Cover Story: Clean Coal Combustion: 1

The O&M staff of AES Westover Station wisely took a holistic approach to optimizing combustion within Unit 8's boiler in order to reduce its NO x emissions while maintaining acceptable levels of carbon-in-ash content. The results of major modifications - centered on the addition of a fan-boosted overfire air system - were a 60% reduction in NO x levels, improved unit reliability, and a project payback period measured in months rather than years. The 126-MW AES Westover Station in Johnson City, N.Y., provides an excellent case study of how applying the fundamentals and taking a holistic approach to a combustion problem can yield exemplary results. Westover Station Unit 8 is a tangentially-fired unit manufactured by Combustion Engineering (now Alstom Power) whose original steam conditions were 620,000 lb/hr of main steam at 1,475 psig. Superheat and reheat temperatures are 1,005F. The unit now has a gross output of 88 MW. The steam generator's furnace measures 24 ft, 10 in. deep by 25 ft, 4 in. wide. The boiler's 16 burners at four elevations are fed by four Raymond No. 533 deep-bowl pulverizers.