NOx reburning in oxy-fuel combustion: A comparison between solid and gaseous fuels

In the development of oxy-fuel combustion, reburning of nitrogen oxides, recycled with the flue gases, has been investigated for primary NOx control. Reduction of between 50 and 80% of the recycled nitrogen oxides has been measured. The present work evaluates the performance of gaseous and solid fuels as agents for reduction of nitrogen oxides by comparing experimental and modelling work performed at Chalmers University of Technology with different fuels. It is shown that the reduction is similar during propane and lignite firing, but that the lignite has slightly higher reduction efficiency. Differences in combustion temperature and heterogeneous effects are possible explanations.

► The reburning reduction process is essential to the emission of NOx from oxy-fuel combustion.
► Reburning reduction is favoured by high recycle ratios, sub-stoichiometric conditions, and controlled combustion temperatures.
► Compared to air-firing, reburning during oxy-combustion is more sensitive to the combustion temperature.
► Propane and the lignite investigated showed similar reduction capability, although, the reduction was slightly higher during lignite firing.
► Furthermore, the modelling shows that the type of hydrocarbon released or supplied does not affect the reburning chemistry to a great extent.