Characteristics of negative DC discharge in a wire–cylinder configuration under coal pyrolysis gas components at high temperatures

Abstract

This work aims to provide a comprehensive understanding of negative DC discharge under coal pyrolysis gas components (CO₂, H₂, N₂, CH₄, CO) and air. The characteristics of negative DC discharge were studied in a wire–cylinder configuration at an ambient temperature range of 20–600 °C by analyzing V–I characteristics, discharge photographs, and gas composition. With increasing temperature, corona onset voltage, spark breakdown voltage and operational voltage range for corona discharge decrease, but discharge current and electron current ratio increase. Discharge current of CO₂ is higher than that of air due to the difference of electronegativity. During CO₂ discharge, with the increase of output voltage, three types of discharge are successively observed, namely corona, glow and arc. However, during H₂ discharge, only glow discharge is observed. Temperatures significantly affect the capability of CO to attach electrons. The discharge characteristic of CO is similar to the electronegative gas media at 20 °C and the non-electronegative gas media when the temperature exceeds 350 °C. Chemical reactions and carbon generation are observed during the CH₄ and CO discharge process. The product of carbon filaments under the CH₄ gas medium leads to discharge current volatility and short circuit. These results assist in understanding the property of ESP at high temperatures.