Experiment on low NO_x combustion characteristics by flue gas dilution in air and fuel sides

Control of NO_x has been a major issue in designing combustion systems, since NO_x plays a key role in ozone depletion and the generation of photochemical smog. Flue gas recirculation (FGR) is one of the well-known methods to control NO_x emission. The recirculated flue gas in fuel stream, that is, the fuel induced recirculation (FIR) could enhance a much greater reduction in NO_x per unit mass of recirculated gas, as compared to the conventional FGR in air. The effect of FGR/FIR methods on NO_x reduction in turbulent swirl flow flame in laboratory scale using N₂ and CO₂ as diluent gases to simulate flue gases were studied. The NO reduced following the diluent recirculation ratio increasing and CO₂ dilution is more effective because of large temperature drop due to the larger specific heat compared to N₂. FIR is more effective to reduce NO emission that FGR when the same recirculation ratio of dilution gas is used. This is an abstract of a paper presented at the 30th International Symposium on Combustion (Chicago, IL 7/25-30/2004).