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 found to cause explosions of sulphur dust clouds in 5 trials. In these trials the atmospheres contained 33.9 vol.%, 40 vol %, 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 would be considerably higher than the oxygen concentration in air, it may be concluded that a brush discharge cannot ignite dust-air mixtures at atmospheric conditions.