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

Abstract

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 O2 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 O2 in O2/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 O2, the oxidation rate of HCN still increases with the increase in pressure due to the higher partial pressure of O2. Moreover, NO emissions decrease with the increase in pressure because high pressure promotes the conversion of NO to N2. 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 O2. Unlike fuel-rich conditions, CO2 exhibits an inhibitory effect on the emissions of NO under high concentration of O2.