OCR Text |
Show 9 nozzle. The tertiary stream improved char burnout effectively even on staged firing, as shown in Fig.12. Flame behavior is compared in Fig.S and we can also note the tertiary stream giving better flame ignition. Effect on NOx emissions The effect emissions was of the discussed presence of here. We the tertiary normally used stream on NOx NOx conversion instead of actual NOx emissions by an expression of ppm basis. Volume basis NOx emissions is directly inf luenced by the recycle flue gas flow, which can playas a dilution medium. NOx conversion was roughly estimated with ignoring thermal-NOx emissions. It was apparently noted that NOx conversion did not affected so significantly by the presence of the tertiary stream, as shown in Fig.II and Fig.12. Especially, on staged firing, NOx conversion was kept same or below than that without tertiary stream. Consequently, a combustion performance curve, on the relation between unburnt carbon against NOx emissions, was desirably shifted below the original relation curve, as shown in Fig.13. CONCLUSION We experimentally clarified the followings on the combustion characteristics of 02/recycle flue gas combustion in comparison with air combustion, in the bench-scale testing. (1) Flame was unstable at below 30% of the O2 conc. in the secondary stream. (2) Unburnt carbon became higher, however, it was improved by increasing O2 cone. in the secondary stream. Moreover, supplying pure O2 directly to burner throat through an injection nozzle solved the unstability of flame and eventually enhanced char burnout performance. |