Investigation on the operating characteristics of a 350 MWe supercritical CFB boiler with a polygonal furnace

Highlights: • The operating performance of a 350 MWe supercritical CFB boiler was investigated. • The bed temperature uniformity was favorable. • The temperature uniformity of cyclone entrances was better than that of exits. • The uniformity of circulating ash temperatures and bed temperatures is improved. • NO_x and SO₂ emissions were lower than the Chinese ultra-low emission limits. -- Abstract: A 350 MWe supercritical circulating fluidized bed (CFB) boiler with an optimized cyclone separator arrangement and an innovative polygonal furnace was successfully demonstrated. The boiler exhibited excellent uniformity in terms of bed material fluidization, bed temperature distribution, flue gas temperature distribution, and circulating ash temperature distribution. The standard deviation of the cross-sectional bed temperatures in the lower part of the furnace ranged between 12 and 20 °C under four different boiler loads. The bed temperature distribution on the rear wall was more uniform than that on the front wall. The flue gas temperature uniformity among three cyclone separator entrances was better than that among their exits. The flue gas temperature deviation between the middle cyclone separator entrance and exit was higher than that of the other two cyclone separators. The optimized cyclone separator arrangement improved the circulating ash temperature uniformity, and the circulating ash temperature deviation among three loop seals was 12–25 °C. During a continuous 168-hour trial operation, the average emission concentrations of NO_x and SO₂ were 17.1 mg/m³ and 22.1 mg/m³ (at 6% O₂), respectively, which were lower than the Chinese ultra-low emission limits.