Studies on Enhancement of Reburning for Advanced NOx Control in Coal-Fired Boilers

This paper summarizes an experimental study which was conducted to investigate the chemical constraints of the reburning process and identify reburning configurations for optimal NOx reduction. Tests were performed on a bench scale tunnel furnace to characterize and optimize the fuel-rich reburning zone and the fuel-lean burnout zone independently. Detailed measurements of unburned hydrocarbons, CO, NH3, and HCN were made at the reburning zone exit. The influence of the concentrations of reactive species was examined as were temperature effects for both the reburning and burnout zone. Results indicated that reburning zone chemistry was not rate limiting. The impacts of temperature and burnout zone oxidation were of major importance. Integration of the optimum reburning and burnout zone configurations resulted in increased NOx reduction. Over 80 percent reduction in NO x emissions was achieved with ammonium sulfate injection in the burnout zone under optimum reburning conditions