Experimental study on the explosion suppression characteristics of polyethylene dust by ammonium polyphosphate

The hazardous repercussions of dust explosions involving polyethylene (PE) have been the subject of studies aimed at alleviating such risks. In this pursuit, this study undertakes experiments on explosion suppression, utilizing a 20-L explosion sphere apparatus. The inhibitory properties of ammonium polyphosphate (APP) are assessed through an appraisal of pressure and flame propagation behavior. In addition, the thermal stability of the samples and residues resulting from deflagration are systematically assessed to unveil the inhibitory mechanism of APP on PE dust. The findings reveal that At an APP:PE ratio of 1:1, the pressure peak vanishes and the flame deflagration fails to sustain efficient combustion, indicating complete suppression of PE dust at this concentration. Additionally, the activation energies for PE and APP-PE under different pyrolysis atmospheres were determined employing the FWO method. The average activation energies for PE were found to be 69.32 kJ/mol in an air atmosphere and 175.79 kJ/mol in a nitrogen atmosphere. Similarly, the average activation energies for APP-PE were determined to be 177.91 kJ/mol in an air atmosphere and 245.06 kJ/mol in a nitrogen atmosphere. Notably, the incorporation of APP results in a considerable increase in the average activation energy of PE, signifying the retardation of the oxidative pyrolysis process of PE particles. By employing SEM, Raman spectroscopy, and XPS testing methods, it is observed that the heating-induced decomposition of APP results in the formation of polyphosphoric acid, which acts as a strong dehydrating agent and interacts with carbonaceous substances in the flame retardant system, leading to the formation of a compact, expanded carbon layer wrapping around the surface of PE dust. Furthermore, the carbonization process of high-temperature pyrolysis products of APP significantly enhances the graphitization degree of PE explosion products. Moreover, the application of APP inhibits the fracture of CC and CO bonds in PE, resulting in improved thermal oxidative resistance of PE dust. The combination of pyrolysis property testing and deflagration residue analysis demonstrates that PE inhibition by APP exhibits synergistic effects of both a physical and chemical nature.