. The quantitative comparison of the experiments and the theoretical solution needs more accurate and more detailed data. In this study the test particles were generated from water with an atomizer. This is a simple way to produce the steady aerosol flow and the water has the advantage of being non-toxic and always keeping spherical droplets with nearly unit density. Furthermore, the water droplet has a larger charge capacity (er ¼ 80.7) and can holds more charge due to the field charging under the same corona discharge condition, which is very useful for the submicron particles. The study of Schwinning [9] on the wettype ESP has already showed that the use of water droplets as agglomeration nuclei can be possible. The size distribution and the number concentration of the particles were measured with a PDA. The PDA works dependent on laser. This method has no effect on the fluid field and the agglomeration of particles. And the size of the sampling point makes the measurement of the details in the fluid field become possible. The assumption that the agglomeration of the particles, charging effect and the wall losses do not affect each other is only an approximation. In fact these and some other different processes taking place in the agglomerator may be dependent upon each other. However, the main goal of this study was to evaluate the effect of the DC electric field. The changes of the other agglomeration processes can all be attributed to the DC electric field. 5. Conclusion This research shows that electrical agglomeration could be one of the possible methods to decrease the number concentration of small particles. With the effect of DC electric field, the percentage of sub-micron sized particles decreased 10.7% and the count median diameter of particles increased 3.7%. Acknowledgements This project was supported by the National Natural Science Foundation of China (no. 10472057) and the Tsinghua Basic Science Foundation (no. Jc2001033).
ARTICLE IN PRESS 86
B. Tan et al. / Journal of Electrostatics 65 (2007) 82–86
References [1] S. Ylatalo, E. Kauppinen, J. Hautanen, J. Joutsensaari, P. Ahonen, T. Lind, J. Jokiniemi, M. Kilpelainen, On the determination of electrostatic precipitator efficiency by differential mobility analyzer, European Aerosol Conference, Oxford, J. Aerosol Sci. 23 (1) (1992) 795–798. [2] L.Z. Wang, X.R. Zhang, K.Q. Zhu, An analytical expression for the coagulation coefficient of bipolarly charged particles by an external electric field with the effect of Coulomb force, J. Aerosol Sci. 36 (2005) 1050–1055. [3] M. Kobashi, Particle agglomeration induced by alternating electric fields, Ph.D. Thesis, Stanford University, 1979. [4] T. Watanabe, An electrostatic agglomeration apparatus with multipole electrodes, Criepi Report ET 880 1988.
[5] T. Watanabe, T. Suda, Submicron-size carbonic particle agglomeration by an electrostatic agglomeration apparatus, in: S. Masuda, K. Takahashi (Eds.), Proceedings of the Third International Aerosol Conference, vol. 2, Kyoto, Japan, 1990, pp. 749–752. [6] S. Masuda, K. Fujibayashi, On electrodynamics of charged dust particles under an AC quadrupole electric field—theoretical treatment, J. Inst. Electrical Eng. Japan 90 (1970) 861–869. [7] J. Hautanen, M. Kilpelainen, E. Kauppinen, J. Jokiniemi K. Lehtinen, Electrical agglomeration of aerosol particles in alternating electric field, Aerosol Sci. Technol. 22 (1995) 181–189. [8] A. Laitinen, J. Hautanen, J. Keskinen, E. Kauppinen, J. Jokiniemi, K. Lehtinen, Bipolar charged aerosol agglomeration with alternating electric field in laminar gas flow, J. Electrostat. 38 (1996) 303–315. [9] G.M. Schwinning, Proceedings of the Seventh International Conference on Electrostatic Precipitation, Korea, 1998, pp. 522–533.