Experimental and numerical simulation research on fire suppression efficiency of dry powder mediums containing molybdenum flame retardant additive

In order to cope with the frequent fire accidents in modern society, it is crucial to develop efficient fire extinguishing agents to stamp out fires in its early stage. In this work, a new composite ultrafine dry powder extinguishing agent containing ammonium molybdate ((NH₄)₂MoO₄) is prepared, and its fire extinguishing efficiency is studied. The cup burner experimental results show that with the increase of the mass fraction of (NH₄)₂MoO₄, the flame temperature drop and flame height variation rate show a trend of increasing and then decreasing, while the MEC and extinguishing time present a trend of a decrease and then an increase. It is indicated that the composite dry powder has the best fire extinguishing efficiency when the mass fraction of (NH₄)₂MoO₄ is 7%. Besides, in terms of the pyrolysis results of TGA and DSC, it is found that the degree of thermal decomposition is significantly promoted under the condition of 7% addition. Based on the gas-solid two-phase flow theory and multiphase flow model, a simplified simulation model of the cup burner is established by the ANSYS-FLUENT software to analyze the variation of temperature and particle motion trajectory. The simulation results demonstrate that the ultra-fine dry powder mediums have a good dispersibility after entering the cup burner. This can achieve a full submerged state at a faster speed, and the flame temperature of the entire fire suppression stage is consistent with the experimental results. This article mainly develops the application of fire extinguishing media in the field of fire protection from the perspective of process safety.