Progress in Energy and Combustion Science, Vol.24, No.5, 385-408, 1998
NOx control through reburning
Reburning is a process whereby a hydrocarbon fuel is injected immediately downstream of the combustion zone to establish a fuel-rich zone in order to convert nitric oxide to HCN. The reburning fuel can be gaseous (e.g., natural gas), solid (e.g., coal char or wood) or liquid (e.g., residual oil). Typically, the amount of reburning fuel used is 10-30% of the total fuel. This technology is practiced commercially with nitric oxide reduction levels of 35-65%, depending on the type and scale of the boiler or combustion, the primary and reburning fuels and other variables. Current research and development are suggesting several advanced reburning concepts including injection of ammonia or urea aft of the reburning fuel injection. Nitric oxide reductions of over 90% are anticipated. In this mini-review, a review of reburning technologies, measurements and mechanisms is presented. Predictive methods for reburning are also discussed. Recent work on reburning, including development of a global reburning reaction rate, is summarized, and results of application of a comprehensive combustion model to reburning measurements are summarized.
Keywords:NITRIC-OXIDE;COMBUSTION SYSTEMS;NITROGEN CHEMISTRY;NATURAL-GAS;REDUCTION;COAL;CARBON;MODEL;CHAR;MECHANISMS