Flame propagation analyses of aluminium coated with various concentrations of stearic acid based upon elementary reaction simulation

Abstract

Coated aluminium, a novel material, has been employed in a multitude of applications. However, the thermal physicochemical properties of certain coated materials can elevate the ignition sensitivity and exacerbate explosion hazard of coated aluminium powder, posing serious thermal risks throughout the production, processing and storage. To render a theoretical basis for the prevention and mitigation of stearic acid-aluminium (SA-Al) dust explosion accidents, the flame propagation and elementary reaction sensitivity characteristics of SA-Al dust with various stearic acid concentrations were analysed by experiment and numerical simulation. Results showed that as the SA coating concentration increased from 0 % to 20 %, the flame propagation behaviour changed from dust-driven to gas-driven combustion, the flame luminous intensity and temperature abated gradually, and the average flame propagation velocities and free radical accumulation tended to first increase and then decrease, reaching maximum value in the 10 % SA-Al explosion. There may be synergistic combustion effect during Al cores and SA coating, which reflected in that a series of branch chain reactions of H and OH of SA in the initial combustion stage resulted in the accelerating melting and the forward explosion reaction kinetics of Al cores. Concurrently, the accelerated combustion of Al intensified the pyrolysis and oxidation of unburned SA-Al particles.