Journal of Safety and Environment

To explore the mechanism of CO₂'s influence on the explosion characteristics of H₂, experiments on H₂/CO₂/air mixture explosions were conducted, and the impact patterns of varying volume fractions of CO₂ on H₂ explosions were obtained. Key elementary reactions and radicals during the explosion process were extracted using Chemkin-Pro, and subsequently, key elementary reactions were simulated using Materials Studio software. The experimental results indicate that, with the increase in the volume fraction of CO₂, both the maximum explosion pressure and the rate of pressure rise exhibit a decreasing trend. Conversely, as CO₂ is incorporated into the H₂ mixture, an increase in the concentration of CO₂ correlates with a prolonged duration to achieve the peak explosion pressure. Additionally, this leads to a reduction in the peak explosion pressure, thereby exerting a more pronounced inert effect on H₂ detonations. When the volume fraction of H₂ reaches 25%, the impact of CO₂ volume fraction on the maximum explosion pressure gradually becomes apparent, and its effect on the maximum pressure rise rate is at a stage of controllable gain. When the H₂ volume fraction reaches 29.5%, further increasing the CO₂ volume fraction particularly enhances the detonation inerting effect. Simulation results indicate that CO_2+·H = CO+·OH is a critical branching reaction in the impact of hydrogen explosions. CO_2+·H readily accepts electrons, while CO+·OH more readily donates electrons. Compared to CO+·OH = ·H+CO₂, the reaction CO_2+·H = CO+·OH involves a lower intermolecular energy barrier, making the reaction more likely to proceed. As the volume fraction of CO₂ increases, the chemical inerting effect strengthens, while the contribution of chemical inerting weakens. Under conditions where the CO₂ and H₂ volume fractions are 5% and 29.5%, respectively, the chemical inerting contribution reaches its maximum, accounting for 21.81% of the total inerting effect. The chemical inerting effect of CO₂ primarily manifests in its consumption of ·H free radicals to form intermediates, thereby reducing the reaction rates of key chain reactions such as ·H+O₂ =·O+·OH and ·H+H_2O = ·OH+H₂. This reduction tends to saturate as CO₂ concentration increases.