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

Abstract

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/NH 3 co-combustion at O 2 /N 2 and O 2 /CO 2 atmospheres through experiments and molecular dynamics studies. The results demonstrate that increasing the combustion temperature enhances the formation of NO with the NH 3 blending ratio is 0–60 %. When coal and NH 3 are burned together, the emission of NO is lower at O 2 /CO 2 atmosphere compared to that at O 2 /N 2 atmosphere. Reactive force field molecular dynamics (ReaxFF MD) simulation results show that the effect of high concentration of CO 2 on nitrogen conversion is mainly related to temperature. When the temperature is low, the physical characteristics of CO 2 with large specific heat capacity inhibits the conversion of NH 3 to NO. However, at high temperature, CO 2 participates in the reaction in large amounts, which increases the number of OH radicals in the combustion process and promotes the conversion of NH 3 to NO. The results show that with the increase of combustion temperature, the conversion of nitrogen-containing intermediates to NO is promoted. Furthermore, the reactive molecular dynamics simulation revealed the transfer pathway of N atoms in NH 3 during co-combustion process at two atmospheres.