Visualization and analysis of a Re-entrained particle with an electrostatic precipitator using PIV method

Abstract

With the increasing demand for electric power and economic growth, the amount of gas emitted from power plants by power generation and diesel engines of ships and automobiles is increasing. In particular, exhaust gas contains black carbon, which is one of the pollutants that significantly influence global warming and must therefore be suppressed. It is considered that an electrostatic precipitator (ESP), which is an air purification device that uses plasma technology, can solve the problem. ESP is a mechanism that generates ion wind and electric charge by electric discharge, charges the passing particulate matter, and collects it on the ground (GND) electrode. During the dust collection process, particles charged with the discharge of ESP come into contact with the collecting electrode, and the particles lose the charge, thereby becoming neutral. With time, some of the collected particles detach from the GND electrode owing to the influence of electrostatic induction and the primary fluid. These particles are called re-entrained particles (RPs), and the phenomenon is called re-entrainment; this decreases the collecting efficiency of the ESP. The RP was successfully visualized and confirmed in this study using the particle image velocimetry (PIV) method with dry ESP, and it is beneficial for the problems that ESP may encounter during the development and application process. As a result, the movement velocity of particles and the re-entrained number of particles per second were increased by increasing the applied voltage of the plate electrode. Furthermore, the discharge current of the back needle electrode, the distance between the high voltage electrode, and the number of collected particles on the GND electrode significantly affected the re-entrained number of particles per second.