Analysis of the Current-Voltage Characteristic during the Corona Discharge in Wires-To-Planes Electrostatic Precipitator under Variable Air Humidity

Abstract

In the present work an experimental investigation has been carried out on the influence of the air humidity or the water vapor injected in the incoming air flow on DC corona discharge parameters in a wire-to-planes electrostatic precipitators. To characterize the behavior of the corona discharge for both positive and negative corona, the current-voltage characteristics are subjected to an analysis using the model of Cooperman which derives the quadratic Townsend law and the general formula proposed by Meng et al. The experimental results show that the discharge current is strongly influenced by the level of air humidity. Moreover, the corona current becomes very small with the applied voltage beyond Hr = 90%, because the particle size is increased by condensation. It was demonstrated that the Coopeman model is reliable to determine the mobility of the charge carriers in this system.

High-Voltage Electrodes in Moist Air Accumulate Charge That is Retained after Removing the Electric Field

“…As the applied voltage increased from 1.5 to 5.5 kV for a 1 cm gap space, an increase in the onset current was measured. This relationship, discussed in previous studies, − is due to the increase in the electric field at the surface of the anode which leads to an increase in the total positive space charge, more ionizing collisions, and a greater number of charged ions contributing to the onset current …”

“…As the relative humidity in the air gap between electrodes is increased, three key trends are observed: (1) the corona onset voltage decreased, 39,42,45−49 (2) the steady corona current increased for low DC voltages (<7 kV for d = 1 cm) 39,42,45,46 and decreased for high DC voltages, [40][41][42][43][44][45]50 and (3) the positive ions' mobility decreased. [42][43][44][45][46]49 In our work, the corona onset current (charge rate in Figure 5a) at 5.5 kV, 70%RH was comparable to the onset current at 3.5 kV, 90% RH indicating an increase in relative humidity decreased the voltage required to initiate the observed current, corroborating the first key trend described above. For each voltage tested, the corona onset current increased with increasing relative humidity as observed by previously mentioned studies.…”

Evaluating Performance Indices of Electrostatic Precipitators

“…Another method of assessing the ESP performance is comparing the effect of changing geometric parameters on the resulting corona current-voltage (I-V) characteristics of an ESP [7][8][9][10][11][12][13]. This method involves measuring the value of the corona discharge at each voltage value, where higher corona current values imply more deposition.…”