Discharge current of water electrospray with electrical conductivity under high-voltage and high-flow-rate conditions

Abstract

Recently, several attempts have been made to implement electrospray for electrostatic precipitators (EPs) to reduce water consumption and prevent dust from being rescattered from dry EPs. In particular, the electrospray droplet size in EPs should be sufficiently large to collect dust in the exhaust gas flow, which requires a considerably larger electrospray flow rate than that required for typical applications. In addition, in the case of water electrospray, a high supply voltage is required because of its high surface tension. In this study, the characteristics of water-based electrospray were investigated under a high voltage and high flow rate. Three types of fluids—distilled water, tap water, and saline solution—were used to test for different conductivities under an electric charge with a negative current. The corona discharge and spray trajectories were visualized to determine the spray stability. To verify the influence of the spray current, the waveform of the electrospray was also analyzed under both dry- and wet-spray conditions. From this comparison, a portion of the spray current was estimated out of the total discharge current, which is the sum of the corona discharge and the spray current. The flow rate and voltage of the test were limited at 20 mL/min and −50 kV, respectively. In contrast with previous low flow rate studies, our results showed that the discharge current increased rapidly under flow rates above 6 mL/min, leading to arc discharge. Thus, it is important to adjust the flow and conductivity to guarantee stable and efficient water-based electrosprays.