Premixing Gas and Air to Reduce NOx Emissions With Existing Proven Gas Turbine Combustion Chambers

Abstract

In the case of the burners employed in KWU gas turbine combustion chambers, the entire primary air is supplied through the swirlers associated with the burners. It is thus relatively easy to add natural gas to this air uniformly before it enters the combustion zone. This results in a particularly low NOx combustion process provided that the air to fuel ratio is being maintained within a certain range. The supplementary equipment to premix the fuel and air does not affect the burner performance when the fuel is supplied in the conventional way by means of gas or oil nozzles. Consequently, the gas turbine will be started up and loaded in the usual manner. In the high load range the burners are then switched over to premixed combustion operation. A small amount of fuel through the central gas nozzle stabilizes the flame in the case of a sudden load decrease. Combustion chambers already in service can be retrofitted with the new premixing equipment to reduce NOx emissions to about one third of the original values. The combustors can be operated with liquid fuels together with steam or water for NOx reduction in the conventional way.