A reactive molecular dynamics study of HCN oxidation during pressurized oxy-fuel combustion

In the present work, HCN oxidation during pressurized oxy-fuel combustion is studied using reactive molecular dynamics (ReaxFF MD) simulations. The effects of CO2, pressure, and O-2 concentration on HCN oxidation are investigated. Under fuel-rich conditions, CO2 reduces the overall oxidation rate of HCN due to the lower diffusion coefficient of O-2 in O-2/CO2 environment. On the other hand, CO2 increases the amount of OH radicals through the reaction of CO2 + H -> CO + OH at high temperatures. Although high pressure reduces the diffusion coefficient of O-2, the oxidation rate of HCN still increases with the increase in pressure due to the higher partial pressure of O-2. Moreover, NO emissions decrease with the increase in pressure because high pressure promotes the conversion of NO to N-2. Furthermore, CO2 reduces the amount of CN, which is an important intermediate for the reduction of NO at high temperatures. Due to this reason, a positive effect of CO2 on the emissions of NO is observed. Additionally, the oxidation rate of HCN increases with the increase in the concentration of O-2. Unlike fuel-rich conditions, CO2 exhibits an inhibitory effect on the emissions of NO under high concentration of O-2.