Experimental Study on the Inhibition of Hydrogen/Methane/Air Explosion by Potassium Oxalate Water Mist

Abstract The suppression characteristics of hydrogen/methane/air explosion by water mist with potassium oxalate (K2C2O4·H2O) additive were experimentally investigated in this work. The effects of pure water mist and K2C2O4·H2O-modified water mist on flame morphology, average flame propagation speed, maximum flame acceleration, explosion pressure, and maximum pressure rise rate were systematically analyzed. Results indicated that the inhibition efficiency of pure water mist is limited and reaches saturation with increasing concentration, while the addition of K2C2O4·H2O significantly enhances the explosion suppression performance. With the increase of K2C2O4·H2O mass fraction, the average flame propagation speed and maximum flame acceleration are gradually reduced, the peak explosion pressure and maximum pressure rise rate are observably decreased, and the time to reach peak pressure is obviously delayed. When the mass fraction of K2C2O4·H2O is above 6%, the pressure evolution curve is transformed from a three-stage mode to a four-stage mode. Based on TG-DSC experimental analysis, the thermal decomposition process of K2C2O4·H2O is determined as dehydration and decomposition to produce K2CO3 and CO. The physical–chemical synergistic explosion suppression mechanism is revealed, in which physical effects including endothermic cooling, inert dilution, and flame destruction provide favorable conditions for chemical inhibition, and chemical chain termination reduces heat release and strengthens physical suppression. The findings can provide theoretical support for the safety protection of hydrogen/methane/air systems.