Physical Mechanisms Governing the Oxidation of Volatile Fuel Nitrogen in Pulverized Coal Flames

Abstract

The general problem of volatile fuel nitrogen oxidation in pulverized coal flames is considered. A review of field and pilot data indicates that physical mechanisms which control the local ratio of oxygen to volatile nitrogen are of paramount importance in determining nitrogen oxide emissions, This ratio can be viewed as being controlled both by the manner in which nitrogen evolution occurs during coal combustion and by mixing induced through aerodynamic or process changes. Theoretical results presented support the view that physical phenomena during coal particle volatilization can radically alter micro mixing between volatile nitrogen and air and are used to interpret a step change in fuel nitrogen conversion observed at very high temperatures. Data resulting from special experimentation on self-sustaining pulverized fuel flames are presented and interpreted in the light of fundamental physical mechanisms controlling contact between nitrogeneous species and oxygen. Unsolved problems and fruitful research approaches are identified