The weakening effect of the inhibition of CO2 on the explosion of HCNG with the increase of hydrogen: Experimental and chemical kinetic research

Abstract

To explore the inhibitory effect of CO2 on HCNG (Hydrogen enriched compressed natural gas) explosion and its chemical kinetic mechanism, the explosion pressure and flame of CO2/HCNG/Air (hydrogen ratio: 0–0.6, CO2 addition: 3 vol%, 6 vol%, and 9 vol%) were tested in a 20 L spherical explosion tank at normal temperature and normal pressure. The experiment results shown that: as the addition of CO2 increases, the inhibition effect on HCNG explosion flame and pressure becomes more obvious. The larger the H2 ratio, the more difficult it is to inhibit HCNG explosion flame and pressure. To explore the chemical kinetics reasons for the above laws, the chemical kinetic parameters (such as free radical formation rate and temperature sensitivity coefficient) of the explosion reaction under the above conditions were calculated by CHEMKIN-PRO. The results indicate that CO2 mainly acts as a stable third body in the reaction system, thereby slowing down the growth of explosion chain reactions. In addition, as the main product of the CH4 oxidation reaction, CO2 has a certain weakening effect on the CH4 oxidation reaction. As the proportion of H2 increases, the elementary reactions such as 3# and 84# that generate ·H radicals are promoted, increasing the concentration of ·H radicals in the reaction system. Therefore, the dominant role of 38# on the temperature rise of the reaction system is enhanced, and the contribution of the CH4 oxidation reaction to the temperature rise of the reaction system is weakened. This is the chemical kinetic reason that CO2 has a weak inhibitory effect on the energy release of the HCNG explosion reaction when the proportion of H2 is large. The research results can provide a theoretical basis for the development of HCNG explosion prevention and control technology.