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

Abstract

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 Pex 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.