Experimental investigation of the lower explosion limit of hybrid mixtures of methane and lycopodium dust

In this work, lower explosion limits of methane, lycopodium dust and methane-lycopodium dust hybrid mixtures were determined under the same testing conditions based on the 20 L sphere vessel. The measured results were compared with the values calculated by the Le Chatelier's law, the Bartknecht curve and the Jiang method. The results showed that the combination of methane prepared in concentrations below its lower explosion limit and the lycopodium dust in concentrations below its minimum explosion concentration rate was still a mixture with a hazard of explosion. The minimum explosion concentration of lycopodium dust decreased with the increase of methane concentration in the hybrid mixtures. The lower explosion limit of methane-lycopodium dust hybrid mixtures couldn't be accurately calculated by the Le Chatelier's law, the Bartknecht curve or the Jiang method. The lower explosion limit of hybrid mixtures of methane and lycopodium dust calculated by the Le Chatelier's law were smaller than the measured values for the mixtures with the methane concentration φ/φ_L < 0.5, but bigger for the mixtures with the methane concentration φ/φ_L>0.5. The Bartknecht curve was suitable for predicting the lower explosion limit of the hybrid mixtures with the methane concentration φ/φ_L>0.5. But for the hybrid mixtures with a methane concentration φ/φ_L < 0.5, the calculated values were smaller than the measured ones, whereas the Jiang method was unsuitable for predicting the lower explosion limit of the hybrid mixtures of methane and lycopodium dust.