Numerical Simulation Of Field Characteristics And Particle Motion In An Electrostatic Precipitator

Because of stricter environmental laws and regulations, the emission standards of coal-fired boiler will be more and more important. At present, electrostatic precipitator(ESP) is one the most widely used gas-sold separator, and it has many advantages such as high collection efficiency, low pressure drop and low cost for maintenance.In this thesis, three-dimensional numerical models for single-wire and multiple-wire ESP are built up to study how the electric field affects the inner characteristics of ESP. The governing equation for gas phase is the incompressible Reynolds-averaged Navier-Stocks equation with standard k-? model for the consideration of turbulence. The electric field is governed by Poisson’s equation and the electric current conservation equation. The charging equation is then added to the computational model, and the discrete phase model based on Lagrangian approach is used to present particle trajectory and position. The main research contents and results are as follows:(1) The influence of electrohydrodynamic(EHD) flow to the inner characteristics is analyzed, while the gas flow characteristics of traditional inertial separator and electrostatic precipitator are compared. Two couples of vortices are generated in front and at the back of electrodes because of the existence of EHD flow. With the increasing of inlet velocity, the two couple of vortex cores moves to opposite directions. The EHD flow influences the turbulent intensity by both increasing the turbulent dissipation and production turbulent kinetic energy.(2) The gas field and particle trajectory are simulated. It is found that the inlet velocity, applied voltage and the diameter of particle influence the particle collection efficiency. The change of particle charging is also analyzed here.(3) Numerical model of wet electrostatic precipitator(WESP) is built based on the ESP model. The Euler multi-phase model was used to gas liquid two-phase flow, and the DPM is adapted to simulation particle motion. The charging model is fulfilled by experimental verification, and the interrelation of circulating water and collection efficiency is studied. It is found that with the increasing of circulating water, the collection efficiency increases. But at low circulating water, the collection efficiency decrease first and then increase with the increasing of particle diameter.