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Abstract :
[en] In order to investigate the effect of CO2 addition in the combustion air of a yellow flame
burner, tests have been performed during which different volume flow rates of CO2 have
been injected. For all the tests performed, the burner consumption and the oxygen mole
fraction in the flue gas have been kept quite constant, say at about 240 kW and 1.8 % (on dry
basis) respectively. For the interpretation of the flame radiation results, tests have also been
performed with N2 injection. The results gathered (for CO2 and N2 addition up to 4.8 % and
7.4 % in volume respectively) show that the thermal efficiency and the CO emission of the
boiler are not affected. For small amounts of CO2 or N2 volume flow rates, there is a slight
decrease of the NOx emission and the flame radiation. If the quantity of the additive is
increased above a critical value, the flame becomes unstable and one observes first a sudden
increase of the NOx emission and the flame radiation and then a decrease. That sudden
increase is explained by the change of the flame shape and geometry.
