10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Numerical Analysis of Electric Field Distribution in Wire-to-plate Type Electrostatic Precipitator
KOHEI ITO, Akinori Zukeran, Yoshihiro Kawada, Tomohiro Taoka, Kenji Shibata, Kanagawa Institute of Technology
Abstract Number: 148 Working Group: Combustion
Abstract Electrostatic precipitator (ESP) has been used for exhaust gas purification in order to suppress air pollution. Numerical analysis is effective for development of ESP. In this study, the electric field distribution under corona discharge in a wire-to-plate type ESP was analyzed using general purpose finite element method analysis software COMSOL Multiphysics® Ver.4.3b, and the result was fitted to the experimental result.
A two-dimensional model of wire-to-plate type ESP was calculated. The gap between the wire electrode (Tungsten, φ=0.26 mm) and the grounded plate electrode (Stainless, L=40 mm) was 15 mm. The space was the air, a potential of -10 kV was applied to the surface of the wire electrode, and the surface of the grounded plate electrode was 0 V. The ion density of 4.53×1015 m-3 was given to the surface of the wire electrode, and the other boundaries were 0 m-3. The ion density on the surface of the wire electrode was adjusted, whereby the calculated peak value of the current density distribution on the surface of the grounded electrode was equal to the experimental value. The number of the mesh division was approximately 400 thousand. The fundamental equations are Poisson equation (1) and negative ion continuous equations (2):
−∇·εrε0∇V=ρ (1) ∂Nn⁄∂t+∇·(−Dn∇Nn−µnENn)=0 (2) where εr is the relative permittivity, ε0 is the dielectric constant of vacuum, V is the potential, ρ is the space charge density, Dn is the diffusion constant of negative ion, µn is the mobility of negative ion and E is electric field. The space charge density ρ is obtained from the following equation.
ρ=−eNn (3) where e is elementary charge and Nn is the negative ion density.
The electric field intensity near the surface of the wire electrode was the highest of approximately 1×107 V/m, and the intensity has minimum value at the location between the wire electrode and the grounded plate electrode. The electric field intensity at the center on the surface of the grounded plate electrode was high due to space charges, and that decreased with increasing the distance from the center. The discharge current was calculated from the electric field intensity near the surface and the ion density, which were calculated by finite element method as following equation:
I=ρµnER (4) where I is the discharge current, R is the circumference of the wire electrode. The calculated discharge current was 0.901 mA/m, which was almost equal to the experimental value of 0.875 mA/m. This result indicates that the electric field distribution calculated using COMSOL Multiphysics is validity.
References Y.Kawada, H.Shimizu, A.Zukeran “Considerations of suitable grounded electrode length of pre-charge in two-stage-type electrostatic precipitator” in Proc. Comf. Rec. 2017 IEEE Ind. Appl. Soc. Annu. Metting, Oct.1-5, 2017, pp.1-7, DOI:10.1109/IAS.2017.8101686
Keywords Simulation, Corona Discharge, Electric Field, Electrostatic Precipitator.