Staged-Air Ratio Optimization within a Cold Small-Scale Model for a MBEL Down-Fired Pulverized-Coal 300 MW (electrical) Utility Boiler

Abstract

To eliminate large combustion differences between zones near the front and rear walls, as well as to decrease the high carbon content in the fly ash in Mitsui Babcock energy limited (MBEL) down-fired pulverized-coal boilers, a 45° staged-air declination method was put forward in our previous work. To establish optimal staged-air ratio settings with this staged-air declination, cold airflow experiments were conducted within a small-scale model of a MBEL down-fired pulverized-coal 300 MW (electrical) utility boiler. We investigated the aerodynamic field at six different staged-air ratio settings of 0, 10, 15, 20, 25, and 30%. At the setting of 0%, an essentially symmetric W-shaped flow field appeared in the lower furnace, although some asymmetries arose in the dry bottom hopper and zones near the staged-air port outlet. For settings of 10, 15, 20, and 25%, a well-formed symmetric W-shaped flow field appeared in the lower furnace, and the extent of the flow field symmetry along the furnace center in the zone...