Ignition of dust clouds by brush discharges in oxygen enriched atmospheres

Brush discharge ignitions of sulphur dust in oxygen-enriched atmospheres have been established. From a total of approximately 300 trials, brush discharges were able to start explosions of sulphur dust in three trials. In these trials the atmospheres contained 55 vol%, 60 vol% and 70 vol% oxygen, respectively. The work is motivated by the fact that no brush discharge ignition of dust-air mixtures has been observed in laboratory trials, despite an equivalent energy of the discharge above the minimum ignition energy of some dusts. By adding oxygen to the atmosphere in which the brush discharge is generated, the dust-air mixture will be more prone to ignition. If the critical oxygen concentration to establish ignition of very sensitive dusts such as sulphur is considerably higher than the oxygen concentration in air, it may be stated that a brush discharge cannot ignite dust-air mixtures at atmospheric conditions. High-speed video recordings show that all three ignitions occurred at the top edge of an evolving dust cloud. The research is still ongoing. (C) 2001 Elsevier Science Ltd. All rights reserved.