Experimental study on suppression of hydrogen-blended natural gas explosion by composite powder in full-scale confined space: Mechanism and scale effect

To address industrial-scale explosion risks of hydrogen-blended natural gas, this study used a 25.2 m 3 full-scale enclosure to investigate suppression by a novel ABC/NaHCO 3 composite powder (3:7) with N 2 /CO 2 propellants on 9.5% hydrogen-blended natural gas–air mixtures. Under incomplete suppression, the powder significantly reduced explosion pressure, with optimal concentrations of 500 g/m 3 (N 2 ) and 400 g/m 3 (CO 2 ), lowering P max to 64 kPa and 79 kPa, respectively. Complete suppression was observed in some but not all replicate tests, most frequently (3 of 4) for CO 2 at 600 g/m 3 . Flame imaging revealed a dynamic “heating–decomposition–inhibition–cooling” cycle. Compared with a 2 m 3 platform, scale-up raised the critical complete suppression concentration from a deterministic value of 100 g/m 3 to a probabilistic range of 500–600 g/m 3 . These findings provide essential data and a theoretical basis for industrial-scale hydrogen-blended natural gas explosion suppression design.