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OVERFIRE AIR TECHNOLOGY FOR TANGENTIALLY FIRED UTILITY BOILERS BURNING WESTERN U.S. COAL
Citation:
Burrington, R., J. Cavers, AND A. Selker. OVERFIRE AIR TECHNOLOGY FOR TANGENTIALLY FIRED UTILITY BOILERS BURNING WESTERN U.S. COAL. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/7-77/117.
Description:
The report gives results of an investigation and evaluation of the effectiveness of overfire air in reducing NOx emissions from tangentially fired boilers burning Western U.S. coal. Results are compared with those obtained during phase II, 'Program for Reduction of NOx from Tangentially Coal Fired Boilers.' Both programs investigated the effect that variations in excess air, unit slagging, load, and overfire air had on unit performance and emissions. The effect of biasing combustion air through various out-of-service fuel nozzle elevations was also investigated. The effect of overfire air operation on waterwall corrosion potential was evaluated during 30-day baseline and overfire air corrosion coupon tests. Overfire air operation for low NOx optimization did not significantly increase corrosion coupon degradation. Overfire air operation and reductions in excess air levels were effective in reducing NOx emissions. NOx reductions of 20-30% were obtained when operating with 15-20% overfire air. These reductions occurred with the boilers operating at a total unit excess air of about 15-25%, measured at the economizer outlet. Unit loading exhibited a minimal effect on NOx emissions. Waterwall slag conditions had wide and inconsistent effects on NOx emission levels.