TDF Low NO_x Burner and Windbox Modifications for Emissions Control on a TURBO Furnace

摘要

J.P. Madgett Station is located in Alma, Wisconsin. The boiler is a TURBO fired unit, manufactured by Riley Power Inc., a Babcock Power Inc. company (formerly Riley Stoker). The unit is designed to operate at a maximum continuous rating (MCR) of 2,700,000 pph of superheated steam at an outlet pressure of 1,900 psig and a temperature of 955°F. The reheater is designed for 2,425,000 pph of steam flow with an outlet pressure of 462 psig and outlet temperature of 955°F. This boiler was originally equipped with twenty-four (24) directional flame burners and four (4) Riley Ball Tube Mill pulverizers. The unit was designed to fire sub-bituminous coal. The burners were producing sustained NO_x emissions of 0.66 lb/MBTU with average CO emissions of 52 ppm. NO_x emissions needed to be reduced substantially to meet regulation requirements. Dairyland Power Cooperative contracted Riley Power Inc. to retrofit the unit with twenty-four (24) Tilting Directional Flame (TDF) Burners and Windbox modifications to improve NO_x emissions control. The aim was to achieve post-retrofit NO_x emission levels of ≤ 0.331 lb/MBtu over the range of loads, while maintaining CO emissions below 100 ppm and unburned carbon (UBC) levels below 1% by weight. The modifications to the combustion system associated with the TDF low NO_x burner installation combined with mill system tuning/optimization to improve coal flow distribution between burner lines resulted in a final NO_x emission of 0.271 lb/MBtu, an overall reduction of more than 18%. And, this level of NO_x reduction was achieved without the use of an overfire air system. Furthermore, the CO emissions and UBC levels were below the specified requirements with CO at 69 ppm (at 3% O_2) and UBC less than 1% by weight. This paper will describe the TDF burner design, modifications made to the windboxes, adjustments made to the existing mill system, start-up issues, and final results.