Low NOx emission of rotary regenerative combustion system (RRX)

We have developed an energy conserving regenerative rotary combustion syste m (RRX burner) which is combined with a regenerative type air pre-heater an d can be operated continuously. In our first report, we discussed "Heat transfer characteristics of the RRX burner" (Kagaku Kogaku Ronbunshu, 1996) and the second report discussed on "Combustion characteristics of the RRX burner" (Kagaku Kogaku Ronbunshu, 1 997). We discuss the technology of low NOx emission when the rotary air nozzle ex it areas are changed to 88 degrees, 35 degrees and 15 degrees. The results show that the narrower the air exit angle combustion gets, the lower the NO x emission. In the case of angle 15 degrees, NOx emission is less than 9 pp m. We assume that the reaction speed is quite faster than the mixing speed bet ween a fuel, air and flue gas in the furnace, and estimate a flame length a nd NOx emission based on the velocity and concentration formulas of Beer an d Chigier. The estimation results coincide a ell with the experimental results, so it means that flue gas recirculation inside a furnace helps to attain low NOx.