Effect of CO2/N2 on explosion vent behavior of lycopodium/air mixtures in a 20-L sphere

Abstract

To investigate the inerting effect of CO2/N2 on the explosion venting behaviors of lycopodium/air, a standard 20 L spherical chamber, with a thermo-gravimetric analyzer TGA Q500 was adopted to determine the explosion severity and mechanism of inhibition. In the heat flow of the N2 atmosphere and CO2 atmosphere, the pyrolysis processes of lycopodium powder show obvious differences from 370°C approximately. Through the whole explosion process, CO2 plays a key role and it can effectively cut off the contact between dust and oxygen. The particles with free radicals decomposed from heat lycopodium powder such as nitrogen and carbon will react lowly under the blocking effect of CO2. Meanwhile, carbon, nitrogen and other atoms can participate in chain reaction and react with active groups, which greatly reduces the risk of powder explosion. The explosion pressure Pex and the maximum reduced pressure Pred were obtained with lycopodium powder explosion under a wide range of CO2 concentrations. Compared with the pure physical suppression principle of N2 in the explosion process, CO2 can participate in the explosive reaction more effectively, and hence has a better suppression effect of the explosion than N2. An unexpected behavior has been found in relation to the explosion venting behavior. Under the smaller vent diameter or at higher static activation overpressures, the suppressive effects of carbon dioxide to lycopodium/air venting explosion are better than those of nitrogen.