新型靜電集塵器之研究

Abstract

Many previous experimental and numerical modeling studies have been conducted to improve the performance of the electrostatic precipitators (EPs) which are used widely in industries to control particulate matter emissions. In this study, two new types of EPs, wire-on-plate electrostatic precipitator (WOP-EP) and multipoint-to-plane electrostatic precipitator (MPP-EP) were investigated for the control fine and nanosized particles with the advantages of low pressure drop and high particle collection efficiency. In conventional EPs, the discharge wires are placed in between two grounded collection plates. In the present new WOP-EP, discharge wires are placed directly on the surface of a dielectric plate to replace one of the collection plates. The new WOP-EP was designed and tested at the aerosol flow rate of 15 and 30 L/min for reducing particle contamination on discharge wires, prolonging the operation time and facilitating the cleaning of the collection plate. In addition, two configurations of the MPP-EPs were also tested at the aerosol flow rate of 30 and 40 L/min to remove nanoparticles and sub-micron particles. Furthermore, in order to develop better understanding of the experimental results, the numerical model for predicting the voltage-current (V-I) characteristic of EPs was developed. Eulerian and Lagrangian numerical methods were adopted as well to predict the collection efficiency of particle with diameter dp ≤ 100nm and dp> 100nm, respectively. Test results show that when the WOP-EP was initially clean at the applied voltage of +18kV, the total collection efficiency ranged from 90.9-99.7 % and 98.8-99.9% for particle electrical mobility diameter of 16.5 to 1870 nm at the aerosol flow rate of 30 and 15 L/min (residence time of 0.36 s and 0.72s), respectively. Numerical results for the particle collection efficiency show good agreement with experimental results for particles with the diameter of 70-400nm, and over-predict the collection efficiency for particles below 70nm and above 400nm. The disagreement is maybe due to the partial charging effect, the influence of the dielectric plates, and very low concentration of large particles as well as the ion quenching phenomenon, respectively. Whereas in MPP-EPs, the collection efficiency ranged from 96.2–99.4% and 95.5–97.6% at applied voltage of +16kV and the flow rate of 30 L/min for MPP-EP2 and MPP-EP1, respectively. Simulated results for particle collection efficiency are in reasonable agreement with the experimental data for the particle diameter of 19.5-100nm, and underestimation of the collection efficiency occurs for particles above 100nm which needs to be improved in future studies. Present WOP-EP and MPP-EPs could be used as efficient particle removal devices and the present model could facilitate the design and scale-up of these EPs to control fine and nanosized particles.

Many previous experimental and numerical modeling studies have been conducted to improve the performance of the electrostatic precipitators (EPs) which are used widely in industries to control particulate matter emissions. In this study, two new types of EPs, wire-on-plate electrostatic precipitator (WOP-EP) and multipoint-to-plane electrostatic precipitator (MPP-EP) were investigated for the control fine and nanosized particles with the advantages of low pressure drop and high particle collection efficiency. In conventional EPs, the discharge wires are placed in between two grounded collection plates. In the present new WOP-EP, discharge wires are placed directly on the surface of a dielectric plate to replace one of the collection plates. The new WOP-EP was designed and tested at the aerosol flow rate of 15 and 30 L/min for reducing particle contamination on discharge wires, prolonging the operation time and facilitating the cleaning of the collection plate. In addition, two configurations of the MPP-EPs were also tested at the aerosol flow rate of 30 and 40 L/min to remove nanoparticles and sub-micron particles. Furthermore, in order to develop better understanding of the experimental results, the numerical model for predicting the voltage-current (V-I) characteristic of EPs was developed. Eulerian and Lagrangian numerical methods were adopted as well to predict the collection efficiency of particle with diameter dp ≤ 100nm and dp> 100nm, respectively. Test results show that when the WOP-EP was initially clean at the applied voltage of +18kV, the total collection efficiency ranged from 90.9-99.7 % and 98.8-99.9% for particle electrical mobility diameter of 16.5 to 1870 nm at the aerosol flow rate of 30 and 15 L/min (residence time of 0.36 s and 0.72s), respectively. Numerical results for the particle collection efficiency show good agreement with experimental results for particles with the diameter of 70-400nm, and over-predict the collection efficiency for particles below 70nm and above 400nm. The disagreement is maybe due to the partial charging effect, the influence of the dielectric plates, and very low concentration of large particles as well as the ion quenching phenomenon, respectively. Whereas in MPP-EPs, the collection efficiency ranged from 96.2–99.4% and 95.5–97.6% at applied voltage of +16kV and the flow rate of 30 L/min for MPP-EP2 and MPP-EP1, respectively. Simulated results for particle collection efficiency are in reasonable agreement with the experimental data for the particle diameter of 19.5-100nm, and underestimation of the collection efficiency occurs for particles above 100nm which needs to be improved in future studies. Present WOP-EP and MPP-EPs could be used as efficient particle removal devices and the present model could facilitate the design and scale-up of these EPs to control fine and nanosized particles.