The Particle Dynamics In Typical Configurations Of ESPs

Electrostatic precipitators (ESPs) are ones of the most common particulate control devices used to cleaning fly ash and particles from coal fired boilers, cement factories and many other industrial processes. In order to satisfy the requirement specified in the modified standards about air pollution control, the enhancement and optimization of ESPs is becoming an important challenge in this field. Considering the practical particle size distribution, the effects of the fluid flow, particle properties, electric field and the main geometric parameters affecting the performances of ESPs are evaluated by integrated theoretical analysis and numerical simulations in the present paper.The numerical results show that both overall mass and aerosol number collection efficiencies are higher for particles in the front and back part of the particle size distribution spectrum at the fore part of ESPs. The particles in the middle part of the spectrum are collected later. Particle charging kinetics and turbulent particle dispersion influence the collection of fine particles, especially. The turbulent fluctuation can disperse particles away from the collecting plates and results the distribution of particles becoming uniform in the cross section. The effect of turbulent dispersion coefficient is more important for the fine particle transportation in the channel, because the migration velocity of the particles is small, and the deposition rate of fine particles can be enhanced with increasing the turbulent dispersion coefficient.The results also indicate that the size distribution remains in lognormal form along ESPs channels without significant deviation. Both geometric mean diameter and geometric standard deviation drop quickly as particles enter into ESPs, then the rate of decrease slows down, and particle collection efficiencies also slow down along the ESPs. As a result, increasing the length or width of the collecting plates could have no benefit for improving the collection efficiency.The numerical results of electrical characteristics in a zigzag channel prove that it has a larger voltage gradient near the corona wires and higher average electric field strength near the collecting walls comparing with wire-plate configurations, and the regime of applied voltage could be increased to improve the conditions of particle collection. Normal width of the channel and small size of corona wire have more advantages for ESPs when back ionization can be negligible, and the effect of high ionic mobility is not obvious for improving the electric conditions in ESPs.