Method of reducing nox emissions from a stationary combustion turbine

Abstract

Hydrocarbon fuel is combusted in a combustion turbine by a method which produces NO.sub.x emmissions below an ultra-low standard. In the method, first, a mix of hydrocarbon fuel and air in a primary flow thereof is burned in a primary combustion zone so as to produce a flow of hot gas of a temperature above that required for an efficient catalytic reaction and which contains NO.sub.x at levels below a low standard but above the ultra-low standard. Next, the hot gas is mixed with hydrocarbon fuel in a secondary flow thereof in a mixing and vaporization zone to provide a flow of heated fuel mixture of a temperature above that required for an efficient catalytic reaction. Thereafter, the heated fuel mixture is inefficiently catalytically reacted in a first catalytic element fuel to provide a flow of effluent gas of a temperature above that required for an efficient catalytic reaction and which contains NO.sub.x at levels below the ultra-low standard and CO and unburned hydrocarbons (UHC) at levels above an acceptable standard. Then, the CO and UHC in the effluent gas flow is mixed in a mixing completion zone to produce a flow of heated mixed effluent gas of a temperature above that required for an efficient catalytic reaction. Finally, the heated mixed effluent gas is efficiently catalytically oxidized in a second catalytic element to provide a flow of exhaust gas having emissions which contains NO.sub.x at levels below the ultra-low standard and CO and UHC at levels below the acceptable standard.