NOx EMISSIONS FROM PULVERIZED-COAL ARCH-FIRED BOILERS.

A study has been conducted to asses the NO//x emission characteristics of three subbituminous pulverized-coal arch-fired utility boiler configurations. These boiler arrangements are unique in that the coal is introduced downward from the arch into the furnace with the bulk of the combustion air added through the front wall perpendicular to the flame jet. Inherent staged combustion conditions are thereby generated which have been shown to be conducive to low NO//x emissions. Field tests were conducted to determine as-found NO//x emission levels and the influence of combustion modifications on these emissions. NO//x levels (corrected to 3 percent O//2 ) ranged from 200 ppm to 350 ppm. The lowest emissions were emitted from the largest (275 MW) boiler. Variations in excess air, air flow injection distribution between burner and front wall, burner stoichiometry, and coal properties were shown to reduce NO emissions by 5 to 35 percent. Analyses of the designparameters of these boilers have been made directed at determining the promary conditions conducive to low NO//x emission levels.