Suppression Mechanism of Nano-Fe ₂ O ₃ Composite Suppressant Against PAN Explosions

A composite powder combining nano-Fe2O3 and 100 μm 5A zeolite molecular sieve (zeolite-Fe2O3) was prepared via an in situ synthesis process, as a suppressant against polyacrylonitrile (PAN) dust explosions. The microstructure and elemental composition of the composite suppressant were characterized via SEM, EDS, XRD, and FTIR analysis. Its suppression performance and mechanism against PAN dust explosions at different mass fractions (10 wt%–30 wt%) were evaluated in a 20 L explosion sphere and a transparent pipeline explosion propagation system. The results indicate that nano-Fe2O3 was successfully coated onto the surface of the zeolite molecular sieve, yielding an impurity-free composite powder with high dispersibility. Explosion suppression tests demonstrate that PAN dust exploded most intensely at the concentration of 500 g/m3, with maximum explosion pressure Pmax = 0.661 MPa and maximum pressure rise rate of (dp/dt)max = 31.64 MPa/s. As the mass fraction of the composite suppressant increased, the Pmax and (dp/dt)max of PAN dust both drop markedly, extending explosion delay time and substantially containing flame propagation. Adding 30 wt% suppressant effectively blocks PAN dust explosions. Suppression mechanism analysis reveals that the zeolite molecular sieve intercepts combustible volatiles from PAN decomposition via physical adsorption while absorbing explosion heat at the same time. Nano-ferric oxide scavenges ·OH and ·O radicals in the explosion chain reaction via a cyclic catalytic reaction, interrupting the chain reaction, thereby effectively suppressing explosions. The research provides an innovative idea as well as a theoretical basis for developing composite suppressants against polymer dust explosions.