An experimental study on the effects of temperature and pressure on negative corona discharge in high-temperature ESPs

High-temperature ESPs are proposed to improve energy efficiency and avoid damage to downstream equipment in integrated gasification combined cycle and pressurized fluidized-bed combustion. In this study, the effects of temperature and pressure on negative corona discharge characteristics were compared. Gas temperature varied from 373 K to 1073 K, and pressure varied from 30 kPa to 100 kPa to achieve the same gas density. The additional corona current ΔIt induced by high temperature was calculated, and the additional ion current ΔIi and electron current ΔIe were studied. A wire-type electrode, a spiral electrode, a ribbon electrode, and four gas compositions (N2/CO2/SO2/air) were investigated in the plate-type discharge configuration. Results show that corona current increases more rapidly with increasing gas temperature than that with decreasing pressure at the same gas density. The current density is 0.87 mA/m at 973 K and atmosphere pressure, which is higher than 0.45 mA/m at 30.9 kPa and room temperature. An additional temperature effect on corona discharge is proposed apart from the decrease of gas density as temperature increases. ΔIt increases with increasing temperature because of enhanced molecule kinetic energy and ionization rate. The electron-carried current is important at temperatures above 873 K. ΔIe/ΔIt increases from 0 to 0.941 when temperature increases from 773 K to 973 K. Compared with the ΔIt of wire and spiral electrodes, the ΔIt of ribbon electrode is significantly larger because of the enhanced electron avalanche and secondary electron emission. Negative corona discharge does not occur in N2, and corona onset voltages are in the following sequence: CO2 > SO2 (6000 ppm) > air, which is determined by gas molecule ionization energy. ΔIt/IP is smaller in gas atmosphere with strong electronegativity.