Patent ID: 6325003
Filing Date: 2001-12-04
Classification: F23B,F23C,F23J

Abstract:
A method for reducing nitrogen oxide (NO.sub.x) emissions formed during the combustion of a carbonaceous fuel, said method comprising the steps of:a) introducing a carbonaceous fuel containing fuel-bound nitrogen into any carbonaceous fuel burner, wherein primary carrier air mixed with a carbonaceous fuel and preheated secondary air at a temperature in a range of about 400.degree. F. to 700.degree. F. is added in a first stage to produce a fuel gas at a stoichiometric air-to-fuel ratio in a range of about 0.55 to 0.75;b) introducing the fuel gas from the first stage into a second stage of partial oxidation in a boiler furnace by introducing preheated tertiary air into the fuel gas to yield an overall stoichiometric air-to-fuel ratio of about 0.80 to 0.99;c) introducing the fuel gas from the second stage of partial oxidation in the boiler furnace, the fuel gas flowing through a radiant section of the boiler furnace to produce a flue gas; andd) introducing the gas into a third stage of oxidation wherein preheated overfire air is introduced into the boiler furnace to substantially complete combustion.