Alternative fuel reburning

Advanced reburning is a NO x control technology that couples basic reburning with the injection of nitrogen agents and promoter compounds. Pilot scale experiments were conducted in which efficiency of basic and advanced reburning processes were characterized with a wide range of reburn fuels. Test fuels included natural gas, pulverized coal, coal pond fines, biomass, refuse derived fuel, and Orimulsion. Process variables that were studied included reburn fuel type, reburn fuel heat input, reburn zone residence time, initial NO x concentration, nitrogen agent injection temperature, and promoter type and amount. Reburn fuel properties found to affect the performance most significantly include fuel nitrogen content, volatiles, and ash constituents. Basic reburning performance for the tested solid fuels was found to approach that of natural gas reburning, with over 70% NO x reduction achievable at reburn heat inputs above 20%. Advanced reburn tests were conducted in which reburning was coupled with injection of nitrogen agents and promoters. The most effective promoter compounds were found to be alkalis, most notably sodium compounds. At reburn heat input of 10%, NO x reductions in the range of 85%–95% were achieved with natural gas and biomass advanced reburning.