Effect of CO2 on explosion limits of flammable gases in goafs

Abstract

In order to reduce the number of accidents due to explosions of flammable gases in the goaf of coalmines, the conditions for explosion of flammable gases and their explosion limits, affected to a considerable extent by CO2, are explored. With the use of our experimental equipment suitable for the study of explosion of polybasic explosive gas mixtures, we investigated the effect of CH4/H2=10/1 and CH4/C2H4=10/1 gases mixed with CO2 on their explosion limits. The results indicate that after adding CO2, the explosion limit of the CH4/H2 (or C2H4) =10/1 gas mixtures decreased markedly with increasing amounts of CO2. When the amount of CO2 exceeded 25%, the CH4/C2H4=10/1 flammable gas mixture did not lead to explosions. Similar results were obtained when the amount of CO2 exceeded 23% in the CH4/H2=10/1 flammable gas mixture. We also compared the explosion limits and the explosion suppression effect of N2 or CO2 on the explosion limits of the CH4+CO and CH4+C2H4 dual explosive gas mixtures. Along with the increases in the amounts of CO2 or N2, the area of the explosion limits of gas mixtures decreased. Under the same conditions, the explosion suppression effect of CO2 was greater than that of N2. CO2 has clearly the better suppression effect on the explosion of flammable gases in goafs.