FORMATION AND REDUCTION OF NOX IN PRESSURIZED FLUIDIZED-BED COMBUSTION OF COAL

This paper described an experimental and modelling study of NOx format ion and reduction in pressurized fluidized bed combustion (PFBC) of co al. The aim was to evaluate the Thermal DeNO(x) process with NH3 injec tion and staged combustion in PFBC as measures for the reduction of NO x emissions, and to develop a mathematical model for the emission of N Ox. Experiments with NH3 injection and staged combustion in a 1.6 MW P FBC test rig burning bituminous coal showed that both methods were abl e to reduce the emission of NOx by 50-70% under optimum conditions. La boratory experiments were performed to elucidate the nitrogen chemistr y under PFBC conditions and were used as input to the model. These exp eriments included an investigation of the release of nitrogen during d evolatilization of coal and a kinetic study of important reactions for NOx formation and reduction catalyzed by char and bed material sample d from the test rig. The model is based on the two-phase theory of the bed and includes coal devolatilization, combustion of char and volati le matter, and NOx formation and reduction by homogeneous and heteroge neous reactions. The NOx emissions calculated with the model are in qu alitative agreement with the emissions from the 1.6 MW test rig.