Retrofitting oxy-fuel technology in a semi-industrial plant: Flame characteristics and NO production from a low NO burner fed with natural gas

This paper reports part of the results of the campaigns performed on a low NO x burner, firing natural gas in oxy-fuel conditions. The results of combustion tests on burning natural gas with different flue gas recycle rates are presented, with a particular emphasis on NO x production that might affect retrofitting of oxy-fuel technology in conventional boilers. The process and flame characterisation performed on natural gas provides a valuable set of experimental data for the technological development of oxy-combustion burner technology with recycled flue gas, especially in retrofitting scenarios. The data can be used to develop a better understanding of the chemical and physical phenomena involved in oxy-fuel combustion and can provide modellers with a valuable hint for the development of specific sub-models for oxy-combustion simulation. Since is seems technologically unfeasible to reduce down to zero the presence of nitrogen in recycled flue gases, due to air in-leakages, the presence of relatively small amounts of nitrogen in crucial location in the burner provides a thermal NO x source, depending on local levels of temperature and oxygen concentration.