Numerical simulation of electrostatic precipitator considering the dust particle space charge

The coupled electric field, gas-particle flow and particle charging processes are simulated using Eulerian-Lagrangian method in Computational Fluid Dynamics (CFD), for a wire-plate electrostatic precipitator with four-wire electrodes configuration. The effects of particle charging on the electric field distribution, V–I characteristics and particle collection efficiency are investigated, as the entry particle loading/concentration varies from 0 up to 50 g/Nm³ for a particle size of 0.25–5.0 μm under fixed gas velocity of 1.0 m/s. The results show that the electric field can be distorted significantly by the secondary electric field generated by the space charges on the floating particles, which mostly reduces particle collection efficiency, except at a very low loading. A maximum collection efficiency exists at a particle loading that depends on particle size. Under fixed voltage applied, the corona current decreases as particle loading/concentration increases. As particle loading increases to some point, the corona current from the downstream wires can be extinguished completely (corona quenching). At high particle loadings, corona ion charges may fail to reach the plate due to the absorption of passing particles. The electric streamlines in a small zone around the last wire reverse direction locally. A charged particle, once falls accidently within the zone, could be trapped and be attracted to the same wire. Thus this wire is subject to heavier dust deposition. The significance of ion transfer and space charge of fine dust particles is clarified systematically.