Premixing dry low nox emissions combustor with lean direct injection of gas fule

Abstract

Lean premixed combustion of a hydrocarbon fuel and air is combined with lean direct injection of hydrocarbon fuel and carrier fluid such as air or inert gas or a mixture of air and inert gas into a combustor downstream of the premixed reaction zone in order to achieve extremely low levels of emissions of oxides of nitrogen at the high combustor exit temperatures required by advanced heavy duty industrial gas turbines. One or more premixing fuel nozzles are used to supply a lean mixture of hydrocarbon fuel and air to the main or primary reaction zone of a gas turbine combustor. This lean fuel/air mixture has an adiabatic flame temperature below the temperature that would result in substantial thermal NOx formation. After this low temperature reaction has been completed, additional fuel and carrier fluid are injected into the products of combustion downstream of the main reaction zone in order to raise the temperature of the mixture to the level required to operate an advanced, high efficiency, heavy duty industrial gas turbine at high load. Formation of nitrogen oxides in the region after this secondary fuel and carrier fluid injection is minimized by partial premixing of fuel and carrier fluid prior to ignition and by minimizing the residence time between the secondary fuel injection and the turbine first stage inlet.