Alleviating gas/particle flow deflection and asymmetric combustion in a 600 MW e supercritical down-fired boiler by expanding its furnace throat space

Cold-modeling gas/particle flow experiments and numerical simulations on coal combustion were performed for evaluating the furnace throat effect on the flow-field deflection and asymmetric combustion in a 600 MWe supercritical down-fired boiler. At the furnace design setting (CW = 0.529), a severely deflected gas/particle flow field appears, corresponding to a badly asymmetric combustion pattern with poor burnout and high NOx emissions. Shrinking the furnace throat from CW = 0.529 to CW = 0.500 apparently aggravates both the experimental and simulated flow-field deflection and meanwhile deteriorates asymmetric combustion. In contrast, expanding the furnace throat space to CW = 0.558 improves greatly the above problems and the flow-field symmetries are generally acceptable, accompanied by improved burnout rate and lowered NOx emissions. Findings in this work suggest that new down-fired boiler designs should be equipped with a larger furnace throat space under the circumstances with a short upper furnace aggravating the asymmetric upper furnace configuration effect.