Numerical Simulation Study on Different Exhaust Air Transfer Conditions and Safety of Pulverized Coal System

Enhancing the safety of pulverizing systems is crucial for ensuring safe operation in the power industry. In this study, the exhaust air transfer system of a 330 MW power unit was investigated through numerical simulations. The internal flow field, the temperature distribution, and the CO concentration in the primary airbox under five exhaust air transfer conditions were analyzed. Furthermore, the effects of varying hot air velocity and temperature on the low-velocity region and combustible gas accumulation were examined to determine optimal safety conditions. The results indicate that, among the five conditions, the 100% B exhaust air transfer leads to the largest low-velocity region, the highest average CO mass fraction, and the greatest deflagration risk, whereas the 75% A exhaust air transfer condition ensures higher safety. Increasing the hot air velocity from 1 m/s to 10 m/s improves flow characteristics and reduces volatile matter accumulation, with lower velocities associated with higher CO concentrations. In contrast, raising the hot air temperature from 560 K to 610 K has a smaller effect on the flow characteristics, although higher temperatures correspond to slightly increased CO levels. In practical operation, maintaining an A/B exhaust air ratio of 75%A/25%B or keeping the hot air velocity above 5 m/s and the hot air temperature below 580 K is most beneficial for the safe operation of the pulverizing system.