ABSTRACT
This chapter discusses combustion control methods for Nitrogen oxide (NOx) reduction. Nitrogen oxides are actually a combination of two different chemical species, nitric oxide (NO) and nitrogen dioxide (NO2). At normal combustion temperatures, the nitric oxide form predominates and is usually more than 95% of the total. NOx is formed by one of the three mechanisms in a combustion process: thermal NOx, fuel or chemically bound NOx, and prompt NOx. Most NOx emissions from combustion processes are generated from thermal fixation of nitrogen in the combustion air. The fuel used as auxiliary fuel in a thermal oxidation system can also affect NOx emissions. This effect is due to differences in adiabatic flame temperature with gaseous fuels and fuel nitrogen content with liquid fuels. Fuel-induced recirculation (FIR) is similar to flue gas recirculation, except that the flue gas is mixed with auxiliary fuel upstream of the burner instead of combustion air.
