Study on flow characteristics of pulverized coal in eccentrically bent coal hopper

Fig. 1 The macroscopic particle distribution of pulverized coal particles at 9 s and 13 s:(a) semi-vertex angle75°; (b) semi-vertex angle 65°;(c) semi-vertex angle55°; (d) semi-vertex angle45°; (e) semi-vertex angle35°; (f) semi-vertex angle 25°; (g) semi-vertex angle15°. • The discharge characteristics of eccentrically bent hoppers is simulated by DEM. • A regression model is established to fix the contact parameters of coal powder. • A smaller semi-vertex angle is conducive to the flow of pulverized coal. • The unloading stability of the eccentric conical coal hopper is better. Particle blockage is a persistent issue during the discharge of coal bunkers. To achieve stable and rapid discharge, an eccentrically bent hopper is proposed, and this structure combines the advantages of both curved and eccentric hoppers. This paper employs Discrete Element Method (DEM) to investigate the discharge characteristics of eccentrically bent hoppers with semi-vertex angles ranging from 15° to 75°. The results show that when the semi-vertex angle exceeds 45°, the average mass flow rate of pulverized coal does not change significantly with semi-vertex angle, and the velocity distribution of coal particles during discharge exhibits an asymmetric pattern. In contrast, when the semi-vertex angle is less than 45°, the average mass flow rate increases obviously as the semi-vertex angle decreases, and the asymmetry of velocity distribution during discharge is reduced. Furthermore, the stability of coal particle discharge with respect to the semi-vertex angle is analyzed using the coefficient of variation ( C v ) over both the stable discharge period and the entire discharge process. When semi-vertex angle is greater than 45°, the discharge stability of pulverized coal is relatively poor. As semi-vertex angle is less than 45°, the C v remains at a stable value, indicating smooth and stable discharge of pulverized coal.