To increase the unit capacity and improve the primary fan operating safety

optimization of hot primary air duct for the pulverizing system needs to be carried out. Through numerical simulation using the Fluent software

the optimal modification scheme for flue duct between the air preheater hot primary air outlet to the coal mill inlet was ascertained. The results show that

from the economic point of view

whether the unit capacity is increased or not

the investment recovery period of the primary air duct retrofitting is long and the energy saving potential is small. However

in the aspect of operating safety

optimizing the hot primary air duct is quite necessary when increasing the unit capacity. This conclusion was well-verified by the practical engineering application of optimal modification. The fan operating point was further away from the stall zone and its safety was significantly improved in spite of limited energy saving effect after the hot primary air duct retrofit.