Suppression characteristics and mechanisms of five typical powder suppressants in large-scale enclosed spaces for hydrogen-blended natural gas/air explosions

The injection of a certain amount of hydrogen into natural gas pipelines has been proven as an efficient hydrogen transportation solution. Numerous valve chambers are generally used in pipeline transportation systems, and leaks or explosions of CH₄/H₂ mixtures in these valve chambers can have extremely severe consequences. Therefore, it is important to study the explosion suppression characteristics of common suppression materials for CH₄/H₂ mixtures in large-scale enclosed spaces. In the present study, a 2 m³ explosion suppression experimental platform was designed to conduct CH₄/H₂ explosion suppression experiments using five types of pure powder materials: silica (SiO₂), zeolite, calcium carbonate (CaCO₃), ammonium di-hydrogen phosphate (NH₄H₂PO₄), and sodium bicarbonate (NaHCO₃). It was found that SiO₂ and zeolite had almost no suppression effect on CH₄/H₂ explosions in the large-scale enclosed space, whereas NH₄H₂PO₄ and NaHCO₃ both exhibited significant suppression effects. CaCO₃ had no prominent suppression effect on the explosion pressure of CH₄/H₂; however, it yielded a certain suppression effect on explosion temperature. The suppression effectiveness of NH₄H₂PO₄ and NaHCO₃ was maximized at their optimal concentrations. Furthermore, the inhibition mechanisms of these experimental materials were analyzed from four aspects: thermal insulation, cooling, dilution, and interruption of chain reactions. It was observed that the CH₄/H₂ explosion suppression behaviors of the selected inhibitors in the large-scale enclosed space was more complex compared to those in a small-scale space. Some inhibitors exhibited different explosion suppression characteristics from those reported in previous research. The findings of this work provide important guidance for CH₄/H₂ explosion suppression in industrial enclosed spaces and also offer new insights into the selection and modification of inhibitors.