Evaluation on cold modeling flow field for a down-fired 600 MWe supercritical boiler with multi-injection and multi-staging: A burner location experimental optimization and its validation by real-furnace measurements

This work presents a burner location optimization by cold modeling experiments and its validation by real-furnace measurements for a new down-fired 600 MWe utility boiler with a low-NOx combustion technology. By recording flow field measurements within a 1:20-scaled model of the furnace, cold airflow experiments were conducted at various burner location settings, i.e., the ratio (denoted by Cl) of the distance between the burner centerline and the front (rear) wall to the arch depth is 35%, 39%, 42%, 46%, and 49%, respectively. Meanwhile, at normal full load industrial-size experiments were performed with measurements taken of gas temperatures in the near wing-wall region, carbon content in fly ash, and NOx emissions. At settings of 35% and 39%, flow field and velocity distributions along certain cross-sections as well as penetration depths of downward airflows were well-formed symmetric along the furnace center. At the left three higher settings, a deflected flow field appeared in the lower furnace, with the downward airflow near the rear wall being directed upward earlier than that near the front wall. With increasing the Cl value from 42% to 49%, the flow-field deflection became turbulent. To establish a symmetric flow field along with an appropriate airflow penetration depth, a burner location setup of Cl = 39% was finally installed in the furnace. As expected, industrial-size data revealed that with the optimized burner location, excellent furnace performance characterized by symmetric combustion, good burnout, and low NOx emissions, appeared within the furnace.

► Down-fired boilers suffer from asymmetric combustion and high NOx emissions.
► A low-NOx down-fired combustion technology specially for these problems was implemented in a newly designed boiler.
► Cold airflow experiments were conducted to establish an optimal burner location for the boiler.
► An optimal burner location on the furnace arch was found at Cl = 39% for the furnace.
► Real-furnace measurements confirmed that the furnace achieved symmetric combustion, good burnout, and low NOx emissions.