氨煤混烧耦合机制对火焰特性与NOx排放影响的数值模拟研究OA

Ammonia-coal co-firing represents a promising pathway for emission reduction;however,controlling NOx emissions during this process remains a critical research priority.While extensive studies have explored the impact of key parameters on NO emissions,flame temperature,and burnout rates,there remains a lack of in-depth analysis from the perspectives of chemical reaction kinetics and fluid dynamics.To elucidate the coupling mechanisms of ammonia-coal co-firing and their effects on flame characteristics and NOx emissions,this study established a three-dimensional numerical model for a drop-tube furnace based on the Eddy Dissipation Concept(EDC)turbulence-chemistry interaction model and a detailed chemical kinetic mechanism.The results indicate that spatial overlap of ammonia and coal flames leads to the formation of a high-temperature coupled flame,which promotes thermal NO formation.Conversely,when the flames are separated,the upstream combustion consumes oxygen,thereby inhibiting the combustion of downstream fuel and lowering the downstream flame temperature.The location of ammonia injection significantly affects local oxygen molar concentrations,which in turn alters ammonia oxidation pathways and reaction rates;notably,under oxygen-rich conditions,the formation of NO2-which is difficult to reduce-is favored,leading to a significant increase in NO emission molar concentrations.This study proposes a dimensionless number,Ver(the velocity ratio of ammonia to the upstream flow),to describe the distribution of the ammonia-rich zone.An increase in Ver expands the ammonia oxidation reaction zone,which is detrimental to NO control.Overall,to minimize NOx emissions,strong coupling between ammonia and coal flames should be avoided,and ammonia injection near the burnout zone is preferred to balance the effects of oxygen molar concentration and the reaction zone.This study provides an essential theoretical basis for the optimized design and operation of ammonia-coal co-firing systems.