Experimental study of electrostatic precipitator performance and comparison with existing theoretical prediction models

Abstract

A laboratory-scale single-stage electrostatic precipitator (ESP) was designed, built and operated in a wind tunnel. As a first step, a series of experiments were conducted to seek the operating conditions for increasing the particle collection efficiency by varying basic operating parameters including the wire-to-plate spacing, the wire radius, the air velocity, the turbulence intensity and the applied voltage. As the diameter of the discharging wires and the wire-to-plate spacing are set smaller, the higher collection efficiency has been obtained. In the single-stage multiwire ESP, there exists an optimum wire-to-wire spacing which provides maximum particle collection efficiency. As the air velocity increases, the particle collection efficiency decreases. The turbulent flow is found to play an important role in the relatively low electric field region. In the high electric field region, however, particles can be deposited on the collection plates readily regardless of the turbulence intensity. The experimental results were compared with existing theories and Zhibin and Guoquan (Aerosol Sci. Technol. 20 (1994) 169–176) was identified to be the best model for predicting the ESP performance. As the second step, the influence of particle contamination at the discharging electrode and at the collection plates were experimentally measured. The methods were sought for keeping the high collection efficiency of ESP over elapsed time by varying the magnitude of rapping acceleration, the time interval between raps, the types of rapping system (hammer/vibrator) and the particle re-entrainment. The rapping efficiency and the particle re-entrainment were increased with increasing magnitude of rapping acceleration and time interval between raps. However, when the thickness of deposited fly ash layer is sufficiently high, the concentration of re-entrained particles starts decreasing abruptly due to the agglomeration force which can interact among deposited particles. The combined rapping system is found more effective for removing deposited particles than the hammer rapping system only.