LOW-NO_x Pulverized Coal Nozzle Tip Design for Tangentially-Fired Furnaces at Mirant's Potomac River achieves 21-33 NOx reduction at a very low cost

摘要

This paper describes results of using Computational Fluid Dynamics (CFD) to design low-NOx pulverized coal nozzle tips for a tangentially-fired furnace. The coal nozzle design was installed on five 725,000 1b/hr (steam flow), balanced draft, tangent tube boilers. The utility installed the new coal nozzles in order to achieve NOx reductions required to meet corporate environmental objectives. The new patent pending coal nozzle design modifies the coal injection angle in order to burn the coal volatiles in a fuel-rich environment. This limits the available oxygen to combine with the fuel nitrogen species in the volatiles, thereby reducing NOx. Several variations of the design were analyzed with the CFD model, and the predicted NOx reduction for the selected design was 25%. The utility has started the five tangentially-fired units with the new low-NOx coal nozzle design installed. Measured NOx reductions varied from 21 to 33%, with CO emissions < 35 ppm at 2% O2, and LOI being less than baseline levels. This provided a very ingenious NOx reduction that was retrofit in a one-week outage and a new baseline for additional NOx reduction in the future.