Experimental study of a string-based counterflow wet electrostatic precipitator for collection of fine and ultrafine particles

Figures & data

Figure 1. Schematic of the experimental setup for characterizing the performance of the string-based collectors

Figure 2. Schematics of (a) the rectangular and (b) the cylindrical configuration on the left and (c) the particle pre-charger and the front view of the particle pre-charger used in this study on the right

Table 1. Parameters and test conditions used to study the string-based WESP performance

Parameters	Conditions	Notes
Applied voltage [kV]	0– 10	Bias voltage for string collectors, ΔVc
	7– 7.6	Bias voltage for particle pre-charger, ΔVp
Air velocity [m/s]	2.3– 4.5	In WESP
	0.7– 1.5	In particle pre-charger
Water flow rate per string [g/s]	0.01– 0.135	${\dot{m}}_{\mathrm{L}\mathrm{p}\mathrm{s}}$
Air inlet temperature [^oC]	30– 40	–

Figure 3. Schematics of the numerical simulation domains for (a) the rectangular WESP and (b) the cylindrical WESP

Figure 4. (a) Voltage-current curve and (b) average particle size distribution at the inlet of the particle pre-charger

Figure 5. Effect of the water flow rate per string on the fractional collection efficiency of the cylindrical WESP

Figure 6. Collection efficiencies as a function of the liquid-to-gas flow rate ratio for different WESP devices. We compare our device with previously reported WESP devices; electrostatic droplet spray (Pilat 1975), cylindrical WESP for DPM (Saiyasitpanich et al. 2006), flat-plate WESP (Kim et al. 2011), electrospray tower scrubber (Kim et al. 2014), cross flow string-based WESP (Ali et al. 2016), wire-to-plate WESP (Yang et al. 2017), and self-flushing WESP (Su et al. 2018)

Table 2. Comparison of the experimental conditions and performance metrics of the present design with those of previous WESP designs

Collection type	Particle diameter [μm]	Water flow rate [kg/s]	Air flow rate [kg/s]	Air velocity [m/s]	Collection efficiency [%]	Air flow rate/collector volume [(m^3/s)/m^3]	Liquid to gas flow ratio [(kg/s)/(kg/s)]
Cylindrical WESP (Saiyasitpanich et al. 2006)	0.02–0.8	0.05	0.056	2.3	90–99	2.5	0.89
Single-stage parallel plate WESP (Lin et al. 2010)	0.02–0.6	0.0005	0.0008	0.076	97–99.7	0.538	6.25
Flat-plate WESP (Kim et al. 2011)	0.02–0.5	0.003	0.0016	1	70–95	2.4	1.88
PVC cylindrical WESP (Kim et al. 2012)	0.05–2	0.0083	0.0035	1	99–99.7	2.44	2.37
Cross flow string based WESP (Ali et al. 2016)	1.61–8.84	0.04	3.24	3	60–80	1.25	0.012
Membrane based WESP (Wang et al. 2016)	0.01–10	10^−4	0.002	0.4	65–93	2.67	0.05
Spray-type WESP (Du et al. 2016)	0.3–2.5	0.0042	0.181	2.35	35–69	0.783	0.023
Wire-to-plate WESP (Yang et al. 2017)	0.02–9	0.03	0.03	1.16	85–99	1.1	1
Pulsed corona WESP (Kuroki et al. 2017)	0.02–0.4	0.0004	7 x 10^−5	0.21	80–99	0.816	6.246
Self-flushing WESP (Su et al. 2018)	0.07–2.5	0.007	0.031	3	60–72	1	0.22
Charged water drop WESP (Teng, Fan, and Li. 2020)	0.02–3.8	0.001	0.013	0.19	93–99	0.78	0.077
String-based Cylindrical WESP (Present study)	0.01–2.5	10^−5	0.0015	3	80–99	4.36	0.0066

Figure 7. Experimentally measured and predicted (Cochet’s model) fractional collection efficiencies for the cylindrical and the rectangular WESP at different collector bias voltages. The experimental and predicted values are presented as the symbols and the lines, respectively

Figure 8. Effect of the gas velocities in the collector on the experimentally measured and predicted (Cochet’s model) fractional collection efficiencies for the cylindrical and the rectangular WESP. The experimental results and predicted values are presented as the symbols and the lines, respectively

Figure 9. (a) Number of charges on particles obtained using our numerical simulation and using Cochet’s model as a function of the particle size. The numerical simulation and the Cochet’s model results are presented as the symbols and the dashed line, respectively, and (b) Numerically simulated particle trajectories in the cylindrical collector (domain size = 12.5 mm × 600 mm, inlet airflow velocity = 3 m/s, number of particles at inlet = 100, particle diameter, d_p = .1 μm, average number of charges on the particle, Q_p = 11.5, applied voltage = 10 kV)

Figure 10. (a) Schematics of the numerical simulation domain for the cylindrical WESP with bead profiles along the string. (b) Effect of the water flow rate per string on the bead spacing (obtained from experiments) and the collection efficiency (obtained from experiments and numerical simulation for particles with 0.1 μm diameter). The experimental and numerical simulation results are presented as the solid and hollow symbols, respectively

Pilat, M. J. 1975. Collection of aerosol particles by electrostatic droplet spray scrubbers. J. Air Pollut. Control Assoc. 25 (2):176–78. doi:10.1080/00022470.1975.10470070.

 Web of Science ®Google Scholar

Saiyasitpanich, P., T. C. Keener, M. Lu, S.-J. Khang, and D. E. Evans. 2006. Collection of ultrafine Diesel Particulate Matter (DPM) in cylindrical single-stage wet electrostatic precipitators. Environ. Sci. Technol. 40 (24):7890–95. doi:10.1021/es060887k.

 PubMed Web of Science ®Google Scholar

Kim, H.-J., B. Han, Y.-J. Kim, K.-D. Hwang, W.-S. Oh, S.-Y. Yoo, and T. Oda. 2011. Fine particle removal performance of a two-stage wet electrostatic precipitator using a nonmetallic pre-charger. J. Air Waste Manage. Assoc. (1995) 61 (12):1334–43. doi:10.1080/10473289.2011.603994.

 PubMed Web of Science ®Google Scholar

Kim, H.-G., H.-J. Kim, M.-H. Lee, and J.-H. Kim. 2014. Experimental study on the enhancement of particle removal efficiency in spray tower scrubber using electrospray. Asian J. Atmos. Environ. 8 (2):89–95. doi:10.5572/ajae.2014.8.2.089.

 Google Scholar

Ali, M., H. Pasic, K. Alam, S. A. N. Tiji, N. Mannella, T. Silva, and T. Liu. 2016. Experimental study of cross-flow wet electrostatic precipitator. J. Air Waste Manage. Assoc. (1995) 66 (12):1237–44. doi:10.1080/10962247.2016.1209258.

 Web of Science ®Google Scholar

Yang, Z., C. Zheng, Q. Chang, Y. Wan, Y. Wang, X. Gao, and K. Cen. 2017. Fine particle migration and collection in a wet electrostatic precipitator. J. Air Waste Manage. Assoc. 67 (4):498–506. doi:10.1080/10962247.2016.1260074.

 Web of Science ®Google Scholar

Su, L., Q. Du, Y. Wang, H. Dong, J. Gao, M. Wang, and P. Dong. 2018. Purification characteristics of fine particulate matter treated by a self-flushing wet electrostatic precipitator equipped with a flexible electrode. J. Air Waste Manage. Assoc. 68 (7):725–36. doi:10.1080/10962247.2018.1460635.

 PubMed Web of Science ®Google Scholar

Lin, G.-Y., C.-J. Tsai, S.-C. Chen, T.-M. Chen, and S.-N. Li. 2010. “An Efficient Single-Stage Wet Electrostatic Precipitator for Fine and Nanosized Particle Control.” Aerosol Science and Technology 44 (1): 38–45. doi:10.1080/02786820903338298.

 Google Scholar

Kim, J.-H., H.-J. Yoo, Y.-S. Hwang, and H.-G. Kim. 2012. “Removal of Particulate Matter in a Tubular Wet Electrostatic Precipitator Using a Water Collection Electrode.” The Scientific World Journal. doi:10.1100/2012/532354.

 Google Scholar

Wang, X., J. Chang, C. Xu, J. Zhang, P. Wang, and C. Ma. 2016. “Collection and Charging Characteristics of Particles in an Electrostatic Precipitator with a Wet Membrane Collecting Electrode.” Journal of Electrostatics 83 (October): 28–34. doi:10.1016/j.elstat.2016.07.007.

 Google Scholar

Du, Q., L. Su, H. Dong, J. Gao, Z. Zhao, D. Lv, and S. Wu. 2016. “The Experimental Study of a Water-Saving Wet Electrostatic Precipitator for Removing Fine Particles.” Journal of Electrostatics 81 (June): 42–47. doi:10.1016/j.elstat.2016.03.004.

 Google Scholar

Kuroki, T., S. Nishii, T. Kuwahara, and M. Okubo. 2017. “Nanoparticle Removal and Exhaust Gas Cleaning Using Gas-Liquid Interfacial Nonthermal Plasma.” Journal of Electrostatics 87 (June): 86–92. doi:10.1016/j.elstat.2017.04.007.

 Google Scholar

Teng, C., X. Fan, and J. Li. 2020. Effect of charged water drop atomization on particle removal performance in plate type wet electrostatic precipitator. J. Electrost. 104 (March):103426. doi:10.1016/j.elstat.2020.103426.

 Google Scholar