Effects of coexisting H2 and CO in O2 atmosphere on microscopic combustion reaction characteristics of bituminous coal molecules via ReaxFF MD simulation

Injecting gases rich in H 2 and CO into blast furnaces offers a promising pathway for low-carbon ironmaking by significantly reducing carbon emissions. However, previous macro-scale computational fluid dynamics simulations have indicated severe oxygen competition between the injected gases and coal, yet have failed to capture the underlying molecular-level interactions. Crucially, the coupling impacts of coexisting H 2 and CO on key oxidizing species and the surface chemical environment during coal combustion remain entirely unexplored, leaving the microscopic competitive combustion mechanism of gases and solid carbon unclear. In this study, weight loss, non-bonding interactions, radical evolution, and reaction frequencies during coal combustion were investigated using ReaxFF MD simulation, thereby revealing the synergistic mechanism underlying the influence of injected H 2 and CO on coal combustion. Results show that adding CO suppresses early-stage coal combustion via consuming ⋅OH, which inhibits ring-opening and oxidation of coal and via non-bonding interactions that form a steric hindrance on the coal surface to block effective O 2 collisions. In the H 2 , CO and O 2 mixed atmosphere, increasing the H 2 ratio mitigates ⋅OH depletion. Nevertheless, the steric hindrance exerted by CO persists, resulting in a lower initial burn rate compared to pure O 2 conditions. This study provides theoretical insights for co-injecting gas and pulverized coal in blast furnaces.