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 373K to 1073K, and pressure varied from 30kPa to 100kPa to achieve the same gas density. The additional corona current DIt induced by high temperature was calculated, and the additional ion current DIi and electron current DIe 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 0.87mA/m at 973K and atmosphere pressure, which is higher than 0.45mA/m at 30.9kPa and room temperature. An additional temperature effect on corona discharge is proposed apart from the decrease of gas density as temperature increases. DIt increases with increasing temperature because of enhanced molecule kinetic energy and ionization rate. The electron carried current is important at temperatures above 873K. DIe/DIt increases from 0 to 0.941 when temperature increases from 773K to 973K. Compared with the DIt of wire and spiral electrodes, the DIt 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 (6000ppm)>air, which is determined by gas molecule ionization energy. DIt/IP is smaller in gas atmosphere with strong electronegativity.