Combustion Flexibility of a Large-Scale Down-Fired Furnace with Respect to Boiler Load and Staging Conditions at Partial Loads

Abstract

Down-fired boilers, designed especially for industry-firing low-volatile coals such as anthracite and lean coal, suffer similarly from various problems, such as poor burnout, high NOx emissions, and asymmetric combustion. A new down-fired combustion technology was developed specially for these problems and finally trialed in a 600-MWe supercritical boiler. To evaluate the flexibility of this technology application with respect to boiler load and air-staging conditions at partial loads, industrial-size measurements (taken of gas temperatures and species concentrations in the furnace, CO and NOx emissions in the flue gas, and carbon in fly ash) were performed within the furnace at different boiler loads (i.e., 370, 450, and 600 MWe) and staged-air damper openings (i.e., 10, 30, and 45% at 450 MWe), respectively. It was found that a relatively symmetric gas temperature distribution pattern developed for all settings, despite asymmetric burner operation models at 450 and 370 MWe. Decreasing boiler load reduce...