Preparation and fire extinguishing mechanism of novel fire extinguishing powder based on recyclable struvite

Struvite is a common adverse waste in sewage treatment plants. To evaluate the feasibility of struvite as an extinguishing agent, a novel DOPO-VTS (vinyltrimethoxysilane and 9,10-dihydro-9-oxa-10-phosphaphenan-threne-10-oxa) modified struvite ultra-fine powder with stable performance was prepared using an economic synthesis method, and the extinguishing property and mechanism were deeply analyzed. The local oil basin test showed that the fire extinguishing effect of DOPO-VTS modified struvite was significantly better than that of commercial ABC (NH4H2PO4) dry powder and blank struvite without modification. By coating DOPO-VTS on struvite, the original agglomeration problem was solved, and the liquidity index (angle of repose) was 34 degrees, better than ABC (NH4H2PO4) dry powder (37 degrees) and blank struvite (40 degrees). Besides, under the protection of DOPO-VTS, the overall thermal stability and hydrophobic effect were also improved. The DOPO-VTS modified struvite could maintain fire extinguishing activity at a temperature close to 100 degrees C, 40 degrees C higher than blank struvite, which not only widened its storage environment, but also helped to extinguish the fire at the root of the flame. Furthermore, a large number of P-O groups were generated during the pyrolysis of DOPO-VTS modified struvite, greatly improving its fire extinguishing performance. In addition, the physicochemical reaction during the extinguishing process, including heat absorption/release, particle size distribution, composition, and structural evolution, and gas phase product analysis, were comprehensively studied. Combined with the fire extinguishing experiment results, temperature,and smoke changes, three kinds of extinguishing mechanisms were confirmed: cooling ef-fect, asphyxiation, and chemical effect.