Full-scale CFD investigation of gas-particle flow, interactions and combustion in tangentially fired pulverized coal furnace

Investigations suggest the need for better understanding of reactive gas-particle turbulent flow phenomena in full-scale energy systems. Numerical study was done in 350 MWe utility boiler tangentially fired furnace to clarify selected issues, such as turbulence modulation, particles dispersion, energy transfer between phases, combustion process and flame, by using an in-house developed combustion code. Numerical experiments demonstrated remarkable complexity of flow and interphase exchange. Maximal decrease in average turbulence kinetic energy of 33% due to dispersed phase was predicted for representative monodispersed coal; augmentation obtained for large particles could become attenuation due to the particles size change during combustion. Grinding fineness of polydispersed coal affected the flow, combustion and flame considerably. Fine grinding (R90 = 48.40%) provided ascending flame, higher furnace exit temperature and decrease in turbulence energy, compared with coarse grinding (R90 = 73.85%). Combustion of each particle size class of coal is completed at different vertical levels, influencing the flame position. Diagrams based on numerical predictions were proposed to enable efficient estimations of combustion and flame characteristics in the case-study furnace, for various coal qualities and mass fractions and changed distributions of coal particle size classes over the burner tiers, while necessity for further investigation was pointed out as well.