99/02132 Gas reburning for high efficiency NO x control. Boiler durability assessment : Folsom, B. A. et al. Proc., Annu. Meet. Air Waste Manage. Assoc., 1996, 89, rp13904/1–rp13904/15

Abstract

During Gas Reburning, natural gas is injected above the burner area to produce a slightly fuel-rich zone where NO{sub x} may be reduced by 60--70%. Overfire air injection completes the gas combustion. During gas reburning, the furnace walls in the reburning zone are exposed to reducing conditions and this suggests the potential for increased tube wastage. EER conducted comprehensive GR field evaluations on three US utility boilers in an effort to confirm the emission reduction and evaluate boiler impacts including tube wastage. All of the units were operated initially with GR over a range of boiler conditions to determine the optimum settings. Subsequently, the boilers were operated with GR during normal load-following operations (long term testing). The results showed that NO{sub x} emissions were reduced by over 60% in all cases. Another important goal was to determine if gas reburning caused significant deterioration of the boiler tubes. This entailed a comprehensive program of boiler durability assessment including ultrasonic tube thickness measurements prior to and after GR operation, destructive analysis of boiler tube specimens, and periodic visual observations. As this paper shows, no significant waste of tubes was found.