Synergistic inhibition of H2/CH4 explosions by CO2/modified KHCO3 powder

To ensure the safety of hydrogen/methane (H2/CH4), the ordinary KHCO3 powder was refined and modified. CO2 and ultrafine KHCO3 powder were selected as explosion suppression materials. A 20 L spherical gas explosion system was used to study the inhibition effects of CO2 and KHCO3 separately and when combined on the explosion of H2/CH4. The suppression of CH4 explosion by ultrafine KHCO3 powder was first analyzed under dusting pressure, revealing an optimal performance with 30 g/m3 ultrafine KHCO3 powder at 0.4 MPa. CO2 exerted an beneficial inhibitory effect on H2/CH4 explosion when the hydrogen content was less than 40%. However, when less than 5% CO2, the H2/CH4 explosion inhibition effect was better when the proportion of hydrogen was above 40%.The combined presence of CO2 and 30 g/m3 KHCO3 inhibitors led to a synergistic inhibitory effect. The combined presence of 30 g/m3 KHCO3 powder and 5, 7.5, or 10% CO2 inhibited the explosions of 9.5% CH4 and H2/CH4 with hydrogen contents of 20 and 40%. The composite explosion inhibitor had a significant effect when the proportion of hydrogen was below 60% but had almost no inhibitory effect on 29.59% hydrogen/air. The mechanism of the inhibition of H2/CH4 explosion and the role of CO2 in the synergistic inhibition were analyzed. The presence of CO2 played a key role in providing time for the endothermic decomposition of KHCO3 powder. The radical products were consumed to achieve a synergistic effect.