Simplified kinetic models describing the fate of coal nitrogen under fuel-rich combustion conditions

Abstract

Twenty three sets of experimental data describing CO, CO₂, H₂, O₂, NO, NH₃, and HCN concentration profiles for fuel-rich pulverized coal combustion in plug flow configurations were correlated by a simple kinetic mechanism. A comprehensive mechanism covering the entire fuel-rich zone was formulated by combining models describing short and long time scale combustion. Short time scale phenomena (up to 0.6 seconds) including coal devolatilization were handled by developing global semi-empirical models based on fundamental concepts. Kinetic parameters for the proposed mechanism were estimated by using a non-linear regression technique. This model then allowed the prediction of major and nitrogenous species evolved in the early stages of combustion and yielded reasonable predictions of all these species concentrations. For the long time scale phenomena (up to 3 seconds) an existing model was used. Under most experimental conditions the extended model yielded good predictions of nitrogenous species from known process variables.