Effects of electrode materials and dimensions of an electrostatic spray scrubber on water droplet charging for dust removal

Authors: LI, X - The Ohio State University; KNIGHT, R - The Ohio State University; HOCTER, J - The Ohio State University; ZHANG, B - The Ohio State University; ZHAO, L - The Ohio State University; Zhu, Heping

Submitted to: Journal of Air and Waste Management Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2022
Publication Date: 12/29/2022
Citation: Li, X., Knight, R.M., Hocter, J.S., Zhang, B., Zhao, L., Zhu, H. 2022. Effects of electrode materials and dimensions of an electrostatic spray scrubber on water droplet charging for dust removal. Journal of Air and Waste Management Association. 72(12):1442-1453. https://doi.org/10.1080/10962247.2022.2120564.
DOI: https://doi.org/10.1080/10962247.2022.2120564

Interpretive Summary: Particulate matter is a major air pollutant in poultry facilities. An experimental scrubber with electrostatically-charged spray droplets was previously designed to remove submicron particles. However, the effect of key design factors on the droplet charging performance is still not fully understood. In this research, charge to mass ratios were quantified for droplets charged by various electrode materials along with other key variables such as applied voltage, nozzle height, and electrode dimension. The electrode materials were stainless steel, copper, and high-purity graphite. Test results demonstrated that among the three electrode materials tested, the stainless steel electrode was the best to charge droplets, followed by copper. The optimal inner diameter of electrode, nozzle height and charging voltage were then determined for the stainless steel electrodes to achieved the highest charge-to-mass ratio of droplets. As a result, a linear regression model was developed with optimal key parameters to design the best-performance electrode for electrostatic spray scrubbers to maximize the particulate matter removal efficiency.

Technical Abstract: Droplet charging is an effective method to enhance dust removal efficiency using an electrostatic spray scrubber (ESS). However, effects of the materials and dimensions of different electrodes on droplet charging efficiency have not been studied systematically. In this study, ring-shaped electrodes were selected to test effects of three types of electrode materials (copper, stainless steel, and graphite) with various dimensions on droplet charging efficiency. A Faraday pail charge measurement device was used to measure the droplet charge generated by the electrodes. A reduced factorial design with four factors was used in this study to investigate the charging efficiency affected by the factors. The four factors tested were electrode material, electrode diameter, nozzle height, and applied voltage. A 304L stainless steel electrode was found to achieve higher droplet charge-to-mass ratio (CMR) values than identically shaped electrodes made from either copper or graphite. The optimal stainless steel electrode inner diameter was 100 mm. The 304L stainless-steel electrode with this optimal diameter and a height of 45 mm achieved the highest mean CMR of 0.435 ± 0.002 mC kg-1 at an applied voltage of -11 kV with the bottom of the nozzle tip positioned 15 mm below the top of the electrode.