Experimental study and molecular dynamics simulation on co-combustion of pulverized coal and NH3 at O2/N2 and O2/CO2 atmospheres

The use of ammonia as a co-combustion fuel instead of fossil fuel combustion is an important way to reduce carbon emissions from coal-fired power plants. This paper investigates the NO emission characteristics of coal/ NH3 co-combustion at O2/N2 and O2/CO2 atmospheres through experiments and molecular dynamics studies. The results demonstrate that increasing the combustion temperature enhances the formation of NO with the NH3 blending ratio is 0-60 %. When coal and NH3 are burned together, the emission of NO is lower at O2/CO2 atmosphere compared to that at O2/N2 atmosphere. Reactive force field molecular dynamics (ReaxFF MD) simulation results show that the effect of high concentration of CO2 on nitrogen conversion is mainly related to temperature. When the temperature is low, the physical characteristics of CO2 with large specific heat capacity inhibits the conversion of NH3 to NO. However, at high temperature, CO2 participates in the reaction in large amounts, which increases the number of OH radicals in the combustion process and promotes the conversion of NH3 to NO. The results show that with the increase of combustion temperature, the conversion of nitrogencontaining intermediates to NO is promoted. Furthermore, the reactive molecular dynamics simulation revealed the transfer pathway of N atoms in NH3 during co-combustion process at two atmospheres.