Study on flame properties and molecular dynamics of MAP suppression for polyethylene dust explosion

The effect of ammonium dihydrogen phosphate (MAP) on polyethylene (PE) dust explosions was analyzed through experiments and molecular dynamics simulations. The vertical tube explosion experiments showed that the maximum propagation distance of the explosion flame decreased with the increase of MAP mass fractions. The simultaneous thermal analysis experiments revealed that the addition of MAP enhanced the thermal stability of the powder and reduced the combustion exotherm. The molecular dynamics simulation showed that in the pyrolysis system, The groups such as NH3 derived from MAP participated in and slowed down the PE decomposition process and led to the decrease of hydrocarbon gas production, such as the number of C2H4 production decreased from 161 to 112. In the combustion system, oxygen-containing groups induced the initial decomposition of PE and generated CO2 and CH2O, while MAP and its decomposition products preempted the oxygencontaining groups, resulting in the interruption of the chain reaction of PE decomposition and combustion and generating a large amount of H2O, which accounted for 26.67 % of its total generation pathways. Moreover, it was also observed from the perspective of product distribution that increasing the temperature could accelerate and deepen reactions but did not change the suppression mechanism.