Enhanced size-dependent efficiency of removal of ultrafine particles: New solution of two-stage electrostatic precipitator with thermophoresis

Abstract

Two-stage electrostatic precipitators (ESPs) are effective at removing ultrafine particles (UFPs) from gases; however, they fall short in capturing particles with diameters of less than 100 nm. In this study, an effective solution for removal of particles smaller than 300 nm was proposed. Our self-designed system combines a two-stage ESP with thermophoresis. We employed a combination of experimental and numerical simulation methods to examine the effects of temperature and thermophoresis on particle removal efficiency influenced by electrostatic forces. In our experiments, particle removal efficiency was positively correlated with gas temperature up to 75 °C, beyond which removal efficiency was no longer correlated with temperature. The findings also indicate that the introduction of thermophoresis improves particle removal efficiency, with the maximum increase approaching 8 %. However, this effect only occurs for particles smaller than 50 nm. The increase in the length of the thermophoresis segment and the decrease in inlet gas flow rate both enhance particle removal efficiency due to thermophoresis. Numerical simulations confirmed the experimental finding that nanoscale particles are more easily captured at higher temperatures. The simulations also revealed that the primary reasons for the enhanced removal efficiency are twofold: greater electric field strength and higher particle charge resulting from a higher temperature.