Explosion behaviors of hybrid C₂H₂/CaC₂ dust in a confined space

In order to investigate the explosion process of calcium carbide (CaC₂) dust in the acetylene (C₂H₂) atmosphere, the explosion characteristics of C₂H₂ gas and C₂H₂/CaC₂ dust gas-solid two-phase mixture were studied using a 20-L spherical vessel, and the chemical composition of solid residues after explosion were also analyzed. Experimental results showed that the P_ex values of C₂H₂ gas explosion rose first and then remained stable with the increasing stoichiometric ratio values (φ) of C₂H₂/air, while the (dP/dt)_ex values tended to increase at early stage and then decrease, the inflection point of (dP/dt)_ex values was φ = 1.78. The explosion severity and risk of C₂H₂ gas were enhanced by adding CaC₂ dust, and the optimum additive concentration of CaC₂ dust was 100 g/m³. In the oxygen atmosphere, the C₂H₂/CaC₂ hybrid explosion was divided into two stages when the concentration of CaC₂ dust was over 300 g/m³. The explosion risk of the first stage (Stage Ⅰ) was much more serious, while the explosion severity of the second stage (Stage Ⅱ) was much more fierce. The solid residues of hybrid explosion only contained CaO in the oxygen atmosphere, however, Ca(OH)₂ and CaO were detected in the solid residues in the air atmosphere, owing to the combustion heat of C₂H₂ gas in oxygen was higher than that in air. The hydrolysis reaction time of CaC₂ particle with large particle size was prolonged, and the diffusion of solid product layer and surface chemical reaction both influenced the hydrolysis process according to the shrinking core model. Based on the explosion and chemical analysis experiments, the explosion mechanism of C₂H₂/CaC₂ dust gas-solid two-phase mixture was analyzed systematically.