Staged combustion for reducing nitrogen oxides

摘要

A combustion method is provided for carrying out combustion with reduced generation of nitrogen oxides. The combustion method involves partially combusting a fluid fuel stream with a low velocity oxidant and thereafter mixing and combusting the resulting product with a secondary oxidant stream diluted with ambient gas. The velocity of the secondary oxidant stream is either increased to reduce the nitrogen oxides emission level or adjusted to provide the desired secondary oxidant/low velocity oxidant ratio which is useful for further decreasing the formation of nitrogen oxides. Normally, increasing the ratio and/or velocity further decreases the nitrogen oxides emission level. When liquid fuel is employed, it is atomized with atomizing fluid in such a manner to produce a liquid fuel stream having a very narrow spray angle. The production of such a stream allows the burner to be operated without water cooling. Moreover, such a stream, when combined with the above combustion method, unexpectedly provides effective and efficient combustion with reduced generation of nitrogen oxides.