The use of wood as a reburning fuel in combustion systems

A hardwood and softwood have been evaluated as reburning fuels and compared to coal and natural gas. The use of wood to reduce NO, a pollutant whose emissions are becoming increasingly regulated, is attractive for several reasons. Wood contains little nitrogen, as compared with coal, resulting in lower NO production from fuel nitrogen. In addition, wood contains virtually no sulfur, so SO{sub 2} emissions are reduced in direct proportion to the coal replacement. Wood is a regenerable biofuel; when a fossil fuel is replaced by a biofuel, there is a net reduction in CO{sub 2} emissions. Finally, since reburning fuels are normally 10-20% of the total heat input, large quantities of wood are not necessary, as compared to firing 100% wood. Results showed that a reduction of 50-60% NO was obtained with approximately 10% wood heat input. Reburn zone stoichiometry was the most important variable; highest reductions were found at a stoichiometry of 0.85 and reductions fell to 30% at a stoichiometry of 1.0. The reduction was strongly dependent on initial NO concentration and only slightly dependent upon temperature; increased temperature increased NO reduction. Finally, the results suggest that wood is as effective as natural gas or coal as amore » reburning fuel.« less