Multiphase Flow Mechanism Of Electrostatic Precipitator

Electrostatic precipitator(ESP) is an important kind of environment protection equipment, with the deepening of environmental protection, dust collection efficiency of the existing electrostatic precipitators needs to be improved, and the air distribution is one of the important factors of dust collection efficiency. The dust movement in dusty gas is a complex three-dimensional gas- solid flow. In this thesis, an improved three-dimensional multiphase flow model of ESP is build based on the gas-solid flow theory and computational fluid dynamics, the field effect of corona electric field and the characteristics of the dusty gas flow are analyzed in detail. The main contents and conclusions are outlined as follows:(1) Summarized and analyzed the charge gas-solid two-phase flow theory, analyzed the force of charged particles, applied the Renault transport theory, established a Reynolds transport equations for charged gas-solid two-phase flow. Derived the continuity equations, energy equations and momentum equations of the continuous phase and discrete phase in charged gas- solid two-phase flow, established the basic equations for Charged Gas Solid Two-phase Flow.(2) Coupled solving the Poisson equation of electric potential and continuity equation of current, analyzed the Volt-ampere characteristic, electric field intensity and current density distribution characteristics of different electrode structures, compared the numerical simulation results of Matlab in this thesis with the experimental results in references,the relative error is less than 5%, the method is validity, these conclusions can be get from the simulation.â‘ The distribution of electric field intensity and current density get the maximum value on the surface of corona wires. Once leaving the corona area, the values reduced rapidly, the value of zero can be obtained at the middle of the adjacent two corona wires,and the distribution is almost uniform in other areas of the discharge space.â‘¡The halo voltage rises with the decrease of electrodes interval. The volt-ampere characteristic curves move to the upper left when the electrodes interval increases and move to the upper right when the plates interval increases.â‘¢The root mean square and maximum relative errors obtain the minimum value and the current density get an uniform distribution on the conditions of electrodes interval at 18 cm, plats interval at 25 cm and voltage at 60 kV.(3) Establishing a three-dimensional multi-phase flow model of electrostatic precipitators. Changing the airflow distribution boards and the corona electric field, the transient information of flow field under different working conditions can be acquired.Analyzed the changing of flow field characteristics, get the following conclusions.â‘ Two vortexes with reverse curl generated around the corona lines, which have remarkable affection to the dust particle movements. The dimensions of the vortex decreases with the number increase of the corona lines.â‘¡According to different forces, the electric field can be divided into two parts, the charged part which affected mainly by ionic wind and the promotion part which affected mainly by electric field force. In charged area, dust particles affected by the vortex significantly. Within the vortex, ion concentration is higher where close to the corona line, the dust particles charged easier. Vortex intensity is larger, the charged particles will enter the promotion area with uniform air distribution. In the promotion area,charged particles move to the dust collecting plate and be captured under the electric field force.