Establishing an overall symmetrical combustion setup for a 600 MWe supercritical down-fired boiler: A numerical and cold-modeling experimental verification

The aim in this work is to establish an overall symmetrical combustion setup for a 600 MWe supercritical down-fired boiler via evaluating effects of various factors (related with the upper furnace parameters and combustion system) on asymmetric combustion. Firstly, based on comparing the flow-field symmetry and performance parameters at the furnace outlet, effects of various factors (such as the dimensionless upper furnace height CH2, boiler nose depth CL, upper/lower furnace depth ratio CW, furnace arch's burner location CD, burner span CS, and staged-air angle θ) were numerically determined under coal-combustion conditions. Secondly, three combined setups that considering all these factors were numerically compared. With CW and CD fixed at the boiler's design levels, applying an integrated solution consisting of lengthening upper furnace to CH2 = 1.125, shortening burner span to CS = 0.387, and performing a sharp staged-air declination, developed symmetrical combustion plus apparent improvements in burnout and NOx emissions. Under these circumstances, maintaining CL at its original value of 0.298 and meanwhile setting θ at 45°, which corresponded to the combined setup 2 in this work, attained the best performance parameters at the furnace outlet. In view of the cold-modeling experiment also confirming the symmetrical gas/particle flow-field formation, the combined setup 2 was finally recommended as an overall symmetrical combustion setup for the down-fired boiler.